苯硫酚各种形态在金上的拉曼光谱研究

用Gaussian 98程序在B3LYP/6-311＋G**(C, H, S)水平上计算得到苯硫酚(TP)的一套校正因子, 对苯硫酚各频率进行了势能分布(PEDs)分析, 并对各振动模式进行了详细的指认. 同时, 在B3LYP/6-311＋G**(C, H, S)/LANL2DZ(Au)水平上优化得到苯硫酚的各种形态与金结合, 即C₆H₅SH-Au, C₆H₅SAu, C₆H₅S^－-Au的平衡构型, 且在此基础上得到了C₆H₅SH-Au, C₆H₅SAu, C₆H₅S^－-Au三种形态的计算拉曼谱图. 其中苯硫酚金盐(C₆H₅SAu)的拉曼谱图与实验得到的苯硫酚在金溶胶中的谱图是一致的, 由此很好地证明了TP与金形成苯硫酚金盐.     

RGO/C3N4复合材料的制备及可见光催化性能

通过半封闭一步热裂解法和改进的Hummers法分别制备了类石墨氮化碳(C₃N₄)和氧化石墨烯(GO),再利用光还原方法制得还原氧化石墨烯/氮化碳(RGO/C₃N₄)复合材料。采用X射线衍射(XRD),场发射扫描电镜(FESEM),X射线光电子能谱(XPS),紫外-可见漫反射吸收光谱(DRS),光致荧光(PL)和傅里叶变换红外光谱(FTIR)等测试技术对复合材料进行表征。以罗丹明B(RhB)为探针分子在可见光下考察RGO/C₃N₄复合材料的光催化活性,结果表明：RGO的引入显著提高了C₃N₄的光催化活性,且6.0%RGO/C₃N₄复合物的光催化活性最高,可能的原因是RGO具有优良的传导和接受电子性能,抑制了C₃N₄光生电子-空穴的复合机率,进而提高了光催化活性。     

Bi3TaO7/MXene纳米片异质结的制备及光催化降解磺胺嘧啶钠

分别以五水合硝酸铋（Bi （NO₃）₃·5H₂O）和五氯化钽（TaCl₅）作为Bi源和Ta源,采用静电吸附和溶剂热法在2D Ti₃C₂的表面原位生长0D Bi₃TaO₇纳米颗粒制备Bi₃TaO₇/Ti₃C₂复合光催化材料。通过各种物理化学表征研究了2D Ti₃C₂纳米片对Bi₃TaO₇/Ti₃C₂复合光催化材料微结构的影响。通过可见光下降解磺胺嘧啶钠（SD-Na）溶液来评价所制备样品的光催化性能。实验结果表明,Bi₃TaO₇/Ti₃C₂复合材料的光催化性能明显增强。在最优条件下（Ti₃C₂与Bi₃TaO₇的质量比为0.02）制备的BT2展现出最高的光催化活性,其降解SD-Na溶液的表观速率常数是纯Bi₃TaO₇的2.8倍。Bi₃TaO₇/Ti₃C₂复合光催化材料性能的显著提高归因于Ti₃C₂/Bi₃TaO₇异质结的形成有利于光生载流子的快速转移和分离。     

高温下硅酸锂吸收CO2的研究

以SiO₂和Li₂CO₃为反应原料，采用高温固相法于不同温度下合成了一系列可在高温500~750 ℃之间直接吸收CO₂的硅酸锂(Li₄SiO₄)材料。采用扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)分别观察和评价了合成材料的表面形貌与结构特征，用热重分析仪(TG)研究了硅酸锂材料吸收CO₂的性能。实验结果表明，在750 ℃下煅烧6 h即可合成出吸收CO₂性能良好的硅酸锂材料，在CO₂气氛下，于700 ℃保持约15 min即可达到吸收平衡，其吸收量约达43%(wt)左右。与文献报道相比，材料的合成条件有所改善，材料吸收CO₂的容量也有较大提高。     

N和F共掺杂C3N4的制备及其可见光催化性能

针对氮化碳（C₃N₄）光生电荷易复合、光催化性能有限的不足,我们制备N和F共掺杂C₃N₄（NF-C₃N₄）,以提升其光催化性能。利用NH₄F在高温下原位分解产生的HF和NH₃,对C₃N₄刻蚀的同时实现N和F双元素共掺杂。以氯化铵（NH₄Cl）为对照,制备N掺杂C₃N₄（N-C₃N₄）。利用扫描电子显微镜（SEM）、能谱仪（EDS）、X射线光电子能谱（XPS）、X射线衍射（XRD）、比表面积测试和电化学表征手段研究N、F共掺杂对C₃N₄形貌、成分、结构和物化性质等的影响规律。相比于C₃N₄和N-C₃N₄,NF-C₃N₄呈多孔状,比表面积增大,光生电荷的生成、分离和转移均被促进,NF-C₃N₄光催化还原Cr （Ⅵ）的速率是C₃N₄的2.6倍、N-C₃N₄的1.7倍。进一步考察了不同前驱体（尿素、双氰胺和三聚氰胺）对制备C₃N₄的影响,发现以尿素为前驱体的C₃N₄与NH₄F的质量比为3∶2时,NF-C₃N₄呈现最佳的光催化性能。催化剂用量、光照强度、空穴捕获剂浓度的增加和pH的降低均能提高Cr （Ⅵ）还原速率。在NF-C₃N₄浓度为0.1 g·L^-1、pH=3、c_EDTA-2Na=2 mmol·L^-1、40 min可见光照射后,Cr （Ⅵ）去除率达到90%。5次循环实验表明,优化制备的NF-C₃N₄光催化还原Cr （Ⅵ）的性能保持良好,具有较高的稳定性。     

Co/C3N4 NTs复合纳米材料的制备及光催化性能

采用化学还原法将非贵金属钴纳米颗粒沉积到氮化碳纳米管（C₃N₄ NTs）内外管壁,制备了Co/C₃N₄ NTs复合光催化剂。使用多种分析表征手段对Co/C₃N₄ NTs的形貌和结构进行分析,并比较Co负载量对复合材料可见光光催化产氢性能的影响。结果表明,该金属-半导体异质结可有效增强光生电子-空穴的分离速率。经可见光照射2 h后,当Co负载量为质量分数5%时具有最佳产氢量,且产氢速率为纯C₃N₄ NTs的1.7倍。     

金属硫族非超四面体In-Sn-S团簇的合成、结构及电催化氧还原反应性能

开发由金属In和Sn参与构筑的金属硫族非超四面体(non-Tn)团簇材料,对于实现该类材料的结构多样性及丰富其光电应用十分重要。利用溶剂热法合成了一系列新的 non-Tn 团簇化合物(C₇H₁₃N₂)[InS₂] (1)、(C₇H₁₃N₂)₄[In₂S₁₁Sn₃] (2)和(C₇H₁₃N₂)₃[In₃S₁₂Sn₃] (3),其中C₇H₁₃N₂=质子化1,5-二氮杂双环[4.3.0]壬-5-烯。3种化合物由{SnS₄}、{InS₄}或{InS₅}三个配位单元之间以边共享或顶点共享的方式组合而成。电催化氧还原反应(ORR)研究表明,化合物1~3的还原峰电位分别为0.60、0.64和0.65 V,含有Sn(Ⅳ)的化合物2和3表现出更好的催化性能。不仅如此,Koutecky-Levich图分析表明,化合物中In和Sn的组成比例对其ORR催化路径有明显的调节作用。     

g-C3N4/CaTi2O5复合材料制备及其光催化性能

利用类石墨氮化碳（g-C₃N₄）和亚稳相钙钛氧化物（CaTi₂O₅）固相法制备C₃N₄/CaTi₂O₅复合材料。利用X射线衍射（XRD）、金相显微镜、扫描电子显微镜（SEM）及附带能谱分析仪（EDS）和N₂吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计（UV-Vis）测试了样品的光吸收性能,研究C₃N₄与CaTi₂O₅物质的量之比（n_C3N4/nCaTi₂O₅）对C₃N₄/CaTi₂O₅复合样品的物相结构和微观形貌的影响,同时考察C₃N₄/CaTi₂O₅复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明：相比纯C₃N₄和CaTi₂O₅样品,C₃N₄/CaTi₂O₅复合样品在可见光下具有较高的光催化性能,随着n_C3N4/nCaTi₂O₅增加,样品的光催化降解率随之增加而后降低,当n_C3N4/nCaTi₂O₅=1：1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

助剂对Ni/SiO2催化剂微观结构及二硝基甲苯催化加氢性能的影响

采用等体积浸渍法制备了负载型Ni/SiO₂催化剂,研究了Ce、Zr、La、Co和Fe助剂对催化剂微观结构及其催化二硝基甲苯（DNT,C₆H₃CH₃（NO₂）₂）加氢制备甲苯二胺（TDA,C₆H₃CH₃（NH₂）₂）性能的影响。通过XRD,BET,H₂-TPD、H₂-TPR和XPS技术对催化剂进行了表征。结果表明,助剂的引入促进了Ni物种在载体表面的分散,减小了Ni晶粒的尺寸,使得NiO晶粒更易还原。添加La、Fe和Zr助剂增加了有效的Ni活性中心数,有利于催化活性的提高,其中,添加La助剂制备的催化剂催化性能最优,DNT转化率和TDA选择性分别为98.1%和99.1%。但Co和Ce助剂的加入降低了化学氢吸附量,使得有效的Ni活性中心数降低,降低了催化剂的催化活性。     

C60及其衍生物非线性光学材料的研究进展

介绍了非线性光学性质的原理以及目前研究的具有这种特殊性质的功能材料的结构特点和应用. C₆₀具有的特殊结构, 使其在众多领域成为了研究的重点. C₆₀本身就具有良好的非线性光学性能, 对其修饰得到的各种衍生物更体现优良的性质, 尤其是目前人们大量研究的富勒烯高分子化功能材料具有非常快速的非线性响应时间. 因此重点介绍了C₆₀及其衍生物的结构、非线性光学原理、性质和国内外最新的研究状况.     

Investigation on mechanical properties, durability and micro-structural development of steel slag blended cements

To improve the properties of steel slag blended cements, a chemical activator was added into blended cements, the mechanical properties and durability of steel slag blended cements were investigated. The results show that steel slag in blended cement pastes presents low hydraulic activity and makes practically no contribution to strength development. After the addition of chemical activator, the mechanical properties and durability of ternary blended cements are increased significantly. The hydration process and micro-structural development of blended cement was investigated by isothermal calorimeter and scanning electric microscope, respectively. Steel slag started hydration in the first 3?days in the presence of chemical activator, steel slag and granulate blast furnace slag reacted with Ca(OH)₂ to form a dense microstructure as curing proceeded. Therefore, both early and late compressive strengths of steel slag blended cement with 35% cement clinker and 30% steel slag can be comparable with those of Portland cement.     

REINFORCEMENT OF CALCIUM PHOSPHATE CEMENTS WITH PHOSPHORYLATED CHITIN

Phosphorylated chitins (P-chitins) as the additives of calcium phosphate cements (CPCs) were prepared by thephosphorylation of chitin with phosphorus pentoxide in methanesulfonic acid. Their physical properties and effects on CPCsfrom monocalcium phosphate monohydrate (MCPM) and calcium oxide (CaO) or dicalcium phosphate dihydrate (DCPD)and calcium hydroxide [Ca(OH)_2] were investigated. Addition of P-chitin (M_w = 2.60×10~4; degree of substitution, DS =0.68) to the liquid phase in amounts up to 3 wt% for MCPM and CaO cements or 1.5 wt% for DCPD and Ca(OH)_2 cementscould enhance the mechanical strength considerably while little influence on the setting time was observed. However, furtheraddition of P-chitin will cause no setting.     

Hydration and Hardening of Apatitic Cement

Abstract

Hydroxyapatite (HAp) with the general formula Ca₁₀ z(HPO₄)z (PO₄) 6-z (OH) a-z · nH₂O has become of particular interest as a bio-restorative material having good compatibility with living hard tissues. In this work, hydration and hardening properties of water-setting apatitic cements were presented. Ca₃(PO₄)2 with the formd α (α-TCP) itself was an apatitic cement which could hydrate and harden alone, and formed HAp or Ca₈H₂ (PO₄) 6 · 5H₂O (OCP). Other apatitic cements were prepared by mixing at least two compounds selected from Ca HPO₄ · 2H₂O (DCPD), α-TCP, Ca₄(PO₄)aO (TeCP) and CaCO₃. The hydraulic reaction of α-TCP was accelerated by using water-soluble additives such as NaCl, NH₄Cl, NH₄ -citrate, etc. Another way for the acceleration was the addition of DCPD. The combination α-TCP/DCPD was developed with the expectation of the reaction α-TCP + DCPD + H₂O → 1/2 OCP. Hydraulic reactions of combinations TeCP/DCPD (Brown and Chow, 1983) and DCPD/CaCO₃ were also investigated. Various setting times above 4 min were obtained at 37–40°C by using different additives and combinations. The setting and hardening was considered to be due to the entanglement of HAp or OCP microcrystals formed on original powder particles. The resulting porously hardened bodies had porosities of 46 –80%, compressive strenghts of 2–30MPa, diametral tensile strengths of 0.1–3.5MPa. These apatitic cement pastes showed different DSC characteristics;d-TCP: exothexmic peak at 70–105°C, α-TCP/DCPD:two exo. and two endothermic peaks in the range of 40 to 120°C, TeCP/DCPD:two exothermic peaks in the range of 30 to 80°C, and DCPD/CaCO₃:endothermic peak at 70–100 °C.     

Improvement of surface cementitious properties of coarse fly ash by dehydration and rehydration processes

Owing to poor bonding between coarse fly ash particles and hydration products, gap-graded blended cements with fly ash usually show lower compressive strengths than Portland cement. Surface cementitious properties of coarse fly ash were improved by dehydration and rehydration processes in the present study. The results show that during the calcination at 750?°C, C?CS?CH gel is mainly transformed into a new nesosilicate, which is similar to a less crystalline C₂S. The formation of melilite from hydration products is also noticed at 900?°C, however, this will not contribute to rehydration of calcined fly ash. Rehydration of new generated nesosilicate on the surface of coarse fly ash leads to a better bonding between coarse fly ash particles and hydration products. As a result, both early and late mechanical properties of gap-graded blended cements containing 25% cement clinker and 39% calcined coarse fly ash are higher than those of 100% Portland cements.     

Thermodynamics and kinetics of hydrogen absorption–desorption of vanadium synthesized by aluminothermy

This paper studies the addition (0–40% w/w) of natural zeolite (NZ, 84% clinoptilolite) in blended cements made with Portland cement (PC) with low and medium C₃A content. The isothermal calorimetry was used to understand the effect of NZ on the early cement hydration. For low C₃A cement, the addition of NZ produces mainly a dilution effect and then the heat released curve is similar to plain cement with lower intensity. For medium C₃A cement, the curve shows the C₃S peak in advance and a high intensity of third peak attributed to C₃A hydration. The high cation fixed of NZ reduces the ions concentration (especially alkalis) in the mixing water stimulating the PC hydration. The flowability decreases when the NZ replacement level increases. Results of Fratini’s test show that NZ with both PCs used presents slow pozzolanic activity. At early age, XRD and FTIR analyses confirm that hydration products are the same as that of the corresponding PC and the CH is progressively reduced after 28 days and some AFm phases (hemi- and monocarboaluminate) appear depending on the NZ percentage and the PC used. For low replacement levels, the compressive strength is higher than the corresponding PC from 2 to 28 days. For high replacement levels, the early compressive strength is lower than that of corresponding plain PC and the pozzolanic reaction improves the later compressive strength of blended cements.     

Fast physics-chemical and calorimetric characterization of natural pozzolans and other aspects

This research reports on the effects of including natural pozzolans in two Portland cements with different mineralogical compositions, with and without excess gypsum at amounts equivalent to 7.0% SO₃. The main analytical techniques used to study these effects were: the amount of water needed to make a paste of normal consistency, the 2-day Frattini pozzolanicity test and conduction calorimetry. The results obtained showed that these natural pozzolans caused contradictory (accelerating and retarding) effects on the rheology of the resulting cements, depending on the mineralogical composition of the respective Portland clinkers as well as the reactive chemical composition of the pozzolans, in particular their reactive alumina content (Al₂O₃ ^r−). The addition of gypsum also caused acceleration and delays in the calorimetric evolution of the resulting pastes, which proved to be heavily dependent upon the more or less aluminic chemical character of the natural pozzolans studied. This, in turn, was conditioned by the higher or lower Al₂O₃ ^r− content (for the SiO₂ ^r− content was of a very similar order of magnitude in all three pozzolans analyzed). The Al₂O₃ ^r− content was likewise responsible for paste behaviour in the afore-mentioned trials and analyses, and the pozzolanic activity exhibited by the compound was found to be more specific than generic, indirectly stimulating C₃A hydration more intensely and rapidly than C₃S hydration in PC1, one of the two Portland cements used. Indeed, when these natural pozzolans exhibited such prior pozzolanic activity in the second cement studied, PC2, the hydration of its 79.5% of C₃S was not indirectly stimulated to the same degree; rather, the contrary effect was observed, i.e., this cement was physically diluted by the three pozzolans. Pozzolan O stimulated hydration directly and non-directly more than indirectly, while pozzolan C acted conversely, and A exhibited varying combinations of the two patterns. The physical state of the reactive alumina, Al₂O₃ ^r−, in these three natural pozzolans, must be more amorphous than vitreous, i.e., resembling metakaolin more than fly ash in this regard. That notwithstanding, the reactive alumina content in each pozzolan must have conditioned the water/cementitious material ratio obtained for the respective blends with both types of Portland cement (a finding that could be used in future for speedy, simple, reliable and economical characterization), as well as their specific pozzolanicity developed and the rate and total heat of hydration generated by such blended cements.     

Thermal,viscoelastic, and mechanical properties of DCPD-containing polymers

The thermal, viscoelastic, and mechanical properties of cured dicyclopentadiene (DCPD)-containing polymers prepared from novel DCPD-modified unsaturated epoxypolyesters and styrene were evaluated. This was accomplished using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, three-point bending test, and Brinell’s hardness. The thermal, viscoelastic, and mechanical properties of DCPD-containing polymers were strongly dependent on chemical structure. The cross-linking density (υ _e) of obtained networks increased with increasing content of carbon–carbon double bonds in the poly(ester) structure. In addition, the introduction of DCPD rings into the poly(ester) structure increased the rigidity of the molecular backbone. It resulted in obtaining polymers which showed great improvement in mechanical properties including remarkably higher storage modulus ( E_{20 ^°\textC}^￠ E_{{20\,{}^{\circ}{\text{C}}}}^{'} ), flexural modulus at bending (E _mod), hardness, lower extension at maximum force (ε-F _max), as well as higher thermal stability. These good properties make these materials highly promising as potential candidates for structural applications.     

Calorimetry of portland cement with silica fume and gypsum additions

The use of active mineral additions is an important alternative in concrete design. Such use is not always appropriate, however, because the heat released during hydration reactions may on occasion affect the quality of the resulting concrete and, ultimately, structural durability. The effect of adding up to 20% silica fume on two ordinary Portland cements with very different mineralogical compositions is analyzed in the present paper. Excess gypsum was added in amounts such that its percentage by mass of SO₃ came to 7.0%. The chief techniques used in this study were heat conduction calorimetry and the Frattini test, supplemented with the determination of setting times and X-ray diffraction. The results obtained showed that replacing up to 20% of Portland cement with silica fume affected the rheology of the cement paste, measured in terms of water demand for normal consistency and setting times; the magnitude and direction of these effects depended on the mineralogical composition of the clinker. Hydration reactions were also observed be stimulated by silica fume, both directly and indirectly – the latter as a result of the early and very substantial pozzolanic activity of the addition and the former because of its morphology (tiny spheres) and large BET specific surface. This translated into such a significant rise in the amounts of total heat of hydration released per gram of Portland cement at early ages, that silica fume may be regarded in some cases to cause a synergistic calorific effect with the concomitant risk of hairline cracking. The addition of excess gypsum, in turn, while prompting and attenuation of the calorimetric pattern of the resulting pastes in all cases, caused the Portland cement to generate greater heat of hydration per gram, particularly in the case of Portland cement with a high C₃A content.     

Heat of hydration of high reactive pozzolans in blended cements: Isothermal conduction calorimetry

A study was carried out comparing silica fume (SF) and dealuminated kaolin (DK) as pozzolanic materials in blended cements. Ten, 20 or 30 wt% of SF or DK were substituted for Portland cement. The kinetics of hydration up to 45 h were studied using isothermal conduction calorimetry. Blends containing pozzolanic materials usually have decreased heats of hydration compared to pure cement during the period of C₃S hydration, i.e. during the main hydration peak. Depending on the chemical composition and the activity of the pozzolan, the reaction taking place with the lime typically contributes to the heat output after the main hydration peak.The pozzolanic activity of DK is the principal factor and heat evolution increases with respect to pure PC mortar, during the first 15 h. The presence of hydrated silica (silanol groups) in DK increases the pozzolanic activity especially before and during induction period. The acidic silanol sites are capable of a fast acid-base reaction with the alkalis and with any Ca(OH)₂ present in cement during the induction period.     

Synthesis,moisture resistance,thermal, chemical and SEM analysis of macro-defect-free (MDF) cements

The results, presented here discusses the Macro-Defect-Free (MDF) cements prepared from the blends of sulfoaluminate ferrite belite (SAFB) clinkers, ordinary Portland cement (OPC), Al₂O₃ and poly(butyl acrylate) (PBA), styrene/acrylonitrile co-polymer (SACP) or sodium polyphosphate (poly-P). Though MDF cements have several attractive properties, their utilization has been limited due to the insufficient moisture resistance. It is a very challenging task for scientists and technologist to improve the moisture resistance of MDF cements. Therefore, the new MDF cements were subjected to various moist atmospheres to investigate their moisture resistance. The most significance of this work is the improvement of moisture resistance of the studied MDF cements. The aim of this work was to understand the effects of polymers, Al₂O₃, OPC and SAFB clinkers in the raw mix and delayed drying on MDF cements and also on their subsequent moisture resistance and thermal stability as well as to discover the new properties of these materials. Their chemical, thermal and scanning electron microscopic (SEM) analysis was also carried out before and after exposure to moisture. PBA was found to be the most suitable polymer for MDF cement synthesis, since the samples containing PBA showed the highest resistance to moisture. There are three main temperature regions on TG curves of both series of MDF cement samples. The significant differences in SEM of MDF cements before and after moisture attack and with different polymers were observed. This revised version was published online in July 2006 with corrections to the Cover Date.