Methods of production of flexible electrodes for foil batteries

Conclusions An investigation was made of various methods of manufacture of flexible electrode strips sintered from carbonyl nickel powder, for electric batteries. Strip of adequate flexibility is obtained only in those cases where its porous layers have a granular structure and the pores between individual granules are 100–400 in size.Translated from Poroshkovaya Metallurgiya, No. 12 (96), pp. 43–46, December, 1970.     

Reaction of titanium carbide with water

Summary Contrary to the generally held view that carbides of the transition metals of groups IV and V are inert with respect to water, the authors show on the example of titanium carbide that the carbides are decomposed by water, although the extent of attack is not more than 5–30 atomic layers, i. e., not more than 100–150 A.The hydrolysis of TiC proceeds according to the reaction: TiC+xH₂O CH₄ + TiO₂ · xH₂O.Methane is the principal constituent of the gaseous hydrolysis products, and consequently it is possible to regard carbides of the transition metals of groups IV and V as methane derivatives. Hydrogen evolution in both carbides of group V and nonstoichiometric carbides of group IV is believed to take place as a result of the presence of free electrons in the carbides. The complex polymer acid TiO₂ · xH₂O undergoes dissociation, which becomes intensified in the course of time and results in a rise of hydrogen ion concentration. TiC powder particles are negatively charged. With the results obtained it is possible to choose suitable dispersion media for such powder metallurgical operations as fine milling, slip casting, and others.Translated from Poroshkovaya Metallurgiya, No. 6(54), pp. 53–57, June, 1967.     

Preparation of ferric oxide for ferrites based on goethite synthesis by an ammoniacal method

Conclusions It is shown that goethite (yellow ferrie oxide pigment) synthesis by an ammoniacal method offers a suitable means of obtaining, from technical iron vitriol, high-purity ferric oxide with stable properties fulfilling the requirements for ferrite-grade ferric oxide. The ferric oxide is distinguished by its high reactivity after high-temperature (850–900°C) heat treatment. Its physicochemical properties are close to those of 1360 WF grade ferric oxide manufactured by the Bayer Co. of West Germany [5]. The key process parameters in the production of ferric oxide by this method are: goethite synthesis pH 4.0–4.5, synthesis temperature 70–75°C, amount of seed 8–10% of the goethite content at the end of synthesis, and ferric oxide calcining temperature 850–900°C.Translated from Poroshkovaya Metallurgiya, No.4(160), pp. 82–88, April, 1976.     

Reaction between silicon nitride and magnesium oxide during hot pressing

Conclusions Using the methods of microscopical examination, chemical and mass spectrometric analyses, electron probe microanalysis, and weight loss determination, astudy was made of the reaction between technical silicon nitride powder and magnesium oxide. It is shown that the reaction involves not only the formation of forsterite, enstatite, and variable-composition glasses but also diffusion of the main components, with a gradual fall in magnesium concentration over the whole length of the diffusion zone in a model system. In the temperature range 1600–1700°C magnesium atoms drive out of the silicon nitride lattice silicon atoms, which then react with oxygen from the magnesium oxide or air to form silicon monoxide ions in the gaseous phase. The evaporation of the silicon monoxide in the system results in loss of weight, which grows with rise in temperature. The processes of evaporation and dissociation of the starting components, which sharply increase in intensity at 1800°C, make a certain contribution to the loss of weight.Translated from Poroshkovaya Metallurgiya, No. 9(177), pp. 89–96, September, 1977.     

Sintering of brass powders having different oxygen contents

Conclusions As the oxygen content of the brass powders obtained by water atomization increases, the thickness of the oxide films forming around the particle increases in that the quantity of dissolved oxygen remains unaltered. Satisfactory properties of the sintered products can be achieved using powders having an oxygen content up to O.23 wt.% and a uniform thickness of the oxide films. The optimum sintering temperature increases with increasing oxygen content; however, it is possible to establish a regime that ensures attainment of stable properties of the desired level in the materials obtained from the powders containing oxygen in the O.8–O.23 wt.% range.Translated from Poroshkovaya Metallurgiya, No. 4(328), pp. 44–47, April, 1990.     

Prevention of secondary oxidation of steel during continuous casting

Conclusions Secondary oxidation of the metal during casting is one of the basic problems in continuous casting. The solution for any particular case depends on the chemical composition of the steel and the production technique. The use of protective media in the crystallizer almost eliminates rejects due to oxide skin trapped in the ingot.Central Scientific Research Institute of Ferrous Metallurgy. Translated from Metallurg, No. 7, pp. 15–18, July, 1968.     

Methods of manufacture of aluminum powders and their fields of application

Conclusions Aluminum powders, flakes, pastes, and granules are being successfully used in various branches of the national economy, including powder metallurgy. The present-day scale of industrial manufacture of aluminum and aluminum alloy powder products can satisfy virtually all the known demands from industry. There is a need to increase industrial production of aluminum alloy granules by the method of centrifugal casting of melts for the development of granule metallurgy, which enables successfully to process some materials, in particular low-grade and secondary aluminum.Translated from Poroshkovaya Metallurgiya, No. 12(264), pp. 32–37, December, 1984.     

Effect of the degree of deformation on the mechanical properties and structure of extruded semifinished products from granules of aluminum alloys of the system Al-Zn-Mg-Cu

Conclusions On the basis of the investigation described, it may be concluded that, in the preparation of high-quality semifinished products by the technique of extruding granules of Al-Zn-Mg-Cu alloys, reductions of not less than 98–99% should be employed to rupture the double MgO and A1₂O₃ oxide films (at a granule size of 0.8–1.5 mm).Translated from Poroshkovaya Metallurgiya, No. 12 (84), pp. 14–18, December, 1969.     

Effect of sintering conditions on the structure and mechanical properties of P/M aluminum base alloys

Conclusions A magnesium addition promotes densification of Al-Cu alloy specimens sintered for short periods of time in the range 595–635C. Longer sintering at 615 and 635C results in higher specimen porosity. At a temperature above 595C Al-Cu alloys experience severe coarsening. Alloying with magnesium does not significantly affect the structure of the alloys. A magnesium addition improves the mechanical properties of an Al-Cu alloy. The extent to which magnesium alters the mechanical characteristics of heat-treated Al-Cu alloys depends on sintering conditions. The highest strength — 340 MPa and =6% — is exhibited by specimens sintered for 45 min at 595C.Deceased.Translated from Poroshkovaya Metallurgiya, No. 9(297), pp. 29–34, September, 1987.     

Plasma coatings made from magnetite and their use in electrolysis installations

Spraying parameters for plasma coatings made from commercial magnetite powders of different particle size on steel and titanium substrates are studied. On the basis of microstructure, phase composition, and bond strength as functions of the initial particle size optimum spraying parameters are obtained for preparing magnetite coatings 300–1500 m thick. The results are used for spraying active layers on sheets 250 × 500 mm in size for electrodes in electrolytic water purification.Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 52–56, May-June, 1996. Original article submitted June 3, 1994.     

Structure and properties of powders of some composite materials based on wurtzite boron nitride

Conclusions Addition of titanium carbide and zinc or aluminum oxide to a granulating blend of wurtzite boron nitride produces a low-strength sintered mass which disintegrates easily along the BN granule boundaries under mechanical action, ensuring the production of granules of a given grain size.Individual particles of composite material based on wurtzite boron nitride obtained with admixtures of zinc oxide are characterized by good compressive strength.Translated from Poroshkovaya Metallurgiya, No. 6(270), pp. 81–85, June, 1985.     

Preparation and some chemical properties of magnesium silicide

Conclusions A study was made of the synthesis of magnesium suicide from the elements in an inert medium. It was established that the magnesium silicide Mg2Si is obtained after 1.0–1.5 h at 750–800°C in argon with a magnesium excess of 3.0–3.5 wt.% in the starting mixture.Translated from Poroshkovaya Metallurgiya, No. 5 (77), pp. 29–32, May, 1969.     

Effect of oxidation on the strength of silicon nitride base reaction sintered ceramics

Conclusions Oxidation of silicon nitride base reaction sintered material at 1400°C with subsequent removal of the oxide layer makes it possible to increase the strength of the material at 20°C by 20%. On the other hand, short-term strength at 1400°C after such treatment is lower than the strength of nonoxidized specimens, yet it is still greater than the strength of oxidized specimens from whose surface the oxide layer was not removed.The increased strength of specimens after oxidation is mainly connected with the fact that defects in the subsurface layers of ceramics are healed by the oxide phase and that impurities are removed from the inner layers. Reduced strength is usually caused by the formation of an oxide layer with high concentration of defects on the surface of the specimens or by considerable internal stresses arising in the specimen.Translated from Poroshkovaya Metallurgiya, No. 5(281), pp. 40–44, May, 1986.     

Purification of metal powders from oxide films in a jet mill

Conclusions During the jet comminution of metal powders covered with oxide films the latter shear off, and their particles detach themselves from the main volume of material. The amount of oxygen decreases during purification by a factor of 2–17 depending on the oxygen content of the starting material and the latter's hardness and particle size. The removal of oxide films is virtually completed in 5–30 min depending on the properties of the starting powder. For the purification of powders low-pressure (0.5-MPa) compressed air can be employed. During the comminution of powders covered with oxide films, in certain circumstances detached film particles may find their way into the comminuted material.Translated from Poroshkovaya. Metallurgiya, No. 2(230), pp. 1–4, February, 1982.E. A. Filler, of the Special Design and Technology Bureau of the Chemical Engineering Industry, also took part in this work.     

Carburization processes during the sintering of iron-graphite materials

Summary The authors investigated the effect of the oxide content of iron powder on the microstructure and strength characteristics of sintered iron+3% graphite material. It was found that raising the oxide content of the iron powder in the charge results in the formation of abnormal hypereutectic structures and a sharp fall in the compressive strength of the material.Some decrease in the structural abnormality of sintered iron-graphite material prepared from iron powder with a high (2% or more) oxide content is attained by decreasing the duration of sintering and increasing the cooling rate of the sintered material.The use of iron powder with a total Fe content of less than 98% in not recommended.Paper to the Fifth Republican Scientific-Technical Conference on Powder Metallurgy, Kiev, March 29–31, 1966.Translated from Poroshkovaya Metallurgiya, No. 1(49), pp. 14–19, January, 1967.     

Effect of the properties of the surface oxide layers on the oxidation of aluminum powders

Conclusions The oxidation of ASD-4 and AV-000 aluminum powders in the temperature range 293–1773°K has been studied by the thermogravimetry (under conditions of programmed heating), thermal argon desorption, and x-ray phase analysis methods. The stresses generated during heating in the outer oxide films on aluminum particles lead to the formation of cracks in the former, which promotes oxidation of the aluminum. Marked increases have been observed in the oxidation rate and specific surface of the ASD-4 powder at temperatures corresponding to the temperature range of the -Al₂O₃ transition. The finding appears to be linked with an increase in the intensity of crack formation during the polymorphic transformation and with enhanced diffusional mobility in the oxide layers.Translated from Poroshkovaya Metallurgiya, No. 2(302), pp. 1–5, February, 1988.     

Effects of a getter on nio reduction kinetics and metallic nickel particle formation

Studies have been made on the kinetics of nickel oxide powder reduction by hydrogen in the presence of calcium oxide as a water vapor getter. The getter influences the reduction mechanism and the coalescence of the reduced metal as well as the growth of fresh surface. Data are presented on the fresh surface of the nickel powder formed in the presence of calcium oxide and in the absence of it as regards reduction kinetics.Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 79–83, May—June, 1996. Original article submitted June 29, 1994.     

连铸坯表面氧化铁皮除不尽原因及对策

 采用SEM对连铸坯表面氧化铁皮除鳞除不尽的原因进行分析。分析结果表明：Q235B、Q345B和SPA-H连铸坯内层氧化铁皮呈楔形嵌入钢基体中,嵌入钢基体中的氧化铁皮主要为铁橄榄石—Fe2SiO4相,随着钢基体中硅含量的增加,嵌入钢基体中的铁橄榄石相增加,使得内层氧化铁皮与钢基体的附着力增加,造成连铸坯表面氧化铁皮除鳞除不尽。针对连铸坯氧化铁皮除鳞除不尽的原因,提出相应的研究对策：一方面,优化加热炉工艺,控制高压水除鳞前连铸坯温度在1173℃以上;另一方面,优化高压水除鳞系统参数,增加高压水除鳞效果。     

Chemical reaction of aluminum alloy powders with water

Conclusions As a result of an investigation into the reaction of powders of several aluminum alloys with water it was established that the most active with respect to water are aluminum alloys containing magnesium, lithium, zinc, and other active elements. The rates of the reactions of these alloy powders with water are determined by the following factors: alloy composition, water and powder temperatures, and suspension concentration (s1). The highest rate of reaction with water (of the three industrial powders investigated — AMLD, PV-90, and SAS-1) is exhibited by the AMLD alloy powder, which contains lithium. The reaction of such alloy powders with water can be retarded or even completely prevented by the introduction of inhibitors — a measure permitting safe handling (e.g., hydrostatic pressing) of all aluminum alloy powders.Translated from Poroshkovaya Metallurgiya, No. 8(308), pp. 15–19, August, 1988.     

Microstructure Characteristics and Mechanical Properties of Al 413/Mg Joint in Compound Casting Process

Al 413/Mg couples were prepared by the compound casting process. Characterization of the interface by an optical microscope and scanning electron microscope (SEM) showed that a relatively uniform interface composed of three different layers is formed at the interface. The thickness of the interface depended on the melt/insert volume ratio (VR) significantly and was 80?and 470? ??m? in 1.25?and 3?VRs, respectively. The results of the energy dispersive X-ray spectroscopy (EDS), wavelength dispersive X-ray spectroscopy (WDS), and X-ray diffraction analysis showed that the interface layers are mainly composed of Al₃Mg₂, Al₁₂Mg₁₇, and Mg₂Si intermetallic compounds. An accumulation of magnesium oxide films was detected within the (Al₁₂Mg₁₇?+???) eutectic structure of the interface next to the magnesium base metal. Despite different thicknesses of the interface, shear strengths of the Al 413/Mg couples prepared in 1.25?and 3?VRs were almost same. The study of the fracture surfaces of the Al 413/Mg couples revealed that the accumulated magnesium oxide films act as a weak point for initiation of longitudinal cracks and failure of the joint.