壳聚糖/明胶/Y2O3杂化膜的制备、表征和对磷吸附性的研究

用阴离子表面活性剂SDS对Y2O3表面进行改性,并采用溶液共混法制备壳聚糖/明胶/Y2O3杂化膜。采用扫描电子显微镜(SEM)和傅里叶红外光谱仪(FT-IR)对杂化膜的表面形态和基团变化情况等进行表征,并对杂化膜的厚度、断裂强度、断裂伸长率等力学性能以及杂化膜对磷的吸附性能进行测试。结果表明:改性后的Y2O3在杂化膜中分散较均匀;杂化膜中,壳聚糖、明胶、Y2O3颗粒之间存在较强的氢键作用;加入适量的明胶和Y2O3,可以提高杂化膜的断裂强力和断裂伸长率;杂化膜对磷的平衡吸附量可以达到0.42mg/g。     

明胶/壳聚糖复合膜的制备与表征

采用流延法制备了明胶/壳聚糖复合膜,通过对复合膜结构及力学、热学、光学等性能进行表征,探究了壳聚糖对复合膜性能的影响。结果表明:明胶与壳聚糖共混相容性较好,复合膜均一透明。通过添加壳聚糖和甘油可以明显改善明胶/壳聚糖复合膜的抗拉强度、断裂伸长率、热稳定性及吸水性能;随壳聚糖含量的增加,透明度下降,壳聚糖添加量为30%(质量分数)时,透明度为79.4%(透光率小于80%)。研究认为通过壳聚糖与甘油对明胶进行改性可以不同程度地改善明胶膜的力学性能、吸水性能,能够满足其在不同领域的应用。     

PET/SiO_x基高阻隔性抑菌膜的制备和表征

分别采用紫外辐照和硅烷偶联剂(KH550)对聚酯(PET)/SiO_x膜的SiO_x镀层进行表面改性以制备PET/SiO_x/壳聚糖-纳米ZnO复合膜。水接触角测试发现,相比于紫外辐照,KH550改性能显著改善SiO_x的表面亲水性,从而成功制备得到PET/SiO_x/壳聚糖和PET/SiO_x/壳聚糖-纳米ZnO复合膜。随后采用电子扫描显微镜(SEM)观测复合膜的微观形态,并对该膜的力学性能、阻隔性和抑菌性进行了表征。SEM照片显示,该复合膜表面光滑,断面呈现层状结构。对该膜的力学性能测试结果发现,表面镀层(SiO_x)使PET膜的力学性能有所改善,但涂层(KH550、壳聚糖和壳聚糖-纳米ZnO)对PET/SiO_x膜的力学性能无显著影响。SiO_x镀层能有效改善PET膜的阻隔性,KH550涂层使PET/SiO_x膜的阻隔性进一步提高,壳聚糖及壳聚糖-纳米ZnO涂膜使复合膜的阻氧性进一步提高,而使其阻水性略有降低。此外,PET/SiO_x/壳聚糖及PET/SiO_x/壳聚糖-纳米ZnO膜对金黄色葡萄球菌及大肠杆菌均有良好的抑菌作用,其中PET/SiO_x/壳聚糖-纳米ZnO膜的抑菌性最强。该类膜有望应用于未来的保鲜包装。     

氧化石墨烯基复合材料对Cr(Ⅵ)的吸附研究

以氧化石墨烯(GO)、氧化铈(CeO2)和改性壳聚糖(DCS)为原料,采用溶液共混法合成氧化石墨烯基复合材料(DCG)。研究了DCG对Cr(Ⅵ)的静态吸附性能,考察了DCG用量、Cr(Ⅵ)质量浓度、吸附时间和吸附温度对吸附效果的影响。实验结果表明,DCG质量浓度为2g/L、废水中Cr(Ⅵ)质量浓度为20mg/L、吸附温度为25℃、吸附时间为90min时吸附效果最好。傅里叶变换红外光谱、扫描电子显微镜和X射线衍射分析表明,DCG为较厚的片层结构,片层表面附着大量点状物,羟基、羧基和氨基为主要活性吸附位点。复合材料DCG明显改变了GO、CeO2和DCS三者的团聚性和亲水性,充分发挥了各自的吸附性能。     

自组装的壳聚糖/SiO2杂化膜

以硅溶胶为晶种,使硅酸钠在壳聚糖膜中自组装形成SiO2微粒和晶须,并得到壳聚糖/SiO2杂化膜(以下简称杂化膜).用电子扫描电镜观察了SiO2微粒和晶须的形貌,研究杂化膜在水中的溶胀率,杂化膜的拉伸强度、伸长率和弹性模量等力学性能,杂化膜的热稳定性能.结果表明:杂化膜内SiO2为长3.0～6.0 μm,宽150m的晶须,以及直径为3.0μm的微粒;当膜内SiO2质量分数为7.5%时,杂化膜的力学性能达到最佳,其拉伸强度、弹性模量和断裂伸长率分别为38.39MPa、2383.02MPa、19.82%;随着杂化膜内SiO2质量分数从2.5%增加到12.5%,其溶胀率从112.0%下降到83.7%;杂化膜在200～800 nm波长范围的吸光度也逐渐降低;杂化膜的分解温度为314℃,高于单纯壳聚糖膜的分解温度290℃,表明SiO2晶须与壳聚糖杂化可提高壳聚糖膜的热稳定性.     

细菌纤维素/聚乙烯醇/胶原蛋白复合膜的制备及表征

以细菌纤维素(BC)膜为基材,聚乙烯醇(PVA)和胶原蛋白(COL)为增强材料制备了复合膜,并采用碳化二亚胺(1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐(EDC·HCl)为交联剂对制备的复合膜进行交联处理。利用红外光谱、扫描电镜、X射线衍射、热重分析、拉伸强力、吸水性能等测试手段对复合膜的化学结构、微观结构及性能进行了研究。研究表明,PVA和COL均匀地被吸附并沉积于BC的三维网络结构中,或包裹在BC纤维上;与BC/PVA/COL复合膜相比,采用EDC·HCl交联后的复合膜的溶胀性能降低,热降解稳定性和拉升强力得到了增强,断裂延伸率略有下降;但相对于BC膜来说,复合膜的拉伸强度和断裂伸长率都有较大程度的提升。     

细菌纤维素/聚乙烯醇/胶原蛋白复合膜的制备及表征EI北大核心CSCD

以细菌纤维素(BC)膜为基材,聚乙烯醇(PVA)和胶原蛋白(COL)为增强材料制备了复合膜,并采用碳化二亚胺(1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐(EDC·HCl)为交联剂对制备的复合膜进行交联处理。利用红外光谱、扫描电镜、X射线衍射、热重分析、拉伸强力、吸水性能等测试手段对复合膜的化学结构、微观结构及性能进行了研究。研究表明,PVA和COL均匀地被吸附并沉积于BC的三维网络结构中,或包裹在BC纤维上;与BC/PVA/COL复合膜相比,采用EDC·HCl交联后的复合膜的溶胀性能降低,热降解稳定性和拉升强力得到了增强,断裂延伸率略有下降;但相对于BC膜来说,复合膜的拉伸强度和断裂伸长率都有较大程度的提升。     

壳聚糖/Y2O3/聚丙烯无纺布复合膜的制备及其性能研究

采用戊二醛作为交联剂,采用溶液共混和表面延流法制备壳聚糖/Y2O3/聚丙烯无纺布复合膜。采用IR、DSC、SEM对复合膜进行表面结构表征;对复合膜的结合牢度以及复合膜对磷的吸附性能进行测试。结果表明:壳聚糖和Y2O3颗粒都比较均匀分散在复合膜的表面;处理后的复合膜吸热峰值没有明显变化;当壳聚糖固定时,复合膜的结合牢度随Y2O3用量的增加逐渐降低,当Y2O3用量固定时,复合膜的结合牢度随壳聚糖用量的增加逐渐增大。聚丙烯无纺布经过壳聚糖/Y2O3处理后,对磷具有一定吸附作用,吸附性能优于纯壳聚糖涂敷膜。     

聚吡咯/壳聚糖复合膜的制备及其对Cu(Ⅱ)和Cr(Ⅵ)吸附机制

以聚吡咯(PPy)和壳聚糖(CS)为原料,制备PPy/CS复合膜,通过红外、孔径分析、热分析和SEM等手段对其结构进行表征,并研究了PPy/CS复合膜对Cu(Ⅱ)和Cr(Ⅵ)吸附性能的影响及吸附机制,考察了pH值、吸附时间、溶液起始浓度等因素对吸附率的影响.结果表明,初始浓度对吸附率影响最大;在pH=3.5、温度为33...     

改性壳聚糖吸附Cr(Ⅵ)的应用研究进展

Cr(Ⅵ)是一种对生物和人体高度有毒的重金属离子。改性壳聚糖对Cr(Ⅵ)的吸附是去除含Cr(Ⅵ)废水中Cr(Ⅵ)的一种有效方法。壳聚糖通过分子中的氨基和羟基等功能团与Cr(Ⅵ)离子发生吸附作用。通过改性可以提高壳聚糖的物理稳定性和吸附容量等。综述了壳聚糖的化学和复合改性在吸附Cr(Ⅵ)方面的研究进展。     

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.     

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.     

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.     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.     

n-PbTep+−Pb1−xSnxTe heterojunctions prepared by a modified hot wall technique

$\text{n-PbTe}\text{p}{}^{\mathrm{+}}\text{?}\text{Pb}{}_{\mathrm{1?x}}\text{Sn}{}_{\mathrm{x}}\text{Te}$ heterojunctions with a long wavelength spectral cutoff (λ_c ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with R_oA equal to 170 Ω cm² and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given.     

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.     

Reactive plasma deposited SixCyHz films

Si_xC_yH_z films have been prepared at 200°C by reactive plasma deposition from SiH₄ and CH₄ diluted in helium in a tubular reactor. These films have a ratio s (equal to $\text{Si}\text{(}\text{Si+C}\text{))}$ ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH₄-CH₄-He plasma have been performed and the results are related to the composition of the deposited layers.     

Core-current-enhanced domain-wall pinning in nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon

We have studied the influence of surface fields H/sub p/ (generated by either direct or alternating core current) on soft magnetic properties of amorphous and nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon. While in an amorphous ribbon the coercive field H/sub c/ decreases with H/sub p/, in the same optimally annealed ribbon (H/sub c/=1.3 A/m, M/sub m//spl ap/M/sub s/) H/sub c/ increases with H/sub p/ for all the explored types of H/sub p/ (static and dynamic with different phases with respect to that of the magnetizing field H). The unexpected increase of H/sub c/ in nanocrystalline ribbon is associated with the influence of H/sub p/ on the surface and main (inner) domain structure. Here, we develop a model that takes into account this influence and explains the experimental results.     

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.