Al^3＋/Mo^6＋双离子取代ZrV2O7中Zr^4＋/V^5＋实现近零膨胀

采用固相烧结法制备了Zri_(1-x)Al_(2-x)V_(2-x)Mo_xO_7(0≤x≤0.9),并通过调整Al^(3+)/Mo^(6+)对ZrV_2O_7中的Zr^(4+)/V^(5+)离子替代量来实现近零膨胀,对于较小的x值(x≤0.3),材料保持了与ZrV_2O_7相同的立方相结构.随着Al^(3+)/Mo^(6+)替代量的增加,(Al/Zr)^-和(Mo/V)^+之间的库仑相互作用逐渐加强,这种库仑相互作用导致材料中未发生畸变的立方相晶体结构逐渐减少.当x≥0.7时,材料中立方相晶体结构完全消失.在425-750 K温度区间内,Zr_(0.5)Al_(0.5)M_(0.6)O_7展示出近零膨胀性质(-0.39×l0^(-6)K^(-1)).Zr_(0.5)Al_(1.5)V_(1.5)Mo_(0.5)O_7的低热膨胀性能可能与Al^(3+)/Mo^(6+)对ZrV_2O_7中Zr^(4+)/V^(5+)部分替代引起部分晶体结构发生的畸变及其对未替代部分的晶格结构的影响有关.

正压水煤气余热锅炉防磨瓦腐蚀失效分析

不锈钢腐蚀问题严重影响锅炉的运行安全,1Cr20Ni14Si2不锈钢防磨瓦在水煤气余热锅炉中运行被腐蚀甚至断裂,对正压水煤气立式余热锅炉过热器不锈钢防磨瓦断裂失效进行研究。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和电子能谱分析仪(EDS)设备对锅炉1Cr20Ni14Si2不锈钢失效防磨瓦的表面腐蚀褐色粉末、不锈钢表面和人为断面成分进行测试。XRD测试结果表明表面褐色粉末存在多种金属氧化物和硫化物;EDS实验检测结果表明:不锈钢表面含大量S和O。这说明1Cr20Ni14Si2不锈钢在焦化炉中易被S腐蚀而失去不锈钢特性。EDS结果分析发现不锈钢Ni含量明显低于国标要求含量,降低了不锈钢韧性并降低其防腐蚀性能。烟气中S、C和O经腐蚀孔隙进入材料内部加速不锈钢内部腐蚀。研究结果对水煤气余热锅炉防磨瓦材料选型和防磨结构优化具有指导意义。

基于半导体制冷技术的小型冷热箱设计

本设计以半导体制冷片TEC1-12706和单片机STC89LE52AD为核心,采用多级制冷的核心方法,辅以微处理器模块、按键设计模块、温度采集模块、温度显示模块、电路驱动模块、制冷散热模块。根据传感器采集的温度与预设温度间的对比结果,结合"弱电控制强电"的思想,控制半导体制冷片TEC1-12706的工作状态,实现制冷或制热功能。

碳纳米团簇向碳纳米纤维相转变机理研究

为了能够快速且大面积生长碳纳米纤维,研究碳纳米纤维的形成、转变及在各种物理、化学环境下的反应机理,应用等离子化学气相沉积(PECVD)方法,以CH4为反应气体,FeCl2为催化剂在玻璃衬底上生长碳纳米薄膜.应用扫描电镜(SEM)观察了碳纳米纤维薄膜的表面形貌,拉曼(Raman)光谱分析了碳纳米纤维的结构组成.结果表明,无催化剂时薄膜主要由纳米团簇构成,而催化作用下薄膜呈纤维状生长,纳米纤维为典型的碳纳米管石墨特征峰.在温度,气压,催化剂等反应条件中,FeCl2催化剂对碳纳米薄膜的取向生长起决定性作用,通过调节催化剂的浓度与分布,可有效改变碳纳米纤维的密度与分布.

P替代对ZrV2O7介电与电导性能的影响

采用固相烧结法制备ZrV 2-x P x O 7系列材料,研究了P替代对ZrV 2O 7介电和电导性能的影响。研究发现,ZrV 2-x P x O 7系列材料的高频介电常数随着P含量的增加而降低;材料的离子弛豫极化和晶界极化速率随P含量的增加先变大后变小,其介电弛豫时间随P含量的增加先增大再减小,其中ZrV 1.6 P 0.4 O 7具有最大的介电弛豫时间,为5.63×10-4 s。由于P和V离子半径和电负性的差异,P的加入会导致晶格畸变和散射几率变化。室温下,ZrV 2-x P x O 7系列材料的电导率对P的含量非常敏感,ZrV 1.6 P 0.4 O 7具有最大电导率,为5.83×10-5 S·cm-1。对ZrV 1.6 P 0.4 O 7进行变温特性测试发现,其活化能为0.19 eV。对ZrV 2-x P x O 7系列材料的电导率和介电的研究对拓展此类材料在电子器件方面的应用具有重要意义。

关于惠斯通电桥的一点讨论

为精确测量电阻,讨论了用惠斯通电桥测量电阻时比率臂的取值问题,通过3组实验数据的比较,得出比率臂取值在千欧时能够给出比较好的测量结果.

低密度TMPTA泡沫的制备及表征

低密度聚合物泡沫在惯性约束聚变靶及电磁内爆靶中应用十分广泛。以三羟甲基丙烷三丙烯酸酯(TMP-TA)为聚合单体,安息香甲基醚为引发剂,通过紫外光引发生成凝胶,经超临界干燥得到TMPTA泡沫材料。通过红外光谱仪和元素分析仪确定了TMPTA单体中官能团转化率及泡沫纯度的表征。实验结果表明,聚合反应过程中,在1636cm-1附近碳碳双键(C=C)的转化率为40.48%,泡沫为高纯度的低密度TMPTA泡沫,机械强度可满足核磁内爆靶(Z-pinch)靶装配的需求。

论平衡记分卡及其对企业管理的重要作用

平衡计分卡被誉为20世纪最重要的管理工具和方法,对企业的战略管理具有重要影响。文章首先解读了平衡计分卡的概念及其发展历程;其次分别从财务、客户、内部流程、学习与成长四个维度分析了平衡计分卡的基本内容,并从企业管理的实际出发,提出了从四个维度可供选择的评价指标;最后,深入探讨了平衡计分卡对企业管理产生的重要影响和积极作用。

High Solubility of Hetero-Valence Ion （Cu^2＋） for Reducing Phase Transition and Thermal Expansion of ZrV1.6P0.4O7

Large thermal expansion at room temperature and high phase transition temperature of ZrV2O7 limit its practical applications and are reduced by the high solubility of hetero-valence ion （Cu^2＋） on the basis of an equal-valence substitution of P^5＋ for V^5＋. The temperature-dependent Raman spectra show that Zr0.9CU0.1V1.6P0.4O6.9 maintains a normal parent cubic structure till 173 K and transforms to a 3 × 3 × 3 cubic superstructure below 173K. Temperature dependent x-ray diffraction patterns of Zr0.9CU0.1V1.6P0.4O6.9 show near zero and negative thermal expansion. High solubility of lower valence Cu^2＋ relates to an equal-valence substitution of smaller pH for P^5＋, which extends the bond angle of V（P）-O-V in ZrV1.6P0.4O7 close to 180°. The change of microstructure is considered to be responsible for reduced phase transition temperature and thermal expansion.

Lithium ion batteries cathode material: V_(2)O_(5)

Among all the known electrode materials, vanadium pentoxide(V_(2)O_(5)) has high reversible capacity. It is a very valuable material for research of the complexity, rich structure and morphology. However, it also has some disadvantages,such as poor cycle stability, low discharge voltage, low conductivity and Li^(+) diffusion coefficient. In this regard, researchers have carried out a lot of research, such as using various methods to improve the nanostructures, introducing heterostructures,introducing point defects or cation doping in the crystal structure, etc. The electrochemical performance of V_(2)O_(5)has been significantly improved in reversible capacity, high-rate capacity and long-term cycle stability. In this paper, V_(2)O_(5)based nanostructure with different chemical composition are briefly introduced, and it covers V_(2)O_(5)nanomaterials with different morphology, including 1D nanorods, nanobelts, nanotubes, 2D leaf like nanosheets and other nanosheets, and 3D hollow structures, porous nanostructures, porous eggshell microsphere structures. The composite nanomaterials of V_(2)O_(5)and different carbonaceous supports are also introduced. Finally, the V_(2)O_(5)composite materials doped with cations are discussed. The electrochemical performance of V_(2)O_(5)based electrode can be improved effectively by obtaining appropriate nanostructure and optimized chemical composition.

The phase transition, hygroscopicity, and thermal expansion properties of Yb_(2-x)Al_xMo_3O_(12)

Materials with the formula Yb2-xAlxMo3O12 （x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8） were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffraction, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3012 solid solutions crystallize in a single monoclinic phase for 1.7 〈 x 〈 2.0 and in a single orthorhombic phase for 0.0 〈 x 〈 0,4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhonlbic phase transition temperature of A12Mo3012 can be reduced by partial substitution of A13＋ by Yb3＋, and the Yb2-zAlxMo3012 （0.0 〈 x 〈 2.0） materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of A13＋ for Yb3＋ in Yb2Mo3012 decreases its hygroscopicity, and the linear thermal expansion coefficients after complete removal of water species are measured to be -9.1 x 10-6/K, -5.5 x 10-6/K, 5.74 x 10-6/K, and 9.5 x 10 6/K for Ybl.sAlo.2（MoO4）3, Yb1.6Alo.4（MoO4）3, Ybo.4All.6（Mo04）3, and Ybo.2Al1.8（MoO4）3, respectively.

论公司财务管理在应对经济转型过程中的作用——以星业科技公司为例

在宏观经济发展转型过程中,企业的发展战略及经营决策也需要进行调整和适应,在这个过程中,财务管理工作如何发挥更大的价值是企业管理者需要深思的问题。论文以广州星业科技股份有限公司的案例为研究对象,结合作者的工作经历,研究总结了在应对经济转型过程中公司财务管理发挥更大价值作用的具体措施,包括提高预算的准确性、加强管理会计工作、切实做好融资和资金管理工作等。

Negative thermal expansion and photoluminescence in solid solution(HfSc)_(0.83)W_(2.25)P_(0.83)O_(12-δ)

A solid solution of （HfSc）0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm （47） and exhibits negative thermal expansion （NTE） property with low anisotropy in thermal expansion. The coefficients of thermal expansion （CTEs） for a, b, and c axes are -1.41×10^-6 K^-1, -2.23×10^-6 K^-1, and -1.87×10^-6 K^-1, respectively. This gives rise to volume and linear CTEs of -3.10×10^-6 K^-1 and -1.03×10^-6 K^-1, respectively. Besides, it exhibits also intense photoluminescence from 360 nm to about 600 nm. The mechanism of NTE and the correlation of the PL with axial thermal expansion property are discussed.

Laser scattering, transmittance and low thermal expansion behaviors in Y2-x（ZnLi）xMo3O12 by forming regular grains

Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y2-x(ZnLi)xMo3O12(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn^2+ and Li+for Y^3+ in Y2Mo3O12 resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y2-x(ZnLi)xMo3O12 could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.

Conductive property of Zr_(0.1)Fe_(0.9)V_(1.1)Mo_(0.9)O_7 with low thermal expansion

Low thermal expansion materials are mostly ceramics with low conductive property, which limits their applications in electronic devices. The poor conductive property of ceramic ZrV_2 O_7 could be improved by bi-substitution of Fe and Mo for Zr and V, accompanied with low thermal expansion. Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 has electrical conductivity of 8.2× 10^(-5) S/cm and 9.41× 10^(-4) S/cm at 291 K and 623 K, respectively. From 291 K to 413 K, thermal excitation leads to the increase of carrier concentration, which causes the rapid decrease of resistance. At 413–533 K, the conductivity is unchanged due to high scattering probability and a slowing increase of carrier concentration. The conductivity rapidly increases again from533 K to 623 K due to the intrinsic thermal excitation. The thermal expansion coefficient of Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 is as low as 0.72× 10^(-6 )K^(-1) at 140–700 K from the dilatometer measurement. These properties suggest that Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 has attractive application in electronic components.

Near-zero thermal expansion of In2(1-x)(HfMg)xMo3O12 with tailored phase transition

Solid solutions of In2（1-x）（HfMg）xMo3O12 are synthesized by solid state reaction with the aim to reduce the phase transition temperature of In2Mo3O12 and improve its thermal expansion property.The effects of（HfMg）^6＋ incorporation on the phase transition and thermal expansion are investigated.It is shown that the monoclinic-to-orthorhombic phase transition temperature obviously decreases and the coefficient of thermal expansion（CTE） of the orthorhombic becomes less negative and approaches to zero with increasing the content of（HfMg）^6＋.A near zero thermal expansion covering the case at room temperature（RT） is achieved for the solid solutions with x ≥ 0.85,implying potential applications of this material in many fields.

Phase transition and thermal expansion property of Cr_(2-x)Zr_(0.5x)Mg_(0.5x)Mo_3O_(12) solid solution

Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12（x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9） are synthesized, and the effects of Zr4＋ and Mg2＋ co-incorporation on the phase transition, thermal expansion, and Raman mode are investigated. It is found that Cr2-xZr0.5xMg0.5xMo3O12 crystallize into monoclinic structures for x 〈 1.3 and orthorhombic structures for x _〉 1.5 at room temperature. The phase transition temperature from a monoclinic to an orthorhombic structure of Cr2Mo3O12 can be reduced by the partial substitution of （ZrMg）6＋ for Cr3＋. The overall linear thermal expansion coefficient decreases with the increase of the （ZrMg）6＋ content in an orthorhombic structure sample. The co-incorporation of Zr4＋ and Mg2＋ in the lattice results in the occurrence of new Raman modes and the hardening of the symmetric vibrational modes, which are attributed to the MoO4 tetrahedra sharing comers with ZrO6/MgO6 octahedra and to the strengthening of Mo-O bonds due to less electronegativities of Zr4＋ and Mg2＋ than Cr3＋, respectively.

A Negative Thermal Expansion Material of ZrMgMo_(3)O_(12)

A material with the formula ZrMgMo_(3)O_(12) having negative thermal expansion is presented and characterized.It is shown that ZrMgMo_(3)O_(12) crystallizes in an orthorhombic symmetry with space group Pnma(62)or Pna21(33)and exhibits negative thermal expansion in a large temperature range(αl=-3.8×10^(-6) K^(-1) from 300 K to 1000 K by x-ray diffraction andαl=-3.73×10^(-6) K^(-1) from 295 K to 775 K by dilatometer).ZrMgMo_(3)O_(12) remains the orthorhombic structure without phase transition or decomposition at least from 123 K to 1200 K and is not hygroscopic.These properties make it an excellent material with negative thermal expansion for a variety of applications.

ZrV_(2-x)P_xO_7固溶体的相变与热膨胀性质的研究

本文采用固相烧结法制备了ZrV2-xPxO7(x=0,0.2,0.4,0.6,0.8,1)系列材料.粉末X射线衍射(XRD)分析表明,所制备材料的结构为单一立方相.应用变温拉曼光谱研究该材料相变,变温拉曼光谱研究结果表明,材料起始相变温度随着P5+替代V5+量的增加逐渐降低,x=0,0.4,0.8,1对应的相变温度分别为383K,363K,273K,213K.热膨胀测试结果表明:随着P替代量的增加正—负膨胀转变温度先降低后增加,x=0,0.2,0.4,0.6,0.8,1对应的正—负膨胀转变温度分别为429K,403K,372K,390K,398K和435K.本文指出了该系列材料存在两个相变过程,为设计和制备ZrV2O7基室温附近的负热膨胀材料奠定了良好的基础.

Y_(2-x)(LiMg)_xMo_3O_(12)固溶体吸水性与热膨胀性能研究

Y2-x(LiMg)xMo3O12固溶体(x=0、0.1、0.3、0.5、0.7、0.9、1.1、1.3、1.5、1.7、1.9和2.0)采用固相法制备。当x=0时,由于严重吸水,拉曼峰宽化。随着(LiMg)掺入量的增加,拉曼峰趋于尖锐并发生劈裂,说明固溶体的吸水性得到明显的降低,结晶性能提高,变温拉曼光谱显示失水对应的温度也在降低。在900cm-1和370cm-1附近出现的新峰,与Li-O和Mg-O的振动有关。随着(LiMg)量的增加,Li-O和Mg-O的振动加强,并导致MoO4与YO6振动减弱,也可能与热膨胀系数的变化有关。