杂化材料中有机小分子形态对阻尼性能影响

通过动态力学热分析仪(DMA)和差示扫描热分析仪(DSC)研究了由氯化聚乙烯(CPE)与2,2-甲撑双-(4-乙基-6-叔丁基苯酚)(EBP)和(2-羟基-3-环己基-5甲基)-苯环(ZKF)组成的杂化材料的阻尼性能.对于CPE/EBP杂化材料的DMA分析表明,除了含质量分数为5%的EBP外,CPE/EBP杂化材料呈现了两个明显损耗峰,在CPE基体的玻璃化温度以上出现了一个新的损耗峰.这表明在CPE/EBP杂化材料中,CPE富集相与EBP富集相是共同存在的.然而,CPE/ZKF杂化材料只有一个损耗峰,而且峰的高度随着ZKF含量的增加而明显增加.DSC研究表明,CPE/ZKF杂化材料中的ZKF以无定形态存在.研究结果说明小分子EBP和ZKF在基体材料中的存在形态对构成的杂化材料的阻尼性能产生很大的影响.     

加工工艺对CPE/AO2246阻尼性能与形态结构的影响

利用氯化聚乙烯(CPE)与有机小分子2,2亚甲基-双(4-甲基-6-叔丁基苯酚)(AO2246)采用不同工艺制备了有机杂化阻尼材料,通过动态力学分析(DMA)、差示扫描量热(DSC)、扫描电镜(SEM)和红外光谱(FT-IR)考察了材料的动态力学性能和微观结构。研究结果表明,AO2246在基体CPE中的分散状态对体系的阻尼性能影响较大。在未经热压的CPE/AO2246体系中,AO2246以三维谷粒结晶存在,造成体系的损耗因子(tanδ)比基体的还要低;而经过热压工艺的CPE/AO2246体系,AO2246与CPE产生了有机杂化,使体系的tanδ峰值获得较大的提高,同时玻璃化温度向高温方向移动,改善了体系的阻尼特性。红外光谱图表明,高温热压工艺的AO2246分子间产生了氢键作用的新的吸收峰,从而进一步提高了体系的阻尼性能。     

EPDM/ENR宽温域阻尼材料的制备及阻尼机理

采用饱和非极性三元乙丙橡胶(EPDM)和不饱和强极性环氧化天然橡胶ENR-50制备出EPDM/ENR-50二元共混阻尼材料。利用扫描电镜/X射线能谱分析、原子力显微镜分析表明,该共混体系拓宽阻尼温域的机理在于两相中硫化剂的迁移,即共混硫化交联过程中,饱和非极性的EPDM相中的硫化剂向极性不饱和的ENR-50相迁移,导致二元共混物中ENR-50交联密度比其单独硫化时高,阻尼内耗峰向高温方向外扩,而EPDM相的交联密度比单独硫化时低,阻尼内耗峰向低温方向外扩,最终得到了温度范围从-72.3℃到52.9℃(tanδ0.13)的宽温域阻尼材料。为了改进二元共混橡胶的阻尼性能和力学性能,进一步制备了EPDM/ENR-50/氯丁橡胶(CR)三元共混阻尼材料,所得三元共混胶的有效阻尼(tanδ0.3)温域范围超过120℃,同时材料具有良好的力学性能。     

七孔涤纶纤维对CPE-AO2246微观结构和性能的影响

利用氯化聚乙烯(CPE)、2,2-亚甲基-双(4-甲基-6-叔丁基苯酚)(AO2246)和三维卷曲七孔中空涤纶纤维(SHPF)制备了一系列的SHPF/CPE AO2246三元复合材料.通过DMA、SEM、SW230吸声仪以及HD026NE电子织物强力仪等对复合材料的微观结构和性能进行了测试及分析.结果表明,加入的SHPF纤维充当了结晶诱导作用,在复合材料中产生了大量AO2246的包覆式结晶,从而加速了网络结构的形成;含有20％质量比(以CPE和AO2246总质量为基)纤维的SHPF/CPE-AO2246复合材料的最大储能模量是未加纤维的3倍多,由于复合材料的储能模量增幅较大而使其损耗因子下降较快,但材料损耗模量-温度曲线下的面积(LA)随纤维含量增加而增大,说明材料的阻尼耗能能力并未下降;SHPF纤维的加入使材料的力学性能获得了较大的改善,中空网络结构的形成赋予三元复合材料吸声性能.     

羧基丁苯/受阻酚阻尼材料的性能研究

通过向极性的橡胶基体羧基丁苯(CSBR)中添加受阻酚,制备了一系列羧基丁苯/受阻酚阻尼材料.通过动态力学分析表明,受阻酚与基体CSBR具有较好的相溶性,并且该类材料具有很好的阻尼性能.这种材料中受阻酚与基体橡胶形成了分子间的氢键,在受到交变的机械应力作用下,氢键会断裂而消耗大量的能量,从而具有良好的阻尼性能.这类材料的玻璃化转变温度较高,损耗因子(tanδ)出峰位置都高于室温,这类阻尼材料可以应用于室温附近,解决了橡胶材料只能用作低温阻尼材料使用的问题.     

七孔涤纶纤维对CPE-AO2246微观结构和性能的影响

利用氯化聚乙烯(CPE)、 2, 2-亚甲基-双( 4-甲基-6-叔丁基苯酚) (AO2246)和三维卷曲七孔中空涤纶纤维(SHPF)制备了一系列的SHPF/CPE-AO2246三元复合材料。通过DMA、 SEM、 SW230吸声仪以及HD026NE电子织物强力仪等对复合材料的微观结构和性能进行了测试及分析。结果表明, 加入的SHPF纤维充当了结晶诱导作用, 在复合材料中产生了大量AO2246的包覆式结晶, 从而加速了网络结构的形成; 含有20%质量比(以CPE和AO2246总质量为基)纤维的SHPF/CPE-AO2246复合材料的最大储能模量是未加纤维的3倍多, 由于复合材料的储能模量增幅较大而使其损耗因子下降较快, 但材料损耗模量-温度曲线下的面积(LA)随纤维含量增加而增大, 说明材料的阻尼耗能能力并未下降; SHPF纤维的加入使材料的力学性能获得了较大的改善, 中空网络结构的形成赋予三元复合材料吸声性能。     

DOPO超分子作用阻尼硅材料的动态力学性能

以9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)接入多乙烯基硅油中制得具有超分子作用的硅橡胶阻尼材料(DOPO-PMVSPVMQ)。研究了材料基团之间的超分子作用及其对材料阻尼性能的影响,建立具有超分子修正项的分数阶导数Kelvin-SI模型。采用模型对材料的动态力学性能进行了表征,研究其在不同环境条件下的性能变化情况。模型可以准确有效地对材料在不同温度(240～420 K)、不同频率(1～100 Hz)下的存储模量及损失模量进行描述。材料的存储模量及损耗因子都随着温度的升高逐渐减小,随频率的增加逐渐增大。在研究的温度及频率范围内材料的模量在0.4～0.8 MPa之间,损耗因子在0.15～0.3之间。在宽温宽频范围内,模型修正项贡献率在30%～60%之间。随着温度的升高、频率的增加贡献率逐渐下降,但仍然在20%以上。     

受阻酚/羧基丁腈橡胶复合材料的结构及动态力学性能

将羧基丁腈橡胶(XNBR)和受阻酚2,2′-亚甲基双-(4-甲基-6-叔丁基苯酚) (AO-2246)混合制备出挤压和未挤压AO-2246/XNBR复合材料,并对其结构及动态力学性能进行了研究。研究结果表明,AO-2246在XN2BR基体中的分散状态对体系的动态力学性能影响较大。在未挤压样品中,大部分AO-2246分子以晶体颗粒的形式存在,体系的损耗因子(tanδ)比纯XNBR基体低;而在挤压样品中,由于热压淬火过程中两组分发生杂化,体系的tanδ值明显增大,体系的阻尼性能显著提高。差示扫描量热(DSC)分析和扫描电镜(SEM)观察表明,当AO-2246质量分数高于40%后,杂化体系中AO-2246以3 种形态存在：杂化形态、微相分离态以及结晶态,它们共同对体系的动态力学性能产生影响。AO-2246质量分数为50%的杂化体系的tanδ峰峰值高达3.5,同时该峰位置由低温区向高温方向移动至室温附近,从而使AO-2246/XNBR复合材料成为一种极具潜力的高性能阻尼材料。     

三元互穿聚合物网络材料阻尼性能研究

采用同步法制备了聚氨酯 /环氧树脂 /丙烯酸酯三元互穿聚合物网络 (IPN) ,采用动态力学分析法研究了IPN的阻尼性能 ,以及影响材料阻尼性能的因素。研究结果表明 :三元互穿聚合物网络力学损耗因子≥ 0 .6的温度范围在 2 8～ 75℃ ;≥ 1 .4 ,表现出优异的高温阻尼性能     

POSS/聚合物杂化材料研究进展

多面体低聚倍半硅氧烷(POSS)作为一种特殊的纳米级有机-无机杂化材料,可以与聚合物进行分子级复合,得到具有特殊性能的POSS/聚合物杂化材料,这成为近年来材料科学领域的研究热点之一。从POSS/聚合物杂化材料制备方法出发,主要介绍了几类典型的POSS/聚合物杂化材料的结构和性能,并对POSS/聚合物杂化材料的应用前景进行了展望。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.     

Tc trend in high-Tc superconductors

In our previous works, we have shown that most existing ceramic superconductors can be considered to be built of superconductor-semiconductor composite and we have estimated the change in phonon spectrum of the intrinsic superconductor unit if a semiconductor unit is attached to it. Moreover, the proximity effect under the size quantization condition has been examined in the superconductor-semiconductor composite. Each of the stated effects by itself could causeT _c enhancement in general as more semiconductor blocks are added to the system. We extend our study in this paper to analyze the combined actions of phonon spectral change and proximity effect without size quantization condition onT _c variation in members of the Tl₁ series of high-T _c superconductors. Our results indicate that an optimumT _c is obtained if the stated effects are included in the idealized unit cells of the superconductors made up of a superconductor-semiconductor array.     

Anomalous Hall Effect in Sn1?x?yMnxEuyTe and Sn1?x?yMnxEryTe Mixed Crystals

The Anomalous Hall Effect (AHE) was investigated in IV–VI ferromagnetic semimagnetic semiconductors of Sn_1–x Mn _x Te codoped with either Eu or Er. The analysis of experimental data is as follows. Hall resistivity and magnetization showed that AHE coefficient R _s depends on temperature and its value decreases with thetemperature increase. We observe that above ferromagnet–paramagnet transition temperature R _s changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of R _s , particularly change of the sign.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

Effect of pressure onTc in La2-xBaxCuO4 withx=0.125

The superconducting transition temperature,T _c , of La_2–x Ba _x CuO₄ has been measured under high pressure up to 8 GPa.T _c is found to change drastically at the pressure where the structural phase transition takes place. This finding clearly indicates that there exists an intimate relation between the crystal structure and superconductivity.