Effect of atmosphere on phase transformation in plasma-sprayed hydroxyapatite coatings during heat treatment

Chen, Jiyong; Tong, Weidong; Cao, Yang; Feng, Jiaming; Zhang, Xingdong

doi:10.1002/(sici)1097-4636(199701)34:1<15::aid-jbm3>3.0.co;2-q

Cited by 131 publications

(67 citation statements)

References 3 publications

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“…4,5) Since amorphous calcium phosphate is thermodynamically meta-stable, an appropriate thermal treatment could induce significant crystallization; consequently, as-sprayed HACs with a post-heat treatment in vacuo or in atmosphere can improve the phase purity and crystallinity. 2,[6][7][8] However, the high heating temperatures tend to undermine the structural integrity of HA because of the decomposition of crystalline HA phase in the TCP and TP phases.…”

Section: Introductionmentioning

confidence: 99%

“…This is a result of compensation of missing OH À groups with surrounding H 2 O molecules. [7][8][9][10] The investigation focused on clarifying the microstructural differences between the above-mentioned vacuum and autoclaving hydrothermal post-heat treatment of plasma-sprayed hydroxyapatite coating with respect to the bonding strength of both samples.…”

Section: Introductionmentioning

confidence: 99%

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A Comparison of the Microstructural Feature and Bonding Strength of Plasma-Sprayed Hydroxyapatite Coatings with Hydrothermal and Vacuum Post-Heat Treatment

et al. 2005

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Plasma-sprayed hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HA) is an attractive biomaterials because it can provide the osteoconductivity and osseointegration to form a chemical bonding to bone. In order to improve the properties of HA, the post-heat treatment was performed and the effect of an ambient atmosphere on phase purity, crystallinity and bonding strength of plasma-sprayed HA coatings (HACs) was investigated. On the basis of quantitative analysis in crystallinity and phase content, autoclaving hydrothermal treatment was found to be effective for the elimination of impurity phases and amorphous calcium phosphate. It should be noted that plasma-sprayed HACs with a crystallinity of 84.5% and very low impurity phase content of 1.4 mass% can be obtained through a low temperature (200 C) hydrothermal treatment. Experimental evidence confirmed that the saturated steam atmosphere plays an important role in lowering the heating temperatures and promoting HA crystallization. Furthermore, hydrothermal-treated HACs show superiority in prominent OH À and PO 4 3À groups than vacuum heating HACs. In addition, the bonding strength of the coating layer also can be improved from 35.7 MPa (vacuum heating) to 39.4 MPa (150 C hydrothermal treatment). From the evaluation of microstructural features and properties, an excessively high heating temperature will cause contraction with HA crystallization resulting in detrimental large cracks that lead to bonding degradation. Consequently, hydrothermal treatment seems very promising as a way of improving the properties of HA coatings.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Comparison of the Microstructural Feature and Bonding Strength of Plasma-Sprayed Hydroxyapatite Coatings with Hydrothermal and Vacuum Post-Heat Treatment

et al. 2005

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“…On the basis of the previous investigation, post-heat treatment in the aqueous atmosphere especially with water molecules could accelerate the crystallization of amorphous HA and transform the impurity phases to a stable crystal HA phase, because the water molecules compensate the missing OH À groups from the dehydration of HA. [15][16][17][18] Furthermore, not only H 2 O molecules, but the treating temperature accompanied by a specific steam pressure (especially in autoclaving treatment) also influenced the crystallization ability of HA. The difficulties of post-heat treatment without hydrothermal condition including the elimination of impurity phase as well as crystallinity and bonding strength of HACs layer have been recognized.…”

Section: Introductionmentioning

confidence: 99%

Effect of Hydrothermal Treatment on Microstructural Feature and Bonding Strength of Plasma-Sprayed Hydroxyapatite on Ti-6Al-4V

et al. 2004

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The effects of hydrothermal treating temperature on bonding strength pertaining to the microstructural evolution of plasma-sprayed hydroxyapatite coatings (HACs) on Ti-6Al-4V substrate were investigated. On the basis of the observed microstructure, the as-sprayed amorphous and impurity phases, such as -Ca 3 (PO 4 ) 2 , Ca 4 P 2 O 9 and CaO transform into crystalline HA after performing the hydrothermal treatment. Additionally, ultrafine crystallized particles can be recognized that the nucleation and grain growth occur by hydrothermal treatment at elevated temperatures of 175 C and 200 C. Furthermore, the hydrothermal treatment between 100 C and 150 C shows a significant decrease in microcracks, corresponding to an increase in bonding strength. This study reveals that even a small variation of hydrothermal heating temperature under 200 C can cause significant changes of the microstructural morphologies. Combining the experimental results of spraying defects, microstructural evolution and bonding strength, the knowledge of the hydrothermal-treated HACs will be helpful for the understanding and prediction in the biological stability and mechanical stability of HACs in the long-term clinical use.

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“…The dissolution rate of crystalline HA has been observed to be very low, while that of the amorphous phase HA is considerably high [1]. Various techniques have been used to deposit calcium phosphate on metal substrates such as sputtering, electron beam deposition, laser deposition, and plasma spraying [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. So far, plasma spraying is the only technique being commercialized and most widely used because of its simplicity and cost effectiveness.…”

Section: Introductionmentioning

confidence: 99%

“…However, the heat treatment increases the processing time and cost and can even cause residual stresses in the HA coating due to a thermal expansion mismatch between the coated layer and the metal substrate. This residual stresses may even lead to the cracking of the coating and eventual reduction in its bond strength [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Processing and Development of Nano-Scale HA coatings for Biomedical Application

Rabiei

Thomas

2004

MRS Proc.

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Functionally graded Hydroxyapatite coating with graded Crystallinity across the thickness of the film has been processed and tested as a more effective orthopedic/ dental implant coating. The present study aims to increase the service-life of an orthopedic/ dental implant by creating materials that form a strong, long lasting, bond with the Ti substrate as well as juxtaposed bone. The health relatedness of the new material is to increase bonding between an implant and juxtaposed bone so that a patient who has received joint or dental replacement surgery may quickly return to a normal active lifestyle. Cross-sectional transmission electron microscopy analysis displayed that the films have a graded crystal structure with the crystalline layer near the substrate and the amorphous layer at the top surface. Compositional analysis was performed using SEM-EDX at the top surface as well as STEM-EDX at the cross section of the film. The average calcium to phosphorous ratio at the surface is 1.46, obtained by SEM-EDX, The Ca/P ratios in the crystalline and amorphous layers of the film are 1.6 to 1.7, close to the ratio of 1.67 for HA. INTRODUCTIONIn order to improve the bioactivity of metal implants, Hydroxyapatite (HA: CaJ0(P0 4 )

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Effect of atmosphere on phase transformation in plasma-sprayed hydroxyapatite coatings during heat treatment

Cited by 131 publications

References 3 publications

A Comparison of the Microstructural Feature and Bonding Strength of Plasma-Sprayed Hydroxyapatite Coatings with Hydrothermal and Vacuum Post-Heat Treatment

A Comparison of the Microstructural Feature and Bonding Strength of Plasma-Sprayed Hydroxyapatite Coatings with Hydrothermal and Vacuum Post-Heat Treatment

Effect of Hydrothermal Treatment on Microstructural Feature and Bonding Strength of Plasma-Sprayed Hydroxyapatite on Ti-6Al-4V

Processing and Development of Nano-Scale HA coatings for Biomedical Application

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