Cu-Cu2O/RGO复合材料的制备及NOx气敏性能

采用改进Hummers方法制备氧化石墨(GO).以还原态氧化石墨与铜和氧化亚铜复合(Cu-Cu2O/RGO).对GO和Cu-Cu2O/RGO复合材料进行了TEM、FT-IR、XRD、SEM等表征.研究结果表明,氧化石墨为片状结构,其边缘处存在较为明显的褶皱和折叠,氧化石墨中含有大量的含氧的亲水官能团(如:羧基、羟基、羰基等).而在Cu-Cu2O/RGO复合材料中,Cu和Cu2O粒子能够比较均匀地分布于还原态氧化石墨的层间.另外,在室温下对Cu-Cu2O/RGO复合材料的NOx气体敏感性测试结果发现,当注入NOx后,其电阻下降,反之当脱离NOx时电阻又会上升到平缓位置;而且随着NOx的浓度递减,灵敏度也随之下降,表现出较好的响应-恢复气敏特性.     

氧化石墨烯与氧化锌复合材料的制备及室温NOx气敏性能研究

以Zn(NO3)2·6H2O为锌源,尿素为沉淀剂,氧化石墨烯(GO)为碳源,采用均匀沉淀法合成碱式碳酸锌与氧化石墨烯复合材料前驱体,350℃下焙烧前驱体2h,获得ZnO/GO复合材料,在室温下研究了该复合材料对NOx的气敏性能.通过X射线衍射、拉曼光谱、扫描电子显微镜和透射电子显微镜对材料的形貌和结构进行表征.结果表明,所得样品为六方ZnO与GO复合材料,ZnO纳米粒子较均匀的覆盖在GO的表面.当硝酸锌溶液浓度为0.3mol/L时,所合成的复合材料对NOx有较高的灵敏度,且注入NOx体积浓度97 ppm时,灵敏度为27.5;,响应时间1s,最低检测浓度可达0.97 ppm.     

Ni/NiO纳米复合材料的制备及其室温下NOx气敏性研究

采用静电纺丝法合成了直径为300 nm Ni(CH3COO) 2/PS纳米纤维,并且通过煅烧得到Ni/NiO纳米复合材料.对Ni/NiO纳米复合材料的NOx气敏性检测研究发现,该材料在室温下对97 ppm NOx有很较好的气敏响应,灵敏度可达到30;以上,响应时间小于4 min.     

三维花状Ni(OH)2/CNT纳米复合材料制备及NOx气敏性能研究

为了制备室温下对NOx气敏性能优异的纳米材料,本文采用简单的一步回流法制备出呈三维花状的Ni(OH)2/碳纳米管(CNT)纳米复合材料.分别采用XRD、SEM、TEM等表征手段研究了复合材料的形貌和结构.结果表明:三维花状结构是由Ni(OH)2纳米薄片层层堆叠组装起来的,CNT很好的嵌入在花状结构内.该材料在室温条件下对NOx有较好的气敏性能,当CNT的加入量为20 mg时,对于97 ppm NOx气体响应最快为8 s,灵敏度可达到24;,最低检测限为0.97 ppm.对其气敏机理进行研究发现,CNT的加入,有利于提高该复合材料的导电性能和气体的传输能力.该复合材料具有3D结构和独特的化学组成有望在气敏器件、催化等领域得到广泛的应用.     

三维石墨烯/In2O3/聚吡咯复合材料制备及室温气敏性能

采用两步法制备三维石墨烯/In2O3/聚吡咯(3D-rGO/In2O3/PPy)三元复合材料,首先合成二元复合材料三维石墨烯/In2O3(3D-rGO/In2O3),然后以此为载体,通过吡咯单体的原位聚合得到最终产物.通过XRD、FTIR、FESEM、TEM和氮气吸附-脱附对合成材料进行表征,研究了其室温气敏性能,分析了三元复合材料的气敏机理.结果 表明,复合3D-rGO与PPy后,三元复合材料的工作温度降低至室温,室温时对200ppm NH3的灵敏度达到18.8,对NH3有较高的灵敏度,响应和恢复时间较短.     

MnO2/NiO纳米复合微球的制备及室温NOx气敏性能研究

采用低温沉淀法合成含有Mn和Ni的碳酸盐前驱体.经焙烧处理制备了MnO2/NiO纳米复合微球.采用SEM和XRD研究了复合材料的形貌和结构.结果表明:所制备的MnO2/NiO复合微球直径约为2μm.微球表面纳米粒子稀松的排列,且粒子端口呈介孔结构.在室温下,MnO2/NiO-2薄膜传感器对NOx具有较好的气敏响应.当NOx气体浓度为100 ppm时,灵敏度达36;,响应时间为11s.MnO2/NiO-2传感器对NOx气体的最低检测线为3 ppm.     

Cu2O立方体的制备及其室温下NOx气敏性研究

本文采用无表面活性剂添加的液相回流法合成了边长约为300～600nm、表面粗糙的氧化亚铜立方体.并且在室温下,对氧化亚铜立方体的NOx气敏性检测研究发现,该材料对NOx有很较好的气敏响应,最低检测限可达0.97 ppm,响应时间为69 s,是一种有潜力的气敏材料.     

“三明治”PbS纳米晶/rGO复合材料的制备及其对NH_3的室温气敏性能研究

采用一步溶液法制备"三明治"PbS纳米晶/rGO复合材料,通过X射线衍射仪和场发射扫描电子显微镜对样品的晶体结构和表面形貌进行表征,并制作旁热式气敏元器件,测试其气敏特性。研究结果表明在PbS纳米晶/rGO复合材料中,PbS纳米晶均匀负载在rGO片层上,且复合材料存在类似"三明治"的三维结构。该复合材料在室温下对NH_3具有良好检测能力,对1000 ppm NH_3的灵敏度达到3.45,与纯PbS纳米晶及rGO相比,气敏性能得到显著提升,其最低检测极限为1 ppm,且具有良好的氨气选择性。对"三明治"PbS纳米晶/rGO复合材料气敏机理进行分析认为,rGO加入起到载流子传输层的作用,三维结构增加气体扩散速度及吸附面积。三明治状PbS纳米晶/rGO复合材料因其特殊结构及优异的气敏性能,有望在气敏领域得到广泛应用。     

石墨烯/Fe2O3纳米复合材料的制备及其储锂性能研究

采用软化学方法控制氧化石墨表面含氧官能团的数量,一步完成了石墨烯/Fe2O3纳米复合材料的控制合成.采用XRD和Raman光谱分析及TEM表征复合材料的组成、结构和微观形貌特征,并对石墨烯/Fe2O3复合负极的电化学储锂性能进行了研究.结果表明,石墨烯/Fe2O3复合材料作为锂离子电池负极材料具有较高的储锂容量和倍率性能,充放电循环性能稳定.在100 mA/g的电流密度下循环100次,可逆容量为606 mAh/g,放电效率保持在91;;在2 A/g下放电容量是其在250 mA/g下放电容量的58.2;.     

多级结构CuO微球的制备及室温NOx气敏性能研究

采用一步水热合成方法制备具有多级结构的CuO微球.以聚乙二醇为结构导向剂,通过改变水热温度控制表面形貌.结果表明:制备的CuO微球的直径约为2.1μm,并且球体表面是由纳米棒疏松排列的.这种多级结构增大了材料的比表面积和活性位点.室温下,水热温度为120.C的样品CuO120对NOx表现出优异的气敏性能,最低检测限可达到1 ppm.CuO120对100 ppm NOx的灵敏度为74.4;,响应时间仅为2.6s.同时,CuO120气敏传感器具有很好的选择性和稳定性.     

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.