稀土磁性复合微球的制备及表征

以聚乙二醇磁性胶体粒子为种子 ,运用分散聚合法 ,同时掺入稀土离子 ,制备出表面配位有稀土离子的磁性聚苯乙烯微球 ,该微球粒径为 6 0～ 180 nm,考察了稀土磁性微球的形态和结构。并用电镜、原子吸收光谱、红外光谱对其性质进行了表征。     

巨磁阻生物传感器对磁性聚苯乙烯微球检测

采用改进的悬浮聚合法制备磁性聚苯乙烯微球.利用扫描电子显微镜和振动样品磁强计对所合成磁性微球的尺寸和磁性能进行分析表征.采用巨磁阻生物传感器检测磁性微球的数量.结果表明:磁性微球粒径大小为0.5~50μm,比饱和磁化强度为4.56 A·m²·kg^-1.巨磁阻生物传感器对磁性聚苯乙烯微球数量具有很好的可检测性.在一定的范围内,随着磁性微球数量的增多,传感器的输出信号增强.在磁性微球一定数量的情况下,随着磁性微球粒径的增大,传感器的电阻变化量先增大后减小.     

聚苯乙烯/聚吡咯复合微球催化剂性能

采用种子乳液聚合制备了聚苯乙烯/聚吡咯(PS/PPY)复合微球,以其为载体负载钼活性中心制备了PS/PPY复合微球负载钼系催化剂,系统研究了载体性质对负载型催化剂催化环辛烯环氧化反应的催化活性.结果表明:亲水性的负载型催化剂在以过氧化氢为氧源的催化体系中催化活性较高;聚合物的掺杂离子对催化剂的催化性能具有重要影响,以硝酸铁为氧化剂制备的负载型催化剂的催化活性最高,催化环辛烯环氧化的转化率可以达到90%.     

微米级二氧化硅空心微球的制备及表征

采用硬模板法与溶胶-凝胶法相结合的工艺,以自制的聚苯乙烯(PS)为模板,十六烷基三甲基溴化铵(CTAB)为阳性表面活性剂,正硅酸四乙酯(TEOS)为硅源制备SiO₂空心微球。重点研究升温速率及CTAB、TEOS、氨水用量等工艺参数对SiO₂空心微球形貌的影响规律。采用XRD、TEM、SEM、TG、FTIR对微球的物相、微观形貌及介孔结构等进行表征。结果表明：SiO₂空心微球粒径为2～5μm、壁厚为117 nm;SiO₂空心微球壁会随着升温速率的增加而出现破损现象;随CTAB用量增加,纳米球数量增加且粒径减小;随TEOS用量增加,球壁变厚直至形成纳米球;氨水小于4 mL时,二氧化硅空心微球不能成形,氨水大于4 mL时,二氧化硅空心微球表面粗糙,有实心颗粒;当升温速率为0.5℃/min、CTAB用量为0.05 g、TEOS用量为0.3 mL、氨水用量为4 mL时,且经过抽滤清洗的SiO₂空心微球的形貌最佳。     

含淀粉反相乳液及交联淀粉微球制备

[目的]研究影响含淀粉反相乳液稳定性的因素,优化交联淀粉微球制备工艺.[方法]采用单因素法研究影响反相乳液稳定性的主要因素,用正交试验法确定了合成交联淀粉微球的最佳工艺.[结果]使用0.6%的Span60(HLB=4.70),油、水相体积比为3∶1,水相中淀粉浓度为16%时可形成稳定的W/O型含淀粉反相乳液;制备微球的最佳工艺条件为:油、水相体积比4∶1,淀粉乳浓度16%,交联剂用量3 ml,反应温度45℃,乳化剂用量0.3%;微球产品近似球状,球体表面粗糙,粒径分布均匀,平均粒径μm.[结论]经过优化的制备工艺能够合成粒径均匀的交联淀粉微球.     

壳聚糖/明胶复合微球的制备

采用乳化-凝聚法,在油包水(W/O)体系中制备壳聚糖/明胶(Cs/Gel)复合微球,研究乳化剂用量、搅拌速率和水油比等因素对微球粒径以及脱水过程中的丙酮浓度对Cs/Gel复合微球形貌的影响.研究结果表明:乳化剂浓度较低时,微球的粒径随乳化剂浓度的增加呈降低趋势,当乳化剂浓度高于0.012 g·mL-1时微球粒径不再发生...     

洛伐他汀聚乳酸缓释微球的制备及其体外释药

采用油/水型乳化溶剂挥发法制备了洛伐他汀聚乳酸缓释微球,通过正交试验筛选最优制备工艺;考察了微球的粒径,形态,及载药量、包封率等特征,采用透析法进行微球体外释药研究.结果表明由最佳工艺制备的洛伐他汀聚乳酸微球形态圆整,粒径分布较为均匀.分子量5万聚乳酸制备的微球,载药量32.28%,包封率81.81%,平均粒径65.8μm;分子量3万聚乳酸制备的微球,载药量27.66%,包封率60.84%,平均粒径63.3μm.二者在10d内体外累积释放率分别为34.81%和40.96%,释药动力学符合Higuchi方程.     

由大分子PMMA-DPE引发制备Poly(St-alt-MAn)微球

在1,1-二苯基乙烯(DPE)存在下,以甲基丙烯酸甲酯(MMA)为初始单体,偶氮二异丁腈(AIBN)为引发剂,采用本体聚合法制备出含有DPE片段的大分子引发剂PMMA-DPE;然后以PMMA-DPE为引发剂,以苯乙烯(St)和马来酸酐(MAn)为共聚单体,乙酸异戊酯为溶剂,采用自稳定沉淀聚合法制备了单分散的聚(苯乙烯-马来酸酐)(Poly(St-alt-MAn))的微球.研究了PMMA-DPE的用量对聚合物微球的形态、粒径大小及分布的影响.采用FT-IR,UV-Vis,1H-NMR和GPC对产物的结构进行了表征,并用SEM观察了聚合物微球的形貌.结果表明,PMMA-DPE能够引发St和MAn的共聚合,随着PMMA-DPE用量的增加,聚合反应的转化率呈增大趋势,聚合物微球的粒径呈下降趋势,而粒径分布系数略有增大.     

聚乙烯醇辅助制备SBA-15微球北大核心

SBA-15型介孔二氧化硅(Si O2)是一种重要的具有较大介孔孔径的介孔材料,其中球形SBA-15在色谱分离、药物载体等领域具有重要的应用前景.本文报道了一种以聚乙烯醇(PVA)为添加剂、基于经典正硅酸四乙酯(TEOS)/P123/HCl (aq.)的路径,实现了SBA-15微球的简便制备.所得SBA-15微球具有长程有序的二维六方介孔结构,其介孔孔径为8. 8 nm,比表面积634 m2·g-1和孔体积0. 66 cm3·g-1.本工作还初步考察了包括PVA和不同的合成步骤等对SBA-15微球制备的影响.本法为SBA-15微球的制备提供了一种新的路径.     

壳聚糖微球的制备和动物皮内刺激评价

[目的]研究壳聚糖微球的制备以及其对动物皮内的刺激影响,为壳聚糖微球进一步临床应用提供依据.[方法]以壳聚糖(CS)为原料,通过乳化交联法制备CS微球,显微镜观察壳聚糖微球微观形态,研究微球理化特性受壳聚糖脱乙酰度、壳聚糖醋酸溶液浓度、交联剂用量等工艺条件影响,并将壳聚糖微球进行兔子皮内刺激试验.[结果]优化得出壳聚糖微球制备工艺为壳聚糖醋酸质量浓度0.3g/L,Span80为油相体积的8%,油水相体积比3:1,交联时间1 h.该壳聚糖微球不会对兔子产生损害.[结论]壳聚糖微球符合医疗器械生物学评价要求,为壳聚糖微球进一步临床应用奠定了基础.     

Grain refining of structural steels by dispersion of fine oxide particles

Steel toughness has been greatly improved in the last two decades by adopting innovative technologies such as advanced steelmaking, grain refinement and thermo-mechanical treatment. The technology of oxide metallurgy is not a simple part of either chemical metallurgy or physical metallurgy. It aims at the generation of finely dispersed oxides by chemical metallurgy and using these oxides together with the methods of physical metallurgy such as IGF (intragranular ferrite) technology and phase transformation. Oxide metallurgy can be an effective way in addition to the conventional austenite grain refinement to obtain higher toughness for structural steels.     

Preparation of amorphous Ni-Pd-P particles by melt ejection

Amorphous spherical particles with diameters of 0.5 to 1.4 mm have been prepared by melt ejecting Ni-rich Ni-Pd-P alloys into stirred cold water with 1 vol pct surfactive agent. The sphericity of the amorphous particles defined by the difference in diameter was better than 98 pct. Particle diameters (d) are 2 to 3 times larger than the orifice diameter (2r) of the quartz nozzle. The size ratio has been interpreted by the Raplace’s relation (d = 4r) derived from the assumption that an internal pressure of molten alloy is equal between cylindrical stream and spherical droplet. From the result that no spherical amorphous particles are formed in the cold water without surfactive agent, a significant decrease in the surface tension of coolant by the addition of surfactive agent is essential in the formation of spherical liquid particles from the ejected melt stream. The amorphous particles with diameters below about 1.0 mm exhibit hardness, crystallization temperature, and heat of crys-tallization similar to those from the amorphous ribbon with about 40 μm thickness. However, the onset temperature and heat of relaxation are lower by 16 K (4.2 pct) and larger by 130 J/mol (13 pct), respectively, for the particles. It is thus concluded that the amorphous spherical particles have the same thermal stability as that of the amorphous ribbon and its structure is in a more disordered state as compared with the ribbon sample.     

内氧化法制备MgO弥散强化铁基材料

采用机械合金化—低温表面氧化—高温内氧化—还原处理制备MgO弥散强化铁粉后再经放电等离子(SPS)烧结制备MgO弥散强化铁基材料,并通过SEM和EDS对材料的组织和断口进行分析。结果表明:添加MgO能够细化晶粒,并均匀地分布于基体中,MgO颗粒尺寸200nm~1μm。添加MgO强化后,材料的拉伸断口由粗大的韧窝变成细小的等轴韧窝;MgO弥散强化铁基材料烧结体的室温力学性能得到有效提高,Fe+1.0%MgO的抗拉强度为342.6MPa,屈服强度为276.3MPa,硬度为61HRB,相对于纯铁分别提高了20.5%、54.2%和84.8%。     

微乳液法制备纳米二氧化硅粉末

采用微乳液法制备了高比表面积纳米SiO2粉末,考察了微乳液体系的配制、反应物浓度、反应温度、焙烧温度、共沸蒸馏脱水工艺对纳米SiO2性能的影响。并通过氮气吸附法(BET)、透射电镜(TEM)、红外光谱分析(IR)、X射线衍射(XRD)等方法对样品进行了表征。研究结果表明,制备粉末的工艺参数对样品性能影响较大,在较佳工艺条件下制备的纳米SiO2粉末近似呈球形,粒径为15-35nm,比表面积达580-630m2／g。共沸蒸馏工艺能完全脱去凝胶中残余的水分,防止因含水胶体干燥引起的粉末硬团聚,从而提高粉末的比表面积。     

A nonoverlap model for the dispersion of spherical particles

The dispersion of randomly positioned spherical particles can be characterized in terms of probability functions for the center to center spacings to its neighbors. This model is used with a correction procedure for describing the dispersion of nonoverlapping spherical particles. Modification of the random model to account for the bias introduced by excluding overlap is carried out by setting the neighbor probability functions equal to zero for radial distances which cause overlap, and then renormalizing the functions. Comparison of the probability distributions and their moments for the nonoverlap model with Monte Carlo simulation data show that it provides a valid approximation for the dispersion of spherical particles with volume fractions as high as 30 pct. The effects of volume fraction and size distribution of the particles upon the nonoverlap probability functions and their moments are described. Radial density functions are also calculated for both the random and the nonoverlap models.     

A nonoverlap model for the dispersion of spherical particles

The dispersion of randomly positioned spherical particles can be characterized in terms of probability functions for the center to center spacings to its neighbors. This model is used with a correction procedure for describing the dispersion of nonoverlapping spherical particles. Modification of the random model to account for the bias introduced by excluding overlap is carried out by setting the neighbor probability functions equal to zero for radial distances which cause overlap, and then renormalizing the functions. Comparison of the probability distributions and their moments for the nonoverlap model with Monte Carlo simulation data show that it provides a valid approximation for the dispersion of spherical particles with volume fractions as high as 30 pct. The effects of volume fraction and size distribution of the particles upon the nonoverlap probability functions and their moments are described. Radial density functions are also calculated for both the random and the nonoverlap models. Formerly with Division of Minerals Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA.