膨胀蛭石/聚(丙烯酸钾-丙烯酰胺)高吸水性复合材料的制备、性能及表征

以N,N'-亚甲基双丙烯酰胺为交联剂,过硫酸钾为引发剂,丙烯酸和丙烯酰胺为单体,采用新型水溶液聚合法合成了膨胀蛭石/聚(丙烯酸钾-丙烯酰胺)高吸水性复合材料.考察了交联剂用量、引发剂用量、单体浓度、中和度、反应温度、单体质量比及膨胀蛭石含量对吸水倍率的影响,试验结果表明,当蛭石含量为30%(相对单体质量,下同)时,交联剂用量为0.04%,引发剂为1.1%,中和度为75%(相对丙烯酸物质的量),单体浓度为50%,反应温度为75℃,吸水倍率最高可达1048g/g.最后,采用SEM、IR对其结构及组成进行了表征.     

反应条件对海藻酸钠/聚N-异丙基丙烯酰胺水凝胶温度及pH敏感性能的影响研究

以海藻酸钠(SA)和N-异丙基丙烯酰胺(NIPAM)为原料,采用水溶液聚合法制备了具有温度和pH值双重敏感性的海藻酸钠/聚(N-异丙基丙烯酰胺)水凝胶.在不同温度、不同pH值条件下,考察了单体浓度、交联剂用量、引发剂用量和反应温度对该凝胶溶胀度的影响,结果表明,凝胶有良好的温度和pH敏感性能,单体浓度、交联剂用量、引发剂用量和反应温度对凝胶的溶胀度均有较大影响.     

聚(丙烯酸盐共聚丙烯酰胺)/膨胀蛭石高吸水性复合材料的制备

以N,N'-亚甲基双丙烯酰胺为交联剂,过硫酸钾为引发剂,丙烯酸和丙烯酰胺为单体,采用新型溶液聚合法制备了聚(丙烯酸盐共聚丙烯酰胺)/膨胀蛭石高吸水性复合材料.考察了交联剂用量、引发剂用量、单体浓度、中和度、反应温度、膨胀蛭石含量及单体质量比对吸水倍率的影响,试验结果表明:当膨胀蛭石含量为20 wt%时,交联剂用量为0.04 wt%,引发剂为1.3 wt%,中和度为80%,单体浓度为50 wt%,反应温度为80℃,吸水倍率与吸收0.9wt%的NaCl溶液倍率分别为1262 g/g和92 g/g.探讨了添加矿物提高其耐盐性的机理.     

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。     

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.     

N-乙烯基吡咯烷酮-苯乙烯磺酸钠共聚物凝胶电解质的合成及性能研究

以N-乙烯基吡咯烷酮(NVP)和对苯乙烯磺酸钠(SSS)为原料,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,通过自由基水溶液聚合制备NVP与SSS共聚物P(NVP-co-SSS)凝胶电解质。研究了温度、引发剂和交联剂用量对聚合物凝胶电解质吸水性能及电导率的影响。结果表明:温度为70℃、引发剂用量为1.5%(wt,质量分数,下同)、交联剂用量为1.0%时,其吸水率为18.57g/g、电导率最大为(3.58×10-3)S/cm。对其热性能及机械性能的研究均表明其可以满足作为超级电容器聚电解质的使用要求。     

聚丙烯酸钠/硅藻土复合树脂制备条件对其粘附性能的研究

以N,N-亚甲基双丙烯酰胺为交联剂,过硫酸钾为引发剂,采用水溶液法制备出聚丙烯酸钠/硅藻土复合吸水树脂,探讨中和度、单体浓度、引发剂用量、交联剂用量以及硅藻土用量等因素对其粘附性能的影响,采用红外光谱分析复合吸水树脂的分子结构,以正交试验方法分析得到最优工艺条件,在中和度为70%、引发剂为0.2%、交联剂为0.14%、硅藻土为10%、单体浓度为25%时复合吸水树脂的粘附力具有最大值。     

无N2下合成钠基膨润土/P(AA-AM)复合吸水树脂的研制

以N,N'-亚甲基双丙烯酰胺为交联剂,过硫酸钾为引发剂,丙烯酸(AA)和丙烯酰胺(AM)为单体,采用水溶液聚合法合成出钠基膨润土复合聚丙烯酸钠-丙烯酰胺复合吸水树脂.研究了钠基膨润土的添加量、交联剂用量、引发剂用量、中和度及AM的用量对吸水倍率的影响.结果表明,钠基膨润土用量为40%,交联剂用量为0.025%,引发剂用量为0.3%,AM用量为12%及AA的中和度为80%时,吸蒸馏水倍率与吸收0.7%NaCl溶液倍率分别为422.28 g/g和65.80 g/g.     

用于稠化胶体的高吸水树脂的制备及吸水性能研究

以丙烯酸和丙烯酰胺为单体,N,N-亚甲基双丙烯酰胺为交联剂,过硫酸钾为引发剂,采用水溶液聚合法制备了高吸水树脂。通过正交实验法研究了单体浓度、丙烯酸中和度、引发剂用量和交联剂用量对树脂吸水倍率的影响。最终获得了在蒸馏水中吸水倍率高达3114g/g,在质量分数0.9%NaCl溶液中吸水倍率达157g/g的高吸水树脂,该树脂能够用作稠化胶体的稠化剂来提高胶体的实用性能。     

耐盐性魔芋葡甘聚糖吸水树脂的制备

以魔芋葡甘聚糖(KGM)为原料接枝丙烯酰胺、丙烯酸制备耐盐性吸水树脂,研究了接枝共聚反应单体及KGM质量配比、中和度、交联剂浓度、引发剂浓度、乙二胺四乙酸(EDTA)质量分数对吸水树脂吸液倍率的影响,通过Box-Behnken实验设计对制备条件进行优化。结果表明,丙烯酰胺与丙烯酸质量比为0.192,交联剂浓度为0.067g/mol,引发剂浓度为0.439g/mol,中和度为90%,乙二胺四乙酸(EDTA)质量分数为12.2%时,该耐盐性树脂吸生理盐水倍率达125g/g,吸纯水倍率达700g/g。     

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.