Download or read book Development Of Pressureless Sintered Silicon Carbide boron Carbide Composites for Armour Applications written by T. Williams and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Silicon Carbide Ceramics 1 written by S. Somiya and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discovered by Edward G. Acheson about 1890, silicon carbide is one of the oldest materials and also a new material. It occurs naturally in meteorites, but in very small amounts and is not in a useable state as an industrial material. For industrial require ments, large amounts of silicon carbide must be synthesized by solid state reactions at high temperatures. Silicon carbide has been used for grinding and as an abrasive material since its discovery. During World War II, silicon carbide was used as a heating element; however, it was difficult to obtain high density sintered silicon carbide bodies. In 1974, S. Prochazka reported that the addition of small amounts of boron compounds and carbide were effective in the sintering process to obtain high density. It was then possible to produce high density sintered bodies by pressureless sintering methods in ordinary atmosphere. Since this development, silicon carbide has received great attention as one of the high temperature structural ceramic materials. Since the 1970s, many research papers have appeared which report studies of silicon carbide and silicon nitride for structural ceramics.
Download or read book The Investigation of Pressureless Sintered Boron Carbide silicon Carbide Composites written by Zhengfei Chen and published by . This book was released on 2006 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Silicon Carbide Ceramics written by S. Somiya and published by Springer Science & Business Media. This book was released on 1991-08-31 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon carbides have major industrial uses as high temperature structural ceramic materials. These two volumes are translated from the Japanese and provide a comprehensive account of the seminal work going on in Japan.
Download or read book Processing of Boron Carbide written by Namtae Cho and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although the relative densities of pressureless sintered specimens were lower than that of commercially produced hot-pressed B4C, their (Vickers) hardness values were comparable. For 4.45cm diameter and 1.35cm height disk shaped specimens, pressureless sintered to at least 93.0% relative density, post-hot isostatic pressing resulted in vast increases in relative densities (e.g. 100.0%) and hardness values significantly greater than that of commercially produced hot-pressed B4C. The densification behavior of 20-40nm graphite-coated B4C nano-particles was studied using dilatometry, x-ray diffraction and electron microscopy. The higher than expected sintering onset from a nano-scale powder (15008C) was caused by remnant B2O3 not removed by methanol washing, keeping particles separated until volatilization and the carbon coatings, which imposed particle to particle contact of a substance more refractory than B4C. Solid state sintering (1500-18508C) was followed by an arrest in contraction attributed to formation of eutectic liquid droplets of size more than 10X the original nano-particles. These droplets, induced to form well below known B4C-graphite eutectic temperatures by the high surface energy of nano-particles, are interpreted to have quickly solidified to form a vast number of voids in particle packing, which in turn, impeded continued solid state sintering. Starting at 22008C, a permanent liquid phase formed which facilitated a rapid measured contraction by liquid phase sintering and/or compact slumping.
Download or read book Carbide Nitride and Boride Materials Synthesis and Processing written by A.W. Weimer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 675 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbide, Nitride and Boride Materials Synthesis and Processing is a major reference text addressing methods for the synthesis of non-oxides. Each chapter has been written by an expert practising in the subject area, affiliated with industry, academia or government research, thus providing a broad perspective of information for the reader. The subject matter ranges from materials properties and applications to methods of synthesis including pre- and post-synthesis processing. Although most of the text is concerned with the synthesis of powders, chapters are included for other materials such as whiskers, platelets, fibres and coatings. Carbide, Nitride and Boride Materials Synthesis and Processing is a comprehensive overview of the subject and is suitable for practitioners in the industry as well as those looking for an introduction to the field. It will be of interest to chemical, mechanical and ceramic engineers, materials scientists and chemists in both university and industrial environments working on or with refractory carbides, nitrides and borides.
Download or read book Advances in Ceramic Armor written by Swab and published by John Wiley & Sons. This book was released on 2009-09-28 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains over 30 papers on the development and incorporation of ceramic materials for armor applications. Topics include impact and penetration modeling, dynamic and static testing to predict performance, damage characterization, non-destructive evaluation and novel material concepts.
Download or read book Field Assisted Sintering of Refractory Carbide Ceramics and Fiber Reinforced Ceramic Matrix Composites written by Sean Gephart and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The sintering behaviors of silicon carbide (SiC) and boron carbide (B4C) based materials were investigated using an emerging sintering technology known as field assisted sintering technology (FAST), also known as spark plasma sintering (SPS) and pulse electric current sintering (PECS). Sintering by FAST utilizes high density electric current, uniaxial pressure, and relatively high heating rate compared to conventional sintering techniques.This effort investigated issues of scaling from laboratory FAST system (25 ton capacity) to industrial FAST system (250 ton capacity), as well as exploring the difference in sintering behavior of single phase B4C and SiC using FAST and conventional sintering techniques including hot-pressing (HP) and pressure-less sintering (PL). Materials were analyzed for mechanical and bulk properties, including characterization of density, hardness, fracture toughness, fracture (bend) strength, elastic modulus and microstructure. A parallel investigation was conducted in the development of ceramic matrix composites (CMC) using SiC powder impregnation of fiber compacts followed by FAST sintering.The FAST technique was used to sinter several B4C and SiC materials to near theoretical density. Preliminary efforts established optimized sintering temperatures using the smaller 25 ton laboratory unit, targeting a sample size of 40 mm diameter and 8 mm thickness. Then the same B4C and SiC materials were sintered by the larger 250 ton industrial FAST system, a HP system, and PL sintering system with a targeted dense material geometry of 4x4x0.315 inches3 (101.6x101.6x8 mm3). The resulting samples were studied to determine if the sintering dynamics and/or the resulting material properties were influenced by the sintering technique employed. This study determined that FAST sintered ceramic materials resulted in consistently higher averaged values for mechanical properties as well as smaller grain size when compared to conventionally sintered materials. While FAST sintered materials showed higher average values, in general they also showed consistently larger variation in the scattered data and consequently larger standard deviation for the resulting material properties. In addition, dynamic impact testing (V50 test) was conducted on the resulting materials and it was determined that there was no discernable correlation between observed mechanical properties of the ceramic materials and the resulting dynamic testing.Another study was conducted on the sintering of SiC and carbon fiber reinforced SiC ceramic matrix composites (CMC) using FAST. There has been much interest recently in fabricating high strength, low porosity SiC CMC's for high temperature structural applications, but the current methods of production, namely chemical vapor infiltration (CVI), melt infiltration (MI), and polymer infiltration and pyrolysis (PIP), are considered time consuming and involve material related shortcomings associated with their respective methodologies. In this study, SiC CMC's were produced using the 25 ton laboratory unit with a target sample size of 40 mm diameter and 3 mm thickness, as well as on the larger 250 ton industrial FAST system targeting a sample size of 101.6x101.6x3 mm3 to investigate issues associated with scaling. Several sintering conditions were explored including: pressure of 35-65 MPa, temperature of 1700-1900°C, and heating rates between 50-400°C/min. The SiC fibers used in this study were coated using chemical vapor deposition (CVD) with boron nitride (BN) and pyrolytic carbon to act as a barrier layer and preserve the integrity of the fibers during sintering. Then the barrier coating was coated by an outer layer of SiC to enhance the bonding between the fibers and the SiC matrix. Microstructures of the sintered samples were examined by FE-SEM. Mechanical properties including flexural strength-deflection and stress-strain were characterized using 4-point bend testing. Tensile testing was performed on the larger 101.6x101.6x3 mm samples. The microstructures of samples sintered using the 25 ton laboratory FAST system showed a reduction in porosity and good adhesion between the fiber-fiber and fiber-matrix interface. The microstructures of samples sintered on the 250 ton industrial FAST system showed a reduction in porosity, but there was visible reaction of the fiber and fiber coatings with the surrounding matrix. Additionally, there was significant radial cracking of the fibers visible in the microstructures.There is gap in the understanding of sintering behavior between laboratory and industrial scale FAST systems. The vast majority of publications on FAST sintering have been primarily focused on small sample geometries (20 mm diameter, less than 3 mm thick). A study was coordinated to investigate the thermal properties during heating and cooling using a 250 ton industrial FAST system at 900°C using B4C and SiC materials inside the graphite die assembly. The thermal properties were then compared to the resulting material properties of the identically sintered B4C and SiC to approximately 94% relative density, at a temperature of 1950°C, pressure of 45 MPa, 10 minute hold, and heated at a rate of 100°C/min. The study determined that at 900°C there were significant thermal gradients within the system for the examined materials, and that these gradients correlated well with the material property difference of the samples sintered at higher temperatures where the gradients are presumably larger due to an increase in radiative heat loss. The observed temperatures throughout the graphite were significantly different between B4C and SiC. These temperatures also correlated well with the material properties of the sintered products which showed more substantial variation for B4C when compared to SiC which was overall less affected by thermal gradients. This was attributed to the intrinsic thermal conductivity difference between the two subject materials which was manifested as thermal gradients throughout the material and graphite die assembly. Additionally, both the observed temperature gradients throughout the graphite die assembly and the difference in temperature reading between the optical pyrometer and thermocouples were significantly larger for the 250 ton FAST system than previous publications have demonstrated experimentally or via modeling of smaller laboratory scale systems. The findings from this work showed that relative to conventional sintering methods, the FAST process demonstrated comparable or improved material and mechanical properties with a significantly shorter processing cycle. However, the results demonstrated on the 25 ton laboratory scale unit were significantly different compared to results for the same materials sintered using the 250 ton industrial scale unit. The temperature gradients observed on the 250 ton FAST unit were significantly larger than previous reports on smaller FAST units. This result showed future efforts to scale up the FAST sintering process while maintaining similar results will require careful attention to minimizing temperature gradients. This could potentially be achieved by reducing radiative heat loss during processing and/or optimizing the graphite die design and implementing heat spreaders in specific locations dependent on the host material's thermal and electrical properties as well as the sample geometry.
Download or read book Pressureless Sintering of Boron Carbide Whisker Reinforced Alumina Matrix Composites written by Xuan Lin and published by . This book was released on 1995 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Microstructural Optimization of Solid state Sintered Silicon Carbide written by Lionel Ruben Vargas-Gonzalez and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, the development of theoretically-dense, clean grain boundary, high hardness solid-state sintered silicon carbide (SiC) armor was pursued. Boron carbide and graphite (added as phenolic resin to ensure the carbon is finely dispersed throughout the microstructure) were used as sintering aids. SiC batches between 0.25-4.00 wt.% carbon were mixed and spray dried. Cylindrical pellets were pressed at 13.7 MPa, cold-isostatically pressed (CIP) at 344 MPa, sintered under varying sintering soaking temperatures and heating rates, and varying post hot-isostatic pressing (HIP) parameters. Carbon additive amounts between 2.0-2.5 wt.% (based on the resin source), a 0.36 wt.% B4C addition, and a 2050°C sintering soak yielded parts with high sintering densities (~95.5-96.5%) and a fine, equiaxed microstructure (d50 = 2.525 ℗æm). A slow ramp rate (10°C/min) prevented any occurrence of abnormal grain growth. Post-HIPing at 1900°C removed the remaining closed porosity to yield a theoretically-dense part (3.175 g/cm3, according to rule of mixtures). These parts exhibited higher density and finer microstructure than a commercially-available sintered SiC from Saint-Gobain (Hexoloy Enhanced, 3.153 g/cm3 and d50 = 4.837 ℗æm). Due to the optimized microstructure, Verco SiC parts exhibited the highest Vickers (2628.30 " 44.13 kg/mm2) and Knoop (2098.50 " 24.8 kg/mm2) hardness values of any SiC ceramic, and values equal to those of the "gold standard" hot-pressed boron carbide (PAD-B4C). While the fracture toughness of hot-pressed SiC materials (~4.5 MPa m1/2) are almost double that of Verco SiC (2.4 MPa m1/2), Verco SiC is a better performing ballistic product, implying that the higher hardness of the theoretically-dense, clean-grain boundary, fine-grained SiC is the defining mechanical property for optimization of ballistic behavior.
Download or read book Improved Silicon Carbide for Advanced Heat Engines written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-08 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines is studied. Injection molding was the forming method selected for the program because it is capable of forming complex parts adaptable for mass production on an economically sound basis. The goals were to reach a Weibull characteristic strength of 550 MPa (80 ksi) and a Weibull modulus of 16 for bars tested in four-point loading. Statistically designed experiments were performed throughout the program and a fluid mixing process employing an attritor mixer was developed. Compositional improvements in the amounts and sources of boron and carbon used and a pressureless sintering cycle were developed which provided samples of about 99 percent of theoretical density. Strengths were found to improve significantly by annealing in air. Strengths in excess of 550 MPa (80 ksi) with Weibull modulus of about 9 were obtained. Further improvements in Weibull modulus to about 16 were realized by proof testing. This is an increase of 86 percent in strength and 100 percent in Weibull modulus over the baseline data generated at the beginning of the program. Molding yields were improved and flaw distributions were observed to follow a Poisson process. Magic angle spinning nuclear magnetic resonance spectra were found to be useful in characterizing the SiC powder and the sintered samples. Turbocharger rotors were molded and examined as an indication of the moldability of the mixes which were developed in this program. Whalen, Thomas J. Unspecified Center...
Download or read book Advances in Silicon Carbide Processing and Applications written by Stephen E. Saddow and published by Artech House. This book was released on 2004 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn the latest advances in SiC (Silicon Carbide) technology from the leading experts in the field with this new cutting-edge resource. The book is your single source for in-depth information on both SiC device fabrication and system-level applications. This comprehensive reference begins with an examination of how SiC is grown and how defects in SiC growth can affect working devices. Key issues in selective doping of SiC via ion implantation are covered with special focus on implant conditions and electrical activation of implants. SiC applications discussed include chemical sensors, motor-control components, high-temperature gas sensors, and high-temperature electronics. By cutting through the arcane data and jargon surrounding the hype on SiC, this book gives an honest assessment of today's SiC technology and shows you how SiC can be adopted in developing tomorrow's applications.
Download or read book Materials Science of Carbides Nitrides and Borides written by Yury G. Gogotsi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 371 pages. Available in PDF, EPUB and Kindle. Book excerpt: A survey of current research on a wide range of carbide, nitride and boride materials, covering the general issues relevant to the development and characterisation of a variety of advanced materials. Topics include structure and electronic properties, modeling, processing, high-temperature chemistry, oxidation and corrosion, mechanical behaviour, manufacturing and applications. The volume complements more specialised books on specific materials as well as more general texts on ceramics or hard materials, presenting a survey of materials research as a key to technological development. After decades of research, the materials are being used in electronics, wear resistant, refractory and other applications, but numerous new applications are possible. Roughly equal numbers of papers cover theoretical and experimental research in the general field of materials science of refractory materials. Audience: Researchers and graduate students in materials science and engineering.
Download or read book Improved Silicon Carbide for Advanced Heat Engines written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-11-02 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines is studied. Injection molding was the forming method selected for the program because it is capable of forming complex parts adaptable for mass production on an economically sound basis. The goals were to reach a Weibull characteristic strength of 550 MPa (80 ksi) and a Weibull modulus of 16 for bars tested in four-point loading. Statistically designed experiments were performed throughout the program and a fluid mixing process employing an attritor mixer was developed. Compositional improvements in the amounts and sources of boron and carbon used and a pressureless sintering cycle were developed which provided samples of about 99 percent of theoretical density. Strengths were found to improve significantly by annealing in air. Strengths in excess of 550 MPa (80 ksi) with Weibull modulus of about 9 were obtained. Further improvements in Weibull modulus to about 16 were realized by proof testing. This is an increase of 86 percent in strength and 100 percent in Weibull modulus over the baseline data generated at the beginning of the program. Molding yields were improved and flaw distributions were observed to follow a Poisson process. Magic angle spinning nuclear magnetic resonance spectra were found to be useful in characterizing the SiC powder and the sintered samples. Turbocharger rotors were molded and examined as an indication of the moldability of the mixes which were developed in this program. Whalen, Thomas J. Unspecified Center...
Download or read book Silicon Carbide written by I. N. Frantsevich and published by Springer. This book was released on 1970 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ceramic Armor and Armor Systems II written by Eugene Medvedovski and published by John Wiley & Sons. This book was released on 2012-04-11 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains papers on the development and incorporation of ceramic materials for armor applications. Topics include impact and penetration modeling, dynamic and static testing to predict performance, damage characterization, non-destructive evaluation and novel material concepts.
Download or read book Suspension Processing and Pressureless Sintering of Silicon Carbide Whisker reinforced Alumina matrix Composites written by Hae-Weon Lee and published by . This book was released on 1990 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt:
