Preparation of iridium nano-and submicroparticles on solid substrates by direct surface growth and drop-drying assembly

Iridium nanoparticles (IrNPs) and submicroparticles (IrSMPs) with different shapes were synthesized and assembled on indium thin oxide (ITO) and Si substrates using two different methods: direct surface growth and drop-drying assembly. The obtained IrNPs and IrSMPs were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The IrSMPs (or IrNPs) with disc-like shape and irregular shapes were obtained on ITO substrate by direct surface growth method using polyvinylpy...     

MICROSTRUCTURE AND COMPRESSIVE PROPERTIES OFTi_(50)Al_(48)Mn_2 AND Ti_(50)Al_(48)Cr_2

The microstructure and compressive properties of Ti_(500Al_(48)Mn_2and Ti_(50)Al_(48)Cr_2 alloys are studied in this paper Existence of αx y transforntation in TiAl alloys is confirnted by metallographic examincttion,the transformation temperatuses of Ti_(50)Al_(48)Mn_2 and Ti_(500Al_(48)Cr_2,are 1375and 1373C respeclively,After treating withic x y phase field,themicrostructure of alloys consists of lamellar zones(L)and bulk y_p.,The vohme ratio of L/y_p inctrases with increasing solution treatnient temperature.The third alloying ele-ments of Mn and Cr distribute perfentially over αphase at solution treatment tempera-tures and result in that α_2 and γ lamellae become thicker.The yield strength of Ti_(50)Al_(48)Mn_2 and Ti_(500Al_(48)Cr_2 alloys decreases and the compressibllity increases with in-creasing γ_p volume fraction.     

Ferromagnetic–paramagnetic transition temperature in bulk and nanostructured La_(0.7)Sr_xCa_(0.3-x)MnO_3(x=0.10, 0.15, and 0.20) manganite materials

Series of bulk and nanostructured La_(0.7)Sr_xCa_(0.3-x)MnO_3(x = 0.10, 0.15, and 0.20) manganites were synthesized and characterized using different techniques. In the series, both the bulk and nanostructured La_(0.7)Sr_(0.10)Ca_(0.20)MnO_3 and La_(0.7)Sr_(0.20)Ca_(0.10)MnO_3 manganites have orthorhombic and rhombohedral structures, whereas La_(0.7)Sr_(0.15)Ca_(0.15)MnO_3 manganite has rhombohedral and orthorhombic structures, respectively. Online ultrasonic velocity and attenuation measurements were taken through an indigenously designed ultrasonic setup, and the analysis was done from 300 to 400 K during the aging of the samples to explore the structural/phase transitions. The bulk and nanocrystalline La_(0.7)Sr_xCa_(0.3-x)MnO_3 perovskite samples show the particle size distribution in the range of 197–943 and 24–93 nm, respectively. The addition of Sr~(2+) alters the size of particles, which decrease in size. The observed anomaly in ultrasonic velocities, attenuations, and elastic moduli is correlated with the ferromagnetic–paramagnetic(FM–PM) transition temperature(T_C) in both bulk and nanocrystalline perovskites. In addition, the shift in T_C and the magnitude and width of observed anomaly are correlated with the value of x to study the behavior of T_C.     

Effect of mechanical anisotropy on material removal rate and surface quality during polishing CdZnTe wafers

The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests,and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests.There is a peak of frictional coefficient at the early stage of scratch,and increasing the vertical force will result in the increase of peak value correspondingly.The fluctuation phenomenon of frictional coefficient is generated at high vertical force.The lateral forces show the apparent twofold and threefold symmetries on(110) and(111) planes,respectively.To obtain high surface quality,low polishing pressure and hard direction(< 110 > directions on(110) plane and <112 > directions on(111) plane) should be selected,and to achieve high material removal rate,high polishing pressure and soft direction(<001> directions on(110) plane and < 121 > directions on(111) plane) should be selected.     

等离子熔覆高硼Fe-Cr基涂层的组织与性能

采用常压弧光等离子体在碳钢表面制备高硼Fe-Cr基合金涂层.采用扫描电镜、X射线衍射仪、能谱仪、显微硬度计等对熔覆层的相、组织和显微硬度进行了分析.结果表明,熔覆层中的主晶相是γ-Fe(Ni),Fe_2 B;熔覆层由大量等边L形、长条状Fe_2 B初晶相、γ-Fe(Ni)与硼化物的共晶体组成,共晶体呈片层状、菊花状.熔覆层与基体呈冶金结合,界面组织呈扇形共晶、树枝晶等形态.熔覆层的硬度为1 100～1 400 HV0.2,约是基体硬度(290 HV0.2)的4倍.靠近熔覆层的基体由于淬火效应硬度提高到600 HV0.2左右.

Abstract：

A harden coating of Fe-Cr based alloy, containing high boron, was produced on midium carbon steel plate by plasma cladding process. The phases, microstructures and microhardness of the cladding coating were investigated by Scanning Electron Microscopy ( SEM ) , X-ray Diffractometer ( XRD ) , Energy-dispersive Spectroscopy (EDS) and microhardness tester. The chief phases of the cladding coating are γ-Fe(Ni)and Fe_2B. The microstructures of cladding coating were consisted of Fe_2B with shapes of equilateral L or lath and eutectic of γ-Fe(Ni)and borides, and the eutectic presented itself with lamella or rosette shape. An excellent metallurgical interface between the coating and the substrate appeared. The micro-structures of the layer near the interface exhibit fan-shaped or dendritic structure. The microhardness value of the cladding coating was 1 100 - 1 400HV_(0.2) and was about 4 times of the substrate (290HV_(0.2)). The microhardness of the substrate near the interface increased to 600HV_(0.2) because of quenching.     

第四届国际淬火与畸变控制会议在京举办

由国际热处理及表面工程联合会(International Federation for Heat Treatrnent and Surface Engineering)、中国机械工程学会和美国金属学会(ASM International)主办，中国机械工程学会热处理学会承办的第四届国际淬火与畸变控制学术会议(4th International Conference on Quenching and Control of Distortion)于2003年11月22～24日在北京顺利召开。来自世界各地     

Corrosion Resistance of Ti_3Al/BN Abradable Seal Coating

Ti–Al mixed powder(Ti:Al = 3:1 in atomic ratio) and Ti3 Al intermetallic alloy powder mechanically clad hexagonal BN to fabricate Ti Al/BN and Ti3Al/BN composite powders. The corresponding porous abradable seal coatings(named as TAC-1 and TAC-2, respectively) were deposited using vacuum plasma spray(VPS) technology, and their corrosion behavior was studied via salt spray corrosion and electrochemical tests. Phase compositions and microstructures of these coatings before and after corrosion were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) facilitated with energy dispersive X-ray spectrometer(EDS). The results showed that spontaneous passivation of TAC-1 and TAC-2 granted the coatings excellent corrosion resistance than that of commercial Al/BN coating. Additionally, TAC-2 exhibited higher corrosion potential(Ecorr) and breakdown potential(Ebp) but a lower corrosion current density(icorr) than TAC-1. A small quantity of the corrosion product(Al(OH)3and Al O) could be detected on the surface of TAC-1, while no corrosion product appeared in TAC-2. The non-uniform elements distribution in the metal matrix of TAC-1 resulted in localized corrosion and relatively poor corrosion resistance compared to TAC-2.     

Microstructure of directionally solidified Cu-Cr composites

Cu-Cr composites were prepared by self-made directional solidification equipment with the high temperature gradient and double-zone heating. The microstructural evolution was investigated during the directional solidification with the different solidification rate for Cu-1.0%Cr, Cu-1.7%Cr and Cu-5.6%Cr alloys, respectively. It is shown that for the hypoeutectic Cu-1.0%Cr alloy, the general microstructures consist of primary α(Cu) phase and the rod-like or needle-like (α β) eutectics, and for the hypereutectic Cu-1. 7%Cr and Cu-5.6%Cr alloys, α(Cu)phase, primary β(Cr) phase and (α β) eutectics coexist. With the increase of the solidification rate, the morphology evolution of every phase is that, 1st cellular(dendrite) of α(Cu) phase thins and cellular(dendrite) spacing shortens gradually, (α β) eutectics set in α(Cu) cellular or dendrite, and primary β(Cr) phase distributes unevenly on α (Cu) matrix, whose morphology undergoes the change from dendrite to particle.     

NANOCOMPOSITE COATINGS WITH ENHANCED HARDNESS

The article reviews the present state of the art in the magnetron sputtering of hart and superhard nanocomposite coatings. It is shown that there are (1) two groups of hard and superhard nanocomposites : ( i ) nc-MN/hard phase and ( ii ) nc-MN/soft phase, (2) three possible origins of the enhanced hardness: (i) dislocation-dominated plastic deformation, (ii) cohesive forces between atoms and (iii) nanostructure of materials, and (3) huge differences in the microstructure of single- and two-phase films. A main attention is devoted to the formation of nanocrystalline and/or X-ray amorphous films. Such films are created in a vicinity of transitions between (i) crystalline and amorphous phases, (ii) two crystalline phases of different chemical composition or (iii) two different preferred orientations of grains of the same material from which the coating is composed. The existence of the last transition makes it possible to explain the enhanced hardness in single-phase films. The thermal stability and oxidation resistance of hard nanocomposite films is also shortly discussed.     

Simultaneous Determination of Zirconium and Hafnium by Dual System and Dual Wavelength Spectrophotometry

A dual system and dual wavelength spectrophotometry(DSDWS)used to simultaneously determine Zrand Hf were proposed.《Zr(Hf)-xO-CTMAB》and《Zr(Hf)-CAB-CDMAA-Triton X-100》were chosenas a pair of chromophoric systems.The difference of chromophoric behaviours between Zr and Hf is in-creased by the addition of hydrogen peroxide as masking agent and by adjustment of acidity.The apparentmolar absorptivities of Zr and Hf are 2.0×10~5 and 5.0×10~4 L·mol~(-1)·cm~(-1)respectively.The proce-dure is simple and rapid.