Low-pressure plasma spraying

It has already been mentioned that one of most used forms of Ni is Raney Ni which is obtained from Ni-Al or Ni-Zn alloys by leaching A1 or Zn in alkaline solution. However, the properties of the resulting electrocatalyst appear to depend on the nature of the precursor [135], Methods of application of the alloys are various [135]. A particularly convenient one is the so-called LPPS (low pressure plasma spray) [146]. Raney Ni prepared in this way has shown that lower Ihfel slopes can be obtained, thus suggesting a real electrocatalytic effect (Fig. 11). On such highly porous Ni it is possible that the proportion of particularly active sites (at the edges and peaks of crystallites [262] increases considerably. However, the effect of temperature on the Tafel slope is more than anomalous [248] suggesting indeed some temperature-induced surface modifications. In fact, recrystallization phenomena are observed which can be minimized by means of small additions of Ti, Mo or Zr. The... 

Several methods effectively apply thin coatings to substrates. One process commonly employed for TBC fabrication is thermal plasma spraying. For this technique, the bond coat is deposited with low-pressure plasma spraying, and the Zr02 top coat is then created using atmospheric plasma spraying.A potential problem with this method is coating fracture due... 

Low-pressure plasma spraying (LPPS), a.k.a vacuum plasma spraying (VPS) is the injection within an evacuated spray chamber of metal or ceramic powder... 

Heimann, R.B. and Vu, T.A. (1997) Low-pressure plasma-sprayed (LPPS) bioceramic coatings with improved adhesion strength and resorption resistance. /. 

Heijlijers HJ, Driessens FC, Verbeeck RM (1979) Lattice parameters and cation distribntion of solid solutions of calcium and strontium hydroxylapatite. Calcif Tiss Inti 29 127-131 Heimann RB, Vu TA (1997) Low-pressure plasma-sprayed (LPPS) bioceramic coatings with improved adhesion strength and resorption resistance. J Thermal Spray Technol 6 145-149 Heimann RB, Vu TA, Wayman ML (1997) Bioceramics coatings State-of-the-art and recent development trends. Eur J Mineral 9 597-515... 

The ability of Ti-Cr-Al alloys to form protective alumina scales raises the possibility of applying them as protective coatings. Coatings have been successfully applied to y substrates by sputtering, low-pressure plasma spraying, high-velocity... 

At an industrial applications, the TBC coverings can be produced by thermal spraying method in the air plasma spray (APS) atmosphere, at lowered pressure low pressure plasma spray (EPPS) from APS or by the electron beam physical vapor deposition method (EB-PVD), these are all dry-route processes. By these processes, coatings have different microstructures lamellar microstructure consisting... 

Mur] Murakam, K., Okamoto, T., Miyamoto, Y, Nakazono, S., Rapid Solidifieation and Self-Annealing of Fe-C-Si Alloys by Low-Pressure Plasma Spraying , Mat. Scl Eng. A -Struct. Mai Prop. Microstr. Proc., 117, 207-214 (1989) (Experimental, Meehan. Prop., Morphology, 14)... 

Figure 6 (A) Cross-section of a TBC deposited by air plasma spraying (APS). The plate-like structure is evident in the coating shown by the inset figure, the bond coat is NiCoCrAlY fabricated by low pressure plasma spraying (LPPS) (B) Cross-section of a TBC deposited by electron beam physical vapom deposition (EBPVD) on a Pt-enriched y+y bond coat. Note the coliunnar microstructure of the coating.

Attempts have been made to produce hard, dense boron carbide coatings by air plasma and low pressure plasma spray (LPPS) processes, but all techniques have so far proved unsuccessful. 

The TBCs deposited by plasma spraying consist (adjacent to the metallic substrate Inconel, Hastelloy, Ti6Al4V) of a dense MCrAlY (M = Ni, Co) alloy bond coat which is laid down by low-pressure plasma spraying (LPPS), followed by a porous stabilized zirconia top coat in the thickness range of 300 to lOOOgm (Cernuschi et al., 2004), as shown schematically in Figure 7.39. During operation. 

For applications requiring higher density coatings with a strong adhesion to the substrate, low-pressure plasma spray is employed where spraying is done in an inert-gas container operating at a reduced pressure. Vacuum plasma spray is another thermal spray process which is used to improve purity of the deposited material and to reduce porosity and defect content, albeit at a higher cost than air plasma spray. 

Zotov, R, Hospach, A., Mauer, G., Sebold, D., and VaCen, R. (2012) Deposition of Lai ,5r ,fei Co 03 a coatings with different phase compositions and microstructures by low-pressure plasma spraying thin film (LPPS-TF) process. 

IGC Intermagnetics General LPPS low-pressure plasma spraying... 

Mas] Masahashi, N., Watanabe, S., Hanada, Sh., Microstmcture and Oxidation Behaviour of Low Pressure Plasma Sprayed Iron Aluminides , ISU Int., 41(9), 1010-1017 (2001) (Crys. Stmcture, Experimental, Meehan. Prop., 16)... 

---