无水乙醇对双层油酸包覆结构中物理吸附层的影响

研究了无水乙醇洗涤次数对油酸包覆的Fe3O4磁性纳米颗粒表面包覆结构的影响。采用FT-IR和TGA联合表征了油酸包覆的Fe3O4磁性纳米颗粒经过无水乙醇洗涤前后表面包覆结构的变化,采用TEM观察了油酸包覆后Fe3O4磁性纳米颗粒的形貌。实验结果表明经过无水乙醇5次洗涤后,油酸包覆的Fe3O4磁性颗粒为双层包覆结构;经过无水乙醇20次洗涤后,无水乙醇将双层油酸包覆结构中的物理吸附层洗掉,造成双层油酸包覆的Fe3O4磁性颗粒演变为单层包覆结构。     

表面活性剂对磁流体稳定性及外层包覆结构的影响

采用化学共沉淀法制备粒径分布均匀的纳米Fe3O4颗粒,用油酸钠和聚乙二醇4000(PEG4000)对纳米Fe3O4颗粒进行表面修饰,制得分散稳定的纳米Fe3O4磁流体,通过电动电位(Zeta电位)、粒径测试、离心沉淀、红外光谱分析(FT-IR)和热分析(TG)对修饰后的纳米Fe3O4颗粒进行了稳定性能评价与结构表征。结果表明,油酸钠与纳米Fe3O4颗粒存在两种不同类型的化学键作用;增大油酸钠加入量不会改变Fe3O4颗粒表面包覆结构,但是,其在纳米Fe3O4颗粒表面的吸附量呈先增加后降低的趋势;PEG4000物理吸附于油酸钠包覆的纳米Fe3O4颗粒表面,PEG4000的加入会进一步提高磁流体的稳定性。     

快速热解法制备炭包覆纳米金属磁性颗粒(英文)

以简单金属前躯体为原料通过快速热解法制备炭包覆纳米金属磁性颗粒,通过透射电镜、X-射线衍射、热重-示差扫描同步热分析及振动样品磁强计等对产物形貌、结构、成分与磁性能进行表征。结果表明:采用该方法制备的炭包覆纳米金属磁性颗粒形状为近球形颗粒,粒径均一,其中炭包覆镍纳米磁性颗粒的粒径集中在10nm～30nm范围,炭包覆铁纳米磁性颗粒粒径则在50nm～60nm范围;所制炭包覆纳米金属磁性颗粒在室温下具有顺磁性,其磁性能随金属颗粒含量的变化而改变。该方法有望发展成一种工艺简单,可进行连续工业化生产炭包覆纳米金属磁性颗粒的方法。     

酸碱度对纳米Fe_3O_4磁性流体性能的影响

采用化学共沉淀法制备纳米Fe3O4磁性颗粒,并用油酸钠对其进行包覆改性,以煤油为基液制备出煤油基Fe3O4磁流体。对比分析了pH值=5和10.5条件下油酸钠包覆的Fe3O4磁性颗粒的性能差异,得出油酸钠在pH值=5时可以更好地包覆在Fe3O4磁性颗粒表面,其饱和磁化强度为58.0A·m2/kg,在此基础上制备出的磁流体的饱和磁化强度为20.2A·m2/kg,并且Fe3O4磁性颗粒分散较均匀。而油酸钠在pH值=10.5时包覆的Fe3O4磁性颗粒,其饱和磁化强度虽然高一些(67.8A·m2/kg),但制备出的磁流体稳定性较差,出现较为明显的沉降现象。     

柠檬酸修饰的磁性Fe_3O_4纳米颗粒制备及其弛豫性能

采用共沉淀法制备了柠檬酸修饰的磁性Fe3O4纳米颗粒。通过改变反应过程中柠檬酸的量,研究柠檬酸加入量对纳米颗粒粒径的影响。通过透射电子显微镜、红外、热重、震动样品磁强计等表征手段对制备的磁性纳米颗粒进行表征。结果显示,随着柠檬酸加入量的增加,纳米颗粒的粒径减小,单位质量的颗粒表面包覆的柠檬酸量增大,比饱和磁化强度降低。最后研究了它们的磁共振弛豫性能,发现随着纳米颗粒粒径的逐渐减小,纵向弛豫率和横向弛豫率都显著减小,表明柠檬酸小分子可以成为磁性纳米颗粒造影剂合成有效的调控分子。     

Fe3O4水基磁流体的制备及表征

采用化学共沉淀法制备了具有超顺磁性的纳米Fe3O4颗粒,并在清洗之后对其进行了双层包覆,首先用油酸钠进行第一层包覆,然后分别用聚乙二醇(PEG-)6000和十二烷基苯磺酸钠(SDBS)完成第二层包覆,从而得到了稳定的Fe3O4水基磁流体。分别用XRD、IR、TEM和VSM对所得产物进行了表征,探讨了表面活性剂包覆机理和加入时机。研究表明,所得磁流体具有良好的分散性和稳定性,未包覆的Fe3O4颗粒的饱和磁化强度为80.380emu/g,用油酸钠和PEG-6000双层包覆后的颗粒的饱和磁化强度达到60.529emu/g。以PEG-6000为外层包覆剂的磁流体的分散稳定性优于以SDBS为外层包覆剂的磁流体的分散稳定性。     

电弧法制备碳包覆铁纳米微粒的纯化研究

利用钨电极电弧法制备了碳包覆铁纳米微粒,采用酸洗加磁选的方法对初产物进行了纯化.用透射电子显微镜、X射线衍射仪和振动样品磁强计对产物的形貌结构、物相组成以及磁性能进行了表征分析.结果表明:该纯化方法可以有效地去除产物中未被包覆或碳包覆不完整的铁颗粒及各类碳杂质,纯化后的产物以包覆多层碳膜的铁纳米颗粒为主;粉体的磁滞回线也表明经纯化后产物的磁性能得到了明显提高.     

超声辅助磁性纳米Fe3O4粒子表面有机改性研究

采用超声粉碎分散团聚磁性纳米Fe3O4粒子,用油酸对分散好的磁性粒子表面进行改性.结果表明,在纳米Fe3O4中油酸用量为0.5mL、超声次数为15次、每次2min、间隔时间为15s、pH值为7.5的条件下,改性效果最好,改性指数为0.87.红外光谱分析证明,油酸通过-COOH的"均化"与纳米Fe3O4粒子的表面结合实现了包覆改性,无分解和其它化学反应发生,改性效果良好.     

油酸对微波水热法制备的纳米Fe_3O_4的影响

采用微波水热法制备纳米Fe3O4,并用油酸对其进行表面改性,获得油酸包覆的Fe3O4纳米粒子。利用XRD、FT-IR、TEM和振动样品磁强计对Fe3O4纳米粒子的结构、形貌、磁性能进行表征。结果表明:表面改性使得油酸分子中—COOH和Fe离子形成化学键;改性后的纳米Fe3O4粒子为粒度均匀的球形,具有良好的分散性,平均粒径约8nm;该产物具有超顺磁性,饱和磁化强度为61.8emu/g。     

化学共沉淀法制备油溶性Fe_3O_4纳米颗粒

采用化学共沉淀法制备粒径小于10 nm的油溶性Fe3O4纳米颗粒,对其结构和性能进行表征,并讨论氨水加入方式对Fe3O4纳米颗粒形貌和产率的影响。结果表明:油酸成功包覆在反尖晶石型Fe3O4纳米颗粒的表面,并使其在多种油性溶剂中具有良好的分散性能;磁滞回线显示制得的Fe3O4纳米颗粒具有良好的超顺磁性;氨水加入方式的改变对Fe3O4纳米颗粒的生长具有明显的影响,进而影响Fe3O4纳米颗粒的产率。     

FTIR spectral characterization of thin film coatings of oleic acid on glasses Part II Coatings on glass from different media such as water, alcohol, benzene and air

Oleic acid thin film was coated on soda-lime-silicate (SLS) glass from different coating media such as benzene, ethyl alcohol, water and air with different coating times and concentrations. When the coating medium is benzene, relatively more COO-metal ion complexes formed on the substrate surface, resulting in a coating layer with a more rigid and ordered structure. This was caused by a high solubility of oleic acid and a lower metal dissolution rate of the glass substrate in the medium. The coating time was a less important factor on the ordering of molecular chains than the coating medium was. The effect of concentration was more significant when oleic acid is coated from ethyl alcohol or water rather than from benzene. When oleic acid is coated from benzene, the most highly-ordered molecular structure of coating layer was obtained even at lower concentration. This investigation reveals that the dissolution behavior of the substrate, the solubility of the coating material and the dissociation behavior of metal-carboxylate (COO-M) complexes significantly influence the interaction mechanism between the coating material and the substrate. These factors can be controlled by the selection of an appropriate coating medium; thus, we can design organic thin films with optimized properties.     

正交试验法优选正硅酸乙酯包覆铝粉的条件

为提高铝粉的耐腐蚀性,研究了片状铝粉原料的表面预处理方法,以达到有效除去表面脂肪酸的目的,以正硅酸乙酯为原料,利用溶胶-凝胶法(Sol-Gel)在表面预处理后的铝粉表面包覆一层SiO2薄膜,以达到增加铝粉耐腐蚀性的目的。将包覆完的铝粉置于一定浓度的盐酸溶液中,以相同时间内的析氢量作为评价标准,通过正交试验的极差分析与方差分析优选出最佳的包覆条件。结果显示:铝粉耐腐蚀性的因素影响大小为正硅酸乙酯添加量>温度>时间>H2O添加量>催化剂添加量;包覆15 g铝粉的最佳工艺条件为温度55℃,反应时间6 h,TEOS添加量12 g,H2O添加量16 g,NH3·H2O添加量1 g;采用最佳方案制备的包覆型铝粉具有较好的耐腐蚀性能。     

Superparamagnetic iron oxide nanoparticles: effect of iron oleate precursors obtained with a simple way

The objective of the study was to investigate the effect of different amounts of iron oleate precursor with different oleic acid amounts on the properties of the synthesised nanoparticles by thermal decomposition. The iron oleate precursors which formed from oleic acids in the order of 0.5, 1.0, 1.5 and 2.0 g, and 0.1 g iron powder was prepared under 200 °C seperately, using a facile solvothermal method under study. Thermal analysis of iron oleat precursors by a thermogravimetric analysis (TGA) revealed that the different amount of oleic acid was seen to have an impact on the thermal properties of iron oleat complexes. During the synthesis of nanoparticles, iron oleate complex in 1-hexadecane kept refluxing for 3 h under air atmosphere resulting in the formation of nanoparticles. The fourier transform infrared spectra measurements and the TGA analysis disclosed that nanoparticles were coated with oleic acid. To the X-ray diffraction patterns, all samples are iron oxide nanocrystals and their crystal sizes increased from 6.4 to 9.8 nm with decreasing oleic acid. Also, the sizes of nanoparticles were found to be in same range as confirmed with the surface observation by a transmission electron microscope. The magnetic properties obtained from a vibrating sample magnetometer revealed that all nanoparticles are superparamagnetic at room temperature. Also, their saturation magnetizations were up to 33.2 emu/g. It is seen that the nanoparticles are superparamagnetic with the desired structural and corresponding magnetic properties and therefore, they could be thought to be convenient for biomedical applications as the particles can be transferred to aqueous phase.     

Feasibility of TEOS coated CoFe2O4 nanoparticles to a GMR biosensor agent for single molecular detection

Magnetic properties of 200 nm ferrimagnetic CoFe2O4 nanoparticles before and after coating with TEOS were explored and compared to soft ferrimagnetic MgFe2O4 nanoparticles (200 nm) to evaluate the feasibility as an in-vitro GMR SV (giant magnetoresistance spin-valve) biosensor agent for single molecular detection (SMD). It was found that the magnetic degradation (or variation) of TEOS coated CoFe2O4 and MgFe2O4 nanoparticles are dominantly affected by the chemical dispersion process, which is carried out in the oleic acid (OA), oleylamine (OL), or OA+OL surfactant, before starting major coating process. In addition, the TEOS coating thickness controlled by TEOS concentration and pH level in the buffer solution prominently influenced on the magnetic degradation of TEOS coated nanoparticles. According to the experimental analysis results, the magnetic degradation of TEOS coated nanoparticles is mainly attributed to the variation of particle dipole interaction caused by the degree of particle aggregation depending on TEOS coating process conditions. The TEOS coated CoFe2O4 nanoparticles exhibited a higher magnetic stability for a GMR biosensor agent, e.g., small variation of remnant magnetization, saturation magnetization and magnetic coercivity, than that of MgFe2O4 nanoparticles at the different coating process conditions. The physical and chemical analysis confirmed that this is primarily due to its higher magnetic anisotropy. The experimentally verified high biocompatibility as well as the stably maintained magnetic properties of TEOS coated CoFe2O4 nanoparticles demonstrate that CoFe2O4 nanoparticles can be considered as one of the promising ferrimagnetic nanoparticle sensor agent for an SMD GMR SV biosensor.     

New magnetic fluid developed with natural organic compounds biocompatible

This work was developed with an aqueous suspension of maghemite nanoparticles and colloidal emulsions with nanoparticles of magnetite. The nanoparticles were synthesized by co-precipitation method. The first was the magnetic emulsion nanoparticles of maghemite dispersed in the aqueous extract obtained from the leaf embauba (Cecropia Obtusifolia), whose tree is native to Central and South America. Thereby achieving the magnetic fluid extract embauba stabilized with ionic buffer solution pH 7.4. A second emulsion was prepared with colloidal magnetite nanoparticles with surfaces previously coated with oleic acid as a means of dispersing and using the oil extracted from in nature seed Andiroba (Carapa Guianensis), tree of the Brazilian Amazon. These new magnetic fluids the nanoparticles were characterized by Photoacoustic spectroscopy (PAS) to determine the coating layer of molecules on the surfaces of nanoparticles. In aqueous ionic magnetic fluid Cecropia Obtusifolia (MFCO) chlorogenic acid contributes to the electron density in the presence of four groups alcohols, a ketone group and a carboxylic group. In magnetic fluid-based oil andiroba MFAD PAS spectra show that oleic acid molecules are tightly linked on the surface of the nanoparticles.     

FTIR spectral characterization of thin film coatings of oleic acid on glasses: I. Coatings on glasses from ethyl alcohol

Oleic acid was coated on soda lime–silicate, soda-silicate, and silica glasses from ethyl alcohol. The coating properties of oleic acid were related to the structure, composition, and dissolution properties of the glasses. The bonding mechanism between the organic coating and the glass surface for each different composition of the glass was revealed by analysis of the diffuse reflectance infrared Fourier transform (DRIFT) spectra. The metal ions on the soda lime–silicate glass surface produced metal-(Na-, Ca-, and Al-) oleates through the formation of metal–carboxylate complexes. Two different structural types were present for calcium-oleate. Some of the oleic acid coated undissociatively on the glass surface through hydrogen bonding. Oleic acid reacted with the surface of the soda-silicate glass, which possessed less Na2O content than the soda lime–silicate glass did, completely dissociating, producing only sodium-oleate species because of the high diffusion and dissolution rates of Na+ ions. Oleic acid formed only hydrogen bonds with silanol groups on silica glass. The coated organic layer on soda lime–silicate glass possessed a more ordered and compact structure than either on silica glass or in pure oleic acid. The metal ions on the soda lime–silicate glass surface strongly coordinated to COO– ions from the oleic acid and made the alkyl chains of the oleates more rigid and oriented, consequently causing the coated layer to be more ordered and compact. This structural result caused the dimeric pairs of COOH groups of undissociatively adsorbed oleic acid molecules to be closer, possessing stronger hydrogen bonds than occurring on the silica glass surface. These results suggest that the composition of the glass is one of the most important factors for determining the coating mechanism involving oleic acid.     

亲疏水性SiO2复合有机树脂包覆对FeSiCr磁粉芯性能的影响

研究了亲疏水性SiO₂复合有机树脂对FeSiCr磁粉芯性能的影响以及退火热处理对磁粉芯磁性能的影响。将FeSiCr合金粉末经磷化处理后,分别采用疏水性、亲水性两种不同类型的SiO₂复合有机树脂对粉体进行绝缘包覆,经压制成型并固化制备成FeSiCr磁粉芯。结果表明,采用偶联改性亲水性SiO₂复合有机树脂的包覆效果明显优于疏水性SiO₂复合有机树脂包覆。随着SiO₂添加量的增加,磁粉芯的体电阻率和矫顽力增加,而密度、饱和磁化强度及磁导率降低;采用质量分数0.5%疏水性SiO₂复合有机树脂包覆工艺制备的FeSiCr磁粉芯退火后综合性能最优,在20 mT,100 kHz测试条件下,磁损耗仅为49.84 kW/m³,相比于采用纯树脂包覆工艺制备的磁粉芯损耗下降了16.9%。退火热处理能够有效提高FeSiCr磁粉芯的磁性能。     

亲疏水性SiO2复合有机树脂包覆对FeSiCr磁粉芯性能的影响

研究了亲疏水性SiO₂复合有机树脂对FeSiCr磁粉芯性能的影响以及退火热处理对磁粉芯磁性能的影响。将FeSiCr合金粉末经磷化处理后,分别采用疏水性、亲水性两种不同类型的SiO₂复合有机树脂对粉体进行绝缘包覆,经压制成型并固化制备成FeSiCr磁粉芯。结果表明,采用偶联改性亲水性SiO₂复合有机树脂的包覆效果明显优于疏水性SiO₂复合有机树脂包覆。随着SiO₂添加量的增加,磁粉芯的体电阻率和矫顽力增加,而密度、饱和磁化强度及磁导率降低;采用质量分数0.5%疏水性SiO₂复合有机树脂包覆工艺制备的FeSiCr磁粉芯退火后综合性能最优,在20 mT,100 kHz测试条件下,磁损耗仅为49.84 kW/m³,相比于采用纯树脂包覆工艺制备的磁粉芯损耗下降了16.9%。退火热处理能够有效提高FeSiCr磁粉芯的磁性能。     

AIN粉末有机物表面处理及水解动力学

在AIN粉末表面涂覆油酸和8-羟基喹啉,有效地提高了AIN的耐水性．该粉末在40℃温水中至少稳定70h;但随水温升高稳定性变差,在60～80℃的水中发生水解反应．反应动力学呈扩散控制和固相表面化学反应控制两个阶段,均为一级反应,活化能分别为125kJ／mol和114kJ／moL产生上述现象的原因归于有机膜吸附在AIN表面,增加了水分子向AIN表面扩散的阻力,从而提高了AIN的耐水性．但这种吸附是物理吸附,水温升高时,在高动能水分子作用下解吸,导致AIN迅速与水反应．上述观点由TG－DTA、XRD和IR分析所证实．     

Improved magnetic properties of iron-based soft magnetic composites with a double phosphate-SiO2 shells structure

Herein a double shells structure was proposed to overcome the drawbacks such as poor heat resistance, incomplete insulation and high core loss coating of iron-based soft magnetic composites (SMCs) with single shell structure. The surface of the iron powder was coated with a double shells structure composed of an inner phosphate coating and an outer SiO₂ coating through phosphating and hydrolysis successively. Subsequently, the effects of different SiO₂ addition amount on the microstructure of iron powder and magnetic properties of SMCs were studied. The introduction of SiO₂ in the double shells structure inhibited the decomposition and failure of phosphating layer after being annealed at a high temperature. The iron powder coated with the phosphate-SiO₂ insulating layer was still effective after annealing in a N₂ atmosphere at 570 °C, achieving the purpose of eliminating residual stress and improving magnetic properties. The optimal process parameters were set at 0.2 wt% phosphoric acid and 0.5 wt% tetraethyl orthosilicate to fabricate the phosphate-SiO₂ double shells. The iron-based SMCs presented excellent magnetic properties with B_s of 1.29 T and P_s of 169.2 W/kg (measured at 1 T and 1 kHz). In addition, the core loss of SMCs introduced with SiO₂ is 83% lower than that of SMCs produced by the phosphating process. This paper provides a feasible method for improving the magnetic properties of SMCs.