纳米掺铝氧化锌(ZAO)粉体的制备研究进展

掺铝氧化锌(ZAO)是一种具有广阔的应用前景和发展潜力的复合氧化物半导体。综述了化学沉淀法、溶胶-凝胶法、水热法、沸腾回流法和络盐法等ZAO纳米粉体常用的制备方法,并对其进行了比较评价。     

掺铝氧化锌薄膜表面织构机制的研究

采用氯化铵(NH4Cl)溶液对磁控溅射技术制备的掺铝氧化锌(AZO)薄膜进行表面织构,并对其表面织构机制进行研究.研究结果表明NH4Cl溶液优先与间隙锌、间隙铝等缺陷和晶界处的堆积铝反应,而较大的相对应力和稀疏表面有助于间隙锌、间隙铝等缺陷和堆积铝的形成.它们对NH4Cl对AZO薄膜的表面织构很关键.     

铝、钇共掺片状氧化锌的制备及其光催化性能

用氯化锌、氢氧化钠、九水合硝酸铝和六水合硝酸钇为原料,并采用低温水浴法制备了铝、钇共掺的片状氧化锌,并通过扫描电镜(SEM)、X射线衍射(XRD)、紫外可见光谱(UV-Vis)等方法对Al-Y/ZnO进行表征;利用亚甲基蓝溶液(MB)作为有色污染物,研究了片状氧化锌中不同掺杂量的Al和Y元素对其光催化性能的影响。结果表明,当Al的掺杂量为3%,Y的掺杂量为3%时,ZnO的表面状态得到了明显改善,生成更多的羟基自由基;同时增加光生电子空穴对的浓度,显著提高ZnO的光催化性能;经过1 h紫外汞灯照射,其降解率达到94.63%;且经过5次循环使用后,3%Al-3%Y/ZnO的降解率依旧能达到85%以上,具有良好的光催化性能和循环稳定性。     

熔盐法合成ZnO纳米微粉

采用熔盐法制备得到了单一六方纤锌矿结构的ZnO纳米微粉,并对其反应条件进行了研究。通过XRD、TEM和BET等分析手段对纳米粉的形貌结构进行表征,通过TG分析对反应过程进行研究。通过调控焙烧温度、熔盐含量、焙烧时间等反应条件,可以将其平均粒径尺寸有效控制在50～150nm范围。结果表明,通常所得ZnO纳米微粉晶化程度高,团聚较少,粒径分布较均匀;但熔盐含量较低时,微粉产物中将生成一定量的ZnO纳米棒。     

氧化锌掺杂铝纳米片的制备及其气敏性能研究

采用水热法,以油酸为形貌控制剂,硝酸铝为铝源,制备了氧化锌掺杂铝纳米片,对其进行了XRD、SEM和EDS表征。考察了制备物对甲醇、乙醇、丙酮、异丙醇、正丁醇、DMF等六种气体的气敏性能,并对其气敏机理进行了简要分析。结果表明,掺杂3%Al的ZnO样品晶粒尺寸变小,为带微孔的层状纳米片,EDS能谱表明样品含有Zn、O和Al元素。样品对正丁醇、丙酮的灵敏度较高,100ppm时分别为164和70,对丙酮的响应和恢复时间分别为7s和29s。     

中频直流磁控反应溅射法制备掺铝氧化锌薄膜的研究

利用中频直流磁控反应溅射法(MF-DC-MS)在玻璃衬底上制备了掺铝氧化锌(AZO)透明导电薄膜。利用X射线衍射(XRD)、四探针法和分光光度计深入研究了衬底温度对AZO薄膜的结构、电学和光学特性的影响。研究结果表明3h的沉积使AZO薄膜丧失了(002)c轴择优取向。随着衬底温度由210℃升高到270℃,AZO薄膜的电阻率从7.5×10-3Ω.cm降低到2.5×10-3Ω.cm。高于270℃后,电阻率又略有升高。电阻率的变化趋势可从薄膜微观结构的角度得到合理解释。随着衬底温度的升高,AZO薄膜的吸收边先发生了蓝移。高于270℃后,又发生了红移。利用Burstein-Moss效应分析了AZO薄膜吸收边的蓝移和红移。该结果和电阻率的结果相印证。     

纳米氧化锌的制备

以硫酸锌和碳酸铵为原料,直接沉淀法制得纳米氧化锌的前驱体,然后煅烧得到纳米氧化锌.采用 TG-DTG、XRD和TEM等测试手段对其进行了表征.结果表明,前驱体为Zn4(OH)6CO3.通过控制煅烧温度、反应温度和反应物浓度可以得到不同粒径的球形纳米氧化锌.得出了最佳制备工艺条件.     

掺铝氧化锌透明导电薄膜的表面织构研究

利用中频直流磁控反应溅射法在玻璃衬底上首先制备了掺铝氧化锌(AZO)透明导电薄膜,然后利用5%的氯化铵(NH4Cl)溶液对制备的AZO薄膜进行表面织构。利用扫描电子显微镜(SEM)、四探针法和分光光度计分别测量并研究了织构前后薄膜的表面形貌、电学和光学特性。研究结果表明NH4Cl水溶液容易控制AZO的表面织构过程,并且可以获得较好的绒面。表面织构后,薄膜在可见光波段的平均反射率从12%降低到7.86%,而电阻率略有增大,该结果和表面织构结果一致。     

纳米级氧化锌的制备

论述了新材料纳米级氧化锌的制备。首先论述了由于纳米级材料特有的量子尺寸的效应等特种性能 ,它在量子器件、太阳能利用、图象记录、压电等方面有着广泛的应用 ;进一步叙述了用液—液法除铁、锰、铜等重金属 ,制备了纳米级氧化锌。所用原料廉价易得 ,制备工艺简单 ,既降耗节能 ,也无环境污染。制备的新材料纳米级氧化锌 ,经测试粒径在 5 0nm左右 ,球形体 ,比表面积大于 5 0m2 / g。     

AZO@C柔性纳米纤维的制备与性能

以聚乙烯醇(PVA)为原料,成功制备了新型掺铝氧化锌包覆碳结构(AZO@C)的柔性纳米纤维。首先通过静电纺丝制备PVA初生纳米纤维,经过热处理工艺提高纳米纤维的耐水性,然后采用水热合成法在其表面包覆一层锌铝氢氧化物,再经过在500℃高温条件下烧结,PVA表面包覆的锌铝氢氧化物发生脱水反应形成致密的掺铝氧化锌(AZO)纳米粒子,同时PVA纳米纤维在高温煅烧中被炭化,形成一种新型AZO@C纳米复合材料。采用红外光谱(FT-IR)、热重分析仪(TGA)、扫描电镜(SEM)等对纳米纤维结构与性能进行测试及表征,AZO@C纳米纤维的平均直径为(320±45)nm。并通过太阳光下降解甲基橙实验证明了AZO@C柔性纳米纤维的光催化降解性能。     

Preparation and optical properties of GaN nanocrystalline powders

Abstract

GaN nanocrystalline powders were synthesised by decomposition of gallium nitrate, followed by nitrogenising with ammonia under different temperature. X-ray diffraction (XRD) and the transmission electron microscopy (TEM) indicated that the crystallinity of the powder is improved and the average size of the GaN nanocrystallites increases from 4·8 to 23·9 nm as the temperature increases from 850 to 1050°C. The Raman spectra displayed four broadened peaks corresponding to A₁ (LO), A₁ (TO), E₁ (TO) and E₂ (high) modes of würtzite GaN respectively. Two additional modes at 252 and 421 cm^–1 attributed to boundary phonons activated by the finite size effects and octahedral Ga–N₆ bonds were observed respectively. A strong blue photoluminescence (～353 nm) was detected for room temperature measurement, indicating that the GaN nanocrystalline powders have few defects and high quality.     

Preparation and characterization of highly dispersed nanocrystalline rutile powders

A highly dispersed nanocrystalline rutile powder (NRP) having ultrafine and narrow-distributed diameters was successfully prepared via an improved conventional liquid one-step method by introducing dioctyl sulfosuccinate sodium salt (AOT) surfactant in the peptization reaction anaphase. The average grain size of the product is 10-20 nm. The effects of the titanium tetrabutoxide (Ti(OBu)₄) to ethanol volumetric ratio, the precipitation temperature, the peptization temperature and the presence of dioctyl sulfosuccinate sodium salt (AOT) on the preparation of NRP were studied. A new procedure for synthesizing NRP is proposed, and the optimum conditions for preparing NRP were obtained. The TEM, XRD, SEM and FT-IR results were also investigated in this work.     

Preparation of nanocrystalline YSZ powders by the plasma technique

A plasma synthesis method has been devised to produce nanosize YSZ powders with various yttria contents. The powders are synthesized by introducing a mixture of coarse-grained zirconia and yttria into an r.f. inductively coupled plasma flame. The average particle size of the as-prepared powders is in the range 20–40 nm and the specific surface area is 18–50 m²g^–1. The phase and granulometric composition of the produced powders depend on the degree of evaporation of raw powders, reagent concentration in the gas flow and quenching rate, and on the content of Y₂O₃. Up to 5.5 mol% yttria, the major phase of nanosize powders is tetragonal ZrO₂, mostly as the non-transformable (t) form. For yttria contents higher than 6 mol%, the major phase is cubic ZrO₂.     

Preparation and characterization of indium-doped tin dioxide nanocrystalline powders

The precursors of SnO₂ or In₂O₃/SnO₂ nanocrystalline powders have been prepared by the sol-precipitation method. The precursors are calcined at different temperatures to prepare SnO₂ or In₃O₃/SnO₂ nanocrystalline powders with different particle sizes. The reaction conditions, such as the concentration of reactants, the surfactant, pH value, the amount of indium oxide doped, and the reaction temperature and time, have been studied. The nanocrystallites are examined by differential thermal analysis (DTA)/thermogravimetric analysis (TGA), X-ray diffraction (XRD), IR spectroscopy and transmission electron microscopy (TEM).     

ZAO粉体制备及其电导率性能研究

采用水相共沉淀法,在ZnCl2和AlCl3·6H2O的混合溶液中添加聚乙二醇6000,并滴加不同浓度氨水制备了ZAO前驱体,然后煅烧得到ZAO粉体.利用XRD、SEM和数显电导率仪分别对ZAO粉体的结构和物相、形貌、尺寸和导电性能进行分析,以及探讨了氨水浓度、pH值、反应温度、煅烧温度、煅烧时间对ZAO粉体导电性能的影...     

Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.     

Preparation of nanocrystalline bredigite powders with apatite-forming ability by a simple combustion method

Nanocrystalline bredigite (Ca₇MgSi₄O₁₆) powders were synthesized by a simple solution combustion method. Phase pure bredigite powders with particle sizes ranging from 234 to 463 nm could be obtained at a relatively low temperature of 650 °C. The apatite-forming ability of the bredigite powders was examined by soaking them in a stimulated body fluid. The compositional and morphological changes of the powders before and after soaking were analyzed by X-ray diffraction and scanning electron microscopy and the results showed that hydroxyapatite was formed after soaking for 4 days.     

Vacuum annealing of nanocrystalline WC powders

The effect of vacuum annealing temperature on the chemical and phase compositions, particle size, and lattice strain of nanocrystalline tungsten carbide (WC) powders with a particle size from 20 to 60 nm has been studied by X-ray diffraction and electron microscopy. The results demonstrate that vacuum annealing of WC nanopowders at t _ann ≤ 1400°C is accompanied by a marked decrease in carbon content and changes in phase composition due to carbon desorption from the surface of the powder as a result of the interaction of carbon with oxygen impurities. In addition, annealing leads to an increase in particle size due to coalescence of aggregated nanoparticles and reduces the lattice strain of the powder.     

绒面ZAO透明导电膜的制备工艺研究

绒面ZAO(ZnO∶Al,氧化锌铝)透明导电膜在硅基薄膜太阳能电池领域应用前景广阔,本文利用直流磁控溅射方法,采用氧化锌铝陶瓷靶材制备了ZAO透明导电膜,并用自制的腐蚀液对膜层进行腐蚀以便形成太阳能电池所需要的表面凹凸起伏的绒面结构。研究了不同镀膜温度对膜层性能的影响,不同退火条件下膜层热稳定性的变化情况,不同腐蚀时间下膜层电阻、透过率以及表面形貌的变化,结果表明,在相同真空度、溅射功率和节拍的情况下,220℃下制备的ZAO透明导电膜膜层性能最好,腐蚀时间为30 s时获得的绒面效果好。