磷酸三钠十二水合物脱水过程的研究

通过热重分析（TG）、差热分析（DSC）、X射线粉末衍射（PXRD）和扫描电镜（SEM）研究了磷酸三钠十二水合物（Na₃PO₄·12H₂O）在303.15~413.15 K温度范围内的脱水过程。研究结果发现,磷酸三钠十二水合物在303.15~393.15 K温度范围内逐渐脱去11个结晶水,且脱水过程包含多步反应。分别通过Ozawa方程和Friedman方程计算其在不同脱水率下的活化能,二者得到结果一致性较好。整个脱水过程可以分为4个阶段,其脱水机理有所不同。不同温度下脱水产物的PXRD和SEM图表明其属于通道型包容水合物,在脱水过程中晶格结构发生了变化。     

五水柠檬酸钠连续结晶动力学研究

研究了五水柠檬酸钠的连续结晶过程。利用马尔文激光粒度分析仪对不同温度和停留时间下连续结晶过程产品的粒度分布进行分析。通过实验数据和粒度无关生长模型,分别计算了连续结晶过程中五水柠檬酸钠晶体生长与成核速率方程。研究表明,在33.3℃的连续结晶过程中,五水柠檬酸钠的成核速率较生长速率对溶液的过饱和度变化更敏感,增加溶液过饱和度更易形成较小粒度的晶体。     

球形氟化锶的控制合成研究

以氢氧化锶和氟化铵为原料,柠檬酸三钠为络合剂,通过水热法制备出由纳米立方体自组装形成的球形氟化锶颗粒。考察了柠檬酸三钠与氢氧化锶物质的量比、氢氧化锶浓度和水热时间对产物物相及形貌的影响,并探讨其形成机理。采用扫描电镜（SEM）、X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）和X射线能谱分析（EDS）等手段对产物形貌和物相进行了表征。结果表明在柠檬酸三钠与氢氧化锶物质的量比为1∶1、氢氧化锶浓度为0.08 mol/L、水热时间为6 h条件下,制备的球形氟化锶形貌规整、粒径均一,过程中加入的柠檬酸三钠对球形结构的形成具有重要作用。     

Dehydration Sequence of Gibbsite by Electron-Beam Irradiation in a TEM

To understand the dehydration mechanisms of aluminum hydrates, the dehydration sequence of gibbsite (γ-Al(OH)₃) by electron-beam irradiation has been investigated using transmission electron microscope (TEM). The electron diffraction pattern indicates the formation of chi-alumina in the initial dehydration stage. The intensity distribution in the diffraction pattern of chi-alumina is explained by the random close-packed structure of oxygen/hydroxyl containing gibbsite layer structure. Further irradiation transforms χ-alumina to η- or γ-alumina and to a phase having a more ordered structure. The dehydrated product at this stage consists of crystallites and voids several nanometers in diameter.     

五水硫酸铜结晶水的热失重分析

用差热分析方法确定了脱去结晶水时的温度,并研究了硫酸铜在脱水过程中的焓变。结果表明：在升温速率为10 K/min时,五水硫酸铜的脱水过程分为三步,三步的焓变与文献值误差分别是7.67%、6.60%、5.42%。     

Low-Temperature Formation of Aluminum Orthophosphate

Factors influencing the low-temperature formation of AIPO₄ and its precursor phases, AIPO₄· x H₂O (1 x 2), were investigated. AIPO₄ formed by reaction between 33.3 wt% H₃PO₄ solution and alumina. Five aluminas (three anhydrous and two hydrated) were utilized. Each differed in particle size, surface area, and crystallinity. The reaction temperatures investigated were 113°, 123°, and 133°C. The high-surface-area aluminas were sufficiently reactive in the phosphoric acid solution at these temperatures to produce crystalline reaction products. However, only hydrated forms of AIPO₄, AIPO₄· x H₂O (1 x 2), crystallized directly out of solution. x generally decreased as the curing temperature was increased. Upon dehydration of these hydrated reaction products, anhydrous AIPO₄ was formed, primarily in the berlinite and/or cristobalite modifications. Both the temperature of reaction and the alumina used influence the hydrates that form. In turn, the hydrates which form, the macroscopic assemblages into which they may crystallize, and the morphologies of the crystallites all affect the polymorphic form and the crystallinity of the anhydrous AIPO₄ phase ultimately produced on dehydration. Phase-pure and highly crystalline AIPO₄-cristobalite (the high-temperature modification) was formed by the dehydration of AIPO₄·H₂O at a temperature as low as 113°C.     

Structural investigation on water-induced phase transitions of poly(ethylene imine), Part IV: Changes of intra- and intermolecular hydrogen bonds in the hydration processes as revealed by time-resolved Raman spectral measurements

Poly(ethylene imine) (PEI) exhibits water-induced phase transitions among four kinds of crystalline hydrates; anhydrate (EI monomer unit/water molecule = 1/0), hemihydrate (1/0.5), sesquihydrate (1/1.5) and dihydrate (1/2). The chain conformation changes from a double helix in the anhydrate to a planar-zigzag form in the three types of hydrates. Time-resolved Raman spectral measurements have been successfully performed for the first time in the hydration processes of PEI using light and heavy waters. Raman spectral profiles characteristic of each crystal form were obtained in the frequency region of 30–3500 cm⁻¹. Exchange of water from H₂O to D₂O was helpful for shifting the many overlapped bands to identify the characteristic bands. Details of the change in intra- and intermolecular hydrogen bonds have been clarified by quantitative interpretation of the observed Raman spectral data. The conformational disordering occurring in the transition process from the double-stranded helices to the planar-zigzag chains was also discussed.     

Sol-Gel Preparation of Pb(Zr0.50Ti0.50)O3 Ferroelectric Thin Films Using Zirconium Oxynitrate as the Zirconium Source

Lead zirconium titanate (Pb(Zr_0.5Ti_0.5)O₃, PZT) ferroelectric thin films were successfully deposited on platinum-coated silicon substrates and platinum-coated silicon substrates with a PbTiO₃ interlayer by using a modified sol–gel spin-coating process, using zirconium oxynitrate dihydrate as the zirconium source. The precursor solution for spin coating was prepared from lead acetate trihydrate, zirconium oxynitrate dihydrate, and tetrabutyl titanate. The use of zirconium oxynitrate instead of the widely used zirconium alkoxide provided more stability to the PZT precursor solution and a well-crystallized structure of PZT film at a relatively low processing temperature. PZT films that were annealed at a temperature of 700°C for 2 min via a rapid thermal annealing process formed a well-crystallized perovskite phase of PZT films and also had nanoscale uniformity. The microstructure and morphology of the prepared PZT thin films were investigated via X-ray diffractometry, transmission electron microscopy, and atomic force microscopy techniques. The values for the remnant polarization ( P ) and coercive electric field ( E ) of the PZT films that were obtained from the P–E loop measurements were 3.67 μC/cm² and 54.5 kV/cm, respectively.     

二水硫酸钙在硫酸铵溶液中的溶解度测定

采用电感耦合等离子体发射光谱法（ICP-AES）测定了二水硫酸钙在硫酸铵溶液中（298.15～348.15 K）的溶解度,利用E-DH方程对实验数据进行关联,总平均相对偏差为2.81%;并考察了E-UDH方程的理论预测值,与实验值对比,总平均相对偏差为4.13%。实验和理论研究结果表明：在同离子效应和盐效应协同影响下,二水硫酸钙在（NH₄）₂SO₄-H₂O体系中溶解度随硫酸铵浓度增加先降低后又增大,在298.15～348.15 K温区内,溶解度突变点硫酸铵浓度为0.07～0.08 mol·kg^-1;随溶液中硫酸铵浓度增加,温度对二水硫酸钙溶解度的影响更趋显著。研究结果对磷石膏矿化烟气CO₂的过程设计具有指导意义。     

Dehydration and rehydration of mesolite: An in situ FTIR study

The dehydration and rehydration processes of mesolite belonging to NAT group of zeolites were investigated using in situ Fourier Transform Infrared spectroscopy (FTIR). The thermal induced variations of the water molecule bending (ν₂), the stretching (ν₃ and ν₁) modes and the corresponding second order modes in the wavenumber region 4000–8000 cm⁻¹ were followed as indicative of the dehydration process. Observed spectral variations were well correlated with thermogravimetric studies and indicate that the mesolite dehydrates in three stages (470; 510 and 650 K). Anomalous spectral variations of 4600 cm⁻¹ at first stage indicate that the dehydration is triggered by the expulsion of water coordinating AlO₄ tetrahedron. Partial rehydration (up to 85%) at second stage indicates disordering of natrolite and scolecite layers. During the third stage mesolite completely dehydrates, causing the destruction of framework.     

催化环己醇脱水制备环己烯的研究进展

环己烯是一种具有广泛用途的有机化合物,合成环己烯催化剂的研究对于环己烯的生产具有重大影响.评述了对甲苯磺酸、苯磺酸、甲烷磺酸、固载甲烷磺酸、强酸性阳离子交换树脂、六水三氯化铁、五水四氯化锡、二水氯化亚锡、三氯化铝、硅铝酸盐、活性炭负载单质碘、硫酸锆、Ti4+-阳离子交换树脂、一水硫酸氢钠、硫酸氢钾、固体超强酸、杂多酸、...     

Microstructure evolution of hydration products and strength change of hydratable alumina-bonded castables below 1250°C

There have been reports that strength of hydratable alumina (HA)-bonded castables without silica fume drops significantly at 600°C and decreases substantially again at 1000°C. But the strength variation of the HA-bonded castables during the intermediate temperature range has not been investigated and elaborated from the perspective of phase evolution and microstructural change in the castables. In this work, the relationship between the change in the strength of castables and the microstructural characteristics of the HA-bonded castables was investigated. The phase and microstructure evolution of HA-bonded castables between 110°C and 1250°C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). It has been found that strength drops of the HA-bonded castables during heating process do not mainly happen at the temperature at which HA hydrates decompose, but at the temperature at which the structure of dehydrated HA hydrates disintegrates.     

Effect of the bio-salt trisodium citrate in the dyeing of cotton

Sodium chloride and trisodium citrate have been studied as exhausting agents for dyeing bleached cotton fabrics with reactive, direct and solubilised vat dyes. The effect of dye concentration, exhausting agent concentration, dyeing time and temperature were studied and the resulting shades obtained by dyeing with trisodium citrate and sodium chloride were compared. Dye uptake values were estimated and found to be higher for trisodium citrate than for sodium chloride. The total dissolved solids content of the spent liquors was lower with trisodium citrate than with sodium chloride.     

玉米秸秆热解特性及动力学分析

以玉米秸秆为原料, 利用热重分析法研究其热解的特性及动力学。根据TG和DTG曲线, 研究玉米秸秆的热解特性, 采用Flynn-Wall-Ozawa(FWO)和Kissinger-Akahira-Sunose(KAS)两种等转化率法计算玉米秸秆热解的活化能, 并结合主曲线法和Coats-Redfern(C-R)法探讨了玉米秸秆热解遵循的机理方程。研究结果表明: 玉米秸秆热解过程可分为干燥脱水、过渡、主热解和炭化4个阶段, 随着热解升温速率增大, TG和DTG曲线向高温侧偏移; 利用FWO和KAS法计算得到的表观活化能分别为181.7和181.5 kJ/mol; 利用主曲线法和C-R法求解出玉米秸秆热解的机理方程遵循Avrami-Erofeev方程, 当α=0.1~0.5时, n=3, f(α)=1/3(1-α)[-ln(1-α)]^-2; 当α=0.5~0.7时, n=2, f(α)=1/2(1-α)[-ln(1-α)]^-1。     

Effects of Sulfate, Pyrophosphate, and Citrate Ions on the Physicochemical Properties of Cements Made of β-Tricalcium Phosphate-Phosphoric Acid-Water Mixtures

Several additives were selected to increase the setting time of calcium phosphate cements made of β-tricalcium phosphate (β-TCP; β-Ca₃(PO₄)₂)-phosphoric acid-water mixtures. The effects of the additives, i.e., sulfate, pyrophosphate, and citrate ions, are presented in this study. The results show that they all increased the setting time of the cement. Their effectiveness at increasing the setting time is in the order pyrophosphate > citrate > sulfate. The effect of sulfate ions on the setting time is increasingly large below a concentration of 0.1 M . Above that concentration, calcium sulfate dihydrate (CSD; CaSO₄-2H₂O) crystals nucleate and act as nuclei for dicalcium phosphate dihydrate (DCPD; CaHPO₄-2H₂O) crystals, which are the normal product of the setting reaction. This decreases the setting time and decreases the DCPD crystal size, resulting in an increase of the tensile strength of the cement.     

Structures and catalysis of new Nb dimers on SiO2

New Nb dimers on four kinds of SiO₂, which were prepared by the reaction between [Nb(η⁵-C₅H₅H- μ -(η⁵, η¹-C₅H₄)]₂ and surface OH groups of SiO₂, followed by chemical treatments, were found to have different structures with different bond distances and coordination numbers of Nb-Nb characterized by extended X-ray fine structure (EXAFS). These Nb dimers were active and selective for the dehydration of ethanol. The rate constant for ethene formation was affected by adsorbate-adsorbate or Nb-Nb interaction. The ratio of the rate constants for intra- and inter-molecular dehydration was also controlled by changing the Nb structures. On a SiO₂ the direct Nb-Nb bond was not observed, while the dimeric structure with bridging oxygen was formed after exposure to ethanol at 523 K. It was suggested that on this catalyst ethanol dehydration proceeds in conjunction with the formation-breaking cycle of Nb-Nb bond.     

SnO2-Cu2O/CNTs复合催化剂的制备及对FOX-12热分解的催化性能

以氯化铜、四氯化锡和碳纳米管为原料,采用浸渍法和液相化学沉积法相结合制得SnO2-Cu2O/CNTs复合催化剂,采用XRD、SEM、TEM、EDS等对催化剂进行表征,并用DsC研究催化剂对FOX-12热分解特性的影响.结果表明,纳米金属氧化物以5～10nm的球形颗粒形态附着在碳纳米管表面,分散较均匀.催化剂使N-脒基脲...     

柠檬酸交联纤维素凝胶材料的制备与性能表征

以天然纤维素为原料,柠檬酸（CA）为交联剂,柠檬酸三钠（TSC）为催化剂,经“环酐-酯化”反应制备了一种具备空间化学交联结构的纤维素凝胶材料。使用红外光谱仪、扫描电镜和X射线衍射仪分别表征了该种凝胶材料的化学结构和微观结构,并研究了该种凝胶材料的相关性能。结果表明,纤维素大分子聚集体在制备过程中发生了重结晶;随着初始纤维素浓度增大,凝胶材料的堆积结构逐渐致密并出现明显的分型特质。凝胶材料的热分解温度为280～350℃;比热容为7.564～15.660J/(g?K);热导率为0.43～0.51W/(m?K);吸水率为72.6%～96.7%;储能模量为52.948～162.59MPa。良好的储热、隔热性能和储能模量使得该种材料有望应用在保温包装夹层材料领域。     

Microstructure and Electrical Properties of Chemically Prepared Nb2O5-Doped SrTiO3 Ceramics

Chemically homogeneous SrTiO₃ powders of submicrometer size were obtained by alcohol dehydration and subsequent calcination of citrate/format solutions. Nb₂O₅-doped SrTiO₃ was prepared with various Sr:Ti ratios resulting in an anomalous increase in the dielectric constant ( K 'up to ∼8000) for donor-doped SrO-excess SrTiO₃. No semiconducting behavior was observed for donor-doped TiO₂-excess SrTiO₃ when fired in air. Therefore, a "brick-wall" type of microstructure was formed as a result of the excess SrO, giving rise to anomalously high dielectric constants.     

Permeability of High-Alumina Refractory Castables Based on Various Hydraulic Binders

This work investigated the changes in the permeability of high-alumina self-flowing refractory castables based on calcium aluminate cement (CAC) and hydratable alumina binder (HAB) pretreated between 110° and 1650°C. Permeability constants k ₁ and k ₂ were fitted from Forchheimer's equation based on airflow tests conducted at room temperature. The results indicated that dehydration was the main contributing factor for increased permeability in bodies pretreated up to 600°C and that sintering effects prevailed between 900° and 1650°C. Castables based on HAB were less permeable than those based on CAC, a behavior ascribed to the type of hydrates formed and to the particle-packing features of the matrix and the matrix–aggregate interfaces.