Nanoimprint Lithography:A Processing Technique for Nanofabrication Advancement

Nanoimprint lithography(NIL) is an emerging micro/nano-patterning technique,which is a high-resolution,high-throughput and yet simple fabrication process.According to International Technology Roadmap for Semiconductor(ITRS),NIL has emerged as the next generation lithography candidate for the22 nm and 16 nm technological nodes.In this paper,we present an overview of nanoimprint lithography.The classfication,research focus,critical issues,and the future of nanoimprint lithography are intensively elaborated.A pattern as small as 2.4 nm has been demonstrated.Full-wafer nanoimprint lithography has been completed on a 12-inch wafer.Recently,12.5 nm pattern resolution through soft molecular scale nanoimprint lithography has been achieved by EV Group,a leading nanoimprint lithography technology supplier.

Unexpected/contrary behavior of aerosol mass concentration in response to the individual components'concentration reduction in Kitakyushu,Japan

In the suburbs of Kitakyushu,Japan,the inorganic aerosol mass concentration(IAM)was about 32.7μg/m^(3),with the aerosol pH of 3.3.To study the thermodynamics of aerosol when its individual components'concentration is reduced,sensitive tests were performed using the ISORROPIAⅡmodel,in which the seven control species—TNaCl,TNH_(4)^(+),TSO_(4)^(2-),TNO_(3)^(-),TMg^(2+),TK^(+),and TCa^(2+)—were taken into account.IAM and inorganic aerosol pH after reducing TNaCl,TNO_(3)^(-),TMg^(2+),TK^(+),and TCa^(2+)responded linearly(0%≤concentration reduction ratio(CRR)≤100%,with the exception of 100%in TNaCl);the nonlinear variations of these two parameters could be observed by controlling TNH_(4)^(+)and TSO_(4)^(2-).Unexpected aerosol behavior occurred at 100%reduction of TNaCl,which was caused by the sudden increase of NO_(3)^(-),NH_(4)^(+),and aerosol liquid water content(ALWC);the increase of IAM was also observed after controlling TSO_(4)^(2-)(60%≤CRR≤100%)and TCa^(2+)(0%≤CRR≤100%),which was mainly related to the variation of ALWC driven by the response of CaSO_(4).Multiple regression analysis showed that ALWC was statistically and strongly related to the variations of NO_(3)^(-),Cl-,SO_(4)^(2-),HSO_(4)^(-),HNO_(3),and NH_(3)(P<0.05),with regression coefficients of 1.68,5.23,1.83,2.81,0.34,and 0.57,respectively.The highest coefficient(5.23)was found for Cl^(-),revealing that sea salts significantly influenced particle responses.Overall,this study comprehensively investigated aerosol characteristics and inner responses for the reduction of components,which is of great significance for a better understanding of atmospheric chemistry in Kitakyushu,Japan.

复杂颗粒悬浮液流变特性及其微介观机理研究综述

颗粒悬浮液由离散颗粒相和连续流体相构成,具有非牛顿、凝胶化等特殊的流变行为并在近年来受到广泛关注.大量研究表明,悬浮液组成和外场作用都影响其内部微观结构的形成或破坏,表现为宏观复杂的流变行为,因此建立微介观颗粒结构与宏观流变的联系是颗粒悬浮液研究的关键.本文从由刚性球形颗粒与不可压牛顿流体组成的理想颗粒悬浮液出发,介绍了其宏观流变理论与微观物理模型.在此基础上,分别从颗粒相、流体相和外场作用的角度综述了复杂颗粒悬浮液的研究进展.复杂颗粒相往往具有更加复杂的受力、变形和运动特征.我们重点介绍了非球形、柔性颗粒和活性颗粒三种类型颗粒悬浮液宏观流变性质与单颗粒动力学以及微介观结构的关联.对复杂流体相而言,我们归纳了流体相为纯黏性流体、屈服应力流体及黏弹性流体悬浮液黏度的研究进展,并介绍了引入第二连续相流体的毛细悬浮液的流变行为及其与液桥结构的联系.此外,我们从外场作用的角度,介绍了电、磁场等对流变性质的调控及恒压场剪切测试对稠密颗粒悬浮液本构模型的启发.最后,本文从颗粒相、流体相及本构理论的角度,对颗粒悬浮液研究的问题与前景进行了展望.

Preparation and 3D printing of high-thermal-conductivity continuous mesophase-pitch-based carbon fiber/epoxy composites

To meet the requirements of spacecraft for the thermal conductivity of resins and solve the problem of low thermal conduction efficiency when 3D printing complex parts,we propose a new type of continuous mesophase-pitch-based carbon fiber/thermoplastic polyurethane/epoxy(CMPCF/TPU/epoxy)composite filament and its preparation process in this study.The composite filament is based on the high thermal conductivity of CMPCF,the high elasticity of TPU,and the high-temperature resistance of epoxy.The tensile strength and thermal conductivity of the CMPCF/TPU/epoxy composite filament were tested.The CMPCF/TPU/epoxy composites are formed by 3D printing technology,and the composite filament is laid according to the direction of heat conduction so that the printed part can meet the needs of directional heat conduction.The experimental results show that the thermal conductivity of the printed sample is 40.549 W/(m·K),which is 160 times that of pure epoxy resin(0.254 W/(m·K)).It is also approximately 13 times better than that of polyacrylonitrile carbon fiber/epoxy(PAN-CF/epoxy)composites.This study breaks through the technical bottleneck of poor printability of CMPCF.It provides a new method for achieving directional thermal conductivity printing,which is important for the development of complex high-performance thermal conductivity products.

DLVO作用力对非布朗悬浮液的流变学和微观结构的影响

悬浮液的宏观流变特性往往与它们的微观结构变化密不可分,一些实验研究表明DLVO相互作用,即由于悬浮颗粒表面电荷而产生的微观排斥力和吸引力,对悬浮液的微观结构,特别是对团簇的形成有重大影响.在这项研究中,通过结合DLVO作用力与水动力和摩擦接触的数值模拟研究了非布朗悬浮液的流变特性及其微观结构.本文确定了不同的机制来解释排斥性和黏附性悬浮液的不同流变反应,揭示了颗粒团簇的演变和悬浮液流变学之间的重要联系.在排斥性系统中,排斥力和水动力之间的竞争以及由此产生的最小颗粒分离分布的变化是在低剪切率下第一次剪切变稀的原因.剪切增稠是在高剪切率下观察到的,并且由颗粒接触主导.吸引力的增强加大了悬浮液的黏度,同时掩盖了剪切增稠,即使在第一次剪切变稀的条件下,颗粒也会进行接触。第二法向应力差表现出与黏度相似的演变,而第一法向应力差主要是由波动主导的。微观结构分析显示,摩擦性团簇出现在排斥性悬浮液中,随着剪切率的增加,其数量和尺寸都在增长.另一方面,强吸引力悬浮液中的团簇会分解成更小的团簇,导致黏度降低.形状各向异性的计算表明,排斥性悬浮液中的摩擦性团簇倾向于在模拟箱中均匀地膨胀,而在高吸引强度下,团簇在强剪切时趋向于圆柱形.我们在微观结构方面的研究可以帮助弥合微观演化和宏观流变反应之间的差距,从而为非布朗悬浮液的本构模型的建立作出贡献.

双辊铸轧非晶复合材料条带的微观组织与力学性能

本文设计并制造了一种能够制备高质量非晶复合材料条带的新型配有水冷铜板的双辊铸轧原型机.利用该轧机在不同温度下成功制备了具有三种不同体积分数β-Ti枝晶的非晶复合材料带材(简称BT30,BT48和BT60),并通过一系列三点弯曲试验研究了其力学性能.结果表明,在高温下轧制的带材,高温元素在中间区域富集,导致成分分布不均.此外,由于铸轧过程中热力耦合导致在非晶复合材料中存在较大的内应力,这会显著影响其力学性能.新型铸轧设备为制备非晶复合材料带材提供了新的途径,基于该设备进行的研究深化了对非晶复合材料带材微观组织及力学性能的理解.

Pollution characteristics of atmospheric dustfall and heavy metals in a typical inland heavy industry city in China

Through field sampling of atmospheric dustfall in regions of Zhuzhou City, China for a period of one year, the deposition fluxes of atmospheric dustfall and five heavy metals contained inside, including Cr, As, Cd, Hg and Pb, were analyzed. Meanwhile the enrichment factor and index methods were used to analyze the pollution characteristics of heavy metals of atmospheric dustfall in Zhuzhou. The annual deposition flux of atmospheric dustfall in Zhuzhou was 50.79 g/（m^2.year）, while the annual deposition fluxes of Cr, As, Cd, Hg and Pb were 9.80, 59.69, 140.09, 0.87 and 1074.91 mg/（m^2.year）, respectively. The pollution level of atmospheric dustfall in Zhuzhou was relatively lower compared with most other cities in China, but the deposition fluxes of As, Cd, Hg and Pb in atmospheric dustfall in Zhuzhou were much higher than that in most cities and regions around the world. Cd is the typical heavy metal element in atmospheric dustfall in Zhuzhou, and both the enrichment factor and pollution index of Cd were the highest. Cd, Hg, Pb and As in atmospheric dustfall were mainly from human activities. According to the single-factor index, Nemerow index and pollution load index analyses, the atmospheric dustfall in Zhuzhou could easily cause severe heavy metal pollution to urban soil, and the most polluting element was Cd, followed by Pb, As and Hg. Only the pollution level of Cr lay in the safety region and mainly originated from natural sources.

Pollution sources of atmospheric fine particles and secondary aerosol characteristics in Beijing

To investigate the secondary formation and pollution sources of atmospheric particles in urban Beijing,PM2.5 and its chemical components were collected and determined by URG-9000 D ambient ion monitor(AIM) from March 2016 to January 2017.Among water-soluble ions(WSIs), NO3-,SO42- and NH4+(SNA) had the largest proportion(77.8%) with the total concentration of 23.8 μg/m3.Moreover,as fine particle pollution worsened,the NO3-,SO4<sup>2- and NH4+ concentrations increased basically,which revealed that secondary aerosols were the main cause of particle pollution in Beijing.Furthermore,the particle neutralization ratio(1.1),the ammonia to sulfate molar ratio(3.4) and the nitrate to sulfate molar ratio(2.2) showed that secondary aerosols are under ammonium-rich conditions with the main chemical forms of NH4 NO3 and(NH4)2 SO4,and vehicle emission could be the main anthropogenic source of secondary aerosols in Beijing.Source analysis further indicated that secondary aerosols,solid fuel combustion,dust and marine aerosol were the principal pollution sources of PM2.5,accounting for about 46.1%,22.4% and 13.0%,respectively,and Inner Mongolia and Hebei Provinces could be considered as the main potential sources of PM2.5 in urban Beijing.In addition,secondary formation process was closely related with gaseous precursor emission amounts(SO2,NO2,NH3 and HONG),atmospheric ozone concentration(O3),meteorological conditions(temperature and relative humidity) and particle components.Sensitive analysis of the thermodynamic equilibrium model(ISORROPIA Ⅱ)revealed that controlling total nitrate(TN) is the effective measure to mitigate fine particle pollution in Beijing.

The pollution levels, var iation character istics, sources and implications of atmospheric carbonyls in a typical rural area of North China Plain during winter

Atmospheric carbonyls were measured at a typical rural area of the North China Plain(NCP)from November 13 to December 24,2017 to investigate the pollution characteristics,sources and environmental implications.Fifteen carbonyls were detected,and formaldehyde,acetaldehyde and acetone accounted for about 81% at most.The concentration of the total carbonyls in heavily polluted days was twice more than that in clean days.In contrast to other carbonyls,m-tolualdehyde exhibited relatively high concentrations in the clean days in comparison with the polluted days.The ratios of three principal carbonyls to CO showed similar daily variations at different pollution levels with significant daytime peaks.Multiple linear regression analysis revealed that the contributions of background,primary and secondary sources to three principal carbonyls showed similar variation trends from the clean level to the heavily polluted level.The OH formation rate of formaldehyde showed a similar variation trend to its photodegradation rate,reaching the peak value at noon,which is important to maintain relatively high OH levels to initiate the oxidation of various gas-phase pollutants for secondary pollutant formation at the rural site.OH radical consumption rate and ozone formation potential(OFP) calculations showed that formaldehyde and acetaldehyde were the dominant oxidative species among measured carbonyls.As for OH radical consumption,n-butyraldehyde and m-tolualdehyde were important contributors,while for ozone formation potential,n-butyraldehyde and propionaldehyde made significant contributions.In addition,the contribution of carbonyl compounds to secondary organic aerosol(SOA) formation was also important and needs further investigation.

Kinetic and product studies of Cl atoms reactions with a series of branched Ketones

The rate constants for the C1 atom reaction with three branched ketones have been measured at 298 ± 2 K and 760 Torr using the relative rate method in the absence of NO. The rate constants values obtained （in units of 10^-10 cm^3/（molecule.sec）） are： k（2-methyl-3-pentanone） = 1.07 ± 0.26, k（3-methyl-2-pentanone） =1.21 ± 0.26, and k（4-methyl-2-pentanone） = 1.35 ± 0.27. Combining the chemical kinetic data obtained by this study with those reported for other ketones, a revised Structure Activity Relationship （SAR） parameter and R group reactivity （kR of R（O）R＇ and CHx （x = 1, 2, 3） group reactivity （kCHx） toward C1 atoms were proposed. In addition, the products from the three reactions in the presence of NO were also identified and quantified by using PTR-ToF-MS and GC-FID, and the yields of the identified products are： acetone （39% ± 8%） ＋ ethanal （78% ± 12%）, 2-butanone （22% ± 2%） ＋ ethanal （75% ± 10%） ＋ propanal （14% ± 1%） and acetone （26% ± 3%） ＋ 2-methylpmpanal （24% ± 2%）, for C1 atoms reaction with 2-methyl-3-pentanone, 3-methyl-2-pentanone and 4-methyl-2-pentanone, respectively. Based on the obtained results, the reaction mechanisms of C1 atoms with these three ketones are proposed.

Year-round observation of atmospheric inorganic aerosols in urban Beijing:Size distribution,source analysis,and reduction mechanism

To investigate particle characteristics and find an effective measure to control severe particle pollution,year-round observation of size-segregated inorganic aerosols was conducted in Beijing fromJanuary to December,2016.The sampled atmospheric particles all presented bimodal size distribution at four pollution levels(clear,slight pollution,moderate pollution and severe pollution),and peak values appeared at the size range of 0.7-2.1μmand>9.0μm,respectively.As dominant particle compositions,NO_(3)^(-),SO_(4)^(2-),and NH_(4)^(+)in four pollution levels all showed significant peaks in fine mode,especially at the size range of 1.1-2.1μm.Secondary inorganic aerosols accounted for about 67.6%(36.3%(secondary sulfates)+31.3%(secondary nitrates))of the total sources of fine particles in urban Beijing.Severe pollution of fine particles was mainly caused by the air masses transported from nearby western and southern areas,which are industrial and densely populated region,respectively.Sensitivity tests further revealed that the control measures focusing on ammonium emission reduction was the most effective for particle pollution mitigation,and fine particles all showed nonlinear responses after reducing ammonium,nitrate,and sulfate concentrations,with the fitting curves of y=-120.8x-306.1x^(2)+290.2x^(3),y=-43.5x-67.8x^(2),and y=-25.8x-110.4x^(2)+7.6x^(3),respectively(y and x present fine particle mass variation(μg/m3)and concentration reduction ratio(CRR)/100(dimensionless)).Overall,our study presents useful information for understanding the characteristics of atmospheric inorganic aerosols in urban Beijing,as well as offers policy makers with effective measure for mitigating particle pollution.