稻壳灰对固井水泥石性能影响研究

本实验通过在实验室制备稻壳灰并测试其相关性能,然后将稻壳灰按照实验设定的方案加入水泥中,待其水化硬化再从宏观和微观两个方面进行分析,以此来评价稻壳灰对固井水泥石的影响因素。结果表明:稻壳灰含有孔状结构,是一种多孔材料,同时它易磨,易制备,经过研磨后的稻壳灰比表面积较大,微集料填充效应良好。另外本实验探究得出稻壳灰掺量为12%时,养护得到的水泥石试样早期强度同比净浆一天增长15%~20%,两天增长25%~30%,因此可得出稻壳灰能改善固井水泥石的早期强度,最佳掺量为12%。利用XRD、SEM、EDS和TG等实验设备分析稻壳灰提高固井水泥石早期强度的原理为稻壳灰可以使水泥石中不同粒度的原料呈最密堆积,提高水泥石的致密度;稻壳灰中的高活性Si O2会与水泥的水化产物Ca(OH)2发生火山灰反应促进水泥的二次水化,生成了大量胶凝相即水化硅酸钙,提高水泥石的力学性能和改善水泥石微观结构。     

硬化水泥净浆基于纳米压痕的相态识别与水化程度计算

采用纳米原位压痕手段测量硬化水泥净浆中单一相态的代表性微观力学性能,并采用纳米点阵压痕研究各相态的含量。研究对象囊括水灰比为0.3、0.4、0.5的纯水泥净浆和水灰比为0.3情况下含50%、70%矿渣掺量复合体系,共5种配比,以表征它们的相态分布和微观力学性质的异同点。掺矿渣的试件中含有明显多的复合相,因此提出三相模型测算复合相中未水化物的体积分数。此外,提出基于纳米压痕技术计算纯水泥和掺矿渣水泥试件水化程度的方法,结果吻合于热重分析的结果,其中纯水泥净浆中复合相较少,计算得到的水化程度优于对掺矿渣水泥试件的计算。     

跨尺度模拟硬化水泥净浆力学性能:微观物相的影响

采用纳米压痕实验测量硬化水泥净浆中未水化物、水化产物和孔隙等微观物相的力学性能,并基于背散射电镜（BSE）图像的灰度分析计算各微观物相的含量。在得到各微观物相含量和力学性能的基础上,针对水泥净浆的弹性模量进行均一化建模,并讨论各微观物相及其模量的选取对跨尺度模拟硬化水泥净浆力学性能的影响。通过微米压痕的实测净浆模量验证模型及参数选取的可靠性。提出在硬化水泥净浆力学性能的多尺度模型中,需要选取12 GPa作为孔隙有效模量,并将水化产物划分为低密度的水化硅酸钙凝胶（LD-CSH）和高密度的水化硅酸钙凝胶（HD-CSH）两种物相,而不同种类的未水化物可被视作一种物相。在此基础上,使用Mori-Tanaka模型或自洽模型计算得到的净浆模量与实测净浆模量吻合。     

冲击荷载下高韧性水泥基复合材料动态力学特性与微结构演化研究

为提升水泥基材料静态力学性能、抗冲击特性及为减少温室气体排放而降低水泥用量,以硅粉为矿物掺合料(掺量为10%,质量比)、钢纤维为功能组分(掺量为2%,体积比),并匹配高效减水剂(掺量为1.5%～2.0%,质量比)制备高韧性水泥基复合材料,通过准静态抗压/抗折强度、分离式霍普金森压杆试验和采用水化微量热仪、热重分析仪,分别研究了高韧性水泥基复合材料准静态/动态力学特性及其微结构演变特征。结果表明：冲击荷载下(冲击速率为0.5 MPa/s)水泥基材料典型破坏过程分为三阶段,高韧性水泥基复合材料受作用后仅出现局部浆体剥落、飞散现象,而基准组体系均发生显著破坏直至整体破碎;硅粉在10%掺量下有效提升了水泥基复合材料体系早期和后期的准静态力学性能,1 d天龄期下抗压强度和抗折强度最高可达61.4 MPa、23.9 MPa,也显著提升了动态抗压强度至123.3 MPa(28 d天龄期)。微结构演变结果表明：硅粉和减水剂复合作用下浆体水化放热速率主峰提前,且主要水化产物——氢氧化钙含量减少,降低了浆体内部氢氧化钙分布的取向性,有助于改善浆体微结构。     

高速水流下空蚀热效应对水泥水化产物的破坏

随着坝工技术的提高和水力资源的深入开发利用,高坝建设发展迅速,其泄量大、流速高时的泄洪消能和抗空蚀保护问题是目前建设中的主要技术难题。区别于传统对高速水流引发空蚀的力学破坏定义,本研究从热学角度阐述了空蚀引起破坏的机理。本研究利用超声波空蚀仪进行不同类型水泥净浆空蚀试验,综合空蚀破坏面表面分析和对空蚀破坏后的水泥水化产物微观成分分析,对空蚀在硬化水泥表面产生的热效应进行测定和研究分析,初步讨论空蚀热效应对混凝土结构的破坏机理。试验结果表明,空蚀对水泥净浆表面的破坏不仅是简单的力学破坏,同时空蚀热效应还可以造成水泥水化产物的部分分解。具体而言,经过6 h超声空蚀试验后的试样,水化凝胶损失量不低于40%,氢氧化钙的损失量在25%以上,这对硬化水泥浆体的劣化有较为显著的影响。     

改性水稻秸秆对水泥基材料性能影响研究

为了减少农作物纤维废弃造成的污染,研究了利用植物纤维制备建筑材料的工艺,首先采用碱煮法对植物纤维进行改性,然后将其分别与聚丙烯纤维按照不同的比例加入到水泥净浆中进行比较,结果表明:植物纤维在水泥净浆中的分散比加入聚丙烯纤维均匀,经过改性后的秸秆纤维对水泥凝结硬化时间无明显影响,随掺量增加,水泥净浆的抗折强度呈先增后减趋势,且在掺量为4.5%时最高,与未掺纤维的参照组相比抗折强度提高了11%,抗压强度降低了近24%。并将其掺入砂浆中,砂浆抗干缩性能得到改善,植物纤维掺量为6.0%时砂浆干燥收缩值比基准组下降了37%,在本研究掺量条件下,与加入聚丙烯纤维相比,加入秸秆纤维对水泥净浆的抗折强度和抗压强度影响较小,原因在于其分散性更好。     

微组分对磷铝酸盐水泥耐水性的影响初探

以净浆力学强度及Ca”和[A1O4]^5-离子溶出浓度为耐水性评价指标，研究了微组分石膏对磷铝酸盐水泥（phosphoaluminate cement，PALC）的影响，并通过S电位、XRD和孔结构等技术分析了其耐水性机理。结果表明：在浸水过程中，掺石膏和未掺石膏的磷铝酸盐水泥硬化浆体的力学性能均在不断提高，Ca^2＋和[AIO4]^5-的溶出浓度不断减小。相比较而言，掺石膏的磷铝酸盐水泥试样在浸水早期的力学性能和离子溶出浓度较未掺的变化不大，但在长期浸水的过程中，前者力学性能明显高于后者，而Ca^2＋和EAIO4]^5-溶出浓度却显著下降，这表明在磷铝酸盐水泥中掺入石膏，对其早期耐水性影响不大，但对长期耐水性的提高是十分有利的。     

内掺氯离子与硫酸根离子在水泥净浆中的交互作用

模拟南海海水中阴离子浓度,采用氯离子、氯离子与硫酸根离子复合盐溶液分别作为拌合水制备水泥净浆,通过XRD定量分析、SEM及离子滴定等测试方法对不同标养龄期的水泥净浆进行微观分析,研究内掺氯离子和硫酸根离子在水泥净浆中的交互作用。结果表明,在内掺氯离子条件下,含氯离子的盐溶液作为拌合水拌合水泥净浆迅速生成Friedel盐(FS);氯离子的存在有抑制钙矾石(Ettringite,AFt)生成的作用;当氯离子浓度为3. 5%(质量分数)、硫酸根离子浓度为0. 5%(质量分数)时,硫酸根离子的引入促进了AFt向FS转化,提高化学结合氯离子的量;水化早期化学结合即氯离子参与反应形成FS占主导,硫酸根离子起到辅助作用;水化后期物理吸附即C-S-H凝胶对离子的吸附作用增强,对化学结合氯离子有一定的抑制作用。     

玉米秸秆糖醇黑液化学改性制备木质素基减水剂的研究

玉米秸秆糖醇黑液在100~140℃下与甲醛、Na_2SO_3溶液(摩尔比0.6~0.8)发生磺化、磺甲基化反应2~4h,制备出木质素基减水剂,由傅里叶变换红外光谱表征其结构。通过减水率、凝结时间及抗压强度分析木质素基减水剂对水泥水化的作用规律,并结合X射线衍射和扫描电镜研究木质素基减水剂对水泥水化进程的影响。结果表明:改性制备的木质素基减水剂,可有效减缓水泥初期水化,促进后期水化,对水泥颗粒有良好的分散效果;水灰比0.35、掺量为1.2%时,减水率为17.5%,达到高效减水剂标准;掺加减水剂试样的初凝、终凝时间均显著延长,能有效提高水泥硬化体抗压强度。     

氧化石墨烯对水泥净浆流动度及水泥石结构和性能的影响

采用Hummers法及超声破碎分散法制备了氧化石墨烯(GO)纳米相分散液,研究了GO对水泥净浆流动度和水泥石微观结构的影响,用FT-IR、AFM、XRD及SEM对GO及水泥石结构进行了表征。结果表明GO的掺入降低了净浆流动性,每增加0.01%的GO需要增加0.02%的聚羧酸系减水剂(PCs)以保持水泥净浆流动度在3 h内在200 mm以上,GO的掺入能够使水泥石的微观结构发生明显的变化,当GO/PCs掺量为0.01%/0.24%~0.03%/0.28%时,水化龄期7 d的水泥石出现了大量分散均匀的花状微晶体,当GO/PCs掺量为0.05%/0.32%~0.07%/0.36%时,同龄期水泥石中出现大量的片状晶体,在水化龄期延长到28 d时有转化为密实结构的趋势,结果说明GO具有调控水泥水化产物形貌的能力及增强增韧的作用,此研究结果对于提高水泥基材料的力学性能具有重要意义。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.