Materials Literature
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The enzymes phosphotransacetylase (PTA) and acetate kinase (AK) catalyze the conversion of acetyl coenzyme A to acetate in the fermentation of Clostridium acetobutylicum. The acetate-producing step is an important element in the acidogenic fermentation stage and generates ATP for clostridial cell growth. The genes pta…
Aromatic diamines react with pyromellitic dianhydride in solvents such as dimethyl-acetamide to form solutions of high molecular weight polyamic acids. These soluble polymers can be converted to insoluble aromatic polyimides. The aromatic poly imides exhibit zero strength temperatures above 700°C. and possess excellen…
Other| August 01, 1996 Ab initio calculations on aluminosilicate Q 3 species; implications for atomic structures of mineral surfaces and dissolution mechanisms of feldspars J. D. Kubicki; J. D. Kubicki NCCOSC RDT&E, Remediation Research Laboratory, San Diego, CA, United States Search for other works by this author on:…
This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and ...Read More
Abstract Synthetic hectorite clay minerals were hydrothermally crystallized with direct incorporation of a series of five water-soluble polyvinyl alcohols (PVA) of molecular weights from 9000-146,000. The molecular weight of PVA had little effect on the success of hydrothermal hectorite synthesis, d-spacing or the amo…
The sintering of ultrafine γ‐Al 2 O 3 powder (particle size ∼10–20 nm) prepared by an inert gas condensation technique was investigated in air at a constant heating rate of 10°C/min. Qualitatively, the kinetics followed those of transition aluminas prepared by other methods. Measurable shrinkage commenced at ∼ 1000°C…
Abstract 13 C NMR analysis of the chain‐end distribution of poly(propylenes) prepared using the highly active catalyst system MgCl 2 /TiCl 4 /diether—AlEt 3 has revealed particularly high proportions of butyl chain‐ends in polymers prepared at relatively low hydrogen pressures. This indicates that the high sensitivity…
We have performed a molecular-dynamics simulation for a sample of amorphous ${\mathrm{SiO}}_{2}$ subject to a compression-decompression process at ambient temperature, using a recently proposed two-body potential model. For moderate compression the simulated glass maintains the ideal tetrahedral coordination and displ…
Abstract Enzymatic ring‐opening polymerization of a 16‐membered lactone, 15‐pentadecanolide (PDL), has been carried out in bulk using various lipases of different origin as catalyst. The polymerization with Pseudomonas fluorescens lipase (lipase PF) catalyst afforded the corresponding polyester in high yields. The rat…
During sample preparation, the coarse fraction (> 2 mm) of soils is commonly excluded from further analytical determinations. Our results demonstrated, however, that the coarse fragments of soils derived from sandstone in Tuscany, Italy, are not chemically inert. From an intensive study of the clasts from three profil…
We calculate the free energy of a model for a polymer melt in a computer simulation of the bond-fluctuation model and determine the entropy of the melt over a wide range of temperatures, including the region close to the glass transition. The results are compared with the Gibbs-DiMarzio theory, a theory by Flory for s…
Thick films of lead zirconate titanate of the morphotropic phase boundary composition, Pb(Zr 0.52 Ti 0.48 )O 3 , have been fabricated on platinum‐buffered silicon using a modified sol–gel spin‐coating technique. Crack‐free films of 12‐μm thickness can be uniformly deposited on 3‐in.‐diameter wafers with high yield and…
Recently, it has been argued that a strong electron-phonon interaction arising from the Jahn-Teller splitting of the outer Mn $d$ level plays a crucial role in understanding the nonmetal-to-metal transition observed in the ${\mathrm{La}}_{1\ensuremath{-}x}{A}_{x}\mathrm{Mn}{\mathrm{O}}_{3}(A=\mathrm{C}\mathrm{a},\phan…
Crosslinking behavior of internal acetylene units linked para to the aromatic rings was investigated by preparing polyimide from 4,4′-diaminodiphenylacetylene (p-intA) and 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). Polyimide was also prepared from 1,4-phenylenediamine (PDA) and 6FDA for compari…
The glass transition, onset crystallization, solidus, and liquidus temperatures of a ZBLAN glass have been measured by differential thermal analysis in a sealed Pt ampoule. The onset crystallization was observed at 335°C for a powdered glass, while for a monolithic glass, prepared by in situ quenching in the Pt capsul…
UV-curable transparent epoxy adhesives have been specifically developed for the fabrication of optical communictions precision devices. The newly developed adhesives using cylohexane type fluoro-epoxy as the base resin and speherical quartz filler have extremely low volume shrinkage of 1.2% during curing and the cured…
In order to evaluate the thermal conductivity of oxidized fuel pellets of leaker fuel rods, UO2+x samples with x between 0.00 and 0.20 were prepared by an oxidation or a sintering method. Sample thermal diffusivities were measured by using a laser flash method from 300 to 1,400 K and their thermal conductivities were…
An alternating copolymer of N-methylmaleimide and isobutene was produced by a radical precipitation polymerization method. The copolymer thus produced is a new class of transparent polymeric material that shows a unique balance of optical, thermal, and mechanical properties. The visible light transmittance was more th…
High‐purity alumina powder with submicrometer particle size was colloidally dispersed and classified in either water or ethanol to remove agglomerates from as‐received powder. After the slurries were dried, fine alumina particles cohered to form agglomerates, which were “hard” when formed in a water slurry, and “soft”…
Cathodic and anodic behaviour of aluminium has been investigated in AlCl3DMSO2—dimethylsulfone—(1 mole/kg) electrolyte at 130 °C by current reversal chronopotentiometry (CRC) and chronoamperometry. Al deposition study showed that a diffusion-limited current density close to 83 mA cm−2 is reached for potentials less th…