石墨烯-MXene光热脱盐膜的制备及协同增强界面光蒸汽脱盐性能的研究

界面太阳能蒸发脱盐是一种低成本、环保、高效的海水淡化技术。通过自组装方法合成了2D-2D交联结构的石墨烯-MXene光热脱盐膜,讨论了不同厚度光热膜的微观结构、形貌、浸润性、光吸收等特性,以及这些特性与光热蒸发脱盐性能的关系。结果表明,1 kW/m^(2)太阳光辐照下,最优石墨烯-MXene光热脱盐膜在0.2 mol/L盐水中的最高蒸发速率可以达到1.68 kg/(m^(2)·h),效率为85.38%。

面向双碳目标的水淡技术:生物质碳用于界面太阳能光蒸汽转化技术的研究进展

面向碳达峰、碳中和目标,针对当前人们所面临的淡水紧缺和能源危机,研究者们致力于寻找低碳、环保和可持续发展的解决途径。近年来,研究者们对利用“绿色能源--太阳能”和“蓝色能源---海洋”以可持续生产淡水给予极大的关注,试图获得高的能源转化效率以解决淡水与清洁能源两大资源问题,并以此降低碳排放,为碳中和目标助力。界面太阳能光蒸汽转化技术是目前缓解淡水危机极有效的手段之一,凭借其高效的太阳能热利用、出色的光热转化率和高的水蒸发产量而备受关注。界面系统主要包括光吸收器和蒸发装置。其中,碳基光热材料是光吸收器的热门选材之一,尤其生物质碳具有绿色环保、价格低廉、可再生以及变废为宝等优点而颇受欢迎。本文系统地梳理并阐述了基于生物质碳的太阳能光蒸汽转化系统中的材料设计、系统设计、亲水设计、水传输通道设计和抗盐设计,简述了生物质碳的光热转化机理和光热系统的性能评估,最后从实际应用的角度总结了生物质碳在海水淡化和电能生产中的应用研究,并针对当前该领域所面临的挑战和机遇提出了未来几年内的研究热点。

GO/PVA阵列结构吸收体高效光蒸汽转化

将氧化石墨烯(GO)均匀分散于聚乙烯醇(PVA)水溶液中,烘干制备出表面平整的GO/PVA膜。利用激光刻蚀工艺对GO/PVA膜的表面进行处理得到LT-GO/PVA膜,研究LT-GO/PVA膜的微观结构、物理性能及其作为光热转化器件的性能。结果表明:LT-GO/PVA膜表面形成了3D多孔阵列结构,可促进太阳光的吸收,减少漫反射造成的能量损耗;LT-GO/PVA膜表面开始从亲水性向疏水性转变,可促进水的快速蒸发与分离,在1 kW/m^(2)的光强度下,其光热水蒸发速率为1.827 kg/(m^(2)·h),光热转化效率为89.4%。

基于等离激元微纳结构的太阳能界面光蒸汽转换

作为人工微纳结构与光热转换的融合,太阳能光蒸汽转换成为近年来太阳能热利用领域的研究热点之一.基于人工微纳结构的等离激元吸收体,能够在整个太阳光谱范围内实现高效的光子捕获.等离激元吸收体表面和内部的光致局域加热,促成了高效的液气相变.与碳基吸收体相比,等离激元吸收体不但可将入射太阳光局域在亚波长尺度内,形成致密的热点,而且其吸收光谱可灵活调控.围绕等离激元吸收体的光蒸汽转换体系,还具有热响应快、材料抗腐蚀、可回收等优势,可用于海水淡化、污水处理、灭菌消毒等水处理领域.本文从光吸收和热局域两个角度阐述了等离激元光蒸汽转换系统的设计与优化,并对其应用前景作了展望.

基于气凝胶的界面太阳能光蒸汽转化技术的研究进展

淡水,乃是具有战略意义的全球性问题,对人类生存、经济发展和社会进步至关重要。面向碳中和、碳达峰目标探寻绿色环保的水淡技术,研究者将目光投向了新兴的太阳能海水淡化技术。近年来,新型界面太阳能光蒸汽转化系统因其高效的产水效率、可编程的蒸发装置和丰富的材料选择而迅速成为海淡技术的典型代表,界面系统的构筑主要包括光吸收器材料设计制备和蒸发装置的构建。在众多光热材料候选者中,气凝胶因其轻质、多孔以及低热导率而脱颖而出,表现出了优异的光吸收、热管理和水输运能力,并为光吸收器和蒸发器一体化提供了极佳的实现途径。如何通过调控气凝胶的组成与结构以及蒸发器的构建,减少其在光蒸汽转化过程中的能量损失,并将其投入实际运用正逐渐成为该领域的研究重点。本文系统地梳理并阐述了近年来气凝胶用于界面太阳能光蒸汽转化技术的研究进展,详细分类讨论了不同材料的光热转化机制以及不同种类气凝胶的性能特点,探讨了气凝胶在海水淡化方面的最新应用,同时分析了其优缺点及所面临的挑战,并简单总结了气凝胶的结构设计与亲疏水改性方法,最后对应用于界面太阳能光蒸汽转化的气凝胶材料进行了总结与展望。

冷蒸汽-原子吸收分光光度法测定3种含汞中成药中汞的含量

目的建立冷蒸汽-原子吸收分光光度法测定3种含汞中成药中汞含量的检测方法。方法样品经微波消解后,原子吸收法测定汞的含量。结果汞的回收率为96.9%,RSD=6.3%(n=6)。结论本方法简便、准确、重复性好,可用于该制剂的质量控制。

氢化物发生及冷蒸汽-原子吸收分光光度法测定金银花中砷和汞的含量

目的建立氢化物发生及冷蒸汽-原子吸收分光光度法测定金银花饮片中砷和汞含量的检验方法。方法样品经微波消解后,原子吸收法测定砷和汞的含量。结果砷和汞的回收率分别为107.1%和96.8%,RSD分别为2.3%和3.1%(n=6)。结论本方法简单、准确、重复性好,可用于现行药典中重金属及有害元素的检查。

太阳能驱动多级海水淡化器件的设计及其集水率探究

以太阳能驱动为主的界面光蒸汽转化技术是目前广泛使用的一种海水淡化技术,然而,以其为基础制备的海水淡化多级器件依然面临着制备方法复杂、价格昂贵、集水率不高等问题。为解决上述问题,使用廉价易得的紫铜板、碳纤维和粘胶基非织造布等材料,制备了能大幅增加光吸收率的碳纤维阵列光热层,快速供水的粘胶基非织造布水通道和蒸发层,以及快速冷凝水收集的疏水集水层,并以上述3部分为基础构筑太阳能驱动多级海水淡化器件。在确定器件最佳间距为3 mm,级数为十级之后,该器件在一个模拟太阳光照下实现了高达2.05 kg/(m^(2)·h)的集水率。该器件充分利用了潜热实现了高效的水收集,为后续多级界面蒸发器件的设计提供了一种新的思路。

Porosity sensitivity of A356 Al alloy during fiber laser welding

In order to decrease the metallurgical porosity and keyhole-induced porosity during deep penetration laser welding of Al and its alloys, and increase the mechanical properties of work-piece, the effects of welding parameters such as laser power, welding speed and defocusing value on both kinds of porosities were systemically analyzed respectively, and the shape and fluctuation of plume of the keyhole were observed to reflect the stability of the keyhole. The results show that increasing laser power or decreasing laser spot size can lead to the rising of both number and occupied area of pores in the weld; meanwhile, the plume fluctuates violently over the keyhole, which is always companied with the intense metallic vapor, liquid metal spatter and collapsing in the keyhole, thus more pores are generated in the weld. The porosity in the weld reaches the minimum at welding velocity of 2.0 m/min when laser power is 5 kW and defocusing value is 0.

One-step fabrication of TiO2/graphene hybrid mesoporous film with enhanced photocatalytic activity and photovoltaic performance

We synthesized a mesoporous film based on TiO2-reduced graphene oxide(RGO)hybrids using a one-step vapor-thermal method without the need for an additional annealing process.The vapor-thermally prepared TiO2-graphene hybrid(VTH)features unique structures with an ultra-large specific surface area of^260 m^2 g^-1 and low aggregation,giving rise to enhanced light harvesting and increased charge generation and separation efficiency.It was observed that a mesoporous film with uniform pore distribution is simultaneously obtained during the VTH growth process.When a 5.0 wt%RGO VTH film was used as the active layer in photocatalysis,the highest photocatalytic activity for degradation of methyl orange was achieved.For another,when a 0.75 wt%RGO VTH film was used as the photoanode in a dye-sensitized solar cell,the power conversion efficiency reached 7.58%,which represents an increase of 73.1%compared to a solar cell using an a photoanode of pure TiO2 synthesized by a traditional solvothermal method.It is expected that this facile method for the synthesis of TiO2/graphene hybrid mesoporous films will be useful in practical applications for preparing other metal oxide/graphene hybrids with ultra-high photocatalytic activity and photovoltaic performance.

Quantitative Analysis of Lignocellulosic Components of Non-Treated and Steam Exploded Barley, Canola, Oat and Wheat Straw Using Fourier Transform Infrared Spectroscopy

Rapid and cost effective quantification of lignocellulosic components （cellulose, hemicelluloses and lignin） of agricultural biomass （barley, canola, oat and wheat） is essential to determine the effect of various pre-treatments （such as steam explosion） on biomass used as feedstock for the biofuel industry. Fourier Transformed Infrared （FTIR） spectroscopy was considered as an option to achieve this objective. Regression equations having R2 values of 0.89, 0.99 and 0.98 were developed to predict the cellulose, hemicelluloses and lignin compounds of biomass, respectively. The average absolute difference in predicted and measured cellulose, hemicellulose and lignin in agricultural biomass was 7.5%, 2.5%, and 3.8%, respectively.

Vapor Sensing Theoretical Study on Optical Microcavities

When the organic vapors absorbed to the surface of porous silicon(PS), capillary condensation takes place due to the porous structure of the PS layer, accordingly resulting in the effective refractive index changing. For PS multi-layer microcavities, the different resonant peaks shift in the reflectivity spectrum of porous silicon microcavities(PSMs). The optical sensing model is set up by applying Bruggeman effective medium approximation theory, capillary condensation process and transfer matrix theoretically analytical method of one-dimensional photonic crystals. At the same time, comprehensively researched on are the sensing characteristics of PSMs which are exposed to give concentration organic vapors. At last, made is the theoretical simulation for sensing model of the PSMs in case of saturation by using computer numerical calculation, and found is the linearity relation between the refractive index of organic solvent and the peak-shift. At the same time deduced is the peak-shift as a function of the concentration of ethanol vapors.

界面太阳能蒸汽发生系统的研究进展与展望

太阳能蒸汽发生是一种通过光热转换过程利用太阳能的可靠、环保、成本低廉的技术,其中界面太阳能蒸汽发生系统以其光热转换、热管理、输水逸汽、外围装置的高度集成以及精细设计的特点,借助微结构光子学、材料改性加工、热结构设计、机械设计等技术,能高效(蒸发效率高)、快速(蒸发速率高)地从块状水体甚至大气中吸取水分并通过太阳能转换的热能产生蒸汽,从而产出淡水、无机盐和能量。界面太阳能蒸汽发生技术以其广阔应用前景吸引了学者们的研究兴趣。本综述介绍了界面太阳能蒸汽发生系统的工作原理与组成材料;按光热转换、热管理、疏水逸汽等部分从宏微观结构设计角度总结了设计、优化策略;通过介绍具体的应用展示了界面太阳能蒸汽发生系统的外围装置;最后总结了界面太阳能蒸汽发生系统的研究进展并对其未来发展进行了展望。

Characteristics of the Water Steam Turbocompressors Applied in the Concentrator Systems

The main geometrical and operating parameters of the water steam centrifugal compressors working in various concentrator operating conditions are realized in this paper. The interdependence between centrifugal stage pressure ratio, peripheral Mach number and impeller peripheral speed, as well the influence of the concentrator system capacity on the dimensions of the centrifugal compressor are determined to obtain the range of reasonable usage of the centrifugal thermocompression systems in the industrial concentrators. The high peripheral impeller speed, high Mach number and high pressure ratio cause separated jet-wake flow and transonic flow phenomena in the water steam centrifugal compressor flow field. The calculating methods for 3-D viscid unsteady transonic fluid flows in the turbocompressors are discussed and the results of CFD simulations and experimental investigations are used for optimal design of the water steam centrifugal compressor flow field. The application of the centrifugal compressor in the industrial concentrators with thermocompression systems and the influence on the energy efficiency of the systems are analyzed. Significant increment of the energy efficiency of the industrial concentrators can be achieved by introduction of the thermocompression systems.

Thermal behavior of silicon-copper micro vapor chamber for high power LEDs

Micro vapor chamber(MVC) for light emitting diodes(LEDs) can be designed and fabricated to enhance the heat dissipation efficiency and improve the reliability. In this paper, we used photoresist SU-8 and electroforming copper(Cu) to fabricate three kinds of wick structures, which are star, radiation and parallel ones, and the substrate is silicon with thickness of 0.5 mm. Electroforming Cu on silicon to make micro wick structure was a critical step, the ampere-hour factor was used, and accordingly the electroforming time was predicted. The composition of electroforming solution and parameters of electroforming were optimized too. After charging and packaging, thermal behavior tests were carried out to study the heat dissipation performance of MVCs. When the input power was 8 W, the parallel wick structure reached the equivalent temperature of 69.0 °C in 226 s, while the others were higher than that. The experimental results prove that the wick structures have significant influence on the heat transfer capability of MVCs.

Carbon nanocomposites with high photothermal conversion efficiency

Photothermal conversion for water vapor gen- eration is a novel strategy and an efficient way to utilize solar energy, which has great potential for water purification and desalination. In this review, the development of photothermal conversion and the classification of absorbers for solar vapor generation systems are presented, especially in recent devel- opment of carbon nanocomposites （carbon nanotubes and graphene） as solar vapor generation devices. Combined with recent progresses and achievements in this field, we discuss the challenges and opportunities for photothermal conversion based on carbon nanocomposites as well as their promising applications.

Quantum optical devices based on four-wave mixing in hot rubidium vapor

In this paper,we briefly review the recent experimental progresses in quantum optics based on four-wave mixing(FWM) processes in hot rubidium vapor,particularly our two recent experiments in quantum information.We have experimentally produced strong quantum correlations between three bright beams generated by two cascaded FWM processes.The intensity difference squeezing with the cascaded system is enhanced to(-7.0±0.1)d B from the(-5.5±0.1)d B/(4.5±0.1)d B with only one FWM process.Also,this system can be easily extended to multiple modes using multiple FWM processes.Besides,we have also successfully realized a cascade all-optical transistor(AOT),which is driven by a very weak light beam about 800 photons in total.The required probe power for achieving a switching efficiency of 50% can be as low as 180 p W,and it can manipulate a light beam with power of 5.0×106 times more,which proves the cascade of the AOT.Both experiments may find wide applications in quantum information and optical communication.

Mode splitting of a cavity with a high-density birefringence rubidium vapor in the superstrong coupling regime

The mode splitting in a system with Doppler-broadened high-density two-level atoms in the presence of magnetic field inside a relatively long optical cavity is studied in the superstrong coupling regime(atoms-cavity coupling strength g√N is near or larger than the cavity free-spectral range?FSR).The effect of a magnetic field applied along the quantization axis is used to break the polarization degeneracy of the cavity and thereby introduce birefringence(or Faraday rotation)into the medium.The cavity modes are further split in the presence of the magnetic field compared with the normal case of the multi-normal-mode splitting of the two-level system near the D2 line of87Rb.The dependence of the mode splitting on the magnetic field and the temperature is studied.The theoretical analysis according to the linear dispersion theory can provide a good explanation.