Materials Literature
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The authors examine the problems involved in the application of the Maxwell stress equations for finite-element force calculations on magnetised ferrous cores. They also study the effect of the tangential magnetic field strength H/sub t/ on the accuracy of the force calculation. An effective H/sub t/ value is presente…
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We report the observation of an optically isotropic phase in the new disc-like mesogen 2,3,7,8,12,13-hexa(octadecanoyloxy)truxene. On cooling, this optically isotropic phase goes over into a nematic phase, while on heating a columnar phase grows in. To our knowledge this is the first example of a pure discotic mesogen…
The chemical compensation of p-type conducting polymers by ammonia gas can occur by several mechanisms, which lead to products of very different quality.
Abstract The influence of the removal of various diluents, pore forming agents from the porous styrene‐ethylstyrene‐acrylonitrile‐divinylbenzene copolymers on the structure of the matrix was investigated by several methods. The most advantageous pathway to preserve the initial structural edifice of the porous networks…
The crystal structures of piperidinium trichlorocuprate(II)[Hpip][CuCl3], and piperazinium hexachlorodicuprate(II), [H2pipz][Cu2Cl6], have been determined by X-ray diffraction techniques. [Hpip][CuCl3] is monoclinic, space group C2/c, with a= 18.385(7), b= 8.439(4), c= 11.878(5)Å, and β= 103.63(5)° while [H2pipz][Cu2C…
A novel, microporous, hydrophilic polyether urethane-urea (PEUU) vascular graft was compared with expanded PTFE in the canine carotid artery. At implantation times ranging from 4 h to 6 months, all the PEUU grafts were found to be occluded while of the PTFE grafts, only those implanted for 1 week and 6 months were blo…
A Preisach hysteresis model for the case in which Everett's function, E(H/sub 1/, H/sub 2/), has been defined from measurements of the magnetization change from a turning point H/sub 1/ to the field H/sub 2/. E(H/sub 1/, H/sub 2/) is the integral of the Preisach density function, whose symmetry imposes the relation E(…
Co2(CO)8, when absorbed in the gas phase, in vacuo, on fully dehydrated MgO, forms a variety of carbonyl clusters both neutral and ionic. These clusters disintegrate into monometallic species upon dosing with either CO or NH3, resulting in Co(CO)–4 and Co2+(CO)n(n= 2 or 3) with CO and Co(CO)–4 and Co2+(NH3)6 with NH3,…
Thin continuous metal coatings and a scanning electron microscope-generated spot size in the range of the visualized particles, are necessary prerequisites if one hopes to extract high-resolution topographic information in the scanning electron microscope. Chemical fixation and dehydration in organic solvents at room…
LaNi5 のような水素吸蔵合金を負極材料として使用するニッケル-水素電池を開発する上での解決もすべき問題点の一つは合金負極の高温域における容量低下である。本研究では, このような温度特性の改善を自的として, LaNi5 の Ni を Cu, Cr, Mn あるいは Al で部分置換した一連の合金を取り上げ,置換金属の種類と負極電位の関係ならびに放電容量の温度およびセル内圧依存性を平衡水素圧の点から検討した。その結果, LaNi5 の N iを Cu, Cr, Mn あるいは Al で部分置換するとこの順に平衡水素圧が低下するが, 同時に負極の平衡電位 (開路電位) が貴側に移動し, 電池電圧の低下をもたらすことが明らかとなった。…
Abstract Das Festwalzen weist nunmehr eine fast 60jährige Tradition auf und ist heute insbesondere in der Automobilindustrie fester Bestandteil zahlreicher Fertigungsprozesse. An der Entwicklung des Verfahrens hatte das Institut für Werkstoffkunde der TH Darmstadt großen Anteil. Nach einem kurzen historischen Rückblic…
Experiments were conducted to quantify the magnitude of galvanic currents and potentials that exist between metals (iron, copper, titanium, aluminum, chromium, and nickel) and their corrosion products in oxygen-containing environments. Current measurements using a zero resistance ammeter and potential measurements of…
Quantitative analyses by crossed immunoelectrophoresis were carried out on 31 eyes of 26 cataract patients, age 4-80 years, to detect age changes in the human aqueous humor especially in the following aqueous humor proteins: prealbumin, albumin, alpha 1-acid glycoprotein and transferrin. There was a significant correl…
Abstract The mechanical anisotropy of oriented PVDF sheet is examined using a variety of experimental techniques. The mechanical behavior is similar to that observed previously for low‐density polyethylene and nylon and consistent with a parallel lamellar crystalline structure. The s 31 compliance is reduced in magnit…
AM1 calculations are reported which demonstrate that the classical hydrogen migration in porphyrin occurs via a two-step mechanism, not a synchronous-concerted mechanism as has been previously supposed; the implications of this mechanism on tautomerization dynamics are discussed.
Phase transformations and the resultant microstructures of partially-stabilized zirconia (PSZ) are briefly reviewed with a special interest in the nature of phase transformations. The martensitic tetragonal-to-monoclinic transformation, which plays a principal role in toughening of PSZ, accompanies lattice defects suc…
Recent ideas on the mechanisms controlling the initial stages of plastic flow at cracks in intrinsically brittle materials, at the ductile-brittle transition, are reviewed. New experiments on precracked specimens of Si are reported, which confirm earlier work that the ductile-brittle transition is controlled by disloc…
The driving-force-generating principle of an actuator made of shape memory alloy (SMA) is based on the thermal elastic martensitic transformation, a kind of elastic phenomenon. As a result, conventional SMA actuators which use a circular pulley have tended to exhibit undesirable characteristics such as the maximum gen…
Some aspects of the testing of polymer blends by Dynamic Mechanical Thermal Analysis (DMTA) are reported. Compatibility of the blend components, which has a major influence on physical properties, can be well characterised. Data are presented for various types of blends, both compatible and incompatible. Plasticisatio…