X7R型BaTiO3基复相陶瓷的制备和表征

本文使用ZBSO纳米复合物作为助烧剂,利用溶胶-凝胶法制备了钛酸钡(高温组元,记为BT)和Nb、Co、Nd掺杂钛酸钡基(低温组元,记为BTCNC)复相陶瓷。研究了高低温组元比例对陶瓷相组成,微观结构和介电性能的影响。实验结果表明,当高低元配比为0.83BT~0.17BTNCN时,加入0.25 wt%的助烧剂,所得复相陶瓷在1 200℃烧结6h后,其介电性能满足X7R标准,最大容温变化率小于13%。     

低能量离子束辐照磁控溅射沉积超硬质nc-TiN/nc-Cu纳米复合膜

利用诱导型等离子体辅助双靶磁控溅射法在Si（100）基板表面沉积Cu含量（原子分数）为0～10．0％的Ti—Cu—N膜,研究了Cu含量对薄膜结构及硬度的影响．结果表明,添加少量Cu可极大地提高薄膜硬度．Cu含量为2．0％的Ti—Cu—N薄膜具有超硬特性,硬度HV达到42,约为纯TiN薄膜硬度的2倍．超硬质Ti—Cu—N薄膜为nc-TiN／nc—Cu纳米复合薄膜,具有柱状晶结构．薄膜的超硬特性源于薄膜的纳米复合结构．     

单分散粒径可控γ-Fe2O3纳米颗粒的制备及表征

采用溶剂热法制备出具有尺寸可调、分散性好和强磁性的纳米γ-Fe2O3颗粒。分别采用XRD、XPS、FESEM、TEM和超导量子干涉仪(SQUID)对其结构、组分、形貌和磁性进行表征,研究氯化铁的浓度,不同的表面活性剂和反应温度对磁性纳米颗粒结构形貌和直径的影响。结果表明:制备得到的产物为反尖晶石结构、具有单分散性的γ-Fe2O3纳米颗粒,粒径在50~400 nm之间可调。反应温度对纳米颗粒的相组成和形貌影响比较显著,在140℃下得到α-Fe2O3相,在160℃下得到γ-Fe2O3相,而在180与200℃下得到Fe3O4相。纳米颗粒尺寸随着氯化铁浓度的增加而增大,随着十二烷基苯磺酸钠(SDBS)的加入而减小。在室温下,γ-Fe2O3纳米颗粒具有较强磁性,当粒径为50 nm时其矫顽力可以达到1.4 kA/m。这将在磁性复合光催化剂和生物医学领域具有潜在的应用价值。     

液力变矩器上盖与连续块MAG点固焊专机控制系统设计

针对液力变矩器连接块要求焊台定位精度高及生产上高效、高质的要求,从控制系统硬件和软件两方面进行了阐述,详细介绍了如何利用德国SIEMENS公司的SINUMERIK 810T CNC集成数控系统的优良性能,提高整个焊接专机系统的可靠性和自动化程度,并给出了系统结构框图和程序流程图。     

Synthesis of Fe-Ni-B-Si-Nb amorphous and crystalline composite coatings by laser cladding and remelting

Amorphous and nanocrystalline composite coatings are synthesized by laser cladding and remelting. The result of X-ray diffraction shows that an amorphous structure and some crystalline phases occur in the coatings. The microstructure of the coatings is different with different amounts of Si in the coatings. The fracture appearance suggests that brittle fracture occurs in coatings. There are some oxides, borides and metal compounds appearing on the surface of Fe₃₂Ni₃₂Si₁₆B₁₈Nb₂ and Fe₃₀Ni₃₀Si₂₀B₁₈Nb₂ coatings. The abrasion resistance of the coatings will be improved with the increase of amorphous phases. The coatings along the depth direction can be divided into three regions which are an amorphous and crystalline composite layer, a clad layer and a diffusion layer, respectively. The experiments show that Si plays a critical role in fabricating a Fe-based amorphous composite coating.     

摩擦副状态监测最佳参数选择的研究

以45^#钢对45^#钢滚滑复合摩擦副为研究对象，通过检测摩擦副运转过程中各种参数的变化．得到了对该类摩擦副状态变化最为敏感的监测参数，为摩擦副状态监测参数的选择提供了依据。     

Effects of Heat Input on Microstructure and Mechanical Properties of Laser-Welded Mg-Rare Earth Alloy

The effects of heat input on the quality of laser-welded Mg-rare earth alloy NZ30K were studied. Using a 15-kW high-power CO₂ laser, the microstructure and mechanical properties of welded joints under different heat inputs had been analyzed and tested. It is found that the welding heat input plays an important role in laser welding of NZ30K. Good welded joint without macroscopic defects can be obtained using the proper heat input. With the increasing heat input, welding penetration gets deeper, the width of the heat-affected-zone becomes larger, and the distribution of precipitates changes concentration. Tensile tests display that the ultimate tensile strength (UTS) of the welded joint tends to increase at first with the increasing heat input. After the welded joint gets full penetration, the UTS remains almost the same, although the heat input is increased.     

Effect of Cu Nanoparticles on the Tribological Performance of Attapulgite Base Grease

This study investigated the effect of Cu nanoparticles on the tribological properties of attapulgite base grease. It was found that the friction reduction ability and antiwear property of the base grease can be improved with the addition of Cu nanoparticles. Under the lubrication of grease containing Cu nanoparticles, a smoother and more compact tribofilm was formed on the rubbing surface. The tribofilm is mainly composed of Cu, FeO, Fe₂O₃, FeOOH, CuO, and SiO. In addition, the content of iron oxides and silicate oxide formed in the tribofilm was increased by the introduction of Cu nanoparticles.     

Preparation and characterization of Ag-doped BaTiO3 based X7R ceramics

Ag-doped BaTiO₃ based X7R (temperature coefficient of capacitance within the range of ±15% between −55 and +125 °C) ceramics with different amounts of silver (0.0-20.0 mol%) were prepared in this paper. The X-ray diffraction analysis indicated that no phases other than BaTiO₃ and silver were observed in the ceramics. The energy dispersive X-ray spectroscopy analysis showed that the silver particles presented homogeneous distribution in the BaTiO₃ ceramics. The dielectric properties of Ag-doped ceramics were investigated. A small amount of silver (<0.5 mol%) and a large amount of silver (>2.0 mol%) could both improve the sintered density and permittivity, but more content of silver (0.5-2.0 mol%) would decrease the relative density and permittivity. Specially, the temperature coefficient of capacitors of the ceramics doped with 20 mol% silver still met the X7R characteristics, and the room temperature permittivity of the ceramics was 6823, which was the highest dielectric constant in the BaTiO₃ based X7R ceramics.