Synthesis and characterization of magnetic bioactive glass-ceramics containing Mg ferrite for hyperthermia

Novel magnetic bioactive glass-ceramics (M GC) were synthesized by doping Mg ferrite to wollastonite–fluorapatite-containing glass-ceramics. The phase composition was investigated by XRD. The magnetic property was measured by VSM. The in vitro bioactivity was investigated by simulated body fluid (SBF) soaking experiment. Cell growth on the surface of the material was evaluated by co-culturing osteoblast-like ROS17/2.8 cells with M GC. The results showed that CaSiO₃, Ca₂MgSi₂O₇, Ca₅(PO₄)₃F and Fe₂MgO₄ were the main phases of M GC. Under a magnetic field of 10,000 Oe, the saturation magnetization and coercive force of M GC were 7.2 emu/g and 175 Oe, respectively. After soaking in SBF for 14 days, a lot of hydroxyapatite containing CO₃^2? was observed on the surface of M GC. The experiment of co-culturing cells with M GC showed that osteoblast-like ROS17/2.8 cells could attach well on the surface of M GC. The material has the potential to be used as thermoseeds for hyperthermia.     

Synthesis, characterization and magnetic properties of nanocrystalline Ni-Zn-Co ferrites

Nanocrystalline magnetic particles of Ni_0.7−xZn_0.3Co_xFe₂O₄ with x lying between 0.0 and 0.3 were synthesized by combustion method using metal nitrates, sucrose and polyvinyl alcohol (PVA). The synthesized powders where characterized by X-ray diffraction and Transmission electron microscopy (TEM). The average crystallite size determined from XRD data using Scherrer formula lie in the range of 20-30 nm. TEM micrographs show a well defined nano-crystallite state with an average particle size of around ~ 10 nm. The electron diffraction patterns confirm the spinel crystal structure of the ferrite. Magnetic properties measured at room temperature by vibrating sample magnetometer (VSM) reveal an increase in saturation magnetization with increase in cobalt concentration. Non-linear increase in saturation magnetization is related to surface effects and method of preparation.     

Synthesis and characterization of nickel ferrite magnetic nanoparticles

Nickel ferrite (NiFe₂O₄) nanoparticles are prepared by a polyvinyl alcohol (PVA) assisted sol-gel auto-combustion method. The structure, composition, morphology and magnetic properties of the gel precursor are characterized by powder XRD, FT-IR, TGA, HR-SEM, TEM, HR-TEM and VSM. XRD confirms the formation of single-phase nickel ferrite with space group of Fd3m and inverse spinel structure. The vibration properties of nanoparticles are analysed by FT-IR spectrum. The thermal decomposition of the gel precursors is investigated by TGA. HR-SEM and TEM images show that the particles have spherical shape with particle size in the range of ∼30 nm and consistent with XRD result. The magnetic properties of these nanoparticles are studied for confirming the ferromagnetic behaviour at room temperature.     

Synthesis, characterization and devitrification behaviour of an yttrium containing boroaluminate glass

The glass forming region in the B₂O₃-Al₂O₃-Y₂O₃ composition diagram has been determined by a melting and quenching procedure at temperatures up to 1800°C. Different physical characteristics (density, coefficient of thermal expansion, glass transition and crystallization peak temperatures) have been determined for a 35B₂O₃-40Al₂O₃-25Y₂O₃ glass composition (in mol.%). By using a predictive model and some NMR structural data, different elastic moduli (Young's modulus, bulk modulus, shear modulus and Poisson's ratio) have been calculated. The devitrification behaviour has also been studied. Internal crystallization is the dominant mechanism and a new (Y, Al)BO₃ ternary phase has been characterized by X-ray powder diffraction. The temperature and time nucleation dependence have been determined from DTA experiments as well as the crystallization kinetics (i.e. the Avrami exponent and the activation energy for crystal growth).     

Preparation and structural characterization of vulcanized natural rubber nanocomposites containing nickel-zinc ferrite nanopowders

Single-phase polycrystalline mixed nickel-zinc ferrites belonging to Ni0.5Zn0.5Fe2O4 were prepared on a nanometric scale (mean crystallite size equal to 14.7 nm) by chemical synthesis named the modified poliol method. Ferrite nanopowder was then incorporated into a natural rubber matrix producing nanocomposites. The samples were investigated by means of infrared spectroscopy, X-ray diffraction, scanning electron microscopy and magnetic measurements. The obtained results suggest that the base concentration of nickel-zinc ferrite nanoparticles inside the polymer matrix volume greatly influences the magnetic properties of nanocomposites. A small quantity of nanoparticles, less than 10 phr, in the nanocomposite is sufficient to produce a small alteration in the semi-crystallinity of nanocomposites observed by X-ray diffraction analysis and it produces a flexible magnetic composite material with a saturation magnetization, a coercivity field and an initial magnetic permeability equal to 3.08 emu/g, 99.22 Oe and 9.42 x 10(-5) respectively.     

Apatite-forming ability and magnetic properties of glass-ceramics containing zinc ferrite and calcium sodium phosphate phases

Fine particles of zinc ferrite (ZnFe₂O₄) and calcium sodium phosphate [NaCaPO₄] were crystallized in bulk x(ZnO, Fe₂O₃)(65?x)SiO₂20(CaO, P₂O₅)15Na₂O (6 ≤ x ≤ 21 mol %) glassy matrix by heat treatment. Initial magnetization curves reveal that samples with x = 6 and 9 mol % zinc–iron oxide exhibit both ferrimagnetic and paramagnetic contributions, whereas, samples with x > 9 mol % zinc–iron oxide exhibit only ferrimagnetic contribution. This observation is supported by the disappearance of the electron paramagnetic resonance (EPR) absorption line centered at g ≈ 4.3 in samples with x > 9 mol % zinc–iron oxide. Apatite-forming ability of the glass-ceramic samples was investigated by examining apatite formation on the surface of the samples treated in simulated body fluid (SBF). Increase in apatite-forming ability was observed with an increase in zinc–iron oxide content. The results obtained have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass-ceramic composition. A good correlation has also been observed between the magnetic nature of the samples and their apatite-forming ability. These materials are expected to find application as thermo-seeds in hyperthermia treatment of bone cancer.     

Preparation and gas-sensing characteristics of nanocrystalline spinel zinc ferrite thin films

Zinc ferrite is a promising sensor material. In this paper, thin films of nanocrystalline zinc ferrite were deposited on alumina substrates by nebulization of a 0.01-M solution of a mixture of ZnCl/sub 2/ and FeCl/sub 3/ in ethanol (Zn:Fe=1:2) followed by pyrolysis and annealing in flowing air. The resulting films were characterized by X-ray diffraction and scanning electron microscopy, and the gas-sensing properties of as-deposited films were also investigated.     

Synthesis and characterization of zinc ferrite nanoparticles obtained by self-propagating low-temperature combustion method

The self-propagating low-temperature combustion method was used to produce nanocrystalline particles of zinc ferrite. The products were characterized for chemical and phase composition, morphology and magnetic properties. The results obtained showed the formation of single-phase zinc ferrite nanoparticles with an average particle size of about 40 nm. As-synthesized powder displayed good magnetic property. Due to the simplicity and low cost of this process, it could also become a valuable starting point for the generation of other mixed and complex ferrites.     

锌铁氧体的合成及磁电性能

用化学共沉淀法制备了系列锌铁氧体微粉。借助于TG-DTA、XRD、SEM、VSM和PNA技术,对干凝胶的热分解过程、产物的物相、微观结构、磁性能和介电常数进行了研究。结果表明,随煅烧温度的提高,锌铁氧体微粉的粒径增大,磁性也增强;尖晶石结构的块状锌铁氧体具有负电阻率温度系数,而且随着煅烧温度的提高,介电常数减小。     

The magnetic behaviour of nanostructured zinc ferrite

We have investigated a series of nanostructured ZnFe₂O₄ samples produced by mechanical activation (mean particle sizes d ～50-8 nm) by variable temperature neutron diffraction measurements (2-535 K) supported by DC magnetisation measurements (4.2-300 K). The systematic increase in the mean inversion parameter (c ～0.04-0.43) with increasing milling time is accompanied by a gradual decrease in the occurrence of the long range antiferromagnetic ordering observed in the starting ZnFe₂O₄ material, as well as a gradual decrease in the related diffuse short range order peak. The neutron diffraction patterns of particles with d < ～15 nm and c> ～0.2 are consistent with the occurrence of ferrimagnetic order and exchange interactions of the type Fe³⁺A—O^2?—Fe³⁺ [B]. Diagrams summarising the magnetic regions of nanostructured ZnFe₂O₄ are presented. The magnetic behaviour overall agrees well with the enhanced magnetisation and ferromagnetic behaviour reported for nanostructured, ultrafine and thin films of ZnFe₂O₄ by other groups using mainly magnetisation and Mössbauer spectroscopy measurements.     

喷射-共沉淀法合成纳米晶CoFe2O4及磁性能

用喷射-共沉淀法成功地制备了纳米晶CoFe2O4铁氧体粉料.研究了不同合成温度对产物晶体结构、微观形貌和磁性能影响.结果表明:喷射-共沉淀法制备的粉料颗粒细小均匀、形状完整.600℃下煅烧1.5h,样品晶粒尺寸为29nm左右,平均颗粒尺寸小于100nm.室温下,样品比饱和磁化强度随煅烧温度增加而增大.850℃煅烧1.5 h时,其比饱和磁化强度Ms为88.6A·m2·kg-1.当晶粒大小为29nm时,纳米晶CoFe2O4铁氧体矫顽力达到最大值64.5kA·m-1,随后又随晶粒尺寸增大而减小.这可能归因于纳米磁性材料存在强烈的晶粒尺寸效应.     

Facile synthesis of nanocrystalline zinc ferrite via a self-propagating combustion method

Macroporous nanocrystalline zinc ferrite with single spinel-phase was prepared by a facile self-propagating combustion method using zinc nitrate, iron nitrate and glycine. The as-prepared ZnFe₂O₄ were characterized by X-ray diffraction (XRD) analysis, N₂ adsorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectrum (EDS). The magnetic properties of the prepared ZnFe₂O₄ were also studied.     

Preparation and characterization of magnesium-aluminium-silicate glass ceramics

Synthesis of machinable quality magnesium aluminium silicate (MgO-Al₂O₃-SiO₂) for fabrication of insulators/spacers usable in high voltage applications under high vacuum conditions has been carried out following two different routes i.e. (i) sintering route, and (ii) glass route. A three-stage heating schedule involving calcination, nucleation and crystallization, has been evolved for the preparation of magnesium aluminium silicate (MAS) glass ceramic with MgF₂ as a nucleating agent. The effect of sintering temperature on the density of compacted material was studied. Microstructure and machinability of samples obtained from both routes were investigated. They were also characterized for microhardness. Initial studies on material obtained by glass route reveal that these samples are superior to those obtained from sintered route in respect of their high voltage breakdown strength and outgassing behaviour. Outgassing rate of 10⁻⁹ Torr l·s⁻¹ cm⁻² and breakdown strength of 160 kV/cm were obtained. Different types of spacers, lugs, nuts and bolts have been prepared by direct machining of the indigenously developed glass ceramic.     

Fe基纳米晶／铁氧体复合材料磁粉芯制备及其软磁性能

用Mn-Zn铁氧体溶胶对Fe73.5Cu1Nb3Si13.5B9纳米晶包覆,模压成型制备复合磁粉芯,并研究了铁氧体溶胶量、热处理工艺及测试温度等因素对复合材料磁粉芯软磁性能的影响.实验结果表明,随着铁氧体溶胶量的增加,磁粉芯的磁导率减小,而Q值却随铁氧体溶胶量的增加有微小的增大.复合材料磁粉芯在热处理工艺为2h,500℃时,测试频率为500kHz,磁导率达到最大值.复合磁粉芯的品质因数Q值在200～1000kHz频段中,具有波动性,Q值在500kHz时达到51.测试温度对复合磁粉芯的磁导率和品质因数均有影响,测试温度从30℃升高到80℃时,磁导率从60.1降低到58.4,变化率为2.8%,而品质因数从59下降到54.     

Modification of dielectric and mechanical properties of rubber ferrite composites containing manganese zinc ferrite

Spinel ferrites constitute an important class of magnetic materials. Polycrystalline ferrites are a complex system composed of crystallite grain boundaries and pores. Manganese zinc ferrites have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. Composite materials are ideally suited for many modern applications where ceramic materials have some drawbacks. The mouldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn_(1−x)Zn_xFe₂O₄ (MZF) were synthesized for different ‘x’ values in steps of 0.2. These pre-characterized ceramic ferrites were then incorporated in a natural rubber matrix. The dielectric properties of the ceramic manganese zinc ferrite and RFC were also studied. A program based on G programming was developed with the aid of LabVIEW package to automate the dielectric measurements. The dielectric permittivity of the RFC were then correlated with that of the corresponding dielectric permittivity of the magnetic filler and matrix by a mixture equation, which helps to tailor properties of the composites.     

Synthesis and structural characterization of novel porous zinc substituted nanohydroxyapatite powders

This study reports the synthesis of new porous nanohydroxyapatites (HAPs) substituted with different Zn contents (HAP_Zn) employing calcium and zinc nitrates and diammonium hydrogen phosphate as precursors. The synthesis was conducted in the presence of a surfactant, L-asparagine, for controlling the pore size distribution and morphology of obtained nanopowders, using a co-precipitation route. Thus a new approach leading to HAP_Zn nanopowders with improved nucleation and crystallization ability was developed. After maturation treatment of dispersions and filtration, the precipitate was lyophilized and ground. Part of the samples was calcined at 300°C for 1 h. The zinc content in the nanoHAPs varies from 0.2 to 10 wt% (substitution degree of Ca by Zn from 0.3 to 15.8 mole %). XRD investigations indicated HAP as the unique phase present and the nanostructured nature of the obtained HAPs. FTIR spectra also confirmed the presence of HAP structure. TEM, SEM, and AFM images showed the morphology of the HAP_Zn samples. BET analysis led to the characterization of specific surface area and porosity for the samples. The new nanopowders are designed to be used in orthopedic surgery, particularly for the treatment of osteoporosis and as bone substitutes, and in dentistry for remineralization of enamel.     

Synergetic effects of pulse constraints and additives in electrodeposition of nanocrystalline zinc: Corrosion,structural and textural characterization

Pulse electrodeposition was to produce nanocrystalline (nc) zinc from alkaline non-cyanide electrolyte with primary and secondary additives. The combined effect of pulse parameters (ON-time (T_ON), OFF-time (T_OFF), pulse peak current density (I_P)) and additives on the corrosion properties (evaluated using electrochemical techniques) of zinc electrodeposits are elucidated in terms of surface morphology (using scanning electron microscope), topography and root mean square (RMS) roughness (using atomic force microscope), crystallite size, its orientations and relative texture co-efficient (RTC, %) were evaluated using X-ray diffraction. The corrosion resistance of zinc electrodeposits obtained at constant T_ON and I_P enhanced (i.e., low I_corr and high R_ct values) with increased T_OFF. At constant T_OFF and I_P, the I_corr values increased and R_ct values decreased with T_ON while the former decreases and latter increases with I_P at constant T_ON and T_OFF. The inclusion of primary and secondary additives into the electrolyte produced nc zinc electrodeposits at 5 Adm^?2, showed enhanced protective properties (I_corr—16 μA cm^?2 and R_ct—481.8 Ω cm^?2). Fine grained due to high negative overpotential, reduced roughness and higher percentage of basal plane [0 0. 2] orientation have major impact for the enhanced corrosion resistances.     

Role of Mn+2 ions in monitoring structural,optical, magnetic and electrical properties of manganese zinc ferrite nanoparticles

Journal of Materials Science: Materials in Electronics - Nanocrystalline manganese zinc ferrite powders with chemical composition MnxZn1?xFe2O4 were prepared using the combustion method. The...