Internal segregation of nanoparticles irradiated by laser radiation

The effect of the removal of zinc from brass nanoparticles has been experimentally discovered upon irradiating their suspension in ethanol by laser radiation. The analysis of the absorption spectra of nanoparticles shows that brass nanoparticles are transformed to copper nanoparticles during irradiation. The results are interpreted in terms of the high-pressure-induced modification of the phase diagram of nanoparticles. This pressure is caused by, first, the small radius of nanoparticles and, second, the pressure of the surrounding-liquid vapors upon the laser heating of nanoparticles.     

Spatial heterogeneity of the double-pulse laser plasma of copper alloys

The propagation processes of the plasma excited by double laser pulses in multicomponent copper alloys have been investigated. The methods to study direct and reverse substance deposition from the erosion plume have been developed. The spatial heterogeneity of the brass and bronze ablative plasma composition has been exhibited. With the use of laser beam defocusing relative to the sample surface, the propagation velocities of various elements in the ablative plasma have been estimated.     

Features of the surface morphology of brass and bronze upon irradiation with a high power ion beam

The change in the morphology and surface composition of copper alloys (brass LS 59-1, bronzes BrOS 10-10 and BrAJ 9-4) upon irradiation with a high power ion beam of nanosecond duration is studied. It is shown that craters are mainly formed at the location of lead or sulfur inclusions. The reverse deposition of zinc onto the surface of brass is found. Possible mechanisms of these phenomena are considered.     

金属特性对激光诱导击穿光谱最佳实验参数的影响

采用波长为532nm的单脉冲激光诱导两种金属样品铜和锌,产生等离子光谱,固定激光能量40mJ、门宽100ns、光谱仪入射狭缝0.1mm、ICCD增益100等参数,研究金属样品物理化学特性对汇聚透镜焦点到样品表面距离、ICCD采集延迟等最优化实验参数的影响.实验中分别选取铜样品Cu（I）521.82nm和锌样品Zn（I）481.053nm谱线作为LIBS信号,实验测定的透镜焦点在距样品表面不同距离处的LIBS信号强度,结果表明铜和锌样品的聚焦透镜焦点分别在样品表面内距表面的距离为5mm和5.5mm时得到光谱信号强度最大;铜和锌的ICCD探测延时分别为1300ns和1100ns时等离子体光谱信号的信噪比最大并具有可观测的强度,依据铜和锌样品物理化学特性的差异对实验结果进行了合理的分析与讨论,为后续研究金属样品LIBS技术的基底效应、纳米结构增强激光诱导击穿光谱机理提供数据参考.     

发射光谱法研究微波增强微秒级脉冲辉光放电中样品原子的 …

利用自制微波增强微秒级脉中辉光放电装置，研究了黄铜样品原子的激发和扩散过程，结果表明，当放电气压低于１８０Ｐａ时，微波等离子体与辉光放电很好的耦合，当气压大于２００Ｐａ时，由于样品原子分别受到脉冲辉光放电与微波等离子体的激发，同一条共振线出现了在时间上独立的两个发射峰。利用两发射峰之间的关系可以计算出该工作条件下铜原子和锌原子的扩散速度分别约为１５０和１２９ｍ／ｓ，而辉光放电的最强激发点的约离溅射     

Structural evolution of copper alloys under high-power ion-beam irradiation

Structural and phase transformations in copper and its alloys—brass and bronze, irradiated by a high-power ion beam are investigated by X-ray diffraction and scanning-electron microscopy. It is established that the phase reconstruction in brass is caused by the partial removal of zinc from the surface and its diffusion toward the surface from deeper surface layers. Copper and bronze undergo only structural transformations induced by the growth of stresses of type I, II, and III and dislocation density.     

Calibration-free laser-induced breakdown spectroscopy for quantitative elemental analysis of materials

The application of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) for quantitative analysis of materials, illustrated by CF-LIBS applied to a brass sample of known composition, is presented in this paper. The LIBS plasma is produced by a 355?nm pulsed Nd:YAG laser with a pulse duration of 6?ns focussed onto a brass sample in air at atmospheric pressure. The time-resolved atomic and ionic emission lines of Cu and Zn from the LIBS spectra recorded by an Echelle spectrograph coupled with a gated intensified charge coupled detector are used for the plasma characterization and the quantitative analysis of the sample. The time delay where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the elemental analysis of samples from the LIBS spectra, is deduced. An algorithm relating the experimentally measured spectral intensity values with the basic physics of the plasma is developed. Using the algorithm, the Zn and Cu concentrations in the brass sample are determined. The analytical results obtained from the CF-LIBS technique agree well with the certified values of the elements in the sample, with an accuracy error <1%.     

纳秒激光诱导紫铜黄铜等离子体特征参数的对比研究

基于1064 nm Nd:YAG激光器,对比研究了紫铜和黄铜等离子的特征参数。洛仑兹函数拟合Cu I 324.75 nm得到紫铜和黄铜等离子体的电子密度分别是3.61017 cm-3和3.31017 cm-3。为了减小谱线自发辐射跃迁几率不确定性和测量误差带来的计算误差,采用改进型迭代玻耳兹曼算法精确求解紫铜等离子体和黄铜等离子体的电子温度分别是6316 K和6051 K,分析表明,两种等离子体特征参数的差异主要是由于黄铜中的锌元素的电离能（9.39 eV）大于铜元素的电离能（7.72 eV）而造成的。实验数据证实激光诱导的紫铜和黄铜等离子体满足局部热力学平衡模型和光学薄模型。     

金纳米与磁场作用下LIBS检测灵敏度改善研究

针对激光诱导击穿光谱技术（LIBS）中等离子体的发射光谱增强问题,提出一种磁场增强LIBS与纳米颗粒增强LIBS（NELIBS）相结合的方法。采用热蒸发法在样品表面沉积一层直径20 nm的金纳米颗粒。利用波长为1 064 nm,最大能量为200 mJ的Nd∶YAG脉冲激光器在室温,一个标准大气压下对纯铜和黄铜进行诱导击穿。调整激光能量为30~110 mJ,分别使用传统LIBS、磁场增强LIBS、NELIBS以及两种方法结合对纯铜进行激光诱导击穿,得到特征谱线(Cu Ⅰ 521.8 nm)的强度增强因子和信噪比,并对其增强机理进行分析。在相同环境下使用四种方式对黄铜和纯铜进行诱导击穿以探测样品中的微量元素。当在样品表面沉淀金纳米颗粒或者将沉淀有金纳米颗粒的样品放在磁场中进行诱导击穿时,发现纯铜样品的光谱中存在Mg元素的特征谱线Mg Ⅱ 279.569 nm,黄铜样品的光谱中存在Si元素的特征谱线 Si Ⅰ 251.611 nm。实验结果表明：单独施加磁场约束或增加纳米金颗粒均可以有效增强等离子体光谱强度,但增强效果弱于两种方法结合,磁场约束对光谱的增强效果弱于NELIBS的增强效果。当结合NELIBS与磁场约束LIBS时,谱线增强因子最高可达14.3(Cu Ⅰ 521.8 nm),相比于磁场增强LIBS和NELIBS,最大增强因子分别提高了28%和59%。四种情况中当激光脉冲能量逐渐增大时,等离子体向外膨胀的强度增大,磁场产生的洛伦兹力束缚等离子的能力相对减弱,同时纳米金颗粒对等离子体发射光谱的增强作用被削弱,谱线强度降低,等离子体的增强因子逐渐减小后趋于稳定。通过NELIBS与磁场约束LIBS结合方式,不仅可以有效提高等离子体的发射谱线强度,改善光谱信号信噪比,而且传统LIBS方法中由于谱线强度低、背景噪声大而无法探测的微量元素可以被探测到,LIBS技术对微量元素的探测能力得到显著提高,微量元素的探测下限变得更低。NELIBS与磁场约束LIBS结合的方法具有更高的灵敏度和准确度,为激光诱导击穿光谱技术的谱线增强方法提供了新的思路,在该领域具有广阔的应用前景。     

Variations in the Concentrations of Cu and Zn and in the Ratio of Cu to Zn in Whole Blood and Hair Samples from Hepatocellular Carcinoma Patients and from Healthy Controls in Taiwan

An atomic absorption spectrophotometer was used to determine concentrations of copper and zinc and the ratio of Cu to Zn in samples of whole blood and hair from hepatocellular carcinoma (HCC) patients (n=51) and from healthy controls (n=50) in Taiwan. Our results indicate that the HCC patients have higher copper concentrations and higher ratios of Cu to Zn than do the healthy controls both in whole blood and hair samples, but only the concentration of copper and the ratio of Cu to Zn in whole blood were significantly different (p<0.001 and p<0.05). Conversely, a lower concentration of zinc was found in whole blood and hair samples of HCC patients. Similarly, only the concentration of zinc in whole blood showed a significant difference (p<0.001). We concluded that the whole blood concentrations of copper and zinc and the ratio of Cu to Zn seemed to have a higher correlation with HCC. Thus, we suggest that a sample of whole blood may be a more suitable diagnostic sample than is a hair sample for HCC.     

Phase diagrams of laser-processed nanoparticles of brass

Nanoparticles of brass are prepared by ablation of a brass target in ethanol using radiation of a copper-vapor laser at various laser fluences. The nanoparticles are characterized by TEM and optical spectroscopy. The multipulse laser irradiation leads to formation both the nanoparticles in liquid and well-ordered micro-structures on a surface of a target. It is revealed that both the morphology and absorption spectra of brass nanoparticles depend on presence of the micro-structures. Nanoparticles with the various phase diagrams are formed from a flat brass surface and from the same surface with micro-structures. The results are compared with a model of phase diagrams, in which size and composition effects are taken into account.     

Formation of periodic structures by laser ablation of metals in liquids

Experimental results are presented on ablation of metals (W, Cu, brass and bronze) in a liquid environment (e.g., ethanol or water) by irradiation with either a pulsed copper vapor laser (0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). The target material is ejected into surrounding liquid in the form of nanoparticles. In a certain range of laser parameters (fluence and number of laser shots) the surface of the solid target is composed of micro-cones having a regular structure. The distance between neighboring micro-cones in the structure depends on the laser spot size. The structures allow the observation of up-conversion of the laser frequency due to generation of the second harmonics in the eye retina.     

Surface characterization of copper, zinc and brass in contact with tap water inhibited with phosphate ions

The composition of the surface layers has been investigated on copper, zinc and brass in contact with moderately hard, highly carbonated and chloride rich artificial tap water (ATW). Cyclic voltammetry, reflectance spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy have been used to identify the changes in composition that result from the incorporation of sodium orthophosphate to ATW. The results showed that when PO₄³⁻ is added, the film changes its composition and it also becomes thinner, denser and more compact. On copper, the presence of CuO in the passive film can be correlated to the improvement in the corrosion behavior in the presence of phosphate ions. In the case of brass, the development of a thinner, compact and less porous Zn₃(PO₄)₂ layer hinders Cu(I) dissolution. A mechanism explaining the effect of this inhibitor is proposed, which accounts for the experimental results.     

Characterization of Schottky barrier diodes fabricated from electrochemical oxidation of α phase brass

By careful selection of chloride ion concentration in aqueous sodium chloride, electrochemical oxidation of α phase brass is shown to permit fabrication of either p-type copper (I) oxide/metal or n-type zinc oxide/metal Schottky barrier diodes. X-ray photoelectron and Auger electron spectroscopies provide evidence that barrier formation and rectifying qualities depend on the relative surface abundance of copper (I) oxide and zinc oxide. X-ray diffraction of the resulting diodes shows polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional I/V characteristics of these diodes show good rectifying qualities. When neither of the oxides dominate, the semiconductor/metal junction displays an absence of rectification.     

Characteristics of zinc behavior during laser welding of zinc “sandwich” sample

To address the problem of the zinc being easily gasified in laser welding of galvanized steel, laser welding of a zinc “sandwich” sample was performed to experimentally investigate the behavior and characteristics of the zinc inside and outside the keyhole, including the observation of the keyhole, the zinc vapor and zinc plasma, and the calculation of the electron temperature of the zinc plasma. Based on the principle of imaging amplification, the detected multi-points can be located precisely in order to study the distribution of the electron temperature of the zinc plasma. The results show that the zinc behavior played an important role in the formation of the weld-joint and the zinc plasma altered the energy distribution at the top of the keyhole whose diameter has been enlarged in the welding process. For both continuous-wave laser and pulsed laser welding of zinc “sandwich” sample, the average electron temperature of the zinc keyhole plasma was higher than that of the zinc plasma plume outside the keyhole. In the welding process, the continuous wave laser with higher input energy results in higher position of the zinc plasma with higher electron temperature above the sample surface. More zinc vapor resulted in a higher average electron temperature of the plasma.     

Mechanodynamic diffusion of helium atoms into porous copper

Mechanodynamic penetration of helium atoms into porous copper compressively strained at 4.2 K is studied. Porous copper is obtained by vaporizing zinc out of brass in vacuum at a temperature of 800°C for 8 h. The number of helium atoms which penetrated into the sample increased monotonically with strain to reach 2.9 × 10¹⁶ atoms/cm² at ? = 42%. This amount of helium is two and even more orders of magnitude larger than that obtained from the data available thus far on mechanodynamic penetration of atoms of an external medium into crystalline and amorphous materials under strain. The relations obtained suggest that specific types of helium traps determine the kinetics of mechanodynamic diffusion of helium into solids.     

Combination of spark discharge and nanoparticle-enhanced laser-induced plasma spectroscopy

A combination of spark discharge and nanoparticle-enhanced laser-induced plasma spectroscopy is investigated. Depositing Au nanoparticles at the surface of a brass target can enhance the coupling of the target and the laser. More atoms in the brass sample are excited. As a secondary excitation source, spark discharge reheats the generated plasma, which further amplifies the enhancement results of nanoparticles. The spectral intensity with the spark discharge increases more obviously with nanoparticle concentration increasing than without the spark discharge. Also, plasma temperature and electron density are calculated by the Boltzmann plot and Stark broadening. The changes in the plasma temperature and electron density are consistent with the spectral emission changes.     

纳秒激光诱导紫铜黄铜等离子体特征参数的对比研究

基于1064 nm Nd:YAG激光器,对比研究了紫铜和黄铜等离子的特征参数。洛仑兹函数拟合Cu I 324.75 nm得到紫铜和黄铜等离子体的电子密度分别是3.61017 cm-3和3.31017 cm-3。为了减小谱线自发辐射跃迁几率不确定性和测量误差带来的计算误差,采用改进型迭代玻耳兹曼算法精确求解紫铜等离子体和黄铜等离子体的电子温度分别是6316 K和6051 K,分析表明,两种等离子体特征参数的差异主要是由于黄铜中的锌元素的电离能（9.39 eV）大于铜元素的电离能（7.72 eV）而造成的。实验数据证实激光诱导的紫铜和黄铜等离子体满足局部热力学平衡模型和光学薄模型。     

非完全消解-火焰原子吸收光谱法测定虾皮中的铁、铜、锌和锰

用非完全消解法处理虾皮样品,即在低温下用浓硝酸-过氧化氢(3+1)混合酸消解样品,再用乳化剂OP溶解未消解的油脂而配制成无色透明的溶液,将此溶液用火焰原子吸收光谱法测定其中铁、铜、锌和锰元素的含量。建立了快速测定虾皮中微量元素的火焰原子吸收光谱法。对样品处理条件、混合酸中杂质及共存OP的干扰进行了实验,铁、铜、锌和锰的检出限(3S/k)分别为0.021、0.047、0.008、0.026m g.L-1。该法测定虾皮中铁、铜、锌和锰的含量,所得结果与灰化法测定结果一致。     

Dual-pulse laser-induced breakdown spectrometry of bronze alloys and coatings

The possibilities of using dual-pulse laser atomic-emission spectroscopy for both the estimation of elemental concentrations in bronzes and layer-by-layer analysis of a bronze coating on steel bead wire have been examined. Two methods have been proposed to lower the radiation flux density q in studies of thin metallic layers. These were based respectively on using optical filters and defocusing the radiation with respect to a sample surface. It has been found that the decrease of q results in reducing the influence of tin on copper evaporation under dual-pulse laser irradiation.