水热法合成红色绿柱石的光谱特征研究及应用
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摘要
采用常规宝石学测试方法,配合紫外可见光谱技术(UV-Vis)及傅里叶变换红外光谱技术(FTIR),对美国犹他州天然红色绿柱石及俄罗斯水热法合成红色绿柱石的宝石学特征、紫外可见吸收光谱特征、中红外光谱(MIR)特征及近红外光谱(NIR)特征进行了综合对比研究。结果表明,常规宝石学测试方法很难将上述两类宝石区别开来;紫外可见光吸收光谱对鉴定天然和合成红色绿柱石的能力很有限;同时这两种宝石的中红外吸收光谱(MIR)没有明显的特征差异,其吸收位置和吸收强度基本一致。但在2 000～9 000cm-1红外波段,天然红色绿柱石与水热法合成红色绿柱石的吸收频率差异明显,因此具有独特的鉴别特征。进一步研究表明,天然红色绿柱石在3 500～4 000cm-1之间没有强吸收峰,几乎不含结构水,但在3 300～3 600cm-1之间有非常弱的吸收带(峰值为3 418cm-1),因此有可能有其他形式的水。水热法合成红色绿柱石样品的近红外光谱特征表明,其在3 500～4 000cm-1之间及5 000～5 800cm-1之间均显示有强烈的水的振动吸收:其在5 000～5 800cm-1有弱的Ⅰ型水吸收峰和强Ⅱ型水吸收峰,可以归属为分子水的弯曲和伸缩的合频振动;其在7 000～7 500cm-1之间显示的弱Ⅰ型水的吸收峰和强的Ⅱ型水的吸收峰可以归属为水的倍频振动。因此,水热法合成红色绿柱石中的结构水归属Ⅰ型水与Ⅱ型水的混合型,其在3 500～4 000及5 000～5 800cm-1范围水的近红外吸收光谱特征可作为区别天然和水热法合成红色绿柱石的依据。通过紫外可见光光谱、中红外光谱以及近红外光谱等光谱分析手段可以初步判断红色绿柱石中是否含水、水的赋存状态、以及不同类型水的相对强度和频率,为区分天然与水热法合成红色绿柱石提供诊断性证据。
By using conventional gemological test methods,then combining the UV-Visible spectroscopy(UV-Vis)and Fourier transform of infrared spectral technology(FT-IR),this research focuses on the natural Utah red beryl and Russian hydrothermal synthetic red beryl,which are studied by the gemological characteristics,the UV-visible absorption spectrum,the mid-infrared absorption spectrum(MIR)and the near-infrared spectrum(NIR)characteristics.The results showed thatit is difficult to discriminate the natural red beryl and the hydrothermally synthesized red beryl through the conventional gemological test methods.Also,there is limited ability of UV-visible absorption spectrum to identify the natural and synthetic red beryl.At the same time,the mid-infrared absorption spectrum(MIR)of these two kinds of gems has no obvious difference.Their absorption position and absorption intensity are basically similar,which only show the vibration characteristics of the silicate crystal structure of beryl.As for spectrum of 2 000～9 000cm-1 scope,there is obvious difference between the natural red beryl and hydrothermal synthesis red beryl.Therefore,the near-infrared absorption spectrum could be used as aunique identification characteristic to differentiate them.Further studies have shown that the natural red beryl sample contains little structural water.However,there exists a very weak absorption band between 3 300～3 600cm-1 and this might be other forms of water in the natural red beryl sample.It could be concluded that the natural red beryl sample contains certain water,and it might be the channel water.The near-infrared spectrum characteristics of the hydrothermal synthetic red beryl samples show that it has strong water vibration absorption between 3 500～4 000 and 5 000～5 800cm-1.There exist two types of water in the range of 5 000～5 800cm-1,which include the weak absorption peak(typeⅠ water)and the strong absorption peak(typeⅡ water),which can be attributed to the combined vibration of flexural vibration and stretching vibration of water;the weak typeⅠ water absorption peak and the strong typeⅡ water absorption peak are also shown in the range of 7 000～7 500cm-1,which can be attributed to the double frequency vibration of water.This means the hydrothermally synthesized red beryl is mixed with typeⅠstructural water to typeⅡstructural water.It could be concluded that the near-infrared absorption spectrum(NIR)characteristics of hydrothermal synthesis of red beryl samples in the range of 3 500～4 000 and 5 000～5 800cm-1 can be used as the basis for distinguishing natural and hydrothermal synthesis of red beryl.According to whether or not the red beryl has water,the state of occurrence of water,and the relative intensity and frequency of different types of water,the UV-VIS spectroscopy,the mid-infrared absorption spectroscopy(MIR),and the near-infrared spectroscopy(NIR)can be used as an important basis for accurately providing diagnostic evidence for distinguishing natural and hydrothermal synthesis of red beryl.
By using conventional gemological test methods,then combining the UV-Visible spectroscopy(UV-Vis)and Fourier transform of infrared spectral technology(FT-IR),this research focuses on the natural Utah red beryl and Russian hydrothermal synthetic red beryl,which are studied by the gemological characteristics,the UV-visible absorption spectrum,the mid-infrared absorption spectrum(MIR)and the near-infrared spectrum(NIR)characteristics.The results showed thatit is difficult to discriminate the natural red beryl and the hydrothermally synthesized red beryl through the conventional gemological test methods.Also,there is limited ability of UV-visible absorption spectrum to identify the natural and synthetic red beryl.At the same time,the mid-infrared absorption spectrum(MIR)of these two kinds of gems has no obvious difference.Their absorption position and absorption intensity are basically similar,which only show the vibration characteristics of the silicate crystal structure of beryl.As for spectrum of 2 000～9 000cm-1 scope,there is obvious difference between the natural red beryl and hydrothermal synthesis red beryl.Therefore,the near-infrared absorption spectrum could be used as aunique identification characteristic to differentiate them.Further studies have shown that the natural red beryl sample contains little structural water.However,there exists a very weak absorption band between 3 300～3 600cm-1 and this might be other forms of water in the natural red beryl sample.It could be concluded that the natural red beryl sample contains certain water,and it might be the channel water.The near-infrared spectrum characteristics of the hydrothermal synthetic red beryl samples show that it has strong water vibration absorption between 3 500～4 000 and 5 000～5 800cm-1.There exist two types of water in the range of 5 000～5 800cm-1,which include the weak absorption peak(typeⅠ water)and the strong absorption peak(typeⅡ water),which can be attributed to the combined vibration of flexural vibration and stretching vibration of water;the weak typeⅠ water absorption peak and the strong typeⅡ water absorption peak are also shown in the range of 7 000～7 500cm-1,which can be attributed to the double frequency vibration of water.This means the hydrothermally synthesized red beryl is mixed with typeⅠstructural water to typeⅡstructural water.It could be concluded that the near-infrared absorption spectrum(NIR)characteristics of hydrothermal synthesis of red beryl samples in the range of 3 500～4 000 and 5 000～5 800cm-1 can be used as the basis for distinguishing natural and hydrothermal synthesis of red beryl.According to whether or not the red beryl has water,the state of occurrence of water,and the relative intensity and frequency of different types of water,the UV-VIS spectroscopy,the mid-infrared absorption spectroscopy(MIR),and the near-infrared spectroscopy(NIR)can be used as an important basis for accurately providing diagnostic evidence for distinguishing natural and hydrothermal synthesis of red beryl.
引文
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[5] LI Xiao-jing,YU Lan(李晓静,虞澜).Spectroscopy and Spectral Analysis(光谱学与光谱分析),2018,38(1):54.
[6] QI Li-jian,YUAN Xin-qiang(亓利剑,袁心强).Journal of Gems and Gemology(宝石和宝石学杂志),2005,7(4):21.
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[8] WEN Lu(闻辂).The Infrared Spectroscopy of Minerals(矿物红外光谱学).Chongqing:Chongqing University Press(重庆:重庆大学出版社),1989.77.
[9] PENG Wen-shi,LIU Gao-kui(彭文世,刘高魁).Minerals Infrared Spectrograms(矿物红外光谱图集).Beijing:Science Press(北京:科学出版社),1982.347.
[10] ZHOU Wei-ning,ZHANG Chang-long(周卫宁,张昌龙).Journal of Synthetic Crystals(人工晶体学报),2002,31(5):509.
[11] LI Xiao-jing,ZU En-dong(李晓静,祖恩东).Bulletin of the Chinese Ceramic Society(硅酸盐通报),2016,35(4):1318.
[2] ZHONG Qian,LIAO Zong-ting(钟倩,廖宗廷).Journal of Gems and Gemology(宝石和宝石学杂志),2016,18(6):8.
[3] LI Xiang-qi,DAI Ta-gen(李湘祁,戴塔根).Journal of Central South University(中南工业大学学报),1999,30(1):1.
[4] QI Li-jian,XIA Yi-ben(亓利剑,夏义本).Journal of Gems and Gemology(宝石和宝石学杂志),2002,4(3):8.
[5] LI Xiao-jing,YU Lan(李晓静,虞澜).Spectroscopy and Spectral Analysis(光谱学与光谱分析),2018,38(1):54.
[6] QI Li-jian,YUAN Xin-qiang(亓利剑,袁心强).Journal of Gems and Gemology(宝石和宝石学杂志),2005,7(4):21.
[7] Gagan C.Journal of Gems and Gemology(宝石和宝石学杂志),2009 11(1):28.
[8] WEN Lu(闻辂).The Infrared Spectroscopy of Minerals(矿物红外光谱学).Chongqing:Chongqing University Press(重庆:重庆大学出版社),1989.77.
[9] PENG Wen-shi,LIU Gao-kui(彭文世,刘高魁).Minerals Infrared Spectrograms(矿物红外光谱图集).Beijing:Science Press(北京:科学出版社),1982.347.
[10] ZHOU Wei-ning,ZHANG Chang-long(周卫宁,张昌龙).Journal of Synthetic Crystals(人工晶体学报),2002,31(5):509.
[11] LI Xiao-jing,ZU En-dong(李晓静,祖恩东).Bulletin of the Chinese Ceramic Society(硅酸盐通报),2016,35(4):1318.
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