Articoli di riviste: "Colloidal pastes"

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Madeline, J. B., M. Meireles, J. Persello, C. Martin, R. Botet, R. Schweins e B. Cabane. "From colloidal dispersions to colloidal pastes through solid-liquid separation processes". Pure and Applied Chemistry 77, n. 8 (1 gennaio 2005): 1369–94. http://dx.doi.org/10.1351/pac200577081369.

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Solid-liquid separation is an operation that starts with a dispersion of solid particles in a liquid and removes some of the liquid from the particles, producing a concentrated solid paste and a clean liquid phase. It is similar to thermodynamic processes where pressure is applied to a system in order to reduce its volume. In dispersions, the resistance to this osmotic compression depends on interactions between the dispersed particles.The first part of this work deals with dispersions of repelling particles, which are either silica nanoparticles or synthetic clay platelets, dispersed in aqueous solutions. In these conditions, each particle is surrounded by an ionic layer, which repels other ionic layers. This results in a structure with strong short-range order. At high particle volume fractions, the overlap of ionic layers generates large osmotic pressures; these pressures may be calculated, through the cell model, as the cost of reducing the volume of each cell. The variation of osmotic pressure with volume fraction is the equation of state of the dispersion. The second part of this work deals with dispersions of aggregated particles, which are silica nanoparticles, dispersed in water and flocculated by multivalent cations. This produces large bushy aggregates, with fractal structures that are maintained through interparticle surface-surface bonds. As the paste is submitted to osmotic pressures, small relative displacements of the aggregated particles lead to structural collapse. The final structure is made of a dense skeleton immersed in a nearly homogeneous matrix of aggregated particles. The variation of osmotic resistance with volume fraction is the compression law of the paste; it may be calculated through a numerical model that takes into account the noncentral interparticle forces. According to this model, the response of aggregated pastes to applied stress may be controlled through the manipulation of interparticle adhesion.

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Poon, Wilson C. K. "Colloidal Glasses". MRS Bulletin 29, n. 2 (febbraio 2004): 96–99. http://dx.doi.org/10.1557/mrs2004.35.

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AbstractThis article reviews recent advances in understanding amorphous glassy states in dense colloidal suspensions with or without short-range interparticle attractions. Experiments, theory, and simulation show that two kinds of glassy states are possible, dominated respectively by repulsion and attraction. Under suitable conditions, a small change in the interparticle potential can lead to a transition between these two kinds of colloidal glasses that entails sharp changes in material properties such as the shear modulus. This may provide novel routes for fine-tuning the properties of industrial pastes and slurries.

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Dewitte, Charlotte, Alexandra Bertron, Mejdi Neji, Laurie Lacarrière e Alexandre Dauzères. "Chemical and Microstructural Properties of Designed Cohesive M-S-H Pastes". Materials 15, n. 2 (12 gennaio 2022): 547. http://dx.doi.org/10.3390/ma15020547.

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Concretes can be exposed to a magnesium attack in several environments leading to the formation of magnesium silicate hydrates (M-S-H) and brucite (MH). The formation of M-S-H is likely to alter the properties of the cement matrix because it is linked to the decalcification of C-S-H. However, relatively few data on M-S-H exist in the literature. In order to characterize, physically and mechanically, the M-S-H phase, pure M-S-H cohesive pastes are needed. This work studies the formation of cohesive M-S-H pastes made with MgO-to-SiO2 atomic ratios of 0.78, 1 and 1.3, from two types of silica (silica fume or colloidal silica) and under 20 °C and 50 °C thermal curing. X-ray diffraction and thermogravimetric analyses confirmed that the consumption of brucite and the formation of M-S-H were quicker with a 50 °C curing. Energy-dispersive X-ray spectroscopy and microtomography showed that colloidal silica enabled a better distribution of the particles than silica fume. Microstructural characterizations were conducted under the protocol with colloidal silica and 50 °C thermal curing. Porosity investigations allowed to describe the M-S-H pastes as highly porous materials with a low content of micropores in comparison with mesopores. The type of mixing influenced the mesopore size distribution.

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Athira, K., e T. Shanmugapriya. "Investigation on effect of colloidal nano-silica on the strength and durability characteristics of red mud blended Portland cement paste through tortuosity". Materiales de Construcción 72, n. 347 (5 settembre 2022): e293. http://dx.doi.org/10.3989/mc.2022.01922.

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A novel binder system for cement-based composites depending upon the strength and durability characteristics is introduced in this study. The possibility of calcined red mud cement pastes with and without colloidal nano-silica (CNS) over Ordinary Portland Cement paste (OPC) at three W/B ratios (0.3, 0.4, 0.5) is evaluated. The optimum percentage of cement replacement by red mud (15%) was selected from compressive strength values of different cement replacements (5%, 10%, 15%, and 20%). Colloidal nano-silica (CNS) was added at 0.5%, 1%, 1.5%, and 2 % to the selected red mud cement paste. Water absorption, sorptivity, resistance to sulfate attack, and resistance to acid attack tests were conducted for optimum red mud cement paste with and without CNS. The experimental results are explained based on tortuosity with empirical formulas and mathematical models of pore network distribution. The tortuosity is directly proportional to the inter-connectivity of the pores. The mixes with 15% calcined red mud and 1.5% CNS replacement performed better strength and durability at all W/B ratios. The mix (R15NS1.5) with minimum tortuosity value results in the higher overall performance of the paste. The mixes with a 0.3 W/B ratio give high-performance cement paste compared to higher W/B ratios.

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Kunz, Simon, Maria Pawlik, Wolfgang Schärtl e Sebastian Seiffert. "Polymer- vs. colloidal-type viscoelastic mechanics of microgel pastes". Colloid and Polymer Science 296, n. 8 (24 giugno 2018): 1341–52. http://dx.doi.org/10.1007/s00396-018-4352-5.

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Yune, Jeremy H., Inna Karatchevtseva, Peter J. Evans, Klaudia Wagner, Matthew J. Griffith, David Officer e Gerry Triani. "A versatile binder-free TiO2 paste for dye-sensitized solar cells". RSC Advances 5, n. 37 (2015): 29513–23. http://dx.doi.org/10.1039/c4ra14247k.

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In this study, binder-free TiO₂ colloidal pastes have been prepared using a variety of heterocyclic bases with diverse characteristics to produce robust photoanodes for dye-sensitized solar cells (DSSC) from a single cast film thickness of 5 micron.

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Zemánek, David, e Lenka Nevřivová. "Development and Testing of Castables with Low Content of Calcium Oxide". Materials 15, n. 17 (26 agosto 2022): 5918. http://dx.doi.org/10.3390/ma15175918.

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Colloidal silica is used in many kinds of industry. It is an aqueous dispersion of SiO2 nanoparticles. SiO2 colloidal solutions are commercially available in different concentrations, with different particle sizes and are stabilized with different ions. Colloidal SiO2 was used in this study as a cement replacement in refractory castable. The present study, in its first stage, offers an assessment of five different SiO2 colloidal solutions. The particle size of the solutions was 15 nm, the particle concentration was 30% and 40% and the colloidal solutions were stabilized with Na+, OH− and Cl− ions. The effect of the colloidal solutions on selected characteristics of the refractory pastes and on their mineralogical composition after firing at 1000 °C and 1500 °C was described. The most suitable SiO2 colloidal solution from the first stage was subsequently used for the refractory castable test samples’ preparation in the second stage. Refractory castables, unlike paste, contain a coarse aggregate (grog) up to a grain size of 6 mm. Four types of coarse refractory grog were evaluated. Their effect on selected characteristics of the refractory castable and on its mineralogical composition after firing at 1000 °C and 1500 °C was described. The selected characteristics, within the scope of this study, include bulk density, apparent porosity, cold modulus of rupture and linear changes after firing. Finally, the study describes the effect of the sol particle concentration and the effect of pore size distribution on corrosion resistance and on the internal structure of the material. Mineral and chemical compositions and microstructures of both the raw materials and designed aggregates were thoroughly investigated by the means of X-ray fluorescence spectroscopy, powder X-ray diffraction and scanning electron microscopy. An analysis of the transition zone between corrosive media (K2CO3) and tested castables showed better corrosion resistance for a sol-gel castable than an ultra-low cement castable.

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Avery, Michael P., Susanne Klein, Robert Richardson, Paul Bartlett, Guy Adams, Fraser Dickin e Steve Simske. "The Rheology of Dense Colloidal Pastes Used in 3D-Printing". NIP & Digital Fabrication Conference 30, n. 1 (1 gennaio 2014): 140–45. http://dx.doi.org/10.2352/issn.2169-4451.2014.30.1.art00036_1.

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Sikora, Pawel, Krzysztof Cendrowski, Mohamed Abd Elrahman, Sang-Yeop Chung, Ewa Mijowska e Dietmar Stephan. "The effects of seawater on the hydration, microstructure and strength development of Portland cement pastes incorporating colloidal silica". Applied Nanoscience 10, n. 8 (4 marzo 2019): 2627–38. http://dx.doi.org/10.1007/s13204-019-00993-8.

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AbstractThis contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial effect of seawater was reflected in an improvement in compressive strength for up to 14 days of hydration, while in the 28 days compressive strength values were comparable to that of cement pastes produced with demineralized water. The combination of seawater and NS significantly promotes cement hydration kinetics due to a synergistic effect, resulting in higher calcium hydroxide (CH) production. NS can thus react with the available CH through the pozzolanic reaction and produce more calcium silicate hydrate (C-S-H) gel. A noticeable improvement of strength development, as the result of the synergistic effect of NS and seawater, was therefore observed. In addition, mercury intrusion porosimetry (MIP) tests confirmed significant improvements in microstructure when NS and seawater were combined, resulting in the production of a more compact and dense hardened paste structure. The optimal amount of NS to be mixed with seawater, was found to be 3 wt% of cement.

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Hou, Lixia, Cuicui Li e Xuede Wang. "The Colloidal and Oxidative Stability of the Sesame Pastes during Storage". Journal of Oleo Science 69, n. 3 (2020): 191–97. http://dx.doi.org/10.5650/jos.ess19214.

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Hernández, Ana C., Mahmoud E. Awad, Williams Meléndez, Gema González, Alberto López-Galindo, Rita Sánchez-Espejo, Fátima García-Villén e César Viseras. "Colloidal and Thermal Behaviors of Some Venezuelan Kaolin Pastes for Therapeutic Applications". Minerals 9, n. 12 (4 dicembre 2019): 756. http://dx.doi.org/10.3390/min9120756.

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This work contributes to the knowledge of colloidal and thermal properties of some important primary-originated kaolin deposits from Bolivar State, Venezuela, and their possible use as semisolid formulations in medicinal muds for topical applications. Eight selected high purity kaolin samples were characterized. Rheological and thermal properties were correlated to physico-chemical characteristics of the clay suspensions (pH, Ca2+, and Mg2+ cation desorption and surface charge). Most of the studied kaolin pastes showed adequate viscosities, acceptable skin safe pH, and good thermal properties for pelotherapeutic uses. Three of the studied samples, in particular, showed very high kaolinite purities (>92% kaolinite), elevated viscosities (>1 Pa·s), and good thermal and pH performances for topical application.

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Moudir, Naïma, Nadji Moulaï-Mostefa e Yacine Boukennous. "Silver micro- and nano-particles obtained using different glycols as reducing agents and measurement of their conductivity". Chemical Industry and Chemical Engineering Quarterly 22, n. 2 (2016): 227–34. http://dx.doi.org/10.2298/ciceq150106036m.

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Synthesis of silver micro- and nano-particles for the preparation of conductive pastes for the metallization of solar cells was realized by chemical reduction in the presence and absence of poly(vinyl-pyrrolidone) (PVP). Silver nitrate was used as a precursor in the presence of three polyols (ethylene glycol, di-ethylene glycol and propylene glycol) tested at experimental temperatures near their boiling points. Six samples were obtained by this protocol. Three silver powders obtained without the use of PVP have a metallic luster appearance; however, the samples produced using an excess of PVP are in the form of stable colloidal dispersions of silver nano-particles. Structural characterizations of samples using a scanning electron microscope and X-ray diffractometer show a good crystallinity and spherical morphology. From DSC and TGA analyses, it was noticed that all the nano-silvers present in the colloidal suspension have the same thermal behavior.

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Han, Seong Ho, Yubin Jun, Tae Yong Shin e Jae Hong Kim. "CO2 Curing Efficiency for Cement Paste and Mortars Produced by a Low Water-to-Cement Ratio". Materials 13, n. 17 (2 settembre 2020): 3883. http://dx.doi.org/10.3390/ma13173883.

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Curing by CO2 is a way to utilize CO2 to reduce greenhouse gas emissions. Placing early-age cement paste in a CO2 chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO2 uptake can be quantitatively evaluated by measuring CO2 gas pressure loss in the pressure vessel. A decrease in CO2 gas pressure is observed with all cement pastes and mortar samples regardless of the mix proportion and the casting method; one method involves compacting a low water-to-cement ratio mix, and the other method comprises a normal mix consolidated in a mold. The efficiency of the CO2 curing is superior when a 20% concentration of CO2 gas is supplied at a relative humidity of 75%. CO2 uptake in specimens with the same CO2 curing condition is different for each specimen size. As the specimen scale is larger, the depth of carbonation is smaller. Incorporating colloidal silica enhances the carbonation as well as the hydration of cement, which results in contributing to the increase in the 28-day strength.

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Saviello, Daniela, Abeer Alyami, Maddalena Trabace, Rodorico Giorgi, Piero Baglioni, Antonio Mirabile e Daniela Iacopino. "Plasmonic colloidal pastes for surface-enhanced Raman spectroscopy (SERS) of historical felt-tip pens". RSC Advances 8, n. 15 (2018): 8365–71. http://dx.doi.org/10.1039/c7ra13464a.

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Plakhin, Vadim A., Yuriy G. Khabarov e Viacheslav A. Veshnyakov. "Synthesis of Colloidal Silver Using Lignosulfonates". Lesnoy Zhurnal (Forestry Journal), n. 6 (1 dicembre 2021): 184–95. http://dx.doi.org/10.37482/0536-1036-2021-6-184-195.

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Colloidal silver solutions can be used as catalysts for carrying out various chemical transformations of organic substances and solving the problems of disposal of toxic compounds, as well as antibacterial agents for combating pathogenic microflora, in the manufacture of lubricants and light-absorbing materials, coatings, sensors, conductive pastes, and high-performance electrode materials. The research purpose is to study the synthesis of colloidal silver using a solution of technical lignosulfonates (LST) as a stabilizer. Colloidal silver was synthesized as a result of the reduction-oxidation (redox) reaction of Ag(I) cations with glucose at 100 °C in the presence of lignosulfonates. The reaction was carried out in an alkaline medium, which is provided by the addition of ammonia water. Electronic spectroscopy was used to control the synthesis of colloidal silver. After the reaction, the solution turned dark brown and an intense absorption band with a maximum at 400 nm appeared on the electron spectra. The effects of reagent consumption and synthesis duration were studied. It was found that the optimal reagent consumption in the colloidal silver synthesis is as follows: 2.5–5 g glucose / g Ag, 0.3–1 g LST / g Ag, and 3–5 g NH3 / g Ag. The synthesis duration is 2–5 min. The resulting colloidal silver solution is stable for several months. Partial stratification without precipitation is observed during the solution storage. It is shown experimentally that the stratification is followed by a redistribution of colloidal silver particles. Electron spectroscopy confirmed the absence of colloidal silver particles in the upper layer. The reaction kinetics has been studied in experiments carried out under thermostatically controlled conditions at temperatures from 50 to 100 °C. The kinetic dependence is described by a first-order equation at the initial stage of the reaction, the duration of which depends on the temperature. The duration of the active part of the kinetic curves is 15–90 % of the total reaction time. The logarithm of the rate constant on the active section was proved to depend linearly on the reverse thermodynamic temperature (pair correlation coefficient is 0.9887). The activation energy was 47 kJ/mol. For citation: Plakhin V.A., Khabarov Yu.G., Veshnyakov V.A. Synthesis of Colloidal Silver Using Lignosulfonates. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 184–195. DOI: 10.37482/0536-1036-2021-6-184-195

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Weerasinghe, Hasitha C., George V. Franks, Johan D. Plessis, George P. Simon e Yi-Bing Cheng. "Anomalous rheological behavior in chemically modified TiO2 colloidal pastes prepared for flexible dye-sensitized solar cells". Journal of Materials Chemistry 20, n. 44 (2010): 9954. http://dx.doi.org/10.1039/c0jm02063j.

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Björnström, Joakim, e Itai Panas. "Antagonistic effect of superplasticizer and colloidal nano-silica in the hydration of Alite and Belite pastes". Journal of Materials Science 42, n. 11 (giugno 2007): 3901–7. http://dx.doi.org/10.1007/s10853-006-0467-z.

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Lu, Zichen, Xiangming Kong, Chaoyang Zhang, Feng Xing e Yanrong Zhang. "Effect of colloidal polymers with different surface properties on the rheological property of fresh cement pastes". Colloids and Surfaces A: Physicochemical and Engineering Aspects 520 (maggio 2017): 154–65. http://dx.doi.org/10.1016/j.colsurfa.2017.01.067.

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Zhang, Chaoyang, Xiangming Kong, Jianwei Yu, Daniel Jansen, Joachim Pakusch e Shengxian Wang. "Correlation between the adsorption behavior of colloidal polymer particles and the yield stress of fresh cement pastes". Cement and Concrete Research 152 (febbraio 2022): 106668. http://dx.doi.org/10.1016/j.cemconres.2021.106668.

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Han, Kaidong, Tengfei Guo, Xin Shu, Jinyan Shi e Qianping Ran. "Structural build-up of cement pastes - Underlying mechanisms considering the particle packing, colloidal interactions and hydration kinetics". Construction and Building Materials 438 (agosto 2024): 137030. http://dx.doi.org/10.1016/j.conbuildmat.2024.137030.

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Fedotov, G. N., S. A. Shoba, D. A. Ushkova, D. I. Potapov e I. V. Gorepekin. "EFFECT OF SOIL GELS ON HYSTERESIS PHENOMENA IN SOILS". Доклады Российской академии наук. Науки о Земле 512, n. 2 (1 ottobre 2023): 308–12. http://dx.doi.org/10.31857/s2686739723600637.

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Based on the analysis of the exist mechanisms of the hysteresis of soil water retention curve (WRC), as well as ideas about the nanostructural organization of soils, it is concluded that hysteresis can be caused either by stable (non-colloidal particles) or labile (gels) parts of the solid phase of soils. Due to the fact that until now the main attention has been paid to the study of the effect of stable solid phase of soils on the hysteresis of WRC, it was proposed to investigate the effect of soil gels on hysteresis. For this purpose, the effect of moisture content of soil samples prepared by drying and moistening on the initial viscosity of soil pastes was studied. It has been established that well-pronounced hysteresis is observed for samples of all studied soil types. To explain the hysteresis, two mechanisms based on changes in soil gels in the humidification-drying processes are proposed. One of them is based on the slowness of swelling and shrinkage of soil gels when they absorb and release water. The second is on the greater hydrophobicity of the surface of gels containing less water, and water slipping on hydrophobic areas of the surface with a decrease in the viscosity of pastes. Thus, the conducted studies have shown that hysteresis phenomena in soils are caused by soil gels and their changes during drying and moistening of soils.

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Peruzzi, Greta, Alessandro Ciccola, Adele Bosi, Ilaria Serafini, Martina Negozio, Nagmeldeen Morshed Hamza, Claudia Moricca et al. "Applying Gel-Supported Liquid Extraction to Tutankhamun’s Textiles for the Identification of Ancient Colorants: A Case Study". Gels 9, n. 7 (25 giugno 2023): 514. http://dx.doi.org/10.3390/gels9070514.

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The identification of the dyes present on a linen fragment from the tomb of Pharaoh Tutankhamun is the objective of the present study. Fiber optic reflectance spectroscopy (FORS) was applied to the archaeological sample for preliminary identification of the dyes and to better choose the extraction methodology for different areas of the sample. The innovative gel-supported micro-extraction with agar gel and the Nanorestore Gel® High Water Retention (HWR) gel were applied to the archaeological sample after testing of the best concentration for the extraction of the agar gels substrates, performed on laboratory mock-ups by means of UV–Vis transmittance spectroscopy. Immediately after extraction, Ag colloidal pastes were applied on the gel surface and Surface Enhanced Raman Scattering (SERS) analysis was performed directly on them. The combination of information deriving from FORS and SERS spectra resulted in the successful identification of both indigo and madder and, in hypothesis, of their degradation products.

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Flatt, Robert J., Nicos Martys e Lennart Bergström. "The Rheology of Cementitious Materials". MRS Bulletin 29, n. 5 (maggio 2004): 314–18. http://dx.doi.org/10.1557/mrs2004.96.

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AbstractThe introduction of a new generation of dispersants in concrete allow this material to exhibit self-compacting properties in its fresh state and high durability and mechanical strength in its hardened state. These properties translate into many practical advantages for the construction field.Two of the most important are reducing the ecological impact of this sector of industry and reducing the labor-intensive work associated with placing ordinary concrete by vibration. In this article, it will be shown that knowledge of colloidal science has proven essential in the development of this new generation of dispersants for concrete. Indeed, the polymer molecules used in these dispersants are specifically designed to induce steric repulsion between cement particles, reducing their agglomeration and allowing high workability of fresh concrete prior to setting. While the linkage between interparticle forces and the rheological behavior of cement pastes is still only semiquantitative, recent advances in the modeling of concrete rheology show very promising results in terms of handling aggregates with a wide distribution of particle sizes and shapes. However, accurate modeling requires reliable input on the interaction of the dispersant with the hydrating cement at the molecular level, which is identified as a future research challenge.

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Echeverry-Cardona, Laura M., Natalia Álzate, Elisabeth Restrepo-Parra, Rogelio Ospina e Jorge H. Quintero-Orozco. "Time-Stability Dispersion of MWCNTs for the Improvement of Mechanical Properties of Portland Cement Specimens". Materials 13, n. 18 (18 settembre 2020): 4149. http://dx.doi.org/10.3390/ma13184149.

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This study shows the energy optimization and stabilization in the time of solutions composed of H2O + TX-100 + Multi-Wall Carbon Nanotubes (MWCNTs), used to improve the mechanical properties of Portland cement pastes. For developing this research, sonication energies at 90, 190, 290, 340, 390, 440, 490 and 590 J/g are applied to a colloidal substance (MWCNTs/TX-100 + H2O) with a molarity of 10 mM. Raman spectroscopy analyses showed that, for energies greater than 440 J/g, there are ruptures and fragmentation of the MWCNTs; meanwhile at energies below 390 J/g, better dispersions are obtained. The stability of the dispersion over time was evaluated over 13 weeks using UV-vis spectroscopy and Zeta Potential. With the most relevant data collected, sonication energies of 190, 390 and 490 J/g, at 10 mM were selected at the first and the fourth week of storage to obtain Portland cement specimens. Finally, we found an improvement of the mechanical properties of the samples built with Portland cement and solutions stored for one and four weeks; it can be concluded that the MWCNTs improved the hydration period.

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Idone, Ambra, Monica Gulmini, Anne-Isabelle Henry, Francesca Casadio, Lauren Chang, Lorenzo Appolonia, Richard P. Van Duyne e Nilam C. Shah. "Silver colloidal pastes for dye analysis of reference and historical textile fibers using direct, extractionless, non-hydrolysis surface-enhanced Raman spectroscopy". Analyst 138, n. 20 (2013): 5895. http://dx.doi.org/10.1039/c3an00788j.

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Holovan, A. P., T. V. Krupska e V. V. Тurov. "Film stimulating coatings for seeds based on silica mixtures". Himia, Fizika ta Tehnologia Poverhni 12, n. 1 (30 marzo 2021): 52–57. http://dx.doi.org/10.15407/hftp12.01.052.

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For improve the quality of harvests, modern farms in many countries widely use fertilizers of mineral and natural origin. To mitigate the negative impact on the environment, they try to minimize the amount of mineral fertilizers applied to the soil by creating composite systems. In particular, powdered composite materials are known based on highly dispersed silica and microquantities of mineral fertilizers, which are applied to the surface of the seeds by dusting. The aim of this work was to develop a new generation of film stimulating coatings based on mixtures of hydrophobic AM-1-300 and hydrophilic A-300 silicas, mineral fertilizers and bioactive components. Mixtures of hydrophilic and hydrophobic silicas in the ratio 1:1 and 1:2 were used to obtain a pasty composite with the given stimulating properties; colloidal starch solution; medium salts of mineral acids, bioactive components “Humifriend” and fungicide “Fital”. Such composite systems were applied directly to the surface of sowing material, grains of wheat variety “Natalka” before sowing in sand and on filter paper, according to DSTU 4138-2002. During the study, the following parameters were measured: seed germination energy, germination and morphological characteristics of wheat germs, which consisted in measuring the length of the root and stem. It is shown that when editing certain amounts of bioactive components to the composition of stimulating pasty composites, it is possible to program the properties of future films and powders: to increase morphological characteristics, uniformity of germination and fungicidal characteristics of composites. It has been found that the presence of mineral fertilizers in pasty composites of silicas mixtures 1:1 and 1:2 has a positive effect on the uniform germination of wheat seeds in the sand and on the filter paper. Instead, the presence in the pastes of the active ingredients “Fital” and “Humifriend”, regardless of the environment where the seeds germinated, there is a significant slowdown in the growth of wheat germ in both environments. It has been found that an excess of hydrophilic silica in the pasty composite leads to the development on the surface of the grains of mycosis lesions, regardless of the germination environment. Therefore, stimulant pastes based on 1:2 silica mixtures must contain fungicides of mineral or biological origin.

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Chuong, T. H., e P. V. Nga. "INFLUENCE OF SILICA COLLOID ON RHEOLOGY OF CEMENT PASTE WITH SUPERPLASTICIZER". ASEAN Journal on Science and Technology for Development 25, n. 1 (19 novembre 2017): 73–80. http://dx.doi.org/10.29037/ajstd.233.

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Information of rheological behavior of binder paste is important for proportioning high slump concrete mixture at low water to cement ratios. This paper presents experimental data on the rheological property of silica colloid incorporated binder paste using naphthalene based and polycarboxylate based superplasticizer, compared to that of silica fume incorporated binder paste. Experimental data showed that silica colloid incorporated binder is compatible to tested superplasticizers in the all investigated range of silica colloid content, whereas the pastes incorporated with high silica fume content (over 10%) indicated incompatibility, especially to naphthalene based superplasticizer. There was also found out saturated content of superplasticizer corresponding to every kind of binder and water-binder ratio, with and without set retarding admixture.

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Razhina, E. V., E. S. Smirnova, O. V. Gorelik, A. V. Stepanov e Y. S. Pavlova. "Analysis of the functional and technological potential of the use of Jerusalem artichoke in food production: an overview of the subject field". Proceedings of the Voronezh State University of Engineering Technologies 85, n. 1 (25 aprile 2023): 143–48. http://dx.doi.org/10.20914/2310-1202-2023-1-143-148.

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Jerusalem artichoke is a tuber of the asteraceae family, it is important as a natural food fortifier of food products, including fermented milk, meat, confectionary, bakery products. Jerusalem artichoke is used to produce extracts, syrups, pastes, powders intended for food enrichment. Jerusalem artichoke is contain biologically active substances, including a unique carbohydrate complex consisting of fructose and its polymers (inulin). Currently, concentrates with different functional and technological properties are produced from jerusalem artichoke, which determine the water-absorbing ability, chemical composition and colloidal processes. The review is devoted to the analysis of literature sources, including scientific articles in Russian and foreign journals in order to study the range of food products with the addition of different concentrates of jerusalem artichoke and study their chemical and technological properties. The range of concentrates used for food enrichment is presented. The general patterns of influence of concentrates on the technological properties of finished products were revealed. The authors have shown that not all concentrates have a positive effect on the structure of the finished product. The chemical composition of various jerusalem artichoke concentrates was analyzed. Concentrates with a high carbohydrate composition had a high nutritional value: dried tubers, pulp additive, powder. The analyzed concentrates had a low fat content, which confirms the possibility of use in dietary and therapeutic nutrition. The analyses of the vitamin composition of concentrates was carried out, vitamin C was the predominant. The most common type of Jerusalem artichoke widely used in various sectors of the food industry (powder) was determined.

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Lyu, Xin, Ke Yang, Qiang Fu, Zhen Wei e Shuai Liu. "Experimental Study of Reinforcing Broken Gangues by Colloid Cement Slurry". Shock and Vibration 2021 (22 aprile 2021): 1–14. http://dx.doi.org/10.1155/2021/5522809.

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Studies on jet grouting materials mainly focus on the aggregates in cement or the environment where they are maintained and rarely deal with the cohesiveness, reinforcement load-bearing characteristics, and surface spalling. In this study, cement slurries with different colloid contents were prepared to explore the characteristics and reinforcement effect of broken gangues. These were then subjected to mechanical testing to measure the strength and axial strain performance, and the failure modes and failure patterns were discussed. The results indicated that the colloid component has a significant strengthening effect on the early strength of the samples. As the age increased, the sample axial strain and elastic modulus of the colloid cement paste increased as the colloid component provides viscoelasticity when it resists deformation. The sample strength of cement paste decreases after the addition of broken gangue while the strength of class E samples increases significantly during each age. The cement paste sample showed penetrating splitting failure, the colloidal component effectively controlled the peeling of sample surface, and the failure mode after adding gangue was relatively complicated. The instability modes of the samples are divided into dispersed load-bearing instability and cumulative load-bearing instability, and the content of colloid components affects the failure mode of the samples. A colloid component proportion of 23.33% is the optimal choice, which has an obvious reinforcement effect on the broken gangue.

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30

Chen, Chi-Yao, Zih-Yao Shen e Maw-Tien Lee. "On Developing a Hydrophobic Rubberized Cement Paste". Materials 14, n. 13 (1 luglio 2021): 3687. http://dx.doi.org/10.3390/ma14133687.

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It is well known that most cement matrix materials are hydrophilic. For structural materials, hydrophilicity is harmful because the absorption of water will induce serious damage to these materials. In this study, crumb rubber was pretreated by partial oxidation and used as an additive to develop a hydrophobic rubberized cement paste. The pretreated crumb rubber was investigated using Fourier-transform infrared spectrometry (FT-IR) to understand the function groups on its surface. The pyrolysis oil adsorbed on the surface of the crumb rubber was observed by FT-IR and nuclear magnetic resonance (NMR) spectroscopy. A colloid probe with calcium silicate hydrate (C–S–H) at the apex was prepared to measure the intermolecular interaction forces between the crumb rubber and the C-S-H using an atomic force microscope (AFM). Pure cement paste, cement paste with the as-received crumb rubber, and cement paste with pretreated crumb rubber were prepared for comparison. FT-IR, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to understand the microstructure of the pastes. The static contact angle was used as the index of the hydrophobicity of the pastes. Experimental results showed that the hardened cement paste containing partially oxidized crumb rubber had excellent hydrophobic properties with an insignificant reduction in the compressive strength.

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Dreves, Alexander, Nils Andersen, Pieter M. Grootes, Marie-Josée Nadeau e Carl-Dieter Garbe-Schönberg. "Colloidal matter in water extracts from forest soils". Environmental Chemistry 4, n. 6 (2007): 424. http://dx.doi.org/10.1071/en07057.

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Environmental context. Little is known about the proportion of tiny dispersed particles and true solutions in soil water although the distinction has a major influence on transport processes of organic matter, fertiliser and pollutants in soils and thus, e.g., on carbon storage, and its role in global warming. Our study has found a noticeable amount of tiny particles (range 17 nm to 1.0 μm) in filtered soil water, that have a different chemical composition and a lower bioavailability of their organic components in comparison to the soluble part. This significant occurrence and the ecological relevance of colloids for the transport and storage of soil constituents highlights the need to partition soil water content into ‘particulate’ and ‘dissolved’ since the access to soil pores determines particle transport. Abstract. Water-extracted organic matter (WEOM) is widely used as a surrogate for natural organic matter in soil water in the investigation of soil carbon dynamics. Information about the dissolved or colloidal nature of the organic matter is scarce since dissolved organic matter (DOM) is simply operationally defined by filtration: ‘DOM is what passes through the filter’. Water extracts of two topsoil horizons from both a deciduous (Steinkreuz) and a coniferous (Rotthalmünster) forest, located in Bavaria (Germany), were filtered through a 1-μm quartz filter and analysed regarding the amount of colloids in the range ~17 nm to 1.0 μm, the chemical composition and the radiocarbon concentration of both the colloidal and the dissolved fraction separated by high-speed centrifugation. Up to 13.9 wt-% of the total charge of the water extracts belongs to the colloidal fraction. The colloidal fraction has a higher relative proportion of metals and older organic C than the dissolved fraction. This demonstrates the dual nature of WEOM and the need for a more careful definition of DOM.

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32

Liu, Yu-Chang, Yun-Fang Lu, Yz-Zhen Zeng, Chi-Hung Liao, Jen-Chieh Chung e Tsong-Yang Wei. "Nanostructured Mesoporous Titanium Dioxide Thin Film Prepared by Sol-Gel Method for Dye-Sensitized Solar Cell". International Journal of Photoenergy 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/619069.

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Abstract (sommario):

Titanium dioxide (TiO2) paste was prepared by sol-gel and hydrothermal method with various precursors. Nanostructured mesoporous TiO2thin-film back electrode was fabricated from the nanoparticle colloidal paste, and its performance was compared with that made of commercial P25 TiO2. The best performance was demonstrated by the DSSC having a 16 μm-thick TTIP-TiO2back electrode, which gave a solar energy conversion efficiency of 6.03%. The ability of stong adhesion on ITO conducting glass substrate and the high surface area are considered important characteristics of TiO2thin film. The results show that a thin film with good adhesion can be made from the prepared colloidal paste as a result of alleviating the possibility of electron transfer loss. One can control the colloidal particle size from sol-gel method. Therefore, by optimizing the preparation conditions, TiO2paste with nanoparticle and narrow diameter distribution was obtained.

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33

Nabil, Mahmoud, I. V. Perez-Quintana, M. Acosta, J. A. Mendez-Gamboa e R. Castro-Rodriguez. "Morphological, Structural, and Optical Bandgap Characterization of Extracted ZnO Nanoparticles from Commercial Paste". Advances in Materials Science and Engineering 2021 (1 ottobre 2021): 1–7. http://dx.doi.org/10.1155/2021/9926544.

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Abstract (sommario):

ZnO nanoparticles (NPs) were extracted from a commercial paste in both colloidal and precipitate forms. The Zetasizer analysis performed on the colloid showed ZnO NPs ranging from ∼30 nm to ∼100 nm. Thin films of ZnO were deposited on glass substrates by spin-coating technique from a mixture of the extracted colloid and precipitate. The scanning electron microscope (SEM) images showed uniformly arranged, mesoporous, and nanostructured ZnO particles of different shapes, with an estimated film thickness of 0.67 μm. Analysis by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD) confirmed the presence of ZnO in the films, with no impurities or remnants of other materials. The XRD analysis showed a polycrystalline nature of the films and identified a pure phase formation of the hexagonal wurtzite structure. The average crystallite size calculated from the diffraction peaks is ∼43.25 nm. The calculated crystal tensile strain is 1.954 × 10−3, which increases the crystal volume by 0.728% compared with the crystal volume of standard ZnO. The calculated crystal parameters are a = b = 3.258 Å and c = 5.217 Å. The calculated dislocation density (d) and bond length Zn–O (L) are 5.35 × 10−4 nm−2 and 2.695 Å, respectively. Ultraviolet-visible absorption spectra showed an optical band gap of ∼3.80 eV.

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Stadnyk, Igor, Oksana Bodnarchuk, Kateryna Kopylova, Pylyp Petrov, Larysa Bal-Prylypko e Sergiy Narizhnyy. "Modification of the properties of milk-fat emulsions with the phase structure of "oil in water" in the dependence on the mass part of the lipoid and the stabilizing systems". Potravinarstvo Slovak Journal of Food Sciences 15 (27 agosto 2021): 741–48. http://dx.doi.org/10.5219/1389.

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The composition and properties of cream with fat levels from 30% to 70% were investigated. It has been established that the decrease of fat level and, accordingly, the increase of plasma level in the cream leads to significant changes in the physicochemical parameters of the fat emulsion. Accordingly, the production of low-fat dairy products requires adjustment of the cream properties. It has been shown that using different doses of structure stabilizers: QNA colloid as a consistency stabilizer in the amount of from 1 to 2% and the Dimodan emulsifier U/G – from 0 to 1 % (Danisco, Denmark) changes the physicochemical properties (effective viscosity, sedimentation stability) and organoleptic properties (consistency, taste) of cream with fat level 40%. It has been conducted mathematical modeling, aimed to calculate dosing for improving the properties of milk-fat emulsions, structure formation and further ensuring of the necessary consistency of cream pastes. Optimal doses of colloid QNA as a consistency stabilizer and a U/G Dimodan emulsifier have been determined. It has been established that their content should be 1,0% and 0,5%, relatively, for pastes with a fat level of 40%. The effectiveness of the joint action of consistency stabilizers and emulsifiers in obtaining milk-fat emulsions were defined by the level of effective viscosity. Moreover, the use of the emulsifier had less effect on the effective viscosity of the milk-fat emulsions. It has been found that using the structure stabilizers could improve the formation of low-fat products and the formation of the desired paste-like consistency of high-fat cream with a fat level of 70%. Thus, it is possible to adjust the composition and properties of raw material as a basis for milk-fat emulsions by optimizing the ratio of structure stabilizers. Comparative evaluation of the physicochemical properties of milk-fat emulsions and high-fat cream makes it possible to predict their potential for conversion into a creamy paste with a given consistency.

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TAMAKI, Yukimichi, Rie YAMAKI, Zutai ZHANG, Yasuhiro HOTTA e Takashi MIYAZAKI. "Experimental Paste-paste Type Phosphate-bonded Investment with Colloidal Silica Solution". Dental Medicine Research 30, n. 1 (2010): 36–41. http://dx.doi.org/10.7881/dentalmedres.30.36.

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36

Du, Shangfei, Yucheng Geng e Xingchen Wu. "Synthesis Of Bio-Degradable Copolymers from Sodium Alginate and Konjac Glucomannan Via Dehydration and Ca2+ Cross-Linking". Highlights in Science, Engineering and Technology 74 (29 dicembre 2023): 1063–68. http://dx.doi.org/10.54097/6cj05v38.

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Abstract (sommario):

The study aimed to develop bio-degradable, grafted copolymers using sodium alginate and Konjac-glucomannan. Sodium alginate, extracted from seaweed, and Konjac-glucomannan, derived from the Konjac plant, form a brown, viscous paste in pH 4.0-7.0 liquids. Sodium alginate is known for its solubility, stability, and viscosity. The research involved mixing different ratios of sodium alginate and Konjac-glucomannan with water and glycerol as a compatibilizer. These combinations were used to create various colloid-polymer pastes, and their properties were assessed. Glycerol played a vital role in enhancing performance and compatibility. Two processing methods were employed. The first method involved immersing the pastes in a calcium chloride solution, enabling cross-linking through Ca^2+ ions. This formed films with distinct properties, including strength, brittleness, elasticity, and solubility. The second method involved dehydration, drying the pastes to form films with different properties than the cross-linked films. The resulting films exhibited diverse characteristics depending on the ratios of sodium alginate and Konjac-glucomannan. Cross-linked films demonstrated varying levels of strength, brittleness, elasticity, and solubility due to the network structure formed during cross-linking. Dehydrated films, obtained by removing water molecules, exhibited unique properties. This study contributes to the field of bio-degradable copolymers by successfully developing grafted copolymers using sodium alginate and Konjac-glucomannan. These natural polymers hold promise for sustainable materials in applications like packaging, drug delivery, and biomedical engineering. Further research is necessary to optimize copolymer compositions and processing techniques in order to fully harness their potential. Understanding the structure-property relationships will enable the customization of copolymers for specific applications, advancing the development of eco-friendly materials for a greener future.

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Petrera, Lucia, Lu Allington-Jones e Kieran Miles. "Large reptiles, localised solutions: investigating alternative delivery systems for the treatment of oversized pyritic specimens". Geological Curator 11, n. 3 (giugno 2020): 213–16. http://dx.doi.org/10.55468/gc1489.

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Ethanolamine thioglycolate and sepiolite paste is a traditional method for localised treatment of pyrite oxidation products, but there are drawbacks to the technique. The paste can be difficult to apply, especially on non-horizontal surfaces, and is occasionally ineffective. This article documents trials of solvent gel delivery systems and proposes Laponite RD (a synthetic colloidal clay) as an effective alternative.

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Yustiani, Evira Bella, Putri Nur Anggraini, Shobih Shobih, Eri Widianto, Lilis Retnaningsih, Syoni Soepriyanto, Imam Santoso e Natalita Maulani Nursam. "Colloidal TiO2-Modified Mesoporous Electron Transport Layer in Perovskite Solar Cells". Jurnal Elektronika dan Telekomunikasi 23, n. 2 (31 dicembre 2023): 115. http://dx.doi.org/10.55981/jet.599.

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Abstract (sommario):

The electron transport layer (ETL) is a crucial part in perovskite solar cells (PSC) as it specifically governs the charge extraction at the perovskite/ETL interface. In this study, methylammonium lead iodide-based PSCs with an n-i-p structure were fabricated and modified by adding colloidal TiO2 into the mesoporous TiO2 film as ETL. The effect of the colloidal TiO2 addition on the PSC performance was investigated for ETL comprising different types of TiO2 particles, i.e. P25 and anatase TiO2. Despite producing lower performance than the PSC made with commercial paste, the power conversion efficiency of the PSCs could be improved with the introduction of colloidal TiO2 solution. An optimum condition was observed depending on the type of TiO2 particle, where the best performing device was achieved with colloidal TiO2 of 0.4 and 0.2 mL for P25 and anatase TiO2, respectively. The amount of colloidal TiO2 in samples with P25 overall had less impact than the samples with anatase TiO2.

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Çiftçi, Deniz, Talip Kahyaoglu, Sadettin Kapucu e Sevim Kaya. "Colloidal stability and rheological properties of sesame paste". Journal of Food Engineering 87, n. 3 (agosto 2008): 428–35. http://dx.doi.org/10.1016/j.jfoodeng.2007.12.026.

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40

Aslam, Sarmad, Abdul Waqar Rajput, Amir Abbas, Anwar Ul Aleem e Saad Aslam. "Online structural health monitoring of polymer composite structure using gold nanoparticles (AuNPs)". Mehran University Research Journal of Engineering and Technology 43, n. 2 (7 aprile 2024): 157. http://dx.doi.org/10.22581/muet1982.3085.

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Abstract (sommario):

A mechanism for online structural health monitoring of composite structure was established by developing highly sensitive strain gauges based on colloidal Gold Nano Particles (AuNPs). They were synthesized using well known Turkevich-Frens method followed by phase transfer in chloroform using surfactant Cetyltrimethylammonium bromide (CTAB). Flexible Strain gauges / smart sensors were formed by mixing colloidal AuNPs-chloroform solution in polystyrene (PS) – chloroform solution and depositing their thick paste on hand-made flexible thermoplastic polyurethane (TPU) film. These sensors were used as strain gauges on composite substrates for tensile testing. The developed AuNP based strain gauges were found to have 10 times higher sensitivity than normal metal foil strain gauges.

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Nair, Nishant A., e T. S. Viswanathan. "β-CaSiO3 and colloidal n-SiO2 based blended cement composites- their properties, regression analysis and micro-characterization studies". Materiales de Construcción 73, n. 350 (12 aprile 2023): e312. http://dx.doi.org/10.3989/mc.2023.304722.

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Abstract (sommario):

This paper examines the effect on mechanical properties such as compressive strength, flexural strength, and dynamic modulus of elasticity (DYE) of different proportions of wollastonite (β-CaSiO3) and colloidal nano-silica (n-SiO2) partially replacing cement. Durability indicators (water absorption, sorptivity and sulphate treatment test) were also examined to ascertain the quality of hardened paste mixes with respect to the control mix. The regression models were found for mechanical properties using different parameters from the results obtained, and statistical relations were established and validated. Regression analysis shows the significance of every parameter considered and model for the prediction of mechanical strengths. Finally, the results were substantiated by the microstructural characterization by FESEM. β-CaSiO3 and colloidal n-SiO2 replaced cement by 15%, and 1.5%-6% with an offset of 1.5%, respectively at low (0.25), medium (0.40) and high (0.55) water/binder (w/b) ratio. FESEM micrographs showed dense Calcium-silicate-hydrate (CSH) gel and stratlingite (CASH) was formed by blended cement paste mixes containing β-CaSiO3 and n-SiO2. n-SiO2 at 3% and CaSiO3 at 15% replacements of cement (NS3 mix) was the optimum replacement level for the cement paste mix. Analysed regression model suggests that the models and parameters were found significant and can also be used for prediction (based on R2 values and p-value).

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Segets, Doris. "(Invited) In Situ Characterization during Electrode Processing: The Role of Hidden Parameters". ECS Meeting Abstracts MA2023-02, n. 55 (22 dicembre 2023): 2670. http://dx.doi.org/10.1149/ma2023-02552670mtgabs.

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Abstract (sommario):

Micron and nano-sized functional materials play a key role for future technologies that are currently developed in the field of energy conversion (electrolysers, fuel cells) and electrocatalysis (N2 fixation, CO2 reduction reaction). While new materials with outstanding properties are continuously developed, they rarely find their way into – urgently needed – large scale production and industrial applications.1 One reason for this are hidden parameters that occur during ink formulation, coating (and decal transfer), cell assembly, and operation. We propose the development of coherent workflows that help us to identify reliable correlations. These should be developed for each electrocatalyst, bridging synthesis, electrode and gas diffusion electrode (GDE) / membrane electrode assembly (MEA) fabrication, and testing. All information, including “negative” results like crack formation, delamination, structural ageing and dissolution, must be reported until the relevant hidden parameters are deciphered, and the design chain is understood. Then, materials and electrodes derived from complementary processes and exhibiting subtle variations in composition and structure, can be evaluated against each other. However, this implies to fill the “blackbox” between technical catalysts and electrochemical testing in flow cells, GDEs or MEAs, with quantitative data on powders, ink formulations and coating properties. In the past years, we developed a toolbox of methods that starts from key control characteristics for technical catalysts, i.e., Pt/C for polymer electrolyte membrane fuel cells, that thereon enable the in situ analysis of ink formulations and pastes during the dispersion process and at application concentration.2,3 This is followed by the assessment of the resulting coatings from large-area crack analysis down to the level of surface roughness and pore size characteristics.4 Finally, this input is connected with performance and stability testing results to enable the comparison of different materials, the assessment of structure property relations, and ultimately to establish inline process control during electrode manufacturing. In this contribution, the developed methods will be summarized and related to their current limitations and prospects, in particular for unraveling hidden parameters during electrode fabrication and MEA assembly as well as in line process control. Literature [1] Siegmund, Daniel; Metz, Sebastian; Peinecke, Volker; Warner, Terence E.; Cremers, Carsten; Grevé, Anna; Smolinka, Tom; Segets, Doris; Apfel, Ulf-Peter; Crossing the Valley of Death : From Fundamental to Applied Research in Electrolysis, JACS Au 1 (2021), 527 – 535. [2] Bapat, Shalmali; Segets, Doris; Sedimentation Dynamics of Colloidal Formulations through Direct Visualization : Implications for Fuel Cell Catalyst Inks, ACS Applied Nano Materials 3 (2020), 7384 – 739. [3] Bapat, Shalmali; Giehl, Christopher; Kohsakowski, Sebastian; Peinecke, Volker; Schäffler, Michael; Segets, Doris; On the state and stability of fuel cell catalyst inks, Advanced Powder Technology 32 (2021), 3845 – 3859. [4] Jaster, Theresa; Albers, Simon; Leonhard, Armin; Kräenbring, Mena-Alexander; Lohmann, Heiko; Zeidler-Fandrich, Barbara; Özcan, Fatih; Segets, Doris; Apfel, Ulf-Peter; Enhancement of CO₂RR product formation on Cu-ZnO-based electrodes by varying ink formulation and post-treatment methods, JPhys Energy 5 (2023), 024001.

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Manso, J., L. Agüí, P. Yáñez‐Sedeño e J. M. Pingarrón. "Development and Characterization of Colloidal Gold‐Cysteamine‐Carbon Paste Electrodes". Analytical Letters 37, n. 5 (gennaio 2004): 887–902. http://dx.doi.org/10.1081/al-120030285.

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Nakahara, Akio, Tomoki Hiraoka, Rokuya Hayashi, Yousuke Matsuo e So Kitsunezaki. "Mechanism of memory effect of paste which dominates desiccation crack patterns". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, n. 2136 (26 novembre 2018): 20170395. http://dx.doi.org/10.1098/rsta.2017.0395.

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Abstract (sommario):

When a densely packed colloidal suspension, called a paste, behaves as plastic fluid, it can remember the direction of its motion it has experienced, such as vibrational motion and flow. These memories kept in paste can be visualized as the morphology of crack patterns that appear when the paste is dried. For example, when a paste remembers the direction of vibrational motion, all primary desiccation cracks propagate in the direction perpendicular to the direction of the vibrational motion that the paste has experienced. On the other hand, when a paste remembers the direction of flow motion, all primary cracks propagate along the flow direction. To find out the mechanism of memory effect of vibration, we perform experiments to rewrite memory in paste by applying additional vibration to the paste along a different direction before the paste is dried. By investigating the process of rewriting memory in paste, we find the competitive phenomena between quasi-linear effect and nonlinear effect, which were studied in each theoretical model based on residual tension theories. That is, at the initial stage of the memory-imprinting process of the vibrational motion, the mechanism predicted by the quasi-linear analysis based on residual tension theory holds, but, as the paste is vibrated repeatedly, the mechanism shown by the nonlinear analysis gradually come to play a dominant role in the memory effect. This article is part of the theme issue ‘Statistical physics of fracture and earthquakes’.

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Makowska, Agnieszka, Krzysztof Dwiecki, Piotr Kubiak, Hanna Maria Baranowska e Grażyna Lewandowicz. "Polymer-Solvent Interactions in Modified Starches Pastes–Electrokinetic, Dynamic Light Scattering, Rheological and Low Field Nuclear Magnetic Resonance Approach". Polymers 14, n. 15 (22 luglio 2022): 2977. http://dx.doi.org/10.3390/polym14152977.

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Abstract (sommario):

Starch paste is a very complex dispersion that cannot be clearly classified as a solution, colloid or suspension and many factors affects its properties. As these ambiguities constitute a barrier to technological development, the aim of this study was to investigate the interaction of starch macromolecules with water by analysing the results of rheological properties, low field nuclear magnetic resonance (LF NMR), dynamic light scattering (DLS) and ζ potential analyses. Starch pastes with a concentration of 1%, prepared with distilled water and buffered to pH values of 2.5, 7.0 and 9.5 were analysed. It was proved that the pH buffering substantially decreased the values of consistency index but the pH value itself was not significant. LF NMR studies indicated that the dissolution of starch in water resulted in a reduction in spin-lattice as well as spin-spin relaxation times. Moreover, changes in relaxation times followed the patterns observed in rheological studies. Electrokinetic and DLS analyses showed that potential values are primarily influenced by the properties of the starches themselves and, to a lesser extent, by the environmental conditions. The conducted research also showed complementarity and, to some extent, substitutability of the applied research methods as well as exclusion chromatography (a method not used in this work).

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Wang, Feng, Pingan Chen, Xiangcheng Li e Boquan Zhu. "Effect of Colloidal Silica on the Hydration Behavior of Calcium Aluminate Cement". Materials 11, n. 10 (28 settembre 2018): 1849. http://dx.doi.org/10.3390/ma11101849.

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Abstract (sommario):

The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO2 nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO2 nanoparticles.

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Tiwary, Narendra Kumar, Arunima Shukla e Ashok N. Bhaskarwar. "Aeration of Cement and Cement Mortar Paste through Colloidal Gas Aphrons". Journal of Materials in Civil Engineering 30, n. 12 (dicembre 2018): 04018318. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0002510.

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48

Stygar Lopes, Marina, Daniele Cristina Potulski, Lívia Cássia Viana, Mayara Elita Carneiro, Graciela Inês Bolzon de Muniz e Alan Sulato de Andrade. "NANOCELLULOSE OBTAINED MECHANICALLY BY DIFFERENT COLLOID GRINDING INTENSITIES". FLORESTA 50, n. 1 (20 dicembre 2019): 897. http://dx.doi.org/10.5380/rf.v50i1.58690.

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Abstract (sommario):

Recent advances in nanocellulose technology have enabled production of materials for various applications with attractive properties. The aim of this work was to analyze the nanofibrillated cellulose of Eucalyptus sp. obtained by different grinding intensities. Delignified Eucalyptus sp. kraftpulp was used to obtain the nanofibrillated cellulose in the mechanical grinding process, with 2, 10 and 20 passes. Images were captured by scanning and transmission electron microscopy to observe cellulose structures. For each mechanical treatment, three films were produced, which were used to evaluate the crystallinity index. Viscosity measurement evaluated the influence of mechanical treatment on nanofibrillated cellulose. Microscopic analysis showed that the mechanical process promoted fiber defibrillation, resulting in the exposure of microfibrils in all treatments evaluated. Differences were not verified in the conformation and dimensions of the structures for the different numbers of passes, and the nanofibrils presented average diameter of approximately 30 nm. The mechanical process to obtain the nanofibrillated cellulose reduced of the crystallinity index and the viscosity of the nanofibrillated cellulose compared to cellulose before processing. The average particle size declined with rising number of grinder passes.

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Zhang, Wen Li, e Jian Guo Jin. "A Method for the Determination of Ceramic Paste Plasticity". Advanced Materials Research 177 (dicembre 2010): 594–97. http://dx.doi.org/10.4028/www.scientific.net/amr.177.594.

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Abstract (sommario):

The forming property of clay is one of the most important processing properties. Mineral composition and plasticity of various kinds of clays were determined, and the relations among yield value, degree of deformation and mineral composition were analyzed. According to the relations between acting force and distance between colloidal particles in clay-water system, the determining method of plasticity index II was set up, and compared with the traditional determining methods. The results show that the determining method of plasticity index II can better reflect the effect of clays on the plasticity of body by the comparison of determined values in different ways with the actual plasticity of body, the plasticity indexes II of different kinds of clays have relations of summation with the plasticity of body. The forming property of clay can be reasonably evaluated by plasticity index II.

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Su, D. S., U. Bloeck, B. Meißner, F. Willig e M. Giersig. "Characterization of Nanoporous TiO2 Membranes Used as Electrodes for Injection Solar Cells". Microscopy and Microanalysis 5, S2 (agosto 1999): 804–5. http://dx.doi.org/10.1017/s1431927600017347.

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Abstract (sommario):

High efficiency solar cells require large surface layers as acceptor [1], Nanoporous titanium dioxide film is an optimun choice for that purpose. For instance, porous titanium dioxide film of one micrometer thickness, prepared by colloidal chemistry, has a porous surface whose area is 100 times larger than the surface of a compact planar film. Obviously, accessibility to surface and crystal phase of the titanium dioxide are of prime importance. In this work, we characterize nanoporous titanium dioxide membranes on Si substrate by means of high-resolution transmission electron microscopy and electron diffraction.Colloidal TiO2 sols were prepared by a wet chemical method [2]. The resulting colloidal TiO2 sol was autoclaved in a titanium autoclave for 12h at 230°C. A portion of the autoclaved sol was concentrated under vacuum at 30°C until a concentration of 20% TiO2 (by weight) was reached. 40% (by weight of Ti02) carbowax was added to this paste and stirred over night at room temperature.

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