Ning C Y, Wang Y J, Lu W W, Qiu Q X, Lam R W M, Chen X F, Chiu K Y, Ye J D, Wu G, Wu Z H, Chow S P
Department of Orthopaedics & Traumatology, University of Hong Kong, Hong Kong.
J Mater Sci Mater Med. 2006 Oct;17(10):875-84. doi: 10.1007/s10856-006-0176-9.
The poor mechanical property of hydroxyapatite was the major problem for load bearing and implant coating in clinical applications. To overcome this weakness, a bioactive gradient coating with a special design composition of hydroxyapatite (HA), ZrO2, Ti, bioglass was developed. This 120 microm coating with an upper layer of 30-50 microm porous HA produced by computer controlled plasma spraying which maintained energy level of the plasma which ensure proper melting of powder. The crystal size of the coating was 18.6-26.2 nm. Transformation of t-ZrO2 to m-ZrO2 reduced the thermal stress that weakened the coating and lowered down interfacial strength of the coating and metal substrate. Thermal stress of sprayed coating was 16.4 MPa which was much smaller than the sample without thermal treatment of 67.1 MPa. Interfacial strength between the coating and metal substrate was 53 MPa which is much higher than conventional Hydroxyapatite coating. Based on XRD analysis crystallinity of HA approached 98%. Therefore, high temperature treatment improved long term stability of the coating through improved crystallinity of hydroxyapatite and reduced other impure calcium phosphate phase.
羟基磷灰石较差的力学性能是其在临床应用中用于承重和植入涂层时的主要问题。为克服这一弱点，开发了一种具有特殊设计成分的生物活性梯度涂层，其由羟基磷灰石（HA）、ZrO2、Ti、生物玻璃组成。这种120微米的涂层具有30 - 50微米的上层多孔HA，通过计算机控制的等离子喷涂制备，该过程维持了等离子体的能量水平，确保粉末适当熔化。涂层的晶体尺寸为18.6 - 26.2纳米。t-ZrO2向m-ZrO2的转变降低了削弱涂层并降低涂层与金属基体界面强度的热应力。喷涂涂层的热应力为16.4兆帕，远小于未经热处理样品的67.1兆帕。涂层与金属基体之间的界面强度为53兆帕，远高于传统羟基磷灰石涂层。基于XRD分析，HA的结晶度接近98%。因此，高温处理通过提高羟基磷灰石的结晶度并减少其他不纯磷酸钙相，改善了涂层的长期稳定性。
