过量油酸钠加入对磁流体表面包覆结构的影响

通过研究过量油酸钠的加入对磁流体中Fe3O4纳米颗粒表面包覆结构的影响来探讨油酸钠形成牢固双层包覆结构的条件。结果表明，在反应温度为80℃，反应时间为30min，反应pH-5的条件下，过量油酸钠在Fe3O4颗粒表面可以形成双层包覆结构，但第二层物理吸附层与第一层化学吸附层结合力低，极易脱落；Fe3O4颗粒表面包覆结构不随油酸钠加入量的改变而改变；随着油酸钠加入量的增加，油酸钠在Fe3O4颗粒表面的吸附量呈先增加后降低的变化规律。最后提出反应介质水的pH值是控制Fe3O4颗粒表面形成油酸钠双层包覆结构的关键因素。     

“一锅法”合成油酸包覆Fe_3O_4及油酸用量对其性能的影响

采用"一锅法",即在"共沉淀法"合成纳米Fe_3O_4颗粒之前,直接加入油酸(表面活性剂),合成了油酸包覆的纳米Fe_3O_4颗粒。并通过X射线衍射仪(XRD)、透射电子显微镜(TEM)、振动样品磁强计(VSM)、热重分析仪(TGA)对颗粒进行了表征,重点研究了油酸用量对纳米Fe_3O_4颗粒的结构、成分、形貌、尺寸、磁化强度的影响。结果表明,在实验中,油酸与Fe_3O_4摩尔比为0.4时,采用"一锅法"可合成9nm左右、分散性良好、饱和磁化强度在56A·m2/kg的纳米Fe_3O_4颗粒。     

白蛋白包覆纳米Fe3O4磁性粒子的制备与表征

目的：制备用于肿瘤靶向治疗的纳米级Fe3O4磁性粒子。方法：采用液相共沉淀法制备纳米Fe3O4颗粒,通过高温固化法使得白蛋白固化包覆磁性Fe3O4磁性粒子。结果：X-Ray衍射分析表明制得的纳米Fe3O4为反尖晶石结构,晶粒平均粒径为17．9nm;白蛋白包覆的磁性纳米粒子的平均粒径为341nm。结论：纳米Fe3O4及其白蛋白包覆的磁性粒孚可用作药物的载体,适用于肿瘤靶向治疗的进一步研究。     

纳米磁性Fe3O4的研究进展

纳米Fe3O4是一种多功能磁性材料，在磁记录材料、磁流体、催化、医药、颜料等方面具有广泛的应用。综述了近年来纳米Fe3O4颗粒的液相化学制备方法：共沉淀法、微乳化法、溶胶-凝胶法、水热法、溶剂热法等的研究现状以及最新的研究成果，对上述各种制备方法的优缺点进行了分析和比较。简单介绍了磁性纳米Fe3O4的应用以及发展趋势，并提出其今后发展要重点控制颗粒结构形态及其磁性能等。     

Fe3O4磁性颗粒的表面改性研究

采用溶胶-凝胶法对超细磁性颗粒表面改性以包覆SiO2的保护层,研究制备适用于磁性液体、具有可耐特殊条件的纳米磁性颗粒的改性方法,以适应特殊环境对磁性液体的性能要求,并对表面改性后的磁性颗粒进行了组成和性能的测试.     

Fe3O4/PSt/TiO2多层包覆电磁响应微球的制备

首先采用分散聚合法将自制的Fe3O4磁流体和苯乙烯反应合成有磁核的Fe3O4/PSt磁性聚合物微球，然后，用非均匀成核水解反应在Fe3O4/PSt微球外包覆无定形二氧化钛，获得Fe3O4/PSt/TiO2复合微粒。用红外光谱、扫描电镜和热分析对粒子的形貌和结构进行了表征。并测试了微粒的介电性能和磁性，结果表明，所制得复合微粒有良好的电、磁响应性。     

利用正交试验讨论工艺条件对Fe3O4纳米颗粒磁性的影响

利用正交实验探索了化学共沉淀法制备Fe3O4纳米颗粒的影响因素:[Fe3+];[Fe3+]:[Fe2+];氨水用量倍数;乙醇浓度;晶化时间;晶化温度等参数对Fe3O4纳米颗粒饱和磁化强度和均匀性等性能的影响.通过对极差分析找出了在试验条件范围内Fe3O4粉末的饱和磁化强度达到最大值的工艺条件,即D3A3F4B3E5C4:[Fe3+]=0.1mol/L;合成温度60℃;NH4OH用量倍数=2;晶化时间30min;[Fe2+]:[Fe3+]=0.7;乙醇质量分数16%此论文的工作是为本实验室将要使用的磁性液体自动化制备系统的运用做前期准备.同时也是为本实验室相关项目的磁性液体的制备提供参考.     

双层包覆对铝粉耐腐蚀性能的影响

为了提高铝粉的耐腐蚀性能,在铝粉表面进行了无机-有机、有机-无机双层包覆,研究了反应温度、反应时间、引发剂偶氮二异丁腈(AIBN)用量、分散剂聚乙烯基吡咯烷酮(PVP)用量、n(SiO2)/n(Al)、n(H2O)/n(SiO2)对包覆效果的影响.结果表明,无机-有机包覆的最优条件是:反应温度65℃;反应时间1h;引发剂用量0.030 g,分散剂用量为0.500 g.而有机-无机双层包覆的最优条件是:n(SiO2)/n(Al)=20%,反应温度为30℃,n(H2O)/n(SiO2)=10.与原料铝粉相比,无机、有机单层包覆的缓蚀效率分别为66.1%、80.0%,而无机-有机双层包覆与有机-无机双层包覆铝粉的缓蚀效率分别可达96.4%、97.9%,即通过在铝粉表面进行双层包覆可有效地提高其耐腐蚀性能.     

葡聚糖包覆纳米Fe3O4颗粒的研究

采用化学共沉淀法制备了葡聚糖包覆的纳米Fe3O4颗粒,平均粒径为6nm,包覆层厚度约为3～5nm,纳米Fe3O4粒径分布较窄.红外光谱分析可知,葡聚糖与纳米Fe3O4主要以氢键结合,结合Zeta电位和热重分析,分散作用主要是空间位阻作用,葡聚糖的包覆量约为10%.吸光度测试表明,随着葡聚糖用量的增加,悬浮液的稳定性提高.用量为25%时,悬浮液在室温下静止1周,无分层现象.包覆样的饱和磁化强度为60emu/g,具有良好的超顺磁性.     

纳米铁粉对硅油基Fe3O4磁流体的性能影响

针对传统Fe3O4磁流体饱和磁化强度低、传热性差等缺点,以等离子体蒸发法自行制备的纳米颗粒为添加剂,研究了纳米铁粉对低粘度硅油基Fe3O4磁流体性能的影响.研究结果表明:(1)铁粉经过渡液分散后加入的效果远优于直接加入;(2)在Fe与Fe3O4颗粒质量比＜3的前提下,纳米铁粉的加入对磁液密度及粘度影响不明显;(3)纳米铁粉的加入能明显提高磁液的饱和磁化强度,当铁粉的加入量达到Fe3O4的3倍时,比饱和磁化强度达到3.2A·m2/kg,提高了近7倍.     

Interface layer effect on the stress distribution of a wafer-bonded bilayer structure

The interface layer plays an important role in stress transfer in composite structures. However, many interface layer properties such as the modulus, thickness, and uniformity are difficult to determine. The model developed in this article links the influence of the interface layer on the normal stress distribution along the layer thickness with the layer surface morphology before bonding. By doing so, a new method of determining the interfacial parameter(s) is suggested. The effects of the layer thickness and the surface roughness before bonding on the normal stress distribution and its depth profile are also discussed. For ideal interface case with no interfacial shear stress, the normal stress distribution pattern can only be monotonically decreased from the interface. Due to the presence of interfacial shear stress, the normal stress distribution is much more complex, and varies dramatically with changes in the properties of the interface layer, or the dimensions of the bonding layers. The consequence of this dramatic stress field change, such as the shift of the maximum stress from the interface is also addressed. The size-dependent stress distribution in the thickness direction due to the interface layer effect is presented. When the interfacial shear stress is reduced to zero, the model presented in this article is also demonstrated to have the same normal stress distribution as obtained by the previous model, which does not consider the interface layer effect.     

Influence of sintering temperature on the properties of high Tc bismuth layer structure ceramics

Bismuth layer structure Ca_0.82(NaCe)_0.09Bi₄Ti₄O₁₅ piezoelectric ceramics were prepared by the conventional ceramic technique. Sintering characteristic of Ca_0.82(NaCe)_0.09Bi₄Ti₄O₁₅ was discussed. The X-ray powder diffraction pattern showed a single phase of bismuth oxide layer structure having general formula (Bi₂O₂)²⁺(A_m−1B_mO_3m+1)²⁻ with m=4. Scanning electron microscope (SEM) micrographs of the natural surface of ceramic samples indicated that the anisotropy of growth of grains becomes stronger with the increase in the sintering temperature. With the increase in the sintering temperature, the resistivity and piezoelectric constant d₃₃ increased to a maximum value and then decreased, but the dielectric constant ε₃₃^T/ε₀ decreased. The Curie temperature and the capacitance temperature stability of the ceramics were improved with the increase in the density.     

Influence of surfactants on the structure of the adsorption layer in the system: Carboxymethylcellulose/alumina

The influence of surfactants: anionic SDS, nonionic Triton-100 and their mixture (SDS/TX-100) on the structure of the adsorption layer in the system: carboxymethylcellulose (CMC)/alumina (Al₂O₃) was measured. The surface charge density of alumina and its zeta potential were determined in the presence of the CMC macromolecules and the surfactant particles. In order to gain more information about the structure of adsorption layer the amount of CMC adsorption in the presence of surfactants as well as the thickness of the CMC adsorption layer were determined. It was proved that in the presence of surfactants mixture (SDS/TX-100) the amount of adsorption of CMC is the highest and the obtained adsorption layer is the thickest. On the other hand, when Triton X-100 is added to the measured system the polysaccharide conformation is closely packed. The amount of adsorption is large but the thickness of the adsorption layer is relatively low. In the presence of SDS macromolecules of CMC form conformation expanded towards the bulk solution. Such a conformation is characterized by the smaller amount of adsorption of polymer but the larger thickness of the adsorption layer.     

Influence of the structure of a modifier layer on the compatibility of polymers with a modified montmorillonite

The dependence of the compatibility of a modified montmorillonite with different-polarity polymers on the structure of a modifier layer formed on the montmorillonite surface has been investigated. It is shown that the layers forming an ordered structure in the interplane spaces of the clay do not provide an exfoliation of the silicate plates of the clay or a significant intercalation of polymer chains into the interlayer space of the montmorillonite. An optimum structure of a modifier layer, providing a significant intercalation of polymer chains into the interlayer spaces of the montmorillonite and an exfoliation of the clay in its compounds with a maleinized polypropylene, obtained by mixing in a melt, has been determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 35–40, September–October, 2005.     

Influence of polymeric residue on the thermal conductivity of suspended bilayer graphene

The thermal conductivity (κ) of two bilayer graphene samples each suspended between two microresistance thermometers was measured to be 620 ± 80 and 560 ± 70 W m(-1) K(-1) at room temperature and exhibits a κ ∝ T(1.5) behavior at temperatures (T) between 50 and 125 K. The lower κ than that calculated for suspended graphene along with the temperature dependence is attributed to scattering of phonons in the bilayer graphene by a residual polymeric layer that was clearly observed by transmission electron microscopy.     

Preparation of carboxyl-coated polystyrene nanoparticles using oleic acid

Novel carboxyl group-decorated crosslinked polystyrene nanoparticles were prepared via the soapless emulsion polymerisation of styrene and divinyl benzene with oleic acid as functional comonomer. The existence of the surface carboxyl group was verified by zeta potential analysis. Particle sizes of the functional nanoparticles prepared with the proposed method were found to be in the range of 60-100-nm by transmission electron microscopy and dynamic light scattering analyses. Functionalised nanoparticles are proposed as carriers for biomolecules or drugs.     

透波层厚度对结构吸波材料吸收峰的影响

采用弓形法测试反射率,研究透波层的厚度对结构吸波复合材料吸收峰的影响。结果显示,在4~18 GHz范围内,厚度对其吸波性能具有显著影响:透波层厚度为0.95 mm时,结构吸波材料的吸收峰值最高,达-22.6 d B;其吸收峰值先随透波层厚度的增加而增强,而后逐渐减弱,透波层厚度对吸收峰值的影响可用二次多项式描述;吸收峰的位置随透波层的厚度增加向低频方向漂移,其漂移位移与透波层厚度线性相关,满足一次线性方程。     

采用油酸和月桂酸改进磁流变液稳定性的实验研究

鉴于油酸和月桂酸2种表面活性剂对磁流变液稳定性所起到的不同的作用,制备了若干种不同配比的以油酸和月桂酸共同添加的磁流变液,测量它们的零场粘度、力学性能和沉降率-时间曲线,研究了月桂酸、油酸和羰基铁粉3种成分的含量对于磁流变液稳定性和力学性能的影响。结果表明合理的添加油酸和月桂酸对于制备零场粘度小且稳定性优良的磁流变液具有显著的效果。     

Influence of stearic acid on the structure and rheological behavior of injection-molded ZTA suspensions

The zirconia-toughened-alumina (ZTA) composite powder was exposed to a prior ball milling treatment with a small amount of stearic acid (SA) before the traditional blending process. The effect of different amounts of stearic acid on surface properties of the powder, the particle size distribution of the powder, and the rheological properties of the suspension were systematically studied within the design of experiments. Fourier transformation infrared spectroscopy (FTIR) analysis was used to prove the chemical interaction between the stearic acid and the ZTA powder. The effects of SA content on the particle sizes and their distribution were carefully examined. Rheological properties such as viscosity, yield stress, and power law exponent of the suspensions were determined within a temperature range of 140–170 °C. The optimal content of SA to improve the properties of the suspensions was found to be 3 wt.%.