Quality control of hot-pressed silicon nitride dielectric materials

Conclusions Exceeding an optimum temperature in the pressing of silicon nitride parts leads to the appearance of conducting inclusions (SiC and free Si) in specimens, while pressing at temperatures below the optimum temperature increases the porosity of specimens and hence the amount of water absorbed by them. With rising conducting inclusion content the electrical conductivity, , and tan of a material grow and its E_br falls. Increasing porosity has, by increasing water absorption, a similar effect. The coefficient of losses at a frequency of 1 kHz can be employed as a criterion for assessment of the quality of dielectric materials based on silicon nitride.Translated from Poroshkovaya Metallurgiya, No. 3(231), pp. 53–59, March, 1982.     

Effects of chemicothermal treatment of aluminum nitride powders on the structure and properties of the resulting hot-pressed ceramic

Preliminary treatment in hydrogen for aluminum nitride powders (before hot pressing) affects the strengthening and structuring of the ceramic. There is a positive effect from the gas heat treatment on account of recrystallization during sintering and increase in plasticity of the aluminum nitride due to the hydrogen dissolved in the lattice.Materials Science Institute, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1/2(377), pp. 76–81, January–February, 1995.     

Comparative examination of the corrosion and electrochemical properties of chrome nitride and carbonitrides

Translated from Poroshkovaya Metallurgiya, No. 4(316), pp. 88–91, April, 1989.     

Nonstoichiometry and physical properties of hot-pressed manganese-zinc ferrites

Conclusions Changing the pressure in the hot pressing of manganese-zinc ferrites affects both the composition and state of the solid-phase system and the structural characteristics of specimens. With rise in hot-pressing pressure, the Fe²⁺ concentration, density, Curie temperature, and degree of inversion increase; there is also a tendency for the initial magnetic permeability to fall and for the crystallite size to grow. An interrelationship is shown to exist between the Fe²⁺ content of manganese-zinc ferrospinel on the one hand and the degrees of nonstoichiometry and inversion on the other.Translated from Poroshkovaya Metallurgiya, No. 8(236), pp. 80–85, August, 1982.     

Structure and properties of hot-pressed boron carbide base ceramics

Translated from Poroshkovaya Metallurgiya, No. 7(331), pp. 16–20, July, 1990.     

Influence of oxidation on the strength of hot-pressed silicon nitride ceramic at high temperatures

The authors thank L. V. Lavriv and O. V. Ivashchenko for their help in conducting the experiments.     

热压碳化硼材料的纳米摩擦性能研究

用原子力/摩擦力显微镜对碳化硼样品进行了表面形貌的微观分析。在载荷为1～6μN下,研究了Si_3N_4探针扫描碳化硼表面时摩擦力的分布。结果表明,摩擦力的变化与扫描处的试样表面形貌有关,表面形貌变化斜率越大处,摩擦力增加得越多。由于试样较平整,摩擦力的分布也是比较均匀的。碳化硼材料纳米摩擦因数随载荷的增加而显著增加。     

二苯碳酰二肼分光光度法测定氮化硅铁中铬

氮化硅铁是一种重要的耐火材料,实验研究了应用二苯碳酰二肼分光光度法测定氮化硅铁中铬元素含量的分析方法。针对试样分解方法、氧化条件、显色条件、干扰消除等进行了试验研究,确定了最佳分析条件。试样于镍坩埚中以2 g氢氧化钠作为熔剂在650 ℃熔融10 min分解,在热水中浸取熔块后,以氢氟酸、高氯酸冒烟除去试样中的硅元素。用硫酸(1+9)溶解盐类后,在硫酸介质中以2.0 mL 10 g/L高锰酸钾溶液氧化铬至正六价,再加入过量的200 g/L碳酸钠溶液沉淀分离铁、镍等共存元素,最后在0.05～0.2 mol/L硫酸中利用铬与二苯碳酰二肼反应显色对其进行了测定。应用实验方法对氮化硅铁样品进行测定,测定值与电感耦合等离子体原子发射光谱法(ICP-AES)测定值一致,测定结果的相对标准偏差(RSD,n=11)小于2%;加标回收试验结果表明回收率为101%。     

Manufacture of silicon nitride parts and properties of silicon nitride

Conclusions A study was made of the manufacture of parts from silicon nitride powder and of some properties of this compound. It was established that the composition of the material in which parts are packed during sintering exerts a strong influence on the strength properties and other characteristics of the resulting silicon nitride. Explanations are offered for the low microhardness of this material and the mechanism of its erosion wear.Translated from Poroshkovaya Metallurgiya, No. 4 (112), pp. 53–56, April, 1972.     

Scale resistance of chromium nitride sintered under high pressures

Translated from Poroshkova Metallurgiya, No. 10(322), pp. 97–100, October, 1989.     

Corrosion resistance of cermets based on titanium nitride

Conclusions The corrosion resistance of the cermets based on TiN with (Ni, Mo, Cr)-binder containing 10–15% Cr, is higher than that of KKhN-15 alloy and MNTs-20 German silver in solutions of acids: 5% HCl, 7% HNO₃ and 10% H₂SO₄.The resistance of the cermets based on titanium nitride is 5% HC1 decreases in the sequence: TiN-Cr > TiN-Ni, Mo, Cr > TiN > TiN-Ni, Cr > TiN-Ni, Mo > TiN-Ni.The corrosion resistance of the TiN-Cr cermets is slightly higher than the resistance of TiN. This is associated with the formation of the double nitride (Ti, Cr)N.Alloying theTiN-(Ni, Mo) cermet with 10–15% chrome results in high corrosion resistance and satisfactory physicomechanical properties.The corrosion resistance of the alloys with a high binder content (>25%) decreases as a result of its preferential dissolution which leads to separation of the titanium nitride grains. In addition to selective dissolution of nickel and molybdenum, the corrosion process in these alloys is also determined by dissolution of chrome.Translated from Poroshkovaya Metallurgiya, No. 1(337), pp. 77–81, January, 1991.