TYPES OF H2O IN HUMAN ENAMEL AND IN PRECIPITATED APATITES
TYPES OF H2O IN HUMAN ENAMEL AND IN PRECIPITATED APATITES
复制标题
DOI：
10.1007/bf02013245
复制
发表时间：
1978-01-01
期刊：
影响因子：
--
通讯作者：
LEGROS, R
中科院分区：
文献类型：
--
作者：
LEGEROS, RZ;BONEL, G;LEGROS, R
利用x射线衍射、红外吸收光谱和热重分析对人类牙釉质和沉淀磷灰石中的“H2O”类型进行了表征。晶格参数（主要是α-轴尺寸）和红外吸收带特征的变化与热解温度为100 ~ 400℃时的失重以及先前点燃的样品的再水化和再点燃的影响有关。本研究表明，在200℃以下，“H2O”的损失是可逆的，不会导致这些磷灰石晶格参数的显著变化，而在200 ~ 400℃之间，“H2O”的损失是不可逆的，会导致α-轴维数的收缩。提出了两种类型的“H2O”存在于这些磷灰石中：(a)吸附的H2O -具有可逆性，在200℃以下热不稳定性，并且对晶格参数没有影响；(b)晶格h2o -具有不可逆性，在200 ~ 400℃之间具有热不稳定性，并能诱导人牙釉质和沉淀磷灰石α-轴尺寸的膨胀。晶格H2O被认为是由于这些磷灰石中的H2O取代oh和/或hpo4取代po4。吸附水的损失导致这些磷灰石光谱中OH吸收带的锐化。在含有少量CO32−的沉淀磷灰石中，由于P2O74−基团的存在，晶格水的损失导致P−O−P吸收带的出现。人牙釉质磷灰石α-轴值为9.445±0.003A，比矿物磷灰石α-轴值为9.442A或合成oh -磷灰石α-轴值为9.442A，这可能是由于该磷灰石中存在H2O晶格、Cl-for-OH以及较大阳离子（如Sr、Ba、Pb、K）协同取代Ca所致。
Types of “H2O” in human enamel and in precipitated apatites are characterized using X-ray diffraction, infrared (IR) absorption spectroscopic and thermogravimetric analyses. Changes in lattice parameters (principally in the α-axis dimensions) and in the character of the IR absorption bands are correlated with weight losses at pyrolysis temperatures of 100° to 400°C and with effect of rehydration and reignition of previously ignited samples.This study demonstrated that the loss of “H2O” below 200°C is reversible and causes no significant change in the lattice parameter of these apatites, whereas loss of “H2O” between 200° and 400°C is irreversible and causes a contraction in the α-axis dimension. It is proposed that two general types of “H2O” are present in these apatites: (a)adsorbed H2O—characterized by reversibility, thermal instability below 200°C, and lack of effect on lattice parameters; and (b)lattice H2O—characterized by irreversibility, thermal instability between 200 and 400°C, and induction of expansion in the α-axis dimensions of human enamel and precipitated apatites. Lattice H2O is assumed to be due to H2O-for-OH and/or HPO4-for-PO4substitutions in these apatites. Loss of adsorbed H2O caused sharpening of the OH absorption bands in the spectra of these apatites. Loss of lattice H2O caused the appearance of P−O−P absorption bands (due to the presence of P2O74−group) in precipitated apatites containing small amounts of CO32−.The observed larger α-axis of human enamel apatite, i.e., 9.445±0.003A, compared to that of the mineral or synthetic (prepared at 1000°C) OH-apatite, i.e., 9.442A, may be attributed to the presence of lattice H2O, Cl-for-OH, and concerted substitutions of larger cations (e.g., Sr, Ba, Pb, K) for Ca in this apatite.