Dehydration and recrystallization of radiation-damaged titanite under thermal annealing

Abstract

Dehydration of oriented sections of a radiation-damaged titanite crystal, CaTiSiO₅, at temperatures up to 1500K was analysed using infrared spectroscopy. The IR spectra of the untreated sample show only a very weak orientational dependence. The absence of sharp absorption peaks at wave number near 3486 cm^?1 in metamict titanite shows that the local environmental configurations of OH species in the metamict titanite differ strongly from that of crystalline titanite. The OH spectra of radiation-damaged titanite can be decomposed into two components: the first component shows anisotropic and sharp spectral features while the second component consists of a broad spectral feature like those observed in disordered silica glasses. It is proposed that the first component is related to the crystalline part of the titanite sample while the second is from the defected and disordered part which suffered strong radiation damage. With increasing annealing temperature, a decrease in the broad absorption between 2500 and 3200 cm^?1 is accompanied by a recovery of sharp IR bands near 3486 cm^?1 which display the same orientational dependence as undamaged single crystals. Annealing the sample at 1000K leads to the line profiles and orientational dependence of the main OH stretching bands near 3486cm^?1 that are virtually identical with those of crystalline, undamaged titanites. At temperatures above 1500 K, the crystal starts to melt and the orientational dependence of the IR absorption is destroyed. The recrystallization processes are quantified and discussed in terms of a percolation behaviour of amorphous and crystalline titanite. It is proposed that hydrogen transport is strongly enhanced during recrystallization.     

羚羊角及其角塞的傅里叶红外光谱快速识别研究

采用傅里叶变换红外光谱(FTIR)技术,对羚羊角、羚羊角塞以及二者的混合物进行了对比研究。结果表明:羚羊角的红外光谱主要由蛋白质组分的特征吸收峰组成,而羚羊角塞的红外光谱主要由蛋白质和磷酸钙组分的特征吸收峰构成,二者的酰胺谱带、C—O伸缩振动谱带以及CH基团的伸缩振动谱带也均有明显区别。通过上述差异,可有效地鉴别羚羊角、角塞以及掺有角塞的羚羊角样品。该研究为羚羊角的掺伪和杂质检查提供了快速、科学的新方法,也为羚羊角的成分与质量评价体系研究提供了一定的信息。     

红外吸收峰的强度与反常吸收现象

红外光谱测量有时需要在强的背景信号下得到弱的样品吸收峰,如在大量溶剂中测量溶质的红外光谱.理论上,只要某一组分在背景样品和待测样品的含量(分子个数)完全一致,则该组分的光谱信号就不会出现在最终的红外光谱图上.而实际测量时结果并非总如此.本文在测量聚苯乙烯及硬脂酸的“基线”时发现,在样品吸收较强的峰位(吸光度A＞1.0)...     

利用2DCOS进行多组分混合气体傅里叶变换红外光谱分析中同分异构体谱峰的辨别

在利用傅里叶变换红外光谱进行混合气体定量分析中,针对烃类尤其是同分异构体等构成的混合气体其谱图特征相似、吸收峰严重交叠,不易进行特征吸收成分的判别和特征变量选择的问题,为增强谱峰分辨力,采用广义二维相关光谱和傅里叶变化红外光谱对烃类混合气体分析中同分异构体进行辨别,以异丁烷和正丁烷的红外光谱及受浓度扰动组成的光谱组为例进行二维相关红外光谱分析。通过观察全波段和主吸收峰波段单组分气体的傅里叶变换红外光谱,可知其谱图相似,吸收峰严重交叠,如果混合在一起,将基本无法辨别何种分子结构及成分。通过广义二维相关光谱的变换,其二维相关光谱的同步谱和异步谱可以清晰地辨别出异丁烷和正丁烷的特征吸收峰及其各自强度,实验结果可知,异丁烷在2 893,2 954和2 977 cm-1,正丁烷在2 895和2 965 cm-1具有强的吸收特征谱线。分析结果初步验证了二维红外相关光谱在多组分混合气体傅里叶变换红外光谱定量分析中谱分辨率增强方面的应用。     

七种牛肝菌的红外光谱鉴别

运用傅里叶变换红外光谱、二维相关谱及主成分分析对7种同属牛肝菌进行分析鉴别。结果显示：7种牛肝菌的原始光谱总体特征相似,主要由蛋白质、多糖等的吸收峰组成,但在吸收峰强度、位置仍存在差异。对样品进行二维相关红外光谱分析,在二维相关红外光谱1 680～1 300 cm-1范围内,茶褐牛肝菌和双色牛肝菌出现了6个明显的自动峰;小美牛肝菌出现了5个明显的自动峰;灰褐牛肝菌和美柄牛肝菌出现4个明显自动峰;美味牛肝菌和铜色牛肝菌自动峰相对较少,只出现了3个明显的自动峰;而且自动峰和交叉峰的强度、位置也存在较大差异。同样在二维相关红外光谱1 150～920 cm-1范围内,不同牛肝菌的同步谱中自动峰和交叉峰的数量、强度和位置也不同。对光谱1 800～800 cm-1范围内的二阶导数进行主成分分析,所有样品均区分开,其分类正确率达100%。结果表明,傅里叶变换红外光谱结合二维相关红外光谱或者主成分分析可以有效地区分茶褐牛肝菌、小美牛肝菌、双色牛肝菌、灰褐牛肝菌、美柄牛肝菌、美味牛肝菌和铜色牛肝菌。该方法对于分类鉴别蘑菇是一种快速、准确、有效的方法。     

XRF,PXRD和FTIR的广藿香主要组分测定与表征

中药的质量控制和评价在现代化医学发展中起着至关重要的作用。为了客观和高精度的鉴别中药材特性,实现对中药材质量稳定性的控制,利用XRF,PXRD和FTIR对广藿香的主要组分及微结构进行测定,建立了基于XRF,PXRD和FTIR鉴别中药材主要组分及产地特征的新方法。实验结果表明,广藿香中含有K,Ca,Cl,Si和P等多种元素,独有的元素特征谱是广藿香形成药效好的道地药材的部分物质基础。广藿香含有大量的晶态物质及少量非晶态物质,且Ca在其中以CaC_2O_4·H_2O状态存在,被检样品中该晶体物质含量的多少与相关锐峰的强弱成正比。对FTIR谱峰进行了归属与分析,提供了醇类、黄酮及草酸钙等物质的化学组分信息。该法联用XRF,PXRD和FTIR技术从元素、原子和分子微观层面客观地表征了广藿香主要组分及微结构的相关信息,避免了单独使用某种方法的片面性,能避免因复杂的前处理导致样品固有组分的改变,具有快速、简洁、再现性好及易于接受等优点,为广藿香及其他中药材的质量控制和品质评价提供一种新方法。     

Multi-band metamaterial absorber topology for infrared frequency regime

In this paper, a new multiband metamaterial absorber design is proposed and the numerical characterization is carried out. The design is composed of three layers with differently sized quadruplets in which the interaction among them causes the multiband absorption response in the infrared frequency regime. In order to characterize the absorber and explain the multiband topology, some parametric studies with respect to the dimensions of the structure are carried out and the contributions of the quadruplets to the absorption spectrum are analyzed. According to the results, it is found that the proposed metamaterial absorber has five bands in the infrared frequency regime with the absorption levels of: 98.90%, 99.39%, 86.46%, 92.80% and 97.96%. Moreover, the polarization dependency of the structure is examined and it is found that the design operates well as a perfect absorber with polarization independency in the studied frequency range.     

Infrared spectra of catalysts and adsorbed molecules

The infrared absorption spectra of water adsorbed on Al₂O₃ and NiO-Al₂O₃ catalysts have been studied in the range 4000–1200 cm^–1. For all the catalysts, broad bands are observed at 3400 and 1640 cm^–1, characteristic of the stretching and bending vibrations of the OH groups in liquid water. The bands observed in the spectrum of alumina prepared from suspension in isopropyl alcohol are produced by water molecules and isopropyl alcohol molecules absorbed on the catalyst surface. The influence of treatment with heavy water and thermal treatment on the position of the infrared absorption bands in the spectrum of alumina is discussed.     

Correlation between structural and optical properties of ion beam synthesized β-FeSi2 precipitates in Si

The structural and optical properties of β-FeSi₂ precipitates produced by ion beam synthesis have been investigated by transmission electron microscopy, photoluminescence (PL) analysis and near infrared transmission measurements. The PL spectrum of β-FeSi₂ precipitates in a dislocation free sample has been observed to consist of a sharp line at 1.54 μm and a weak peak at 1.46 μm. Optical transmission measurements showed a direct band gap about 0.8 eV smaller than in continuous β-FeSi₂ film. Calculation of the electronic bands of β-FeSi₂ for different values of the lattice parameters indicates that this reduction can be ascribed to band distortion provided by the lattice strain.     

模拟月壤发射率光谱测量实验及精度评定

基于月球样品反射光谱的月表矿物识别和成分反演能力受到月球环境的严重影响,仅限于月球表面5％的成熟度较低的区域。相比之下,包含大量硅酸盐矿物的月球样品发射光谱不仅光谱特征明显,而且受月表大气、温差和真空等环境的影响较小,是研究月表成分和物理特性的新途径。因此,对于嫦娥五号月球探测器采集的月球实地样品的发射光谱测量不仅可用于月表硅酸盐类矿物的成分分析,而且可以作为遥感研究中可见光-近红外光谱的有效补充。但是,实验室发射光谱测量中最大的难题是寻找最佳的实验方法和仪器,以便获得准确可靠的光谱数据。研究以模拟月壤样品为测量对象,分别在实验室大气、氮气冷背景和模拟真空环境中,利用TurboFT 102F和Bruker VERTEX 70V两种仪器,设计和实施了傅里叶光谱法、独立黑体法和反射率法三种发射率测量实验,并利用误差传播定律和已有Apollo样品发射率光谱对实验获得的发射率光谱进行了精度分析与评定。发现在异常复杂和困难的模拟月球真空测量环境构建完成之前,密闭实验室环境中的反射率法发射率光谱特征最明显,测量精度最高,可以作为目前月球样品发射率光谱测量的最佳选择。研究希望能为嫦娥五号采集的月球样品发射率光谱测量实验提供理论基础和技术参数。     

Photoluminescence studies of nitrogen-doped TiO2 powders prepared by annealing with urea

Photoluminescence and excitation spectra have been investigated for undoped and nitrogen-doped TiO₂ powders at low temperatures. A broad luminescence band peaking at 2.25?eV is observed in the undoped TiO₂ powders. The 2.25?eV luminescence band exhibits a sharp rise from 3.34?eV in the excitation spectrum reflecting the fundamental absorption edge of anatase TiO₂. On the other hand, the N-doped TiO₂ powders obtained by annealing with urea at 350 and 500°C exhibit broad luminescence bands around 2.89 and 2.63?eV, respectively. The excitation spectra for these luminescence bands rise from the lower energy side of the fundamental absorption edge of anatase TiO₂. The origin of the luminescence bands and N-related energy levels formed in the band-gap of TiO₂ are discussed.     

Birkhoff’s theorem in f(T) gravity up to the perturbative order

The transmission of liquid argon has been measured, wavelength resolved, for a wavelength interval from 118 to 250?nm. The wavelength dependent attenuation length is presented for pure argon. It is shown that no universal wavelength independent attenuation length can be assigned to liquid argon for its own fluorescence light due to the interplay between the wavelength dependent emission and absorption. A decreasing transmission is observed below 130?nm in both chemically cleaned and distilled liquid argon and assigned to absorption by the analogue of the first argon excimer continuum. For not perfectly cleaned argon a strong influence of impurities on the transmission is observed. Two strong absorption bands at 126.5 and 141.0?nm with approximately 2 and 4?nm width, respectively, are assigned to traces of xenon in argon. A broad absorption region below 180?nm is found for unpurified argon and tentatively attributed to the presence of water in the argon sample.     

BeAl2O4:Cr3+紫外光谱的研究

在强场理论的基础上,本文考虑了组态相互作用,拟合了各能级位置,并对其紫外光谱进行了讨论.     

红外光谱在中药定性定量分析中的应用

红外光谱灵敏度高、操作简便、谱带的专属性强,特别适合于中药材的无损快速鉴别和定量分析,它正在成为中药质量控制方面的一种有效手段。文章综述了红外光谱在中药定性和定量研究中的应用现状,对红外光谱在中药材(同一药材不同部位,不同产地、品种的同种中药材,易混淆、真伪中药材等)和中成药(中药配方颗粒和注射剂等)的鉴别分析与有效成分含量测定等方面的应用进行了详细评述。随着傅里叶变换红外光谱和计算机技术的不断发展,它必将在中国中药的现代化和国际化道路上起到关键作用。     

Some electronic spectra of dibenzofuran

The low-energy electronic states of dibenzofuran have been investigated by absorption and emission spectroscopy. The absolute intensity of absorption parallel to the a and b axes of a single crystal at room temperature has been measured from 32 000 to 42 000 cm^?1, and qualitative information about the strength of the c-axis absorption was obtained from a study of finely-ground dibenzofuran compressed in KBr discs. The symmetries of three transitions were determined and tentative assignments of two others were made. The absorption bands in the spectrum of the crystal held at 4.2 K remained broad, an effect attributed to exciton-phonon interaction. Spectra of dibenzofuran in a polycrystalline n-heptane matrix at 4.2 K were sharp and vibrational analyses of fluorescence and phosphorescence are given in terms of the known ground state fundamentals.     

超细0.4nm直径单壁碳管的光学特性

由于纳米碳管的优异机械特性及其丰富多采的光学和电学特性，它自1991年被发现以来一直受到科学家的青睐，纳米碳管研究已成为当今世界上发展最迅速，竞争最激烈的科学前沿领域之一。怎样才能把纳米碳管做得更细小，尺寸更均匀以及如何使众多的纳米碳管排列规整，一直是纳米碳管研究中的难题。我们利用多孔的沸石晶体作为载体，首次成功地研制出了尺寸均一，排列规整的超细单壁纳米碳管，这些超细纳米碳管具有独特的性能，低温下（＜20K）甚至呈现出前所未有的一维超导现象。详细介绍了这些超细单壁纳米碳管的制备过程，并着重介绍其在可见光区的光吸收，光发射以及二次谱波的倍频特性。     

Ca4LaNbMo4O20:Pr3+荧光粉的发光性质

采用高温固相法成功制备出荧光粉Ca₄LaNbMo₄O₂₀:Pr³⁺,通过X射线衍射分析了样品的结构,其结构与CaMoO₄结构相似。在Ca₄LaNbMo₄O₂₀:Pr³⁺的激发光谱中出现了NbO₄^3-和MoO₄^2-的电荷迁移(CTS)吸收和Pr³⁺离子的4f→4f5d激发跃迁,以及Pr³⁺-金属离子的价间电荷迁移(IVCT)吸收;另外在420~520 nm处,还观测到属于Pr³⁺离子的典型f-f激发跃迁。发射光谱中,在452 nm激发下,主要出现绿光和红光两种发射,其峰值位于490 nm和607 nm处,分别是Pr³⁺的³P₀→³H₄和¹D₂→³H₄的跃迁作用;在紫外287 nm激发下出现NbO₄^3-和MoO₄^2-发射和Pr³⁺离子的4f5d→4f跃迁宽带,以及Pr³⁺离子的4f→4f发射峰。     

Rapid microwave-assisted synthesis and electrochemical characterization of gold/carbon nanotube composites

Hybrid nanostructures composed of gold nanoparticles (NPs) and carbon nanotubes (CNTs) have been prepared by a microwave-assisted method in the mixed solvents of oleylamine and oleic. The morphology, structure and composition of as-obtained Au/CNT composites are characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD). The composites show characteristic plasmon absorption of Au NPs in the Ultraviolet–visual spectrum. Fourier transform infrared spectrum shows the successful introduction of functional groups on the surface of CNTs, which are crucial factors to assist the nucleation in situ of Au NPs on the surface of CNTs. Electrochemical measurements show the enhancement electrochemical response for the gold electrode modified with Au/CNT composites.     

聚乙烯薄膜材料的红外光谱研究

由于红外吸收光谱法具有许多突出的优点,因此它在许多领域有广泛的应用。在薄膜、合成纤维、橡胶、塑料等高聚物的研究方面,用于单体、聚合物、添加剂的定性、定量和结构分析。一般高聚物的红外光谱中谱带的数目很多,而且不同种类的物质其光谱很不相同,特征性很强。此外红外光谱法的制样和实验技术相对比较简单,它适用于各种物理状态的样品。本实验研究以高聚物薄膜材料做样品,对样品高聚物进行红外光谱分析,分析表明,本实验所用样品高聚物成分为聚乙烯材料,这个实验结果也表明,用红外光谱法鉴定高聚物的组成非常有效。红外光谱法用于定量组分分析,与其它测量方法相比,具有制样简单方便、重复性好和测量精度高的特点。     

在溴化钾粉末中掺入大量α-炭化硅压片的异常红外透射光谱研究

在光谱学实践中，通常由于带测样品颗粒在本征吸收峰附近产生可观的附加散射消光，致使表观吸收峰偏离实际位置，从而得到不的光谱，这就是我们常要采取措施尽量避免的克里斯坦森（Christiansen）效,这一就是在制作压片（例如溴化钾）时，待测样品含量要少（少于2％）。在一次实验中，当在KBr粉末中掺入大量（而非正常要求的少许）的α-SiC微粉后，得到了一个在1052.33cm^-1处有一个尖峰的中红外透射谱。我们发现，这个新现象非常有趣，它与克里斯坦森效应表面上相反，但都可用Lorentz色散模型给予精确地解释。于是称它为反克里斯坦森效应，在该效应出现的频率处两种材料的折射率相等，且吸收系数都非常小。这个新现象也非常有意义，它可用来制造新型的带通滤波器以及准确测定某些材料的折射率等。