Continuum source tungsten coil atomic fluorescence spectrometry

A simple continuum source tungsten coil atomic fluorescence spectrometer is constructed and evaluated. The heart of the system is the atomizer: a low-cost tungsten filament extracted from a 150 W light bulb. The filament is resistively heated with a small, solid-state, constant-current power supply. The atomizer is housed in a glass chamber and purged with a 1 L/min flow of a conventional welding gas mixture: 10% H(2)/Ar. A 25 μL sample aliquot is pipetted onto the tungsten coil, the liquid is dried at low current, and then the atomic vapor is produced by applying a current in the range 3.5-5.5 A. The atomization current does not produce temperatures high enough to excite atomic emission. Radiation from a 300 W xenon lamp is focused through the atomic vapor, exciting atomic fluorescence. Fluorescence signals are collected using a hand-held charge-coupled device (CCD) spectrometer. Simultaneous determination of ten elements (Ag, Bi, Cr, Cu, Ga, In, Mg, Mn, and Tl) results in detection limits in the range 0.3 to 10 ng. The application of higher atomization currents (10 A) leads to straightforward detection of atomic emission signals with no modifications to the instrument.     

JY Ultima2ICP-OES光谱仪测定Ta-2.5W和Ta-10W中钨元素的分析方法研究

采用发射光谱仪建立发射光谱法测定Ta-2.5W和Ta-10W中钨含量的方法。使用高纯氢氧化钽基体的纯钨标准溶液制作工作曲线,钨的分析线为209.475 nm,方法的线性范围为1.25%~15.00%,加标回收率在93.0%~99.0%之间,测定结果的RSD值(n=11)小于0.8%。     

Fraunhofer effect atomic absorption spectrometry

The dark lines in the solar spectrum were discovered by Wollaston and cataloged by Fraunhofer in the early days of the 19th century. Some years later, Kirchhoff explained the appearance of the dark lines: the sun was acting as a continuum light source and metals in the ground state in its atmosphere were absorbing characteristic narrow regions of the spectrum. This discovery eventually spawned atomic absorption spectrometry, which became a routine technique for chemical analysis in the mid-20th century. Laboratory-based atomic absorption spectrometers differ from the original observation of the Fraunhofer lines because they have always employed a separate light source and atomizer. This article describes a novel atomic absorption device that employs a single source, the tungsten coil, as both the generator of continuum radiation and the atomizer of the analytes. A 25-microL aliquot of sample is placed on the tungsten filament removed from a commercially available 150-W light bulb. The solution is dried and ashed by applying low currents to the coil in a three-step procedure. Full power is then applied to the coil for a brief period. During this time, the coil produces white light, which may be absorbed by any metals present in the atomization cloud produced by the sample. A high-resolution spectrometer with a charge-coupled device detector monitors the emission spectrum of the coil, which includes the dark lines from the metals. Detection limits are reported for seven elements: 5 pg of Ca (422.7 nm); 2 ng of Co (352.7 nm); 200 pg of Cr (425.4 nm); 7 pg of Sr (460.7 nm); 100 pg of Yb (398.8 nm); 500 pg of Mn (403.1 nm); and 500 pg of K (404.4 nm). Simultaneous multielement analyses are possible within a 4-nm spectral window. The relative standard deviations for the seven metals are below 8% for all metals except for Ca (10.7%), which was present in the blank at measurable levels. Analysis of a standard reference material (drinking water) resulted in a mean percent recovery of 91%. This report attempts to give an historical perspective on the development of a novel atomic spectrometer based on the Fraunhofer effect.     

Synthesis and NO2-sensing properties of one-dimensional tungsten oxide nanowire bundles

Tungsten oxide nanowires were synthesized by solvothermal method with tungsten hexachloride (WCl6) as precursor. X-ray diffraction, field emission scanning electron microscope and transmission electron microscope characterizations indicated that the as-synthesized nanowires are single phase monoclinic W18O49. With WCl6 concentration increasing, the bundled nanowire became shorter and thicker. The gas-sensing properties of W18O49 nanowire towards NO2 gas were evaluated and the results showed that the optimal gas sensitivity is achieved at 150 degrees C and the thinner nanowire exhibits the higher sensitivity. The results indicate that tungsten oxide nanowire is a promising gas-sensing material for high performance and low power cost NO2 gas sensor.     

Bi／Bi2O3晶格复合热电薄膜的制备及其性能研究

利用射频磁控溅射法在玻璃基片上制备Bi／Bi2O3晶格复合热电薄膜,考察了溅射功率对单层Bi薄膜表面粗糙度和热电性能的影响,结果表明,当溅射功率为22W时,薄膜具有最小的表面粗糙度16.3nm,电导率和功率因子分别为2．9×10^4S／m和5．74μV／k^2m,单层Bi薄膜最佳的工作温度为85～105℃。Bi／Bi2O3晶格复合热电薄膜最佳的溅射层数为5层,其电导率和功率因子分别为9．0×10^4S／m和21．0μN／k^2m,分别比单层Bi薄膜提高了2．1倍和2．65倍。     

Elemental determination of microsamples by liquid film dielectric barrier discharge atomic emission spectrometry

In this study, a new liquid-film dielectric barrier discharge (LFDBD) atomic emission source was developed for microsample elemental determination. It consists of a copper electrode, a tungsten wire electrode, and a piece of glass slide between them, which serves as the dielectric barrier as well as the sample plate. The sample solution with 1 mol L(-1) nitric acid, when deposited onto the surface of the glass slide, forms a thin liquid film. The plasma is generated between the tip of the tungsten wire electrode and the liquid film surface when alternating-current (ac) high voltage (peak voltage ~3.7 kV, frequency ~30 kHz) is applied on the electrodes. Qualitative and quantitative determinations of metal ions in the sample solution were achieved by atomic emission measurements in the plasma and were demonstrated in this study with elements Na, K, Cu, Zn, and Cd. Detection limits were in the range from 0.6 ng (7 μg L(-1)) for Na to 6 ng (79 μg L(-1)) for Zn. Repeatability, expressed as relative standard deviation from seven repetitive analyses of samples with analyte concentrations at 1 mg L(-1), varied from 2.1% to 4.4%. Compared with other liquid discharge systems that operate at atmospheric pressure, the current system offers several advantages: First, it eliminates the use of a sample flow system (e.g., syringe or peristaltic pump); instead, a small aliquot of sample is directly pipetted onto the glass slide for analysis. Second, it is a microanalysis system and requires sample volume ≤80 μL, a benefit when a limited amount of sample is available. Third, because the sample is applied in aliquot, there is no washout time, and the analysis can be easily extended to sample array for high-throughput analysis. The proposed LFDBD is promising for in-field elemental determination because of its simplicity, cost effectiveness, low power supply, and no inert gas requirement.     

Tunable high-power narrow-spectrum external-cavity diode laser at 675 nm as a pump source for UV generation

High-power narrow-spectrum diode laser systems based on tapered gain media in an external cavity are demonstrated at 675 nm. Two 2 mm long amplifiers are used, one with a 500 μm long ridge-waveguide section (device A), the other with a 750 μm long ridge-waveguide section (device B). Laser system A based on device A is tunable from 663 to 684 nm with output power higher than 0.55 W in the tuning range; as high as 1.25 W output power is obtained at 675.34 nm. The emission spectral bandwidth is less than 0.05 nm throughout the tuning range, and the beam quality factor M(2) is 2.07 at an output power of 1.0 W. Laser system B based on device B is tunable from 666 to 685 nm. As high as 1.05 W output power is obtained around 675.67 nm. The emission spectral bandwidth is less than 0.07 nm throughout the tuning range, and the beam quality factor M(2) is 1.13 at an output power of 0.93 W. Laser system B is used as a pump source for the generation of 337.6 nm UV light by single-pass frequency doubling in a bismuth triborate (BIBO) crystal. An output power of 109 μW UV light, corresponding to a conversion efficiency of 0.026% W(-1), is attained.     

Low power design of CMOS 5-GHz voltage-controlled oscillator from narrowband to wideband with switching capacitor module

In this study, we demonstrated low power and low phase noise of the complementary cross-coupled voltage-controlled oscillators (VCOs). Two chips are implemented by TSMC standard 0.18-mum complementary metal-oxide semiconductor (CMOS) process. The first one that employed a memory reduction tail transistor technique is operated from 5.17 to 5.85 GHz at a supply voltage of 1.2 V whereas its tuning range is 12.3%. The power consumption is 1.8 mW whereas the measured phase noise is -126.6 dBc/Hz at 1-MHz frequency offset from 5.17 GHz. The other employed switching capacitor modules to achieve wide tuning range and minimise phase noise, it operated from 3.64 to 5.37 GHz with 38% tuning range. The power consumption is 13.7 mW by a 1.8 V supply voltage and the measured phase noise in all tuning ranges is less than -122 dBc/Hz at 1-MHz frequency offset.     

A 200–500-W transformer-type inductive light source operated at a frequency of 150–400 kHz

The results are given and discussed of experimental investigations of the electrical (voltage and current of inductance coil, loss of power in a ferrite magnetic circuit) and photometric (light flux and light output) characteristics of a 200–500-W transformer-type inductive fluorescent light source operated at frequency f = 150–325 kHz. The high light output (80–85 lm/W) at high power of 300–400 W and low frequency of 150 kHz is attained owing to low loss of power (4.5–6.5 W) in the magnetic circuit and inductance coil.     

流延法制备单片式直接碳固体氧化物燃料电池组及其性能研究

本研究针对小型电源应用, 提出一种基于单片电解质的直接碳固体氧化物燃料电池组的设计和制备方法。采用流延成型的工艺制备YSZ平板式电解质, 通过在生坯上打孔作为电解质两侧电极的电连接通道, 在单片电解质平板上制备四节串联的电池组, 有效面积为5.6 cm ²。采用5 g担载5wt% Fe催化剂的活性炭为燃料, 对电池组的输出性能及稳定性进行测试。结果表明: 850 ℃下电池组的开路电压为3.80 V, 最大输出功率为1.66 W, 对应的功率密度为296 mW×cm ^-2。同时, 测得的四节串联电池组中的第一节单电池的最大输出功率密度为294 mW×cm ^-2, 说明该电池组中各单电池一致性良好。在800 ℃下, 电池组在300 mA的恒电流下放电11 h, 放电容量为8.42 W×h, 燃料利用率达到了~30%。本研究可以为开发直接碳固体氧化物燃料电池在便携式和分布式电源方面的应用提供参考 依据。     

High Accuracy On-Line Calibration System for Current Transformers Based on Clamp-Shape Rogowski Coil and Improved Digital Integrator

To solve the problems of the existing on-site calibration methods, for instance, the methods need power off, and the standard transformers have large volume, heavy weight and small dynamic range, this paper proposes a high accuracy on-line calibration method for current transformers. By using a clamp-shape Rogowski coil as the standard current transformer, instead of traditional electromagnetic transformer, the volume and weight are reduced greatly, and the power of the line needn’t to be interrupted. The output signal of the clamp-shape Rogowski coil needs to be integrated, and to overcome the problems of analog integrator, which have temperature and zero drift, a high accuracy digital integrator is proposed in the paper to improve the accuracy and stability of the signal processing circuit. Test results indicate that the accuracy of the whole calibration system can reach up to 0.05 accuracy class. The on-line calibration system can calibrate the traditional and electronic current transformers when the line is energized.     

Interaction of highly dissociated low pressure hydrogen plasma with W-C thin film deposits

Thin film deposits of carbon and tungsten on stainless steel substrate were prepared by RF sputtering of a tungsten target in acetylene atmosphere. At the target bias of − 1700 V and the target current of 30 mA cm^− 2, a rather uniform film containing 50 at.% of C and 50 at.% of W was deposited. The thickness of the deposited film was about 1 μm. Samples were exposed to highly dissociated hydrogen plasma created by a microwave discharge at the power of 1000 W. Some samples were heated additionally by concentrated solar radiation. After plasma treatment, the samples were characterized by X-Ray Diffraction and Auger Electron Spectroscopy. The results showed that aggressive hydrogen plasma allows for the removal of carbon from the deposits at moderated temperatures. Prolonged treatment showed formation of highly crystalline pure tungsten, and finally the tungsten film interacted with the substrate forming a thin film rich of Fe₇W₆ compound. The range of temperature and/or treatment time for the removal of carbon from the W-C film was found very narrow.     

A high-power low-pressure iodine lamp pumped by glow discharge

We present the working characteristics of a high-power UV-VUV electric-discharge lamp filled with a working mixture of helium and iodine vapor (He-I₂) at a low pressure (0.1–1.5 kPa) and pumped by a dc glow discharge at a power of 15–200 W. The power of the total output UV radiation and the main emission peak at λ = 206.2 nm were studied as dependent on the electric power supplied to the glow discharge and on the partial pressure of helium in the He-I₂ mixture. The emission characteristics of the glow discharge plasma were studied in the spectral range from 200 to 350 nm. In this range, the lamp is operating predominantly on a resonance emission line of excited iodine atoms (λ = 206.2 nm, FWHM = 0.10–0.12 nm) and on a system of electronic-vibrational bands of excited iodine molecules with the main peak at λ = 342 nm. The contribution of the resonance emission due to excited iodine atoms to the total UV emission from the glow discharge plasma does not exceed 50%. The optimum partial pressure of helium is within 400–800 Pa. The total UV radiation power of the lamp operating in the optimum regime reaches 25 W at an efficiency of η ≤15%.     

Microstructure and mechanical properties of biocompatible high density Ti–6Al–4V/W produced by high frequency induction heating sintering

High frequency induction heating sintering method is used for sintering of the metal and ceramics powder. This technique has been used to produce high density compacts, containing as small grains as possible of powders. The alloy of Ti–6Al–4V was modified by addition of 2.5, 5, and 10 wt.% tungsten through powder metallurgy. Ti–6Al–4V/W was prepared by high-energy mechanical milling. The use of the high frequency induction heating sintering technique allows sintering to nearly full density at comparatively low temperatures and short holding times, and therefore suppressing grain growth. Different process parameters such as sintering temperature, and applied pressure have been investigated. The obtained compacts are characterized with respect to their densities, grain morphologies and pore distributions as well as hardness. Ti–6Al–4V/W powder precursors have been successfully compacted and consolidated to densities exceeding 98.8%. The maximum compressive strengths were obtained at sintering temperature 1000 °C for the samples containing 5% W, and at 1100 °C for the samples with 10% W. Maximum hardness was obtained 45 HRC at 1100 °C for 10% W.     

Optical emission from metal targets bombarded by 5–20 keV argon ions

The spectral composition of optical emission from high-purity iron (99.99% Fe), zirconium (99.98% Zr), and tungsten (99.96% W) targets bombarded by 5–20 keV Ar⁺ ions has been studied. The ion-bombardment-induced emission spectra of all metals exhibit two broad bands in the visible and IR spectral range. The first band is assigned to the emission from thermal spikes representing nanosized regions heated to 5000–6000 K, which are formed at the target surface in the course of evolution of high-density atomic collision cascades. The presence of an IR emission band is explained by the integral heating of targets to 500–800 K in the course of ion irradiation. This interpretation is confirmed by agreement between the experimentally measured and calculated temperatures in the region of thermalized collision cascades and the relative intensities of emission bands.     

First-principles models for phase stability and radiation defects in structural materials for future fusion power-plant applications

Generic materials-related problems foreseen in connection with the operation of a fusion power plant present a major challenge for the development of magnetically confined fusion as a commercial power generation option. In this review, we focus on the predictive capabilities of first-principles-based atomistic models for radiation defects and phase stability of body-centred cubic Fe–Cr-based ferritic-martensitic and ferritic steels and tungsten alloys, which are presently under consideration as candidate structural materials for the first wall and diverter applications. Density-functional calculations predict that low-Cr iron alloys are stabilized by intra-atomic exchange, giving rise to magnetism and changes in interatomic chemical bonding. Magnetic effects are also responsible for the fact that the atomic structure of radiation defects in iron and steels is different from the structure of defects formed under irradiation in non-magnetic body-centred cubic metals, for example vanadium or tungsten. Ab initio-based magnetic cluster expansion-based Monte–Carlo simulations showed unusual non-collinear magnetic configurations forming at interfaces and around Cr precipitates in FeCr alloys. In W–Ta and W–V alloys, ab initio calculations helped to identify several low temperature ordered inter-metallic phases that are not included in the existing phase diagrams based on high-temperature experimental data. Ab initio calculations have also made it possible to predict atomic structures of point defects formed in these alloys under irradiation.     

生理参数遥测系统无线供能模块的设计

能量供应问题是动物生理参数遥测系统实现长期稳定工作的关键,基于电磁感应的无线供能技术是解决这一问题的有效途径.为向动物生理参数遥测系统提供稳定、安全的能量,从能量传输的稳定性与电磁生物安全性两方面出发,对能量传输模块进行优化设计,实现了由长方形截面发射线圈和三维接收线圈组成的无线供能模块,能够在Φ10.5 mm×11 mm接收空间内提供至少150 mW有效功率,传输效率不小于2.64%.遥测系统的活体实验证实了该供能方式的可行性.     

金属和SiC复合薄膜的应力及应力梯度控制技术

等离子增强化学气相沉积（PECVD）SiC谐振器的制作面临导电和应力及应力梯度控制问题．为了解决导电问题,采用金属W作为导电材料,它耐断腐蚀,可简化工艺．使W薄膜应力最小的溅射条件为：Ar压力2．0Pa,功率300W,反溅射工艺;为了解决应力梯度问题,采用双层金属结构、退火和离子注入3种手段．在离子注入电压120keV、剂量1．6×10^16cm^-2、不退火的条件下,可以得到应力梯度最小、结构完好的PECVD SiC谐振器.     

Narrow-linewidth vertical-cavity surface-emitting lasers for oxygen detection

The use of vertical-cavity surface-emitting lasers (VCSEL's) for optical detection of atmospheric oxygen is described. The VCSEL's were custom designed for single-mode emission in the 763-nm wavelength range, with low noise and narrow optical linewidth. Using standard wavelength modulation spectroscopy and a second-harmonic detection scheme with a 1-m air path, we determined an oxygen concentration resolution of 0.2%. Because of its small size, low power dissipation, and good tunability characteristics, the VCSEL promises to be an attractive light source for use in compact, low-cost optical sensor microsystems for trace gas detection.     

Low voltage cycling of programmable metallization cell memory devices

Future nanoscale memory technologies must ultimately be able to operate at power supply voltages in the order of 0.6 V or less. We have demonstrated in this work that it is possible to utilize symmetric program-erase (P-E) cycling for Ag/Ag-Ge-S/W programmable metallization cell devices at voltages below 0.6 V and still maintain an OFF/ON resistance ratio well in excess or 10 over a wide range of program and erase currents (0.27, 1.6, 55 and 220 μA) as set by a series resistance. The distributions of resistance values for 10(4) P-E cycles indicate that the margins between the highest on- and lowest off-state resistances are sufficient for unambiguous differentiation in all but the lowest current case in which there is some overlap. In addition, there is no substantial change in switching speed for up to 1.5 × 10(6) P-E operations, the maximum number of cycles attempted in this study.