静电纺In2O3纳米纤维的光致发光性能研究

利用静电纺丝技术结合高温煅烧方法制备了一系列多孔结构的一维In2O3无机纳米纤维,并探讨了煅烧温度对产物发光性能的影响及其发光机理.利用热重仪(TGA)、X射线衍射仪(XRD)、傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)分析了产物的热分解情况、晶型、组分和形貌;通过紫外-可见光谱仪和荧光分光光度计分析研究了一维In2O3纳米纤维的光吸收性能和光致发光性能.结果表明:静电纺前驱体复合纳米纤维成型良好,经500℃、600℃、700℃、800℃高温煅烧后仍保持纤维结构,但纤维直径明显减小,当煅烧温度达到800℃时,纤维出现中空结构;不同温度下煅烧所得In2O3均为立方铁锰矿型;随着煅烧温度的升高,In2O3纳米颗粒粒径逐渐增大;In2O3纳米纤维的的最大紫外吸收峰位于300nm左右;在室温下,In2O3纳米纤维经274nm光激发后在553 nm处出现较强的绿光发射峰.     

共沉淀法制备Gd2Zr2O7纳米粒子

采用反向滴定共沉淀法制备了Gd2Zr2O7纳米粒子,用XRD、SEM、TEM、TG-DTA等测试手段分析了煅烧温度和时间、体系温度、pH值、初始浓度、表面活性剂含量(SDBS)对前驱体的物相、形貌及晶粒大小的影响。结果表明:五种因素分别对Gd2Zr2O7相变化无影响,以氨水做沉淀剂经反向滴定,当体系温度为0℃、母盐溶液初始浓度为0.01mol/L、pH值为11、SDBS含量2wt%时,在1100℃煅烧3 h制备出近球形的Gd2Zr2O7纳米粒子,粒径约40 nm。     

氨配合法控制合成片状纳米氧化锌

以次氧化锌为原料,采用氨配合法制备片状纳米氧化锌.制备过程包括氨浸、净化、脱氨、煅烧等工序.重点研究了添加剂用量、反应温度、空气流量、锌氨络合溶液浓度对片状纳米氧化锌前驱体形貌的影响,以及煅烧温度和煅烧时间对片状纳米氧化锌产品影响.利用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)对产品进行表征.结果表明:在添加剂的加入量为0.5;(质量分数)、反应温度为90 ℃、空气流量为7 L· min-1、锌氨络合溶液浓度为1.13 mol· L-1,煅烧温度为350 ℃,煅烧时间为6 h条件下,制备的产品为片状纳米氧化锌,片层厚度在10 nm左右,产品纯度达99.13;.     

Ba(Co1/3Nb2/3)O3微波介质陶瓷预烧温度研究

采用传统固相法制备Ba(Co1/3Nb2/3)O3微波介质陶瓷。研究了预烧温度对其物相组成、显微结构、烧结性能、微波介电性能的影响。结果表明:在不同预烧温度下制备的陶瓷样品主晶相为复合钙钛矿结构的Ba3CoNb2O9,900℃、1000℃有微量Ba3Nb5O15生成。最佳预烧温度为1100℃,在1380℃烧结4 h时,εr=31.8,Q×f=60164GHz,τf=-15×10-6/℃。合适的预烧温度能有效抑制第二相的生成,提升材料致密度,促使主晶相B位有序排列,进而降低介电损耗。     

溶液燃烧法制备纳米硼酸铝及其表征

以九水硝酸铝、硼酸、甘氨酸、尿素为原料,通过溶液燃烧法制备了纳米硼酸铝.分别采用热重-差热分析(TG-DTA)、X射线衍射(XRD)分析、扫描电子显微镜(SEM)测试手段,对产物前驱体及最终产物作表征,探讨了燃烧剂种类、煅烧温度、煅烧时间、原料配比等工艺参数对产物物相、形态、粒度等的影响.结果表明,以甘氨酸为燃烧剂,n(硝酸铝)∶n(甘氨酸)=3∶5,煅烧温度为1200℃,煅烧时间为4h时,可合成结晶度较好、规则的纳米硼酸铝(Al18B4O33)颗粒,其平均粒径在80 nm左右.     

铝掺杂超细氧化锌粉体的制备与性能研究

本文以Zn(NO3)2·6H2O和Al(NO3)3·9H2O为原料采用均匀沉淀法制备了Al掺杂ZnO(ZAO)超细粉体,用XRD、SEM、纳米粒度分析仪及四探针电阻仪等对ZAO超细粉体进行了测试表征.研究了反应温度、煅烧温度、反应物浓度、Al掺杂量及分散剂添加量对ZAO超细粉体形貌、尺寸及电阻率的影响.研究结果表明:制备的ZAO粉体为纤锌矿结构;煅烧温度为550℃时,ZAO晶相形成很好;随着Al掺杂量的增加,ZAO粉体电阻率降低,晶格常数减小,但当Al掺杂量大于2.0 mol;时,生成尖晶石相,其电阻率反而上升.     

水热-固相法制备Gd2Zr2O7纳米粒子

以Gd2O3和ZrOCl2.8H2O为原料,氨水为矿化剂,在200℃和12～30 h的水热条件下合成的前驱体,经固相反应获得Gd2Zr2O7纳米粒子。用X射线衍射(XRD)、热重差热(TG-DTA)、傅立叶变换红外光谱(FT-IR)、扫描电镜(SEM)等测试手段分析了样品合成过程的物相变化、产物结构及形貌特征。结果表明:在n(Gd)∶n(Zr)=1∶1,水热合成温度200℃,pH=11,保温24 h,合成的前驱体经1000℃、2 h煅烧获得分散性好、形貌近球形、粒径约23nm的Gd2Zr2O7纳米粒子。     

钙钛矿型Ba0.5Sr0.5Co0.8Fe0.2O3-δ透氧膜材料的制备及其透氧性能的研究

通过甘氨酸硝酸盐法(GNP)合成了钙钛矿型Ba0.5Sr05Co0.8Fe0.2O3-δ(BSCF)复合氧化物粉体.经压制、烧结后,得到了BSCF烧结体试样,还通过硝酸溶液浸蚀处理对烧结体试样进行了表面浸蚀处理.采用X射线衍射仪(XRD)对煅烧后的粉体进行了相成分分析;采用扫描电子显微镜(SEM)及能谱仪(EDS)对烧结体和表面浸蚀后烧结体样品的微观组织和成分进行了表征;对烧结体的致密度、电导率进行了测试分析,并在自制的氧渗透装置上测定了BSCF钙钛矿膜的透氧量,分析了温度和不同氧分压差等对膜透氧性能的影响.实验结果表明,甘氨酸-硝酸盐法所制备的前驱体粉末在900℃煅烧3h后可获得具有单一钙钛矿结构的BSCF粉体,1100℃煅烧的BSCF烧结体的电导率在600℃时最大达到38.15 S·cm-1.其透氧量随着温度和氧分压差的升高而增大,且硝酸表面浸蚀处理后,BSCF膜片的透氧性能有明显提高,透氧速率提高1.6～4.5倍.850℃,20;O2-80;N2混合气体/He条件下,浸蚀后的透氧膜片的透氧量达到2.36 mL/cm2 · min,而未浸蚀透氧膜片的透氧量仅为1.36 mL/cm2·min.     

纳米TiO2薄膜的制备与光催化性能研究

以四氯化钛为前驱体,采用水解沉淀法,在不同的水解温度下,在硅藻土基多孔陶瓷上负载纳米TiO2薄膜,结合XRD和TEM对负载的纳米TiO2粒径进行了表征。对比分析了测试方法及水解温度对纳米TiO2粒径的影响。以罗丹明B为目标降解物,考察了水解温度对光催化剂活性的影响。结果表明:样品经550℃煅烧后,TiO2薄膜为锐钛矿型;水解温度为50℃时TiO2粒径小于水解温度为75℃时所负载纳米TiO2粒径;两种方法所测TiO2粒径有一定差异:dXRD>dTEM;水解温度为50℃所负载纳米TiO2薄膜,紫外光照300 min,对罗丹明B的去除率为89.9%,而75℃时,样品在紫外光照330 min,对罗丹明B的去除率为78.6%。     

反应温度和时间对纳米氧化镁形貌和结构的影响

以六水合氯化镁(MgCl2·6H2O)为镁源,水合肼(N2H4·2H2O)为沉淀剂,采用化学共沉淀法制备纳米氢氧化镁前驱体煅烧得到分散性良好的不同纳米结构的氧化镁(MgO)纳米片.通过XRD、SEM、TEM对产物的结构和形貌进行分析,初步研究了反应温度和时间对MgO纳米片的形貌和结构影响,分析了MgO多孔纳米片的生长机理.结果表明:25℃,24h下MgO纳米片大小均一尺寸在20～40 nm;当温度升高到100℃,72 h生长的多孔MgO纳米片缺陷多,是晶粒相互连接起来的,纳米孔洞在10 nm;140℃72 h制备的多孔纳米片尺寸均一在100～200nm.因此可以通过调节反应温度和时间来控制多孔氧化镁纳米片结构.     

Crystal and Molecular Structures of C6H5CH2SOCH2CONHCH2C6H5 and C6H5SOCH2CON(iC3H7)2

Abstract  The crystal structures for two of the ligands C₆H₅CH₂SOCH₂CONHCH₂C₆H₅ (1) and C₆H₅SOCH₂CON(ⁱC₃H₇)₂ (2) have been determined by X-ray diffraction. These compounds crystallize in orthorhombic system with space groups and cell parameters, Pca21(no. 29), a = 8.4600(5) ?, b = 5.3534(5) ?, c = 32.136(2) ?, V = 1455.42(15) ?³ and Pna21(no. 33) a = 17.5563(11) ?, b = 5.7902(4) ?, c = 14.2866(9) ?, V = 1452.30(16) ?³, respectively. These molecules are stabilized in solid state by various intra and intermolecular hydrogen bonding interactions to give polymeric structures. The reported IR spectra of these compounds in solid state could be explained on the basis of the observed intermolecular hydrogen bonding interactions. Index Abstract  The title compounds C₆H₅CH₂SOCH₂CONHCH₂C₆H₅ (1) and C₆H₅SOCH₂CON(ⁱC₃H₇)₂ (2) were prepared by the oxidation of corresponding sulfides with H₂O₂/SeO₂ in methanol and their structures were determined. The structures show that the SO and CO groups are having “anti” configuration in 1 and “syn” configuration in 2. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Enantiomorphism of the Ca3Ga2Ge4O14 compound and comparison of the Ca3Ga2Ge4O14 and Sr3Ga2Ge4O14 structures

The absolute crystal structures of two enantiomorphic forms of the Ca₃Ga₂Ge₄O₁₄ crystals (a = 8.075(1) ?, c = 4.9723(6) ?, space group P321) with the positive and negative senses of the optical activity are determined using X-ray diffraction analysis. The final R factors are as follows: R = 1.75% and R _w = 2.57% for the crystal with the positive sense of the optical activity and R = 1.86% and R _w = 2.78% for the crystal with the negative sense of the optical activity. The replacement of the Ca²⁺ ions by larger Sr²⁺ ions (with the formation of the Sr₃Ga₂Ge₄O₁₄ compound) leads to an anisotropic expansion of the crystal lattice (with a more considerable increase in the lattice parameter a as compared to the lattice parameter c), a change in the occupation of the 1a and 3f positions by the Ga³⁺ and Ge⁴⁺ ions, and symmetrization of the octahedra and tetrahedra forming the structural framework. The shape of the dodecahedron changes so that its size along the polar electric axis 2 increases significantly. This change is the main factor responsible for the increase in the piezoelectric activity of the Sr₃Ga₂Ge₄O₁₄ compound as compared to the piezoelectric activity of the Ca₃Ga₂Ge₄O₁₄ compound. Original Russian Text ? B.V. Mill, A.A. Klimenkova, B.A. Maximov, V.N. Molchanov, D.Yu. Pushcharovsky, 2007, published in Kristallografiya, 2007, Vol. 52, No. 5, pp. 816–823.     

Potentiodynamic polarization studies on amorphous Zr46.75Ti8.25Cu7.5Ni10Be27.5, Zr65Cu17.5Ni10Al7.5, Zr67Ni33 and Ti60Ni40 in aqueous HNO3 solutions

Potentiodynamic polarization studies were carried out on virgin specimens of Zr-based bulk amorphous alloys Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5 and Zr₆₅Cu_17.5Ni₁₀Al_7.5, and conventional-type binary amorphous alloys Zr₆₇Ni₃₃ and Ti₆₀Ni₄₀ in solutions of 0.2 M, 0.5 M and 1.0 M HNO₃ at room temperature. The values of the corrosion current density (I_corr) for the bulk amorphous alloy Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5 were found to be comparable with those of Zr₆₅Cu_17.5Ni₁₀Al_7.5 in 0.2 M and 0.5 M HNO₃, but the value of I_corr for the former was almost three times more than that of the latter in 1.0 M HNO₃. In the case of conventional binary amorphous alloys, Ti₆₀Ni₄₀ showed lower value of I_corr as compared to Zr₆₇Ni₃₃ in 0.5 M and 1.0 M HNO₃ and a comparable value of I_corr in 0.2 M HNO₃. In general, the binary Ti₆₀Ni₄₀ displayed the best corrosion resistance among all the alloys in all the cases and the corrosion current density (I_corr) for all the alloys was found to increase with the increasing concentration of nitric acid. It is noticed that the bulk amorphous alloys do not possess superior corrosion resistance as compared to conventional binary amorphous alloys in aqueous HNO₃ solutions. The observed differences in their corrosion behavior are attributed to different alloy constituents and composition of the alloys investigated.     

Ionic conduction in As2S3---Ag2S, GeS2---GeS---Ag2S and P2S5---Ag2S glasses

The glass-forming region in the system P---S---Ag was determined and density, thermal expansion, dc conductivity and the transport number of Ag ions were measured for P₂S₅---Ag₂S glasses found in the P---S---Ag system. The results for the transport number measurement show that P₂S₅---Ag₂S glasses are purely ionic conductors owing to the Ag ion migration, like most of the As₂S₃---Ag₂S and GeS₂---GeS---Ag₂S glasses reported previously. Glass structure and ionic conduction processes in As₂S₃---Ag₂S, GeS₂---GeS---Ag₂S and P₂S₅---Ag₂S glasses are discussed, based on their ionic conductivity and density data. The structural concept of -Ag₂S was applied to these glasses, which suggests that the Ag ions in the glasses are distributed in the available Ag ion sites in the non-conducting framework composed of both S anions and As, Ge or P cations. In each system the ionic conductivity increases linearly with increasing Ag⁺/total cation (%) in glass composition, the determining factor being the activation energy for ionic conduction alone. Thus, the activation energy in these glasses depends predominantly upon the molar ratio of Ag ions to total cation in the glass, irrespective of the kind of system. Small differences in the activation energy among the three systems can be interpreted as arising from differences in the field strength of As, Ge and P cations.     

Precipitation of In2O3 nano-crystallites from glasses in the system Na2O/B2O3/Al2O3/In2O3

Glasses in the system Na₂O/B₂O₃/Al₂O₃/In₂O₃ were melted and subsequently tempered in the range from 500 to 700 °C. Depending on the chemical composition, various crystalline phases were observed. From samples without Al₂O₃, In₂O₃ could not be crystallized from homogeneous glasses, because either spontaneous In₂O₃ crystallization occurred during cooling, or other phases such as NaInO₂ were formed during tempering. The addition of alumina, however, controlled the crystallization of In₂O₃. Depending on the crystallization temperature applied, the crystallite sizes were in the range from 13 to 53 nm. The glass matrix can be dissolved by soaking the powdered glass in water. This procedure can be used to prepare nano-crystalline In₂O₃-powders.     

Phase separation and crystallization in the system SiO2-Al2O3-P2O5-B2O3-Na2O glasses

The phase separation and crystallization behavior in the system (80 − X)SiO₂ · X(Al₂O₃ + P₂O₅) · 5B₂O₃ · 15Na₂O (mol%) glasses was investigated. Glasses with X = 20 and 30 phase separated into two phases, one of which is rich in Al₂O₃-P₂O₅-SiO₂ and forms a continuous phase. Glasses containing a larger amount of Al₂O₃-P₂O₅ (X = 40 and 50) readily crystallize and precipitates tridymite type AlPO₄ crystals. It is estimated that the phase separation occurs forming continuous Al₂O₃-P₂O₅-SiO₂ phase at first, and then tridymite type AlPO₄ crystals precipitate and grow in this phase. Highly transparent glass-ceramics comparable to glass can be successfully obtained by controlling heat treatment precisely. The crystal size and percent crystallinity of these transparent glass-ceramics are 20-30 nm and about 50%, respectively.     

Crystal growth of NdAl3(BO3)4 from K2O/MoO3/Nd2O3/B2O3/KF flux

NdAl₃(BO₃)₄ single crystals were grown by the flux method and the TSSG technique using a K₂O/3MoO₃/B₂O₃/0.5Nd₂O₃/KF flux system. Light-violet clear crystals could be obtained. The effects of fluoride on the growth of NAB crystals were investigated. As the content of KF was gradually increased, the growth form of NAB was changed from the equant to the columnar and the primary crystalline region of NAB was shrinked. At the ratio of KF/K₂O = 0.75, NAB crystals could not be grown.     

Spectroscopic properties of Er-doped Na2O-Sb2O3-B2O3-SiO2 glasses

Spectroscopic properties of Er³⁺-doped Na₂O-Sb₂O₃-B₂O₃-SiO₂ glasses have been investigated for developing 1.5-μm broadband fiber amplifiers. An intense 1.5-μm near infrared emission with a broad full width at half maximum (FWHM) of 88 nm has been obtained for Er³⁺-doped 5Na₂O-20Sb₂O₃-35B₂O₃-40SiO₂ glass upon excitation with a 980 nm laser diode. The obtained emission cross-section of the ⁴I_13/2 → ⁴I_15/2 transition and the lifetime of the ⁴I_13/2 level of Er³⁺ ions are 6.8 × 10⁻²¹ cm² and 0.36 ms, respectively. It is noted that the product of the emission cross-section and the FWHM of the glass, σ_e × FWHM, is as great as 598.4 × 10⁻²¹ cm² nm, which is comparable or higher than that of Er³⁺-doped bismuth-based and tellurite-based glasses. These special optical properties encourage in identifying them as important materials for potential applications in high performance optics and optical communication networks.     

The growth and structure of Pb3Ga2Ge4O14 and Ba3Ga2Ge4O14 single crystals

Conditions for the flux synthesis of Pb₃Ga₂Ge₄O₁₄ and Ba₃Ga₂Ge₄O₁₄ single crystals and their solid solutions Pb_{3 − x} Ba_xGa₂Ge₄O₁₄ are studied. Structural analysis showed that the Ga³⁺-and Ge⁴⁺-cation positions in flux-grown Pb₃Ga₂Ge₄O₁₄ and Ba₃Ga₂Ge₄O₁₄ single crystals are not mixed. __________ Translated from Kristallografiya, Vol. 49, No. 2, 2004, pp. 325–328. Original Russian Text Copyright ? 2004 by Bezmaternykh, Vasil’ev, Gudim, Temerov. This work was presented at the National Conference on Crystal Growth (NCCG-2002, Moscow).     

Refinement of the crystal structures of the La3Ta0.5Ga5.5O14 and La3Nb0.5Ga5.5O14 compounds

This paper reports on the results of accurate X-ray structural investigations of single crystals La₃Ta_0.5Ga_5.5O₁₄ (a = 8.2260(1) ?, c = 5.1207(1) ?, R/R _w = 1.09%/1.10%, 3868 unique reflections) and La₃Nb_0.5Ga_5.5O₁₄ (a = 8.2237(1) ?, c = 5.1247(1) ?, R/R _w = 1.02%/1.03%, 3735 unique reflections) (space group P321, Z = 1, sinϑ/λ|_max ≈ 1.34 ?⁻¹ for both compounds). Using sets of data with a large number of high-angle reflections makes it possible to reliably compare the crystal structures by applying statistical tests. The structural differences between the La₃Ta_0.5Ga_5.5O₁₄ and La₃Nb_0.5Ga_5.5O₁₄ crystals are weakly pronounced, which correlates with the closeness of their piezoelectric characteristics. Original Russian Text ? A.P. Dudka, B.V. Mill, Yu.V. Pisarevsky, 2009, published in Kristallografiya, 2009, Vol. 54, No. 4, pp. 599–607.