Modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic nanoparticles by L-dopa or dopamine as an enzyme support

Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.     

Surface organic modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic nanoparticles

The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-O- Si bond and an organic coating layer also was formed. Fe3O4 nanoparticles were spheres partly with mean size of 18,8 nm studied by TEM, which was consistent with the result 17.9 nm calculated by Scherrer＇s equation. KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.     

Controlled synthesis and magnetic properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> walnut spherical particles and octahedral microcrystals

Magnetite Fe₃O₄ walnut spherical particles and octahedral microcrystals were successfully synthesized from K₄ [Fe (CN)₆], K₃ [Fe (CN)₆] and NaOH reagents via a simple hydrothermal process. And the uniform morphology of octahedral microcrystals was obtained in the presence of ethylene glycol. The morphology and structure of products were characterized by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the Fe₃O₄ walnut spherical particles and octahedral microcrystals were single crystals with the face-center cubic structure and with size distributions from 2.2 to 8.6 μm and 1.6 to 12.5 μm, respectively. Their magnetic properties were detected by a vibrating sample magnetometer at room temperature. The walnut spherical particles exhibited a ferromagnetic behavior with the coercive force (Hc), saturation magnetization (Ms) and remanent magnetization (Mr) being 150.57 Oe, 97.634 and 12.05 emu/g, respectively. For the octahedral microcrystals they were 75.28 Oe, 101.90 and 6.69 emu/g, respectively. Different sizes of walnut spherical particles were controlled synthesized through adjusting the NaOH concentration. It was found that ethylene glycol molecules have a significant effect on the formation of Fe₃O₄ octahedra. A possible mechanism was also proposed to account for the growth of these Fe₃O₄ products. Supported by Fund of weinan Teachers University (Grant No. 08YKZ008), the National Natural Science Foundation of China (Grant No. 20573072) and Doctoral Fund of Ministry of Education of China (Grant No. 20060718010)     

Synthesis and characterization of a new Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> pillared triple-layered perovskite KSr<Subscript>2</Subscript>Nb<Subscript>3</Subscript>O<Subscript>10</Subscript>

A n-Hexyl NH₃Sr₂Nb₃O₁₀ is obtained by the stepwise ion-exchange reaction, then is dispersed in aqueous solution of trinuclear acetato-hydroxo iron (III) nitrate, [Fe₃(OCOCH₃)₇OH·2H₂O]NO₃, and the interlayer potassium cations of the perovskite niobate are exchanged with the partially hydrolyzed trinuclear acetato complex ions. On heating, the exchanged complex ions are converted into iron oxide pillars which keep the perovskite sheets apart. The product is characterized by XRD, SEM, EDAX and surface area measurement respectively. Zhang Hui: Born in 1970 Funded by the National Natural Science Foundation of China (No. 50002007), Major Program of Ministry of Education (No. 0201) and Open Foundation of State Key Lab of Advanced Tech. for Materials Synthesis and Processing.     

Nanocomposite films of V<Subscript>2</Subscript>O<Subscript>5</Subscript>−MoO<Subscript>3</Subscript> xerogel with poly ethylene oxide intercalation

Poly ethylene oxide (PEO)_x−V₂O₅−V₂O₅−MoO₃ (x=0, 0.5, 1) films were prepared by the sol-gel method. The synthesis and structure of the films were investigated by XRD, TG-DTA, FTIR, etc. The results show that V₂O₅−MoO₃ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1. 7898 nm at x=1 after the nanocomposite films were dried, and PEO in the interlayer changes the interface structure by forming hydrogen bonds with V=0 bands. CV measurement indicates that the intercalation of PEO improves insertion/extration properties of Li⁺ ions in the interlayer. ZHENG Jin-xia: Born in 1976 Funded by the National Natural Science Foundation of China (No. 50172036) and Natural Science Foundation of Hubei Province(No. 2001ABB083)     

Self-Propagating High-Temperature Reduetive Synthesis of TiB2-Al2O3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis（SHS） method with reductive process from B2O3-TiO2-AI system. X-ray diffraction（XRD） and scanning electron microscopy（SEM） analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy （TEM） and high resolution electron microscopy （HREM） observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

Preparation and ferroelectric properties of Bi<Subscript>3.4</Subscript>Ce<Subscript>0.6</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films grown by sol-gel method

We have investigated the preparation and properties of Bi_3.4Ce_0.6Ti₃O₁₂ thin films. The Bi_3.4Ce_0.6Ti₃O₁₂ thin films were fabricated on the Pt/Ti/SiO₂/Si substrates using sol-gel method. The structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The thin films showed a perovskite phase and dense microstructure. The dielectric constant and the dissipation factor of the Bi_3.4Ce_0.6Ti₃O₁₂ thin films were about 172 and 0.031 at 1 kHz, respectively. The 2P _r and 2E _c of the Bi_3.4Ce_0.6Ti₃O₁₂ thin films were 67.1 μC/cm² and 299.7 kV/cm, respectively, under an applied field of 600 kV/cm. The Bi_3.4Ce_0.6Ti₃O₁₂ film did not show fatigue up to 4.46×10⁹ switching cycles at a frequency of 1 MHz, and showed good insulating behavior according to the test of leakage current. Supported by the Natural Science Foundation of Hubei Province (Grants No. 2004ABA082)     

Fabrication and magnetic properties of Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanocomposite permanent magnetic material

Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanometer magnetic material was fabricated through rapid solidification, crystallization and nitridation of Sm-Fe (Ti) alloy. The effect of combination of rapid solidification and Ti alloy addition on the phase formation and microstructure of the Sm-Fe alloy is investigated in this paper. The microstructure of amorphous phase and dual-phase nano-grain crystals before and after crystallization annealing were observed using a high-resolution transmission electron microscope (HREM). The dual-phase nano-grains after annealing were compacted together with a clear interface with the direct exchange-coupling mechanism. Different annealing processes were used to examine the melt-spun alloy. Comparison of the images of SEM showed that annealing at 750℃ for 10 min was most suitable to get homogeneous and nano-grains. No obvious kink was detected in the second quadrant of the hysteresis loop like a single hard magnet, and strong exchange coupling was found between hard magnets and soft magnets.     

Dielectric Behavior of BaTiO3／ PVDF Nanocomposites In-situ Synthesized by the Sol-Gel Method

BaTiO3/ PVDF nanocomposites were prepared via in-situ growth of nanosized BaTiO3 particles in PVDF matrix by using the sol-gel method. The present elements of BaTiO3/ PVDF nanocomposites were analyzed by an electron probe X-ray microanalyser. Nanosized BaTiO3 grown in the composite films was characterized by an X-ray diffractometer and a transmission electron microscope, and the dielectric properties of the composite films were measured. The distribution of BaTiO3 nanoparticles in-situ grown in the PVDF matrix was examined using a scanning electron microscope.     

Synthesis and characterization of (PEO)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>−(V<Subscript>0.85</Subscript>Mo<Subscript>0.15</Subscript>)<Subscript>2</Subscript>O<Subscript>5</Subscript> nanocomposite films

(PEO) _x −(V_0.85Mo_0.15)₂O₅(x=0,0.5,1.0) nanocomposite films were prepared by a modified sol-gel method. The structure of the films was analyzed by XRD, and the DC electrical conductivity. Cyclic voltammogram and optical spectral transmittance were investigated. The results show that the (V_0.85Mo_0.15)₂O₅ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1.7897 nm at x=1.0. The introduction of MoO₃ improved the DC electrical conductivities of the films due to the generation of V₄₊ to maintain the electrical neutrality of the oxides. PEO intercalated in the interlayer of (V_0.85Mo_0.15)₂O₅ oxides has interaction with the oxides, enhancing the amount of Li⁺ ions inserted into the interlayer of the oxides. Moreover, the intercalation of PEO into the interlayer of (V_0.85Mo_0.15)₂O₅ oxides improved the cathodic electrochromic property in near ultraviolet region and anodic electrochromic property in visible range. JIANG Cong-sheng: Born in 1963 Supported by the Science Foundation of Hubei Province (Grant No. 2001ABB083)     

Microstructures and mechanism of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al composites fabricated by the reaction between SiO<Subscript>2</Subscript> and molten aluminum

Al₂ O₃/Al composite was fabricated by the reaction between SiO₂ and molten aluminum. The microstructures of the composite obtained under different reaction conditions were analyzed. The formation mechanism of the composite microstructure was discussed. Results show that the reaction kinetics is influenced remarkably by the reaction temperature, reaction time and the quantity of SiO₂. The morphologies of Al₂O₃ have different features, depending on the reaction temperature. The composite has equaxed Al₂O₃ grains when materials reacted below 1200°C, and the composite is composed of a large number of fine Al₂O₃ grains and aluninum. The composite has a frame-shaped Al₂O₃ microstructure at the reaction temperature of above 1250°C. CHENG Xiao-min: Born in 1964 Funded by the National Natural Science Foundation of China (No. 91522)     

Synthesis of Ti3SiC2/TiB2 Composite by In-situ Hot Pressing （HP） Method

Ti3SiC2/TiB2 composite was successfully obtained by hot pressing Ti/TiC/Si/B4C power mixtures.Volume fraction of TiB2 in Ti3SiC2/TiB2 composite can not exceed 10%.Incorporation of excessive TiB2 will affect the reactions process.TiC and Ti5Si3 were two important intermediate phases during the whole reactions.The microstructure characteristics of the Ti3SiC2/TiB2 composites were analyzed using scanning electron microscopy （SEM） and transmission electron microscopy （TEM）.The experimental results show that the grains of Ti3SiC2/TiB2 composite are structured in a layered form,and the formation of TiB2 particles as reinforcements with elongated or equiaxed shape distributes in Ti3SiC2 matrix.     

Effect of La doping on microstructure and ferroelectric properties of Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films prepared by sol-gel method

The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.     

Novel preparation and XPS analysis of V<Subscript>2</Subscript>O<Subscript>5</Subscript> xerogel

The V₂O₅ sol was fabricated by ultra-fast quenching. The vanadium with low valence (V⁴⁺) was found in V₂O₅ xerogel films by XPS analysis. The technology of oxygen top-blown was applied to analyze the XPS spectrum difference of V₂O₅ xerogel when the powder of V₂O₅ was melting in air or in oxygen atmosphere. The results show that the different melting atmosphere has certain influences on the chemical valence of V₂O₅ xerogel. ZHU Quan-yao: Born in 1968 Funded by the National Natural Science Foundation of China (No. 50172036, No. 59802009)     

Orientation of Bi<Subscript>3.2</Subscript>La<Subscript>0.8</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> ferroelectric thin films with different annealing schedules

Fatigue-free Bi_3.2La_0.8Ti₃O₁₂ ferroelectric thin films were successfully prepared on p-Si (100) substrates using metalorganic solution deposition process. The orientation and formation of 5-layers thin films were studied under different processing conditions using XRD. Experimental results indicate that increase in annealing time at 700 °C after preannealing for 10 min at 400 °C can remarkably increase (200)-orientation of the films derived from the precursor solutions with two contents of citric acid. Meanwhile, high content of citric acid increases the film thickness and is conducive to the a-orientation of the films with the preannealing, and low concentration of the solution is conducive to the c-orientation of the films without the preannealing.     

Synthesis and characterization of biomimetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/coke magnetic nanoparticles composite material

A composite material (Fe₃O₄/Coke) using coke supported Fe₃O₄ magnetic nanoparticles was successfully prepared via an in-situ chemical oxidation precipitation method and characterized by SEM, XRD, Raman, and FTIR. The results showed that the Fe₃O₄ nanoparticles existed steadily on the surface of coke, with better dispersing and smaller particle size. The catalytic ability of Fe₃O₄/Coke were investigatied by degrading p-nitrophenol (P-NP). The results showed that the apparent rate constant for the P-NP at 1.0 g·L^?1 catalyst, 30 mmol·L^?1 H₂O₂, pH=3.0, 30 °C and the best ratio of Coke/Fe₃O₄ 0.6, was evaluated to be 0.027 min^–1, the removal rate of COD_Cr was 75.47%, and the dissolubility of Fe was 2.42 mg·L^–1. Compared with pure Fe₃O₄, the catalytic ability of Fe₃O₄/Coke in the presence of H₂O₂ was greatly enhanced. And Fe₃O₄/Coke was a green and environmental catalyst with high catalytic activity, showing a good chemical stability and reusability.     

High-temperature oxidation behavior of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiAl matrix composite in air

The oxidation behavior of Al₂O₃/TiAl in situ composites fabricated by hot-pressing technology was investigated at 900° in static air. The results indicate that the mass gains of the composites samples decrease gradually with increasing Nb₂O₅ content and the inert Al₂O₃ dispersoids effectively increase the oxidation resistance of the composites. The higher the Al₂O₃ dispersoids content, the more pronounced the effect. The primary oxidation precesses obey approximately the linear laws, and the cyclic oxidation precesses follow the parabolic laws. The oxidized sample containing Ti₂AlN and TiAl phases in the scales exhibits excellent oxidation resistance. The oxide scale formed after exposure at 900°C for 120 h is multiple-layered, consisting mainly of an outer TiO₂ layer, an intermediate Al₂O₃ layer, and an inner TiO₂+Al₂O₃ mixed layer. From the outer layer to the inner layer, TiO₂+Al₂O₃ mixed layer presents the transit of Al-rich oxide to Ti-rich oxide mixed layer. Near the substrate, cross-section micrograph shows a relatively loose layer, and micro- and macro-pores remain on this layer, which is a transition layer and transferres from Al₂O₃+TiO₂ scale to substrate. The thickness of oxide layer is about 20 μm. It is also found that continuous protective alumina scales can not be observed on the surface of oxidation scales. Ti ions diffuse outwardly to form the outer TiO₂ layer, while oxygen ions transport inwardly to form the inner TiO₂+Al₂O₃ mixed layer. Under long-time intensive oxidation exposure, the internal Al₂O₃ scale has a good adhesiveness with the outer TiO₂ scale. No obvious spallation of the oxide scales occurs. The increased oxidation resistance by the presence of in situ Al₂O₃ particulates is attributed to the enhanced alumina-forming tendency and thin and dense scale formation. Al₂O₃ particulates enhance the potential barrier of Ti ions from M/MO interface to O/MO interface, thereby the TiO₂ growth rate decreases, which is also beneficial to improve the oxidation resistance. Moreover, the multi-structure of the TiO₂+Al₂O₃ mixed layer decreases the indiffusion of oxygen ions and also avails to improve the high temperature oxidation resistance of the as-sintered composites. Supported by the Special Program for Education Bureau of Shaanxi Province, China (Grant No. 08JK240) and Scientific Research Startup Program for Introduced Talents of Shaanxi University of Technology, China (Grant No. SLGQD0751)     

Preparation and characterization of superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/CNTs nanocomposites dual-drug carrier

Fe₃O₄/carbon nanotubes (Fe₃O₄/CNTs) nanocomposites were prepared by polylol high-temperature decomposition of the precursor ferric chloride and CNTs in liquid triethylene glycol. After surface modification with hexanediamine, folate was covalently linked to the amine group of magnetic Fe₃O₄/CNTs nanocomposites. The products were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. Then Fe₃O₄/CNTs were used as a dual-drug carrier to co-delivery of the hydrophilic drug epirubicin hydrochloride and hydrophobic drug paclitaxel. The results indicated that the Fe₃O₄/CNTs had a favorable release property for epirubicin and paclitaxel, and thus had potential application in tumor-targeted combination chemotherapy.     

Formation of bulk ferromagnetic nanostructured Fe<Subscript>40</Subscript>Ni<Subscript>40</Subscript>P<Subscript>14</Subscript>B<Subscript>6</Subscript> alloys by metastable liquid spinodal decomposition

Nanostructured Fe₄₀Ni₄₀P₁₄B₆ alloy ingots of 3–5 mm in diameter could be synthesized by a metastable liquid state spinodal decomposition method. For undercooling ΔT > 260 K, the microstructure of the undercooled specimen had exhibited liquid state spinodal decomposition in the undercooled liquid state. The microstructure could be described as two intertwining networks with small grains dispersed in them. For undercooling ΔT > 290 K, the overall microstructure of the specimen changed into a granular morphology. The average grain sizes of the small and large grains are ≅ 30 nm and ≅ 80 nm, respectively. These prepared samples are soft magnets with saturation magnetization B _s ≅ 0.744 T. Supported by the Hong Kong Research Grants Council the National Natural Science Foundation of China (Grant No. 50861007) and Xinjiang University Doctoral Research Start-up Grant (Grant No. BS050102)     

The influence of mo additive on the microstructure and property of Ti/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite

The influence of Mo on the microstructure, bending strength and HV of Ti/Al₂O₃ composite was studied, and the influence mechanism was analyzed. The results indicate that after the addition of Mo, the composite organization is finer and phases distribution is better-proportioned which make the microstructure denser, the bending strength and HV of composite are also increased to a degree. But the bending strength increases first then decreases with the increasing of Mo content, so the appropriate Mo content for the Ti/Al₂O₃ composite is to be further confirmed. WANG Zhi: Born in 1962 Funded by Natural Science Foundation of China (No. 50232020) and Natural Science Foundation of Shandong Province (No. 2002F21)