卤水侵蚀对水泥粉煤灰浆体微结构影响

采用XRD、29Si和27Al MAS NMR测试技术,研究了粉煤灰掺量和侵蚀龄期对卤水侵蚀下水泥-粉煤灰浆体水化产物相组成、含铝相产物迁移与转变、C-S-H凝胶微结构变化的影响规律.研究结果表明:卤水侵蚀导致浆体Ca (OH)2含量降低,AFm和TAH向AFt转变,同时生成大量Friedel盐,C-S-H凝胶中Al[4]脱出;随粉煤灰掺量增加,浆体中AFt、AFm和TAH生成量降低,C-S-H的MCL和Al[4]/Si增大,Friedel盐生成量先增后减;侵蚀早期,水泥-粉煤灰浆体结构疏松,AFt生成量较纯水泥高,后期浆体致密性提高,抑制卤水侵蚀,AFt生成量较少,C-A-S-H脱铝作用减弱.     

高温养护下粉煤灰在大体积混凝土中效应机理研究

以大掺量粉煤灰胶凝材料硬化浆体为研究对象,结合XRD、FTIR、NMR等仪器进行测试分析,研究高养护制度下粉煤灰掺量对其水化相C—S—H凝胶硅氧四面体聚合程度的影响规律。结果表明：高温养护的硬化浆体,其水化相C—S—H凝胶硅氧四面体聚合程度和Al原子取代Si原子的程度,在各个养护龄期始终高于常温养护的硬化浆体。     

高温养护下粉煤灰效应机理研究

大体积混凝土施工过程中,为降低水化热而采用大量的粉煤灰替代水泥,故对高掺量粉煤灰水泥的水化硬化机理进行深入系统的研究具有重要的意义.以大掺量粉煤灰胶凝材料硬化浆体为研究对象,结合XRD、FTIR、NMR等测试分析,研究高养护制度下粉煤灰掺量对其水化相C-S-H凝胶硅氧四面体聚合程度的影响规律.结果表明:高温养护的硬化浆体,其水化相C-S-H凝胶硅氧四面体聚合程度和Al原子取代Si原子的程度,在各个养护龄期始终高于常温养护的硬化浆体.     

干湿循环下MgSO4侵蚀对UHPC相组成及其微结构的影响机理

UHPC在海洋工程建设中具有良好的应用前景,但海洋环境中存在的腐蚀性离子和干湿循环作用将会影响UHPC的微观结构,进而影响其耐久性能.通过XRD,SEM-EDS,29 Si和27 Al NMR等方法研究了干湿循环下MgSO4侵蚀和养护制度对UHPC微结构的影响.结果表明:干湿循环下MgSO4侵蚀可促进UHPC浆体中AFt和Mg(OH)2生成,降低C-S-H凝胶的Al[4]/Si和Ca/Si,并促进TAH和硅氧链上脱离的Al向AFt和AFm转化;210℃-2 MPa压蒸养护过程可降低UHPC浆体中的Ca(OH)2和SiO2含量,提高UHPC浆体的水化程度和致密度,并形成Al[4]/Si较高且Ca/Si较低的C-S-H凝胶;压蒸养护可减少侵蚀作用下AFt和Mg(OH)2的生成,有效削弱MgSO4干湿循环侵蚀对UHPC浆体中C-S-H凝胶的脱铝和脱钙作用,并减少Al相转化程度.     

压蒸条件下花岗岩石粉对UHPC性能的影响

研究了在压蒸条件下花岗岩石粉取代石英粉掺量对超高性能混凝土力学性能(3d、180 d抗压/抗折强度)和微观结构(水化产物、C-S-H凝胶平均分子链长)的影响,并探明两者之间的关系.XRD、SEM-EDS、29Si NMR测试结果表明:3 d、180 d胶凝浆体水化产物主要为低钙硅比、本征强度较高的tobermorite晶体.随着花岗岩石粉取代率增加,混凝土抗压/抗折强度先增加后减小,当取代率为50％时,其180 d抗压强度≥190 MPa、抗折强度≥40MPa;且随着取代率的增加,C-S-H凝胶平均分子链长降低、Al[4]/Si增加;在相同取代率时,平均分子链长为180d＞3d,Al[4]/Si为180 d＜3 d.高温和高压条件下,C-S-H凝胶平均分子链长不是混凝土性能的单一影响因素,混凝土抗压强度与C-S-H凝胶平均分子链长不直接相关.     

高炉镍铁渣粉在水泥基复合胶凝材料中的水化特性研究

通过对不同高炉镍铁渣掺量的水泥-高炉镍铁渣粉复合胶凝材料水化放热速率、高炉镍铁渣粉的反应程度、硬化浆体化学结合水含量以及水化产物中C-S-H凝胶Ca/Si的测定,分别研究了水泥-高炉镍铁渣粉复合胶凝材料的早期、中长期水化进程、浆体微观形貌以及水化产物特点等水化特性.研究结果表明:高炉镍铁渣的掺入会降低水化放热速率,并推迟水化加速期放热峰的出现时间;在复合胶凝体系中,随着高炉镍铁渣粉掺量的增大,其反应程度和硬化浆体中化学结合水含量将降低.复合胶凝材料水化生成的C-S-H凝胶的Ca/Si低于水泥,且随着水化的进行呈降低趋势;高炉镍铁渣粉中的Al,在水化过程中会取代部分Si进入C-S-H凝胶中,形成C-A-S-H凝胶.     

硫酸盐侵蚀条件下C–(A)–S–H组成-结构演化的量化分析

采用Fourier变换红外光谱、综合热分析、~(29)Si魔角自旋核磁共振及透射电镜-能谱等方法,研究了5%Mg SO_4(质量分数)溶液干湿循环作用下硅酸盐水泥及高抗硫酸盐水泥砂浆中水化硅酸钙凝胶(C–(A)–S–H)结构变化。结果表明:硫酸盐易侵蚀C–(A)–S–H凝胶中[Al O_4]桥氧四面体,[Si O_4]长链中Q~1(二聚体或硅链尾端)也易受Mg SO_4侵蚀形成M/C–(A)–S–H凝胶;硫酸根与阳离子桥接,形成–Si–O–M~(2+)–1/2SO_4~(2–)结构吸附于C–(A)–S–H凝胶表层。采用托贝莫来石/羟基硅钙石混合模型(T/J model)推演了硅酸盐水泥和高抗硫酸盐水泥中C–(A)–S–H凝胶在Mg SO_4溶液中干湿循环后的结构差异,给出了侵蚀后C–(A)–S–H组成化学式。提升抗Mg SO_4侵蚀能力在于控制膨胀产物(石膏及AFt)及C–(A)–S–H凝胶中[Al O_4]桥氧四面体含量。     

用~(27)Al MAS NMR分析铝掺杂水化硅酸钙结构中铝的配位状态（英文）

制备了具有宽范围Ca/(Si+Al)比和Al/Si比的铝掺杂水化硅酸钙(C-A-S-H)系列样品,采用~(27)Al魔角旋转固体核磁共振技术(~(27)Al MAS NMR)半定量研究了Al在C-A-S-H结构中的配位状态。结果表明:Al在C-A-S-H结构的配位形式和位置主要取决于其初始Ca/(Si+Al)比和Al/Si比。当初始Ca/(Si+Al)比低时(0.6和0.8),Al只能取代硅酸盐链硅氧四面体结构中四配位的Si,以Al[4]的形式存在;随着Ca/(Si+Al)比的增加,部分Al开始形成Al[5]和Al[6],且随着Al/Si比的增加,Al[4]的含量减小,Al[5]和Al[6]的总量增加,但Al[4]还是占主要比例,Al[5]的量非常少。Al[4]既可取代桥四面体中的Si也可取代配对四面体中的Si,但优先取代的是桥四面体中的Si,两者取代比并非恒定,而是随着初始Ca/(Si+Al)比和Al/Si比的变化而变化。     

聚乙烯醇对溶液沉淀法制备的水化硅酸钙纳米结构的影响

通过溶液沉淀法制备了初始钙硅比为1.0～1.7的掺杂PVA的水化硅酸钙(C-S-H-PVA)系列样品,研究了C-S-H-PVA的纳米结构特征.结果表明:PVA的加入增加了C-S-H的层间距,影响了C-S-H的层间结构;C-S-H-PVA样品的Fourier变换红外光谱中出现了CH2/CH伸缩振动峰,29Si核磁共振(NMR)谱中出现了1个Q1峰和2个Q2峰,而且PVA的加入使Q1、Q2峰向更负方向偏移,使Q2/Q1的比值以及硅酸盐链的平均链长(MCL)增长,说明PVA能增加C-s-H结构中的硅氧四面体聚合度.随着钙硅比的增加,C-S-H-PVA样品的29Si NMR谱中Q1、Q2峰的化学位移向正方向偏移,Q2/Q1的比值以及MCL减小,这一变化规律与未掺PVA的C-S-H样品的变化规律类似.     

硫酸盐侵蚀对不同养护制度UHPC水化产物微结构的影响

采用29Si和27Al MAS NMR、XRD、SEM等测试技术研究了硫酸盐侵蚀对不同养护制度的超高性能混凝土(UHPC)水化产物微结构的影响.结果表明:标准养护和80 ℃高温蒸汽养护条件下,UHPC水化产物主要为C-S-H、Ca(OH)2、AFt、AFm和TAH;210 ℃、2 MPa蒸压养护8 h后,水化产物主要为tobermorite、Ca(OH)2和TAH.硫酸盐侵蚀对不同养护制度的UHPC抗压强度和水化产物微结构的影响微弱,但可促进210 ℃蒸压养护的UHPC胶凝浆体中TAH向AFm和AFt的转化.同时硫酸盐侵蚀180 d时,C-S-H凝胶MCL和Al[4]/Si略有降低,但降低幅度较小,UHPC具有良好的抗硫酸盐侵蚀能力.     

Physicochemical effects of nanosilica on C3A/C3S hydration

In this paper, C₃A-gypsum and C₃A-C₃S-gypsum model cement systems with and without nanosilica were studied. The effects of nanosilica on the early stage cement hydration, particularly C₃A hydration, were assessed through the heat of hydration (isothermal calorimetry), phase assemblage (quantitative X-ray diffraction), zeta potential, ion concentration measurements, and morphology (scanning electron microscopy) examinations. The results indicate that while promoting C₃S hydration, nanosilica retarded C₃A hydration in both the systems studied. The retardation was caused by the adsorption and coverage of nanosilica on C₃A surfaces through the electrostatic interaction, thus decreasing the C₃A dissolution rate and hindering the precipitation of hydration products. Consequently, the reduced gypsum consumption rate and the seeding effect of nanosilica further promoted C₃S hydration. These findings suggest that nanosilica and other silica-based nanoparticles can physicochemically influence hydration of cement-based materials, and a better understanding of these influencing mechanisms can help optimize performances of nanoparticle-modified cement-based materials.     

C Br F_3

Freon FE 1301(CBrF_3)已开始作为灭火剂使用。該物无毒,对于多种金属、橡胶、合成树脂等都不侵蝕。作为灭火剂,它的效力按同等重量計算,是四氯化碳的6～11倍,二氧化碳的3.5～7倍,重碳酸鈉等的粉末灭火剂的約2倍左右。过去灭火剂的作用,可分为:(I)冷却,(2)遮断氧气,(3)可燃物与火焰隔断。CBrF_8也多少有这些灭火作用,并能轉移急遽的或激烈的火焰,与燃燒中間物体     

Effect of BaCO3 on C3A hydration

Ba ions are known to immobilise sulfates by forming BaSO₄. The use of BaCO₃ as a full or partial substitute for gypsum to regulate C₃A (3CaO·Al₂O₃) hydration was consequently studied with a view to establishing its correct dosage in sulfate-resistant cements presently under development.The hydration rate of synthetic C₃A was determined in the presence of varying percentages of gypsum, BaCO₃, and gypsum + BaCO₃ by running conduction calorimetry analyses on early age (up to 20 h) samples. The hydration products were subsequently identified with XRD, FTIR and DTA/TG.The addition of (20–42 wt.%) BaCO₃ to C₃A neither regulated the speedy reaction of the latter with water nor reacted with the aluminate. Gypsum + BaCO₃ blends proved able to regulate C₃A hydration; the heat flow curves for the mixes studied exhibited an induction period, an indication that gypsum acted as a C₃A hydration regulator whilst at the same time reacting with BaCO₃ to form barite.     

常怀"空杯心态"——来自3C审核的感悟

2008年度．笔者作为强制性产品认证审查员参加了防冻剂产品强制性认证的审核。审核过程中,在老审核员的指导和帮助下,我学到了很多审核的专业知识和技巧,也改变了过去一些错误的想法和认识。令我感触颇深的是．作为一个审核员应该如何怀着一种“空杯心态”去对待新拓展的审核领域甚至每一次的审核任务。     

碳三加氢反应器的优化操作

建立了碳三加氢反应器平推流模型,模型计算结果与生产数据吻合.根据模型的计算结果对生产装置进行了调整.适当降低反应压力可以减少绿油生成量,但不会影响加氢效果.存在最佳循环比,在最佳循环比下操作,即可以控制床层温升,又可以维持丙炔、丙二烯的高转化率.     

Facile Hydrogenolysis of C(sp3)–C(sp3) σ Bonds

The modification of benzylic quaternary, tertiary, and secondary carbon centers through palladium‐catalyzed hydrogenolysis of C(sp³)–C(sp³) σ bonds is presented. When benzyl Meldrum's acid derivatives bearing quaternary benzylic centers are treated under mild hydrogenolysis conditions – palladium on carbon and atmospheric pressure of hydrogen – aromatics substituted with tertiary benzylic centers and Meldrum's acid are obtained with good to excellent yield. Analogously, substrates containing tertiary or secondary benzylic centers yield aromatics substituted with secondary benzylic centers or toluene derivatives, respectively. Furthermore, this strategy is used for the high yielding synthesis of diarylmethanes. The scope of the reductive dealkylation reaction is explored and the limitations with respect to steric and electronic factors are determined. A mechanistic analysis of the reaction is described that consisted of deuterium labelling experiments and hydrogenolysis of enantioenriched derivatives. The investigation shows that the C(sp³)–C(sp³) σ bond‐cleaving events occur through a hybrid S_N1/S_N2 mechanism, in which the palladium center displaces a carbon‐based leaving group, namely Meldrum's acid, with inversion of configuration, followed by reductive elimination of palladium to furnish a C−H bond.

     

Implications for C3S kinetics from combined C3S/CA hydration

This study was performed to understand the influence of a critical amount of CA on the kinetics of C₃S hydration. For this purpose, monoclinic C₃S was blended with 15 wt.% CA and investigated by heat flow calorimetry and in situ XRD at 23°C at a water to cement ratio of 0.5. The binary mixture shows 3 distinct heat flow maxima where the underlying C₃S dissolution is proceeding stepwise. The C₃S dissolution rates during the 3 steps are varying strongly, depending on the hydrate phase precipitated during the respective reaction step. Comparison of these dissolution rates with a pure C₃S reference sample allows the conclusion that the dissolution rate of pure C₃S after the heat flow maximum might be governed by either the remaining available reactive surface of C₃S or a diffusion‐controlled process, which would both be influenced by the respective hydrate phase precipitating on the C₃S surface.     

先进的C3M技术

C3M技术是米其林公司对轮胎制造技术的一场革命，它不仅设备简单、拆装方便、占地面积只有30m^2，而且把传统的轮胎成型工艺从三工段四步操作改为成型硫化一体的一道工序。现在C3M技术已从试生产阶段推广应用阶段。     

肺炎链球菌补体结合蛋白C3-BP的纯化及其免疫效果

目的对9V型肺炎链球菌补体结合蛋白C3-BP进行纯化及免疫效果分析。方法通过三氧醋酸沉淀、离子交换层析、凝胶过滤层析和亲和层析等方法,从9V型肺炎链球菌培养上清中提取C3-BP,Lowry法检测其浓度,SDS-PAGE检测其纯度及大小,Western blot检测其补体C3结合活性。将纯化蛋白免疫NIH小鼠,ELISA法测定小鼠血清IgG抗体,MTT法测定小鼠脾淋巴细胞增殖情况,活菌攻击,检测其交叉保护效果。结果经纯化的表面蛋白C3-BP,其相对分子质量约为90 000,为单链蛋白,浓度为0.21 mg/ml,纯度为90.7%,具有与补体C3结合的特性。免疫小鼠后,抗体滴度达到1∶38 802。免疫组小鼠脾脏与胸腺淋巴细胞代谢活性明显增强,与对照组相比,二者刺激指数之间差异有显著意义。9V型C3-BP免疫小鼠后,不仅对9V型肺炎链球菌株有保护作用,对2型、6B型和14型肺炎链球菌菌株也有保护作用。结论摸索出了一种纯化肺炎链球菌表面蛋白C3-BP的方法,纯化的C3-BP具有不依赖血清型的交叉保护作用,而且体液免疫及细胞免疫效果良好。