Papers by Keyword: RF Plasma

Abstract: . The calculation of nominal values of the matching device for the modified plasma chemical etching installation "Plasma 600T" was based on the estimated values of the discharge impedance (plasma). It turned out that for optimal performance, one can use a matching device consisting of two capacitors whose capacitances are: С₁ [20; 1000] pF, С₂ [4; 100] pF, and inductor with inductance 2,5 μH.

Abstract: Ar\H₂\CH₄ gas mixture was utilized to grow nanocrystal diamond films in a RF plasma enhanced CVD system. CH₄\ H₂ ratios were changed to study the effect of plasma radicals on the deposit, in which optical emission spectroscopy (OES) was applied to analyze the plasma radicals. It was found that H_α, H_β, H_γ, CH, C₂ were the main radicals in the plasma. Among them, the CH intensity of OES was usually quite strong and increased sharply when the ratio of CH₄/H₂ was greater than 3%. The intensity of C₂ was weak and basically unchanged with the addition of methane. This study can provide a new possible technical application for depositing NCD films.

Abstract: Surface hardening on local bolt (C = 0.071%) with Radio Frequency (RF) - plasma nitrocarburizing apparatus has been carried out. Some local bolt component was cleaned with distilled water. The type of material of local bolt component was low carbon steel, carbon concentration 0.071%. After that the local bolt component was cleaned with acetone. The natural oxide layer on the surface of the local bolt material was etched with HF for 1 until 3 minutes. The local bolt component was cleaned again with distillation water. Then the local bolt component was sprayed with nitrogen gas. After that the local bolt component was hardened on the material surface with RF plasma nitrocarburizing at a temperature of 400 °C, for holding time 7 hours. Sample number 1 was sample before nitrocarburization. Sample number 2 was sample after nitrocarburization at a temperature of 400 °C, for 7 hours. Then the local bolt component was cut with mower as samples for microstructure observed. The samples were mounted, polished, and etched for microstructure observation with optical microscope. The surface hardness of the samples was tested with O.M.A.G micro-hardness Vickers, MHX 10, apparatus. The expenses tracking was 300 grf, and the times tracking was 15 seconds. The results show that the hardness of sample of bolt before nitrocarburization was 154.5 Kgf/mm², after the sample was nitrocarburized at a temperature of 400 °C for 7 hours, the maximum hardness on the surface increased up to 205.6 Kgf/mm². Matrixes on the base material were austenite, ferrite, and perlite.

Abstract: A study of surface hardening on local bolts (C=0.01%) at a temperature of 400°C for 5 and 6 hours with nitrocarburizing using RF-plasma apparatus. The objective of this experiment was to seek a surface material of local bolts that is more resistant to friction and having better surface uniformity, higher hardness and higher corrosion resistance. The experiment was conducted on the local bolts (C = 0.01%) with a radio-frequency (RF) plasma nitrocarburizing equipment. The nitrocarburization was done on the local bolts at a temperature of 400°C, with a variation of nitrocarburizing times of 5 and 6 hours. The results showed that the average hardness of local bolt samples before nitrocarburization was 136.08 kgf/mm². After nitrocarburization at a temperature of 400°C for 5 hours, the average hardness of local bolt samples was 199.1 kgf/mm². After nitrocarburization at a temperature of 400°C for 6 hours, the average hardness of local bolt samples was 201.12 kgf/mm². The matrixes on the base material were ferrite, austenite, and pearlite.

Abstract: Spherical niobium powders were synthesized by (RF) argon plasma with irregular niobium powders in this paper. The objective of the present work was to investigate how the feeding rate influence the spheroidization efficiency. The phase composition, morphology and particle size distribution of the powders before and after spheroidization were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser micron sizer (LMS). The results show that niobium powders after plasma processing have good dispersity and smooth surfaces, and their spheroidization ratio is almost 100%. The apparent density and flowability of the powder with the spheroidization efficiency 100% is 4.35 g/cm³ and 12.51 s/(50g), respectively. With the increasing of the feeding rate, the spheroidization ratio of niobium powders drops gradually.

Abstract: Spherical molybdenum powders were synthesized by (RF) plasma with irregular molybdenum powders. The powder characteristics and spheroidization efficiency of the feeding rate for obtain the spherical molybdenum powders were studied. The phase composition and morphological properties of the powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). As a result, the fine spherical powders composed of pure molybdenum with favorable dispersity and its surface became smooth. The spheroidization efficiency of synthesized powders was almost 100 % at feeding rate of 5g/min. LMS analysis indicated that the as-prepared powder had narrow particle size distribution and the spheroidization efficiency of the sample decreases gradually as increasing of the feeding rate. The RF plasma spheroidization of molybdenum powder is an ideal route synthesis of well- spherical molybdenum powders used as near net-shape technology and powder metallurgy.

Abstract: Nickel nanoparticles were synthesized from liquid precursor via H-plasma reduction route. XRD patterns revealed that pure metallic nickel powders could be obtained when nickel ammine complex aqueous solution was used as precursor. FESEM showed that the products are composed of well-dispersed nanospheres with an average diameter less than 100 nm. The tap density is about 3.85g/cm³, and the sheet resistance of the conductive film prepared using the nickel particles is about 58mΩ.

Abstract: Spherical tungsten powders were synthesized by (RF) argon plasma with irregular tungsten powders in this paper. The microstructure and crystallographic phases of the synthesized powders were characterized using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The results showed that fine spherical powder composed of pure tungsten phase with favorable dispersity and its surface becomes smooth. The spheroidization efficiency of synthesized powders was almost 100 %, and the particle size distribution became narrower after spheroidization treatment. The spheroidization efficiency of the sample decreases gradually as increasing of the feeding rate. The RF plasma spheroidization of tungsten powder is an ideal route synthesis of well- spherical metallic tungsten powders which is widely used in thermal spraying and metal injection moulding process.

Abstract: A non invasive ex-situ harmonic probe technique was used to characterize the plasma-generated harmonics of Ar/O2 plasma. To extract the harmonics, we used an iterative least-squares curve fitting algorithm and taking into account the presence of parasitic electrical elements. This study reports the influence of the process parameters on the harmonic response (from 2nd to 7th) to reveal the most sensitive electrical measurements that represent faithfully the evolution of the plasma. The electrical response of the matching network and the electrical model circuit chamber was taken into account.