Preparation and characterization of collagen/chitosan poly (ethylene glycol)/nanohydroxyapatite composite scaffolds

Porous three‐dimensional collagen/chitosan scaffolds combined with poly (ethylene glycol) (PEG) and hydroxyapatite were obtained through a freeze‐drying method. Physical cross‐linking was examined by dehydrothermal treatment. The prepared materials were characterized by different analyses, eg, scanning electron microscopy (SEM), measurements of porosity and swelling, mechanical properties, and resistance to enzymatic degradation. The porosity of scaffolds and their swelling ratio decreased with the addition of hydroxyapatite. Moreover, after exposure to collagenase, the collagen/chitosan matrices containing PEG showed much faster degradation rate than matrices with the addition of hydroxyapatite. The results indicated that the addition of hydroxyapatite led to improvement of stiffness. The highest degree of porosity and swelling were demonstrated by collagen/chitosan/PEG matrices without hydroxyapatite.     

具有光导性的磁性高分子粒子的合成与表征

采用分散聚合法合成了表面带羟基、内核为四氧化三铁的磁性高分子粒子 ,再用酯化法在粒子表面共价结合有机光导分子酞菁 ,得到了同时具有光导性和磁响应性的磁性高分子粒子     

Synthesis and properties of sol-gel submicron silica powders doped with partly oxidized iron particles

Magnetic powders based on metallic iron crystallites encapsulated in submicron-sized spherical silica particles have been obtained and investigated. The metallic iron clusters have been produced by the exploding wire method. The silica shells have been prepared via the modified sol-gel Stöber method and the metallic particles have been entrapped by occlusion during the silica powder formation. The entrapped iron particles are partially oxidized due to the nature of the synthetic methods employed. The obtained hybrid materials have been investigated by electron microscopy, X-ray diffraction, magnetic and ζ-potential techniques. Such materials can be employed in such applications as e.g. magnetically-controlled drug vectors or electromagnetic field-shielding.     

Influence of iron content on thermal stability of magnetic polyurethane foams

Magnetorheological (MR) materials are a group of smart materials which have the controllable magnetic properties with an external magnetic field. Magnetic foams, a specific type of MR solids, were synthesized from flexible polyurethane (PU) foams and carbonyl iron particles. Effects of the carbonyl iron particles on the thermal stability of the magnetic foams have been studied. Thermogravimetric analysis (TGA) was applied to characterize the thermal degradation process of the magnetic foams and then the apparent activation energy of degradation was calculated by using Ozawa's method [Ozawa T. A new method of analyzing thermogravimetric data. Bulletin of the Chemical Society of Japan 1965; 38: 1881-1886.]. The carbonyl iron particles were found to improve the thermal stability of magnetic foams in nitrogen by showing higher 10 wt% loss temperature, slower weight loss rate and higher apparent activation energy than pure PU foams. But the magnetic foams were observed to have slightly worse thermal stability in air than pure PU foams at the earlier degradation stage. At the later degradation stage, the magnetic foams exhibited the higher activation energy than pure PU foams in air.     

Preparation of composite materials containing iron in a cross-linked resin host based on styrene and divinylbenzene

Iron composite materials based on styrene/divinylbenzene network hosts were produced using aqueous suspension polymerization. The effects of different kinds of porogen agent, toluene, toluene/n-heptane mixture or a toluene solution of polyphenyleneoxide on the bulk density, swelling in toluene and ferromagnetic properties of these materials were evaluated. The specific area and average porous diameter of network resins were characterized by BET and BJH methods, while the iron content was determined by atomic absorption spectrometry. The morphology of the composites was studied by both optical microscopy and scanning electron microscopy with energy dispersive X-ray analysis. All the spherical beads, irrespective of their sizes, have agglomerated iron particles located only on their surface. The particles have exhibited ferromagnetic behavior, with a coercivity of 328.69 Oe. The porogen agents used affect the iron particle distribution on the bead surfaces.     

Synthesis and characterization of magnetic poly(divinyl benzene)/Fe3O4, C/Fe3O4/Fe, and C/Fe onionlike fullerene micrometer-sized particles with a narrow size distribution

Magnetic poly(divinyl benzene)/Fe(3)O(4) microspheres with a narrow size distribution were produced by entrapping the iron pentacarbonyl precursor within the pores of uniform porous poly(divinyl benzene) microspheres prepared in our laboratory, followed by the decomposition in a sealed cell of the entrapped Fe(CO)(5) particles at 300 °C under an inert atmosphere. Magnetic onionlike fullerene microspheres with a narrow size distribution were produced by annealing the obtained PDVB/Fe(3)O(4) particles at 500, 600, 800, and 1100 °C, respectively, under an inert atmosphere. The formation of carbon graphitic layers at low temperatures such as 500 °C is unique and probably obtained because of the presence of the magnetic iron nanoparticles. The annealing temperature allowed control of the composition, size, size distribution, crystallinity, porosity, and magnetic properties of the produced magnetic microspheres.     

Synthesis and characterization of heat-stabilized albumin magnetic microspheres

Human serum albumin magnetic microspheres containing 30% iron oxide particles were synthesized by a heat-stabilization process. The average diameter, the size distribution and the morphology were characterized by scanning electron microscopy, atomic force microscopy and transmission electron microscopy. The distribution of the iron oxide nanoparticles within the microspheres was confirmed by the contrast obtained in the morphology by backscattered electron imaging in scanning electron microscopy. Energy-dispersive X-ray spectroscopy showed the presence of iron in the microspheres. The cabbage like surface structure in some of the microspheres obtained in scanning electron microscopy can be better understood by atomic force microscopy. This peculiar surface structure in the microsphere may be due to the cross-linking in the protein molecule by heat. The amount of iron oxide in the microsphere was analyzed by atomic absorption spectroscopy. The magnetic properties of the particles were measured in a superconducting quantum interference device magnetometer. Received: 12 September 2000 Accepted: 5 February 2001     

原位沉析法制备磁性氧化铁羟基磷灰石/壳聚糖棒材

首先通过化学沉淀法制备磁性氧化铁羟基磷灰石(Fe3O4/HA),然后以壳聚糖(CS)为基体,利用原位沉析法将Fe3O4/HA与CS复合,制得磁性Fe3O4/HA/CS复合材料.经XRD、粒径分布和PPMS测试,结果表明了Fe3O4/HA复合物的生成.系统研究了磁性Fe3O4/HA/CS棒材力学性能的影响因素,最终确定Fe3O4与HA质量比为3∶17,磁性Fe3O4/HA与CS质量比为9∶91时,棒材的力学性能最优,弯曲强度可达到87.0 MPa,弯曲模量1.57 GPa.     

Magnetic hollow poly(N-isopropylacrylamide-co-N,N′-methylenebisacrylamide-co-glycidyl acrylate) particles prepared by inverse emulsion polymerization

To prepare functionalized magnetic polymer particles that are thermally responsive, inverse emulsion copolymerization of N-isopropylacrylamide, N,N′-methylenebisacrylamide and glycidyl acrylate (GA) was investigated in paraffin oil in the presence of γ-Fe₂O₃ nanoparticles dispersed in a water/glycerol mixture. The resulting polymer particles were characterized regarding the morphology, size, polydispersity, iron content, and the temperature-dependent phase transition using optical microscopy, transmission electron microscopy, scanning electron microscopy, atomic absorption spectroscopy, and differential scanning calorimetry. Magnetic properties were examined using hysteresis loop measurements and by analyzing the magnetic susceptibility with respect to temperature. We have also investigated the influence of the concentration of γ-Fe₂O₃ and GA in monomers on properties of the particles (morphology, size, and presence of oxirane groups). The particles possessed a hollow structure as a result of phase separation between water/glycerol hydrophilic solvents in the polymerization feed and the forming polymer. Depending on the concentration of γ-Fe₂O₃ in the monomer phase, the magnetic hollow particles contained 5–24 wt% iron. In water, the particles gradually collapsed when the temperature was raised to 40 °C because the elevated temperature weakened hydration and the PNIPAAm chains gradually became more hydrophobic.     

Synthesis and characterization of monodisperse magnetic composite particles for magnetorheological fluid materials

Monodisperse magnetic composite particles (MCP) were prepared and characterized for a study of magnetic field-responsive fluids. Magnetic composite particles used are iron oxide-coated polymer composite particles, which were synthesized through in situ coating of iron oxide onto pre-existing polymer particles by the reduction of ferrous fluids. For a uniform and bulk coating of iron oxide, the porous structure was introduced into the substrate polymer particles through a two-step seeded polymerization method. Moreover, surface cyano-functionality was born from acrylonitrile unit of substrate polymer and it played an important role in obtaining successful uniform coating. The structure of the composite particle was analyzed by using a thermo gravimetric analysis (TGA) and a X-ray diffraction (XRD) analysis. The magnetization property of the particle was also observed. Then, the rheological properties of monodisperse magnetorheological (MR) suspensions of magnetic composite particles were examined under a magnetic field using a parallel-plate type commercial rheometer. From the rheological measurements, it was found that MR properties of the magnetic composite suspensions are dependent on the iron oxide content and the fluid composition.     

Colloidal nanocomposite hydrogel particles

Quaternary ammonium salt, (3-acrylamidopropyl)-trimethylammonium chloride was used to synthesize nanohydrogel and composite particles such as inorganic–organic hybrid composites and hydrogel nanoparticles with magnetic properties utilizing a water-in-oil microemulsion system. The positively charged cationic monomer was chosen to promote silica hydrolysis and condensation to prepare silica-hydrogel nanocomposite particles with interesting morphologies. It was shown that highly monodisperse, completely charged nanohydrogel can be used to encapsulate ferrite particles. Furthermore, it was also confirmed that cationic nanohydrogel particles with variant morphology can be prepared by employing suitable silica precursor. Morphology, structure, properties, and size of nanocomposite materials were explored utilizing transmission electron microscopy, atomic force microscopy, and vibrating sample magnetometer.     

In situ metal particle preparation in cross-linked poly(2-acrylamido-2-methyl-1-propansulfonic acid) hydrogel networks

Anionic hydrogels of poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) were prepared with a different amount of cross-linker extent and used for in situ preparation of magnetic and metal particles. The metal particles with various sizes were obtained inside the three-dimensional polymer matrixes by absorption of the corresponding metal ions from their aqueous solutions followed by the reduction in the presence of strong reducing agent. In addition to iron particles, cobalt, nickel, copper nanoparticles, and CdS, quantum dot has been prepared by utilizing hydrogel matrix as a template for inorganic/organic composite synthesis. It was observed that the amount of cross-linkers (0.5%, 0.75%, and 1% with respect to monomer mole ratio) used in this study for bare p(AMPS) has not significantly influenced the morphology of the hydrogels or the size of the iron particles while having great effect on swelling of p(AMPS) hydrogels in water. Copolymeric hydrogels of AMPS with acrylamide in different composition were also prepared. Thermogravimetric analysis and transmission electron microscopy results showed that the AMPS content of the copolymeric hydrogel has great impact on both the metal ion loading capacity and the size of the resultant metal particles.     

Synthesis of dandelion-like three-dimensional nickel nanostructures via solvothermal route

The objectives of the present research are synthesizing three-dimensional （3D） nickel nanostructures and investigating their magnetic properties. Thus a template-free method was used to prepare 3D dandelion-like nickel nanostructures via reducing of nickel chloride with hydrazine hydrate in ethylene glycol solution at 100 ℃. The resulting Ni nanostructures were characterized by means of powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and selected-area electron diffraction （SAED）. And the magnetic properties of the 3D Ni nanostructures were measured as well. Results indicated that solvothermal process could be successfully used to prepare 3D dandelion-like nanostructures of Ni at a relatively mild temperature of 100℃. And the conclusions were made as follows： as-prepared Ni samples had obvious shape anisotropy and were composed of fine nanocrystallites, while they had significantly enhanced ferromagnetic properties than bulk Ni and Ni nanoparticles.     

交流碳弧法合成碳包碳化铁纳米晶

采用交流碳弧法高效合成碳包碳化铁纳米晶磁性微粉,磁性微粉产率达90%以上.用热重分析法(TG)测得磁性微粉中Fe的质量分数为17.5%.X射线衍射(XRD)分析结果表明,在碳包碳化铁微粉中存在Fe₃C和Fe₅C₂两种结构形式,不含纯Fe晶粒,碳层结构与石墨相似.在透射电镜(TEM)下观察了纳米晶的形貌和粒径分布,碳化铁纳米晶尺寸分布在3～10nm,并呈颗粒状分散在碳层中,碳层为巴基管和巴基葱的堆积体,形状各异,尺寸分布在几十纳米到几微米之间.讨论了碳包碳化铁纳米晶的形成机理.测定了磁性微粉的磁滞回线,其饱和磁感应强度Bs,剩磁Br和矫顽力Hc分别为2.6×10^-2T,2.5×10^-3T和5.52kA/m.     

Synthesis, morphology, and magnetic characterization of iron oxide nanowires and nanotubes

We have explored the synthesis of iron oxide particles, tubes, and fibrils within the pores of nanoporous polycarbonate and alumina membranes. The membranes contain uniformly distributed cylindrical pores with monodispersed diameters (varying between 20 and 200 nm) and thicknesses of 6 and 60 microm, respectively. By hydrolysis and polymerization of iron salts, particles of different sizes and phases were formed in the pores, building iron oxide particle nanowires. Alternatively, by the sol-gel technique, using as reagents metalloorganic compounds, fibrils and tubes of different iron oxide phases were prepared. Structural and morphological investigations performed using scanning electron microscopy and transmission electron microscopy revealed ordered iron oxide particle wires, tubes, and fibrils formed inside the membrane nanopores. Magnetic characterization was accomplished with a vibrating sample magnetometer. Below the blocking temperature (T(B)), the magnetic behavior of the nanowires was governed by dipolar interaction between nearest-neighbor nanoparticles inside the pore, whereas the energy barrier, and therefore the T(B) value, was mainly governed by dipolar interaction between magnetic moments over larger (interpore) distances. As expected, crystalline iron oxide nanotubes exhibited magnetic perpendicular anisotropy due to their magnetocrystalline and shape anisotropy.     

两亲磁性高分子微球的合成与表征

在Fe3O4磁流体存在下 ,通过苯乙烯与聚氧乙烯大分子单体 (MPEO)分散共聚制备两亲磁性高分子微球 .研究了聚氧乙烯大分子单体对微球粒径的影响 .用扫描电子显微镜 (SEM)、原子力显微镜 (AFM)表征了磁性微球的粒径、表面形貌以及表面粗糙度 ,用傅立叶红外光谱 (FTIR)鉴定了共聚物的结构 .随着聚合物中聚氧乙烯大分子单体含量的增加 ,微球表面的粗糙度增加 ,通过改变共聚物中MPEO的含量 ,可以得到含有 0 4～ 3 5mg g羟值的两亲磁性高分子微球     

Effect of the swelling degree on the formation of magnetite nanoparticles in hydrogels

Composites containing magnetite nanoparticles in poly(acrylamide-co-hydroxyethylacrylate) cross-linked using poly-ethylene-glycol-diacrylate were prepared and characterized. The magnetite was synthesized in situ in the polymer network by treatment with a water solution of Fe (II) and Fe (III). The salts were then coprecipitated by exposing the swollen gels to ammonia vapors and the obtained magnetic gels dried. The ratio acrylamide (AM)/hydroxyethylacrylate (HEA) was varied to compare matrices with different hydrophilicity. Moreover solutions with different concentration of iron salts were used to swell the gels. The effect of both the network composition and the concentration of iron salts in the swollen polymers on the final structure and properties of the dried magnetic polymers were studied. The investigation was carried out by means of electron diffraction, X-ray diffraction, vibrating sample magnetometry, small angle X-ray scattering and transmission electron microscopy. The coercivity of the magnetic composites prepared was close to zero and they provided super-paramagnetic properties. The decrease of the acrylamide content in the polymer gel and of the iron salts concentration in the swelling aqueous solution leads to the formation of amorphous particles of iron oxide. The average sizes of the magnetite nanoparticles obtained are compared.     

基于Pickering乳液的磁性高强水凝胶的制备及性能表征

合成了一种磁性Fe3O4纳米颗粒稳定的水包油(O/W)Pickering乳液并以其作为交联剂,在适宜条件下引发单体丙烯酰胺聚合来制备了一种新型的磁性高强复合水凝胶.采用X射线衍射(XRD)及场发射扫描电子显微镜(SEM)分别对磁性Fe3O4纳米颗粒和复合水凝胶的结构进行了表征,结果表明Pickering乳胶粒子较均匀地分布在复合凝胶网络中.溶胀性能测试及溶胀动力学分析表明复合水凝胶具有良好的溶胀性能,能够吸收自身干重100倍左右的水,其溶胀过程不遵循Fickian扩散模型;拉伸测试表明该水凝胶具有优异的力学性能,其拉伸强度能够达到150 kPa左右,断裂伸长率能够达到300%左右,并且当其承受的应力释放后能快速地恢复到初始形态.磁性能测试的结果显示该水凝胶具有良好的磁性.     

Preparation and characterization of BiFeO3 ceramic

From the technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate materials is limited. One of them, BiFeO₃, has critical conditions for synthesizing single phase since the temperature stability range of the phase is very narrow. Hence, various aspects of BiFeO₃ system have to be studied.

Fine particles of BiFeO₃ are obtained using a wet chemical route (combustion technique) and compared with the same product prepared by classic solid state reaction. The sintering programs have been varied in order to investigate the mechanism reactions and to show the relation between the microstructures and the magnetoelectric behavior.

The samples are characterized by using various techniques: X-ray diffraction (XRD) study is carried out for phase determination and lattice parameter calculations; scanning electron microscopy (SEM-EDX) and TEM to find out grain size and morphology; differential thermal analysis (DTA) to determine transformations of the starting materials. The obtained bulk materials were characterized (density, porosity, etc.) and correlated with the phase composition present in the samples. Electric and magnetic properties were evaluated.

This study underlines the role of the preparation route on the structural and morphological characteristic of the obtained materials and their influence on the magnetoelectric behavior.     

Synthesis and Characterization of Magnetic TiO2/SiO2/NiFe2O4 Composite Photocatalysts

Magnetic TiO2/SiO2/NiFe2O4 composite photocatalytic particles with high crystalline TiO2 shell were synthesized via a mild solution route.The prepared composite particles were characterized with X-ray diffraction(XRD),transmission electron microscopy(TEM),high resolution transmission electron microscopy(HRTEM),scanning electron microscopy(SEM),ultraviolet-visible(UV-Vis) spectroscopy and vibrating sample magnetometer(VSM).The results show that the obtained TiO2/SiO2/NiFe2O4 composite particles were composed...