Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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      28 January 2000, Volume 16 Issue 01 Previous Issue    Next Issue
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    Research Articles
    Universality and specificity of fractal dimension of fractured surfaces in materials
    Chiwei LUNG, Shenggang WANG
    J. Mater. Sci. Technol., 2000, 16 (01): 1-4. 
    Abstract   HTML   PDF (637KB)
    After calculation on the fracture angles under various conditions of special surface energies with different symmetry operations of rotation, the complicated behavior of dependence of fractal dimension on the structure of crystal is shown. It is found that the crack propagates along the weakest crystal plane no matter what the direction of the maximum stress is if the anisotropy is sufficiently strong, and then, the fractal dimension of the fractured surfaces might be determined by the approximate fractal structure already existed in the material. Specificity of the fractal dimension of fractured surfaces would be easy to appear in this case. Reversely, the crack propagates along the direction of the maximum stress no matter what direction of the weakest crystal plane is if the anisotropy is sufficiently weak. Universality of the fractal dimension of fractured surfaces would be possible to appear in this case. In many real materials, universality and specificity of the materials are associated. The fractal dimension measured may more or less be influenced by the structure of materials and it shows its universality through the specificity of materials.
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    Effect of crystallinity on electrochemical insertion/extraction of Li in transition metal oxides - Part II: TiO2, V2O5 and MoO3
    Tomoki TSUMURA, Michio INAGAKI
    J. Mater. Sci. Technol., 2000, 16 (01): 5-14. 
    Abstract   HTML   PDF (1915KB)
    Electrochemical insertion/extraction sf Li on cathode materials of anatase type TiO2, quasi-layered structure V2O5 and layered structure MoO3 was measured on samples of which structures were well characterized and showed a wide range of crystallinity. On the basis of experimental results on structure, morphology and charge-discharge characteristics, the effect of crystallinity of the cathode materials on electrochemical Li insertion/extraction performance was discussed. These three transition metal oxides were classified as one group on the basis of whether the crystallinity of these oxides affects to the performance or not, LiMn2O4 and LiCo0.5Ni0.5O2 belongs to the former group and TiO2, V2O5 and MoO3 to the latter.
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    Structure of the intermetallic compound Ni3Al synthesized under compression of the powder mixture of pure elements Part II: Influence of alloying by boron on the phase composition and the microstructure of grains of the main phase
    M. V.Fedorischeva, V.E.Ovcharenko, O.B.Perevalova, E.V.Kozlov
    J. Mater. Sci. Technol., 2000, 16 (01): 15-18. 
    Abstract   HTML   PDF (894KB)
    The Ni3B phase was formed when boron (0.5 at. pet B) was added to the intermetallic of stoichiometric and off-stoichiometric (Ni-24 at. pct Al) compounds. In the alloy of stoichiometric composition the particles of Ni3B phase has the size around 0.1 mu m and is located on the grain boundary of the main phase. The decreasing of concentrations of Al in the off-stoichiometric alloy leads to increase in the degree of the long-range order parameter, increasing the concentrations of boron in the solid solution and decreasing its localization on the grain boundary. Microalloying of boron leads to increasing in the fraction of grain monodomains with dislocations up to 0.7 in the alloy of the off-stoichiometric composition and up to 1 in the alloy of the stoichiometric composition. It was established the correlation between the degree of the concentration inhomogeneity, average density of the dislocations and the average long range-order parameter.
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    Nucleation and oriented textured growth of diamond films on Si(100) via electron emission in hot filament chemical vapor deposition
    Wanlu WANG, Kejun LIAO, Biben WANG
    J. Mater. Sci. Technol., 2000, 16 (01): 19-22. 
    Abstract   HTML   PDF (725KB)
    Oriented textured diamond films were obtained on Si(100) substrate via electron emission in hot filament chemical vapor deposition (HFCVD). A de bias voltage relative to the filament was applied to the tungsten electrode between the substrate and the filament. The nucleation and subsequent growth of diamond films were characterized by scanning electron microscopy and Raman spectroscopy. The experimental results showed that the electron emission from the diamond coating on the electrode played a critical role during the nucleation. The maximum value of nucleation density was up to 10(11) cm(-2) on pristine Si surface at emission current of 250 mA. The effect of the electron emission on the reactive gas composition was analyzed by in situ infrared absorption, indicating that the concentration of CH3 and C2H2 near the substrate surface was extremely increased. This may be responsible for the enhanced nucleation by electron emission.
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    Transparent conducting ZnO : Al films on different organic substrates deposited by r.f. sputtering
    Yuan CHEN, Deheng ZHANG, Qingpo WANG, Jin MA, Tianlin YANG
    J. Mater. Sci. Technol., 2000, 16 (01): 23-26. 
    Abstract   HTML   PDF (669KB)
    Transparent conducting ZnO:Al films with good adhesion, low resistivity and high transmittance have been prepared on polyptopylene adipate (PPA), polyisocyanate (PI) and polyester substrates by r.f. magnetron sputtering. The structural, electrical and optical properties of the obtained films were studied. The polycrystalline ZnO:Al films with resistivity as low as 5.76 x 10(-4) Omega.cm, carrier concentration 9.06 x 10(20) cm(-3) and Hall mobility 11.98 cm(2) V-1 s(-1) were produced on PPA substrate by controlling the deposition parameters. The average transmittance of films on PPA is similar to 80% in the wavelength range of visible spectrum. The films on PPA substrates have better electrical and optical properties compared with the films on other kinds of substrates.
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    Electromagnetic confinement and shaping for plate-form p
    Jun SHEN, Jianguo LI, Hengzhi FU, Junyi SU
    J. Mater. Sci. Technol., 2000, 16 (01): 27-32. 
    Abstract   HTML   PDF (1005KB)
    The relationship between melt shape, electromagnetic pressure and magnetic field is studied for electromagnetic confinement and shaping of plate-form part. The results of experimental observation and theoretical inference can be summarized as follows. As the melt thickness a is large enough, causing the ratio of plate thickness to current theoretic skin depth a/delta larger than 2.2, the electromagnetic pressure acting on melt can be simply expressed as P-m = B-2/2 mu, and the melt shape would be known only by measuring the distribution of magnetic flux density As a is small and makes the ratio a/delta less than 2.2, the melt shape and electromagnetic pressure for confining and shaping are determined not only by magnetic flux density B but also by melt thickness a, electromagnetic parameter mu gamma and current frequency f. In this paper, an equation used to calculate electromagnetic pressure acting on "thin plate-form melt" is brought forward. The equation gives a precise relationship between electromagnetic pressure factor p and melt thickness a, electromagnetic parameter mu gamma and current frequency f.
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    Effect of melt quenching on martensite transformation in Fe-Ni alloy
    E.N.Blinova, A.M.Glezer, M.N.Pankova
    J. Mater. Sci. Technol., 2000, 16 (01): 33-36. 
    Abstract   HTML   PDF (943KB)
    The main features of martensite transformation in melt-quenched Fe-31.4% Ni alloy on cooling below room temperature have been studied. It is found that the ribbon 50 similar to 60 mu m thick, prepared by spinning technique, is a natural composite in which isothermal and surface martensite are not formed, while athermal martensite forms at lower temperature, all factors being the same, as compared to the alloy of the same composition and grain size, prepared by recrystallization.
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    General properties of low-frequency power losses in Fe-based nanocrystalline soft magnetic alloys
    Yanzhong ZHANG, Huijuan JIN, Ying SHI
    J. Mater. Sci. Technol., 2000, 16 (01): 37-44. 
    Abstract   HTML   PDF (1295KB)
    The dependences sf the power loss per cycle on frequency f and amplitude flux density B-m have been investigated for the three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys in the ranges of 10 Hz less than or equal to f less than or equal to 1000 Hz and 0.4 T less than or equal to B-m less than or equal to 1.0 T. The total loss P is decomposed into the sum of the hysteresis loss P-hyst, the classical eddy current loss P-el and the excess loss P-exc. P-hyst has been found to be proportional to B-m(2) and f. The behavior of P-exc/f vs f being equivalent to P/f vs f clearly exhibits nonlinearity in the range not more than about 120 Hz, whereas the behavior of P/f vb f roughly shows linearity in the range far above 100 Hz and not more than 1000 Hz. In the range up to 1000 Hz, P-hyst is dominant in the original high permeability state and the state of low residual flux density, whereas P-exc, in the state of high residual flux density is dominant in the wider range above about 100 Hz. The framework of the statistical theory of power loss has been used for representing the behavior of P-exc/f vs f. It has been found that the number n, of the simultaneously active "Magnetic Objects" linearly varies as n = n(0) + H-exc/H-0 as a function of the dynamic field H-exc in the range below about 120 Hz, whereas n approximately follows a law of the form n = n(0) + (H-exc/H-0)(m) with 1 < m < 2 in the range far above 100 Hz and not more than 1000 Hz. The values of the field Ho in principle related to the microstructure and the domain structure have been calculated for the three states.
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    Effect of molybdate ions on the corrosion behaviour of Ti alloys
    Magda.M.A.Gad, Kamal.E.Mohamed, Abdelwahab A.El-Sayed
    J. Mater. Sci. Technol., 2000, 16 (01): 45-49. 
    Abstract   HTML   PDF (973KB)
    Titanium alloys are extensively used in power, chemical and petroleum industries as constructional materials for vessels and heat transfer tubes. Moreover they are candidate materials for nuclear waste disposal. These alloys have superior resistance to localized forms of corrosion compared to stainless steels and Ni-base alloys. However, this resistance is not as remarkable in crevice corrosion conditions in some aggressive media. Electrochemical corrosion tests were conducted on two ASTM Ti grades namely, Ti-2 and Ti-12 in extremely low pH acidic environment. Results indicated that Ti-2 has less resistance to both general and crevice corrosion attack than Ti-12. Both alloys possess better resistance to general corrosion than to crevice corrosion. Also, results showed that the molybdate addition improves remarkably the resistance of Ti-2 to both types of attack. The increase of molybdate ions concentration from 0.03 mol/L to 0.15 mol/L made Ti-2 to be as resistant as, or somewhat higher than, Ti-12. The elecrochemical findings were further supplemented by optical examination of the corroded surface.
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    Formation of ultrafine metal particles and metal oxide precursor on anodized Al by electrolysis deposition
    Lingchuan LI
    J. Mater. Sci. Technol., 2000, 16 (01): 50-54. 
    Abstract   HTML   PDF (1119KB)
    Nickel was deposited by ac electrolysis deposition in the pores of the porous oxide film of Al produced by anodizing in phosphoric acid. Ultrafine rod-shaped Ni particles were formed in the pores. At the same time a film of Ni oxide precursor was developed on the surface of the porous oxide film. The Ni particles and the Ni oxide precursor were examined by SEM, TEM and X-ray diffraction. The thickness of the barrier layer of the porous oxide film was thin and it attributed to the formation of the metal particles, while the formation of the oxide precursor was associated with the surface pits which were developed in the pretreatment of Al.
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    Mechanical behaviour and microstructure evolution of superplastic Mg-8.4 wt pct Li alloy and effect of grain size and phase ratio on its elongation
    Furong CAO, Jianzhong CUI, Jinglin WEN, Fang LEI
    J. Mater. Sci. Technol., 2000, 16 (01): 55-58. 
    Abstract   HTML   PDF (1074KB)
    Mechanical properties and microstructure evolution of Mg-8.4 wt pet Li alloy have been investigated. The superplastic elongation-to-failure 920% at 573 K and initial strain rate of 5 x 10(-4) s(-1) at low nominal stress 2 MPa has been demonstrated. It was shown through optical microstructure that the average grain sizes at gauge length section before and after superplastic tension and at grip section were 7.5 mu m, 31.7 mu m and 20 mu m respectively, indicating significant deformation induced grain growth and static grain growth. Comparison of experiment data with published data for superplastic Mg-Li alloys shows that fine grain size and about 50 to 50 phase ratio contribute to achieving the largest superplasticity. Some related research works in other alloys are compiled and further evidences to such theoretic argument are provided.
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    Microstructural features of friction-welded Ti-6Al-4V joint
    Daqian SUN, Zhenan REN, Zhenfeng ZHOU, T.North, Yang ZHAI, S.Sathian
    J. Mater. Sci. Technol., 2000, 16 (01): 59-62. 
    Abstract   HTML   PDF (1116KB)
    Microstructural features of friction-welded Ti-6Al-4V joint have been investigated by both optical microscope and transmission electron microscope (TEM). The microstructure of the welded joint is not uniform. It can be classified into the phase transformed region(P), the deformed region(D) and the region of unchanged base metal(B). In the phase transformed region, the microstructure consists of platelike, acicular and equiaxed alpha phase plus beta phase between them and the dislocations can be observed in some or phase particles. The equiaxed alpha phase mainly distributes in the near center of rod specimen. The quantity of platelike and acicular alpha phase and the size of the grains increase progressively along the radial direction of the rod type welded joint. In the deformed region, the grains are reoriented and the microstructure consists of the elongated alpha phase containing a lot of dislocations and intergranular beta phase.
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    Microstructure and properties of plasma spraying boron carbide coating
    Yi ZENG, Jingwei FENG, Chuanxian DING
    J. Mater. Sci. Technol., 2000, 16 (01): 63-66. 
    Abstract   HTML   PDF (1330KB)
    Microstructure of plasma spray boron carbide coating was studied by SEM and TEM. Its physical, mechanical and electrical properties were measured. The results showed that high microhardness, modulus and low porosity of B4C coating were manufactured by plasma spray. It was lamellar packing and dense. The B4C coating examined here contained two principal structures and two impurity phase besides major phase. The relatively small value of Young's modulus, comparing with that of the bulk materials, is explained by porosity. The Fe impurity phase could account for the relatively high electrical conductivity of boron carbide coating by comparing with the general baron carbide materials.
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    The method of single peak Fourier analysis of measuring the size of mosaic block and microstrain by X-ray diffraction
    Ming CHANG
    J. Mater. Sci. Technol., 2000, 16 (01): 67-70. 
    Abstract   HTML   PDF (676KB)
    The values of mosaic block size and microstrain measured by the method of Voigt function are sometimes largely erroneous and difficult to be revised. In this paper, the causes of the "hook effect" which inevitably exists in the method of Fourier analysis are explained, then the method for resolving this effect is put forward, and finally the method of hypothetical function is used to simplify the method of the Fourier analysis from multi-peak to single-peak. By introducing the parameter m, this method can not only indicate the degree of errors, but also revise them as well. It is simple, clear and able to accomplish the intricate pattern calculation quickly by the aid of computer. In the end, we argue the identity between method of the approximate function and the Fourier analysis, and give a more accurate proportional coefficient k.
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    Thermodynamic stability of LiFeO2 in molten carbonate fuel cell
    Licheng YAN, Wencong LU, Yimin DING, Jianhui MNG, Nianyi CHEN, Guangyi CAO, Jianxin ZHU
    J. Mater. Sci. Technol., 2000, 16 (01): 71-72. 
    Abstract   HTML   PDF (248KB)
    LiFeO2, as one of candidate cathode materials or additive for molten carbonate fuel cell, has been found to be thermodynamically unstable in CO2 atmosphere at 650 degrees C (the condition of molten carbonate fuel cell) both by computation and experimental confirmation.
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    Effects of distribution of induced defects on positron diffusion
    Xinzhang ZHOU, Jian JIANG, Chiwei LUNG
    J. Mater. Sci. Technol., 2000, 16 (01): 73-75. 
    Abstract   HTML   PDF (320KB)
    The effects of distribution of induced defects on the positron diffusion was studied by using the point-source diffusion model and delta function method.
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    A research on investment casting technology of Ti alloys
    Huiguan WAN, Xiumei QI, Jing TIAN, Yuyong CHEN, Weiqiang ZHA, Jun JIA
    J. Mater. Sci. Technol., 2000, 16 (01): 76-78. 
    Abstract   HTML   PDF (545KB)
    In this research, the materials and the compositions of the surface slurries were chosen by considering the characteristics of Ti investment casting. The effects of solid-liquid ratios on the properties of the slurry and the effects of baking temperatures on the flexural strength have also been investigated. Flawless shells having smooth inner surface were manufactured with proper technology. Ti and its alloys were melted and poured by water-cooled Cu crucible vacuum induction furnace. The qualities of the investment castings made accordingly were studied and analyzed.
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    Formation mechanism of curved martensite structures in Cu-based shape memory alloys
    Yujun BAI, Qiquan SHI, Guili GENG, Dongsheng SUN, Xiufang BIAN
    J. Mater. Sci. Technol., 2000, 16 (01): 79-81. 
    Abstract   HTML   PDF (824KB)
    The curved martensite structures have been observed in CuZnAl-based shape memory alloys by both transmission electron microscope and optical microscope. It was found that the curved martensite structures observed in as-solution treated, as-aged and as-trained alloys usually occurred around dislocation tangles or precipitate, at the plate boundary or grain boundary, and when the growing plates collided with each other or alternate mutually.
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    Activity of VO in molten ternary CaO-SiO2-VO slag
    Yanwen TIAN, Yuchun ZHAI, Xin ZHANG
    J. Mater. Sci. Technol., 2000, 16 (01): 82-84. 
    Abstract   HTML   PDF (386KB)
    The activity of VO in molten ternary CaO-SiO2-VO slag has been determined by chemical equilibrium method, using tin as the solvent metal. The relation between the activity and the content of VO, as well as the effect of slag basicity on activity of VO, are discussed.
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    A prediction of the excess partial molar free energies of MgCl2 in the KCl-MgCl2-LiCl molten salt system containing MgCl2 below 0.5 from thermodynamic properties of binary systems
    Quanru ZHANG, Yuangao LI, Zheng FANG
    J. Mater. Sci. Technol., 2000, 16 (01): 85-87. 
    Abstract   HTML   PDF (489KB)
    The thermodynamical properties of MgCl2 in KCl-MgCl2-LiCl molten electrolytes containing MgCl2 below 0.5 (mole fraction, the same below) have been determined from the interchange energies of two binary systems KCl-MgCl2 and LiCl-MgCl2, by means of a model on the assumptions that the electrolytes in the solution are treated as independent particles instead of their ion forms and the interchange energy between the component pair KCl-LiCl is ignored when compared with those of component pairs KCl-MgCl2 and MgCl2-LiCl. The interchange energies, omega(KCl-MgCl2) and omega(MgCl2-LiCl) are obtained as -70000 and -13800 J.mol(-1), from the corresponding binary solutions, respectively.
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    Oxidation behaviour of sputtered Ni-3Cr-20Al alloy
    Guofeng CHEN, Hanyi LOU
    J. Mater. Sci. Technol., 2000, 16 (01): 88-90. 
    Abstract   HTML   PDF (958KB)
    The oxidation behavior of sputtered Ni-3Cr-20Al coating at 900 degrees C in air was investigated. A dense Al2O3 layer was formed on the sputtered Ni-3Cr-20Al coating after 200 h oxidation. However, owing to the segregation of Ni3Al during oxidation process at high temperature, the spinel NiAl2O4 was also formed in the Al2O3 layer. It was found that the formation of NiAl2O4 had no detrimental effect on the oxidation resistance of the sputtered Ni-3Cr-20Al coating due to the excellent adhesion shown by the Al2O3 and NiAl2O4 complex oxide scale.
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    New phase Ti3Co2Si in the Ti-Co-Si ternary system at 1100℃
    Xianhua HU, Guoliang CHEN, Cinca Ion, Kequan NI
    J. Mater. Sci. Technol., 2000, 16 (01): 91-93. 
    Abstract   HTML   PDF (580KB)
    A new phase with the appropriate composition of Ti3Co2Si is found to exist at 1100 degrees C. The X-ray diffraction of this phase can not be indexed by any other phase in the Ti-Co-Si ternary system and show this phase to be hexagonal with the lattice parameter of a=0.676 nm, c=0.732 nm, c/a=1.0825.
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    High quality SiGe layer deposited by a new ultrahigh vacuum chemical vapor deposition system
    Guangli LUO, Xiaofeng LIN, Peiyi CHEN, Peixin TSIAN
    J. Mater. Sci. Technol., 2000, 16 (01): 94-96. 
    Abstract   HTML   PDF (525KB)
    An ultrahigh vacuum chemical vapor deposition (UHV/CVD) system is developed and the details of its construction and operation are reported. Using high purity SiH4 and GeH4 reactant gases, the Si0.82Ge0.18 layer is deposited at 550 degrees C. With the measurements by double crystal X-ray diffraction (DCXRD), transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS) techniques, it is shown that the crystalline quality of the SiGe layer is good, and the underlying SiGe/Si heterointerface is sharply defined.
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ISSN: 1005-0302
CN: 21-1315/TG
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