Volume 34,Issue 4,2005 Table of Contents
2005, 34(4):505-509.
Abstract:
Nanocrystalline materials are the most attractive materials in the field of materials science and engineering in the world. Nano-crystallization of metallic glasses is an effective way to prepare nanocrystalline materials. Here main nano-crystallization methods, including thermal crystallization, electrical crystallization, mechanical crystallization and crystallization under pressure etc. Their principle, problems associated as well as recent technological development are reviewed. The research progress in Tsinghua university in nano-crystallization of Bulk Metallic Glasses(BMG) treated by high density pulse current is simply reported.
Nanocrystalline materials are the most attractive materials in the field of materials science and engineering in the world. Nano-crystallization of metallic glasses is an effective way to prepare nanocrystalline materials. Here main nano-crystallization methods, including thermal crystallization, electrical crystallization, mechanical crystallization and crystallization under pressure etc. Their principle, problems associated as well as recent technological development are reviewed. The research progress in Tsinghua university in nano-crystallization of Bulk Metallic Glasses(BMG) treated by high density pulse current is simply reported.
2005, 34(4):510-514.
Abstract:
As frontiers of technology, electromagnetic cold crucible technology has been applied to melting and forming of reactive metals, refractory and rare metals. The basic theory and the advantages of this technology are introduced. Constructions of cold crucible and electrical parameters effect on the use of cold crucible are discussed. To be more specific, the constructions of cold crucible include numbers and shape of segment, weight of cold crucible and width of slit, and electrical parameters include frequency, voltage and current intensity. Other factors, such as physical properties of the metal, positions of the shield and the induction coil, are also discussed. Research and application of cold crucible technology in the world are overviewed and difficulties in applying this technology are pointed out. Cold crucible technology will be a hopeful and important technique in the 21st century.
As frontiers of technology, electromagnetic cold crucible technology has been applied to melting and forming of reactive metals, refractory and rare metals. The basic theory and the advantages of this technology are introduced. Constructions of cold crucible and electrical parameters effect on the use of cold crucible are discussed. To be more specific, the constructions of cold crucible include numbers and shape of segment, weight of cold crucible and width of slit, and electrical parameters include frequency, voltage and current intensity. Other factors, such as physical properties of the metal, positions of the shield and the induction coil, are also discussed. Research and application of cold crucible technology in the world are overviewed and difficulties in applying this technology are pointed out. Cold crucible technology will be a hopeful and important technique in the 21st century.
2005, 34(4):515-520.
Abstract:
Biocompatible carbon/carbon composites have good mechanical properties close to those of bone, which make them great potential as orthopedic implants in human body. Biomedical carbon types as bone implants, its response to bone tissue and bioactive modification of carbon/carbon composites were reviewed. On the basis of this summary, the structure of bioactive coating on carbon/carbon composites, which is composed of hard internal layer inhibiting the release of carbon particles and bioactive layer, is suggested, and the details are also presented correspondingly. Finally, the medical prospects of carbon/carbon composites as bone implants are shown with some problems need to be solved.
Biocompatible carbon/carbon composites have good mechanical properties close to those of bone, which make them great potential as orthopedic implants in human body. Biomedical carbon types as bone implants, its response to bone tissue and bioactive modification of carbon/carbon composites were reviewed. On the basis of this summary, the structure of bioactive coating on carbon/carbon composites, which is composed of hard internal layer inhibiting the release of carbon particles and bioactive layer, is suggested, and the details are also presented correspondingly. Finally, the medical prospects of carbon/carbon composites as bone implants are shown with some problems need to be solved.
2005, 34(4):521-525.
Abstract:
The density of molten Ni-Ta alloys has been measured by a modified pycnometric method. It is found that the density of the molten Ni-Ta alloys decreases with a rise in temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of molten Ni-Ta binary alloys increases with the increase of temperature and tantalum concentration. The partial molar volume of tantalum in molten Ni-Ta binary alloy has been approximately calculated.
The density of molten Ni-Ta alloys has been measured by a modified pycnometric method. It is found that the density of the molten Ni-Ta alloys decreases with a rise in temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of molten Ni-Ta binary alloys increases with the increase of temperature and tantalum concentration. The partial molar volume of tantalum in molten Ni-Ta binary alloy has been approximately calculated.
2005, 34(4):526-530.
Abstract:
利用XRD，TEM研究了渗氢后Ti6Al4V合金的组织变化。在渗氢0．302％(质量分数，下同)及0．490％的试样中发现了面心立方的氢化物巧和大量的斜方结构的马氏体α”。提出了1种基于扩散的由βH共析转变生成α及fcc结构的片状氢化物δ的机制，并指出氢的引入可能诱发马氏体转变。在室温拉伸试验中发现在氢含量不高于0．102%时不发生氢致脆化。氢化物δ和马氏体α″在Ti6Al4V合金的氢脆中起主要作用，氢化物δ既有利于裂纹的萌生又有利于裂纹的扩展，而马氏体α″对裂纹的扩展具有重要的作用，二者共同促进了Ti6Al4V合金的室温高氢含量氢脆。
利用XRD，TEM研究了渗氢后Ti6Al4V合金的组织变化。在渗氢0．302％(质量分数，下同)及0．490％的试样中发现了面心立方的氢化物巧和大量的斜方结构的马氏体α”。提出了1种基于扩散的由βH共析转变生成α及fcc结构的片状氢化物δ的机制，并指出氢的引入可能诱发马氏体转变。在室温拉伸试验中发现在氢含量不高于0．102%时不发生氢致脆化。氢化物δ和马氏体α″在Ti6Al4V合金的氢脆中起主要作用，氢化物δ既有利于裂纹的萌生又有利于裂纹的扩展，而马氏体α″对裂纹的扩展具有重要的作用，二者共同促进了Ti6Al4V合金的室温高氢含量氢脆。
2005, 34(4):539-543.
Abstract:
Predication on initial discharge capacity of AB5-based hydrogen storage was done by adapting the simulated annealing method to artificial neural network (ANN). The parameters in cooling schedule were determined and their influences on network predication performance were discussed in experiments. A practical cooling regime was established then, and a network with better performances was obtained by combining simulated annealing algorithm with gradient descent method.
Predication on initial discharge capacity of AB5-based hydrogen storage was done by adapting the simulated annealing method to artificial neural network (ANN). The parameters in cooling schedule were determined and their influences on network predication performance were discussed in experiments. A practical cooling regime was established then, and a network with better performances was obtained by combining simulated annealing algorithm with gradient descent method.
2005, 34(4):544-548.
Abstract:
采用分离式霍普金森压杆(SHPB)技术,研究了孔隙率对泡沫铝在高应变速率(700s(-1)~~2600s(-1)~)条件下力学性能的影响,并与准静态条件下(1×10(-3)~s(-1)~)的性能进行了对比。实验发现泡沫铝在准静态和动态条件下呈现逐层破坏的特征,从而在应力-应变曲线上出现一平台区;由于铝合金本身存在的应变速率敏感性和多孔材料中气体的作用,使泡沫铝的平台应力随应变速率的增加而增大,当孔隙率较低时,增加尤为明显;泡沫铝的应变速率敏感度随应变的变化而变化。
采用分离式霍普金森压杆(SHPB)技术,研究了孔隙率对泡沫铝在高应变速率(700s(-1)~~2600s(-1)~)条件下力学性能的影响,并与准静态条件下(1×10(-3)~s(-1)~)的性能进行了对比。实验发现泡沫铝在准静态和动态条件下呈现逐层破坏的特征,从而在应力-应变曲线上出现一平台区;由于铝合金本身存在的应变速率敏感性和多孔材料中气体的作用,使泡沫铝的平台应力随应变速率的增加而增大,当孔隙率较低时,增加尤为明显;泡沫铝的应变速率敏感度随应变的变化而变化。
2005, 34(4):549-551.
Abstract:
研究了近α型TA15，α β型Ti6Al4V及亚稳定β型TB83种钛合金断裂韧性与屈服强度、强度极限的关系，提出了屈强差的概念。结果表明：屈强差增大，断裂韧性增加，且对Ti6Al4V和TB8两者之间有线性关系；β热变形或β热处理是提高屈强差和断裂韧性的有效方法。
研究了近α型TA15，α β型Ti6Al4V及亚稳定β型TB83种钛合金断裂韧性与屈服强度、强度极限的关系，提出了屈强差的概念。结果表明：屈强差增大，断裂韧性增加，且对Ti6Al4V和TB8两者之间有线性关系；β热变形或β热处理是提高屈强差和断裂韧性的有效方法。
2005, 34(4):552-556.
Abstract:
The effect of rare earth oxides, that is, La2O3,CeO2,Nd2O3 and Y2O3, on the electrochemical performance of hydrogen storage electrode was investigated. The results show that the four rare earth oxides, except Y2O3, are all beneficial to the electrochemical performance of the hydrogen storage electrode, including activation, high rate discharge, discharge voltage and cycle life. For the cycle life, the more the rare earth oxides, the better the cycle life is; but there exists an optimum value of the oxides for the 1 C discharge capacity and discharge voltage, The results are due to three reasons: (1) rare earth oxides increase the contact resistance among the hydrogen storage alloy particles; (2) rare earth oxides have catalysis; (3) rare earth oxides can stabilize the catalyst Ni on the surface of hydrogen storage alloy and prevent the hydrogen storage alloy from being further oxidized.
The effect of rare earth oxides, that is, La2O3,CeO2,Nd2O3 and Y2O3, on the electrochemical performance of hydrogen storage electrode was investigated. The results show that the four rare earth oxides, except Y2O3, are all beneficial to the electrochemical performance of the hydrogen storage electrode, including activation, high rate discharge, discharge voltage and cycle life. For the cycle life, the more the rare earth oxides, the better the cycle life is; but there exists an optimum value of the oxides for the 1 C discharge capacity and discharge voltage, The results are due to three reasons: (1) rare earth oxides increase the contact resistance among the hydrogen storage alloy particles; (2) rare earth oxides have catalysis; (3) rare earth oxides can stabilize the catalyst Ni on the surface of hydrogen storage alloy and prevent the hydrogen storage alloy from being further oxidized.
2005, 34(4):557-561.
Abstract:
用恒电流充放电和脉冲放电方法研究了含银添加剂对富镧AB5型贮氢合金电极电化学性能的影响。结果表明Ag添加剂加快了氧的电化学复合速度，延长了贮氢合金的使用寿命。含银添加剂MH／Ni电池在-20℃和55℃下的1C放电容量、循环寿命和高倍率(5C，10C，15C，20C)脉冲放电性能均高于空白电池。对不同温度下的含银添加剂MH电极进行了电化学阻抗谱和循环伏安实验，分析认为MH电极在25℃与55℃下的高倍率放电性能受氢扩散控制，而在0℃下则受电极表面的电子转移控制。
用恒电流充放电和脉冲放电方法研究了含银添加剂对富镧AB5型贮氢合金电极电化学性能的影响。结果表明Ag添加剂加快了氧的电化学复合速度，延长了贮氢合金的使用寿命。含银添加剂MH／Ni电池在-20℃和55℃下的1C放电容量、循环寿命和高倍率(5C，10C，15C，20C)脉冲放电性能均高于空白电池。对不同温度下的含银添加剂MH电极进行了电化学阻抗谱和循环伏安实验，分析认为MH电极在25℃与55℃下的高倍率放电性能受氢扩散控制，而在0℃下则受电极表面的电子转移控制。
2005, 34(4):562-564.
Abstract:
为了解释锆合金在LiOH水溶液中耐腐蚀性能降低的原因，将3组粉状Zr-4合金样品分别放在500℃空气中、500℃过热蒸汽中和350℃的0．1mol／L LiOH水溶液中进行腐蚀，当氧化膜厚度约为1．5gm时，用XRD分析这3组样品的晶体结构。将一片状Zr-4合金样品在350℃的0．04mol／L LiOH水溶液中腐蚀2d，用SIMS检测Li^ 和OH^-在氧化膜剖面上的分布。根据实验结果提出OH^-在氧化膜中比O^-2扩散速度快，使t—ZrO2加速向m-ZrO2转变，导致Zr-4合金腐蚀速度加快。
为了解释锆合金在LiOH水溶液中耐腐蚀性能降低的原因，将3组粉状Zr-4合金样品分别放在500℃空气中、500℃过热蒸汽中和350℃的0．1mol／L LiOH水溶液中进行腐蚀，当氧化膜厚度约为1．5gm时，用XRD分析这3组样品的晶体结构。将一片状Zr-4合金样品在350℃的0．04mol／L LiOH水溶液中腐蚀2d，用SIMS检测Li^ 和OH^-在氧化膜剖面上的分布。根据实验结果提出OH^-在氧化膜中比O^-2扩散速度快，使t—ZrO2加速向m-ZrO2转变，导致Zr-4合金腐蚀速度加快。
2005, 34(4):565-568.
Abstract:
In order to further reveal the whole diffusion characters and distribution behaviors of Ga impurity in SiO2/Si system, the changeable concentration laws of Ga impurity at puny region of the nearby Si surface, under different temperatures and different atmosphere in invariable resource diffusion, finite resource diffusion and re-oxygenation process are investigated by SRP. The results are as follows: the low concentration region forms in invariable resource diffusion process; the reversed diffusion character happens in finite resource diffusion process; the exceptional segregation comes into being in re-oxygenation process.
In order to further reveal the whole diffusion characters and distribution behaviors of Ga impurity in SiO2/Si system, the changeable concentration laws of Ga impurity at puny region of the nearby Si surface, under different temperatures and different atmosphere in invariable resource diffusion, finite resource diffusion and re-oxygenation process are investigated by SRP. The results are as follows: the low concentration region forms in invariable resource diffusion process; the reversed diffusion character happens in finite resource diffusion process; the exceptional segregation comes into being in re-oxygenation process.
2005, 34(4):569-572.
Abstract:
对定向凝固DZ4合金机械预变形和热处理后的持久寿命与断裂行为进行了测试与分析，研究了再结晶对定向凝固DZ4合金持久行为的影响机制。结果表明，定向凝固DZ4合金机械预变形和热处理后在其表面形成再结晶层。再结晶层对定向凝固DZ4合金持久寿命的影响很大，表面130gm的再结晶使其持久寿命下降33％。再结晶层本身的强度极低、再结晶层与基体的变形不协调以及界面所具有的缺口效应导致了定向凝固DZ4合金机械预变形和热处理后持久强度的下降。
对定向凝固DZ4合金机械预变形和热处理后的持久寿命与断裂行为进行了测试与分析，研究了再结晶对定向凝固DZ4合金持久行为的影响机制。结果表明，定向凝固DZ4合金机械预变形和热处理后在其表面形成再结晶层。再结晶层对定向凝固DZ4合金持久寿命的影响很大，表面130gm的再结晶使其持久寿命下降33％。再结晶层本身的强度极低、再结晶层与基体的变形不协调以及界面所具有的缺口效应导致了定向凝固DZ4合金机械预变形和热处理后持久强度的下降。
2005, 34(4):581-585.
Abstract:
A CMTP yield function considering texture-component information is directly used in finite element code ABAQUS, taking friction and blank holder force into account, to simulate the earing of 3104 aluminum alloy sheet during deep drawing. The predictions obtained from CMTP yield function are compared with those from Barlat 1991 yield function and experimental earing profiles. The thickness variation induced by deep drawing is also described. Further improvements in the accuracy of the simulations are also discussed. Reasonable agreement is obtained between the predictions from CMTP yield function and the measured earing profiles. The predictions of earing behavior of 3104 aluminum alloy sheets from CMTP yield function is more accurate than from Barlat 1991 yield function. The thickness variation of blank in the simulation is accorded with the practice process, which shows increasing the friction and blank holder force enable the height of earing to increase.
A CMTP yield function considering texture-component information is directly used in finite element code ABAQUS, taking friction and blank holder force into account, to simulate the earing of 3104 aluminum alloy sheet during deep drawing. The predictions obtained from CMTP yield function are compared with those from Barlat 1991 yield function and experimental earing profiles. The thickness variation induced by deep drawing is also described. Further improvements in the accuracy of the simulations are also discussed. Reasonable agreement is obtained between the predictions from CMTP yield function and the measured earing profiles. The predictions of earing behavior of 3104 aluminum alloy sheets from CMTP yield function is more accurate than from Barlat 1991 yield function. The thickness variation of blank in the simulation is accorded with the practice process, which shows increasing the friction and blank holder force enable the height of earing to increase.
2005, 34(4):586-588.
Abstract:
利用扫描电镜（SEM），俄歇能谱分析（AES），X射线衍射分析（XRD）和电化学等技术，研究了磁控溅射沉积Al-Zn镀层的结构及其对铀的保护性能。结果表明施加偏压显著地影响Al-Zn镀层的结构和保护性能，在-100V偏压下沉积的Al-Zn镀层，其组织更致密，成分有择优重溅射现象并伴有合金相生成，更有利于铀的防腐保护。
利用扫描电镜（SEM），俄歇能谱分析（AES），X射线衍射分析（XRD）和电化学等技术，研究了磁控溅射沉积Al-Zn镀层的结构及其对铀的保护性能。结果表明施加偏压显著地影响Al-Zn镀层的结构和保护性能，在-100V偏压下沉积的Al-Zn镀层，其组织更致密，成分有择优重溅射现象并伴有合金相生成，更有利于铀的防腐保护。
16 Study on Structure of Vacuum Fusion Sintering NiCrBSi Alloy Coating Containing Rare Earth Yttrium
2005, 34(4):589-592.
Abstract:
In virtue of electron energy spectrometer, X-ray diffractometer and scanning electron microscope, the effects of rare earth yttrium on chemical composition and structure of the vacuum fusion sintering NiCrBSi alloy coating were studied. The results show that rare earth yttrium changes chemical component of alloy coating and hinders the dilution of Fe for NiCrBSi alloy coating owing to the diffusion of Fe atom in alloy coating from steel matrix. Rare earth yttrium makes Fe content in alloy coating decrease, eliminates needle phase of alloy coating mostly, and gets globular phase of alloy coating deposited and refined further. New second phases Cr7C3 and Ni2B are also precipitated from vacuum fusion sintering NiCrBSi alloy coating containing rare earth yttrium.
In virtue of electron energy spectrometer, X-ray diffractometer and scanning electron microscope, the effects of rare earth yttrium on chemical composition and structure of the vacuum fusion sintering NiCrBSi alloy coating were studied. The results show that rare earth yttrium changes chemical component of alloy coating and hinders the dilution of Fe for NiCrBSi alloy coating owing to the diffusion of Fe atom in alloy coating from steel matrix. Rare earth yttrium makes Fe content in alloy coating decrease, eliminates needle phase of alloy coating mostly, and gets globular phase of alloy coating deposited and refined further. New second phases Cr7C3 and Ni2B are also precipitated from vacuum fusion sintering NiCrBSi alloy coating containing rare earth yttrium.
2005, 34(4):593-596.
Abstract:
TiO2 nano thin film and TiO2/ZnFe2O4 nano composite thin film were prepared on glass substrate by dip coating process. The films were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photo-electron spectrum (XPS), atom force microscope (AFM), Uv-vis spectroscope, etc. The obtained films were analyzed and were proved to be anatase alone. At the same time, the photo absorption edge of the composite film was red-shifting. Finally, photocatalytic decomposition properties of methylene blue were tested and discussed.
TiO2 nano thin film and TiO2/ZnFe2O4 nano composite thin film were prepared on glass substrate by dip coating process. The films were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photo-electron spectrum (XPS), atom force microscope (AFM), Uv-vis spectroscope, etc. The obtained films were analyzed and were proved to be anatase alone. At the same time, the photo absorption edge of the composite film was red-shifting. Finally, photocatalytic decomposition properties of methylene blue were tested and discussed.
2005, 34(4):597-600.
Abstract:
发明了1种能够在钛材表面无氢式一次性形成金属碳化物的三栅极离子渗镀新方法。系统工作时所产生的等离子从空隙处直接奔向工件待处理表面，从而无氢式一次性在金属材料表面形成由镀层、或扩散层或渗镀层构成的金属碳化物表面改性合金层。利用该方法在纯钛(TA2)基材表面进行了一次性无氢式渗碳和C，Mo共渗的试验。试样的x射线衍射分析(XRD)、辉光放电分析(GDA)等测试结果表明，在钛基表面形成了具有金属碳化物及碳扩散次层的渗镀合金层，渗镀成分呈现明显的梯度分布，厚度在20μm以上，最高硬度可达13000MPa。
发明了1种能够在钛材表面无氢式一次性形成金属碳化物的三栅极离子渗镀新方法。系统工作时所产生的等离子从空隙处直接奔向工件待处理表面，从而无氢式一次性在金属材料表面形成由镀层、或扩散层或渗镀层构成的金属碳化物表面改性合金层。利用该方法在纯钛(TA2)基材表面进行了一次性无氢式渗碳和C，Mo共渗的试验。试样的x射线衍射分析(XRD)、辉光放电分析(GDA)等测试结果表明，在钛基表面形成了具有金属碳化物及碳扩散次层的渗镀合金层，渗镀成分呈现明显的梯度分布，厚度在20μm以上，最高硬度可达13000MPa。
2005, 34(4):601-604.
Abstract:
钙磷陶瓷表面形成的类骨磷灰石层对材料诱导新骨生成起非常重要的作用。利用体外模拟装置首次研究了新工艺制备的含CO3^2-的双相HA／β-TCP多孔陶瓷相组成对表面类骨磷灰石形成的影响。结果表明，具有不同相组成的该种陶瓷因CO3^2-的存在，导致类骨磷灰石晶体的形成时间有不同程度的提前。并且相组成在β-TCP含量较低时(HA／β-TCP之比为9／1)，该陶瓷也能在较短的作用时间内形成类骨磷灰石晶体。此外还有缺钙羟基磷灰石晶体的形成。类骨磷灰石晶体的形成情况随β-TCP含量的增加而越来越好。且相组成以HA／β-TCP比值为6／4时类骨磷灰石的形成情况最好。相组成的优化有利于该陶瓷材料骨诱导性的提高，进而有利于骨缺损的快速修复。
钙磷陶瓷表面形成的类骨磷灰石层对材料诱导新骨生成起非常重要的作用。利用体外模拟装置首次研究了新工艺制备的含CO3^2-的双相HA／β-TCP多孔陶瓷相组成对表面类骨磷灰石形成的影响。结果表明，具有不同相组成的该种陶瓷因CO3^2-的存在，导致类骨磷灰石晶体的形成时间有不同程度的提前。并且相组成在β-TCP含量较低时(HA／β-TCP之比为9／1)，该陶瓷也能在较短的作用时间内形成类骨磷灰石晶体。此外还有缺钙羟基磷灰石晶体的形成。类骨磷灰石晶体的形成情况随β-TCP含量的增加而越来越好。且相组成以HA／β-TCP比值为6／4时类骨磷灰石的形成情况最好。相组成的优化有利于该陶瓷材料骨诱导性的提高，进而有利于骨缺损的快速修复。
2005, 34(4):605-608.
Abstract:
Bi2Te3/polyaniline composites were prepared by mechanical blending and the electrochemical properties were studied with lithium anode model cell Li|LiPF6(EC+DMC) |Bi2Te3/PAn. A reversible capacity of about 480mAhg-1 has been obtained in the first cycle. The reversible capacity keeps about 200 mAhg-1 in the first 20 cycles. The mechanism of lithium insertion into Bi2Te3/PAn was analyzed by ex situ XRD.
Bi2Te3/polyaniline composites were prepared by mechanical blending and the electrochemical properties were studied with lithium anode model cell Li|LiPF6(EC+DMC) |Bi2Te3/PAn. A reversible capacity of about 480mAhg-1 has been obtained in the first cycle. The reversible capacity keeps about 200 mAhg-1 in the first 20 cycles. The mechanism of lithium insertion into Bi2Te3/PAn was analyzed by ex situ XRD.
2005, 34(4):609-611.
Abstract:
The electrochemical properties of doped 5% carbon nanotubes(CNTs) LaNi5 electrode have been investigated. The CNTs were synthesized by chemical vapor deposition method (CVD) using lanthanum nickel alloy(LaNi5) as the catalyst. Three-electrode system was introduced to test the electrochemical hydrogen storage behaviors of CNTs with Ni(OH)2/NiOOH as the assistant electrode and Hg/HgO as the reference electrode. 6mol/L KOH was used as the electrolyte, and the high discharge capacity was measured of 385 mAh/g at a discharge current of 100 mA/g. The doped 5% CNTs LaNi5 electrodes showed higher electrochemical hydrogen storage capacities and a longer cycle life than those of the un-droped CNTs. In addition, the discharge capacity decay was only 15% after 100 cycles.
The electrochemical properties of doped 5% carbon nanotubes(CNTs) LaNi5 electrode have been investigated. The CNTs were synthesized by chemical vapor deposition method (CVD) using lanthanum nickel alloy(LaNi5) as the catalyst. Three-electrode system was introduced to test the electrochemical hydrogen storage behaviors of CNTs with Ni(OH)2/NiOOH as the assistant electrode and Hg/HgO as the reference electrode. 6mol/L KOH was used as the electrolyte, and the high discharge capacity was measured of 385 mAh/g at a discharge current of 100 mA/g. The doped 5% CNTs LaNi5 electrodes showed higher electrochemical hydrogen storage capacities and a longer cycle life than those of the un-droped CNTs. In addition, the discharge capacity decay was only 15% after 100 cycles.
2005, 34(4):612-616.
Abstract:
Tensile properties, fracture characteristics and microstructures of 7055 aluminum alloy containing Ag in the T6, T73 and RRA conditions were investigated. The results of the investigations show that RRA treatment retains the strength of 7055-T6 with a higher electrical conductivity close to that of 7055-T73, but its elongation decreases greatly; SEM fractographs reveal that intergranular cracking and shear-type transgranular cracking were both present on the fracture appearance of 7055-T6 specimen. After T73 treatment, the fractographs consist of dimple-type transgranular cracking with minor intergranular cracking. With 7055-RRA specimen, intergranular cracking dominates with minor dimples distributed on the fracture surface. The types and volume fraction of precipitates, width of PFZ (Precipitate Free Zones ) and the ability of precipitates to impede dislocations varied with heat treatment regimes.
Tensile properties, fracture characteristics and microstructures of 7055 aluminum alloy containing Ag in the T6, T73 and RRA conditions were investigated. The results of the investigations show that RRA treatment retains the strength of 7055-T6 with a higher electrical conductivity close to that of 7055-T73, but its elongation decreases greatly; SEM fractographs reveal that intergranular cracking and shear-type transgranular cracking were both present on the fracture appearance of 7055-T6 specimen. After T73 treatment, the fractographs consist of dimple-type transgranular cracking with minor intergranular cracking. With 7055-RRA specimen, intergranular cracking dominates with minor dimples distributed on the fracture surface. The types and volume fraction of precipitates, width of PFZ (Precipitate Free Zones ) and the ability of precipitates to impede dislocations varied with heat treatment regimes.
Chen Song
,
Hu Changyi
,
Yang Jiaming
,
Cai Yunzhuo
,
Guo Junmei
,
Wang Yun
,
Deng Deguo
,
Pan Zaifu
2005, 34(4):617-621.
Abstract:
Several methods were given for metallographic preparation of iridium/rhenium composite obtained by chemical vapor deposition. Rhenium layer microstructure include column grain zone and fine grain zone near the iridium layer. Grain size was measured in both zones. Features of annealing twin crystal, V etch net and void of Kirkendall in grain boundary were studied. Grain image and growth features are studied through second electronic image of Iridium layer microstructure. Kinetic equation of Iridium grain growth is achieved.
Several methods were given for metallographic preparation of iridium/rhenium composite obtained by chemical vapor deposition. Rhenium layer microstructure include column grain zone and fine grain zone near the iridium layer. Grain size was measured in both zones. Features of annealing twin crystal, V etch net and void of Kirkendall in grain boundary were studied. Grain image and growth features are studied through second electronic image of Iridium layer microstructure. Kinetic equation of Iridium grain growth is achieved.
2005, 34(4):622-626.
Abstract:
运用弥散强化原理，分别选用Ag颗粒和Ni颗粒作为增强体，以63Sn37Pb共晶钎料为基体，制成金属颗粒增强锡铅基复合钎料。在再流焊条件下，弥散分布的增强体与基体冶金结合，在增强体表层形成一薄层金属间化合物，从而使复合钎料蠕变性能大幅度提高。试验证明：在相同条件下，与基体钎料63Sn37Pb相比，5％Ag(体积分数，下同)和10％Ag颗粒增强锡铅基复合钎料蠕变寿命分别提高了8倍和6倍，同时抗拉强度和剪切强度均得到提高；5％Ni和10％Ni颗粒增强锡铅基复合钎料蠕变寿命分别提高了84倍和185倍，但剪切强度和延伸率均明显降低。
运用弥散强化原理，分别选用Ag颗粒和Ni颗粒作为增强体，以63Sn37Pb共晶钎料为基体，制成金属颗粒增强锡铅基复合钎料。在再流焊条件下，弥散分布的增强体与基体冶金结合，在增强体表层形成一薄层金属间化合物，从而使复合钎料蠕变性能大幅度提高。试验证明：在相同条件下，与基体钎料63Sn37Pb相比，5％Ag(体积分数，下同)和10％Ag颗粒增强锡铅基复合钎料蠕变寿命分别提高了8倍和6倍，同时抗拉强度和剪切强度均得到提高；5％Ni和10％Ni颗粒增强锡铅基复合钎料蠕变寿命分别提高了84倍和185倍，但剪切强度和延伸率均明显降低。
2005, 34(4):627-631.
Abstract:
In the producing process of 7075 aluminum alloy by CREM method, the effects of electromagnetic field with low frequency on the evolution of solidifying front shape, non-dendritic structure, liquidus and solidus temperature of non-equilibrium freezing, solidification interval, flow pattern and temperature field have been experimentally investigated. An explanation is also given to the mechanism of CREM process on restraining macro-segregation of solute elements in 7075 aluminum alloy ingot by DC cast.
In the producing process of 7075 aluminum alloy by CREM method, the effects of electromagnetic field with low frequency on the evolution of solidifying front shape, non-dendritic structure, liquidus and solidus temperature of non-equilibrium freezing, solidification interval, flow pattern and temperature field have been experimentally investigated. An explanation is also given to the mechanism of CREM process on restraining macro-segregation of solute elements in 7075 aluminum alloy ingot by DC cast.
2005, 34(4):632-634.
Abstract:
Monodispersed spherical Y2O3:Eu3+ nanocrystallines were successfully prepared by a novel gel-network coprecipitation process. The effect of reaction conditions on the resulting particles was investigated. XRD, TEM and fluorescence spectra were used to characterize the samples. The results show that the samples are spherical with a particle size of 13 nm~25 nm. Compared with micronscale Y2O3:Eu3+, a clear red shift occurs in the excitation spectrum of Y2O3:Eu3+ nanocrystalline prepared by the method.
Monodispersed spherical Y2O3:Eu3+ nanocrystallines were successfully prepared by a novel gel-network coprecipitation process. The effect of reaction conditions on the resulting particles was investigated. XRD, TEM and fluorescence spectra were used to characterize the samples. The results show that the samples are spherical with a particle size of 13 nm~25 nm. Compared with micronscale Y2O3:Eu3+, a clear red shift occurs in the excitation spectrum of Y2O3:Eu3+ nanocrystalline prepared by the method.
2005, 34(4):635-638.
Abstract:
采用Gleeble—1500D热模拟试验仪，就预设加热温度对55w％(Ti C) 45w％Fe压坯在大热流密度条件下燃烧合成过程的影响进行了研究。结果表明：在各预设加热温度条件下，体系的反应起始温度均在400℃以下，且随预设加热温度的升高，体系燃烧反应起始温度下降。同时讨论了在电场作用下体系燃烧合成的机理。认为：由于粉末压坯结构的不连续性，外加电场将对其产生能量有特有贡献，导致在低温条件下压坯获得巨大的能量而发生反应。
采用Gleeble—1500D热模拟试验仪，就预设加热温度对55w％(Ti C) 45w％Fe压坯在大热流密度条件下燃烧合成过程的影响进行了研究。结果表明：在各预设加热温度条件下，体系的反应起始温度均在400℃以下，且随预设加热温度的升高，体系燃烧反应起始温度下降。同时讨论了在电场作用下体系燃烧合成的机理。认为：由于粉末压坯结构的不连续性，外加电场将对其产生能量有特有贡献，导致在低温条件下压坯获得巨大的能量而发生反应。
2005, 34(4):639-642.
Abstract:
用熔渗反应无压烧结技术制备了MoSi2-SiC复合材料，对制备过程的影响因素进行了分析。研究结果表明：在渗硅温度为1450℃时，反应生成颗粒细小、弥散分布的SiC相，从而使得材料具有较高的抗弯强度；当渗硅温度升高至1750℃时，生成的SiC相发生再结晶长大，使得材料强度下降。成型压力对熔渗硅样品强度影响不大。MoSi2-SiC复合材料的抗弯强度随SiC相含量的增加在增强相含量为40％时存在一极大值，这是由于当SiC数量超过40％后，SiC粒子的团聚、长大使弥散强化作用降低，从而使材料的断裂强度降低；复合材料电阻率随第二相含量的增加而增加。
用熔渗反应无压烧结技术制备了MoSi2-SiC复合材料，对制备过程的影响因素进行了分析。研究结果表明：在渗硅温度为1450℃时，反应生成颗粒细小、弥散分布的SiC相，从而使得材料具有较高的抗弯强度；当渗硅温度升高至1750℃时，生成的SiC相发生再结晶长大，使得材料强度下降。成型压力对熔渗硅样品强度影响不大。MoSi2-SiC复合材料的抗弯强度随SiC相含量的增加在增强相含量为40％时存在一极大值，这是由于当SiC数量超过40％后，SiC粒子的团聚、长大使弥散强化作用降低，从而使材料的断裂强度降低；复合材料电阻率随第二相含量的增加而增加。
2005, 34(4):643-647.
Abstract:
采用电弧熔炼(CA)和机械合金化(MA)技术制备了晶粒尺寸差别较大的Cu-Ni固溶体合金，并研究了它们在800℃空气中的氧化行为。结果表明：MACu-50Ni合金的氧化速率高于CACu-50Ni合金；而MACu-70Ni合金的氧化速率却低于CACu-70Ni合金。合金表面氧化膜外层均是CuO层，但相邻的内层则差别较大，其中，CACu-50Ni，CACu-70Ni和MACu-50Ni合金的内层是Cu2O和NiO的混合氧化物层，而MACu-70Ni合金内层则是较厚且致密均匀的NiO层。晶粒细化促使合金表面氧化膜内层由Cu2O和NiO的混合氧化物层向单一的NiO层转变。
采用电弧熔炼(CA)和机械合金化(MA)技术制备了晶粒尺寸差别较大的Cu-Ni固溶体合金，并研究了它们在800℃空气中的氧化行为。结果表明：MACu-50Ni合金的氧化速率高于CACu-50Ni合金；而MACu-70Ni合金的氧化速率却低于CACu-70Ni合金。合金表面氧化膜外层均是CuO层，但相邻的内层则差别较大，其中，CACu-50Ni，CACu-70Ni和MACu-50Ni合金的内层是Cu2O和NiO的混合氧化物层，而MACu-70Ni合金内层则是较厚且致密均匀的NiO层。晶粒细化促使合金表面氧化膜内层由Cu2O和NiO的混合氧化物层向单一的NiO层转变。
Xie Zhiwei
,
Wang Guoqing
,
Yang Yuanzheng
,
Kuang Tongchun
,
Bai Xiaojun
,
Xie Guangrong
,
Hu Shejun
2005, 34(4):648-652.
Abstract:
采用电弧离子镀技术、TC7双相钛合金靶沉积TiAlCrFeSiBN薄膜，研究了这种多元膜的显微硬度、高温氧化性能和组织结构。结果表明：这种多元膜具有优于TiN膜的显微硬度；具有不同于TiN膜的显微组织，其最显著的特征是存在较多细小的钛滴，这些钛滴与膜之间的融合效果很好；膜层上孔隙较少；具有TiN的面心立方结构，与TiN膜相比，具有更加明显的择优取向趋势。
采用电弧离子镀技术、TC7双相钛合金靶沉积TiAlCrFeSiBN薄膜，研究了这种多元膜的显微硬度、高温氧化性能和组织结构。结果表明：这种多元膜具有优于TiN膜的显微硬度；具有不同于TiN膜的显微组织，其最显著的特征是存在较多细小的钛滴，这些钛滴与膜之间的融合效果很好；膜层上孔隙较少；具有TiN的面心立方结构，与TiN膜相比，具有更加明显的择优取向趋势。
2005, 34(4):653-656.
Abstract:
采用真空热压工艺制备了含SiC颗粒体积分数分别为5%,15%和25%的SiC颗粒增强铝基复合材料,利用Hopkinson高速压杆冲击实验系统对其从静态到动态(应变率为3.3×10-3s-1～5.2×103s-1)的压缩破坏响应进行了研究,结合其光学显微镜分析变形组织,分析了不同体积分数SiCp/Al复合材料高应变率压缩载荷下,材料的变形和微观损伤机理.结果表明,复合材料存在应变率敏感性,SiC含量的增加导致复合材料应变率敏感性的增加,以垂直于载荷方向的增强相颗粒的剪切开裂为主要破坏模式.
采用真空热压工艺制备了含SiC颗粒体积分数分别为5%,15%和25%的SiC颗粒增强铝基复合材料,利用Hopkinson高速压杆冲击实验系统对其从静态到动态(应变率为3.3×10-3s-1～5.2×103s-1)的压缩破坏响应进行了研究,结合其光学显微镜分析变形组织,分析了不同体积分数SiCp/Al复合材料高应变率压缩载荷下,材料的变形和微观损伤机理.结果表明,复合材料存在应变率敏感性,SiC含量的增加导致复合材料应变率敏感性的增加,以垂直于载荷方向的增强相颗粒的剪切开裂为主要破坏模式.
2005, 34(4):657-660.
Abstract:
在自制的气-固连续固定床反应器上,在反应温度为145℃,氢气体积流速为140ml/min,空速为10g/(g·cat)的条件下,对采用传统浸渍方法制备的载钯量为1.25%(质量分数)的Pd/C催化剂的寿命进行评价。其实验结果表明,Pd/C催化剂是氯乙酸母液混酯选择性加氢脱氯制备氯乙酸甲酯优良的催化剂。为了找到催化剂失活的原因,分别对反应前后的催化剂进行了XRD,差示热分析(DTA)和X射线光电子光谱(XPS)分析。结果表明,催化剂表面炭化物沉积是催化剂失活的主要原因,积炭物中以物理吸附的非永久性积炭为主,并可以通过惰性气体吹扫而除掉。
在自制的气-固连续固定床反应器上,在反应温度为145℃,氢气体积流速为140ml/min,空速为10g/(g·cat)的条件下,对采用传统浸渍方法制备的载钯量为1.25%(质量分数)的Pd/C催化剂的寿命进行评价。其实验结果表明,Pd/C催化剂是氯乙酸母液混酯选择性加氢脱氯制备氯乙酸甲酯优良的催化剂。为了找到催化剂失活的原因,分别对反应前后的催化剂进行了XRD,差示热分析(DTA)和X射线光电子光谱(XPS)分析。结果表明,催化剂表面炭化物沉积是催化剂失活的主要原因,积炭物中以物理吸附的非永久性积炭为主,并可以通过惰性气体吹扫而除掉。
2005, 34(4):661-664.
Abstract:
采用高能球磨方法制备了Mg-Ni非晶，并用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、差热分析仪(DTA)、电池综合性能测试仪等分析了该非晶的热稳定性、活化性能、电化学稳定性以及容量衰减机理等。结果表明：Mg-Ni非晶在室温下首次活化即可达到最大容量440mAh．g^-1，具有较好的充放电活化特性，但是其容量衰减较快，其主要原因有：非晶相在充放电过程中逐渐晶化形成Mg2NiH4，Ni相；Mg被电解液腐蚀生成Mg(OH)2；非晶颗粒经多次循环后产生粉化。在Mg-Ni中添加适量的镧可提高其热稳定性、电化学稳定性且不影响其活化性能。
采用高能球磨方法制备了Mg-Ni非晶，并用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、差热分析仪(DTA)、电池综合性能测试仪等分析了该非晶的热稳定性、活化性能、电化学稳定性以及容量衰减机理等。结果表明：Mg-Ni非晶在室温下首次活化即可达到最大容量440mAh．g^-1，具有较好的充放电活化特性，但是其容量衰减较快，其主要原因有：非晶相在充放电过程中逐渐晶化形成Mg2NiH4，Ni相；Mg被电解液腐蚀生成Mg(OH)2；非晶颗粒经多次循环后产生粉化。在Mg-Ni中添加适量的镧可提高其热稳定性、电化学稳定性且不影响其活化性能。
2005, 34(4):665-669.
Abstract:
NdFeB powders produced by melting spun and gas atomization are blended with nylon 12 binder and injected to make bonded magnet. Powder morphological analysis of the two kinds of powder is tested as well as powder size and size distribution. The rheological behaviors of both feedstock are pseudo-plastic fluid. Homogeneity of feedstock matches Boltzmann function and the irreversible loss of residual magnetism accords with exponent function. The critical powder loading rate, homogeneity and the rheological behavior of feedstock made by gas atomization are better than those of the melt spun.
NdFeB powders produced by melting spun and gas atomization are blended with nylon 12 binder and injected to make bonded magnet. Powder morphological analysis of the two kinds of powder is tested as well as powder size and size distribution. The rheological behaviors of both feedstock are pseudo-plastic fluid. Homogeneity of feedstock matches Boltzmann function and the irreversible loss of residual magnetism accords with exponent function. The critical powder loading rate, homogeneity and the rheological behavior of feedstock made by gas atomization are better than those of the melt spun.
2005, 34(4):670-672.
Abstract:
Molybdenum Coating was sprayed on 45 steel substrate using novel electrothermal explosion directional spray. Microstructure and composition of the coating were analyzed with SEM and EDS, respectively. Hardness of the coating was tested by hardness testing machine. Grain sizes of Mo coating were measured. It shows that the grain of molybdenum coating is very fine. The maximum hardness of the coating is up to HV=1411, 3 times of the sprayed molybdenum material. The coating is dense and the porosity is little. EDS shows that oxidation do not occur during the spraying process.
Molybdenum Coating was sprayed on 45 steel substrate using novel electrothermal explosion directional spray. Microstructure and composition of the coating were analyzed with SEM and EDS, respectively. Hardness of the coating was tested by hardness testing machine. Grain sizes of Mo coating were measured. It shows that the grain of molybdenum coating is very fine. The maximum hardness of the coating is up to HV=1411, 3 times of the sprayed molybdenum material. The coating is dense and the porosity is little. EDS shows that oxidation do not occur during the spraying process.
