Volume 0,Issue 1,2002 Table of Contents
2002(1).
Abstract:
The Co free over stoichiometric alloy Ml (NiMnAlFe) 5.4 were prepared using conventional cast, rapid solidification (melt spinning) and annealing processes. The microstructure and electrochemical properties of these alloys were investigated comparatively. XRD analyses show that three kinds of the alloys are all composed of main phase with CaCu 5 structure and the second phase (AlNi 3), but the amount of the second phase in the melt spinning alloy is less, and the second phase in annealed alloy disappeared. The electrochemical analyses show that the melt spun and annealed alloys all have better cycling stability than that of conventional cast alloy, but their discharge capacity and high rate dischargeability are little lower than that of conventional cast alloy.
The Co free over stoichiometric alloy Ml (NiMnAlFe) 5.4 were prepared using conventional cast, rapid solidification (melt spinning) and annealing processes. The microstructure and electrochemical properties of these alloys were investigated comparatively. XRD analyses show that three kinds of the alloys are all composed of main phase with CaCu 5 structure and the second phase (AlNi 3), but the amount of the second phase in the melt spinning alloy is less, and the second phase in annealed alloy disappeared. The electrochemical analyses show that the melt spun and annealed alloys all have better cycling stability than that of conventional cast alloy, but their discharge capacity and high rate dischargeability are little lower than that of conventional cast alloy.
2002(1).
Abstract:
The oxidation behavior of MoSi 2 Mo 5Si 3 composites at low temperature has been investigated by thermogravimetric analyses, X ray diffraction technique and SEM. The results showed that the oxidation was accelerated with the increase of Mo 5Si 3. "PEST" phenomena was caused in couse of low temperature oxidation when the content of Mo 5Si 3 exceeded 16%(mass fraction). The SiO 2 films were not distributed continuously on the surface of composite due to great amount of MoS 3 whiskers, and oxidation was accelerated.
The oxidation behavior of MoSi 2 Mo 5Si 3 composites at low temperature has been investigated by thermogravimetric analyses, X ray diffraction technique and SEM. The results showed that the oxidation was accelerated with the increase of Mo 5Si 3. "PEST" phenomena was caused in couse of low temperature oxidation when the content of Mo 5Si 3 exceeded 16%(mass fraction). The SiO 2 films were not distributed continuously on the surface of composite due to great amount of MoS 3 whiskers, and oxidation was accelerated.
2002(1).
Abstract:
研究了机械合金化过程中粉末形态和微结构的变化 ,通过扫描电子显微镜 ,清楚地观察到粉末颗粒的破碎和集聚复合过程 ,以及复合颗粒的形成。通过 X射线衍射详细分析了球磨过程中的晶格常数、晶粒度和微观应变的变化。球磨的最终产物为非晶 ,α- Fe(Mo)和 Mo。通过优化工艺 ,Nd Fe1 0 .5Mo1 .5Nx 氮化物获得了较佳的磁性能
研究了机械合金化过程中粉末形态和微结构的变化 ,通过扫描电子显微镜 ,清楚地观察到粉末颗粒的破碎和集聚复合过程 ,以及复合颗粒的形成。通过 X射线衍射详细分析了球磨过程中的晶格常数、晶粒度和微观应变的变化。球磨的最终产物为非晶 ,α- Fe(Mo)和 Mo。通过优化工艺 ,Nd Fe1 0 .5Mo1 .5Nx 氮化物获得了较佳的磁性能
2002(1).
Abstract:
CaS:Ce 3+ ,Sb 3+ phosphors with the green color were firstly synthesized by microwave radiation method. The phosphor materials have been characterized by XRD?SEM and the fluorescent spectroscopy. The result shows that the CaS:Ce 3+ , Sb 3+ phosphors possess the cubic structures. The different shapes and submicro scales of the phosphors can be obtained upon doping the different fluxes in the same concentration of Sb 3+ ion in a microwale field. Ce 3+ can sensitize Sb 3+ , and enhance the fluorescent intensity of CaS:Sb 3+ efficiently.
CaS:Ce 3+ ,Sb 3+ phosphors with the green color were firstly synthesized by microwave radiation method. The phosphor materials have been characterized by XRD?SEM and the fluorescent spectroscopy. The result shows that the CaS:Ce 3+ , Sb 3+ phosphors possess the cubic structures. The different shapes and submicro scales of the phosphors can be obtained upon doping the different fluxes in the same concentration of Sb 3+ ion in a microwale field. Ce 3+ can sensitize Sb 3+ , and enhance the fluorescent intensity of CaS:Sb 3+ efficiently.
2002(1).
Abstract:
The electrical and optical properties of CdIn 2O 4 films produced by RF reactive sputtering have been investigated. The IR reflection R of the CdIn 2O 4 films as a function of oxygen concentration and heat treatment is discussed. Experiment results show that the IR reflection R of the CdIn 2O 4 films is very high, indicating that the CdIn 2O 4 films are good IR reflection films and can be used as heat preservation films.
The electrical and optical properties of CdIn 2O 4 films produced by RF reactive sputtering have been investigated. The IR reflection R of the CdIn 2O 4 films as a function of oxygen concentration and heat treatment is discussed. Experiment results show that the IR reflection R of the CdIn 2O 4 films is very high, indicating that the CdIn 2O 4 films are good IR reflection films and can be used as heat preservation films.
2002(1):1-3.
Abstract:
Progress in magnetic functional materials and applications since 1996 is reviewed, the contents for 1999 2000 include: (1) giant magnetdresistance and giant magnetoimpedance materials; (2) giant magnetooptical effect and magnetooptical imaging new materials; (3) magnetic fluid for extensive applications; (4) microwave gyromagnetic devices; (5) magnetically levitated vehicles.
Progress in magnetic functional materials and applications since 1996 is reviewed, the contents for 1999 2000 include: (1) giant magnetdresistance and giant magnetoimpedance materials; (2) giant magnetooptical effect and magnetooptical imaging new materials; (3) magnetic fluid for extensive applications; (4) microwave gyromagnetic devices; (5) magnetically levitated vehicles.
2002(1):4-7.
Abstract:
作为高温结构材料，TiAl金属间化合物在航空、航天领域颇具应用潜力。而燃烧合成技术正被越来越多地用于制备TiAl金属间化合物。为了有效地控制反应过程从获得理想的组织结构，必须深入了解其反应机制。本文综述了燃烧合成TiAl反应机制的文献报道。
作为高温结构材料，TiAl金属间化合物在航空、航天领域颇具应用潜力。而燃烧合成技术正被越来越多地用于制备TiAl金属间化合物。为了有效地控制反应过程从获得理想的组织结构，必须深入了解其反应机制。本文综述了燃烧合成TiAl反应机制的文献报道。
2002(1):8-12.
Abstract:
Aluminum nitride(AlN) has excellent thermal, electrical and mechanical properties, and attracts more and more attention. This paper relates the development of fabricating high thermal conductivity AlN ceramics process, including powder preparation, molding, sintering. It is suggested that research on low cost powder preparation technology and net shape molding technology are valuable.
Aluminum nitride(AlN) has excellent thermal, electrical and mechanical properties, and attracts more and more attention. This paper relates the development of fabricating high thermal conductivity AlN ceramics process, including powder preparation, molding, sintering. It is suggested that research on low cost powder preparation technology and net shape molding technology are valuable.
2002(1):13-16.
Abstract:
根据固体与分子经验电子理论，通过键距差（BLD）方法，计算了Ti(C0.7,N0.3)的价电子结构，讨论了其价电子结构与硬度和塑性间的关系。指出Ti(C,N)固溶体的硬度较TiC，（Ti,W)C低，较TiN高，其塑性较TiC,(Ti,W)C高，较TiN低。并指出材料晶体相同时，其价电子结构的最强键nA可作为硬度高低的比较指标，其∑n.可用来比较塑性的相对高低。
根据固体与分子经验电子理论，通过键距差（BLD）方法，计算了Ti(C0.7,N0.3)的价电子结构，讨论了其价电子结构与硬度和塑性间的关系。指出Ti(C,N)固溶体的硬度较TiC，（Ti,W)C低，较TiN高，其塑性较TiC,(Ti,W)C高，较TiN低。并指出材料晶体相同时，其价电子结构的最强键nA可作为硬度高低的比较指标，其∑n.可用来比较塑性的相对高低。
2002(1):17-21.
Abstract:
DCSB method is used to evaluate the burn resistant properties of Ti 40, Alloy C and Ti 6 4 three atmosphere conditions in this paper. The results show that Ti40 and Alloy C display good burn resistance as compared with Ti 6 4, and that the addition of nitrogen into air can decrease burning rate of titanium alloys. Burning interfaces were observed and analyzed by SEM and EDAX. It is found that which indicates that vanadium is preferentially immigrated to the surface to form V 2O 5 upon Ti40 and Alloy C burning. As a result the surface layer in burning zone is V enriched and Cr leaned, while the burned products and the oxidized layer close to matrix interface are V leaned and Cr enriched. The mixed oxidized layer is very dense, and can inhibite oxygen diffusion into the matrix, and prevent V in the matrix from diffusion into burning zone.Although Al can be preferentially immigrated to the surface to form Al 2O 3 upon Ti 6 4's burning, but it is too less in content to improve the alloy's burn proof ability.
DCSB method is used to evaluate the burn resistant properties of Ti 40, Alloy C and Ti 6 4 three atmosphere conditions in this paper. The results show that Ti40 and Alloy C display good burn resistance as compared with Ti 6 4, and that the addition of nitrogen into air can decrease burning rate of titanium alloys. Burning interfaces were observed and analyzed by SEM and EDAX. It is found that which indicates that vanadium is preferentially immigrated to the surface to form V 2O 5 upon Ti40 and Alloy C burning. As a result the surface layer in burning zone is V enriched and Cr leaned, while the burned products and the oxidized layer close to matrix interface are V leaned and Cr enriched. The mixed oxidized layer is very dense, and can inhibite oxygen diffusion into the matrix, and prevent V in the matrix from diffusion into burning zone.Although Al can be preferentially immigrated to the surface to form Al 2O 3 upon Ti 6 4's burning, but it is too less in content to improve the alloy's burn proof ability.
2002(1):22-25.
Abstract:
The hardening curve exhibits sigmoid shape in metastable austenite stainless steel at low temperature due to strain induced martensite transformation during deformation. The hardening exponent n values derived from Hollomon equation in each 1 5% of nominal strain are found not to be constant. Furthermore, both the n values and the hardening rate present parabola with increase of strain, while n values decrease correspondingly with increase of strain rate.
The hardening curve exhibits sigmoid shape in metastable austenite stainless steel at low temperature due to strain induced martensite transformation during deformation. The hardening exponent n values derived from Hollomon equation in each 1 5% of nominal strain are found not to be constant. Furthermore, both the n values and the hardening rate present parabola with increase of strain, while n values decrease correspondingly with increase of strain rate.
2002(1):26-30.
Abstract:
An experimental set up of travelling magnetic field excited by supper power permanent magnet was designed, which has obviously refine function for metal solidification structure. Theory of travelling magnetic field excited by permanent magnet was researched: mathematics model was built, analysis solutions of magnetic component force parallel to slab was obtained. It was confirmed that the magnetic component force was existed through round and slab of cast metal experiment. When travelling magnetic field was imposed properly during metal solidification, solidification structure of 100% fine equiaxed crystal could be obtained.
An experimental set up of travelling magnetic field excited by supper power permanent magnet was designed, which has obviously refine function for metal solidification structure. Theory of travelling magnetic field excited by permanent magnet was researched: mathematics model was built, analysis solutions of magnetic component force parallel to slab was obtained. It was confirmed that the magnetic component force was existed through round and slab of cast metal experiment. When travelling magnetic field was imposed properly during metal solidification, solidification structure of 100% fine equiaxed crystal could be obtained.
2002(1):31-36.
Abstract:
系统研究了Ti46Al8.5Nb0.1C0.2B合金简称0．1C0.2B合金在760℃～815℃，140MPa-400MPa的蠕变条件下的蠕变性能和蠕变机制。研究表明，在同等蠕变条件下同其它钛铝合金相比，0．1C0.2B合金最小蠕变速率降低2倍－10倍，蠕变应力提高50MPa-150MPa，如此优越蠕变抗力主要来自于高铌合金化对钛铝合金的固溶强化及间隙原子的沉淀强化。
系统研究了Ti46Al8.5Nb0.1C0.2B合金简称0．1C0.2B合金在760℃～815℃，140MPa-400MPa的蠕变条件下的蠕变性能和蠕变机制。研究表明，在同等蠕变条件下同其它钛铝合金相比，0．1C0.2B合金最小蠕变速率降低2倍－10倍，蠕变应力提高50MPa-150MPa，如此优越蠕变抗力主要来自于高铌合金化对钛铝合金的固溶强化及间隙原子的沉淀强化。
2002(1):41-43.
Abstract:
Diffusion joining of beryllium and HR 1 stainless steel with interlayer by hot isostatic pressing(HIP) (Cu layer or Cu/Ni layer) was investigated in this paper. The basic evaluations of bonded joints were made through metallurgical observation, SEM, AES, XRD, MPM and tensile testing. For Be/Cu/316L joint, Cu interlayer blocks the diffusion of Fe into Be, but Ni is gathered at Cu/316L interface and the crack is formed at this field. For Be/Cu/Ni/316L joint, the diffusion depth increases further. Change of Composition, mechanical property with distance in diffusion zone is smooth, and the tensile strength is about 50 MPa.
Diffusion joining of beryllium and HR 1 stainless steel with interlayer by hot isostatic pressing(HIP) (Cu layer or Cu/Ni layer) was investigated in this paper. The basic evaluations of bonded joints were made through metallurgical observation, SEM, AES, XRD, MPM and tensile testing. For Be/Cu/316L joint, Cu interlayer blocks the diffusion of Fe into Be, but Ni is gathered at Cu/316L interface and the crack is formed at this field. For Be/Cu/Ni/316L joint, the diffusion depth increases further. Change of Composition, mechanical property with distance in diffusion zone is smooth, and the tensile strength is about 50 MPa.
15 Microstructure and Electrochemical Properties of Co-free Over-stoichiometric
Alloys Ml(NiMnAlFe)5.4
2002(1):44-47.
Abstract:
详细研究了过化学计量经无钴合金Ml(Ni0.82Mn0.07Al0.06Fe0.05)5.4在常规熔铸、快速凝固、退火处理不同制备条件下的组织结构和电化学性能。X射线衍射（XRD）分析表明，常规熔铸合金由CaCu5型主相加少量的第二相（AlNi3)组成，而快速凝固合金的第二相析出得到一定程度的抑制，常规熔铸合金经1000℃退火处理后，部分第二相溶解消失。电化学测试表明，与常规熔铸合金相比，快速凝固和退火处理均大大提高了合金的电化学循环稳定性，但活化性能和高倍率放电性能稍有下降。快速凝固合金的电化学容量有所提高，而退火合金的放电容量与常规熔铸合金的基本相当。
详细研究了过化学计量经无钴合金Ml(Ni0.82Mn0.07Al0.06Fe0.05)5.4在常规熔铸、快速凝固、退火处理不同制备条件下的组织结构和电化学性能。X射线衍射（XRD）分析表明，常规熔铸合金由CaCu5型主相加少量的第二相（AlNi3)组成，而快速凝固合金的第二相析出得到一定程度的抑制，常规熔铸合金经1000℃退火处理后，部分第二相溶解消失。电化学测试表明，与常规熔铸合金相比，快速凝固和退火处理均大大提高了合金的电化学循环稳定性，但活化性能和高倍率放电性能稍有下降。快速凝固合金的电化学容量有所提高，而退火合金的放电容量与常规熔铸合金的基本相当。
2002(1):48-51.
Abstract:
通过热重分析（TGA）、X射线衍射（XRD）和扫描电镜（SEM）研究了MoSi2-Mo5Si3复合材料的低温氧化行为，指出材料低温氧化时，随Mo5Si3量增多，材料氧化加剧，当Mo5Si3含量超过16％（质量分数）时发生“PEST”现象，所形成的SiO2由于MoS3晶须的大量存在，使其不能均匀连续地分布于材料表面，从而加剧了氧化。
通过热重分析（TGA）、X射线衍射（XRD）和扫描电镜（SEM）研究了MoSi2-Mo5Si3复合材料的低温氧化行为，指出材料低温氧化时，随Mo5Si3量增多，材料氧化加剧，当Mo5Si3含量超过16％（质量分数）时发生“PEST”现象，所形成的SiO2由于MoS3晶须的大量存在，使其不能均匀连续地分布于材料表面，从而加剧了氧化。
2002(1):52-55.
Abstract:
将组成分别为Nd3.5Dy30.0Fe65.5Nb0.4B1.1和Nd33.5Fe30.5Co35.0Nb0.4B1.1（质量百分数）的铸态Nd-Fe-B合金按比例进行混合，使合金中的（Dy Co)总量基本保持不变，让Dy和Co的相对含量发生变化，采用粉末冶金工艺生产Nd-Fe-B磁体。结果发现：磁体的Br随着含Co合金比例的增加线性增大，iHc随着含Co合金比例的增加线性减小，但磁体的磁通可逆温度系数却只在较小的范围内变化。这说明当（Dy Co)含量保持在一定范围内时，既可以通过增加Dy含量降低磁体的温度系数也可以通过增加Co含量降低磁体的温度系数。在此研究的基础上，通过调整初始合金的成分和工艺,制成了磁性能为18MGOe/23kOe-25MGO3/15kOe、磁通可逆温度系数为－0．018％／℃-0.026%/℃的高稳定性，低温度系数Nd-Fe-B系列磁体。
将组成分别为Nd3.5Dy30.0Fe65.5Nb0.4B1.1和Nd33.5Fe30.5Co35.0Nb0.4B1.1（质量百分数）的铸态Nd-Fe-B合金按比例进行混合，使合金中的（Dy Co)总量基本保持不变，让Dy和Co的相对含量发生变化，采用粉末冶金工艺生产Nd-Fe-B磁体。结果发现：磁体的Br随着含Co合金比例的增加线性增大，iHc随着含Co合金比例的增加线性减小，但磁体的磁通可逆温度系数却只在较小的范围内变化。这说明当（Dy Co)含量保持在一定范围内时，既可以通过增加Dy含量降低磁体的温度系数也可以通过增加Co含量降低磁体的温度系数。在此研究的基础上，通过调整初始合金的成分和工艺,制成了磁性能为18MGOe/23kOe-25MGO3/15kOe、磁通可逆温度系数为－0．018％／℃-0.026%/℃的高稳定性，低温度系数Nd-Fe-B系列磁体。
18 The Effect of Oxidation Temperature on Oxidation Behavior of (Fe+Cr)-Modified Multi-component Films
2002(1):56-59.
Abstract:
对Fe Cr改性多元氮化物薄膜，即（TiFeCr)N多元膜的高温氧化行为进行了研究，结果表明：（1）这种多元膜膜在600℃以上温度下的氧化增重均低于TiN膜，加热至600℃膜层仍保持良好的光泽，加热至800℃膜层仍保持完整，没有类似TiN膜的局部脱落现象，这种多元膜具有优于TiN的抗高温氧化性能；（2）600℃氧化1h后，X射线衍射（XRD）谱上没有出现类似于TiN场合下出现的氧化铜的谱线。说明这种多元膜可以有效地抑制铜基体的氧化，具有优于TiN膜的保护性能。
对Fe Cr改性多元氮化物薄膜，即（TiFeCr)N多元膜的高温氧化行为进行了研究，结果表明：（1）这种多元膜膜在600℃以上温度下的氧化增重均低于TiN膜，加热至600℃膜层仍保持良好的光泽，加热至800℃膜层仍保持完整，没有类似TiN膜的局部脱落现象，这种多元膜具有优于TiN的抗高温氧化性能；（2）600℃氧化1h后，X射线衍射（XRD）谱上没有出现类似于TiN场合下出现的氧化铜的谱线。说明这种多元膜可以有效地抑制铜基体的氧化，具有优于TiN膜的保护性能。
2002(1):60-63.
Abstract:
研究了机械合金化过程中粉末形态和微结构的变化，通过扫描电子显微镜，清楚地观察到粉末颗粒的破碎和集聚复合过程，以及复合颗粒的形成。通过X射线衍射详细分析了球磨过程中的晶格常数、晶粒度和微观应变的变化。球磨的最终产物为非晶，α-Fe(Mo)和Mo。通过优化工艺，NdFe10.5Mo1.5Nx氮化物获得了较佳的磁性能。
研究了机械合金化过程中粉末形态和微结构的变化，通过扫描电子显微镜，清楚地观察到粉末颗粒的破碎和集聚复合过程，以及复合颗粒的形成。通过X射线衍射详细分析了球磨过程中的晶格常数、晶粒度和微观应变的变化。球磨的最终产物为非晶，α-Fe(Mo)和Mo。通过优化工艺，NdFe10.5Mo1.5Nx氮化物获得了较佳的磁性能。
2002(1):64-68.
Abstract:
The effect of W content and preheat temperature on phase components and powder size of combustion synthesized product in Ti W C system were studied. With the decrease of W content, the combustion temperature is increased and the combustion reaction mechanism is changed to melt solution prepicitation from diffusion solution in solid state. Preheating mixtures would result in the same effect. As a result, the combustion reaction becomes complete, single phase (Ti, W)C is synthesized advantageously and the powder size increases with the decrease of W content and the increase of preheat temperature. Meanwhile, the necessary preheat temperature for synthesizing single phased(Ti, W)C increases with the increase of W content.
The effect of W content and preheat temperature on phase components and powder size of combustion synthesized product in Ti W C system were studied. With the decrease of W content, the combustion temperature is increased and the combustion reaction mechanism is changed to melt solution prepicitation from diffusion solution in solid state. Preheating mixtures would result in the same effect. As a result, the combustion reaction becomes complete, single phase (Ti, W)C is synthesized advantageously and the powder size increases with the decrease of W content and the increase of preheat temperature. Meanwhile, the necessary preheat temperature for synthesizing single phased(Ti, W)C increases with the increase of W content.
2002(1):69-72.
Abstract:
首次采用微波辐射法快速合成了亚超细CaS:C^3 ,Sb^3 高效绿光磷光体，发现Ce^3 与Sb^3 离子之间存在着能量传,租是属于多极子相互作用的共振传递，因而Ce^3 对CaS:Sb^3 的发光有明显的敏化和增强。微波场作用下合成的双掺磷光体的激发峰与发射峰值分别恒定在259nm 和523nm处，并没有像传统高温固相合成法那样，随掺杂离子浓度的增大而发生红移现象。SEM照片显示，采用含不同一价阳离子（Na^ ,K^ ,NH4^ )无机盐作助熔剂制得的亚超细CaS:Ce^3 ,Sb^3 磷光体平均粒径为300nm-500nm，但其晶体形貌分别为立方形、球形和团聚状的雪花形，其中球形磷光体荧光最强。
首次采用微波辐射法快速合成了亚超细CaS:C^3 ,Sb^3 高效绿光磷光体，发现Ce^3 与Sb^3 离子之间存在着能量传,租是属于多极子相互作用的共振传递，因而Ce^3 对CaS:Sb^3 的发光有明显的敏化和增强。微波场作用下合成的双掺磷光体的激发峰与发射峰值分别恒定在259nm 和523nm处，并没有像传统高温固相合成法那样，随掺杂离子浓度的增大而发生红移现象。SEM照片显示，采用含不同一价阳离子（Na^ ,K^ ,NH4^ )无机盐作助熔剂制得的亚超细CaS:Ce^3 ,Sb^3 磷光体平均粒径为300nm-500nm，但其晶体形貌分别为立方形、球形和团聚状的雪花形，其中球形磷光体荧光最强。
22 Films
2002(1):73-75.
Abstract:
研究了射频反应溅射三元化合物CdIn2O4薄膜的电学和光学性质，讨论了反应气体中氧气浓度和热处理对CdIn2O4薄膜红外反射率的影响，实验结果表明，CdIn2O4薄膜在红外区域具有很高的反射率，是一种极好的红外反射膜。用它用为冰箱内保温膜和室内及冷库保温窗玻璃，效果十分明显，是一种极好的保温和节能膜。
研究了射频反应溅射三元化合物CdIn2O4薄膜的电学和光学性质，讨论了反应气体中氧气浓度和热处理对CdIn2O4薄膜红外反射率的影响，实验结果表明，CdIn2O4薄膜在红外区域具有很高的反射率，是一种极好的红外反射膜。用它用为冰箱内保温膜和室内及冷库保温窗玻璃，效果十分明显，是一种极好的保温和节能膜。
2002(1):76-80.
Abstract:
介绍了扇形轧辊步进轧机的工作原理，СШ－175M，ПК－600，СШС－750等型号步进轧机各工作部件的功能、技术特性及使用特点。
介绍了扇形轧辊步进轧机的工作原理，СШ－175M，ПК－600，СШС－750等型号步进轧机各工作部件的功能、技术特性及使用特点。
