Tsui Y C, Doyle C, Clyne T W
Department of Materials Science and Metallurgy, University of Cambridge, UK.
Biomaterials. 1998 Nov;19(22):2031-43. doi: 10.1016/s0142-9612(98)00104-5.
Heat treatment and the introduction of a Ti bond coat have been applied to hydroxyapatite (HA) coatings sprayed using different plasma powers and gas mixtures. Attempts were made in this way to achieve optimal coating properties for orthopaedic implants. In particular, the effects on the degree of crystallinity, the adhesion, the OH ion content and the purity were evaluated. Heat treatment at 700 C for 1 h in air proved to be effective in increasing the crystallinity, regaining the OH- ion and removing other non-HA compounds, although it caused a significant decrease in the degree of adhesion (interfacial fracture toughness) for those specimens sprayed at high powers. This heat treatment was found to induce significant transformation of amorphous HA to the crystalline form, while not detrimentally changing the properties of the underlying Ti-6Al-4V substrates. Precoating with a 100 microm Ti layer increased the adhesion of the HA coatings on Ti-6Al-4V substrates, primarily by providing a rougher surface and promoting better mechanical interlocking. Changes in coating properties during immersion in biological fluids were also studied and were found to depend critically on the chemical composition of the fluids. Small precipitates formed on the coating surfaces when immersed in Ringers solution. These might account for the apparent drop in the degree of crystallinity when measured using X-ray diffraction. A significant drop in the interfacial adhesion was found for those coatings sprayed at high powers. This could be offset by prior precoating with a titanium bond coat and suitable heat treatment. In summary, the following processing sequence is suggested in order to achieve optimum coating properties: precoating the substrate with a layer of Ti (approximately 100 microm), spraying HA at a sufficiently high-power level (depending on particle size and gas mixture) and heat treatment at 700 degrees C for 1 h in air.
已经对使用不同等离子体功率和气体混合物喷涂的羟基磷灰石（HA）涂层进行了热处理和引入钛粘结涂层。通过这种方式试图实现用于骨科植入物的最佳涂层性能。特别评估了对结晶度、附着力、OH离子含量和纯度的影响。在空气中700℃下热处理1小时被证明有效地提高了结晶度，恢复了OH - 离子并去除了其他非HA化合物，尽管对于那些高功率喷涂的试样，其附着力（界面断裂韧性）显著降低。发现这种热处理可诱导无定形HA显著转变为结晶形式，同时不会对下面的Ti - 6Al - 4V基体的性能产生不利影响。用100微米厚的钛层预涂覆增加了HA涂层在Ti - 6Al - 4V基体上的附着力，主要是通过提供更粗糙的表面并促进更好的机械互锁。还研究了涂层在生物流体中浸泡期间的性能变化，发现其严重依赖于流体的化学成分。浸泡在林格氏溶液中时，涂层表面形成小沉淀。当使用X射线衍射测量时，这些可能解释了结晶度明显下降的原因。对于那些高功率喷涂的涂层，发现界面附着力显著下降。这可以通过预先用钛粘结涂层预涂覆和适当的热处理来抵消。总之，为了获得最佳涂层性能，建议采用以下加工顺序：用一层钛（约100微米）预涂覆基体，以足够高的功率水平（取决于颗粒尺寸和气体混合物）喷涂HA，并在空气中700℃下热处理1小时。
