六铝酸钙材料的合成及其显微结构研究

分别采用轻质碳酸钙和活性氧化铝 ,或纯铝酸钙水泥和活性氧化铝为初始原料 ,反应烧结合成了六铝酸钙 (CA6)材料 ,研究了原料和成型压力对合成材料的烧结性能和显微结构的影响 ,同时借助于XRD、TG -DSC、SEM和EDAX等测试手段对其反应过程、物相变化和显微结构进行了分析和观察。研究结果表明 :(1) 130 0℃时 ,合成材料的主晶相为刚玉相和CA2 ,并开始有CA6形成 ;温度升至14 0 0℃ ,CA6大量生成 ;15 0 0℃时反应完成 ,产物全部为CA6相。 130 0～ 15 0 0℃时 ,上述反应表现为体积膨胀过程 ,试样的体积密度和径向线收缩率随温度的变化不大 ;而高于 15 0 0℃时 ,试样明显趋向烧结 ,体积密度升高 ,线收缩率加大。采用纯铝酸钙水泥和活性氧化铝合成的试样的体积密度均高于采用轻质CaCO3 和活性氧化铝的 ,尤其在烧成温度高于 15 0 0℃时。坯体的成型压力对这两种合成试样的烧结性能均没有显著影响。 (2 )合成六铝酸钙材料的晶粒形貌与合成工艺有关 ,制备片状晶粒的六铝酸钙材料需满足两个条件 :一是晶核有足够的发育空间 ,二是从晶核生长形成片状结构需足够的物质扩散。采用纯铝酸钙水泥和活性氧化铝为原料的试样 ,其CA6晶核很容易发育成片状晶形 ,且随着坯体成型压力的增加 ,片状CA6有向等轴状发展的趋势 ;采用     

Kinetics of volume expansion during infusion of Ringer’s solution based on two volume model

In this work mathematical models were developed to represent the kinetics of volume changes of fluid spaces associated with infusion of Ringer’s solution. During infusion of Ringer’s solution, the human body is assumed to be characterized by the two-fluid space model which has second volume space in addition to the first volume so that fluid exchanges between these two spaces are possible. Various infusion types were tested to accommodate different medical situations. Volunteers were given Ringer’s solution and the changes in blood hemoglobin were detected. From the comparison with experimental data, the two-fluid space model was found to represent adequately the kinetics of human volume expansion during infusion of Ringer’s solution.     

纳米TiO2复合铁钛防锈颜料的研制及产业化进展

介绍了纳米TiO2复合铁钛防锈颜料的制备原理、工艺、技术指标;描述了铁钛防锈涂料的配方、性能检验和产业化进展情况.     

In-situ studies of electron field emission of single carbon nanotubes inside the TEM

Electron field emission characteristics of individual multi-walled carbon nanotubes (MWCNTs) were investigated in situ inside the transmission electron microscope (TEM). For a single MWCNT it was found that while field-emission can hardly occur from the side of the nanotube, a curved nanotube may result in finite side emission and the best emission geometry is the top emission geometry. Current-voltage (I-V) measurements made at different vacuum conditions and voltage sweeps emphasize the importance of the adsorbates on the electron field emission of MWCNTs. For a contaminated MWCNT, although the field emission current was reduced, the stability of its emission was improved. A current of up to several tens of μA was observed for a single MWCNT, but it was found that long time emission usually results in drastic structure damage that may lead to sudden emission failure.     

Effect of temperature on polymer migration II: Concentration equation

Polymer migration is a generally well-known phenomenon in a flow field, and it has been verified that the sources of such phenomena are nonhomogeneity of the flow, concentration effects and hydrodynamic interactions between the polymer molecules. In addition, temperature effects were found to be another source of polymer migration. The Langevin equation for a polymer molecule was first derived from single chain dynamics using a kinetic theory for the bead-spring elastic harmonic dumbbell model, as described in part I (reference [1]). In this paper the diffusion equation and concentration profile of the polymer molecules induced by a temperature gradient are obtained from the Fokker-Planck equation. A new differential operator is also introduced to calculate the concentration profile. From the concentration equation obtained in the general flow geometry, we find that in dilute polymer solution there are significant effects on the polymer migration not only due to the nonhomogeneity of the flow field but also due to temperature gradients.     

Dependence of properties of liquid crystalline aromatic copolyesters on monomer sequence-copolyesters derived from terephthalic acid, 2,7-naphthalenediol and p-hydroxybenzoic acid

Summary An aromatic copolyester with the ordered sequence of terephthalic acid (TA)-p-hydroxybenzoic acid (HB)-2,7-naphthalenediol (ND)-p-hydroxybenzoic acid (HB) was prepared and its properties were compared with those of the corresponding random copolyester having the same overall monomer composition. Thermal and crystallizing properties of the two polymers are quite different. The former exhibits significantly higher glass transition and melting temperatures than the latter. The former's degree of crystallinity also is much higher than the latter's. Both polymers are thermotropic and form nematic melts.     

功能性建筑涂料照亮市场

功能性建筑涂料除了具备普通建筑涂料的装饰作用外，还能起到某种功能性作用。随着国民经济的快速发展，其应用也越来越普遍，可以预期，功能性建筑涂料的实用性，拓宽建筑涂料的应用范围。本文作者庚晋介绍了几种功能性建筑涂料的特点、主要用途、最新研究动态、施工方法、市场前景等。     

Blends of chlorinated isotactic polypropylene with poly(ethylene-co-vinyl acetate) I. Effect of component polymers composition on the blend miscibility

Chlorinated isotactic polypropylenes (CPP) having various chlorine contents were blended with poly(ethylene-co-vinyl acetate)s (EVA) having various vinyl acetate (VA) contents. The blends were made by casting films from dilute THF solutions and miscibility of the blends was identified by single glass transition temperature, which was confirmed by DSC and dynamic mechanical measurements. Based on the miscibility data from a large number of CPP/EVA combinations, a miscibility map was depicted where CO equivalent weight (CO-EQW) of EVA was plotted against chlorine equivalent weight (Cl-EQW) of CPP. Though an attractive interaction between CPP and EVA could be detected in all the miscible and immiscible blend pairs, miscibility of the CPP/EVA blends could solely be observed in a relatively narrow range of Cl-EQW ca. 65–100 and CO-EQW ca. 170–230.     

Morphologies and microstructures of tree-like carbon produced at different reaction conditions in a CVD process

Centimeter-size multi-branched tree-like carbon structures have been generated by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor and investigated by means of SEM, TEM, and EDX. It is found that a temperature of 1000-1200 °C and a carrier gas flow rate of 1000-2500 ml/min are necessary for the generation of the carbon trees. Their morphologies and microstructures change greatly with the changing reaction conditions. The fractal dimensions of the trees are calculated to quantitatively investigate the influence of different reaction temperatures on the morphologies.     

A survey of traffic-based routing metrics in family of expected transmission count for self-organizing networks

Self-Organizing Networks (SONs) are attractive for applications where flexibility, resilience, and a large network service area are required. In order to meet the requirements of those applications, the principal issue is to guarantee efficient routing in SONs. Hence, the design and selection of appropriate routing metrics is important. A mass of metrics have been proposed in the past several decades. Among all the metrics, Expected Transmission Count (ETX) has drawn the most attention. Since the proposal of ETX, many ETX-based or extended metrics have been proposed. ETX and its descendants compose the ETX family. This paper is an attempt to analyze, compare and summarize traffic-based routing metrics in the ETX family. Details of each routing metric are presented and analyzed. Some of our viewpoints on the principal for designing metrics in SONs are presented.