磁场对超细镍粉的磁性能及电磁屏蔽性能的影响

分别在水和乙二醇溶液中,于搅拌条件下采用液相还原法制备超细镍粉,研究反应过程中外加磁场对产物形貌及性能的影响。结果表明,水中得到的产品为刺球状颗粒,外加磁场对产物的形貌影响不大;乙二醇中得到类球形颗粒,加磁场后得到短链状结构。外加磁场使超细镍粉的饱和磁化强度值降低而矫顽力值升高。将水体系中得到的超细镍粉作为导电填料制备电磁屏蔽涂料,结果发现外加磁场条件下得到的超细镍粉/树脂复合涂料在130 MHz～1.5 GHz频段内具有更好的电磁屏蔽性能。     

细粒径石蜡微胶囊相变材料的制备与性能

采用阳离子和非离子复配乳化剂,通过原位聚合制备以丙烯酸酯为壁材,石蜡为芯材的细粒径微胶囊相变材料.采用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、差示扫描量热(DSC)、热重(TG)及激光粒度仪分析表征了微胶囊相变材料的化学结构、表面形貌和热性能.结果表明,乳化剂的种类和壁材单体的配比对微胶囊性能有重要的影响.当采用阳离子和非离子复配乳化剂,壁材中单体甲基丙烯酸甲酯(MMA)与丙烯酸(AA)的质量比为9∶1时,微胶囊相变材料呈球形且表面光滑紧凑,尺寸仅为0.2~0.35μm,具有良好的储热能力,相变潜热高达169 J/g;微胶囊中壁材对石蜡芯材的分解具有明显热阻滞作用,分解温度比纯石蜡提高了150℃.     

High‐Performance Magnetic Refrigerant Featuring One‐Dimensional Gd‐O Chains and O‐Gd3 Triangles

Magnetic cooling at low temperature has attracted intensive interest in cryogenics research, which may become important as cooling medium for long‐wave photon detectors to support space exploration. Here, we report a Gd‐based quaternary magnetic refrigerant material, Gd₅BSi₂O₁₃, containing chains of face‐shared GdO₉ polyhedra and geometrically frustrated OGd₃ triangles. Magnetic measurements indicate that Gd₅BSi₂O₁₃ exhibits a large magnetocaloric effect (MCE) about 1.74 times that of the practical magnetic refrigerant GGG (−ΔS_m=67.0 J kg⁻¹ K⁻¹). We analyzed the origin of the large MCE by comparing Gd^III‐containing compounds with different structures and concentrations of Gd^III.     

十八烷/聚(St-MMA)相变微胶囊制备及表征

采用乳液聚合的方法,分别选取聚苯乙烯(PS)、聚甲基丙烯酸甲酯(PMMA)或苯乙烯和甲基丙烯酸甲酯的共聚物为壁材,正十八烷为芯材,十二烷基苯磺酸钠(SDBS)为乳化剂,制作相变储能微胶囊。用粒径分析仪、透射电子显微镜(TEM)、热重分析仪(TG)和示差扫描量热测试仪(DSC)对微胶囊的形貌、相变热性能和热稳定性分别进行表征。结果表明:壁材选取两者共聚物,当两种单体的比例为St∶MMA=1∶5,SDBS用量为1.5g(总质量的3%)时,微胶囊粒径大小均匀,粒子分散性好,壁材的包裹性好。微胶囊的放热峰为起始温度为27.3℃,终止温度为31.9℃,相变温度为28.9℃,相变焓为48.4J/g。TG表明长期使用温度不能超过131℃。IR分析微胶囊中含有芯材和壁材。这种十八烷/聚(St-MMA)相变微胶囊可以用于诸能材料。     

哑铃型磁金介孔硅复合微球的制备及磁/光热催化性能测定

以金纳米粒为种子采取外延氧化生长氧化铁的方式,制备了哑铃型磁金纳米复合材料(Au-Fe_3O_4);以十六烷基三甲基溴化铵(CTAB)和F127为双模板剂通过溶胶凝胶法进一步包覆了介孔二氧化硅层(Au-Fe_3O_4@mSiO_2)。所制备Au-Fe_3O_4纳米粒子呈哑铃型,单分散性较好,尺寸分布均一,粒径为12～15 nm。Au-Fe_3O_4@mSiO_2复合物磁热性能与浓度和外加磁场强度成正比;浓度为25 mg·mL~(-1)时,磁场电流从25.5 A增大到42.5 A,溶液升温速率从0.39℃·min~(-1)增大到0.76℃·min~(-1)。Au-Fe_3O_4@mSiO_2复合物光热性能与浓度和激光照射功率密度成正比;复合物浓度为25 mg·mL~(-1)时,功率密度从0.3 W·cm~(-2)增大到1.2 W·cm~(-2),溶液升温速率从0.69℃·min~(-1)增大到2℃·min~(-1)。相同浓度的复合物溶液,光热性能明显优于磁热性能。浓度为25 mg·mL~(-1)的AuFe_3O_4@mSiO_2复合物催化S-亚硝基谷胱甘肽(GSNO)释放NO的反应在60 min时达到持续稳定释放,释放量最大为9.743μmol·L~(-1)。     

石墨烯/正十八烷微胶囊的制备与及其热性能研究

以石墨烯/正十八烷为芯材,三聚氰胺-尿素-甲醛树脂(MUF)为壁材,苯乙烯马来酸酐共聚物(SMA)为乳化剂,采用乳液聚合法制备相变微胶囊.系统研究了石墨烯对于正十八烷微胶囊性能的影响.采用场发射扫描电子显微镜(FE-SEM)、傅里叶变换红外光谱分析仪(FTIR)、拉曼光谱仪、X射线衍射仪(XRD)、Hot Disk热常数分析仪、示差扫描量热仪(DSC)和热重分析仪(TGA)对相变微胶囊的外貌形态、晶型结构和热性能进行表征和分析.结果表明,微胶囊呈圆球形且光滑,粒径约为1~30μm.当石墨烯添加量为0.1 g时,微胶囊的形貌无明显变化.当加入过量石墨烯时,微胶囊出现了明显的团聚现象.XRD测试表明,包覆于微胶囊中的石墨烯没有使微胶囊的结晶峰位置发生明显的偏移,这对于微胶囊的实际应用是有利的.微胶囊的相变热焓和包覆率随着石墨烯的加入而不断减小,但芯材的过冷现象得到了明显的改善.石墨烯对于微胶囊传热性能的提升有着显著的效果.当石墨烯的添加量为0.2 g时,微胶囊的导热系数为0.092 W·m-1·K-1,与纯微胶囊相比提高了约51%,这说明石墨烯改善了传统相变微胶囊的传热性能,提升了相变微胶囊的应用性能.     

盐酸掺杂聚苯胺的制备及性能研究

本文用溶液聚合法制备盐酸掺杂聚苯胺,测定了体系酸度对聚苯胺电导率的影响,及盐酸掺杂聚苯胺在不同条件下经过热处理后的电导率,采用TGA、XRD等方法,研究了热处理过程对聚苯胺结构的影响。结果表明,当热处理温度为90℃时,电导率高于初始值,当热处理温度高于100℃时,电导率开始下降,到达220℃时,电导率下降了约4个数量级。在氮气中聚苯胺电导率的衰减比空气中小,聚苯胺经热处理后在浓硫酸中的溶解性会明显降低。本文还探讨了去掺杂、氧化和化学交联等盐酸掺杂聚苯胺的热降解机理。     

Preparation and Performance of Lignin-Based Multifunctional Superhydrophobic Coating

Superhydrophobic coatings have drawn much attention in recent years for their widespread potential applications. However, there are challenges to find a simple and cost-effective approach to prepare superhydrophobic materials and coatings using natural polymer. Herein, we prepared a kraft lignin-based superhydrophobic powder via modifying kraft lignin through 1H, 1H, 2H, 2H-perfluorodecyl-triethoxysilane (PFDTES) substitution reaction, and constructed superhydrophobic coatings by direct spraying the suspended PFDTES-Lignin powder on different substrates, including glass, wood, metal and paper. The prepared lignin-based coatings have excellent repellency to water, with a water contact angle of 164.7°, as well as good friction resistance, acid resistance, alkali resistance, salt resistance properties and quite good self-cleaning performance. After 30 cycles of sand friction or being stayed in 2 mol/L HCl, 0.25 mol/L NaOH and 2 mol/L NaCl solution for 30 min, the coatings still retain super hydrophobic capability, with contact angles higher than 150°. The superhydrophobic performance of PFDTES-Lignin coatings is mainly attributed to the constructed high surface roughness and the low surface energy afforded by modified lignin. This lignin-based polymer coating is low-cost, scalable, and has huge potential application in different fields, providing a simple way for the value-added utilization of kraft lignin.     

Effects of MWNTs on phase change enthalpy and thermal conductivity of a solid-liquid organic PCM

The effects of multi-walled carbon nanotubes (MWNTs) on the phase change enthalpy (ΔH) and the thermal conductivity (κ) of a solid-liquid phase change materials (PCM), palmitic acid (PA), have been investigated. The results showed that both the ΔH and the κ of the composite were lower than that of PA when the loading of MWNTs was small. As the concentration of MWNTs in the composites increased, the ΔH of the composites was slightly improved and then decreased linearly. However, the κ of the composites was monotonously increased from the minimum value. When the loading of MWNTs increased to 5% and no surfactant was added, the κ of the composite was enhanced to be 26% higher than that of PA. The κ of the composite could be enhanced by CTAB instead of SDBS when the loading of MWNTs was small, as SDBS showed no obvious effect on the κ of the composites. Furthermore, the effects of surface modification of MWNTs on the ΔH and the κ of the composites have also been investigated.     

层状前体镍铁水滑石及磁性材料的制备及表征

提出了利用镍铁水滑石作为磁性前体再经高温焙制备尖晶石型铁氧体思路，深 入研究了水滑石的制备工艺及结构性能并初步探讨了其焙烧后的磁学性能。由共沉 淀法合成了Ni/Fe摩尔比为2，3，4，6的镍铁水滑石，XRD结果表明镍铁比为3时晶 形较为理想，且随着晶化温度的升高及晶化时间的延长，水滑石的晶体结构规整性 增强。热重-差热结果显示镍铁水滑石的分解有两个过程，当镍铁比为3时，水滑石 的热稳定性相对最高。高温焙烧后的镍铁水滑石具有磁性。     

Magnetic phase transitions and specific heat of single crystalline cupric oxide

The antiferromagnetic phase transitions in a CuO single crystal are studied by specific heat in magnetic fields up to 6T. The magnetic field dependence of the incommensurate-to-commensurate-antiferromagnetic transition atT _L is found to be highly anisotropic.T _L is observed to increase nonlinearly for B_a c-axis, whereas, a linear reduction is observed forB _a b-axis. The magnetic field dependence ofT _L and the jumps in magnetic susceptibility atT _L are explained thermodynamically using the Clausius-Clapeyron equation.We thank Dr. T. Chattopadhyay for providing the CuO crystal. We thank K. Ripka and the Röntgen service of the institute for technical assistance.     

L-精氨酸铜配合物的磁性、铁电与热重研究

为了合成和研究具有磁性和铁电双重性能的配合物,本文选用L-精氨酸(L-Arg)配体与硝酸铜制备了一个配合物,其组成为[Cu(L-Arg)2]2+(NO3-)2·3H2O(1),单晶X射线衍射分析表明,该配合物的晶体结构属于单斜晶系手性空间群C2。磁性和铁电性能测试表明该配合物具有弱的铁磁行为和铁电双重性能。热分析显示该配合物在77-150℃失去自由水,从243℃开始分解。     

磁性微胶囊的制备及其药物缓控释性能

用乳液-凝胶法制备了磁性壳聚糖/海藻酸钠微胶囊. 在壳聚糖/海藻酸钠微胶囊中掺入Fe3O4磁性中空球, 使微胶囊具有磁靶向性能. 以头孢拉定作为模型药物研究了载药磁性微胶囊的载药量、包封率及药物缓控释性能等. 结果表明, 提高头孢拉定的初始浓度可以提高载药量, 却不利于提高药物的包封率. 所制备的微胶囊在各种缓冲溶液中长时间内具有显著的缓释效果, 并具有pH 刺激响应释放的性能, 即在模拟胃液中的药物释放率大大降低, 而在模拟体液和肠液中的释放时间大大延长, 可达50 h以上. 另外, 在外加磁场作用下, 微胶囊表现出良好的磁定向运动性能, 为磁靶向药物输送提供基础.     

Relationship between properties of fluorinated graphite intercalates and matrix composition Part III. Intercalates with 1,2-dichloroethane

A series of PA-TD mixtures were prepared and their thermal properties were studied by DSC and thermal conductivity measurement. The phase diagram of the binary system was constructed, which showed an eutectic behavior for the solid-liquid equilibrium line. The eutectic composition of the binary system was at the mass fraction of TD near 0.7 with an eutectic temperature of about 29°C. At TD side, PA was partially miscible in the TD solid matrix and the solid phase transition of TD had an effect on the solidus line. The eutectic composition mixture could be viewed as a new phase change material with large thermal energy storage capacity.     

石蜡/膨胀石墨/石墨烯复合相变储热材料的制备及性能

以石蜡(PA)作为相变储热材料、 膨胀石墨(EG)作为主导热材料和支撑材料, 石墨烯气凝胶(GA)作为导热增强材料和辅支撑材料制备了PA/EG/GA复合相变材料, 研究了GA添加量对复合相变材料相变温度、 相变潜热、 导热性能以及循环稳定性的影响. 结果表明, 所制备的80%PA-17%EG-3%GA复合相变材料导热性能良好, 循环稳定性出色. 与80%PA-20%EG复合材料相比, 该材料的相变温度、 相变潜热以及循环稳定性无明显变化, 但导热系数由4.089 W/(m·K)提升到了5.336 W/(m·K), 显示出良好的应用前景.     

磁性流体的制备、应用及其稳定性的解析

本文概括地介绍了磁性流体的特性和制备方法, 重点论述了磁性流体的应用,对磁性流体的稳定性进行了解析。     

Recent Advances in Preparation and Applications of Magnetic Framework Composites

Metal‐organic frameworks (MOFs) offer ample characteristics, such as easy synthesis, high surface area, tunable porosities, open metal sites, post‐synthesis modification, making them attractive for diverse applications. Since magnetic particles can be positioned and separated by a magnetic field, magnetic framework composites (MFCs) have attracted tremendous attention. In this review, different methods of preparing MFCs, including direct mixing, in‐situ growth of magnetic particles, embedding method, layer‐by‐layer growth method and encapsulation method, will be discussed in detail. Moreover, their applications in catalysis, adsorption, biomedicine and sensing will also be introduced.     

1，4－二羟基蒽醌与稀土离子的配位聚合物制备和性质

制备了三价稀土离子Ｌｎ￣（３＋）（Ｌｎ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｂ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ和Ｙ）与１，４－二羟基蒽醌的配位聚合物。考察了这些配合物的热稳定性、磁性、导电性和红外光谱。     

镝钴铁氧磁流体的制备与性质研究(英文)

为了提高磁流体的抗氧化能力,制备了镝钴铁氧磁流体.利用古埃磁天平研究了温度对磁性和稳定性的影响;研究了稀土镝磁性能的改性、表面活性剂的表面改性,并从理论上进行了分析.利用X射线衍射仪(XRD)、透射电镜(TEM)对制得的磁粒子的组成、结构及粒径进行了分析.     

Magnetic nano- and microparticles in biotechnology

Both synthetic and biologically produced magnetic nano- and microparticles exhibit several types of responses to external magnetic field which have been already employed in various areas of biosciences, biotechnology, medicine, environmental technology, etc. This short review shows selected important biotechnological applications of magnetic particles, and the biological processes leading to biogenic magnetic particles formation. Presented at the 1st Nanomaterials and Nanotechnology Meeting, Nano Ostrava, Ostrava, Czech Republic, 1–4 September 2008.