基于EBSD技术的超低碳IF钢中铁素体晶粒尺寸表征

借助电子背散射衍射(EBSD)技术对超低碳IF钢铁素体晶粒尺寸的表征方法进行了研究与探讨。结果显示,对于具有较强织构的IF钢来讲,铁素体晶粒显示以5°为晶内最大取向差进行晶粒尺寸的测量与统计更为准确,与金相法显示的晶界轮廓基本吻合。利用该表征方法测量晶粒尺寸,不仅可以给出晶粒尺寸的平均值、最大值和最小值,还可以给出晶粒尺寸分布图。     

Ti-6A1-4V合金冶金结构的超声频谱试验

本文叙述了用超声频谱技术对Ti-6Al-4V合金的冶金结构所进行的试验。试验结果表明,宏观晶粒的尺寸与超声衰减的大小之间并无直接联系,而显微结构的差异是有可能用超声频谱曲线的不同加以表征的。     

爆炸法制备超细金刚石粉末的提纯与性质研究

研究了利用爆炸合成法制备的超细金刚石的提纯工艺；对提纯样品的晶粒尺寸分布和平均晶粒尺寸进行了表征和分析，并对超细金刚石的热稳定性做了研究。     

304不锈钢固溶产物晶粒尺寸的超声无损表征研究

304不锈钢在1080℃下分别固溶1,2h,水淬后进行超声检测,以探讨无损评价304不锈钢固溶产物晶粒尺寸的可行性与表征参数。研究表明:固溶处理后,超声波速度逐渐降低,衰减系数明显增大;延长固溶时间,声速缓慢降低,衰减系数继续增大。频谱分析表明:固溶处理后,峰值频率明显降低,峰值幅度不断增大。分析认为:上述现象的产生与固溶处理对材料晶粒尺寸的作用以及晶粒尺寸对超声波传播的影响作用相关。基于最小二乘法拟合得到:横波声速vt、纵波声速vl与平均晶粒尺寸d线性相关:vt=-0.49254d+3188.40138,vl=-0.07632d+5772.88964;衰减系数与晶粒尺寸符合如下规律:α=1.2605×10-15 d6.5012+0.0995。     

纯Al纳米晶体材料的力学性能研究

以纯铝粉(99.7%)为原料,采用不同的球磨参数(球料比、球磨时间),利用高能球磨法在室温下制备了具有纳米晶粒的纯Al体材料.通过X射线衍射(XRD)及显微硬度等手段,对不同球磨工艺参数下制备的纯Al体材料的晶粒尺寸及力学性能进行了测试和分析,并对样品的晶粒尺寸与硬度之间的关系进行了深入的探讨.研究发现,所制备的纯Al纳米晶体材料的平均晶粒尺寸在47～66nm范围内;随着球磨时间的延长,样品的显微硬度呈现出先升高后降低再升高的趋势,并在球磨时间为5h时,球磨样品的硬度达到最高值;屈服强度与晶粒尺寸之间符合正的Hall-Petch关系.     

考虑晶粒尺寸影响的硬度预测模型

目的研究了晶粒尺寸对冷成形过程中材料硬度变化的影响。方法通过不同的退火处理,获得了具有不同晶粒尺寸的材料。采用压缩试验、压痕试验和有限元模拟相结合的方法,研究了不同初始晶粒尺寸条件下材料硬度与等效应变的关系。结果初始晶粒尺寸d对材料初始硬度HV0、硬化系数K、硬化指数n有较大影响,随着晶粒尺寸的增大,它们呈减小趋势。同时提出了一个考虑晶粒尺寸影响的硬度预测模型,并进行了实验验证,硬度的预测值与测量值吻合较好。结论该模型能准确预测具有不同初始晶粒尺寸的材料在冷成形过程中的硬度分布。     

阳极弧等离子体制备纳米镍粉的微结构研究

利用X射线衍射(XRD)、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段,对阳极弧放电等离子体技术制备的不同晶粒尺寸的纳米镍粉体的晶体结构、晶格参数、形貌、粒度进行性能表征。实验结果表明:阳极弧等离子体法制备的纳米镍粉体的晶格常数均大于完整单晶镍的晶格常数,晶格畸变表现为晶格膨胀。18 nm~52 nm之间纳米粉的晶格常数随着晶粒尺寸的减小而增大,晶格畸变量与晶粒尺寸的倒数成正比。     

纳米SnO2基气敏元件对甲醛气体的检测（英文）

采用溶胶-凝胶法制备了纳米SnO2粉末,利用X射线衍射仪(XRD)以及原子力显微镜(AFM)对材料的晶体结构及晶粒尺寸进行了表征.采用制备的纳米SnO2作为基底材料,掺杂纳米TiO2粉末(SnO2与TiO2的物质的量之比为9∶1)以及少量的Ag+(物质的量百分比为0.2%~0.4%),以此材料制成气敏元件,检测了元件的甲醛气敏性能.结果表明:该元件在工作温度为300℃时,对200×10-6的甲醛具有较好的敏感性,在不同的工作温度下,元件表现出良好的气敏选择性.理论计算表明,气体分子轨道能量的差异是元件气敏选择性的定性因素.     

微波辅助-水相共沉淀法纳米ITO粉体的制备及其表征

利用微波辅助-水相共沉淀法,在InCl3和SnCl4混和溶液中添加PEG-6000,并滴加体积比1∶4浓度的氨水,并在不同反应温度(35～75℃)下制备了ITO前驱体,在温度800℃煅烧1h后得到纳米ITO粉体。利用SEM对纳米ITO粉体的形貌进行表征,用XRD对其结构、晶粒度和堆垛层数进行了表征,同时用纳米粒度Zeta电位分析仪对相应颗粒度进行了测试。讨论了微波辅助下不同反应体系温度对制备的纳米ITO粉体的形貌和尺寸的影响,并探讨了其机理,研究结果表明,随着反应体系温度的上升,纳米ITO粉体形貌由球形转为棒形,其晶体结构不变,晶粒粒径和颗粒度随着增大;反应体系温度的升高使纳米ITO晶粒不同晶面的晶粒度不同程度地增大,以及不同晶面垂直方向晶面不同程度地增多,是球形ITO晶粒成为棒形ITO晶粒的基础。     

钇铝石榴石(YAG)粉体的溶胶凝胶法制备

本文以Y_2O_3、Al(NO_3)_3以及柠檬酸为原料,采用溶胶凝胶法在不同温度下烧结合成了YAG粉体,利用XRD,SEM和能谱分析等测试技术对粉体的物相结构及粉体形貌进行了分析表征。结果表明,采用溶胶凝胶法成功地合成了晶粒尺寸为30-60nm的YAG粉体,并确定了在1200℃下可烧成很好的YAG晶相结构,随着煅烧温度的升高,YAG平均晶粒尺寸增大。     

Secondary electron emission of Y2O3-Mo cermet cathode

Y₂O₃-Mo cermet cathodes were prepared by mechanical mixing of Y₂O₃ and Mo powder. The prepared cermet cathode provides a certain secondary emission yield (3.09), about 1.8 times lower than that for the cathode prepared by sol-gel method. It was found that the cathode prepared by sol-gel method had a smaller grain size, which could be attributed to its higher emission property. The energy distributions of primary electrons in the cathodes with different grain sizes have been simulated by Monte Carlo method. Based on the calculation results, the emission models of the cathodes are established and presented. The cathodes with different grain sizes exhibited different ways of emission. Two types of emission, of reflection emission and transmission emission, existed in the cathode with small grain sizes whereas only transmission emission existed in the cathode with large grain sizes.     

晶粒尺寸对FeS2薄膜微应变及光吸收特性的影响

采用不同厚度的Fe膜在673K热硫化20h制备出具有不同晶粒尺寸的FeS2薄膜，分析并测定了薄膜组织结构、微应变及光吸收性能．结果表明，Fe膜硫化形成的FeS2薄膜厚度在120—550nm范围内变化时，可导致平均晶粒尺寸在40-80nm之间变化．FeS2晶粒尺寸的变化造成了晶体面缺陷密度的变化，可引起微观内应力水平、缺陷能级分布和晶界势垒高度的变化，进而使得薄膜的微应变、点阵畸变度、光吸收系数及禁带宽度等物理特性随晶粒尺寸的增加而降低．     

玻璃纤维复合材料孔隙率对超声衰减系数及力学性能的影响

在0.1~0.6 MPa热压压力条件下, 制备了不同孔隙率含量的玻璃纤维布/618环氧树脂层压板试件。采用超声C扫描及烧蚀密度法测定了试件的超声衰减系数与平均孔隙率, 并通过金相显微分析对孔隙的分布、 形状及尺寸进行了表征。讨论了孔隙率对层压板拉伸、 弯曲和层间剪切性能及超声衰减系数的影响规律, 获得了使力学性能下降的临界孔隙率及衰减系数值。结果表明, 随着固化压力减小, 孔隙率从0.976%增加到5.268%, 抗拉强度、 弯曲强度和层间剪切强度均下降, 衰减系数由1.460 dB·mm^-1增加到2.150 dB·mm^-1, 使力学性能下降的临界衰减系数约为1.5 dB·mm^-1。     

Investigation of the lattice expansion for Ni nanoparticles

Nickel nanoparticles with various grain sizes were successfully prepared by anodic arc discharge plasma method. The samples prepared by this method were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected-area electron diffraction (SAED) to determine the crystal structure, lattice parameter, morphology and particle size. The experiment results indicate that the crystal structure of the samples is FCC structure as same as the bulk materials. The lattice parameters for Ni nanoparticles are always larger than the equilibrium values of the perfect single crystal lattice respectively, the lattice parameter increase significantly with the decrease of the grain size, the lattice expansion was found, and the expansion quantity of the lattice parameter is in direct proportion to the reciprocal of grain size. The values of the unit cell volume increase remarkably with the decrease of the grain size. The lattice expansion is the result of the interfacial energy and surface tension mutual attraction of Ni nanoparticles, this phenomenon can be explained according to the thermodynamic theory.     

Automatic vision-based grain optimization and analysis of multi-crystalline solar wafers using hierarchical region growing

Solar power has become an attractive alternative source of energy. The multi-crystalline solar cell has been widely accepted in the market because it has a relatively low manufacturing cost. Multi-crystalline solar wafers with larger grain sizes and fewer grain boundaries are higher quality and convert energy more efficiently than mono-crystalline solar cells. In this article, a new image processing method is proposed for assessing the wafer quality. An adaptive segmentation algorithm based on region growing is developed to separate the closed regions of individual grains. Using the proposed method, the shape and size of each grain in the wafer image can be precisely evaluated. Two measures of average grain size are taken from the literature and modified to estimate the average grain size. The resulting average grain size estimate dictates the quality of the crystalline solar wafers and can be considered a viable quantitative indicator of conversion efficiency.     

On the modeling of the static recrystallization considering the initial grain size effects

Modeling of the static recrystallization in deformed copper specimens with different initial grain sizes is carried out based on a previous dislocation–grain size interaction model and a Monte Carlo simulation. From the dislocation–grain size interaction model, the stored energy of the deformed copper is calculated considering the interaction of the dislocations due to the different initial grain sizes. Then, utilizing the stored energy and Monte Carlo simulation the kinetic of recrystallization and recrystallized grain sizes are obtained. The JMAK plots of the modeling results show that, in conditions of 2D modeling and site-saturated nucleation, the Avrami exponent is 2 ± 0.1. The time for 50% recrystallization and recrystallized grain size increase by increasing the initial grain size at a specific strain and are consistent with the experimental data.     

溶液pH值对直接沉淀法制备CaF2纳米粉体的影响

以Ca（NO3）2和KF为原料,采用直接沉淀法制备CaF2粉体,借助XRD、SEM、粒径分析方法研究了溶液pH值对产物CaF2粉体晶粒尺寸、颗粒大小及分布的影响,结果表明,在碱性条件下所得CaF2沉淀的晶粒尺寸比在酸性条件下所得CaF2沉淀的小,溶液pH值为13.7时,制备出晶粒大小仅20nm的CaF2纳米粉体。     

Characterization of Grain Size and Yield Strength in AISI 301 Stainless Steel Using Ultrasonic Attenuation Measurements

AISI 301 stainless steel samples were annealed over the temperature range of 800?C1200°C for 60?minutes to produce different grain sizes. These samples were characterized by ultrasonic immersion technique, tensile test, and optical microscopy. The attenuation of ultrasonic waves measured at a frequency of 20?MHz showed a good correlation with average grain size, hardness, and yield strength of AISI 301 stainless steel samples. A?new equation was derived for calculation of yield strength on the basis of ultrasonic wave attenuation and Hall-Petch relation.