Effect of boron nitride addition on some properties of aluminosilicate refractories

Conclusions An addition of 10–60 wt.% of boron nitride significantly alters the thermal conductivity, thermal expansion, and the elastic modulus of aluminosilicate refractories.As the boron nitride content is increased from 1–60% the strength of specimens heated in a nitrogen atmosphere with an oxygen content of 0.02% decreases.During cyclic heat treatment in an oxidizing atmosphere between 900 and 20°C additional bonds develop between the particles of the aluminosilicate and the oxygen-free additive. As a result the strength of the specimen increases.The thermal shock resistance of the specimens increases with an increase in the amount of boron nitride addition. Specimens with 40–50% boron nitride addition are in practice insensitive to temperature drops in the range 20–2400°C.Aluminosilicate refractories with the addition of 30–40 wt.% of boron nitride can be used as lining material in high temperature systems with brief nonsteady or cyclic work schedules.Translated from Ogneupory, No. 4, pp. 36–39, April, 1968.     

Effect of some properties of aluminosilicate refractories on their glass resistance

Conclusions The glass resistance of aluminosilicate blocks with similar porosity values depends mainly on the quantitative ratios of crystalline and glassy phases, their chemical composition, and the grain size of the mullite. The higher the crystalline phase concentration in the refractory (mullite and mullite+ corundum) the fewer the impurities (oxides of iron, titanium, calcium, sodium, potassium, etc.), and the coarser the grains of mullite, then the lower their corrosion by molten glass.An increase in the glass resistance of aluminosilicate blocks can be achieved by using pure clays and kaolins, and also by using high temperatures for firing, longer soaking periods, and also mineralizing additives.Translated from Ogneupory, No.6, pp. 40–44, June, 1970.     

Changes in the properties of aluminosilicate refractories under prolonged reducing conditions

Conclusions Studies of corundum and aluminosilicate refractories of dense and granular structures in an atmosphere of hydrogen and dissociated ammonia at 1200, 1500, and 1700°C in periods of 175 and 50 h showed that the resistance of the products increases with an increase in the alumina concentration and density. The maximum resistance is exhibited by corundum products. In the aluminosilicate refractories there is some additional sintering of the material with the separation of mullite and glass. Simultaneously on the surface of the specimens we detected deeper mineralogical changes, accompanied by the decomposition of the mullite, with the formation of corundum, silicon monoxide, and glass.The changes in the phase composition are accompanied by a change in the structure, and an increase in the creep. Considering that a reduction in the temperature of 100°C causes a reduction in the creep by approximately a half [26], it can be recommended that corundum refractories should be used (under a load of 2 kg/cm²) in a reducing atmosphere at temperatures of up to 1550–1600°C, sillimanite up to 1450–1500°C, kaolin and chamotte (high-grog) up to 1300°C, with a reduction in the load and an increase in the density, the temperature of application for the products examined, especially corundum, can be increased.Translated from Ogneupory, No.5, pp.26–32, May, 1972.     

Wetting of aluminosilicate refractories with cast iron

Conclusions The magnitude of the wetting angle of molten cast iron on aluminosilicate refractories depends on the structure, phase composition, and physicochemical properties of the solid material and the melt. An increase in the temperature from 1140 to 1500°C causes the wettability of the refractories by molten cast iron to increase as a result of the increase in the content and chemical activity of the liquid phase in the refractory.An increase in the open porosity of sintered kaolin refractories from 8 to 16% results in a decrease in the wetting angle of cast iron at 1350 and 1500°C from 122 to 108° and from 119 to 102°, respectively; at 1140°C the wetting angle increases with the open porosity.The largest wetting angles of cast iron occur on high-density mullite and kaolin refractories containing a minimum of glass phase.Translated from Ogneupory, No. 5, pp. 35–38, May, 1978.     

Wettability of aluminosilicate refractories with molten steel

Conclusions An increase in the Al₂O₃ content of the base causes the wetting angle of steel 10kp to increase with an increase in the temperature from 1490 to 1620°C.Chromium-nickel steel wets refractories to a greater degree than rimmed steel. In this case the wetting angle is largest on mullite-corundum refractories containing 75–78% Al₂O₃.The introduction of small amounts of modifying additives in the form of MgO and Cr₂O₃+ ZrSiO₄ into mullite-corundum and corundum refractories causes the wetting angle to increase by 7–10° and helps to increase the resistance of the refractory materials to the action of rimmed steel.Translated from Ogneupory, No. 4, pp. 53–56, April, 1978.     

Action of high temperature gas streams on zirconia refractories

Conclusions We investigated the erosion resistance of zirconia stabilized with CaO in the temperature range 1700–2350°C as a function of a gas current velocity of from 300 to 730 m/see.The erosion rate increases exponentially with temperature rise, and its dependence on the velocity of the current approximates to a linear rule. The highest erosion rate is noted in the first hours of the gas current action on the specimens, which is connected with the removal of impurities and weakly bonded grains, and also the formation of a surface layer of material.The erosion rate essentially depends on the composition and structure of the material.Incorporating potassium in the gas current increases the erosion rate 10–25%, but does not alter the nature of the relationship between the erosion and temperature of the current and its action time.Translated from Ogneupory, No. 6, pp. 45–50, June, 1968.     

Influence of addition of pyroxene raw material on the mechanical properties of aluminosilicate refractories

Conclusions A qualitative interpretation of the results of mechanical tests of specimens was obtained and the influence of the structure of a refractory on its strength properties was confirmed. It was shown that addition of pyroxene raw material in a quantity of 5–15 wt.% to an aluminosilicate base makes it possible to increase the bend strength by 7–35% and the heat resistance by 2.0–2.5 times and to decrease the abrasive wear of the parts by 2–4 times.Translated from Ogneupory, No. 4, pp. 32–34, April, 1990.     

Andalusite transformation and properties of andalusite-bearing refractories fired in different atmospheres

We found in our research that andalusite aggregate fired in a reducing atmosphere exhibits a lower mullitization rate than that fired in an air atmosphere. For investigating the effect of atmosphere on the transformation of andalusite and the properties of andalusite-containing refractories, andalusite powder (≤0.074?mm) and refractories containing andalusite aggregate (3–1?mm) were fired in air and carbon embedding, respectively. The phases and microstructure of the andalusite fired in both atmospheres were characterized by X-ray diffraction and scanning electron microscopy, respectively. The correlations of the properties of the andalusite-bearing refractories with the firing atmospheres were investigated in terms of volume stability, mechanical strength, and thermal shock resistance. The difference in the properties of the refractories was discussed with respect to the varied transformation rates of andalusite, and in terms of the different viscosities of the silica-rich glass caused by the different atmospheres.     

Beneficiation of aluminosilicate and magnesia secondary refractories

Conclusions The use of magnetic separation will enable us to separate from the refractory scrap, metal, slag, and refractories from the working zone impregnated with metal, and will ensure the production of standardized material in terms of chemical and grain-size composition and refractoriness. The exception is the chamotte scrap from steel-melting articles because of the low refractoriness (1500°C).The magnetic separation should be carried out in stages with a high magnetic field strength.Translated from Ogneupory, No. 1, pp. 40–43, January, 1987.     

Future application of aluminosilicate refractories for aluminum electrolyzers. Part 4. Wettability of aluminosilicate refractories with molten industrial electrolyte and sodium fluoride

Optical microscopy is used to determine wetting angles for aluminosilicate refractories with molten industrial electrolyte and NaF. Kinetic wetting parameters and interaction of electrolyte with refractory are determined. It is shown that removal of silicon from refractory also occurs in the form of silicon monoxide. It is established that aluminosilicate refractories, prepared with addition of mullite-corundum chamotte, are wetted worse by fluoride salts, but the corrosion resistance of them is better than for refractories prepared by normal technology. __________ Translated from Novye Ogneupory, No. 1, pp. 17–21, January 2008.     

Main factors affecting the thermal stability of aluminosilicate refractories

It is shown that the partial pressure of oxygen and thermocycling in variable gas media are the main factors characterizing the thermal stability of aluminosilicate refractories. The obtained functional dependences of the variation of the properties of the refractories are described by equations.     

海泡石和稀土对镍催化剂性能的影响

本文研究了海泡石和稀土Sm镍催化剂的苯加氢活性及CO_２甲烷化活性的影响，并用XPS、活性比表面积及CS_２中毒等方法表征了催化剂的表面性质。结果表明，海泡石和稀土Sm能提高镍催化剂的加氢活性和抗毒性，并能增大活性镍的比表面及镍上的电子云密度，降低CO_２甲烷化反应的活化能。     

Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 2. Resistance of aluminosilicate refractories to the action of commercial electrolyte

Data are provided for laboratory studies of the resistance of aluminosilicate refractories to the action of commercial electrolyte. It is established that refractory ShPD_M-45, prepared using a mullite-corundum chamotte, is most resistant to electrolyte action. Results are provided for studies in the change of mineral composition and phase transformations in aluminosilicate refractories during reaction with commercial electrolyte. It is shown that long-prismatic titanium-containing mullite is more resistant to the action of the fluoride ion than short-prismatic material. __________ Translated from Novye Ogneupory, No. 10, pp. 26–32, October 2007. Part 1 of the article was published in Novye Ogneupory No. 9 (2007).     

Study of the properties of nickel oxide and nickel as precursors for the tartaric acid-NaBr-modified nickel catalyst

Nickel oxide was prepared by the decomposition of nickel hydroxide and then the nickel oxide was reduced to form the nickel catalyst. The properties of the nickel oxide and the reduced nickel were studied in relation to the enantio-differentiating ability (e.d.a.) of a tartaric acid-NaBr-modified reduced nickel catalyst. The modified nickel catalyst prepared from nickel oxide with less non-stoichiometric oxygen produced a high e.d.a. for the hydrogenation of methyl acetoacetate. The high crystallinity of the nickel oxide and the resultant nickel would be required to attain a high e.d.a.     

Prospects for using aluminosilicate refractories for aluminum electrolyzers. Part 1. Features of the structure of aluminosilicate refractories intended for aluminum electrolyzers

Comparative analysis is provided for the structure and properties of aluminosilicate refractories grade ShPD. It is established that refractory ShPD_M-45, produced with the use of an addition of mullite-corundum chamotte surpasses in all characteristics refractories prepared by the normal technology. Refractory ShPD_M-45 may be recommended for use in aluminum electrolyzers. __________ Translated from Novye Ogneupory, No. 9, pp. 20–23, September 2007.