Replacement of alkali silicate solution with silica fume in metakaolin-based geopolymers

A metakaolin(Mk)-based geopolymer cement from Tunisian Mk mixed with different amounts of silica fume(SiO_2/Al_2O_3 molar ratio varying between 3.61 and 4.09) and sodium hydroxide(10M) and without any alkali silicate solution, is developed in this work. After the samples were cured at room temperature under air for 28 d, they were analyzed by X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, environmental scanning electron microscopy, mercury intrusion porosimetry, ~(27)Al and ~(29)Si nuclear magnetic resonance(NMR) spectroscopy, and compression testing to establish the relationship between microstructure and compressive strength. The XRD, FTIR, and ~(27)Al and ~(29)Si NMR analyses showed that the use of silica fume instead of alkali silicate solutions was feasible for manufacturing geopolymer cement. The Mk-based geopolymer with a silica fume content of 6 wt%(compared with those with 2% and 10%), corresponding to an SiO_2/Al_2O_3 molar ratio of 3.84, resulted in the highest compressive strength, which was explained on the basis of its high compactness with the smallest porosity. Silica fume improved the compressive strength by filling interstitial voids of the microstructure because of its fine particle size. In addition, an increase in the SiO_2/Al_2O_3 molar ratio, which is controlled by the addition of silica fume, to 4.09 led to a geopolymer with low compressive strength, accompanied by microstructures with high porosity. This high porosity, which is responsible for weaknesses in the specimen, is related to the amount of unreacted silica fume.     

煤矸石热活化和胶凝化过程中硅铝的配位

为了煤矸石综合利用,用红外谱图和固体核磁共振,研究煤矸石热处理及胶凝化过程中S i和A l的配位变化。研究表明,在煤矸石热活化和水泥制备过程中六配位的铝逐渐转变为四配位的铝。活化煤矸石胶凝化过程中,六配位的铝也逐渐转变为四配位铝,形成铝硅酸盐。水泥胶凝过程中,四配位铝逐渐转变为六配位的铝。通过热活化手段增加煤矸石中四配位铝含量可以提高煤矸石胶凝性能。     

Synthesis of cage-like octa(trimethylsiloxy)silsesquioxane

Cage-like octa(trimethylsiloxy)silsesquioxane [ (Me₃SiO)SiO_1.5]₈ has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me₄NO)-SiO_1.5]₈ with chlorotrimethylsilane. The silicate octamer can be selectively formed by the reaction of tetraethoxysilane Si(OEt)₄ with aqueous tetramethylammonium hydroxide in equal molar ratio. Elementary analysis, FT-IR,¹H,¹³C,²⁹Si NMR are used to characterize these silsesquioxanes.     

硅酸四(氯乙基)酯的合成及表征

以四氯化硅和环氧乙烷为原料,合成新型硅卤协同阻燃剂硅酸四(氯乙基)酯.探讨反应物质的量比、反应温度以及反应时间等对产品收率的影响,筛选出最适宜的工艺条件为:四氯化硅与环氧乙烷的物质的量比为1∶4.2,反应温度为25～50℃,反应时间为2h,产品收率为98%.并采用FTIR、1 H-NMR、极限氧指数等技术表征了硅酸四(氯乙基)酯的分子结构及相关性能.     

New evidence for microstructural evolution model of acid-activated montmorillonite

Ca-montmorillonite samples from Choushan treated at various acid concentrations were studied using chemical analysis, XRD, ²⁹Si and ²⁷Al MAS NMR, to investigate the microstructure of the activated montmorillonites. With the increase of acid concentration and dissolution of cations of montmorillonite, the intensity of d(001) decreased obviously and significant changes of the microstructure of Si and Al occurred. There were two new types of structural units of Si atoms formed: (SiO)₃SiOH units and Q⁴(0Al) units. For Al atoms, in the course of activation, the removal of one of a pair of octahedral aluminium atoms from montmorillonite removed two hydroxyl groups and left the other aluminum of the pair in the four-fold coordination. The ²⁷Al signal at δ 54.0 corresponding to Al^Ⅳ arose from the four- coordinated Al in the octahedral sheet. This study first con-firmed, by ²⁹Si and ²⁷Al MAS NMR spectra, that the model of microstructural evolution for activated montmorillonite postulated by Thomas et al. (1950) is correct.     

Synthesis of kalsilite from microcline powder by an alkali-hydrothermal process

The properties of aluminosilicate kalsilite have attracted the interest of researchers in chemical synthesis, ceramic industry, biofuels, etc. In this study, kalsilite was hydrothermally synthesized from microcline powder in a KOH solution. The microcline powder, rich in potassium, aluminum, and silicon, was collected from Mountain Changling in Northwestern China. The effects of temperature, time, and KOH concentration on the decomposition of microcline were investigated. The kalsilite and intermediate products were characterized by means of wet chemistry analysis, X-ray Diffraction (XRD), infrared spectrometry (IR), 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR), 27Al MAS NMR, and scanning electron microscope (SEM). With increasing temperature, the microcline powder transforms into a metastable KAlSiO₄ polymorph before transforming further into pure kalsilite. A mixture of both kalsilite and metastable KAlSiO₄ polymorph is obtained when the hydrothermal reaction is carried out within 2 h; but after 2 h, kalsilite is the predominant product. The concentration of KOH, which needs to be larger than 4.3 M, is an important parameter influencing the synthesis of kalsilite.     

Microstructure and cementitious properties of calcined clay-containing gangue

To investigate the optimum calcination temperature and cementitious properties of gangue, the microstructure of clay-containing gangue calcined at different temperatures was analyzed by X-ray diffraction (XRD), infrared spectroscopy (IR), and magnetic angle spinning nuclear magnetic resonance (MAS NMR). The results show that the structure of kaolinite in the gangue sample calcined at 500℃ is destroyed. The XRD spectra show the disappearance of illite at about 800℃ and the formation ofmullite at about 1000℃. With the increase in calcination temperature, octahedral (6-coordinated) aluminum is transformed to tetrahedral (4-coordinated) aluminum gradually. For the gangue sample calcined at 700℃, the 29Si MAS NMR sharp peak of Q4 (framework silicate-quartz) is left. Compared with kaolinite in gangue, the thermal transformed temperature of pure kaolinite is lagged. On the basis of the microstructure and cementitious properties of calcined gangue, the results can be concluded, in order to obtain metakaolinite, the optimum calcination temperature of this gangue is about 500℃, and the optimum temperature is about 700℃ for activated SiO₂ and Al₂O₃.     

Hydration mechanism of a cementitious material prepared with Si-Mn slag

A cementitious material was prepared by mixing 80wt% Si-Mn slag powder, 10wt% lime, and 10wt% anhydrite. The compressive strength of mortar samples reaches 51.48 MPa after 28 d curing. The analyses of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that much ettringite is formed in the sample cured for 3 d, and C-S-H gel increases rapidly during subsequent curing. Nuclear magnetic resonance (NMR) analysis of 29Si and 27Al and infrared spectroscopy (IR) analysis show that aluminum decomposition from tetrahedral network of the slag glass and its subsequent migration and re-combination play an important role in the process of hydration and strength development of the samples.     

具有强酸性锆掺杂有序介孔硅材料的合成

通过三嵌段的共聚物做模板制备了一系列具有不同锆含量、强酸性的介孔硅材料,获得的样品通过x射线衍射分析、透射电镜分析、氮气吸附脱附、紫外可见光谱、热重分析等技术进行了表征.研究结果发现,当样品中硅和锆的物质的量比大于4时,锆物种能被完全引入到有序介孔硅结构的骨架中;然而,当样品中硅和锆的物质的量比小于4时,会出现一个由无...     

碳还原粉煤灰制备SiC/Al2 O3系复合材料

在氩气气氛下,以粉煤灰为原料,石墨为还原剂,研究碳还原粉煤灰制备SiC/Al2 O3系复合材料的反应过程,并探索其制备的工艺条件.利用X射线衍射分析还原产物的物相变化规律,使用扫描电镜和能谱仪观察复合材料的微观结构.结果表明：在1673 K粉煤灰中石英相与碳反应生碳化硅,1773 K莫来石相基本分解完全.随着反应温度的升高,生成碳化硅和氧化铝含量增加,较合适的温度条件为1773~1873 K;保温时间的延长,有利于碳化硅和氧化铝的生成,较好的保温时间为3~4 h;增加配碳量对碳化硅和氧化铝的生成有促进作用,较合适的C/Si摩尔比为4~5.在制备出的SiC/Al2 O3复合材料中碳化硅在产物中分散较为均匀,并且粒度小于20μm.     

两种土壤聚合物碱激发剂的激发效果对比

采用大液固比的方法对比研究了氢氧化钠和硅酸钠溶液对偏高岭石的激发作用,将反应到一定时间的浆体进行分离,对分离后的溶液和粉体分别进行分析.研究结果表明:(1)随反应时间的延长,偏高岭土与硅酸钠溶液反应分离后溶液中Si的聚合度增加,溶解的Al单体与溶液中的硅酸根离子聚合,分离后的粉体既有被碱侵蚀后的硅氧的碎片,也有铝单体与硅酸根离子聚合的胶团;(2)随反应时间的延长,偏高岭土与氢氧化钠溶液反应分离后溶液中的Si和Al含量不断增多,但硅和铝没有发生聚合,分离后粉体仅是偏高岭石在碱侵蚀下生成的碎片;(3)硅酸钠溶液中的硅酸根离子对土聚反应起到了重要的作用.     

以K[Al（OH）4]铝化硅胶的研究

以Ｋ〔Ａｌ（ＯＨ）４〕对硅胶进行铝化。用ＸＰＳ（光电子能谱）、ＩＲ（红外）、ＭＡＳＮＭＲ（魔角核磁共振）以及异戊醇脱水反应表征了铝化胶样品。结果表明，硅胶经后可以产生Ｂｒｏｎｓｔｅｄ和Ｌｅｗｉｓ酸性。Ｂｒｏｎｓｔｅｄ酸性的产生不排除Ｋ〔Ａｌ（ＯＨ）４）〕与硅胶表面羟基综合并在以后的热处理中转化为六配位的铝氧化物，从而显示ｌｅｗｉｓ酸性。铝化硅胶由于具备了酸性，产生了醇脱水的催化活性。     

Relationship between polymerization degree and cementitious activity of iron ore tailings

The aim of this study is to understand the relationship between the polymerization degree and cementitious activity of iron ore tailings. In light of the poor usage of iron ore tailings, stockpile samples from Tangshan were studied in terms of their ability to become cementitious materials. Compound thermal activation was used to improve the cementitious properties of the tailings, while analyzing methods, such as X-ray diffraction (XRD), infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectrometer (XPS), were employed to study the changes in phase and structure under different activation conditions. The results reveal clear relationships between the binding energies of Si2p and O1s, polymerization degree, and cementitious activity of iron ore tailings.     

CHEMICAL COMPOSITION AND ELECTRONIC STRUCTURE OF ZEOLITES STUDIED BY X-RAY PHOTOELECTRON SPECTROSCOPY AND 29Si MAS NMR

采用光电子能谱和Si核磁共振及化学分析方法研究了五种不同分子筛钠型和钾型的化学组成.结果发现,分子筛的表面Al/(Si+Al)比和骨架Al/(Si+Al)比与其体相Al/(Si+Al)比具有一致性,其电子结构与其组成及阳离子有关.分子筛表面晶格氧碱强度与其铝含量成正比,与阳离子的电负性成反比.     

4A分子筛对聚磷酸铵/季戊四醇膨胀阻燃剂协同作用的TGA/XPS研究

利用TGA/XPS技术比较研究聚磷酸铵/季戊四醇(APP/PER)-4A与APP/PER体系的热行为.通过热失重及Si/Al原子比和结合能等数据绘图,对图中曲线进行了详细的分析.对比研究表明TGA的第3热失重峰明显降低,XPS的Cls相对谱峰强度随温度明显增加.4A分子筛在低温下对APP/PER膨胀阻燃体系发生催化酯化反应,在高温下Si/Al原子比升高,产生表面层动力学运动.酸的活性增加,有利于APP/PER膨胀阻燃体系.     

Structural state of adularia from Hishikari, Japan

Adularia sample was collected from epithermal Au-, Ag-bearing quartz-adularia veins from Hishikari, Japan. This adularia is rich in K, Or=94.63, clear, transparent, fine-grained and closely associated with quartz. In this study, it was determined by XRD, IR and²⁹Si,²⁷Al MAS NMR methods. The adularia studied is of high sanidine with triclinic domains in it. The occupancy of Al 2t₁=0.60, IR ordering θ=0.15.²⁹Si NMR spectrum of this adularia shows a broad triplet peak, i.e. 3 poorly separated peaks at −94.9, −96.7, −99.9. This kind²⁹Si NMR spectrum for natural high sanidine has never been reported before. And the²⁷Al NMR spectrum gives an asymmetry peak with chemical shift at 58.7 extending slightly to the low frequency. Under a violent boiling environment, Hishikari adularia rapidly crystallized from a supersaturated solution.     

硅酸甲基三(氯乙基)酯的合成及表征

以四氯化硅、甲醇和环氧乙烷为原料,合成硅卤协同阻燃增塑剂硅酸甲基三(氯乙基)酯.探讨反应物质的量比、反应温度及反应时间等对产品收率的影响.最适宜的工艺条件:四氯化硅与甲醇的物质的量比为1∶1,四氯化硅与环氧乙烷的物质的量比为1∶3.2,反应温度为30℃,反应时间为2 h,产率为98%.并采用FTIR,1H-NMR,极限氧指数等技术表征化合物硅酸甲基三(氯乙基)酯的分子结构及性能.     

新型无机高分子复合絮凝剂聚合硅酸铝铁混凝效果研究

以AlCl3·6H2 O ,FeCl3·6H2 O ,硅酸钠和盐酸为原料 ,以无水碳酸钠为碱化聚合剂 ,制备出了一系列聚合硅酸铝铁 (PAFSC)复合无机高分子絮凝剂 ;通过烧杯实验 ,比较了PAFSC和PAC对各种水样的混凝效果 .结果表明 :PAFSC较PAC具有更好的混凝效果 ;其制备工艺、Al Fe Si摩尔比对PAFSC的混凝效果有一定的影响 ,在Al Fe Si摩尔比一定的情况下 ,共聚法制备的PAFSC(共 )的混凝效果优于复合法制备的PAFSC(复 )的混凝效果 ;在制备工艺一定的情况下 ,随着Al Fe Si摩尔比中Fe和Si摩尔数增加 ,PAFSC絮凝剂的混凝效果变好 .此外 ,pH值对PAFSC的混凝效果也有一定的影响 .     

碱激发对粉煤灰活性的影响

研究了粉煤灰的物理化学特性,设计了四种方案对粉煤灰进行改性,旨在扩大粉煤灰的应用. 通过对比改性前后Na2SiO3-粉煤灰试块的强度,使粉煤灰在改性前后的反应速度通过试块的强度得以体现. 扫描电镜照片显示,在机械粉磨结合化学激发处理后,坚硬的外壳大部分被破坏. 27Al的核磁共振图谱显示宽峰变窄. 29Si的核磁共振谱表明,Q0消失,Q2增多,Q4减少. 说明加入强碱并同时机械粉磨可有效破坏粉煤灰的玻璃微珠外壳及硅铝网络结构,可增强粉煤灰的潜在活性.     

Synthesis of a novel triple-site diphosphinoamine （PNP） ligand and its applications in ethylene tetramerization

A novel triple-site diphosphinoamine （PNP） ligand was synthesized and characterized. In combination with Cr（Ⅲ） and methylaluminoxane （MAO）, it generated active catalytic systems for ethylene tetramerization toward 1-octene with high catalytic activity and long lifetime. The effects of reaction temperature, molar ratio of AI/Cr and molar ratio of ligand/Cr on catalytic activity and selectivity to 1-octene were studied with reaction kinetics of the catalytic system for ethylene tetramerization described. At the AI/Cr molar ratio of 100, the catalytic activity is up to 2.29×10^6 g· mol^-1 （Cr）· h^-1 and the selectivity to 1-octene is 49.65 wt%.