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991.
Grain-boundary resistivity in yttria-containing tetragonal zirconia polycrystalline (Y-TZP) materials dominates the total resistivity. Impedance measurements combined with microstructural studies suggest that post-sintering heat treatments (in particular the cooling rate) influence the location of the grain-boundary phase which, in turn, has a significant effect on the grain-boundary resistivity. Higher cooling rates from the sintering temperature lead to reduction in the grain-boundary resistivity. In both alumina-containing and relatively pure tetragonal zirconia polycrystals, post-sintering heat treatments have a less conspicuous effect. The activation energy associated with the grain-boundary resistivity was independent of the post-sintering heat treatments but was 25 to 30 kJ mol–1 higher than that for the oxygen-ion conduction within the grains at low temperatures. 相似文献
992.
L. Vandewalle 《Journal of Materials Science Letters》1989,8(2):147-149
993.
994.
995.
The ring shape is a good solution to the study of the magnetization processes of magnetic materials because demagnetizing fields are easily avoided. However, when small samples are investigated, the magnitude of the field applied is necessarily limited by the low number of primary winding turns, and by the cross section of the wire itself. The use of sequential-type techniques for high current supply allows this problem to be avoided. One-cycle power production from the 50 Hz AC-line voltage is a simple example of such techniques. An electronic device designed around a commercial integrated circuit is described. A full period of current of 20-ms duration is applied to the load with a magnitude ranging from 0 to 100 A. Magnetization parameters of soft polycrystalline ring ceramics approaching the saturation region are studied as an application. The fitness to measure such characteristic parameters as saturation magnetization and magnetic hardness is shown 相似文献
996.
P. E. Donovan 《Journal of Materials Science》1989,24(2):523-535
The geometry of plastic flow under spherical and Vickers indentors in Pd40Ni40P20 metallic glass has been investigated by sectioning and etching. The surface pile-ups and slip lines around the indentations are found to be only a small part of the total deformation. Beneath the surface extensive plastic zones are formed in which material is moved radially away from the indentor, but this movement is produced by slip on surfaces of high shear stress rather than by direct radial flow or compaction. Networks of cracks or incipient cracks also form around an indentation but are not normally visible until the material is etched. 相似文献
997.
A voltage-controlled oscillator (VCO) with sine wave output has been built using a tunable inductor along with a tunable capacitor to operate at frequencies ranging from 100 kHz to over 20 MHz. The method of tuning the inductor by changing the permeability of its ferrite core and the ability to extend the frequency response of the core are discussed. Dynamic characteristics of the VCO are explained with examples of a parallel and series tank implementation 相似文献
998.
J. M. Richards M. I. Darby R. Baggott G. H. Wosteim Holm B. Yates G. Dorey L. N. Phillips 《Journal of Materials Science》1989,24(2):584-589
The effects of defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates have been measured. The defects studied were cut fibre plies, omission of polymer films and local delamination produced by the inclusion of foreign matter. Of these it was found that only cut plies had a significant detrimental effect on the strength of a laminate. For specimens with two cut plies, the failure stress, tensile, flexural and compressive in the remaining continuous plies was the same as in the defect-free material, provided that the cut plies were widely separated. However the failure stresses were 15–18% lower in the continuous plies in the specimens containing two cut plies which were more closely spaced and in specimens containing four cut plies. 相似文献
999.
Results of scanning electron microscopy (SEM) and energy dispersive X-ray analytical (EDAX) investigations, conducted on some elevated structures displayed by flux grown rare earth orthochromite, RCrO3 (R = La, Yb) crystals, are presented. The peculiar structures exhibited by crystal surfaces indicate imperfections and impurity phases. EDAX of elevated structures reveals the various phases to be composed of lead associated materials which may probably be either Pb2CrO5 or Pb2OF2 (flux). Other secondary crystallization of impurity phases, ROF (R = La, Yb) is illustrated in the case of RCrO3 (R = La, Yb) crystals. The elevated structures illustrate their non-stoichiometric behaviour. Precipitation of impurity phases and formation of imperfections during the growth of RCrO3 (R = La, Yb) crystals and their effect on the crystalline quality is discussed. 相似文献
1000.
L. B. Getsov A. Ya. Madorskii N. N. Mozzhukhina A. G. Tereshchenko E. E. Yushchenkov 《Strength of Materials》1989,21(1):92-98
Leningrad. Translated from Problemy Prochnosti, No. 1, pp. 71–76, January, 1989. 相似文献