高温下C11A7·CaF2矿物稳定性的研究

研究了高温下C11A7·CaF2的稳定性,并测定其熔点;探讨了利用Raman光谱分析方法判定氟铝酸盐相存在的可能性.结果表明:C11A7·CaF2是一致熔融化合物,其熔点为1465℃,高温下它并不存在传统观点所认为的分解反应;与C12A7不同,经高温煅烧所得的C11A7·CaF2晶体结构中不含OH-离子;Raman光谱上在520cm-1处是否出现吸收谱带可以作为测试样品中是否存在C11A7·CaF2晶体的判据.     

图表1-17 用兰京公式求临界载荷

截面积A em,P=口·A应力口砧起p户视应力助固定)铸铁硬钢人软钢祷为一端固定一1为两端铰接,二盛为两端固定木材 当柱长还不需要用欧拉公式计算长度(L/K小于。、/而)且用纯压缩公式(『=尸/A)计算又过长(L/K>30)时,柱的临界载荷〔压曲强度)采用兰京公式计算。即:(1)I岛0.4D汾,A=二D”J,所以『二一一一一一下一万一了下万一二’.…“.‘. ,a 1 iJ、一 1十一.碑云)l 阴\丈、/ 尸二『·A············,··…(2) 式中,,。为材料的抗压强度(公斤/厘米2),a为实验常数,(T。与a的数值如表1一7所列。m为由两端支承方法决定的常数,可…     

图表1-2 载荷、截面积和应力

直径d截面积A2 .000 在截面积为A(厘米“)的棒上施加尸公斤的拉伸(压缩或剪切)(参看图卜1,a为拉伸,b为压缩,c为剪切)载荷时,产生对拉伸、压缩为: 『一暑(公斤/厘米2卜·····……(l)的应力(拉伸、压缩、剪切)。图表1一2是表示这一关系的。 此外,求圆棒的截面积A时,设棒直径为d(厘米)则A二晋d,(厘米2)······……(3)对剪切为: 尸_.___二_,=万(公厅/厘术‘)””·‘……(乙) 在A轴的左面刻有直径d,因此求圆截面时可以直接用d代替面积A。对于各种材料的许用应力由于使用条件及其他原因不能一概而论,而对在一般机械上使用的各种材料,…     

锂离子电池负极材料石墨烯复合氧化铋的电化学性能研究

通过水热法制备Bi_2O_3-rGO复合物作为高性能锂离子电池负极材料。Bi_2O_3颗粒均匀分布在石墨烯片层中,形成网络结构。Bi_2O_3-rGO复合物负极材料表现出了优异的电化学性能,在100 m A/g的电流密度下,首次放电比容量为1 438.6 m A·h/g,循环100次后容量为312.1 m A·h/g,高于未包覆的Bi_2O_3粉末(首次放电比容量为1 709.6 m A·h/g,循环100次后容量为47 m A·h/g),且在800 m A/g的电流密度下,容量仍有239.1 m A·h/g。Bi_2O_3-rGO复合物优异的电化学性能主要归因于高的电子导电率、大的比表面积及低程度的结构坍塌。     

建立"匹配理论"的工艺配方体系(连载二)

2原料特性要匹配的因素2.4原料中硅酸盐矿物Si-O结构选择匹配烧水泥的校正原料都以硅酸盐矿物组成为主的原料。如粘土、辉绿岩中的硅酸盐矿物:粘土:高岭土A l4犤Si4O10犦·8H2O层状结构石英SiO2架状结构辉绿岩:辉石Ca(M g·Fe2 ·Fe3 Ti·A l)犤(Si·A l)2O6犦单链结构角闪石C a2·N a(M g·Fe)4(A l·Fe3 )犤(Si·A l)4O11犦2(O H)2双链结构这就要明确硅酸盐校正原料:(1)原料中硅酸盐矿物的Si-O结构形式直接影响原料的物化特性,见表4。(2)水泥烧成反应中无论多复杂的Si-O结构体,都要解聚到活性的犤SiO4犦4-去参与固相和液相…     

新型蜂窝浸渍树脂及对位芳纶纸蜂窝性能

制备了一种适用于对位芳纶纸蜂窝的新型浸渍树脂——F·JN-5-07A/B树脂,并对其黏度和固化特性进行了表征,结果表明,改性后的F·JN-5-07A/B树脂在25～70℃具有适中的对位芳纶纸蜂窝浸渍工艺黏度(11～14 Pa·s),并且在70℃恒温1 h后的黏度升至68 Pa·s;固化温度较改性前降低了109.7℃,大...     

高取向富锂正极材料的合成及电化学性能

以六亚甲基四胺(HMT)为导向剂,通过水热法,在不同温度下合成了六边形薄片状的高取向三元前驱体NixCoyMn1-x-y(OH)2,采用氯化钾与氯化钠的混合熔盐法对前驱体进行煅烧后得到高取向富锂正极材料。经X射线衍射、扫描电镜等表征,材料具有良好的层状结构,在(003)晶面具有很高的择优取向。电化学测试结果表明,在0.1 C倍率下(20 m A/g),材料的首次放电容量为282.5 m A·h/g;1 C倍率下经30次循环放电容量从195.7 m A·h/g降至178.8 m A·h/g,容量保持率为91.4%;当倍率分别为2 C和5 C时,材料的放电容量分别为150.6 m A·h/g和110.0 m A·h/g。材料具有良好的循环稳定性和倍率性能。     

豆腐为原料的多孔炭的制备及其储锂性能研究

以富含蛋白质的豆腐为原料,经冷冻干燥和炭化过程制备出多孔炭材料,利用SEM、FTIR、XPS、Raman以及XRD等分析手段研究了所得炭材料的物理化学性能。将其作为锂离子电池负极材料使用时,在50 mA·g~(-1)的电流密度下,首次恒流充电容量可达817.6 m A·h·g~(-1),循环10次可维持351.9 m A·h·g~(-1)的可逆比容量,当电流密度上升至2 A·g~(-1)时,仍可维持76.5 mA·h·g~(-1)的可逆比容量,表明多孔炭材料具有良好的电化学性能。     

结构有序的Si/void/C/graphene纳米复合结构的制备及储锂性能

采用简单的超声、冷冻干燥和热还原相结合的自组装方法,设计和构建了纳米硅核/间隙/无定形碳壳层/石墨烯(Si/void/C/graphene)三维有序纳米复合结构。在该结构中,纳米硅核与碳壳层之间的空隙有效避免了硅的巨大体积膨胀对碳层的破坏,大幅度提高了锂离子电池的循环稳定性;将Si/void/C纳米结构嵌入在石墨烯层与层之间,利用石墨烯卓越的导电性和柔韧性,进一步缓冲了硅材料的体积效应和提高了复合材料的导电性能。该复合材料在4200 m A·h·g~(-1)(1 C)电流密度下循环1000次后比容量仍高达1603 m A·h·g~(-1);在67 A·g~(-1)(16 C)的高倍率下,比容量仍有310 m A·h·g~(-1),显示出了在锂离子电池负极材料领域的巨大应用潜力。     

纳米多孔NiO类空心微球负极材料的制备与储锂性能

以NiCl_2·6H_2O、尿素、葡萄糖为原料采用水热法制备了NiO前体,将前体在空气中烧结最终得到NiO电极活性材料。该NiO样品具有镂空结构的类空心球形貌,且由50~100 nm初级纳米颗粒构成。对该NiO样品作为锂离子电池负极材料的储锂性能进行了研究,结果发现赝电容效应对该材料储锂容量和倍率性能有重要贡献。因独特的空心纳米结构和赝电容效应,该材料表现出出色的电化学循环稳定性和优异的大倍率充放电性能。在500m A·g~(-1)电流密度下,100圈充放电循环后放电比容量为650 m A·h·g~(-1),容量保持率达86.6%;在10 A·g~(-1)的超高倍率下,其稳定放电比容量仍高达432 m A·h·g~(-1)。     

一种新颖的流量测量装置--弯管流量计

从流体力学的基本原理出发，本文介绍了一种新颖的流量测量装置——弯管流量计。本章详细推导了弯管传感器的流量计算公式，并讨论了其在实际应用中应注意的几个问题。     

Network properties: 2. A broadline n.m.r. study of molecular motions in some multicomponent crosslinked polymers

A series of multicomponent polymers of known structure and consisting of poly(vinyl trichloroacetate) crosslinked with poly(methyl methacrylate) (PMMA) have been examined by broadline n.m.r. Both enhanced and retarded rotation of the α-methyl groups on the PMMA chains, compared with those in PMMA homopolymer, have been observed. A previous assessment of the morphologies of the same polymers, based on the results of dilatometric studies, has been extended. The modifications to the rotations of the α-methyl groups have been correlated with the morphologies of the multicomponent polymers and it is proposed that both effects arise as a result of changes in the distribution of conformations adopted by the PMMA chains in the multicomponent polymers compared with that in the pure homopolymer.     

A fully automated four-probe d.c. conductivity technique for investigating solid electrolytes

A fully automated four-probe d.c. conductivity technique has been described for investigating the conductivity of solid electrolytes as a function of temperature and time. The technique is equally applicable to semiconducting and superconducting materials. With full automation, the time for data acquisition is very short and the reproducibility is high. Several uncertainties associated with manual recording of data are reduced. Some applications of the technique have been described. Various sources of error associated with collection of data have been considered and limitations and advantages of the techniques have been discussed.     

Modeling of poly(ethylene terephthalate) reactors. II. A continuous transesterification process

A comprehensive mathematical model for a continuous transesterification process has been built so as to enable prediction of the influence of different process and operational variables on productivity and by-product formation. The influence of temperatures and temperature profiles, of residence time and residence time distribution, and also of the number of reactors in series has been investigated. The modeling has been done as close to the industrial practice as possible. Important pragmatic implications from the point of view of operation of continuous transesterification are highlighted.     

A broad-line n.m.r. investigation of methyl motion in poly(methylmethacrylate)

Broad line n.m.r. measurements have been carried out over a wide range of temperatures on poly(methylmethacrylate) (PMMA) and several selectively deuterated forms of this polymer. The line shapes and second moments for the different samples were examined in the light of theoretical calculations based on possible structural models. A spectrum subtraction procedure was particularly useful in confirming the conclusions drawn from consideration of second moment data. A consistent set of conclusions was obtained for the motion of the methyl groups.     

Modelling of poly(ethylene terephthalate) reactors. III. A semibatch prepolymerization process

A mathematical modelling of a semibatch prepolymerization process has been undertaken. Prepolymerization conducted at constant temperature and pressure and with a predetermined variation in temperature and pressure has been studied. Influence of DMT and TPA addition during prepolymerization has also been examined. The focus has been on investigation of the influence of processing and operational variables on productivity and side product formation, which controls product quality. The results of this investigation (which are applicable only up to DP ? to 30) are borne out by the limited experimental data available in the literature. Important pragmatic implications of the results of the work in terms of design and operation of prepolymerization reactors have been emphasized.     

中国芦荟与库拉索芦荟的化学成份比较研究

本文对云南省元江县引种的产于云南元江河谷的野生中国芦荟 (简称元江芦荟 )及库拉索芦荟进行了比较研究。研究结果表明 ,二种芦荟的主要化学成份基本一致 ,分布部位也相同。均含有芦荟中具有生理活性的特征化合物、氨基酸、维生素、矿物质等成份 ,但是某些成份的含量有差异。元江芦荟是一种具有发展潜力的芦荟品种。目前这方面的研究未见报导     

Fundamentals of plasticating extrusion. I. A theoretical model for melting

A steady state model for melting in a screw extruder has been developed based on the assumption that a stable solid bed of polymer granules is melted by heat that is conducted from a hot barrel and heat that is generated by viscous dissipation in the film that separates the solid bed and the surface of the barrel. The solid bed gradually decreases in width, as it proceeds in the channel, until it disappears at which point the melting is terminated. The model predicts the solid bed width profile and the required length of melting in terms of physical properties, operating conditions, and geometry of the screw. The model has been tested based on experimental data.     

The raw linseed oil acetone foots test. I. A centrifuge tube and method for rapid determination

Summary A rapid method, requiring less than one hour to apply, has been developed for determining the acetone foots content of linseed oils using centrifugal force to compact the foots layer instead of the force of gravity. Application of the method requires the use of a centrifuge tube of novel design. Conditions known to affect the results obtained by the A.S.T.M. gravity test have been investigated as they apply to the centrifuge test and found to have little or no effect on the results of the latter test. Correlation of the percentage of centrifugal foots under stated conditions with percentage of foots by the gravity method has been determined for both the heated and chilled tests. Under the conditions chosen for the centrifugal test the magnitude of the heated test result is about the same as the processing shrink sustained when these foots are removed in practice. The reproducibility of the method, based on this work, is equal to or better than the gravity test now in use for trading linseed oil. A modification of this test has been developed specifically for use on crude soybean oil and a paper describing it is in preparation.     

Modeling of poly(ethylene terephthalate) reactors. I. A semibatch ester interchange reactor

A comprehensive model for a semibatch ester interchange reactor has been developed with a view to investigate the effect of various process and operational variables on the DMT conversion rate as well as the by-product formation. The influence of important variables such as EG-to-DMT ratio, catalyst concentration, and operational variables such as temperature and pressure has been considered. Definite conclusions concerning the choice of the desirable range of process and operational variables to maximize productivity and minimize by-product formation have been reached.