High-temperature Plasma Jet Research Articles

Rapidly solidified Al-alloy powders produced by the plasma melt and rapid solidification (PMRS) method

Plasma spraying is a line-of-sight process involving the injection of a powder feedstock into a high-temperature plasma jet. Rapidly solidified powder in the size range < 1–50 μ m can be produced through the fragmentation of the molten or semi-molten particles upon impact on a solid substrate. This paper reports the production of rapidly solidified powders in the systems AlSi, AlTi and AlNi using the plasma melt and rapid solidification (PMRS) technique. The experiments show the process/microstructure relationship in the production of these powders. Examination of the powders was carried out using metallographic techniques involving optical microscopy, scanning electron microscopy (SEM) with EDAX and X-ray diffractometry (XRD). The particle-size distribution of the powders was obtained by a X-ray sedimentation method. The results show that the particle-size distribution and microstructure of the powder are dependent on a number of factors which include the substrate rotating speed, the distance between the plasma torch and the rotating substrate, the plasma gas composition and the initial size of the powders. For low melting-point alloys such as AlSi, the determining factor is the rotating substrate speed; however, for high melting-point alloys such as AlTi, the auxiliary gas flow is an important factor.

Heating of polymer particles in plasma-jet sputtering

The heating of polymer particles on interaction with a high-temperature plasma-jet flux is considered. The distribution of the particle temperature fields at various Biot numbers is established.

Preparation of spherical particles of Ba2YCu3O7?x superconductor by plasma spraying

Ground angular powder of pre-synthesized Ba2YCu3O7−x was introduced into a high-temperature plasma jet flame with argon as the plasma gas. Morphological changes in the particles and in microstructural features, as well as phase changes, were observed on the plasma-sprayed powder. Spherical particles with various surface topographies were formed: smooth surface with fine grain structure; spiky surface; and polygonal surface structure. X-ray phase analysis showed that the plasma-sprayed powder was a mixture of solidified crystalline and amorphous phases from the liquid state, while the metallic composition of the starting powder was retained. The plasma-sprayed particles were subsequently annealed for 20 to 80 h in air at temperatures up to 1123 K. The superconductor phase was recovered by this heat treatment, while the particles became porous with morphological changes in surface topography.

Ablation experiments of heat-resisting ceramics SiC and Si3N4 in high-temperature Ar plasma free jets.

Experimental measurements of the ablation properties of the fine ceramics SiC and Si3N4 are performed in an atmospheric high-temperature argon plasma jet. The effective heat of ablation is measured for the heat flux of 1.2∼2.6×104 kW/m2. It is found to be about 2×104kJ/kg for Si3N4 and 5∼8×104kJ/kg for SiC. In addition, features of the ablated surface of the materials are observed with the aid of an electron microscope, and on this basis, the mechanism of the ablation is discussed.

On a Self-Absorption of Radiation in a High Temperature Plasma Jet

On a Self-Absorption of Radiation in a High Temperature Plasma Jet

Radiated Power From a 2-In. Sphere of High Temperature Air at Pressures to 50 Atm

R energy losses in high temperature plasma jet operation can become quite significant at elevated pressures. A calculation has been performed, and is illustrated in Fig. 1, which gives the power in kilowatts radiated by a spherical volume of ionized air two inches in diameter. In the calculation the reflected emissive power is not accounted for, since the reflectivity is small and the re-absorption of power by the plasma is also small. The calculations were performed for enthalpy values of 4000, 8000 and 16,000 Btu per lb at pressures up to 50 atm. The radiated power Pr has been expressed as follows