Materials Literature
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The crystal structure of poly (p-benzamide) was determined by the X-ray diffraction method. All reflections were indexed by an orthorhombic unit cell with dimensions of a=7.74(2), b=5.27(1), and c=12.82(5)Å The space group symmetry was P212121. The unit cell contains two 21-helix polymer chains. The detailed structure…
Abstract Copper, cobalt, nickel and tin metal complexes of 4‐amino‐3‐hydrazino‐5‐thio‐1,2,4‐triazole (I) have been prepared and their structure identified through IR and electronic spectra measurements. The cobalt and nickel have been found to be octahedral; on the other hand, a mixed structure is proposed for the cop…
Le saccharose dissous dans l'eau de gâchage intervient tres tot dans le processus d'hydratation
A study of the stability of two types of carbon resistive paste based on polyimide is reported. Experiments on electrical properties of these thick-film resistors at elevated temperatures are recorded, and the electrical conduction mechanism in thick-film resistors is demonstrated. The conduction mechanism follows clo…
Abstract Hamiltonian circuits with associated word an n -cycle, in Schreier right coset graphs for symmetric groups S n mod cyclic groups Z n , correspond to change ringing principles on n bells for which the plain course is the extent; that is, neither bobs nor singles are required. This connection is made explicit f…
Composite oxide films were formed anodically on hydroxide-covered aluminum in a boric acid/borate solution at 40, 60, 80, and 95°C, and then relaxed by allowing water to penetrate into the voids in the oxide films. After relaxation, specimens were re-anodized with a low current to measure the time-variation in the ano…
The variation of the open circuit potential (OCP) of aluminium with time (60–200 h) of immersion in 1M NaCl solution has been studied. The effect of aluminium purity and surface treatment, oxygen content and pH of the solution, and inhibitor additions were investigated. The two mixed potentials generally observed were…
Arteries of mice were studied by a silver impregnation technique, by the Picrosirius-polarization method and by transmission electron microscopy. The histochemical results obtained coincided with the electron-microscopic observations in showing the presence of two distinct collagen populations, segregated into differe…
The electron-density distribution in a crystal of LiTaO3 has been investigated with the single-crystal X-ray diffraction method. The crystal has the cell dimensions a=5.15329(7) and c=13.7806(5) Å with the space group R3c and Z=6. Residual electron densities due to anharmonic thermal vibration were observed around the…
The magnetization process in NiFeMo alloys with vanishing anisotropies and variable grain sizes has been investigated through complementary hysteresis loop studies and Barkhausen effect experiments. It is found that the coercive field H varies as s/sup -1/, while the constants a and b of the Rayleigh law I=aH+bH/sup 2…
The main pollinators of Calotropis procera (Arr.) A.IT. f. subsp. hamiltonii (WIGHT) AL1 in the area of Karachi are males and females of Xylocopa pubescens SPIN. and females of X . fenestrata (F.) (Anthophoridae). Workers of Apis florea F . (Apidae) are minor pollinators. The activity of the pollinators (measured as t…
22% Cr-3% Mo duplex stainless steels in which Ni and N contents were varied independently were prepared and base metal and TIG weld metal were subjected to pitting corrosion tests in 6% FeCl3. The critical pitting temperature at which pitting corrosion occurred was evaluated and the pitting site was observed. The pitt…
The breakdown of SF/sub 6/ when static and impulse voltages are applied at small values (from 10/sup -4/ bar-mm to 1 bar-mm) of the product pd was investigated. It was found that the prevailing breakdown mechanism up to 8*10/sup -3/ bar-mm was the Townsend mechanism. Between 8*10/sup -3/ and 5.5 bar-mm the Townsend an…
As for the steels for wheel rim, CC killed steel will be more prevalent instead of rimmed steel in accordance with the increase of CC ratio in steel production. In addition, from the point of weight reduction of cars, high strength steels are tried to put into practice. As far as wheel rim is concerned, flash weldabil…
The dynamic-compression properties of carpet are expected to play an important role in their mechanical performance. An investigation is described in which the dynamic properties were measured by using a reaction mass-vibration system at frequencies in the range 20–85 Hz. The dynamic-compression modulus and damping we…
Cathodic delamination of neoprene-to-steel adhesive bonds prepared using a proprietary vulcanizing adhesive and primer was investigated using Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Chlorinated rubber in the adhesive and primer was stable during immersion in NaOH solu…
A series of dealuminated mordenites has been studied by infrared structural spectroscopy. Linear correlations were found between the wavenumber and the relative absorbance of one specific skeletal vibration and the structural aluminium content as determined by 27Al m.a.s.n.m.r. spectroscopy. Based on these results thi…
Failure analysis was conducted on three modular cast-iron globe valves of different sizes used in flowing seawater cooling systems. The 3-in. valve suffered from cavitation corrosion and erosion cracks. In the larger valves, intensified localised attack was found under voluminous scales. In all valves, galvanic corros…
Abstract This article focuses on the machining of reactive metals which refer collectively to the elements titanium, hafnium, and zirconium. It provides guidelines for machining titanium and titanium alloys and describes machining operations, such as turning, milling, drilling, tapping, reaming, grinding, and sawing,…
In South Africa and in the rest of the world, the two mica minerals that have the most important commercial value are muscovite and vermiculite. Muscovite has been making a comparatively small but steady contribution to South Africa's mineral exports since about 1960. Vermiculite mining and concentration were started…