稀土气相扩渗法制备K_(0.5)WO_3钨青铜及其导电性的研究

采用气相扩渗稀土法,以取代型杂多酸盐K1[7Pb(CuW11O39)2]·30H2O为前躯体,制备了K0.5WO3钨青铜,利用IR、XRD、TG-DTA、XPS等手段对扩渗前后的物质进行了结构表征,结果表明前躯体的笼型Keggin结构已被破坏,扩渗后的主要产物是K0.5WO3。同时用四探针法和交流阻抗谱测试了扩渗前后物质的电导率,扩渗后样品的电导率σ=1.07×10-3s·cm-1,有望可作为固体电介质材料。     

Sr1-xBaxNb2O6钨青铜铁电陶瓷的结构与介电性能研究

通过固相反应法合成了Sr1-xBax Nb2O6(SBN)钨青铜型铁电陶瓷,并对其结构、介电性能进行了系统的研究.结果表明在所研究的成分范围内,SBN陶瓷均形成了四方钨青铜相,但是SBN25陶瓷的主相为焦绿石相,其他3种成分的SBN陶瓷均为四方钨青铜单相.SBN陶瓷均存在一个明显的弥散介电峰,峰值温度随x的增加从室温(SBN25)升高到130℃左右(SBN60);同时峰值温度随频率往高温偏移,为典型的弛豫铁电相变.     

溶胶-凝胶法制备铯钨青铜粉体的影响因素研究

采用溶胶凝胶法制备铯钨青铜（CsxWO3）粉体。系统研究了分散剂、煅烧温度和反应物铯钨摩尔比对铯钨青铜粉体晶相、形貌、晶粒平均粒径及光学性能的影响。分别采用热重分析仪（TGA）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、紫外可见近红外分光光度计（UV/VIS/NIR Spectrophotometer）对所制铯钨青铜粉体进行表征。结果表明：分散剂为PEG-600、煅烧温度为600℃和反应物铯钨摩尔比为0.33时,可制得晶型完整,分散性和近红外屏蔽性能均较好的铯钨青铜Cs0.3WO3粉体,其中Cs0.3WO3涂层的可见光透过率在80%以上,近红外阻隔率在70%左右。     

稀土催渗下的20MnSi钢渗硼工艺研究

本文以20MnSi钢为基材,对其进行稀土催渗下的固体粉末渗硼工艺研究.结果表明,稀土-硼共渗下20MnSi钢可形成连续针齿状形貌特征的硼化物层,其物相为单一Fe2B相.提高渗硼温度可明显增加渗层厚度,为获得良好的渗硼效果,应在较高渗硼温度进行为宜.随渗硼时间增加,渗硼层厚度先较快增加,后缓慢增加,渗层厚度与时间符合抛物线规律.稀土添加量较高或较低均对渗硼速度不利,存在一个最佳稀土添加量(10％左右),使催渗效果最好.     

稀土元素对K17[Sm（CuW11O39）2]·23H2O的扩渗及导电性研究

采用气相扩渗法,对K17[Sm（CuW11O39）2]·23H2O化合物进行了稀土Er热扩渗,经ICP测试表明,微量Er已渗入到化合物中,利用XRD对扩渗前后的结构进行了表征,表明扩渗后生成了新物质。测试了扩渗前后试样的电导性,结果发现,扩渗后试样的电导率比扩渗前提高了10s倍,为杂多化合物的应用提供了基础数据。     

稀土元素对K17[Sm（CuW11O39）2]·23H2O的扩渗及导电性研究

采用气相扩渗法，对K17[Sm（CuW11O39）2]·23H2O化合物进行了稀土Er热扩渗，经ICP测试表明，微量Er已渗入到化合物中，利用XRD对扩渗前后的结构进行了表征，表明扩渗后生成了新物质。测试了扩渗前后试样的电导性，结果发现，扩渗后试样的电导率比扩渗前提高了10s倍，为杂多化合物的应用提供了基础数据。     

钨青铜型(TB)材料

钨青铜型材料具有优异的铁电、压电、热释电、非线性光学性能而逐渐得到广泛的关注。本文从结构的角度上，对钨青铜型材料进行了分类介绍，并详细介绍了其中四方钨青铜材料的发展过程以及发展趋势。     

溶胶-凝胶法制备铯钨青铜粉体的影响因素

采用溶胶-凝胶法制得铯钨青铜(CsxWO3,0.20x0.30)粉体,系统考察了铯钨物质的量比、分散剂种类和煅烧温度对铯钨青铜粉体晶相、形貌、晶粒平均粒径及光学性能的影响。利用TGA、SEM、XRD、紫外-可见-近红外分光光度计对所制铯钨青铜粉体进行了结构表征。结果表明:反应物铯钨物质的量比为0.33、分散剂为PEG-600、煅烧温度为600℃、煅烧时间为2 h时,可制得晶型完整,分散性和近红外屏蔽性能均较好的Cs0.30WO3粉体,其中,Cs0.3WO3涂层的可见光透过率在85%以上,近红外阻隔率在70%左右。     

铯钨青铜改性PVC薄膜隔热和红外线阻隔性能

以丙烯酸酯共聚物和铯钨青铜纳米粉体为主要组分,添加PVPK-20,D626,K-80,K-92,K-63,K-61作为分散剂,采用球磨法制备铯钨青铜浆料,将其添加在PVC中制备具有隔热和红外线阻隔功能的薄膜。系统研究了研磨时间、分散剂种类和用量对铯钨青铜浆料的均一性和稳定性的影响,K–61的分散效果最好;在研磨时间相同的情况下,随着分散剂K-61用量的增加,铯钨青铜浆料的均一性和稳定性逐渐变好,当其用量超过4%时可获得良好的分散效果。在此基础上研究铯钨青铜浆料对PVC薄膜隔热和红外线阻隔性能的影响,在研磨时间相同情况下,随浆料中K-61用量的增加,PVC薄膜的红外线阻隔率增大,太阳能总透射比和可见光透射率减小。PVC中添加1.3%的浆料(K-61用量为4%,研磨72 h)所制薄膜在950 nm,1400 nm和全红外波段的红外线阻隔率分别为52.4%,60.1%和58.4%,太阳能总透射比为0.531,红外灯照射1 min温度上升6.3℃,可见光透射率为68.5%,在玻璃门窗隔热节能领域具有良好的应用前景。     

11-钨锌杂多酸盐催化合成乙酸乙酯

合成了K8[CdZnW11O39（H2O）]、K8[NiZnW11O39（H2O）]和K8[CuZnW11O39（H2O）]3种具有Keggin结构的钨锌混配型杂多酸盐催化剂,以无水乙醇和冰乙酸为原料,催化合成乙酸乙酯。探讨了酸醇物质的量的比,催化剂的用量,反应时间和反应温度对酯化率的影响及催化剂的重复使用情况。结果表明反应最佳条件为：酸醇摩尔比为2.0,催化剂用量为原料质量的1%,反应时间为6.0 h,反应温度80℃,催化剂在连续使用5次情况下活性无明显下降。     

Synthesis of Potassium Tungsten Bronze Nanosheets by Phase Transformation

Single‐crystalline potassium tungsten bronze nanosheets were prepared by reducing potassium tungsten oxide nanosheets grown on a W foil. The nanosheets showed no evident shape change before and after reduction. Morphology, structure, and composition analyses revealed that a phase transformation from orthorhombic potassium tungsten oxide to hexagonal potassium tungsten bronze occurred. Better field emission with lower turn‐on field was measured from potassium tungsten bronze nanosheet film. The effects of reduction treatment on field emission performance are discussed.     

Synthesis, Structure, and Electrochemical Characterization of Nanocrystalline Tantalum and Tungsten Nitrides

Nanocrystalline tantalum and tungsten nitrides were synthesized by a two-step ammonolysis reaction of transition metal chlorides. The first step involves ammonolysis of tantalum and tungsten chlorides at room temperature using anhydrous chloroform as the solvent. A second step consists of heat treatment of these as-prepared powders under anhydrous NH₃ atmosphere leading to the formation of tantalum and tungsten nitride nanocrystallites at relatively low temperature (600°–675°C). The ammonolysis, nitridation, structure, morphology, surface area, density, and electronic conductivity of the nitrides obtained were studied and characterized. The electrochemical responses of these nitrides were also measured by cyclic voltammetry using 1 M KOH electrolyte.     

纳米WO3掺杂CNTs材料的制备及其气敏性能测试

通过水热法合成纯WO3,并采用原位水热合成的方法制备不同碳纳米管掺杂量(0.2%,0.4%,0.6%,0.8%,1.0%)WO3/CNTS复合材料。复合之前,从四种纯WO3(K2SO4为添加的矿化剂且含量依次为15 g、30 g、40 g、0 g)中选取一种气敏性能最好的合成工艺。结果表明无K2SO4的合成工艺较好,同时对四种纯WO3进行了XRD表征,结果显示无K2SO4的氧化钨为两相晶体,且粒径较小。纯WO3与S-WCNTS掺杂制备复合材料,然后由复合材料制备气敏元件,对H2S进行气敏测试,结果表明S-WCNTS含量为0.6%的复合材料效果最佳,恢复性好且工作电压较低,可达2.68 V,且检出限可达到3 mg/kg,连续曲线的测定也较好。     

一种新型聚醚离子液体电解质的制备和表征

以端羟基聚环氧氯丙烷(PECH)、N-甲基咪唑(NMIM)为原料,制备了一种新型的含端羟基的聚醚离子液体(NMIM-g-PECH)。考察了反应温度、反应配比、反应时间、接枝PECH的数均相对分子质量对反应接枝率的影响;用红外光谱和核磁共振氢谱对聚醚离子液体进行了结构表征;对聚醚离子液体的溶解性、电化学稳定性和离子导电性进行了分析。结果表明合成聚醚离子液体的较优工艺条件为:反应时间10h,反应温度40℃,n(PECH中氯甲基):n(NMIM)=1.0:1.8,PECH的数均相对分子质量为1000,此条件下反应接枝率可达82.3%;所得聚醚离子液体具有良好溶解性、电化学稳定性、离子电导性能,质量分数为5%的这种聚醚离子液体甲醇溶液室温电导率可达2.40×10-3S/cm。     

Growth of tungsten bronze phase out of niobate perovskite phase for opto-ferroelectric applications

Engineering the optical bandgaps of classic ferroelectrics from the typical ultraviolet range down to the visible range is an emerging methodology of developing the next-generation optoelectric and opto-ferroelectric devices including ferroelectric solar cells, light-driven transistors and modulators, and multi-sensors/energy harvesters. Recently, a material interface comprised of a pseudo-morphotropic phase boundary between the tungsten bronze and perovskite phases of the KNBNNO [(K,Na,Ba)_x(Ni,Nb)_yO_z] has been reported to be an effective approach for bandgap engineering while retaining excellent ferroelectricity and piezoelectricity of the perovskite-phased KNBNNO. However, this approach requires the compositions of the materials to be determined at the synthesis stage, leaving little room for any further modification of the microstructure and functional properties at the post-processing stage. This paper presents a post-processing method, that is, atmospheric annealing in N₂ and O₂, to grow the necessary tungsten bronze phase out of the perovskite phase in the KNBNNO. This method is advantageous over the previously reported because it enables to grow the tungsten bronze–perovskite interface region independent of the initial composition. The distinctive electrical properties and the giant tunability of photoconductivity of the tungsten bronze phase, the perovskite phase, and the interface are characterized in detail in this paper, supporting the exploitation of fabricating opto-ferroelectric devices using the reported method which is compatible and comparable with some of the post-processing methods applied in the silicon industry.     

Thermal and electrical properties of a high entropy carbide (Ta,Hf, Nb,Zr) at elevated temperatures

The thermal and electrical properties were measured for a high entropy carbide ceramic, consisting of (Hf, Ta, Zr, Nb)C. The ceramic was produced by spark plasma sintering a mixture of the monocarbides and had a relative density of more than 97.6%. The resulting ceramic was chemically homogeneous as a single-phase solid solution formed from the constituent carbides. The thermal diffusivity (0.045–0.087 cm²/s) and heat capacity (0.23–0.44 J/g•K) were measured from room temperature up to 2000°C. The thermal conductivity increased from 10.7 W/m•K at room temperature to 39.9 W/m•K at 2000°C. The phonon and electron contributions to the thermal conductivity were investigated, which showed that the increase in thermal conductivity was predominantly due to the electron contribution, while the phonon contribution was independent of temperature. The electrical resistivity increased from 80.9 μΩ•cm at room temperature to 114.1 μΩ•cm at 800°C.     

Near Infrared Absorption of Tungsten Oxide Nanoparticle Dispersions

Homogeneous dispersions of reduced tungsten oxide and tungsten bronze nanoparticles with ternary additives Na, Tl, Rb, and Cs have been prepared in the wet process and examined for optical properties. The dispersions of reduced tungsten oxide and tungsten bronze nanoparticles are found to show a remarkable absorption of near infrared light while retaining a high transmittance of visible light. This property is highly suitable for solar control filters in automotive and architectural windows.     

Thermal behavior of polyaniline films and polyaniline–polystyrene blends

In this article, a study of the thermal behavior of polyaniline films and polyaniline–polystyrene blends is presented. Transport measurements (electrical conductivity and thermoelectric power) at high temperature and thermogravimetric analysis show that an irreversible degradation is observed near 450 K for films doped with DiOHP and near 500 K for films doped with CSA. In both cases, the thermoelectric power is the most sensitive parameter to electrical degradation during the heating of conducting films. Electrical conductivity measurements during heating–cooling cycles show a diminution of the room temperature conductivity after evaporation of the solvent (water, m‐cresol). A model of cluster with a variable diameter allows interpreting this phenomenon by assuming the existence of a sensitive frontier to the solvent at the periphery of conducting clusters. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1848–1855, 2002; DOI 10.1002/app.10468