ZrO2纳米颗粒在Ni-ZrO2复合镀层中的分散性对镀层结构及性能的影响

研究了ZrO2纳米颗粒以单分散态和团聚态在Ni-ZrO2复合镀层中存在时,对Ni-ZrO2复合镀层结构与性能的影响.采用复合电沉积方法,分别在加有和未加有分散剂的条件下,制得了Ni-ZrO2复合镀层.扫描电镜(SEM)和X射线衍射(XRD)分析表明,利用分散剂MZS可以得到ZrO2纳米颗粒在Ni基质上均匀单分散的Ni-ZrO2纳米复合镀层.而未使用分散剂的复合镀层,ZrO2纳米颗粒在镀层中发生团聚,分散性差.ZrO2纳米颗粒在Ni-ZrO2复合镀层中的分散态不同,也将影响镀层中Ni的结晶择优取向.ZrO2纳米颗粒单分散的纳米复合镀层较ZrO2纳米颗粒团聚态的复合镀层的硬度大大提高.     

PET/纳米SiO2复合材料的制备I. 纳米SiO2在PET单体EG中的分散性研究

以EG为分散介质，研究了分散方法，分散剂的种类，分散剂的浓度及分 散时间为纳米SiO2在EG中分散性的影响，用TEM对其分散情况进行表征，并对其分散机理进行探讨与研究。其结果表明，不同的分散方法，不同种类的分散剂及不同的分散剂浓度，不同的分散时间对SiO2在EG中的分散性有不同的影响。     

纳米ZrO2粒子在镀液中的分散悬浮与单分散Ni-ZrO2纳米复合镀层的制备

表面能高的纳米颗粒在镀液中极易团聚,而使镀层失去纳米特性,为了解决这个问题,对纳米颗粒在镀液中的团聚与分散机理进行了论述.以高分子聚电解质为分散剂,在镀镍溶液中实现了ZrO2纳米粒子的单分散,并在此纳米复合镀镍溶液中制备出单分散Ni-ZrO2纳米复合镀层.分析了分散剂用量与ZrO2纳米粒子悬浮分散性间的相关性,对制备的纳米复合镀层的结构和性能进行了研究.结果表明,高分子聚电解质的用量对ZrO2纳米粒子在镀液中的分散性能有较大的影响,其间存在一最佳值(5 g/L),同样它对镀层的硬度仍存在5 g/L这一最佳值.     

纳米ZrO_2、Al_2O_3单相及混合粉体的分散稳定性研究

以蒸馏水和无水乙醇作为分散介质,研究了六偏磷酸钠(NaPO3)6、聚乙二醇和聚丙烯酸对纳米Al2O3、纳米ZrO2单相及其混合粉体悬浮液分散稳定性的影响。结果表明:纳米Al2O3、ZrO2单相粉体在乙醇中的分散性较好,两者的混合粉体在水或乙醇中的分散性差别不大,主要取决于分散剂的种类,当pH=6～8时悬浮液最稳定,其中以聚丙烯酸为分散剂时分散效果最佳,六偏磷酸钠次之,聚乙二醇最差。     

纳米ZrO2在液相中分散的研究进展

综述了纳米ZrO2在液相中的分散机理和分散方法,详细分析了溶液中的pH值、离子强度、分散剂用量和结构及液体介质对纳米ZrO2悬浮液稳定性的影响,论述了表征纳米ZrO2悬浮液稳定性的几种方法.     

冷冻介质对纳米TiO_2粉体分散的影响

为了解决纳米TiO2的分散问题,在冷冻介质中以复合分散剂对纳米二氧化钛颗粒进行分散,并采用透射电子显微镜对其分散情况、粒径大小进行测试。结果表明:在冷冻介质中纳米二氧化钛在复合分散剂(m(聚丙烯酸钠)∶m(三聚磷酸钠)=1∶1)时纳米颗粒可以均匀分散,可以得到几纳米大小的分散体系。分散介质的温度是影响纳米颗粒分散的关键因素,并给出相应理论分析。其中,配合、且复合分散剂与二氧化钛的质量比为1.5∶1时分散效果最好。对纳米二氧化钛颗粒的分散而言,冷冻技术和分散剂配比起了关键作用     

纳米SiC颗粒对Al2O3基体中ZrO2约束稳定的影响

采用热压的方法制备了纳米SiC颗粒复合的Al2O3-ZrO2陶瓷材料，研究了纳米SiC颗粒对样品烧结性能以及对Al2O3基体中ZrO2约束稳定的影响。结果表明，纳米SiC颗粒的加入影响样品的烧结性能。处于晶界的纳米SiC颗粒降低了基体材料对ZrO2颗粒的约束，不利于四方相ZrO2在室温下的保留。     

有机分散介质中纳米SiC粉体稳定悬浊液的制备

纳米粉体的稳定分散是制备微观结构均匀、缺陷少的纳米复相陶瓷坯体的关键。本文中采用Zeta电位、粒度分析、SEM等测试技术分析了超声震荡和HF酸洗对SiC纳米粉体的影响;对比研究了乙醇、乙二醇以及75%乙醇和25%乙二醇混合液作为分散介质,聚乙二醇为分散剂时纳米SiC粉体在不同pH下的分散稳定性,确定了粉体最佳超声震荡的最佳时间;探讨了酸洗的作用;并在乙二醇中,以1%PEG为分散剂,pH=10条件下获得了纳米碳化硅粉体的高稳定分散悬浮液。     

纳米TiO2的分散性及其改性内墙乳胶漆降解甲醛性能研究

实验研究了不同分散剂对纳米TiO2在水溶液中分散的影响，采用沉降实验测定纳米TiO2粉体的分散性，结果表明分散剂海川5040和分散剂六偏磷酸钠对纳米TiO2的分散效果比较好。将纳米TiO2粉体的添加量、粒径、晶型等对改性乳胶漆甲醛降解率的影响做系统的研究，结果表明纳米TiO2粉体的添加量在2％时光催化效果比较好。随着粒径的减小，纳米TiO2改性乳胶漆对甲醛的光催化降解能力有了明显的提高。通过对纳米TiO2改性乳胶漆光催化降解甲醛能力的重复性检测，表明纳米TiO2改性乳胶漆的光催化能力具有一定的持久性。     

纳米TiO_2在液相中的分散性研究

探讨了纳米TiO2颗粒在水分散介质中的分散工艺,研究了机械搅拌、无机电解质、表面活性剂等对TiO2分散性的影响。研究结果表明,以水作分散介质,通过机械搅拌并加入无机电解质Na4P2O7·10H2O、(NaPO4)6和表面活性剂山梨醇、三乙醇胺、OP-10、SDBS,以及选择合适的pH值可制备出分散稳定性良好的纳米TiO2分散体系。     

Quasi-One-Dimensional Natures in (Et n Me4−n Z)[Pd(dmit)2]2

We studied one of possible ground states for Pd(dmit) ₂ salts in a dimerized two-band Hubbard model. By using a strong-coupling expansion, we obtained an effective dimer model which has a quasi-one-dimensional Fermi surface. In the insulating phase, it leads to the Heisenberg model on an anisotropic triangular lattice. We calculated effective exchange coupling strengths within the second order perturbation theory and found that both ferromagnetic and antiferromagnetic couplings are possible. Similarities to and differences from Ni(dmit) ₂ salts are discussed.     

Crystal growth of Ti n O2n-1 oxides(n=2 to 9)

Crystals of titanium oxides, Ti _n O_2n-1 with n=2 to 9, were grown by chemical vapour transport. Chlorine was found to be the best transporting agent. Apart from Ti₂O₃, for which crystals up to 7 mm long were obtained in 6 days, all phases were obtained in conditions leading to very low growth rates and a shift in composition between the charge and growth zones. It is shown that this shift is governed by the equilibrium oxygen pressure in the transport tubes and can be accurately predicted. Most of the millimetresize samples obtained were twinned.     

Exchange Interactions and Ferromagnetism of Pr_(n+1)Co_(3n+5)B_(2n)-type Compounds

In present investigation exchange interactions of Pr_(n+1)Co_(3n+5)B_(2n)-type compounds have been evalu-ated in the light of molecular-field theory. The exchange interactions and ferromagnetism in thesecompounds are discussed in terms of lattice parameters and interatomic distance between Co atom.     

Vapor-phase growth of Bi2Sr2Ca n−1Cu n O x (n= 1–3) single crystals

High-quality platelike Bi₂Sr₂Ca _n?1Cu_nO_x (n= 1–3) single crystals with superconducting transition temperatures T _c=10, 85, and 110 K, respectively, are prepared by vapor-phase growth in closed cavities produced in a melt fluxed with KCl. The effect of synthesis and growth conditions on the T _c of the crystals is analyzed. The morphology of the crystals suggests that the most perfect, well-faceted crystals grow via vapor transport with constant feeding from the charge.     

n（Zn）/n（Zr）对催化剂CuO-ZnO-ZrO2的结构及其合成甲醇性能的影响

采用并流沉淀法制备了一系列不同n(Zn)/n(Zr)时的CuO-ZnO-ZrO2甲醇合成催化剂,运用X射线衍射仪(XRD)、N2物理吸附(BET)和H2程序升温还原(H2-TPR)等手段对催化剂进行了表征分析。在固定床反应器中进行CO2加H2合成甲醇的活性评价研究,考察了n(Zn)/n(Zr)在催化剂中的作用。结果表明,当n(Zn)/n(Zr)=4/1时,CO2转化率最高;当n(Zn)/n(Zr)=1/4时,甲醇的选择性最好;当n(Zn)/n(Zr)=4/1或1/4时,有效降低了副产物CO的含量,此时的甲醇催化活性最好。     

Blocking of 3(2 n–k ) Designs

3(2 ^n–2) designs may be divided into two blocks, one of size 2 ^n–1 and the other of size 2 ^n–2 by blocking on one of the defining contrasts and into three blocks of size 2 ^n–2 by blocking on all three defining contrasts. Blocking on an effect which is not a defining contrast gives two blocks of 3(2 ^n–3) runs each. In this paper these methods are applied to 3(2 ^n–k ) designs with twelve or twenty-four points. The designs considered are the 3(2^4–2) and 3(2^5–2) designs with all main effects and all two factor interactions estimable (assuming that higher order interactions are negligible), and saturated main effect plans with twelve points and up to eleven factors.     

The Thermal Conductivity and Thermal Diffusivity of Liquid n-Alkanes: C n H2n+2 (n=5 to 10) and Toluene

Experimental values of the thermal conductivity and the thermal diffusivity of six pure liquid n-alkanes (C _n H_2n+2; n=5 to 10) and toluene are presented in the temperature range of –20 to 70°C under atmospheric or saturation pressure. Measurements were made with the transient hot-wire method, and in the analysis, the temperatures T and T (associated with both and ) were used. In the present work, the values of thermal diffusivity were corrected by the factors k _f (=1.0076 to 0.9892) for data sets obtained with different configurations of the experiment, in which the factors were determined by reference to the thermal diffusivity of n-heptane [= _s/(c _p )_s] at 298.15 K calculated from the volumic heat capacity (c _p )_s as a reference material for heat capacity and the experimentally obtained thermal conductivity _s. The uncertainty of the data is estimated to be 0.48% for the thermal conductivity (absolutely measured) and about 1.8% for the thermal diffusivity (with a coverage factor of k _p =2; p=95%).     

The stability and optical gap of zinc oxide clusters (ZnO)n (n = 2-18)

The stability and the optical band gap of the Zinc Oxide clusters (ZnO)n (n = 2-18) are investigated by using density functional theory (DFT) and the time-dependent density functional theory (TD-DFT), respectively. The differences between the HOMO-LUMO gap (delta(h-l)) and the optical gap (delta(opt)) are dramatic for small clusters (2 < or = n < or = 5). As the increasing of the cluster size, the differences become small. The results indicate that the stability and the optical gap are related to the sizes and symmetries of the clusters. Further, it is shown that the structures have much greater impact on the optical gap, there is the dipole-forbidden transition in the optical gap for high symmetric structures.     

New Candidates for Superconductors; A Series of Layered Oxysulfides (Cu2S2)(Sr n+1 M n O3n−1)

We have discovered three new layered transition-metal oxysulfides ; (Cu ₂ S ₂ )(Sr ₂ CuO ₂ ), (Cu ₂ S ₂ )(Sr ₂ NiO ₂ ) and (Cu ₂ S ₂ )(Sr ₃ Sc ₂ O ₅ ), whose compositions are generally formulated as (Cu ₂ S ₂ )(Sr _n+1 M _n O _3n–1 ). Their structures consist of alternate stackings of perovskite-based MO ₂ plane(s) and Cu ₂ S ₂ layers, showing great similarity to cuprate superconductors when the Cu ₂ S ₂ layer is considered as the blocking layer. The formation of these phases is limited by the ion size of M and elasticity of the Cu ₂ S ₂ layer. The newly found (Cu ₂ S ₂ )(Sr ₂ CuO ₂ ) posseses the horizontally extended tetragonal CuO ₂ plane, making itself a possible candidate for a new superconductor.