异丙醇铝溶胶-凝胶掺杂的SiO2-Al2O3/PEG导热增强型定形相变储能材料

以异丙醇铝(AIP)与正硅酸乙酯(TEOS)为溶胶前驱体、 聚乙二醇(PEG)为相变组分, 经超声辅助溶胶-凝胶过程制备了SiO₂-Al₂O₃/PEG 导热增强型定形相变储能材料。利用FTIR和XRD对SiO₂-Al₂O₃/PEG进行结构表征及结晶性能测定, 利用DSC与TGA研究其热性能与热稳定性, 利用显微热台与数码拍照技术测试材料的定形效果; 利用热导率仪测定了材料的导热系数。结果表明, SiO₂-Al₂O₃/PEG的相变焓值可以达到100 J/g以上, 低于300 ℃时具有良好的热稳定性, 当SiO₂-Al₂O₃/PEG中的铝硅质量比为0.2:1时, 其导热系数可达0.414 W/(m·K), 导热性能比纯PEG提高39.3%, 并具有良好的定形效果。     

聚乙二醇/白炭黑复合相变储热水泥板的性能研究

以聚乙二醇(PEG)为相变材料、白炭黑(WCB)为定形载体,通过高频超声共混法制备出PEG质量含量为70%的聚乙二醇/白炭黑复合相变储热材料(PEG/WCB-PCM),借助比表面积分析仪、差示扫描量热仪(DSC)及热重分析仪(TGA)对PEG/WCB-PCM的多孔结构、储热特性及热稳定性进行测试与表征;将PEG/WCB-PCM与水泥砂浆混合,制备出新型复合相变储热水泥立方体及水泥板,并对其表观密度、抗压强度、导热系数及储热调温性能进行实验。结果表明:PEG/WCB-PCM的定形效果主要得益于WCB的多孔网络状结构,PEG/WCB-PCM的相变焓高达114.8J/g且在300℃以下温度范围内热稳定性良好;随着PEG/WCB-PCM掺量的增加,复合相变储热水泥立方体的表观密度及抗压强度都呈下降趋势,因此应合理控制PEG/WCB-PCM的掺量;尽管PEG/WCB-PCM的掺入会影响复合相变储热水泥板的导热系数,但储热调温实验表明,PEG/WCB-PCM在水泥板中能起到显著的储热调温作用,可作为一种绿色节能材料应用到建筑节能领域。     

石蜡/SiO_2储能相变材料的制备与热性能研究

以工业石蜡为相变芯材,在硅烷偶联剂参与下,通过溶胶-凝胶法制备石蜡/SiO2储能相变材料。并利用透射电子显微镜,热重分析,傅里叶红外光谱仪和方差扫描量热法等测试技术对石蜡/SiO2储能相变材料的结构和性能进行了测试和分析,最后利用瞬态热线法对石蜡/SiO2储能相变材料的导热系数进行了测试。结果表明,石蜡/SiO2储能相变材料的相变芯材石蜡在吸热熔化后不会渗漏;石蜡/SiO2储能相变材料中石蜡的含量约为39%时,相变温度和相变潜热分别为39.15℃和59.33J/g;石蜡/SiO2储能相变材料的导热系数为0.0845 W/(m·K),可作为一种良好的保温隔热建筑材料。     

二元脂肪酸/SiO2复合相变储能材料的制备与表征

针对适用于建筑领域的相变储能材料,选用癸酸(CA)分别与月桂酸(LA)、肉豆蔻酸(MA)和棕榈酸(PA)复合制备了二元低共熔脂肪酸作为储能材料。通过施罗德公式计算得到二元低共熔脂肪酸的混合比例和理论相变温度。基于CA-MA优异的性能,采用溶胶-凝胶法制备CA-MA/SiO2定形相变储能材料。采用FT-IR、SEM、DSC、TG对CA-MA/SiO2的结构、形貌、热性能和热稳定性进行了分析。结果表明,制备的3种二元低共熔脂肪酸适合于建筑领域。CA-MA较好地被固定在SiO2多孔网络中,储能材料和SiO2之间仅为物理结合,没有新物质的生成。定形相变储能材料的相变温度为20.96℃,相变焓为70.17J/g,相变温度适中,相变焓高,热稳定性好。     

Synthesis of stearic acid/Si02 hybrid phase change materials by ultrasound assisted

在超声波的促进作用下,以正硅酸乙酯为溶胶前驱体、硬脂酸为相变组分,经溶胶一凝胶过程制备了硬脂酸／SiO2复合定形相变储能材料。为了研究硬脂酸／SiO2复合定形相变储能材料的制备工艺,考察了不同超声功率对材料制备过程中加强两相传质作用的辅助效果的影响以及不同种类催化剂对材料制备过程中溶胶一凝胶过程的影响,最后确定出具有良好定形效果下材料的最大硬脂酸质量分数为60％。超声辅助酸碱复合催化法制备硬脂酸／SiO2材料具有无需添加助溶剂和表面活性剂、凝胶速度快、方法简便的优点。对硬脂酸／SiO2复合定形相变储能材料进行了FTIR结构表征和DSC、TG热性能及热稳定性测试,产品的相变焓值达91．46J／g,在低于175℃具有良好的热稳定性。     

高定形聚乙二醇/剑麻纤维素/彭胀石墨相变储能材料的研制及热性能

以聚乙二醇(PEG)作为相变组分,以高导热的膨胀石墨(EG)和富合羟基的剑麻纤维素(CSF)作为相变支撑组分,分别利用自制的超声辅助真空设备进行动态灌注或机械搅拌进行熔融共混制备了不同PEG用量的定形相变储能材料(PCMs).采用扫描电子显微镜、高分辨率光学相机、差示扫描量热仪、Hot disk-导热仪、热重分析仪等技术测试了PEG基复合PCMs的微观形貌、定形性、储热性能、导热率及稳定性.结果表明,新颖的动态灌注法制备的PEG基复合相变材料呈现出更致密的微观形态,更好的储热性能和更高的导热率及热稳定性.同时,实验发现由于CSF大量的极性羟基和多孔隙结构,当CSF质量分数为30％,EG质量分数为1％时,复合材料表现出极好的定形效果.     

高定形聚乙二醇/剑麻纤维素/膨胀石墨相变储能材料的研制及热性能

以聚乙二醇(PEG)作为相变组分,以高导热的膨胀石墨(EG)和富含羟基的剑麻纤维素(CSF)作为相变支撑组分,分别利用自制的超声辅助真空设备进行动态灌注或机械搅拌进行熔融共混制备了不同PEG用量的定形相变储能材料(PCMs)。采用扫描电子显微镜、高分辨率光学相机、差示扫描量热仪、Hot disk-导热仪、热重分析仪等技术测试了PEG基复合PCMs的微观形貌、定形性、储热性能、导热率及稳定性。结果表明,新颖的动态灌注法制备的PEG基复合相变材料呈现出更致密的微观形态,更好的储热性能和更高的导热率及热稳定性。同时,实验发现由于CSF大量的极性羟基和多孔隙结构,当CSF质量分数为30%,EG质量分数为1%时,复合材料表现出极好的定形效果。     

纳米SiO2-Al2O3/聚酰亚胺杂化薄膜的制备及表征

用溶胶-凝胶法制得二氧化硅(SiO2)及三氧化二铝(Al2O3)溶胶,将其掺入到聚酰胺酸基体中,得到SiO2-Al2O3/聚酰亚胺杂化薄膜,并对其结构性能进行了研究.结果表明,薄膜材料中SiO2和Al2O3粒子分散均匀,与有机相存在键合;材料热分解温度有所提高.     

超声辅助溶胶凝胶法制备硬脂酸/SiO2定形相变储能材料

在超声波的促进作用下, 以正硅酸乙酯为溶胶前驱体、 硬脂酸为相变组分, 经溶胶-凝胶过程制备了硬脂酸/SiO₂复合定形相变储能材料。为了研究硬脂酸/SiO₂复合定形相变储能材料的制备工艺, 考察了不同超声功率对材料制备过程中加强两相传质作用的辅助效果的影响以及不同种类催化剂对材料制备过程中溶胶-凝胶过程的影响, 最后确定出具有良好定形效果下材料的最大硬脂酸质量分数为60%。超声辅助酸碱复合催化法制备硬脂酸/SiO₂材料具有无需添加助溶剂和表面活性剂、 凝胶速度快、 方法简便的优点。对硬脂酸/SiO₂复合定形相变储能材料进行了FTIR结构表征和DSC、 TG热性能及热稳定性测试, 产品的相变焓值达91.46 J/g, 在低于175℃具有良好的热稳定性。      

SiO_2基复合相变材料的制备及性能研究

利用正硅酸四乙酯(TEOS)溶胶-凝胶反应制备了SiO2基复合相变材料,采用了DSC、SEM、FTIR分别对复合材料热性能、形貌和结构进行了表征。结果表明:芯材癸酸比PEG1000和棕榈酸更适合用于建筑和纺织领域。转速为800r/min时,癸酸/SiO2复合材料相变焓为105.3J/g。FT-IR和SEM表征了相变材料与SiO2之间的结合方式和形貌特征。     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.