Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-molybdenum Disilicide Ceramics and Dual Composite Architectures PDF Download
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Author: Ryan Joseph Grohsmeyer Publisher: ISBN: Category : Languages : en Pages : 261
Book Description
"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500°C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500°C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500°C for 15 ZrB2-MoSi2 ceramics hot pressed using fine, medium, or coarse ZrB2 starting powder with 5-70 vol.% MoSi2, referred to as FX, MX, and CX respectively where X is the nominal MoSi2 content. MoSi2 decomposed during sintering, resulting in microstructures with ZrB2 cores and (Zr[subscript 1-x]Mo[subscript x])B2 shells via surface and grain boundary diffusion. Flexure strength at RT (700-800 MPa for FX, 560-720 MPa for MX, and 440-590 MPa for CX) was controlled by the maximum ZrB2 grain size, and toughness (2.7-3.9 MPa·m[superscript 1/2]) did not trend with MoSi2 content. At 1500°C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500°C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa. Four ZrB2-MoSi2 DCAs were fabricated by dispersing granules of selected ZrB2-MoSi2 compositions in matrices of different ZrB2-MoSi2 compositions. Strength limitation at 1500°C by differential oxidation of granules and matrix was resolved by compositional adjustment, but microcracking due to granule-matrix CTE mismatch limited strength to ~140 MPa at RT and ~360 MPa at 1500°C. The granule-matrix interface did not deflect cracks, and the toughness at 1500°C was 6.1-6.9 MPa·m[superscript 1/2], similar to that of conventional ZrB2-MoSi2 ceramics. CTE matching via addition of a third phase and use of a weak granule-matrix interface are recommended areas of focus for future development of high-temperature DCAs"--Abstract, page iv.
Author: Ryan Joseph Grohsmeyer Publisher: ISBN: Category : Languages : en Pages : 261
Book Description
"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB2-MoSi2 ceramics at room temperature (RT) and 1500°C in air, and fabrication of ZrB2-MoSi2 dual composite architectures (DCAs) for use near 1500°C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500°C for 15 ZrB2-MoSi2 ceramics hot pressed using fine, medium, or coarse ZrB2 starting powder with 5-70 vol.% MoSi2, referred to as FX, MX, and CX respectively where X is the nominal MoSi2 content. MoSi2 decomposed during sintering, resulting in microstructures with ZrB2 cores and (Zr[subscript 1-x]Mo[subscript x])B2 shells via surface and grain boundary diffusion. Flexure strength at RT (700-800 MPa for FX, 560-720 MPa for MX, and 440-590 MPa for CX) was controlled by the maximum ZrB2 grain size, and toughness (2.7-3.9 MPa·m[superscript 1/2]) did not trend with MoSi2 content. At 1500°C toughness increased with MoSi2 content and ZrB2 grain size, and strength of FX and MX was controlled by oxidation damage at 1500°C. Strength of CX followed the opposite trend, with C10 exhibiting a strength of ~600 MPa. Four ZrB2-MoSi2 DCAs were fabricated by dispersing granules of selected ZrB2-MoSi2 compositions in matrices of different ZrB2-MoSi2 compositions. Strength limitation at 1500°C by differential oxidation of granules and matrix was resolved by compositional adjustment, but microcracking due to granule-matrix CTE mismatch limited strength to ~140 MPa at RT and ~360 MPa at 1500°C. The granule-matrix interface did not deflect cracks, and the toughness at 1500°C was 6.1-6.9 MPa·m[superscript 1/2], similar to that of conventional ZrB2-MoSi2 ceramics. CTE matching via addition of a third phase and use of a weak granule-matrix interface are recommended areas of focus for future development of high-temperature DCAs"--Abstract, page iv.
Author: Dileep Singh Publisher: John Wiley & Sons ISBN: 1118059875 Category : Technology & Engineering Languages : en Pages : 320
Book Description
This book is a collection of papers from The American Ceramic Society's 35th International Conference on Advanced Ceramics and Composites, held in Daytona Beach, Florida, January 23-28, 2011. This issue includes papers presented in the Mechanical Behavior and Performance of Ceramics & Composites Symposium on topics such as processing-microstructure properties correlations; fracture mechanics, modeling and testing; tribological properties; applications; and processing.
Author: Dileep Singh Publisher: John Wiley & Sons ISBN: 1118173082 Category : Technology & Engineering Languages : en Pages : 322
Book Description
This book is a collection of papers from The American Ceramic Society's 35th International Conference on Advanced Ceramics and Composites, held in Daytona Beach, Florida, January 23-28, 2011. This issue includes papers presented in the Mechanical Behavior and Performance of Ceramics & Composites Symposium on topics such as processing-microstructure properties correlations; fracture mechanics, modeling and testing; tribological properties; applications; and processing.
Author: J. P. Singh Publisher: John Wiley & Sons ISBN: 1118491831 Category : Technology & Engineering Languages : en Pages : 338
Book Description
With contributed papers from the 2011 Materials Science and Technology symposia, this is a useful one-stop resource for understanding the most important issues in the processing and properties of advanced ceramics and composites. Logically organized and carefully selected, the articles cover the themes of the symposia: Innovative Processing and Synthesis of Ceramics, Glasses and Composites; Advances in Ceramic Matrix Composites; Solution-Based Processing of Materials; and Microwave Processing of Materials. A must for academics in mechanical and chemical engineering, materials and or ceramics, and chemistry.
Author: Sumin Zhu Publisher: ISBN: Category : Ceramic materials Languages : en Pages : 360
Book Description
"The first part of this dissertation was aimed at studying the densification of ZrB2 ceramics by pressureless sintering techniques. Various processes have been applied to coat ZrB2 powders with polymer precursors, which were used to produce C after charring. After sintering at 1900°C, relative density increased of ~70% for uncoated ZrB2 to >99% for ZrB2 coated with at least 1.0 wt% C. Thermodynamic analysis suggested that C reacted with and removed oxide impurities (ZrO2 and B2O3) that were present on the ZrB2 particle surfaces, which promoted densification by minimizing grain coarsening"--Abstract, leaf iv.
Author: Connor Charles Wittmaier Publisher: ISBN: Category : Languages : en Pages : 65
Book Description
"The mechanical properties and processing parameters of boride ceramics in foam and laminate architectures were evaluated. The ceramic reticulated foam was produced through a polymer substrate replication technique and the hardness and compressive strength were tested. The laminate structure was tested to evaluate the flexure strength and work of fracture as a function of temperature. The foam architecture was produced using a TiB2 slurry coating on a polyurethane reticulated foam preform. Foams sintered to 2150°C displayed an average grain size of 8.9 ± 7.3 [mu]m, and a hardness of 17.3 ± 2.4 GPa. Crush testing foams were sintered at 1975°C, and displayed a specific strength of 208 ± 63 kPa with an overall porosity of 97%. For these specimens, it is likely that microcracking lowered the hardness, but the overall strength was controlled by the bulk density. The laminate structures were fabricated using alternating layers of ZrB2 and C-10 vol% ZrB2. The structures were fabricated through the shaping of ceramic loaded thermoplastic polymers that underwent burnout and hot pressing cycles. These specimens had strong phase ZrB2 layers that were about 150 [mu]m thick alternating with weak phase layers that were about 20 [mu]m thick. Specimens exhibited a maximum flexure strength of 311 ± 10 MPa at 1600°C, and an increased work of fracture compared to conventional ZrB2 ceramics. The maximum fraction of inelastic work of fracture occurred at room temperature, and decreased as temperature increased. This was reflected in the length of the crack path through the specimen. Deflected cracks travelled through the center of the C-ZrB2 layers in the material in Mode II fracture"--Abstract, page iv.
Author: Derek Scott King Publisher: ISBN: Category : Ceramic materials Languages : en Pages : 214
Book Description
"The microstructure, hardness, fracture toughness, Young's modulus, strength and Weibull modulus of silicon carbide-titanium diboride (SiC-TiB2) ceramics were studied. First, SiC-TiB2 ceramics with 15 vol.% TiB2 particles were processed using two green processing methods, spray drying (ST) and ball milling (SiC-15TiB2). In addition, SiC-TiB2 ceramics with TiB2 contents ranging from 0 to 100 vol.% were produced to determine a TiB2 content that produced the best combination of mechanical properties. From spray drying, segregation of the TiB2 particles in ST led to a granule-like microstructure and spontaneous microcracking in the final ceramic. In ceramics containing 20 and 40 vol.% TiB2, the TiB2 particle sizes were also large enough to allow for spontaneous microcracking. Spontaneous microcracking decreased the hardness from 28 GPa for SiC to 24 GPa for SiC-TiB2 with TiB2 contents of 80 vol.% or higher. In contrast, fracture toughness increased from 2 MPa·m1/2 for SiC to ~6 MPa·m[superscript 1/2] for SiC containing 40 vol.% TiB2 or more. Using a two-parameter Weibull analysis, SiC with 20 vol.% TiB2 had the highest average strength (522 MPa), followed by SiC-15TiB2 (500 MPa), then SiC with 40 vol.% TiB2 (420 MPa), and ST (380 MPa). While microcracking in ST lowered the strength, hardness, and elastic modulus compared to SiC-15TiB2, the granule-like microstructure combined with microcracking, narrowed the flaw size distribution of ST and boosted the Weibull modulus of ST to 21 compared to 12 for SiC-15TiB2, which had a uniform distribution of TiB2 particles. The Weibull moduli of SiC containing 20 and 40 vol.% TiB2 was also boosted to 17, compared to 12 for a TiB2 content of 15 vol.%. To maximize each property, TiB2 particle sizes should be kept just below the spontaneous microcracking threshold to prevent spontaneous flaw formation"--Abstract, leaf iv.
Author: Eric William Neuman Publisher: ISBN: Category : Borides Languages : en Pages : 259
Book Description
"Research presented in this dissertation focused on the mechanical behavior of ZrB2 based ceramic at elevated temperatures. Flexure strength, fracture toughness, and elastic modulus were measured at temperatures up to 2300°C for three compositions: monolithic ZrB2 (Z); ZrB2 - 30 vol% SiC - 2 vol% B4C (ZS); and ZrB2 - 10 vol% ZrC (ZC). In argon, Z, ZS, and ZC had strengths of 210 (at 2300°C), 260 (at 2200°C), and 295 MPa (at 2300°C), the highest temperatures tested for each composition. Fractography was used extensively to characterize the strength limiting flaws as a function of temperature. Strength of ZS in argon was controlled by the SiC cluster size up to 1800°C, and the formation of B-O-C-N phases that bridged SiC clusters above 2000°C. For ZC, surface flaws introduced during specimen preparation were the source of critical flaws in the material up to 1400°C, sub-critical crack growth of surface flaws between 1600 and 2000°C, and microvoid coalescence above 2000°C. It was also shown that thermal annealing at either 1400, 1500, or 1600°C improves the strength and modulus of ZS at temperatures between 800°C and 1600°C. Heat treatment at 1400°C for 10 hours produced the largest improvement in strength, 430 MPa at 1600°C versus 380 MPa for the as processed material. As a whole, the research pointed to several key microstructural features currently limiting the mechanical properties at the highest temperatures. In particular, removal of unfavorable secondary phases, and improved control over microstructure, should be promising methods to improve the elevated temperature properties of ZrB2 ceramics."--Abstract, page iv.
Author: Ryan Joseph Grohsmeyer
Author: Ryan Joseph Grohsmeyer
Author: Dileep Singh
Author: Dileep Singh
Author: J. P. Singh
Author: Sumin Zhu
Author: Connor Charles Wittmaier
Author: Derek Scott King
Author: Eric William Neuman
Author: Caroline Dorothea Sagel-Ransijn
Author: