高分子网络凝胶法制备纳米ZnO的结构性能研究

采用高分子网络凝胶法制备了ZnO粉末样品。通过X射线衍射、扫描电镜等测试方法研究了样品的物相组成、微观形貌。X射线衍射测试结果显示,样品的衍射峰尖锐,各特征峰显示完整,与标准PDF卡片比对,证实粉末样品的物相为ZnO。使用Scherrer公式计算得到的晶粒度大小约为31.28nm,晶格常数分别为3.247和5.208。使用扫描电镜观测不同放大倍数下的样品形貌,发现晶粒外观形貌显现完整,晶粒尺寸大小与XRD测试结果相吻合。结果表明,实验成功制备了高质量的ZnO纳米多晶粉体,可以用于后续实验。     

Impurity Distribution in Polycrystalline Aluminum Nitride Ceramics

Convergent-beam electron diffraction and diffuse darkfield imaging of transmission electron microscopy were used to obtain qualitative information regarding the distribution of impurities in polycrystalline AIN. Impurities are distributed homogeneously within the grains of a given ceramic, but an amorphous grain-boundary phase on the order of 1 to 2 nm in thickness is observed between the AIN matrix grains.     

水热法制备Bi_4Si_3O_(12)粉体

以B i2O3和S iO2为原料,一定浓度的双氧水为溶剂,采用水热法制备了硅酸铋(B i4S i3O12)粉体。用X射线衍射和扫描电子显微镜分析了合成粉体的相结构和形貌,用单因素实验法研究了反应时间、反应温度以及双氧水浓度对产物物相组成的影响,结果表明,在220℃下反应48 h,H2O2浓度4%~6%的条件下,可以合成微米级的纯相硅酸铋。     

Iron particles in carbon nanotubes

Nanometer-size iron-rich particles in carbon nanotubes have been studied by transmission electron microscopy with and without in situ and ex situ heating. Several remarkable results were found; a high temperature phase (γ-Fe) of iron stable at low temperatures and preferential presence of iron and iron carbide in carbon nanotubes. Based upon these experimental results, thermodynamics of the Fe-C phase diagram and its kinetics were used to explain the non-uniform distribution of iron and iron carbide, which also yielded a deeper insight into the formation of carbon nanotubes. Some of the results also allowed describing the role of the graphitic structure in retaining the high temperature phase (γ-Fe) of iron at low temperatures. Furthermore, methods have been demonstrated with which γ-Fe can be produced in carbon nanotubes intentionally or in a large quantity. Selected area electron diffraction patterns of iron inside nanotubes demonstrated the crystallographic relationship of the iron to the nanotube axis along with phase changes of the iron. This paper summarizes the findings and draws further conclusions on the particle shape inside multiwalled carbon nanotubes.     

Microscopical study of carbon/carbon composites obtained by chemical vapor infiltration of 0°/0°/90°/90° carbon fiber preforms

The microstructure of carbon/carbon composites obtained by isothermal, isobaric chemical vapor infiltration (CVI) of carbon fiber preforms consisting of aligned fiber bundles separated by fiber fleeces was studied comparatively by polarized light microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED). Deposition rate as well as matrix microstructure do not differ in the aligned fiber bundles and fiber fleeces exhibiting different local surface area/volume ratios. The matrices which are homogeneously textured according to PLM exhibit pronounced spatial texture gradients at the sub-μm-scale if investigated by SAED. The texture gradients appear to be independent on the infiltration time, distance between fibers but evidently depend on the total methane pressure. TEM and SEM observations show a thin high-textured layer between the fiber and the medium-textured transitional layer below the high-textured matrix layer containing columnar grains. This thin layer replicates the surface unevenness of the fiber surface while it is absent at the initial carbon fiber surface before infiltration.     

新型CdS/TiO_2纳米复合材料的制备及其可见光催化性能研究

采用浸渍法和水热法相结合制备了新型的CdS/TiO_2纳米复合材料,并采用X射线衍射(XRD)、透射电子显微镜(TEM)、UV-Vis吸收光谱(UV- VIS)、电子自旋共振谱(ESR)等对样品进行了表征,XRD、TEM表明所制备的新型CdS/TiO_2粒径小、分散均匀,TiO_2以锐钛矿型存在,CdS以高分散的立方相和六方相存在,对比直接法制备的CdS/TiO_2,新型的CdS/TiO_2对活性艳红X-3B具有明显提高的可见光催化活性;大量的束缚单电子氧空位及电子之间强相互作用是新型CdS/TiO_2可见光催化活性提高的主要原因.     

仿古铸铁腐蚀产物的形貌、结构的演化历程及其危害性研究

The immersion corrosion of archaeological iron in solution（0.06mol·L^- 1NaCl＋0.03mol·L ^-1 Na2SO4＋ 0.01mol·L^- 1 NaHCO3）simulating soil water composition was presented.The evolution of archaeological iron from iron to iron oxide and to iron oxy-hydroxides compounds was investigated by scanning electron microscope（SEM） and X-ray diffraction（XRD）analysis.According to the morphology,phase composition,and transformation process,the contributions of each corrosion product to archaeological iron were discussed.     

Investigation of hot pressed ZrB2–SiC–carbon black nanocomposite by scanning and transmission electron microscopy

Hybrid ZrB₂-based composite having 10 vol% nano-sized carbon black and 20 vol% SiC was fabricated by vacuum hot pressing at 1850 °C under 20 MPa for 60 min. The microstructure and sinterability of the as-sintered ceramic was studied by X-ray powder diffraction, scanning electron microscopy, X-ray spectroscopy, scanning transmission electron microscopy and transmission electron microscopy analyses. A fully-dense hybrid composite could be achieved by hot pressing method under the aforementioned conditions. No new in-situ phase formation was detected after sintering process. Although the densification progressed in a non-reactive manner, the addition of carbonaceous material assisted the sinterability acting as the surface oxides cleaner. The precise phase and nanostructural investigations of the prepared ceramic verified the partial graphitization of carbon black and conversion of amorphous nano-additive into crystalline graphite nano-flakes.     

Crystallization of a Cerium Phosphate Glass

Cerium phosphate glass containing 21 mol% cerium oxide and 79 mol% phosphorus oxide was prepared by melting a mixture of cerous oxalate and ammonium dihydrogen phosphate under normal atmospheric conditions. A heat-treatment schedule was obtained from DTA of this glass. Specimens of heat-treated samples for TEM observations were prepared by chemical and mechanical polishing techniques to observe the progress of nucleation, phase separation, and crystallization of this glass. Phase separation in the glass foil was also followed by electron-beam heating in the microscope. The crystalline compounds separated were identified by using electron and X-ray diffraction techniques.