激光快速成型TC4合金显微组织及力学性能

采用金相显微镜、扫描电镜、电子拉伸机等，研究了激光快速成型TC4合金沉积态在平行沉积方向和垂直沉积方向的组织和力学性能.结果表明:激光快速成型TC4合金沉积态宏观组织沿沉积方向生长的粗大β柱状晶呈明暗相间的条带状结构，具备典型的魏氏组织特征;垂直沉积方向的强度比平行沉积方向的强度高，但塑性低;合金断口为韧窝状断口，垂直沉积方向的断口韧窝尺寸比平行沉积方向的小.     

Investigation on preparing boron nitride by nitriding pure boron at 1200–1550 1C

Boron nitride (BN) was prepared by nitriding pure boron (B) deposited on carbon substrates by chemical vapor deposition (CVD). Thermodynamic analysis of preparing BN by nitriding CVD B at 1200–1550 1C was firstly performed. And then, the effects of nitridation conditions, including temperature, nitridation atmosphere and CVD B microstructure, on the conversion of B to BN were analyzed by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Results show that the conversion degree of B to BN firstly increased and then slightly decreased with rising temperature. The nitridation degree was controlled by mutual actions between the nitridation of B and consumption of the effective nitrogen source (NH3). The morphology of products and the reaction mechanism between B and N were influenced by nitridation temperature. At high temperatures (1400–1500 1C), BN with highly ordered microstructure was produced. On using N2–H2 as nitridation atmosphere instead of NH3–H2– N2, no BN was obtained in the studied temperature range. The microstructure and component of BN obtained in nitridation process were little affected by the microstructure of CVD B.     

Study of titanium nitride for Iow-e coating application

The paper reports our novel work on chemical vapor deposition coating of titanium nitride （TIN） thin film on glass for energy saving. TiN films were deposited on glass substrates by atmospheric pressure chemical vapor deposition （APCVD） using titanium tetrachloride （TiCl4） and ammonia （NH3） as precursors. As a result, TiN films with a thickness of 500 nm were obtained. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscopy （AFM）, four-point probe method and optical spectroscopy were respectively employed to study the crystallization, microstructure, surface morphology, electrical and optical properties of the coated TiN films. The deposited TiN films are of NaCI structure with a preferred （200） orientation. The particles in the film are uniform. The reflectivity of the TiN coating in the near-infrared （NIR） band can reach over 40%, the visible transmittance is approximately 60%, and the visible refiectivity is lower than 10%. The sheet electrical resistance is 34.5 Ω. According to Drude theory, the lower sheet resistance of 34.5 Ω gives a high reflectivity of 71.5% around middle-far infrared band. The coated films exhibit good energy-saving performance.     

Rapid directionally solidified microstructure characteristic and fracture behaviour of laser melting deposited Nb–Si–Ti alloy

Aiming at achieving fine and directionally-solidified microstructure of Nb-Si based alloy,Nb,Si and Ti powder particles were utilized as the raw materials,and laser melting deposition(LMD) experiments were conducted with1500 W and 2000 W laser power,respectively.The microstructure characteristic,micro-hardness,and indentation fracture toughness were examined by scanning electron microscope(SEM),X-ray energy dispersive spectrometer(XEDS) and X-ray diffraction(XRD).The results showed that the two ...     

High-temperature frictional wear behavior of MCrAlY-based coatings deposited by atmosphere plasma spraying

Al₂O₃-Cr₂O₃/NiCoCrAlYTa coatings were prepared via atmosphere plasma spraying (APS). The microstructure and phase composition of the coatings were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser confocal scanning microscopy (LSCM), and transmission electron microscopy (TEM). The dry frictional wear behavior of the coatings at 500℃ in static air was investigated and compared with that of 0Cr25Ni20 steel. The results show that the coatings comprise the slatted layers of oxide phases, unmelted particles, and pores. The hot abrasive resistance of the coatings is enhanced compared to that of 0Cr25Ni20, and their mass loss is approximately one-fifteenth that of 0Cr25Ni20 steel. The main wear failure mechanisms of the coatings are abrasive wear, fatigue wear, and adhesive wear.     

Different effects of substrates on the morphologies of single-walled carbon nanotubes

In this work, different effects of substrates on the morphologies of single-walled carbon nanotubes （SWNTs） are studied. SWNTs were produced by floating catalytic chemical vapor deposition using CH4 as carbon source gas and Ar as carrier gas. Then the SWNTs were deposited on lithography-patterned different substrates. The as-grown SWNTs at the boundaries between SiO2 and metal were characterized by scanning electron microscopy, atomic force spectroscopy and Raman spectroscopy. It is found that SWNTs deposited on low-conductivity substrates trend to have curved morphologies and some of them form rings, while SWNTs deposited on metal sub- strates remain straight and orientated. The mechanism of these effects was also discussed, which is closely related to the thermal conductivities and the principle of energy dissipation.     

离子轰击碳膜诱导碳纳米尖端的形成和生长

用CH4、NH3和H2为反应气体,利用等离子体增强热丝化学气相沉积系统在沉积有碳膜的Si上制备了碳纳米尖端.用扫描电子显微镜、原子力显微镜和Raman光谱表征了碳膜的结构,以及用扫描电子显微镜和X射线光电子谱表征了碳纳米尖端的结构,结果表明碳膜是凸凹不平的非晶碳膜,碳纳米尖端是由sp2结构的碳组成.根据有关离子的溅射和沉积机制,分析了离子轰击碳膜诱导碳纳米尖端的形成和生长.     

喷射沉积Al-20Si-5Fe-3Cu-Mg

利用喷射沉积技术制备了Ａｌ－２０Ｓｉ－５Ｆｅ－３Ｃｕ－１Ｍｇ合金,借助扫描电镜（ＳＥＭ）,Ｘ－射线衍射和拉伸试验等手段研究了喷射沉积合金的微观组织和力学性能,分析了Ｆｅ对合金挤压和热处理后的组织变化,拉伸试验结果表明,喷射沉积Ａｌ－２０Ｓｉ－５Ｆｅ－３Ｃｕ－１Ｍｇ合金具有比粉末冶金Ａｌ－２０Ｓｉ－３Ｃｕ－１Ｍｇ合金更高的高温（３００℃）强度。     

Simple method to rapidly fabricate chain-like carbon nanotube films and its field emission properties

A simple process to fabricate chain-like carbon nanotube (CNT) films by microwave plasma-enhanced chemical vapor deposition (MPCVD) was developed successfully. Prior to deposition, the Ti/Al₂O₃ substrates were ground with Fe-doped SiO₂ powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 V/μm are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.     

Characterization of Fe3Si-based coatings on low silicon steel by pulsed Nd:YAG laser cladding

The Fe₃Si based coating was produced on the Fe-1 Si steel surface by a pulsed Nd:YAG (yttrium aluminum garnet) laser. Its phase constitution and microstructure were characterized by using X-ray diffraction (XRD), optical microscope (OM), and field emission scanning electron microscope (FESEM) with associated energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The hyperfine structure of the coating was studied by Mrssbauer spectra (MS) and the magnetic property was also measured at room temperature by a vibrating sample magnetometer (VSM). The obtained coating is pore and crack-free with dense microstructure and high Si content. The metallurgical bonding between the coating and the substrate was realized. The microstructure of the coating is typical fine dendrites. The major phase was confirmed by XRD and TEM to be the ordering D0₃ structured Fe₃Si phase. In addition, there were smaller amounts of the Fe₅Si₃ phase and the γ-Fe phase in the coating. Compared with the substrate, the laser cladding coating has a lower saturation magnetization and a higher coercive force. The poor magnetic property might be because of rapid solidification microstructure and phase constitution in the coating.     

喷射沉积Al-20Si-5Fe-3Cu-1Mg合金的微观组织与力学性能

利用喷射沉积技术制备了Al－20Si－5Fe－3Cu-1Mg合金,借助扫描电镜（SEM）,X-射线衍射和拉伸试验等手段研究了喷射沉积合金的微观组织和力学性能,分析了Fe对合金挤压和热处理后的组织变化．拉伸试验结果表明,喷射沉积Al－20Si-5Fe-3Cu-1Mg合金具有比粉末冶金Al-20Si-3Cu-1Mg合金更高的高温（300℃）强度．     

Mechanical properties of TiO2-hydroxyapatite nanostructured coatings on Ti-6Al-4V substrates by APS method

TiO₂-hydroxyapatite (HA) nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy (SEM). It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder (212 nm) extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.     

激光非晶化处理的研究

本文采用5～10kW高功率和高扫描速度的CO_2激光束在铸态共晶试样上第一次获得了激光非晶态.用金相显微镜和扫描电镜分析了激光非晶态熔区的组织特征及转变的过程.用显微硬度计检测了激光非晶化熔区的硬度分布,并研究了成分、冷却条件及不同激光工艺参数对熔区硬度分布的影响.用X射线衍射分析了激光熔区的表层白亮组织,确认了非晶态的存在.     

Influence of deposition time on the morphology and optical properties of SiO<Subscript>2</Subscript>-ZnO composite photonic crystals

SiO2 photonic crystal were successfully prepared by vertical deposition and then used as a template to fabricate SiO2-ZnO composite photonic crystals on ITO substrates by electrodeposition and subsequent calcination. A number of different deposition times were used. The morphologies of the silica opals and SiO2-ZnO composite photonic crystals were investigated by scanning electron microscopy. It was found that ZnO particles grew randomly on the surfaces of the silica spheres when the deposition time was short. As the deposition time was increased, the ZnO particles grew evenly on the surfaces of the silica spheres so that the interstitial space of the silica template was filled with ZnO particles. Reflectance spectra of the SiO2-ZnO composite crystals revealed that all of the fabricated photonic crystals exhibit a photonic band gap in the normal direction.     

Surface characteristics and corrosion resistance of biodegradable magnesium alloy ZK60 modifi ed by Fe ion implantati on and deposition

The ZK60 magnesium alloy has been modified by Fe ion implantation and deposition with a metal vapor vacuum arc plasma source. The surface morphology, phase constituent and elemental distribution are determined by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer and Auger electron spectroscopy. The results show that Fe thin film is deposited on ZK60 alloy and the corresponding thickness increases from 2.73 μm to 6.36 μm with increasing deposition time. A transition layer mainly composed of Mg, Fe and O elements is formed between Fe thin film and ZK60 substrate. The potentiodynamic polarization tests reveal that a high corrosion potential and a low corrosion current density are detected for the Fe deposited ZK60 alloy, indicating the improvement of corrosion resistance. The tensile deformation test indicates that the Fe deposited film on the ZK60 substrate can sustain 1% tensile strain without any cracks.     

A new inorganic azo dye and its thin film: MoO4N4H6

Thin films of hydrazine molybdenum （MoO4N4H6）, a new inorganic azo dye, were synthesized and deposited on a commercial glass substrate using the chemical bath deposition technique. Subsequently, the optical transmission, reflectivity, absorption, refractive index, and dielectric constant of hydrazine molybdenum were investigated using an ultraviolet-visible spectrophotometer. In addition, the film structure was analyzed by mid-infrared spectroscopy. The spectra of the films were found to be in line with those in the literature. The surface properties of all films were examined using a computer-controlled digital scanning electron microscope with a secondary electron detector. The areas of application and the technological advantages of this material were also considered.     

Microstructure and properties of SiC gradiently coated Cf/C composites prepared by a RCLD method

The SiC gradiently coated carbon fiber/carbon (C_f/C) composites were prepared by a two-step rapid chemical liquid deposition (RCLD) method. The microstructure and properties of the composites were investigated using X-ray diffraction, scanning electron microscopy together with energy dispersive X-ray analysis, bending tests, and oxidation tests. The experimental results show that the surface layer of the composites is composed of SiC, pyrocarbon, and carbon fibers. Their inner area consists of pyrocarbon and carbon fibers. The SiC content gradiently decreases with increasing distance from the outer surface to the center of the composites. Furthermore, the thickness of the SiC layer increases with increasing tetraethylorthosilicate content and deposition time. SiC coatings have no significant influence on the bending strength of the composites. However, the oxidation resistance of the composites increases with increasing thickness of the SiC layer.     

Highly <Emphasis Type="Italic">C</Emphasis>-axis oriented LiNbO<Subscript>3</Subscript> thin film on amorphous SiO<Subscript>2</Subscript> buffer layer and its growth mechanism

LiNbO3 waveguiding films with highly C-axis orieatation and superior crystallographic quality have been deposited on the amorphous SiO2 buffer layer of Si wafer by pulsed laser deposition (PLD) technique. X-ray diffraction,high-resolution electron transmission microscopy and atomic force microscopy were applied to characterizing the quality and orientaion of LiNbO3 thin film, and the optimized depositioa coaditioas have been determined for C-axis oriented growth. LiNbO3 thin films on amorphous SiO2 buffer layer were composed of intimate arrangements of quadrangular single crystal domain (150 nm x 150 nm) with C-axis orientatioa, and displayed sharp interface structures. The measurements of prism coupling technique indicate that the laser can be coupled into the LiNbO3 film and TE and TM waveguiding modes were detected. In addition, the possible mechanism of oriented growth on amorphous buffer layer and “film-substrate effects“ were discussed briefly, which suggests that its growth mechanism is likely analogous to the Voimer model with characteristics of three-dimensional islands nucleation on the smooth crystal surface.     

扫描速度对硅钢表面激光熔覆层组织和硬度的影响

在低硅钢表面激光熔覆Fe-Si粉末制备高硅熔覆层,研究了激光扫描速度对熔覆层宏观形貌、相组成、显微组织、成分及硬度分布等的影响.结果表明,不同扫描速度条件下熔覆层表面均由-αFe(Si),-γFe(Si)和FeSi2组成;随扫描速度增大,熔覆层的组织有细化的趋势,组织不均匀性得到改善;同时,熔覆层厚度减小,导致稀释率减小,使熔覆层平均硅含量提高,显微硬度提高.通过调整激光扫描速度,获得了无裂纹缺陷,且与基体呈良好冶金结合的熔覆层,最佳扫描速度为2.5 mm/s.     

Anisotropy of nickel-based superalloy K418 fabricated by selective laser melting

Selective laser melting (SLM) is a promising additive manufacturing (AM) technology for fabricating the near net-shaped parts by selectively melting and solidifying a thin powder layer with a high-intensity laser beam according to the CAD data for arbitrary components. In this work, Ni-based superalloy K418 samples were fabricated by selective laser melting (SLM). To evaluate the anisotropic mechanical behavior of the SLM processed K418 samples with layer-by-layer melting, the samples were manufactured parallel (transverse specimens) and vertical (longitudinal specimens) to the building direction on the substrate. The microstructural anisotropy analysis was performed by optical microscopy (OM) and scanning electron microscopy (SEM). Electron backscatter diffraction (EBSD) analysis was used to identify their crystallographic preferred orientation (texture) and to correlate the anisotropy of the mechanical strength with the texture of the material. The results showed that the transverse specimens had slightly higher yield strength, but much significantly higher ductility than that of the transverse specimens with the elongated columnar grains along the building direction.