Download or read book Particle Size and Morphology Control of Negative Thermal Expansion Materials written by Leah C. Kozy and published by . This book was released on 2008 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Negative Thermal Expansion Material Cubic ZrW2O8 on Polycarbonate Composites written by Xiaodong Gao and published by . This book was released on 2015 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on control of thermal expansion of polymers has attracted significant attention, since polymers exhibit excellent mechanical and electronic properties, but suffer from high thermal expansion due to the thermal motion of their long molecular chains. Such problems can be addressed through formation of composites that contain an inorganic filler material. Filler materials reduce the thermal expansion of polymers through restriction of polymer chain motion. One particular area of interest is the introduction of negative thermal expansion (NTE) materials into polymer composites. The NTE property is expected to have an additional effect on the reduction of the coefficient of thermal expansion (CTE) of the composites. Several papers have demonstrated successful reduction of the CTE of polymer composites using cubic ZrW2O8, however, it is still unclear how much of this effect is caused by the NTE behavior, and how much is due to chain stiffening. To address whether the use of expensive NTE materials is justified, this project is designed to investigate the exact effects of NTE and chain stiffening on the reduction of thermal expansion of polymer composites. This objective was achieved through the preparation and testing of two sets of composites containing isomorphic particles with opposite thermal expansion (ZrW2O8 and ZrW2O7(OH)2¿2H2O),which possess identical chain stiffening effects. The first goal of the project was to synthesize two different particles that have identical morphology but opposite thermal expansion, with cubic ZrW2O8 as the NTE material of choice. The initial idea was to use a-Al2O3 (corundum), which has a known positive CTE value, as the second material. This phase can be obtained through heat treatment of AlOOH at about 1100 °C. The synthesis of AlOOH with controlled morphologies based on choice of synthetic conditions has been reported. Attempts on the synthesis of AlOOH were made through two different routes. Neither of them delivered particles with similar size as cubic ZrW2O8. Additionally, it was found that the heat treatment at high temperature caused sintering of the particles, resulting in the formation of large particles. To circumvent this problem, the precursor of ZrW2O8, ZrW2O7(OH)2¿2H2O, was used as the counterpart for the comparison, since the topotactic transformation between the two phases results in unchanged morphology, giving rod-like shape for both materials. The synthesis of ZrW2O7(OH)2¿2H2O was optimized to prepare particles with small size, high crystallinity, and good resistance to hydration after converting to the cubic NTE phase. The effects of acid concentration and reaction time were explored. The products were examined by powder X-ray diffraction (PXRD) and scanning electron microscopy, and the hydration rates were also estimated based on the PXRD patterns. Final reaction conditions were chosen as 6 M HCl at 230 °C for 7 d. The coefficient of thermal expansion was determined for ZrW2O7(OH)2¿2H2O using Pawley refinements of variable temperature PXRD data, and values of ¿a = 11 × 10-6 ± 1 × 10-6 K-1 and ¿c = 2.6 × 10-6 ± 0.3 × 10-6 K-1, respectively, were found. Rietveld refinements were carried out on PXRD patterns of both types of particles mixed with silicon to estimate their amorphous content. Results indicated that both particles were close to fully crystalline. To improve the interaction between the particles and polymer, surface modification was carried out via in-situ polymerization in the presence of the particles using triphosgene and bisphenol A as monomers. Soxhlet extraction was used to purify the recovered particles. Thermogravimetric analysis was used to determine the surface coverage of the products and the presence of unbound polymer, and the required time for extraction was revealed to be 96 h based on the TGA results. Infrared spectroscopy was also used to examine the modified particles, which confirmed the presence of surface bound oligomers. Optimization of synthetic conditions, including monomers ratio, reaction time and amount of particles, was carried out to obtain the highest possible coverage. It was found that the optimum ratio for the monomers is between 2.2 : 1 and 1.3 : 1. Leveling off was observed for the surface coverage after 21 h of reaction time. Smaller amounts of particles gave higher surface coverages, but resulted in very low quantities of recovered particles due to losses during recovery steps. To recover more particles from a single batch reaction, the particles were subjected to two consecutive modification steps, resulting in both high coverage and high recovered amounts. The precursor particles could be modified under the same optimum conditions found for NTE particles. The interaction between the particles and polymer was found to be improved after the modification. Solution casting was used to prepare the composite films. A custom made glass vessel was created to provide an inert atmosphere with reduced pressure. This can lower the moisture level and increase the evaporation rate of the casting solvent, which can prevent moisture deposition and crystallization of the polymer. The interaction between the two phases was further enhanced through reprecipitation blending. Under optimized conditions, composite films loaded with bth types of particles were prepared with weight loadings ranging from 2 wt% to 25 wt%. Films with loadings above 12 wt% showed agglomeration on optical images. The homogeneity of the particle dispersion within the films was still acceptable based on combustion analysis. Several properties of the composites were measured, including tensile properties, thermal stability, glass transition temperature and coefficient of thermal expansion. All films without agglomeration showed enhance thermal stability. On the other hand, most films with agglomeration exhibited slightly lower thermal stability. Similar trends were seen for the stress and strain at yield for both types of composites. The composites with lower thermal stability showed lower stress and strain at yield than pristine PC films, whereas the rest showed similar values for these two properties. The Young’s modulus of both types of composite films was found to slightly increase with the addition of the filler particles. All composites exhibited similar values as pristine PC. However, the local structure of the two types of the composites was revealed to be different by dynamic mechanical analysis. The films loaded with the precursor particles exhibited earlier softening than pristine PC, while a delay in softening was found for the ones loaded with NTE particles. The coefficient of thermal expansion (CTE) was measured for the film samples at the University of Mulhouse. This instrument produced faulty numbers that required corrections for instrument contributions. The correction for instrument contributions was checked by comparing the corrected values of three selected film samples to values obtained through analysis at West Kentucky University. The composites blended with NTE particles showed consistently lower CTE values than pristine PC and decreased with increased particle loading, whereas the values of the other set of composites showed no clear trends. Overall, considering the errors associated with the CTE values, the difference caused by the NTE behavior of the particles may not be very significant. Additional samples with higher loadings need to be tested to obtain a clearer picture, and data should be collected on well calibrated instruments to reduce errors.

Download or read book Negative Thermal Expansion Materials written by D.J. Fisher and published by Materials Research Forum LLC. This book was released on 2018-01-15 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: In everyday life, minute thermally-induced elongations are essentially invisible to the naked eye; but even minute expansions can fatally degrade device processing and performance in – for example – the semiconductor industry. Materials which, astonishingly, contract upon heating offer the great advantage of being able to tune the overall thermal expansion of composite materials or to act as thermal-expansion compensators. The development of these negative thermal expansion materials has advanced rapidly during the past fifteen years, and a wide variety of materials of differing types has now been identified, as well as a number of intriguing mechanisms which help to avoid the apparent inviolable tendency of size to increase with temperature. The present work is the most up-to-date summary of the current range of negative thermal expansion materials and of the associated mechanisms. Negative Thermal Expansion Materials, Thermomiotic Behavior, Thermal Stress-Fracture, Thermal Expansion of Composites, Thin-Film Design, Metamaterials

Download or read book Towards the Control of Thermal Expansion From 1996 to Today written by Andrea Sanson and published by Frontiers Media SA. This book was released on 2019-08-08 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Some Low and Negative Thermal Expansion Materials written by Támas Varga and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The high-pressure behavior of several negative thermal expansion materials was studied by different methods. In-situ high-pressure x-ray and neutron diffraction studies on several compounds of the orthorhombic Sc2W3O12 structure revealed an unusual bulk modulus collapse at the orthorhombic to monoclinic phase transition. In some members of the A2M3O12 family, a second phase transition and/or pressure-induced amorphization were also seen at higher pressure. The mechanism for volume contraction on compression is different from that on heating. A combined in-situ high pressure x-ray diffraction and absorption spectroscopic study has been carried out for the first time. The pressure-induced amorphization in cubic ZrW2O8 and ZrMo2O8 was studied by following the changes in the local coordination environments of the metals. A significant change in the average tungsten coordination was found in ZrW2O8, and a less pronounced change in the molybdenum coordination in ZrMo2O8 on amorphization. A kinetically frustrated phase transition to a high-pressure crystalline phase or a kinetically hindered decomposition, are likely driving forces of the amorphization. A complementary ex-situ study confirmed the greater distortion of the framework tetrahedra in ZrW2O8, and revealed a similar distortion of the octahedra in both compounds. The possibility of stabilizing the low thermal expansion high-temperature structure in AM2O7 compounds to lower temperatures through stuffing of ZrP2O7 was explored. Although the phase transition temperature was suppressed in MIxZr1-xMIIIxP2O7 compositions, the chemical modification employed was not successful in stabilizing the high-temperature structure to around room temperature. An attempt has been made to control the thermal expansion properties in materials of the (MIII0.5MV0.5)P2O7-type through the choice of the metal cations and through manipulating the ordering of the cations by different heat treatment conditions. Although controlled heat treatment resulted in only short-range cation ordering, the choice of the MIII cation had a marked effect on the thermal expansion behavior of the materials. Different grades of fluorinert were examined as pressure-transmitting media for high-pressure diffraction studies. All of the fluorinerts studied became nonhydrostatic at relatively low pressures ( -1 GPa).

Download or read book Advanced Ceramics for Energy and Environmental Applications written by Akshay Kumar and published by CRC Press. This book was released on 2021-11-25 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Ceramics possess various unique properties and are able to withstand harsh environments. The aim of this book is to cover various aspects of the advanced ceramics like carbides, nitrides and oxides for energy and environment related applications. Advanced ceramics with additional functionality propose significant potential for greater impact in the field of energy and environmental technologies. This book focuses on the nanostructured ceramics synthesis, properties, structure-property relation and application in the area of energy and environment. It covers the high impact work from around 50 leading researchers throughout the world working in this field. This will help metallurgists, biologists, mechanical engineers, ceramicists, material scientists and researchers working in the nanotechnology field with inclusion of every aspect of advanced ceramics for energy and environmental applications.

Download or read book Negative Thermal Expansion Materials written by Wayne Miller and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Non hydrolytic Sol gel Synthesis and Characterization of Materials of the Type AA M3O12 written by Tamam Issa Baiz and published by . This book was released on 2010 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, there has been an increased interest in negative thermal expansion (NTE) materials, which contract upon heating. Materials exhibiting this property have the potential for achieving better control of thermal expansion through the synthesis of composite materials with more desirable expansion coefficients. By introducing NTE materials into these composites, it is possible to offset the positive thermal expansion of other components in the composite. As a result, these NTE materials can find use in a wide range of applications such as optics, electronics, tooth fillings and any other area where exact positioning of parts over a wide range of temperatures is crucial. A family of materials that has been known to show NTE are A2M3O12 compounds, where A can be a variety of trivalent cations and M can be Mo or W. Previous work on this system has shown that the thermal expansion is highly dependent on the type of trivalent cation employed. However, in spite of the interest in these 2M3O12 compounds, little research has been dedicated to synthesizing materials containing two aliovalent cations instead of just one or two trivalent cations. In fact, the first example of a heterosystem with +2 and +4 cations was not reported until 2004. This dissertation presents results of investigation and characterization of these mixed cation systems, and the change in the thermal expansion properties. The first goal of the research presented herein was to synthesize mixed cation systems using a lower temperature route, and then compare the materials synthesized using low temperature methods with those synthesized using the ball-milling method. This will ensure the validity of applying a lower temperature method to these mixed cation systems. A non-hydrolytic sol-gel (NHSG) method was used, which is based on the reaction of metal alkoxides with metal halides to form M-O-M linkages, with alkyl halides as byproducts. With this method, MgHfW3O12 and MgZrW3O12 were successfully synthesized. When compared to samples prepared by the ball-milling method, many distinct differences were observed. The first was that unlike with the ball-milling method where the desired materials required extended heat treatments at high temperatures (1050-1100 °C, 17-24 h), the NHSG method allowed the synthesis of these compounds after reacting at 130 °C for as little as 3 d and subsequent heat treatment to temperatures as low as 540 °C for as little as 2 h. Furthermore, SEM showed that with the NHSG method, micronsized particles with defined morphology were formed, instead of the large, chunky particles observed when ball-milling was used. This significant change in particle size and morphology is very important for potential applications since it leads to better homogeneity of the components in a composite. Once these results were obtained, the same NHSG method was applied to other combinations of 2+ and 4+ cations. The second goal of the project was to extend the use of the NHSG method to materials of the type A2M3O12 where A is a trivalent method. These types of materials have been previously made using traditional solid state methods. However, previous research in our group has shown that it is possible to access new metastable phases when using lower temperature routes. With the NHSG method, MgZrMo3O12 was made for the first time, as well as a new polymorph of Y2W3O12. Materials made were then characterized using a variety of analytical techniques. These included thermograviometric-differential thermal analysis, powder X-ray diffraction, variable temperature powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and synchrotron experiments. High pressure studies were also carried out in an attempt to study how the synthesized materials behave when subjected to pressure.

Download or read book Low and Negative Thermal Expansion Materials written by David A. Woodcock and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanoparticle Technology Handbook written by Masuo Hosokawa and published by Elsevier. This book was released on 2007-10-19 with total page 645 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoparticle technology, which handles the preparation, processing, application and characterisation of nanoparticles, is a new and revolutionary technology. It becomes the core of nanotechnology as an extension of the conventional Fine Particle / Powder Technology. Nanoparticle technology plays an important role in the implementation of nanotechnology in many engineering and industrial fields including electronic devices, advanced ceramics, new batteries, engineered catalysts, functional paint and ink, Drug Delivery System, biotechnology, etc.; and makes use of the unique properties of the nanoparticles which are completely different from those of the bulk materials. This new handbook is the first to explain complete aspects of nanoparticles with many application examples showing their advantages and advanced development. There are handbooks which briefly mention the nanosized particles or their related applications, but no handbook describing the complete aspects of nanoparticles has been published so far. The handbook elucidates of the basic properties of nanoparticles and various nanostructural materials with their characterisation methods in the first part. It also introduces more than 40 examples of practical and potential uses of nanoparticles in the later part dealing with applications. It is intended to give readers a clear picture of nanoparticles as well as new ideas or hints on their applications to create new materials or to improve the performance of the advanced functional materials developed with the nanoparticles. * Introduces all aspects of nanoparticle technology, from the fundamentals to applications. * Includes basic information on the preparation through to the characterization of nanoparticles from various viewpoints * Includes information on nanostructures, which play an important role in practical applications.

Download or read book Low Thermal Expansion Glass Ceramics written by Dieter Krause and published by Springer Science & Business Media. This book was released on 2006-03-30 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: This completely revised edition features new sections on glass-ceramic applications and their performance, CDC-grinding, and laser gyroscopes containing Zerodur®., providing an overview of Schott's activities for scientists, engineers, and managers.

Download or read book Ordered Mesoporous Materials written by Dongyuan Zhao and published by John Wiley & Sons. This book was released on 2012-11-26 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mesoporous materials are a class of molecules with a large and uniform pore size, highly regular nanopores, and a large surface area. This book is devoted to all aspects and types of these materials and describes, in an in-depth and systematic manner, the step-by-step synthesis and its mechanism, as well as the characterization, morphology control, hybridization, and applications, of mesoporous molecular sieves. In so doing, it covers silicates, metal-doped silicates, nonsilicates, and organic-inorganic hybrids. Although the emphasis is on synthesis, the expert authors also discuss characterization and applications, ranging from catalysis and biochemistry to optics and the use of these materials as templates for nanomaterial synthesis. Both the fundamentals and the latest research results are covered, ensuring that this monograph serves as a reference for researchers in and newcomers to the field.

Download or read book Spark Plasma Sintering of Materials written by Pasquale Cavaliere and published by Springer. This book was released on 2019-02-18 with total page 781 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes spark plasma sintering (SPS) in depth. It addresses fundamentals and material-specific considerations, techniques, and applications across a broad spectrum of materials. The book highlights methods used to consolidate metallic or ceramic particles in very short times. It highlights the production of complex alloys and metal matrix composites with enhanced mechanical and wear properties. Emphasis is placed on the speed of the sintering processes, uniformity in product microstructure and properties, reduced grain growth, the compaction and sintering of materials in one processing step, various materials processing, and high energy efficiency. Current and potential applications in space science and aeronautics, automation, mechanical engineering, and biomedicine are addressed throughout the book.

Download or read book Encyclopedia of Materials written by K. H. J. Buschow and published by . This book was released on 2001 with total page 1008 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accompanyind CR-ROM conrtains The Encyclopedia of Materials Science and Technology on a web access disc.

Download or read book Freezing Colloids Observations Principles Control and Use written by Sylvain Deville and published by Springer. This book was released on 2017-01-19 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of the freezing of colloidal suspensions and explores cutting-edge research in the field. It is the first book to deal with this phenomenon from a multidisciplinary perspective, and examines the various occurrences, their technological uses, the fundamental phenomena, and the different modeling approaches. Its chapters integrate input from fields as diverse as materials science, physics, biology, mathematics, geophysics, and food science, and therefore provide an excellent point of departure for anyone interested in the topic. The main content is supplemented by a wealth of figures and illustrations to elucidate the concepts presented, and includes a final chapter providing advice for those starting out in the field. As such, the book provides an invaluable resource for materials scientists, physicists, biologists, and mathematicians, and will also benefit food engineers, civil engineers, and materials processing professionals.

Download or read book Handbook of Thermal Plasmas written by Maher I. Boulos and published by Springer Nature. This book was released on 2023-02-20 with total page 1973 pages. Available in PDF, EPUB and Kindle. Book excerpt: This authoritative reference presents a comprehensive review of the evolution of plasma science and technology fundamentals over the past five decades. One of this field’s principal challenges has been its multidisciplinary nature requiring coverage of fundamental plasma physics in plasma generation, transport phenomena under high-temperature conditions, involving momentum, heat and mass transfer, and high-temperature reaction kinetics, as well as fundamentals of material science under extreme conditions. The book is structured in five distinct parts, which are presented in a reader-friendly format allowing for detailed coverage of the science base and engineering aspects of the technology including plasma generation, mathematical modeling, diagnostics, and industrial applications of thermal plasma technology. This book is an essential resource for practicing engineers, research scientists, and graduate students working in the field.

Download or read book Magnetism and Structure in Functional Materials written by Antoni Planes and published by Springer Science & Business Media. This book was released on 2010-02-11 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetism and Structure in Functional Materials addresses three distinct but related topics: (i) magnetoelastic materials such as magnetic martensites and magnetic shape memory alloys, (ii) the magnetocaloric effect related to magnetostructural transitions, and (iii) colossal magnetoresistance (CMR) and related manganites. The goal is to identify common underlying principles in these classes of materials that are relevant for optimizing various functionalities. The emergence of apparently different magnetic/structural phenomena in disparate classes of materials clearly points to a need for common concepts in order to achieve a broader understanding of the interplay between magnetism and structure in this general class of new functional materials exhibiting ever more complex microstructure and function. The topic is interdisciplinary in nature and the contributors correspondingly include physicists, materials scientists and engineers. Likewise the book will appeal to scientists from all these areas.