Microstructure,grain orientation,and properties of ITO ceramics sintered with various heating rates

In this study, the microstructure, grain orientation, electrical resistivity, nanohardness, and fracture strength were systematically investigated in ITO ceramics sintered with different heating rates. It was found that ITO ceramics sintered at 1600°C consist of main phase (In₂O₃) and secondary phase (In₂SnO₅) and the distributions of coarse grains with high indium content and fine grains with high tin content are interval. The higher heating rate was found to refine the grain size and increase the {1000} textured secondary phase. The increase in electrical resistivity of ITO ceramics was due to the decrease in oxygen vacancies caused by the reducing oxide decomposition. Moreover, the nanohardness of fine grains was found to be higher than that of coarse grains due to the reinforcement effect of Sn element. Besides, the increase of heating rate is beneficial to enhance the fracture strength due to the higher resistance of grain boundary to fracture propagation and the predominantly intergranular fracture.     

用原子显微镜纳米压痕法研究Gr／Al复合材料热循环后的微观力学性能

采用原子力显微镜纳米压痕法测量了Gr/Al复合材料热循环后界面附近的纳米硬度和塑性变形能力的分布。随热循环次数的增加,纤维和基体中的纳米硬度小,而基体的塑性变形能力增加。纳米硬度和塑性变形能力的大小是随距纤维／基体界面的距离的变化而变化的。纳米硬度的变化可提供有关残余应变方面的信息,这是因为材料内部局部区域的弹性或塑性残余应变会影响此处的硬度大小。     

多层膜体系微硬度实验的有限元数值模拟

使用FEPG软件编程,对维氏压头的微硬度实验进行模拟,建立了一种针对膜基体系有限元计算的新模型,该模型考虑了边界摩擦和实时跟踪接触因素,在对TiN单层膜和TiN／Ti／TiN／Ti／TiN／Ti6层膜压痕的模拟分析后,得出“载荷-压痕对角线长度关系曲线”和“硬度-载荷关系曲线”以及塑性区分布图,并对微硬度实验中的压头的压入深度相对于单层膜膜层厚度和多层膜中组分膜膜层厚度的取值进行了讨论,与其他文献中的实验比较,结果吻合。说明模型是合理的,结果是可靠的,对实际应用具有指导意义,并为理论分析提供了研究方法。     

多孔氧化铝模板的纳米力学性能测试与分析

为了掌握多孔氧化铝模板的纳米力学性能,采用二次氧化法制备孔径在30～40nm之间且高度有序的纳米阵列氧化铝模板,并使用扫描电子显微镜(SEM)对其形貌进行表征;在原位纳米力学测试系统上进行微压痕实验,对样品表面力学性能(纳米硬度、模量)进行测试;利用原子力成像功能对实验区域扫描成像,在纳米尺度下观察和分析样品形貌.结果表明,AAO模板在同一深度处对应的硬度、模量值明显高于相应的基体材料铝,膜基体系的抗载能力明显提高;在压入深度为70～240nm时,AAO膜板的硬度和模量值分别为5.8GPa和106GPa,但从深度250nm时开始出现减小趋势;单晶铝与压针的接触为理想刚塑性接触,AAO模板与压针的接触为弹塑性接触.     

Microstructure and Mechanical Properties of a Low Carbon Bainitic Steel

A low carbon bainitic steel with microstructure of granular bainite (GB), acicular ferrite (AF), and bainitic ferrite (BF) is obtained under different deformation and cooling rate. The effect of deformation and cooling rate on microstructural characteristics such as the type of the matrix, the size, and area fraction of the martensite–austenite (M–A) constituents is investigated. In addition, the nanohardness of these three kinds of matrix as well as that of the M–A constituents in them is characterized. Further, the effect of matrix and M–A constituents on strength–toughness balance is studied. Results indicate that deformation expands the transformation region. The size as well as the area fraction of the M–A constituent decreases with the increasing of the cooling rate. After deformation, the area fraction of the M–A constituents increases. Nanohardness of GB, AF, and BF increases orderly, but that of the M–A constituents in them decreases accordingly. The nanohardness of the M–A constituent is significantly affected by its carbon concentration. AF is the optimum microstructure having superior strength–toughness balance.     

CAB玻璃基底不同方法制备的SiO2膜层性能研究

采用IAD、IBS、MS等三种方法在CAB玻璃上制备了SiO2膜层,通过纳米压痕和划痕仪测量了膜层的纳米硬度和摩擦系数;利用傅里叶转换红外光谱仪对薄膜光谱性能进行了测量;利用SEM,观测膜层表面和断面形貌。结果表明:不同方法制备的SiO2膜层,聚集密度、硬度和摩擦系数不相同,其中,IBS法制备膜层硬度最高,MS法所制备膜层,硬度略低,而IAD法制备的膜层硬度最低;摩擦系数上,IBS法和IAD法相当,较MS法制备的膜层摩擦系数要高。从成膜基理上,对上述结论给出了理论分析。根据试验结果,选用MS法作为CAB玻璃保护膜的制备方法。     

Mechanical and tribological properties of TiN and SiCN nanocomposite coatings deposited using methyltrichlorosilane

The paper examines nanocomposite coatings based on TiN and SiCN obtained by plasma-enhanced chemical vapor deposition (PECVD) using methyltrichlorosilane (MTCS) as one of the precursors. The nanocomposite coatings demonstrate four types of structures depending on deposition modes: nc-TiN, nc-TiN/a-SiCN, nc-TiNC/nc-TiSi₂/a-SiCN, and nc-TiNC/nc-TiCl₂/a-SiCN. The nanohardness and elastic modulus of the coatings reach 31 and 350 GPa, respectively. The coatings on substrates of hard alloys, high-speed steel, and silicon increase the nanohardness of the base from 10 to 100%. The correlation between the H/E ratio and wear resistance is not observed. The coatings deposited at low radiofrequency powers demonstrate good adhesion to silicon substrates. It is shown that the use of MTCS as the main precursor allows one to obtain hard and wear-resistant nanocomposite coatings. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 125–133, 2008.     

单晶硅在氮离子注入前后的力学性能研究

以微机电系统常用的单晶硅材料和经氮离子注入单晶硅后形成的表面改性层为研究对象,在原位纳米力学测试系统上进行微压痕实验,对样品的表面纳米硬度进行了测试。同时,还通过该仪器的原子力成像功能对实验区域扫描成像,在纳米尺度下观察和分析形貌。结果表明:单晶硅在氮离子注入前后的纳米硬度值与载荷有很大关系。通过对微压痕和原子力图像的分析,表明单晶硅在氮离子注入后的纳米硬度值有所降低,其主要原因是氮离子注入后导致晶格抵抗变形的能力降低。