Characteristics of the ignition of the drops of organic coal–water fuels based on waste oils and industrial oils

For expanding raw-material and energy supply sources in large- and small-scale power engineering, organic coal–water fuels (OCWFs) based on typical waste coal (the filter cake of K coal) and automobile and turbine oils with a weight concentration of 10% were prepared. The delay times of ignition and complete combustion, the minimum temperatures of ignition, and the maximum temperatures of combustion were determined for the OCWF drops of different compositions. It was shown that the ignition characteristics of the OCWF compositions based on oils before and after of base service differed insignificantly. The experimental results demonstrated that it is reasonable to use a wide group of industrial and automobile oils with different service life periods as the components of OCWFs.     

Alkyl-tetralin base oils synthesized from coal-based chemicals and evaluation of their lubricating properties

Naphthenic base oil is an important lubricating base oil and very scarce in the global petroleum resources. Herein, a series of alkylated tetralin fluids similar to naphthenic base oils were produced by the alkylation of tetralin and a-olefins(n-hexene, n-octene, n-decene) with ionic liquid Et₃NHCl/AlCl₃ as the catalyst, where the applied raw materials are totally derived from the coal chemical industry.The product composition could be controlled by adjusting the feeding ra...     

Influence of the temperature dependence of the thermophysical properties of coal–water fuel on the conditions and characteristics of ignition

The results of an experimental study and mathematical simulation of the ignition of coal–water fuel (CWF) particles, the main thermophysical characteristics of which (thermal conductivity (λ), heat capacity (C), and density (ρ)) depend on temperature, are reported. Based on the results of the numerical study, the influence of changes in the thermophysical properties upon the heating of the main bed of fuel on the conditions and characteristics of its ignition was analyzed. The ignition delay times (t _i) of CWF particles were determined under the typical furnace conditions of boiler aggregates. As a result of the mathematical simulation of the process of CWF ignition, it was established that the temperature dependence of thermophysical characteristics can exert a considerable effect on the characteristics and conditions of ignition. In this case, it was found that the ignition of coal–water drops is possible under the conditions of their incomplete dehydration. A good agreement of the theoretical ignition delay times of the CWF particles and the experimental values of t _i was established.     

Clarifying the effect of sintering conditions on the microstructure and mechanical properties of β-tricalcium phosphate

The effect of the sintering conditions (temperature and time) on the microstructure (density and grain size) and mechanical properties (hardness, elastic modulus, and strength) of β-tricalcium phosphate (β-TCP) bioceramics fabricated from Ca-deficient commercial powders is analyzed. Contrary to current general opinion, it is demonstrated that the optimal sintering temperature to maximize the mechanical performance of this β-TCP material is not necessarily below the β ? α transformation temperature (1125 °C). In particular, optimal performance was achieved in samples sintered at 1200 °C for 3 h, since it was not until higher temperatures or longer sintering times that microcracking develops and mechanical properties are degraded. It is argued that the residual stresses developed during this reversible transformation do not lead to microcrack propagation until sufficiently large starting flaws develop in the microstructure as a consequence of grain growth. Implications of these findings for the processing routes to improve sintering of this important bioceramic are discussed.     

Studies on the adhesive properties of neoprene–phenolic blends

Polychloroprene (neoprene) rubber in combination with phenolic resins is a versatile adhesive formulation. The phenolic resin used in this case was derived from a mixture of cardanol, a meta-substituted naturally-occurring substance, and phenol. Cardanol is the main ingredient of cashew nut shell liquid (CNSL), a renewable resource. This study aims to investigate the adhesive properties of cardanol-based resin when used in combination with two grades of polychloroprene rubber. The effects of varying the solid content and resin content, choice of resin, fillers, crosslinking agents, adhesion promoters, solvents, etc. in the adhesive formulations were also studied. Moreover, relative proportions of rubber and resin that give optimum adhesion performance were identified. The results show that cardanol-phenol-formaldehyde resin is an effective ingredient in adhesives for bonding aluminium to aluminium and SBR to SBR. The addition of 3-aminopropyltriethoxysilane to the formulation improves the bond strength of metal-to-metal specimens.     

Effects of the pretreatment of a cemented carbide surface on its properties and on the properties of diamond coatings deposited by oxygen–acetylene flame CVD

The influence of the pretreatment of the WC (6% Co) surface on its properties (i.e. roughness, grain size and chemical composition) and on the properties of flame-deposited coatings have been studied. The surface treatments included the action of an oxidizing oxygen/acetylene flame at 1000 °C, scratching with diamond particles (14–20 μm), mixture with iron (<45 μm) in an ultrasound bath, and seeding with a nm-sized diamond suspension. An acid treatment was included in the pretreatment sequence. It is found that the oxidizing flame and the seeding decrease the surface roughness of the substrate as well as the diamond coatings, at the same time increasing the adhesion of the coating. Ultrasound scratching with the diamond/iron suspension increases the roughness of both the substrate and the diamond coating and decreases the adhesion of the coating. Scratching with diamond particles shows a similar but lesser effect. Except for scratching with diamond, all the surface pretreatment procedures lead to an increase in the density of diamond particles: this increase is greatest for seeding. Our results indicate that good adhesion and a small surface roughness are best obtained by the use of an oxidizing flame followed by acid treatment and seeding with nanoparticles.     

Effect of γ-radiation on the structure and thermal properties of polyacrylonitrile fibres

-Radiation significantly affects both the initial structure and the thermal properties of PAN fibres. The following are probably the most important results of radiation exposure: the temperature of the beginning of cyclization decreases; the exothermic nature of cyclization decreases so that the weight losses in the region of the m.p. decrease, indicating destructive processes in the polymer chain; when irradiated samples are heated, intermolecular cross-links form with the participation of oxygen; the duration of oxidation of the fibres before a given density level is attained is reduced significantly.St. Petersburg University of Design and Technology. Translated from Khimicheskie Volokna, No. 3, pp. 18–21, May–June, 1995.     

Coagulation–bubbling–ultrafiltration: Effect of floc properties on the performance of the hybrid process

A novel hybrid process of coagulation–bubbling–ultrafiltration was proposed to study membrane fouling phenomena by surface water. Relationship of bubbles, flocs and the hollow fibers was explored. When applying less than 20 mL/min gas flow rate, membrane fouling was accelerated with air bubbles introduced. When gas flow rate increased further to 40 mL/min and 60 mL/min, TMP showed a two-stage development trend, which was a fast development in the first few hours followed with a relatively slow development after about 4 h. Unified membrane fouling index (UMFI) increased from 0.00216 (without bubbles) to 0.00274 m²/L (40 mL/min gas flow rate) and 0.00219 m²/L (60 mL/min gas flow rate). As gas flow rate increased, bubble size became bigger, and its distribution range became wider, resulting in higher shear rate in the ultrafiltration column, which led to severe floc breakage. Flocs of small size and compact structure accelerated membrane fouling, resulting in highest UMFI value under 40 mL/min gas flow rate. However, under 60 mL/min gas flow rate, with largest bubbles and highest shear rate examined in this study, concentration polarization was effectively limited. As a result, TMP development slowed down when pore blockage reached equilibrium.     

The effect of the surface nanostructure and composition on the antiwear properties of zirconia–titania coatings

This study describes the preparation, surface imaging and tribological properties of titania coatings modified by zirconia nanoparticles agglomerated in the form of island-like structures on the titania surface. Titania coatings and titania coatings with embedded zirconia nanoparticles were prepared by the sol–gel spin coating process on silicon wafers. After deposition the coatings were heat-treated at 500 °C or 1000 °C. The natural tendency of nanoparticles to form agglomerates was used to build separated island-like structures unevenly distributed over the titania surface having the size of 1.0–1.2 μm. Surface characterization of coatings before and after frictional tests was performed by atomic force microscopy (AFM) and optical microscopy. Zirconia nanoparticles were imaged with the use of transmission electron microscopy (TEM). The tribological properties were evaluated with the use of microtribometer operating in ambient air at technical dry friction conditions under normal load of 80 mN. It was found that nanocomposite coatings exhibit lower coefficient of friction (CoF) and considerably lower wear compared to titania coating without nanoparticles. The lowering of CoF is about 40% for coatings heated at 500 °C and 33% for the coatings heated at 1000 °C. For nanocomposites the wear stability was enhanced by a factor of 100 as compared to pure titania coatings. We claim that enhanced tribological properties are closely related to the reduction of the real contact area, lowering of the adhesive forces in frictional contacts and increasing of the composite hardness. The changes in materials composition in frictional contact has secondary effect.     

Studies on the effects of γ-radiation on the mechanical properties of Nylon 6–12 fibers

Summary Commercial nylon 6–12 fibers were subjected to various doses of -radiation. The mechanical and some thermal properties, as compared to those of non-irradiated fibers, show changes which are discussed in terms of the radiation-matter interactions.     

The effects of promoters on catalytic properties and deactivation–regeneration of the catalyst in the synthesis of dimethyl carbonate

The effects of different alkali metal promoters in PdCl₂-CuCl₂/activated carbon (a.c.) catalyst on the reaction performance for synthesizing dimethyl carbonate (DMC) by gas-phase oxidative carbonylation of methanol were studied. The bulk and surface properties of catalyst PdCl₂-CuCl₂-CH₃COOK/a.c. were characterized by XRD, XPS, and AAS techniques. On the basis of catalyst characterization and activity evaluation, the functions of promoters were further investigated, and the deactivation–regeneration of catalyst PdCl₂-CuCl₂-CH₃COOK/a.c. was also discussed. The results show that the space time yield (STY) of DMC on catalysts with different alkali metal promoters ranks in the following order: K>Na>Li. The main reason for catalyst deactivation is the loss of chlorine. Fortunately, during the preparation of the catalyst, the interaction between CH₃COOK and PdCl₂ or CuCl₂ that results in the formation of KCl limits the loss of chlorine. An obvious increase of the catalyst lifetime and catalytic activity is observed by treating fresh catalyst with a methanol solution of methyl chloroacetate. If deactivated catalyst is treated with a methanol solution of methyl chloroacetate in N₂ stream at 200 °C for 4 h and then treated in N₂ stream at 200 °C for 2 h, the catalytic activity can be restored effectively and the regeneration induction period can be shortened. The catalytic activity after two times of regeneration can still be restored to 93% of the fresh catalyst. The run time of this catalyst is up to 300 h.     

Influences of heat-treatment on the microstructure and properties of silica–titania composite aerogels

Silica–titania composite aerogels were synthesized via ambient pressure drying by using water glass and titanium tetrachloride as raw materials. The influences of heat-treatment at different temperature with different heating rate on the microstructure and properties of the composite aerogels were investigated by differential thermal analyzer, Fourier transform infrared spectrometer, X-ray diffraction, nitrogen adsorption–desorption, scanning electron microscope and transmission electron microscope analysis. The results indicate that the silica–titania composite aerogels heat-treated at 250 °C exhibited highest specific surface area, pore volume and average pore diameter. When the heat-treatment temperature was higher than 450 °C, the –CH₃ groups on the surface of silica–titania composite aerogels would transform into –OH groups gradually, and in the meantime, the composite aerogels network structure would be destroyed gradually and the crystallinity of TiO₂ would be improved with the increase of heat-treatment temperature. Particularly, heat-treatment at temperatures above 750 °C would cause serious damage to the network structure of the composite aerogels. The adsorption/photocatalytic activity experiments showed that the composite aerogels heat-treated at 550 °C exhibit highest darkroom adsorption efficiency, and the 650 °C-heat-treated samples exhibited highest efficiency for removing the Rhodamine B from water.     

Physico-chemical properties of lignin–alginate based films in the presence of different plasticizers

A lignin–alginate blended film was prepared in the presence of three different plasticizers, viz. glycerol, epichlorohydrin (EPC) and poly(ethylene glycol) (PEG) and the effect of each plasticizer was studied on physico-chemical properties of the blended film. Lignin extracted from Acacia wood by alkali extraction process was blended with alginate to obtain lignin–alginate film in the presence of different plasticizers. A film plasticized with glycerol displayed higher solubility and swelling percentage as compared to EPC and PEG plasticized films. The highest tensile strength was observed for film plasticized with PEG, and none of the plasticizers made any significant change on the bursting strength of the film. Incorporation of lignin considerably improved the light barrier properties of the films. Fourier transform infrared spectroscopy study of films suggested the existence of hydrogen bonding between lignin–alginate in the presence of plasticizers. In addition, EPC plasticized film displayed highest thermal stability, as confirmed by thermogravimetric analysis. Further studies demonstrated that plasticizers significantly affected the physico-chemical properties of the blended films. In conclusion, lignin–alginate film plasticized with EPC presented better physico-mechanical and light barrier properties which could be used in packaging and coating applications.     

Effect of the reaction conditions on the properties of poly(4,4′-diphenylether-1,3,4-oxadiazole)s

Summary Poly(4,4-diphenylether-1,3,4-oxadiazole)s have been prepared by polycondensation of 4,4-diphenylether dicarboxylic acid and hydrazine sulphate, HS, in poly(phosphoric acid), PPA, under different reaction condictions. The products were characterized by viscometry, gel permeation chromatography, ¹H-NMR spectrometry and thermogravimetric analysis. Dense membranes have been prepared and submitted to gas transport and wide angle X-ray diffraction, WAXD, experiments. The differences found in permeability and selectivity parameters, as well as in density and WAXD results, are discussed in terms of their solution viscosities and hydrazide repeat unit contents.     

The composition of edible oils modifies β-sitosterol/γ-oryzanol oleogels. Part I: Stripped triglyceride oils

The role of the fatty acid (FA) composition of triglycerides (TAGs) on sterol/sterol ester oleogels has been studied. Minor oil components of three vegetable oils with varying degrees of unsaturation (iodine values, IV) were removed. Typical oil quality parameters were determined before and after the treatment, and oleogels were produced using all six oils. Characteristic gel properties such as transition temperatures, mechanical properties and microstructure were tested. The results were compared regarding the impact of IV and the stripping procedure. Minor components were essentially removed during stripping, resulting in significantly different oil properties such as peroxide value, free FA and viscosity. However, peroxides formed rapidly in stripped flaxseed oil. Gel–sol transition temperatures and enthalpies were higher in gels from untreated oils and decreased with IV in samples with stripped oils. In contrast, the sol–gel transition was suppressed due to minor oil components in untreated oils. The effect of IV on gel formation was much less and linked to a lower solvent viscosity in more unsaturated oils. Nevertheless, gel firmness was significantly higher in oleogels from untreated oils and decreased slightly with IV in stripped oils. That was associated with differences in the arrangement of network building blocks, which was confirmed using atomic force microscopy. This study showed that the FA composition of TAGs has a limited effect on oleogel properties compared to those of minor oil components. The next part of this study focuses on modifying oleogel properties by adding selected minor components to stripped oils at varying concentrations.     

Study of molding structures and physicomechanical properties of carbon-ceramic composite materials of the SiC–C system

The microstructure of composite materials of the composition SiC–C is analyzed. It is established that they are a separate group of materials containing a ceramic matrix. The ceramic matrix experiences tensile stresses, as a result of which within the composite material a traditional internal stress field is distorted. The ceramic matrix increases strength at carbon phase boundaries of the composite material, and it reduces porosity. An excess of ceramic material reduces strength and thermal stress resistance. Requirements are provided for porosity of the structure that govern the optimum field of material composition.     

Optimization of the magnetic properties and microstructure of Co–La substituted strontium hexaferrite by varying the production parameters

The aim of this paper was to improve the magnetic properties of magnetoplumbite-type (M-type) strontium hexaferrite substituted with Co²⁺–La³⁺ produced by conventional ceramic forming techniques. The effect on the magnetic properties of varying the composition of the target compound Sr_1−xLa_xFe_12−yCo_yO₁₉ and the primary and secondary firing temperatures was investigated. Microstructure studies and XRD phase analysis indicated that optimum values of the remanent magnetization B_r and coercive field H_cj were obtained with a primary firing temperature of 1240 °C and a final firing temperature of 1180 °C, where (x=y)_th ¹=0.15, (y/x)_exp ²=0.75 and the molar ratio of ferric oxide to strontium oxide=5.8. The optimized magnetic properties obtained under these conditions were B_r=4070 Gs, H_cj=4710 Oe, (H_k/H_cj)=82.     

Influence of synthesis parameters on the properties of LiFePO4/C cathode material☆

The influence of sintering temperature,carbon content and dispersive agent in ball-milling was investigated on the properties of Li Fe PO_4/C prepared using Fe_2O_3,NH_4H_2PO_4,Li_2CO_3 and glucose via solid state reaction.X-ray powder diffraction,scanning electron microscopy and charge–discharge test were applied to the characterization of the Li Fe PO_4/C samples synthesized under different conditions.Sintering temperature affects the crystallite/particle size and degree of crystallinity of LiF eP O_4,formation of Fe_2 P and maintenance of carbon in LiF e PO_4/C.Carbon maintenance is favored by low sintering temperature,and 700 °C is optimum for synthesis of LiF eP O_4/C with superior electrochemical performance.A higher carbon content in the range of 4.48%–11.03% results in a better rate capability for Li Fe PO_4/C.The dispersive agent used in ball-milling impacts the existent state of carbon in the final product which subsequently determines its charge–discharge behavior.The sample prepared at700 °C by using acetone as the dispersive agent in ball-milling exhibits an excellent rate capability and capacity retention without any fade at 0.1C,1C and 2C,with corresponding average discharge capacities of 153.8,128.3and 121.0 m A·h·g~(-1),respectively,in the first 50 cycles.