Materials Literature
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This paper describes a simple and reliable method of improving the surface insulation strength of a spacer used in vacuum. The method is to roughen the spacer surface to an average roughness R/sub a/ higher than 1 or 2 /spl mu/m. The material of the spacer examined is SiO/sub 2/, PMMA, PTFE or Al/sub 2/O/sub 3/ and th…
For more than 25 years, various techniques have been introduced for the nondestructive measurement of the space charge distribution in solid dielectrics. All these techniques can be classified into a set of three methods: (i) the thermal method, (ii) the pressure-wave-propagation method and (iii) the electro-acoustic…
Abstract Commercially available biodegradable aliphatic polyesters, i.e., high molecular weight poly(ϵ‐caprolactone) (PCL) and polylactide (PLA), were melt blended with a well‐known natural and biodegradable polysaccharide: starch either as corn starch granules or as thermoplastic corn starch after plasticization with…
A protein Raman spectrum comprises discrete bands representing vibrational modes of the peptide backbone and its side chains. The spectral positions, intensities, and polarizations of the Raman bands are sensitive to protein secondary, tertiary, and quaternary structures and to side -chain orientations and local envir…
The use of organometallic precursors allows the synthesis in mild conditions of nanoparticles of uniform small size (1–3 nm) and of clean surface, which can be stabilized by polymers or ligands. These nano-objects display an interesting surface chemistry comparable to that of molecular species. This involves classical…
Pectin and lignin are both very important noncellulosic substances occurring in hemp fibers. The main task in preparing hemp fibers for textile applications is to remove these noncellulosic substances without damage to the fiber cellulose. Pectin and lignin in hemp before and after chemical processing are characterize…
Two important advances over the past 40 years enable the optimization and management of the structural integrity of components in high performance applications. First, the solid mechanics conununity established linear elastic fracture mechanics as the premier framework for modeling the damage tolerance of fracture cri…
We have prepared samples of nominal type Ba 8 Cu x Ge 46− x by induction melting and solid state reaction. Analysis shows that these materials form type-I clathrates, with a copper content between x = 4.9 and 5.3, nearly independent of the starting composition. We used x-ray powder diffraction and single-crystal elect…
The microstructure in Y 2 O 3 ‐stabilized tetragonal zirconia polycrystal (Y‐TZP) sintered at 1300°–1500°C was examined to clarify the role of Y 3+ ions on grain growth and the formation of cubic phase. The grain size and the fraction of the cubic phase in Y‐TZP increased as the sintering temperature increased. Both t…
Progress in tissue-engineering research has renewed optimism about the possibility of constructing a physiologically functional blood vessel substitute in the laboratory. To this end, we have explored the use of defined mechanical stimulation to further the development of vascular tissue analogs. We now report our fin…
We present first-principles transport calculations for ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ using the linearized-augmented plane-wave method and the relaxation time approximation. We considered the effects of hydrostatic pressure and uniaxial stress up to 4 GPa. Doping was included for electrons and holes at levels up…
It is shown that in a heterostructure where screening is eliminated, the Ampére-Maxwell law of electrodynamics implies that a dc or ac spinomotive force can be inudced with a time rate of change of a transverse electric field, and the magnetic analog of Ampére law implies that a dc or ac spin current can generate a tr…
Challenges facing the scaling of microelectronics to sub-50 nm dimensions and the demanding material and structural requirements of integrated photonic and microelectromechanical systems suggest that alternative fabrication technologies are needed to produce nano-scale devices. Inspired by complex, functional, self-as…
Contrasting magnetic properties were obtained from bulk Mn-doped ZnO synthesized under different processing conditions. While a ferrimagnetic phase transition was observable in a Zn0.95Mn0.05O sample processed at 1170 K, no such transition was found for a sample with the same composition processed at 1370 K. The detai…
We deposited graded-index SiO2 films using glancing angle deposition to produce high-transmission antireflection coatings on glass. Because of the accurate control over the thin-film microstructure provided by this technique, we were able to create graded densities with a Gaussian profile resulting in transmission val…
This account describes the synthesis, characterization, and applications to catalysis of dendrimer-encapsulated metal nanoparticles (DEMNs). These materials are synthesized by a template approach in which metal ions are sorbed into the interior of dendrimers and then subsequently chemically reduced to yield nearly siz…
We analyzed samples of antigorite, lizardite and fibrous chrysotile, three representative minerals of the serpentine group, to determine their chemical and structural properties, and their FT-Raman spectra. The low-frequency region of the spectrum (1200– 200 cm –1 ), which corresponds to the lattice-vibration modes, w…
At high temperatures, SiC and Si 3 N 4 react with water vapor to form a SiO 2 scale. SiO 2 scales also react with water vapor to form a volatile Si(OH) 4 species. These simultaneous reactions, one forming SiO 2 and the other removing SiO 2 , are described by paralinear kinetics. A steady state, in which these reaction…
Temperature-dependent rf-ion trap mass spectrometry and first-principles simulations reveal the detailed reaction mechanism of the catalytic gas-phase oxidation of CO by free Au(2)(-) ions in the presence of O(2). A metastable intermediate with a mass of Au(2)CO(3)(-) was observed at low temperatures. Two alternative…
Current state‐of‐the‐art environmental barrier coatings (EBCs) for Si‐based ceramics consist of three layers: a silicon bond coat, an intermediate mullite (3Al 2 O 3 ·2SiO 2 ) or mullite + BSAS ((1− x )BaO· x SrO·Al 2 O 3 ·2SiO 2 , 0 ≤ x ≤ 1) layer, and a BSAS top coat. Areas of concern for long‐term durability are en…