水合偏硼酸钾的热化学研究

Hydrated potassium monoborate(KBO₂·4/3H₂O) was obtained from an aqueous solution in a mole ratio of K₂O∶B₂O₃=2∶1 and characterized by powder X-ray diffraction(XRD)， infrared spectroscopy(FT-IR) and Raman spectroscopy. The enthalpy of solution of hydrated potassium monoborate， KBO₂·4/3H₂O， in approximately 1mol·dm^-3 aqueous hydrochloric acid was determined. Together with the previously determined enthalpies of so-lution of H₃BO₃ in approximately 1mol·dm^-3 HCl(aq) ，and of KCl in aqueous(hydrochloric acid+boric acid)， the standard molar enthalpy of formation of -(1411.11±0.84)kJ·mol^-1 for KBO₂·4/3H₂O was obtained from the standard molar enthalpies of formation of KCl(s)， H₃BO₃(s)， and H₂O(l). The standard molar entropy of formation of -422.94J·K^-1·mol^-1 and standard molar entropy of 163.47J·K^-1·mol^-1 for KBO₂·4/3H₂O were calculated from the thermodynamic relations. A group contribution method is applicable to KBO₂·4/3H₂O.     

硼酸镁过饱和溶液稀释和酸化过程中的Raman光谱

用纯水和恒沸点盐酸对六硼酸镁过饱和水溶液进行稀释和酸化,使用激光Raman光谱记录反应过程。对光谱峰进行归属。讨论了溶液中含硼量和pH值对硼氧配阴离子存在形式的影响,对多聚硼氧配阴离子在溶液中的存在形式及其相互作用机理进行了初步探讨。     

四硼酸钾水溶液结构

研究了298.15和323.15K广泛浓度范围内四硼酸钾溶液pH,并根据化学反应平衡常数和牛顿迭代法计算获得了溶液化学物种分布图.典型样品用拉曼光谱进行核实.研究表明,高浓溶液中存在主要化学物种是B4O5(OH)24-,次要化学物种是B3O3(OH)4-和B(OH)4-.用X射线散射法研究了298和323K高浓四硼酸钾溶液结构.用几何模型定量描述B4O5(OH)42-,B3O3(OH)-4和B(OH)-4离子内、离子间、分子间的相互作用,并用最小二乘法进行精修.模型计算和精修给出硼氧六元环内原子间距和配位数,并与晶体结构很好一致,表明高浓溶液中离子内有序程度较高.同时给出K+和硼酸根离子水合数和水合距离,以及接触离子对的结构信息,并进一步简单讨论温度和浓度变化对溶剂结构的影响.     

Pt/TiO2光催化分解四硼酸钾水溶液制氢

研究了以四硼酸钾溶液作反应体系，在1%Pt／TiO2光催化剂的作用下光催化分解水制氢的反应，发现该体系能使放氢速率明显提高．放氢速率还随B4O7^2-浓度的增大而增大．在此基础上，还对B4O7^2-的作用机理进行了探讨，BRO7^2-在该反应体系中主要是通过物理作用有效的阻止了逆反应的发生，从而使放氢速率得以提高．     

过饱和五硼酸钠溶液结构

用快速X射线衍射法测量了298和323K时过饱和五硼酸钠溶液的时间空间平均结构,得到了溶液径向分布函数.通过模型设计及理论计算获得了B-B、B-O、O-O、Na-O、Na-B原子对相互作用的理论偏径向分布函数,并讨论了浓度和温度对五硼酸钠溶液结构的影响.在五硼酸钠过饱和溶液中六水合Na+形成八面体结构,其平均配位数随浓度和温度变化不大,作用距离随温度升高及浓度减小而减小;给出了溶液中主要硼酸盐离子B3O3(OH)4-、B5O6(OH)4-和B(OH)3的水合结构,较高温度及较高浓度有利于更高聚合的多聚硼酸根离子的形成;浓度对硼酸盐离子的第一水合层的水合数影响较大,在较浓的五硼酸钠过饱和溶液中,五硼酸根离子的一个端氧单齿配位到Na+上形成离子对,Na-B特征距离为0.328nm.     

CuO/Al2O3催化剂高温固相反应的原位XRD和Raman研究

采用原位XRD和激光Raman光谱等技术对CuO/Al2O3系列催化剂高温下的表面组成和体相结构的变化进行研究.结果表明,随着焙烧温度升高,CuO首先与载体Al2O3发生固相反应生成CuAl2O4.CuAl2O4层能阻止外层CuO进一步向载体Al2O3扩散,从而使部分CuO稳定在CuO/Al2O3催化剂的表层.     

四水五硼酸铯及其饱和溶液的振动光谱分析

硼氧配阴离子存在形式及其相互作用受溶液温度、ｐＨ值、总硼浓度及金属阳离子存在等多种因素的影响。振动光谱[1]能有效地用于鉴定和表征固体硼酸盐,。近年来,ＦＴ ＩＲ和Ｒａｍａｎ光谱已用于研究硼酸盐水溶液的结构[2 5],但仅对溶解度较大的硼酸盐才能获得基团特征振动频率。Ｒａ ｍａｎ光谱有利于测量高含硼水溶液中的样品而没有在ＦＴ ＩＲ光谱中的来自于水的干扰,硼酸盐水溶液中的硼氧配阴离子存在形式可以通过差示ＦＴ ＩＲ光谱技术[6]来研究。本文采用这两种物理测试技术,研究了易溶性水合五硼酸铯及其饱和溶液,分别对其ＦＴ Ｉ…     

过饱和硼酸盐水溶液的Raman光谱

制备了MgO·2B₂O₃-H₂O,Na₂O·5B₂O₃-H₂O和MgO·3B₂O₃-H₂O的过饱和水溶液.采用激光喇曼光谱研究了这些过饱和水溶液,并对光谱频率进行了归属.讨论了过饱和水溶液中硼氧配阴离子的存在形式和相互作用机理.     

掺杂Sb对纳米TiO2薄膜的超亲水性和微结构的影响

用溶胶-凝胶法将纳米TiO2:Sb薄膜沉积在玻璃基板上.研究了掺杂浓度对薄膜的光致超亲水性、薄膜结构和晶相转变的影响.结果表明,纯TiO2薄膜中， TiO2不仅以无定型态存在，而且还以板钛矿和锐钛矿的形式存在.掺杂Sb提高了TiO2由无定型向板钛矿和锐钛矿转变的速率.掺入适量的Sb后， TiO2薄膜表现出更好的光致超亲水性.由XRD谱可算出薄膜的晶粒大小为13.3～20.0 nm.     

Na2O-P2O5系晶体微结构形态的拉曼光谱研究及其ab initio计算

本文采用激光拉曼光谱仪测量了磷酸钠二元系(1-x)Na₂O·xP₂O₅(x=0.25,0.33,0.50,1.0)几种晶体的拉曼光谱,比较并解释了随化学组成而变化微结构单元的拉曼振动模。同时用Gaussian 98W量子化学软件从头计算了这几种化合物的拉曼光谱。实验和计算均表明,磷酸盐晶体的基本结构单元为磷氧四面体[PO₄],并且晶体中磷氧四面体的伸缩模振动频率与连接中心磷原子的桥氧数密切相关,随桥氧数增加而升高。此外还解释了模拟图谱与实验谱差异的原因。     

Small Potassium Clusters

The molecules K ₂ , K ₃ , and K ₄ (structure shown on the right) have been isolated in krypton matrices at 15 K and characterized by Raman spectroscopy. Comparison of the experimental data with density functional calculations supports the prediction that potassium clusters are not only bonded by the valence electrons, but that there is also a contribution from the core electrons.     

Order-disorder transition in the Nd2−yYyZr2O7 system: Probed by X-ray diffraction and Raman spectroscopy

A series of compositions having the general formula Nd_2−yY_yZr₂O₇ have been synthesized by heating of mixtures of oxides of the components cation and characterized by X-ray diffraction and Raman spectroscopy. Rietveld analysis on the XRD data of all the compositions has been performed which revealed a decrease in lattice parameter as a function of y in the series Nd_2−yY_yZr₂O₇ (y=0.0-0.8). Subsequently, a biphasic region starts which continues for y=1.2 and 1.6. The other end member, i.e. Y₂Zr₂O₇ is found to be defect fluorite. On the other hand, Nd³⁺ has been used as surrogate material for Am³⁺, which is a minor actinide found in spent nuclear fuel. In the pyrochlore range, the increasing trend of the x-parameter of 48f oxygen indicates the enhancement of disorder in the system. Raman spectroscopy has been employed to validate the data obtained from XRD. The involvement of 48f oxygen in disorder has also been verified by Raman spectroscopic investigation.     

三氧化二硼和五硼酸钠水合物非晶结构

X射线衍射法测量了三氧化二硼及五硼酸钠水合物的非晶结构, 通过非晶衍射实验数据处理, 得到了它们的径向分布函数(RDF). 模型定量计算, 得到了其短程有序结构, 三氧化二硼水合物非晶中75%的硼参与形成平面硼氧六元环(boroxol), 给出了环内ortho-B-O, meta-O-O, meta-B-B和para-B-O相互作用的距离和作用数, 支链与硼氧六元环之间的夹角为125°±15°; 五硼酸钠水合物非晶中, 由两个硼氧三角形(B_△)和一个硼氧四面体(B_□)构成的两个变形六元环通过公共顶点(B_□)相连而形成五硼酸阴离子, 高度有序的离子内相互作用占绝对优势. 六配位Na^＋与五硼酸阴离子中一端氧相连, Na-B特征距离为0.330 nm.     

LiAlyCo0.96-yMg0.04O2(y=0.3,0.7)的合成及相行为的DTA研究

用柠檬酸配位聚合法合成了LiAl_yCo_0.96-yMg_0.04O₂(y=0.3,0.7)粉体,采用DTA方法和X射线衍射分析研究了烧结温度对不同铝含量材料相行为的影响.实验结果表明,铝掺杂量低(y=0.3)时,在600℃烧结就可得到具有α-NaFeO₂结构的单相固溶体.而铝掺杂量高(y=0.7)时,在600和700℃烧结都有γ-LiAlO₂相出现,直到烧结温度升高到800℃才得到单相固溶体.     

Covalent Organic Framework (COF‐1) under High Pressure

COF‐1 has a structure with rigid 2D layers composed of benzene and B₃O₃ rings and weak van der Waals bonding between the layers. The as‐synthesized COF‐1 structure contains pores occupied by solvent molecules. A high surface area empty‐pore structure is obtained after vacuum annealing. High‐pressure XRD and Raman experiments with mesitylene‐filled (COF‐1‐M) and empty‐pore COF‐1 demonstrate partial amorphization and collapse of the framework structure above 12–15 GPa. The ambient pressure structure of COF‐1‐M can be reversibly recovered after compression up to 10–15 GPa. Remarkable stability of highly porous COF‐1 structure at pressures at least up to 10 GPa is found even for the empty‐pore structure. The bulk modulus of the COF‐1 structure (11.2(5) GPa) and linear incompressibilities (k_[100]=111(5) GPa, k_[001]=15.0(5) GPa) were evaluated from the analysis of XRD data and cross‐checked against first‐principles calculations.     

高温高压水中干酪根热解的拉曼光谱原位研究

利用对顶砧压腔装置,以金刚石作为顶砧,通过观测和采用拉曼光谱对干酪根在高温高压水中热解的具体过程进行了原位研究.由于金刚石顶砧只在约1 332 cm-1波数出现一个很强很尖锐的峰,因此用于压 标的石英、介质水以及样品干酪根的拉曼峰都未受影响.测试了在450℃和850 MPa条件下干酪根变化的拉 曼峰.随着温度和压力的增加,干酪根在1 600 cm-1波数附近由于芳香环振动引起拉曼峰的最大峰位置 (vmax)和半高宽(FWHM)存在转折变化.在干酪根热解之前,其芳香环结构和无序结构之间的缺陷向有序化变化.而对于干酪根的热解过程,先是热解为液相碳氢化合物,随后进一步热解为更小分子的成分,如 CH4.干酪根的热解过程与压力密切相关,增加压力对热解存在抑制作用.     

Hydration Behaviour of Mixtures of Cement and Fly Ash with High Sulphate and Chloride Content

DTA/TG thermoanalytical investigations and X-ray diffractometry were carried out which demonstrate the effect of MSW fly ash on the hydration reactions of pozzolanic cement. The MSW fly ash has high content of calcium sulphate, alkali chlorides and heavy metals. During the first curing period the calcium aluminate reacts with the sulphate to form ettringite. In that period also the presence of syngenite is noted in the pastes. With the growth of the fly ash content of the mixture there is a lengthening of the period in which the hydration reactions of the calcium silicates are inhibited. Subsequently with the progress of hydration in the pastes the CSH phase develops and the formation of calcium chloroaluminate phase is observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation, XRD and Raman spectroscopic studies on new compounds RE2Hf2O7 (RE=Dy, Ho, Er, Tm, Lu, Y): Pyrochlores or defect-fluorite?

A series of compositions with the general formula RE₂Hf₂O₇ (RE=Dy, Ho, Er, Tm, Y and Lu) was prepared by a standard solid-state route and characterized by powder X-ray diffraction (XRD) and Raman spectroscopy. As per theoretical modeling reported in literature, some of these materials were predicted to exist in pyrochlore lattice. However, a careful X-ray diffraction, Raman spectroscopic and synchrotron radiation-XRD study revealed that under the experimental conditions used in the present investigation, out of all the RE₂Hf₂O₇ samples only Dy₂Hf₂O₇ has got a tendency to form a pyrochlore structure. All the other (Ho, Er, Tm, Lu, Y) hafnates crystallize in a defect-fluorite structure. In order to further ascertain these inferences, a few more RE₂Hf₂O₇ samples (La, Nd, Sm) i.e., with larger RE³⁺ ions were also prepared and the results were compared.