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Review of the Working Fluid Thermal Stability for Organic Rankine Cycles

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Journal of Thermal Science 2019年第4期28卷 597-607页

作者： DAI Xiaoye SHI Lin qian weizhong Department of Chemical Engineering Tsinghua UniversityBeijing 100084China Department of Energy and Power Engineering Tsinghua UniversityBeijing 100084China

The organic Rankine cycle(ORC)is an efficient power generation technology and has been widely used for renewable energy utilization and industrial waste heat *** stability is a significant property of ORC working fluids and is the primary limitation for working fluid selection and system *** paper presents a review of the working fluid thermal stability for ORCs,including an analysis of the main theoretical method for thermal stability,a summary of the main experimental method for thermal stability,a summary of the decomposition experimental results for working fluids,and a discussion of the decomposition influence on ORC *** research trends of thermal stability are also discussed in this paper.

关键词： organic Rankine cycle(ORC) working fluid thermal stability

Ionic liquid coated single-walled carbon nanotube buckypaper as supercapacitor electrode

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Particuology 2013年第4期11卷 409-414页

作者： Chao Zheng weizhong qian Yuntao Yu Fei Wei Beijing Key Laboratory of Green Reaction Engineering & Technology Department of Chemical EngineeringTsinghua University

Effect of stacking structure of single-walled carbon nanotubes （SWCNTs） on its performance as electrode of supercapacitor was investigated in the present work. Considering SWCNTs easily formed bundles due to strong van de Waals attraction between tubes, we proposed first dispersion of SWCNTs by ionic liquids （ILs） of 1 -ethyl-3-methyl imidazolium tetrafluoroborate （EMIMBF4）, followed by fabrication of buckypa- per by compression. The debundling effect of ILs on SWCNTs increased the interface between electrode and electrolyte, decreased electrical resistance, and, consequently, increased performance of the superca- pacitor. Since ILs, used to disperse SWCNTs, also functioned as electrolyte in supercapacitor, our method is a simple way to prepare buckypaper electrode with high performance.

关键词： Carbon nanotubesBuckypaperSupercapacitorlonicliquids

Mesoporous tubular graphene electrode for high performance supercapacitor

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Chinese Chemical Letters 2018年第4期29卷 599-602页

作者： Jiarui Tian Chaojie Cui Chao Zheng weizhong qian Department of Chemical Engineering Tsinghua University

We report the fabrication of mesoporous tubular graphene（MTG） by a chemical vapor deposition method using Mg O@Zn O core-shell structure as the template. The unique bi-directional ions transfer in unstack graphene layers and high mesopore ratio of MTGs allows capacitance reach 15 μF/cm^2 at 0.5 A/g, and11 μF/cm^2 at 10 A/g, which is closer to theoretical value（21μF/cm^2） than SWCNTs and DWCNTs at either low or high rate. Meanwhile, MTGs exhibited good structural stability, high surface area（701 m^2/g）, high conductivity（30 S/cm） and low oxygen ratio（0.7 atom%）, allowing excellent SC performance. The 4 V EDLC using MTGs and EMIMBF_4 electrolyte exhibited high energy density in wide range of high power density and excellent cycling stability, showing strong potential in EDLC and other electrochemical energy storage systems, in addition, showing significant factor of ion transfer distance for high performance SCs especially operating at high voltage using ionic liquid electrolyte.

关键词： Graphene Carbon nanotube Ionic liquids Supercapacitor Core-shell structure

Carbon nanotubes for supercapacitors:Consideration of cost and chemical vapor deposition techniques

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Journal of Natural Gas Chemistry 2012年第3期21卷 233-240页

作者： Chao Zheng weizhong qian Chaojie Cui Guanghui Xu Mengqiang Zhao Guili Tian Fei Wei Department of Chemical Engineering Tsinghua UniversityBeijing 100084China

In this topic, we first discussed the requirement and performance of supercapacitors using carbon nanotubes （CNTs） as the electrode, including specific surface area, purity and cost. Then we reviewed the preparation technique of single wailed CNTs （SWNTs） in relatively large scale by chemical vapor deposition method. Its catalysis on the decomposition of methane and other carbon source, the reactor type and the process control strategies were discussed. Special focus was concentrated on how to increase the yield, selectivity, and purity of SWNTs and how to inhibit the formation of impurities, including amorphous carbon, multiwalled CNTs and the carbon encapsulated metal particles, since these impurities seriously influenced the performance of SWNTs in supercapacitors. Wish it be helpful to further decrease its product cost and for the commercial use in supercapacitors.

关键词： supercapacitor carbon nanotubes: chemical vapor deposition catalysis methane

Large scale production of carbon nanotube arrays on the sphere surface from liquefied petroleum gas at low cost

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Chinese Science Bulletin 2007年第21期52卷 2896-2902页

作者： ZHANG qiang HUANG JiaQi WEI Fei XU GuangHui WANG Yao qian weizhong WANG DeZheng Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical Engineering TsinghuaUniversity Beijing 100084 China

Liquefied petroleum gas (LPG), a cheap industrial material, is used as carbon source to produce carbon nanotube (CNT) arrays on ceramic spherical surface on a large scale in the floating catalyst process. The ceramic spheres provide huge surface area and good mobility, leading to the mass production of CNT arrays continuously. The arrays obtained from the surface are of good alignment, and the purity is as high as 97.5%. With the decrease of the growth temperature, CNTs in the array form with small-diameter of about 13 nm can be obtained. Therefore, with the industrial fuel as carbon source and the ceramic sphere as substrate, CNT arrays can easily be produced on large scale at low cost.

关键词：液化气生产量成本碳纳米管阵列

Neural Machine Translation by Fusing Key Information of Text

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Computers, Materials & Continua 2023年第2期74卷 2803-2815页

作者： Shijie Hu Xiaoyu Li Jiayu Bai Hang Lei weizhong qian Sunqiang Hu Cong Zhang Akpatsa Samuel Kofi qian Qiu Yong Zhou Shan Yang School of Information and Software Engineering University of Electronic Science and Technology of ChinaChengdu610054China Science and Technology on Altitude Simulation Laboratory Sichuan Gas Turbine Establishment Aero Engine Corporation of ChinaMianyang621000China School of Power and Energy Northwestern Polytechnical UniversityXi’an710072China School of Computer Science Southwest Petroleum UniversityChengdu610500China Department of Chemistry Physics and Atmospheric SciencesJackson State UniversityJacksonMS 39217USA

When the Transformer proposed by Google in 2017,it was first used for machine translation tasks and achieved the state of the art at that *** the current neural machine translation model can generate high quality translation results,there are still mistranslations and omissions in the translation of key information of long *** the other hand,the most important part in traditional translation tasks is the translation of key *** the translation results,as long as the key information is translated accurately and completely,even if other parts of the results are translated incorrect,the final translation results’quality can still be *** order to solve the problem of mistranslation and missed translation effectively,and improve the accuracy and completeness of long sentence translation in machine translation,this paper proposes a key information fused neural machine translation model based on *** model proposed in this paper extracts the keywords of the source language text separately as the input of the *** the same encoding as the source language text,it is fused with the output of the source language text encoded by the encoder,then the key information is processed and input into the *** incorporating keyword information from the source language sentence,the model’s performance in the task of translating long sentences is very *** order to verify the effectiveness of the method of fusion of key information proposed in this paper,a series of experiments were carried out on the verification *** experimental results show that the Bilingual Evaluation Understudy(BLEU)score of the model proposed in this paper on theWorkshop on Machine Translation(WMT)2017 test dataset is higher than the BLEU score of Transformer proposed by Google on the WMT2017 test *** experimental results show the advantages of the model proposed in this paper.

关键词： Key information transformer fusion neural machine translation

Near carbon‑zero cycle from VOCs capture to carbon fixation

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Carbon Neutrality 2022年第1期1卷 249-256页

作者： Zefang Yin Chaojie Cui Xiang Yu Wanghua Zhao Dexi Lin Yu Zhang Kang Li weizhong qian Department of Chemical Engineering Tsinghua UniversityBeijing 100084China Sinochem Quanzhou Petrochemical Co.Ltd. Quanzhou 362103Fujian ProvinceChina Sinopec Engineering Group Luoyang R&D Center of Technologies Luoyang 471003Henan ProvinceChina

A new technical route of organic matter capture and carbon fixation is proposed in response of the increasingly strict emission standards of volatile organic compounds(VOCs)in petrochemical industry and the Chinese national strategic development goals of carbon peak and carbon neutralization.A closed loop from raw materials to adsorbents for gas treatment can be achieved by two key technical characteristics:(1)construct a new mesoporous adsorbent with complete desorption and regeneration function by carbon nanotubes(CNTs);(2)convert gaseous organic matter which cannot be recycled in liquid/gas state to *** realizes the resource integration of"turning waste into treasure"and maximizes the carbon emission reduction effect of waste gas treatment process without consuming extra precious fossil fuel,compared with the traditional technologies of VOCs treatments,including combustion or catalytic ***’s more,the increase in supply of various green electricity is expected to change the current situation of large investment and heavy cost burden of environmental protection technology,and make a great contribution to the national carbon peak and carbon neutrality policy.

关键词： Carbon nanotubes Volatile organic compounds Waste gas treatment Carbon emissions Closed loop

Mechanical Behavior of Single and Bundled Defect-Free Carbon Nanotubes

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Accounts of Materials Research 2021年第11期2卷 998-1009页

作者： Yunxiang Bai Hongjie Yue Rufan Zhang weizhong qian Zhong Zhang Fei Wei Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China CAS Key Laboratory of Nanosystem and Hierarchical Fabrication and CAS Center for Excellence in Nanoscience National Center for Nanoscience and TechnologyBeijing 100190China

CONSPECTUS:Superstrong materials can be utilized in many fields such as bulletproof vests,airframes,suspension bridges,flywheel energy storage,*** one of the strongest materials,carbon nanotubes(CNTs)can potentially be used to fabricate superstrong ***,the tensile strength of CNTs is impaired a lot by defects,and the CNT fibers prepared so far have strengths much lower than that of a single CNT,showing a“size effect”.The conventional study of solid mechanics is usually based on the assumption that materials contain ***-free ultralong CNTs can hopefully help us avoid the“size effect”of nanomaterials and produce superstrong CNT *** would also provide a system for the study of the mechanical behavior of ideal solids with a nonlocalized“quantum stress singularity”.In this Account,we discuss our recent studies on the mechanical behavior of defect-free single CNTs and CNT ***,we introduce the defect-free structure of ultralong CNTs,which is one type of ideal ***,we review the investigation of the static tensile properties and dynamic fatigue resistance and their temperature-dependence of single centimeters long defect-free *** results showed that defect-free CNTs have superior comprehensive mechanical properties,including superstrength,-toughness,*** from traditional materials,the fatigue lifetime and fracture of CNTs are dominated by the first single-bond-sized defect(quantum stress singularity),showing“superbrittleness”.Third,by using a gas flow focusing in situ synthesis method as well as a synchronous tightening and relaxing strengthening strategy,we successfully fabricated CNT bundles with tensile strengths approaching that of single CNTs and showed that the“size effect”can be *** addition,the advantages and promising future of using CNTs in flywheel energy storage are ***,we provide our perspectives on the challenges and future directions in this field.

关键词： singularity fatigue Bundle

高温煅烧Mo改性的Fe/MgO催化剂用于制备管径分布均一的单壁碳纳米管

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催化学报 2008年第7期29卷 617-623页

作者：温倩骞伟中魏飞清华大学化工系绿色反应工程与工艺北京市重点实验室北京100084

研究了在以甲烷化学气相沉积法制备单壁碳纳米管的过程中高温煅烧预处理(900℃煅烧10h)对Mo改性Fe/MgO催化剂的作用.发现这种预处理有利于Fe在催化剂中的稳定和分散,从而制备出管径均一的单壁碳纳米管.采用能谱元素分析、高分辨透射电镜... 详细信息

研究了在以甲烷化学气相沉积法制备单壁碳纳米管的过程中高温煅烧预处理(900℃煅烧10h)对Mo改性Fe/MgO催化剂的作用.发现这种预处理有利于Fe在催化剂中的稳定和分散,从而制备出管径均一的单壁碳纳米管.采用能谱元素分析、高分辨透射电镜、X射线衍射、比表面积测量、拉曼光谱和热重分析对样品进行了表征.结果表明,在碳纳米管生长的过程中,铁元素在催化剂表面富集,单壁碳纳米管生长于富集铁的纳米颗粒上,并存在碳管直径与铁颗粒尺寸的依赖关系.Mo存在时可煅烧形成FeMoO4复合氧化物,后者比MgFe2O4相更加稳定.Mo/Fe比例对提高单壁碳纳米管的生长密度、纯度与管径均一性等均有明显影响.上述研究对进一步精确控制制备单壁碳纳米管有重要意义.

关键词：单壁碳纳米管化学气相沉积铁-钼/氧化镁催化剂煅烧管径分布