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Journal of Materials Sciences & Technology
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1997, Vol.13 No.4
Online: 1997-07-28
Articles
 
Articles
241 N.H.Marcn(Oxford University Oxford, England)
Cluster and Condensed Phase Properties of Light Elements (especially B, C, N, Na and Si)
Amorphous forms of C will first be compared and contrasted with amorphous Si, the differences in chemical bonding being emphasized in relation to atomic structure. After a brief discussion of ordered layers of graphite and of BN, some attention will be focused on BN cages and polymers and on C nanotubes. Finally properties of Na metal clusters will be discussed, including fission of such charged clusters
1997 Vol. 13 (4): 241-244 [Abstract] ( 216 ) [HTML 1KB] [PDF 392KB] ( 221 )
245 W.H.Soe and R.Yamamoto(Institute of Industrial Science, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106, Japan )
Mechanical Properties of Polycrystalline TiN/TaN Multilayers
Polycrystalline TiN/TaN multilayers were grown by reactive magnetron sputtering on WC-Co sintered hard alloy Substrates. Multilayer structure and composition modulation amplitudes were studied using X-ray diffraction method. Hardness and elastic modulus were measured by nanoindentation tester. For A>8.0 nm, hardness is lower than rule-of mixtures value of individual single layer, and increased rapidly with decreasing A, peaking at hardness values≈33% higher than that at A=4.3 nm. As a result of analysing the inclination of applied load for indenter displacement on P-h curve (△P/△h), this paper exhibits that the enhancement of the resistance to dislocation motion and elastic anomaly due to coherency strains are responsibie for the hardness change
1997 Vol. 13 (4): 245-248 [Abstract] ( 222 ) [HTML 1KB] [PDF 417KB] ( 370 )
249 M.Oda; K.Setoguchi; E.Fuchita and C.Hayashi(UFP Division, Vacuum Metallurgical Co., Ltd., 516 Yokota, Sanbu-cho, Sanbu-gun, Chiba-pref., Japan 289-12)
Preparation and Application of Ultra Fine Particles
UFPs are formed using gas evaporation methods. In the gas evaporation methods, configuration of UFPs are controlled to form chain-like shape, complex, and isolated UFP. UFP films can be formed through the gas deposition method, where formed UFPs are ejected out of a nozzle and deposited on a substrate, forming patterns
1997 Vol. 13 (4): 249-254 [Abstract] ( 210 ) [HTML 1KB] [PDF 3501KB] ( 247 )
255 Chiwei LUNG(International Centre for Materials Physics, Institute of Metal Research,Chinese Academy of Sciences, Shenyang 110015, China)
Multirange Fractals in Materials: Applications to Fracture and Mechanical Alloying under Ball Milling
A new model of multirange fractals is proposed to explain the experimental results observed on the fractal dimensions of the fractured surfaces in materials. A new expIanation to the WilIiford's multifractal curve on the relationship of fractal dimension with fracture properties in materials has been given. It shows the importance of fractorizing out the effect of fractal structure from other physical causes and separating the appropriate range of scale from multirange fractals.Mechanical alloying process under ball milling as a non-equilibrium dynamical system has been also analyzed
1997 Vol. 13 (4): 255-259 [Abstract] ( 199 ) [HTML 1KB] [PDF 511KB] ( 234 )
260 Reinhard L■ck(Max-Planck-Institut fur Metallforschung, Institut fur Werkstoffwissechaft,Seestraβe 75,D-70174 Stuttgart, Germany)
Magnetothermal Analysis of Nanocrystallization of Amorphous and Relaxations of Nanocrystalline Materials
For a few years it has been realized that nanocrystalline phases can be formed during crystallization of amorphous alloys annealed isothermally below the crystallization temperature of usual heating experiments. Data of this transformation monitored by the measurement of magnetic susceptibility are presented. A method using a magnetic balance with electronic stabilisation and combined computer facilities is applied. Constant heating and cooling rates as well as isothermal heat treatments are used. Magnetic measurements are able to detect the onset of the transformation of amorphous Ni-P alloys much earlier than was possible with differential scanning calorimetry. The transformation kinetics can be analyzed by means of the Avrami plot based on the Johnson-Mehl-Avrami equation.The kinetics of solid state reactions in the nanostructured material can be investigated similarly. Formation of a Ni-phase in a nanostructured Hf-Ni alloy could be detected in a very early stage, where calorimetric methods are not sensitive. Segregation phenomena could be detected from the experiments even after long time. The sensitivity of the applied method is not dependent on the heating rate as the sensitivity of scanning calorimetry is
1997 Vol. 13 (4): 260-264 [Abstract] ( 217 ) [HTML 1KB] [PDF 455KB] ( 216 )
265 Nobuo Tanaka (Dept. of Applied Physics, School of Engineering, Nagoya University, Nagoya, 464-01, Japan)
Studies of Atomic Structure and Physical Properties of Metal Clusters in MgO by HREM and Nano-probe Methods
Nanometer-sized metal clusters were prepared inside single crystalline MgO films by vacuum co-deposition of metals and MgO. The atomic structure was studied by high-resolution electron microscopy (HREM) and nm-area electron diffraction. The size of the clusters is ranging from 1 nm to 3 nm without those larger than 5 nm, and most of them have definite epitaxial orientations with the MgO matrix films. The character of the composite films is very much useful for the studies of various kinds of physical properties with anisotroPy. The physical properties such as electric transport, magnetic, optical absorption, sintering and catalytic ones were thus measured on the same samples analyzed by HREM by using high sensitivity apparatus with interest of clarifying the retationship between the atomic structure and physical properties
1997 Vol. 13 (4): 265-270 [Abstract] ( 223 ) [HTML 1KB] [PDF 3605KB] ( 337 )
271 Jizhong ZHANG; Xaodong YANG and Hengde LI(Dept. of Materials Science & Engineering, Tsinghua University, Beijing 100084, China)Xiaoyan YE(Dept. of Chemistry, Tsinghua University, Beijing 100084, China)
Long-range Correlations in Iodide Cluster Aggregates
The morphology of tin iodide deposits grown during gas-solid transformation demonstrated longrange correlations. These iodide deposits include basically two kinds of forms: fractal structure and dendritic-like structure. The fractal structure was a sort of tin iodide cluster aggregation.Each fractal structure was composed of numerous tin iodide clusters that connected or disconnected with each other. The average size of fractal structures is between 10 and 22 μm. The dendritic-like structure was also composed of many tin iodide clusters. These clusters aggregated and formed a dendritic pattern
1997 Vol. 13 (4): 271-273 [Abstract] ( 203 ) [HTML 1KB] [PDF 1200KB] ( 221 )
274 Guanghou WANG(National Lab. of Solid State Microstructures, Nanjing University, Nanjing 210093, China)Fengqi LIU(Center for Advanced Studies in Science and Technology of Microstructures, Nanjing 210093, China)
Structures and Properties of LiF Cluster-assembled Nanofilms
We have studied structures and properties of nanostructured films prepared with nanometersized lithium fluoride(LiF) clusters by inert gas condensation method, and then characterized by transmission electron microscope, Fourier transform infrared spectra and Raman scattering spectra, etc. Following important results are obtained: Multi-order-like Raman scatterings from LiF clusters are obtained, including the fine structure of the spectra. The observed Raman peaks are discussed in terms of surface optical modes, Lo. To, LA modes and their combination form.As the cluster size decreases, the phonons are confined in nanoscale so that the q vector selection rule is relaxed or even totally free of q conservation, and prohibition at the first- and third-order scatterings in the bulk LiF crystal is relaxed. The sudece modes appear and play an important role in Raman scattering processes. The infrared absorption spectra are obtained with different deposition conditions. When the clusters are in the medium size range from ～7 to 15 nm, most infrared absorption peaks are second-order feature, and no single surface mode emerges. For the smaller clusters, molecular-like vibration is observed whereas the broad band of long wavelength transverse-optical modes appear from 580 to 400 nm-1 for the clusters larger than 19 nm
1997 Vol. 13 (4): 274-279 [Abstract] ( 244 ) [HTML 1KB] [PDF 554KB] ( 359 )
280 Baoy WANG; Yuexia WANG; Qiang GU and Tianmin WANG(Dept. of Materials Science, Lanzhou University, Lanzhou 730000, China)
Calculation of Point Defects in NiAl Alloy
The potential functions of the F-S model for ordered high-temperature intermetallic compound NiAl with a B2 structure are constructed. Using the potential, the point defects properties were studied by molecuIar dynamics method, the results are in good agreement with that by EAM method and the experiment values. Meanwhile, the results clarify the experiments of two recovery stages in quenched NiAl alloy, and indicate that the two stages are corresponding to the recovery of Ni vacancies and of Al vacancies
1997 Vol. 13 (4): 280-283 [Abstract] ( 233 ) [HTML 1KB] [PDF 421KB] ( 240 )
284 Qing JIANGt; Zhonghang SUI; Jianchen LI and Xiaoya XU(Dept. of Materials Science and Engineering, Jilin University of Technology, Changchun 130025, China)
Specific Heat and Interface Energy of Nanostructured ZrAlNiCuCo Alloy
The specific heat of the nanostructured crystals, the glass, the liquid and the crystals for a ZrAINiCuCo alloy has been measured by using the differential scanning calorimeter. The specific heat value and its temperature coefficient of the nanostructured crystals are larger than that of the relaxed glass and of the crystals. Through measuring crystallization enthalpies and specific heat of the alloy in different states, the enthalpy difFerences among the crystals, the liquid and the nanostructured crystals are calculated and the intedece energies of nanostructured crystals are estimated. The stability and the grain size limit of the nanostructured crystals are discussed.
1997 Vol. 13 (4): 284-288 [Abstract] ( 223 ) [HTML 1KB] [PDF 497KB] ( 255 )
289 R.Ramamoorthy; S.Ramasang and A.Narayanasamy(Dept. of Nuclear Physics, University of Madras, Guindy Campus, Madras-600 025, India)
Impedance and Magnetization Studies of Ultrafine Ni-Zn Ferrite
Ultrafine Ni0.5Zn0.5 Fe2O4 powder was prepared by PVA aided chemical method. The powder and sintered pellets were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and complex impedance (Cl) analysis. The particles are found to be in the size range of 15 to 26 nm for various annealing temperatures. The coercivity, saturation magnetisation, Neel temperature and electrical conductivity are found to vary with sintering time at 800℃ for the pellet samples. The variations in the above intrinsic properties are explained qualitatively
1997 Vol. 13 (4): 289-292 [Abstract] ( 204 ) [HTML 1KB] [PDF 403KB] ( 336 )
293 Wen DAI and Jiaxun YANG(Cryogenic Lab., Chinese Academy of Sciences, Beijing 100080, China)Baogen SHEN and Dexin LI(Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China)Zhengxiang GAO(Dept. of Physics, Peking University, Beijing 100871
Effect of Introduction of Light Rare-Earth into Heavy Ones on Magnetic Properties of the Alloys
The magnetic properties in Dy-Y, Dy-Nd, Dy-Pr and Gd-Dy-Nd alloy systems have been studied. (GdDy)100-xNdx (x=0, 10, 20 and 30) enter into their sole ferromagnetic ordering phases at temperatures from 165 to 235 K, therefore, this kind bf alloy can be used as new magnetic refrigerants
1997 Vol. 13 (4): 293-295 [Abstract] ( 195 ) [HTML 1KB] [PDF 288KB] ( 211 )
296 Xiaoyan YE and Lili CAO(Dept. of Chemistry, Tsinghua University, Beijing 100084, China)Jizhong ZHANG and Hengde LI(Dept. of Materials Scieuce & Engineering, Tsinghua University, Beijing 100084, China)
Coacervate Structures of CdI_2 Thin Film Grown during Phase Transformation
The microstructure of CdI2 thin film grown during vapor-phase deposition was investigated by scanning electron microscopy (SEM). The thin film deposited on Si crystal consists of numerous sunflower-like aggregates. These aggregates display well self-assembly characteristics. The size of Sunflower-like aggregates is between 12 and 44 μm. Each sunflower-like aggregate is surrounded with many adjacent wings-"petals". The structure of central region of the "sunflower" is obviously difFerent from that of the "petal". Electron spectroscopy for chemical analysis (ESCA) was employed in determining the chemical valence of the thin film. Self-organization efFect is used to explain the coring growth process of CdI2 thin film
1997 Vol. 13 (4): 296-298 [Abstract] ( 209 ) [HTML 1KB] [PDF 1098KB] ( 241 )
299 M. Ohyama(Dept. of Electrical Engineering, Tokyo National College of Technology, Tokyo, Japan)
Electrical and Optical Properties of Gase Thin Films
The structure, electrical transport, and optical properties of GaSe films fabricated by means of radio-frequency (RF) magnetron sputtering in Ar were investigated. The as-sputtered GaSe films were amorphous, and their optical energy gap Eg are 1.9～2.6 eV. The effect of the synthesis conditions on the optical and electrical properties of the GaSe films has also been studied
1997 Vol. 13 (4): 299-301 [Abstract] ( 204 ) [HTML 1KB] [PDF 293KB] ( 342 )
302 Guolong TAN; Jian WU and Xijun WU(Dept. of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China)
Sensitivity to Combustible Gas for ZnO Thin Films
A fine polycrystalline ZnO thin film with 0.3～0.6 μm grain size was obtained by sol-gel process and a consequential heat treatment at 500℃. The process of preparing ZnO thin film was analysed. The sensitivity and conductivity of ZnO thin films as combustible gas (CO, CH4,H2) sensor as well as the influence of catalyst and pH value of the precursor on its sensitivity were studied in detail. The structure characteristics of ZnO thin film by different process were irlvestigated by X-ray diffraction, thermal analysis and photoelectron spectrometer. The atomic ratio of Zn to O on the surface of ZnO thin film was found to be 1.14:1 measured from XPS result. The conductivity of the thin film increases greatly when doped with Al3+ ion but decreases while doped with Na+ ion
1997 Vol. 13 (4): 302-305 [Abstract] ( 232 ) [HTML 1KB] [PDF 384KB] ( 333 )
306 Tao ZHU;Gaorong HAN; Gaoling ZHAO and Zishang DING(Dept. of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China)( State Key Lab. of Magnetism, Institute of Physics, Chinese Academy of Sciences, P.O.Box 603,Beijing 100080, China)
A Preliminary Raman Investigation of the Lead Titanate Thin Films via Sol-Gel Process
Raman spectra of the PbTiO3 films via sol-gel process were investigated by using a Jobin Yvon U1000 system. Compared with the Raman spectra of the PbTiO3 single crystals, Raman peaks of PbTiOs films shift downward, which is attributed to the stress effect in the PbTiO3 films exerted by the substrate and the size effect on the Raman frequencies
1997 Vol. 13 (4): 306-308 [Abstract] ( 219 ) [HTML 1KB] [PDF 1070KB] ( 247 )
309 Xiangcheng SUN; Mingchuan YANG; Feng YE; Xiukui SUN and Wenduo WEI(State Key Lab. for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)Yingda YU and Dehai PING(Lab. of Atomic Imaging of Solids, Institute of Metal Resea
Synthesis and Characterization of Mixed Al+AlN Nanoparticles
Mixed Al+AlN nanoparticles were synthesized by an active plasma-metal reaction method. Mean particle size of the mixed Al+AlN nanoparticles is about 30-50 nm. Defects were found in some AlN particles. Moreover, the AlN ratio and its particle size in mixed Al+AIN nanoparticles obtained in different atmospheres (N2+Ar) increase with increasing N2 particle pressure, and the specific sudece areas of the mixed Al+AlN nanoparticles increase with the AlN ratio. The surface degradation of the Al+AlN exposed to air is estimated by the infrared absorption spectra
1997 Vol. 13 (4): 309-311 [Abstract] ( 211 ) [HTML 1KB] [PDF 925KB] ( 256 )
312 Xiangcheng SUN;Feng YE; Xaoping SONG; Mngchuan YANG and Xiukui SUN (State Key Lab. for RSA, Institute of Metal Research, Chinese Academy of Sciellces, Shenyang 110015, China)
Surface Degradation of Bulk AlN+Al Nano-composites
Bulk AlN + Al nanocomposite materials were Synthesized by sintering the compacts of AlN and Al nanoparticles, which were produced by an active plasma-metal reaction method. The sudeces of as-prepared nanocomposite was investigated by X-ray photoelectron spectroscopy (XPS).Results show the surfaces are much degraded and the degradation products are alumina(Al2O3),boehmite(AIOOH), bayerite(AI(OH)3) layer. The mechanism of degradation behaviour in moist environment was also discussed
1997 Vol. 13 (4): 312-314 [Abstract] ( 236 ) [HTML 1KB] [PDF 233KB] ( 233 )
315 Zuolin CUI; Zhikun ZHANG; Chuncheng HAO; Lifeng DONG; Zhaoguo MENG and Liyan YU(Research Center of Nanostructured Materials, Qingdao Institute of Chemical Technology Qingdao 266042, China)
Nano-composite Particles Synthesized by a Hydrogen Arc Plasma
Nano-composite particles can be synthesized by a hydrogen arc plasma method, which possesses the advantages of high productivity, controllable size distribution and low electric energy consumption comparing with conventional gas condensation method. With this method, not only the nanoparticles of metals and alloys, but also the nano-composite particles with shell structure can be synthesized. The microstructures, compositions and the formation mechanism of the nano composite particles were studied
1997 Vol. 13 (4): 315-317 [Abstract] ( 220 ) [HTML 1KB] [PDF 947KB] ( 265 )
318 Feng YE; Mingchuan YANG; Xukui SUN and Wenduo WEI(State Key Lab. for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)
Size Distribution of Ti-Fe Nanoparticles
Ti-Fe nanoparticles with different concentrations were synthesized by gas condensation method.It is found that the size distribution of single phase nanoparticles obeys log normal distribution,and that of multiple phase nanoparticles is quite different. If it is assumed that the size distribution of each phase in multiple phase nanoparticles obeys log normal distribution as that of single phase particles. the calculated distribution curve is agreeable to the empirical curve. The inferences from the hypothesis are also supported by experimental results
1997 Vol. 13 (4): 318-320 [Abstract] ( 200 ) [HTML 1KB] [PDF 1072KB] ( 238 )
321 Zhe SONG; Qing LI and Lian GAO(State Key Lab. of High Performance Ceramics & Superfine Microstructure, Shanghai Institute of Ceramics,Chinese Acadmey of Sciences, Shanghai 200050, China)
Preparation and Properties of Nano-TiO_2 Powders
This paper reports the preparation of nano-TiO2 (about 10 nm) powder by the method of precipitation. In detail, some breparation conditions were investigated in order to find out how to control the grain size and reduce the agglomeration of powders. Also, the reflex spectra of nano-scale powders with different grain size were studied. It tvas found that the wave length and width of reflex spectra are connected with the grain size of nano-TiO2 powders
1997 Vol. 13 (4): 321-323 [Abstract] ( 231 ) [HTML 1KB] [PDF 1226KB] ( 301 )
324 Yuping ZENG; Dongliang JIANG; Shouhong TAN and Jingkun GUO(Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China)
Tape Casting of Al_2O_3-TiB_2/Al_2O_3-Nano-TiC Multilayer Composites
Ceramic tapes, containing Al2O3-25 wt pct TiB2(B) and Al2O3-25 wt pct nano-TiC (c), have been obtained by tape casting process. Numerous tapes (about 60～80 tapes) were prepared by stacking in turn the composition (B) and (C), laminating under 10 MPa pressure, eliminating the solvent and burning out the polymer additives. The final green bodies were hot pressed at 1750℃ and 30 MPa. The composite has a bending strength of 568 MPa and a fracture toughness of 5.8 M Pa·m1/2. SEM analysis exhibits that Al2O3 particle growth was inhibited by TiC particles in C. but TiB2 particles could not hinder Al2O3 growth in B. The curves of GTA indicates that all organic additives could be removed completely above 600℃
1997 Vol. 13 (4): 324-326 [Abstract] ( 206 ) [HTML 1KB] [PDF 1110KB] ( 246 )
327 S.M.Scholz;J.Dutta and H.Hofmann(Lab. de Technologie des Poudres, Departement de Materiaux, Ecole Polytechnique Federale de Lausanne,1015 Lausanne, Switzerland)H.Hofmeister (Max-Planck-Institut fur Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany)
Raman Spectroscopic Study of Silicon Nanopowders
Vibrational properties of silicon nanopowders are discussed with reference to Raman spectroscopic measurements. The powders were produced in a low pressure rf plasma from the cluster induced agglomeration of positive ions formed during the dissociation of silane. Influence of thermal treatment and the crystallization phenomena of the powder were studied. Raman spectroscopic measurements reveal size quantization effects for the particles as well as the existence of partially ordered regions in the apparently amorphous primary particles. The crystalline and amorphous volume fraction in the material were calculated from the relative spectraI intensities. The results obtained in these experiments are consistent with the observations from recent high resolution transmission electron microscopy studies of these powders
1997 Vol. 13 (4): 327-332 [Abstract] ( 224 ) [HTML 1KB] [PDF 1726KB] ( 314 )
333 Xiuchun YANG(Dept. of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China)Gaorong HAN;Xiabin ZHANG; Piyi DU and Zishang DING(Dept. of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China)Ze ZHA
Photoluminescence of Nanometer SiC Powder
Photoluminescence of nanometer SiC powder was found firstly. By TEM, SAED, FTIR and chemical analyses, it is suggested that the quantum confinement effect of nanometer β-SiC be responsible for the blue light and violet emission
1997 Vol. 13 (4): 333-335 [Abstract] ( 194 ) [HTML 1KB] [PDF 1003KB] ( 228 )
336 Danyu JIANG; Chen ZHANG; Jianlin SHI;Tingrong LAI and Dongsheng YAN(Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China)
Microstructure and Mechanical Properties of Dy-α-sialon/Nano-size SiC Composites
The composite of Dy-α-sialon/10 wt pct nano-size SiC particles has been prepared from precursor powders of Si3N4, AIN, Al2O3, Dy2O3 and nano-size β-SiC. The hardness, toughness and bending strength of the composite at ambient temperature are a little higher than those of Dy-α-sialon.while the bending strength is maintained up to 1000℃ and about 2 times more than that of Dy-α-sialon at the same temperature. The fracture surfaces show that the grain size of the composite is smaller than that of Dy-α-sialon, and both Of them have predominately transgranular mode of fracture. It is believed that the decrease of the bending strength of Dy-α-sialon at elevated temperature is caused by the viscous flow of the grain boundary phase, while the addition of nanosize SiC particles effectively increases the viscosity of the grain boundary phase and therefore prevents the strength loss of Dy-α-sialon/nano-size SiC composites at elevated temperature
1997 Vol. 13 (4): 336-338 [Abstract] ( 218 ) [HTML 1KB] [PDF 980KB] ( 259 )
339 Cheng ZHANG;Danyu JIANG; Qiang LI and Weiying SUN (Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China)
Densification and Microstructure of β-sialon/Nano-size SiC Composites
β-sialon/nano-size SiC composite ceramic with DyAG(Dy3Al5O12) as grain boundary phase was fabricated through hot-pressing. The effect of nano-size SiC on densification, phase composition, microstructure and mechanical properties of the materials was studied
1997 Vol. 13 (4): 339-341 [Abstract] ( 192 ) [HTML 1KB] [PDF 1201KB] ( 207 )
342 Zhongming CHEN;Shouhong TAN; Zhaoquan ZHANG and Dongliang JIANG(Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China)
High Preformation SiC-AlN Composites
High performance SiC-AlN composites were fabricated by hot-pressing with Y2O3 as additive via liquid phase sintering. The SiC-AlN composites containing 5 vol. pct AlN exhibit superior mechanical properties with flexural strength, fracture toughness and Vickers hardness of 1131 MPa,6.1 MPa·m1/2 and 28.6 GPa respectively Microstructure observations indicate that the grain size of the composites is obviously inhibited due to the formation of solid solution. TEM-EDS analysis demonstrates the existence of the solid solution. In addition, subgrain boundaries induced by dislocations in the matrix SiC grains, seem to divide a large grain into numerous nano-sized small grains, which significantly increase the mechanical properties of the composites
1997 Vol. 13 (4): 342-344 [Abstract] ( 215 ) [HTML 1KB] [PDF 2039KB] ( 239 )
345 Nianqiang WU;Zhizhang LI;Guangxin WANG and Jinming MU(Dept. of Materials Science and Engineering, Zhejiang University Hangzhou 310027, China)
Formation of a FCC Al_(54)Ti_(23)C_(23) Metastable Phase by Ball Milling
The powder mixture of Al, Ti and graphite has been mechanically alloyed in a planetary ball mill.The structural evolution of as-milled powder sample has been characterized by XRD, DTA. The results show that the amorphous phase is formed first at an early milling stage, then crystallization occurs during further milling, leading to formation of a nanocrystalline fcc metastable phase. In contrast, during annealing the amorphous phase is crystallized to the equilibrium phase instead of the fcc phase. This indicates that crystallization during ball milling is different from that induced by annealing
1997 Vol. 13 (4): 345-347 [Abstract] ( 199 ) [HTML 1KB] [PDF 1051KB] ( 232 )
348 Jing SUN;Lian GAO and Jingkun GUO(Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China)
Rheology Study of Suspension Formed by Different Nano-size Y-TZP
The rheological properties of slurries formed by different nano-size Y-TZP have been studied.The viscosity is sensitive to solid loading especially for high solid content level. The dispersant NH4PAA can improve the flowability efficiently. The smaller ceramic particles need to adsorb more dispersant to the flowability. Under the same solid content, the smaller the particles, the higher the viscosity of its slurry
1997 Vol. 13 (4): 348-350 [Abstract] ( 190 ) [HTML 1KB] [PDF 241KB] ( 230 )
351 Qiang LI;Lian GAO;and Dongsheng YAN(State Key Lab. of High Performance Ceramics & Superfine Microstructure, Shanghai Institute of Ceramics,Chinese Academy of Sciences, Shanghai 200050, China)
Blue-shift of Nano-Y_2O_3 : Eu~(3+) Emission Spectra Excited by X-ray
Nano-Y_2O_3:Eu~(3+) powder was prepared by the homogeneous precipitation. With controlling the conditions of the reaction, nano powders with different grain size were obtained. It is found that the blue-shift phenomena exist in the nano-Y2O3:Eu3+ emission spectra excited by X-ray. The wave lengths of the peak (5D0→7F2) are related with the grain size of the powder
1997 Vol. 13 (4): 351-353 [Abstract] ( 203 ) [HTML 1KB] [PDF 1011KB] ( 323 )
354 Yuanda DONG and Xueming MA(School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China)Yuanzheng YANG(Dept. of Mechanical Engineering(2), South China University of Technology, Guangzhou 510641, China)Fangxin LIU and Genmiao WA
Mechanically Driven Alloying and Structural Evolution of Nanocrystalline Fe_(60)Cu_(40) Powder
Highly supersaturated nanocrystalline fcc Fe60Cu40 alloy has been prepared by mechanical alloying of elemental powders. The phase transformation is monitored by X-ray diffraction (XRD),Mossbauer spectroscopy and extended X-ray absorption fine structure (EXAFS). The powder obtained after milling is of single fcc structure with grain size of nanometer order. The Mossbauer spectra of the milled powder can be fitted by two subspectra whose hyperfine magnetic fields are 16 MA/m and 20 MA/m while that of pure Fe disappeared. EXAFS results show that the radial structure function (RSF) of Fe K-edge changed drastically and finally became similar to that of reference Cu K-edge, while that of Cu K-edge nearly keeps unchanged in the process of milling. These imply that bcc Fe really transforms to fcc structure and alloying between Fe and Cu occurs truly on an atomic scale. EXAFS results indicate that iron atoms tend to segregate at the boundaries and Cu atoms are rich in the fcc lattice. Annealing experiments show that the Fe atoms at the interfaces are easy to cluster to α-Fe at a lower temperature, whereas the iron atoms in the lattice will form γ-Fe first at temperature above 350℃, and then transform to bcc Fe
1997 Vol. 13 (4): 354-358 [Abstract] ( 199 ) [HTML 1KB] [PDF 473KB] ( 186 )
359 Xisheng YE;Jian SHA and Zhengkuan JIAO(Dept. of Physics, Zhejiang University, Hangzhou 310027. China)Zifei PENG and Lide ZHANG(Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China)
Structural Phase Transition in Nanostructured TiO_2
Using DTA (difFerential thermal analysis) measurement on nanostructured TiO2, we find two endothermic peaks on the DTA curve. From XRD (X-ray diffraction) analysis of the original nanostructured TiO2 and its heat-treated samples, we obtain the following results: the first endothermic peak corresponds to the desorption of physical or chemical absorption, the second one is related to the structural phase transition from brookite to anatase then to rutile, and this structural phase transition is beneficial to the grain growth of nanocrystal
1997 Vol. 13 (4): 359-360 [Abstract] ( 228 ) [HTML 1KB] [PDF 194KB] ( 211 )
361 Jian SHA;Xisheng YE; Bin CHEN; Qirui ZHANG and Zhengkuan JIAO(Dept. of Physics, Zhejiang University Hangzhou 310027, China)Guanglie LU(Central Lab., Hangzhou University Hangzhou 310028, China)Zifen PENG and Lide ZHANG(Institute of Solid State Physics, Chi
Structure Transition of Nanocrystalline Fe_2O_3
A structure transition of Fe2O3 nanocrystal was studied by using DTA and TG thermal analysis and X-ray diffraction method. We found that size increase of the nanocrystals is larger after the structure transition than that before the transition. It means that the structure transition is beneficial on growth of nanocrystals
1997 Vol. 13 (4): 361-363 [Abstract] ( 191 ) [HTML 1KB] [PDF 287KB] ( 245 )
364 Yanqi WANG and Xijun WU(Dept. of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China)Linhua YE; Limin TONG and Yonghang SHEN(Dept. of Physics, Zhejiang University, Hangzhou 310027, China)
Application of Nanopowder to High Temperature Single Crystal Fiber Sensor
ZrO2, CuO, Al2O3 and SiO2 mixed nanopowder was used to coat the head of sapphire single crystal fiber for improving the properties of high-temperature single crystal fiber sensor. The result indicates that the head coated with above mixed nanopowder shows better optical stability,shorter response time and higher thermal shock resistance, in comparison with the head coated with coarse-grained particles with the same chemical compositions
1997 Vol. 13 (4): 364-366 [Abstract] ( 221 ) [HTML 1KB] [PDF 237KB] ( 297 )

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