Synthesis of γ-Al_2O_3 nanoparticles by chemical precipitation method

Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor AI（OH）3 sols are produced by using 0.1 mol/L Al（NO3）3·9H2O and 0.16 mol/L （NH4）2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024%（volume fraction） surfactant PEG600, and reacting at 40℃, 1000 r/min stirring rate for 15min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80℃ for 8h, final calcined at 800℃ for 1h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH^7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m^2/g in BET specific surface area, 7 - 11 nm in pore diameter, and not lower than 99.93% in purity.

DFT Studies on Thermal Stabilities,Electronic Structures,and ^(13)C Chemical Shifts of C_(24)O_2 Based on Fullerene C_(24)(D_6)

Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 （D6） and C24O have been performed using density functional theory （DFT） method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C24O2 isomers at the ground state have been calculated at the B3LYP/6-31G（d） level of theory. And the 1,4,2,5-C24O2 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies, IR spectrum, and 13C chemical shifts of various C24O2 isomers have been calculated and analyzed.

Effect of Chemical Doping and Ion Implantation on Cond uctivity of Poly(p-phenylene vinylene) Derivatives

The surface conductivity of poly [ 2-methoxy-5-（3＇-methyl） butoxy]-p-phenylene vinylene （PMOMBOPV） films doped with FeCl3 and H2SO4 by chemical method and implanted by N^＋ ions was studied and the comparison of environmental stability of conductive behavior was also investigated. The energy and dose of N^＋ ions were in the rang 15～35 keV and 3. 8×10^15～9. 6×10^16 ions/cm^2, respectively. The conductivity of PMOMBOPV film was enhanced remarkably with the increases of the energy and dose of N^＋ ions. For example, the conductivity of PMOMBOPV film was 3. 2×10^-2S/cm when ion implantation was performed with an energy of 35 keV at a dose of 9. 6 × 10^14 ions/cm^2 , which was almost seven orders of magnitude higher than that of film unimplanted. The environmental stability of conductive behavior for ionimplanted film was much better than that of chemical doped films. Moreover, the conductive activation energy of ion-implanted films was measured to be about 0.17 eV.

Quantum Chemical Calculation on Preparation of YBa＿2Cu＿3O＿（7－δ） Powders by Hydrolysis of Metal Alkoxides

The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relationship between frontier orbitals and organic chemical reactions. Based on the above results. properexperimental conditions for the preparation of homogeneous ultra-purity. submicro high-T_cYBa_2Cu_3O_(7-δ) superconducting powders are proposed.

α-Co(OH)_2的制备及其超级电容特性

以氯化钴为原料,聚乙烯吡咯烷酮(PVP)为分散剂,采用化学沉淀的方法制备出由纳米粒子组成的片状α-Co(OH)2.用红外光谱对所制样品的组分进行分析,用X射线衍射和场发射扫描电子显微镜表征产物的结构和形貌,用循环伏安和恒电流充放电等测试方法对其电化学性能进行研究.研究结果表明,由纳米粒子组成的片状α-Co(OH)2表现出优良的电化学性能,单电极比电容高达1220 F/g.

稳定的α-Ni(OH)_2研究进展

α -Ni(OH) 2 因具有较高的放电比容量 ,有望成为镍电极的活性物质。综述了用锌、铁、锰、钴和铝取代的α -Ni(OH) 2 的制备工艺及其电化学性能。在探讨α相不稳定的原因及如何使其稳定于强碱中的基础上 ,展望了其应用前景。

反渗透浓水中去除SO_4^(2-)的实验研究

为了缓解反渗透浓水所带来的严重污染问题,实验通过采用不同处理方法,分析对比了浓水中Ca2+、Mg2+和SO42-的去除情况。结果表明,化学沉淀法对Ca2+和Mg2+的去除较为乐观,去除率高达85%以上,而对SO42-的去除很不理想;但从其它3种去除SO42-的方法中可以明显看出,钙矾石法对SO42-的去除效果最佳,且去除率可达到88%。主要原因是AlO2-的生成是形成钙矾石的关键,且在pH为11~12时缓慢投加氢氧化钙可以最大限度地去除浓水中的SO42-。此外,石膏晶体法不但不能去除SO42-,反而起到相反作用;氢氧化钙和聚合氯化铝絮凝沉淀法也不能通过生成沉淀物的方式来去除SO42-。因此,可将化学沉淀法和钙矾石法作为反渗透浓水的有效处理方法。

α-Co(OH)2的制备及其电化学性能研究

以CoCl2.6H2O和NH3.H2O为原料,室温下采用直接沉淀法成功制备了-αCo(OH)2.用红外光谱(FT-IR)、X射线衍射(XRD)和场发射扫描电子显微镜(FE-SEM)表征了产物的结构和形貌;用循环伏安、恒电流充放电等测试方法对其性能进行了研究.结果表明,该产物表现出优良的电化学性能,单电极比电容可达890 F.g-1,有望成为超级电容器的电极材料.

化学共沉淀法制备铝掺杂α-Ni(OH)_2的控制条件

采用化学共沉淀法制备掺杂Al的α—Ni（OH）2，用正交实验研究pH值、掺杂Al的含量、陈化时间、反应温度等制备因素对活性物质放电比容量的影响，并用极差法分析各制备因素影响的显著性。结果是，制作性能优良的掺杂Al的α—Ni（OH）2的最佳条件为：反应温度40～50℃，掺杂10％摩尔含量的Al，陈化12～16h，pH值7．5～9．5；各因素对活性物质放电比容量影响的显著性顺序为：掺杂Al的含量〉pH值〉反应温度〉陈化时间，在选择合成条件下制备的样品电极具有较好的充放电效率和活性物质利用率，电化学阻抗较小，最大放电比容量为345．2mAh·g^-1。

Cl^-和Zn^(2+)阴阳离子复合掺杂α-氢氧化镍的结构与电化学性能

采用化学共沉淀法,制备出Cl-和Zn2+阴阳离子复合掺杂α-Ni(OH)2粉体。样品材料利用XRD、EDS、SEM、IR、DSC-TG和粒度测试仪进行结构形态及物理特性表征分析。同时以其为活性物质合成镍正极材料并组装MH-Ni电池,测试其充放电、循环可逆特性和交流阻抗等电化学性能。实验结果表明,在掺杂物质摩尔比为Cl-:Zn2+=1:3时,Cl-和Zn2+复合掺杂α-Ni(OH)2为层状结构,结晶水含量较高,热分解温度低。其MH-Ni电池在以80mA/g恒流充电5h,40mA/g恒流放电至终止电压为1.0V的充放电制度下,电化学极化阻抗较小,放电比容量为354.08mAh/g,放电平台平稳、中值电压高达1.313V,且经过多次充放电循环后,其电极活性物质仍然保持α-Ni(OH)2状态,电极过程结构稳定,循环可逆性较好,具有较高的电化学活性。

新的固体超强酸ZrO_2-SnO_2-MnO_2/SO_4^(2-)的制备

用化学共沉淀法并用乙二醇作为分散剂制备复合氧化物基ZrO2＿SnO2＿MnO2/SO42-固体超强酸,并对影响酸强度的各种因素进行了考察。确定三种元素最佳物质的量之比、分散剂的用量、硫酸的最佳浓度、浸泡时间、烧结温度等,并对其在乙酸乙酯的酯化反应中的催化作用进行了考察,表明其有一定的活性。通常将几种离子的溶液共沉淀,本实验中把MnO2直接加入到溶液中与Zr4+、Sn4+进行共沉淀,制得了含MnO2的固体超强酸,这方面尚未见过有关报道。

Preparation and structure characteristics of nano-Bi_2O_3 powders with mixed crystal structure

The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi（NO3）3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffraction and transmission electron microscopy, respectively. The results show that under the optimum condition that 300g/L Bi（NO3）3 reacts at 90℃ for 2h, the Bi2O3 powders with 60nm on the average and 99.5% in purity are obtained. The prepared nano-Bi2O3 powders contain a mixed crystal structure of monoclinic and triclinic instead of traditional structure of monoclinic α-Bi2O3. And the mixed crystal structure is stable in air. The reason for the appearance of the mixed crystal structure may be that the ionic radius ratio of Bi 3+ to O 2- changes easily during the formation of nano-Bi2O3 particles by a chemical precipitation method.

Preparation and properties of nano-sized SnO_2 powder

SnO 2 powder was prepared by chemical precipitation method. Effects of starting materials concentration, pH value of final system and treating temperature on the particle size were investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The parameters of chemical precipitation were optimized. It is concluded that the concentration of starting material and pH value of final system has little effect on the SnO 2 particle size, but heat treatment do greatly affect the particle size. If the treating temperature is lower than 500 ℃, the particle size has a good stability; otherwise, the particle size remarkably increases with increasing temperature. The dispersing agents have various influences on SnO 2 powder as the polarity of dispersing agents changed.

Direct Synthesis of Al_2O_3-modified Li(Ni_(0.5)Co_(0.2)Mn_(0.3))O_2 Cathode Materials for Lithium Ion Batteries

To improve the cyclic stability at high temperature and thermal stability, the spherical Al2O3-modified Li（Ni0.5Co0.2Mn0.3）O2 was synthesized by a modified co-precipitation method, and the physical and electrochemical properties were studied. The TEM images showed that Li（Ni0.5Co0.2Mn0.3）O2 was modified successfully with nano-Al2O3. The discharge capacity retention of Al2O3-modified Li（Ni0.5Co0.2Mn0.3）O2 maintained about 99% after 200 cycles at high temperature（55 ℃）, while that of the bare one was only 86%. Also, unlike bare Li（Ni0.5Co0.2Mn0.3）O2, the Al2O3-modified material cathode exhibited good thermal stability.

Chemial Bond and Stability of Adsorption of [Au(AsS_3)]^(2-)on the Surface of Kaolinite

Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS 3)] 2- on the surface of kaolinite.The correlation among structure,chemical bond and stability was discussed.Several models were selected with [Au(AsS 3)] 2- in different directions and sites.The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au-O covalent bond,so these models are more stable than those with gold above or under the layer.The models with gold near to [AlO 2(OH) 4] octahedra are more stable than those with gold near to the vacancy without aluminium.These two stable tendencies in kaolinite-[Au(AsS 3)] 2- are stronger than that in kaolinite-Au systems.The interaction between [Au(AsS 3)] 2- and kaolinite is stronger than that between gold and kaolinite,and this interaction is strong enough to form the surface complexes.

Cr^(3+)掺杂α-Al_(2)O_(3)粉末的结构及其发光性能

采用化学沉淀法合成了α-Al_(2)O_(3):Cr^(3+)发光粉体,并对其结构和发光性能进行了研究.α-Al_(2)O_(3):Cr^(3+)粉末分散性较好,吸收光谱在可见光区由一系列驼峰状宽带吸收峰组成.在411 nm激发下,粉末主发射峰位于695 nm处,属于Cr^(3+) R线发射.Cr^(3+)最佳掺杂浓度为0.5 mol%,经过计算此时晶格内Cr^(3+)之间距离大约为20A,α-Al_(2)O_(3)为强晶体场环境.Cr^(3+)掺杂浓度继续增大后,晶格内Cr^(3+)浓度增大、离子间距离减小、无辐射跃迁增多,出现浓度淬灭现象,导致发光强度降低.

锌镍电池及其α-Ni(OH)_2正极材料的研究

综述了化学均相沉淀法合成α-Ni(OH)_2的方法,在适宜的温度、p H值、镍盐浓度及添加相关的活性剂下能够得到容量高、电压大、循环性能好的α-Ni(OH)_2材料。另外,通过掺杂不同的金属盐来改变其性能,并添加Zn盐、Al盐、Mn盐、铁盐、稀土金属盐等化合物,改良α-Ni(OH)_2结构。其中掺杂Al盐得到的α-Ni(OH)_2性能最好。综述了化学沉淀法以外的一些其它合成α-Ni(OH)_2的方法。

Sandwich Complexes of the As_4～(2-) Aromatic Ring with Some Transition Metals

The equilibrium geometries, energies, harmonic vibrational frequencies, and nucleus independent chemical shifts （NICS） of the new type sandwich structures [As4MAs4]^n- （M = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt; n = 0, 1 or 2） are investigated at the B3LYP level. All the [As4MAs4]^n- species adopt staggered （D4d） conformations as their stable structures and eclipsed （D4h） conformations as their transition states, and once the sandwich complexes are formed, the As4^2- square properties remain unchanged. The NICS calculation confirms that the complexes of Fe, Co, and Ni are aromatic with negative NICS values, and those of Ru, Rh, and lx exhibit slight aromaticity, while those of Pd, Os, and Pt show slight antiaromaticity.

Synthesis, Structure and Quantum Mechanical Calculations of Methyl 2-(5-((Quinolin-8-yloxy)-methyl)-1,3,4-oxadiazol-2-ylthio)-acetate

The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.

Eu^(3+)掺杂γ-Al_(2)O_(3)粉末的结构及其发光性能

通过化学沉淀法得到γ-Al_(2)O_(3):Eu^(3+)发光粉末,并分析其结构和发光特性。经研究得出:(1)掺杂Eu^(3+)会抑制氧化铝的结晶过程,γ-Al_(2)O_(3)的禁带宽度随着掺杂浓度的增加而降低,最佳的Eu^(3+)掺杂浓度为4%(摩尔分数),浓度继续增加时,会发生淬灭现象,使得发光强度降低;(2)在396nm监测波长下,最强发射峰约为618 nm,对不同发射峰的比值得,在γ-Al_(2)O_(3)晶格中,Eu^(3+)掺杂进入后大多数占据的位置是是非中心对称;(3)对于纯氧化铝粉末中的Cr^(3+)杂质,在未掺杂时出现发射峰,但由于量少,与Eu^(3+)的发射峰发生重合,只在695nm有一发光强度极低的发射峰。