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FengXIAO LiangFANG 《材料科学技术学报》2003,19(5):388-390
The density of molten Ni-Co-Al alloy was measured using a modified pycnometric method. It has been found that the density of the molten Ni-Co-Al alloy decreases with increasing temperature, Co concentration and the ratio of Co concentration to Ni concentration in the alloy. The coefficient of volume expansion of the molten Ni-Co-Al alloy decreases with increasing Co concentration and the ratio of Co concentration to Ni concentration. The temperature coefficient of density increases with increasing the Co concentration or the ratio of Co concentration to Ni concentration in the alloy. The density of the molten Ni-Co-Al alloy as functions of both temperature and Co concentration was expressed. 相似文献
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Feng XIAO Liang FANGDepartment of Materials Science Engineering Chongqing Institute of Technology Chongqing China 《材料科学技术学报》2003,19(5)
The density of molten Ni-Cd-Al alloy was measured using a modified pycnometric method.It has been found thatthe density of the molten Ni-Co-Al alloy decreases with increasing temperature Co Concentration and the ratioof Co concentration to Ni concentration in the alloy.The coefficient of volume expansion of the molten Ni-Co-Al alloy decreases with increasing Co concentration and the ratio of Co concentration to Ni concentration.Thetemperature coefficient of density increases with increasing the Co concentration or the ratio of Co concentration toNi concentration in the alloy.The density of the molten Ni-Co-Al alloy as functions of both temperature and Coconcentration was expressed. 相似文献
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Peng ZHANG Yunhui DU Hanwu LIU Daben ZENG Jianzhong CUI Limin BADepartment of Mechanical Engineering Beijing Jiaotong University Beijing ChinaDepartment of Mechanical Engineering Tsinghua University Beijing ChinaMetal Forming Department Northeastern University Shenyang ChinaAnshan Automobile Fittings Factory Anshan China 《材料科学技术学报》2004,20(2):193-195
Fe-AI compound at the interface of steel-mushy AI-20Sn bonding plate was studied quantitatively. The relationship between ratio of Fe-AI compound at interface and bonding parameters (such as preheat temperature of steel plate, solid fraction of AI-20Sn slurry and rolling speed) was established by artificial neural networks perfectly. The results show that when the bonding parameters are 505℃ for preheat temperature of steel plate, 34.3% for solid fraction of AI-20Sn slurry and 10 mm/s for rolling speed, the reasonable ratio of Fe-AI compound corresponding to the largest interfacial shear strength of bonding plate is obtained. Its value is 72%. This reasonable ratio of Fe-AI compound is a quantitative criterion of interfacial embrittlement, that is, when the ratio of Fe-AI compound at interface is larger than 72%, interfacial embrittlement will occur. 相似文献
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Suwei YAO Haixia WU Weiguo ZHANG Hongzhi WANG Sugiyama Laboratory of Surface Technology Department of Applied Chemistry School of Chemical Engineering Technology Tianjin University Tianjin China 《材料科学技术学报》2005,21(3):307-310
Granular CoxCu1-x alloy films were prepared by electrodeposition at room temperature directly onto semiconducting Si substrate. X-ray diffraction (XRD) revealed that the as-deposited films formed single phase metastable fcc alloy structure. The fcc lattice parameter αwas found to decrease linearly with increasing Co concentration x in the studied range. The giant magnetoresistance (GMR) of the films was improved after annealing. Pure Co fcc diffraction peaks were observed in the diffractogram of the annealed sample, indicating phase separation occurred upon annealing. The optimal annealing temperature was 450℃. The maximum of magnetoresistance (MR) ratio 8.21% was obtained for the Co20Cu80 thin film after annealing at 450℃for 1 h. The saturation field decreased upon annealing in the MR curves of Co20Cu80 film. 相似文献
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EssamA.Kishar 《材料科学技术学报》2002,18(3):263-265
The hydration reaction of a mixture of tricalcium aluminate(C3A)and gypsum with the molar ratio of 1:3 was carried out at room temperature and a water/solid ratio of 4.0.The hydration was carried out in presence of 0,1 and 3% stearic acid and the mixes were designated as A,B and C,respectively.Ettringite was the only hydration product formed in the presence and absence of stearic acid.Phase composition,microstructure,infra-red analysis as well as degree of hydration were carried out for the different hydration mixtures.The rate of ettringite formation in the presence of 3% stearic acid was accelerated during the first half hour of hydration,and then retardation was occurred.In the presence of 1% stearic acid the ettringite formation was accelerated first till 3 days,then retardation was observed at later hydration ages. 相似文献
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Effects of Austenite Stabilization on the Onset of Martensite Transformation in T91 Steel 总被引:1,自引:0,他引:1
The influences of thermal stabilization of austenitic on the onset temperature for a martensite transformation in T91 ferritic heat-resistant steel were studied by high-resolution differential dilatometer. The phase transformation kinetic information was obtained by adopting lever rule from the recorded dilatometric curves. The results show that an inverse stabilization, featured by the damage of "the atmosphere of carbon atoms" and the increase of the starting temperature for martensite transformation takes place when the T91 ferritic steel is isothermally treated above the Ms point, and it becomes strong with increasing the holding time. While the continued temperature for martensite transformation decreases gradually when isothermally holding at a temperature below Ms point. The observed inverse stabilization behavior could be attributed to the relatively high temperature of Ms point in the explored T91 ferritic heat-resistant steel. 相似文献
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Qiong Chen Yongqin Chang Changjing Shao Jing Zhang Jun Chen Mingwen Wang Yi Long 《材料科学技术学报》2014,30(11):1103-1107
Nanocrystalline zirconia (ZrO2) powders were prepared by a sol-gel process followed by annealing treatments from 500 to 1200 ℃. Phase transformation, microstructural features and photoluminescence properties were characterized by X-ray diffraction, transmission election microscopy and photoluminescence spectra, respectively. The results show that both monoclinic phase and tetragonal phase exist in the nanocrystalline ZrO2 powders at annealing temperature in the range of 500-900 ℃, and the concentration of monoclinic phase increases with increasing the annealing temperature. Tetragonal phase is totally transformed to monoclinic phase when annealing temperature is up to 900 ℃. The average grain size of the powders also increases when annealing temperature increases. Two emission peaks centered at 390 nm (named as /390) and 470 nm (named as /470) exist in the photoluminescence spectra, and the intensity ratio of /390 to /470 decreases with increasing annealing temperature. The grain size is proposed to be responsible for the phase transformation in the nanocrystalline ZrO2 powders. 相似文献
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ZnO nanoparticles of different sizes were prepared by varying the molar ratio of glycine and zinc nitrate hexahydrate as fuel and oxidizer (0.1, 0.8, 1.11, 1.3, 1.5, 1.7, 2.0) by simple solution combustion method. UV-Visible spectrophotometry studies show that, the band gap of the prepared ZnO nanoparticles increases with increasing fuel to oxidant (F/O) molar ratio up to 1.7 revealing the formation of ZnO nanoparticles. The decrease in band gap for the sample of F/O molar ratio 2.0 is due to an increase in particle size. Powder X-ray diffraction patterns of the prepared samples show the formation of single phase ZnO nanoparticles and the particle size decreases with increasing F/O molar ratio up to 1.7. Surface morphology of the prepared samples was studied by scanning electron microscopy and it was observed that, the porosity increases with increasing F/O molar ratio. DC electrical conductivity at room temperature and in the temperature range of 303-563 K was studied for all the samples and the results revealed that, the sample of F/O molar ratio 1.7 has low electrical conductivity at room temperature and high EAR (high temperature activation energy) compared to other samples. 相似文献
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Yi Ding Zheng Zhang Baohe Luo Qingliang Liao Shuo Liu Yichong Liu Yue Zhang 《Nano Research》2017,10(3):980-990
A cobaltosic-oxide-nanosheets/reduced-graphene-oxide composite (CoNSs@RGO) was successfully prepared as a light-weight broadband electromagnetic wave absorber.The effects of the sample thickness and amount of composite added to paraffin samples on the absorption properties were thoroughly investigated.Due to the nanosheet-like structure of Co3O4,the surface-to-volume ratio of the wave absorption material was very high,resulting in a large enhancement in the absorption properties.The maximum refection loss of the CoNSs@RGO composite was-45.15 dB for a thickness of 3.6 mm,and the best absorption bandwidth with a reflection loss below-10 dB was 7.14 GHz with a thickness of 2.9 mm.In addition,the peaks of microwave absorption shifted towards the low frequency region with increasing thickness of the absorbing coatings.The mechanism of electromagnetic wave absorption was attributed to impedance matching of CoNSs@RGO as well as the dielectric relaxation and polarization of RGO.Compared to previously reported absorbing materials,CoNSs@RGO showed better performance as a lightweight and highly efficient absorbing material for application in the high frequency band. 相似文献
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《材料科学技术学报》2020,(2)
A simple method to synthesize high-content ternary carbide Ti_3AlC_2 nanoparticles from Ti, Al, and C starting elemental powders without ball milling in NaCl–KCl molten salt was reported. The effects of mass ratio of the salt to starting materials, temperature, reaction time, and Al molar ratio on preparation of Ti_3AlC_2 were investigated. The Ti_3AlC_2 formation is dramatically influenced by temperature and mass ratio of the salt to raw materials: a higher temperature and higher mass ratio of the salt to raw materials are more preferable for Ti_3AlC_2 powder formation. Homogenous Ti_3AlC_2 powder with particle size of ■nm is synthesized by 3Ti/Al/2C starting elemental powders in NaCl–KCl molten salt at 900℃ for 10 h, 950℃ for 5h, or 1000℃ for 2h, respectively, when the mass ratio of the salt to 3Ti/Al/2C starting materials is 10:1. 相似文献
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将Bi2O3掺杂到用溶胶—凝胶法制备的La0.6Sr0.33MnO3(LSMO)微粉中,XRD测量结果证实有过量的Bi析出。随着Bi掺杂量的增加,LSMO/(Bi2O3)x/2材料电阻率发生明显变化,在x=(0—0.10)摩尔比的掺杂范围内,电阻率先上升后突然下降。当X=0.1时,电阻率比未掺杂样品下降了一个数量级。Bi掺杂对低温和室温磁电阻有着完全不同的影响。低温下,随掺杂量增加,磁电阻下降;室温下Bi的微量掺杂可以使磁电阻增大,掺入x=0.03Bi使室温磁电阻由-4.4%提高到-5.6%。 相似文献
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将La0.67Sr0.33MnO3(LSMO)、Ag2O及TiO2粉混合经高温烧结后制备了钙钛矿相/xAg两相复合体系(x是Ag与钙钛矿材料的物质的量比),系统地研究了Ag-Ti的共掺杂对LSMO电性和磁电阻效应的影响.0.07摩尔比Ti4+离子的B位掺杂使LSMO的居里温度降至室温.Ag的掺入对Tc影响不大,Tp逐渐升高.由于钙钛矿颗粒属性的改善和金属导电通道的出现,材料的电阻率明显下降.Ag掺杂使室温磁电阻得到显著增强,室温下从x=0.30样品中得到最大的磁电阻,约为32%,是La0.67Sr0.33MnO3样品的8倍,La0.67Sr0.33Mn0.93Ti0.07O3样品的1.6倍. 相似文献
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利用溶胶-凝胶法(sol-gel)制备了多晶类钙钛矿型稀土锰氧化物La0.60Sr0.40-xKxMnO3(x=0.00,0.15,0.20,0.30)。发现K+取代部分Sr2+后,可使样品的居里温度降至室温附近,并且使样品的室温磁电阻比替代前明显增大。在1.8T的磁场下,x=0.30的样品磁电阻峰值为21%,相应的峰值温度为304K。而母体La0.60Sr0.40MnO3的磁电阻峰值仅为6.4%,峰值温度为373K。可见K+离子替代使室温附近样品的庞磁电阻效应有了明显的改善。 相似文献
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采用溶胶一凝胶(sol-gel)法制备了名义组分为La0.67Sr0.33-XCuXMnO3(x=0~0.33)的多晶样品,发现用Cu替代少部分Sr后样品的室温磁电阻比替代前的明显增大.在1.8T磁场作用下,当x=0.15时,磁电阻峰值为27.7%,峰值温度为306K,当温度低于306K时磁电阻值随温度的升高而增大,当温度高于306K时磁电阻值随温度的升高而减小;当x=0.1时,在295K-310K温度之间磁电阻值达19%左右,受温度影响很小;因此在提高了室温磁电阻值的同时,又提高了磁电阻的温度稳定性.这对于该类磁电阻材料的应用具有很大意义. 相似文献
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在BaTiO3(BT)-Nb2O5-ZnO系统中引入硼硅酸盐助烧剂,加入Gd、Nd稀土氧化物以期获得中烧X7R陶瓷材料.研究发现,保持Gd用量不变,随着Nd用量在0.1 wt%~0.7 wt%范围内增大,陶瓷室温介电常数呈现单调递减趋势,而对电容量高温变化率的影响很小;保持Nd用量不变,随着Gd掺杂量的增加,室温介电常数先减少后增大,电容量高温变化率下降.实验发现,BT陶瓷的电容量高温变化率和微观应力分数成正比例关系变化.Gd、Nd共掺杂BT系统的电容量高温变化率受Gd控制而受Nd影响不大.在空气中于1140℃下烧成的BaTiO3陶瓷材料的主要性能指标达到:ε298K>3000,tgδ≤1.0%,ρ≥1011Ω.cm,-55℃~+125℃范围内最大电容量变化率不超过±7.5%. 相似文献
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在La0.67Ca0.33MnO3和La0.67Ba0.33MnO3中用Dy对La进行了置换研究。结果发现,随掺Dy量的增加,两类材料的居里温度和金属-绝缘体相变温度单调下降,峰值电阻率单调增加。在Ca系样品中,掺入13%的Dy后,在5T的磁场下,最大磁电阻比达到7900%。在Ba系样品中.掺Dy对磁电阻的影响要小得多。掺Dy对材料性质的影响可以用晶格效应来解释,但晶格效应产生的作用与碱土离子的品种有明显关系。 相似文献