Key Engineering Materials Vols. 336-338

Abstract: The electronic structure and magnetic properties of Ni/Al2O3/Ni tunnel junctions with O-terminated and Al-terminated interface models are investigated by first-principles discrete variational method with the local-spin-density approximation. The results show that the interface atomic has an important effect on interface electronic state and spin polarization as well as TMR ratio. For the O-terminated and Al-terminated interface models, spin polarization at Fermi level of Ni layers exhibit negative. It is found that absolute value of spin polarization as well as TMR ratio of Al-terminated interface models is much larger than that of O-terminated interface, which shows over-oxidization of Al layer could deteriorate magnetoresistance properties.

Abstract: The surface morphology of film material directly affects its physical performance. It is of great significance for finding out its prospective physical performance to characterize the surface morphology of film material. It is hard to characterize them with some conventional methods. The surface morphology of film material was described from the fractal point of view, and the dimension was correlated with the resistivity of material. The [100]-orientated diamond film was primarily investigated. The results show that the greater the crystal grain is, the more uniform and regular the orientation is; and the more compact the arrangement is, the greater the fractal box dimension is. Moreover, when fractal box dimensions were within a certain range approximately from 2.92 to 2.97, it presents positively correlative relation with the logarithm of resistivity, Log(ρ), which resembles the Logistic curve. However, when the other dimensions are beyond the range mentioned above, resistivity doesn’t change with the increase in dimensions of fractal. This study will conduce to illustrating the relationship between the structure of crystal exemplified by arrangement and physical performance as well as material preparation.

Abstract: This paper presents the effects of ceramic fillers on light reflectance and arc resistance of PTFE(polytetrafluoroethylene) for nozzle of circuit breaker. In arc environment of a circuit breaker, radiation generated from arcing is considered to play a key role in transport mechanism of arc energy to the wall. Adding some ceramic fillers into PTFE material is expected to be efficient for improving the endurance against arc radiation. In this experiment, three kinds of ceramic fillers for achieving good endurance in the high temperature were used. Light reflectance and arc resistance of PTFE composites were investigated. The arc resistance of PTFE composites increased with the amount of ceramic fillers. The light reflectance of PTFE composites filled with ceramic fillers increased in the long wavelength region and decreased largely in the short wavelength region in comparison with that of pure PTFE.

Abstract: A wet-chemical deposition method was developed to synthesize CeO2-mica pearlescent pigment using CeO2 as the coating material and mica as the base material. The main factors affecting the synthesis processes were studied. The optimum conditions were obtained were as: the coating reaction temperature is 70 ~ 80°C, cover ratio is 30 ~ 40%, stirring velocity is about 170 r/min, pH value is 6.50 ~ 7.50, heating rate is 3 ~ 5°C/min and heat treatment temperature is 800°C. The crystal phases and the microstructure of the pearlescent pigment powders were also analyzed by DTA-TG, XRD and SEM.

Abstract: It is the easy and widely used way to make light calcium carbonate and magnesium carbonate from dolomite by carbonizing process. During this process, the dolomite is calcined at different temperature, from 700°C to 950°C to get the mixture including either calcium carbonate and magnesia or calcia and magnesia. Then the mixture is blended with water in different temperature from room temperature to 80°C. As a result, it is supposed to get calcium hydroxide and magnesium hydroxide, but XRD analysis reveals that it is not accord with the theory. Magnesium hydroxide can not be obtained during this reaction. After the carbonization process, the calcium carbonate and a kind of mixture which is composed with different crystal phase of Mg5(CO3)4(OH)2[H2O]4 have been produced, instead of magnesium carbonate. The magnesia is gotten when the mixture is calcined at 450~750°C.

Abstract: The citations to articles published in Applied Physical Letters (APL) and Journal of the American Ceramic Society (JACS) were analyzed. For each journal, 199 articles published in 1995 were randomly selected and the number of citations in each year, CY, to these articles during 1996 ~ 2004 were recorded. It was found that CY reaches its maximum in 1997 for APL and in 1999 for JACS. During the first three years after the year when the articles were published, the number of self-citations to the articles published in APL is about two times of that in JACS. These results seem to indicate that the impact factor, which is defined as the ratio of the number of citations to a journal to the number of articles published in this journal over a two-year period, is not comparable for different journals in different fields.

Abstract: The grain characteristics of four kinds of ZrO2 nanocrystalline powders were manifested and discussed in this paper. The grain size of sample 1 tested by XRD, TEM and BET is consistent. The agglomeration coefficient of Sample 1 is higher, about 62.5, and the span of grain distribution is 14.58. The grain sizes of Sample 2 and 3 tested by XRD, TEM and BET are different. These differences identify the crystalline domain including 2~3 unite, which make the departure spheres in TEM. There are more soft agglomerates in Sample 2 with the agglomeration coefficient of 25.71 and the span of grain distribution being 18.94 than that in Sample 3 with the agglomeration coefficient of 6.89 and the span of grain distribution being 8.91. The grain sizes of Sample 4 tested by XRD, TEM and BET are obviously different. That identifies the large hard agglomerates.

Abstract: This paper analyzed 6 public ceramic companies listed in Chinese “A” share market, comparing their profit ratio from principal business, return of net assets, equity structure and principal business scope with each other. The conclusion is that the capability to earn profit is poor among them, then we discussed about how to improve companies’ profitability.

Abstract: Two different designs of high fracture toughness micro-laminate ceramics were produced containing 50 μm thick Si3N4 layers and 100 μm thick Si3N4 + TiN layers. The first design with external tensile layers had a predicted maximum apparent fracture toughness of 10.5 MPa m1/2. The second design with external compressive layers had a predicted maximum apparent fracture toughness of 18.0 MPa m1/2. The fracture toughness of these micro-laminates was tested by the SEVNB method. A stiff testing machine was used to measure the R-curve behavior by observing crack growth in single notched specimens. A soft testing machine was used to measure the R-curve behavior using several specimens with notches at different depths.

Abstract: The morphology and phase structure of Al/Cu explosive compounded interface were observed by scanning electron microscope, high-resolution transmission electron microscope and X-ray energy spectrometer. The results reveal that the interface of Al/Cu appears wave-like structure, with an average wavelength of 1.0mm and crest height of 0.3mm. Every wave has its front-nest. The wavelike interfaces are composed of microcrystal compound layer, non-crystal and nanocrystal. Several kinds of compounds such as Al9Cul2, Al4Cu9, Al2Cu, η-AlCu, β-AlCu3 and unidentified phase structure were found in Al/Cu interface. There are some bent lattice fringes around the front-nest. The research of microstructure in anchoring area revealed the nature of explosive cladding in metallurgical anchoring.