改善喷射沉积多孔材料开裂行为工艺的研究

介绍了多孔金属材料的致密化过程及塑性变形,分析了其轧制开裂行为规律,研究了多孔金属材料在外框限制轧制中的轧制过程及避免多孔材料开裂的工艺措施。

基体碳对C/CF/Cu复合材料的影响

采用树脂碳化和碳气相沉积相结合的方法制备了碳/碳纤维(C/CF)先驱丝,用压力浸渗凝固成型方法制备了碳/碳纤维/铜(C/CF/Cu)复合材料,借助于扫描电镜下复合材料界面和相分布观察以及显微硬度和滑动摩擦磨损测试,探讨了基体碳(树脂碳化碳和沉积碳)对C/CF/Cu复合材料成型、显微硬度及摩擦磨损的影响.结果表明,碳化和碳气相沉积处理的C/CF先驱丝相对致密并阻碍铜液的压力浸渗成型,但该先驱丝硬度高于碳化处理的C/CF先驱丝.碳化和碳气相沉积处理的C/CF/Cu复合材料滑动摩擦磨损耐磨性高于纯铜,而且滑动摩擦系数也高于纯铜.C/CF/Cu复合材料是一种具有摩阻功能的复合材料.

冷喷涂技术及其系统的研究现状与展望

与传统的热喷涂相比,冷喷涂具有沉积温度低、沉积效率高、孔隙率低,以及粉末在沉积过程中不易发生氧化、分解、相变和纳米结构材料的晶粒长大等问题,这使得氧化敏感、温度敏感和相变敏感等材料的高质量涂层制备成为可能。更值得一提地是,近年来冷喷涂工艺与设备的大力发展使冷喷涂作为一种快速固态成形工艺,在金属增材制造和航空航天等关键零部件的损伤修复中得到应用。鉴于目前冷喷涂技术受到国内学者和工业界越来越多的关注,基于大量的文献调研和长期对国内外冷喷涂研发动态的跟踪,对冷喷涂材料种类、涂层典型组织结构与性能及其工艺和设备系统的发展进行了总结。首先,简介了冷喷涂系统的组成结构、喷涂材料的种类及涂层的组织结构与性能;其次,探讨了高压/低压冷喷涂和真空冷喷涂工艺及其设备的发展现状,讨论了基于喷枪或喷嘴设计的冷喷涂工艺设计与优化,如内孔冷喷涂、脉冲式气体冷喷涂和径向冷喷涂,介绍了针对其他技术辅助传统冷喷涂工艺的发展,包括激光辅助冷喷涂、静电辅助冷喷涂、磁场辅助冷喷涂、搅拌摩擦加工辅助冷喷涂增材制造等;最后,指出了冷喷涂工艺及系统发展尚存的关键问题,并对其材料研究和工业应用进行了展望。

Effect of boron/phosphorus-containing additives on electrodeposited CoNiFe soft magnetic thin films

CoNiFe,CoNiFeB and CoNiFeP soft magnetic thin films were prepared by cyclic voltammetry method.The morphologies,composition and structures were characterized by scanning electron microscope（SEM）,energy-dispersive X-ray spectroscope（EDS） and X-ray diffractometer（XRD）.The soft magnetic properties were investigated through vibrating sample magnetometer（VSM）.The corrosion resistance was investigated through Tafel polarization and electrochemical impedance spectroscopic（EIS）.The results show that all the electrodeposited CoNiFe,CoNiFeB and CoNiFeP films are mixtures of crystalline and amorphous phases,and high amount of boron/phosphorus-containing additives favors the formation of amorphous state.Nanostructure is obtained in CoNiFe and CoNiFeB films.The inclusion of boron causes the film more dense and also increases its corrosion resistance.Meanwhile,the inclusion of boron lowers its coercivity（Hc） from 851.48 A/m to 604.79 A/m,but the saturation magnetic flux density（Bs） is almost unchanged.However,the addition of phosphorus greatly increases the film particle size and decreases its corrosion stability.The coercivity（Hc） of CoNiFeP film is also highly increased to 12485.79 A/m,and its saturation magnetic flux density（Bs） is greatly decreased to 1.25 T.

Characterization of SiC nanowires prepared on C/C composite without catalyst by CVD

SiC nanowires were prepared on C/C composite surface without catalyst by chemical vapor deposition（CVD） using CH3 SiCl3 as precursor.SEM images of the CVD-product reveal that some long nanowires have grown to tens of micrometers with some gathered as a ball.Some short nanowires agglomerate like chestnut shell with many thorns accompanied by some deposited nano-particles.XRD,Raman-spectrum and FTIR patterns indicate that the product is a typical β-SiC.TEM images show that the nanowires have a wide diameter range from 10 to 100 nm,and some thin nanowires are bonded to the thick one by amorphous CVD-SiC.A SiC branch generates from an amorphous section of a thick one with an angle of 70° between them,which is consistent with the [111] axis stacking angle of the crystal.SAED and fast Fourier transform（FFT） patterns reveal that the nanowires can grow along with different axes,and the bamboo-nodes section is full of stacking faults and twin crystal.The twisted SiC lattice planes reveal that the screw dislocation growth is the main mechanism for the CVD-SiC nanowires.

Effect of heat treatment on microstructure and mechanical property of extruded 7090/SiC_p composite

The ultra high strength SiC particles （SiCp） reinforced Al-10%Zn-3.6%Mg-1.8%Cu-0.36%Zr-0.15% Ni composite was prepared by spray co-deposition. Microstructures of the extruded and different heat-treated bars were analyzed by transmission electron microscopy （TEM） and energy dispersive spectrometry （EDS）. Grain size of the composites prepared by two-stage solution is smaller than that by single-stage solution. After single-stage solution aging treatment, fine precipitates of both η and AlZnMgCu-rich phase can be found both intragranularly and intergranularly. While after the two-stage solution, an amorphous Si-Cu-Al-O （5 nm） layer appears at the interface. The addition of Ni and Zr modified the influence of the two-stage solution and inhibited the growth of the 7090/SiCp composite grain size. Heat treatments can significantly improve the fracture toughness of the composite. The fracture toughness first decreases then increases with the elongation of the aging time.

Preparation and mechanical properties of carbon/carbon composites with high textured pyrolytic carbon matrix

Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon （C/C） composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.

Fabrication of superaligned carbon nanotubes reinforced copper matrix laminar composite by electrodeposition

A new kind of laminar metal matrix nanocomposite（MMC） was fabricated by an electrodeposition process with copper and superaligned carbon nanotubes film（SACNT film）.The SACNT film was put on a titanium plate and then a layer of copper was electrodeposited on it.By repeating the above process,the laminar Cu/SACNT composite which contains dozens or hundreds of layers of copper and SACNT films was obtained.The thickness of a single copper layer was controlled by adjusting the process parameter easily and the thinnest layer is less than 2 μm.The microscopic observation shows that the directional alignment structure of SACNT is retained in the composite perfectly.The mechanical and electrical properties testing results show that the tensile and yield strengths of composites are improved obviously compared with those of pure copper,and the high conductivity is retained.This technology is a potential method to make applicable MMC which characterizes high volume fraction and directional alignment of carbon nanotubes.

In-situ homogeneous synthesis of carbon nanotubes on aluminum matrix and properties of their composites

Using nickel catalyst supported on aluminum powders, carbon nanotubes （CNTs） were successfully synthesized in aluminum powders by in-situ chemical vapor deposition at 650 ℃. Structural characterization revealed that the as-grown CNTs possessed higher graphitization degree and straight graphite shell. By this approach, more homogeneous dispersion of CNTs in aluminum powders was achieved compared with the traditional mechanical mixture methods. Using the in-situ synthesized CNTs/Al composite powders and powder metallurgy process, CNTs/Al bulk composites were prepared. Performance testing showed that the mechanical properties and dimensional stability of the composites were improved obviously, which was attributed to the superior dispersion of CNTs in aluminum matrix and the strong interfacial bonding between CNTs and matrix.

增/减材柔性制造及加工系统构成形式

将柔性制造的思想引入到增/减材制造中,形成增/减材柔性制造工艺。阐述了该工艺的内涵及加工范围,确立了增/减材柔性制造工艺流程,描述了各组成工序的特点,详细阐述了增/减材柔性制造中材料沉积、材料去除两工序内部及其之间的多种柔性加工方式。在此基础上,确立了增/减材柔性制造系统的设备构成及其相互关系,给出了加工设备的总体布局。为进一步研究该工艺的加工序列规划及各种构成设备具体结构形式等方面打下基础。

Synthesis and Photoluminescence of Amorphous Silicon Oxycarbide Nanowires

Synthesis of amorphous SiCO nanowires was carried out by means of direct current are discharge. Free-standing SiCO nanowires were deposited on the surface of a graphite crucible without any catalyst and template. The SiCO nanowires were analyzed by XRD, SEM, TEM, XPS, and FTIR. The SiCO nanowires were typically 20-100 gm in length and 10-100 nm in diameter as measured by SEM and TEM. The XPS and FTIR spectroscopy analysis confirmed that the Si atoms share bonds with O and C atoms in mixed SiCO units. The PL spectrum of the SiCO nanowires showed strong and stable white emissions at 454 and 540 nm. A plasma-assisted vapor-solid growth mechanism is proposed to be responsible for the formation of the SiCO nanowires.

3D打印在PCB制造中的应用

3D打印与普通喷墨打印机的工作原理基本相同，主要区别在于打印材料和层积过程，3D打印技术虽然技术先进、应用广泛，但也有非常多的制约因素。本篇将主要讨论从3D打印技术中提到的各个概念如何应用到PCB的制造，以及相对于传统PCB制程有哪些优势、技术限制和展望等，本人参与过字符和阻焊油墨一体打印机的评估测试与应用，所以会更多地谈到字符和阻焊油墨一体的3D打印机在PCB制造中的应用。

Effects of polyaniline on electrochemical properties of composite inert anodes used in zinc electrowinning

In order to search for a suitable anode material used in zinc electrowinning in place of Pb-Ag alloy,Al/Pb-PANI（polyaniline）-WC（tungsten carbide） composite inert anodes were prepared on aluminum alloy substrate by double pulse electrodeposition（DPE） of PANI and WC particles with Pb2＋ from an original plating bath.Thereafter,anodic polarization curves,cyclic voltammetry curves and Tafel polarization curves for the composite inert anodes obtained under different PANI concentrations in the original plating bath were measured,and the microstructural features were also investigated by scanning electron microscopy（SEM）.The results show that Al/Pb-PANI-WC composite inert anode obtained under PANI concentration of 20 g/L in the original plating bath possesses uniform microstructures and composition distributions,higher electrocatalytic activity,better reversibility of electrode reaction and corrosion resistance in a synthetic zinc electrowinning electrolyte of 50 g/L Zn2＋,150 g/L H2SO4 at 35 °C.Compared with Pb-1%Ag alloy,the overpotential of oxygen evolutions for the composite inert anode are decreased by 185 mV and 166 mV,respectively,under 500 A/m2 and 1000 A/m2.

Design and 3D Printing of Scaffolds and Tissues

A growing number of three-dimensional(3D)-print- ing processes have been applied to tissue engineering. This paper presents a state-of-the-art study of 3D-printing technologies for tissue-engineering applications, with particular focus on the development of a computer-aided scaffold design system; the direct 3D printing of functionally graded scaffolds; the modeling of selective laser sintering(SLS) and fused deposition modeling(FDM) processes; the indirect additive manufacturing of scaffolds, with both micro and macro features; the development of a bioreactor; and 3D/4D bioprinting. Technological limitations will be discussed so as to highlight the possibility of future improvements for new 3D-printing methodologies for tissue engineering.

热壁CVD制备铂薄膜的沉积室内壁材料选择研究

选择合适的沉积室内壁材料是热壁化学气相沉积制备Pt薄膜过程中降低前驱体在沉积室内壁上大量消耗,进而保证沉积室内Pt前驱体分压的关键。本研究对比了Pt在镍基高温合金,备选沉积室内壁材料——有氧化层的Cu以及紫铜表面的沉积的难易程度,发现在有氧化层的Cu的表面Pt薄膜很难沉积,因此当镍基高温合金为沉积基体时有氧化层的Cu可以作为热壁CVD的沉积室内壁衬底材料,但是只能一次性使用。

Wear mechanism for spray deposited Al-Si/SiC_p composites under dry sliding condition

Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10-220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

Preparation and characteristics of C/C composite brake disc by multi-cylindrical chemical vapor deposition processes

The C/C composite brake discs were prepared by tri-cylindrical chemical vapor deposition （CVD） process. The optimum processing parameters were as follows： deposition temperature was 830 - 930 ℃, the gas- flow rates of N2 and propylene were 4.8 - 5.2 m^3/h and 5.8 - 6.2 m^3/h, respectively, the furnace pressure was 4.5 - 5.5 kPa and the deposition time was 200 h. The effects of processing parameters on the densified rates, thermal-physical property and mechanical performance of C/C composite brake discs were studied. The results show that density, heat conductivity, bend strength and abrasion ratio of the multi-cylindrica brake discs are 1. 02 - 1. 78 g/cm^3 , 31 W/（m·K）, 114 MPa and 7μm/s, respectively, which are approximately similar to those of the singlecylindrical ones. The gas tlow rate has no relation to the number of the cylinder and furnace loading. The utilization ratio of carbon can be improved by multi-cylinder CVD process without changing the characteristics of brake disc.

In situ TiB2/Cu composites fabricated by spray deposition using solid-liquid and liquid-liquid reactions

In situ TiB2/Cu composites were fabricated by both solid-liquid(S-L)and liquid-liquid(L-L)reactive spray deposition in combination with cold rolling and annealing.The microstructure and properties of the fabricated TiB2/Cu composites were investigated.The results show that the reactive mode and rolling treatment are the main factors affecting the microstructure and properties of the TiB2/Cu composite.The in situ reaction in the L-L reaction can be carried out more completely.By controlling the rolling and annealing process,the relative density and the properties of the as-deposited composites are optimized.The comprehensive performance of the deformed TiB2/Cu composite prepared by L-L reactive spray deposition(401 MPa and 83.5%IACS)is better than that by S-L reactive spray deposition(520 MPa and 20.2%IACS).

High-Throughput Multi-Plume Pulsed-Laser Deposition for Materials Exploration and Optimization

A high-throughput multi-plume pulsed-laser deposition （MPPLD） system has been demonstrated and compared to previous techniques. Whereas most combinatorial pulsedlaser deposition （PLD） systems have focused on achieving thickness uniformity using sequential multilayer deposition and masking followed by post-deposition annealing, MPPLD directly deposits a compositionally varied library of compounds using the directionality of PLD plumes and the resulting spatial variations of deposition rate. This system is more suitable for high-throughput compound thin-film fabrication.