Nd:NaY(WO4)2晶体生长与性能研究

Nd:NaY(WO4)2(简称Nd:NYW)是一种性能优良的激光晶体.本文采用提拉法生长出了四方晶系白钨矿结构的Nd:NYW晶体,通过TG-DTA分析得到晶体的熔点为1208.7℃,并分析了晶体的吸收光谱.通过比较Nd:NaBi(WO4)2(简称Nd:NBW)和Nd:NYW的红外光谱和拉曼光谱结果,认为二者结构基本相同,为四方晶系、白钨矿结构、I41/a空间群.     

固相反应调控合成不同形貌的ZnO纳米晶体

用不同锌盐与氢氧化钠,通过固相反应合成ZnO纳米材料,研究不同原料配比、锌盐种类和表面活性剂对ZnO纳米晶体形貌的影响。用XRD、FE-SEM分析了ZnO产物的物相组成与显微形貌。研究结果表明:当锌盐与氢氧化钠的物质的量比为1∶2时,合成的ZnO晶体均呈颗粒状,以Zn(NO_3)_2和ZnCl_2为锌盐,得到的ZnO纳米晶体平均粒度分别为50nm和60nm,而以Zn(CH_3COO)_2为锌盐,得到的ZnO晶体粒度为80~620nm;当锌盐与氢氧化钠的物质的量比为1∶5时,以Zn(NO_3)_2和Zn(CH_3COO)_2为锌盐,合成的ZnO呈薄片状,以Zn(NO_3)_2为锌盐,得到的ZnO晶体片厚30nm,片长180nm,而以Zn(CH_3COO)_2为锌盐,得到的ZnO晶体片厚50nm,片长500nm,当锌盐为ZnCl_2时,其产物呈颗粒状,晶体粒度为120~400nm;原料中添加表面活性剂(十二烷基苯磺酸钠),对产物的形貌有较大影响,以Zn(NO_3)_2为锌盐,与氢氧化钠的物质的量比分别为1∶2和1∶5时,可分别得到片状与颗粒状的ZnO。     

锶掺杂对钛酸镧钡陶瓷结构相变和拉曼电荷效应的影响

采用X射线衍射(XRD)和拉曼光谱(RS)技术调查了(Ba0.97-x La0.03Sr x)Ti0.9925O3(x=0.015-0.2)陶瓷的结构特征.结果表明:当x≤0.1时,晶体维持在四方结构,当Sr含量增加到0.2时,晶体由四方相变为伪立方相.伴随着结构相变,Sr掺杂对(Ba0.97La0.03)Ti0.9925O3陶瓷的拉曼电荷效应产生影响.     

溶液pH值对PbWO4晶相和形貌的影响

在30℃下,以Na2WO4和Pb(NO3)2为原料,通过沉淀反应制备PbWO4晶体。考察Pb(NO3)2溶液的pH值对PbWO4的晶型和形貌的影响。通过XRD、Raman和SEM等表征,发现在酸性和碱性溶液中分别得到了梭状和八面体状的四方晶相PbWO4晶体,而在中性溶液中,得到单斜晶相PbWO4纳米带,表明pH值显著影响Pb-WO4的晶型和形貌。室温下,以300nm为激发波长研究产物的固体荧光光谱,发现碱性条件下得到的四方相Pb-WO4八面体具有最强的绿发光带,表明PbWO4的荧光性质受其晶型和形貌影响。     

2,5-二(2-羟丙氨基)-1,4-苯醌的合成

以对苯二酚和异丙醇胺为原料,并以乙醇为溶剂直接合成2,5-二(2-羟丙氨基)-1,4-苯醌.实验结果表明,对苯二酚和异丙醇胺的物质的量比为1∶4,在50℃下反应3h为最佳实验条件,产率达到65.31%,产物为红色针状晶体.对产物结构用红外、紫外、核磁及质谱进行了表征.     

六角状SmF3:Eu3+纳米晶体的制备与表征

采用水溶液沉淀法成功地制备了具有六角状结构的SmF3Eu3 纳米晶体. 分别采用了X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和光致发光光谱仪(PL)等手段对产物的晶体结构、形貌、光致发光性能进行了表征.结果表明产物为纯相六方晶系的SmF3晶体,且具有由规则六方状结构、尺寸分布较均匀等特点.最后对掺杂5mol%Eu3 离子的SmF3晶体的发光光谱作了初步的分析,发现其在波长为325 nm的激发源激发下,发出强烈的红光且单色性较好.     

PZN-PMN-PT铁电晶体的生长及表征

本文采用高温溶液法制备了PZN-PMN-PT晶体,利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)分析了晶体的结构和微观形貌,通过偏光显微镜和介电温谱观测了晶体电畴和介电性能随温度的变化.研究结果表明,采用高温溶液法可以制备出纯钙钛矿相结构的PZN-PMN-PT晶体,晶体颗粒呈淡黄色多面体形态,最大尺寸为4mm×2.5mm×2mm,电畴的消光角为45°,三方四方相变温度达113℃,居里温度高达246℃.PZN-PMN-PT晶体的三方四方相变温度和居里温度均高于PZN-PT和PMN-PT晶体.     

微波辐射条件下SAPO-5分子筛的合成与表征

以异丙醇铝、磷酸、正硅酸乙酯为反应原料,三乙胺作为模版剂,功率800 W、180℃微波辐射30min合成了粒径均一、具有AFI拓扑结构的SAPO-5分子筛,系统研究了Al2O3与SiO2摩尔比和HF添加量等因素对产物长径比和晶体形貌的影响。采用XRD、SEM等分析手段对产物进行表征。结果表明,n(Al2O3)/n(SiO2)可以控制晶体尺寸的大小以及长径比,HF的存在影响晶体的成核及分散性。     

水热合成纳米羟基磷灰石粉末及其结构表征

羟基磷灰石 (HA)已广泛用作人体硬组织的修复和替换材料 ,采用CaCO3 和CaHPO4·2H2 O的混合物为前驱物 ,在 2 0 0℃下经 8h的水热处理获得了晶粒完整、粒度在 10 0nm以下的柱状或针状HA晶体。借助X射线衍射(XRD)、扫描电镜 (SEM)及红外光谱 (FTIR)对HA的晶相组成、形貌、大小及化学组成进行了分析。实验结果表明 :当前驱物钙磷比Ca/P为 1.2时 ,水热产物主要为Ca2 P2 O7,前驱物钙磷比Ca/P为 1.6 7和 2 .0时 ,水热产物只有HA ,并且随Ca/P比的增加 ,进入磷灰石结构的结构CO3 2 -的量增加 ,引起晶格畸变 ,晶粒尺寸降低。这种纳米晶体在形态、结构和组成上与人骨相似 ,更有利于作为生物医用材料应用     

新型锶配位聚合物的合成和晶体结构

用一种柔性三酸N,N′,N″-三(羧基甲基)-1,3,5-苯基三甲酰胺(H3TCMBT)与硝酸锶反应,得到了一个结构新颖的配位聚合物[Sr2(HTCMBT)2(H2O)7]n,并用元素分析、傅里叶变换红外光谱以及单晶X射线衍射对其进行了表征.该晶体属单斜晶系,Cc空间群,晶胞参数a=1.325 70(16)nm,b=2.374 9(3)nm,c=1.353 26(16)nm,α=γ=90.00°,β=104.781(2)°,V=4.119 7(9)nm3,Z=4,R1=0.043 2,wR2=0.109 6.配合物中的Sr(II)采取了单帽四方反棱柱的九配位构型和单帽八面体的七配位构型,并通过羧基氧的桥连形成二核簇;配体则以二聚体形式出现.以二核簇和二聚体为结点,晶体可简化为一种较为少见的单结点4-连接三维网络,其拓扑结构属于neb型,施莱夫利(Schlfli)符号为{66}.     

Effect of nucleating agents on microstructure and mechanical properties of SiO2-Al2O3-ZrO2 glass-ceramics

SiO2-Al2O3-ZrO2 glasses with different nucleating agents were crystallized under special processing schedule. The microstructure and mechanical properties of the glass-ceramics in SiO2-Al2O3-ZrO2 system were investigated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction and three-point bending method. The results show that ZrO2 is not an effective nucleating agent in SiO2-Al2O3-ZrO2 system, while TiO2 is effective for the separation of spinel, and P2O5 facilitates solubility of ZrO2 in glass and crystallization. The main crystalline phases of the glass-ceramics are spinel, anorthite and tetragonal zirconia. With the increase of ZrO2 content in the glass, glass-ceramics show higher bending strength （120 MPa） than others.     

SnO2及SnO2／Fe2O3复合微米材料的合成及表征

本文首先以SnCl2·2H2O为主要原料,无水乙醇为溶剂,利用溶剂热法于180℃反应24h得到了SnO2微球;再以所制备的SnO2微球为前驱体,FeCl3·6H2O为主要原料,通过水热法得到SnO2／Fe2O3复合材料．利用X射线粉末衍射仪（XRD）和扫描电子显微镜（SEM）对所得产物进行了表征．结果表明：所得的SnO2为四方锡石型,形貌为微球,平均直径约为2．0μm;复合后得到的SnO2／Fe2O3微球平均直径约为2．5μm．其中,Fe2O3为六方赤铁矿型,在复合物的表面以小颗粒的形式存在,尺寸约为200nm．另外,也对SnO3与SnO2／Fe2O3微球的形成过程进行了讨论．     

Preparation and properties of dental zirconia ceramics

Y2O3-stabilized tetragonal zireonia polyerystalline (Y-TZP) ceramics with high-performance were prepared for dental application by use of the micro-emulsion and two-step sintering method.The crystal phase,morphology,and microstructure of the reaction products were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and transmission electron microscopy (TEM).XRD results show that the ceramics mainly consist of tetragonal zirconia.Physical and mechanical properties test results show that the bending strength,fracture toughness,and the density of full sintered Y-TZP ceramics are llS0 MPa,5.53 crown machined with this material by CAD/CAM system exhibits a verisimilitude configuration and the material's expansion coefficient well matches that of the glaze.These results further indicate that the product can be used as a promising new ceramic material     

Synthesis and Characteristic of a New Niobate:Ba_5NaCo_0.5Nb_9.5O_30

A new niobate crystal was synthesized for the first time in BaO-Na2O-Co2O3 -Nb2O5 system by solid state reaction and the flux method. The new compound was studied by X-ray diffraction, electron probe. N-ray microanalysis, chemical analysis and SEM. The result of the X-ray diffraction shows that Ba5 NaCo0.5 Nb9.5 OK) belongs to tetragonal tungsten bronze structure with space group P4bm( 100) and lattice parameters a = b = 12.4453(2) A, c = 3. 9770 (3) A and Z = 1. The structure of the compound is different from that of Ba4Na2Nb10O30     

High Dielectric Constant and Low-loss Dielectric Ceramies of Sr5LnTi3Ta7O3o （Ln= La,Nd, Sm and Y）

Polycrystalline Sr5LnTi3Ta7O30 （Ln=La, Nd, Sm and Y） ceramics were prepared as single-phase materials through conventional solid-state ceramics method. The structure was characterized by X-ray diffraction method and scanning electron microscopy （SEM）. The dielectric properties were measured from room temperature to 400℃. All compounds are paraelectric phases adopting the filled tetragonal tungsten bronze （TB） structure at room temperature. At 1 MHz their dielectric constant （ετ） varied from 109 to 139, dielectric loss changed from 0.003 3 to 0.005 8, and the temperature coefficients of the dielectric constant （τε） moved from -710 to -880×10^-6℃^-1.     

梭形Fe_5(PO_4)_4(OH)_3·2H_2O的一步水热法制备及生长机理研究

采用可控的一步水热法制备出了具有对称棱边的梭形Fe5(PO4)4(OH)3·2H2O产物。利用X-射线衍射、场发射扫描电子显微镜、透射电子显微镜等手段对产物进行了表征,发现产物的生长机理符合Ostwald熟化过程。研究表明:在180℃下反应96h后会得到多臂形貌的纯相Fe5(PO4)4(OH)3·2H2O产物,且在低温下更容易获得纯相的Fe5(PO4)4(OH)3·2H2O梭形产物。此外研究发现,产物在500℃热处理后具有较好的形貌和尺寸上的热稳定性。     

Preparation and characterization of nanocrystalline SnO2 thin film by electrodeposition technique

A novel process for preparing tin oxide thin films directly on copper foil by electrodeposition was developed. An optimal preparation technology to obtain SnO2 thin films was proposed with current density of 8 mA/cm2, the time of deposition of 120 min, the concentration of tin dichloride of 0.02 mol/L and the concentration of dissociated acid of 0.03 mol/L. The phase identification, microstructure and morphology of the thin films were investigated by thermogravimetric analysis and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectra,scanning electron microscopy and transmission electron microscopy. The as-deposited thin film was composed of SnO2·xH2O was obtained by drying at room temperature. Nanocrystalline SnO2 thin film having tetragonal structure with average grain size in the range of 8 to 20 nm and porous, uniform surface was obtained by heat-treating the as-deposited film at 400 ℃ for 2 h. Electrochemical characterization shows that SnO2 film can deliver a discharge capacity of 798 mAh/g and the SnO2 film with smooth surface and annealed at 400 ℃ for 2 h has better cycle performance than that with rough surface and annealed at 150 ℃ for 10 h.     

二氧化锡微球的制备、表征及其性能研究

介绍了以二水氯化亚锡(SnCl2·2H2O)作为主要原料,无水乙醇和N-N二甲基甲酰胺作为复合溶剂,采用溶剂热法在140℃反应24h成功地制备了二氧化锡微球.通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)对所制备样品的物相、结构和形貌进行了表征.结果表明:所制备的SnO2具有纯的四方相结构,形状球体,直径约为3μm,且反应温度、反应时间及复合溶剂配比等对样品尺寸、形貌及微球形成过程等均有一定的影响.最后通过紫外可见分光光度计对其光学性能进行了研究.     

氧环境扫描电镜对氧化物的荷电补偿

在(5×10~(-3))～(2×10~(-2))Pa的氧环境扫描电镜(SEM)中观察到由入射电子束辐照引起的Al_2O_3、SiO_2等氧化物荷电现象得以减轻。氧化物受激氧解吸,使样品表面的氧空位成为荷电势阱而产生荷电。通过氧气氛中提供的氧离子对表面缺陷的修复作用,使氧化物的荷电现象得到补偿。氧环境扫描电子显微分析方法是针对氧化物类绝缘材料荷电的一种简便的、自动调节的荷电补偿方法。Al_2O_3的俄歇电子能谱证明,在6×10~(-6)Pa的氧压下可以完全消除Al_2O_3的表面荷电。     

Self-Propagating High-Temperature Reductive Synthesis of TiB_2-Al_2O_3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis(SHS) method with reductive process from B2O3-TiO2-Al system. X-ray diffraction(XRD) and scanning electron microscopy(SEM) analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.