智能型AMPS/DMAEMA水凝胶的电敏感性能

以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)和甲基丙烯酸N,N-二甲氨基乙酯(DMAEMA)为单体,N,N′-亚甲基双丙烯酰胺为交联剂,过硫酸铵和亚硫酸氢钠为氧化还原引发剂,采用水溶液聚合法制备了AMPS/DMAEMA水凝胶,考察了样品水凝胶在外加直流电场刺激下的消溶胀动力学和弯曲行为.结果表明,DMAEMA单体含量和施加电压大小对水凝胶的电敏感性能有着显著影响.用一级动力学方程能够较好地描述水凝胶在接触电压刺激下的消溶胀过程.在非接触电压刺激下,单体摩尔比,n(AMPS):n(DMAEMA)=9:1的水凝胶向负极弯曲;单体摩尔比n(AMPS):n(DMAEMA)=5:5的水凝胶向正极弯曲;单体摩尔比n(AMPS):n(DMAEMA)=7:3的水凝胶随着非接触电压的增大,出现先向负极弯曲,后向正极弯曲的现象.     

电场敏感性AM/DMDAAC共聚水凝胶的合成和性能

以丙烯酰胺(AM)和二甲基二烯丙基氯化铵(DMDAAC)为单体,N,N′-亚甲基双丙烯酰胺为交联剂,过硫酸铵和亚硫酸氢钠为氧化还原引发剂,采用水溶液聚合法制备了AM/DMDAAC水凝胶。考察了样品水凝胶的离子强度敏感性和pH敏感性,以及在外加直流电场刺激下的消溶胀动力学。结果表明,样品水凝胶具有灵敏的离子强度敏感性,在NaCl质量分数为0.3%左右发生体积相变;对pH变化不敏感,具有很好的酸碱耐受性;DM-DAAC单体含量对水凝胶的电敏感性能有显著影响。     

聚丙烯酰胺/丙烯酸钾互穿网络多孔水凝胶的制备和性能

以丙烯酸、丙烯酰胺为单体,过硫酸钾为引发剂,N,N′-亚甲基双丙烯酰胺为交联剂,利用水溶液聚合法和乙醇致孔法制备了聚丙烯酰胺/丙烯酸钾互穿网络多孔水凝胶.采用红外光谱(FTIR)和扫描电镜(SEM)等分析技术对水凝胶进行了表征,研究了水凝胶的溶胀行为和吸0.9％NaCl(质量分数,下同)盐水的能力.实验结果表明,该多孔水凝胶具有较快的吸水速率,其最高吸水倍率可达3600g/g,吸0.9％NaCl盐水倍率最大可达120g/g,凝胶粉末能在8min内达到溶胀平衡.     

Poly(DMAM-co-AA)水凝胶的合成

以N,N-二甲基丙烯酰胺(DMAM)与丙烯酸(AA)为单体,N,N-亚甲基双丙烯酰胺(NMBA)为交联剂,过硫酸铵为引发剂,采用水溶液聚合法合成了DMAM和AA的共聚物水凝胶。实验证明,加热温度、引发剂用量和反应体系中单体总浓度对聚合产物的吸水能力没有明显影响,但随着对反应溶液的加热温度升高、引发剂用量增大、单体总质量分数增大,聚合反应能够达到的最高温度就越高,达到最高温度的时间缩短。DMAM和AA的物质的量比偏离1越远,水凝胶的吸水能力越强。交联剂的质量分数为0.5%时,水凝胶的吸水能力最大。     

黄原胶/聚乙烯醇互穿网络水凝胶的电刺激响应行为

以戊二醛为交联剂,制备了黄原胶/聚乙烯醇(XG/PVA)互穿聚合物网络水凝胶,并研究了其吸水率、力学性能和电刺激响应行为。结果表明,在NaCl溶液中,该水凝胶的平衡溶胀比随NaCl溶液离子强度增大而减小,随pH值的增大而增大,当pH≥7时基本保持不变;经离子强度为0.01 mol/L NaCl溶液充分溶胀的XG/PVA互穿聚合物网络水凝胶其弹性模量为0.9844 MPa,拉伸强度为1.5691 MPa,断裂伸长率为1.60;在非接触的直流电场作用下,于NaCl溶液中,该水凝胶发生弯曲,凝胶的弯曲速度和弯曲偏转程度随外加电场的增加而增大;NaCl溶液离子强度对凝胶弯曲行为产生影响,当溶液离子强度I≤0.05时,凝胶向电场负极弯曲,当溶液离子强度I≥0.05时凝胶向电场正极弯曲;在循环电场作用下,其弯曲响应行为具有良好的可逆性。     

P（AAEA/AMPS/AA）超大孔水凝胶的制备及性能

采用泡沫分散聚合法,以自制的4-乙酰基丙烯酰乙酸乙酯（AAEA）和2-丙烯酰胺基-2-甲基丙磺酸（AMPS）、丙烯酸（AA）为单体,过硫酸铵（APS）及N,N,N′,N′-四甲基乙二胺（TMEDA）为氧化还原引发体系,N,N′-亚甲基双丙烯酰胺（MBA）为交联剂,以饱和Na2CO3水溶液为发泡剂,十二烷基磺酸钠为泡沫稳...     

黄原胶/聚乙烯醇互穿网络水凝胶的电刺激响应行为EI北大核心CSCD

以戊二醛为交联剂,制备了黄原胶/聚乙烯醇(XG/PVA)互穿聚合物网络水凝胶,并研究了其吸水率、力学性能和电刺激响应行为。结果表明,在NaCl溶液中,该水凝胶的平衡溶胀比随NaCl溶液离子强度增大而减小,随pH值的增大而增大,当pH≥7时基本保持不变;经离子强度为0.01 mol/L NaCl溶液充分溶胀的XG/PVA互穿聚合物网络水凝胶其弹性模量为0.9844 MPa,拉伸强度为1.5691 MPa,断裂伸长率为1.60;在非接触的直流电场作用下,于NaCl溶液中,该水凝胶发生弯曲,凝胶的弯曲速度和弯曲偏转程度随外加电场的增加而增大;NaCl溶液离子强度对凝胶弯曲行为产生影响,当溶液离子强度I≤0.05时,凝胶向电场负极弯曲,当溶液离子强度I≥0.05时凝胶向电场正极弯曲;在循环电场作用下,其弯曲响应行为具有良好的可逆性。     

N-羟甲基丙烯酰胺/丙烯酸智能水凝胶的合成及性能研究

以N-羟甲基丙烯酰胺(N-MAM)和丙烯酸(AA)为聚合单体,过硫酸铵(APS)和N,N,N′,N′-四甲基乙二胺(TEMED)为引发体系,N,N-亚甲基双丙烯酰胺(MBA)为交联剂采用自由基水溶液聚合法合成了p(N-MAM-co-AA)水凝胶。研究了APS、MBA的用量、单体浓度与单体配比、溶液pH值和温度对水凝胶溶胀性能的影响,同时还研究了凝胶的溶胀-退溶胀动力学。     

AMPS/AA/MA/St共聚吸附剂的合成及性能研究

在交联剂N,N′-亚甲基双丙烯酰胺(NMBA)的作用下,单体2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)、顺丁烯二酸酐(MA)和淀粉(St)以溶液热聚合的方式合成四元共聚吸附剂。采用单因素法探究了反应条件对树脂吸附亚甲基蓝染料性能的影响,得到最佳的树脂合成工艺条件。实验结果表明:n(AMPS)∶n(AA)∶n(MA)∶W(St)=1∶0.5∶0.1∶1.98(wt,质量分数,下同),pH=2,W(NMBA)=0.1%,固含量为31%时,该树脂的吸附量最大,为106.35mg/g。     

冷冻干燥法制备CS/AMPS/PEGDA光交联多孔水凝胶及其性能

以壳聚糖(CS)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)与聚乙二醇二丙烯酸酯(PEGDA)为原料,通过光聚合技术和冷冻干燥法制备了CS/AMPS/PEGDA交联网络多孔水凝胶。采用红外光谱(FTIR)分析了水凝胶的化学结构,通过实时红外(RTIR)监测单体的双键转化率变化,扫描电镜(SEM)观察水凝胶的微观形貌,并测试了它的溶胀性能和热稳定性。结果表明,当CS/AMPS的质量比为1/2时,得到的水凝胶多孔结构规整,孔隙率较高,且能达到较高的平衡溶胀比。在此基础上,将抗癌药物康普瑞丁磷酸二钠(CA4P)以不同浓度载入水凝胶中,综合考察水凝胶的载药量及包封率,得出当CA4P的投药量占水凝胶的7.5wt%时达到最佳载药效果:载药量为3.13%,包封率为41.76%。     

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.