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Dissertations / Theses on the topic 'Solution temperature'
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1
Silvester, Debbie Sue. "Electrochemical studies in room temperature ionic liquids." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:be9e6269-f19a-48de-96e3-41c0c7143d6a.
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The work presented in this thesis involves the application of room temperature ionic liquids (RTILs) as solvents for use in electrochemical experiments. Initially, the fundamentals of electrochemistry is presented, followed by a comprehensive overview of RTILs in terms of their properties, applications and their behaviour as electrochemical solvents compared to conventional aprotic solvents. The results of 8 original studies are then presented as follows: X-Ray photoelectron spectroscopy is used to quantify the concentration of bromide ions in an ionic liquid, and is independently confirmed by potential-step chronoamperometry. The reaction mechanisms and kinetics for the electrochemical reduction of some aromatic nitro compounds (namely nitrobenzene and 4-nitrophenol) are determined. The electrochemistry of phosphorus trichloride and phosphorus oxychloride is studied in detail for the first time, due to the unusual stability of these highly reactive compounds in RTILs. The reductions and oxidations of sodium and potassium nitrate are studied, giving rise to 'melt'-like behaviour. The electrodeposition of sodium oxide on platinum is also demonstrated. The electrochemical oxidation of nitrite and the oxidation and reduction of the toxic gas, nitrogen dioxide, is presented. The oxidation of hydrogen gas is studied in ten RTILs with a range of different cations and anions, and contrasting interactions with the RTIL anions are seen. The electrochemical oxidation of ammonia gas is studied in five RTILs with different anions and a general reaction mechanism is suggested. The reduction of benzoic acid is studied in six RTILs, and the kinetics of the dissociation step are found to be very fast. The first five studies are all carried out in one particular ionic liquid, and the reactions and mechanisms are compared to that observed in conventional aprotic solvents. The last three studies employ several RTILs with different cations and anions to look at the contrasting interaction of protons with the RTIL cation/anion and ultimately help to understand the pH properties of the solvent. The overall findings from the work in this thesis are that some reactions and mechanisms (e.g bromide, nitro derivatives and ammonia) are generally the same in RTILs as in conventional aprotic solvents, but other species (e.g. nitrates, phosphorus derivatives) show remarkably different behaviour. It has also been demonstrated that RTILs are suitable media for the detection of nitrogen dioxide, hydrogen and ammonia gases. This suggests that RTILs could potentially offer many advantages when employed as solvents in electrochemical reactions and in amperometric gas sensors.
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Knight, P. "Temperature jump studies of lyotropic liquid crystals." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234784.
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Zhang, Yiping. "Effects of temperature on foamy solution gas-drive." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/MQ48073.pdf.
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Bordui, Peter Frank. "Crystal growth of KTiOPO₄ from high-temperature solution." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14962.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Vita.
Bibliography: leaves 117-119.
by Peter Frank Bordui.
Ph.D.
5
TAO, ZHU ZHU. "ROOM TEMPERATURE OPERATED SOLUTION-PROCESSED NEAR-INFRARED PHOTODETECTORS." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1539342882165767.
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Seuring, Jan [Verfasser], and Seema [Akademischer Betreuer] Agarwal. "Polymers with Upper Critical Solution Temperature in Aqueous Solution / Jan Seuring. Betreuer: Seema Agarwal." Marburg : Philipps-Universität Marburg, 2012. http://d-nb.info/102807249X/34.
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Guo, Zhonghua. "Room Temperature Tunable Energy Transfer Systems in Different Solvents." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/GuoZ2009.pdf.
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Jangher, Abdulhakim Ali. "Temperature and cosolvent effects of polymer conformations in solution." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/55113/.
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Formulation is a complex science. Many functional molecules require formulation to enhance their aqueous solubility or to promote and protect their function. Understanding the interaction between the formulation components is a necessary first step in that process. This project focuses predominantly on quantifying the interactions (synergistic and antagonistic) that arise when a triblock copolymer Pluronic (PI23) is mixed with the anionic surfactant sodium dodecyl sulfate (SDS), in the presence of the cosolvent, ethanol. The interaction between PI23 and SDS is synergistic, and leads to the formation of mixed micelles at low PI23 concentrations and liquid crystalline phases at high PI23 concentrations. Ethanol is shown to weaken that interaction, introducing antagonistic interactions at low PI23 concentrations. Moreover, we also study the physicochemical characteristics of some new biocompatible responsive polymers with potential biomedical applications. Here, the "formulation" is inherently built into the structure of the polymer-protein construct. These constructs possess a thermo-responsive character, and pulsed-gradient spin- echo NMR (PGSE-NMR) and small-angle neutron scattering (SANS) have been used to examine the solution conformation of these polymers as a function of temperature.
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Rajput, Harish C. "A steady-state analytical solution for MOSFET channel temperature estimation." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/43566.
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A steady state analytical solution for MOSFET (metal oxide semiconductor field effect transistor) channel temperature estimation has been derived and the analytical model has been used to develop a software tool called HeatMOS©. HeatMOS© estimates the MOSFET channel temperature based on information from the device layout and an industry standard BSIM3 compact model. The steady state solution is an approximation for the channel temperature distribution along its length. The HeatMOS© model has been designed to be integrated into a VLSI CAD flow to predict the steady state temperature of a full micro-chip. An equivalent M-network model for steady state temperature can be extended for each MOSFET device in a complete micro-chip. In future work, HeatMOS© can be combined with the models of interconnect to develop a full micro-chip thermal analysis software tool.
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Peuravaara, P. (Petri). "Temperature-dependent chemical shift in the aqueous solution of xenon." Master's thesis, University of Oulu, 2017. http://urn.fi/URN:NBN:fi:oulu-201705232035.
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At standard pressure, the chemical shift of Xe-129 in an aqueous solution of xenon exhibits a maximum as a function of temperature at 311 K, which is in contrast to the well-known density maximum of water at 277 K. In the present work, this phenomenon is studied by means of a molecular dynamics simulation, where the xenon chemical shift is computed quantum-chemically for snapshots of the simulation trajectory. Also, a simple semianalytical model is developed in which the water around the xenon atom is interpreted to form a shell of uniform density. Both approaches are found to be able to qualitatively reproduce the maximum. In addition, the chemical shift in the semianalytical model is seen to result as a product of the local water density around the xenon and a term corresponding to the xenon-water collision energetics. The latter term can be seen to shift the location of the maximum up in temperature, as compared to the temperature of maximum density.
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Morasse, Rick Albert Lionel. "Low-Temperature Solution-Phase Synthesis of Chalcogenide and Carbide Materials." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1513253677021066.
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Mongeau, Ronald. "The effect of solution temperature on the growth and development of NFT lettuce /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65422.
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Foroughi, Paniz. "Synthesis & Fundamental Formation Mechanism Study of High Temperature & Ultrahigh Temperature Ceramics." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3730.
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Borides and carbides of tantalum and hafnium are of great interest due to their ultrahigh temperature applications. Properties of these ceramics including oxidation resistance and mechanical properties might be further improved through solid solution/composite formation. Synthesis of single-phase TaxHf1-xC and TaxHf1-xB2 solid solution powders including nanopowders via carbothermal reduction (CTR) is complicated due to noticeable difference in reactivity of parent oxides with carbon, and also the low solubility of those oxides in each other. Moreover, for TaC-HfC system the solid solution may go through phase separation due to the presence of a miscibility gap at temperatures below 887°C.In this study, a method of low-cost aqueous solution processing followed by CTR was used to synthesize TaxHf1-xC and TaxHf1-xB2 solid solution powders. In fact, method was first used to synthesize boron carbide (B4C) powders as it paves the way for a detailed study on the synthesis of TaxHf1-xC and TaxHf1-xB2 solid solutions powders considering the fact that B4C contains both carbon and boron in its structure. Particular emphasis was given to investigate the influences of starting compositions and processing conditions on phase separation during the formation of both carbide and boride phase(s). It was found that individual TaC-HfC and TaB2-HfB2 phases always form quickly but separately during the CTR process (e.g., at 1600 °C within a few minutes). Those carbides and borides remain phase-separated unless heated to much higher temperatures for long time due to the slow inter-diffusion between them. It was also found that for TaxHf1-xC applying a DC electric field through the use of spark plasma sintering (SPS) system significantly accelerates the inter-diffusion of Ta and Hf leading to formation of a single-phase TaxHf1-xC solid solution at 1600 °C for 15 minutes. On the other hand, for borides alkali metal reduction reaction (AMR) method appears to be an excellent alternative to CTR-based method for formation of a single-phase TaxHf1-xB2 solid solution. In this method, chlorides of tantalum and hafnium are directly reduced using sodium borohydride (NaBH4) giving rise to formation of a single-phase Ta0.5Hf0.5B2 solid solution nanopowders in one step at much lower temperatures (e.g., 700 °C) by avoiding the oxides formation and the associated phase separation of individual borides as observed in the CTR-based process.
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Moreno, W. A. "The development of a new temperature sensor for analytical solution calorimetry." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372130.
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Vasquez, Yolanda. "Low-temperature solution synthesis of alloys and intermetallic compounds as nanocrystals." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3130.
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Stapleton, Jacob D. "SYNTHESIS OF UPPER CRITICAL SOLUTION TEMPERATURE POLYMER FOR APPLICATIONS IN BIOTECHNOLOGY." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501260269518501.
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Jackson, Douglas Anthony. "Experiments on a dilute '3He-'4He solution in a large magnetic field gradient." Thesis, Lancaster University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384881.
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Chang, Liang-Yi Ph D. Massachusetts Institute of Technology. "Development of low-temperature solution-processed colloidal quantum dot-based solar cells." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/88364.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Solution-processed solar cells incorporating organic semiconductors and inorganic colloidal quantum dots (QDs) are potential alternatives to conventional solar cells fabricated via vacuum or high-temperature sintering processes for large-area, high-throughput, and low-cost manufacturing. In this work, we explored two types of solution-processed QD-based solar cells: all-inorganic solar cells and organic/inorganic hybrid solar cells. In the all-inorganic device, three QD deposition techniques (spin coating, dip coating, and spray coating) were first experimented in order to prepare high-quality QD thin film for the photovoltaic application. The device was based on the heterojunction formed between dip-coated PbS QD layers and CdS thin film that was deposited via a solution process at 80°'C. The resultant device, employing a 1,2-ethanedithiol ligand exchange scheme, exhibits comparable power conversion efficiency (3.5%) to that of high-temperature (260°C) sintered or sputtered ZnO/PbS (PbSe) QD devices. The initial device yield issue associated with the pinhole formation was addressed, and a procedure for the fabrication of reproducible devices was formulated. The demonstration of this device is a step towards low-cost solar cell manufacturing. Through a combination of thickness-dependent current density-voltage characteristics, optical modeling, and capacitance measurements, the combined diffusion length and depletion width in the PbS QD layer is found to be approximately 170 nm. In the organic/inorganic hybrid device, poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers and CdS QDs were employed as electron donors and acceptors, respectively. Crystalline P3HT nanofibers, grown from amorphous P3HT solution, were blended with CdS QDs to form bulk heterojunctions. By adding a large quantity of poor solvent to the blended solution, we demonstrated preferential decoration of CdS QDs onto P3HT nanofibers and stronger interaction between these two materials. The resultant device also showed improved open-circuit voltage, short-circuit current density, and power conversion efficiency.
by Liang-Yi Chang.
Ph. D.
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Jeong, Yesul. "Investigation of low-temperature solution-processed thin-film transistors for flexible displays." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11507/.
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This thesis describes the electrical behaviour of solution-processed zinc oxide thin film transistors (ZnO TFTs) fabricated at low temperature. First, the electrical properties of solution-processed ZnO films are reported. Spin-coated ZnO films annealed at 150 °C exhibit significant sensitivity to the ambient environment. However, their stability can be improved by hydrogen plasma treatment. Zinc oxide TFTs (channel width/length = 4000/200 μm) fabricated by chemical spray pyrolysis at the low process temperature of 140 °C are investigated. The resulting transistors exhibit a saturation mobility of 2 cm2/Vs measured in air; this value is reduced to 0.5 cm2/Vs under vacuum. The effect of hydrogen plasma treatment on spin-coated ZnO TFTs is then studied. The electrical characteristics of untreated TFTs exhibit large hysteresis and a positive threshold voltage shift on repeated measurements. These effects are reduced by the hydrogen plasma and an increase in carrier mobility is observed. In a further investigation, a solution-processed silicon dioxide gate insulator for application in the TFTs is used; a perhydropolysilazane (PHPS) precursor is spin-coated with subsequent thermal treatment to form the SiO2 layer. Exposure to oxygen plasma leads to an acceleration of the conversion reaction, resulting in good insulating properties (leakage current density of ~10-7 A/cm2) and TFT performance (channel width/length = 1000/50 μm, carrier mobility of 3.2 cm2/Vs, an on/off ratio of ~107, a threshold voltage of -1.3 V and a subthreshold swing of 0.2 V/decade). Finally, a photolithographic process is introduced for the fabrication of ‘short’ channel solution-processed ZnO TFTs. Optimum processing conditions are established and used for the fabrication of transistors having various channel dimensions. Devices with a minimum channel length of 5 μm possessed a mobility of 1.5 x 10-2 cm2/Vs, on/off ratio of 106 and good contact between the S/D electrodes and the semiconductor. The relatively low mobility could originate from gate insulator roughness caused by the photolithographic processes.
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Lin, Yen-Hung. "Large-area flexible electronics based on low-temperature solution-processed oxide semiconductors." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/38442.
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Due to their high charge carrier mobility, optical transparency and mechanical flexibility, thin-film transistors (TFTs) based on metal oxide semiconductors represent an emerging technology that offers the potential to revolutionise the next-generations of large-area electronics. This thesis focuses on the development of high-performance TFTs based on low-temperature, solution-processed metal oxide semiconductors that are compatible with inexpensive flexible plastic substrates. The first part of the dissertation describes an ultraviolet light assisted processing method suitable for room-temperature activation of ZnO nanoparticles and their application as semiconducting channels in TFTs. The impact of the semiconductor/dielectric interface on electrical performance is studied using different device configurations and dielectric surface-passivation methods. Furthermore, a nanocomposite concept is proposed in order to assist electron transport between different crystalline domains. Using this approach, TFTs with electron mobilities of ~3 cm2/Vs are demonstrated. The second part of this work explores a carbon-free, aqueous-based Zn-ammine complex route for the synthesis of polycrystalline ZnO thin-films at low temperature and their subsequent use in TFTs. Concurrently, the development of a complementary high-κ oxide dielectric system enables the demonstration of high-performance ZnO TFTs with electron mobilities > 10 cm2/Vs and operation voltage down to ~ 1.2 V. This low-temperature aqueous chemistry is further explored using a facile n-type doping approach. Enhancement in electrical performance is attributed to the different crystallographic properties of the Al-doped ZnO layers. The final part of the thesis introduces a novel TFT concept that exploits the enhanced electron transport properties of low-dimensional polycrystalline quasi-superlattices (QSLs), consisting of sequentially spin-cast layers of In2O3, Ga2O3 and ZnO deposited at temperatures < 200 °C. Optimised oxide QSL transistors exhibit electron mobility values of > 40 cm2/Vs - an order of magnitude higher than devices based on single binary oxide layers. Based on temperature dependent electron transport and capacitance-voltage measurements, it is reasoned that the enhanced electrical performance arises from the presence of quasi two-dimensional electron gas-like systems formed at the carefully engineered oxide heterointerfaces buried within the QSLs.
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Coulter, Robert A. "Alloying effects on high temperature deformation behavior of nickel aluminide intermetallics." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1382.
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Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xi, 94 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 88-89).
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Thongnuanchan, Bencha. "A low temperature alkoxyamine designed for use in nitroxide-mediated miniemulsion polymerization." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/a-low-temperature-alkoxyamine-designed-for-use-in-nitroxidemediated-miniemulsion-polymerization(9dddd46a-9756-41a2-8b66-66fac7d360c9).html.
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The basis for this research project is based on the discovery in the previous research that 2,2' ,5-trimethyl-3-( I-phenylethoxy)-4-tert-butyl-3-azahexane, (Styryl- TITNO) is able to control bulk polymerization of styrene at temperature as low as 70°C. The principle objective of this project was to evaluate the feasibility of using Styryl- TITNO to control radical solution and miniemulsion polymerizations at temperatures below 100°C. Styryl- TITNO was shown to effect solution polymerizations of both n-butyl acrylate (BA) and styrene below 100°C. Polymerization temperature was shown to be a crucial parameter for achieving control in Styryl- TITNO -mediated polymerizations. Good control of the number-average molecular weight (Mn) and molecular weight dispersity for the polymerization of BA was observed at 90°C. However, a lower temperature of 70 °C is required for good control of styrene polymerization. Living characteristics of polymer chains were demonstrated by a sequential chain extension of TITNO -terminated PBA with styrene at 90°C to form poly(n-butyl acrylate)- block-poly[(n-butyl acrylate)-co-styrene], [pBA-b-P(BA-co-PS)], block copolymers. An improvement in livingness in these reactions was observed when the second P(BAlstyrene) block was formed at 70°C after the first PBA block was produced at 90°C. Kinetics studies facilitated determination of the activation-deactivation equilibrium constant (K), which for styrene polymerization at 90°C (K = 4.1 x 10.9 mol L-J at 90°C and 3.0 x 10-9 mol L-J at 70 "C) is nearly an order of magnitude higher than that for BA polymerization at the same temperature (K = 8.5 x 10-11 mol L-I). This is the reason why BA polymerization shows better control than styrene polymerization at 90°C. The activation energy (Ea) for thermolysis of Stryl- TITNO is 104.1 kJ mol", which is relatively low compared to the literature values of Ea for various styryl alkoxymines. This explains why Styryl- TITNO is able to effect polymerization at temperatures as low as 70 "C. The studies of Styryl- TITNO-mediated miniemulsion polymerizations at 90 "C indicate that accumulation of free TITNO• in the particles is an issue for use of Styryl- TITNO in miniemulsion polymerizations. The use of L-ascorbic acid (L-AA) and L-ascorbic acid 6-palmitate (L-AAP) as nitroxide scavengers to reduce the level of free TITNO • in the polymerization was investigated. The best result was observed for the polymerization of BA in the presence of 5.35 mol% of L-AAP relative to Styryl- TITNO, which attained 48% conversion after 5 h. The chain extension of isolated TITNO -terminated PBA, TITNO -PBA, was used to examine the livingness of - polymer -chains before the rate of polymerization was severely retarded. The livingness of TITNO-PBA was evidenced by a shift of the staring PBA molecular weight distribution towards higher molecular weight, which provides solid evidence that the majority of polymer chains remained living. Thus, it can be concluded with certainty that the accumulation of free TITNO• was mainly responsible for the suppression of polymerization in miniemulsion polymerizations mediated by Styryl- TITNO.
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Buckley, Donovan O. "Solution of Nonlinear Transient Heat Transfer Problems." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/302.
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In the presented thesis work, meshfree method with distance fields was extended to obtain solution of nonlinear transient heat transfer problems. The thesis work involved development and implementation of numerical algorithms, data structure, and software. Numerical and computational properties of the meshfree method with distance fields were investigated. Convergence and accuracy of the methodology was validated by analytical solutions, and solutions produced by commercial FEM software (ANSYS 12.1). The research was focused on nonlinearities caused by temperature-dependent thermal conductivity. The behavior of the developed numerical algorithms was observed for both weak and strong temperature-dependency of thermal conductivity. Oseen and Newton-Kantorovich linearization techniques were applied to linearized the governing equation and boundary conditions. Results of the numerical experiments showed that the meshfree method with distance fields has the potential to produced fast accurate solutions. The method enables all prescribed boundary conditions to be satisfied exactly.
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Talyzin, Alexandr. "New Fullerene Materials Obtained in Solution and by High Pressure High Temperature Treatment." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5138-1/.
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Zhang, Jiaqi. "Investigation of low-temperature solution processed metal oxide for organic and perovskite photovoltaics." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/56933.
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In the solar energy arena, there is a considerable market for portable, lightweight, and flexible solutions for solar energy harvesting, in which organic and perovskite photovoltaics are two promising candidates. Cathode-bottom device architecture is commonly used in organic and perovskite photovoltaics due to its long-term stability. However, in this structure the electron transport layer (ETL) adjacent to the cathode commonly requires high temperature annealing, which limits the use of flexible substrates. In this thesis, low temperature processed ZnO thin films are applied as ETLs in organic and perovskite solar cells with two fabrication methods employed: i) sol-gel chemistry and ii) aqueous ammonia approach. In terms of ZnO films by two methods, the relationship between the film composition and the film properties (optical, electrical, surface morphological) is elucidated. The low temperature processed ZnO by sol-gel chemistry, which was previously commonly considered as amorphous ZnO, has been confirmed consisting of ZnO nanoparticles embedded in an extended amorphous organic matrix in our study. The aqueous processed counterpart has been confirmed containing only ZnO nanoparticles. The distinct compositional difference of two low temperature processed films results in some interesting comparisons, not only in the film properties but also when applied in the organic and perovskite solar cells. In addition, the influence of film processing temperature, in a range from as-cast to 450 ˚C high temperature, is investigated. We have proved that sol-gel and aqueous processed ZnO films both are effective ETLs in the application of OPVs. Specially, the work function of the ETLs shows significant impact on the device performance. In the application of perovskite solar cells, despite the intrinsic nature of the thermal instability of perovskite when fabricated on ZnO, the ZnO/PCBM bilayer ETLs with two ZnO processing routes both enable all-low- temperature, thermal stable, low hysteresis and high performance devices.
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Pauwels, Hélène. "Etude theorique et experimentale du comportement des elements traces lors des processus d'interaction eau-roche." Paris 7, 1988. http://www.theses.fr/1988PA077136.
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Le modele de dissolution d'une solution solide est etendu aux mineraux silicates faisant intervenir des reactions acido-basiques. Ce modele permet une approche theorique du comportement des elements en traces lors des processus d'interaction eau-roche: la dissolution et la precipitation. L'evolution de la solution aqueuse jusqu'a l'etat stationnaire est decrite. Une liste des parametres fixant la concentration des elements traces est donnee. Leur comportement est etudie experimentalement et il est compare a celui des elements majeurs
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Walden, Ronald Francis. "Influences of supraoptimal root-zone temperature on the medium solution and growth of woody nursery crops." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/39733.
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Powers, Gerald W. "The effect of temperature on the solvent removal from solution-cast thin polymer films." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182868409.
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Garimella, Narayana. "Multicomponent Interdiffusion in Austenitic NI-, FE-NI-Base Alloys and L12-NI3AL Intermetallic for High-Temperature Applications." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3894.
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Interdiffusion in multicomponent-multiphase alloys is commonly encountered in many materials systems. The developments of multicomponent-multiphase alloys require control of microstructure through appropriate heat treatment, involving solid-state transformations, precipitation processes, and surface modification, where the interdiffusion processes play a major role. In addition, interdiffusion processes often control degradation and failure of these materials systems. Enhanced performance and reliable durability always requires a detailed understanding of interdiffusion. In this study, ternary and quaternary interdiffusion in Ni-Cr-X (X = Al, Si, Ge, Pd) at 900[degrees]C and 700[degrees]C, Fe-Ni-Cr-X (X = Si, Ge) at 900[degrees]C, and Ni3Al alloyed with Ir, Ta and Re at 1200[degrees]C were examined using solid-to-solid diffusion couples. Interdiffusion fluxes of individual components were calculated directly from experimental concentration profiles determined by electron probe microanalysis. Moments of interdiffusion fluxes were examined to calculate main and cross interdiffusion coefficients averaged over selected composition ranges from single diffusion couple experiments. Consistency in the magnitude and sign of ternary and quaternary interdiffusion coefficient were verified with interdiffusion coefficients determined by Boltzmann-Matano analysis that requires multiple diffusion couples with intersecting compositions. Effects of alloying additions, Al, Si, Ge and Pd, on the interdiffusion in Ni-Cr-X and Fe-Ni-Cr-X alloys were examined with respect to Cr2O3-forming ability at high temperature. Effects of Ir, Ta and Re additions on interdiffusion in Ni3Al were examined with respect to phase stability and site-preference. In addition, a numerically refined approach to determine average ternary interdiffusion coefficients were developed. Concentrations and moments of interdiffusion fluxes are employed to generate multiple combinations of multicomponent interdiffusion coefficient as a function of moments. The matrix of multicomponent interdiffusion coefficients corresponds to the lowest order of the moment. It yields real and positive eigen values which provides reliable average interdiffusion coefficients for the selected composition range.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr PhD
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Wang, Ying. "Cellulose fiber dissolution in sodium hydroxide solution at low temperature dissolution kinetics and solubility improvement /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26632.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Deng, Yulin; Committee Member: Banerjee, Sujit; Committee Member: Frederick, James; Committee Member: Hsieh, Jeffery; Committee Member: Ragauskas, Arthur J.. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Nxawe, Sinovuyo. "Effects of regulating hydroponic, solution temperature on plant growth, accumulation of nutrients and other metabolites." Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/843.
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Thesis (Dissertation (Masters Degree(Horticultural Science))--Cape Peninsula University of Technology, 2011The experiment was conducted with the objectives of establishing effects of regulating hydroponic solution temperatures on the chlorophyll content and photosynthesis processes, accumulation of anthocyanins and flavonoids, nutrient uptake and growth and development of pregnant onion (Ornithogalum longibracteatum L.) in the glasshouse during winter periods in 2009 and 2010. The plants were exposed to four hydroponic solution temperatures (control (10 - 15°C), 26°C, 30°C and 34°C). The treatments were arranged in a complete randomized design.Results from this study conducted in the glasshouse in 2009 and verified in 2010 showed that photosynthesis rate (A) and the gas exchange parameters [stomata conductance (gs), intercellular CO2 concentration (Ci) and transpiration (E)] were significantly increased by elevating the hydroponic solution temperatures to 26-30°C compared with the control and then decreased significantly at 34°C. Furthermore, increasing hydroponics solution temperature from 26°C to 34°C significantly increased the levels of flavonoids and anthocyanins in roots, bulbs, shoots and flowers of O. longibracteatum in both years 2009 and 2010.Warming of the hydroponic solution to 26, 30 and 34oC significantly increased the uptake of (N, P, K, Ca, Mg, S, Na Fe, Cu Zn, Mn and B and Mo) in organs of O. longibracteatum (root, bulbs shoot, and whole plant) in 2009 and verified in 2010. The control treatments 10/15°C (day/night) had the lowest uptake of most nutrients.Results from the two years study also showed that plant growth parameters such as number of bulbs per plant, bulb circumference, flower stalk length, flower length, and dry and fresh weights of root, bulb, shoot and flower respectively were significantly increased by warming the hydroponic solution. Elevating the hydroponic solution temperature to a range of 26 - 30°C induced best growth and produced the highest dry matter yield in O. longibracteatum under glasshouse conditions whereas further increase to 34°C resulted in reduced growth and yield.
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Hess, Whitney Rochelle. "Exploring the versatility of lead sulfide quantum dots in low-temperature, solution-processed solar cells." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109683.
Full textAbstract:
Thesis: Ph. D. in Physical Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2017.Page 161 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (pages 151-160).
Solution processability and optoelectronic tunability makes lead sulfide quantum dots (PbS QDs) promising candidates for low-temperature, solution-processed thin film solar cells. Central to this thesis is the crucial role of QD surface chemistry and leveraging surface modification to prepare QDs suitable for optoelectronic device applications. The work presented here explores the versatility of PbS QDs integrated into two main device architectures, where the primary role of the QD is unique in each case. In p-i-n planar perovskite solar cells, efforts to utilize PbS QDs as a hole transport material and the effects of size tuning and surface passivation with cadmium on device characteristics are discussed. A combination of QD size reduction and minimal cadmium-to-lead cation exchange is found to improve the open circuit voltage and hole extraction into the PbS QD layer. In ZnO/PbS QD heterojunction solar cells, the feasibility of preparing fully inorganic, halometallate-passivated PbS QD inks for use as the absorber layer is discussed. A modified biphasic ligand exchange strategy is presented and in order to further elucidate electronic passivation in these QD ink systems, optical properties were investigated with steady state and time-resolved photoluminescence. Significantly, PbS QDs exhibit comparable quantum yields in solution before and after ligand exchange and no significant trap state emission was observed in solution and in film. Ink devices were fabricated with one- and two-layer depositions, which significantly reduce fabrication time compared to traditional layer-by-layer deposition, and devices exhibit anomalous efficiency improvement throughout storage in air.
by Whitney Rochelle Hess.
Ph. D. in Physical Chemistry
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Mullenix, Nathan Joel. "Fully Coupled Model for High-Temperature Ablation and a Reative-Riemann Solver for its Solution." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271035105.
Full text
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Alnoor, Hatim. "Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications." Doctoral thesis, Linköpings universitet, Fysik och elektroteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-141753.
Full textAbstract:
One-dimensional (1D) nanostructures (NSs) of Zinc Oxide (ZnO) such as nanorods (NRs) have recently attracted considerable research attention due to their potential for the development of optoelectronic devices such as ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). The potential of ZnO NRs in all these applications, however, would require synthesis of high crystal quality ZnO NRs with precise control over the optical and electronic properties. It is known that the optical and electronic properties of ZnO NRs are mostly influenced by the presence of native (intrinsic) and impurities (extrinsic) defects. Therefore, understanding the nature of these intrinsic and extrinsic defects and their spatial distribution is critical for optimizing the optical and electronic properties of ZnO NRs. However, identifying the origin of such defects is a complicated matter, especially for NSs, where the information on anisotropy is usually lost due to the lack of coherent orientation. Thus, the aim of this thesis is towards the optimization of the lowtemperature solution-based synthesis of ZnO NRs for device applications. In this connection, we first started with investigating the effect of the precursor solution stirring durations on the deep level defects concentration and their spatial distribution along the ZnO NRs. Then, by choosing the optimal stirring time, we studied the influence of ZnO seeding layer precursor’s types, and its molar ratios on the density of interface defects. The findings of these investigations were used to demonstrate ZnO NRs-based heterojunction LEDs. The ability to tune the point defects along the NRs enabled us further to incorporate cobalt (Co) ions into the ZnO NRs crystal lattice, where these ions could occupy the vacancies or interstitial defects through substitutional or interstitial doping. Following this, high crystal quality vertically welloriented ZnO NRs have been demonstrated by incorporating a small amount of Co into the ZnO crystal lattice. Finally, the influence of Co ions incorporation on the reduction of core-defects (CDs) in ZnO NRs was systematically examined using electron paramagnetic resonance (EPR).
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Erickson, Kristy M., and University of Lethbridge Faculty of Arts and Science. "Thermodynamics of aqueous solutions." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2007. http://hdl.handle.net/10133/529.
Full textAbstract:
Relative densities and relative massic heat capacities have been measured for aqueous solutions of triflic acid (CF3SO3H), sodium triflate (NaCF3SO3), gadolinium triflate (Gd(CF3SO3)3), dysprosium triflate (Dy(CF3SO3)3), neodymium triflate (Nd(CF3SO3)3), erbium triflate (Er(CF3SO3)3), ytterbium triflate (Yb(CF3SO3)3), and yttrium triflate (Y(CF3SO3)3) at T = (288.15, 298.15, 313.15, and 328.15) K and
p = 0.1 MPa. The resulting densities and massic heat capacities have been used to calculate out apparent molar volume and apparent molar heat capacity data for each of the investigated aqueous systems. The concentration dependencies of the apparent molar volumes and apparent molar heat capacities have been modeled using Pitzer-ion interaction equations. Single ion volumes and heat capacities have been calculated using estimates of the apparent molar properties at infinite dilution obtained from the Pitzer-ion interaction equations. These single ion values have, where possible, been compared with those previously reported in the literature.
Also, relative densities have been measured for aqueous solutions of CF3SO3H, Gd(CF3SO3)3, Nd(CF3SO3)3, and Yb(CF3SO3)3 at T = (323.15, 348.15, 373.15, and 423.15) K and p = (5.00, 10.00, and 15.00) MPa. The resulting densities have been used to calculate apparent molar volumes. The concentration dependences of these properties have also been modeled using Pitzer-ion interaction equations. The apparent molar volumes have been used to calculate single ion volumes which, in turn, have been compared with those previously reported in the literature.
This thesis also attempts to model the temperature, pressure, and concentration dependencies of the reported apparent molar properties of each system investigated using an equation of state commonly referred to as the density model. Where possible, the results of this model have been compared with those results from models previously reported in the literature.xiv, 148 leaves ; 29 cm.
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Kim, Sang-Tae 1970. "Oxygen isotope systematics in carbonate-water systems : influence of temperature, solution chemistry, and kinetic isotope fractionation." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111838.
Full textAbstract:
The oxygen isotope fractionation between HCO3-/CO 32- and H2O was determined experimentally in order to elucidate the precipitation mechanisms of orthorhombic carbonate minerals in solutions. The oxygen isotope composition of BaCO3 (witherite), precipitated quantitatively from solutions of various pH and the relative contribution of carbonic acid species to DIC (total dissolved inorganic carbon) at each pH in these solutions were used to generate the following fractionations at 25°C: 1000lnaHCO -3-H2O =30.53+/-0.08 1000lna&parl0;CO 2-3-H2 O&parr0;=23.17+/-0.08Based upon the above oxygen isotope fractionation and the oxygen isotope systematics of aragonite and witherite obtained from various precipitation experiments, it was discovered that CO32- rather than the more abundant HCO3- ions are preferentially incorporated into the growing carbonate crystal. Furthermore, it was proposed that the faster deprotonation kinetics of isotopically light HCO 3- ions and the preferential incorporation of light CO3 2- isotopologues could account for the kinetic isotope effects observed in these carbonate minerals.
Aragonite was inorganically precipitated from Na-Ca-Mg-Cl-HCO3 solutions at 0, 5, 10, 25, and 40°C to determine the temperature dependence of the equilibrium oxygen isotope fractionation between this mineral and the parental solution. To establish a reliable relationship between temperature and oxygen isotope fractionation as well as discount potential experimental artifacts, three different precipitation protocols were employed but statistically identical results were obtained under the conditions investigated. In addition, the extent of kinetic isotope effects induced by variations of the precipitation rate, pH, and Mg2+ concentration of the parent solutions, were thoroughly tested to establish that equilibrium oxygen isotope fractionation occurs.
In order to obtain accurate oxygen isotope compositions of the aragonite precipitates by the conventional phosphoric acid dissolution method, a statistically reliable acid fractionation factor for aragonite (and calcite) was also determined from pure natural aragonite (and calcite) specimens. From a large number (i.e., 29 and 60 individual analyses for aragonite and calcite, respectively) of replicate total oxygen isotope analyses and the isotopic composition of the acid-liberated CO2 between 25 to 75°C, the following two new equations are proposed: 1000lnaCO2&parl0;ACID &parr0;-Calcite=3.59&parl0; 103/T&parr0;-1.79 1000lnaCO2&parl0;ACID &parr0;-Aragonite=3.39&parl0; 103/T&parr0;-0.83
By combining the new acid fractionation factor of 1.01063 for aragonite at 25°C with the oxygen isotope data from the synthesis experiments determined in this study, a new relationship is reported for the temperature dependence of the aragonite-water oxygen isotope fractionation over the temperate range of 0-40°C: 1000lnaaragonite-water=17. 88+/-0.13&parl0;103/T&parr0; -31.14+/-0.46
This new experimental calibration of the aragonite-water fractionation yields a positive aragonite-calcite oxygen isotope fractionation over the temperature range investigated, in agreement with theoretical calculations. This result also provides a baseline to quantify vital or kinetic effects that are frequently observed in natural abiogenic or biogenic aragonite minerals.
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Kozanoglu, Selin. "Polymerization And Charaterization Of N-vinylcaprolactam." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609947/index.pdf.
Full textAbstract:
Poly(N-vinylcaprolactam), PNVCL, is a nonionic, nontoxic, water soluble, thermally
sensitive and biocompatible polymer. It contains hydrophilic carboxylic and amide
groups with hydrophobic carbon-carbon backbone chain so its hydrolysis does not
produce small amide compounds which are often not desired for biomedical
applications. Moreover PNVCL possesses lower critical solution temperature,
(LCST) in the range of physiological temperature (32-34 oC). These properties make
the polymer suitable for use in some biotechnology applications such as implantation
of artificial organs and tissues, purification of enzymes, proteins and living cells, and
in drug release systems.
In this study PNVCL was synthesized by free radical polymerization with solution
technique. Polymerization was done at different temperatures for different time
periods in an oil bath. The activation energy for polymerization was found from
Arrhenius plot as 108.4 kJ/mol. Polymer was characterized by FT-IR, 1H-NMR and
13C-NMR, DSC, TGA and XRD techniques. FT-IR and NMR measurements
confirmed that the polymerization proceeded through the vinyl group.
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Riva, Raphaël. "Solution d'interconnexions pour la haute température." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0064/document.
Full textAbstract:
Le silicium a atteint sa limite d’utilisation dans de nombreux domaines tels que l’aéronautique. Un verrou concerne la conception de composants de puissance pouvant fonctionner en haute température et/ou en haute tension. Le recours à des matériaux à large bande interdite tels que le carbure de Silicium (SiC) apporte en partie une solution pour répondre à ces besoins. Le packaging doit être adapté à ces nouveaux types de composants et nouveaux environnements de fonctionnement. Or, il s’avère que l’intégration planaire (2D), composé de fils de câblage et de report de composants par brasure, ne peut plus répondre à ces attentes. Cette thèse a pour objectif de développer un module de puissance tridimensionnel pour la haute température de type bras d’onduleur destiné à l’aéronautique. Une nouvelle structure 3D originale constituée de deux puces en carbure de silicium, d’attaches par frittage d’argent et d’une encapsulation par du parylène HT a été mise au point. Ses différents éléments constitutifs, les raisons de leur choix, ainsi que la réalisation pratique de la structure sont présentés dans ce manuscrit. Nous nous intéressons ensuite à un mode de défaillance particulier aux attaches d’argent fritté : La migration d’argent. Une étude expérimentale permet de définir les conditions de déclenchement de cette défaillance. Elle est prolongée et analysée par des simulations numériquesSilicon has reached its usage limit in many areas such as aeronautics. One of the challenges is the design of power components operable in high temperature and/or high voltage. The use of wide bandgap materials such as silicon carbide (SiC) provides in part a solution to meet these requirements. The packaging must be adapted to these new types of components and new operating environnement. However, it appears that the planar integration (2D), consisting of wire-bonding and soldered components-attach, can not meet these expectations. This thesis aims to develop a three dimensional power module for the high temperature aeronautics applications. A new original 3D structure made of two silicon carbide dies, silver-sintered die-attaches and an encapsulation by parylene HT has been developed. Its various constituting elements, the reason for their choice, and the pratical realization of the structure are presented in this manuscript. Then, we focus on a failure mode specific to silver-sintered attaches : The silver migration. An experimental study allows to define the triggering conditions of this failure. It is extended and analyzed by numerical simulations
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Zheng, Yueming. "Temperature Dependency of Some of the Thermodynamical Properties of Aqueous Binary-Mixture Systems." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278376/.
Full textAbstract:
The temperature dependence of the refractive index and the density of aqueous binary mixtures of water and ethyl alcohol (C₂H₅OH) were measured by using a modified Michelson interferometer and a narrow glass capillary tube over the temperature range of 278≤T≤353 K for solutions of 100, 75,65, 50, 25, 10 and 0 volume percent ethyl alcohol. The temperature was cycled over both increasing and decreasing directions to explore hysteresis in the cycling. The data are discussed and compared with the Lorentz-Lorenz (LL) formula. A more accurate formula which fits the experimental data better than the LL relation was derived. An attempt was made to determine the nature of the solvent-solute interaction through any changes that were found in the refractive index for He-Ne laser light and IR diode signals and to analyze the refractive index and density results to test the accuracy of the available mixing rules in predicting the refractive index values and the density of binary systems. Conductivity measurements (d. c.) over the temperature range 278≤T≤353 K of aqueous solutions of NaCl at various concentrations were made and used to establish transport properties of ions in solution. The dynamical properties of the electrolytes were used to establish the nature of hydrogen bonding in aqueous binary mixture systems. Rate equations for ion formation and recombination were used to establish the temperature ranges in which hydrogen bonding dominated in forming polymeric species. From experimental data on the binary mixtures with water, a better understanding of water in its different functions and aggregation is possible. The water molecule itself and its response to the environment are understood when suitable studies are made of the forces in the system. In this work, some qualitative aspects of the interactions and dynamics of the water molecule have been investigated. Classical molecular dynamics simulations were tried to explain some of the thermodynamical properties of the water molecule.
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MIRANDA, CARLOS A. de J. "Obtencao da tensao de clivagem e nivel de confiabilidade na determinacao da temperatura de referencia de acos ferriticos na transicao .Abordagem numerica experimental." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10734.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:43:27Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:57:46Z (GMT). No. of bitstreams: 1 06630.pdf: 9701259 bytes, checksum: 3a0ddeea466df64d4d1c1cf28780f43d (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Angel, Adam M. "Influence of Solution Composition and Temperature on the Strontium Content of Amorphous Calcium Carbonate and Subsequent Calcite." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23714.
Full textAbstract:
The Sr/Ca ratios in calcium carbonate fossils are used by the paleooceanographic community to infer past environmental conditions, such as sea surface temperature and ocean chemistry. The processes of biogenic calcification that produce these chemical signatures are complex and not fully understood, however, and vital effects are known to affect the trace element composition of the CaCO3 biomineral products. The recent discovery that calcifying organisms produce amorphous calcium carbonate (ACC) as an intermediate phase during the crystallization process calls into question whether this pathway to mineral formation affects trace element distributions in the final product. This non-classical mineralization process raises the question of whether the Sr/Ca ratios of the final products are dependent upon temperature. That is, what is the temperature dependence of Sr/Ca ratios in calcite produced via ACC compared to the measurements obtained from calcite grown by the classical process in laboratory experiments and from biogenic settings. The goal of this study is to determine the effects of solution chemistry and temperature on the Sr composition of ACC and resultant crystalline CaCO3. Two types of experiments were designed: First, experiments were conducted to synthesize inorganic ACC in a batch reactor for a suite of selected chemical compositions and allowing this intermediate phase to transform into calcite in the reactant solution. In a second series of experiments, ACC was precipitated by a flow-through method to compare results to the batch reactor experiments. The experimental design focused on determining the Sr/Ca ratio and Sr distribution coefficients (KD, Sr) of the amorphous and final crystalline products. Mg/Ca ratios of 5/1 were found to suppress Sr uptake into ACC by a factor of 25% when the initial Sr solution had concentration of one millimolar. ICP-AES data collected across the 18" to 30"C range showed that the Sr/Ca ratio in both ACC and the resultant calcite was independent of temperature. Upon transformation, the Sr/Ca ratios of both the ACC and calcite product were found to be similar, showing that Sr/Ca ratios were independent of the transformation process. Analysis of the data determined KD, Sr values of 0.564(±0.006) for ACC and 0.466(±0.009) for the resultant calcite in the 18-30"C temperature range.
The findings show that the Sr/Ca ratios of ACC and the transformed calcite are independent of temperature. However, the corresponding KD, Sr values exceed those reported for calcite grown by classical processes by an order of magnitude. The findings for the inorganic calcite yield KD, Sr values up to four times higher than those found in biogenic calcites. Because the findings of this study show that Sr/Ca is independent of temperature, this study calls into question whether previously reported Sr/Ca measurements in biogenic calcites should be revisited. It is plausible that biological factors have a significant influence on trace element incorporation into biogenic calcite. Vital effects, such as the influence of macromolecules during the ion uptake process, may regulate the apparent Sr/Ca versus temperature trends observed in marine paleontology. Higher KD, Sr values in marine calcifiers may indicate that organisms use the non-classical mineralization pathway in whole or in part. Future studies of trace element incorporation in calcifying species should consider the pathway to mineralization in tandem with interpretations of environmental controls on distribution coefficients.
Master of Science
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Asselin, Edouart. "High temperature and high pressure corrosion of Ni-based alloys and stainless steels in ammoniacal sulphate solution." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/30709.
Full textAbstract:
The corrosion characteristics of Alloy 625 (UNS 00625, Ni - 22 Cr - 10 Mo) in
oxygenated ammoniacal sulphate environments are determined at room temperature and
pressure and up to high temperatures and pressures (673 K, 250 bar) commensurate with
the process of supercritical water oxidation (SCWO). Electrochemical methods such as
linear polarization, potentiodynamic polarization and impedance spectroscopy are used.
It is found that the electrochemical and morphological response is dictated by the
alloying element Cr and the formation of a Cr(III) oxide. Mo and, to a lesser extent Ni,
are found to dissolve readily. Thermodynamic analysis of the Ni-NH₃-H₂O system,
including new Pourbaix diagrams at temperatures as high as 653 K , has shown that Ni -
ammine formation is possible at moderate temperatures but that the stability of these
complexes decreases substantially with temperature. According to one of the models
investigated, which is based on the only available high temperature equilibrium constant
data, Ni-ammines become unstable above approximately 473 K .
Impedance spectroscopy has shown that transpassive dissolution of the alloy's ptype,
cation conducting, Cr(III) oxide occurs at temperatures as low as 373 K and total
pressure (oxygen saturated) as low as 40 bar. As temperature and pressure are increased
the corrosion process is increasingly diffusion controlled. Transpassive dissolution
results in the thinning and eventual total removal of the alloy's protective semiconductor
barrier layer. Cation ejection from the barrier layer into the solution and porous outer
layer phase results in precipitation of a Cr(III) scale (oxide or hydroxyl-oxide) at the
alloy surface which acts as a diffusion barrier. It is hypothesized that the outer layer is
either physically removed at supercritical conditions due to rapid dissolution and grain boundary attack of the alloy or chemically removed by solution acidification due to the
formation of sulphuric acid at high density supercritical conditions.
Alloys 625, 316 L, Ni - 20 Cr and pure Nb are tested at SCWO conditions and it
is found that the corrosion resistance increases with Cr content and Nb is found to
perform well in sulphate containing SCWO solutions at oxygen concentrations up to 4 m.
It is also confirmed in this work that maximum material loss occurs in the high-density
supercritical region of the reactor.
New Pourbaix diagrams for Nb at elevated temperatures (348 and 368 K) are
calculated and compared to electrochemical and weight loss measurements performed in
concentrated acids. Through electrochemical experiments in concentrated sulphuric and
hydrochloric acids, Nb is found to be an ideal candidate for the high-density supercritical
sections of SCWO reactors.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Silva, André Francisco Pinelas da. "ThermoDroid: Android based solution for temperature physiological assessment." Master's thesis, 2019. http://hdl.handle.net/10773/29642.
Full textAbstract:
Currently, the recognition of emotions has assumed an important role
in the domain of human computer interaction. However, the devices
used are, as a rule, invasive and limit the freedom of movement of the
individual.
This dissertation proposes Thermodroid, a non-intrusive, non-contact,
portable and inexpensive system for psychophysiological assessment
through variations in face skin temperature. A low-cost infrared sensor
is used for its measurement through thermal imaging.
Thermodroid has an Android-based interface for controlling, acquiring,
storing and analyzing data, communicating via Bluetooth. It can be connected
to a Kafka message broker for writing and storing the received
data and, as proof of concept of ”stream processing”, calculating the
maximum and minimum of the thermal values of each captured thermal
image that it receives.
Thermodroid was tested in a psychophysiology case study addressing
the impact that tobacco health warning images in cigarette packaging
have on emotions. Thermodroid was able to capture the thermal images,
extracting the thermal data of the skin of the face, as well as the
physiological signals necessary for the emotional detection, for its later
comparison and analysis. Although the observed results suggest that
we were able to capture credible reactions to the presented images,
such as a discrimination between arousal levels and a correlation with
galvanic skin response, a more in-depth analysis should be performed
to validate them.
The obtained outcomes point to the feasibility of the use of contactless
and low cost thermal imaging in the detection of emotions and do not
dismiss the usefulness of the system for supporting a more complex
recognition of emotional scenarios.Atualmente, o reconhecimento de emoções tem assumido um papel importante no domínio da interação humano computador. No entanto, os aparelhos utilizados são, por norma, invasivos e limitam a liberdade de movimentos do indivíduo. Nesta dissertação propõe-se o Thermodroid, um sistema não intrusivo, sem contacto, portátil e de baixo custo para avaliação psico-fisiológica através das variações de temperatura da pele da face. Recorre-se a um sensor de infravermelho de baixo custo para a sua medição através de imagens térmicas. O Thermodroid possui uma interface baseada em Android para controlo, aquisição, armazenamento e analise dos dados, comunicando via Bluetooth. Pode ser ligado a um ”message broker” Kafka para escrita e armazenamento dos dados recebidos e, como prova de conceito de ”stream processing”, calculo dos máximos e mínimos dos valores térmicos de cada imagem térmica capturada que recebe. O Thermodroid foi testado num caso de estudo de psicofisiologia abordando o impacto que as imagens de advertência de saúde presentes nos maços de tabaco tem sobre as emoções. O Thermodroid mostrou-se capaz de capturar as imagens térmicas, extraindo os dados térmicos da pele da face, bem como os sinais fisiológicos necessários `a deteção emocional, para a sua posterior comparação e analise. Embora os resultados observados sugiram que fomos capazes de capturar reações credíveis `as imagens apresentadas, tal como uma discriminação entre os níveis de ”arousal” e uma correlação com a resposta galvânica da pele, uma análise mais aprofundada deve ser realizada para os validar. Os resultados obtidos apontam para a viabilidade da utilização de imagiologia térmica sem contacto e de baixo custo na deteção de emoções, e não descartam a utilidade do sistema para apoiar um reconhecimento de cenários emocionais mais complexos.
Mestrado em Engenharia de Computadores e Telemática
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Lin, Bo-Sheng, and 林伯昇. "Characteristics of ZnO Nanorod Synthesised by Low Temperature Aqueous Solution." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/05325602201647564145.
Full textAbstract:
碩士崑山科技大學
光電工程研究所
98
In this thesis, ZnO nanorods were synthesized on the glass substrates in a solution of Zn(NO3)2．6H2O and HTMA at 90℃ The morphologies and microstructures of the ZnO films and nanorods are characterized by X-ray diffraction (XRD) patterns, atomic force microscopy (AFM), scanning electron microscopy (SEM), and photoluminescence (PL). First, the ZnO seed layer was deposited on glass structure by the RF sputtering system to study the effect of ZnO nanorods. The effects of different annealing temperature on the seed layer growth have been investigated in this study. The microstructure was investigated by glazing incident X-ray diffraction and high resolution transmission electron microscopy. The property of luminescence was measured by PL. Second, after the growth of ZnO seed layer, the substrate with ZnO seed layer is placed in the low temperature aqueous solution under different experimental conditions, which the aqueous solution of Zn(NO3)2•6H2O and C6H12N4 was prepared. The Zn(OH)2 would be supersaturated, and ZnO nanorods would be precipitated and grown on seed layer. The effects of aqueous solution with different concentration on the growth of ZnO nanorods investigation including surface morphology and microstructure was carried out by XRD, SEM and AFM measurements. Also, optical properties were determined by PL analyses.
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Yang, ChuaHao, and 楊家豪. "Grown of carbon nanostructures by low-temperature aqueous solution method." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/96419061886904564060.
Full textAbstract:
碩士明志科技大學
材料工程研究所
100
This study present a simple method to produce a lot of carbon as micro and nanostructure in aqueous solution at low temperature (85 °C). The structures have been observed two basic units by transmission electron microscopy (TEM): thin carbon nanoribbons, monolayer graphene. This method addition to obtain two basic units and found that synthesize multi-wall carbon nanotube (MWCNTs) without catalyst and carbon basin-shape structure. We further found that the carbon nanoribbons can self-assembly to form ribbon type of graphite nanofibers, carbon nanorings and MWCNTs without catalyst. The basin-shape structure where constitute came from the graphene and nanoribbons edge of fracture. The MWCNTs can become thicker by sticking nanoribbons on the wall, and growth to the micrometers for future.
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Wang, Chen-Yun, and 王貞雲. "Zinc Oxide Nanowires Synthesized by Low-temperature Aqueous Solution Method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/8bm48k.
Full textAbstract:
碩士國立臺北科技大學
材料科學與工程研究所
95
In this study, zinc oxide nanowires was successfully grown on ZnO/Si substrate using low-temperature aqueous solution method. We firstly study the influences of the ZnO buffer layer on the Si substrate on the crystal direction of zinc oxide nanowires. Then the effects of solution concentration, growth time, and the ratio of Zn(NO3)2 and C6H12N4 in the solution on the morphology and size of zinc oxide nanowires were also investigated. Our experimental results indicate that the zinc oxide nanowires have uniform C-axis preferred orientation when the zinc oxide buffer layer grows along [0001] direction. The surface roughness of zinc oxide buffer layer would affect the nucleus sites of zinc oxide nanowires, the higher the surface roughness is, the larger number of the nucleus sites is, which leads to high number density of nanowires grown. If the solution is stirred incessantly, the growth rate of the nanowires increases. The diameter of zinc oxide nanowires is determined by the concentration of solution. In our experiment, we can obtain the high quality columnar grain with hexagonal structure when the concentration of solution is 0.05 M. If the content of Zn(NO3)2 is more than C6H12N4, the length of zinc oxide nanowires is almost equal and is increased with an increase of reaction time. We also can obtain other geometries of zinc oxide such as ZnO thin film or ZnO nanotube, by suitably controlling the processing parameters of reaction time and concentration.
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Lee, Jun-Hong, and 李俊鴻. "Study on CdZnTe Crystals Prepared by Temperature Gradient Solution Growth." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/62593877334284087540.
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Wu, Jun-Sheng, and 吳俊昇. "ZnO nanorods and nanoneedles grown by low-temperature solution method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/v83824.
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碩士國立虎尾科技大學
光電與材料科技研究所
95
In this study, we have made efforts to develop a novel chemical-liquid deposition technique for the low-temperature growth of highly oriented and densely packed ZnO nanorods on substrates through homogeneous nucleation of the zinc oxide seed layer for growing well-aligned ZnO nanorod arrays on the substrate. The results exhibite that the size of nanorod strongly depends on [Zn2+] concentration. Furthermore, the as-grown vertical ZnO nanowires were characterized by XRD, FE-SEM, Micro-Ranman and Micro-PL. Where the morphology of ZnO seed layers, pH, growth temperature and concentration of zinc salt in aqueous solution were important parameters to determine the nanorod growth.
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Chang, Che-Chang, and 張哲彰. "Characterizaion of ZnO Nanorod Synthesized from Low-Temperature Aqueous Solution." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/x8wj4f.
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碩士國立東華大學
材料科學與工程學系
100
In this study, zinc nitrate hydrate (Zn(NO3)2·6H2O) and equimolar hexamethylenetetramine (C6H12N4, HMT) aqueous solution is used as precursors. ZnO nanorods arrays are grown on different substrates from low temperature(<100 °C) chemical synthesis method. ZnO nanorods can be grown on arbitrary substrates with introducing a ~10 nm-thick of seed layer on substrates before the growth of ZnO nanorods. The ZnO nanopartical seeds are prepared by thermally decomposing of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) colloid solution in ethanol at 200-350 °C. The diameter and length of ZnO nanorods are controllable by means of changing the seed nanopartical solution concentration, seed layer thickness, reaction concentration, and reaction time. The crystallinity and optical properties are indicated by x-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM) and photoluminescence (PL) measurements.
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Chiang, Yu-Hsin, and 蔣育欣. "ZnO nanorods thin film transistors by the low-temperature solution method." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/30524680601974200737.
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碩士國立中正大學
光機電整合工程所
98
In this thesis, ZnO nanorods were fabricated by two-step process. In the first instance, the substrate was pre-coated seed layer by sol-gel spin-coating method before growing nanorods . Secondly, ZnO nanorods thin film were synthesized by Chemical bath deposition (CBD). ZnO nanorods thin films were measured by SEM, XRD and photo- luminescence spectra to get there physical characteristic. We fabricated the field effective transistor by using these ZnO nanorods thin films and measured I-V curve of these transistors. We obtained the ZnO nanorods thin film with field effect by 0.075 M of solution concentration, 75 ℃ of growth temperature and 90 minutes of growth time. The characteristic of devices were that Ion/Ioff ratio was 1.78 and channel mobility was 1.247 cm2/Vs has been determined. As we demonstrate here, the technique is easily controlled, low temperature, and low cost, and can be used to produce ZnO nanorods thin films with field effect.