钾明矾基低共熔相变储热材料的制备与研究

以钾明矾(KAl(SO4)2·12H2O)为基元,分别加入不同质量比例的七水硫酸镁(MgSO4·7H2O)和芒硝(NaSO4·10H2O)混合均匀后加热融化,研究制备出的低共熔材料的相变温度、潜热释放平台及过冷和相分离变化情况.结果表明,七水硫酸镁和钾明矾在任意比例下的混合都能制得低共熔相变储热材料,共晶点在质量比5∶5附近,相变温度41.19℃,持续放热时间长,过冷度1.15℃,无相分离现象出现;而以芒硝与钾明矾混合制备低共熔相变储热材料,共晶点在质量比2∶8附近,相变温度50.10℃,过冷度1.2℃且无相分离现象出现.这两种处于共晶点成分(附近)的低共熔相变储热材料都是很有潜力的低温相变储热材料.     

物理法制备芒硝基复合相变材料及其性能研究

以芒硝(Na2SO4· 10H2O)为主相变材料,采用物理共混法,筛选出合适添加辅助材料组成多元混盐体系,制备出相变温度在25℃左右的Na2SO4· 10H2O基复合相变材料,研究了原料配比对相变材料相变温度和相变潜热的影响.通过热重分析、T-history曲线、差示扫描量热法等表征了制备的芒硝基相变储能材料性质.结果表明:二元相变材料相变温度随着Na2CO3·10H2O增加而先降低后增大;相变材料相变潜热密度基本不变.三元相变材料相变温度随着NaCl、KCl、NH4Cl量增加相变温度降低;相变材料相变潜热密度相比于二元体系有所减小,且在一定范围内随着成核剂硼砂含量的增加该体系相变潜热密度基本保持不变,过冷度有明显下降.当Na2SO4· 10H2O量为86.4;、Na2CO3 · 10H2O量为9.6;、NaCl量为4;,对该配方改性添加3;的硼砂和0.1;的羧甲基纤维素钠时,此相变材料的相变温度为24.6℃,过冷度为0.3℃,相变潜热密度为179.6 J/g.     

纳米粉体对Na2SO4·10H2O过冷及相分层现象的影响

采用物理和化学分散相结合的方法分别制备了Cu-Na2SO4·10H2O,Al-Na2SO4·10H2O及C-Na2SO4·10H2O纳米复合相变储能材料,探讨纳米Cu粉,纳米Al粉及纳米C粉对Na2 SO4·10H2O过冷及相分层的影响,并对CNa2 SO4·10H2O复合相变储能材料的导热系数,热扩散系数,比热,相变潜热及形貌进行分析.结果表明:纳米材料的添加使得Na2 SO4·10H2O的过冷显著降低,分别为1.8℃,2.1℃,1.2℃;纳米Cu粉及纳米Al粉复合相变储能材料相变循环后失效,而纳米C粉复合相变储能材料无明显相分层现象;随着纳米C含量的增加,复合相变储能材料导热系数增高,热扩散系数增高,比热降低,复合相变储能材料在融化和结晶状态下,导热系数都随着温度升高而增大;相变循环50次后的4; C-Na2SO4·10H2O复合材料相变潜热值为188.3 J/g.     

二维石墨烯片增强芒硝基复合相变材料导热性研究

探究了二维石墨烯片(GNPs)对复合相变材料导热性的影响,以芒硝基复合相变材料(SCNa)为原料,制备出石墨烯片增强芒硝基复合相变材料(SCNaG).探讨了GNPs添加量对SCNa相变材料导热率的影响,并对其过冷机理进行了讨论.结果表明:复合相变材料导热系数随着GNPs添加量呈线性增加,当GNPs=0wt;时,相变材料导热系数为0.854 W/(m·K);当GNPs=3wt;时,相变材料导热系数为1.405 W/(m·K);随着GNPs添加量的增大相变材料过冷度先减小后增大,当GNPs=0.5wt;时,过冷度低于纯SCNa相变材料,为2.5℃C,当GNPs=3wt;时,过冷度增大至10.9℃.GNPs的添加量对相变材料相变温度影响不大,相变潜热略有减小.     

不同载体的Na2SO4·10H2O基定形相变材料的制备和热性能研究

基于节能减排的重要性,针对Na2 SO4·10H2 O基相变材料相变过程中液相泄露和长期使用的热稳定性问题,采用直接浸渍的方法将其封装入不同载体(SiO2气凝胶、X型分子筛、膨胀珍珠岩、活性炭和硅藻土)中,成功制备了不同载体的定形相变材料.通过SEM、XRD、DSC等表征方法,测定了饱和吸附时各自的相变材料占比分别为80.0;、82.2;、76.9;、89.2;及60.6;;并且从热性能、机械性能、成本等方面综合对比了不同载体的性能,发现膨胀珍珠岩(EP)是性价比最优的载体材料.进一步对Na2 SO4·10H2 O/EP复合相变材料进行了熔冻循环实验测试,经过100次循环实验,热值损耗保持在15;以内,过冷度稳定在10℃以内,热稳定性良好.     

水热法合成Zn1-xCoxO室温稀磁半导体

本文采用水热法,在430℃,填充度为35;,3mol/L KOH作为矿化剂,反应时间为24h,合成了Zn1-xCoxO晶体.当在Zn(OH)2中添加一定量的CoCl2·6H2O为前驱物时,水热反应产物中,可以获得多晶体形态的掺杂Zn1-xCoxO晶体.电子探针测量表明,随着前驱物中CoCl2·6H2O添加量的增加,晶体中的Co实际掺入量也随着增加.采用超导量子干涉磁强仪测量材料的磁性,发现在室温以下,水热法合成的Zn1-xCoxO晶体的磁化强度随温度变化很小,在300K存在明显的磁饱和现象和磁滞回线,表明具有室温下铁磁性.     

束状三水碳酸镁晶体合成及动力学研究

以NH4HCO3与MgCl2·6H2O为反应物料,采用低温液相法合成了束状三水碳酸镁晶体,采用XRD,SEM、FTIR对合成的试样进行了测试表征,确定了制备束状三水碳酸镁晶体的最佳制备条件:MgCl2·6H2O与NH4HCO3的反应初始浓度均为0.15 mol/L,反应温度40℃、反应时间60 min,反应初始溶液pH =9.3.在此基础上,初步建立了束状三水碳酸镁晶体的动力学模型.     

金属离子掺杂ZnO晶体的制备及其光催化性能的研究

本文采用水热合成法,以3 mol/L KOH为矿化剂,填充度为35;,分别在ZnO中添加SnCl4·5H2O、CoCl2·6H2O、NiCl2 ·6H2O作为前驱物,温度430℃,反应24h,合成几种金属离子掺杂的ZnO晶体.采用扫描电镜(SEM)和X射线衍射(XRD)对其形貌进行了表征.并与用同种方法合成的纯ZnO的光催化效率进行了对比.结果表明:金属离子掺杂的ZnO晶体和用同种方法合成的纯ZnO晶体对亚甲基蓝均具有光催化活性,其中Sn掺杂的ZnO晶体的光催化性能较好,并且经过10次循环实验后仍保持较高的催化效率.     

一步水热法制备无水硫酸钙晶须

以生石膏为原料,六水氯化镁为形貌控制剂,采用水热法一步合成了无水硫酸钙晶须.借助SEM、TEM、XRD和XPS等测试手段考察了水热条件对无水硫酸钙晶须的影响,研究了无水硫酸钙晶须的生长过程.结果表明:镁/钙摩尔比n(MgCl2·6H2O)/n(CaSO4· 2H2O)=2.5,反应温度180℃,反应时间2h,可生长出长度为20 ～ 40 μm,直径0.5～2 μm的无水硫酸钙晶须.无水硫酸钙晶须生长过程为:片状CaSO4·2H2O-纤维状CaSO4·0.5H2O-纤维状CaSO4.     

两级反应器制备Zn2+原位掺杂型LDHs纳米晶

采用两级反应器,将盐溶液MgCl2·6H2O、AlCl3·6H2O、ZnCl2·6H2O和沉降剂Na2CO3、NaOH进行反应成功制备出Zn2+原位掺杂型LDHs纳米晶.采用XRD、TEM、TG分析了Zn2+掺杂对MgAl-CO3 LDHs晶体结构、形貌与热稳定性的影响.结果表明:当[Mg2+ +Zn2+]/[Al3+] =2,[Mg2+]/[Zn2+] =4时,对MgAl-CO3 LDHs晶体结构影响最小,此时晶体形貌也相对较规则;原位掺杂后,95℃晶化2h为最佳晶化时间;Zn2+掺杂LDHs纳米晶在0 ～450℃范围内热稳定性降低,在450 ～550℃范围内热稳定性提高,且残渣量由46.57;提高到58.58;.     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

Photoluminescence characteristics of Mg- and Si-doped GaN thin films grown by MOCVD technique

We have studied the optical, structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respectively. The different carrier concentrations were obtained in the GaN thin films by varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films at low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor–acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN thin films. The dominance of the blue and the yellow emissions increased in the PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of the films, respectively. Both the doped and the undoped films exhibited hexagonal structure and polycrystalline nature. Mg-doped GaN thin films showed columnar structure whereas Si-doped films exhibited spherical shape grains.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solubility of Ag2O into the Na2O–B2O3–Al2O3 system

The solubility of Ag₂O was measured for the Na₂O–B₂O₃ and Na₂O–B₂O₃–Al₂O₃ system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag₂O for the Na₂O–B₂O₃ system above the melting point of Ag for the first time. It was found that the addition of Na₂O decreases the solubility of Ag₂O while the addition of Al₂O₃ had little effect on the solubility. The effect of Na₂O and Al₂O₃ on the solubility of Ag₂O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag₂O in Na₂O–B₂O₃–Al₂O₃ melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver.     

Selinidin: Crystal structure generated by C–H···O, C–H···π and π-π interactions

The title compound, 9,10-dihydro-8,8-dimethyl-2-oxo-2H,8H-benzo[1,2-b:3,4-b']dipyran-9-yl-2-methyl-2-butenoate, C₁₉H₂₀O₅, was isolated from the roots of Selinum vaginatum. The compound crystallizes into monoclinic space group P2 ₁ with unit cell parameters: a = 12.830(2) Å, b = 9.041(1) Å, c = 14.983(1) Å, β = 95.09(1)°, Z = 4. The crystal structure has been determined using direct methods and refined by full-matrix least-squares to a final R value of 0.0529 for 3142 observed reflections. There are two independent molecules, A and B, per asymmetric unit. In both the molecules, the coumarin nucleus is planar. However pronounced differences are observed in the conformation of dihydropyran ring which has a half-chair conformation with an 8β-9α orientation in molecule A and is intermediate between half-chair and sofa in molecule B. Differences also occur in the conformation of the 2-methylbutenoyloxy side chain at C9 due to the different geometry of C–H···π interactions in molecules A and B. Molecules A and B are connected by π–π interactions between their coumarin fragments forming dimers. The dimers interact through C–H···O and C–H···πhydrogen bonds.     

Chromene and Imidazole Based D-π-A Chemosensor Preparation and Its Anion Responsive Effects

We have designed and synthesized the colorimetric chemosensor through the reactions of 2-(4H-chromen-4-yildene)malonitrile and 4-imidazolecarboxaldehyde. Due to its well conjugated D-π-A system and the existence of NH- fragment in structure, we expected that the chemosensor can detect anion using NH- fragment in the imidazole moiety of the structure. In this regard, UV-Vis absorption spectra were measured to investigate sensing properties of the probe toward different anions in DMSO. This chemosensor can detect both fluoride and cyanide ion with absorption change in intensity. In addition, pH sensing property was also investigated upon the addition of hydroxide ion. These properties are related to the deprotonation effect. The ICT system in this molecule was also observed by the computational approach using Material Studio 4.3 package.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

Considerations on the structure and physical properties of B2O3-SiO2 and GeO2-SiO2 glasses

Data of density, refractive index and thermal expansion coefficient for B₂O₃-SiO₂ and GeO_2-SiO₂ glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B₂O₃, GeO₂ and SiO₂. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO₃, GeO₄ and SiO₄ units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B₂O₃ or GeO₂ in the concerned glasses.