Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
The boron nitride (BN) coating was applied on Hi-Nicalon by chemical vapor deposition (CVD) from boron trichloride, ammonia and hydrogen gases mixture. The BN coating contained hexagonal BN and 10 at. % carbon. The 3-D woven BN coated Hi-Nicalon fiber-reinforced SiC composite was fabricated by CVI+PIP combined process…
Solid-particle erosion of an environmental barrier coating on silicon nitride substrates and a diamond thin film on silicon have been studied for impact angles of 20 and 90°, using 100 and 240 grit alumina and silicon carbide abrasives at 50 and 100 m/s. Weight-loss measurements are combined with scanning electron mic…
Carbon fiber reinforced silicon carbide matrix composites (C\SiC) are a promising material for use in many high temperature structural applications. The proposed applications are primarily in aerospace, i.e., nozzles, thrusters, turbopumps, brakes, and heat shields. However, the susceptibility of carbon fiber to oxida…
Elastic modulus (E) and proportional limit stress (PL) determined from uniaxial tensile tests of ceramic matrix composites (CMCs) are conceptually unambiguous material properties. However, consistent experimental determination of E and PL has been problematic even when using full-consensus standards such as ASTM Test…
Abstract— The temperature dependence of residual DC voltage was studied based on the adsorption and desorption of ions in the liquid‐crystal (LC) layer to and from the interface between the LC and alignment layers during the application of an external DC offset voltage. The relaxation process of the adsorbed ions duri…
The influence of nano-or micro-sized SiC additions on the high-temperature behavior of Si3N4 materials was studied. Comparing a Si3N4-SiC composite with a monolithic Si3N4 material with the same chemical composition of the grain boundary phase, no significant effect of the nano-or micro-sized SiC additions on the mech…
Instrumented Hertzian indentation testing was performed on several grades of SiCs and the results and preliminary interpretations are presented. The grades included hot-pressed and sintered compositions. One of the hot-pressed grades was additionally subjected to high temperature heat treatment to produce a coarsened…
The oxidation of the carbon within C/SiC decreases strength and life which inhibits its utilization in long-term (100 hr), reusable applications. Before promising protection methods can be evaluated for preventing carbon oxidation, it is useful to first study the oxidation problem. The oxidation rates of the carbon co…
β-Si3N4 seeds were prepared by doping commercial Si3N4 with the rare earth, Y2O3. Based on limited data, four-point flexural strength was found to be 925–1025 MPa for unseeded A2Y6–Si3N4 (Si, N, containing 2 wt.% AI2O3 and 6 wt.% Y2O3 as sintering aids) and 750–950 MPa for seeded A2Y6–Si3N4. Fracture toughness was fou…
The authors present an experimental study of Cr∕Sc multilayer mirrors optimized for the detection of the nitrogen Kα-emission line (λ=3.16nm) at a grazing incidence around 23°, for electron probe microanalysis applications. The multilayers were deposited onto silicon substrates using a dc magnetron sputtering system.…
CMCs (Ceramic Matrix Composites) are attractive material for structural component applications in gas turbine engines because of their excellent high temperature properties and lower specific weight by comparison with Ni base super alloy. In ESPR (Research and Development of Environmentally Compatible Propulsion Syste…
Abstract To investigate the mechanism of fiber structure development for poly(trimethylene terephthalate) (PTT) in high‐speed spinning, the PTT fiber was spun with take‐up speeds from 1 to 8 km/min and simultaneously birefringence and diameter in spin‐line were measured by on‐line measurement system. The orientation‐i…
In this paper, we present a methodology to simulate heat transfer within an isolated carbon nanotube attached to an etched tungsten tip during field emission of an electron beam. The simulations predict the field enhancement, emission current, temperature of the carbon nanotube, and distribution of electrons arriving…
Woven, SiC/SiC Ceramic Matrix Composites (CMCs), manufactured by the slurry-cast, melt-infiltration process are under consideration as combustor liner materials in aircraft gas turbine engines. Tensile properties (elastic modulus, proportional limit strength, in-plane tensile strength, and strain to failure) of the CM…
The absence of a plastic phase in boron carbide and its failure at shock impact velocities just above the Hugoniot elastic limit (HEL) has been the subject of several experimental investigations. Furthermore, the common presence of contaminants, such as disordered graphitic inclusions, oxygen, etc., needs to be addres…
The transthickness tensile strength (TTS) of 2-D CVI-SiC/SiC composites reinforced with Tyranno SA fibers was evaluated by the diametral compression test. The effect of specimen size and specimen shape on the magnitude of the TTS were studied and the results were analyzed using Weibull statistics. Specimens failed alo…
Abstract Photo‐ and thermal stabilities of poly(propylene) (PP)/SiO 2 nanocomposites were studied by varying the particle size of the SiO 2 nanoparticles. It was found that smaller SiO 2 nanoparticles improved the stabilities of the nanocomposites by depressing the size of spherulites. The phenomenon was successfully…
The stress relaxation behavior of SN88, SN2S3, and NCX-5102 silicon nitride materials were experimentally determined in tension at 1300°C using buttonhead specimens. Specimens were held at constant strain after being loaded at 10 MPa/s to an initial stress of 276 MPa (40 ksi) or 414 MPa (60 ksi). The subsequent decay…
ZrC–based fibers and powders with –20 nm crystallite size were prepared by carbothermal reduction of zirconia/carbon mixtures. The reactant mixtures were prepared by solution-based processing in which zirconium 2, 4–pentanedionate (ZTP) was the zirconia-bearing precursor and phenol-formaldehyde resin was the carbon-be…
We report the magnetic and magnetotransport properties of Ca doped La1−xCaxCrO3 (x=0, 0.1, 0.2, and 0.3). Both the magnetic and transport properties are very sensitive to Ca substitution. The Néel temperature TN decreases substantially with increasing calcium doping concentration from 290to160K. A weak ferromagnetic s…