Materials Literature
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Abstract We report a “delayed neutralization” process for the preparation of highly‐ordered aluminosilicate MCM‐41 molecular sieves with high thermal and hydrothermal stability, and sharp pore size distribution. However, the structural order and pore size are dependent on the carbon chain length. In the mixture surfac…
The microstructure of a silicon carbide-carbon solid-solution powder (SiC-C), obtained from a fine powder of silicon and thermal expansive graphite, is investigated by X-ray powder diffraction methods. The microstructure is characterized by Williamson-Hall analysis and the strain-field model suggested by van Berkum et…
Abstract The hydrothermal reactivity of a smectite saturated with K was studied experimentally at 300°C and 100 bar in (Na,K) chloride solutions (Na/K = 0, 50 and 100, liquid/solid ratio = 10/1). X-ray diffraction, TEM and microprobe results show: (1) a partial to total dissolution of the initial smectite layers; and…
Hexokinase I governs the rate-limiting step of glycolysis in brain tissue, being inhibited by its product, glucose 6-phosphate, and allosterically relieved of product inhibition by phosphate. On the basis of small-angle X-ray scattering, the wild-type enzyme is a monomer in the presence of glucose and phosphate at pro…
Liposomes are microscopic vesicles composed of phospholipid bilayers surrounding discrete aqueous compartment. Eventhough phospholipid bilayers are formed spontaneously in water, their conventional preparation methods involve either organic solvents or detergent molecules. Organic solvents may create a serious safety…
A new adamantane-based bis(ether anhydride), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]adamantane dianhydride, was prepared in three steps starting from nitrodisplacement of 4-nitrophthalonitrile with the potassium phenolate of 2,2-bis(4-hydroxyphenyl)adamantane. A series of adamantane-containing poly(ether imide)s were…
Dense TiB ceramics (99.6% of theoretical) with a grain size of ∼5 µm have been fabricated by reaction hot pressing of TiB 2 and titanium for 2 h at 1900°C and 28.5 MPa. The TiB ceramics exhibit a fracture toughness ( K IC ) of 4.5 MPa·m 1/2 and a bending strength (sigma b ) of 360 MPa. Electrical resistivity (rho) is…
The oxidation behavior of reaction‐bonded silicon carbide (RBSC) and the effect of oxidation on the room‐temperature flexural strength of RBSC were investigated. Four different types of RBSC, each having various SiC particle‐size distributions and free silicon contents, were exposed to air at 1300°C for up to 200 h. P…
Chromium carbide thin films are synthesized on Si(100) substrates by a pulsed Nd:YAG laser deposition method at different substrate temperatures. Glancing-angle X-ray diffraction shows that a crystalline chromium carbide film can be prepared at the substrate temperature of 700°C. Grain size of the films, examined with…
A high-pressure Raman study of BaCeO3 was performed at room temperature. This perovskite compound undergoes two phase transitions at about 22 and 28 GPa. The increase in the number of bands is an indication that the symmetry is lowered and that the compound does not evolve towards the ideal cubic perovskite structure…
Structural (X-ray diffraction), melting (differential scanning calorimetry), as well as mechanical (tensile tests) characterizations on uncrosslinked ethene–propene copolymer samples, obtained using a metallocene-based catalytic system and having an ethene content in the range 80–50% by mol, are reported. Samples with…
Reinvestigation of the structural and vibrational properties of the typical perovskite ${\mathrm{KMnF}}_{3},$ exhibiting two antiferrodistortive structural phase transitions, was performed using x-ray powder diffraction and Raman spectroscopy in the range between 30 and 300 K. The x-ray-diffraction work has unambiguou…
A chemical synthesis technique that uses polyacrylic acid (PAA) to prepare nanocrystalline Li 0.3 Zn 0.4 Fe 2.3 O 4 was investigated. Phase‐pure spinel that had an average particle size of ∼13 nm was synthesized at a low temperature (450°C) for 30 min. The average particle size was dependent on the firing temperature…
The effects of phason disorder on the dynamical structure factor of Fibonacci chains are studied, and the existence of a coherent phason field in real quasicrystals is addressed. The neutron-scattering response is modeled for coherent and random phasons. The results show that coherent and random phasons can be disting…
(001)-oriented and oxygen-deficient ZnO thin films are prepared by pulsed laser deposition on quartz fused, (100) silicon and (001) sapphire substrates, respectively. The structural, electrical and optical properties of the as-grown films are characterized with various techniques. The Raman measurements reveal additio…
Thermal accommodation of 1 kg and 50 kg weights to ambient air under different storing conditions and change of apparent mass due to temperature differences between weight and air have been measured. Physical models taking account of different heat transfer processes and of convective forces of flowing air acting on t…
The influence of polar species on the transport of charge carriers in molecular solids is reviewed. Guest molecules with permanent dipole moments introduced into molecular crystals can act as traps localizing carriers provided certain energetic conditions are fulfilled. In this case their polar character may manifest…
The (isomorphous) structures of Bi(14)WO(24), tetradecabismuth tungsten tetracosaoxide, and Bi(14)MoO(24), tetradecabismuth molybdenum tetracosaoxide, have been solved and refined using neutron powder diffraction data in the space group I4/m. The metal-atom array is fully ordered in terms of composition, and in terms…
Abstract Sorption of several organic and inorganic cations on illite (Clay Minerals Society Source Clay Imt-2) was determined experimentally and results compared to model calculations. The cations studied were crystal violet (CV + ), benzyltrimethylammonium (BTMA + ), benzyltriethylammonium (BTEA + ), Ca 2+ , Mg 2+ ,…
This paper describes a new micromachining technique for fabrication of semiconducting yttrium barium copper oxide (YBCO) microbolometers using magnesium oxide (MgO) as the sacrificial layer. This type of bolometer can be operated at room temperature, providing a low-cost alternative for more expensive cryogenically co…