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Progress in InkJet Technique and Its Applications
GAO Chen,HUANG Sun-Xiang,CHEN Lei,LIU Chi-Hui,LIU Xiao-Nan,BAO Jun
2004 Vol. 19 (4): 714722
Abstract(
2191 )
PDF(3990KB)(
4272
)
Ink-jet technique has the advantages of simplicity, cost-effectiveness and high spatial resolution. Besides the inkjet printer, the technique has many potential applications in freeforming, microfabrication, MEMS, biochip and materials synthesis. The pioneer works in these fields were reviewed, and an 8-nozzle combinatorial inkjet synthesizer developed in our group was demonstrated, its performance and applications were also discussed.
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Optimization of Crucible Descending Rate during the Crystal Growth of CdZnTe by a Vertical Bridgman Method
LI Wan-Wan,SANG Wen-Bin,MIN Jia-Hua,YU Fang,ZHANG Bin,WANG Kun-Shu,CAO Ze-Chun
2004 Vol. 19 (4): 723732
Abstract(
2401 )
PDF(1018KB)(
1057
)
During the crystal growth by VBM, the relationships between crucible descending rate and crystal growth rate greatly influence the crystal quality. In this paper, finite element method (FEM) was used to simulate the growth process of CdZnTe crystal and the effects of different crucible descending rates on crystal growth rate and solid-liquid interface configuration were studied as well. Simulations show that when crucible descends at the rate of about 1mm/h, which nearly equals to crystal growth rate, nearly flat solid/liquid interface and little variation of axial temperature gradient near it can be attained, which are well consistent with the results of experiments. Therefore, CdZnTe crystal with low dislocation density can be obtained by employing and adjusting appropriate crucible moving rate during the crystal growth.
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Properties and Defects of Sr2+-doped α-BBO Crystal
LIU Jun-Fang,HE Xiao-Ming,XU Jun,ZHOU Guo-Qing,ZHOU Sheng-Ming
2004 Vol. 19 (4): 733737
Abstract(
1939 )
PDF(1089KB)(
1068
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High-quality Sr2+-doped α-BBO crystals were grown by the Czochralski method. The result of X-ray diffraction indicates that the grown crystals are α-BBO crystal. The results of transmission and birefractive indices show that Sr2+ ions do not affect the optical properties of α-BBO. The measurements of DSC-TG and thermal expansion coefficient of Sr2+-doped α-BBO crystal manifest that Sr2+ ions also do not influence the thermal properties of α-BBO. Meanwhile, the study of defects investigated by chemical etching illustrates that the quality of seed crystal is the most important factor of the quality of as-grown crystals.
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Optical Properties of α-sialon Doped with Different Earth Elements
SU Xin-Lu,WANG Pei-Ling,CHEN Wei-Wu,CHENG Yi-Bing
2004 Vol. 19 (4): 738742
Abstract(
1947 )
PDF(1269KB)(
1056
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By spark plasma sintering (SPS) and post-sintering heat treatments at 1700℃ for 7h and 17h respectively, the optical transmission of R0.33Si9.3Al2.7O1.7N14.3 (R=Gd, Y and Er) in 4000~1500cm-1 (2.5~6.6μm) was studied. The results indicate that fully densified specimens obtained by SPS are with homogenous distributed α’ grains. Among three SPS-ed specimens, Y α-sialon ceramic has the highest transmittance and it reaches 56% for the specimen with 0.5mm in thickness. The heat treatment for 7h causes the decrease in optical transmittance due to the formation of the second crystallized phase in the specimens. The optical transmittance of specimens can be improved by suitable heat treatment, and the maximum optical transmittance value of Gd117 can be increased from 47% as SPS-ed to 56% after heat-treated at 1700℃ for 17h.
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Preparation and Study of Porous Si3N4 Ceramics with High Strength by Gelcasting
ZHANG Wen,WANG Hong-Jie,ZHANG Yong,JIN Zhi-Hao
2004 Vol. 19 (4): 743748
Abstract(
2437 )
PDF(778KB)(
4931
)
Porous Si3N4 ceramics with high strength, uniform structure and relative high porosity were obtained by gelcasting. The mechanical performances and micro-structure of the porous Si3N4 ceramics were studied and the reasons were discussed. It was showed that using proper techniques, green bodies with high strength, uniform structure and good machining proparey could be got. Results show that the sintered porous Si3N4 ceramics have strength more than 150MPa and porosity up to 50%. SEM shows that porous are formed by the banding-up of pillar β-Si3N4. The uniform porous distribution and pillar structure are the main reasons for good mechanical performances.
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Preparation and Characterization of Nanometer-sized Magnetic Photocatalyst TiO2/SiO2/Fe3O4
LIAO Zhen-Hua,CHEN Jian-Jun,YAO Ke-Fu,ZHAO Fang-Hui,LI Rong-Xian
2004 Vol. 19 (4): 749754
Abstract(
2071 )
PDF(603KB)(
1419
)
By using nanometer-sized Fe3O4 as support, TiO2/SiO2/Fe3O4 coated particles were prepared by a sol-gel method. Its structure and morphology were characterized by XRD, TEM, and element analysis methods. The photocatalytic reactivity of TiO2/SiO2/Fe3O4 was studied with methyl orange solution. The results indicate that the TiO2/SiO2/Fe3O4 two-double coated particles are composed of SiO2 mesosphere and anatase TiO2 crust. The new photocatalyst has not only excellent photocatalytic activity but also good magnetic property that can make the callback easy.
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Aluminium Semi-Alkoxide Sol-Gel Synthesis and Sintering Behavior of MgAl2O4 Spinel Powder
YUAN Ying,ZHANG Shu-Ren,YOU Wen-Nan
2004 Vol. 19 (4): 755760
Abstract(
2141 )
PDF(493KB)(
1278
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MgAl2O4 spinel nanometer powders were synthesized via sol-gel process of aluminium isopropoxide that hydrated in the solution of magnesium nitrate with tetrahydrofuran being stabilizer. The crystallization process of MgAl2O4 precursor and the effect of calcination temperatures on spinel grain size and sinterability were investigated by DTA, XRD and TEM. The results indicated that this method could lower the formation temperature of MgAl2O4 apparently. Monolithic spinel nanometer powders were produced at the temperature as low as 900℃, with primary particle sizes of about twenty nanometers. The powder calcined at 900℃ showd best sinterability, and dense spinel ceramic with 99% relative density could be obtained at the sintering temperature as low as 1600℃.
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Syntheses of Nanocrystalline Mg-Al-LDHs and PO43-, P2O74- Anion-Pillared Layered Double Hydroxides under the Conditions of Microwave
ZHANG Ze-Jiang,LAN Bin,FENG Liang-Rong,LU Shao-Jie,QIU Fa-Li
2004 Vol. 19 (4): 761766
Abstract(
1991 )
PDF(557KB)(
1033
)
Nanocrystalline [Mg-Al-CO3] layered double hydroxides were prepared by using microwave irradiation and varied rate of dripping alkali. Then [Mg-Al-PO4] and [Mg-Al-P2O7] layered double hydroxides were successfully synthesized by the direct reaction of free PO3-4 and P2O4-7 with [Mg-Al-CO3] layered double hydroxides precursor using microwave technique and the anion-intercalation method. By using this method [Mg-Al-CO3] layered double hydroxides with a particle size of about 10nm to 40nm were produced. The effect of microwave and the rate of dripping alkali on [Mg-Al-CO3] layered double hydroxides was discussed. And the samples thus obtained were characterized by FT-IR, TEM and XRD. The results show that the initial interlayer carbonate ions can be completely replaced by PO3-4 and P2O4-7 under the controlled microwave conditions employed in a short time.
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Preparation of VO2 Nanopowders and Their Properties
FU Qun,CHU Xiang-Feng,LIN Chen,LEI De-Ming,ZHENG Chen-Mou
2004 Vol. 19 (4): 767771
Abstract(
1888 )
PDF(396KB)(
1025
)
VO2 nanopowders with various stoichiometries and crystalline states were prepared by pyrolyzing the precursor, (NH4)5[(VO)6(CO3)4(OH)9]·10H2O, at low temperature in a mixed flow of air and N2. The adsorption properties of crystal, quasi-crystal and amorphous state nano-VO2-powders were studied. DSC results indicate that VO2.025 exhibits a phase transition at 70.1℃ and has the maximum phase transition heat in the range from VO1.985 to VO2.071. The unit-cell parameters of various stoichiometry VOx were determined. The results show that the unit-cell volume of the monoclinic VOx phase increases linearly from the oxygen-deficient VO2 to the oxygen-rich VO2.
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Photoluminescence of Trivalent Europium Ion Doped GdAl3 (BO3)4 Phosphor
WANG Yu-Hua,Tadashi Endo,DU Yun-Kun
2004 Vol. 19 (4): 772778
Abstract(
1911 )
PDF(399KB)(
1030
)
Single phase of Gd1-xEuxAl3(BO3)4(0≤x≤1) was obtained by the evaporation of its nitrate solution, and calcinations at 1000℃ for 24h. Ultraviolet (UV) and vacuum ultraviolet (VUV) luminescent properties of Eu3+ in GdAl3(BO3)4 were systematically studied. In GdAl3(BO3)4:Eu3+, rare earths are located in noncentrosymmetric sites, and the predominant emission of Eu3+ is 5D0→7F2. GdAl3(BO3)4:Eu3+ shows intense red emission with CIE chromaticity coordinates of (0.645, 0.330) under 147nm excitation, it indicates that this phosphor is a promising new luminescent material for application in plasma display panel (PDP). The VUV excitation spectra of activated GdAl3(BO3)4:Eu3+ are composed of two broad bands. The 158nm excitation band is assigned to the energy level of BO3 groups and the other band centered at 258nm is assigned to the charge transfer transition between Eu3+ and O2-. The GdAl3(BO3)4:Eu3+ shows maximum intensity emission for the doped 50at% of Eu3+ under 258nm excitation and 5at% of Eu3+ under 147nm excitation, respectively. Therefore, the energy relaxation pathway to the Eu3+ sites should be different.
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Solid Phase Reaction Process of Cordierite Powders Prepared by Sol-Gel Method and Its Sintering
XIE Zhi-Yong,LIANG Hui,XU Ming-Xia,XU Ting-Xian
2004 Vol. 19 (4): 779783
Abstract(
2108 )
PDF(588KB)(
1117
)
The TEOS, stoichiometric magnesium nitrate and aluminum nitrate, and some carbamide were dissolved in the solution of CH3CH2OH-H2O. The solution was heated at 100℃ and then transformed into gelatinate. The dried gelatinate calcined at high temperature and a compound of MgO, Al2O3 and SiO2 could be obtained. The powder calcined at different temperatures and the sample sintered at 1350℃ for 2h were examined by using XRD. The X-Ray diffraction studies indicate that the forms of the matrix when heat-treated come through a progress from amorphous compound to α-cordierite, with the appearance and disappearance of μ-cordierite, spinel and β-SiO2. The whole sample sintered at 1350℃ is made of α-cordierite. The highest density of the samples is 99.5%. The SEM micrograph of the sample shows that the grain is flake. The densification process of pure cordierite ceramics was investigated.
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Hydrothermal Synthesis Process of Magnesium Oxysulfate Whiskers
LIU Feng,XIANG Lan,JIN Yong
2004 Vol. 19 (4): 784788
Abstract(
2301 )
PDF(650KB)(
1617
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Magnesium oxysulfate whiskers (5Mg(OH)2·MgSO4·3H2O) with a diameter of 0.5--1.0μm and a length of 30--50μm were synthesized via precipitation in room temperature followed with the hydrothermal reaction, using MgSO4 and NaOH as the raw materials. The experimental results indicate that the addition of magnesium hydroxide increases the specific conductance of the magnesium sulfate hydrothermal solution obviously, implying that magnesium oxysulfate whiskers may be formed via the dissolution of Mg(OH)2 followed with the interaction of Mg2+, SO42- and OH^- ions. The hydrothermal process of the whiskers is controlled by the crystal growth step and the corresponding kinetic model is as follows: -dc/dt=0.438(c-0.417)4.
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Electrochemical Fabrication of Titanium(Ⅳ) Compound Nanowire Arrays
LIU Su-Qin,TANG Li-Na,HUANG Ke-Long
2004 Vol. 19 (4): 789794
Abstract(
1948 )
PDF(1305KB)(
1086
)
Titanium compound nanowire arrays were fabricated into the pores of anodic alumina membrane by electrodeposition under DC and pulsed current. Through scanning electron microscopy and cyclic voltammeter, the effects of deposition conditions such as the electronic signals and applied voltages on the quality of prepared nanowires were investigated. Dense Ti(Ⅳ) compound arrays were obtained by using pulsed eletrodeposition.
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Influence of Dipping Time on LiCoO2 Whisker Arrays and Their Electrochemical Properties
ZHOU Ying-Ke,HE Ben-Lin,SHEN Cheng-Min,LI Hu-Lin
2004 Vol. 19 (4): 795800
Abstract(
1826 )
PDF(1037KB)(
992
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LiCoO2 whisker array were prepared by using porous anodic aluminium oxide (PAA) template in sol solution containing Li(OAc) and Co(OAc)2 for different dipping time. Electron microscope results show that with the dipping time increasing, the lengths of the LiCoO2 whisker increase, the distribution becomes more uniform and the crystal lattice disfigurement decreases. X-ray diffraction investigation demonstrates that LiCoO2 whisker is a layered structure of LiCoO2 crystal. Electrochemical tests show that LiCoO2 whisker array electrodes have good electrochemical reversibility and higher capacitance.
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Electrochemical Investigation on the Interface Performances of LiMn2O4/LiPF6-(EC+DEC) Solution
Lu Dong-Sheng,LI Wei-Shan
2004 Vol. 19 (4): 801808
Abstract(
1793 )
PDF(578KB)(
1141
)
The Changes in interface performances of LiMn2O4/LiPF6-(EC+DEC) solution with before and after charge-discharge cycling and storage were investigated by impedance technique combined with cyclic voltammetry. The resistance and the capacitance of the surface film increase significantly during the first several cycles, but nearly remain unchanged later. The charge- transfer resistance increases, but the interface capacitance nearly remains unchanged. The surface film resistance decreases at the early stage during storage but then increases a little with time. The charge-transfer resistance increases significantly after storage, especially at the early stage during storage. The surface film capacitance and interface capacitance nearly remain unchanged during storage. Possible mechanisms for the changes in these interface performances were explained.
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Effects of B-site Ion(Al, Cr) Substitution on the Ionic Conductivity of Li3xLa2/3-xTiO3
HE Lian-Xing,YOO Han-Ill,LI Yi
2004 Vol. 19 (4): 809816
Abstract(
2144 )
PDF(382KB)(
950
)
The effect of B-Site aliovalent ion (Al, Cr) substitution on the ionic conductivity of Li3xLa2/3-xTiO3 was investigated. The results show that partial substitution of smaller Al3+ for Ti4+ is effective to enhance the ionic conductivity of Li3xLa{2/3-xTiO3. At 300K, the maximum bulk conductivity of (1.58±0.01)×10-3S·cm-1 observed from the composition of (Li0.39La0.54)1+y/2AlyTi1-yO3 with y=0.02(x=0.13), is the highest yet reported for known perovskite solutions at room temperature. The conductivity enhancement is due to the substitution-induced bond strength change rather than due to bottleneck size change for Li migration, TiO6-octahedron tilting or A-site cation ordering.
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Dielectric and Piezoelectric Properties of (Na0.8K0.2)0.5Bi0.5TiO3 Ceramics
LI Yue-Ming,CHEN Wen,XU Qing,ZHOU Jing,LIAO Mei-Song
2004 Vol. 19 (4): 817822
Abstract(
1937 )
PDF(400KB)(
1021
)
Dielectric and piezoelectric properties of (Na0.8K0.2)0.5Bi0.5TiO3 ceramics were investigated. The results show that ferroelectric-antiferroelectric and antiferroelectric-paraelectric phase transition with relaxor characteristic occur from room temperature to 500℃, leading to the two peaks of electric permittivity to temperature. At room temperature, it has relative high remanent polarization Pr=29.4μC/cm2 and low conceive field Ec=2.8kV/mm. The polarized ceramics have good piezoelectric properties such as piezoelectric constant d33=120pC/N, electromechanical coupling factor Kp=28.5%, frequency constant Nφ=2916Hz·m, as well as minimum resonance frequency temperature coefficient at 120℃.
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Effect of Na+ on Dielectric Properties of ANT System
LI Ling-Xia,GUO Wei,WU Xia-Wan,WANG Hong-Ru,ZHANG Zhi-Ping,YU Hao-Ming
2004 Vol. 19 (4): 823826
Abstract(
1745 )
PDF(445KB)(
906
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he Ag2O-Nb2O5-Ta2O5 (ANT) system is a novel high frequency high permittivity ceramic material which can be sintered below 1150℃. The doping of Na+ can replace A site ions (Ag+) in ANT to form ANNT system. In this paper proper Na+ ions were introduced into ANT system. XRD, SEM, and energy spectrum analysis show that proper Na+ addition makes the lattice parameter reduced, i.e. the capacity of octahedron reduced, the dielectric dissipation factor of the system is improved efficiently because of depression of relaxation polarization of Nb5+, and the dielectric properties of the system are as follows: ε>500, tgδ≤5×10-4, αc=+12ppm/℃,ρv>1012Ω·cm.
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Preparation and Study of the Perovskite-type La(1-x-y)CaxSryMnO3 Ceramics
XU Chu-Dong,LIN Guo-Cong,ZHANG Jin-Xiu
2004 Vol. 19 (4): 827831
Abstract(
2073 )
PDF(421KB)(
945
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A series of nanocrystalline powder of La(1-x-y)CaxSryMnO3 was prepared by sol-gel technique, then was pressed and annealed to form ceramic. The results of magnetic measurement show that the Curie temperature of all the samples varies from 250K to 330K, and the maximal absolute value of (dM/dT) varies from 1.353 to 3.392A·m2/kg·K. The differential scanning calorimetry (DSC) measurements indicate that the latent heat in phase transition changes from 0.852 to 2.381J/g and increases with the increase of the maximal absolute values of (dM/dT). In addition, the maxial absolute value of (dM/dT) of La0.8-xCa0.20SrxMnO3(x=0.05, 0.08, 0.10) is also larger. Their Curie temperatures are adjacent to room temperature and they can be used as magnetic refrigeration materials at about room temperature.
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HAP·TCP Composite Biomaterials Strengthened by Spinel
LIU Bing,RUAN Jian-Ming
2004 Vol. 19 (4): 832838
Abstract(
2016 )
PDF(1092KB)(
1052
)
Ca10(PO4)6(OH)2·Ca2(PO4)3-MgAl2O4 (HAP·TCP-Spinel) composite biomaterials were synthesized by chemical deposition and followed by powder metallurgy technique. Microstructures were characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction(XRD), scan electron microscopy(SEM), and transmission electron microscopy(TEM). TEM observation shows that a perfect combination is presented in the interface between HAP crystals and Spinel crystals. The effects of composition on mechanical properties investigated show that the highest compressive strength and bending strength are σb=212MPa and σt=352MPa respectively, matching the composition of 62.5wt% of HAP in the composite. Similar to HAP, the composite is available to adsorb serum protein and albumin protein, though the amount of protein adsorption on the surface of the composite is significantly less than that on surface of HAP.
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Preparation of Thermally Stable Nanohydroxyapatite by Microwave Process
YANG Zheng-Wen,JIANG Yin-Shan,WANG An-Ping,LI Fang-Fei
2004 Vol. 19 (4): 839844
Abstract(
1987 )
PDF(349KB)(
1087
)
Nanosized hydroxyapatite powders were prepared by a microwave process using Ca(NO3)2·H2O and(NH4)2HPO4 as starting materials. The powder is composed of rod-shaped particle that is about 30nm in width and 80~200nm in length. The synthesized powders were measured by X-ray diffraction, transmission electron, infrared spectroscopy and thermogravimetric analysis. Various parameters such as time and power of microwave irradiation have significant effects on thermal stability of hydroxyapatite. The results show that the decomposition temperatures of HAP increase with time prolonging and power increasing of microwave irradiation. When the time and power of microwave irradiation are 1h and 700W, and the sample treated at 500℃ for 3h, HAP is still stable at 1200℃.
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Microwave Plasma Sintering of Porous HA/β-TCP Biphasic Bioceramics
JI Jin-Gou,RAN Jun-Guo,GOU Li,WANG Fang-Hu,SUN Lu-Wei
2004 Vol. 19 (4): 845851
Abstract(
2119 )
PDF(869KB)(
1011
)
Aimed at solving the problems on sintering of Ca-P bioceramics by using a conventional furnace, such as high sintering temperature, long holding time, large grain size and the difficulty to enhance the bioactive and the mechanical strength simultaneously, porous HA/β-TCP biphasic bioceramics were prepared by using a microwave plasma method. The properties of specimens were compared to those of specimens sintered by a conventional furnace. The comparison shows that plasma sintered specimens exhibit a higher linear shrinkage and densification rate, smaller grain size and higher compressive strength. After incubating in SBF, the amount of bone-like apatite formed on the specimens sintered by microwave plasma is more than that of specimens sintered by a conventional furnace. The results indicate that porous HA/β-TCP biphasic bioceramics sintered by microwave plasma have better mechanical properties and also may have better biological properties.
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Effects of Dispersed Medium and Mineralizer CaF2 on the Synthesis of α-Tricalcium Phosphate
CAI Shu,WANG Yan-Wei,LI Jin-You,GUAN Yong-Hui,YAO Kang-De
2004 Vol. 19 (4): 852858
Abstract(
1948 )
PDF(447KB)(
1123
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The starting powders selected for solid-state reaction to synthesize alpha-tricalcium phosphate (α-TCP) were CaHPO4·2H2O and CaCO3. The effects of dispersed medium and mineralizer CaF2 on the synthesis of α-TCP and phase transformation were investigated. The results show that a metastable high temperature phase (α-TCP) prepared by calcining the nonstoichiometric hydroxyapatite powder with poor crystallization obtained by grinding the mixture in distilled water is more stable than those prepared by grinding the mixture in an ethanol system. A new and easy route, based on the solid-state reaction and the addition of CaF2, was developed to synthesize alpha-calcium phosphate (α-TCP). For samples containing 1.0wt% and 1.5 wt% CaF2, calcined in the range of 1350℃ to 1450℃ and 1350℃ to 1480℃, respectively, a pure phase α-TCP was obtained. The transition energy of β-TCP to α-TCP during cooling process is decreased by adding some mineralizer CaF2. It will be helpful to keep the metastable high temperature phase (α-TCP) at room temperature. The stability of α-TCP in the course of furnace cooling is also related to the content of CaF2.
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Chemically Compatibility Analysis of 3Y-TZP/Fe-Al Composite
LI Jia,YIN Yan-Sheng,LIU Jun-You,FAN Run-Hua
2004 Vol. 19 (4): 859864
Abstract(
2139 )
PDF(730KB)(
1007
)
The chemically compatibility of iron aluminide with zirconia matrix was analyzed by thermodynamic theory. The results show that the chemical interaction between iron aluminide intermetallic and zirconia matrix will not take place when Al<42at%, and this result was certified by XRD,SEM and HREM. HREM image exhibits that the interface between Fe3Al and 3Y-TZP is clean, and no reaction phase exists at the interface. The atom arrangement beside interface between Fe3Al and ZrO2 is partly corresponding, existing at semicoherent state. The mismatch degree δ of spacing between planes in crystal is 30%, and the dislocation induced by mismatch exists at interface.
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Preparation of Modified Kaolinite/Titanium Oxide Coated Composite Particles and High Electrorheological Activity
WANG Bao-Xiang,ZUO Zhao-Yang,ZHAO Xiao-Peng
2004 Vol. 19 (4): 865870
Abstract(
1982 )
PDF(436KB)(
1103
)
Modified kaolinite/titanium oxide composite was prepared by the combination of sol-gel technique and mechanochemical method. The analysis of XRD and FT-IR shows that the surface of modified kaolinite is coated by porous titanium oxide. Furthermore the electrorheological effect is associated with the titanium oxide mass percent in the composite particle. When the content of titanium oxide in the composite is 34%, E=3kV/mm, and particle/silicone oil volume fraction is 25%, the yield stress of modified kaolinite/titanium oxide composite ERF is 7 kPa, which is 9 times of that of kaolinite ERF. The improvement of dielectric properties can well explain the increase of ER effects.
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Characterizing Damage Evolution of Three-dimensional Braided C/SiC Composite with AE Technology
PAN Wen-Ge,JIAO Gui-Qiong,WANG Bo,GUAN Guo-Yang
2004 Vol. 19 (4): 871875
Abstract(
1899 )
PDF(524KB)(
1260
)
An approach toanalyze the tensile behavior and damage evolution of three-dimensional braided C/SiC composite.Monotonic tensile tests were performed. Acoustic emission (AE) was used to monitor damage extension during test.Damage evolution was analyzed and different damage phases were determined by AE characteristic parameters data. Critical damage stress described with AE cumulates energy waw also defined.
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Field Activated Combustion Synthesis of Tungsten Carbide (Ⅱ) --Field-activated Pressure-assisted Combustion Synthesis
JIANG Guo-Jian,ZHUANG Han-Rui,LI Wen-Lan,Shon In-jin
2004 Vol. 19 (4): 876880
Abstract(
1936 )
PDF(330KB)(
1013
)
The field-activated pressure-assisted combustion synthesis (FAPACS) process was utilized to produce and densify tungsten carbides material from tungsten and carbon powders with different mole ratios. The effects of the temperature, the reactants composition on the products composition, density and microhardness were investigated. The relative densities of end-products are from 81.1% to 84.2%. Vickers microhardness measurements (at 1kg force) on the dense samples gave values from 731kg·mm-2 to 498kg·mm-2.
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In Situ Preparation of Hard Ceramic Coating Containing α-AL2O3 on TC4 Alloy
SUN Xue-Tong,JIANG Zhao-Hua,Li Yan-Ping,XIN Shi-Gang,YAO Zhong-Ping
2004 Vol. 19 (4): 881886
Abstract(
2059 )
PDF(856KB)(
982
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Ceramic coatings containing α-Al2O3 were prepared on Ti-6Al-4V alloy by an alternat-ing-current micro-plasma oxidation (MPO) method in solutions of sodium aluminate. The Knoop hardness (HK) and coating-substrate adhesion of MPO coatings were measured by the microhardness tester and ball-on-plate impact tester. Influences of the electrolyte concentration and cathodic to anodic current ratio Ic/Ia on the phase composition and mechanical properties of coatings were discussed. The results show that the coating formed at weak aluminate solution (≤0.05mol/L) consists of TiO2 and Al2TiO5; at high aluminate concentration (0.15-0.20mol/L) consists of TiO2, Al_2TiO5 and α-Al_2O_3. The content of α-Al2O3 increases with the decreasing Ic/Ia ratio. HK of coatings containing α-Al2O3 varies within 1100-1600 Hk50g which is much higher than that of Ti substrate and even the coating not containing α-Al2O3. Distribution profile of HK from interface toward the coating surface shows that HK gradually increases and reaches the maximum value around 35--45μm. In addition, there is no spallation after impact tests observed by SEM, which indicates MPO coatings have the excellent interfacial adhesion with the titanium substrate. The cycle thermal shock tests show that, the thinnest film possesses the highest number of cycles.
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Nucleation of Nano-Diamond Films for X-Ray Mask Substrates
LI Dong-Hui,LIU Zhi-Ling,YE Tian-Chun,CHEN Da-Peng,LU Fan-Xiu
2004 Vol. 19 (4): 887894
Abstract(
1886 )
PDF(1017KB)(
1053
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Diamond films are essential to next generation X-ray lithography mask. The affection of different process parameter to nucleation density and nucleation quality were investigated by controlling substrate-temperature, changing growth-time and CH4 concentration etc., and some high-density nucleation samples were obtainted. Mean time, pregrowth process after nucleation of diamond films was improved and dominant growth of major island was restrained effectively. The results show that the nucleation process can be optimized as 14% of CH4 concentration, 700℃ of substrate-temperature, 14min of nucleation. The optical properties and stress distribution of free-standing diamond membranes can be improved greatly.
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Hall Measurements, FTIR and EPR for n-Type Boron and Phosphorus Co-doped Diamond Films
HU Xiao-Jun,LI Rong-Bin,SHEN He-Sheng,DAI Yong-Bing,HE Xian-Chang
2004 Vol. 19 (4): 895901
Abstract(
2328 )
PDF(468KB)(
1192
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Low resistivity n-type diamond films were prepared by boron and phosphorus co-doping with the ion implantation method. Hall effect measurements show that the samples have nearly equivalent carrier concentration while the Hall mobility and conductivity of B-P co-doped diamond films are higher than those of P doped diamond films. FTIR measurements show that the formation of B-H complexes passivates the acceptor of boron and prevents the phosphorus from passivating by boron. EPR and Raman measurements indicate that the B-P co-doped diamond films have more perfect lattice than those of P doped diamond films, which is benefit to improve the carrier mobility and decrease the resistivity.
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Dielectric and Thermal Properties of Diamond Film/Alumina Composite
WANG Lin-Jim,FANG Zhi-Jun,ZHANG Ming-Long,SHEN Hu-Jiang,XIA Yi-Ben
2004 Vol. 19 (4): 902906
Abstract(
2030 )
PDF(321KB)(
1413
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The feasibility of diamond film coated alumina ceramics used as the packaging substrate of integrated circuits with ultra high speed and high power was studied. The measurement results of dielectric properties of the diamond film/alumina composites show that CVD diamond films can effectively reduce the dielectric constant of the composite. Carbon ions implantated into alumina substrates prior to the diamond deposition can reduce the dielectric loss of the composite from 5×10-3 to 2×10-3, and make the composite have better frequency stability. The thermal conductivity of the composite can obviously increase by CVD diamond film. With increasing the thickness of diamond film, the thermal conductivity of the composite will monotonously increase. The composite has a dielectric coefficient of 6.5 and a thermal conductivity of 3.98W/cm·K when the thickness of diamond film is up to 100μm.
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Microstructure and Optical Properties of Hydrogenated Amorphous Silicon Nitride Films Deposited by Helicon Wave Plasma Enhanced Chemical Vapor Deposition
YU Wei,HOU Hai-Hong,HE Jie,WANG Hua-Ying,FU Guang-Sheng
2004 Vol. 19 (4): 907911
Abstract(
2370 )
PDF(347KB)(
1317
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The atomic configurations and optical properties of hydrogenated amorphous silicon nitride (a-SiNx:H) films deposited by helicon wave plasma enhanced chemical vapor deposition (HWP-CVD) were analyzed by using Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-VIS) spectroscopy. The results reveal that the films show different Si/N ratio and hydrogen bonding mode at the various ratio between the silicon and nitrogen containing gases (R), For nitride-rich samples, hydrogen has a chemical preference to bind to nitride. On the other hand, for silicon-rich samples, hydrogen atoms bind preferentially to silicon. The optical band gap, Eg and E04 of a-SiNx:H films decrease gradually with the increase of R, which is attributed to the increase of disorder degree of the a-SiNx:H film microstructure. Additionally, the correlation between (E04--Eg) and the slop of Tauc plot, B for the a-SiNx:H films is established.
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Synthesis of Spherical Titanium Dioxide Nanocrystals by O2+Ar Arc Plasma Method
WANG Yi,CUI Zuo-Lin,ZHANG Zhi-Kun
2004 Vol. 19 (4): 912916
Abstract(
2171 )
PDF(509KB)(
971
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Spherical nanocrystals of titanium dioxide (TiO2) were synthesized by inflight oxidation of titanium (Ti) metal-atoms in argon-oxygen thermal plasma. Morphology investigation shows that these nanoparticles obtained are perfectly spherical and dispersible. Their average grain sizes are about 20nm. XRD analysis reveals that these spherical nanoparticles are totally crystalline, comprised of anatase and rutile or their composite.
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Hydrothermal Synthesis of Nanocrystal FeS2 by the Seed-Induced Method
WU Rong,ZHENG Yu-Feng,ZHANG Xiao-Gang,SUN Yan-Fei,XU Jin-Bao
2004 Vol. 19 (4): 917920
Abstract(
2141 )
PDF(434KB)(
1440
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FeS2(Pyrite) nanocrystals were synthesized successfully by the hydrothermal reaction using FeS2 crystalline seed with EDTA and tartaric acid as complex additives to optimize the preparation condition. The properties of the particles were investigated by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the product is single-phase pyrite with an ellipse-like shape and the average particle size of about 20nm. In the ultraviolet-visible range, pyrite shows a strong absorptivity between 215--314nm and the direct band gap takes place blue shift. The mechanism of formation of FeS2 nanocrystal was discussed in terms of the growth process.
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Preparation and Characteristic of New Type Nano Rare Earth Electrocatalyst for PEMFC
YANG Shu-Ting,CAO Zhao-Xia,ZHANG Yan-Feng
2004 Vol. 19 (4): 921925
Abstract(
2005 )
PDF(441KB)(
1174
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Nano rare earth alloy was prepared by a supersonic co-precipitation and low temprature reduction synthesis method. The research of XRD, SEM, TEM indicates that the particle size of the sample powder is about 20nm, and the test results by PEMFC electrochemistry workstation show that the sample powder modified by Pt has good electrocatalytic activity due to its good hydrogen transfer power.
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High Permeability Ni-Cu-Zn Ferrite Prepared by Combined-size Particles Processing
WANG Yi-Lin,ZHAO Mei-Yu,WU Wen-Jun
2004 Vol. 19 (4): 926930
Abstract(
1920 )
PDF(809KB)(
1150
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The processing with a physical method by using combined-size particles to decrease firing temperature for Ni-Cu-Zn ferrite was reported. As the densification process can be accelerated by selecting suitable ratio of nano-particles and micro-particles, the firing temperature was decreased and high initial magnetic permeability was held above 700 for Ni0.13Cuo.26Zn0.64Fe1.9804 ferrite. The initial magnetic permeability of the low firing (900℃) ferrite prepared by combined-size powders with 10% nano-sized powders was 764.
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Continuous Mass Production of Carbon Nanotube Using Secondary Fluidized Bed
CHEN Fei,ZHANG Xiao-Bin,SUN Yan-Lin,CHENG Ji-Peng,LI Yu
2004 Vol. 19 (4): 931934
Abstract(
2014 )
PDF(490KB)(
1129
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Continuous mass production of carbon nanotubes with chemical vapor deposition was studied by using secondary fluidized bed. Parameters such as temperature and flow rate were investigated. The yield of carbon nanotube is 200g/h. TGA and Raman analysis show the purity of the product is over 50%, but not well graphited. Optimized condition acquired is N25000sccm, C2H21000sccm at 750℃. Hydrogen reduction is not necessary and the catalyst can be reused after purification.
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Femtosecond Laser Induced Growth of LiNbO3 Crystal in Glass
JIANG Xiong-Wei,QIU Jian-Rong,ZENG Hui-Dan,ZHU Cong-Shan
2004 Vol. 19 (4): 935938
Abstract(
1892 )
PDF(212KB)(
1105
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Crystal of LiNbO3 was space-selectively induced in Li2O-Nb2O5-SiO2 glass by using a focused femtosecond laser with high repetition rate. The light, which emits from the focal point of the laser, turns from white light to green-blue one as the laser irradiates for a few seconds. The luminescence spectra of the emission from the focal point demonstrate that the green-blue light is the second harmonic generation of the incident femtosecond laser. Micro-Raman spectra demonstrate that LiNbO3 crystal is precipitated in the irradiated region of the glass.
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Synthesis and Structure Characteristic of Three-dimensional Ordered Macroporous SnO2 and SnO2/SiO2 Materials
WU Quan-Zhou,SHEN Yong,SUN Zhen-Fan,LI Yu-Guang
2004 Vol. 19 (4): 939942
Abstract(
1772 )
PDF(617KB)(
1127
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By using SnCl2·2H2O and tetraethyl orthosilicate as raw materials, polystyrene colloidal crystal with diameter of 585nm as template, three-dimensional ordered macroporous (3DOM) SnO2 and SnO2/SiO2 were successfully synthesized. SEM observation shows that 3DOM SnO_2 has a pore size of 453~500nm, and 3DOM SnO2/SiO2 has a pore size of 500nm. And such macropores connect with each other by small windows. Compared with the polystyrene colloidal crystal used, the 3DOM materials show shrinkage to some extent in pore size. The study indicates that it is difficult to obtain ordered pore structure when SnCl2 is used as precursor directly. But addition of tetraethyl orthosilicate or conversion of SnCl2 solution to oxide sol favors the formation of the highly ordered macroporous structure. XRD measurement indicates that the walls of the 3DOM materials are made of SnO2 nanoparticles with particle sizes around 17nm.
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Effects of Heat Treatment and Doping of Nb5+ on Sensitivity Properties of TiO2-based Material
PEI Su-Hua,SUN Hai-Bo,WANG Qiang,SUN Zhen-Cui,SHI Li-Wei
2004 Vol. 19 (4): 943947
Abstract(
1840 )
PDF(246KB)(
964
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Titanium is a premium metal-oxide material sensitive to trimethylamine (TMA) gas. To obtain high sensitivity and low power of elements, annealing in N2, doping with Nb5+ and long-time sintering were applied to improve the conductivity of TiO2-based sensitive materials. It is concluded that low oxygen pressure can enhance self-semiconductorization. Doping with 10% Nb5+ that substitutes for Ti4+ and long-time sintering that promotes conversion from Ti3+ to Ti4+ can improve conductivity of material and stability of elements. As a result, a new method is procured to make low-resistance sensor with high sensitivity and good selectivity.
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Effect of Adsorption Processes on the Rheology of A12O3-H2O-PAA Suspensions
LI Deng-Hao,GUO Lu-Cun
2004 Vol. 19 (4): 948952
Abstract(
2080 )
PDF(318KB)(
1146
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The rheological behaviors of α-Al2O3-H2O-PAA suspensions prepared by two-stage adsorption (at two different pH values) were studied. The results show that the stability of the suspension with a final pH 6.5 is improved considerably if it experiences an adsorption stage at pH above the iep of the alumina. The pH values of the first adsorption stage have a great impact on the stability of slurries. When the pH value increases from 8.0 to 10.0, the viscosity of the slurry decreases and the stability is enhanced. But when the pH reaches 11.0, the viscosity of the slurry increases and the stability declines. Increasing the time of the first adsorption stage is helpful to the stabilization of suspensions, due to improved homogeneity of the distribution of PAA on the particle surfaces.
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Synthesis of Slag α-sialon Powder by SHS and Properties of Slag α-sialon Ceramics
JIANG Jiu-Xin,CHEN Wei-Wu,WANG Pei-Ling,CHENG Yi-Bing,ZHUANG Han-Rui,YAN Dong-Sheng
2004 Vol. 19 (4): 953957
Abstract(
2122 )
PDF(520KB)(
1117
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(Ca,Mg) a-sialon powder containing rather pure α-sialon phase (abbreviated as salg α-sialon) was synthesized successfully by self-propagating high-temperature synthesis (SHS) technique, using slag as a raw material. The slag α-sialon powder was pressure-less and hot-pressed and the mechanical properties, the scour resistance to YAG, SiC, the erosion resistance to acid of slag a-sialon ceramics were studied. The results show that slag α-sialon ceramics have good mechanical properties and excellent scour resistance to YAG and SiC and erosion resistance to acid.
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Preparation of Thick CVD Diamond Film on Copper Substrate
MA Bing-Xian,YAO Ning,YANG Shi-E,GAO Guan-Yin,ZHANG Bing-Lin
2004 Vol. 19 (4): 958960
Abstract(
1895 )
PDF(381KB)(
1146
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Diamond thin and thick films were prepared on clean copper substrates by a MWCVD method. The films automatically come off from copper substrates owing to weak adhesion. But micrograph and Ramman spectroscopy show that the films have higher nucleation density and higher quality. These indicate that copper is an ideal substrate for the preparation of thick diamond films.
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