Optimization of Dielectric Properties of Suspension Plasma Sprayed Hydroxyapatite Coatings

Abstract

Conventional plasma torch was adapted to spray very fine Ca 5 (PO 4 ) 3 OH (hydroxyapatite, HA) precursors having sizes ranging from a few hundreds of nanometers to a few micrometers. The powders were put in suspension with distilled water and antidispersive agent. A home made suspension feeder, including two peristaltic pumps, delivered the suspension into atomizer and therefrom injected into plasma jet. The suspension flow rate was electronically controlled. The resulting coatings had the thickness of a few tenths of lm. The electrical properties of the coatings including breakdown voltage and loss factor of suspension sprayed hydroxyapatite coatings sprayed onto aluminium substrates were also tested.The influence of such experimental factors as power input to plasma, pressure of atomizing gas, spray distance and suspension feed rate on the responses being the electrical properties was investigated using a 2 4 design of experiments (DOE). The mathematical models relating the responses with the factors were created and the significant factors were selected.

Two zones microstructure of suspension plasma sprayed hydroxyapatite coatings

“…The previous study of suspension plasma sprayed HA was made with the use of a spray-dried powder which was crushed using a milling machine with zirconia balls prior to the formulation and the formulated suspension was injected using an atomizer [8,14]. The present paper aims at development of coatings with the use of HA powder homesynthesized from calcium nitrate and diammonium phosphate [15].…”

“…The technology has been used to spray the coatings of e.g. titania [3,4], zirconia [5,6] and hydroxyapatite [7,8]. The coatings sprayed with the use of radial injection of suspension into arc generated plasma are generally porous.…”

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings

“…Lowdensity liquid has to penetrate the core of the jet in order for the heat treatment to result in a coating formation. Two major injection systems include atomization and continuous jet injection and are discussed elsewhere (Ref [5][6][7][8][9][10].…”

Design of the synthesis of fine HA powder for suspension plasma spraying

“…The latter is a bioceramic material used intensively as plasma sprayed coating to promote osseointegration of the femoral stems [7,8]. The previous study of suspension plasma sprayed HA was made with the use of a spray-dried powder which was crushed using a milling machine with zirconia balls prior to the formulation [6,9]. The present paper shows the synthesis of HA produced starting from calcium nitrate and diammonium phosphate.…”

“…The technique was reviewed recently [2] and can be used to obtain relatively thin ceramic coatings of TiO 2 [3,4], yttria stabilized zirconia (by similar technique of in which sol is used to spray, [5]) and hydroxyapatite [6]. The latter is a bioceramic material used intensively as plasma sprayed coating to promote osseointegration of the femoral stems [7,8].…”