天然文石-方解石的高温相变及热膨胀性质
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P578.6+1

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国家自然科学基金资助项目(40972028,41520104004,41672036)


High-temperature phase transition and thermal expansivity of natural aragonite-calcite
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    摘要:

    利用高温粉末X射线衍射研究了高纯地质成因文石从室温到1 073 K的相变过程以及文石和方解石的热膨胀性质,并分析了地质成因与生物成因文石的差异和影响因素。结果表明:斜方晶系的文石在693~733 K转变为三方晶系的方解石,相变临界温度为723 K,摩尔体积增加5.97%;文石在300~663 K的体积热膨胀系数αV)(10-5/K)随绝对温度T(K)的变化规律为:αV)=3.59(79)+7.17(170)×10-3 T,文石的热膨胀具有强烈的各向异性[轴向热膨胀系数αc) > αb) > αa)];方解石在733~973 K的热膨胀系数α(10-5/K)为:αV)=3.78(25),αa)=-0.27(2),αc)=4.31(29),a轴具有负热膨胀。生物成因的文石相变温度比合成和地质成因文石低60~140 K,粉末状文石相变温度低于单晶和未被破坏的整块文石;粉末状的生物成因文石和方解石与非生物成因的文石和方解石的热膨胀系数接近,然而整块的生物成因的文石有更小的热膨胀系数。

    Abstract:

    The phase evolution of high purity natural aragonite from room temperature to 1 073 K and the thermal expansivity of both aragonite and calcite were studied by using high-temperature powder X-ray diffraction, and the difference and influencing factors of geological and biogenic aragonite were analyzed. The results show that orthorhombic aragonite transforms to trigonal calcite at 693~733 K with the critical temperature Tc=723 K and an increase in molar volume by 5.97%. The variation of volume thermal expansion coefficient of aragonite with the absolute temperature T(K) at 300~663 K is α(V) (10-5/K)=3.59(79)+7.17(170)×10-3 T. The expansion of aragonite is strongly anisotropic, with the axial expansion decreasing in order of α(c) > α(b) > α(a). The thermal expansion coefficients α (10-5/K) of calcite at 733~973 K are α(V)=3.78(25), α(a)=-0.27(2), and α(c)=4.31(29), with negative thermal expansion for the a axis. The phase transition temperature of biogenic aragonite is 60~140 K lower than that of synthetic and geological aragonite, and that of pulverized aragonite is lower than that of single crystal and undisturbed aragonite. Pulverized biogenic aragonite and calcite have similar thermal expansion coefficients to non-biogenic aragonite and calcite; however, the uncrashed biogenic aragonite has a smaller thermal expansion coefficient.

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杨华,刘琼,2021,天然文石-方解石的高温相变及热膨胀性质[J].岩石矿物学杂志,40(1):142~152.

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  • 收稿日期:2020-05-18
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  • 在线发布日期: 2021-01-16
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