具有可控气孔的低熔高强纳米陶瓷结合剂

结合剂中的理想气孔不但可以最大效率地容屑、断屑、贮存冷却液、润滑剂,而且对结合剂强度的影响最小。本文介绍了自主研制的具有可控气孔的低熔高强纳米陶瓷结合剂的烧结工艺和气孔结构特性。通过改变造孔剂的粒度和掺入量,可以获得近于无气孔的致密型和具有均匀分布的圆形理想气孔的结合剂,气孔孔径和数量可控,并且气孔率可以在大范围内调整。该适合制备较大磨削接触面积的工具如抛磨工具等。     

纳米铝颗粒增强Sn1.0Ag0.5Cu钎料性能及机理

通过机械混合的方法，制备Sn1.0Ag0.5Cu-xAl复合钎料.采用DSC、STR-1000型微焊点强度测试仪及SEM，研究了纳米铝颗粒对低银Sn1.0Ag0.5Cu钎料组织与性能的影响.结果表明，微量纳米铝颗粒的添加对钎料的熔化温度影响较小，其熔点均在226.9~229.0℃之间.随着纳米Al元素含量的增加，钎料的润湿角逐渐减小，力学性能逐渐增加，当纳米Al元素的添加量为0.1%时，焊点的拉伸力达到最大，为7.1 N.此外，Sn1.0Ag0.5Cu-0.1Al钎料的内部组织得到显著细化，焊点界面金属间化合物的生长也得到明显抑制，主要归因于纳米颗粒对金属间化合物生长的吸附作用.     

Direct conversion of wolframite ore to tungsten carbide nano particles

The present work describes the synthesis of WC nano particles directly from wolframite ore which is the main source of tungsten (W). The systematic experimental conditions describe that high purity WC nano particles of nearly 12 nm can be synthesized using solvo-thermal route and selecting appropriate experimental condition (particle size, carbon source and heating temperature).     

Synthesis and characterization of hexagonal nano tungsten carbide powder using multi walled carbon nanotubes

Tungsten carbide nano particles were formed by carburizing tungsten/tungsten oxide/non-stoichiometric tungsten oxide particles obtained from a wire explosion process with multi walled carbon nano tubes (MWCNT). The produced powder is confirmed to be hexagonal tungsten carbide from wide angle X-ray diffraction analysis. Carburization of tungsten nano particles with MWCNT shows the presence of tungsten sub-carbides in the produced tungsten carbide particles. Transmission electron micrographs show that the tungsten carbide particles are of spherical shape and the geometric mean size of the particles obtained is about 19 nm.     

Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

TiC based steel bonded carbides with the addition of nano TiN were prepared by vacuum sintering techniques.The microstructure was investigated using scanning electron microscopy（SEM） and transmission electron microscopy（TEM）,and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides,the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.     

MAfHEMAfICAL MODEL FOR MELTING PROCESSES OF SOLID ARTICLES IMMERSED IN METAL BATHS

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Portable nano probe for micro/nano mechanical scratching and measuring

A nano probe system which can measure precise micro parts or optical parts in nanometer range resolution and scratch contact force in mN scale was demonstrated. The nano probe was originally designed for on-machine measuring applications and one kind of contact type measuring probes was designed for miniaturized or microfactory system. It ideally should be of small size and able to measure surface topography in nanometer scale. A commercial capacitive displacement sensor was proposed. It was a new concept i...     

Melting behavior of nanosized lead particles embedded in an aluminum matrix

Molecular dynamics (MD) simulations, employing semi-empirical glue-type (similar to embedded atom method) many-body potentials, have been used to model the melting behavior of nanosized Pb particles embedded in an Al matrix. All the Pb particles studied melt well above the bulk melting temperature, with the melting point elevation displaying a damped periodic trend with increasing Pb particle size. By inspecting snapshots derived from the simulations, it is also possible to conclude that melting occurs via nucleation at {1 0 0} interfaces. A phenomenological model, based on the consideration of interfacial energy, volume expansion and lattice mismatch, has been developed to describe this interesting melting behavior. Our model leads to the conclusion that the periodic variation of melting point with size is due to an oscillatory strain energy contribution arising from the large size mismatch of Pb and Al atoms.     

Portable nano probe for micro/nano mechanical scratching and measuring

A nano probe system which can measure precise micro parts or optical parts in nanometer range resolution and scratch contact force in mN scale was demonstrated. The nano probe was originally designed for on-machine measuring applications and one kind of contact type measuring probes was designed for miniaturized or microfactory system. It ideally should be of small size and able to measure surface topography in nanometer scale. A commercial capacitive displacement sensor was proposed. It was a new concept in nano probe systems which can measure the displacement of shaft driven by the variation of surface topography. The nano probe mainly consisted of three parts: a capacitive displacement sensor, a porous type air slide and a contact probe part with various tip radiuses. The porous type air slide assured the shaft slided smoothly with controllable normal force in mN scale and had high positioning accuracy. The probe part which was directly in contact with target surface, can be applied to micro/nanoscale scratching as well as the measurement of sample topography by a simple tip change.     

Preparation and characterization of nano hydroxyapatite sol

Nano hydroxyapatite has special biological effects when it interacts with cells. The method of preparation of nano hydroxyapatite crystals in water and the stability of hydroxyapatite sol are reported. Nanometer sized hydroxyapatite crystals were synthesized by precipitation with monocalcium phosphate and calcium hydroxide. The size of the crystals is 30 - 50 nm as determined by laser light scattering and transmission electron microscopy (TEM). The shape of the crystals particles is either sphere or rod-shaped. Beijing Synchrotron Radiation Facility (BSRF) micro-probe X-ray fluorescence analysis and TEM analysis reveal that hydroxyapatite crystals can pass human liver cancer cell membrane in the form of particles.     

Preparation of ultrafine/nano Mo particles via NaCl-assisted hydrogen reduction of different-sized MoO2 powders

The current study investigated the effects of the amount of NaCl addition, particle size of MoO₂, temperature (under isothermal condition) and heating rate (under non-isothermal condition) on the morphology, particle size and dispersivity of prepared Mo by hydrogen reduction of MoO₂. The formation of sufficient dispersed Mo nuclei and their controllable growth were crucial for transforming the large MoO₂ particles to dispersed ultrafine/nano Mo particles. It was found that in the absence of NaCl, it was hard to control the nucleation and growth of Mo grains, and the morphology and particle size of products still retain those of the raw MoO₂ in the temperature range of 840–1000 °C. However, as the amount of NaCl addition was above 0.05%, it was successful to control the nucleation and growth of Mo. Ultrafine/nano Mo powders with the average particle size from 100 nm to 800 nm were successfully prepared via adjusting the particle size of MoO₂ and temperature under isothermal condition. The use of MoO₂ with small particle sizes can increase the reaction rate and the number of Mo nuclei number, thus improve the particle dispersivity and decrease the particle size. Additionally, after reaction at 900 °C and 1000 °C, the residual Na was reduced to 140 ppm and 33 ppm from the initial value of 380 ppm, respectively. Under non-isothermal condition, the temperatures for the nucleation and growth could be adjusted by changing heating rate and particle size of raw MoO₂ particles. Mo nanoparticles with smaller particle size and better dispersivity were successfully prepared, and the average particle size can decrease to about 80 nm.     

Fabrication of nano Rhizama Chuanxiong particles and determination of tetramethylpyrazine

Rhizama Chuanxiong is a kind of traditional medicinal herb used to promote blood circulation and eliminate wind to relieve pain. In this work, nano Rhizoma Chuanxiong particles were successfully prepared by high speed centrifugal sheering （HSCS） pulverizer. The influence of processing parameters on the size ofRhizama Chuanxiong particles and the different properties between nano Rhizoma Chuanxiong particles and original fine powder were systematically studied by ZetaPALS light scattering granulometric analyzer and optical microscope. The content of effective ingredient tetramethylpyrazine （TMP） was determined by high-performance liquid chromatography （HPLC）. The results illustrate that general Rhizama Chuanxiong powder can be ultrafinely ground to nanometer within 50 min, and the cellular tissues ofRhizoma Chuanxiong are broken into pieces and dispersed stably and homogeneously after being ultrafinely ground. In addition, the active ingredients can dissolve out directly and fully, and the extraction ratio of TMP is increased 32.2% by HSCS processing.     

Characterization of phase transformation and microstructure of nano hard phase Ti（C,N）-based cermet by spark plasma sintering

By means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), the process of densification, the characterization of phase transformation and the microstructure for spark plasma sintering (SPS) nano hard phase Ti(C, N)-based cermet were investigated. It is found that the spark plasma sintering (SPS) enables the nano hard phase Ti(C,N)-based cermet to densify rapidly, however, the full densification of the sintered samples can not be obtained. The rate of phase transformation is significantly quick.When being sintered at 1 200℃ for 8 min, Mo2C is completely dissolved, and TiN dissolves into TiC entirely and disappears. Above 1200℃, Ti(C,N) begins to decompose and the atoms of C and N separate from Ti(C,N) resul-ting in the generation of N2 and the graphite. Due to the denitrification and the graphitization, the density and the hardness of sintered samples are rather low. The distribution of grain size of the sample sintered at 1350℃ covers a wide range of 90-500 nm, and most of the grain size are about 200 nm. The hard phase is not of typical core-rim structure. Oxides on the surface of particles can not be fully removed and present in sample as titanium oxide TiO2.Graphite exists in band-like shape.     

双丝电弧喷涂中粒子交叉飞行行为的在线测量及分析

采用两根具有不同熔点的材料分别作为双丝电弧喷涂的阳极和阴极丝材,采用SprayWatch-2i热喷涂监测系统,通过对融熔粒子飞行中温度的在线测量分析,直接验证了粒子的＂交叉飞行＂现象.利用能谱仪（EDS）定量研究了两极的材料和氧化物在喷涂沉积丘中的分布,并分析了这些分布特征在不同喷涂距离上的变化规律,结果发现,沿喷涂丘的横截面,来自阴极和阳极的扁平化粒子以接近反对称的方式分布.在所测量的两个喷涂距离上,各种成分（包括氧化物）的含量随喷涂距离变化不大.而且电弧喷涂涂层中具有约10 %左右的氧化物含量.     

Contact mode thermal sensors for ultrahigh-temperature region of 2000-3500 K

In this article,we reviewed several existing techniques that were capable of detecting local temperatures in the range of 2000-3500 K in a contact manner.These techniques included several non-standard thermocouples,Seger cones and ultrasonic meters.In particular,ultrasonic meters made of tungsten(W)wires were proven to be working well in nuclear plant for detecting the central temperature of reaction zone.We also presented two alternative approaches.One of them was a kind of singlemetal-based thermal sensor made from W,Mo and Ta wires,which utilized the size effect of Seebeck coefficient and theoretically applicable in contact mode measurement up to 3500 K.The other was a kind of detectors with micro-/nano-patterns,which utilized the size effect of surface melting point of bulky materials.This work should shed light on measurement approaches for ultrahigh temperatures in a variety of practical applications.     

MgO/Cu基复合材料耐电弧侵蚀行为研究

采用放电等离子烧结法(SPS)制备了纳米级MgO陶瓷颗粒增强铜基复合材料(MgO/Cu复合材料),重点研究了MgO颗粒含量对其耐电弧侵蚀性能的影响,阐述了MgO颗粒在电接触过程中的耐电弧侵蚀机理。结果表明,随着MgO颗粒体积分数增加,MgO/Cu复合材料的耐电弧侵蚀性能逐渐提高,当MgO颗粒体积分数为5%时,MgO/Cu复合材料的总体质量损耗和燃弧能量均达到最低值。研究分析表明,高熔点的MgO颗粒有助于改善MgO/Cu复合材料的力学性能和耐电弧侵蚀性能。电弧侵蚀过程中,高熔点MgO颗粒的存在提高了液相铜基体的熔池粘度,减少了电弧喷溅,从而提高了MgO/Cu复合材料的耐电弧侵蚀性能。     

电子封装微纳连接技术及失效行为研究进展

微纳连接技术是电子封装中的关键技术,近年来,随着电子产品逐渐小型化、轻量化的方向发展,各种先进的微纳连接层出不穷,但仍缺少系统的归纳及总结. 文中对引线键合技术,熔化微连接技术、软钎焊技术、纳米焊膏烧结技术、导电胶连接技术、表面活化键合技术及新兴的纳米连接技术等具有代表性的微纳连接技术进行了综述,并针对软钎焊焊点在热载荷、电载荷、机械载荷及多物理场耦合作用下微互连的失效行为研究进行了总结. 结果表明,未来的微纳连接技术将朝向互连尺寸更加微小,互连方法逐渐智能化,互连材料更加绿色,互连焊点更可靠的方向发展. 软钎焊互连焊点的失效行为分析也将逐渐从单一热场、电场载荷的研究拓展至热—电—力多物理场耦合载荷,与实际工况更加贴合,随着如同步辐射,三维X射线等先进表征技术的不断发展,失效行为及机制的研究也将更加精准.     

Carbon films containing transition metal particles of nano and submicron sizes

Aromatic polyimide films containing cobalt compounds were prepared by mixing Co(NO₃)₂ and CoCl₂ with a polyamic acid in solution and following imidization on glass plates. The effect of heat treatment on structure, texture and magnetic property of the films was investigated, and the formation process of ferromagnetic particles of nano and submicron sizes in the films was examined. As the particle sizes increased with increasing heat treatment temperature (HTT), the magnetic property changed from superparamagnetic to ferromagnetic, and the ferromagnetic particles of single magnetic domain transferred to those with multi-magnetic domain by further heat treatment. The distribution of metal particle size became very wide by the heat treatment. Pores were found on the surfaces of the heat-treated films, and pore sizes were very similar to those for the metal particles, suggesting that pores were paths of the particle movements. These results were compared with those obtained previously for the polyimide films containing nickel and iron compounds. Different metal compounds introduced in polyimide films gave different processes of the formation and growth of metal particles and pores as HTT increased.     

Pd掺杂SnO2纳米颗粒的合成、表征和气敏特性（英文）

利用非模板水热法合成了Pd掺杂的SnO2纳米颗粒,并利用透射电镜(TEM)、X射线衍射(XRD)和X光电子能谱(XPS)表征了Pd掺杂对晶体结构、表面形貌、微观结构、热稳定性和表面化学状态的影响。研究发现:水热过程中Pd掺杂对形成的SnO2纳米颗粒大小几乎没有影响,在500°C以下的煅烧过程中,掺杂的Pd可以有效抑制颗粒的生长,但在700°C以上时颗粒生长迅速。XPS结果显示合成样品中Pd的化学状态有三种:Pd0、Pd2+和Pd4+,其中的主化学状态Pd4+有效促进了气敏性能的提高。为了同时提高气敏性能和热稳定性,Pd的最佳掺杂量为2.0%?2.5%(摩尔分数)。     

Performance of nano/micro CBN particle coated tools in superfinish hard machining

A two-stage composite coating method has been developed for coating of nano/micro cubic boron nitride (CBN) particles on cutting tools. Since nano/micro CBN particle coated tools are more cost-effective than solid polycrystalline CBN (PCBN) tools, a comprehensive study on the coated tools is required. This paper studies the performance of these tools in superfinish hard machining. Specimens were machined by a solid PCBN tool and CBN particle coated tools with two different CBN particle size distributions: less than 0.5 and 2 μm. The specimen machined by a tool with small CBN particle coating (less than 0.5 μm) showed more compressive residual stresses and less thermal damage below the machined surface than other specimens. Furthermore, the specimen machined by a tool with small CBN particle showed less residual stress scatter than other specimens. The rolling contact fatigue life was predicted by using a rolling contact fatigue life model. The rolling contact fatigue life predictions indicate that the predicted life of the specimen machined by a tool with small CBN particle coating is longer than that of other specimens. The results thus indicate that a tool with small CBN particle coating provides better performance than other tools in superfinish hard machining.