Tb掺杂CaMnO3氧化物材料热电输运性能的研究

采用溶胶-凝胶法结合陶瓷烧结工艺制备了Tb掺杂CaMnO3基氧化物热电材料,系统研究了Tb掺杂材料物相组成、微观组织和和电输运性能.结果表明,Tb掺杂试样均为单一物相的CaMnO3晶体材料.随着Tb掺杂量的增加,试样晶粒逐渐细化.所得CaMnO3基材料内部晶粒互连,试样结构较为致密.所有Tb掺杂试样电阻率随温度升高而降低,呈明显的半导体传输特性,其中Tb掺杂量为0.14的试样电阻率最低.Tb掺杂试样Seebeck系数绝对值随掺杂量的增加而降低,这是由于Tb掺杂引入的电子型载流子造成的.所有试样功率因子均随温度升高而逐渐增加,并且所有Tb掺杂试样的功率因子均大于未掺杂试样.其中Tb掺杂量为0.08的块体试样功率因子在测试温度最高点973 K时达到最大值2.0×10-4 W·m-1·K-2,远高于未掺杂试样,通过稀土元素Tb掺杂可以优化CaMnO3基过渡金属氧化物材料的电性能.     

Tb3+/Sm3+掺杂KY3F10纳米晶的调制发光和能量转移

采用水热法合成了未掺杂和一系列Tb3 +/Sm3+掺杂KY3F10粉体.发射光谱表明,在300 nm激发下,5m3+:KY3F10中Sm3+发光随其掺杂量的增加而减弱;而在Tb3+单掺和Tb3 +/Sm3+共掺样品中,Tb3+发光在1 mol; ～ 20mol;区间内随其掺杂量的增加而增强.Tb3 +/Sm3共掺样品中存在Tb3+→Sm3+能量转移,最高能量转移效率可达93.70;.由于缺陷发光、交叉弛豫、能量转移的协同效应,无论对于单掺抑或共掺样品,皆可获得暖白光发射.且通过改变掺杂成份或激发波长,可实现基于该KY3F10粉体的蓝、绿、黄绿、黄橙、红橙、粉红等多色发光.     

Ba1-x(Na0.5Bi0.5)xZr0.1Ti0.9O3陶瓷的制备及性能研究

采用固相法制备Ba1-x(Na0.5Bi0.5)xZr01Ti0.O3(x=0,0.05,0.1,0.15,0.2)陶瓷,并研究Bi、Na共同掺杂对BaZr01Ti0.9O3陶瓷结构、相组成、介电和铁电性能的影响.研究表明,Bi、Na共掺杂可以降低BaZr01Ti0.9O3陶瓷的烧结温度,并且在现有的掺杂水平下,所得陶瓷均为单一钙钛矿结构.陶瓷的相对介电常数在x=0.05时,由未掺杂的800增至最大值1700左右.陶瓷的介电损耗随Bi、Na掺杂量的增加,呈增加趋势.铁电性研究表明,随Bi、Na掺杂量的增加,存在漏电流增大的趋势,使得铁电性恶化,当含量超过0.1后呈现非铁电性.由以上可知,掺杂少量的Bi、Na,可以在一定程度上提高BaZr0.1Ti0.9O3陶瓷的介电性.     

锌型复合无机抗菌材料的制备及性能研究

运用溶胶-凝胶法制备出二氧化硅载体,采用液相浸渍法制备得到锌型复合无机抗菌材料.结合响应曲面方法,考察了Zn2+浓度、pH和Tb3+浓度对材料抗菌率的影响,选取了较优制备条件:Zn2+浓度为0.3 mol·L-1,pH值为9,Tb3+浓度为0.01 mol·L-1.以大肠杆菌为菌种,通过稀释涂布平板法,对材料进行抗菌性能检测,抗菌结果表明,掺杂Tb3+后材料抗菌率从76;提高到97;,较优样的最小杀菌浓度为5.5 g/L.通过XRD、FTIR、SEM、EDS和BET方法对材料的结构进行表征,结果表明:载体二氧化硅为无定形态,材料中主要的抗菌成分是纤锌矿结构的ZnO,且呈絮状和花瓣状生长,锌元素质量分数为16.96;,掺杂铽元素后材料的比表面积明显增大,增加了材料与细菌的接触面积,从而抗菌性能显著提高.     

La2O3掺杂对BaTiO3-Nb2O5-Fe2O3陶瓷的晶体结构和介电性能的影响

研究了La2O3 掺杂对BaTiO3-Nb2O5-Fe2O3(BTNF)基陶瓷的晶体结构和介电性能的影响.XRD分析表明:La2O3掺杂陶瓷的(200)和(002)晶面衍射峰都发生了明显分裂,说明陶瓷均以四方相为主晶相.随着La2O3含量的增加,四方率先增大后减小.用SEM研究La2O3对BTNF基陶瓷微观结构的影响,结果表明:随着La2O3掺杂量的增加,试样的晶粒明显变小,La2O3显著的抑制了晶粒的生长.当La2O3掺杂量为0.15 mol;时,陶瓷晶粒生长比较均匀.陶瓷的室温介电常数大体上呈现出先增大后减小的趋势,当La2O3掺杂量为0.15 mol;时,有最大介电常数4562.     

氧化钨掺杂NBT-6BT陶瓷的结构表征与介电弛豫特性研究

采用传统固相反应法制备了WO3掺杂(Na0.5Bi0.)0.94 Ba0.06 TiO3 (NBT-6BT)陶瓷.研究了WO3掺杂对陶瓷样品微观结构和介电弛豫特性的影响.微观结构分析表明:随WO3掺杂,三方-四方共存相逐渐转变为三方相;WO3掺杂对陶瓷的致密度和晶粒尺寸影响不大.随WO3掺杂,陶瓷的介电常数逐渐降低,介电峰变得更加平坦,陶瓷介电常数的温度稳定性提高.居里-外斯和修正的居里-外斯定律较好地描述了陶瓷的弥散相变特征,随WO3掺杂量的增加,弥散指数下降.探讨了该体系陶瓷介电弛豫特性的机理.     

铬锰复合掺杂对氧化铝陶瓷真空耐压性能的影响

在掺有0.5wt; Cr2O3的95;氧化铝瓷基础上掺入0～1.5wt;的MnO2,研究了铬锰复合掺杂即MnO2掺入量对氧化铝陶瓷物相、显微结构、烧结性能、电阻率、介电常数和真空耐压性能的影响.结果表明,MnO2掺杂通过固溶进Al2O3晶格,促进了95;氧化铝陶瓷的烧结和晶粒生长,提高了显微结构的均匀性和致密性.随着MnO2掺入量的增加,材料的电阻率明显下降,介电常数略微减小.铬锰复合掺杂对氧化铝陶瓷真空耐压性能的影响与MnO2的掺入量密切相关.在掺0.5wt; Cr2O3的情况下,当MnO2掺入量为1～1.5wt;时,材料的闪络电压高于未掺杂MnO2的样品,掺1.5wt; MnO2样品的闪络电压最高,达54 kV/cm.     

La2O3对莫来石陶瓷微观组织结构的影响

采共沉淀法制备了高纯度莫来石前驱粉体,掺杂La2O3制备莫来石复合陶瓷.利用XRD、SEM等方法对矿物组成和显微结构进行分析表征,并用X'pert High score Plus软件计算莫来石晶格常数,间接分析La2O3掺杂机理.实验结果表明,La2O3的掺杂改变了莫来石陶瓷的微观组织结构,莫来石晶粒由短棒状转变为网状和层状结构;La2O3的掺杂改变了物相组成,生成La1.66Al23.08O37.04,有助于提高莫来石陶瓷的致密性,在1500℃烧成时试样达到理论密度的95;.     

B位四价Sn4+, Zr4+取代对Ba(Zn1/3Nb2/3)O3系统微观结构的影响

采用传统的固相陶瓷烧结工艺,利用四价正离子Sn4+、Zr4+取代Ba(Zn1/3Nb2/3)O3陶瓷的B位Zn2+、Nb5+,研究其对Ba(Zn1/3Nb2/3)O3系统微观结构的影响.四价Sn4+、Zr4+取代B位Zn2+、Nb5+可以形成固溶体,系统的主晶相仍为立方相.系统晶格常数a随着Sn4+取代量的增加而呈线性增大,相同Sn4+取代量下随着烧结温度的增加,晶格常数a增大.BaZrO3(BZ)的加入可减少第二相的生成.Sn4+、Zr4+均可改善系统烧结特性,加快致密化形成.     

Tb3+-Eu3+共掺杂2ZnO·2.2B2O3·3H2O的制备和发光性能

采用水热法合成了Tb3+和Eu3+共掺的2ZnO.2.2B2O3.3H2O红色荧光粉。通过固定Eu3+的掺杂浓度为3%(物质的量比:Eu∶Zn=3%),改变Tb3+的掺杂浓度(2%～15%),研究Tb3+掺杂浓度对红色荧光粉晶相结构和光学性能的影响。用X射线衍射和荧光光谱仪对样品的结构和发光性能进行表征,结果表明:随着Tb3+掺杂浓度的升高,样品由晶态向无定形的玻璃态转变;Eu3+的发光强度也逐渐增强;Tb3+与Eu3+之间存在能量传递的过程,且当采用不同的激发波长(220 nm和393 nm)激发时,其能量传递的过程也不一样。     

Sol-gel synthesis and characterization of adsorbent and photoluminescent nanocomposites of starch and silica

Using sol-gel method, mesoporous and photoluminescent silica nanocomposites of soluble starch have been synthesized and characterized. Different ratios of H₂O, TEOS and EtOH were used at fixed template (soluble starch) and catalyst (NH₄OH) concentrations to obtain materials of different performances in terms of heavy metal binding from a solution which has been monitored using Cd(II) as representative divalent heavy metal ion. Optimum material was obtained when H₂O, TEOS and EtOH were used in 14:1:2 ratio. This sample was not only an efficient metal ion adsorbent but also had an intense luminescence in ultra-violet region and potentially may be used in silicon-based UV-emitting devices. Metal binding by the material was further enhanced after calcination (at 800 °C in air) while its luminescence had a multipeak profile in UV-visible region. In a batch adsorption study, calcined hybrid composite (0.25 g/L) could remove 98.5% Cd(II) from 100 mg/L Cd(II) solution in 2 h. The chemical, structural and textural characteristics of the synthesized materials have been investigated using Fourier Transform Infrared Spectroscopy (FTIR), X-rays Diffraction (XRD), Thermal Analysis (TGA/DTA), Photoluminescence (PL), Brunauer-Emmett-Teller Analysis (BET) and Scanning Electron Microscopy (SEM).     

Syntheses and structures of N-phenylmaleimidetriazoles and by-products

The syntheses, properties, and structures of N-phenylmaleimidetriazole derivatives are described. Intermediates and by-products are also discussed. 1b. a = 43.997(7) Å, 5.7610(9) Å, 8.245(1) Å, = 99.339(4), C₂/c; 2a. a = 13.646(4) Å, b = 7.744(2) Å, c = 10.612(3) Å, = 91.979(6), P2₁/c. 3a. a = 22.245(1) Å, b = 22.245(1) Å, 10.010(1) Å, P42/n. 3a. a = 11.727(2) Å, b = 14.075(3) Å, c = 16.080(3) Å, = 105.859(3), = 105.331(3), = 98.187(3), P-1. 3b. a = 8.561(3) Å, b = 14.755(5) Å, c = 22.771(7) Å, = 97.006(5), P2₁/c. 3c. a = 10.500(2) Å, b = 12.189(2) Å, c = 13.040(2) Å, = 109.091(3), = 106.089(3), = 101.022(3), P-1. 8a. a = 16.389(8) Å, b = 5.749(3) Å, c = 19.316(3) Å, = 97.467(9), P2₁/n. 8b. a = 5.822(2) Å, b = 10.114(3) Å, c = 16.705(4) Å, = 84.681(5), = 82.840(5), = 75.769(4), P-1. 9b. a = 11.251(1) Å, 13.335(3) Å, 13.376(3) Å, = 102.456(4), P2₁/n. 9c. a = 15.836(3) Å, b = 8.236(2) Å, c = 5.447(3) Å, = 92.551(3), P2₁/c. 10a. a = 13.177(2) Å, b = 14.597(2) Å, c = 5.5505(8) Å, = 110.979(2), Cc. 11a. a = 14.720(2) Å, b = 13.995(2) Å, c = 38.245(6) Å, = 94.430(3), P2₁/n. 12b. a = 15.067(5) Å, b = 20.378(6) Å, c = 8.669(5) Å, = 99.16(4), = 99.32(3), = 105.23(3), P-1. 13b. a = 8.2824(6) Å, b = 10.5245(7) Å, c = 15.518(1) Å, = 92.305(1), = 100.473(1), = 100.124(1), P-1. 15a. a = 15.357(3) Å, b = 7.778(2) Å, c = 22.957(2) Å, Pbca. 16b. a = 18.0384(4) Å, b = 12.474(3) Å, c = 20.078(5) Å, Pbca.     

Surface topography and crystal and domain structures of films of ferroelectric copolymer of vinylidene difluoride and trifluoroethylene

The crystallization of a copolymer from a solution at room temperature is found to lead to the formation of a metastable structure, characterized by the coexistence of ferroelectric and paraelectric phases. The fraction of the latter decreases after annealing above the Curie point. Atomic force microscopy (AFM) has revealed a difference in the surface topographies between the films contacting with air and the films contacting with a glass substrate. The microstructure of copolymer chains has been investigated by ¹⁹F NMR spectroscopy. The chain fragments with “defect” attached monomeric units are ejected to the surface. The character of the ferroelectric domains formed during crystallization and their size distribution are analyzed.

     

Chemistry and Electrocrystallization of Organic Metals and Superconductors

Abstract

Considerable variation in the conditions of electrochemical crystal growth of TMTSF₂X (i.e., constant current versus constant potential, ambient versus inert atmosphere, etc.) and in the purity of the constituents (donor, electrolyte, solvent) does not significantly affect the unusual low-temperature properties of this class of materials. Our results suggest that the electrocrystallization procedure may be self-purifying by selecting for conducting crystal phases with constituents having specific oxidation potentials and solubility properties. However, doping solutions with structurally and chemically similar constituents (i.e., TMTTF, and IO^? ₄ in CIO^? ₄) leads to their incorporation in the crystal structure where they have a profound effect. Several mole percent of these dopants suppress superconductivity in the PF^? ₆ and CIO^? ₄ salts, and increase and broaden the metal-insulator phase transition.     

Hydrothermal Synthesis and Morphology of Thomsonite and Edingtonite

The hydrothermal treatment of different glasses of the composition 2 Na₂O–8 CaO–10 Al₂O₃– 20 SiO₂ and 2 BaO–2 Al₂O₃–6 SiO₂ at one kilobar pressure in a temperature-range between 80 °C and 230 °C lead to the formation of the zeolite-minerals thomsonite (orthorhombic symmetry space-group Pbmn, a = 13.05 Å, b = 13.09 Å and c = 13.22 Å), and edingtonite (orthorhombic symmetry, space-group: P2,2,2, a = 9.55 Å, b = 9.67 Å and c = 6.52 Å). Under the chosen hydrothermal conditions both mineral phases are formed in the whole temperature interval.     

Numerical and experimental analysis of periodic patterns and sedimentation of lysozyme

This paper deals with experimental investigation, mathematical modelling and numerical simulation of the crystallization processes induced by counter diffusion method of a precipitant agent in a lysozyme protein solution. Novel mathematical strategies are introduced to simulate the experiments and in particular to take into account the kinetics of the growth process and the motion of the crystals due to the combined effect of gravitational force and viscous drag if the sedimenting process is allowed (protein chamber free of gel). Comparison between experimental observations and numerical simulations in the presence of convection and sedimentation and without them provides a validation of the model. The crystal formation in gel results modulated in space. If the gel matrix is not present, convective cells arise in the protein chamber due to local inversions in the density distribution associated to nucleation phenomena. As time passes, these vortex cells migrate towards the top of the protein chamber exhibiting a different wave number according to the distance from the gel interface. The sedimentating particles produce a wake due to depletion of protein from the surrounding liquid. The models and the experiments may represent a useful methodology for the determination of the parameters and conditions that may lead to protein crystallization.     

Structural and spectral studies of N-trans-cinnamylidene-m-toluidine and N-trans-cinnamylidene-m-chloroaniline

N-trans-cinnamylidene-m-toluidine (1) C₁₆H₁₅N, and N-trans-cinnamylidene-m-chloroaniline (2) C₁₅H₁₂NCl form isomorphous crystals which are monoclinic, space group P2_l/c, with unit cell dimensionsa=5.967(2),b=13.793(3),c=15.048(5) Å, =91.97(3)° anda=5.868(2),b=13.788(4),c=15.191(4) Å, =91.87(3)°, respectively. The single-crystal X-ray structure determinations of the title compounds revealtrans structures. Ring (A) C_10–15 and ring (B) C_1–6, are practically planar in both structures with dihedral angels of 61.3(3) and 63.6(2)°, respectively.¹H nmr, u.v. and i.r. spectra are also reported.     

Preparation and characterization of PbSe nanopowder and quasi-ceramics

By means of the reduction of Pb(II) and Se(IV) with hydrazine, oval monodispersed PbSe nanoparticles characterized by sizes ～100 nm and the cubic symmetry were obtained. Their compaction and sintering into quasi-ceramic state were performed. The samples were investigated by means of scanning electron microscopy, X-ray diffraction and FTIR spectroscopy. The results obtained are discussed.     

Crystal and molecular structures of benz-p-nitroanilide and benz-p-methoxyanilide

The crystal structures of the two carboxylic amides C₁₃H₁₀N₂O₃ (I) and C₁₄H₁₃NO₂ (II) have been determined by direct methods and refined by full-matrix least squares. The predominant structural feature is the hydrogen bonding (N-H?O=C) which influences the conformations of both structures.     

Structure simulation and study of electronic and dielectric properties of two derivatives of benzamide

First-principles calculations based on density functional theory have been done on the chlorinated phenyl benzamides; 4-chloro-phenyl-benzamide – C13H10ClNO, and 2-chloro-3-chloro-phenyl-benzamide – C13H9Cl2NO. The triclinic structure of 4-chloro-phenyl-benzamide and orthorhombic structure of 2-chloro-3-chloro-phenyl-benzamide have been simulated and the structural parameters have been found out. Electron density of states has been computed in the materials using the electronic structure calculation code of Quantum-Espresso which gives a band gap of 0.74 eV in case of 4-chloro-phenyl-benzamide. This value is close to the value exhibited by semiconducting materials and photonic band gap materials. Band gap in case of 2-chloro-3-chloro-phenyl-benzamide comes out to be 3.08 eV. This value is in the range exhibited by NLO materials. Dielectric constant of the materials has been computed. The value of dielectric constant in 4-chloro-phenyl-benzamide comes out to be 2.78, 3.14, and 3.92 along X, Y, and Z axes, respectively, and the average value comes out to be 3.28. The value of dielectric constant in case of 2-chloro-3-chloro-phenyl-benzamide comes out to be 1.39, 1.53, and 1.34 along X, Y, and Z axes, respectively, and the average value comes out to be 1.42. Thus, additional chlorination is increasing the band gap and decreasing the dielectric constant in phenyl benzamide.