拉曼光谱分析青铜器本体中锈蚀产物

青铜器锈蚀研究能够揭示出青铜器腐蚀机理,为制定科学的保护措施提供重要的参考资料。目前,青铜器锈蚀研究主要从其外部锈蚀产物入手,通过锈蚀组成结构分析,探讨其腐蚀机理。本文选择了保存较好青铜器本体样品进行了内部锈蚀情况研究。首先采用金相制备技术,通过打磨、抛光和超声清洗处理后,制备了断面相组织形态清晰的24件秦早期青铜器青铜本体样品。然后利用共聚焦显微拉曼光谱仪对样品夹杂物进行了光谱学研究,发现其物相为PbCO₃和PbO及Cu₂O,都属于常见的青铜合金腐蚀产物。样品金相组织中圆形或者大面积无规则亮灰色区域为Cu₂O,反映出青铜器表面不仅易于形成一定厚度Cu₂O锈蚀层,在相界之间也容易发生氧化反应生成Cu₂O,存在合金内部和外部同时发生腐蚀生成赤铜矿锈蚀的情况。此外,拉曼光谱分析显示黑灰色物质主要为铅腐蚀产物——PbCO₃和PbO,反映出铅元素的腐蚀过程：Pb→PbO→PbCO₃。在铸造态青铜合金组织中,铅一般呈近圆形颗粒状态分布在相界之间。青铜器内部分布的铅颗粒在土壤埋藏环境中会发生氧化反应生成PbO,再与地下水中溶解的CO2-₃发生化学反应生成比较稳定的PbCO₃。结果表明：外界腐蚀因素(水、溶解氧和碳酸根等)能够通过合金中相界间通道进入青铜器内部,在相界表面逐步发生反应形成以金属氧化物为主的腐蚀产物。     

一青铜耳杯锈蚀的拉曼光谱分析

利用超景深显微镜和激光共聚焦显微拉曼光谱仪,对重庆市云阳县丝栗包遗址出土的一件青铜耳杯的锈蚀产物进行分析。通过分析可知,该耳杯的锈蚀物主要有:磷氯铅矿(Pb_5(PO_4)_3Cl)、白铅矿(PbCO_3)、氧化铅(PbO)、赤铜矿(Cu_2O)、孔雀石(Cu_2CO_3(OH)_2)和蓝铜矿(Cu_3(CO_3)_2(OH)_2)。铅的腐蚀产物由内向外的分布为氧化铅、白铅矿和磷氯铅矿。据此推断锈蚀外层磷氯铅矿的形成过程可能为:铅氧化成氧化铅,之后转换成白铅矿,白铅矿在酸性、富含磷和氯的环境下转变成化学性质稳定的磷氯铅矿。     

两件中国古代青铜错金(银)器表面锈蚀产物的光谱分析

错金银是青铜时代中国青铜器表面的一种贵金属镶嵌装饰技法,目前对这一技艺的研究比较少,更不深入,与其曾经崇高的地位极不相称。目前认知的青铜错金(银)器的制作工艺流程包括:先铸造出青铜器本体,再在青铜器表面錾刻出或预先已铸出图案或铭文所需的凹槽,然后嵌入打制好的金银丝片,最后打磨抛光,达到突出图案和铭文的装饰效果。利用X射线荧光光谱和X射线衍射手段对战国晚期和汉代的两件错金银青铜器本体、表面镶嵌的金丝(片)及锈蚀产物进行了成分及物相分析。两件青铜错金(银)器青铜本体Cu, Sn, Pb合金组成分别为:85.10%, 10.31%, 3.84%和90.15%, 7.68%, 1.86%,合金成分及配比都是中国古代青铜常见的。铜盏表面镶嵌金片的成分Au:70.38%和75.28%, Ag:27.51%和22.50%,相当于17～18 K金,虎形器表面镶嵌金饰的成分Au:85.16%, 88.06%和90.24%, Ag:13.37%, 10.18%和8.11%,相当于20～22 K金。青铜器常见的锈蚀物是各种含Cu, Sn和Pb的氧化物、碳酸盐、硫化物或硫酸盐及铜的氯化物,及石英、碳酸钙、氧化铁等来自土壤的污染物,而所分析的两件错金(银)青铜器锈蚀物中除常见的锈蚀产物外,还发现了在普通青铜器锈蚀物中罕见的铜硝石Cu_2(NO_3)(OH)_3, CuI等矿物。另外,青铜浇铸模拟实验发现,在未锈蚀前,所分析的错金(银)器本体合金颜色与金饰镶嵌物之间的色差不明显,达不到突出贵金属镶嵌物装饰的效果。据此,再结合特殊的锈蚀产物,提出了古代青铜错金银工艺中是否存在金属染色技术环节的设想,希望引起学者的关注。     

云南青铜防腐显微拉曼光谱和EPMA研究

应用显微激光拉曼光谱和EPMA(电子探针技术),对云南的四件青铜器(两件春秋时期的青铜矛和两面元代的青铜镜)的腐蚀情形和防腐技术进行了分析研究。拉曼实验结果表明,云南青铜器表面腐蚀产物的主要成分有Cu2O和CuCO3.Cu(OH)2。利用电子探针技术,确定了青铜器内部和表面的元素成分。本文初步分析了云南四件青铜器防腐技术的应用和发展,春秋战国时期,人们在青铜矛表面涂上一层锡的氧化物涂层以防腐蚀;元代的人则采用合金表面处理技术防腐。事实证明,锡的氧化物涂层的防腐效果最好。对金属文物的研究,显微激光拉曼光谱是一种原位无损检测的有效方法,但还是有某些局限性,若配合以电子探针等测试方法,可以达到更好的效果。     

新干商墓青铜器非晶与纳米晶锈蚀产物结构的分析研究

应用微区X射线衍射仪(μXRD)及高分辨透射电镜(HTEM)分析江西新干商墓出土的青铜器粉状锈蚀产物,结果表明锈蚀产物主要为具有锡石结构的SnO2,晶态形式为非晶与晶粒尺寸为4～5.7nm的纳米晶共混;能谱分析表明样品中除含有大量锡外,还有少量的铜、硅、铅与铁等元素。通过对锈蚀产物的高分辨透射电镜晶格条纹像计算,说明纳米晶SnO2的晶格中并没有其他原子的掺杂;对该锈蚀产物拉曼光谱的分析研究表明,样品不含有表征SnO2的体相拉曼峰,更具有非晶SnO2的特征,而973cm-1的弱而宽的峰表明样品含有非晶的硅酸盐类的锈蚀物,推测锈蚀产物中的少量铜、硅、铅与铁等元素应以非晶的形式存在。     

元代铜镜腐蚀情形的拉曼光谱研究

应用显微拉曼光谱和电子探针技术 ,对云南禄丰出土的元代铜镜腐蚀情形进行研究 ,确定了铜镜本体及其表面腐蚀产物的成分 ,并初步分析了元代青铜镜采用的防腐技术。拉曼实验结果表明 ,铜镜表面腐蚀产物的主要成分有CuCO3 ·Cu(OH) 2 和Cu2 O。实验还发现铜镜表面有一层铁铝合金 ,具有较好的防腐作用。对金属文物的研究 ,拉曼光谱被证明是一种很有效的方法     

拉曼光谱对古青铜矛腐蚀情形的无损研究

应用显微拉曼光谱对云南楚雄万家坝出土的古青铜矛进行无损研究 ,可确定其腐蚀产物的成分及在样品上的位置 ,还可帮助分析青铜矛所经历的腐蚀环境。腐蚀产物的主要成分有 Cu2 O和 Cu CO3.Cu( OH) 2 。本文还辅以电子探针测试 ,对矛尖的抗腐蚀性作了分析研究。与传统的鉴别方法如电镜、X光衍射等分析法相比较 ,拉曼光谱被证实是对金属器物作无损检测的一种非常有用的方法     

蓬莱出土古代青铜器锈蚀产物的显微喇曼光谱分析

首次运用显微喇曼光谱(RM)技术,对山东省蓬莱市登州博物馆馆藏古代青铜器的锈蚀产物进行分析,发现锈蚀产物的成分比较复杂,主要有蓝铜矿、孔雀石、氯铜矿、副氯铜矿、白铅矿、黄铅矾及方解石。证实该馆多数青铜器上白绿色粉状锈蚀产物为氯铜矿及副氯铜矿的混合物,是引发“青铜病”的重要隐患,所以,对这批青铜器进行科学的保护处理迫在眉睫。     

中国国家博物馆藏铜半结跏泥金观音锈蚀产物的光谱分析

铜质文物是中国古代文明发展历程的重要物质载体,具有多重价值。铜质文物在埋藏和保存过程中会发生腐蚀,导致器物表面被多种锈蚀产物覆盖。各类锈蚀产物对文物稳定性的影响不同,其中含氯锈蚀产物最受关注,因其多与“青铜病”有关。“青铜病”是一种由氯离子引发的快速腐蚀现象,可能对铜质文物的本体造成严重危害。因此,锈蚀产物的快速、准确鉴定对铜质文物的保护与研究具有重要意义。本研究以中国国家博物馆藏铜半结跏泥金观音表面锈蚀产物为研究对象,综合利用大幅面X射线荧光成像(MA-XRF)、光纤反射光谱(FORS)、扫描电镜能谱(SEM-EDS)、激光共焦显微拉曼光谱(Raman)几种方法对锈蚀产物成分结构及分布位置进行分析研究。研究结果表明该观音造像表面锈蚀产物主要包括碱式氯化铜(氯铜矿和斜氯铜矿)和蓝铜钠石。此外,还发现了一种含锌的碱式氯化铜,推测其分子式为Cu_3.52-3.64Zn_0.36-0.48(OH)₆Cl₂。这类锈蚀产物在铜质文物表面鲜少发现,该研究结果为其鉴定研究提供了新的参考数据。综合各类分析结果,进一步揭...     

阳离子对硅酸盐玻璃激光拉曼光谱影响的研究

运用拉曼光谱技术研究了Na2O(K2O)—CaO(MgO)—SiO2,Na2O(K2O)—Al2O3—SiO2,Na2O(K2O)—B2O3—SiO2,Na2O(K2O)—PbO—SiO2和PbO—BaO—SiO2五个系统的玻璃。结果表明,阳离子对玻璃近程结构的改造会引起拉曼特征的变化。部分样品是根据古玻璃平均成分在实验室烧制的,这项研究对于运用激光拉曼光谱区分不同系统的古代硅酸盐玻璃有重要意义。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.