Partial oxidation of methane to synthesis gas over some titanates based perovskite oxides

Ca_1–x - _x Sr _x TiO₃-based mixed oxide catalysts containing chromium, iron, cobalt or nickel were prepared and used in the oxidation of methane. The catalyst containing cobalt or nickel showed high activity for the synthesis gas production from methane. In the case of nickel containing catalyst, nickel oxide originally separated from the perovskite structure was easily reduced to nickel metal, which showed synthesis gas production activity. In the case of the cobalt containing catalyst, pretreatment with methane was required for high activity. Reduced metallic cobalt was formed from the perovskite structure, which revealed relatively high selectivity for the oxidative coupling of methane, and afforded synthesis gas production. Both the catalysts also catalyzed carbon dioxide reforming of methane and especially both high activity and selectivity were observed over the nickel containing catalyst.     

Utilization of DTA in determination of crystallization mechanism in SiO2–Al2O3–CaO–MgO(R2O) glasses in presence of various nuclei

The effect of various nuclei on crystallization mechanism of SiO₂–Al₂O₃–CaO–MgO(R₂O) glasses were investigated by differential thermal analysis (DTA) through Matusita, Marotta and modified Kissinger methods. The Avrami constant, n, and the activation energy for crystallization of the most promising specimens containing Cr₂O₃, Fe₂O₃ and TiO₂ in the single, double and triple nuclei series were determined. According to the results the Avrami constants derived from the Marotta method were more consistent with the other experimental observation. While glasses containing TiO₂ as the single nucleant represents surface crystallization and those containing Cr₂O₃ or Fe₂O₃ one-dimensional bulk crystallization, the crystallization mechanism of specimens containing both Cr₂O₃ and Fe₂O₃ and also the glasses containing the triple nuclei, are bulk and two dimensional.     

Synthesis of Epoxycontaining Siliconorganic Compounds

Abstract

Epoxycompounds containing the methyl, phenyl, vinyl, chlormethyl. thienyl and chlorthienyl radicals with molecules containing one siloxane or cyclosiloxane, or two and more siloxane fragments are synthesised for the first time by the hydrosililization of aiylglicidyl ester with organohydrosilanes or siloxanes in the presence of Speier catalizator H₂PtCl₆. The reaction of hydrosililization is studied using infrared spectroscopy and gas-liquid chromatography method. The anionic polymerization of epoxicompounds containing cyclosiloxane fragments using α,β-bis(tetramethilammonium)dimethilsilanolat is carried out.     

A study on mechanical and pressure-sensitive properties of cement mortar with nanophase materials

The mechanical properties and self-monitoring capability of cement mortar containing nano-SiO₂ or nano-Fe₂O₃ were experimentally studied and compared with that of plain cement paste. The results showed that the compressive and flexural strengths measured at the 28th day of cement mortar containing nano-SiO₂ or nano-Fe₂O₃ were both higher than that of plain cement mortar with the same water-binder ratio (w/b). Furthermore, the self-monitoring capability of cement mortar with nano-Fe₂O₃ is also presented in this paper.     

Effect of surface modification using various acids on electrodeposition of lithium

Sulface modification of lithium was carried out using the chemical reaction of the native film with acids (HF, H₃PO₄, HI, HCl) dissolved in propylene carbonate (PC). The chemical composition change of the lithium surface was detected using X-ray photoelectron spectroscopy. The electrodeposition of lithium on the as-received lithium or the modified lithium was conducted in PC containing 1.0 mol dm^–3 LiClO₄ or LiPF₆ under galvanostatic conditions. The morphology of electrodeposited lithium particles was observed with scanning electron microscopy. The lithium dendrites were observed when lithium was deposited on the as-received lithium in both electrolytes. Moreover the dendrites were also formed on the lithium surface modified with H₃PO₄, HI, or HCl. On the other hand, spherical lithium particles were produced, when lithium was electrodeposited in PC containing 1.0 mol dm^–3 LiPF₆ on the lithium surface modified with HE However spherical lithium particles were not obtained, when PC containing 1.0 mol dm^–3 LiClO₄ was used as the electrolyte. The lithium surface modified by H₃PO₄, HI, or HCl was covered with a thick film consisting of Li₃PO₄, Li₂CO₃, LiOH, or Li₂O. The lithium surface modified with HF was covered with a thin bilayer structure film consisting of LiF and Li₂O. These results clearly show that the surface film having the thin bilayer structure (LiF and Li₂O) and the use of PC containing 1.0 mol dm^–3 LiPF₆ enhance the suppression of dendrite formation of lithium.     

Studies in Lithium Oxide Systems: III,Liquid Immiscibility in the System Li2O-B2O3-SiO2

Glasses within the ternary system Li₂O-B₂O₂SiO₂ containing less than 25.6% Li₂Ocan be broadly classified into three groups according to their behavior during cooling or heating. One group, containing either more than 18% Li₂Oor less than 20% SiO₂, yields clear glasses during slow or rapid cooling. The second group, containing approximately 5 to 15% Li₂O and 26 to 90% SiO₂, yields dense white opal glass during slow or rapid cooling. The third group, located at the outer edge of the second group, cools to room temperature as clear glasses but develops opacity when reheated to temperatures between 550° and 8800°C. It has been shown by electron microscopy that the opacity is due to liquid immiscibility, the matrix glass containing well-formed spheres of the dispersed phase. Some of the clear glasses of both groups have been shown to consist of two immiscible phases. The size of the dispersed units in the spontaneous opal glasses and also the reheat opal glasses can be controlled by the variation of the reheat treatments. The phase separation reported here is beyond the resolution of the petrographic microscope and can be detected only with the high resolution of the electron microscope. Accessory evidence is given to show that the phases are non-crystalline.     

Sorption of Fe(III) containing ions on strongly basic anion exchangers AV-17 and Varion-AD

It is shown that sorption isotherms of Fe(III) containing ions from Fe₂(SO₄)₃ solutions on the strongly basic anion exchangers AV-17 and Varion-AD are well described by Langmuir’s equations. Almost all sorption centers of the polymers are energetically homogeneous towards Fe(III) containing ions. The maximum temperature dependence of sorption was found to be about 50°C. The Mössbauer spectra of the Varion-AD retaining Fe(III) containing ions from solution at 30 and 50°C showed the existence of the Fe(III) ions in a single electronic state, i.e., there was an absence of different kinds of Fe(III) compounds. The sorption of Fe(III) containing ions on the polymers essentially decreases with increasing the ionic strength of the Fe₂(SO₄)₃ solution on adding calculated amounts of KNO₃, NaNO₃, NaClO₄ or Na₂SO₄.     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (Inifers)

Summary This paper concerns the synthesis and characterization of new Si-Cl and Si-H end-groups containing polyisobutylenes. The syntheses involved 1) The preparation of polyisobutylenes carrying one or two -CH₂C-(CH₃)=CH₂ termini, ii) Hydrosilylation with H(CH₃)₂-SiCl, H(CH₃)SiCl₂, and HSiCl₃, and iii) Reduction of the Si-Cl groups to yield the corresponding -Si-H termini. A series of model compounds mimicking the end-groups have been synthesized and employed for end-group characterization. These Si-Cl and Si-H containing mono- and difunctional polyisobutylenes may be useful intermediates for the preparation of block and graft copolymers or for the synthesis of various terminal functional groups.     

Electrodeposition of titanium diboride from fused salts

Electrodeposition of TiB₂ has been performed in cryolite-based electrolytes at 960°C and in KF-KCl melts at 800°C. As electroactive species either boron oxide and titanium oxide or potassium tetrafluoroborate and potassium hexafluorotitanate were used. Preparation of coatings from cryolite-based electrolytes containing K2TiF6 and KBF4 was not successful. Coatings prepared from cryolite-based electrolytes containing B₂O₃ and TiO₂ were not coherent. Owing to the relatively high temperature both types of electrolytes undergo thermal decomposition. Electrolysis in potassium fluoride-chloride electrolytes containing KBF₄ and K₂TiF₆ provides coherent coatings with good adhesion to the substrate.     

Formation of Ti-Si composite oxide films on Mg-Al-Zn alloy by electrophoretic deposition and anodization

TiO₂ or SiO₂ nanoparticles dispersed in an acetone solvent containing iodine were deposited on Mg-Al-Zn alloy by electrophoretic deposition (EPD). Subsequently, the composite oxide films were formed on the substrate by anodization in KOH-Na₂SiO₃ aqueous solutions containing TiO₂ or SiO₂ nanoparticles. The films formed by EPD were improved binding with the substrate by anodization under high voltages with sparking, and then the anodic films consisted of Si-Mg or Ti-Si-Mg composite oxides. The film thicknesses of TiO₂ and SiO₂ on the alloy increased with anodization time. In polarization tests, the films anodized under high voltages with sparking in the alkaline solutions had high corrosion resistance. Thus, the composite oxide films formed in the present method were successful in providing corrosion resistance to Mg alloy.     

Electrospray mass spectrometry of the peroxide adduct of a monomeric Fe(III) complex containing a phenol group

Electrospray mass spectral measurements on solutions containing an iron(III) compound containing a phenol group and H₂¹⁶O₂ (or H₂¹⁸O₂) revealed that facile peroxide adduct formation of an end-on type has occurred in the solution, and the difference in mass spectral behavior between the peroxide adducts with H₂¹⁶O₂ and H₂¹⁸O₂ was demonstrated.     

Electrodeposition of Sb, Bi, Te, and their alloys in AlCl3-NaCl-KCl molten salt

The Electrochemistry of Sb, Bi, and Te in AlCl₃-NaCl-KCl molten salt containing SbCl₃, BiCl₃, and/or TeCl₄ at 423 K was investigated by voltammetry, and electrodeposition of the three metals was performed under constant potential control in the melt. The voltammogram on a glassy carbon (GC) electrode in a melt containing 0.025 mol dm⁻³ [M] SbCl₃ showed a couple of redox peak corresponding to the Sb/Sb(III) redox reaction, and a stable layer of pure Sb was deposited under the constant potential control. The voltammograms in the melt containing 0.025 M BiCl₃ or 0.025 M TeCl₄ showed several redox couples. Stable deposit layers of pure Bi and Te were not obtained under the constant potential control, as the deposited layers detached from the electrode and immediately dissolved into the molten salt. Binary alloy deposition was possible in a melt containing BiCl₃ and SbCl₃, and also with BiCl₃ and TeCl₄. A stable Bi-Sb alloy deposit of metallic Sb and Bi-Sb solid solution was obtained at 0.8 and 0.9 V versus Al/Al(III) in the melt containing BiCl₃ and SbCl₃. The atomic ratio of Bi in the deposit was 37% at 0.9 V and 57% at 0.8 V. A stable Bi-Te alloy deposit was also obtained with the molten salt containing BiCl₃ and TeCl₄. The deposited Bi-Te alloy consisted of a mixture of Bi₂Te₃, BiTe, and Bi₂Te. The alloy deposit had good crystallinity and the preferential orientation was the (1 1 0) plane.     

Effect of host sterols on the sterol composition and virulence of a nuclear polyhedrosis virus ofHeliothis zea

The type of sterol in the diet ofHeliothis zea affected not only the sterol composition of the insect larva but also the virulence and/or sterol composition of a single-nucleocapsid nuclear polyhedrosis virus (HzSNPV). This baculovirus, which was purified by differential and sucrose density gradient centrifugation, had a sterol content of 40 ng per 10⁶ polyhedra. When the sterol composition of HzSNPV was characterized by gas liquid chromatography, reversed phase-high performance liquid chromatography, mass spectrometry, proton nuclear magnetic resonance spectrometry and/or ultraviolet spectroscopy, the sterols in the virus were similar to those of the host. The HzSNPV isolated from larvae fed Δ_{5_}, Δ_{0_} or Δ_5,7-sterols contained primarily cholesterol, cholestanol or 7-dehydrocholesterol, respectively. Changes in the sterol composition of HzSNPV affected its LD₅₀, but not LT₅₀, in larvae containing Δ₅-sterols. The LD₅₀ of virus isolated from larvae containing Δ_{0_}, Δ_{5_} and Δ₇-sterols decreased from 275,423 to 32,359 to 5,012 polyhedra/larva, respectively. The latter virus was also more virulent than the one that was isolated from larvae containing Δ_5,7-sterol and had an LD₅₀ of 58,884 polyhedra/larva. In contrast, the LD₅₀ of an HzSNPV (Sandoz, Inc.) containing Δ₅-sterol was not affected by the presence of Δ_{5_}, Δ_{0_} or Δ_5,7-sterols in the tissues of the host (1,413; 1,288 and 355 polyhedra/larva, respectively). The results of this study indicate that the sterol composition ofH. zea can affect the sterol composition of HzSNPV and therefore may affect the ability of this biological control agent to control its economically important insect host.     

Comparison of product selectivity during hydroprocessing of bitumen derived gas oil in the presence of NiMo/Al2O3 catalyst containing boron and phosphorus

A detailed experimental study was performed in a trickle-bed reactor using bitumen derived gas oil. The objective of this work was to compare the activity of NiMo/Al₂O₃ catalyst containing boron or phosphorus for the hydrotreating and mild hydrocracking of bitumen derived gas oil. Experiments were performed at the temperature and LHSV of 340-420 °C and 0.5-2 h⁻¹, respectively, using NiMo/Al₂O₃ catalysts containing 1.7 wt% boron or 2.7 wt% phosphorus. In the temperature range of 340-390 °C, higher nitrogen conversion was observed from boron containing catalyst than that from phosphorus containing catalyst whereas in the same temperature range, phosphorus containing catalyst gave higher relative removal of sulfur than boron containing catalyst. Phosphorus containing catalyst showed excellent hydrocracking and mild hydrocracking activities at all operating conditions. Higher naphtha yield and selectivity were obtained using phosphorus containing catalyst at all operating conditions. Maximum gasoline selectivity of ∼45 wt% was obtained at the temperature, pressure, and LHSV of 400 °C, 9.4 MPa and 0.5 h⁻¹, respectively, using catalyst containing 2.7 wt% phosphorus.     

Study of the effect of mechanically treated CeO2 and SiO2 pigments on the corrosion protection of painted galvanized steel

The effectiveness of mechanically treated CeO₂ particles and SiO₂ particles as active fillers into an organic coating was investigated. For this purpose, different combinations of CeO₂ and SiO₂ particles were added to an epoxy-polyester polymeric matrix: mechanically treated CeO₂ particles, mechanically treated CeO₂/SiO₂ particles and mechanically treated SiO₂ powders (used for comparison). The particles were dispersed into the polymeric matrix and HDG steel panels were coated with the different paints. A strontium chromates containing paint was used as a reference to compare the performances of the other samples. The salt spray results proved the good performance of coatings containing combinations of ceria and silica especially where these had been mechanically treated in a co-milling operation. The paint containing only the mechanically treated SiO₂ particles showed a fairly good resistance in the salt spray chamber considering the scratched samples. The EIS measurements evidenced the good corrosion protection properties of the paints containing the different combinations of mechanically treated CeO₂ and SiO₂ particles. After about 1000 h of immersion in 0.1 M NaCl solution, the samples containing the mix of mechanically treated CeO₂/SiO₂ particles showed impedance values which were comparable with the chromate control sample. The cathodic polarization tests evidenced the low extent of detachment of the coating containing the mix of mechanically treated CeO₂/SiO₂ particles. The electrochemical characterization and neutral salt spray test results proved the effectiveness of the mechanical treated cerium (IV) oxides treated together with SiO₂ as active pigments to improve the corrosion protection of the substrate. The reasons for the synergistic effect of the milled (together or separately) SiO₂ and CeO₂ particles was not clear at all, but a few hypothesis were discussed.     

In-vitro heat-generating and apatite-forming abilities of PMMA bone cement containing TiO2 and Fe3O4

Poly (methyl methacrylate) (PMMA) bone cement is widely used as a filler for repairing bone defects. To improve the effectiveness of the treatment for bone defects caused by metastatic bone tumours, we propose the formulation of PMMA cement containing titania (TiO₂) and magnetite (Fe₃O₄) that offers high bone affinity, making the cement suitable for use in magnetic hyperthermia. The TiO₂ and Fe₃O₄ contents of the PMMA cement varied from 20 to 45 mass%. The various cement samples were evaluated for their apatite-forming ability and heat-generation characteristics. The samples containing TiO₂ in concentrations of 15 mass% or higher formed apatite on their surfaces within 14 days in a simulated body fluid. The heat-generation characteristics of the samples were evaluated by applying an alternating current (AC) magnetic field under the following conditions: |H| = 40 Oe and f = 600 kHz, or |H| = 100 Oe and f = 100 kHz. The surface temperatures of the samples containing 25 and 30 mass% Fe₃O₄ reached 42.3 and 44.8 °C, respectively, at |H| = 40 Oe and f = 600 kHz. During hyperthermia treatment, cancer cells die at temperatures higher than 42 °C, and the cement samples fabricated in this study could reach this temperature. However, since some degree of heat loss will occur in vivo, it is necessary to ensure that the temperature is higher than 42 °C by varying the AC magnetic field. Nevertheless, the fact that the samples containing Fe₃O₄ concentrations of 25 mass% or higher generated enough heat under the AC magnetic field makes them suitable for clinical use in hyperthermia. Thus, PMMA cement containing 15 mass% or more of TiO₂ and 25 mass% or more of Fe₃O₄ should be investigated as a bioactive bone cement with a strong hyperthermia effect.     

SEM studies of electrolytic manganese dioxide

Manganese dioxide is deposited on the anode from MnSO₄ solution (95°C) containing H₂SO₄ and another acid, such as HCl and HNO₃. X-ray diffraction reveals a γ-MnO₂ structure. Addition of 0.1 M HCl or HNO₃ to the MnSO₄ solution containing H₂SO₄ results in lower cell voltage. Scanning electron micrographs of these surface deposits show that, in the case of a MnSO₄ + H₂SO₄ solution, a so-called fibrous microstructure was observed and crystal size became greater when the hydrochloric acid was added up to about 0.1 M.     

Stability of intergranular phases in hot-pressed Si3N4 studied with mechanical spectroscopy and in-situ high-temperature XRD

The impulse excitation technique (IET) and high temperature X-ray diffraction (HTXRD) were used to investigate the intergranular glass phase and its crystallisation behaviour in four hot-pressed silicon nitrides. The internal friction or damping peak height measured with IET near the glass transition temperature, T_g, is used as a qualitative indicator for the amount of residual intergranular amorphous phase after sintering. Silicon nitride powder was hot-pressed with different sintering additives. The silicon nitride containing 4 wt.% Al₂O₃ does not reveal an internal friction peak at T_g, i.e. it does not contain a significant amount of intergranular glass phase. Three other silicon nitrides, containing either 8 wt.% Y₂O₃, 6 wt.% Y₂O₃+2 wt.% Al₂O₃, or 2 wt.% Y₂O₃+4 wt.% Al₂O₃+2 wt.% TiN, do show an internal friction peak near T_g. This “T_g-peak” is nearly unaffected by heating up to 1400 °C in the silicon nitride with Y₂O₃+Al₂O₃+TiN sintering aids, whereas the amount of intergranular glass in the ceramics containing either Y₂O₃+Al₂O₃ or Y₂O₃ as a sintering aid is strongly reduced by subsequent heating. As observed from HTXRD, the onset temperature of crystallisation of the intergranular glass in the ceramic containing Y₂O₃+Al₂O₃ sintering aids is about 1100 °C, with the formation of Y–N-apatite (Y₂₀N₄Si₁₂O₄₈) and O-sialon (Al₀.₀₄Si₁.₉₆N₁.₉₆O₁.₀₄). The O-sialon phase in the yttria and alumina containing ceramics, formed either during sintering or during heat treatment, is not stable at elevated temperatures and dissolves in the intergranular glass phase between 1300 and 1400 °C. The O-sialon phase in the ceramic without Y₂O₃ sintering additive, however, is thermally stable. The presence of Ti⁴⁺ ions in the intergranular glass phase is suggested to inhibit its crystallisation, resulting in a stable high temperature damping behaviour.     

New applications for carbonaceous adsorbents

The most important adsorption properties of carbonaceous adsorbents are based on the microporous structure which can be determined by the mechanism of pore filling at equilibrium and by the diffusion behaviour of adsorbent molecules from the external surface into the grain. New processes of application of granular activated carbon in the gaseous phase besides the solvent recovery have been developed for the adsorption of sulfur containing and radioactive gases and in the aqueous phase for the purification of drinking and wastewater. New carbon molecular sieves are the base for gas separation processes, e.g. O₂- or N₂-recovery from air or H₂-recovery from H₂ containing gases.     

Prevention of surface defects in calendered poly(vinyl chloride) sheets using a succinate-capped poly(caprolactone) additive

Surface defects known as “gas checks” often mar the surfaces of poly(vinyl chloride) (PVC) calendered films. These defects are typically prevented through changes in the calender operating parameters, a costly exercise which also limits the sheet thickness and the production rate. Adding a low concentration of poly(caprolactone) (PCL)-based star-shaped compound can eliminate gas check defects in PVC calendering. The effects of a triheptylsuccinate-terminated PCL with a PCL triol core and number average molecular weight of 540 g/mol (i.e., PCL₅₄₀-[(succ)-C₇]₃) has been investigated on the material, thermal, and processing properties of PVC blends containing diisononyl phthalate (DINP) as a primary plasticizer and PCL₅₄₀-[(succ)-C₇]₃ in low quantities (i.e., 0, 5, or 10 parts per hundred rubber (phr)) as a secondary plasticizer and processing aid. The most significant differences between PVC blends containing PCL₅₄₀-[(succ)-C₇]₃ and those without are in the rheological properties of the PVC blends at higher temperatures and lower angular frequencies. Under these conditions, PVC blends containing 10 phr of PCL₅₄₀-[(succ)-C₇]₃ have a complex viscosity nearly three times higher than those containing only DINP. PVC/PCL₅₄₀-[(succ)-C₇]₃ blends had comparable tensile properties to those containing only DINP, with no significant change in maximum elongation and a small but significant increase of 28% in maximum stress. The addition of PCL₅₄₀-[(succ)-C₇]₃ made it possible to produce calendered films without gas checks that were twice as thick as those produced in its absence. In addition to reduced wastage of marred films, the increased calender operating range for PVC films containing PCL₅₄₀-[(succ)-C₇]₃ has the potential to significantly reduce energy costs for the calendering of thick PVC films.