聚羧酸系减水剂对水泥水化过程的影响

研究了以聚乙二醇800、丙烯酸、顺酐、烯丙基磺酸钠、丙烯酸羟乙酯为原料合成的聚羧酸系XYZ18减水剂对水泥水化过程及微观结构的影响.结果表明,XYZ系减水剂具有缓凝特性,能减少并延缓水泥水化放热;使水泥早期微小晶体大量生长并填充孔隙,气孔细化且分布更加合理,晶体向外伸长使水泥粒子相互搭接而形成网络结构,提高了水泥石的密实性.     

石膏与聚羧酸对C3A水化进程及产物组成的影响

研究了石膏、聚羧酸减水剂对固相法制备的铝酸三钙(C3A)水化反应的影响。结果表明,纯水条件下,C3A水化产物为C3AH6,水化放热总量约为879.99J/g,水化反应2h时放热量达到最大;石膏加入后会使体系水化放热时间延长,同时会改变C3A水化产物组成:石膏加入量较小时,水化产物主要为AFm;石膏过量时,水化产物只有AFt;聚羧酸减水剂的加入也会延缓C3A水化反应,且在同一反应龄期内,随着聚羧酸减水剂掺量的增大,C3A的水化程度呈降低趋势。利用电导率进行测试,可以发现聚羧酸减水剂的加入会降低液相中钙离子浓度,从而延缓了C3A的水化。     

聚羧酸系和萘系减水剂对C3A-CaSO4·2H2O体系水化行为的影响

通过研究C3A-CaSO4·2H2O体系在聚羧酸(PC)和萘系减水剂(FDN)存在的条件下的水化历程和水化产物结构,结合水化热、XRD、IR、SEM等检测手段分析了体系的水化行为及机理。结果表明,PC和FDN在溶解反应期均能促进水化反应的进行;随着水化反应的进行,PC能有效延缓体系水化反应的速度,第1放热峰和第2放热峰分别延迟了约5h和15h,降低体系水化放热,减缓水化产物结构的发展;PC和FDN对后期水化产物结构的发展没有影响。     

聚羧酸系超塑化剂分子结构对C3S水化行为的影响

采用等温量热仪、热分析、扫描电镜等测试手段,研究了3种聚羧酸系超塑化剂(PCs)对硅酸三钙(C3S)水化行为的影响;采用总有机碳测定了不同分子结构的PCs在C3S颗粒上的吸附动力学.结果表明:PCs的掺入大大增加了C3S的诱导期;减缓了C3S的早期水化,但对水化后期发展有利,其中主链为马来酸酐的PC1对C3S水化3d的减缓作用最强;共聚物大部分残留在孔隙液中,其所含的羧酸根含量与对C3S的减缓作用呈线性关系;对C3S诱导期的增加可能是改变了氢氧化钙的临界饱和度.     

聚羧酸减水剂对不同晶型C3S早期水化放热的影响

采用水化微量热仪研究了不同类型聚羧酸减水剂对不同晶型C3S水化放热特性的影响。结果表明:单斜晶系(M)C3S、三方晶系(R)C3S的水化放热速率峰值相比三斜晶系(T)C3S显著降低,且水化放热峰出现延迟,MC3S的水化放热峰延迟最明显。三种晶型C3S的3d水化放热总量由大到小为:TC3S、MC3S、RC3S。不同分子结构的甲氧基聚乙二醇甲基丙烯酸酯系聚羧酸减水剂,主链越短,支链越长,对TC3S的水化延迟作用越大。乙烯基聚乙二醇醚系聚羧酸减水剂对三种晶型C3S的水化放热过程延迟作用由大到小为:RC3S、MC3S、TC3S。对水化放热曲线进行的Krstulovic-Dabic模型研究表明,C3S的水化过程为NG-D类型水化历程。     

葡萄糖酸钠与聚羧酸减水剂的复合效应研究

研究了聚羧酸减水剂与葡萄糖酸钠的复合使用对水泥浆体的凝结时间、净浆流动性、强度、水化热的影响,并采用XRD分析水泥水化产物的变化。结果表明:适量的葡萄糖酸钠能显著提高聚羧酸减水剂的分散性和分散保持性,改善水泥与聚羧酸减水剂的适应性,延长凝结时间,并使3 d7、d强度有所提高;单掺葡萄糖酸钠使水泥水化第2放热峰出现时间延迟2 h,但温峰值及水化热与空白样基本持平,1 d、7 d CH的生成量减少。复合使用葡萄糖酸钠与聚羧酸减水剂时,水泥净浆水化温峰出现时间延迟15 h,水化温峰提高,1 d、7 d CH的生成量较单掺葡萄糖酸钠时有所增大。     

磷酸盐对普通硅酸盐水泥早期水化的影响

针对不同磷酸盐缓凝机理的不确定性问题,通过ICP测定六偏磷酸钠、三聚磷酸钠、焦磷酸钠、磷酸钠和磷酸二氢钠的吸附量及钙离子浓度,同时结合水化热、XRD及水泥浆体流动性的经时变化,揭示了不同磷酸盐对普通硅酸盐水泥的缓凝调控机理。结果表明:不同磷酸盐在水泥颗粒表面的吸附速度如下:六偏磷酸钠三聚磷酸钠焦磷酸钠磷酸钠磷酸二氢钠,即聚磷酸钠的吸附速度大于单磷酸钠;聚磷酸钠与钙离子生成的络合物吸附在水泥颗粒表面抑制水泥水化产物生成、延缓水泥水化的能力强于单磷酸钠与钙离子生成的磷酸钙;聚磷酸钠提高水泥净浆流动度的能力大于单磷酸钠,其中六偏磷酸钠的效果最好,初始流动度最大。     

葡萄糖酸钠与高效减水剂复合使用对水泥水化历程的影响

用直接测温法及X射线衍射技术,系统研究了葡萄糖酸钠与萘系、氨基磺酸盐系及聚羧酸盐系3种高效减水剂复合使用对水泥水化热、水化温峰、温峰出现时间及不同水化龄期Ca(OH)2和钙矾石(AFt)生成量等方面的影响.结果表明:与糖钙和三聚磷酸钠相比,葡萄糖酸钠及其与高效减水剂复合对水泥水化历程的影响规律明显不同.单掺葡萄糖酸钠使水泥水化第2放热峰出现时间延迟,但温峰值及水化热与空白样基本持平,温峰时的Ca(OH)2生成量增大.复合使用葡萄糖酸钠与高效减水剂时,与不同品种高效减水剂复合使用对水泥水化历程的影响不同.     

无机盐对硫酸盐与聚羧酸减水剂相互作用的影响

目的 探讨硫酸盐对聚羧酸减水剂分散效果的影响机理,改善硫酸盐对聚羧酸减水剂吸附性能的影响.方法 在粉煤灰中掺入硫酸钠以改变其体系中硫酸盐的含量,然后在硫酸盐-聚羧酸体系中加入无机盐,采用总有机碳质量浓度(TOC)、ζ电位以及红外光谱等试验.结果 当粉煤灰中硫酸钠质量分数为3％时,加入3％的硝酸钡以后,吸附完成时外加剂溶液中有机碳的质量浓度从898 mg/L增加到914 mg/L,ζ电位的绝对值由11.11 mV提高到14.6 mV;加入3％的氯化钙,吸附完成时外加剂溶液中有机碳的质量浓度从898 mg/L增加到1 141 mg/L,ζ电位的绝对值由11.11 mV提高到15.91 mV;同时当粉煤灰中硫酸钠质量分数为3％时,红外谱中透射率明显下降,但向体系中加入无机盐(3％硝酸钡或3％氯化钙)以后,红外谱中百分比透射率有很大提高.结论 硫酸钠与聚羧酸减水剂本身存在相互作用,粉煤灰中硫酸钠的含量越多对聚羧酸减水剂的吸附量增大,在硫酸盐-聚羧酸体系中加入无机盐,可以减弱硫酸盐对聚羧酸减水剂分散效果的影响.     

Effect of CaCO3 on hydration characteristics of C3A

Hydration products and morphology characteristics of C₃A (tricalcium aluminate)-CaCO₃-H₂O system were studied by means of XRD, DSC, FTIR spectrum analysis and SEM. The results indicate that, the new phases, i.e., C₃A·0.5CaCO₃·0.5Ca(OH)₂·11.5H₂O and C₃A·CaCO₃·11H₂O are found in this system due to the activity of CaCO₃; the formation of C₄AH₁₃ and C₂AH₈ is prohibited and the generation of C₃AH₆ is delayed in the early hydration process. C₃A·0.5CaCO₃·0.5Ca(OH)₂·11.5H₂O is not stable and will be totally transferred within 24 h; C₃A·CaCO₃·11H₂O exists stably once formation, and its flake-like crystalline phases in the early hydration transform to long rod shape, and to finally fine-needle at 28 d.     

Hydration Characteristics of Sodium Sulfate Slag Cement System

The hydration characteristics by thermal analysis ( DTA ) were determined, and an isothermal calorimeter (IC) was used to study the pastes . The experimental results indicate: (1) The main hydration products of SSC are C-S-H( I ) gel with a low Ca/Si ratio, crystalline Thomsonite-type and AFt-type phases containing certain alkali cations; (2) No phases of the AFm-type and high alkaline Ca( OH)2 in SSC system could benefit the hydrated cements to improve its strength and durability; (3) Crystalline Thomsonite-type and AFt-type phases containing Na will greatly reduce free alkali and alleviate the harmness of alkali aggregate reaction ( AAR) in SSC system; (4) Similar to ordinary Portland cement( OPC), the hydration process of SSC could be classified into five stages : initial, induction, acceleration, deceleration and decay; (5) Regardless of the activator used, the apparent activation energy is higher with the increased slag in cement system, and the rising temperature could promote the hydration of SSC.     

Structure and growth phenomena of C60 and C70 single crystals

C₆₀ and C₇₀ single crystals free from solvent contamination grew from their vapour. Large C₆₀ crystals up to a size of about 5 mm×3 mm×3 mm and C₇₀ crystals about 1 mm×1 mm×1 mm were obtained. C₆₀ crystals with fcc structure showed two types of morphological faces, namely {111} and {100}, frequently with twinning on {111} face. C₇₀ crystals obtained have a hcp structure witha=10.1 ? andc=16.7 ?. DSC and X-ray diffraction analysis indicated that C₇₀ crystal underwent phase transition below 100 C. Morphological observation suggests that the growth of C₆₀ and C₇₀ single crystals is based on layer-spreading mechanism. Synopsis of the first author Li Jing, professor, born in 1954, received Ph D degree in 1988, professional interests are physicel chemistry in metallurgy and materials, fullerene chemistry and ceramics.     

Synthesis of C3S by sol-gel technique and its features

Sol-gel method is a technique to synthesize inorganic materials based on wet-chemical reaction theory. The results have shown that reactants tetraethyl orthosilicate (TEOS) and Ca(NO₃)₂·4H₂O can form sol and gel in solution at 50–60 °C, and the cosolvents are propyl alcohol (NPA) and H₂O, the catalyst is HNO₃. This sol-gel is burned for 12 h at 1 350–1 450 °C so that the organic matter, free water (moisture) in sol-gel system are removed and a solid reaction has taken place to form the resulting product. The product has been confirmed to be C₃S by XRD, SEM and ²⁹Si MAS NMR, as well as free lime content of the product which is less than 0.2% was determined by propanetriol-ethanol-method. The analysis determined by EDXA has indicated that the n(Ca)/n(Si) ratio in corresponding to micro-region is close to theoretical value of 3:1. This resulting product is C₃S with Si sites of Q⁰ polymerization, and has higher purity and hydraulic activities at earlier age of hydration.     

TiO2对高C3S熟料烧成的影响

通过外掺TiO₂来改善高C₃S熟料的烧成.配制7个生料样品,其潜在矿物组成均为w(C₃S)=75%、w(C₃A)=7%、w(C4AF)=18%,TiO₂掺量分别为0、05%、10%、15%、20%、25%、30%,在设定的高温下煅烧成熟料,通过化学分析、XRD、SEM/EDS等方法,研究了TiO₂对熟料易烧性、矿相形成、C₃S晶体形貌和熟料强度等的影响.结果表明,掺入少量TiO₂明显提高了熟料的易烧性;当TiO₂掺量小于2%时,f-CaO随TiO₂掺量的增加而显著降低;当TiO2掺量超过2%后,f-CaO随TiO₂掺量的变化不大;当TiO₂掺量达到3%时,在1 350和1 400 ℃温度煅烧的熟料中均发现了CaO·TiO₂新相;掺2%TiO2在1 400℃煅烧条件下的熟料,TiO₂在C₃S中的固溶量约1.7%;掺入适量的TiO₂,熟料中C₃S结晶比较完整、均匀,熟料强度较高.适当掺入TiO₂对改善高C₃S熟料的烧成和提高其强度都是有利的.     

Ti_5Si_3的研究进展

概述了Ti5Si3的物理结构和化学性质,展现出其熔点高、密度低、电阻率低、硬度高、高温强度大、抗高温氧化性能好和化学性质稳定等性质。对Ti5Si3合金材料及其薄膜的固固、固液、固气和气气反应制备工艺及其优缺点进行了较为系统的阐述。并结合Ti5Si3的优良性能,对其在高温结构材料、镀膜材料、电子器件、微电极和微传感器材料领域的应用进行了重点介绍。     

Na+掺杂对LiNi1/3Co1/3Mn1/3O2结构和电化学性质的影响

采用高温固相法成功制备了不同Na+掺杂浓度的Li_1-xNa_xNi_1/3Co_1/3Mn_1/3O₂锂离子电池正极材料,探究了Na元素掺杂对层状氧化物正极材料结构以及电化学性能的影响。通过X射线粉末衍射仪和扫描电子显微镜表征了材料的结构和形貌,结果表明,当x≤0.3时,样品不会出现其它杂相;当x＞0.3时,样品中会出现NaNi_1/3Co_1/3Mn_1/3O₂的杂相。同时随着掺杂浓度的增加,样品的阳离子混排度逐渐增加。电化学性能结果表明,少量Na+的掺入可以提高LiNi_1/3Co_1/3Mn_1/3O₂在0.2C,0.5C下的放电比容量并增强其循环稳定性,但会损坏材料的倍率性能。     

Effect of TiO2 on the formation of clinker with high C3S

Effect of TiO₂ content on the burnability of clinker with high C₃S were investigated by determination of free lime in final product, and the clinker phase formation, microstructural features of C₃S and the solubility of TiO₂ in C₃S were further studied by XRD, SEM/EDS analysis. TiO₂ accelerates the combination of free lime in the samples, free lime content decreases obviously with TiO₂ increasing up to 2% and almost remains above 2%. A new phase CaO·TiO₂ was found when TiO₂ was up to 3%, and samples with TiO₂ displayed well-formed uniform size hexagonal C₃S crystal. The limit of solubility of TiO₂ in C₃S at 1400 °C is about 1.7%.     

MA／AA共聚物钠盐的合成及其表面活性

本文合成了ＭＡ（顺丁烯二酸）／ＡＡ（丙烯酸）共聚物的钠盐，对其结构进行了表征，研究了该共聚物钠盐水溶液的表面性质，采用正交试验的方法探索了合成条件对共聚物钠盐表面活性的影响情况。     

Low pressure synthesis of boron nitride with (C2H5)2O · BF3 and Li3N precursor

Cubic boron nitride(c-BN) was synthesized through benzene thermal method at a lower temperature of 300 °C by selecting liquid (C₂H₅)₂O · BF₃ and Li₃N as reactants. Hexagonal boron nitride(h-BN) and orthorhombic boron nitride(o-BN) were also obtained. The samples were characterized by X-ray powder diffractometry and Fourier transformation infrared spectroscopy. The results show that all the BF₃, BCl₃ and BBr₃ in the same family compounds can react with Li₃N to synthesize BN since the strongest bond of B-F can be broken. Compared with BBr₃, liquid (C₂H₅)₂O · BF₃ is cheaper, less toxic and more convenient to operate. Li₃N not only provides nitrogen source but also has catalytic effect on accelerating the formation of c-BN at low temperature and pressure. Foundation item: Projects(20273007,50372006) supported by the National Natural Science Foundation of China