0020-1685/03/3903- $25.00 © 2003 MAIK “Nauka /Interperiodica” 0271 Inorganic Materials, Vol. 39, No. 3, 2003, pp. 271–275. Translated from Neorganicheskie Materialy, Vol. 39, No. 3, 2003, pp. 337–341. Original Russian Text Copyright © 2003 by Ushakov, Red’kin, Zharkov, Solov’ev. INTRODUCTION There is considerable technological interest in tita- nium nitride because it offers a high heat resistance, superior high-temperature strength, and good corrosion and wear resistance. However, the use of titanium nitride is limited because of its high sintering tempera- ture. One effective way of activating the sintering pro- cess is by using fine powders [1]. For this reason, ever increasing attention has recently been paid to the syn- thesis of ultrafine powders. The most widely used tech- nique for producing titanium nitride ultrafine powders is plasma synthesis [2]. Very recently there has been intense interest in the synthesis of ultrafine powders of refractory compounds, including titanium nitride, via evaporation of bulk materials and subsequent deposi- tion [3]. To evaporate materials, use is made of laser heating, electron beams, electric flashing of wire, and other techniques. The ultrafine titanium nitride powders prepared by such techniques are in a nonequilibrium, high-energy state. The enhanced activity of such pow- ders in compaction and sintering processes is due to the high excess energy associated with the large specific surface area and high density of structural defects. The relaxation processes at defects provide an additional energy and increase the mobility of metal atoms. The chief drawback of such approaches is poor control over the deposition process in supersaturated vapor flows [4]. This reduces the fraction of ultrafine particles, thereby raising the cost of the final product and affect- ing the engineering performance of the articles pro- duced from such powders. The formation of multicom- ponent compounds upon rapid evaporation of materials in reactive atmospheres has not yet been studied in suf- ficient detail. Low-pressure arc discharges are used mainly to gen- erate highly ionized plasma consisting of ions supplied by the electrode material being sputtered [5]. A serious impediment to wide application of low-pressure arc discharges for producing ultrafine powders is the for- mation of large, more than 1 μm in size, particles as a result of electrode erosion. Nevskii [6] showed that high-current low-pressure arc discharges have consid- erable potential for the preparation of ultrafine metal powders. Heating a mixture of an evaporant and plasma gas, followed by rapid quenching, allows one to obtain ultrafine powder with a much narrower particle-size distribution. Among the many parameters influencing the properties of ultrafine powders (porosity, nonmetal inclusions in the cathode, cathode temperature, nature of the plasma gas, magnetic field, and others), the resid- ual gas pressure in the vacuum system was shown to be of prime importance [7]. Increasing the gas pressure in the system reduces the mean energy of the forming par- ticles, which allows one to produce materials with dif- ferent structures, from amorphous to crystalline, and to control the particle size and shape. The purpose of this work was to investigate the effect of gas pressure on the properties of ultrafine tita- nium nitride powders produced by low-pressure arc- discharge synthesis. EXPERIMENTAL AND RESULTS We used the experimental setup described in detail previously [8]. The discharge current through the arc evaporator was 500 A. The longitudinal magnetic field generated by the focusing coil on the cathode surface was 0.1 T. As the cathode material, we used commercial titanium. The chamber was pumped down to 1 mPa and Effect of Gas Pressure on the Properties of Electric-Arc Titanium Nitride Powders A. V. Ushakov*, V. E. Red’kin*, S. M. Zharkov**, and L. A. Solov’ev*** * Krasnoyarsk State Technical University, ul. Akademika Kirenskogo 26, Krasnoyarsk, 660074 Russia ** Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036 Russia *** Institute of Chemistry and Chemical Technology, Siberian Division, Russian Academy of Sciences, ul. Karla Marksa 42, Krasnoyarsk, 660049 Russia e-mail: ushackov@mail.ru Received November 22, 2001; in final form, March 14, 2002 Abstract—Ultrafine titanium nitride powder is prepared by evaporating titanium in a high-current low-pressure arc discharge in a mixture of 20% N 2 and 80% Ar. It is shown that increasing the gas pressure to 32 Pa sharply reduces the particle size and improves the uniformity of the powder in particle size. The possible reasons for the markedly reduced lattice parameter of ultrafine titanium nitride are discussed.