工艺参数对磨削硅晶圆亚表面损伤裂纹的影响

为研究粗磨硅晶圆亚表面微裂纹,采用截面显微观测法,实验研究了粗磨工艺下砂轮进给速率、砂轮转速和硅晶圆转速对晶圆亚表面裂纹的影响.结果表明:磨削后晶圆亚表面斜线裂纹和折线裂纹占70%,中位裂纹、分叉裂纹和横向裂纹占30%,裂纹形状与工艺参数的关系不大.裂纹深度从晶圆圆心向外逐渐增大,〈110〉晶向裂纹深度稍大于〈100〉晶向.裂纹深度随砂轮进给速率增大单调增加,随砂轮转速增大单调减小.裂纹深度与晶圆转速之间的关系复杂,晶圆转速增大时,裂纹深度先是减小,然后增大.提出了磨削工艺参数的优化措施.     

有机硅改性水性环氧树脂的合成研究

将甲基丙烯酸,苯乙烯,丙烯酸丁酯接枝到环氧树脂上,再用γ-氨丙基三乙氧基硅烷（KH-550）对上述接枝型水性环氧树脂进行开环扩链,合成了有机硅改性的水性环氧树脂。采用了IR、TGA和SEM等方法对产物进行了表征和分析,并考察了KH-550用量对乳液及涂膜性能的影响。实验表明：有机硅改性水性环氧树脂的粒径约50nm,在水中有良好的分散性和稳定性,同时其固化物具有良好的物理性能。     

多元校正分光光度法快速测定COD

快速消解分光光度法测定水质化学需氧量是新颁布的环境行业标准,其校正模型采用单波长点测定数据的直线拟合回归分析,存在某些测定波长点计算COD的不确定性和与国标重铬酸盐法的相对偏差较大等问题.应用多元校正法改进回归模型,在高量程和低量程范围内的校正计算结果与GB法测定COD的相对误差为1.42%和4.03%,具有较好的一致性,解决了直线拟合回归不确定性的问题.     

自修复聚脲甲醛微胶囊的制备及成囊机理研究

采用原位聚合法制备了自修复聚脲甲醛包覆环氧树脂微胶囊。考察了原料用量、反应温度、酸化值和固化时间等对微胶囊粒径分布和表面形态的影响,确定了微胶囊的最佳制备工艺。借助显微镜实时监测微胶囊化过程,探讨了微胶囊的成囊机理,并将微胶囊填充到脲醛树脂中。结果表明:采用最佳制备工艺制得的微胶囊包覆率较高、结构紧密、粒度均匀,室温下保存一周后没有出现团聚和破裂;将9%微胶囊添加到脲醛树脂中,微胶囊分散均匀,脲醛树脂复合材料的韧性得到提高。     

Fe3+对聚丙烯腈纤维预氧化反应的影响

在空气气氛中对含有Fe3+的聚丙烯腈(PAN)纤维进行预氧化处理,研究了Fe3+对PAN纤维氰基环构化和纤维结构的影响及其影响机理。结果表明:在相同的预氧化条件下,含有Fe3+的PAN纤维的预氧化程度较低,添加Fe3+后,减缓了PAN纤维预氧化进程;含有Fe的PAN预氧化纤维的体密度较低,氮气气氛下,热失重增加;在PAN纤维预氧化时,纤维表面的Fe元素大部分以Fe3O4的形式包覆在纤维表面,阻碍氧的扩散,延缓PAN纤维预氧化进程。     

Synthesis,X-ray structure,density functional theory (DFT) study on electronic and optical properties of a novel 2D-polyoxovanadate anionic compound

A novel two-dimensional (2D) polyoxovanadate compound KV₃O₈ (1) has been synthesized and characterized crystallographically. The 2D anionic frameworks are built up from distorted VO₆ octahedrons and VO₅ square pyramids which are linked to one another via μ₁-oxo, μ₂-oxo and μ₃-oxo atoms. The energy band structure, density of states (DOS), dielectric constant, refractive index and chemical bonds have been investigated by DFT method. The calculated results indicate that 1 is a semi-conductor (band gap 2.1 eV). The character of the VO interactions is mainly covalent, while that of the K–O interactions is mainly ionic. The top of valence bands and the bottom of conduction bands are mostly built upon O 2p states mixed with V 3d states, and V 3d states mixed with O 2p states, respectively, via covalent P–O interactions. The nature of electronic absorption peak is assigned to be O(2p) → V(3d) charge transfer transition.     

液体石油产品中羰基硫含量的准确测定

介绍了一种分析、测定液体石油产品中羰基硫含量的新方法。该方法利用乙酸汞标准溶液滴定到乙二胺溶液吸收羰基硫,并根据所消耗的乙酸汞标准溶液的体积计算羰基硫含量。实验结果表明,该方法的收率为96.40%,标准偏差为1.54,变异系数为3.60%,这些分析数据具有较好的准确度和可信度;同时,该分析方法也不失为一种实用、有效测定羰基硫的方法。     

对高等职业教育课程改革的理性思考

高职院校致力于课程改革的良苦用心值得肯定,但具体实践中的进展并不顺利。总体上讲,高职课程改革已经陷入进退维谷的两难困境。本文从时代沿革、改革动因、改革理论基础、改革成本与风险等方面,拟对高等职业教育课程改革作些理性探索和思考。     

Evolution of fiber morphology during electrospinning

In this study, the morphological evolution of poly(acrylonitrile) (PAN) nanofibers during electrospinning was examined via immersion precipitation of newly electrospun filaments in ethanol, and subsequently associating the fiber morphologies with the electrospinning distances (2 to 10 cm). We have observed that an uneven fiber stretching happened throughout the electrospinning process. A massive filament‐thinning took place at the initial stage of whipping instability, and fiber stretching at the later whipping stage was mainly concentrated on the bead sections, leading to improved uniformity of the resultant fibers. This work has provided a new insight into the fiber formation mechanism in the electrospinning process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of a novel series of propargyloxyphenyl maleimides and their characterization as thermal‐resistance resins

Novel thermosetting monomers possessing both maleimide and propargyl groups were first designed and synthesized. The monomers included N‐(2‐propargyloxyphenyl) maleimide (2‐PPM), N‐(3‐propargyloxyphenyl) maleimide (3‐PPM), and N‐(4‐propargyloxyphenyl) maleimide (4‐PPM), and their structures were confirmed with Fourier transform infrared (FTIR) spectroscopy, ¹H‐NMR, and elemental analysis. The cure behaviors of these monomers were characterized with differential scanning calorimetry and FTIR spectroscopy, and the results indicated that the monomers had a broader processing window than normal bismaleimide (BMI) resins. The thermal properties of the cured monomers were characterized with thermogravimetric analysis and dynamic mechanical analysis. The 5% mass loss temperatures of the cured monomers were high (ca. 400°C), and the glass‐transition temperatures of cured 2‐PPM, 3‐PPM, and 4‐PPM were 386, 373, and 387°C, respectively, which were much higher than those of typical commercial blended BMI resins. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010