Khor K A, Li H, Cheang P
School of Mechanical and Production Engineering, Advanced Materials Research Centre, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Biomaterials. 2004 Mar-Apr;25(7-8):1177-86. doi: 10.1016/j.biomaterials.2003.08.008.
Microstructure characterization and property evaluation of high velocity oxy-fuel (HVOF) sprayed hydroxyapatite (HA) splats and coatings were conducted in the present study as a function of the proportion of melting that occurred in HA particles during HVOF spray. In vitro behavior of single and folded HA splats in simulated body fluid was also investigated. Results showed that phase composition of as-sprayed HA coatings was influenced significantly by the melt fraction in HVOF sprayed particles. Melt fraction of the HA powders were experimentally determined from particle morphology analysis. It was found that the spray parameters and starting powder size influenced the melt fraction of the particles. In vitro investigation of individual HA splats made from different HA particles revealed decisive role of local phase composition in influencing their dissolution/precipitation behavior during the test. Furthermore, Raman spectroscopy qualitative inspection on the sprayed HA particles (partial melted) revealed that thermal decomposition occurred within the melted part rather than the unmelted zone. Young's modulus and micro-hardness of the as-sprayed particles and coatings were determined using nano-indentation technique. The resolidified zone of the sprayed HA particles exhibited an average Young's modulus value of 41.25 GPa. The measured values ranged from 23.1 to 65.3 GPa. The unmelted part of the HA powders showed a markedly narrower range. Young's modulus value of 83.9 GPa (+/-9.4 GPa) was recorded for this region. This succinctly highlight the difference between the unmelted region and melted regions of a HA particle. Young's moduli values measured on HVOF coatings were found to mirror the trend found in the spheroidised particles and splats with apt fidelity.
在本研究中，对高速氧燃料（HVOF）喷涂的羟基磷灰石（HA）薄片和涂层进行了微观结构表征和性能评估，该评估是作为HVOF喷涂过程中HA颗粒发生熔化比例的函数。还研究了单个和折叠的HA薄片在模拟体液中的体外行为。结果表明，喷涂态HA涂层的相组成受HVOF喷涂颗粒中熔体分数的显著影响。通过颗粒形态分析实验测定了HA粉末的熔体分数。发现喷涂参数和起始粉末尺寸会影响颗粒的熔体分数。对由不同HA颗粒制成的单个HA薄片的体外研究表明，局部相组成在测试期间影响其溶解/沉淀行为方面起决定性作用。此外，对喷涂的HA颗粒（部分熔化）的拉曼光谱定性检查表明，热分解发生在熔化部分而非未熔化区域。使用纳米压痕技术测定了喷涂态颗粒和涂层的杨氏模量和显微硬度。喷涂的HA颗粒的再凝固区的平均杨氏模量值为41.25 GPa。测量值范围为23.1至65.3 GPa。HA粉末的未熔化部分显示出明显更窄的范围。该区域记录的杨氏模量值为83.9 GPa（±9.4 GPa）。这简要突出了HA颗粒未熔化区域和熔化区域之间的差异。发现在HVOF涂层上测量的杨氏模量值忠实地反映了在球化颗粒和薄片中发现的趋势。
