Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga₂O₃) through the utilization of a so-called ammoniating process. Ga₂O₃ nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm² using a mixture of Ga₂O₃, HCl, NH₄OH and H₂O for 2 h. Then, the deposited Ga₂O₃ sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga₂O₃ nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga₂O₃ structure was detected, suggesting a complete transformation of Ga₂O₃ to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga₂O₃ to generate gaseous Ga₂O increase with temperature. The growth mechanism for the transformation of Ga₂O₃ to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga₂O₃. A significant change of morphological structures takes place after a complete transformation of Ga₂O₃ to GaN where the original nanorod structures of Ga₂O₃ diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.     

Synthesis of polycrystalline gallium oxide solar-blind ultraviolet photodetector by Aerosol Deposition

An aerosol deposition method was used to fabricate a solar-blind photodetector (for UV-C) using thin films of β-Ga₂O₃, which is a wide-bandgap oxide material. The Ga₂O₃ films deposited at room temperature presented a polycrystalline structure and a thickness of approximately 4 µm and showed a high transmittance of approximately 70–80 % in the visible region; the transmittance was approximately 60–80 % even after heat treatment up to a 800 °C. The Ga₂O₃ films that were post-annealed at a temperature of 800 °C showed an I_photo/I_dark ratio of approximately 40,000 in the solar-blind region with a light source of 254 nm, together with very good light detection characteristics (initial rising and decay times of 0.45 s and 0.13 s, respectively). Because of the good performances observed for the Ga₂O₃ thin films even at extreme conditions, they exhibit a high potential for use as photodetectors in several applications.     

纳米二氧化锡的多种方法制备、表征及其对比

本文采用共沸蒸馏法、水热法、溶胶-凝胶法分别制备纳米SnO2粉体,所制得的SnO2粉体利用X-射线衍射(XRD)和扫描电子显微镜(SEM)表征。结果表明,3种方法制备得的粉体均为四方金红石结构,共沸蒸馏法所得粉体平均颗粒约为20nm。水热法所得粉体的平均颗粒约为10nm。溶胶-凝胶法所得粉体的平均颗粒约为70nm。研究不同制备方法合成纳米SnO2粉体在合成工艺,生产周期,产物颗粒大小等方面的优缺点。     

Synthesis and characterization of composite Hg-polyaniline powder material

A simple synthesis method is proposed to obtain a composite powder material constituted by polyaniline powder containing mercury droplets closely linked into PANI matrix. ¹⁹⁹Hg solid state NMR spectroscopy indicates that incorporated mercury is in a metallic form and proves a redox reaction between polyaniline (leucoemeraldine form) and an aqueous solution of Hg(I). This composite powder material has been studied by voltammetry with a cavity microelectrode (CME). This electrode appears suitable for characterizing such a material. CME containing Hg-polyaniline (Hg-PANI) powder has been used as an electrochemical microsensor for lead trace analysis by anodic stripping voltammetry of water without electrolyte addition.     

Synthesis and characterization of ZnWO4 ceramic powder

Zinc tungstate (ZnWO₄) ceramic powder has been synthesized by a solid-state reaction method. A broad and intense blue emission at 472 nm has been measured from it with an excitation at 297 nm. Structural properties of this ZnWO₄ ceramic powder have been analyzed by carrying out the XRD, SEM, EDAX and FTIR spectral measurements. Besides these studies, dielectric properties in the frequency range of 200 Hz to 3 MHz at 300 K have also been carried out and all the obtained results are reported here.     

Synthesis and structural properties of lithium titanium oxide powder

Recently, lithium titanium oxide material has gained renewed interest in electrodes for lithium ion rechargeable batteries. We investigated the influence of excess Li on the structural characteristics of lithium titanium oxide synthesized by the conventional powder calcination method, considering the potential for mass production. The lithium excess ratio is controlled by using different weight of Li₂CO₃ powder during calcination. X-ray diffraction (XRD) measurement for the synthesized powder showed that the lithium titanium oxide material with excess lithium content had a spinel crystal structure as well as a different crystal one. In addition, high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) measurement revealed that the lithium titanium oxide powders with a lithium excess ratio of 5–20% exhibited a two phase formation. Inductively coupled plasma — atomic emission spectrometer (ICP-AES) and energy dispersive x-ray spectroscopy (EDX) measurements were used to analyze composition of the lithium titanium oxide powder. These results suggested that the conventional calcination method, considering the potential for mass production, formed two phases according to the Li excess amount in initial raw materials.     

氧化亚铜纳米棒的合成与表征

利用溶剂热法,以五水硫酸铜和氢氧化钠为原料,乙醇为还原剂,在乙醇与去离子水的混合溶剂中,140 ℃条件下溶剂热处理6～10 h制得了不同长径比的氧化亚铜纳米棒.利用X射线粉末衍射仪(XRD)及高分辨透射电镜(HRTEM)对合成产物进行了物相与形貌分析.检测结果显示合成的纳米棒结晶程度良好,尺寸较为均匀.在实验中还发现反应温度与溶剂中的含水量是影响乙醇还原性的主要因素.     

Synthesis and characterization of mercury oxide unusual nanostructures by ultrasonic method

A facile direct synthesis has been done to prepare HgO nanocrystallites of different shapes. The effect of different parameters such as the presence of alkali salts or stabilizers, power of the ultrasound, time of sonicating, and the starting materials on the size, morphology and crystallinity degree of the products were studied. Scanning electron microscopy observations revealed that using of polyvinyl alcohol (PVA) or alkali salts led to different shapes of product.     

大颗粒氧化铈粉体的合成及粒度控制

采用正交试验法,研究了用草酸溶液作沉淀剂,直接沉淀合成大颗粒二氧化铈粉末,并对影响氧化铈粉末粒度的各种因素进行了详细研究。结果表明,适当降低硝酸铈质量浓度可以有效控制氧化铈粉末的粒度;同时沉淀剂浓度、料液酸度、煅烧温度均对氧化铈粉末的粒度有较大影响,得出了制备粒度为30-40μm的大颗粒氧化铈粉体的最佳工艺条件为：硝酸铈质量浓度70 g/L,料液酸度0.5 mol/L,草酸沉淀剂的质量浓度100 g/L,煅烧温度900-950℃。按此工艺参数可以直接合成粒度为38.521μm的氧化铈粉末。     

Thermal plasma spheroidization of aluminum oxide and characterization of the spheroidized alumina powder

Spheroidization of aluminum oxide powder was done by thermal plasma processing. The powder was injected into the plasma jet issuing out of a DC plasma torch. Trajectories of the particles in the plasma jet were seen using a high speed camera and then in-flight velocity and temperature of alumina particles were determined using a ‘Spray Watch’ system. Characterization of the spheroidized powder was done by Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The results showed that increase of the plasma torch power leads to increase in the extent of spheroidization and conversion to γ-alumina. Results obtained showed that the process can be extended to synthesize free flowing alumina powder for thermal spray applications.     

两段碳酸化法分离氧化铝和氧化镓的研究

为了从高铝粉煤灰中提取含量可控的氧化镓和氧化铝的混合物,利用氢氧化镓与氢氧化铝在碱性溶液中析出的酸度不同,采用两段碳酸化的方法,分离出一定量的氧化铝,得到氧化镓和氧化铝的混合物。探讨了第一次碳酸化条件(即不同p H、不同流量、不同温度)对氧化铝和氧化镓分离效果的影响。实验结果表明:p H值为11.23,温度为80℃,CO_2流量为40 m L/min时,最终得到的氧化镓和氧化铝的混合物中,镓的含量为5.7550 mg/g。     

Synthesis and characterization of YAG precursor powder in the hydroxyhydrogel form

Powder precursor in the form of hydroxyhydrogel was prepared from yttrium nitrate and aluminium nitrate, using ammonium hydroxide as precipitant by flash polycondensation technique. Precursor powder obtained in the hydroxyhydrogel form was characterized by TG/DTA, FTIR, SEM and XRD analysis. This method produced material which could be transformed into YAG at comparatively lower temperature (800 °C) and was phase pure.     

水热法制备羟基氧化镓纳米晶体

提供一种以氧化镓为原料,140℃下用水热法制得不同长径比的羟基氧化镓纳米棒和纳米粒子的新工艺。研究了溶液的pH、水热时间及水热温度对纳米羟基氧化镓晶体粒子形态及尺寸的影响。采用X射线衍射（XRD）,透射电镜（TEM）等方法对制备的纳米羟基氧化镓形貌进行了表征。结果表明,溶液的pH增大,羟基氧化镓纳米棒的长径比增大,pH=12时,得到单分散性纳米粒子;延长水热时间,酸性条件下样品形貌基本不变,碱性条件下纳米棒长度及长径比变大;水热温度为180℃时,形成由纳米线组成的骨状纳米棒样品。     

氧化铟纳米粉制备及表征研究

以无机盐为原料，采用液相沉淀法制备纳米氧化铟粉体。研究了沉淀反应条件及沉淀后处理等对纳米氧化铟粉体质量的影响，利用TG-DSC、FT-IR、XRD、SEM和EDS等分析手段对所制纳米氧化铟粉体的结构、粒度、形貌、成分等进行了表征。结果表明：该法制备的氧化铟纳米粉具有立方晶系结构、纯度较高、颗粒均匀呈球形、分散性良好、平均粒径为50nm左右。     

端烯基聚醚大分子单体的合成及表征

用三乙胺为催化剂,叔碳酸缩水甘油酯的环氧基与甲基丙烯酸的羧基进行反应,生成的羟基继续与环氧基团反应,得到聚醚大分子单体。研究了反应时间、反应温度、催化剂用量对叔碳酸缩水甘油酯单体转化率的影响,对合成的大分子单体进行了IR1、H-NMR表征。结果表明,反应单体的配比对叔碳酸缩水甘油酯的转化率有较大的影响,且反应过程中,甲基丙烯酸单体的转化率也会因不同的反应条件而有所变化。适宜的反应条件为90℃,反应10 h,催化剂用量为反应单体总质量的5%,叔碳酸缩水甘油酯的转化率可以达到76.83%。     

Synthesis and characterization of nano-LiMn2O4 powder by tartaric acid gel process

Polycrystalline nano-LiMn₂O₄ spinel powder was synthesized by the tartaric acid gel process and developed without any detectable minor phase at 300 °C. The powders synthesized by the tartaric acid gel process had a relatively smaller particle size, larger specific surface area and narrower particle size distribution than those prepared by the conventional solid state reaction. The average valence of manganese decreased with increasing synthesis temperature and resulted in an increase of the lattice parameter with calcination temperatures. As temperatures were increased to above 500 °C, LiMn₂O₄ underwent phase transition from a cubic to a tetragonal phase by removing oxygen ion in the lattice. From the results of MAS NMR, LiMn₂O₄ spinels formed at 300–800 °C had a large Knight shift of ∼520 and 560 ppm in reference to LiC1.     

Synthesis and structural properties of lithium titanium oxide powder as-synthesized by two step calcination process

A two-step calcination synthesis, considering the potential for mass production, of lithium titanium oxide powder was carried out to fabricate a single Li₄Ti₅O₁₂ phase, which is useful for anode electrode material of Li-based rechargeable battery as well as an electrode for supercapacitor. The final composition is controlled by adding more TiO₂ powder into powder gained at one calcination process during the two calcination process. We investigated the influence of excess TiO₂ on the structural characteristics of lithium titanium oxide synthesized by the two-step calcination method. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) measurements showed that the as-synthesized powder had a spinel crystal structure as well as A composition of 4: 5: 12. In addition, a high resolution transmission electron microscopy (HRTEM) analysis revealed that the fabricated powder exhibited a single crystalline phase formation. These results indicated that the powder synthesized in the one-step calcination process showed coexistence crystalline phases, which are the Li₄Ti₅O₁₂ and Li_2.39Ti_3.4O₈ phase. However, in the two-step calcination process, the powder synthesized showed the single crystalline Li₄Ti₅O₁₂ phase. A very uniform grain size of the as-synthesized powder was shown in a field emission scanning electron microscopy (FESEM). These results suggested that the two-step calcination process can be used for synthesis of single crystalline Li₄Ti₅O₁₂ powder with uniform grain shape and provide motivation to pursue mass production of lithium titanium based oxide powder for bulk type batteries.     

氧化锌铝包覆硼酸钐粉体的制备及性能表征

为了获得具有较低红外发射率和激光反射率的复合材料,通过将氧化锌铝复合于硼酸钐表面的方法,获得了复合效果较好、红外发射率和激光反射率都相对较低的氧化锌铝/硼酸钐纳米复合粒子。用共沉淀法制备了氧化锌铝包覆硼酸钐纳米复合粉体,从包覆前后的电镜照片可以看到包覆层的厚度约为250nm。并且研究了包覆过程中m(硼酸钐):m(氧化锌)、处理硼酸钐所用盐酸的浓度和包覆前驱体的煅烧温度等因素对红外发射率和激光反射率的影响。结果表明,m(硼酸钐):m(氧化锌)为1.5:1、盐酸浓度为0.4mol/L、煅烧温度为650℃时红外发射率和激光反射率最低,最低的红外发射率为0.70、最低的激光反射率为0.73%。     

硫酸镓催化合成对羟基苯甲酸异丁酯

采用硫酸镓为催化剂合成了食用防腐剂对羟基苯甲酸异丁酯。考察了催化剂用量、醇酸物质的量比、反应时间、带水剂种类及用量等因素对产物收率的影响。结果表明,硫酸镓具有催化活性高,易分离回收,操作简单,后处理方便等优势。硫酸镓是合成对羟基苯甲酸异丁酯高效、经济且环境友好的催化剂,有一定工业化应用前景。适宜反应条件为:对羟基苯甲酸0.05 mol,醇酸物质的量比6,催化剂2.0 g,甲苯10 mL,反应时间8 h,产物收率达96.6%。