Influence of Silicate Depolymerisation on the Polycondensation Reaction with Hydroxoaluminate in Alkaline Aqueous Solution

The polycondensation reaction between silicate and hydroxoaluminate in alkaline aqueous solution has been experimentally studied. The time required for the solution to transform to a gel was measured to determine the reaction rate. The addition of alkali hydroxide to the silicate solution was found to strongly accelerate the subsequent reaction of silicate with hydroxoaluminate. The results indicate that the acceleration was caused by depolymerisation of the oligosilicates contained in the water glass, which was used as the source of soluble silicates. The course of oligosilicate depolymerisation in aqueous alkaline solution was experimentally observed by measuring the electrical conductivity of the solution.     

SUGGESTED RELATIONS OF SODIUM SILICATE,ADHESION TENSION,AND ANGLE OF CONTACT TO LIQUID ABSORPTION IN CLAYS1

This is a report of progress of an investigation concerning the effect of electrolytes on the liquid absorption of clays tempered to maximum plasticity. Data curves are presented to show that sodium silicates do have an influence on absorption when the silicates are added to the tempering water. The observed results are explained on the basis that the sodium silicate reduces the angle of contact and increases the adhesion tension of the clay-water system. The results of this paper are suggestive of a possible extension of this principle to explain, a t least in part, some of the phenomena of deflocculation and plasticity.     

Revisiting aqueous alkaline silicates as precursors for sol-gel optical coatings

Alkaline silicates are well-known soluble silica derivatives already widely used for industrial purposes. Nevertheless, their applications for the elaboration of functional optical coatings have largely been discarded by the sol-gel community who mainly focused on alkoxide precursors. The objective of this work is to reconsider the alkaline silicates sol-gel chemistry, targeting optical coatings of a few hundreds of nanometers. The structures of Li⁺, Na⁺, and K⁺ silicate coatings are discussed on the basis of spectroscopic characterizations. We show that a simple washing process allows a postdeposition removal of most alkaline ions, thus preventing the efflorescence effect and improving the aqueous stability of the films. Finally, several examples are shown for the application of alkaline silicates in the elaboration of functional optical coatings following conventional sol-gel chemistry.     

Silane-modified sodium–aluminium silicates — fillers used in polyurethane elastomers

Sodium-aluminium silicates of a high degree of dispersion were obtained. Studies on the surface modification of sodium-aluminium silicates using silane coupling agents are described. The best modifiers, which induced a change of the silicate surface from a hydrophilic to a hydrophobic one, were selected. Physicochemical analyses of the obtained silicates were performed. The methods of evaluating the degree of surface modification of the silicate are presented. Attempts were made to employ the unmodified and modified sodium-aluminium silicates as fillers in polyurethane elastomers. The introduction of sodium-aluminium silicate into urethane elastomer induced increases in composite parameters such as tensile strength, relative elongation, and hardness. The most pronounced reinforcing effects were observed with urethane elastomers filled with sodium-aluminium silicate modified with an aminosilane (A-1120).     

Use of waste water glass as silica supplier in synthesis of pure and Mg-doped lanthanum silicate powders for IT-SOFC application

Water glass in alkali solution (Na₂SiO₃/NaOH) an abundant effluent, generated in the alkaline fusion of zircon sand, represents a potential silica source to be converted in useful silica technological application. Actually, the generation of energy by environmental-friendly method is one of the major challenges for researchers. Solid Oxide Fuel Cells (SOFC) is efficient and environmentally clean technique to energy production, since it converts chemical energy into electrical power, directly. Apatite-type lanthanum silicates are promising materials for application as an electrolyte in intermediate temperature SOFC (IT-SOFC) because of their higher ionic conductivity, in temperatures of range 600–700 °C, than conventional zirconia electrolytes. In this work, pure (La_9,56(SiO₄)₆O_2,34) and Mg-doped (La_9,8Si_5,7Mg_0,3O_26,4) lanthanum silicate were synthesized, from that rich effluent. Using the sol-gel followed by precipitation method, the single crystalline apatite phase of both silicates was obtained by thermal treatment at 900 °C of their precursors. Sintered ceramic samples reached density of higher than 90%.     

Effect of calcium silicate sources on geopolymerisation

Seven different calcium silicate materials were used to investigate the role of calcium in geopolymerisation. At low alkalinity, the compressive strength of matrices prepared with predominantly amorphous calcium silicates (blast furnace slag) or containing crystalline phases specifically manufactured for reactivity (cement) is much higher than when the calcium is supplied as crystalline silicate minerals. The compressive strength of matrices containing natural (crystalline) calcium silicates improves with increasing alkalinity, however the opposite trend is observed in matrices synthesised with processed calcium silicate sources. The difference in compressive strength between matrices synthesised using different calcium silicate sources is significantly reduced at high alkalinity. An insufficient amount of calcium is dissolved from crystalline calcium silicates at relatively low alkalinity to enable formation of calcium silicate hydrate in coexistence with the aluminosilicate geopolymeric gel, and this leads to the poor mechanical properties of such matrices. At high alkalinity, calcium plays a lesser role in affecting the nature of the final binder, as it forms precipitates rather than hydrated gels. Thus, the different calcium silicate sources will not have a major impact on the mechanical properties of these matrices. The effects of different calcium silicates on geopolymerisation are therefore seen to depend most significantly on two factors: the crystallinity of the calcium silicate source, and the alkalinity of the activating solution used.     

Effect of the clay size on the dispersion morphology and emulsion stability of ABS/layered silicate nanocomposites

ABS/layered silicate nanocomposites were synthesized through an emulsion polymerization with different sizes of silicates. The particle sizes of Laponite, Cloisite‐Na and Kunipia‐F are about 20–30, 70–150, and 300–500 nm, respectively. When ABS was synthesized by the emulsion polymerization in the presence of Laponite and Cloisite‐Na, ABS/layered silicate nanocomposite emulsion showed a stable suspension without the precipitation of solid particle. On the other hand, ABS/layered silicate nanocomposite synthesized with Kunipia‐F showed the precipitation of large aggregated particles and the phase separation. Smaller sizes of silicates like Laponite and Cloisite‐Na than polymerized particle worked as resided barrier preventing the emulsion particle from coagulation. Larger size of silicate like Kunipia‐F than emulsion particle was not able to enclose the emulsion particle delicately because of its stiffness and large aspect ratio. The monomers inserted into the intercalated Kunipia‐F connected the ABS particles and clay particles. The Kunipia‐F particles anchored ABS particles around them inducing the aggregation and precipitation of ABS particles. ABS copolymer emulsion and aqueous silicate dispersion were mixed to compare with synthesized ABS/layered silicate nanocomposites and showed a stable suspension. With small amount of Laponite or Cloisite‐Na, nanocomposite emulsion of Kunipia‐F was also stabilized. Laponite and Cloisite‐Na worked as a steric stabilizer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Solid oxide galvanic cells involving exchanged beta-alumina electrolyte

Fe(II), Cu(I), Cu(II), and Zn(II)-exchanged beta-aluminas have been prepared and tested as solid electrolytes in oxide galvanic cells. The values of free enthalpies of Fe₃O₄, CuCrO₂, CuCr₂O₄, and Zn₂SiO₄ of formation at 1070 K have been calculated from the emf results. The reasonable agreement with literature data has been found for all compounds under study.     

聚合物/层状硅酸盐纳米复合材料的研究进展 --层状硅酸盐粘土的有机改性

综述了近年来国内外聚合物/层状硅酸盐纳米复合材料领域中层状硅酸盐有机改性的最新研究进展情况.主要对有机改性剂的结构、作用机理、改性后有机粘土的特性,及其在聚合物基纳米复合材料中的应用进行了详细的阐述.在此基础上,提出了一条新的研究思路.     

Studies of surface chemistry — physico-chemical aspects of porous silicate surfaces

A series of porous silicates are prepared by destabilization (precipitation) of an alkaline silicate with a polyvalent metal salt in aqueous medium. The experimental conditions are optimised in such a manner as to obtain almost all particles with precise control on their size. On an average 98 – 99% of the product is in the particle size range −300 +350 BSS mesh. For the source of silica and alumina, several starting materials of both chemical and natural sources have been used in the synthesis. The porous silicates thus developed are exhaustively characterised for bulk density, oil absorption, specific gravity, pore volume, surface area and particle size distribution. The results obtained show that the surface properties of porous silicates vary over a wide range, although the chemical composition of the products remains practically the same. It is discussed that mode of preparation, the reactants employed and the key process variables ultimately decide the surface properties and the end-use applications.     

Ionic liquid batteries: Chemistry to replace alkaline/acid energy storage devices

Rather than depend on highly acidic or basic electrolytes, ionic liquids are used to create new types of solid state cells which mimic standard alkaline cells, but without the need for caustic electrolytes. Presented here is a non-aqueous approach to primary and secondary power sources, where the pure ionic liquid not only acts as the electrolyte/separator in both liquid and solid state batteries, but as a reactive species in the cell's electrochemical makeup. In this work, batteries are designed using standard cathode and anode materials such as MnO₂/Carbon, PbO₂, NiO, AgO and Zn. However, by using a solid polymer electrolyte composed of an ionic liquid and polyvinyl alcohol, novel types of solid state batteries are demonstrated with discharge voltages ranging up to 1.8 V, dependent upon the type of cathode and anode used. These batteries are characterized by ionic conductivity, initial voltage measurements, and discharge profiles.     

硅化物对麦草碱法蒸煮黑液黏度的影响

为了研究硅对黑液黏度的影响,向麦草碱法蒸煮黑液中添加定量的二氧化硅、麦草灰分和硅酸钠,分析不同硅化物对黑液黏度的影响。研究发现,相对于麦草灰分和二氧化硅,硅酸钠更能增加麦草黑液的黏度。硅酸钠对不同浓度麦草黑液黏度的影响顺序为:高浓黑液≥中浓黑液>低浓黑液。当硅酸钠占黑液总固形物的量大于15%(SiO2计)时,其对低浓度黑液的黏度造成显著影响;当硅酸钠占黑液总固形物的量为13%～15%(SiO2计)时,其对中浓黑液的黏度有显著影响;当硅酸钠占黑液总固形物的量为11%～13%(SiO2计)时,其对高浓黑液的黏度有显著影响。     

A phase-field model for the study of isothermal dissolution behavior of alumina particles into molten silicates

Particle dissolution process refers to the dissolving of one liquid or solid phase into another solvent phase. This process is of vital importance in the engineering material science, and chemical engineering, etc. Here, we develop a phase-field model with diffusion-controlled processes at interfaces for isothermal dissolution of alumina inclusion particles in molten silicates, referred as “slag,” with comprehensive compositions applied in process metallurgy. The interfacial energy between solid inclusion particle and molten silicate can vary with different temperatures and chemical compositions. This model is validated using experimental data of high-temperature confocal laser scanning microscopy (HT-CLSM) technique. Moreover, the developed model is applicable to predict the dissolution behavior of solid particle in a realistic size scale. The possibility of the model application is illustrated with studies of different physical parameters that affect particle dissolution behavior. The phase-field simulations show that inclusion morphology influences both the dissolution profile and time, and the influence decreases with the increased temperature. Increasing same amount of Al₂O₃ component in slag, the increased degrees of the alumina dissolution time in silicates with different V-ratio values, a ratio between the mass percent of CaO and that of SiO₂, are almost the same. If the V-ratio of slag is relatively small, an increased MgO component in the silicate will significantly decrease the particle dissolution time. On the contrary, the change in MgO component in the silicate will have a minor effect if the value of V-ratio is quite large. In order to rapidly dissolve the inclusion, basicity index (BI) of molten silicate should be larger than 1.4. A balance between BI and MgO component in slag is suggested to be considered to design or optimize molten silicate (slag) for its application in the refining process of steel manufacturing.     

硅酸盐色谱分离中性氨基酸性能研究

将硅酸钠与硫酸铜或硫酸锌按等体积混合 ,制得新型无机离子交换剂硅酸铜、硅酸锌 ,分别用其作为色谱载体对中性氨基酸 (甘氨酸 ,丙氨酸 )进行分离 ,与强酸性阳离子交换树脂 0 0 1× 7的色谱行为作了比较。结果表明 ,合成的硅酸盐具有较好的分离性能。通过不同载体分离中性氨基酸 (甘氨酸 ,丙氨酸 )的流出体积的比较 ,硅酸铜的流出体积大于硅酸锌 ,硅酸锌的流出体积大于 0 0 1× 7。结果显示 ,硅酸铜比硅酸锌更适合于分离中性氨基酸 ,具有最好的分离特性     

Calciumβ″-alumina and Nasicon electrolytes in galvanic cells with solid reference electrodes for detection of sulphur oxides in gases

Calcium-β″-alumina and Nasicon were applied as solid electrolytes for SO _x (x=2 or 3) gas detection. The following two galvanic cells with solid reference electrodes were assembled $$\begin{gathered} Pt|O_2 ,CaO||Ca - \beta '' - Al_2 O_3 ||CaSO_4 |SO_3 ,SO_2 ,O_2 |Pt \hfill \\ Pt|O_2 ,Na_2 O||Nasicon||Na_2 SO_4 |SO_3 ,SO_2 ,O_2 |Pt \hfill \\ \end{gathered} $$ Calcium and sodium sulphates were used as auxiliary electrolytes to provide protection of β″-Al₂O₃ or Nasicon electrolytes from chemical reaction with SO₂. The e.m.f. was measured in the temperature range 850–1070 K for five various test gases. The measured e.m.f.s had values a little lower than the calculated ones. The results show clearly that both the cells can act as SO _x electrochemical sensors for temperatures not exceeding 1070 K.     

Epitaxial Growth of Nickel(II) Hydroxide on layer Silicate and Derived Nickel-(Layer Silicate) Nanocomposite

Nickel(II) hydroxide crystals were deposited on a substrate of layer silicates from the liquid phase by decomposing nickel(II) ammine complex solutions dispersed with expandable layer silicates; the (001) planes of the nickel(II) hydroxide aligned parallel to the basal (001) plane of the layer silicates. From these layer silicate complexes with nickel(II) hydroxide, nickel-coated layer silicate composite particulates were derived. Moreover, metal–ceramics alloys, composed of nickel containing uniformly dispersed layer silicates several tens of angstroms in thickness, were produced by sintering the metal-coated ceramic powders.     

三种燃料电池发电技术

燃料电池是一种新型的能量转换装置，本文详细介绍了磷酸型、熔融碳酸盐型以及固体氧化物电解质型三种主要类型的燃料电池的单电池结构、材料、设计及研究方向等几个方面的问题。     

Rheological behavior of polypropylene/layered silicate nanocomposites prepared by melt compounding in shear and elongational flows

Melt rheology and processability of exfoliated polypropylene (PP)/layered silicate nanocomposites were investigated. The nanocomposites were prepared by melt compounding process in the presence or absence of a PP‐based maleic anhydride compatibilizer. PP/layered silicate nanocomposites showed typical rheological properties of exfoliated nanocomposites such as nonterminal solid‐like plateau behavior at low frequency region in oscillatory shear flow, higher steady shear viscosity at low shear rate region, and outstanding strain hardening behavior in uniaxial elongational flow. The melt processability of exfoliated PP/layered silicate nanocomposites was significantly improved due to good dispersion of layered silicates and increased molecular interaction between the PP matrix and the layered silicate organoclay. Small‐angle X‐ray scattering and transmission electron microscopy results revealed that the layered silicate organoclay was exfoliated and good interaction between PP matrix and organoclay was achieved by using the PP‐g‐MAH compatibilizer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3506–3515, 2007     

Preparation and characterization of precipitated zinc silicates

The study aimed to obtain highly dispersed particles of zinc silicate, a potential filler of polymers or a paint pigment, by precipitation from solutions of sodium metasilicate and of zinc salts. The technique of silicate precipitation was worked out, and the conditions causing precipitation were optimized. The temperature, sodium metasilicate solution flow rate and concentration of zinc salts were selected so as to obtain silicates of the lowest possible bulk density, and which had low water‐absorbing capacity and high paraffin oil‐absorbing capacity. In the study, the effects of precipitation parameters were examined on the principal physicochemical properties of the silicates, the structure and uniform character of silicate particles, particle size distribution, and the surface morphology. Particular attention was devoted to the particle size distribution and the tendency to form primary agglomerates (aggregates) and secondary agglomerates, using dynamic light scattering (DLS). Studies were undertaken to develop a technique which could prevent formation of silicate particle agglomerates. With this aim, the silicates' surface was modified either during their precipitation or by the so‐called dry technique. For the modification, silane coupling agents were applied. The extent of silicate surface hydrophobicity was examined by estimation of the enthalpies of immersion of the modified silicate surface. The silicates obtained were tested as fillers of rubber mixtures (in butadiene–styrene rubber). © 2003 Society of Chemical Industry     

Ionic Transport Numbers of Group IIa Oxides Under Low Oxygen Potentials

The ionic transport numbers of BeO, MgO, CaO, and SrO in single-crystal and polycrystalline samples were examined under low oxygen potentials between 900° and 1180°C. The oxygen potentials were fixed by using metal/metal-oxide electrodes in electrochemical cells with the samples of the alkaline earth oxides as solid electrolytes. The electromotive forces of these cells were compared with the emf values obtained from similar cells of high stability using high-purity thoria-based electrolytes. From the results it could be concluded that under comparable conditions of low oxygen pressure the electron transport number increases with increasing ionic radius of the group II element. Only BeO and MgO approach electrolytic behavior, and this occurs at relatively high oxygen pressures (>10^-10 atm).