Fabrication of 2D C/ZrC–SiC composite and its structural evolution under high-temperature treatment up to 1800 °C

Two-dimensional C/ZrC–SiC composites were fabricated by chemical vapor infiltration (CVI) process combined with a modified polymer infiltration and pyrolysis (PIP) method. Two kinds of ZrC slurries (ZrC aqueous slurry and ZrC/polycarbosilane slurry) were employed to densify composites before the PIP process. The as-produced C/ZrC–SiC composites exhibited better mechanical properties than the C/SiC composites densified only by CVI and PIP process. Structural evolution for C/ZrC–SiC composites treated in the range 1200–1800 °C mainly consisted of the change of SiC whiskers and the decomposition of polymer derived ceramic.     

Organization of contemporary systems for transport-warehouse servicing in the manufacture of man-made fibres

Conclusions -- It is necessary to begin the development of contemporary transport—warehouse systems promptly. Delay in development threatens in the future large losses and potential possibilities for new technological equipment.-- Work should be carried out in two directions: development of a complex of automated equipment for transport—warehouse systems; and performing investigative work on developing a complex of program—technical media and a mathematical—statistical model of transport—servicing systems.Translated from Khimicheskie Volokna, No. 5, pp. 50–51, September–October, 1990.     

Mechanisms of breakdown of the structure of glass cloth during impregnation with polymer binders

The basic sources of worsening of the quality indexes of insulating glass cloth and the requirements for the properties of the cloth and binder during impregnation were determined: short pile, gas inclusions, thermodynamic characteristics of binder and monofilament on the binder—monofilament, binder—air, and air—monofilament interface, internal stresses in the structure of the cloth, weave geometry, and position of monofilaments in the complex fibre.Stekloplastik—Sertifikat Co., Moscow. Translated from Khimicheskie Volokna, No. 3, pp. 43–46, May–June, 1994.     

Effect of topaz on the synthesis of mullite in mixtures of kaolinite and alumina

The synthesis of mullite in mixtures of kaolinite and alumina in the presence of small amounts of topaz is studied. Topaz is shown to activate the synthesis of both the primary (from kaolinite) and secondary mullite (through binding silica produced by thermal degradation of kaolinite), decrease the temperature of synthesis by 100°C, and increase the total yield of mullite. Products of the thermal degradation of topaz — mullite and gaseous chemically active fluoride compounds — are shown to play the role of mineralizing agents.Translated from Novye Ogneupory, No. 8, pp. 49 – 53, August, 2004.For previous communication, see Novye Ogneupory, No. 7, 41 – 46 (2004).     

Influence of Temperature on the Properties of Polycarbosilane

A polycarbosilane precursor of SiC fiber was synthesized at high temperature under high pressure from liquid polysilane (LPS), which was obtained by thermal decomposition of poly(dimethylsilane). The effect of reaction temperature on the Si–H bond content, degree of linearity, Si–Si bond content, molecular weight, molecular weight distribution, elemental composition, softening point, and yield of the polycarbosilane (PCS) was studied spectroscopically (FTIR, UV, ¹H-NMR, and ²⁹Si-NMR) and by gel permeation chromatography (GPC). The results showed that the molecular weight, yield and softening point of the PCS increased, the molecular weight distribution broadened, and the Si–Si bond content and degree of linearity decreased when the reaction temperature increased. The Si–H bond content increased when the thermolysis reaction temperature was less than 450°C and decreased when the temperature was over 460°C. Increasing of the reaction temperature affected the composition with a general decrease in the amount of carbon, hydrogen and oxygen in the product. A middle molecular weight region of PCS in the GPC appears when the reaction temperature approaches 450°C; and, the as-synthesized PCS was stable with low Si–Si bond content. Synthetically, the conversion process is initially the formation of PCS by thermal decomposition of LPS, which is followed by an increase in molecular weight via condensation of PCS molecules.     

Modifier for viscose technical yarn based on cotton soapstock acids

Conclusions A new domestic modifier for viscose technical yarn has been synthesized — Amiprin KhS-20, based on distilled fatty acids from cotton soapstock.Specimens of viscose technical yarn have been prepared under the conditions of an experimental unit, using Amiprin KhS-20 modifier. The properties of the yarn obtained are close to those of yarn spun using Berol'-Visko 314 as a modifier.Translated from Khimicheskie Volokna, No. 3, pp. 46–47, May–June, 1989.     

Effect of filler fibres on structure formation in cation-exchange membranes

Conclusions -- An attempt has been made to replace the inert reinforcing filler in ion-exchange membranes with an active material — man-made fibres.-- The membranes prepared conform fully to the requirements imposed on cation-exchange membranes.Saratov Polytechnic Institute. Translated from Khimicheskie Volokna, No. 5, pp. 29–32, September–October, 1992.     

Manpower requirements for the fertilizer sector in sub-Saharan Africa

The manpower requirements are estimated for the fertilizer sector (production, marketing, and use) in sub-Saharan Africa from 1982/83 to 2002/3. The additional technical manpower requirements in sub-Saharan Africa over a 20-year period are about 15,917 persons for fertilizer production, 7959 for fertilizer marketing and 7958 for fertilizer use. It is estimated that, on the average, an additional 1592 persons will be required annually for the fertilizer sector. There is thus a need to establish —through both national and international organizations— appropriate fertilizer training facilities. This will relax serious manpower constraints in fertilizer sector development and thus will accelerate the contribution of fertilizer to economic growth in sub-Saharan Africa.     

Effect of composition,quantity, and synthesis temperature of spinels,and some properties of periclase — Spinel compositions

Conclusions The incorporation of spinel (5–10%) into the composition of the solid solution leads to periclase grain growth and to its sintering. Excess spinel in combinations with periclase over this quantity prevents recrystallization sintering of the specimens.A reduction in the synthesis temperature of most the spinels from 1750 to 1450°C contributes the sintering of the compositions under investigation, and improves their technical properties.In the periclase—spinel compositions the maximum influence on the grain growth and the properties of the specimens is exerted by the temperature conditions used for synthesizing the high-alumina spinels, while the conditions used to obtain the highly chromic spinels, and especially the magnesiochromite, have little or no effect on the technical properties of the fired product.With an increase in the spinel phase concentration from 5 to 30%, and also when there is a change in its composition in the direction from magnesia-alumina spinel to magnesiochromite, such factors as strength, porosity, and spalling are impaired.In the MgO-Mg(Al_1–X, Cr_X)₂O₄ system it is possible to obtain strong, dense, and simultaneously spalling-resistant refractories by using small additions of alumina spinel, synthesized at low temperatures ensuring the completion of the spinel-forming reaction.Translated from Ogneupory, No. 3, pp. 53–57, March, 1971.     

High-alumina products based on kyanite-sillimanite concentrate

Conclusions Kyanite-sillimanite concentrate of the Middle Pridneprov locality is a suitable material for the manufacture of high-alumina products. For making dense fireclay and products with a low porosity, it is necessary to finely grind the concentrate, to make a dense briquet, and to fire the products at 1580–1600°C with a soak time of not less than 6 h.It is expedient to add 10–15% of technical alumina to the batch. At high temperatures, this reacts with the silica that is formed during the decomposition of kyanite and sillimanite, increasing the mullite content of the refractory. This has a favorable influence on the properties of the products.The use of kyanite — siilimanite concentrate for the manufacture of high-alumina refractories decreases the consumption of technical alumina used for making such ware.DeceasedTranslated from Ogneupory, No. 6, pp. 41–46, June, 1969.     

Developing dinas technology using dry mineralizers

Conclusions A study was made of the milling kinetics of new types of calcareous mineralizers — wastes from various industries — for making dinas brick. It is established that the grinding capacities of quartzite and calcareous wastes are practically identical. This facilitates the introduction of mineralizers directly into the dinas body (combined grinding) with the quartzite in preparing finely milled batch constituents.The quality of the brick made with dry mineralizers completely meets the standard requirements for dinas production. The newly developed technology is recommended for introduction in dinas factories.Translated from Ogneupory, No. 8, pp. 19–21, August, 1991.     

Two-stage method of synthesizing polyanthanthroylenebenzimidazole and preparation of a fibre based on it

Conclusions Polyanthanthroylenebenzimidazole has been prepared by a two-stage method. Some principles have been studied, and optimum conditions have been established for the first stage of the synthesis — preparation of the prepolymer.The possibility of cyclizing the prepolymer to polyanthanthroylenebenzimidazole has been demonstrated.Model yarn specimens have been prepared and a preliminary evaluation of their properties has been given.Translated from Khimicheskie Volokna, No. 1, pp. 29–32, January–February, 1987.     

Electropolymerization of chlorinated phenols on a Pt electrode in alkaline solution Part III: A Fourier transformed infrared spectroscopy study

FTIR spectroscopy was employed to investigate high molecular weight substances formed on a platinum electrode surface during the electrochemical oxidation of phenol and its chlorinated derivatives. Potentiodynamic (potential range from –0.80 V to 0.85 V vs SHE; scan rate 200 mV s^–1) and potentiostatic (at 0.78 V vs SHE) electropolymerization was used in alkaline solutions (1 M NaOH) containing 0.1 M of phenol, monochlorophenols, dichlorophenols, trichlorophenols and pentachlorophenol. The IR spectra of the corresponding monomers were recorded for the comparison. The FTIR spectroscopy studies revealed that the polymers formed under potentiodynamic and potentiostatic conditions are of aromatic nature (–C=C– stretching vibrations at 1450–1600 cm^–1), they have ether-linkages (=C—O—C= stretching vibrations at 1100–1300 cm^–1) and quinone groups (–C=O stretching vibrations at 1630–1800 cm^–1 and –C—H out-of-plane bending at 760 cm^–1). The intensities of the hydroxyl group bands in most of the polymers are rather weak compared to those in the corresponding monomers. Vibrations at 2850–2960 cm^–1, which are present in most of the IR spectra of polymers formed under cyclic voltammetry conditions, correspond to the stretching vibrations of the sp³ hybridized C—H bond and suggest that the cleavage of the benzene ring occurs to some extent during electrooxidation–electropolymerization of phenol and its chlorinated derivatives when reaching the potential of oxygen evolution (0.85 V vs SHE).     

Relative efficiency of ammonium polyphosphate and orthophosphates for wheat and their residual effects on succeeding cowpea fodder

The relative efficiency of ortho and polyphosphates as P sources for wheat were studied in a field experiment with five sources—TSP, DAP, NP, APP (solid) and APP (Liquid) at three levels—13, 26 and 39 kg P ha^–1 and the residual effect was studied on a succeeding cowpea (fodder). Both the crops were grown each year at same location. Wheat responded upto 39 kg P ha^–1 in the first year but only upto 26 kg P ha^–1 in the second year. The growth parameters—plant height and dry matter production and yield attributes-ears m^–1, grains ear^–1 and test weight were favourably influenced by P application. The rate of P uptake initially exceeded the dry matter production. Wheat when fertilized with 26 or 39 kg P ha^–1 left behind a significant residual effect to raise the soil P availability and dry matter yield of cowpea. The grain yield of wheat was higher with APP's than with NP or DAP but the residual effect was the highest with NP. The magnitude of build up of soil available P with NP and APP's were similar and higher than DAP or TSP.     

Calculation of reeling devices of the flyer type with a constant radius of rotation

Equations for calculating reeling devices with a constant radius of rotation are proposed. Jamming of the reeling device is not a function of the thread input tension. Correct selection of the parameters of the reeling device will allow completely fabricating packs having a significant ratio of winding and thread carrier diameters. A ratio of 8.5 was confirmed experimentally. The calculation can be used in issuing the initial requirements for equipment with respect to the pack parameters.Malye Tekhnologii Scientific — Production Co., Tver'. Translated from Khimicheskie Volokna, No. 4, pp. 50–53, July–August, 1995.     

Effect of surface-active agents on grinding and compaction of periclase-spinel mixes

Conclusions The principle has been established that by adding a surface-active agent it is possible to accelerate the grinding of a chromite-magnesite mixture and increase the density, and reduce the porosity of periclase-spinel refractories.The main technical requirements for effective use of SFA still-residue SAA's are: a high acid number (over 100), the fullest possible degree of hydrophobization of the original powders during milling, and optimum mix moistening with the right-density sulfite-cellulose liquor solution.The increase which is attained in periclase— spinel refractory densities when SAA is added is explained by lower back expansion of the green ware, closer packing of grains during pressing because of elimination of over 0.5 mm particles by grinding, and more intense sintering due to the presence of a greater amount of under 2 micron material in the mix.Translated from Ogneupory, No. 7, pp. 50–54, July, 1969.     

Metering pump for the manufacture of acetate tape

Conclusions The 11NSh-2.4A metering gear pump has been devised for the manufacture of acetate tape which conforms in technical indices to the requirements of the highest quality category.The economic advantage from introduction of 350 pumps was 22,540 rubles.Translated from Khimicheskie Volokna, No. 4, pp. 44–45, July–August, 1986.     

Effect of Shock–Wave Loading Conditions on the Behavior of a PETN–Based Plastic Explosive

The paper reports results of investigation of the spallation and initiation of an explosive transformation in the plastic explosive formulation TP–83 under shock–wave loading. In the first case, specimens 20 mm thick were impacted by explosive driven steel plates 1.0 and 1.6 mm thick at velocities of 120—420 m/sec, and in the second case, the impact velocity was 430—580 m/sec. In addition, in the second case, specimens 5 mm thick were impacted by copper plates with a thickness of 0.10—0.28 mm accelerated to velocities of 590—1250 m/sec. The loading conditions were calculated in an elastoplastic formulation. The relationships between the loads leading to shock–induced spallation and explosive transformation of the explosive formulation are obtained and represented analytically.     

Effect of rare-earth chromites on sintering of magnesia

The effect of neodymium, cerium, lanthanum, and yttrium chromites, added in amounts of not more than 8%, on the sintering of magnesia in air and in vacuum has been studied. On addition of rare-earth chromites, the initial magnesia is sintered to a density of 0.98. By their sintering action, these chromites fall into the following sequence: neodymium chromite — lanthanum chromite — yttrium chromite — cerium chromite. The highest density (0.98 – 0.99) and the lowest porosity (1–2%) are obtained on addition of 2% of neodymium chromite to magnesia. The process of sintering of magnesia is accompanied by an increase in the size of periclase crystals from 12 to 38–56 µm.Translated from Ogneupory, No. 1, pp. 2–4, January, 1994.     

Physicochemical basis of the sol-gel process giving selective layers of ultrafiltration ceramic membranes from zirconia hydrosol

Selective layers of ceramic ultrafiltration membranes were prepared by the sol-gel method using zirconia hydrosol as the initial material. On the basis of turbidimetric investigations, a compatibility diagram was constructed in the zirconia (sol) — polymer thickener — water system. The results of x-ray phase analysis and thermogravimetric analysis were used to choose the regime for heat treatment of the sol — polymer thickener compositions in order to prepare selective layers. The characteristics of the pore structure of the selective layers meet the requirements imposed on ultrafiltration membranes.