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1
Chan, Kwok-chu Timmy. "Calcium sulphate hemihydrate effect of humidity in storage /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21129526.
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Ling, Yuanbing 1970. "Direct preparation of alpha-calcium sulfate hemihydrate from sulfuric acid." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84283.
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In this work, the crystallization of alpha-calcium sulfate hemihydrate in sulfuric acid solution and the correlation between its properties and preparation conditions by reaction of sulfuric acid with lime (CaO) have been thoroughly investigated. The research involved the study of conversion-dissolution of calcium sulfate dihydrate in H2SO4 solution, the measurement of solubilities, thermo-dynamic calculations and the preparation of alpha-CaSO4 ·0.5 H2O via different methods of reactive mixing of H2SO4 and CaO. It was found that the calcium sulfate solids can saturate the sulfuric acid solutions in only 5 minutes. The solubility of calcium sulfate hemihydrate in 0--3.0M H 2SO4 solution at 100°C was experimentally determined and thermodynamic calculations with the aid of FactSage and OLI have led to establishment of the phase diagram for the CaSO4-H2SO 4-H2O system. An operating window has been determined in terms of H2SO4 concentration, temperature and time within which alpha-hemihydrate can be produced by reaction of lime with H 2SO4. This window is defined as 0.6--1.1M H2SO 4 (steady-state concentrations), 98--105°C and 1 hour retention time. Dihydrate was found to form as intermediate phase quickly converting to hemihydrate. The kinetics of conversion depends on the acidity level.For the standard preparation procedure of adding lime into hot sulfuric acid, alpha-hemihydrate grows in the c-axis direction much more rapidly than in other directions ending in the form of fine needle crystals. Also, independent of the shape of the seed particles, the resultant crystals of hemihydrate are needle-shaped, which suggests a "dissolution-recrystallization" mechanism. Upon prolonged equilibration in their acid-preparation solution hemihydrate needle-shape crystals become fibrous and eventually convert to anhydrite. It is believed that uptake of SO42- instead of Ca2+ is the rate-determining step in the hemihydrate crystallization process. The hot SO42--rich environment rendered most of the additives (particularly organic) tried ineffective. Trivalent cations such as Fe3+ and Al3+, are the only ones found to modify the crystal morphology from needle-shape to small "grain" type morphology.
Slow addition of H2SO4 solution to slaked lime - reverse procedure was found to favor the production of alpha-hemihydrate with column-shaped as opposed to needle-shaped crystal morphology within otherwise the same operating window, 0.6--1.1M H2SO4. Preliminary assessment of the properties of the alpha-hemihydrate materials synthesized in this work showed them to compare satisfactorily with other materials produced by conversion of dihydrate to hemihydrate.
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Nilles, Vera [Verfasser]. "Insights into the Retarding Mechanism of Linear Sodium Polyphosphates on the Hydration of α-Calcium Sulfate Hemihydrate / Vera Nilles." München : Verlag Dr. Hut, 2012. http://d-nb.info/1021072931/34.
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Alvarez-Dalama, Alina 1960. "CALCIUM-SULFITE HEMIHYDRATE CRYSTALLIZATION IN LIQUORS WITH HIGH TOTAL DISSOLVED SOLIDS (GROWTH, SIZE DISTRIBUTION, NUCLEATION, HABIT)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275528.
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Rong, Yi. "Formation du sulfate de calcium hémihydrate de type α à partir de gypse par un procédé de dissolution-cristallisation : étude cinétique expérimentale et modélisation." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM070/document.
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De nombreuses transformations de solides en solution, polymorphiques ou non, en industrie minérale ou pharmaceutique, se déroulent par la dissolution d'un premier solide en vue de la cristallisation du second. Au lieu de la voie traditionnelle de séchage, la transformation du gypse (sulfate de calcium dihydrate) en alpha-bassanite (sulfate de calcium hémihydrate) peut s’effectuer en solution aqueuse : en augmentant suffisamment la température, le gypse devient plus soluble dans l'eau que l’hémihydrate, qui a alors la possibilité de cristalliser. Un appareillage et un mode opératoire originaux ont été conçus pour investiguer la sensibilité de la cinétique de la transformation et des caractéristiques des cristaux d’hémihydrate obtenus à ces conditions opératoires. En effet, cette voie de dissolution-recristallisation permet le contrôle du facteur d'aspect des cristaux d’hémihydrate, voire celui de leur taille moyenne et de leur dispersion de taille, par le choix de ses conditions physico-chimiques : température, pH, utilisation d’additifs, et ensemencement de la solution avec des particules d’hémihydrate appropriées. Les techniques d'analyse images sont développées afin d'identifier le rapport d'aspect des particules. Un modèle cinétique prenant en compte la dissolution du gypse, la nucléation et la croissance du sulfate de calcium hémihydrate, les équilibres en phase aqueuse et de solubilité, a été élaboré, et ses équations résolues avec le logiciel MATLAB. Couplée à une méthode numérique d'optimisation, cette résolution sous MATLAB permet d'examiner la validité des hypothèses sur les processus retenus et d'identifier leurs paramètres cinétiquesIn mineral or pharmaceutical industry, many transformations of solids in solution (polymorphic or not), take place by the dissolution of the first solid and the crystallization of the second solid. Instead of the traditional drying process, the conversion of gypsum (calcium sulfate dihydrate) to alpha-bassanite (calcium sulphate hemihydrate) can be carried out in aqueous solution by increasing the temperature sufficiently. At this moment, the gypsum becomes more soluble in water than the hemihydrate, which then has the possibility to crystallize. An apparatus and an original procedure have been designed to investigate the sensitivity of the kinetics of transformation and the characteristics of the hemihydrate crystals obtained under its operating conditions. In fact, this dissolution-recrystallization route allows to control the aspect ratio of the hemihydrate crystals, and even their average size and size dispersion, by the choice of its physicochemical conditions such as temperature, pH, use of additives, and seeding the solution with the appropriate hemihydrate particles. Image analysis techniques are developed to identify the aspect ratio of the particles.A kinetic model taking into account the dissolution of gypsum, the nucleation and the growth of calcium sulphate hemihydrate and their equilibrium in aqueous phase and solubility had been developed and the equations of this model are solved with the help of MATLAB software. Coupled with a numerical optimization method, this resolution under MATLAB makes it possible to examine the validity of the assumptions on the selected processes and to identify their kinetic parameters
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SIDQUI, MUSTAPHA. "Etude du comportement des osteoblastes et des osteoclastes de rat en culture au contact de biomateriaux a usage odontologique." Paris 7, 1998. http://www.theses.fr/1998PA07GA01.
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陳國柱 and Kwok-chu Timmy Chan. "Calcium sulphate hemihydrate: effect of humidity in storage." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B21129526.
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Girgin, Seref. "Crystallization of alpha-calcium sulphate hemihydrate by aqueous reaction of calcium chloride with sulphuric acid." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102980.
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The crystallization of alpha-calcium sulphate hemihydrate with simultaneous regeneration of HCl by controlling the reaction of H 2SO4 (2.6M-8M) with concentrated CaCl2 (1-3.5M) solution at 80°C was investigated. The research included 3 studies: (a) study of the kinetics and mechanism of CaSO4 dehydrate (DH) conversion to hemihydrate (HH) and anhydrite (AH) in variable composition CaCl2 -HCl media; (b) reactive crystallization of alpha-hemihydrate in a semi-batch reactor configuration following the LaMer Diagram concept; and (c) the study of crystal growth and metal uptake by seeded crystallization with and without the presence of several metal chloride salts. According to the first study, AH is the only stable phase in the range of electrolyte concentration and temperature investigated with DH and HH being either metastable or unstable. In the absence of CaCl2 and at 3M HCl concentration or higher DH converts directly to AH. Maintenance of 0.3M or higher CaCl2 concentration was found to render hemihydrate metastable hence making its production feasible. Solubility estimation of three CaSO4 phases with the aid of OLI Stream Analyser software helped to explain the observed phase transition sequence. SEM characterization further revealed the transition from DH to HH to be governed by the topochemical mechanism.In the reactive crystallization study H2SO4 was the limiting reactant added to the CaCl2 solution up to 0.8 SO 4/Ca molar ratio. The nucleation and growth stages were successfully separated via supersaturation control achieved by regulated addition of the limiting reactant in multiple steps. This separation permitted the growth of the homogeneously nucleated crystals within the metastable zone to needle-shaped hexagonal crystals (acicular habit). Upon recycling (seeding) of the product further growth was achieved, producing crystals with 80 mum - volume based mean crystal diameter- or 100-120 mum length and 10-15 mum diameter. Growth of the seed crystals appeared to follow an agglomeration mechanism. However, in the presence of foreign metal cations (in particular divalent, Mg 2+, Fe2+, Ni2+ and trivalent, Al 3+, Fe3+) crystal growth was severely retarded via their apparent adsorption. Some of the metal cations, namely Na+, Ni2+, Al3+ were found to incorporate into the hemihydrate crystal structure to a variable extent from 0.3g/t for Na to 7g/t for Ni and 11g/t for Al. The chloride uptake was less than 10 ppm.
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Pierre, Alexandre. "Rhéologie de suspensions concentrées de sulfate de calcium." Phd thesis, INSA de Rennes, 2013. http://tel.archives-ouvertes.fr/tel-00910334.
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Ce travail de recherche s'inscrit dans une volonté de développer des suspensions concentrées à application Génie Civil (chapes anhydrites, bétons cirés). Dans ce contexte industriel, l'étude est focalisée sur l'effet de l'introduction d'adjuvants de type polycarboxylate (PCP) sur les propriétés d'écoulement de suspensions formulées avec une anhydrite fortement réactive. Les travaux expérimentaux sont initiés par le développement de protocoles de caractérisation rhéologique étalonné sur un fluide modèle à seuil. Ceci permet d'évaluer l'effet de la taille de l'entrefer, de la rugosité des plateaux, du précisaillement ainsi que du type et de la durée de sollicitation. Nous avons alors défini un protocole unique, exploitable pour identifier la courbe d'écoulement des suspensions concentrées étudiées.. Les propriétés viscoélastiques des suspensions, évaluées aux faibles déformations, sont également caractérisées sous sollicitations oscillantes. Afin d'affiner la connaissance des structures moléculaires des différents adjuvants sélectionnés pour cette étude, des caractérisations physico-chimiques sont réalisées. Elles permettent de distinguer plusieurs paramètres caractéristiques des adjuvants : masse molaire, indice de polymolécularité et sensibilité à la température en fonction d'un milieu alcalin ou neutre. Des mesures d'adsorptions ont également été réalisées sur deux adjuvants. Nous montrons ainsi que le phénomène d'adsorption semble conditionné par les propriétés du milieu, notamment par la présence de chaux. L'étude rhéologique paramétrique montre que des modifications sensibles de la réponse peuvent apparaître en fonction de l'adjuvant utilisé et de la concentration de la suspension. Les évolutions des indicateurs de consistance et de contrainte seuil de mise en écoulement en fonction de la fraction volumique solide et du dosage en adjuvant sont identifiées. Les résultats sont interprétés en ajustant un modèle de type Krieger-Dougherty. L'évolution du paramètre puissance de ce modèle peut être interprétée comme une modification de la forme et de la rugosité du grain couvert par des molécules de PCP adsorbées. Les paramètres moléculaires conditionnant le plus la rhéologie des suspensions concentrées étudiées sont la masse molaire et l'indice de polymolécularité. L'interprétation des résultats est moins tranchée vis-à-vis du seuil de mise en écoulement que vis-à-vis de la consistance. Dès lors, nous avons mis en évidence la relation seuil-consistance. Sur le plan pratique, se restreindre à l'estimation du seuil de mise en écoulement des suspensions devient pertinent. À cette fin, un modèle analytique permettant d'estimer la contrainte seuil de mise en écoulement à partir d'un test d'écoulement libre sur une surface plane est proposé. L'objectif est d'apporter une amélioration aux modèles existants lorsque l'écoulement est à la frontière entre régime d'affaissement et régime d'étalement. L'analyse, qui peut être généralisée à l'étude de tous types de fluides complexes à seuil, conduit à une meilleure évaluation de la contrainte seuil. En croisant l'information de tests d'étalement et de vidange au cône de Marsh, nous montrons ainsi qu'une rhéométrie rustique est tout à fait pertinente pour un usage industriel. La notion d'enrobage de grain est proposée pour modéliser, à l'échelle microscopique, le rôle de l'adjuvant sur l'interaction entre particules. L'ordre de grandeur de la distance interparticulaire estalors estimé entre 1 et 5 nm en exploitant des données de rhéométrie oscillante. Cette approche phénoménologique permet de mettre en évidence l'effet de la fraction volumique solide sur la distance interparticulaire. Finalement, l'étude de la rhéologie des suspensions concentrées est étendue à la transition liquide solide liée aux réactions d'hydratation. Le suivi de l'effort normal exercé sur une géométrie en contact avec la suspension peut s'interpréter comme un indicateur alternatif de prise.
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Kuthadi, Sandeep Kumar. "Laboratory Scale Study of Calcium Sulfate Hydration Forms." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1467.
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This research is part of an ongoing project to create gypsum wallboards with enhanced fire resistance. The main goal of this research is to better understand the dehydration properties of calcium sulfate dihydrate, and the hydration of calcium sulfate hemihydrate as well as anhydrous calcium sulfate. The lab-scale kinetics of these processes were studied using thermogravimetric analysis and sorption analysis. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the products from different processes. In addition to the instrumental studies, small batches were handled in ovens and liquid slurries to better mimic the real world processing of these materials. The effects of temperature, time and humidity were investigated to determine their influence on the kinetics of dehydration/hydration of different hydration forms of calcium sulfate.
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Govender, Desania Raquel. "The burn rate of calcium sulfate dihydrate-aluminium thermites." Diss., University of Pretoria, 2018. http://hdl.handle.net/2263/66196.
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The energetics of cast calcium sulfate dihydrate-aluminium thermites was explored and its
use as a potential metal-cutting tool was investigated. Thermite is a pyrotechnic composition
that undergoes a highly exothermic reaction that burns relatively slowly. It is often used in
cutting, welding and incendiary devices. Consolidation of thermite by casting was chosen to
enable control of the burning front. The base case thermite comprised 60 wt-% calcium sulfate
dihydrate oxidiser and 40 wt-% aluminium fuel. Addition of additives were considered for their
effect on the cast thermite’s setting time, density, surface temperature, reaction products and
burn rate. EKVI and FactSage thermodynamic simulations were used to determine optimum
compositions for the various systems. The thermite powder compositions were sieved before
mixing with water and casting in a mould. The casts were allowed to set for 3 days to form
calcium sulfate dihydrate-aluminium compositions. The copper sulfate pentahydrate additive
was found to significantly decrease the setting time of the casts. The heat of hydration of the
base case was 59 ± 8 J g−1
. The compressive strength reached 2.9 ± 0.2 MPa, the open air
burn rate was 12.0 ± 1.6 mm s
−1 and a maximum surface temperature of 1370 ± 64 °C was
recorded using a pyrometer. Bomb calorimetry indicated an energy output of
7.96 ± 1.07 MJ kg−1
, slightly lower than predicted by the EKVI simulation. The density of the
castings was varied by either adding hollow sodium borosilicate glass spheres or by adding
excess water. The glass spheres resulted in a burn rate that decreased nonlinearly with
decreasing cast density. The excess water made no changes to the burning, except for
increasing the burn rate of the copper sulfate pentahydrate-based thermite. Calcium sulfate in
the casts was also dehydrated by thermal treatments at 155 °C and 200 °C. This resulted in
significant increases in the burn rate due to the porosity created by the evaporation of the
hydration waters. Castings that were thermally treated in an oven at 155 °C were successful
in puncturing part of an aluminium block in confined burn tests. A hole with a diameter of
~13.6 mm and depth of ~7 mm was produced. It is recommended that the composition with
copper sulfate pentahydrate be used as a binder in further tests.Dissertation (MEng)--University of Pretoria, 2018.
Chemical Engineering
MEng
Unrestricted
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Wang, Yuan School of Chemical Engineering & Industrial Chemistry UNSW. "Composite fouling of calcium sulfate and calcium carbonate in a dynamic seawater reverse osmosis unit." Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/26007.
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Deposition of calcium carbonate (CaCO3) and calcium sulfate (CaSO4) causes serious processing problems and limits the productivity of seawater reverse osmosis (RO) desalination. The interactions between CaSO4 and CaCO3 in the dynamic seawater RO systems have been neglected previously because conventional studies mainly focused on individual compounds or mixed compounds in batch systems. The present work evaluates composite fouling behavior of CaSO4 and CaCO3 in a dynamic RO unit. The fouling experiments were performed at constant pressure and velocity by a partial recycling mode which permeate was withdrawn from the system during the recirculation of retentate to simulate the increasing of water recovery level. The fouling phenomena were monitored by the decline of flux. Scanning electron microscopy (SEM) with a combination of elemental dispersive x-ray microanalysis (EDS), and x-ray powder diffraction (XRD) was used to identify the morphological features, chemical compositions and crystalline phases of foulants. The interactions of CaSO4 and CaCO3 were investigated by the comparison between individual CaSO4 or CaCO3 fouling and composite fouling, and by varying SO42-/HCO3- molar ratio of the feed. A recently developed approach, Scaling Potential Index (SPI) incorporated with measured concentration polarization modulus (CP), for assessing the fouling tendency of inorganic salts on the membrane surface was validated in the dynamic tests. In addition, the effectiveness of two generic scale inhibitors, polyacrylic acid (molecular weight =2100, PA) and sodium hexametaphosphate (SHMP) were evaluated. Some of the highlights of the obtained results are as follows: ??????The precipitation kinetics, morphology and adhesive strength of composite scales were different from pure precipitates ??????CaSO4 precipitated as gypsum while CaCO3 precipitated as two crystalline phases: calcite and aragonite ??????The crystalline phases as well as precipitation kinetics were affected by SO42-/HCO3- ratio ??????Scaling Potential Index was able to predict the fouling tendency of CaSO4 and CaCO3 accurately ??????The dosage of PA and SHMP was effective to mitigate fouling Results of this work are significant, not only because they have made contribution to the fundamental understanding of composite inorganic fouling in RO membrane systems which was ignored previously, but also because they may play a key role in the development of scale control.
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Horne, Kerry Allison. "The refining of calcium using a sulfate reducing bacterial system." Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1003974.
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White lime is used in many industries in South Africa but is not produced locally and must be imported. Many technologies have been suggested for the large-scale manufacture of calcium carbonate but these are not necessarily suitable for application in South Africa. This study investigated a chemical preparation of calcium carbonate combined with biological purification Calcium containing materials from the Pretoria Portland Cement, Lime Division factory at Lime Acres in the Northern Cape were studied as the starting materials for the manufacture. Investigation showed that they contained various impurities, including iron and manganese compounds which were largely responsible for the brown-grey colour of the lime products. Complete dissolution of calcium hydroxide, the purest of the potential starting materials, and subsequent hydroxide precipitation was not successful in removing all iron and manganese. Precipitation with sulfide ions was successfill, decreasing levels of metals to below the detection limit of atomic absorption spectrophotometry. Studies of all potential starting materials revealed that the levels of impurities in the starting material did not have a large effect on levels of impurities in the calcium carbonate produced. It was therefore possible to convert the residual calcium oxide or hydroxide in waste lime dusts to white calcium carbonate, a marketable prciduct Recycling of the water and starting material used in the process served to increase, rather than decrease, the purity of the calcium carbonate product. This allows for water conservation as water is not consumed in the process but merely utilised. When waste lime dust was used as the starting material, sulfate was found in the product. While still a white lime, the calcium carbonate was not chemically pure. Sulfate removal was therefore investigated and the use of sulfate-reducing bacteria was studied as a novel application. A mixed sulfate-reducing bacterial population was isolated and found to be hIghly active at sulfate concentrations between 0.2 and 2 ~~~. They were capable of autotrophic growth and could reduce sulfate in solutions with elevated pH and in calcium carbonate suspensions, although they did not grow readily in these media. A process was designed for the production of bulk quantities of calcium carbonate making use of the facilities and materials available at Lime Acres. This was tested using a small scale bench-top reactor series, with favourable results. The process would allow automatic, continuous production of large quantities of white lime using waste lime dust. Provision was also made for manufacture of smaller quantities of pure calcium carbonate using sulfate-reducing bacteria to remove the sulfate impurity.
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Oppici, Maria A. "Sodium sulfate hot corrosion of silicon carbide fiber-reinforced calcium aluminosilicate." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA297663.
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Orellana, Bryan R. "BIOERODIBLE CALCIUM SULFATE BONE GRAFTING SUBSTITUTES WITH TAILORED DRUG DELIVERY CAPABILITIES." UKnowledge, 2014. http://uknowledge.uky.edu/cbme_etds/18.
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Bone regeneration or augmentation is often required prior to or concomitant with implant placement. With the limitations of many existing technologies, a biologically compatible synthetic bone grafting substitute that is osteogenic, bioerodible, and provides spacing-making functionality while acting as a drug delivery vehicle for bioactive molecules could provide an alternative to ‘gold standard’ techniques.
In the first part of this work, calcium sulfate (CS) space-making synthetic bone grafts with uniformly embedded poly(β-amino ester) (PBAE) biodegradable hydrogel particles was developed to allow controlled release of bioactive agents. The embedded gel particles’ influence on the physical and chemical characteristics of CS was tested. Namely, the compressive strength and modulus, dissolution, and morphology, were studied. All CS samples dissolved via zero-order surface erosion consistent to one another. Compression testing concluded that the amount, but not size, of embedded gel particles significantly decreased (up to 75%) the overall mechanical strength of the composite. Release studies were conducted to explore this system’s ability to deliver a broad range of drug types and sizes. Lysozyme (model protein for larger growth factors like bone morphogenic protein [BMP]) was loaded into PBAE particles embedded in CS matrix. The release of simvastatin, a small molecule drug capable of up regulating BMP production, was also examined. The release of both lysozyme and simvastatin was governed by dissolution of CS.
The second part of this work proposed a bilayered CS implant. The physical and chemical properties were characterized similarly to the CS composites above. Release kinetics of directly loaded simvastatin in either the shell, core, or both were investigated. A sequential release of simvastatin was witnessed giving foresight of the composite’s tunability. The sequential release of an antibacterial, metronidazole, loaded into poly(lactic-co-glycolic acid) (PLGA) particles embedded into the shell along with directly loaded simvastatin either in the shell, core, or both layers was also observed. Through controlled release of bioactive agents, as well as a tunable layered geometry, CS-based implants have the potential to be optimized in order to help streamline the steps required for the healing and regeneration of compromised bone tissue.
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Li, Zhibao 1962. "Measurement and chemical modeling of calcium sulfate solubilities in concentrated chloride media." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102677.
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Measurement and chemical modeling of CaSO₄ solubilities in HCl-containing multi-component aqueous chloride solutions have been thoroughly investigated. Solubilities of calcium sulfate dehydrate, hemihydrate and anhydrite in concentrated HCl (up to 12 mol·dm⁻³), CaCl₂ (up to 3.5 mol·dm⁻³) and their mixed aqueous solutions were experimentally determined by using the classic isothermal dissolution method at the temperature range from (283 to 353) K. A self-consistent chemical model based on a single set of model parameters for all three CaSO₄ modifications was developed with the aid of OLI Systems software platform. This was accomplished via regression of experimental solubility data that led to the determination of new Bromley-Zemaitis model parameters for the Ca²⁺---SO₄²⁻ and Ca²⁺ --HSO₄⁻ ion pairs. The model was successfully tested for the estimation of CaSO₄ solubilities in concentrated (up to 20 mol·kg⁻¹) HCl-CaCl₂-H₂O systems up to 373 K. In addition this newly developed OLI-based chemical model was successfully applied to construct the CaSO₄ phase transition diagrams in the HCl-CaCl₂-H₂O system. The effect of various chloride salts (NaCl, MgCl₂, FeCl₂, AlCl₃ and FeCl₃) on the solubility of CaSO₄ phases in aqueous HCl or HCl + CaCl₂ solutions up to 353 K was further investigated by experiment and modeling. This led to the development of a truly global model of CaSO₄ solubility in the H + Na + Ca + Mg + Al + Fe(II) + Cl + SO₄+ H₂O system. The new model makes use of new Bromley-Zemaitis activity coefficient model parameters for many ion pairs consisting of cations (Na⁺, Mg²⁺, Fe²⁺, and Al³⁺) and anions (SO₄⁻, HSO₄⁻, and Al(SO₄)₂⁻), as well as new empirical dissociation constant parameters for the species, MgSO₄(aq), AlSO₄⁺, and Al(SO₄)²⁻. The new model was shown to successfully predict the solubility of calcium sulfate phases in multi-component systems not used in model parameterization.
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Feldmann, Thomas. "Crystallization kinetic investigations of calcium sulfate phases in aqueous CaCl2-HCl solutions." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121477.
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The kinetics and crystal quality of a novel reactive crystallization system leading to the formation of calcium sulfate phases with simultaneous generation of strong hydrochloric acid (up to 9 M ) were investigated. The investigations undertaken in this work relate to a new hydrochloric acid regeneration process currently under industrial development for application in non-ferrous metal hydrometallurgical operations. In particular the thesis is considering the following aspects: (a) the crystal growth kinetics of calcium sulfate α-hemihydrate (HH); (b) calcium sulfate phase transformation kinetics; (c) impurity effects; and (d) crystal modifier effects on calcium sulfate crystal quality. With reference to (a), the surface area-normalized crystal growth rates of calcium sulfate α-hemihydrate were determined in two types of solutions – high CaCl2 (HCl 1.4 M, CaCl2 2.8 M ) and high HCl (HCl 5.6 M, CaCl2 0.7 M ) in a semi-batch reactor operated at constant supersaturation over the temperature range 70°C to 95°C. The growth rate was found to depend only on the reagent supply rate of Ca2+ and SO42– and to obey von Weimarn's second law of crystallization that relates crystal size to supersaturation level. Moreover it was found the width of the particle size distribution to decrease with increasing crystal growth rate. In (b) an investigation of the phase transformation kinetics of calcium sulfate dihydrate (DH) and HH was done by batch experiments over a range of CaCl2 (0.25 M to 4.97 M ), HCl (0 M to 9.43 M ) concentrations and temperatures (40°C to 90°C) including the effect of seeding. Two different mechanisms were identified, a dissolution-precipitation mechanism for the DH to HH and a topotactic reaction mechanism for the HH to AH transformation. Increased temperature and reduced water activity were found to reduce the life-time of the metastable phases DH and HH. In (c) the effects of a wide range of cationic and anionic impurities (K+, Mg2+, Sr2+, Ba2+, Al3+, Fe2+, Fe3+, La3+, Y3+, F– (fluoride), PO43– (phosphate)) on the reactive crystallization of calcium sulfate phases in strong CaCl2 (1.82 M) HCl (6.29 M) solutions at 40°C for DH or 80°C for HH, were determined. It was found by far the uptake of strontium to be the highest in DH and HH among all impurities, caused by a substitution for Ca2+ due to their similar ionic radii. Phosphate was the other impurity that had a detrimental effect as it was taken up significantly during crystal growth. Furthermore, both impurities caused the phase transformation of DH to HH if certain concentration levels were exceeded. Lastly in (d), the effects of a broad range of crystal habit modifiers were investigated in CaCl2-HCl solutions of different strength. The most influential additives were CTAB (cetyltrimethylammonium bromide), polyacrylic acid and polyvinylsulfonic acid. CTAB favored formation of industrially interesting thick slab crystals. In contrast polyacrylic acid resulted in the formation of elongated and thinner crystals explained on the basis of preferential crystal plane adsorption. Polyvinylsulfonic acid had a detrimental effect on DH crystal nucleation and growth explained by its polymeric structure. The ineffectiveness of the majority of additives was attributed to a lack of ionization caused by the high acid solution strength.La cinétique et la qualité cristalline d'un nouveau système de cristallisation réactive menant à la formation des phases de sulfate de calcium avec la génération simultanée de l'acide chlorhydrique (un acide fort, jusqu'à 9 M) ont été étudiées. Les études entreprises dans cette recherche sont reliées à un nouveau procédé de régénération de l'acide chlorhydrique présentement en développement pour des applications industrielles dans des opérations hydrométallurgiques des métaux non-ferreux. Cette thèse considère les aspects suivants: (a) la cinétique de cristallisation du sulfate de calcium α-hémihydraté (HH); (b) la cinétique des transitions de phase du sulfate de calcium; (c) les effets des impuretés sur la cristallisation réactive des phases du sulfate de calcium; et (d) les effets des modificateurs de cristaux dans la qualité cristalline du sulfate de calcium. Concernant (a), les taux de croissance des cristaux de sulfate de calcium α-hémihydraté, normalisés selon l'aire de surface, ont été déterminés dans deux types de solutions–à haute concentration en CaCl2 (HCl 1.4 M, CaCl2 2.8 M) et à haute concentration en HCl (HCl 5.6 M, CaCl2 0.7 M)–avec un réacteur semi-continu opéré à sursaturation constante dans une série de températures allant de 70°C jusqu'à 95°C. Il a été montré que le taux de croissance dépend uniquement du débit d'introduction des réactifs Ca2+ et SO42-, et qu'il obéit à la deuxième loi de cristallisation de von Weimarn reliant la taille du cristal avec le niveau de sursaturation. De plus, il a été trouvé que la largeur de la distribution de tailles des particules diminue lorsque le taux de croissance du cristal augmente. En (b), une étude sur la cinétique des transitions de phase du sulfate de calcium dihydraté (DH) et du HH a été réalisée dans des réacteurs discontinus sur un intervalle de concentrations de CaCl2 (de 0.25 M jusqu'à 4.97 M), de HCl (de 0 M jusqu'à 9.43 M), et de températures (de 40°C jusqu'à 90°C) incluant l'effet de la nucléation. Deux mécanismes de transition ont été identifiés: un mécanisme de dissolution-précipitation pour la transition du DH vers le HH, et un mécanisme à réaction topotactique pour la transformation du HH en AH. Une réduction de la durée de vie des phases métastables, DH et HH, a été trouvée lorsque la température a été augmentée et l'activité avec de l'eau a été réduite. En (c), les effets d'une série d'impuretés cationiques et anioniques (K+,Mg2+,Sr2+,Ba2+,Al3+,Fe2+,Fe3+,La3+,Y3+, F- (fluorure), PO43- (phosphate)) sur la cristallisation réactive des phases du sulfate de calcium dans des solutions à haute concentration de CaCl2 (1.82 M) et HCl (6.29 M) ont été déterminés à 40°C et à 80°C pour le DH et le HH respectivement. Parmi toutes les impuretés, l'incorporation de strontium dans le DH et le HH s'est montrée la plus élevée, par substitution du Ca2+ à cause de la similarité de leurs rayons ioniques. L'autre impureté qui a eu un effet négatif lorsqu'elle a été incorporée de façon significative durant la croissance du cristal est le phosphate. De plus, ces deux impuretés ont engendré une transition de phase du DH vers le HH lorsque certains niveaux de concentration ont été dépassés. Finalement en (d), les effets d'une vaste plage de modificateurs de la morphologie de cristaux ont été examinés dans des solutions de CaCl2-HCl à différentes concentrations. Les additifs les plus actifs ont été le bromure de cétyltriméthylammonium (CTAB), l'acide polyacrylique et l'acide polyvinyle sulfonique. L'utilisation du CTAB a favorisé la formation des plaques épaisses de cristaux, ce qui est d'intérêt industriel, alors que l'acide polyacrylique a engendré la formation des cristaux minces et allongés. Ce comportement avec l'acide polyacrylique, s'explique par la prédilection pour certains plans cristallographiques lors de l'adsorption. L'utilisation de l'acide polyvinyle sulfonique a nui à la nucléation et à la croissance des cristaux, ce qui s'explique par sa structure polymérique.
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Zangaro, Renato Amaro. "Étude et application du sulfate de calcium en cartographie de radiation ionisante." Montpellier 2, 1988. http://www.theses.fr/1988MON20114.
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Zangaro, Renato Amaro. "Etude et application du sulfate de calcium en cartographie de radiation ionisante." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376192249.
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Kedziora, Charlotte. "Propriétés d’usage et mécanismes d’hydratation du système ternaire [Ciment Alumineux – Sulfate de Calcium – Laitier de Haut Fourneau] à haute teneur en sulfate de calcium : De l’approche expérimentale à la modélisation." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0047/document.
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L’étude menée s’attache à évaluer le potentiel d’activation du laitier de haut fourneau dans un liant ternaire constitué de ciment alumineux, de sulfate de calcium et de laitier. Dans ce système ternaire, le constituant majoritaire est le sulfate de calcium. Le potentiel d’un tel système n’est pas encore connu mais cette étude vise à renseigner sur les principaux avantages et limites d’utilisation. D’un point de vue des propriétés d’usage de ce liant, la prise, le durcissement rapide et la montée des résistances sont assurés par le liant ettringitique. Ensuite, et uniquement si la dessiccation est évitée, le laitier de haut fourneau réagit et dans ce cas, l’apport du laitier dans de tels systèmes est double. Il contribue à l’augmentation des performances mécaniques à moyen et long terme et à limiter l’expansion sous eau. D’un point de vue de la compréhension des mécanismes d’hydratation, une démarche expérimentale originale est mise en place et dévoile le potentiel du laitier. Elle est basée sur la comparaison des performances obtenues avec différentes cures. Le potentiel d’hydratation du laitier est amplifié lorsque le système subit un séchage puis une réhydratation. Cependant, les techniques utilisées (diffraction des rayons X et calorimétrie différentielle à balayage) ne sont pas adaptées au suivi et à la quantification de laitier consommé. Ainsi, la compréhension de l’hydratation s’appuie sur des techniques dites indirectes. Une semi-quantification par diffraction des rayons X est réalisée pour le suivi et l’évaluation de la mayénite, le sulfate de calcium (anhydre ou dihydraté), la syngénite et l’ettringite, l’analyse thermogravimétrique permet de mesurer le degré d’hydratation du système, et la porosimétrie mercure informe sur les changements microstructuraux. La plus grosse difficulté dans ces travaux a porté sur le suivi et la quantification des phases amorphes (anhydres ou hydratées), telles que le laitier, les gels de C-S-H et d’AH3, et c’est pour cette raison qu’une approche par modélisation a été mise en place afin d’identifier le rôle de chaque constituant du système ternaire [Ciment Alumineux – Sulfate de Calcium – Laitier] et particulièrement du laitier lors de l’essai de réhydratation. L’approche par modélisation permet de mieux identifier les phénomènes chimiques et physiques ayant lieu lors de l’hydratation du liant. Elle est utilisée pour expliquer les observations macroscopiques (comme les performances mécaniques) et aide à déterminer les cinétique d’hydratation dans le milieu poreux. Le modèle utilisé n’est pas encore parfaitement au point mais il a permis d’identifier les différentes séquences d’hydratation (à savoir que le liant ettringitique réagit dans les premiers instants et qu’ensuite, l’hydratation de l’anhydrite entraine la formation de gypse et l’hydratation du laitier est effective à long terme) et de confirmer que la réaction du laitier est lenteThe potential of activation of a Ground Granulated Blast Furnace Slag has been evaluated into a ternary system comprising of a Calcium Sulfate as major component and a Calcium Aluminate Cement. This system is not well known and the main goal of this study is to determine its main advantages and limitations. From the usage properties point of view, fast setting and initial strengths are governed by the ettringitic binder. Then, and only if the dehydration is avoided, slag reacts. In this case, slag contributes to the increase of mechanical performances at medium and long terms and to limit the expansion under water. From an understanding point of view, the original experimental approach reveals the potential of the slag. It is based on a comparison of performances with different types of curing methods. The potential of hydration of the slag is amplified when the system is dehydrated during a few days and then rehydrated. However, slag contribution is complex to establish because analytical methods to follow-up slag consumption (such as X-ray Diffraction and Differential Scanning Calorimetry analysis) are not well adapted. So, to understand the hydration mechanisms, indirect approaches are used. Semi-quantitative methods by X-ray Diffraction to follow-up the mayenite, calcium sulfate, syngenite and ettringite, ThermoGravimetric Analysis to measure degree of hydration and Mercury Intrusion Porosimetry to identify microstructural changes have been carried. The most important difficulty concerns the identification and quantification of amorphous phases such as slag, C-S-H and AH3. That is why a modelling approach is necessary to understand the role of each compound in the ternary mixture and in particular the obvious contribution of slag during rehydration test. This modelling approach increases knowledge of the physical and chemical phenomena in this ternary binder. It is useful to explain the observed macroscopic properties such as strength and helps to determine the kinetics of hydration in porous environment. Even if this model is still under development, it has allowed identifying the sequences of hydration (ettringitic binder reacts at very initial time, then anhydrite transforms into gypsum and slag reacts at long term) and confirms therefore that the reaction of slag is slow
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Pereira, Rodrigo de Paula [UNESP]. "A atividade antimicrobiana de agentes desinfetantes incorporados ao gesso tipo IV." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/98032.
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pereira_rp_me_arafo.pdf: 718418 bytes, checksum: e3bb9ad8e88ee0f369f92dd6e3ca7045 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Vários protocolos de desinfecção podem ser usados para romper a cadeia de infecção cruzada entre o consultório odontológico e o laboratório de prótese. A inclusão de agentes antimicrobianos à composição do gesso ou a manipulação do gesso com soluções desinfetantes podem ser usados com esta finalidade. O propósito deste estudo foi avaliar a atividade antimicrobiana de dois agentes desinfetantes (digluconato de clorexidina 2% e cloridrato de clorexidina 98%) incorporados ao gesso IV (FujiRock - GC Europe, Leuven, Bélgica) durante sua manipulação. No teste microbiológico de difusão em Agar foram uti l izados os seguintes microorganismos: Escherichia coli, Staphylococcus aureus, Bacilus subtilis e Candida albicans. Amostras com 5 mm de diâmetro e 3 mm de espessura foram separadas em quatro grupos: 1) gesso manipulado com água destilada esterilizada (controle positivo); 2) discos de papel embebidos com solução de digluconato de clorexidina 2% (controle negativo); 3) gesso manipulado com solução de digluconato de clorexidina 2%; 4) gesso com a incorporação de cloridrato de clorexidina 98% em pó, na proporção de 1% da massa do gesso, e manipulado com água destilada esterilizada. Após 1 hora e 24 horas do vazamento do gesso, as amostras foram posicionadas em placas de Petri com meios de cul tura específicos inoculados com as suspensões microbianas. A atividade antimicrobiana dos desinfetantes foi avaliada pelo diâmetro médio dos halos de inibição do crescimento microbiano. Os valores foram analisados pela ANOVA Aninhada (p<0,05) e teste de Tukey para comparações específicas. Os resultados encontrados demonstraram que os agentes desinfetantes analisados apresentaram atividade antimicrobiana quando misturados ao gesso, com exceção para Candida albicans, na qual não houve efeito da solução de clorexidina nos dois períodos de análise...
Many protocols for disinfection procedures can be used to break the chain of cross-contamination between dental office and dental laboratory. The inclusion of antimicrobial agent to the composition of gypsum or the manipulat ion of gypsum with disinfectant substances can be used to that aim. The purpose of this study was to evaluate the antimicrobial activity of two disinfectant agents (2% chlorhexidine digluconate and 98% chlorhexidine hydrochloride) incorporated into type IV dental stone (FujiRock - GC Europe, Leuven, Belgium) at the time of mixing. The microbiological test used was the Agar diffusion test to the following microorganisms: Escherichia coli, Staphylococcus aureus, Bacilus subtilis and Candida albicans. Samples of 5 mm in diameter and 3 mm in length were separated in four groups: 1) dental stone mixed wi th steri le distilled water (positive control); 2) paper disk soaked wi th solution of 2% chlorhexidine digluconate (negative control); 3) dental stone mixed with solution of 2% chlorhexidine digluconate; 4) dental stone wi th incorporation of chlorhexidine hydrochloride 98% powder, in proportion of 1% of the dental stone mass, and mixed with sterile distilled water. The samples were placed, 1 hour and 24 hours after pouring of dental stone, in Petri plates with specific cul ture medium wich were inoculated with the microbial suspensions. The antimicrobial activity of disinfectant was evaluated by the average diameter of microbial growth inhibi tion zones. The data were analyzed with a Nested ANOVA (p<0,05) and Tukey test for specific comparisons. The disinfectant agents analyzed demonstrated antimicrobial effect against microorganisms used in this study, in exception to Candida albicans, against wich there was not effect from chlorhexidine digluconate at two periods of analysis. Significant difference between disinfectantes were found to all microrganisms... (Complete abstract click electronic access below)
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Marraha, Mohamed. "Synthèse et étude physico-chimique des phosphosulfates de calcium de structure [Béta] Ca3(PO4)2." Toulouse, INPT, 1989. http://www.theses.fr/1989INPT025G.
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Ce memoire concerne la synthese, le comportement a haute temperature, la structure et les proprietes physico-chimiques des phosphosulfates et arseniosulfates de calcium de structure bete ca3(po4)2. Le premier chapitre s'interesse au mecanisme de formation des phosphosulfates de calcium. Une etude systematique du systeme ca3(po4)2-caso4 a permis de proposer la formule generale ca21-x(po4)14-2x(so4)2x (0 inferieur ou egal a 1) ou les ions sulfate substituent les ions phosphate dans les sites preferentiels. Le compose limite a pour formule ca20(po4)12(so4)2. Le deuxieme chapitre s'interesse au comportement thermique et a la reactivite du phosphosulfate ca20(po94)12(so4)2. Ce compose se decompose a partir de 1100c en oxxhydroxyapatite phosphocalcique avec elimination des sulfates. Le troisieme chapitre traite d'une nouvelle methode de synthese des phosphosulfates par reaction solide-gaz, entre l'hydroxyapatite et l'oxyde de soufre. Le schema reactionnel fait intervenir des composes intermediaires qui sont le pyrophosphate de calcium beta, le sulfate de calcium et le phosphate tricalcique beta, selon la temperature, la duree de la reaction et le debit gazeux. Le quatrieme chapitre est consacre a l'etude du systeme ca3(aso4)2-caso4. La substitution des ions aso43 par des ions so42 permet de preparer la solution solide ca21-x(aso4)14-2x(so4)2x (0 inferieur ou egal a 1). Le compose limite a pour formule ca20(aso4)12(so4)2
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Nguyen, Tien Dung. "Apport des aluminates de calcium vis-à-vis de la résistance à l'eau des sulfates de calcium hydratés." Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0002.
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Les sulfates de calcium sont des matériaux économiques et écologiques. Pourtant leur utilisation dans le domaine de la construction est assez limitée du fait de leur sensibilité à l’eau. La capacité des ciments alumineux (CAC) à diminuer la sensibilité à l’eau des sulfates de calcium ainsi que les mécanismes d’insensibilisation ont été étudiés. L’insensibilisation à l’eau des sulfates de calcium a été réalisée par ajout de faibles quantités de ciment alumineux (≤ 30%). Quatre sulfates de calcium de nature différente : gypse, hémi-hydrate α et β, anhydrite synthétique ont été étudiés. L’étude des mécanismes d’insensibilisation à l’eau des sulfates de calcium par ajout du ciment Fondu, menée à différentes analyses de la microstructure : IR, DRX, ATD-TG, MEB, a mis en évidence deux approches : la formation de l’ettringite insoluble et la formation du gel d’AH3 qui colle les grains de sulfate de calcium soluble. La nature des phases cristallochimiques du ciment alumineux a des influences sur les caractéristiques mécaniques, la sensibilité à l’eau ainsi que la durabilité des mélanges [sulfate de calcium / CAC]. L’étude des mélanges [anhydrite synthétique / laitier / CAC] offrent des perspectives intéressantes notamment concernant le développement des liants à faible empreinte CO2Calcium sulphate materials are economical and ecological. But their use in the construction is quite limited because of their sensibility to water. The capacity of aluminate cement (CAC) to decrease the water sensibility of calcium sulphate and the mechanisms of insensibilisation were investigated. Waterproofing of gypsum base materials was carried out by addition of small amounts of aluminate cement (≤ 30%). Different nature of calcium sulphates : gypsum, hemihydrate α and β, synthetic anhydrite was studied. The study of mechanisms of insensibilisation to water of calcium sulphate by adding cement Fondu, with different analysis of microstructure : IR, DRX, ATD-TG, MEB, revealed two approaches : formation of ettringite insoluble and formation of gel AH3 that stick soluble grains of calcium sulphate. The nature of phases of aluminate cement has influences on the mechanical properties, sensibility to water and durability of mixtures [calcium sulphate / CAC]. The studies of mixtures [synthetic anhydrite / slag / CAC] offer interesting perspectives for the development of binders with low imprint CO2
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Ait, Kettout Ahcéne. "Influence de la nature des sulfates de calcium sur l'hydratation d'un ciment en présence d'adjuvants." Toulouse 3, 1989. http://www.theses.fr/1989TOU30232.
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L'objectif principal de ce travail est de differencier l'action des sulfates de calcium-gypse et anhydrite - sur le controle du debut d'hydratation du clinker portland, en presence d'adjuvants organiques. L'etude du passage des ions sulfates en solution, a montre que la dissolution des sulfates depend du milieu. Ainsi, dans l'eau pure la quantite d'ions sulfates liberee par l'anhydrite est superieure a celle liberee par le gypse, et ceci en presence ou non de fluidifiants. Par contre dans une suspension de ciment, le gypse se dissout en plus grande quantite que l'anhydrite. Le controle de l'hydratation du ciment portland depend de la quantite d'ions sulfates en solution et de la teneur en aluminate tricalcique. A ciment a faible teneur en aluminate tricalcique (c#3a<9%) ; l'hydration est normale quelle que soit la nature du sulfate de calcium additionne et quel que soit le fluidifiant incorpore. Cela est du au fait que la quantite d'ions sulfates presents en solution, est suffisante pour le controle de la phase aluminate. B ciment a forte teneur en aluminate tricalcique (c#3a>9%) ; le controle de l'hydratation de ce type de ciment depend de la nature du sulfate de calcium utilise. * le gypse se dissout en quantite suffisante pour controler correctement l'hydratation de la phase aluminate meme en presence de fluidifiants. * par contre, l'anhydrite ne libere pas suffisamment d'ions sulfates pour controler l'hydratation des aluminates qui forment rapidement des aluminates de calcium hydrates. Le meme resultat a ete observe lors de l'incorporation de fluidifiants a base de condensat de naphtalene ou de melamine. En additionnant un fluidifiant a base de lignosulfonate gluconate de sodium, on a decele la formation de monosulfoaluminates de calcium et une mauvaise cristallisation des composes hydrates formes (ettringite et portlandite)
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Newton, Peter J. "Sodium sulfate corrosion of silicon carbide fiber-reinforced calcium aluminosilicate glass-ceramic matrix composites." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283703.
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Aranda, Berenger. "Réactivité et durabilité à base de sulfate de calcium et de liants minéraux classiques." Rennes, INSA, 2012. http://www.theses.fr/2012ISAR0001.
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Le Kerysten® est un liant à base de sulfate de calcium produit par calcination flash. Il possède la particularité d’être un mélange d’anhydrite γ (CaSO4) et d’hémihydrate (CaSO4. 0,5H2O) qui semblent se répartir dans un grain complexe qui confère au Kerysten® plusieurs états métastables et stables. L’étude de la prise du Kerysten® a montré qu’il possède une réactivité différente de celle d’un plâtre β commercial et des propriétés mécaniques supérieures, à taux de gâchage équivalent. Ces propriétés sont apportées par le grain complexe du Kerysten®. L’étude d’un mélange à base de 70% de Kerysten® et de 30% de ciment Portland a montré l’existence d’interactions au moment de la prise du liant composite. La prise du gypse est très rapide. L‘obtention d’un squelette de gypse ralentit l’hydratation des phases cimentaires dans le mélange. La précipitation de ces phases se fait alors dans les pores du mélange. Dans ce matériau, le Kerysten® apporte une bonne dureté au matériau aux très jeunes âges tandis que le ciment Portland fournit des résistances mécaniques relativement importantes. Nous avons observé les mêmes phénomènes lorsque nous avons réalisé des mortiers de mélanges avec des proportions de Kerysten® comprises entre 50% et 98%. En particulier, les formulations contenant des proportions en Kerysten® comprises entre 80% et 95% ont des résistances mécaniques, au moins, égales à celles du mortier contenant 100% de ciment Portland. La durabilité du mélange à base de 70% de Kerysten® et de 30% de ciment Portland a été testée dans des solutions d’acide chlorhydrique, d’acide sulfurique, de sulfate d’ammonium et d’eau. Ces attaques chimiques provoquent une dissolution importante de l’hydroxyde de calcium et des sulfates de calcium présents dans ces liants. Elles ont aussi engendré la formation de précipités pouvant contenir du carbonate de calcium ou du gypse associés à des silicates de calcium et des aluminates de calcium. Ces dégradations ont entrainé une chute importante des résistances en flexion 3 points des éprouvettes, mais les résistances en compression restent bonnes ainsi que les duretés. L’ajout de 30% de ciment Portland dans le Kerysten® permet d’améliorer la résistance du mélange face aux agressions chimiques. Cela permet aussi de tirer parti des avantages de chaque constituant du mélange pour résister à ces agressionsKerysten® is a calcium sulfate binder product by “flash calcination”. The binder is originally made of γ-anhydrite (CaSO4) and hemihydrate (CaSO4. 0,5H2O). These two phases form a complex grain which leads to one stable state and two metastable states. To compare the settings of the Kerysten® and a plaster of Paris, we have synthesized both materials with the same quantity of water and the same quantity of retarding admixture. The Kerysten® reacts faster with water than the plaster of Paris. The mechanical properties of the Kerysten® are more important than these of the plaster of Paris. These differences are due to the complex grains of the Kerysten®. We have hydrated a mixture of 70% of Kerysten® and 30% of Portland cement. During the setting, gypsum skeleton has been formed first. This phase has delayed the hydration of the cementitious phases which have precipitated into the porous system. In this material, Kerysten® improves the hardness of the material at early stage and cementitious precipitates improve mechanical strengths. We have studied mortars made with different ratios of Kerysten® and Portland cement. Mortars with small quantities of Portland cement between 5% and 20% have mechanical strengths as important as these of a 100% Portland cement mortar. Prismatic specimens have been made of the mixture of 70% of Kerysten® and 30% of Portland cement. Their durability has been studied under different conditions of chemical attacks: prismatic specimens have been dept in water, in chloride acid, in sulfuric acid and in ammonia sulfate acid for a period of 92 days. Attacks have provoked an important dissolution of calcium hydroxide and calcium sulfate of the materials. Then, calcium carbonate and gypsum have precipitated in the solution. The precipitates contained also cimentitious phases fallen from the porous system. The degradations have caused a strong decrease of the 3-points flexural strengths, whereas the compressive strengths and the hardness have less decreased. An addition of 30% of Portland cement in the Kerysten® improves the chemical resistant of the material. Thanks to Kerysten®, cimentitious phases have been less dissolved. Thanks to Portland cement, strengths stayed good
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Sadok, El-Habib. "Rôles compares des cations étrangers en solution dans l’étape de germination associée à l'hydratation des sulfates de calcium et de l'aluminate mono calcique." Lyon, INSA, 1989. http://www.theses.fr/1989ISAL0058.
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L'objectif de ce travail a concerné l’extension, à d'autres systèmes solide-liquide, du modèle théorique proposé antérieurement par Murat et El-Hajouji pour expliquer le rôle des cations métalliques étrangers dans l'étape de germination associée à la réaction d'hydratation de l'anhydrite orthorhombique. Dans un premier temps, la validité de ce modèle a pu être vérifiée pour la réaction d'hydratation du sulfure de calcium semi hydraté CaSO4l/2H2Oβ. Puis une extension à la réaction d'hydratation de l'alumine mono calcique et du ciment alumineux Sécar 71 (étude par calorimétrie isotherme), a montré que ce modèle ne tenait plus lorsque la paramètre z/r (z charge et r rayon ionique) caractéristique du cation étranger devenait supérieur à 2,5Ǻexp-1. Une explication de ce phénomène est fournie sur la base d'une hypothèse (expérimentalement vérifiée) impliquant la précipitation d'hydroxydes métalliques, provoquée par l 'élévation du PH associée à la dissolution de la phase anhydre : les grains d'hydroxyde métallique jouent le rôle de germes potentiels provoquant une nette augmentation de la vitesse de germination des aluminates de calcium hydratés. Les cations lithium et nickel provoquent pour leur part la précipitation immédiate d'un aluminate métallique (de Li et de Ni) hydraté jouant le même rôle que les hydroxydes métalliques (intervention d'un processus de germination hétérogène), mais conduisant à une valeur particulièrement élevée de la vitesse de germination. Le caractère hétérogène de l'étape de germination a été confirmé pas l'analyse des valeurs de la résistance mécanique, à la compression pure, des produits d'hydratation de Sécar 71. Ces résultats éclairent d'un jour nouveau le déroulement du processus de dissolution non congruente d'une phase solide en milieu aqueux et ses implications dans le développement des résistances mécaniques des géomatériaux.
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Berry, Jeffrey Nicholas. "Sulfate in foraminiferal calcium carbonate : investigating a potential proxy for sea water carbonate ion concentration." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/53536.
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Thesis (M.S.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.Includes bibliographical references (leaves 82-85).
The sulfur content of planktonic and benthic foraminifera was measured in specimens recovered from deep-sea sediment cores and individuals grown in culture. A new method for measuring sulfur in foraminiferal calcium carbonate was developed, employing a high-resolution inductively coupled plasma-mass spectrometer. The sulfur measurements, expressed as sulfur-to-calcium (S/Ca) ratios in the foraminiferal shells, ranged from 0.26 to 6.0 mmol/mol. Most analyses fell in the range of 0.7 to 2.5 mmol/mol. Culturing experiments were conducted in the planktonic foraminifer G. sacculifer to test the hypothesis that S/Ca ratios in the foraminifer are inversely proportional to the carbonate ion concentration in the seawater in which they grow, and hence proportional to the pH of the seawater. The slope of the relationship between cultured G. sacculifer S/Ca and the pH of the seawater medium was -1.92 mmol mol-1/pH unit with a least squares linear correlation coefficient, r2=0.927. The S/Ca ratios of planktonic and benthic foraminifera from Holocene and last glacial period sediments were measured in an effort to use the established relationship of S/Ca and pH to calculate the ocean pH gradient between Holocene and glacial time. The results indicate the pH of global ocean deepwater was 0.10 to 0.15 pH units higher during glacial time than today. Smaller pH gradients were seen for some cores which may have been caused by circulation-induced water mass changes. Surface ocean changes in pH over the Holocene-glacial interval seem to vary from region to region, with up to an 0.2 pH unit increase at the Sierra Leone Rise in glacial time. Benthic foraminifera from coretops in the thermocline of the Little Bahama Bank were analyzed for S/Ca to examine the effects of hydrographic variables on S/Ca. The relationship of S/Ca to pH and [CO3=] has a positive slope, at odds with the expected negative slope from the previous results. The S/Ca results do correlate well with salinity, suggesting that salinity or other hydrographic parameters may also influence foraminiferal S/Ca ratios.
by Jeffrey Nicholas Berry.
M.S.
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DADKHAH, MEHRAN. "Preparation and characterization of a Novel mesoporous bioactive glass/calcium sulfate cement for vertebroplasty application." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2678646.
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Vertebral compression fractures (VCFs) are deformities of the vertebral body that usually do not require an open surgical approach and are often due to osteoporosis or low energy trauma. They may be healed by themselves with a conservative management: brace support and bed rest, combined with the administration of analgesics and bisphosphonates. When the non-surgical approach is not effective, VCFs usually lead to untreatable pain, spine deformity and disability with a proven increase of mortality, especially in patients with poor conditions. Vertebroplasty and kyphoplasty are known as alternative minimal invasive approaches to VCFs. They are two percutaneous spine interventions which are performed with the goal of back pain relief and, when possible, restoring of the vertebral height. Vertebroplasty involves the injection of a bone cement through the trabeculae of the fractured vertebral body. In this procedure, cement injection is performed under continuous radiological control through a needle inserted in the vertebra by a transpedicular percutaneous approach. In kyphoplasty, a balloon tamp is inserted through a vertebroplasty needle in the fractured vertebral body and then is inflated/deflated and the created cavity is filled with the bone cement injected through a needle. In randomized trials it was found that VP and KP are equally safe and significantly superior to conservative treatment.
Injectable bone cements play a critical role in the effectiveness of vertebroplasty and kyphoplasty. Regarding the bone replacement, several investigations have been focused on the materials exhibiting good bioactivity, biodegradability and biocompatibility. Injectable bone cements can be divided into various categories. The first group is polymer based cements which show unique properties due to their flexibility of composition. However, their poor mechanical strength limits their applications. Metals are considered as the second group that has high wear resistance, strength and ductility. However, their high rate of corrosion and low biocompatibility make them undesirable for living tissue. In addition, allergic reactions can occur due to the high diffusion of metal ions. Another group of materials are ceramics which possess generally good biocompatibility. Although these materials have resistance to corrosion and compression, they are brittle with low fracture strength. Calcium phosphate and calcium sulphate cements could be applicable as biomaterials for vertebral
stabilization and augmentation. Nevertheless, their clinical applications have been limited due to some shortcomings. Currently, the number of commercial calcium sulphate-based cements is limited. Therefore, in recent years, several approaches have been proposed to develop the synthetic calcium-based bone cements.
The aim of the present research was the synthesis of a mesoporous bioactive glass (MBG) by spray-drying a mild acidic aqueous synthesis solution. These particles are able to chemically bond to the bone and can be also utilized for targeted drug delivery. In order to synthesis the MBG particles, the classical methods are time-consuming due to the additional steps to obtain the final powders. Moreover, these methods are usually performed with ethanol-based solution which is flammable and expensive. Spray-drying can be considered as a single step production technique to transform a fluid feed to a dried solid powder. In fact, the spray-drying approach can be used as an effective alternative to the standard routes with faster kinetics which allows to produce the particles with controlled size and morphology. It is reported that the spray-dried mesoporous bioactive glasses or functionalized silica have been already produced by spraying synthesis solutions based on flammable solvents (mostly ethanol) under an inert atmosphere.
In general, the effective procedures involve both safety and economic constraints for a future manufacturing scale-up. In this study, MBG particles were produced by the combination of sol-gel synthesis in an aqueous medium and spray-drying technique, which can be a further improvement in terms of safety, cost and environment.
The second aim of this study was to develop an innovative injectable and bioresorbable composite cements based on alpha calcium sulphate hemihydrate as a resorbable matrix, enriched with mesoporous glass particles (to impart bioactivity) and a glass-ceramic radiopaque phase. The present work was in the frame of the European Union Seventh Framework Program (FP7/2007- 2013) under grant agreement no. [280575]-Restoration. During this study, the developed injectable cements were characterized in terms of physical and mechanical properties such as setting time, injectability and compressive strength. Moreover, in vitro bioactivity and degradability of prepared composite cements were assessed in simulated body fluid (SBF). Biological tests using rat bone marrow stromal cells were also carried out in vitro. In addition, further investigations were carried out in vivo by using large animal model (sheep).
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Halfen, Doris Pereira. "Adição de fontes de enxofre e cálcio na dieta de gatos adultos e seus efeitos no ph urinário e equilíbrio ácido-básico." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/149324.
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A urolitíase é um problema recorrente na clínica veterinária considerada como causa de morbidade. As urolitíases são estreitamente associadas ao pH urinário e a nutrição exerce um papel fundamental no controle desta afecção, pois através da manipulação da dieta, pode-se modificar o pH urinário. A dieta possui cátions e ânions na sua composição mineral e a diferença entre íons é medida em miliequivalentes (mEq/kg) e denominado excesso de bases (EB) da dieta, calculado através da equação: (49,9 x Ca) + (82,3 x Mg) + (43,5 x Na) + (25,6 x K) – (64,6 x P) – (62,4 x S) – (28,2 x Cl), sendo a concentração dos elementos em g/kg de MS. A finalidade deste estudo, dividido em dois experimentos, foi avaliar o efeito da adição de fontes de enxofre (S) e cálcio nas dietas de felinos sobre o pH urinário e equilíbrio ácido-básico. A adição de fontes de enxofre objetivou demonstrar a eficácia na acidificação urinária. No primeiro experimento avaliaram-se três diferentes fontes de enxofre: sulfato de cálcio (CaSO4), DL-metionina (DLM) e Metionina hidróxi análoga (MHA) adicionados a uma dieta controle em dois níveis cada um. No tratamento controle não houve adição de acidificantes. No primeiro nível adicionou-se 1,28 g de S/kg e no segundo 2,56 g de S/kg, resultando em sete tratamentos. No segundo experimento duas fontes de cálcio foram avaliadas com o objetivo de pesquisar a eficácia destes sais na alcalinização da urina. No tratamento controle não houve adição de fontes de cálcio. Nos tratamentos 2 e 3 foram adicionados à dieta controle carbonato de cálcio e gluconato de cálcio, respectivamente, nas doses de +160 mEq/kg, resultando em três tratamentos. A urina produzida em cada período de 24 horas teve aferida seu volume, densidade e pH. No segundo experimento foi também medida a excreção urinária de cálcio no período de 72h. O equilíbrio ácido-básico foi avaliado pela hemogasometria de sangue venoso. A DLM no maior nível e o MHA diferiram da dieta controle em relação ao pH urinário (p<0,001) e seu poder acidificante foi maior que o do sulfato de cálcio (p<0,05). As duas fontes de cálcio alcalinizaram a urina, mas o carbonato de cálcio atingiu um pH urinário mais alto que o gluconato de cálcio. Concluiu-se que o efeito diferenciado das fontes de S e cálcio sobre o pH urinário é um indicador de que a participação do cálcio é dependente dos ânions a que está associado, o que leva ao questionamento sobre qual a melhor forma de avaliar sua participação no cálculo do EB.Urolithiasis is a commom problem in the veterinary clinic considered as a cause of morbidity. The urolithiasis are closely associated with urinary pH and nutrition plays a key role in the control of this disease, because through dietary manipulation, it´s possible modify the urinary pH. The diet has cations and anions in their mineral composition and the difference between ions is measured in milliequivalents (mEq/kg) and called base excess (BE) of the diet, calculated by the equation: (49.9 x Ca) + (82, Mg x 3) + (43.5 x Na) + (25.6 x K) - (64.6 x P) - (62.4 x S) - (28.2 x Cl), being the concentration of elements in g/kg DM. The purpose of this study, divided in two experiments, was to evaluate the effect of addition of sources of sulfur (S) and calcium in the diets of cats on the urinary pH and acid-base balance. The addition of sulfur sources aimed to demonstrate the efficacy in urinary acidification. In the first experiment were evaluated three different sources of sulfur, calcium sulfate (CaSO4), DLMethionine (DLM) and Methionine hydroxy analogue (MHA) added to a control diet at two levels each. In the control treatment there was no addition of acidifying. At the first level was added 1.28 g S/kg and in the second 2.56 g S/kg, resulting in seven treatments. In the second experiment two calcium sources were evaluated in order to research the effectiveness of these salts in alkalinize urine. In the control treatment there was no addition of calcium sources. In treatments 2 and 3 were added to the control diet calcium carbonate and calcium gluconate, respectively, at doses of +160 mEq/kg, resulting in three treatments. The urine produced in each period of 24 hours had measured its volume, density and pH. The second experiment also measured the urinary excretion of calcium in the period of 72 hours. The acid-base balance was evaluated by blood gas analysis of venous blood. The DLM at the highest level and MHA differed of the control diet in relation to urinary pH (p<0.001) and their acidifying power was greater than the calcium sulfate (p<0.05). The two sources of calcium alkalinized the urine, but the calcium carbonate reached a urine pH higher than calcium gluconate. It was concluded that the effect of different sources of S and calcium on urinary pH is an indicator that the participation of calcium is dependent of the anions that is associated, which leads to questions about how is the best way to evaluate its participation in calculation of BE.
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El, Mornan Abdelmjid. "Synthèse, comportement thermique et réactivité de la solution solide gypse-brushite (1-x) CaSO4, 2H2O-xCaHPO4, 2 H2O (x<0,2) et de ses produits de déshydratation." Lyon 1, 1990. http://www.theses.fr/1990LYO10186.
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Afin d'expliquer le role propre des ions phosphate syncristallises dans la reactivite, vis-a-vis de l'eau, des produits de deshydratation des phosphogypses industriels, des solutions solides gypse-brushite de formule (1-x) caso#4. 2h#2o-xcahpo#4. 2h#2o (x<0,2) ont ete preparees par coprecipitation en phase aqueuse. La cinetique du phenomene a ete suivie par methode conductimetrique. L'analyse des solides obtenus et leur caracterisation par differentes methodes physico-chimiques (analyse thermique differentielle, diffraction des rayons x, spectroscopie i. R. , meb) ont montre que des solutions solides etaient effectivement obtenues mais pratiquement toujours accompagnees de monetite (cahpo#4 anhydre). Les hemihydrates prepares par deshydratation a 130c et 150c des solutions solides gypse-brushite sont egalement des solutions solides et le suivi, par calorimetrie et conductimetrie, de leur cinetique de rehydratation a permis de mettre en evidence le role fortement inhibiteur de l'ion hydrogenophosphate hpo#4#2# dans le reseau cristallin du dihydrate au cours de formation de celui-ci a partir de la phase aqueuse. Ce travail montre clairement que les ions hydrogenophosphate syncristallises dans le reseau du gypse ont un role predominant par rapport a celui des autres impuretes contenues dans les phosphogypses industriels
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Marden, Torres Sandro. "The influence of chloride on the thaumasite form of sulfate attack in mortars containing calcium carbonate." Thesis, University of Sheffield, 2004. http://etheses.whiterose.ac.uk/6064/.
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Chlorides have been reported to be present in several field cases where thaumasite attack has occurred. However, no published systematic research dealing with the role of chloride in the thaumasite form of sulfate attack could be found in the literature. This research project has been designed through a comprehensive experimental programme to address this issue. This investigation studies the following: the formation of thaumasite in long-term exposure of carbonated systems to sulfate environment; whether or not the presence of chloride affects the thaumasite form of sulfate attack (TSA); the effect of long-term and short-term carbonation on the precipitation of thaumasite; the composition of thaumasite formed in chloride containing solutions; the chloride binding capacity of thaumasite-affected cement matrix; and the use of metakaolin to prevent TSA in carbonated mortar. Mortar samples were cast using siliceous sand and Portland cement replaced by different amounts (0,5 and 15%) of limestone filler, and by 10% metakaolin. Mortar cubes were subsequently stored in deionised water, magnesium sulfate solution, combined sulfate and sodium chloride solution and simulated seawater at 5°C and 20°C. Long-term specimens consisted of Portland cement mortars containing 15% limestone filler, which were exposed to atmospheric carbonation at 5 and 20°C for 5 years, were also immersed in these salt solutions at both temperatures. The mortar cubes were examined regularly every month, and the results of visual assessment recorded. The mineralogy of the deteriorated products was determined by x-ray diffraction (XRD), infrared spectroscopy (IRS). The pH of the solutions was also measured periodically. The composition of the thaumasite and the deteriorated cement matrix was assessed by means of the determination of the unit cell parameters of the crystal, by quantitative infrared spectroscopy (IRS); scanning electron microscopy (SEM); backscattered electron image (BEI) and chemical analyses by energy dispersive X-ray and quantitative x-ray microanalyses. The results indicate that the effect of chloride on sulfate attack is affected by temperature, because it affects the solubility of some minerals and increases the activity of carbonates. At 20°C, the presence of chlorides appears to mitigate sulfate attack by combining with the aluminates of the cement forming Friedel's salt. At this temperature, the main carbonate phases were calcite and aragonite, whereas thaumasite was predominant in all samples at 5°C, which caused damage that increased with increase in the chloride concentration in solution and the carbonate content, as evidenced by increased loss of mass and pH. Because of the demand for an alkaline environment, thaumasite did not precipitate within the long-term carbonated surface areas, but immediately underneath. The formation of thaumasite was not prevented in carbonated specimens after short-term. In the presence of chloride, thaumasite precipitated with lower lattice parameter c, indicative of a higher carbonate to sulfate ratio, and its composition shifted towards the thaumasite end-member of the solid- solution series. Thus, chloride does not seem to enter into thaumasite crystal structure. In addition, the chloride binding capacity of thaumasite-affected areas of the cement is reduced as the residual CSH phase both decalcifies and loses its silicon to give place to the deposition of thaumasite. The performance of metakaolin containing mortars in salt solutions was improved by the pozzolanic effect, but also by an increase in the chloride binding capacity, which reduced the deleterious effect of the chloride on the formation of thaumasite. However, metakaolin-containing samples in magnesium sulfate developed some signs of damage that were detected after 18 months. The interaction between chloride and other ionic species on thaumasite formation in the cement matrix is very complex, and can have some implications to the CaC03 threshold for durable concretes under TSA prone environments and also to the steel corrosion of concrete reinforcement.
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Shih, Wen-Yi. "Formation and control of calcium sulfate dihydrate (gypsum) crystallization on RO membranes and surrogate polymeric surfaces." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1383480211&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Kobata, Robert Steven 1954. "AN AUTOMATED METHOD OF MEASURING ISOLATED MUSCLE CONTRACTION (VERAPAMIL, HALOTHANE, CALCIUM-CHLORIDE, MAGNESIUM SULFATE, GUINEA PIG)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/277003.
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Beltagui, Hoda. "The influence of gypsum on the hydration kinetics and the microstructure of calcium sulfoaluminate cements in sulfate-rich environmnets." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231270.
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Martias, Céline. "Synthèse et caractérisation de matériaux composites à base de sulfate de calcium destinés à la protection incendie." Phd thesis, Toulon, 2011. http://tel.archives-ouvertes.fr/tel-00769952.
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La mise en place de nouvelles normes, de plus en plus contraignantes, est un défi pour l'élaboration de nouveaux matériaux résistants à haute température. Le premier objectif de l'étude est de mettre au point un panneau - coupe-feu 2h à base de plâtre. Il devra présenter à la fois de bonnes qualités d'isolant thermique et des propriétés mécaniques suffisantes pour maintenir l'intégrité d'un ouvrage d'art. Le second objectif est de comprendre, d'une part, l'influence de divers paramètres sur le phénomène de prise du plâtre et d'autre part, de déterminer les propriétés thermomécaniques du composite. Ce type de matériau est obtenu par l'association d'eau, d'une matrice céramique composée essentiellement de sulfate de calcium dihydraté et de charges utilisées en tant que renforts thermiques et/ou mécaniques.Dans une première partie, l'étude porte essentiellement sur la matrice pour laquelle une granulométrie permettant d'optimiser les propriétés mécaniques est déterminée. La matrice est ensuite caractérisée chimiquement. Une étude par calorimétrie isotherme de la réaction d'hydratation du sulfate de calcium semihydraté (plâtre) est réalisée afin de comprendre le mécanisme de prise du plâtre et de maîtriser les temps de prise. Pour cela, on étudie l'influence de la taille des grains, de la quantité d'eau, de la composition chimique du plâtre et de la présence ou non d'adjuvants sur la cinétique d'hydratation du plâtre.Dans une seconde partie, les renforts nécessaires à l'élaboration du composite sont sélectionnés. Les relations entre les quantités de charges et les propriétés thermomécaniques (conductivité thermique, module d'Young, dureté Shore C) du système sont étudiées. Ainsi, une modélisation du comportement du composite sous sollicitations thermique et mécanique est proposée. Cette étude a permis de définir une formulation de panneau présentant de très bonnes propriétés thermiques et des propriétés mécaniques suffisantes pour assurer l'intégrité d'un ouvrage d'art en cas d'incendie. La formulation mise au point a fait l'objet d'un dépôt de brevet (n° BIP207506FR00 en décembre 2010). Cette formulation est actuellement commercialisée par la société EXTHA sous forme de plaques.
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Kuryatnyk, Tetyana. "Insensibilisation à l'eau des mélanges à base de sulfate de calcium par ajout de clinker sulfo-alumineux." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0062/these.pdf.
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Les liants sulfatiques sont des liants économiques mais dont le développement est gêné du fait de leur sensibilité à l'eau. La capacité du clinker sulfo-alumineux à rendre stable à l'eau des mélanges à base de sulfate de calcium ainsi que l'influence de la nature du sulfate de calcium sur les propriétés mécaniques et la microstructure du matériau ont été étudiées. L'insensibilisation à l'eau des mélanges à base de sulfate de calcium a été réalisée par ajout de 30, 50 et 70% de clinker sulfo-alumineux. La présente étude concerne la comparaison des mélanges contenant : gypse naturel et gypse recristallisé ; gypse naturel et β hémi hydrate ; gypse recristallisé et β hémi hydrate. L'étude de l'hydratation des mélanges à base de sulfate de calcium contenant 30, 50 et 70% de clinker sulfo-alumineux a été menée à diverses échéances au moyen de la DRX, ATD - ATG, et de la spectroscopie IR. Il a été montré qu'il se forme de l'ettringite et de la gibbsite quels que soient le rapport sulfate de calcium - clinker sulfo-alumineux ou la nature du sulfate de calcium. Les principaux facteurs déterminant la microstructure et donc les propriétés physiques et la durabilité du matériau ont été retenus : rapport E / S, conditions de conservation (eau ou à l'air), pourcentage de clinker sulfo-alumineux ajouté, nature de sulfate de calcium. A partir de cette étude, il est devenu possible de déterminer la quantité minimale (30%) de clinker sulfo-alumineux assurant la stabilité à l'eau des mélanges. Cependant, il est apparu que les mélanges contenant les deux gypses (naturel ou recristallisé) possèdent une structure cimentaire identique, celle du liant à base d'hémi hydrate est un cas particulierBinders based on calcium sulfate are cheap but vulnerable in water due to their high solubility. The capacity of calcium sulfo-aluminate clinker to stabilize calcium sulfate based binders as well as the influence of the nature of calcium sulfate on the mechanical properties and microstructure of such materials were investigated. Waterproofing of gypsum based binders was carried out by addition of 30, 50 and 70 % of calcium sulfo-aluminate clinker. The present study compares the bihaviour of pastes containing respectively natural gypsum, recristallized gypsum, and β hemi-hydrate. The study of the hydration of calcium sulfate based binders containing 30, 50 and 70 % of calcium sulfo-aluminate clinker has been carried out by means of XRD, DTA, and IR spectrometry. It was pointed out that ettringite and gibbsite are the main hydrates that formed regardless of the calcium sulfate to calcium sulfo-aluminate clinker ratio or the nature of calcium sulfate. The main factors determining the microstructure and thus the physical properties and the durability of material were the following : W / C ratio, conditions of curing (water or in air), percentage of added calcium sulfo-aluminate clinker, and nature of calcium sulfate. From this study, it became possible to determine the minimal quantity (30 %) of calcium sulfo-aluminate clinker ensuring the stability in water of the different mixtures
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Kuryatnyk, Tetyana Pera Jean Derevianko Viktor. "Insensibilisation à l'eau des mélanges à base de sulfate de calcium par ajout de clinker sulfo-alumineux." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?&id=kuryatnyk.
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Pereira, Rodrigo de Paula. "A atividade antimicrobiana de agentes desinfetantes incorporados ao gesso tipo IV /." Araraquara : [s.n.], 2009. http://hdl.handle.net/11449/98032.
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Orientador: João Neudenir Arioli FilhoBanca: Sérgio Sualdini Nogueira
Banca: Vinícius Pedrazzi
Resumo: Vários protocolos de desinfecção podem ser usados para romper a cadeia de infecção cruzada entre o consultório odontológico e o laboratório de prótese. A inclusão de agentes antimicrobianos à composição do gesso ou a manipulação do gesso com soluções desinfetantes podem ser usados com esta finalidade. O propósito deste estudo foi avaliar a atividade antimicrobiana de dois agentes desinfetantes (digluconato de clorexidina 2% e cloridrato de clorexidina 98%) incorporados ao gesso IV (FujiRock - GC Europe, Leuven, Bélgica) durante sua manipulação. No teste microbiológico de difusão em Agar foram uti l izados os seguintes microorganismos: Escherichia coli, Staphylococcus aureus, Bacilus subtilis e Candida albicans. Amostras com 5 mm de diâmetro e 3 mm de espessura foram separadas em quatro grupos: 1) gesso manipulado com água destilada esterilizada (controle positivo); 2) discos de papel embebidos com solução de digluconato de clorexidina 2% (controle negativo); 3) gesso manipulado com solução de digluconato de clorexidina 2%; 4) gesso com a incorporação de cloridrato de clorexidina 98% em pó, na proporção de 1% da massa do gesso, e manipulado com água destilada esterilizada. Após 1 hora e 24 horas do vazamento do gesso, as amostras foram posicionadas em placas de Petri com meios de cul tura específicos inoculados com as suspensões microbianas. A atividade antimicrobiana dos desinfetantes foi avaliada pelo diâmetro médio dos halos de inibição do crescimento microbiano. Os valores foram analisados pela ANOVA Aninhada (p<0,05) e teste de Tukey para comparações específicas. Os resultados encontrados demonstraram que os agentes desinfetantes analisados apresentaram atividade antimicrobiana quando misturados ao gesso, com exceção para Candida albicans, na qual não houve efeito da solução de clorexidina nos dois períodos de análise... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Many protocols for disinfection procedures can be used to break the chain of cross-contamination between dental office and dental laboratory. The inclusion of antimicrobial agent to the composition of gypsum or the manipulat ion of gypsum with disinfectant substances can be used to that aim. The purpose of this study was to evaluate the antimicrobial activity of two disinfectant agents (2% chlorhexidine digluconate and 98% chlorhexidine hydrochloride) incorporated into type IV dental stone (FujiRock - GC Europe, Leuven, Belgium) at the time of mixing. The microbiological test used was the Agar diffusion test to the following microorganisms: Escherichia coli, Staphylococcus aureus, Bacilus subtilis and Candida albicans. Samples of 5 mm in diameter and 3 mm in length were separated in four groups: 1) dental stone mixed wi th steri le distilled water (positive control); 2) paper disk soaked wi th solution of 2% chlorhexidine digluconate (negative control); 3) dental stone mixed with solution of 2% chlorhexidine digluconate; 4) dental stone wi th incorporation of chlorhexidine hydrochloride 98% powder, in proportion of 1% of the dental stone mass, and mixed with sterile distilled water. The samples were placed, 1 hour and 24 hours after pouring of dental stone, in Petri plates with specific cul ture medium wich were inoculated with the microbial suspensions. The antimicrobial activity of disinfectant was evaluated by the average diameter of microbial growth inhibi tion zones. The data were analyzed with a Nested ANOVA (p<0,05) and Tukey test for specific comparisons. The disinfectant agents analyzed demonstrated antimicrobial effect against microorganisms used in this study, in exception to Candida albicans, against wich there was not effect from chlorhexidine digluconate at two periods of analysis. Significant difference between disinfectantes were found to all microrganisms... (Complete abstract click electronic access below)
Mestre
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Sanches, Carlos Vinícius [UNESP]. "Disponibilidade de Ni em um latossolo vermelho distrófico em função da aplicação de gesso agrícola e caracterização fisiológica e bioquímica do algodoeiro." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151924.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O algodoeiro apresenta uma sensibilidade elevada nos sistemas de cultivo. A acidez do solo aliada a alta concentração alumínio e a baixa disponibilidade de cálcio em profundidade podem limitar a produtividade sendo possível verificar distúrbios nutricionais. Nesse contexto, o níquel, nutriente essencial, componente da metaloenzima urease tem sua importância comprovada no metabolismo do nitrogênio e vem sendo estudado como alternativa para melhorar a qualidade do sistema de cultivo por meio da eficiência do uso do nitrogênio disponível. Outra vertente de estudos diz respeito a capacidade do níquel de agir como metal pesado sendo prejudicial para as culturas, dessa maneira faz-se necessário entender a dinâmica desse nutriente dentro dos sistemas de cultivo. Tendo em vista o exposto, o objetivo deste trabalho foi verificar os efeitos da aplicação de diferentes doses de níquel e gesso, e a interação entre os dois sobre o crescimento, produtividade e estado nutricional de plantas de algodoeiro em condições de campo. O experimento foi desenvolvido em dois anos, os tratamentos utilizados foram 0,0; 1,0; 2,0; 6,0; 12 e 16 kg ha-1 de Ni e 0, 200, 400 e 800 kg ha-1 de gesso, aplicados via solo. Utilizou-se o delineamento em blocos ao acaso em um fatorial 6x4 com 3 repetições. Para mensurar o efeito dos tratamentos, os parâmetros de crescimento (altura, diâmetro e número de ramos), estado nutricional (P, K, Ca, Mg, S, Cu, Fe, Mn, Zn e Ni), e produtividade (número de estruturas reprodutivas, produtividade de algodão em caroço, rendimento de fibra e massa de 20 capulhos), foram submetidos a análise de variância e regressão polinomial por meio do software de análise estatística Sisvar 5.1. Há variações na produtividade em função das condições climáticas, em déficit hídrico severo foi possível concluir que o aumento na dose de gesso pode reduzir a produtividade do algodoeiro linearmente, a aplicação de doses de níquel e gesso, nas condições apresentadas nesse experimento, não exercem influência no crescimento e desenvolvimento do algodoeiro. O fornecimento de gesso até 800 kg/ha interfere na absorção de Ni, verifica-se um antagonismo entre cálcio e níquel. O fornecimento de níquel via solo não interfere na absorção de nutrientes com exceção do cálcio. O cálcio exerce antagonismo em relação ao manganês. As doses de níquel não promoveram efeitos positivos ou negativos no crescimento e desenvolvimento do algodoeiro.
The cotton plant has a high sensitivity in the cropping systems. The soil acidity allied to high aluminum concentration and low calcium availability in depth may limit the productivity and develop nutritional disorders. In this context, nickel, essential element, component of metalloenzyme urease, has its importance proven in the nitrogen metabolism. It has been studied as an alternative to improve the cropping system quality through an efficient use of the available nitrogen. Another strand of studies mentions about the nickel capacity to act as a heavy metal and being harmful to the crops, thereby making it necessary to understand this nutrient dynamic within the cropping systems. Based on the foregoing, the objective of this study was to verify the effects of the application of different nickel and gypsum doses, and the interaction between them on the growth, crop yield and nutritional status of cotton plants under field conditions. The experiment was conducted in two years, the treatments used were 0,0; 1,0; 2,0; 6,0; 12 and 16 kg ha-1 of Ni and 0, 200, 400 and 800 kg ha-1 of gypsum, applied via soil. A randomized complete block design was used in a 6x4 factorial scheme with 3 repetitions. In order to measure the treatment effects, the parameters of growth (high, diameter and number of branches), nutritional status (P, K, Ca, Mg, S, Cu, Fe, Mn, Zn and Ni), and crop yield (number of reproductive structures, seed cotton yield, fiber cotton yield and mass of 20 cotton bolls), were submitted to an analysis of variance and polynomial regression through a software of statistical analysis Sisvar 5.1. There are variations in the crop yield in function of the climate conditions; in severe water deficit, it was possible to conclude that the increase in gypsum doses can reduce cotton crop yield linearly. The application of doses of nickel and gypsum, under the conditions presented, do not influence the growth and development of the cotton plants. The supply of gypsum up to 800 kg ha-1 interfere in the absorption of Ni, verifying an antagonism between calcium and nickel. The supply of nickel via soil do not interfere in the nutrients absorption with exception of calcium, which exerts antagonism over manganese. The doses of nickel did not promote positive or negatives effects in the growth and development of the cotton plants.
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Bingol, Onur Rauf. "Hydrothermal-like Synthesis Of Hydroxyapatite From Calcium Sulfates." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612425/index.pdf.
Full textAbstract:
Synthesis of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) from commercial grade plaster of paris (CaSO4&bull0.5H2O, PoP) and gypsum (CaSO4&bull
2H2O) has been performed. HAp synthesis was achieved by reacting 1 M of (NH4)2HPO4 (or 0.5 M of (NH4)2HPO4) solutions with solid calcium sulfate precursors under ambient pressure (1 atm) and hydrothermal-like (2 ±
0.2 atm, 120 °
C) conditions. Under ambient conditions, HAp formation kinetics was investigated at 25 °
C, 50 °
C and 90 °
C using 1 M of (NH4)2HPO4 solution. Conversion to HAp at such low temperature takes more than 21 days and it also promotes formation of additional calcium phosphate with HAp. At 25 °
C, HAp formation started after 7 days accompanied with formation of brushite (CaHPO4&bull
2H2O). At 50 °
C no significant conversion was observed after 6 h. However, at 90 °
C, phase pure HAp was formed after 2 h. On the other hand, under hydrothermal-like conditions, the HAp formation proceed much faster and it was also shown that HAp could be also synthesized from gypsum powders and bulk gypsum pellets. Using 1 M of (NH4)2HPO4 solution, HAp formation from PoP started 15 min and completed almost in 30 min, whereas 0.5 M of (NH4)2HPO4 reactant solution slowed down the conversion. The exact chemical identity of the HAp product of hydrothermal-like reaction was evaluated by post-synthesis calcinations and the thermal phase stability was related with the stoichiometry (Ca/P at ratio) of the HAp. The HAp phase was stable up to 600 °
C and above 600 °
C, &beta
-tricalcium phosphate (&beta
-Ca3(PO4)2, &beta
-TCP) was formed, suggesting that the resultant HAp was calcium-deficient. Mechanical testing by diametrical compression was performed to the HAp samples produced from bulk gypsum pellets. The strength was measured 1.2 MPa with highest solid to liquid (s:l) ratio 3.33 and decreased with s:l ratio. This change was found to be related with the porosity differences due to differences in s:l ratio. Additional mechanical tests were applied to the polycaprolactone (PCL) coated bulk HAp pellets for which the tensile strength was doubled. This study presents an easy and feasible method for production of HAp from a cheap and abundant calcium source &ndash
PoP. In addition, the findings provide a potential processing route for developing irregularly shaped bulk porous HAp structures.
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Hsia, Chungwei. "Mechanisms and rate of solid state diffusion in iridium-hafnium intermetallic compound (iridium(3) hafnium) and calcium sulfate /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487848078448938.
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Poupelloz, Estelle. "Etude des processus de germination-croissance de l'ettringite, seule ou dans un système aluminate tricalcique/sulfate de calcium." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK055.
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L'ettringite Ca6Al2(SO4)3(OH)12.26H2O est l'un des principaux produits d'hydratation des ciments et malgré l'importance de ce composant dans la chimie des ciments, les lois gouvernant ses processus de précipitation ont été très peu étudiées. Ce travail de thèse a donc été centré entièrement sur l'étude de l'ettringite et sur ses mécanismes de germination-croissance.La précipitation d'ettringite a d'abord été étudiée seule à partir de solutions ioniques sursaturées. Les expériences ont été menées dans le but d'étudier séparément les processus de nucléation et de croissance. La Théorie Classique de la Nucléation a été appliquée et a permis la détermination de l'énergie interfaciale de l'ettringite. Une description globale du processus de précipitation de l'ettringite a pu être proposée. Il est apparu que l'ettringite est un hydrate se formant très facilement, de par sa faible énergie interfaciale, et présentant une vitesse de formation élevée dès que ses ions constitutifs sont présents en solution. Après la nucléation primaire homogène, lorsque la quantité de cristaux déjà formés est encore faible, la vitesse de précipitation de l'ettringite dépend surtout du degré de sursaturation de la solution. Lorsque la surface cristalline devient significative, son influence provoque une augmentation de la vitesse de précipitation et des processus simultanés de nucléation secondaire et de croissance ont été mis en évidence.Dans un second temps, la formation d'ettringite a été étudiée lors de l'hydratation d'un système C$_3$A/sulfate de calcium, choisi pour se rapprocher des réactions ayant lieu dans un ciment Portland. Les expériences conduites ont permis de montrer qu'une concentration grandissante en ions sulfate (et en ions calcium) dans la solution accélérait la précipitation d'ettringite. Les résultats obtenus en première partie concernant la facilité et la rapidité de la précipitation d'ettringite seule à partir de solutions sursaturées semblent également valables dans le cas d'une formation d'ettringite lors de l'hydratation d'un système C3A/CaSO4Ettringite Ca6Al2(SO4)3(OH)12.26H2O is one of the main hydration products of cements but despite the importance of this compound for cement chemistry, laws governing its precipitation processes have been poorly studied. This PhD thesis was entirely focused on the study of ettringite and on its nucleation-growth mechanisms.Ettringite precipitation was first studied alone from supersaturated ionic solutions. Experiments were designed in order to study separately processes of nucleation and growth. The Classical Theory of Nucleation was applied and allowed the determination of the interfacial energy of ettringite. A global description of ettringite precipitation process has been suggested. It appeared that ettringite is an easily formed hydrate, because of its low interfacial energy, presenting a high precipitation rate as soon as its constitituve ions are present in solution. After primary homogeneous nucleation, when the quantity of already formed crystals is still low, precipitation rate of ettringite mainly depends on the supersaturation degree of the solution. When the crystalline surface gets significative, it provokes an increase of precipitation rate and processes of secondary nucleation and growth have been identified.Then, formation of ettringite during the hydration of a C$_3$A/calcium sulfate system, chosen to get closer to chemical reactions happening in a Portland cement, was studied. Conducted experiments helped prove that a growing concentration of sulfate ions (and of calcium ions) in solution was speeding up ettringite precipitation. Obtained results about the ease and speed of ettringite precipitation alone from supersaturated solutions seem also valid in the case of ettringite formation during the hydration of a C$_3$A/CaSO$_4$ system
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Silva, Marcos Aurelio Bomfim da 1983. "Propriedades físicas de gessos odontológicos tipo IV desidratados em temperatura ambiente e em forno de microondas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288550.
Full textAbstract:
Orientador: Rafael Leonardo Xediek ConsaniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O objetivo deste estudo foi verificar a influência da secagem em temperatura de laboratório (25±4ºC) e em forno de microondas sobre propriedades físicas de gessos odontológicos tipo IV: Elite Rock, Shera Premium e Durone IV. Os gessos foram proporcionados e espatulados mecanicamente a vácuo seguindo as recomendações dos fabricantes e vazado no molde com auxílio de vibrador mecânico. No Capítulo 1 foi avaliada a alteração dimensional, resistência à compressão e reprodução de detalhes dos gessos desidratados em forno de microondas e em temperatura de laboratório. Dois protocolos de desidratação com diferentes períodos de avaliação foram utilizados para os ensaios de alteração dimensional, resistência à compressão e reprodução de detalhes dos gessos foram utilizados e divididos em 4 grupos com: G1- temperatura de laboratório (25 ± 4ºC) no período de 2 horas; G2- temperatura de laboratório após 24 horas; G3- temperatura de laboratório após 7 dias e G4- microondas com potência de 800 W por 5 minutos após 2 horas. No Capitulo 2 foi avaliada a influência de diferentes potências de radiação do forno de microondas durante a secagem dos gessos sobre a alteração dimensional e resistência à compressão. Foram utilizados seis diferentes métodos de secagem e divididos em seis grupos: G1-temperatura ambiente no período de 2 horas; G2- temperatura ambiente no período de 24 horas; G3- temperatura ambiente no período de 7 dias; G4- microondas com potência de 200 W por 5 minutos; G5- microondas com potência média 400 W por 5 minutos e G6- microondas com potência alta 800 W por 5 minutos. Nos capítulos 1 e 2 para o ensaio de alteração dimensional linear foram confeccionadas amostras utilizando matriz metálica com entalhes de diferentes profundidades e distância entre as linhas de 2,5 mm. Em seguida, a superfície foi escaneada com resolução de 1200 dpi e analisada com software ImageTool 3.0. Para o ensaio de resistência à compressão foram confeccionados moldes de silicone polimerizada por condensação, a partir de uma matriz metálica cilíndrica medindo 20 mm de comprimento por 10 mm de diâmetro. Para o ensaio de reprodução de detalhes executada somente no capítulo 1, a análise foi feita na linha central da matriz reproduzida na superfície da amostra de gesso. Os dados foram submetidos à análise de variância (ANOVA) com dois fatores e as médias ao teste de Tukey com nível de 5% de significância. Capitulo 1: No G1, as três marcas comerciais apresentaram maiores níveis de expansão dimensional sendo diferentes estatisticamente entre os grupos 2, 3 e 4. Para o ensaio de resistência à compressão os gessos Elite Rock e Durone IV não apresentaram diferença estatística significante entre G2 e G4, exceto para Shera Premium não apresentando diferença entre G3 e G4. Os melhores índices de reprodução ocorreram para G3. Capítulo 2: Os valores de alteração dimensional para o gesso Elite Rock foram estatisticamente semelhantes entre G3 e G6 e entre G4,G5 e G2. O gesso Shera Premium apresentou maiores níveis de expansão para G1 em relação a G2, G3, G4, G5, G6. Para o gesso Durone IV o G5 apresentou os menos valores de expansão dimensional. Para as três marcas comerciais utilizadas, a desidratação em forno de microondas com potência de 200 W e em temperatura de laboratório após 7 dias promoveu resistência à compressão sem diferença estatística e significativamente maiores,com exceção do Shera Premium e Durone IV que produziram valores semelhantes com potência de 800 W e 400W respectivamente. Os gessos odontológicos tipo IV apresentaram melhora em suas propriedades com secagem em forno de microondas. A potência de 200 W a 800 W proporcionaram níveis de alteração dimensional similares aos desidratados em temperatura de laboratório após 24 horas e 7 dias. A potência de 200 W produz maiores valores de resistência à compressão para Elite Rock.
Abstract: The objective of this study was to assess the effect of drying laboratory temperature (25 ± 4 ° C) and in microwave oven on the physical properties of dental stone type IV: Rock Elite, Premium and Shera Durone IV. Plasters were proportionate and spatulate mechanically vacuum following the manufacturers recommendations and poured into the mold with the aid of mechanical vibrator. In Chapter 1 we evaluated the dimensional change, compressive strength and detail reproduction of plaster dried in a microwave oven and a temperature of the laboratory. Two different protocols of dehydration for tests of dimensional change, compressive strength and detail reproduction of plaster casts were used and divided into four groups: G1-temperature laboratory (25 ± 4 ° C) in 2 hours, G2- temperature laboratory after 24 hours, G3-temperature laboratory after 7 days and G4-microwave power of 800 W for 5 minutes after 2 hours. In Chapter 2 we evaluated the effects of different energy radiation from the microwave oven during the drying of plaster on the dimensional changes and compressive strength. We used six different methods of drying and divided into six groups: G1-room temperature within 2 hours; G2-room temperature within 24 hours; G3-temperature environment within 7 days: G4-microwave power of 200 W for 5 minutes and G5- average microwave power 400 W for 5 minutes, G6-high microwave power 800 W for 5 minutes. In chapters 1 and 2 for testing dimensional linear samples were prepared using metal matrix with notches of different depths and distance between lines of 2.5 mm. Then the surface was scanned at 1200 dpi and analyzed with software ImageTool 3.0. For testing the compressive strength silicone molds were prepared by condensation polymerized in cylindrical stainless steel mold measuring 20 mm by 10 mm in diameter. To test the reproduction of details performed only in chapter 1, the analysis was performed on the center line of the matrix reproduced on the sample surface of plaster. Data were subjected to analysis of variance (ANOVA) with two factors and the means with Tukey test at 5% level of significance. Chapter 1: In G1 of three commercial brands showed higher levels of dimensional expansion was statistically significant between groups 2,3 and 4. For testing the compressive strength gypsum Durone Elite Rock and IV showed no statistically significant difference between G2 and G4, except for Premium Shera no difference between G3 and G4. The highest rates of reproduction were to G3. Chapter 2: The values of dimensional change to the cast Elite Rock showed statistically similar values among and between G3 and G6, G4, G5 and G2. Gypsum Premium Shera had higher levels of expansion in G1 compared to G2, G3, G4, G5, G6. For plaster Durone IV G5 showed the least values of dimensional expansion. For the three trademarks used, drying in a microwave oven with a power of 200 W and temperature in the laboratory after 7 days promoted the compressive strength and not statistically significantly higher, except for the Premium and Shera Durone IV that produced similar values with power of 800 W and 400W respectively. Dental stone type IV showed improvement in their properties with drying in a microwave oven. The power of 200 W to 800 W gave similar levels of dimensional change in the dehydration temperature of the laboratory after 24 hours and 7 days. The power of 200 W produces higher values of compressive strength for Elite Rock.
Mestrado
Materiais Dentarios
Mestre em Materiais Dentários
45
Tekkouk, Abdelhadi. "Contribution à l'étude des interactions micro-ondes-matière condensée : cas d'un matériau de construction, le sulfate de calcium semihydraté." Lyon 1, 1989. http://www.theses.fr/1989LYO10073.
Full textAbstract:
L'etude cinetique de la reaction d'hydratation sous micro-ondes a ete faite a l'aide d'un calorimetre a balayage original et compare a la cinetique d'hydratation conventionnelle. Les resultats experimentaux montrent que le maximum absolu de la vitesse d'hydratation dont l'existence a ete demontree theoriquement et verifiee experimentalement n'existe pas lors de l'hydratation sous micro-ondes. On obtient une limite imposee par la dissolution. Un modele cinetique a ete elabore. Ce modele justifie l'amelioration des proprietes mecaniques des echantillons en considerant que l'hydradation sous micro-ondes cree un nombre plus consequent de sites de germination et par suite une structure differente des produits formes
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Большаніна, Світлана Борисівна, Светлана Борисовна Большанина, Svitlana Borysivna Bolshanina, Лариса Іванівна Марченко, Лариса Ивановна Марченко, Larysa Ivanivna Marchenko, Олексій Германович Аблєєв, Алексей Германович Аблеев, and Oleksii Hermanovych Ablieiev. "Исследование твердой фазы при гидратации полугидрата сульфата кальция." Thesis, Издательство СумГУ, 2007. http://essuir.sumdu.edu.ua/handle/123456789/19014.
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Benhidjeb, Nadra. "Etude théorique et expérimentale de l'évolution de la structure poreuse lors de la sulfatation de la chaux." Mulhouse, 1996. http://www.theses.fr/1996MULH0442.
Full textAbstract:
L'un des aspects les plus importants de la réaction de la chaux avec SO2 est la formation de produit solide (sulfate de calcium) qui a un volume molaire trois fois supérieur au volume molaire de CaO. La formation de couche de produit entraîne un bouchage de pores à l'intérieur des particules et par conséquent la réaction de sulfatation est ralentie ou même stoppée avant l'utilisation complète de la chaux. Dans cette étude, nous avons développé un modèle de pore pour la réaction CaO-SO2. Ce modèle tient compte de la diffusion dans les pores de la diffusion à travers la couche de produit le long des parois des pores et de la réaction de surface. En prenant une porosité constante, ce modèle tient compte non seulement de la longueur des pores, mais aussi d'une distribution en diamètre de pores. A l'aide de ces calculs, nous avons simulé l'évolution de la surface spécifique et du taux de conversion. Les résultats obtenus à l'aide de ce modèle ont été comparés à ceux obtenus expérimentalement lors des essais en lit fixe traversé
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Hsin-YiLiu and 劉欣宜. "Hill Sachs Lesion Repaired by Injectable Alpha Calcium Sulfate Hemihydrate." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/82448628183765848379.
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碩士國立成功大學
生物醫學工程學系
103
The Hill-Sachs lesion is usually caused by shoulder dislocation at glenohumeral joint which is a ball and socket structure, and the dimension of humeral head is larger than glenoid fossa which makes it unstable and easily being dislocated. The dislocation causes the superior labrum anterior to posterior lesion and impinges into the bone, making engaging Hill-Sachs defect that is participated for the range of motion (ROM) in the 30% to 40% circumscribed. The Hill-Sachs lesion has been reported in high possibility of recurrent anterior dislocations. When the instability of the shoulder gets worse caused by Hill-Sachs defect, the patient will suffer severe pain and the defect should consider surgical repair. Several autologous grafts and synthetic materials have been used as graft material; however, their availability and biocompatibility limit their clinical outcome. Thus, this study investigates to treat the Hill-Sachs lesion with injectable alpha Calcium Sulfate Hemihydrate (αCSH). It is possible to be used inside the human body as bone filler. Virtually, the αCSH has been noticed having the characteristics of the osteo-induction and osteo-conduction in vivo; however, it has never been applied as bone filler to repair the Hill-Sachs defect. This study tests the possibility of using αCSH to repair the Hill-Sachs defect and was divided into three parts including αCSH characterization, in vitro biocompatibility of αCSH and in vivo Hill-Sachs model in rabbits: Part 1 Material preparation: The preparation of αCSH was from heat treatment of Calcium Sulfate Dihydrate (CSD, J.T. Baker) and the heat treatment conditions were evaluated by Differential Scanning Calorimetry (DSC) and Thermogravimetry Analysis (TGA). The result of DSC curve had first endothermic peak (△H=713.54 J/g) at 120-140℃ which means 2H2O converts to 1/2H2O, and there is the second endothermic peak (△H=144.54 J/g) at 140-150℃ for 1/2H2O to non-aqueous. Also, the TGA curve of CSD and CSH shows the decreasing in weight around 119.5℃. Combined the DSC and TGA results we defined the heat treatment temperature at 127℃ under 5kg/cm2 pressure for 9 hours. In the results of X-ray Diffraction (XRD) which match with JCPDS card and Jade system were to identify the completeness of phase transformation. The primary crystal planes of CSD were located at (020), (021), and (041). After 9 hours heat treatment the crystal planes of CSD were convert to αCSH at (010), (310), and (202). In spite of that the XRD still cannot specific determine the kind of crystallize (α or β phase), the microstructure from scanning electron microscopy (SEM) was used to further identify the crystal formation. In the SEM images of CSD with wider arrangement which the particles size were 163.06±11μm in length and 28.45±6.53μm in width (N=5). The microstructure of αCSH were with needle-shaped which particles size were 92.02±63μm in length and 17.31±2.4μm in width (N=5), from H2O evaporation. In addition, the compressive strength of αCSH was tested by Materials Test Systems by following the ASTM 451-99a. The compressive strength of αCSH hardening with DD water was at 5.39±0.42MPa (N=6) and the αCSH with curing agent was enhanced the compressive stress to 9.62±2.05MPa (N=6). However, the curing time of αCSH/DD water and the αCSH/HCl were with no significant difference at 10-14 minutes and with proper hardening time for surgery. (N=6) Besides, the degradation of materials was with similar degradation rate about 25% weight loss after 49 days and the pH value at 5.5-6.0. However the αCSH/ HCl group has a stronger chemical bounding which can effectively control the release of calcium ions in the results of EDS after 49 days. All of the scaffolds had no significant change for the appearance after 49 days degradation. Therefore, the microstructure of hardening material of αCSH/ DD water has an interlocking structure with 58% of porosity (N=10). However, the material of αCSH/HCl demonstrated the glue-like structure with 47% of porosity (N=10). Both materials have a pore size of 10-100 μm which is adequate dimension for cell migration and attachment. Part 2 in vitro test: A human osteoblast-like cell line, MG63 (Homo sapiens bone osteosarcoma), was used to test the biocompatibility of αCSH/DD water, αCSH/HCl, and 15% alginate and followed by ISO-10993-5. The cytotoxicity of αCSH/DD water and αCSH/HCl group which co-cultured with 5×104 cells in 24-well plates in DMEM (Dulbecco’s Modified Eagle Medium) containing 10% Fetal Bovine Serum, 1% penicillin-streptomycin and saturation concentration of material powder. The alginate was coated with 0.1 cc material on the 24-well plates and co-cultured with 5×104 cells. After the incubation of cells with materials for 1, 3, 5, and7 days, absorbance was set at 490 nm to evaluate the cell viability in response to the cytotoxicity of materials. The results of MTS assay shows the co-cultured cells with materials had no significant difference of cytotoxicity compared with control group. (P〉0.05) The cell attachments of materials were followed by ASTM F813-83. The scaffolds were seeded with 5×104 cells on the surface and incubated in 24 well plates, observed at 1, 3, 5 days. They were dehydrated in a graded series of ethanol, treated with 10% paraformaldehyde, coated with gold, and observed by SEM. In the results of microscopy demonstrated that cells were extended and attached on the scaffolds successfully after 1 day. Cells were spread all over the surface of scaffolds and with plenty of secretion, after 5 days. The SEM shows the cells had migrated into the cut in halve scaffold at day 5. In bounding test, the humeral heads of pork were used in the push out test. The material without alginate drops out from the bone defect after immersing in Hank’s solution for 5 minutes. However, the material with alginate was effectively attached on the bone defect and the bounding force had reached to 1.73±0.26 MPa (N=6) Part 3 in vivo test: The Hill-Sachs model was built by creating a defect on rabbit’s humeral head. The size and location of defect to mimic the Hill-Sachs defect was verified by histology and micro-CT after sacrificed. Defect size was 25% of humeral head and the diameter was 7.5mm and the depth was 5mm. The deflection depth was too deep which destroy the bone marrow and cause angiostasis which lead to a failure of attaching the materials into the bone defects. Therefore, the materials were injected two weeks after the surgery. The process of mixing αCSH and hardening solution are1:1 ratio at room temperature with stirring for 60 seconds then it was injected with 15% alginate.αCSH hardening reaction took 10 to 11 minutes of curing time at body temperature (37 °C) The functionality of repairing Hill-Sachs defect after αCSH injection were evaluated by radiography and histology at 4 and 12 weeks postoperatively. CT analysis shows, the bone remodeling had tissue regeneration starting from the edge of defect and the residue of materials were showed on the 2D image after 4 weeks. In contrast, the defect without treatment had no obvious tissue repaired on the 2D image after 4 weeks. However, the material had been completely replaced by the newly bone after 12 weeks. In the result of 3D reorganization, the bone defect had well appearance after 4 and 12weeks (N=6). The value of BV/TV showed that the material groups had obvious difference with defect groups (P〈0.05). Furthermore, there were no significant difference compare with defect group treated with materials after 12 weeks and the control group. (P〉0.05) The histology applied with HE and Masson trichrome staining by paraffin sections for 4μm was use to confirm the bone regeneration. In the results of histology, the bone repaired started from the edge, the plenty of osteoblasts had migrated into the material and the connective tissue showed the connection between newly bone and the material after 4 weeks. However, the defect group had no tissue regeneration on histology after 4 weeks. Besides, the bone regeneration of material group has been completed, comparing with the defect group which was 100-700μm regenerated after 12 weeks. The αCSH/HCl/Alginate provided a simple preparation of injectable performance with great biocompatibility in vitro and bone repaired, which has a potential in repairing the Hill-Sachs defect surgery.
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Chuang, Fu-Yu, and 莊馥瑜. "Study on Calcium Sulfate Hemihydrate added Tricalcium Phosphate/Calcium Citrate Bone Cement Composites." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/43s6mg.
Full textAbstract:
碩士龍華科技大學
化工與材料工程系碩士班
106
Calcium Sulfate Hemihydrate has been used as a bone substitute for more than one hundred years. It has good biocompatibility, good mechanical strength, and short curing time. The disadvantage is that the degradation rate in the human body is too fast, and it is necessary to rely on other chemicals to prolong its absorption. In this study, Calcium Sulfate Hemihydrate was used as the main Bone Cement composite material, Tricalcium Phosphate and Calcium Citrate were added according to different proportions. A series of experiments were carried out on curing time, mechanical properties analysis, weight loss, XRD analysis and surface structure microscopic analysis. According to the result of the experiment, by soaking artificial body fluid experiment found that the Calcium Sulfate Hemihydrate/Tricalcium Phosphate Bone Cement (CSHTCP) and the Bone Cement Calcium Sulfate Hemihydrate/Calcium Citrate Bone Cement (CSHCC), as the soaking time is longer, the surface arrangement is gradually loose, and the weight loss is also greater. Where the pH value of the immersion test, the pH value turn from neutral to weak acid and it meets the pH value of human body. In the XRD analysis , it was found that the lower the pH of the Bone Cement composites, the stronger the peak value, and the crystallized out of the calcium phosphate rock, in which the CSHCC Bone Cement is stronger, and the citrate-containing component accelerates the growth of the brushite.
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Hsieh, Yueh-chih, and 謝岳池. "In-Vitro Study of Calcium Sulfate Hemihydrated and Calcium Carbonate Composites Material." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/8b6x7z.
Full textAbstract:
碩士國立臺北科技大學
材料及資源工程系研究所
99
Because of their excellent biocompatibility, both Calcium carbonate (CaSO4) and Calcium carbonate (CaCO3) are widely used as the bone defect repair materials. However, the fast rate of CaSO4 degradation might cause defects during the implantation, which will obstruct the growth of the bone. Calcium carbonates are used as hydration accelerator and filler component within composites, which reduce the setting time and promote the mechanical strength of calcium composite paste. In this experiment, an optimal incorporation ratio of CaCO3 into CaSO4 bone filler system was introduced. SEM and XRD were used for the characterization of which the crystal structure, physical properties, and mechanical strength of the composite system has been observed. In addition, the analysis was synchronized from the derivation of reaction mechanisms and the presented kinetics trending-graphs. The influences of degradation and biocompatibility were illustrated from Porosity, Flexural Strength, and Compressive Strength of the specimens that were resulting of CaSO4 crystal structures within variations of added CaCO3.