Large-scale synthesis of rutile SnO2 nanorods

A high yield of tin oxide (SnO₂) nanorods was obtained via annealing a nanoscale precursor in the molten salt flux and surfactant. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction and infrared spectroscopy showed that the nanorods are composed of SnO₂ with rutile structure. The surfactant and temperature have a profound influence on the production of SnO₂ nanorods.     

Bright blue photoluminescence from a mixed tin and manganese oxide xerogel prepared via solben hydrothermalben gel process

A new blue photoluminescent material, a mixed tin and manganese oxide xerogel, is prepared via sol-hydrothermal-gel process assisted by citric acid. The composition xerogel exhibits strong blue emission at room temperature, with an emission maximum at 434 nm under short (234 nm) or long-wavelength (343 nm) ultraviolet excitation. The photoluminescent excitation spectrum of the mixed tin and manganese oxide xerogel, monitored at an intensity maximum wavelength of 434 nm of the emission, consists of two excitation peaks at 234 nm and 343 nm. With heat treatment temperature increasing from 110 ℃ to 200 ℃, the blue emission intensity increases remarkably, whereas it is almost completely quenched after being treated at 300 ℃. The carbon impurities in the mixed tin and manganese oxide xerogel, confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, should be responsible for the bright blue photoluminescence.     

Pressure-induced structure change of molten KCl

Abstract

Energy-dispersive X-ray diffraction experiments of molten KCl under high pressure have been carried out by using synchrotron radiation. The diffraction profiles of molten KCl were acquired just above the melting temperature of KCl up to 4 GPa. The reduced structure factor S(Q)'s for molten KCl do not show any change in their primary features, except for a gradual increase in the first peak intensity with increasing pressure. This implies that molten KCl does not show a first-order phase transition, such as the B1-B2 transition, found in solid KCl, but that the local structure in molten KCl must be changed by compression. According to a molecular-dynamics simulation, this change of S(Q) can be explained by a continuous increase in the coordination number of the nearest-neighbor ions in molten KCl with pressure.     

Mössbauer spectra of tin in float glass

Tin is not a major constituent of window glass, but is found at high concentrations in the lower surface of float glass which has been in contact with the molten tin bath. It does not extend far into the surface, but causes the physical and chemical behaviour to differ from that of the upper surface. It is important, therefore, to understand the structural role of tin in silicate glasses and thus its effect on various properties. Mössbauer spectra were taken of three series of glassy materials, namely binary glasses (SnO and SiO₂) in varying proportions, re-melted float glass containing tin, and float glass from a production plant. The binary glasses contained between 20 and 70% tin which was found to be mainly Sn²⁺, with very small amounts of Sn⁴⁺ in some of them. The spectra showed a small decrease in isomer shift with increase in tin content, which is ascribed to the change in molar volume. The re-melted samples were float glass which was mixed with stannous oxalate in appropriate conditions to try and maintain tin in the 2+ state, and contained up to 15% tin by weight. The spectra show both Sn⁴⁺ and Sn²⁺ with rather more in the 4+ oxidation state. The change in the spectra as a function of temperature revealed a large difference in thef-factor (and hence the chemical binding) of the two states. A series of spectra was taken between 17.5 and 900 K for the sample containing 15% tin. From the absorption as a function of temperature thef-factor was determined for both oxidation states, and hence enabled the relative amounts of Sn⁴⁺ and Sn²⁺ present in each sample to be estimated. Measurements of the shift as a function of temperature were also made. The float samples were surface material produced by grinding away all but 0.1 mm of the lower surface of industrially produced float glass. The Mössbauer spectra showed them to be predominantly Sn²⁺, as expected from the reducing atmosphere in the float plant. The concentration and oxidation state of the tin may be estimated from the value of thef-factors and isomer shifts.     

Mößbauer-Effekt im normalleitenden und supraleitenden Zustand von Sn119

The number of Moessbauer quanta from the 23.8 keV state of Sn¹¹⁹ in a tin metal source was measured after attenuation by a 16.1 mg/cm² absorber of tin metal, as a function of temperature above and below the transition point of superconductivity. Source and absorber were kept at the same temperature. The data give evidence of a discontinuous change at the transition temperature: The transmitted intensity is lowered by (1,3±0.15)·10^?3 in the superconducting state of source and absorber. This corresponds to an increase of the Debye-Waller-factor by about 0,4%.     

Influence of Sn-doping in hydrothermal methods on the optical property of the ZnO nanorods

Sn-doped ZnO nanorods with various Sn-doping concentrations were prepared using a low temperature hydrothermal method in an aqueous solution containing zinc nitrate, ammonium hydroxide, and tin acetate. With the increase in the concentration of tin acetate, more Sn atoms replaced Zn atoms in the ZnO lattice, and the amount of Sn in ZnO nanorods increased up to 14 at%. The relative intensity ratio of UV and deep level emission of ZnO nanorods was increased with the increase of Sn-doping level, and four times increase in the intensity ratio of UV to deep level emission was obtained for 14 at% Sn-doped ZnO nanorods compared with undoped ones. A blueshift of UV emission was observed up to 11 at% of Sn concentration, but redshift occurred when the amount of Sn was greater than that.     

自由液态锡表面结构的流体模型

应用SolidWorks 和ANSYS 软件设计了自由液态锡表面流体结构模型,计算了初始流速和热通量不同时液态锡的速度变化和温度变化,得到了流动液态锡的速度分布和温度分布。结果表明,垂直流动方向液态锡流速较为均匀,沿流动方向液态锡流速逐渐增大、液态锡液面厚度逐渐变薄。初始温度为600K 的条件下,热通量为1MW·m⁻² 时,液态锡出口温度为623.38K;热通量为5MW·m⁻² 时,液态锡出口温度为720.18K。在相同条件下使用液态锂作为计算流体,结果表明出口处液态锂的温度低于液态锡的温度。     

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应用SolidWorks和ANSYS软件设计了自由液态锡表面流体结构模型,计算了初始流速和热通量不同时液态锡的速度变化和温度变化,得到了流动液态锡的速度分布和温度分布。结果表明,垂直流动方向液态锡流速较为均匀,沿流动方向液态锡流速逐渐增大、液态锡液面厚度逐渐变薄。初始温度为600K的条件下,热通量为1MW·m?2时,液态锡出口温度为623.38K;热通量为5MW·m?2时,液态锡出口温度为720.18K。在相同条件下使用液态锂作为计算流体,结果表明出口处液态锂的温度低于液态锡的温度。     

Monitoring the thermally induced structural transitions of collagen by use of second-harmonic generation microscopy

The thermal disruption of collagen I in rat tail tendon is investigated with second-harmonic generation (SHG) microscopy. We investigate its effects on SHG images and intensity in the temperature range 25 degrees-60 degrees C. We find that the SHG signal decreases rapidly starting at 45 degrees C. However, SHG imaging reveals that breakage of collagen fibers is not evident until 57 degrees C and worsens with increasing temperature. At 57 degrees C, structures of both molten and fibrous collagen exist, and the disruption of collagen appears to be complete at 60 degrees C. Our results suggest that, in addition to intensity measurement, SHG imaging is necessary for monitoring details of thermally induced changes in collagen structures in biomedical applications.     

Magnetoelectric Properties of the Transient Contacts of Bi85Sb15 Solid Solution with Alloys Containing Lead and Tin

The transient contact resistance for the extruded samples of Bi₈₅Sb₁₅ solid solutions with contact alloys containing lead and tin atoms depending on the thermal annealing, magnetic field intensity and temperature have been investigated. It is shown that observed peculiarities can be explained by the creation in a near-contact region of the intermediate layer doped by Pb and Sn atoms.     

钨在瞬态热流下熔融重凝对脉冲参数的依赖性

为了研究钨在瞬态热流下达到熔融状态后，不同脉冲参数对其熔融重凝行为的影响，实验观察了钨在脉宽5 ms与0.1 ms的脉冲辐照下熔融重凝行为的特征，并考虑熔融层流动驱动力、冷却速率、温度梯度等多项因素，分析了分层结构与柱状晶对热源参数的依赖性。通过计算两种热源参数下的热作用特性分析了钨在脉宽0.1 ms的脉冲辐照下出现柱状晶而在脉宽5 ms的脉冲辐照下未出现的原因。研究发现，高流强和短脉宽的脉冲束流易于促进形成分层结构，其原因是较高流强能引起材料表层熔化层流动，同时较短脉宽能使熔化层流痕来不及恢复平整，而被快速冷却固化；当样品在瞬态热流下发生熔化时，较短的脉宽有利于形成柱状晶，较长的脉宽有利于形成等轴晶粒和出现晶粒长大。     

Characterization of acoustic cavitation in water and molten aluminum alloy

High-intensive ultrasonic vibrations have been recognized as an attractive tool for refining the grain structure of metals in casting technology. However, the practical application of ultrasonics in this area remains rather limited. One of the reasons is a lack of data needed to optimize the ultrasonic treatment conditions, particularly those concerning characteristics of cavitation zone in molten aluminum.The main aim of the present study was to investigate the intensity and spectral characteristics of cavitation noise generated during radiation of ultrasonic waves into water and molten aluminum alloys, and to establish a measure for evaluating the cavitation intensity. The measurements were performed by using a high temperature cavitometer capable of measuring the level of cavitation noise within five frequency bands from 0.01 to 10 MHz. The effect of cavitation treatment was verified by applying high-intense ultrasonic vibrations to a DC caster to refine the primary silicon grains of a model Al–17Si alloy. It was found that the level of high frequency noise components is the most adequate parameter for evaluating the cavitation intensity. Based on this finding, it was concluded that implosions of cavitation bubbles play a decisive role in refinement of the alloy structure.     

脉冲CO2激光烧蚀锡靶等离子体的数值研究

使用一维辐射流体力学程序MULTI模拟了脉冲CO2激光烧蚀平面锡靶的过程,研究了脉冲宽度、峰值功率密度、靶材初始密度对锡等离子体电子密度、电子温度的时空分布的影响,并结合统计分析得到最有利于产生13.5 nm 极紫外光的激光脉冲宽度。模拟结果表明,脉冲宽度为100~200 ns的长脉冲激光产生的等离子体有利于实现极紫外输出的最佳条件,通过分析等离子体的电子密度、电子温度的分布对这一结论进行了解释。临界电子密度区域有效吸收了脉冲能量,而低密度的羽辉对激光与极紫外辐射的吸收很少。采用长脉冲激光,使得辐射极紫外等离子体持续时间更长,是提高极紫外辐射效率的有效手段。同时模拟还发现,靶材初始密度对等离子体参数的影响不大。     

Observation of gap-energy radiation from superconducting tin and indium

Electromagnetic radiation of gap energy was detected by irradiating bulk superconducting tin and indium with 30 and 20 keV electrons, respectively. An ellipsoidal mirror geometry was used to measure the total radiation intensity as a function of temperature. An analysis of the emitted radiation was performed with a parabolic mirror in combination with a Fabry-Perot microwave interferometer. Evidence for the emission of gap radiation in the millimeter range was found.     

Low-temperature vibrational properties of tin nanoparticles in porous glass

The heat capacity has been studied in the temperature range 2.2–40 K and in magnetic fields up to 2 T in tin, which has been embedded in nanometer-size pores in glass having diameter ∼7 nm, in bulk tin and in glass with empty pores. Comparison of the properties of tin nanoparticles and bulk tin has been performed. An increase in the coefficient of electronic heat capacity has been found in nanostructured tin as compared with the bulk tin, and also a considerable deviation of the low-temperature lattice heat capacity from the Debye law in the temperature region T > 3 K has been found. The fact that the density of thermal vibrations in nanocrystalline tin for low energies is higher than in bulk tin has been established using low-temperature heat capacity data.     

混合氯化熔融盐的腐蚀性实验

混合氯化盐是一种非常有前途的高温传热蓄热介质.为了确定混合氯化盐传热蓄热系统适用的金属材料,本文对2520、304、321和316L四种常用不锈钢在混合氯化盐中的腐蚀情况进行了实验研究,并与混合硝酸盐的腐蚀特性进行了对比.结果表明,混合氯化熔盐比混合硝酸盐对四种不锈钢的腐蚀性要大几十倍,混合氯化盐对四种不锈钢腐蚀速率从大到小依次为316L、304、321和2520.     

Melting of isolated tin nanoparticles

The melting of isolated neutral tin cluster distributions with mean sizes of about 500 atoms has been investigated in a molecular beam experiment by calorimetrically measuring the clusters' formation energies as a function of their internal temperature. For this purpose the possibility to adjust the temperature of the clusters' internal degrees of freedom by means of the temperature of the cluster source's nozzle was exploited. The melting point of the investigated tin clusters was found to be lowered by 125 K and the latent heat of fusion per atom is reduced by 35% compared to bulk tin. The melting behavior of the isolated tin clusters is discussed with respect to the occurrence of surface premelting.     

Gravity-free hydraulic jumps and metal femtoliter cups

Hydraulic jumps created by gravity are seen everyday in the kitchen sink. We show that at small scales a circular hydraulic jump can be created in the absence of gravity by surface tension. The theory is motivated by our experimental finding of a height discontinuity in spreading submicron molten metal droplets created by pulsed-laser ablation. By careful control of initial conditions, this leads to solid femtoliter cups of gold, silver, copper, niobium, and tin.     

Application of X-ray radiography to study the segregation process of iron from silicate under high pressure and high temperature

X-ray radiography was applied to observe the segregation process of iron from silicate at high pressure and high temperature in mixtures containing light elements. As the temperature of the hydrogen-containing sample increases, the molten iron becomes coherent. Small droplets of iron sink to the bottom of the chamber, where they merge into a single, large droplet. The small iron droplets exhibit complex motion, moving in random directions. Markedly different behavior is found in the sulfur-containing sample, where no clear motion of the molten iron is observed. Instead, as the sample temperature is increased, the concentration of iron near the wall of the sample chamber gradually increases. These observations demonstrate that the behavior of molten iron changes according to the dissolved elements. This X-ray radiography experiment represents a powerful technique to study the segregation process of molten iron from solid or partially molten silicate, particularly when combined with high-resolution tomography techniques.     

熔融过程中升温和降温对Al特征谱线的影响

为了解决LIBS技术应用于冶金过程成分分析时,温度变化导致测量精度低,重复性差的问题,就温度变化对等离子体的影响进行研究.以Al元素为研究对象,对比分析不同温度下的光谱强度、等离子体电子温度和电子密度,总结了温度上升和下降时光谱强度和等离子体特征参数的变化规律.结果表明,Al元素特征谱线强度随温度上升呈增大趋势,在70...