无机玻璃Li2O·2SiO2的结构松弛(Ⅰ)——TNM唯象模型描述

简介了结构松弛的主要特点及其唯象Ｔｏｏｌ－Ｎａｒａｙａｎａｓｗａｍｙ－Ｍｏｙｎｉｈａｎ模型的建立，产用此模型对无机玻璃在不同老化时间及不同老化温度下的结构松弛行为进行了模拟，得到了４个可调参数Ｘ，β，Δｈ和Ａ，其中β，Δｈ和Ａ不随老化温度及老化时间而发生变化，Ｘ则随老化时间的增加而增大，随老化温度的降低而降低。     

Al掺杂对Li(AlyCo1-y)O2材料结构的影响

报道了在800℃烧结制备的新型锂二次电池正极材料Li(AlyCo_1-y)O₂(y=0,0.11)的X射线衍射结果和由此而揭示的结构演化过程.研究表明,y≤0.5时,材料呈单相,0.6≤y≤0.9时,材料呈两相[Li(AlyCo_1-y)O₂,C-LiAlO₂]共存状态,y=1时,材料又呈单相,为LiAlO₂相.Li(AlyCo_1-y)O₂材料中y值的上限即Al的最大固溶度在0.5左右.在单相区(y≤0.5),随着Al掺杂的增多,Li(AlyCo_1-y)O₂材料晶格结构参数发生变化,a轴缩短,c轴变长,c/a比基本呈线性增加,材料的层状属性更加明显.     

Li3V2(PO4)3电极过程及其锂离子脱嵌动力学研究(Ⅰ)

采用溶胶凝胶法合成了Nasicon化合物Li3V2(PO4)3,采用X射线衍射(XRD)对产品进行了物相分析.采用充放电测试,循环伏安(CV)研究了化合物的电化学性能和锂离子的脱嵌过程,计算出Li+在固相中的扩散系数(10-8 cm2·s-1);采用交流阻抗测试(EIS)研究了Li3V2(PO4)3的电极过程;对两种类型的阻抗图谱提出不同等效电路模型并对结果进行了拟合;研究了Li3V2(PO4)3电极过程动力学以及新鲜电极界面在充放电过程中的变化特性.     

C(膜)/Si(SiO2 )(纳米微粒)/C(膜)热处理的形态及结构分析

用直流辉光溅射+真空镀膜法制备了一种新型结构的硅基纳米发光材料- C(膜)/Si(SiO2)(纳米微粒)/C(膜)夹层膜,并对其进行了退火处理.用TEM、 SEM、 XRD和XPS对其进行了形态结构分析.TEM观察表明: Si(SiO2)纳米微粒基本呈球形,粒径在30 nm左右.SEM观察表明: 夹层膜样品总厚度约为50 μm,膜表面比较平整、致密.400℃退火后,样品表面变得凹凸不平,出现孔状结构; 650℃退火后,样品表面最平整、致密且颗粒均匀.XRD分析表明:制备出的夹层膜主要由SiO2和Si组成,在C原子的还原作用和氧气的氧化作用的共同作用下, SiO2和Si的含量随加热温度的升高而呈现交替变化: 400℃时, C的还原作用占主导地位, SiO2几乎全部被还原成了Si,此时Si含量最高; 400～650℃时,氧化作用占主导地位, Si又被氧化成SiO2, Si含量降低, SiO2含量逐渐上升,在650℃达到最高.XPS分析表明: 在加热过程中, C原子逐渐扩散进入Si(SiO2)微粒层,在650℃与Si反应生成了新的SiC.     

C(膜)/Si(SiO2)(纳米微粒)/C(膜) 的光致发光性质研究

用直流辉光溅射法结合真空镀膜法制备出了一种"多层三明治结构"的光致发光材料-C(膜)/Si(SiO2)(纳米微粒)/C(膜)夹层膜,然后分别在400、650和750℃退火1 h.在波长为250 nm的紫外光激发下,刚制备出来未经退火处理的样品具有一个在398nm(3.12 eV)处的紫光宽带PL1峰.在650℃退火后,又出现了一个在360nm(3.44eV)附近的PL2峰.PL1和PL2峰形状和峰位与退火温度和激发波长无关,但强度却与退火温度和激发波长密切相关.结合形态结构分析可知,紫光PL1峰可用量子限制-发光中心(QC-LCs)模型进行解释:即光激发发生在8iO2微粒内部,而光发射源于SiO2与Si界面上的缺陷中心.紫外荧光PL2峰则源自SiC内部的电子-空穴复合发光.     

配合物[Fe(CTS)2]·5SO4·7H2O的热分解动力学

研究了壳聚糖对Fe2+的吸附行为,并进行了条件优化,得到了较为理想的合成产物.通过红外光谱和紫外光谱进行了表征,进而用化学分析、元素分析确定了配合物的组成,并利用TG-DSC分析,采用常用的22种机理函数,对非等温动力学数据进行了线性回归拟合处理,求得了配合物主要分解阶段热动力学最可机理函数和动力学参数(E和A).     

Ru(bipy)_3~(2 )/Ru(phen)_3~(2 )-C_2O_4~(2-)-Ce~(IV)化学发光反应动力学模型的研究

根据Ru(bipy)_3~(2 )/Ru(phen)_3~(2 )-C_2O_4~(2-)-Ce~Ⅳ(bipy=2,2＇-联吡啶,phen=1,10-邻菲咯琳)化学发光反应建立了该化学发光反应的动力学模型,根据模型计算出该反应的发光强度-反应时间曲线上升及下降阶段的反应速率常数、发光强度最大值及其出现的时间等.发光强度最大值及发光强度-反应时间曲线下的面积均可用于定量分析.     

高长径比管式反应器内壁SiO2与TiO2钝化层的原子层沉积制备及抗积碳性能

采用原子层沉积技术(ALD)在不锈钢微通道管式反应器内壁沉积二氧化硅(SiO₂)和二氧化钛(TiO₂)薄膜, 以抑制碳氢燃料热裂解过程中由于金属催化作用导致的结焦. 使用石英晶体微天平(QCM)测得SiO₂和TiO₂薄膜的生长速率分别为0.15 nm/周期和0.11 nm/周期, 因此可以通过改变沉积周期数精确控制钝化层的厚度. 在结焦实验中, 当钝化膜层较薄时, 其抗积碳钝化作用较弱; 随着钝化薄膜厚度的增加, 其钝化作用逐渐增强, 微通道反应器的运行寿命显著延长. 实验表明, TiO₂薄膜的抗积碳钝化性能普遍优于SiO₂薄膜. 沉积周期数为1000的TiO₂膜层具有最佳的抗积碳钝化效果, 能够使反应器的运行时间延长4~5倍.     

H2分子在Li3N(100)表面吸附的第一性原理研究

采用第一性原理方法研究了H₂分子在两种Li₃N(100)晶面的表面吸附情况. 通过研究Li₃N(100)/H₂体系的吸附位置、吸附能和电子结构, 发现H₂分子在Li₃N(100)晶面主要是化学吸附, 但也可以发生物理吸附. 在表面终止原子为Li和N的Li₃N(100)表面, 吸附的最稳定结构中H₂分子被解离, 最终H原子分别趋于两个N原子的顶位, 形成两个NH基, 吸附能为5.157 eV, 属于强化学吸附|此时H₂分子与Li₃N(100)表面的相互作用主要源于H1s轨道与Li₃N表层N原子的2s, 2p轨道重叠杂化的贡献, 且N-H键为共价键. 在表面终止原子为Li的Li₃N(100)表面, 吸附的最稳定结构中H₂分子也被解离, H原子趋于穴位, 吸附能为2.464 eV, 也属于强化学吸附|此时Li和Ｈ之间为较强的离子键相互作用.     

PbF2·SiO2基玻璃陶瓷的溶胶-凝胶制备及结构转变研究

采用溶胶-凝胶法制备了PbF2·SiO2纳米晶玻璃陶瓷块体;利用TG-DSC和IR技术分析了干凝胶在热处理过程中有机基团的分解及内部原子键合方式的演变;结合XRD和TEM研究了凝胶玻璃中PbF2纳米晶粒的长大过程,并分析了Er3+掺杂的影响.结果表明,采用此方法制备的PbF2.SiO2纳米晶粒玻璃陶瓷具有较好的成形性,晶化温度在320℃左右;经480℃热处理,镶嵌在玻璃基体中的PbF2晶粒尺度约为10-25nm,材料透明性良好.在PbF2·SiO2系统中掺入少量的Er3+,将提高PbF2的晶化温度,降低玻璃陶瓷的显微硬度;掺杂可能对PbF2晶粒表面原子的活性起抑制作用,阻碍晶粒的表面迁移,使晶粒的生长速度明显降低.     

Relaxation of Alkali Glass Exposed to an Electron Beam

Binary potassium and rubidium silicate glasses were irradiated with high-energy electrons. The changes induced in the glasses were observed as a decay of alkali X-ray signals with time. The decay curves displayed incubation periods, connected with changes of the transport mechanism. The electron exposures were interrupted relative to the incubation periods, next the glasses were annealed to enable easier relaxations, and successively irradiated again to finish the decay curve. Relaxation, which depends on the point of the decay curve at which exposure is interrupted, is calculated for the glasses. Relaxation was found to depend strongly on the interruption point with regard to the incubation period. The longer irradiation causes worse recovery of the structure during annealing, especially if the irradiation lasts longer than the incubation time. The larger ions and lower concentration also inhibit relaxation.     

Relaxation electrochemical noise of Li/SOCl2 and Li/MnO2 primary batteries

Journal of Solid State Electrochemistry - Electrochemical noise measurements were carried out on commercially available Li/SOCl2 and Li/MnO2 primary batteries during relaxation following removal of...     

Neue Silicate mit „Stuffed Pyrgoms”︁: CsKNaLi9{Li[SiO4]}4, CsKNa2Li8{Li[SiO4]}4, RbNa3Li8{Li[SiO4]}4 [1] und RbNaLi4{Li[SiO4]}2 [2]

More Silicates with ?Stuffed Pyrgoms”?: CsKNaLi₉{Li[SiO₄]}₄, CsKNa₂Li₈{Li[SiO₄]}₄, RbNa₃Li₈{Li[SiO₄]}₄ [1] and RbNaLi₄{Li[SiO₄]}₂ [2] Single crystals of the new silicates CsKNaLi₉{Li[SiO₄]}₄, CsKNa₂Li₈{Li[SiO₄]}₄, RbNa₃Li₈{Li[SiO₄]}₄ and RbNaLi₄{Li[SiO₄]}₂ as well as powder (Rb-containing compounds only) were obtained for the first time. The samples were prepared by heating well ground mixtures of the binary oxides in Ni and Ag tubes, respectively. The structure determination was carried out by four-circle diffractometer data (MoKα radiation; Siemens AED 2): CsKNaLi₉{Li[SiO₄]}₄: tetragonally prismatic crystals, light yellow; 726 I₀(hkl), R = 4.4%, R_w = 2.8%; a = 1 102.0(6), c = 637.9(5) pm; Z = 2; space group I4/m; 2 CsO_0.55 + Li₄TlO₄ + glas (560°C, 15 d). CsKNa₂Li₈{Li[SiO₄]}₄: tetragonally prismatic crystals, light yellow; 727 I₀(hkl), R = 4.4%, R_w = 2.6%; a = 1 103.5(7), c = 637.7(4) pm; Z = 2; space group I4/m; 1.1 CsO_0.61 + 1.1 KO_0.55 + 1.4 NaO_0.52 + 6.5 Li₂O + 4 SiO₂ (600°C, 60 d). RbNa₃Li₈{Li[SiO₄]}₄: tetragonally prismatic crystals, colourless; 600 I₀(hkl), R = 2.3%, R_w = 2.0%; a = 1 092.08(6), c = 632.76(4) pm; Z = 2; space group I4/m; 4 RbO_0.57 + 3 NaO_0.52 + 6.5 Li₂O + 4 SiO₂ (650°C, 63 d). RbNaLi₄{Li[SiO₄]}₂: monoclinic, ball-shaped, colourless; 1 224 I₀(hkl), R = 3.1%, R_w = 3.1%; a = 1 573.10(13), b = 630.48(5), c = 781.25(8) pm, b = 90.566(8)°; Z = 4; space group C2/m; 1.1 RbO_0.52 + 1.2 NaO_0.45 + 5 Li₂O + 4 SiO₂ (700°C, 40 d).     

Enthalpic Relaxation of 25Na2O·xTiO2·(75-x)SiO2 Glasses

The enthalpic relaxation of the title glasses, studied by differential scanning calorimetry, is well described by a mathematical model based on the stretched exponential relaxation function with the relaxation time proportional to the actual viscosity. The dependence of viscosity on temperature and the fictive temperature was expressed by Mazurin's approximation. The relaxation parameters obtained correlated significantly with the glass composition, indicating the changes in the structural of the TiO₂ role near a TiO₂ content of 3–4 mol%. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and Characterization of a New Organic–Inorganic Hybrid Hydrogel by Using SiO2 Nanoparticles as an Initiator

A new type of organic–inorganic hybrid hydrogel (OIHH) was prepared under low air pressure using SiO₂ nanoparticles as initiator. The obtained OIHH shows a novel microstructure and characteristics, which increased the salt resistance and water absorbance. We investigate the effects of the reaction conditions on the absorption ability. The xerogel shows absorbance of 339.9 and 102.8 g/g for distilled water and for 0.9 wt% NaCl solution. Moreover, a reasonable microstructure of the superabsorbent polymer is shown.     

Study on K+/H+ Exchange for K2O·4TiO2

Potassium tetratitanate (K₂O·4TiO₂) is an artificial mineral whisker with the diameter of 0.5-1 μm and the length 5-20 μm. The interlayered potassium ion exchange reaction for the K₂O·4TiO₂ whisker results in the appearance of many new nonstoichiometric metal titanate whiskers M₂O·nTiO₂ (M are K, H, Na, Cs, Ba, Ru, Co or Pb, etc.). Through the K⁺-H₃O⁺ exchange in solutions,TiO₂ and K₂O·6TiO₂ whiskers were synthesized. Generally, the target product quality and yield are greatly affected by the ion exchange conditions. The optimal synthetic conditions are difficult to obtain. In this paper, a new method was proposed to control the ion-exchange process by applying the ion-exchange reaction thermodynamics and combining with monitoring the multi-ions concentrations with ISE. Ion-exchange thermodynamic model for potassium tetratitanate whisker (K₂O·4TiO₂) was established, and model parameters were calculated through the existent experimental equilibrium data. Ion selective electrode achieved the on-line monitor for K⁺/H⁺ exchange and the equilibrium point was judged. The calculation for the accurate ion concentration was done through the Pitzer equation. Based on the proposed method, the ion-exchange process was controlled and the optimal synthesis conditions could be obtained.     

Structural Phase Transition in Li2C2

Pure polycrystalline Li₂C₂ could be obtained by the reaction of lithium and graphite flakes in an arc-melting furnace. X-ray powder investigations on these samples confirm the crystal structure given by Juza, Wehle, and Schuster (Immm, No. 71, Z = 2) which is isotypic to Rb₂O₂ and Cs₂O₂. At about 500 °C a reversible phase transition (1^st order) to a cubic modification (Fm 3 m, No. 225, Z = 4) has been observed. This high temperature modification can be described as an antifluorite-structure with disordered C₂^2– dumbbells.     

Synthesis of Ag-Colloids in Sol-Gel Derived SiO2-Coatings on Glass

Ag colloid-containing coatings on soda lime glass and fused silica are prepared via the sol-gel process. To incorporate Ag⁺-ions in the coatings homogeneously, they are stabilized by a functionalised silane (aminosilane) and then mixed with the basic sol prepared from 3-glycidoxypropyl trimethoxysilane (GPTS) and tetraethoxysilane (TEOS). Crack-free and transparent coatings with a thickness of 0.5 to 1.2 m, are obtained by heat treatment between 120°C and 600°C. The Ag-colloid formation was monitored by UV-VIS spectroscopy as a function of temperature. The investigations reveal that the substrate has a deciding influence on the Ag-colloid formation caused by alkali diffusion from the substrate into the coating. High resolution transmission electron microscopy (HRTEM) investigations prove that poly-crystalline Ag_xO_y-nanoparticles are formed during thermal densification in the coatings and that this change is accompanied by a vanishing of the yellow colour of the coatings. A post-heat treatment in a reducing atmosphere (90% N₂, 10% H₂) turns back the yellow colour and single-crystalline Ag-colloids can be detected by HRTEM. A suitable choice of the temperature and time conditions allows the control of the colloid size during heat treatment in a reducing atmosphere. For comparison, ion-exchange experiments have been carried out which showed that a spontaneous Ag-colloid formation was achieved in the soda lime substrate at 400°C. Since Ag containing SiO₂-coatings remained colourless after thermal treatment between 400°C and 600°C in air, on soda lime substrates, a remarkable diffusion of Ag⁺ into the substrate was excluded.     

1,2-丙二醇水溶液玻璃化转变与结构松弛

为了考察水含量对1, 2-丙二醇水溶液玻璃化转变和结构松弛参数的影响, 用差示扫描量热法(DSC), 测量了5种高浓度1, 2-丙二醇水溶液(60%、70%、80%、90%、100%, w)玻璃化转变区域的表观比热容. 用5种降温速率(1、2、5、10、20 K·min-1)和10 K·min-1的升温速率获得玻璃化转变的相关参数. 玻璃化转变温度分析结果表明, 虽然水含量增加能从总体上降低体系的玻璃化转变温度, 但与纯羟基类多元醇相比, 水对1, 2-丙二醇的增塑作用并不显著. 结构松弛活化能计算结果表明, 体系水含量的增加能明显降低结构松弛活化能. 脆度分析结果表明, 随着体系水含量增加, 动力学脆度逐渐降低, 但热力学脆度是先升高后降低, 在80%左右达到最大值. 结构松弛协同重排域计算结果表明, 当浓度由60%增加至100%时, 玻璃化转变特征长度由2.79 nm增加至3.57 nm.