Preparation of macroporous methacrylate monolithic material with convective flow properties for bioseparation : Investigating the kinetics of pore formation and hydrodynamic performance

The preparation of macroporous methacrylate monolithic material with controlled pore structures can be carried out in an unstirred mould through careful and precise control of the polymerisation kinetics and parameters. Contemporary synthesis conditions of methacrylate monolithic polymers are based on existing polymerisation schemes without an in-depth understanding of the dynamics of pore structure and formation. This leads to poor performance in polymer usage thereby affecting final product recovery and purity, retention time, productivity and process economics. The unique porosity of methacrylate monolithic polymer which propels its usage in many industrial applications can be controlled easily during its preparation. Control of the kinetics of the overall process through changes in reaction time, temperature and overall composition such as cross-linker and initiator contents allow the fine tuning of the macroporous structure and provide an understanding of the mechanism of pore formation within the unstirred mould. The significant effect of temperature of the reaction kinetics serves as an effectual means to control and optimise the pore structure and allows the preparation of polymers with different pore size distributions from the same composition of the polymerisation mixture. Increasing the concentration of the cross-linking monomer affects the composition of the final monoliths and also decreases the average pore size as a result of pre-mature formation of highly cross-linked globules with a reduced propensity to coalesce. The choice and concentration of porogen solvent is also imperative. Different porogens and porogen mixtures present different pore structure output. Example, larger pores are obtained in a poor solvent due to early phase separation.

In-situ carbon control in the preparation of precursors to boron carbide by a non-aqueous solution technique

Synthesis of high quality boron carbide (B4C) powders is achieved by carbothermal reduction of boron oxide (B2O3) from a condensed boric acid (H3BO3)/polyvinyl acetate (PVAc) product. Precursor solutions are prepared via free radical polymerisation of vinyl acetate (VA) monomer in methanol in the presence of dissolved H3BO3. A condensed product is then formed by flash evaporation under vacuum. As excess VA monomer is removed at the evaporation step, the polymerisation time is used to manage availability of carbon for reaction. This control of carbon facilitates dispersion of H3BO3 in solution due to the presence of residual VA monomer. B4C powders with very low residual carbon are formed at temperatures as low as 1,250 °C with a 4 hour residence time.

Preparation of magnetic porous ceramsite and its application in biological aerated filters

Ceramsite plays a significant role as a biological aerated filter (BAF) in the treatment of wastewater. In this study, a mixture of goethite, sawdust and palygorskite clay was thermally treated to form magnetic porous ceramsite (MPC). An optimization experiment was conducted to measure the compressive strength of the MPC. X-ray diffraction (XRD), scanning electron microscopy (SEM), and polarizing microscopy (PM) characterized the pore structure of the MPC. The results show that a combination of goethite, sawdust and palygorskite clay with a mass ratio of 10:2:5 is suitable for the formation of MPC. The compressive strength of MPC conforms to the Chinese national industrial standard (CJ/T 299-2008) for wastewater treatment. The SEM and PM results also show that the uniform and interconnected pores in MPC were well suited for microbial growth. The MPC produced in this study can serve as a biomedium for advanced wastewater treatment.

Preparation of lamellar and hexagonal forms of mesoporous silica and zirconiaby the neutral amine route: lamellar-hexagonal transformation in the solid state

The chain length of the surfactant and the solvent composition are two of the factors that determine whether the lamellar or the hexagonal form of mesoporous SiO2 (or ZrO2) is formed by the neutral amine route; a lamellar-hexagonal transformation occurs on removal of the amine from the former.

Provinicializing curriculum? On the preparation of subjectivity for globality

The recent availability of international forums devoted expressly to discussing subfields of education such as curriculum studies has brought to visibility preexisting flashpoints that are not easily defused by strict adherence to definition of key terms. The difficulty of translating the term curriculum into “non”-Indo-European root languages, as well as among them, is a case in point and not just an issue of vocabulary. The difficulty of translation indexes a cleavage that is beyond-conceptual and exo-technical. Efforts to locate analogs or equivalents might suggest on the one hand, an ethnocentric preoccupation to extend the reach of a provincial concept (i.e., curriculum), while the effort to avoid or move to the side of such a preoccupation for translation might suggest structures of subjectivity that refuse co-option into foreign frames of reference. Both of these possibilities are, however, constitutive of and pointing to productive interstices from which to reengage and rephrase the weight given to subjectivity and language, to global/local divisions, and to the politics of traveling discourses in educational research.

Preparation of Hexafluorodisilane and Reactions of Hexafluorodisilane and Hexachlorodisilane with Sulfur Trioxide

Hexafluorodisilane has been prepared by the fluorination of hexachlorodisilane or hexabromodisilane by potassium fluoride in boiling acetonitrile, in yields approximating 45 and 60% respectively. Hexafluorodisilane has been characterised by infrared spectral data, vapour density measurements and analytical data. Both hexafluorodisilane and hexachlorodisilane are found to react with sulfur trioxide when heated to 400°C for 12 h. The products of reaction are silicon tetrafluoride, silica and sulfur dioxide with hexafluorodisilane while hexachlorodisilane in addition gives rise to hexachlorodisiloxane.

A new synthetic procedure for the preparation of pyridinium tetrafluoroborate and hexafluorosilicate

Pyridinium tetrafluoroborate (C5H5NHBF4) and pyridinium hexafluorosilicate [(C5H5NH)2SiF6] have been prepared in good yields and high purity by the reaction of pyridinium poly(hydrogen fluoride) with oxides and acids of boron and silicon respectively. The salts have been characterised by melting points, IR, 1H and 19F NMR spectroscopy and chemical analysis.

Twin roller quenching technique and preparation of glasses of high melting ionic solids

A rapid quenching technique with a quenching rate of roughly 106°C/sec has been developed to prepare glassy samples of ABO3 type materials. Glasses of potassium lithium niobate have been prepared by this technique. These glasses have been characterized by x-ray diffraction, electron diffraction and differential scanning calorimetry techniques to assess the quality of the obtained glasses.

An elegant direct route for the preparation of pyridinium, ammonium and alkali metal hexafluorotitanates (IV)

Pyridinium hexafluorotitanate (IV) has been prepared by a one step procedure. Addition of titanium tetrachloride to pyridinium poly(hydrogen fluoride) yields nearly quantitative amounts of pyridinium hexafluorotitanate(IV). Making use of pyridinium hexafluorotitanate as precursor, ammonium and alkali metal (Na, K, Rb, and Cs) hexafluorotitanates have been prepared in good yields. These salts have been characterised by IR, N.M.R. (1H, 13C and 19F), X-ray powder diffraction data and chemical analysis.

Preparation of CaTiO3 fine powders by the hydrothermal method

Fine powders consisting of 0.1–0.5 μm size crystallites of CaTiO3 are prepared at 150–200°C by the hydrothermal method starting from hydrated titania gel and reactive calcium oxide suspended as an aqueous slurry in an autoclave. The resulting high-purity CaTiO3 is characterised by TEM, X-ray powder diffraction, chemical analyses and sintering characteristics. The hydrothermally prepared CaTiO3 powders are sinterable to high-density ceramics below 1400°C. The dc conductivity behaviour of the chemically reduced ceramics is presented.

Hydrothermal preparation of Ba(Ti,Zr)O3 fine powders

Fine powders consisting of aggregated submicron crystallites of Ba(Ti,Zr)O3 in the complete range of Ti/Zr ratios are prepared at 85–130°C by hydrothermal method, starting from TiO2 + ZrO2 · xH2O mixed gel and Ba(OH)2 solution. The products obtained below 110°C incorporate considerable amounts of H2O and OH− within the lattice. As-prepared BaTiO3 is cubic and converts to tetragonal phase after the heat treatment at 1200°C, accompanied by the loss of residual hydroxyl ions. TEM investgations of the growth features show a transformation of the gel to the crystallite. Ba2+ ions entering the gel produce chemical changes within the gel, followed by dehydration, resulting in a cubic perovskite phase irrespective of Ti/Zr. The sintering properties of these powders to fine-grained, high density ceramics and their dielectric properties are presented.

Low-temperature preparation of fine-particle cobaltites

A novel solid-solution precursor method for the preparation of fine-particle cobaltites at low temperatures has been described. The precursors, hydrazinium metal hydrazine carboxylate hydrates, N2H5M1/3Co2/3(N2H3COO)3 · H2O, where M = Mg, Mn, Fe, Co, Ni, and Zn, decompose in air <250°C to yield corresponding metal cobaltites, MCo2O4. Formation of cobaltites has been confirmed by thermogravimetry (TG) weight loss, IR, and X-ray diffraction. Combustion of the precursor in air yields fine-particle cobaltites with surface areas in the range of 12–115 m2g−1 and particle sizes of 1–40 μm. Low decomposition temperatures of the precursors accompanied by the evolution of large amounts of gases appear to control the particle size of the cobaltites.

On the use of oxalates as starting materials for low-temperature preparation of bronzes and other reduced phases

A novel low-temperature method of preparing bronzes of tungsten and vanadium and other reduced phases is reported.

Preparation of cast aluminium alloy-mica particle composites

The optimum conditions for producing cast aluminium alloy-mica particle composites, by stirring mica particles (40 to 120 mgrm) in molten aluminium alloys (above their liquidus temperatures), followed by casting in permanent moulds, are described. Addition of magnesium either as pieces along with mica particles on the surface of the melts or as a previously added alloying element was found to be necessary to disperse appreciable quantities (1.5 to 2 wt.%) of mica particles in the melts and retain them as uniform dispersions in castings under the conditions of present investigation. These castings can be remelted and degassed with nitrogen at least once with the retention of about 80% mica particles in the castings. Electron probe micro-analysis of these cast composites showed that magnesium added to the surface of the melt along with mica has a tendency to segregate around the mica particles, apparently improving the dispersability for mica particles in liquid aluminium alloys. The mechanical properties of the aluminium alloy-mica particle composite decrease with an increase in mica content, however, even at 2.2% the composite has a tensile strength of 14.22 kg mm–2 with 1.1% elongation, a compression strength of 42.61 kg mm–2, and an impact strength of 0.30 kgm cm–2. The properties are adequate for certain bearing applications, and the aluminium-mica composite bearings were found to run under boundary lubrication, semi-dry and dry friction conditions whereas the matrix alloy (without mica) bearings seized or showed stick slip under the same conditions.