Electrophoretically deposited nanosized hydroxyapatite coatings on 316LVM stainless steel for orthopaedic implants

Abstract

Hydroxyapatite is a widely used bioceramic material in implant coatings research because of its bioactive behavior when being deposited onto the metallic implant and compatibility with the human bones composition. The coating of nanosized hydroxyapatite was electrophoretically deposited on a blasted surface of stainless steel 316LVM samples at constant voltage, for different deposition times and subsequently sintered in both, vacuum and argon atmosphere, at 1040 and 1000 °C, respectively. Although sintering temperatures needed to achieve highly dense coatings can cause HAp coating phase changes, the possibility to obtain a bioactive coating on 316LVM substrate, without the coatings phase changes due to the nature of the used stoichiometric nanostructured hydroxyapatite is presented in this work. The thermal stability of the used HAp powder was assessed by DTA-TG analyses over the temperature range of 23-1000 °C, i.e., at the or nearby experimental sintering temperature. The microstructure characterization was accomplished using SEM, while phase composition was determined using XRD.

Nanostructured Hydroxyapatite Coating on Bioalloy Substrates: Current Status and Future Directions

“…The first step involves preparation of a suspension of nanoHA particles (typical mean particle size and range of particle sizes: 160 nm and 35-550 nm, respectively) alone [27] or in combination with carbon black powder (typical mean particle size and range of particle sizes: 360 nm and 120-960 nm, respectively) (the powder serves as the sacrificial template) [25] in a suitable liquid, such as isopropanol [25], methanol [27], acetic anhydride [42], or ethanol [24,43]. After that, the suspension is magnetically stirred for, typically, 24 h, and ultrasonically-dispersed [25][26][27], and then rested for, typically, 1 h (to allow sedimentation of the nanoHA particles, when only these particles are used [27]).…”

“…One, the coated specimen is dried, in room-temperature air [25] [25]. Three, the coated electrode is sintered, at 800 o C, for 1 h [42]; or heated in a previously degassed electric furnace to 800 o C, then heated in argon to 1000 o C at 10 o C min -1 , held at 1000 o C for 1 h, slowly cooled in the furnace, and then removed ("Ar sintered" set) [43]; or heated in a previously degassed electric furnace to 800 o C and then heated in vacuum to 1040 o C at 10 o C min -1 , and then held at 1040 o C for 1 h, slowly cooled in the furnace, and then removed ("vacuum sintered" set) [43]. Four, the green coating is dried in air in room temperature for 24 h and, then, sintered in an argon-purged atmosphere at 900 o C at 1.…”

“…On 316 LVM stainless steel substrate, 1) coatings deposited after 30 s and then vacuum-sintered were thin and compact; for coatings deposited after 60 s and vacuum sintered, the outer layer of agglomerated clusters had cracks through which a continuous inner layer of finer and sintered particles was visible; and for coatings deposited after 30 s and then argon-sintered, the morphology was observable not only at the agglomerates at the surface but also over all of the visible areas [43].…”

Potentiostatic Co-deposition of Nickel and Graphite Using a Composite Counter Electrode

“…These stem from the tendency of the particulates to settle in the solution, resulting in inhomogeneity of the deposits. Systems for introducing fresh particulates and keeping them in suspension through bath agitation or the use of surfactants have been proposed [11][12][13][14]. However, agitation of solution under potentiostat control may lead to instability and loss of control of the working electrode potential.…”

Morphology of Electrophoretically Deposited Films on Electrode Strips

“…While EPD was originally developed as a process for painting metals, 2,3 it is now recognized as a general method for depositing material on any conductive surfaces and has found diverse applications in areas such as thermal barrier coatings, 4,5 transparent ceramics, 6,7 solar cells, 8,9 fuel cells, 10,11 solid state lighting and displays, 12,13 and medical implants. [14][15][16][17][18] The first theoretical treatment of the deposition kinetics of EPD was performed by Hamaker 19 who predicted that the mass of the deposited film on an unpatterned planar electrode is proportional to the charge passed at the electrodes. Later, Avgustinik, et al 20 extended Hamaker's theory to depositions on concentric cylindrical electrodes.…”