ISSN 2095-1701
ISSN 2095-1698(Online)
CN 11-6017/TK
邮发代号 80-972
2019 Impact Factor: 2.657
Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal (RTLM) mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measurement methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fundamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self-actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.
光催化剂由于其优异的性能和同时解决能源需求和环境污染方面的挑战的潜力而引起了广泛的研究兴趣。 实际应用中光催化颗粒需要与它们各自的介质接触才能表现出高效的光催化能。 然而,纳米级的光催化材料后期很难从反应介质中分离出来,不可避免的会导致二次污染和比较差得循环行能。 三维网络结构的水凝胶光催化材料具有高比表面积、高吸附能力和良好的环境相容性等特点,是一种很有前途的光催化剂载体材料。 本文根据水凝胶光催化材料的组成将其分为两类,并对近年来水凝胶光催化材料的制备方法进行了总结。 此外,综述了目前水凝胶光催化材料在能源转化和环境修复中的应用。 并对水凝胶光催化材料所遇到的挑战和发展前景进行了简要阐述。
Ionomer impregnation represents a milestone in the evolution of polymer electrolyte fuel cell (PEFC) catalyst layers. Ionomer acts as the binder, facilitates proton transport, and thereby drastically improves catalyst utilization and effectiveness. However, advanced morphological and functional characterizations have revealed that up to 60% of Pt nanoparticles can be trapped in the micropores of carbon support particles. Ionomer clusters and oxygen molecules can hardly enter into micropores, leading to low Pt utilization and effectiveness. Moreover, the ionomer thin-films covering Pt nanoparticles can cause significant mass transport loss especially at high current densities. Ionomer-free ultra-thin catalyst layers (UTCLs) emerge as a promising alternative to reduce Pt loading by improving catalyst utilization and effectiveness, while theoretical issues such as the proton conduction mechanism remain puzzling and practical issues such as the rather narrow operation window remain unsettled. At present, the development of PEFC catalyst layer has come to a crossroads: staying ionomer-impregnated or going ionomer-free. It is always beneficial to look back into the past when coming to a crossroads. This paper addresses the characterization and modeling of both the conventional ionomer-impregnated catalyst layer and the emerging ionomer-free UTCLs, featuring advances in characterizing microscale distributions of Pt particles, ionomer, support particles and unraveling their interactions; advances in fundamental understandings of proton conduction and flooding behaviors in ionomer-free UTCLs; advances in modeling of conventional catalyst layers and especially UTCLs; and discussions on high-impact research topics in characterizing and modeling of catalyst layers.
Development of active and durable electrocatalyst for oxygen reduction reaction (ORR) remains one challenge for the polymer electrolyte membrane fuel cell (PEMFC) technology. Pt-based nanomaterials show the greatest promise as electrocatalyst for this reaction among all current catalytic structures. This review focuses on Pt-based ORR catalyst material development and covers the past achievements, current research status and perspectives in this research field. In particular, several important categories of Pt-based catalytic structures and the research advances are summarized. Key factors affecting the catalyst activity and durability are discussed. An outlook of future research direction of ORR catalyst research is provided.
金属有机框架 (metal-organic frameworks, MOFs) 材料因其具有高比表面积,可调结构,以及功能多样化等特点而备受关注。目前,MOFs在光催化还原二氧化碳领域已经崭露头角。本文综述了近年来MOFs在光催化还原二氧化碳领域的最新研究进展。此外, 本文讨论了基于MOF的光催化剂的合理设计策略 (功能化原始 MOF结构、MOF -光敏剂、MOF-半导体、MOF-金属和 MOF-碳材料复合材料) 以有效增强光催化二氧化碳还原反应,并对MOFs在光催化还原二氧化碳领域今后的发展进行了展望。
Photoelectrochemical (PEC) water splitting is regarded as a promising way for solar hydrogen production, while the fast development of photovoltaic-electrolysis (PV-EC) has pushed PEC research into an embarrassed situation. In this paper, a comparison of PEC and PV-EC in terms of efficiency, cost, and stability is conducted and briefly discussed. It is suggested that the PEC should target on high solar-to-hydrogen efficiency based on cheap semiconductors in order to maintain its role in the technological race of sustainable hydrogen production.
近年来,固体氧化物燃料电池(SOFC)的电极组件的开发和制造已变得尤为重要,特别是在电极支撑的SOFC出现之后。电极的功能包括促进燃料气体的扩散,燃料的氧化,电子的传输以及电化学反应副产物的传输。在开发具有混合导电性能的替代电极材料和一些其他复合金属陶瓷方面,取得了令人瞩目的进展。在SOFC操作过程中,有必要避免渗碳和硫化问题。本论文论述了一种潜在电极材料,双钙钛矿作为SOFC中的阳极和阴极的各个方面,分析了文献中已研究的150多种SOFC电极组成。已经根据相,结构,衍射图,电导率和功率密度进行了评估,并详细提供了用于确定电极部件的质量的各种方法。这篇综述为未来的研究提出了可能的方向。
Water is perhaps the most widely adopted working fluid in conventional industrial heat transport engineering. However, it may no longer be the best option today due to the increasing scarcity of water resources. Furthermore, the wide variations in water supply throughout the year and across different geographic regions also makes it harder to easily access. To address this issue, finding new alternatives to replace water-based technologies is imperative. In this paper, the concept of a water-free heat exchanger is proposed and comprehensively analyzed for the first time. The liquid metal with a low melting point is identified as an ideal fluid that can flexibly be used within a wide range of working temperatures. Some liquid metals and their alloys, which have previously received little attention in thermal management areas, are evaluated. With superior thermal conductivity, electromagnetic field drivability, and extremely low power consumption, liquid metal coolants promise many opportunities for revolutionizing modern heat transport processes: serving as heat transport fluid in industries, administrating thermal management in power and energy systems, and innovating enhanced cooling in electronic or optical devices. Furthermore, comparative analyses are conducted to understand the technical barriers encountered by advanced water-based heat transfer strategies and clarify this new frontier in heat-transport study. In addition, the unique merits of liquid metals that could lead to innovative heat exchanger technologies are evaluated comprehensively. A few promising industrial situations, such as heat recovery, chip cooling, thermoelectricity generation, and military applications, where liquid metals could play irreplaceable roles, were outlined. The technical challenges and scientific issues thus raised are summarized. With their evident ability to meet various critical requirements in modern advanced energy and power industries, liquid metal-enabled technologies are expected to usher a new and global era of water-free heat exchangers.
为应对全球变暖,控制和减少大气中的二氧化碳浓度至关重要。光催化还原二氧化碳制备燃料为解决该问题提供了方法,不仅能够对二氧化碳进行利用,而且同时生产了能源。目前为止,基于二氧化碳的半导体是在二氧化碳光催化还原中应用最为广泛的材料。因此,本篇小综述对近几年该领域的发展进行了总结。本文首先阐述了以结构工程的方法调控和提升二氧化碳催化剂性能的工作,之后描述了通过添加第二/第三种外源元素合成催化剂来改善二氧化碳催化剂的活性和选择性的工作。最后,本文介绍了基于二氧化碳的多元复合材料在二氧化碳催化还原中的应用。
Energy problems arise with the proliferation of mobile electronic devices, which range from entertainment tools to life saving medical instruments. The large amount of energy consumption and increasing mobility of electronic devices make it urgent that new power sources should be developed. It has been gradually recognized that the human body is highly flexible in generating applicable power from sources of heat dissipation, joint rotation, enforcement of body weight, vertical displacement of mass centers, and even elastic deformation of tissues and other attachments. These basic combinations of daily activities or metabolic phenomena open up possibilities for harvesting energy which is strong enough to power mobile or even implantable medical devices which could be used for a long time or be recharged permanently. A comprehensive review is presented in this paper on the latest developed or incubating electricity generation methods based on human power which would serve as promising candidates for future mobile power. Thermal and mechanical energy, investigated more thoroughly so far, will particularly be emphasized. Thermal energy relies on body heat and employs the property of thermoelectric materials, while mechanical energy is generally extracted in the form of enforcement or displacement excitation. For illustration purposes, the piezoelectric effect, dielectric elastomer and the electromagnetic induction couple, which can convert force directly into electricity, were also evaluated. Meanwhile, examples are given to explain how to adopt inertia generators for converting displacement energy via piezoelectric, electrostatic, electromagnetic or magnetostrictive vibrators. Finally, future prospects in harvesting energy from human power are made in conclusion.
Recent years have witnessed a rapid development of deformable devices and epidermal electronics that are in urgent request for flexible batteries. The intrinsically soft and ductile conductive electrode materials can offer pivotal hints in extending the lifespan of devices under frequent deformation. Featuring inherent liquidity, metallicity, and biocompatibility, Ga-based room-temperature liquid metals (GBRTLMs) are potential candidates to fulfill the requirement of soft batteries. Herein, to illustrate the glamour of liquid components, high-temperature liquid metal batteries (HTLMBs) are briefly summarized from the aspects of principle, application, advantages, and drawbacks. Then, Ga-based liquid metals as main working electrodes in primary and secondary batteries are reviewed in terms of battery configurations, working mechanisms, and functions. Next, Ga-based liquid metals as auxiliary working electrodes in lithium and nonlithium batteries are also discussed, which work as functional self-healing additives to alleviate the degradation and enhance the durability and capacity of the battery system. After that, Ga-based liquid metals as interconnecting electrodes in multi-scenarios including photovoltaics solar cells, generators, and supercapacitors (SCs) are interpreted, respectively. The summary and perspective of Ga-based liquid metals as diverse battery materials are also focused on. Finally, it was suggested that tremendous endeavors are yet to be made in exploring the innovative battery chemistry, inherent reaction mechanism, and multifunctional integration of Ga-based liquid metal battery systems in the coming future.
为更好地预测和分析城市生活垃圾(MSW)在上吸式固定床中的热解气化过程,本文基于Gibbs自由能最小化法,采用Aspen plus软件进行数值模拟。模型中,RYield模块与RGibbs模块相结合用于热解段模拟,而RGibbs模块则单独用于气化段模拟。所述模型主要用于预测和分析不同气化温度、气化剂比例和气化剂种类条件下,热解气化工艺的目标特性参数如热解气化气组分、低热值(LHV)以及碳转化率。预测结果表明,采用上述模型得到的模拟结果与实验结果具有良好的吻合性。最佳的气化温度在750℃左右。水蒸汽为气化剂时,最佳的气化剂比例在0.4左右。采用烟气与水蒸气的混合物作为气化剂,是4种常用气化剂中最具有经济和可循环利用前景的一种。
Hydrogen energy has been regarded as the most promising energy resource in the near future due to that it is a clean and sustainable energy. And the heterogeneous photocatalytic hydrogen production is increasingly becoming a research hotspot around the world today. As visible light response photocatalysts for hydrogen production, cadmium sulfide (CdS) is the most representative material, the research of which is of continuing popularity. In the past several years, there has been significant progress in water splitting on CdS-based photocatalysts using solar light, especially in the development of co-catalysts. In this paper, recent researches into photocatalytic water splitting on CdS-based photocatalysts are reviewed, including controllable synthesis of CdS, modifications with different kinds of cocatalysts, solid solution, intercalated with layered nanocomposites and metal oxides, and hybrids with graphenes etc. Finally, the problems and future challenges in photocatalytic water splitting on CdS-based photocatalysts are described.
Pulsating heat pipe (PHP), or oscillating heat pipe (OHP), a novel type of highly efficient heat transfer component, has been widely applied in many fields, such as in space-borne two-phase thermal control systems, in the cooling of electronic devices and in energy-saving technology, etc. In the present paper, the characteristics and working principles of the PHPs are introduced and the current researches in the field are described from the viewpoint of experimental tests, theoretical analyses as well as practical applications. Besides, it is found that the state-of-the-art experimental investigations on the PHPs are mainly focused on the flow visualization and the applications of nanofluids and other functional fluids, aiming at enhancing the heat transfer performance of the PHPs. In addition, it is also pointed out that the present theoretical analyses of the PHP are restricted by further development of two-phase flow theories, and are concentrated in the non-linear analyses. Numerical simulations are expected to be another research focus, in particular of the combination of the nanofluids and functional fluids.
环境基础设施投资是应对温室气体排放和大气污染的重要环境政策工具。本文利用中国30个省市2003-2015年的面板数据,采用改进的STRIPAT模型,研究了环境基础设施投资对CO2排放、SO2排放和PM2.5污染的影响。结果表明,环境基础设施投资对减缓二氧化碳排放具有积极而显著的作用。此外,环境基础设施投资对SO2排放的影响是波动的,技术创新可以减少PM2.5污染。同时,总体来看,能源强度对温室气体排放和大气污染的影响最大,其次是人均GDP和产业结构。并且,环境基础设施投资对环境问题的影响因地区而异。考虑到本地区的实际情况,建议应根据本地区的实际情况提出更为适当的缓解政策。
电化学储能是有效存储风能、太阳能等间歇可再生能源为数不多手段之一。相较于其它固电池,氧化还原液流电池(Redox Flow Batteries, RFBs)具有安全高和功率容量可自由扩展等优点然而,其能量密度和功率密度低氧化还原电对成分和膜成本高极大限制了全钒液流电池商业化进展。理论上可过三种途径提高液流电池性能,以实现大规模化应用。第,使用更高能量密度电解质,可通过增加氧化还原电对浓度,储存多个电子或提高电池电压来实现第二,选取高动力学反应电对提高电池输出电压,改进电池设计和使用低阻抗膜,从而提高电池的输出功率。第三,降低氧化还原电对组分或膜的成本
为实现上述目标必须设计新的电池反应和电池装置在本篇综述中,作比较了具有应用前景的电池反应,如全液体、浆液或由液体气体和固相结合的混合物。基于能量密度功率密度和成本探讨优氧化还原电对体系亦探讨了溶剂和无机或有机氧化还原电对的选择对电池能的影响
本篇文章从(1)液流电池操作原理;(2)技术标准;(3)基本概念,如全液体,气体/液体,半固,泥浆,氧化还原介质;(4)溶剂包括水溶液和非水溶液;(5)氧化还原活性中心,包括金属和非金属;(6)电池化学成分;(7)重要的氧化还原反应;(8)结论:理想的液流电池是么?这八个方面对氧化还原液流电池进行了全面的综述。
微型燃气轮机具有低碳排放、燃料适应性强等优点,广泛应用于小功率规模分布式供能系统。但其尾气余热利用不充分和发电效率低下的瓶颈问题限制了它的应用。此外,如何保证微型燃气轮机与电网之间的灵活切换也是分布式供能系统安全运行的一个关键问题。因此,为了为上述问题提供参考解决方案,本文对一台自主研制的30kW微型燃气轮机发电机组进行了实验研究。该微型燃气轮机样机由上海交通大学燃气轮机研究所微型燃气轮机研究团队设计,委托重庆涡轮机械有限公司生产制造完成,主要由单级离心压气机、向心透平、燃烧室、高速永磁发电机和控制系统等组成,可实现启动、点火、稳定运行、带负荷运行、并网和停机等功能。实验结果表明,自主研制的微型燃气轮机可在10000rpm~34000rpm的低转速范围内稳定运行,同时,由于燃烧室独特结构方案借鉴轴流式航空发动机燃烧室设计方法,在燃气轮机低转速工况下,燃烧室点火成功率达到98%,可实现宽范围稳定燃烧的性能。所设计的微型燃气轮机发电机组采用了创新型多状态柔性切换控制系统,实现了从启动电机到发电机以及从并网到离网的高效灵活切换,降低了故障发生率。该研究成果可为我国掌握微型燃气轮机自主知识产权体系,逐步实现微型燃气轮机产业化以及突破发达国家技术垄断提供理论借鉴和实验支撑。
近年来,缺陷型UiO-66(Zr)系列MOFs材料因具有超大的比表面积、良好的孔结构和灵活可变的可调控性在催化、功能材料和吸附等领域展示出巨大的应用前景。在合成MOFs时引入缺陷位点用于调控材料的物理化学性质如(能带结构、孔结构等)获得优异的性能是极其具有挑战性的。本文结合近几年的研究成果,综述了缺陷型UiO-66(Zr)系列MOFs材料合成方法、表征技术和应用领域等,以期提供一些合成高性能UiO-66(Zr)系列MOFs材料的思路,促进UiO-66(Zr)系列MOFs材料在各个领域的发展。
本文针对汽油/正庚烷双燃料均质压燃(HCCI)发动机开展了实验与仿真研究,分析了燃料混合比例及可变气门正时策略对发动机燃烧过程及排放水平的作用机制。通过改变汽油比例(GF)(GF=0.1~0.5),以及进气门开启时刻从(IVO=-15°CA ATDC~35°CA ATDC),研究了缸压、放热的变化规律以及对HC和CO排放的影响。结果表明,增加GF和推迟IVO均使燃烧推迟并延长燃烧持续时间,同时会降低放热率峰值及最高平均燃烧温度,其中IVO对燃烧的影响较GF更为明显。HC、CO的排放量随着GF的降低,IVO的提前以及运行负荷的增加而降低
The key technologies of liquefied hydrogen have been developing rapidly due to its prospective energy exchange effectiveness, zero emissions, and long distance and economic transportation. However, hydrogen liquefaction is one of the most energy-intensive industrial processes. A small reduction in energy consumption and an improvement in efficiency may decrease the operating cost of the entire process. In this paper, the detailed progress of design and optimization for hydrogen liquefaction in recent years are summarized. Then, based on the refrigeration cycles, the hydrogen liquefaction processes are divided into two parts, namely precooled liquefaction process and cascade liquefaction process. Among the existing technologies, the SEC of most hydrogen liquefaction processes is limited in the range of 5–8 kWh/ k g L H 2 : liquid hydrogen). The exergy efficiencies of processes are around 40% to 60%. Finally, several future improvements for hydrogen liquefaction process design and optimization are proposed. The mixed refrigerants (MRs) as the working fluids of the process and the combination of the traditional hydrogen liquefaction process with the renewable energy technology will be the great prospects for development in near future.
Absorption heat pump attracts increasing attention due to its advantages in low grade thermal energy utilization. It can be applied for waste heat reuse to save energy consumption, reduce environment pollution, and bring considerable economic benefit. In this paper, three important aspects for absorption heat pump for waste heat reuse are reviewed. In the first part, different absorption heat pump cycles are classified and introduced. Absorption heat pumps for heat amplification and absorption heat transformer for temperature upgrading are included. Both basic single effect cycles and advanced cycles for better performance are introduced. In the second part, different working pairs, including the water based working pairs, ammonia based working pairs, alcohol based working pairs, and halogenated hydrocarbon based working pairs, for absorption heat pump are classified based on the refrigerant. In the third part, the applications of the absorption heat pump and absorption heat transformer for waste heat reuse in different industries are introduced. Based on the reviews in the three aspects, essential summary and future perspective are presented at last.
To solve resource, energy, and environmental issues, development of sustainable clean energy system is strongly required. In recent years, hydrogen has been paid much attention to as a clean energy. Solar hydrogen production by water splitting using a photocatalyst as artificial photosynthesis is a promising method to solve these issues. Efficient utilization of visible light comprised of solar light is essential for practical use. Three strategies, i.e., doping, control of valence band, and formation of solid solution are often utilized as the useful methods to develop visible light responsive photocatalysts. This mini-review introduces the recent work on visible-light-driven photocatalysts developed by substitution with metal cations of those strategies.
To significantly reduce the cost of proton exchange membrane fuel cells, platinum-group metal (PGM)-free cathode catalysts are highly desirable. Current M-N-C (M: Fe, Co or Mn) catalysts are considered the most promising due to their encouraging performance. The challenge thus has been their stability under acidic conditions, which has hindered their use for any practical applications. In this review, based on the author’s research experience in the field for more than 10 years, current challenges and possible solutions to overcome these problems were discussed. The current Edisonian approach (i.e., trial and error) to developing PGM-free catalysts has been ineffective in achieving revolutionary breakthroughs. Novel synthesis techniques based on a more methodological approach will enable atomic control and allow us to achieve optimal electronic and geometric structures for active sites uniformly dispersed within the 3D architectures. Structural and chemical controlled precursors such as metal-organic frameworks are highly desirable for making catalysts with an increased density of active sites and strengthening local bonding structures among N, C and metals. Advanced electrochemical and physical characterization, such as electron microscopy and X-ray absorption spectroscopy should be combined with first principle density functional theory (DFT) calculations to fully elucidate the active site structures.
Electronics, such as printed circuit board (PCB), transistor, radio frequency identification (RFID), organic light emitting diode (OLED), solar cells, electronic display, lab on a chip (LOC), sensor, actuator, and transducer etc. are playing increasingly important roles in people’s daily life. Conventional fabrication strategy towards integrated circuit (IC), requesting at least six working steps, generally consumes too much energy, material and water, and is not environmentally friendly. During the etching process, a large amount of raw materials have to be abandoned. Besides, lithography and microfabrication are typically carried out in “Cleanroom” which restricts the location of IC fabrication and leads to high production costs. As an alternative, the newly emerging ink-jet printing electronics are gradually shaping modern electronic industry and its related areas, owing to the invention of a series of conductive inks composed of polymer matrix, conductive fillers, solvents and additives. Nevertheless, the currently available methods also encounter some technical troubles due to the low electroconductivity, complex sythesis and sintering process of the inks. As an alternative, a fundamentally different strategy was recently proposed by the authors’ lab towards truly direct writing of electronics through introduction of a new class of conductive inks made of low melting point liquid metal or its alloy. The method has been named as direct writing of electronics based on alloy and metal (DREAM) ink. A series of functional circuits, sensors, electronic elements and devices can thus be easily written on various either soft or rigid substrates in a moment. With more and more technical progresses and fundamental discoveries being kept made along this category, it was found that a new area enabled by the DREAM ink electronics is emerging, which would have tremendous impacts on future energy and environmental sciences. In order to promote the research and development along this direction, the present paper is dedicated to draft a comprehensive picture on the DREAM ink technology by summarizing its most basic features and principles. Some important low melting point metal ink candidates, especially the room temperature liquid metals such as gallium and its alloy, were collected, listed and analyzed. The merits and demerits between conventional printed electronics and the new direct writing methods were comparatively evaluated. Important scientific issues and technical strategies to modify the DREAM ink were suggested and potential application areas were proposed. Further, digestions on the impacts of the new technology among energy, health, and environmental sciences were presented. Meanwhile, some practical challenges, such as security, environment-friendly feature, steady usability, package, etc. were summarized. It is expected that the DREAM ink technology will initiate a series of unconventional applications in modern society, and even enter into peoples’ daily life in the near future.
The theoretical modeling, parameters test and model correction for a steam turbine (ST) governor are discussed. A set of ST Governor system model for power system simulation is created based on this research. A power system simulation for an actual power grid accident is conducted using this new model and the comparison between the simulation and actual data show that the results are satisfactory.
This paper contributes an inclusive review of scientific studies in the field of sustainable human building ecosystems (SHBEs). Reducing energy consumption by making buildings more energy efficient has been touted as an easily attainable approach to promoting carbon-neutral energy societies. Yet, despite significant progress in research and technology development, for new buildings, as energy codes are getting more stringent, more and more technologies, e.g., LED lighting, VRF systems, smart plugs, occupancy-based controls, are used. Nevertheless, the adoption of energy efficient measures in buildings is still limited in the larger context of the developing countries and middle income/low-income population. The objective of Sustainable Human Building Ecosystem Research Coordination Network (SHBE-RCN) is to expand synergistic investigative podium in order to subdue barriers in engineering, architectural design, social and economic perspectives that hinder wider application, adoption and subsequent performance of sustainable building solutions by recognizing the essential role of human behaviors within building-scale ecosystems. Expected long-term outcomes of SHBE-RCN are collaborative ideas for transformative technologies, designs and methods of adoption for future design, construction and operation of sustainable buildings.
室温液态金属(LM)是近年来兴起的一大类多功能材料,因其在先进热管理、增材制造、柔性电子、生物医学工程、柔性机器等方面的重大价值而日益受到广泛关注。此类材料异常丰富的功能用途主要源于其同时具有传统金属特性及流体流动的双重属性,熔点是其中最为典型的热物性参数之一,也是液态金属应用于热学领域如相变材料(PCM)、先进散热等的关键因素。目前,学术界已部分引入了一些可行的研究策略,如分子动力学模拟(MD)、经典热力学理论等,以尝试分析液态金属熔化过程的动态特征;而如何结合相图分析、第一性原理模拟计算等多尺度理论工具,对室温液态多元合金的熔点加以分析、预测乃至设计,更是一个至关重要的问题,这对于今后研制可在特定热学场合下发挥作用的新一代液态金属功能材料,具有十分迫切现实的重要价值。本文旨在围绕液态金属的热物理变化规律,探讨其熔化过程中的熔点参数。首先基于研究对象的物理尺度,对研究液态金属熔化相变的经典理论方法进行了梳理和深入解读;其次,总结并评估了可能对液态金属熔化过程产生关键影响的有关参数,如金属组分、环境压强、颗粒尺寸以及过冷度等,对这些参数的深入认识有助于高效筛选乃至尝试设计出具有特定熔点的合金。最后,文章介绍了基于液态金属低熔点特性所衍生出的部分典型应用设计,这些实践表明了前述理论探究的价值所在。最后需要指出的是,液态金属熔化物理学方面的基础探索还存在很大的拓展空间,仍需大量的理论与实验工作。
To reduce the levelized cost of energy for concentrating solar power (CSP), the outlet temperature of the solar receiver needs to be higher than 700 °C in the next-generation CSP. Because of extensive engineering application experience, the liquid-based receiver is an attractive receiver technology for the next-generation CSP. This review is focused on four of the most promising liquid-based receivers, including chloride salts, sodium, lead-bismuth, and tin receivers. The challenges of these receivers and corresponding solutions are comprehensively reviewed and classified. It is concluded that combining salt purification and anti-corrosion receiver materials is promising to tackle the corrosion problems of chloride salts at high temperatures. In addition, reducing energy losses of the receiver from sources and during propagation is the most effective way to improve the receiver efficiency. Moreover, resolving the sodium fire risk and material compatibility issues could promote the potential application of liquid-metal receivers. Furthermore, using multiple heat transfer fluids in one system is also a promising way for the next-generation CSP. For example, the liquid sodium is used as the heat transfer fluid while the molten chloride salt is used as the storage medium. In the end, suggestions for future studies are proposed to bridge the research gaps for > 700 °C liquid-based receivers.
POCl3 diffusion is currently the de facto standard method for industrial n-type emitter fabrication. In this study, we present the impact of the following processing parameters on emitter formation and electrical performance: deposition gas flow ratio, drive-in temperature and duration, drive-in O2 flow rate, and thermal oxidation temperature. By showing their influence on the emitter doping profile and recombination activity, we provide an overall strategy for improving industrial POCl3 tube diffused emitters.