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101.
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103.
Titanium oxides were reduced to metallic titanium using the liquid calcium floating on the molten CaCl2. A part of Ca dissolved into CaCl2 and reacted with TiO2 settled below CaCl2. The by-product CaO also dissolved by about 20 mol pct into CaCl2, which was effective in reducing the oxygen concentration in the obtained Ti particles. The compositional region in the Ca-CaCl2-CaO system was examined for the less oxygen contamination in Ti and the better handling in leaching. A large amount of the
residual calcium oxidized the titanium powder in leaching. The metallic Ti powder less than 1000 mass ppm oxygen could be
obtained only for 3.6 ks using 5 to 7 mol pct Ca-CaCl2 at 1173 K. The powder was slightly sintered like sponge, and contained approximately 1500 ppm Ca. The anatase phae, the intermediate
product in the refining process of TiO2, could be also supplied as raw material as well as rutile. 相似文献
104.
S. Danto P. Houizot C. Boussard‐Pledel X.‐H. Zhang F. Smektala J. Lucas 《Advanced functional materials》2006,16(14):1847-1852
Conditions of formation of bulk tellurium chalcogenide glasses, containing 70–80 at % Te associated to Ga and Ge are described. The characteristic temperatures are measured: the glass‐transition temperature, Tg, is situated in the range 140–185 °C and the difference Tx – Tg, where Tx is the onset crystallization temperature, is in the range 76–113 °C. Moreover, the optical transmission window is exceptional, ranging from 1.99 μm in the bandgap up to 28 μm in the phonon region. Developed within the framework of requirements for the Darwin mission (a search for and study of extrasolar planets), feasibility of infrared optical fibers formed from these glasses is studied. Drawing experiments are conducted with the glass Ga2‐Ge3Te15, which possesses the maximum Tx – Tg, and a first optical fiber is presented. 相似文献
105.
A second-order cross-coupled combline filter which has three finite transmission zeros is presented. The problem of the frequency-invariant coupling in a real circuit is introduced. To make extra transmission zeros, a top metalized dielectric block is used. 相似文献
106.
This paper presents the current understanding of the flame retardant mechanism of Casico?. The study includes the flame retardant effect of each individual component: ethylene–acrylate copolymer, chalk and silicone elastomer, as well as the formation of an intumescent structure during heating. The flame retardant properties were investigated by cone calorimetry and oxygen index tests. To obtain insight into the flame retardant mechanism, heat treatment under different conditions has also been performed. The results indicate that the flame retardant mechanism of Casico is complex and is related to a number of reactions, e.g. ester pyrolysis of acrylate groups, formation of carbon dioxide by reaction between carboxylic acid and chalk, ionomer formation and formation of an intumescent structure stabilized by a protecting char. Special emphasis is given to the formation of the intumescent structure and its molecular structure as evaluated from 13C MAS‐NMR and 29Si MAS‐NMR, ESCA and XRD analysis. After treatment at 500°C the intumescent structure consists mainly of silicon oxides and calcium carbonate and after treatment at 1000°C the intumescent structure consists of calcium silicate, calcium oxide and calcium hydroxide. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
107.
The stress-whitened damage zone that formed ahead of a semicircular notch during slow tensile loading has been measured from
optical micrographs of translucent blends of poly(vinyl chloride) (PVC) with experimental chlorinated polyethylene (CPE) resins.
When the zone was small, the plane strain condition applied and from the elastic stress distribution a constant mean stress
condition was found at the boundary of the crescent-shaped zone. The critical mean stress did not depend on the chlorine content
or the chlorine distribution of the experimental CPE resin used in the blend. While the critical mean stress decreased as
the amount of CPE in the blend was increased, the critical volume strain, calculated from the bulk modulus, was independent
of composition and was thought to be the controlling parameter for stress-whitening. When the zone was larger, the shape was
qualitatively described by concepts of stress redistribution in the presence of a plastic zone ahead of the notch. Macroscopic
flow and necking were only detected near the maximum in the stress-displacement curve. 相似文献
108.
Frdric Boschet Catherine Branger Andr Margaillan Thieo E Hogen‐Esch 《Polymer International》2005,54(1):90-95
The synthesis of 2,2,3,3‐tetrahydro‐perfluoroundecanoyl end‐functionalized polystyrene–poly(ethylene oxide) block (PS‐block‐PEO‐RF) copolymers and their matching PS‐block‐PEO diblock copolymers was carried out by sequential anionic polymerization. Viscometry and 19F NMR studies show that the PS‐block‐PEO copolymers, in contrast to their matching PS‐block‐PEO‐RF copolymers, exhibit a micellar rather than the associative behavior seen for the latter. However, the presence of an excess of fluorinated acid, used for end‐functionalization, produces a reduction of the associative behavior above the overlap concentration, with the fluorinated acid acting like a surfactant. A competition may also occur between PS—and RF—mediated micellization. Copyright © 2004 Society of Chemical Industry 相似文献
109.
Expanded polytetrafluoroethylene (ePTFE) membranes were modified by graft copolymerization with methacryloxyethyl phosphate (MOEP) in methanol and 2‐butanone (methyl ethyl ketone (MEK)) at ambient temperature using gamma irradiation. The effect of dose rate (0.46 and 4.6 kGy h?1), monomer concentration (1–40 %) and solvent were studied and the modified membranes were characterized by weight increase, X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XPS was used to determine the % degree of surface coverage using the C? F (ePTFE membrane) and the C? C (MOEP graft copolymer) peaks. Grafting yield, as well as surface coverage, were found to increase with increasing monomer concentration and were significantly higher for samples grafted in MEK than in methanol solution. SEM images showed distinctly different surface morphologies for the membranes grafted in methanol (smooth) and MEK (globular), hence indicating phase separation of the homopolymer in MEK. We propose that in our system, the non‐solvent properties of MEK for the homopolymer play a more important role than solvent chain transfer reactions in determining grafting outcomes. Copyright © 2005 Society of Chemical Industry 相似文献
110.
This paper proposes a new LDMOSFET structure with a trenched sinker for high‐power RF amplifiers. Using a low‐temperature, deep‐trench technology, we succeeded in drastically shrinking the sinker area to one‐third the size of the conventional diffusion‐type structure. The RF performance of the proposed device with a channel width of 5 mm showed a small signal gain of 16.5 dB and a maximum peak power of 32 dBm with a power‐added efficiency of 25% at 2 GHz. Furthermore, the trench sinker, which was applied to the guard ring to suppress coupling between inductors, showed an excellent blocking performance below ?40 dB at a frequency of up to 20 GHz. These results confirm that the proposed trenched sinker should be an effective technology both as a compact sinker for RF power devices and as a guard ring against coupling. 相似文献