【作者】 江源胜；

【导师】 王小祥；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2011， 硕士

【摘要】 本文实验利用电化学沉积方法在钛金属表面制备不同磷酸钙盐涂层,并系统研究了Zn离子掺杂,电解液浓度等对沉积产物的微观形貌、物相成分、结晶度等方面的影响。全文主要内容分为三个部分：1)以Ca(NO3)2和NH4H2PO4为电解主盐,在电解液中加入Zn(NO3)2,成功制备得到了锌掺杂羟基磷灰石(HAP)涂层。通过控制加入的Zn元素的含量,研究分析了Zn对于羟基磷灰石涂层结晶度、微观形貌、物相成分及涂层与钛基体之间结合力的影响。实验得出：随着电解液中Zn含量的增加,沉积得到的HAP晶体的结晶度逐渐降低,晶体平均尺寸逐渐减小。当Zn含量达到25mol%(Zn/(Zn+Ca))时,沉积不再得到Zn-HAP晶体。同时随着Zn含量的增加,涂层规则六边形微观形貌特征逐渐消失,涂层与钛基体之间的结合力逐渐增大。2)通过改变电解液主盐Ca(NO3)2和NH4H2PO4的浓度,研究了电解液浓度对于电化学沉积磷酸钙盐涂层产物的影响。结果发现：随着电解液浓度的逐渐升高,涂层产物的物相由HAP逐渐向磷酸八钙(OCP)转变,同时微观形貌上观察到了从纳米级规则六边形棒状HAP晶体逐渐转变成微米级带状OCP晶体的过程。此外,本文还从热力学角度上分析了浓度变化导致的这种转变的内在原因。3)通过控制不同电解液浓度沉积过程的沉积时间,从微观形貌上去初步揭示了电化学沉积法制备HAP及OCP的形成机理。文中提出：低电解液浓度(c(Ca2+)=1.2×10-3mol/L)下沉积初期得到的是薄片状的OCP晶体,随着沉积的进行,其通过固—固转变的方式转变成HAP晶体；电解液浓度在一定范围内时(c(Ca2+)=2.4×10-3mol/L～3.6×10-3mol/L),沉积得到的是结晶度较低的HAP晶体,其是通过沉积初期的纳米小颗粒在薄片状OCP前躯体表面定向粘附形成,属于非经典形核方式；当电解液浓度较高(c(Ca2+)>4.8×10-3mol/L)时,形成的OCP晶体则是通过经典形核理论的层—层反应生成。更多还原

【Abstract】 Hydroxyapatite (HAP) and other calcium phosphates (Ca-Ps) were synthesized by electrochemical depositon (ECD) technique.The formation process and mechanism of these Ca-Ps were studied and discussed systematically and detailly in this paper. The main contents of this paper lie in the following three parts:1) Zn-substituted HAP coatings on titanium substrates were obtained by electrochemical deposition in the electrolytes (1.2mM [Ca(NO3)2+Zn(NO3)2] and 0.72mM NH4H2PO4).The influence of Zn on the micro-morphology,phase composition and crystallinity of as-obtained HAP crystals were studied. The results show that the presence of Zn in the electrolyte would deteriorate the crystallinity of HAP significantly and HAP crystals are not obtained when Zn fraction reach 25mol% (Zn/(Zn+Ca)). Moreover, as the Zn fraction increased, the regular hexagonal rod-like character of HAP crystals disappear gradually, and the bonding strength between coating and titanium substrate is improved gradually.2) The influence of electrolytic concentration on the phase composition and morphology of products were discussed. The SEM and XRD results show that regular hexagonal rod-like HAP crystals with high crystallinity are obtained when electrolytic concentrations are relatively low. As electrolytic concentrations increase, the crystallinity of HAP decreased, and the product gradually transform to octacalcium phosphate (OCP). The morphology changes from nano-scaled hexagonal rod-like HAP crystals to micro-scaled belt-like OCP crystals are also observed. In addition, the reason of this concentration-induced phenomenon is analyzed thermodynamically.3) We attempted to reveal the formation mechanism of Ca-Ps by electrochemical deposition in this paper, which is seldom reported by others. By controlling the depositing time, we observed the micro-morphologies changes of products at different stages.It is proposed that thin plate-like OCP were formed at the early stage when electrolytic concentration is low(c(Ca2+)=1.2×10-3mol/L), and it served as precursor that would transform to HAP through solid-solid transformation. At some ranges of electrolytic concentration (c(Ca2+)=2.4×10-3mol/L～3.6×10-3mol/L), the nucleation manner of HAP is correspond to so-called "non-classical nucleation theory" which is widely reported and discoved during crystallization processes in recent years. In this case, the final HAP crystals are formed by the aggregation and oriented attachment of primary nano-particles.When the electrolytic concentration is relatively high(c(Ca2+)>1.2×10-3mol/L),the obtained OCP products are formed through classical nucleation theory.更多还原