Effect of the grain composition of the batch on the structure and properties of periclase refractories

Conclusions The structure and properties of periclase articles have been studied as a function of the quality of the powders and the grain composition of the batch. The possibility of obtaining periclase refractories with a high density (open porosity 8–12%) and heat resistance (11–16 heat cycles into water) is shown. In order to obtain strong dense articles with an enhanced heat resistance, it is recommended that dense powders with a fine-crystal structure be used; additional recrystallization during the high-temperature firing helps to strengthen the articles.The addition of 1% ZrO₂ improves the properties of the articles, which is the result of the strengthening of the diffusion processes capable of forming strong direct bonds between the periclase crystals in the aggregates and the bonding material.Deceased.Translated from Ogneupory, No. 2, pp. 52–57, February, 1979.     

Improving the quality of electrical-engineering periclase by antihydration treatment

Conclusions The treatment of powders of electrical engineering periclase in the silicoorganic liquid GKZh-94 makes it possible to eliminate hydration during storage and to increase the electrical resistivity.The solvent for the GKZh-94 has been selected, and the optimal concentration of its solution to ensure the most effective protection of the periclase powders from hydration has been established.Translated from Ogneupory, No. 6, pp. 25–27, June, 1986.     

Periclase refractories from imported powders

Ten charges with different compositions were obtained from periclase refractories and used to investigate the parameters of periclase articles. The properties of articles of industrial size prepared from imported powders did not differ from those prepared from Satkinsky periclase.Translated from Ogneupory, No. 2, pp. 5 – 7, February, 1995.     

Chromite-periclase roof articles

An investigation of the technology for chromite-periclase roof articles is presented. With a scarcity of periclase powders compositions with 25–30% granular chromium ore and 35% finely milled mixture of periclase and chromite seem a suitable material for chromite-periclase roof linings. It is possible to use charges with 65% scrap. Specifications have been developed, experimental batches produced and tested, and industrial-scale production begun.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 8, pp. 34–37, August, 1996.     

Microhardness of fused periclase

Conclusions The microhardness of fused periclase has been studied. It is shown that the microhardness of periclase is significantly affected by defects in the structure, in particular, by the dislocation density and the presence of impurity oxides.When fused periclase is heat-treated at 1000–1400°C which reduces the dislocation density by approximately two orders of magnitude, the microhardness of periclase is decreased. The reduction in the microhardness helps to increase the electrical resistance of the periclase as a result of both a decrease in the dislocation density and also, obviously, of the change in the packing density of the particles if the electrical resistance is measured in tubular electric heaters.The reduction in the microhardness helps to improve the ease of pressing of the refractory articles manufactured using fused periclase.Translated from Ogneupory, No. 4, pp. 10–13, April, 1984.     

Properties of powders of fused spinels and periclase pulverized by different techniques

The properties of electrofused spinel and periclase powders prepared by different milling techniques are reported. Vibratory milled specimens display a higher structure imperfection of the surface, and the amorphous surface layer differs compositionally from the percursor material. In the pulverized products, contaminating elements (Na, Si, and, to a lesser extent, Fe) tend to migrate towards the surface of particles. Vibro-milled powders show a better sinterability in comparison to jet-milled powders. Pulverization produces little effect on the properties of precursor fused periclase.__________Translated from Novye Ogneupory, No. 12, pp. 36 – 42, December, 2004.     

Microstructural Study of Periclase Powders for Production of Periclase-Carbon Components

Results of a microstructure analysis of periclase powders (from China) of fractions 3 – 1 mm are reported. In the production of refractory materials for the lining of steel ladles, preference should be given to fused periclase powders.     

Sintering of magnesium hydroxide obtained from magnesium chloride solutions

Conclusions We studied two batches of magnesium hydroxide obtained by precipitating out (using dolomite milk) from magnesium chloride solution formed when processing potassium ores.The effect of the compaction pressure, the firing temperature, and prior heat treatment on the sintering process of magnesium hydroxide was investigated.The experimental samples of magnesium hydroxide exhibit high sinterability and facilitate the production of periclase powders (powder bodies) having a porosity of 6.8–9.9% at a firing temperature of 1600°C. The degree of sintering of magnesium hydroxide increases with increasing compaction pressure and firing temperature. Prior heat treatment of the material at 800–1000°C intensifies the sintering process with simultaneous reduction of shrinkage.The studies conducted on the specimens prepared from a fired briquette established that the periclase (magnesite) powder obtained from magnesium hydroxide is suitable for the production of magnesia refractories.A. V. Kushchenko and G. G. Eliseeva (UkrNIIO) participated in this investigation.Translated from Ogneupory, No. 2, pp. 7–10, February, 1988.     

Ways Toward Improving the Technology of Refractories Based on Powdered Periclase

Periclase powders available from domestic (Magnezit JSC) and foreign manufacturers are analyzed for chemical and mineralogical composition. Domestic magnesite is shown to differ from its foreign analogs in smaller values of MgO content, CaO/SiO₂ ratio, and periclase crystal size. A way toward obtaining high-quality powers involves reducing the concentration of SiO₂ in magnesite to 0.2 – 0.5% and increasing the calcination temperature to 2000 – 2100°C to prepare coarse-grained periclase with a crystal size larger than 140 m. The need for developing a technology that would enable fabrication of refractory components with tailored structural properties from periclase powder is emphasized.     

Production of fused periclase from natural raw materials

Conclusions The properties and microstructure of periclase were studied. The influence of the original raw materials on the chemical composition and microstructure of periclase across the zones was established. In any raw material the minimum quantity of periclase impurities is noted in the single-crystal zone, but partial removal of impurities during fusion is not sufficient if the original raw materials do not possess the necessary purity. The use of chemically enriched Tal'sk magnesite improves the properties of periclase and the homogeneity of the block across the zones. It is necessary to carry out systematic research work on the preparation of raw materials and to elucidate the optimum parameters for fusion technology, ensuring improvements in the quality of the periclase.Translated from Ogneupory, No. 7, pp. 5–11, July, 1972.     

Methods of quantitative evaluation of the efficiency of mixing working solutions in man-made fibre manufacture

Conclusions Relationships have been obtained which permit one to estimate quantitatively the efficiency of various liquid media mixers.Methods have been given for solving problems of selecting an optimum structure of the mixing unit in technological schemes and for calculating the mixer volume which ensures obtaining an assigned value of the dispersion of a quality index of the mixture in the outlet stream.Translated from Khimicheskie Volokna, No. 1, pp. 15–17, January–February, 1988.     

A Study of Magnesites of Provenance from the Goluboe Deposit (Krasnoyarskii Krai) and Their Laboratory Tests for Technological Applications at the Kombinat Magnezit Joint-Stock Co.

Results of a preliminary study of the composition and properties of magnesites of provenance from the Goluboe deposit (Krasnoyarskii Krai, Russia) are reported. All magnesites, irrespective of their varietal, structural, and textural features, can be considered as acceptable raw materials. The concentration of impurities and inclusions in a high-quality magnesite does not exceed 1.5%, whereas in low-quality magnesites (2nd grade) they are within 3 – 8% of the total mineral composition. The heat-assisted beneficiation or calcination of raw magnesite yields a material with 98% MgO and a CaO-to-SiO₂ ratio greater than 3, which provides means for producing high-quality periclase powders. Tests conducted under industrial conditions show that using technologies of fine grinding, pelletizing, and calcination at 2100°C makes it possible to prepare dense periclase clinker. Calcination of lumpy magnesite at still higher temperatures is not an efficient technique for dense periclase powders. Clinker technology is shown to be the best way towards obtaining periclase and periclase-containing powders using raw magnesite from the Goluboe deposit.     

Effect of calcium oxide on the hydration activity of the powders of electrical-engineering periclase

Conclusions The hydration activity of the periclase powders depends to a significant extent on the hydration of free calcium oxide. The hydration resistance of the powders can be increased by fixing calcium oxide in the hydration-resistant compounds with silicon and magnesium oxides.It is also necessary to decrease the specific surface of the periclase powders for decreasing their ability to absorb moisture.Translated from Ogneupory, No. 8, pp. 9–12, August, 1988.     

Laboratory-scale technological studies on periclase refractories

Conclusions Laboratory-scale technological studies were carried out for developing the technology of periclase products based on different magnesite powders. Our studies showed the possibility of producing periclase refractories meeting the property specifications of GOST 4689-74 from certain imported powders.Translated from Ogneupory, No. 7, pp. 13–16, July, 1988.     

Structure and properties of fused periclase and periclase-chromite blocks produced from beneficiated starting materials

Conclusions Fused periclase and periclase-chromite blocks containing a high proportion of highmelting oxides of magnesium and chrome were produced from beneficiated starting materials.The structure and properties of the periclase and periclase-chromite were analyzed zonewise in the blocks. The thickness of the block zones with a high content of magnesium oxide and the yield of high-quality periclase and periclase-chromite depend on the degree of purity of the chemical composition of the starting materials.The content of magnesium oxide is highest and the proportion of contaminating oxides low in fused periclase produced from chemically beneficiated Satkin magnesite, and in the monocrystalline subzones of the blocks. An increase in the proportion of chromite in the mix results in a higher porosity and in a higher content of spinel and ferrochrome in the fused material. The properties are optimal in the case of a periclase-chromite material from a mix containing 15–20% chromite.Translated from Ogneupory, No. 3, pp. 37–44, March, 1978.     

Influence of the binder on the strength of a periclase green part

Conclusions The investigations showed that to provide a high quality of periclase parts from difficult-to-sinter powders (Koreisk type) it is desirable to use Solikamsk Combine lignosulfonates, which provide higher strength of the green part and increased properties of the fired parts, as the plasticizing and cementing addition.Translated from Ogneupory, No. 1, pp. 38–40, January, 1990.     

Production technology and quality of fused periclase

Conclusions A relationship was established between certain technological parameters, properties, and structural features of fused periclase.It was shown that the main factors in obtaining high quality periclase are the purity of the raw materials, determining the high MgO concentration in periclase; rational fusing cycle, ensuring migration of the impurities into the skin of the block and governing the features of the structure of the crystals; magnetic separation, permitting the ferromagnetic particles and part of the silicates to be removed; and crushing and milling, ensuring the optimum grain-size composition in the powder.A properly selected combination of these factors will improve the quality of the fused periclase and increase the resistance of periclase thermoelectric heating elements and refractories in service.Translated from Ogneupory, No. 2, pp. 5–10, February, 1979.     

Refractories from fused periclase

Conclusions High-grade refractories can be produced from periclase containing at least 97% MgO by preparing a suitable grain size distribution with a vibro-ground component in the powder, molding in stages at high specific pressures (1500–2000 kg/cm²), and firing for 8 h or more at a high temperature (1750°C or higher).Translated from Ogneupory, No. 6, pp. 5–8, June, 1974.     

Scalable and tunable Y2O3-MgO composite for infrared transparency applications

The process-structure-property correlationships in yttria-magnesia (YM) composite have been investigated. YM composite was synthesized using commercial powders via ball-milling route with three different grinding balls (Si₃N₄, Al₂O₃, ZrO₂) having two different sizes (2 and 5 mm diameter). The alteration in grinding ball material and size produces sintered ceramic having different grain sizes (420–560 nm) and degree of phase mixing homogeneity (0.40–0.70). The contamination induced by the milling ball resulted in changes in Y₂O₃ and MgO defect chemistry, which influenced the grain growth behavior in the YM composite. The hot-pressed composite prepared using 2-mm Si₃N₄ ball-milled powders exhibited the finest grain size (420 nm) and better phase mixing homogeneity (0.63). The subsequent impact was seen on transmittance efficiency (71%) over the 3–7-μm wavelength range, which is ∼85% of the theoretical limit. The findings show that the selection of the right size and type of grinding ball for milling commercial powder is a simple and cost-effective way for scalable production of YM composite with high transmittance efficiency for infrared windows and dome applications.     

Manufacture of periclase plates for gate valves

For the utilization of rejected periclase inserts and drilling wastes from the manufacture of composite valve gates, we suggested that the rejects and wastes be used as a fine-ground component of the charge. Investigations have been conducted of the periclase powders received from rejected inserts and drilling wastes. It has been found that the powders received possess higher activity to sintering and lower hydration ability as compared with common fused periclase powder. We have produced experimental batches of plates with inserts from a charge containing rejected inserts and drilling wastes. The manufactured articles possess high physico-technical characteristics and high operating properties.Translated from Ogneupory, Vol. 35, No. 1, pp. 18 – 21, January, 1994.