Materials Literature
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Alumina and alumina matrix composites containing 5 to 20 volume percent of multi-wall carbon nanotubes (MWNT) were fabricated by hot pressing in Ar atmosphere at 1300°C for 1h with 60 MPa of applied pressure. A powder of α-phase alumina, with 44 nm mean diameter, and arc-derived MWNT were used for these experiments. T…
In this study for the first time the effect of high-pressure CO2 on the coacervation of alpha-elastin was investigated using analytical techniques including light spectroscopy and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic imaging and circular dichroism (CD) spectroscopy. The coace…
The isotropic–nematic (I–N) phase transition in a system of long straight rigid rods of length k on square lattices is studied by combining Monte Carlo simulations and theoretical analysis. The process is analyzed by comparing the configurational entropy of the system with that corresponding to a fully aligned system,…
In order to improve the fabrication process and the performances of SiC/SiC composites, poly(vinylsilane), which is a new type liquid poly(carbosilane) with significant Si-H functionality, was adopted for a matrix precursor in polymer impregnation and pyrolysis (PIP) process. Since the thermal behavior of a precursor…
An oxide\oxide ceramic matrix composite (CMC) with no interphase at the fiber-matrix interface was characterized under monotonic tensile testing and cyclic tensile loading at 23°C and 1200°C. The effect of room temperature moisture exposure on fatigue behavior was also examined at 1200°C. The composite consisted of 10…
Local magnetic moment formation on edges of graphene is studied using the Hubbard model on a honeycomb lattice. The Coulomb interaction is treated with the mean field approximation. Realistic edges of graphene are composed of zigzag and armchair parts. It is found that, on a zigzag part of length n a larger than 3 a ,…
Macro (Taber) wear tests and especially micro (pin-on-disk) tests performed on Al2O3 and B4C, as a function of varying porosity, show wear increasing exponentially with porosity. Al2O3, which was tested over a much more extensive range of porosity, showed a significant change in the porosity dependence of wear at appr…
An experimental technique for evaluation of wettability of ceramic particulate with liquid metal was developed. Wettability tests were conducted by pressure infiltration through uniformly packed powder specimens. The threshold pressures for infiltration can either be used as quantitative measure of wettability or be c…
In-situ reinforced SiC-AIN ceramic alloys having unique microstructure and fracture toughness up to 5.5 MPa · m1/2 were successfully produced. The alloys can be pressureless-sintered to high density at 2050°C with 2 wt% yttria as a sintering aid. The sintered SiC-AIN alloys can achieve a single solid solution at tempe…
Room temperature tensile strengths of single crystal α-Al2O3 fiber (Saphikon), polycrystalline α-Al2O3 fiber (Nextel 610) and 85% Al2O3 -15% SiC2 fiber (Nextel 720) were evaluated in the as-received condition and after long term exposure at 982°C in air. Following an initial 25% loss of strength after a thermal exposu…
A new family of platelet-reinforced ceramics has been developed using a Lanxide DIMOX™ directed metal oxidation process. These materials consist of a metal carbide matrix reinforced with metal diboride platelets and a residual metal phase. Microstructure/property relationships are presented for the ZrB2/ZrCxZr system,…
Reaction-forming methods successfully applied to ceramic monoliths and composites having a wide range of compositions are reviewed. Net-shape capabilities and the potential for high purity are the principal advantages of this processing route for both monoliths and composites. Recent results with several different pro…
A novel method of manufacturing strong Al2O3 bodies with low-shrinkage is presented. Isopressed compacts of attrition-milled Al/Al2O3 mixtures with 35 and 50 vol% Al are heat-treated in two steps at 900°–1150°C and 1200°–1450°C, respectively. Fully reaction-bonded (oxidized and sintered) Al2O3 (RBAO) ceramics exhibit…
The process of ceramic composites has experienced exceptional growth in the last 15 years. Approaches to processing have focused on traditional ceramic consolidation techniques, extensions of existing composite technologies, as well as more novel methodologies such as liquid metal oxidation and vapor infitration. In t…
SiC fibers with excellent thermal stability have been developed by means of reducing their oxygen content. Polycarbosilane fibers were cured by electron beam irradiation in a stream of helium and were pyrolized in an inert atmosphere. These SiC fibers were continuous, in multi-filament form, consisting of Si-1.3C-0.02…
The high-temperature deformation behavior of polycrystalline yttrium aluminum garnet (YAG) has been investigated using constant displacement rate compression tests conducted in vacuum. The behavior in the strain rate regime of 10−5-10−3/S in the temperature range of 1400°-1610°C was studied and compared with available…
Si-Zr-C-O Tyranno Fibers (ZMI and ZE) containing an additive metal (1% zirconium in substitution for 2% titanium in Si-Ti-C-O Tyranno Fibers (LoxM and LoxE)) have been produced with improved properties such as thermal stability and chemical-corrosion resistance. Recently a nearly stoichiometric crystalline Si-Al-C Tyr…
A novel technique for fabricating ceramic matrix composites by the directed oxidation of a molten metal through a mass of filler material is disclosed. A wide range of composites comprising several matrix systems and both particulate and fibrous filler materials have been demonstrated. As examples of these systems, co…
National Aerospace Laboratory of Japan (NAL) has conducted a joint program to develop a continuous fiber reinforced ceramic matrix composite (CMC) for aerospace applications with Ube Industries Ltd., Shikibo Ltd., and Kawasaki Heavy Industries Ltd. The composite is referred to as NUSK-CMC from the initials of the coll…
Stainless-steel specimens (15×15×0.5mm3) containing homogeneously distributed tritium were used for the experiments. To investigate the fate of tritium in the surface region, about 70μm were chemically etched and the regrowth of tritium on the top surface layer determined as function of time by β-ray-induced x-ray spe…