MgO相分离对MgxZn1-xO纳米粉体结构和光学性能的影响

采用溶胶-凝胶法制备了MgxZn1-xO(x=0,0.1,0.2,0.3,0.4,0.5)纳米粉体。X射线衍射谱表明:在较高的温度(850℃以上)下退火,MgxZn1-xO纳米粉体从单一的纤锌矿结构相中分离出MgO相的掺杂浓度x约为0.13,且随着x的增加,MgO相含量呈指数型增长。室温光致发光谱显示:MgO相分离对紫外与绿光发射的相对强度有直接的影响,随着MgO相分离的出现,紫外发光峰蓝移,并随着MgO相的增加,紫外发光峰的强度受抑,绿光发光峰变强。样品的室温透过率显示:MgxZn1-xO的禁带宽度在x=0.1时达到最大值并受MgO相分离的影响而减小。     

溶胶-凝胶法制备高Mg含量Zn1-x MgxO薄膜

采用溶胶-凝胶法在石英玻璃基板上制备了ZB1-xMgxO薄膜,研究退火温度对高Mg含量Zn0.5Mg0.5O薄膜的相组成、相偏析及紫外-可见透过光谱中吸收边移动的影响,当退火温度≤500℃时,Zn0.5Mg0.5O薄膜未发生相偏析现象,且400℃退火处理制备的Zn0.5Mg0.5O薄膜的紫外-可见透过光谱中吸收边蓝移最大.因此,对于高Mg含量Zn0.5Mg0.5O薄膜,退火温度是影响Mg2+在ZnO中固溶度的关键因素,且400℃是其理想的退火温度.在此条件下研究了不同Mg含量对Zn1-xMgO(x=0～0.8)薄膜带隙调节的影响,随着Mg含量的增加,其紫外-可见透过光谱中紫外光区吸收边呈现规律性蓝移,光学带隙值Eg从纯ZnO的3.3 eV调节至4.2 eV.     

Mg掺杂浓度对MgxZn1-xO薄膜结构和光学性能的影响

通过超声喷雾热解工艺在P型<100>Si衬底上制备了不同Mg掺杂浓度的纳米MgxZN1-xO薄膜.通过扫描电镜(SEM)、X射线光电子能谱(XPS)、X射线衍射(XRD)和光致发光(PL)谱的测试对不同Mg掺杂浓度下薄膜的表面形貌、成分、品体结构和光学性能进行了研究.SEM测试结果表明,低Mg掺杂浓度时,MgxZn1-xO表面平整致密,但随Mg浓度的增加,薄膜表而平整度降低.XRD测试结果表明在低浓度下MgxZn1-xO薄膜足ZnO的纤锌矿结构,而没有出现MgO的分相,ZnO的衍射峰峰强随Mg浓度的增加逐渐减弱.不同Mg掺杂浓度下的光致发光谱图均出现了近带边紫外发射峰和可见光发射峰,其中近带边紫外发射峰随掺杂浓度的增大出现了明显的蓝移.     

Cu过量对Cu1+x Al1-x O2(0≤x≤0.04)薄膜结构与光电性能的影响

以单相多晶Cu1+x Al1-x O2陶瓷做靶材,采用射频磁控溅射方法在石英衬底上沉积了Cu过量的Cu1+x Al1-x O2(0≤x≤0.04)薄膜.通过X射线衍射(XRD)、紫外吸收光谱以及电导率的测试,表征了不同含Cu量Cu1+x Al1-x O2薄膜的结构与光电性能.结果表明,沉积态薄膜经退火处理后,由非晶转变为具有铜铁矿结构的纯相Cu1+x Al1-x O2;退火态薄膜在可见光区域的平均透过率约为55;,平均可见光透过率不受Cu含量的影响;退火态薄膜样品的室温电导率随Cu含量的增加而增大,Cu1.04 Al0.96 O2的室温电导率最高,为1.22×10-2 S/cm;在近室温区(200～300 K),退火态薄膜均很好地符合Arrhenius热激活模式.     

热处理工艺对室温制备ZnO:Al薄膜结构与光电性能的影响

采用室温溅射加后续退火工艺制备了ZnO∶ Al透明导电薄膜.研究了热处理工艺对薄膜微观结构和光电性能的影响.研究表明:退火有助于减小Al~(3+)对Zn~(2+)的取代造成的晶格畸变,消除应力,促进晶粒长大,有效提高电子浓度和迁移率,降低电阻率;当溅射功率为80 W、退火温度为320 ℃时,薄膜的电阻率可低至8.6×10~(-4) Ω·cm;退火气氛对薄膜的导电性能有较大影响,真空退火可使吸附氧脱附,大大降低薄膜的方块电阻.而退火温度和退火气氛均对ZnO∶ Al薄膜的透光率没有明显影响,薄膜的透光率在86;以上.     

离子液体辅助溶胶-凝胶法制备ZnO∶Al透明导电薄膜及其光电性能研究

采用溶胶-凝胶法,以离子液体为辅助溶剂,在玻璃衬底上制备了ZnO∶Al(ZAO)薄膜。通过X-射线衍射(XRD)、场发射扫描电镜(FE-SEM)、紫外-可见分光光度计(UV-Vis)和霍尔效应等测试手段,分析了不同Al掺杂浓度ZAO薄膜的微观结构、光学和电学性能。结果表明,所制备的薄膜为非(002)取向的多晶膜。随着Al离子掺杂浓度的提高,薄膜的(002)晶面取向增强,晶粒逐渐由片状向球形转变,电阻率先降低后升高。进一步研究发现,在还原气氛NH3下退火可显著降低薄膜的电阻率,Al掺杂浓度为1 mol%时,薄膜电阻率达到4.7×10-2Ω·cm,可见光透过率平均在80%以上。     

真空退火温度对射频磁控溅射制备非晶In-Ga-Zn-O薄膜性能影响的研究

采用射频磁控溅射技术在室温下玻璃衬底上制备了铟镓锌氧(In-Ga-Zn-O)透明导电薄膜,并对该薄膜进行了真空退火.研究了不同退火温度对In-Ga-Zn-O薄膜结构、电学和光学性能的影响.X射线衍射(XRD)表明,在300℃至500℃退火温度范围内,In-Ga-Zn-O薄膜为非晶结构.随着退火温度的增加,薄膜的电阻率先减小后增大.透射光谱显示退火后In-Ga-Zn-O薄膜在500～ 800 nm可见光区平均透过率超过80;,且在350 nm附近表现出较强的紫外吸收特性.经过退火的薄膜光学禁带宽度随着退火温度的增加先增大后减小,350 ℃最大达到3.91 eV.     

溶胶-凝胶法制备LaNiO3薄膜及其电学性能研究

采用溶胶-凝胶法在SiO2/Si衬底上制备了LaNiO3薄膜,并通过改变退火温度和薄膜厚度对其微结构和电学性能进行了表征测试.X射线衍射(XRD)和电阻率测试结果表明,随着退火温度和厚度的增加,LaNiO3薄膜的结晶质量明显提高,薄膜电阻率也逐渐下降.当退火温度为800℃时,厚度为630 nm的LaNiO3薄膜电阻率最小,达到了1.37 mQ·cm.此外,利用LaNiO3薄膜作为下电极制备的2; Nb-Pb(Zr06Ti0.4)O3薄膜呈良好的钙钛矿相结构,且经过1010铁电循环测试周期以后,2; Nb-Pb(Zr06Ti0.4)O3薄膜的铁电性能未出现明显下降,表明该LaNiO3薄膜是生长PNZT铁电薄膜的优良下电极材料.     

溅射压强和退火气氛对Mg0.2Zn0.8O∶Al紫外透明导电薄膜结构与性能的影响

以自制Mg0.2Zn0.8O∶Al陶瓷为靶材,采用室温溅射后续退火磁控溅射工艺制备了Mg0.2Zn0.8O∶Al紫外透明导电薄膜.研究了溅射压强和退火气氛对Mg0.2Zn0.8O∶Al薄膜结构和光电性能的影响.结果表明:溅射氩气压强不影响薄膜的相结构,但对薄膜的取向生长和结晶质量有一定影响;薄膜的方块电阻随溅射压强的增加先大幅减小后有所增大,溅射气压为2.0 Pa时,薄膜的方块电阻最低;不同溅射气压下制备薄膜的透光范围均已扩展到了紫外区域,而且具有85;以上的高透射率,但溅射气压对薄膜的带隙宽度和透光率没有明显影响;室温下溅射制备的薄膜经真空退火处理后其导电性能显著提高,但在空气中退火处理后其导电性能反而有所下降.     

超声喷雾热解法制备铝掺杂氧化锌薄膜

采用超声喷雾热解法在玻璃衬底上制作了不同浓度Al掺杂的ZnO: Al薄膜(AZO).采用扫描电镜(SEM)、X射线衍射(XRD)、光致发光(PL)、反射光谱(Res)、四探针测试仪等测试了不同Al掺杂浓度下AZO薄膜的表面形貌、晶体结构和光学、电学性能.SEM结果表明低掺杂浓度时AZO表面致密,随着Al浓度的增加薄膜表面孔洞增多,平整度降低.XRD结果表明当nZn/nAl物质的量比为100: 5时, AZO薄膜为c轴择优取向纤锌矿结构.PL谱结果表明不同浓度的Al掺杂AZO薄膜具有近带边紫外发射和深能级发射两个发射峰,且紫外发射峰随着Al3+浓度的增加先蓝移后红移.反射光谱表明所有样品在可见光区的反射率较低..方阻测试结果表明当nZn/nAl为100: 5时,AZO薄膜具有良好的导电性.     

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.