纳米SiO2对静电纺LA-PA/PET复合相变纤维形态和热学性能的影响

以月桂酸和棕榈酸二元低共熔混合物(LA-PA)、聚对苯二甲酸乙二酯(PET)和纳米二氧化硅(SiO2)为原料,通过静电纺丝的方法成功制备了新型的LA-PA/PET/SiO2定形相变复合纤维。分别采用扫描电子显微镜(SEM)和差示扫描量热仪(DSC)研究了纳米SiO2对静电纺LA-PA/PET/SiO2复合相变纤维的形貌结构和热学性能的影响。SEM观察结果显示,随着纳米SiO2的加入,复合相变纤维表面呈现出光滑的形态特点,纤维直径有所降低;且随着纳米SiO2含量的增加而逐渐减小。DSC分析结果表明纳米SiO2的含量对复合相变纤维的熔化焓值和结晶焓值有一定的影响,对相变温度没有显著性的影响。     

PET基定形相变复合纤维的制备

采用静电纺丝技术成功制备了以5种脂肪酸二元低共熔混合物(LA-MA、LA-SA、MA-PA、MA-SA、PA-SA)为固液相变材料,聚对苯二甲酸乙二酯(PET)为支撑材料的定形相变复合纤维。研究了不同种类的脂肪酸二元低共熔物对复合相变纤维的形貌结构、储热性能以及力学性能的影响。研究结果表明这5种定形相变复合纤维的表面均呈现褶皱的形貌特征,同时纤维直径也明显增大。热分析结果表明当改变纤维中脂肪酸二元低共熔物的种类时,复合相变纤维的熔化温度和熔化焓值均随之而变化,其中熔化温度最低为33.23℃,最高为52.82℃,熔化焓值最低为62.75kJ/kg,最高为94.76kJ/kg。力学性能测试结果表明,由于脂肪酸二元低熔物的加入复合相变纤维的拉伸强度减小,断裂伸长率增大。     

负载脂肪酸酯的定形相变复合纤维的制备与性能研究

以单硬脂酸甘油酯(GMS)为固液相变材料,以聚对苯二甲酸乙二酯(PET)纤维为支撑材料,通过静电纺丝方法成功制备了新型的GMS/PET定形相变复合纤维。FE-SEM观察显示随着定形相变复合纤维中GMS含量的增加,纤维直径逐渐增大且直径分布更广,纤维交叉点之间也出现粘连。XRD分析结果表明,静电纺丝过程中GMS和PET纤维基体能够很好地结合,由于PET纤维基体的支撑保护作用阻碍了GMS的结晶,导致结晶度下降。DSC分析结果表明,静电纺GMS/PET定形相变复合纤维是一种相变过程完全可逆的储能材料,其相变焓值随着纤维中GMS含量的增加而逐渐增大,相变焓效率85%。在DSC热循环测试过程中定形相变复合纤维的相变温度和相变焓值几乎没有变化,表明了该材料具有良好的热循环稳定性。     

MES/PET定型相变复合纤维的形貌结构及性能分析

通过制备硬脂酸甲酯/聚对苯二甲酸乙二酯(MES/PET)定型相变复合纤维,研究了MES固-液相变材料和PET支撑材料在定型相变复合纤维中的分布结构。结果表明在静电纺丝过程中MES组分作为分散相被随机地分散在PET纤维基体的连续相中,其在PET纤维中的最大负载量为50wt.%;复合纤维中的MES分子与PET分子之间没有发生化学反应,二者具有良好的相容性;MES/PET定型相变复合纤维的融化和结晶温度分别为39.84℃和27.96℃,融化和结晶焓值达到90.43kJ/kg和88.03kJ/kg;由于PET基体比MES分子具有更好的热稳定性,将PET纤维作为MES固液相变材料的支撑材料,有利于改善定型相变复合纤维的热稳定性;随着MES含量的增加,定型相变复合纤维膜呈现脆性断裂特征,其拉伸断裂强度增加。     

静电纺复合相变纤维的制备与热性能

通过静电纺丝方法成功制备了新型的月桂酸-硬脂酸(LA-SA)/聚对苯二甲酸乙二酯(PET)定形相变复合纤维。场发射扫描电子显微镜(FE-SEM)观察结果显示,随着LA-SA含量的增加,纤维表面的褶皱越来越明显,且纤维直径逐渐增大。差示扫描量热(DSC)分析结果显示,随着LA-SA在纤维中比例的增大,复合纤维的相变温度变化不大,相变焓值逐渐增加。DSC热循环测试结果表明,静电纺LA-SA/PET复合相变纤维是一种相变过程完全可逆的定形相变材料,可以在环境中循环使用。热重(TGA)分析结果表明,LA-SA/PET复合相变纤维分别在135℃～240℃和325℃～500℃温度范围内发生热降解,在相变温度范围(<100℃)内具有良好的热稳定性。     

沉积Ag纳米层改善定型相变复合纤维膜的传热性能

以癸酸(CA)、月桂酸(LA)和肉豆蔻酸(MA)为原料制备了新型的脂肪酸三元低共熔物(CA-LA-MA),并将其作为固-液相变材料,以沉积2 h银(Ag)纳米颗粒的静电纺聚丙烯腈(PAN)纳米纤维膜为支撑材料,通过物理吸附法制备了新型的CA-LA-MA/PAN和CA-LA-MA/PAN/Ag定型相变复合纤维膜。研究了磁控溅射Ag纳米层对定型相变复合纤维传热性能的影响。结果表明,沉积Ag纳米层后定型相变复合纤维膜的储热和放热时间分别缩短了31%和25%。制备的CA-LA-MA/PAN/Ag定型相变复合纤维膜的融化温度和结晶温度分别为19.87℃和11.63℃,融化焓值和结晶焓值分别为123.1 kJ/kg和121.5 kJ/kg。     

具有保温性能的电纺LA/PET纳米纤维复合织物的制备与表征

本文制备了电纺月桂酸(LA)/聚对苯二甲酸乙二醇酯(PET)纳米纤维/机织物的复合织物,并对其进行了表征.选用纯棉纱线、毛纱线、涤棉纱线、腈纶纱线和涤纶纱线分别作为经纬纱线,在实验室制备机织物小样,同时,通过静电纺丝法制备LA/PET纳米纤维,将LA包裹在PET基材之中.之后通过缝合的方式,将电纺LA/PET纳米纤维和机织物构造成三明治结构的复合织物.对纳米纤维的形貌和热性能进行了表征,并分别探究了LA/PET的质量比,机织物组织结构和机织物材料对复合织物保温性能的影响.结果表明:LA/PET纳米纤维呈圆柱形,具有光滑表面,LA和PET展现出良好的相容性,热焓值略低于理论值,但相变温度改变不大.复合织物的热保温性能测试表明,复合织物的保温性能都优于未加入相变材料的织物,同时展现出良好的热循环稳定性.     

具有保温性能的电纺LA/PET纳米纤维复合织物的制备与表征（英文）

本文制备了电纺月桂酸(LA)/聚对苯二甲酸乙二醇酯(PET)纳米纤维/机织物的复合织物,并对其进行了表征。选用纯棉纱线、毛纱线、涤棉纱线、腈纶纱线和涤纶纱线分别作为经纬纱线,在实验室制备机织物小样,同时,通过静电纺丝法制备LA/PET纳米纤维,将LA包裹在PET基材之中。之后通过缝合的方式,将电纺LA/PET纳米纤维和机织物构造成三明治结构的复合织物。对纳米纤维的形貌和热性能进行了表征,并分别探究了LA/PET的质量比,机织物组织结构和机织物材料对复合织物保温性能的影响。结果表明:LA/PET纳米纤维呈圆柱形,具有光滑表面,LA和PET展现出良好的相容性,热焓值略低于理论值,但相变温度改变不大。复合织物的热保温性能测试表明,复合织物的保温性能都优于未加入相变材料的织物,同时展现出良好的热循环稳定性。     

磁控溅射法提高定型相变材料的储热和放热速率

首先采用磁控溅射法在静电纺聚氨酯(PU)纤维膜表面沉积纳米银(Ag)导热金属薄膜,并将其作为支撑材料,通过物理吸附法吸附癸酸-月桂酸-肉豆蔻酸-棕榈酸四元低共熔物(CA-LA-MA-PA),制备出新型的CALA-MA-PA/PU/Ag定型相变复合纤维膜。EDX测试结果显示Ag纳米颗粒已经被成功地沉积到静电纺PU纤维膜上。SEM图像显示经过磁控溅射后静电纺PU纤维的直径明显增加,CA-LA-MA-PA四元低共熔物被均匀地吸附到PU和PU/Ag纤维膜的孔隙结构中。热分析结果表明CA-LA-MA-PA/PU/Ag定型相变复合纤维膜的融化温度和融化焓值分别为17℃和94.81kJ/kg。与CA-LA-MA-PA/PU定型相变复合纤维膜相比较,CALA-MA-PA/PU/Ag定型相变复合纤维膜的储热和放热时间分别缩短了约42%和24%。     

纳米碳化硅改善CPS/PAN相变复合纤维膜的传热速率

以不同质量比例的聚丙烯腈/纳米碳化硅(PAN/SiC)复合纤维膜为支撑材料,以癸酸-棕榈酸-硬脂酸(CPS)三元低共熔物为固-液相变材料,通过物理吸附法制备CPS/PAN/SiC定形相变复合纤维膜。分别采用扫描电子显微镜(SEM)、差示扫描量热仪(DSC)和传热测试装置研究不同含量纳米SiC对定形相变复合纤维膜的形貌特征、储热性能、热能储存和释放速率的影响。SEM图像显示负载不同含量纳米SiC对CPS/PAN/SiC定形相变复合纤维膜的形貌结构没有显著影响。DSC测试结果表明随着支撑纤维膜中SiC颗粒含量的增加,定形相变复合纤维膜的相变温度和相变焓值没有明显变化。根据传热测试数据显示随着纳米SiC含量的增加,定形相变复合纤维膜的融化与结晶时间显著缩短了约20%~46%。     

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.