PEG4000/(NH_4)2SO_4双水相制备超顺磁性Fe_3O_4纳米粒子及性能表征

以PEG4000和(NH_4)2SO_4为双水相体系、二异丙胺为沉淀剂,对共沉淀法进行改进,合成了四氧化三铁(Fe_3O_4)纳米粒子。采用XRD、TEM、VSM、FT-IR等对Fe_3O_4进行性能表征,证明所合成的Fe_3O_4粒子为具有反尖晶石结构、稳定性和分散性良好、尺寸均一、粒径大小为11 nm左右的球形纳米粒子,具备优异的超顺磁性和高磁化强度等特性。同时对反应温度及铁离子浓度比、PEG4000/(NH_4)2SO_4的质量浓度对双水相体系的形成进行条件探索,确定了最优工艺方案为n(Fe2+)∶n(Fe3+)=2∶3、1.0 g Fe Cl2·4H2O、1.2 g Fe Cl3、10 m L二异丙胺,PEG4000/(NH_4)2SO_4双水相体系中PEG4000的质量分数为18%、(NH_4)2SO_4的质量分数为25%,反应温度为60℃,反应时间为1 h。     

高分子改性纳米氧化镁的制备和表征

采用溶胶-凝胶法,以MgCl2·6H2O和NH4OH为原料,以聚乙二醇(PEG)为改性剂进行了纳米MgO的改性研究,并用X-射线衍射仪(XRD)和透射电子显微镜(TEM)及比表面分析仪(ASAP2020)对产物进行了表征。结果表明,PEG不但控制了纳米MgO粒子的形状和大小,还使粒子的结晶度、分散性提高,并且基本上无团聚现象。     

低温直接沉淀法制备钛酸锶纳米粉体的研究

采用低温直接沉淀法,以SrCl_2·6H_2O和TiCl_4为原料,NaOH为沉淀剂合成SrTiO_3粉体。研究了反应时间、反应温度、起始料液浓度,以及分散剂的加入对产物形貌、粒度、分散性的影响。通过对产物进行FTIR、SEM、XRD和粒度表征分析,得出最佳制备条件:当pH=13,温度75℃,时间4h,起始料液浓度(SrCl21.2mol/L、TiCl41.2mol/L),反应体系加入分散剂PEG4000(0.5%),可以制备出低团聚、平均粒度(50~70nm)的纳米级钛酸锶粉体。     

氧化铈纳米带的制备及表征

本文以Ce(NO3)3.6H2O、CO(NH2)2和PEG4000为原料,利用微波水热法制备出了带状纳米氧化铈颗粒。并利用X射线衍射(XRD)、扫描电镜(SEM)对其进行了表征。结果表明:PEG用量为10g/L时,得到了氧化铈纳米带,随着PEG4000浓度的增加,带状结构逐渐消失,当PEG4000为300g/L时,所制备的为规整的球状CeO2。     

纳米SiO2改性聚乙烯醇超滤膜的研究

以聚乙烯醇(PVA)为基膜材料,聚乙二醇(PEG)为添加剂,通过相转化法制备了纳米SiO2/聚乙烯醇膜。考察了PEG的分子量、纳米SiO2的加入量和PEG加入量对PVA膜性能的影响。结果表明,经纳米SiO2改性的PVA膜的性能有了显著的提高,膜的水通量随着PEG分子量和PEG加入量的增大而增大,随着纳米SiO2加入量的增大而减小。     

低温直接沉淀法制备钛酸锶纳米粉体的研究

采用低温直接沉淀法,以SrCl_2·6H_2O和TiCl_4为原料,NaOH为沉淀剂合成SrTiO_3粉体。研究了反应时间、反应温度、起始料液浓度,以及分散剂的加入对产物形貌、粒度、分散性的影响。通过对产物进行FTIR、SEM、XRD和粒度表征分析,得出最佳制备条件:当pH=13,温度75℃,时间4h,起始料液浓度(SrCl21.2mol/L、TiCl41.2mol/L),反应体系加入分散剂PEG4000(0.5%),可以制备出低团聚、平均粒度(50⁷0nm)的纳米级钛酸锶粉体。     

PEG/CNFs相变储能材料非等温结晶动力学研究

通过溶液浇铸法制备了聚乙二醇/纤维素纳米微纤(PEG/CNFs)复合相变储能材料,采用差示扫描量热仪(DSC)研究了CNFs含量对该PEG/CNFs复合材料中PEG结晶行为的影响,并利用Jeziorny、Ozawa和Mo模型对DSC结果进行了非等温结晶动力学分析。结果表明:加入CNFs后,复合材料中PEG的半结晶时间(t1/2)与Avrami指数(n)下降,表明CNFs充当了PEG的成核剂;另外,CNFs含量的增加抑制了PEG晶体的生长,PEG的结晶焓(ΔHPEG)显著下降。     

沉淀法制备纳米ZnO及光催化甲基橙脱色研究

以Zn(NO3)2·6H2O为锌源,(NH4)2CO3和NH3·H2O混合碱为沉淀剂,通过并流沉淀法制备出纳米ZnO粉体,采用XRD和SEM对其进行了表征。以甲基橙为脱色对象,紫外灯(最大吸收波长254nm)为光源,研究了催化剂用量、甲基橙初始浓度、pH值及外加氧化剂(H2O2)对光催化性能的影响。     

影响纳米CeO_2晶粒形貌的因素及机理

以Ce(NO3)3.6H2O为铈源,NH3.H2O为沉淀剂,用普通沉淀法在不同反应条件下制备了粒径、形貌各异的纳米CeO2。研究结果表明,Ce(NO3)3最佳浓度为0.2 mol/L。XRD和IR结果证实了产物的物相结构。TEM分析表明:控制pH可以得到形貌不同的纳米CeO2粒子。用乙醇作溶剂得到了粒径约为15 nm、分布均匀的纳米CeO2颗粒。正加料(沉淀剂滴入盐溶液中)可以得到各种形貌的纳米CeO2;而反加料(盐溶液滴入沉淀剂中)仅能得到针状纳米CeO2颗粒。     

纳米氢氧化镁阻燃剂的制备研究

以氯化镁和氨水为原料,加入适量聚乙二醇(PEG2000)作为表面活性剂,利用直接沉淀法合成了粉末状、粒度均匀且分散性好的纳米氢氧化镁。考察了体系温度、沉淀时间、搅拌速率、反应物配比、PEG2000用量对氢氧化镁颗粒平均粒径的影响,并采用透射电镜(TEM)、X射线衍射(XRD)对颗粒结构进行表征。结果表明,制备纳米氢氧化镁的适宜的工艺条件为:体系温度25℃,沉淀时间20 min,搅拌速率500 r/min,反应物氯化镁和氨水的配比(摩尔比)为1∶3.0,PEG2000用量为1.50 g/mol MgCl2。     

纳米聚丙烯酸酯改性纳米Mg(OH)_2及其在LDPE中的应用

采用纳米聚丙烯酸酯乳液改性纳米Mg(OH)2,通过单螺杆挤出机制备了纳米Mg(OH)2/低密度聚乙烯(LDPE)复合材料,利用红外光谱、扫描电镜、透射电镜等方法对改性前后的Mg(OH)2及Mg(OH)2/LDPE复合材料进行了表征。结果表明:纳米Mg(OH)2表面经纳米聚丙烯酸酯乳液改性后吸附上了一层聚丙烯酸酯;纳米聚丙烯酸酯乳液改性提高了纳米Mg(OH)2的热稳定性,分解温度提高了27℃;改性纳米Mg(OH)2在LDPE基体中分散更为均匀;改性纳米Mg(OH)2的用量为LDPE的15%时复,合材料的拉伸强度比纯LDPE提高了6.5%。     

Effect of Nano–Magnesium Hydroxide on Mechanical and Flame-Retarding Properties of SBR and PBR: A Comparative Study

Magnesium hydroxide [Mg(OH)₂] is one of the potential inorganic fillers. In this work, nanoparticles (37±5 nm) of the magnesium hydroxide were prepared using matrix-mediated growth and control technique, and their size was confirmed by X-ray diffraction technique. Nano-Mg(OH)₂-SBR and nano-Mg(OH)₂-PBR composites with 2–10% (w/w) filler loading were prepared by compounding on laboratory-scale two-roll mill and a compression molding machine. These composites were tested for tensile and physical properties, and the properties were compared with the composites of commercial Mg(OH)₂. The incorporation of nanofiller improved the properties of nanocomposites.     

Electrical,Mechanical, and Thermal Properties of Mg(OH)<Subscript>2</Subscript>/PI Nanocomposite Films

Nano-Mg(OH)₂ particles were prepared by reverse precipitation. Nano-Mg(OH)₂/PI composite films with varying contents of Mg(OH)₂ were successfully prepared by in situ polymerization and thermal imidization. The surface morphology, thermal stability, and the mechanical and dielectric properties of the films were characterized. Results indicated the following: the nanoparticles were homogeneously dispersed in the matrix, thermal stability was reduced, and the Young’s modulus of PI-3% was 2851.6 N/mm² and increased by 155% relative to that of neat PI. The real and imaginary parts of relative permittivity increased, and electric modulus formalism was introduced to determine the dielectric relaxation behavior of the composites in the study. The result from the Cole–Davidson semicircle showed that the increase in nano-Mg(OH)₂ concentration led to an increase in the inhomogeneous distribution of relaxation time. Direct current illustrates that the activation energy of the hopping process exhibits an increasing trend. The aging threshold increased in accordance with the theory of space-charge limited current. Breakdown increased to 323 kV/mm, whereas the pure film was is 292 kV/mm, and the electric property of polyimide improved.     

液相共沉淀法制备氧化铟锡超细粉体材料的研究进展

介绍了液相共沉淀法制备氧化锢超细锡粉体材料的工艺,分析了沉淀剂、反应物的浓度、煅烧的温度和时间、分散剂等四个因素对制备过程及产物的影响。按照三氧化铟和二氧化锡的质量比为9∶1选用铟盐和锡盐；用氨水、尿素或碳酸铵作沉淀剂,并且沉淀剂不同,反应时应控制的pH值和反应时间也不同；反应物In~(3+)的浓度0．2mol／L时可得到接近纳米级的超细氧化铟锡粉体材料；700～800℃煅烧3～5h,可使前驱物成为球状,其团聚现象也可以得到综合平衡；分散剂为硫酸铵、硅烷偶联剂KH570等,对其分散机理作了简要的分析。     

制备纳米／聚合物复合材料时工艺参数的研究

用正交试验法对纳米粉体在聚合物中分散时的工艺参数——主机螺杆转速、加料螺杆转速（加料量）、机筒及机头温度、机头压力对混合效果的影响进行了研究。研究结果表明：影响HDPE／EVA／Nano-Mg（OH）2混合物力学性能的工艺条件的主次顺序为主机螺杆转速、加料螺杆转速、机头压力、机筒及机头温度。     

均相成核—水热法制备纳米氧化锌

制备纳米氧化锌的关键是成核与生长控制。采用尿素为均相沉淀剂 ,结合水热处理 ,温度 130℃ ,反应时间为 3～ 5h制备了粒径小 ,分布窄的纳米氧化锌。Zn2 +的均相成核与其浓度、OH- 的浓度有关 ,体系中Zn(OH) 2 的过饱和度越大 ,则成核数量越多 ,所制备的氧化锌颗粒越小 ;与以氢氧化锌胶体为前驱体的共沉淀技术相比 ,均相沉淀技术有利于氧化锌纳米晶粒均匀生长 ;此外 ,添加有机物作分散剂可以减弱微小晶粒间的叠合生长 ,有利于制备均一性较好的纳米氧化锌。     

碳纤维表面化学涂覆NiO

采用均相沉淀法在碳纤维表面进行了NiO涂覆,研究了沉淀剂种类、脱水方式、沉淀剂浓度、沉淀剂添加速度和沉积反应时间对涂覆效果的影响. 采用SEM和XRD对涂层进行了表征,得到了制备NiO涂层较为合适的工艺条件为：以尿素为沉淀剂,采取缓慢升温的方式脱水,沉淀剂浓度0.20 mol/L,沉淀剂滴加速度2 mL/min,反应时间120 min. 在此条件下制备的NiO涂层厚度均匀,无脱落现象. 抗氧化性测试结果表明,涂覆NiO涂层后,碳纤维的抗氧化性有明显的提高.     

Comparative Study of the Mechanical and Thermal Properties of Polyamide-66 Filled with Commercial and Nano-Mg(OH)2 Particles

In the present work, polyamide-Mg(OH)₂ nanocomposites were prepared via melt intercalation on a twin-screw extruder. Different particle sizes (24, 20, 11 nm) of Mg(OH)₂ were synthesized by in-situ deposition technique and its shape and sizes was confirmed on transmission electron microscope (TEM). Nano-Mg(OH)₂ was added from 1 to 4 wt% in the polyamide. Properties such as tensile strength, elongation at break, hardness, and flame retardency were studied. These results were then compared with commercial Mg(OH)₂-filled composites. There was propounding effect to be observed on properties of polyamide nanocomposites due to uniform dispersion of nano-Mg(OH)₂ and commercial Mg(OH)₂. Moreover, thermal property like thermal degradation was studied on TGA. Extent of dispersion of nano-Mg(OH)₂ was studied along with microcracks generated during tensile testing using AFM. It was found that nano-Mg(OH)₂ is thermally more stable compared to that of commercial Mg(OH)₂. Besides that, T_g and M.T. are studied on DSC.     

Use of new methods of separation of chitosan sulfate to simplify its industrial production

The optimum conditions of separation of chitosan sulfate from the reaction medium by precipitation of CS in an organic precipitator with subsequent precipitation of impurity sulfate ions with a solution of Ba(OH)₂ were determined. This method of separation of CS makes it possible to obtain preparations whose structural characteristics and biological properties satisfy the requirements set for substances for drugs. The dependence of the solubility of CS-Ba on the concentration of polymer in the solution was demonstrated. The effect of the Ba²⁺ cation on the viscosity of dilute solutions, caused by intramolecular interaction of the polymer sulfate groups with Ba²⁺ ions and consequently compacting of the macromolecules, was established.Translated from Khimicheskie Volokna, No. 5, pp. 31–34, September–October, 1995.     

水热法合成β型氢氧化镍纳米片及其生长机理

以硝酸镍为镍源,浓氨水为沉淀剂,水热法合成了花瓣状β型氢氧化镍球和β型氢氧化镍纳米片,其合成方法简单易行。采用XRD和SEM分别对合成的样品进行物相和形貌分析。结果表明:在相同的pH和反应时间条件下,低温下有利于合成花瓣状β型氢氧化镍球,高温下有利于合成β型氢氧化镍纳米片。即当反应时间为48.0 h、pH=9.0时,180℃下合成了花瓣状β型氢氧化镍球;240℃下合成了β型氢氧化镍纳米片。通过考察水热条件对产物形貌的影响,探讨了花瓣状β型氢氧化镍球和β型氢氧化镍纳米片的形成机制。