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Journal of Materials Sciences & Technology
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1999, Vol.15 No.01
Online: 1999-01-28
Research Articles
 
Research Articles
1 Weigang ZHANG, Huiming CHENG, Ge SU, Yueying FAN, Feng LI, Zuhong SHEN, Benlian ZHOU
A Model for Liquid-Diffusion Catalytically Grown Fibrous Carbon Material
A mechanism for the catalytically growth of vapor grown fibrous carbon (VGFC)preparing from the floating catalyst method has been proposed, in which liquid diffusion-determined diffusion of carbon atoms through catalyst particles is described mathematically, and the physical and chemical properties of the catalyst particles during the growth process are taken into account. From the model the growth rate and grown length of VGFC are calculated theoretically which coincides with the experimental data; and the necessity of reducing gas such as hydrogen in preparing VGFC is explained as to reduce Fe3C, which acts as intermediate catalyst shown by the model. Fe3C formed on the surface of γ-Fe will stop the growth of carbon fiber if they can not be reduced at once. Additionally, the growth temperature and diameter of VGFC are also discussed in the paper.
1999 Vol. 15 (01): 1-4 [Abstract] ( 393 ) [HTML 1KB] [PDF 298KB] ( 335 )
5 Xiufeng HAN, Lanying LIN, T.Miyazaki, Fuming YANG, Rengeng XU, Xinhua WANG, Hongge PAN, Changping CHEN
Hydrogenation and Anisotropic Expansions in R3Fe29-xTx (R = Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)
A systematic study of the phase formation, structure and magnetic properties of the R3Fe29-xTx compounds (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy; T = V and Cr) has been performed upon hydrogenation. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions mainly along the a- and b-axis rather than along the c-axis are observed for all of the compounds upon hydrogenation. Hydrogenation leads to an increase in the Curie temperature and a corresponding increase in the saturation magnetization at room temperature for each compound. First order magnetization processes (FOMP) occur in the external magnetic fields for Nd3Fe24.5Cr4.5H5.0, Tb3Fe27.0Cr2.0H2.8, and Gd3Fe28.0Cr1.0H4.2 compounds.
1999 Vol. 15 (01): 5-9 [Abstract] ( 487 ) [HTML 1KB] [PDF 327KB] ( 356 )
10 Shunpu LI, Deqian ZHAO, Shengxu ZHAO, Mingxiang PAN, Xichen CHEN
Growth of the Single Crystal of Peritectic Reaction Induced Phases by “Melting Zone of Different Compositions” Technique
Selecting Ni5Zr compound as a model object, the single crystal growth of peritectic reaction induced phases has been achieved by “melting zone of different composition” technique in this study.
1999 Vol. 15 (01): 10-12 [Abstract] ( 354 ) [HTML 1KB] [PDF 164KB] ( 347 )
13 Xiaming DAI, Qingfeng LI, Mingqin DING, Jiemo TIAN
Thermodynamic Aspect in Synthesis of AlN Powders by Carbothermal Reduction and Nitridation Process
A thermodynamical calculation shows that AlN powders were synthesized in the process by the overall reaction Al2O3(s)+3C(s)+N2(g)=2AlN(s)+3CO(g) and its minimum reaction temperature T0 = 1852 K, if all reactants and products were in standard states. In the practical experiments, AlN phase appeared obviously at only 1300℃, the major reasons are related to the partial pressure of its gaseous product p CO and the mixed free energy. Either increasing N2 flow rate or elevating N2 pressure could lower the synthesis temperature. On the other hand, as the temperature decreases, the equilibrium constant Km also reduces, and the reducing rate strongly depends on the temperature: the lower the temperature, the higher the rate.
1999 Vol. 15 (01): 13-16 [Abstract] ( 346 ) [HTML 1KB] [PDF 240KB] ( 331 )
17 Jihui WANG, Xinchun LU, Shizhu WEN, Hengde LI, Liduo WANG
Structure and Microtribological Mechanism of Teflon Deposited Film
Teflon film was prepared by ion beam enhanced deposition method. The structure and microtribological properties were studied by PHI-5300, FT-IR, XRD and atomic force and friction force microscope (AFM/ FFM). The results show that the deposited Teflon is in crystalline state, and its structure is the same as the bulk Teflon. There are two periods in the friction and wear tests for Teflon film. When the load is less than 70 nN, the micro friction force is linear with the load, and the Teflon does not have the lubricity. But when the load is greater than 70 nN, the friction force of Teflon film will stay nearly constant, and worn marks will be created in the friction and wear process. The worn depth of Teflon film increases linearly with the load.
1999 Vol. 15 (01): 17-20 [Abstract] ( 355 ) [HTML 1KB] [PDF 320KB] ( 327 )
21 Youfen LI, Yanruo HONG, Xiangchong ZHONG, Tingshou LI
Kinetics of Oxidation for β-Sialon in Diphase β-Sialon/Al2O3 Composite
Non-isothermal kinetic research has been carried out on oxidation behavior of β-Sialon in diphase β-Sialon/Al2O3 composite at high temperatures. A kinetic formula is established for non-isothermal oxidation process of β-Sialon. The rate of oxidation process is controlled by chemical reaction at the initial stage and then by diffusion. The apparent activation energies and apparent rate constants at different temperatures are determined by treating TG data of the overall process.
1999 Vol. 15 (01): 21-24 [Abstract] ( 383 ) [HTML 1KB] [PDF 222KB] ( 378 )
25 Jin GUO, Chonghe LI, Nianyi CHEN
Effect of Electrode Constitution on the Discharge Properties of Ni-MH Battery
The discharge capacities for Ni-MH batteries with different electrode constitutions are analyzed by chemical pattern recognition method, and some criteria for improving synthetical discharge properties are obtained. The results show that the thickness of positive and negative electrode are significant in influencing the discharge capacities at both of low and high discharge current, the influence of resistance of positive electrode on discharge capacity is less significant compared with other factors in electrode constitution and the effect of electrolyte on discharge capacity at low discharge current is more significant than that at high discharge current.
1999 Vol. 15 (01): 25-30 [Abstract] ( 457 ) [HTML 1KB] [PDF 330KB] ( 358 )
31 Huiwen ZHU, Hao ZHOU, Xiang WANG, Maosheng TIAN, Qingping KONG
Creep-Fatigue Interaction in an Fe-25Ni-15Cr Based Alloy
The interactions between high temperatures creep and low cycle fatigue in an Fe-25Ni-15Cr based alloy GH132 has been studied under three different loading schedules: (a) continuous cyclic creep, (b) prior creep followed by fatigue, and (c) prior fatigue followed by creep. It is found that the interaction appears nearly linear for all the three schedules. The behavior of interaction in GH132 alloy is different from that previously observed in a GH30 alloy (Nimonic 75 type), in which although the interaction at schedules (a) and (c) was linear, a pronounced negative interaction occurred at the schedule (b), i.e., prior creep followed by fatigue. This difference is found to be associated with the difference in the evolution of microstructure. In the GH132 alloy, no cell structure is formed during the tests, while in the GH30 alloy, cell structure is well developed during prior creep, which impedes the motion of dislocations during sequential fatigue, resulting in a negative interaction between creep and fatigue.
1999 Vol. 15 (01): 31-34 [Abstract] ( 360 ) [HTML 1KB] [PDF 330KB] ( 318 )
35 Zhaochun ZHANG, Hang SU, Nianyi CHEN, Ruiwu PENG
Calculation of Thermodynamic Properties from Two-liquid Coexisting Phase Diagram of Al-In System by Means of NRTL Equation
In this paper, the NRTL equation approach has been used for calculating the activity coefficient and excess Gibbs free energy of the binary alloy system involving two-liquid coexisting phases. The parameters needed for the calculation are the differences of interaction energies (g12-g22), (g21-g11) and nonrandomness constant α, which are determined by solving NRTL equation with the aid of genetic algorithm. The calculation is carried out numerically for Al-In system. The agreement between the calculated and experimentally determined values of activity coefficient and excess Gibbs free energy is rather good, indicating the validity of the NRTL equation for the description of two-liquid coexisting phase alloy systems.
1999 Vol. 15 (01): 35-38 [Abstract] ( 359 ) [HTML 1KB] [PDF 237KB] ( 312 )
39 Mervette El Batouti
Surfactants as Inhibitors for Alkaline Corrosion of Aluminums
Inhibition of aluminum corrosion in NaOH solution by anionic surfactant as sodium (lauryl) sulphate, cationic surfactant as cetyl trimethyl ammonium bromide and non-ionic surfactant as Triton-X 100 has been studied using weight-loss and hydrogen evolution methods. It is found that the inhibition efficiency depends on the type of SAS as well as its concentration. The order of increasing inhibition is as follows ...Thermodynamic parameters are calculated.
1999 Vol. 15 (01): 39-42 [Abstract] ( 401 ) [HTML 1KB] [PDF 229KB] ( 368 )
43 Senying LIU, Dongliang ZHAO, Rongze HU, Chongyu WANG, Ping LUO
Bonding and Fracture Characteristics at α2/γ Interface in TiAl Alloy with B Addition
The bonding characteristics of (0001)α2‖(111)γ interface in two-phase TiAl alloy have been investigated with the recursion method. The results of bond order integral and interaction energy between atoms are presented. The effects of B on atoms bonding both in constituent phase and at the α2/γ interface have been studied. The correlation between the mechanical properties of the alloy and the bonding at the interface has been discussed. The results suggest that B segregation to the interface benefits the ductility. This is supported by therelated experiment.
1999 Vol. 15 (01): 43-47 [Abstract] ( 410 ) [HTML 1KB] [PDF 333KB] ( 317 )
48 Jian CHEN, Baiyun HUANG, J.H.Lee, S.J.Choe, Y.T.Lee
Carbide Formation Process in Directionally Solidified MAR-M247 LC Superalloy
Carbide nucleation, growth and trapping behavior in directionally solidified MAR-M247 LC alloy and the corresponding mechanism have been investigated. Carbide forming element enrichment controls the carbide nucleation and the carbide growth behavior. If the carbide forming element enrichment and the nucleation sites are suitable, carbide nucleation can occur both above and below the liquidus temperature. Heterogeneous carbide nucleation is the preferred nucleation mechanism at low carbide forming element enrichment. Carbide growth occurs mainly at inter-secondary γ dendrite arm area and lower part of the mushy zone. The carbides are subsequently trapped at these positions after growing to a certain size. Some carbide is only partially trapped by the solid-liquid interface and the carbide growth accelerates after being partially trapped. A critical growth rate exists between 2×10-6 m/s and 5×10-6 m/s. The carbide volume fraction decreases in the directionally solidified art at slow growth rate that is caused by the lack of suitable growth site and the low trapping ability of the solid-liquid interface.
1999 Vol. 15 (01): 48-52 [Abstract] ( 372 ) [HTML 1KB] [PDF 494KB] ( 364 )
53 Jiarong LI, Dingzhong TANG, Riling LAO, Shizhong LIU, Zhongtang WU
Effects of Rhenium on Creep Rupture Life of a Single Crystal Superalloys
The slabs of a single crystal superalloy were poured with 2.2% Re, 3.2% Re and 4.2% Re and other element contents of the alloys were basically kept no changed. The effects of Re on the ultimate tensile strength, creep rupture life and rafting of a single crystal superalloy were studied. The results showed that with increasing Re content the ultimate tensile strength decreased but the plasticity increased at 649℃, and the creep rupture life remarkably increased while the plasticity decreased at 982℃/248.2 MPa, 1038℃/206.8 MPa and 1070℃/176.8 MPa for the alloy; on the microstructure aspect, with increasing the creep rupture life of the alloy the rafting was getting bigger and bigger at the same test condition, and the rafting suppressed creep and increased creep rupture life in this single crystal superalloy.
1999 Vol. 15 (01): 53-57 [Abstract] ( 343 ) [HTML 1KB] [PDF 404KB] ( 335 )
58 Juntao LI, Yaping ZONG, Shiming HAO
Effects of Alloy Elements (C, B, Fe, Si) on the Ti-Al Binary Phase Diagram
The α(α2)/γ phase equilibria in Ti-Al-X (X = C, B, Fe, Si in at. pct) ternary systems were studied by equilibrium heat-treatment and EPMA. The results show that the addition of B to the Ti-Al binary system leads to a shift of both α(α2)/[ α(α2)+γ] and [α(α2)+γ]/γ phase boundaries to Al-rich side and 0.1 B addition decreases Tα by 18℃. The addition of C leads to a shift of [α(α2)+γ]/γ phase boundary to Al-rich side but the effect of 0.2 at.pct C addition on Tα is very slight. The addition of Fe results inα(α2)/ [α(α2)+γ] and [α(α2)+γ]/γ phase boundaries shifting to Ti-rich side and 1.0 Fe addition increases Tα by 90~110℃. The addition of Si leads to a shift of α(α2)/α(α2)/ [α(α2)+γ]} phase boundary to Ti-rich side and the 0.3 Si addition increases Tα by 80~110℃. The solubilities for C, B and Si in α(α2) phase are higher than those in the γ phase but the solubility for Fe in α(α2) phase is lower than that in γ phase.
1999 Vol. 15 (01): 58-62 [Abstract] ( 370 ) [HTML 1KB] [PDF 394KB] ( 316 )
63 Qingyan XU, Yuyong CHEN, Qingchun LI
Fabricating of Open-cell Porous Al-Si Alloy with Pressure Penetration Casting
Open-cell porous Al alloy was fabricated by pressure penetration casting. The fabrication of preform was studied in detail. When forming temperature is about 700℃ and binder content is about 10%, preform with high compressive strength is obtained. Good porous Al alloy with pore size (0.5~1.6 mm) and porosity (60%~80%) can be obtained under 100℃superheating of liquid metal and about 1.0MPa applied pressure. The size of the largest sample is up to 100mm in diameter and 100mm in height. With the help of SEM it was found that the obtained material is a three-dimension open-cell porous structure with well distributed and connected with each other pores. Finally theoretical analysis was carried out to explain the effect of fabricating process.
1999 Vol. 15 (01): 63-66 [Abstract] ( 396 ) [HTML 1KB] [PDF 383KB] ( 406 )
67 Luming MA, Guojun LIANG, Jun TAN, Lijian RONG, Yiyi LI
Effect of Hydrogen on Cryogenic Mechanical Properties of Cr-Ni-Mn-N Austenitic Steels
The method of high-pressure hydrogen charging was used to investigate the internal hydrogen effects on cryogenic mechanical properties of two Cr-Ni-Mn-N austenitic steels, 22-13-5 and 21-6-9. Specimens saturated with hydrogen up to 65×10-6~68×10-6were tested in air at temperatures ranging from 77 to 293 K. Hydrogen caused the increase in cryogenic strength, both yield strength and ultimate tensile strength. Hydrogen decreased cryogenic ductility, and the maximum hydrogen embrittlement (HE) tendency was found at a certain low temperature. Cr-Ni-Mn-N austenitic steels showed the feature: δL>ΨL at low temperatures, here, δL andΨL are the hydrogen induced loss rates of elongation and reduction of area, respectively. Hydrogen had less effect on cryogenic Charpy impact toughness and notched tensile strength, however, hydrogen decreased cryogenic fracture toughness of the steels. At temperature below Md, the fracture toughness was obviously decreased due to the formation of strain-induced martensites, whether hydrogen was charged or not.
1999 Vol. 15 (01): 67-70 [Abstract] ( 402 ) [HTML 1KB] [PDF 241KB] ( 334 )
71 Zuolin CUI
Plastic Deformation of Nano-TiO2 Ceramics Prepared by Different Methods
The comparative study of the tensile plastic deformation of nano(n)-TiO2 ceramic prepared by physical gas condensation (P) and chemical hydrolysis precipitation (C) methods was conducted by a gas pressure forming technique at 750-800℃. The results show that n-TiO2 (P) possesses excellent property of tensile plastic deformation comparing with n-TiO2(C). The reason for this is attributed to the surface cleanness and soft agglomeration of n-TiO2(P) particle prepared in relatively clean vacuum condition.
1999 Vol. 15 (01): 71-74 [Abstract] ( 373 ) [HTML 1KB] [PDF 501KB] ( 406 )
75 Wei WANG, Rongfang HUANG, Lishi WEN, Liping GUO, Wenkui WANG
Microstructure and In-plane Resistivity of Cu/Ni Multilayers
The Cu/Ni multilayers were deposited using ion beam sputtering at room temperature and 250℃ respectively. The microstructures of the multilayers including interfacial roughness, grain size and growth direction have been investigated by transmission electron microscopy and X-ray diffraction. The microstructure depends strongly on the substrate temperature and modulation wavelength, bigger grain size and larger interfacial roughness were obtained when the multilayers were deposited at 250℃, and the multilayers ceased to grow epitaxially due to the increasing defects in the multilayers. The resistivity of the multilayers is very sensitive to the microstructure due to the size-effect. In order to study the influence of the microstructure to the resistivity, the in-plane resistivity of Cu/Ni multilayers was measured using four-point probe. The resistivity increases with higher substrate temperature, and it decreases when the modulation wavelength becomes short. The interfacial roughness and grain size have co-contribution to the resistivity. The interface scattering is the main factor that has effect on the resistivity of Cu/Ni multilayers.
1999 Vol. 15 (01): 75-78 [Abstract] ( 352 ) [HTML 1KB] [PDF 415KB] ( 327 )
79 A.A.Hanna, M.Sh.Khalil, H.I.Saleh, A.F.Ali
Study of Sintering Behavior and Electrical Conductivity of Cr-Zn-Fe-O System
A series of chemical compositions based on Cr, Fe and O with Zn as a partially substituting ion has been prepared in the general formula ZnxCr1-xFe2O by coprecipitation method using NH4OH as the precipitating agent at pH=10.3. The prepared samples were identified by both thermal analysis (DTA and TGA) and X-ray diffraction (XRD). It was found that no single phase was obtained for any of the studied compositions but a mixture of different phases was observed, depending on the molar percentage of zinc ion substitution as well as on the sintering temperature. The temperature dependence of the electrical conductivity, σ, of the prepared samples was plotted between 25 and 680℃. It was observed that the electrical conductivity increased with temperature for both samples with x=0.00 and 0.80 Zn ion content while it was nearly temperature independent for samples with intermediate Zn concentration x=0.2 and 0.5 mol fraction. The activation energy, Ea, calculated from the linear relation, lgσ-1000/T for the final mixtures (sintered at 1300℃) was calculated.
1999 Vol. 15 (01): 79-82 [Abstract] ( 325 ) [HTML 1KB] [PDF 227KB] ( 297 )
83 Yanzhong ZHANG
Relations among High-frequency Magnetic Properties and Frequency in Nanocrystalline Fe72.5Cu1Nb2V2Si13.5B9 Alloy
High-frequency magnetic properties, such as core loss, coercivity and amplitude permeability of a newly-developed nanocrystalline Fe72.5Cu1Nb2V2Si13.5B9 alloy in the wide ranges of f=20-1000 kHz, Bm=0.01-0.6T and Bmf=10-40 (T•kHz) have been measured. A large amount of experimental data have been fitted by a computer, thus obtaining several expressions representing the influence of frequency on high-frequency magnetic properties, that are useful in practical applications.
1999 Vol. 15 (01): 83-86 [Abstract] ( 347 ) [HTML 1KB] [PDF 290KB] ( 298 )
87 M.I.El-Hofy, A.M.Donia, M.M.Abou-Sekkina
Electrical Investigation of Some Silver Containing Ceramics Obtained from Coprecipitated Oxalates
Silver-ceramics (Ag2MO2)(M = Co, Ni, or Cu) were prepared through thermal decomposition of coprecipitated oxalates. Pellets of these materials were annealed at 350℃ for different time periods up to 5 h. The effect of annealing time on the transport properties was studied. IR and X-ray spectra were also studied.
1999 Vol. 15 (01): 87-90 [Abstract] ( 495 ) [HTML 1KB] [PDF 227KB] ( 350 )
91 Shunpu LI, Deqian ZHAO, Shengxu ZHAO, Mingxiang PAN, Xicheng CHEN
Growth of the Single Crystal of Solid Solution by “Melting Zone of Different Compositions
Fe (Si) solid solution being selected as a model material, the single crystal growth of solid solution has been achieved by melting zone of different compositions (MZDC) technique in this study.
1999 Vol. 15 (01): 91-93 [Abstract] ( 362 ) [HTML 1KB] [PDF 197KB] ( 357 )
94 Huaping XIONG, Lianmeng ZHANG, Qiang SHEN, Runzhang YUAN
Densification of W-Ni-Cu and W-Fe-Cu Alloys at 1573 K
The tungsten alloys with Ni-Cu and Fe-Cu additives were sintered at 1573 K for 1 h by hot-pressing method. It was found that the alloy relative density can be improved with the addition of Cu when Cu content is not very high, and W95Ni3Cu2 alloy with full density can be obtained on the sintering condition. However, with the Cu content further increasing, the relative density change of W-Ni-Cu alloy and W-Fe-Cu alloy shows different trends: the former tends to decrease obviously, but the latter shows little change. According to the analysis results, the element Cu has different effects on the activation capability of Ni and Fe during sintering of the tungsten alloys.
1999 Vol. 15 (01): 94-96 [Abstract] ( 332 ) [HTML 1KB] [PDF 261KB] ( 279 )

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