塑晶材料及其压卡效应研究发展与展望

随着世界经济的快速发展,以及全球变暖导致的气候问题日益加重,制冷技术对现代社会的影响越来越深入。全氯氟烃(CFCs)和含氢氯氟烃(HCFCs)类氟利昂制冷剂在常规的气体压缩制冷技术中一直占据主要地位,但这一类制冷剂的使用会加剧全球的温室效应。为了实现全球碳中和,寻求高效环保的制冷方案成为科学家们的重点研究方向,而基于外场诱导的固态相变技术就提供了一种很有前景的方案,其中压卡效应备受关注。近年来,科学家们相继在一系列被称为塑晶的材料中发现了庞压卡效应,其熵变比传统的固态相变制冷材料高一个数量级。在此之后,科研界对塑晶材料压卡效应的研究逐渐增多,并不断探寻出新的具有优异性能的塑晶材料作为压卡制冷技术的工质。这极大地促进了压卡制冷技术的发展,为未来实现绿色环保的高效制冷技术提供了更多可能性。本文将简单解释塑晶压卡效应的物理机制,对C_(5)H_(12)O_(2)(NPG)、(NH_(2))C(CH_(2)OH)_(3)(TRIS)以及碳硼烷等几种典型的塑晶材料在压卡效应上的综合表现进行陈述和对比,并对塑晶压卡效应在新型固态制冷技术中的应用进行展望。

塑晶基离子液体合成及其电化学性能

通过简单、易于工业化的重结晶方法制备了高纯1-甲基-1-乙基吡咯烷鎓双(三氟甲基磺酰)亚胺盐(P12TFSI)塑晶化合物.在此化合物中加入30%(摩尔分数,x)双(氟磺酰)亚胺锂(Li FSI)后,得到P12TFSI/Li FSI塑晶基离子液体.采用循环伏安法、恒电压极化法及恒电流充放电法等电化学方法考察了该离子液体的电化学窗口、铝箔集流体的腐蚀性及电池性能.结果表明,该离子液体电解质具有5.00 V的电化学窗口,室温离子电导率达到0.92 m Scm-1,且不腐蚀Al集流体.以该塑晶离子液体作为电解液组装的实验电池Li Co O2/Li表现出良好的充放电特性及循环性能,在较低倍率下能够和使用碳酸酯类电解液组装的实验电池的性能相媲美.在4.50 V高电压下,循环20周后,容量仍能保持在175 m Ahg-1,容量保持率为95.1%.这些结果说明该离子液体在高性能锂二次电池中具有良好的应用前景.

塑晶聚合物电解质在锂离子电池中的应用

采用溶剂挥发法制备了塑晶聚合物电解质膜。通过红外(FTIR),扫描电镜(SEM)对其内部基团结构及形貌进行了表征,采用DSC,万能材料试验机对其热稳定性及机械性能进行测试,采用循环伏安,交流阻抗以及恒流充放电对其电化学性能进行测试。结果表明,塑晶聚合物电解质具有良好的机械性能、较高室温电导率以及较宽的化学稳定窗口,在室温下其电导率约为0.9×10^(-3)S/cm。

超薄型豪华仿塑晶的装饰板

该产品是一种高档次、低成本(1。元/平方米)、大幅面装饰板材,2一3人十几分钟即可生产一块成品。其品强度高、韧性大,防水、防火、耐酸碱。

丁二腈基分子塑晶固态电解质的电化学性能

通过向丁二腈分子塑性晶体中加入固体碘盐和碘分子,制备了碘体系丁二腈基分子塑晶固态电解质。研究了不同阳离子的固体碘盐对丁二腈基固态电解质的相变、扩散系数以及离子电导率的影响。最终以碘化N-乙基吡啶作为固体碘盐与碘分子及丁二腈的摩尔比为2:1:100配制的固态电解质I-和I3-的扩散系数在室温达到1.83×10-6 cm2·s-1与1.22×10-6 cm2·s-1,固态电解质的离子电导率在30℃为1.7 m S·cm-1,制备的电池效率达1.57%。碘化N-乙基吡啶同时又是一种低成本和高成本效能的固体碘盐,更加具有商业应用价值。

新型有机硅基离子塑晶材料作为固态电解质用于锂离子电池（英文）

目的:合成新型的有机硅基离子塑晶材料[DTMA][TFSI],测试材料的物理和电化学性能,研究其掺杂改性并作为固态电解质用于锂离子电池。创新点:1.合成新型的有机硅基离子型塑晶材料;2.将三元复合塑晶材料作为固态电解质在室温下用于锂离子电池。方法:1.通过热性能分析,得到材料的塑晶温度区间和融化熵值(图1和表1);2.通过电导率测试,确定塑晶掺杂对导电性能的影响(图2);3.通过对扣式电池的充放电性能、倍率性能、循环性能以及阻抗的测试(图4~7),得到塑晶复合物作为固态电解质的电化学性能以及电池循环的稳定性和可逆性。结论:1.合成新型有机硅基离子塑晶材料[DTMA][TFSI],塑晶温度区间为–26°C到54°C;2.在纯塑晶IPC中添加10% LiODFB和10%PC,得到复合物的电导率为1×10^(-4) S/cm,提高塑晶作为固态电解质在室温下应用的可行性;3.将复合物用于LiFePO_4/Li半电池测试,在C/20倍率下,电池的放电比容量为144 mA·h/g,库伦效率为99%。在50次循环后,容量保持率为94%;4.测试结果表明,新型有机硅基离子塑晶的复合物可作为固态电解质材料应用于锂离子电池,以及更高能量密度的锂-硫和锂-空电池。

Effect of wire diameter compression ratio on drawing deformation of micro copper wire

A crystal plasticity finite element model was developed for the drawing deformation of pure copper micro wire,based on rate-dependent crystal plasticity theory.The impact of wire diameter compression ratio on the micro-mechanical deformation behavior during the wire drawing process was investigated.Results indicate that the internal deformation and slip of the drawn wire are unevenly distributed,forming distinct slip and non-slip zones.Additionally,horizontal strain concentration bands develop within the drawn wire.As the wire diameter compression ratio increases,the strength of the slip systems and the extent of slip zones inside the deformation zone also increase.However,the fluctuating stress state,induced by contact pressure and frictional stress,results in a rough and uneven wire surface and diminishes the stability of the drawing process.

Microstructural evolution and deformation mechanisms of superplastic aluminium alloys:A review

Aluminium alloy is one of the earliest and most widely used superplastic materials.The objective of this work is to review the scientific advances in superplastic Al alloys.Particularly,the emphasis is placed on the microstructural evolution and deformation mechanisms of Al alloys during superplastic deformation.The evolution of grain structure,texture,secondary phase,and cavities during superplastic flow in typical superplastic Al alloys is discussed in detail.The quantitative evaluation of different deformation mechanisms based on the focus ion beam(FIB)-assisted surface study provides new insights into the superplasticity of Al alloys.The main features,such as grain boundary sliding,intragranular dislocation slip,and diffusion creep can be observed intuitively and analyzed quantitatively.This study provides some reference for the research of superplastic deformation mechanism and the development of superplastic Al alloys.

三羟甲基氨基甲烷/蒙脱土纳米复合贮能材料研究

研究了三羟甲基氨基甲烷 (TAM ) /蒙脱土复合贮能材料的制备方法。用XRD、IR、DSC等方法对其结构及贮能性能进行了分析 ,结果表明 :该材料是一种纳米复合贮能材料 ,不仅具有较高的相转变焓 ,且塑晶失重现象较弱 ,具有良好的使用性能。

半氟烃链作桥链的对称酯类二聚体的合成及介晶性

合成全氟烃链或半氟烃链作为中心桥链的二聚体化合物可能出现新的性能,作为液晶材料具有较大的研究价值.合成了7个以半氟烃链作为桥链的对称酯类二聚体化合物H2n+1CnO-C6H4-COOCH2C6 F12CH2OOC-C6H4-OCnH2n+1(n=4,1a;6,1b;10,1c),H2n+1 CnO-C6H4-C6H4-COOCH2C6F12 CH2OOC-C6H4-C6H4-OCnH2n+1(n=4,2a;6,2b;12,2c)和C6F13CH2CH2COOCH2C6F12CH2OOCCH2CH2C6F13(3).差示扫描量热法(DSC)和偏光显微镜(POM)对其介晶性研究发现:化合物2a具有典型的焦锥扇形织构SA相,化合物2b出现塑晶相.分别比较结构相类似的化合物1a～1c,2a～2c的熔点,发现随着烷氧基链的增长,存在降低趋势.三段半氟烃链的对称酯类二聚体化合物3未观察到介晶性.

压卡制冷材料及技术的现状与展望

压卡制冷材料是一类由压力驱动材料发生固态相变而释放/吸收相变潜热的固体材料。压卡制冷技术是以压卡材料为工质、以压力作为驱动力构建的新兴固态制冷技术。本文从压卡效应基本热力学、压卡材料体系和压卡制冷样机三个方面简要论述该领域的发展现状。近年来压卡材料体系蓬勃发展,涉及金属、无机非金属、有机物、有机-无机杂化材料等。庞压卡效应的发现使有机塑晶材料备受关注,因其大熵变、低驱动压力、成本低廉等优点成为最有希望获得应用的一类材料。相比于此,制冷样机的研制则略显滞后。样机设计中需要解决的核心问题是力-热的有效耦合,选择高导热系数流体作为传热及传压介质,通过调整流体的压力和流速,同时优化压卡制冷工质的几何构型有望获得最佳力-热有效耦合条件。在单级制冷的基础上,采用主动回热式压卡制冷方式可实现连续制冷。

Scale effect mechanism on micro rod upsetting deformation analyzed by crystal plasticity model

To analyze the effect of single grain deformation behaviors on microforming process, a crystal plasticity model was developed considering grains at free surface layer as single grains. Based on the rate-dependent crystal plasticity theory, the analysis of the scale effect mechanism on upsetting deformation of micro rods was performed with respect to specimen dimension, original grain orientation and its distribution. The results show that flow stress decreases significantly with the scaling down of the specimen. The distribution of the grain orientation has an evident effect on flow stress of the micro specimen, and the effect becomes smaller with the progress of plastic deformation. For the anisotropy of single grains, inhomogeneous deformation occurs at the surface layer, which leads to the increase of surface roughness, especially for small specimens. The effect of grain anisotropy on the surface topography can be decreased by the transition grains. The simulation results are validated by upsetting deformation experiments. This indicates that the developed model is suitable for the analysis of microforming processes with characteristics, such as scale dependency, scatter of flow stress and inhomogeneous deformation.

Low temperature quasi-superplasticity of ZK60 alloy prepared by reciprocating extrusion

Fine-grained ZK60 alloy was prepared by 2-pass reciprocating extrusion, and the low temperature superplasticity was conducted in a temperature range from 443 to 523 K and an initial strain rate ranging from 3.3×10^-4 to 3.3×10-2^s^-1. The results show that the alloy has an equiaxed grain structure with an average grain size of about 5.0μm, and the sizes of broken secondary particles and precipitates are no more than 175 and 50 nm, respectively. The alloy exhibits quasi-superplasticity with a maximum elongation of 270% at 523 K and an initial strain rate of 3.3×10^-4 s^-1. The strain rate sensitivity m is less than 0.2 at 443 and 473 K, and it is 0.42 at 523 K. The apparent activation energies at temperature below 473 K and at 523 K are less than 63.2 and 110.6 kJ/mol, respectively At temperature below 473 K, mainly intragranular sliding contributes to superplastic flow. At 523 K, grain boundary sliding is the dominant deformation mechanism, and dislocation creep controlled by grain boundary diffusion is considered to be the main accommodation mechanism.

Improving in plasticity of orthorhombic Ti_2AlNb-based alloys sheet by high density electropulsing

In order to optimize the ductility of orthorhombic Ti2AlNb-based alloys sheet,Ti22Al27Nb sheet was treated by high density electropulsing（J max =6.80 7.09 kA/mm2,tp =110 μs） under ambient condition.Microstructures were observed by SEM,and the tensile properties were also studied using uniaxial tension tests.The experimental results show that electropulsing can refine the microstructures of Ti22Al27Nb sheets.The specimen with the fine and homogeneous microstructures has good plasticity,and its elongation reaches 19.4%.The mechanism about the effect of electropulsing treatment on the microstructure of Ti22Al27Nb sheets was discussed.It was thought that the increase in nucleation rate during phase transformation and a very short treating time were regarded as the main reasons of producing smaller grains and increase in the plasticity by electropulsing.

Microstructure and mechanical properties of AZ61 magnesium alloy prepared by repetitive upsetting-extrusion

The process of repetitive upsetting-extrusion （RUE） was used to achieve severe plastic deformation （SPD） for an as-cast AZ61 magnesium alloy in temperature range of 285-380 ℃. The microstructure and mechanical properties of the as-cast and RUE processed AZ61 alloys were investigated. The results indicated that homogeneous fine-grained structure with mean grain size of 3.5 μm was obtained as the accumulated true strain in the axial direction increased to 4.28 after three RUE passes at 285 ℃. The dominant reason of grain refinement was considered the dynamic recrystallization induced by strain localization. It was also found that the microstructural evolution was affected by temperature and accumulated deformation. The mechanical properties of RUE processed AZ61 alloys were significantly improved owing to grain refinement. Furthermore, the relationship between deformation parameters and mechanical properties of AZ61 alloy prepared by RUE processing was revealed by tensile tests carried out at room temperature.

SURFACE ROUGHNESS EVOLUTION AND FORMABILITY OF INTERSTITIAL FREE SHEET STEEL TO GRAIN SIZE AND SHEET THICKNESS

Experimental study has been conducted for an interstitial free(IF) sheet steel on its surface roughness evolution and formability with respect to grain size and sheet thickness effect. The surface roughness of IF sheet steel is proportional to effective strain, grain size and inversely proportional to sheet thickness; the larger grain reduces the formability by accelerating the surface roughening rate and enhance formability by raising the workhardening rate, while the latter effect plays the dominate role. The grain size effect on surface roughening and formability is more obvious when the sheets are thinner.

Microstructure and texture characterization of superplastic Al-Mg-Li alloy

A novel thermomechanical processing was developed for producing fine grained Al-Mg-Li alloy sheets. The influences of static recrystallization annealing on the grain structure and superplastic behavior were investigated. The results show that the refined microstructure has a variation in the distribution of grain size, shape and texture across the normal direction of the sheet. The surface layer （SL） has fine, nearly equiaxed grains with a rotated cUbeND {001 }（310） orientation, whereas the center layer （CL） has coarse, elongated grains with a portion of a fiber orientation. Increasing static recrystallized temperature results in grain growth in the full thickness, decreasing of grain aspect ratio in the center layer, texture sharpening in the surface layer, but weakening in the center layer as well as decreasing of superplastic elongation. Increasing the annealing temperature also produces an sharpening of the rotated cube {001}（310） component and a decreasing of the a fiber texture in the full thickness of the sheet. The formation mechanisms of recrystallization texture at various temperatures and layers were discussed.

Deformation mechanism of cold ring rolling in view of texture evolution predicted by a newly proposed polycrystal plasticity model

An explicit polycrystal plasticity model was proposed to investigate the deformation mechanism of cold ring rolling in view of texture evolution. The model was created by deducing a set of linear incremental controlling equations within the framework of crystal plasticity theory. It was directly solved by a linear algorithm within a two-level procedure so that its efficiency and stability were guaranteed. A subroutine VUMAT for ABAQUS/Explicit was developed to combine this model with the 3D FE model of cold ring rolling. Results indicate that the model is reliable in predictions of stress-strain response and texture evolution in the dynamic complicated forming process; the shear strain in RD of the ring is the critical deformation mode according to the sharp Goss component （{110}？100？） of deformed ring; texture and crystallographic structure of the ring blank do not affect texture type of the deformed ring;texture evolves rapidly at the later stage of rolling, which results in a dramatically increasing deformation of the ring.

Deformation mechanisms of Mg-3Al-1Zn alloy by polycrystal plasticity modeling

A polycrystal plasticity model was developed to analyze the room-temperature deformation behaviors of Mg-3A1-1Zn alloy（AZ31）.The uniaxial tension and compression tests at room temperature were conducted using cast and extruded AZ31 rods with different textures and combined with the proposed model to reveal the deformation mechanisms.It is shown that,different flow curves of two specimens under tension and compression tests can be simulated by this model.The flow curves of AZ31 extrusions exhibit different shapes for tension and compression due to different activities of tensile twinning and pyramidalc＋a slip.The metallographic and TEM observations showed the equal twinning activities at the initial stage in tension and compression tests and the occurrence of pyramidalc＋a slip in compression of as-cast Mg-3A1-1Zn alloy with increasing the strain,which is consistent with the simulated results by the proposed model.

Crystallization of amorphous NiTi shape memory alloy fabricated by severe plastic deformation

Based on the local canning compression,severe plastic deformation（SPD） is able to lead to the almost complete amorphous nickel-titanium shape memory alloy（NiTi SMA）,in which a small amount of retained nanocrystalline phase is embedded in the amorphous matrix.Crystallization of amorphous NiTi alloy annealed at 573,723 and 873 K was investigated,respectively.The crystallization kinetics of the amorphous NiTi alloy can be mathematically described by the Johnson-MehlAvrami-Kolmogorov（JMAK） equation.NiTi SMA with a complete nanocrystalline phase is obtained in the case of annealing at 573 K and 723 K,where martensite phase transformation is suppressed due to the constraint of the grain boundaries.Crystallization of amorphous NiTi alloy at 873 K leads to the coarse-grained NiTi sample,where（001） martensite compound twin is observed at room temperature.It can be found that the martensitic twins preferentially nucleate at the grain boundary and they grow up towards the two different grains.SPD based on the local canning compression and subsequent annealing provides a new approach to obtain the nanocrystalline NiTi SMA.