氨水草酸沉淀法制备氧化铈超细粉体

采用氨水、草酸为沉淀剂,制备出了D50小于1μm的CeO2超细粉,并进行了粒度,XRD,DTA／TG的表征研究．结果表明,以氨水、草酸作沉淀剂,可以制备CeO2超细粉,沉淀物500℃就可完全分解为CeO2,所制备的CeO2超细粉属于立方晶型,其平均粒径随焙烧温度的升高而增大．     

Structural and optical characteristics of Al_xGa_(1-x)N/AlN superlattice

AlN/Al0.3Ga0.7N superlattices were grown on (0001) sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The superlattice period varies from 6 to 30. The layer thickness of different period stack was designed. GaN or AlGaN template was employed for growing AlN/AlGaN superlattices. Reflectivity, SEM, AFM and XRD data of the AlxGa1-xN/AlN superlattices are presented. It is found that the templates used have an intensive impact on surface roughness and interfacial properties of following AlN/AlGaN superlattices. The result of atomic force microscopy indicates that AlN/AlGaN superlattices grown on GaN template exhibit quasi-two-dimensional growth mode. The resulting superlattice has a smooth surface morphology and distinct interface. No crack is observed in the area of a 2-inch wafer.     

化学沉淀法制备纳米CeO2的工艺研究

以氟碳铈矿为铈源,氨水为沉淀剂,H2O2为氧化剂,加入少量表面活性剂作为分散剂,采用化学沉淀法合成纳米CeO2。研究了氟碳铈精矿溶解反应温度、反应时间、表面活性剂种类和用量、煅烧温度和煅烧时间等因素对纳米CeO2晶粒尺寸的影响,得到了最佳工艺条件,在此条件下得到的纳米CeO2粉末为立方晶体,结晶趋于完整,粒径较小。     

纳米CeO2粉体的制备及应用

对近年来国内外涌现的各种制备纳米CeO2的方法进行了较为详细的评述。重点介绍了纳米CeO2在超精密抛光、汽车尾气净化催化、固体氧化物燃料电池等高科技领域中的应用状况，指出今后研究的方向是纳米CeO2粉体制备过程中的颗粒大小与形貌的控制及其分散性的改善，粉体形核与生长过程中的动态观测与机理研究，以及研究成果的工业化规模生产与应用。     

Structure, optical, and magnetic properties of Mn-doped ZnO films prepared by sputtering

The microstructural,optical,and magnetic properties and room-temperature photoluminescence(PL) of Mn-doped ZnO thin films were studied.The chemical compositions were examined by energy dispersive X-ray spectroscopy(EDS) and the charge state of Mn ions in the ZnO:Mn films was characterized by X-ray photoelectronic spectrometry(XPS).From the X-ray diffraction(XRD) data of the samples,it can be found that Mn doping does not change the orientation of ZnO thin films.All the films prepared have a wurtzite stru...     

纳米CeO2粉末的制备及表征

采用草酸作沉淀剂制备了纳米CeO2粉末，由DTA和TG分析结果可知，温度升高到600℃时，前驱全基本分解完全，随的延长，失重增加．XRD结果表明，粉末为萤石结构，在600℃焙烧1h，粉末的晶粒度为20．15nm，晶胞常数为0.54nm，烧结3h的晶粒度为21．07nm,晶胞常数为0.54nm,TEM分析表明，所有粉末的颗粒形状较规则，分散性良好，无极化处理对分散性影响不大，焙烧1h的粉末平均颗粒度为12－35nm，焙烧3h粉末的颗粒度分布在17－40nm之间。     

MgO掺杂对CeO2-ZrO2材料阻抗特性的影响

利用交流复阻抗分析技术对(MgO,CeO2)复合掺杂ZrO2材料的阳抗特性进行了研究.结果表明,随着MgO掺入量的增加,参与跃迁的氧空位增多,并促进烧结体的密度上升,气孔率降低,导致导电相粒子间的接触电阻减少,提高了(ZrO2)1-x-y(YO1.5)x(MgO)y陶瓷的电导率.     

CeO2基固体电解质材料的掺杂强化

强度低是CeO2基电解质材料的一个主要缺点，实验发现，加入Al2O3可以显增加CeO2基材料的强度，原因是掺杂的Al2O3在CeO2中产生压缩应力；阻碍裂纹的进一步扩展，另外，Al2O3分布在晶界处，将会导致裂纹偏转，最大弯曲强度对应的Al2O3添加剂量摩尔分数为3%，加入Al2O3还可以促进材料烧结，使烧结温度降低到1500℃以下，但会使CeO2基电解质的电导率下降。     

Structural and optical properties of periodically ordered ZnO nanowires

Periodically ordered ZnO nanowire arrays were fabricated by a combination of soft templates created by electron beam lithography and an electrochemical process. Individual ZnO nanowires were precisely placed in desired locations to form two-dimensional periodic structures with specific patterns. Scanning electron microscopy and light diffraction measurements confirmed the long-range ordered structures in the nanowire arrays. Variable temperature photoluminescence revealed both band edge and defect emissions. The obtained photonic structures may have potential applications in optical and optoelectronic devices.     

5-甲基-2-庚烯-4-酮激发态结构动力学的共振拉曼光谱研究

获取了反式-5-甲基-2-庚烯-4-酮（5M2H4O）分别在甲醇、乙腈以及环己烷三种不同极性溶剂中的电子吸收光谱和共振拉曼光谱。探讨了在不同极性溶剂中A-带共振拉曼光谱Franck-Condon（FC）区域的短时动力学。在B3LYP/6-31＋G（p）计算水平下得到了5M2H4O的电子跃迁、几何结构及振动频率。结果表明最强吸收带（A-带220nm）的跃迁主体归属为πH-1→πL＊。结合理论计算及傅里叶拉曼和傅里叶红外实验对共振拉曼光谱的7个基频振动模进行了指认。C=C伸缩振动（ν16）和C=O伸缩振动（ν15）对共振拉曼光谱强度贡献最大,这表明该激发态的结构动力学主要沿着C=C伸缩（ν16）和C=O伸缩振动（ν15）反应坐标进行。     

XPS Study of CeO2/Al2O3 film

The redox capacity of CeO2/Al2O3 thin film which was prepared by sol-gel method has been investigated by X-ray Photoelectron Spectrascopy (XPS). The results showed that the thin film was easier to be reduced and re-oxidized than pure CeO2 powder. The key role played by oxygen vacancies which were created from the interaction between CeO2 and Al,O, was also discussed.     

Mechanical Properties of ZrO2 Ceramic Stabilized by Y2O3 and CeO2

ZrO2 ceramic was made from evenly dispersed ( Y, Ce )-ZrO2 powder with different composi-tions, which was prepared by the chemical coprecipitation, and stabilized by compound additions through appropri-ate techniques. And its mechanical property that is related to the phase content and its microstntcatre was studied by X-ray diffraction(XRD),scan electron microscope(SEM). The results show that Y2O3 has stronger inhibition to the growth of ZrO2 crystal than CeO2 has. TheFEfore, within an appropriate composition range of Y2O3 and CeO2, the higher the content of Y2O3, the lower the content of CeO2, the smaller ZrO2 crystal. Combining this feature and the stabilization technique with complex additions instead of simple addition, ZrO2 ceramic with high density and excellent mechanical properties can be made under normal conditions. It is concluded that the improvement of mecMnical properties originates from the toughening of microcrack, phase transformation and the effect of grain e-vulsions.     

用悬浮液干燥法制备CeO2包覆的ZrO2粉体

讨论了用一种新的表面改性技术制备Al2O3掺杂、CeO2包覆ZrO2纳米粉体的方法。在水-乙醇溶剂中,干燥硝酸铈和单斜相二氧化锆粉体的悬浮液经800℃热分解,可以制备出粒度小于100 nm的Al2O3掺杂、CeO2包覆的单斜相ZrO2粉体。该粉体可以在空气中和1 450℃下无压烧结成致密化Ce-TZP材料,具有KIC=11 MPa m1/2的良好断裂韧性和HV30=750 kg/mm2的硬度。     

磁性壳聚糖微球的制备及其性能

用共沉淀法制备纳米级Fe3O4磁流体,并对其用油酸进行表面改性.采用化学交联法,在分散有磁流体的壳聚糖溶液中,加入适量的戊二醛交联剂,制得内核为磁性Fe304,外层包有壳聚糖的纳米级的磁性壳聚糖复合微球.考察了壳聚糖质量浓度、NaOH滴加量及搅拌速度等因素对磁性壳聚糖微球粒径、粒径分布以及形貌等对复合过程的影响,确定了...     

磁性壳聚糖微球的制备及其性能

用共沉淀法制备纳米级Fe3O4磁流体,并对其用油酸进行表面改性。采用化学交联法,在分散有磁流体的壳聚糖溶液中,加入适量的戊二醛交联剂,制得内核为磁性Fe3O4,外层包有壳聚糖的纳米级的磁性壳聚糖复合微球。考察了壳聚糖质量浓度、NaOH滴加量及搅拌速度等因素对磁性壳聚糖微球粒径、粒径分布以及形貌等对复合过程的影响,确定了制备磁性壳聚糖微球的最佳条件,并用电镜、红外光谱图、粒径分析仪等方法对磁性壳聚糖微球的形态和组成特性进行分析。最后得出平均粒径为348.5 nm,表面富含羟基、氨基和醇羟基等官能团,磁性明显、分散性良好的磁性壳聚糖微球。     

磁性PF微球的制备及性质

运用缩合聚合法制备出PF凝胶，并在此基础上以共沉淀法合成出磁性PF微球，该微球呈珠状，平均粒径为10-20nm，具有较大的蛋白质固载量，可作为载体对多种酶及蛋白质加以固定。结果表明：当PF凝胶的制备条件为：对笨二酚11．1g、甲醛30mL和盐酸4mL时，所制PF凝胶的蛋白固载量最大；当磁性PF微球的制备条件为：PF凝胶添加量2g，pH值在3—4之间，固定时间2h，磁性PF微球能取得最高的蛋白固载量，同时研究了磁性PF微球的磁学性能。     

沉淀法制备纳米二氧化铈及其表征

利用XRD、SEM和TG-DTA分析手段对用两步沉淀法制备的纳米二氧化铈粉进行了初步表征:XRD分析表明,当焙烧温度为200～600℃时,所合成的CeO2粒子属于立方晶系,空间群为O5hFm3m;SEM微观分析表明,CeO2粒子呈球形,粒度随焙烧温度的升高而增大,在400℃焙烧所得到的粒子粒径≤100nm;TG-DTA分析表明,该方法的前驱体结构为Ce(OH)3OOH和CeO2·2H2O的混合物.     

Hydrogenation reaction characteristics and properties of its hydrides for magnetic regenerative material HoCu_2

The hydrogenation reaction characteristics and the properties of its hydrides for the magnetic regenerative material HoCu_2(CeCu_2-type) of a cryocooler were investigated. The XRD testing reveals that the hydrides of HoCu_2 were a mixture of Cu, unknown hydride Ⅰ, and unknown hydride Ⅱ. Based on the PCT(pressure-concentration-temperature) curves under different reaction temperatures, the relationships among reaction temperature, equilibrium pressure, and maximum hydrogen absorption capacity were analyzed and discussed. The enthalpy change ΔH and entropy change ΔS as a result of the whole hydrogenation process were also calculated from the PCT curves. The magnetization and volumetric specific heat capacity of the hydride were also measured by SQUID magnetometer and PPMS, respectively.     

Structural,optical and electrical properties of Li-doped ZnO thin films influenced by annealing temperature

Li-doped Zn O thin films had been grown by radio frequency magnetron sputtering and then annealed under various annealing temperatures. The characteristics of Zn O films were examined by XRD, FESEM, Hall measurement and optical transmission spectra. Results showed that p type conduction was observed in Lidoped Zn O films annealed at 500-600 ℃ and the p type Zn O films possessed a good crystalline with c-axis orientation, dense surface, and average transmission of about 85% in visible spectral region.