Materials Literature
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This work presents a comprehensive investigation of carrier transport properties in light-emitting porous silicon (LEPSi) devices. Models that explain the electrical characteristics and the electroluminescence properties of the LEPSi devices are developed. In metal/LEPSi devices, the forward current density–voltage (J…
Abstract A variety of nonblack fillers are used in the rubber components of tires. Calcium carbonate, clay, precipitated silica, talc and titanium dioxide are used in white sidewall compounds to impart desired physical properties and appearance. Precipitated silica can be used in black sidewall compounds, including no…
Small angle neutron scattering measurements were made on a series of block copolymer micelles that represent model systems for spherical polymer brushes. We find hyperbolic density profiles of the form ${r}^{\ensuremath{-}\ensuremath{\alpha}}$ with values of $\ensuremath{\alpha}$ between 1.05 and 1.35. This as well as…
Polyurethanes are considered to be one of the most bio- and blood-compatible biomaterials known today. By intelligent utilization of principles governing the structure/property relationship of these polymers, one can generate systems which resemble, in principle, the physical-mechanical behavior of living tissue. Thus…
The kinetics of simultaneous dehydroxylation and carbonation of precipitated Mg(OH) 2 were studied using isothermal and nonisothermal thermogravimetric analyses. Specimens were analyzed using X‐ray diffraction, transmission electron microscopy, and through measurements of the volume of carbon dioxide evolved in a subs…
To assess the suitability of bismuth germanate as an electro-optic material for high precision applications, we have confirmed and extended previous data on its refractive index, electro-optic tensor element r(41), and thermal expansion coefficient. In addition, we have measured the thermo-optic coefficient dn/dT, the…
Abstract A model is presented for free expansion polymer foam processing that includes simultaneous nucleation and bubble growth. The nucleation model includes dissolved gas, small critical cluster size, elastic, and non‐ideal solution effects. An influence volume approach, which couples nucleation and bubble growth,…
Abstract A novel class of low-molecular-weight organic gels has been developed; N,N′,N″-tristearyltrimesamide (TSTA) forms gels with various organic solvents, immobilizing solvent at a low concentration of TSTA. The gels, which form fibrous bundles leading to three-dimensional networks, exhibit well-defined sol-gel tr…
Abstract Poly(lactide)s (PLAs) are well known hydrolytically degradable polymers, that are widely used for biomedical applications. However, the intrinsic brittle nature of poly(lactide)s is still poorly understood. The stiffness of a polymer chain, expressed as the characteristic ratio C ∞ plays an important role in…
The 1,2-bis[3,4,5-tris(alkan-1-yloxy)benzamido] ethanes (DA-n , where n is the number of carbons in the alkanyl group) form a high temperature hexagonal columnar (ϕh) liquid crystalline phase when n ' 10, 11, 12, 14, 16 and 18. DA-n with n ' 4, 5, 6, and 7 show at elevated temperatures a distorted hexagonal crystal ph…
Nitinol alloys (Nitinol) exhibit a dramatically enhanced elasticity, known as "superelasticity", which is becoming integral to the design of a variety of new medical products. Elasticity is the most apparent of the advantages afforded by this material, but by no means the only or most important. Also discussed in this…
Crack bifurcation was observed in laminar ceramic composites when cracks entered thin Al 2 O 3 layers sandwiched between thicker layers of Zr(12Ce)O 2 . The Al 2 O 3 layers contained a biaxial, residual, compressive stress of ∼2 GPa developed due to differential contraction upon cooling from the processing temperature…
The evolution of structural and magnetic properties of small chromium clusters towards the bulk is elucidated through a systematic density functional study. A tightly bound C${\mathrm{r}}_{2}$ dimer is found to play a key role in determining the cluster structures. A unique dimer growth route is discovered for cluster…
The ability of some microorganisms to use lactic acid stereocopolymers and copolymers with glycolic acid as sole carbon and energy sources was studied under controlled or natural conditions. First, 14 filamentous fungal strains were tested in liquid cultures, adopting total lactic acid consumption, nitrogen source exh…
A review is given of the optical properties of isotropic chiral media, based on the symmetrized constitutive relations of Condon. The review includes discussion of wave propagation in chiral media, and derivation of the reflection and transmission amplitudes of an isotropic optically active medium, and of a layer rest…
Factors affecting stacking fault formation during the synthetic fabrication of β‐SiC were investigated in the present study. Two main reaction routes in the carbothermal reduction of SiO 2 —solid–solid and solid‐gas reactions—led to the formation of β‐SiC, depending on the vapor pressure of the SiO gas. The β‐SiC form…
The outstanding feature of a diatom is the species-specific design and ornamentation of the silica-based cell wall, termed frustulum. A new frustulum is shaped in a specialized organelle (silica deposition vesicle) and secreted. Proteins in the lumen of this organelle may control the biomineralization process and are…
Abstract Thermoplastic elastomers (TPEs) exhibit the functional properties of conventional thermoset rubber, yet can be processed on thermoplastic fabrication equipment. The great majority of TPEs have hetero-phase morphology, whether the TPE is derived from block copolymers, rubber-plastic compositions or ionomers. G…
An approach to the synthesis of a new class of liquid crystalline (LC) compounds, dendrimers of regular structure with terminal mesogenic groups, was elaborated. LC dendrimers based on the carbosilane dendritic matrix of first generation were synthesized. Cyanobiphenyl, methoxyphenyl benzoate and cholesteryl groups we…
An extended photoluminescence (PL) study of porous silicon is presented. Different PL techniques have been used: continuous wave excited (cw) PL, selectively excited PL, excitation spectroscopy of the PL, time decay of the PL, and time resolved PL. These measurements have been performed on a set of samples of various…