Mechanosynthesis of nanostructured magnetic Ni-Zn ferrite

Nanocrystalline Ni-Zn ferrite (NiZnFe₂O₄) was directly produced by high energy ball milling of stoichiometric mixture of ZnO, NiO, Fe₂O₃ powders. X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), simultaneous thermal analysing (STA), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM) were carried out to characterize the structural, chemical and magnetic aspects of NiZnFe₂O₄ compound. The formation of NiZnFe₂O₄ phase appeared to involve two stages; development of Zn ferrite by diffusion of ZnO in Fe₂O₃ followed by diffusion of NiO in Zn ferrite to form Ni-Zn ferrite. The crystallite size of final product after 60 h of ball milling time was estimated to be 18 nm which increased to 45 nm after annealing at 800 °C for 4 h. After annealing of ball milled powders, the saturation magnetization was increased and coercivity was decreased as lattice defects and internal strain reduced.     

介孔羟基磷灰石的合成及药物释放性能研究

本文采用水热合成法,制备出介孔羟基磷灰石,该材料具有较高比表面积和较大的孔容,药物缓释性能测试表明,材料具有较高的药物组装率和较好药物缓释性能,因此,可以作为药物缓释载体,从而更好地实现对骨组织的修复。     

Synthesis and characterization of Tb/Gd dual-doped multifunctional hydroxyapatite nanoparticles

Tb³⁺/Gd³⁺ dual-doped multifunctional hydroxyapatite (Tb³⁺/Gd³⁺-HAp) nanoparticles with magnetic and luminescent properties were prepared by the co-precipitation method using CaCl₂ and Na₂HPO₄·12H₂O as raw materials and CTAB as a template in alkaline conditions. The products were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). Single hexagonal phase Tb³⁺/Gd³⁺-HAp nanoparticles were obtained by the co-precipitation method and the products were sphere-like morphology with particle sizes ranging from 40 to 100 nm. Crystallinity degree of the products decreased with the Tb³⁺/Gd³⁺ substitute increasing. Photoluminescence (PL) and magnetic properties of the products were also investigated. The results show Tb³⁺/Gd³⁺-HAp nanoparticles are endowed with strong luminescence at 544 nm and prominent paramagnetic behavior, allowing their potential applications in biological labeling. Gd³⁺ ions sensitize the ⁵D₄-⁷F₅ transition emission of Tb³⁺ ions in HAp nanoparticles, and the PL emission intensity increases along with increasing concentration of Gd³⁺ ions. Concentration quenching occurs when the Gd³⁺ concentration exceeds 10 mol%. The magnetization level of Tb³⁺/Gd³⁺-HAp increased steadily with the doping concentration of Gd³⁺ ions.     

Microwave-assisted solution synthesis,microwave sintering and magnetic properties of cobalt ferrite

A simple, soft, and fast microwave-assisted hydrothermal method was used for the preparation of nanocrystalline cobalt ferrite powders from commercially-available Fe(NO₃)₃?9H₂O, Co(NO₃)₂?6H₂O, ammonium hydroxide, and tetrapropylammonium hydroxide (TPAH). The synthesis was conducted in a sealed-vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized by XRD, FE-SEM, TEM, and HR-TEM. After a systematic study of the influence of the microwave variables (temperature, reaction time and nature of the bases), highly crystalline CoFe₂O₄ nanoparticles with a high uniformity in morphology and size, were directly obtained by heating at 130?°C for 20?min using the base TPAH. Dense ceramics of cobalt ferrite were prepared by non-conventional, microwave sintering of synthesized nanopowders at temperatures of 850–900?°C. The magnetic properties of both the nanopowders and the sintered specimens were determined in order to establish their feasibility as a permanent magnet.     

Synthesis of ordered mesoporous carbon/cobalt oxide nanocomposite for determination of glutathione

In the paper, a novel ordered mesoporous carbon/cobalt oxide nanocomposite (OMC–Co) was easily synthesized. After encapsulating cobalt oxide nanoparticles in the wall of the ordered mesoporous carbon (OMC), the mesostructure of the nanocomposite material remained highly ordered and intact. For the first time, OMC–Co material was used to modify the glassy carbon (GC) electrode, and the obtained OMC–Co/GC modified electrode showed strong electrocatalytic properties towards glutathione (GSH). The use of OMC–Co film to mediate the GSH oxidation exhibited remarkably strong and stable electrocatalytic response compared to that seen at OMC/GC electrode. These results showed that the electrocatalytic properties of OMC could be improved when the cobalt oxide nanoparticles were incorporated into this new material. A sensitive GSH sensor was developed based on the OMC–Co/GC electrode, which showed a high sensitivity and a remarkably low detection limit. Moreover, OMC–Co/GC modified electrode can be used for selective amperometric determination of GSH in the presence of glucose, dopamine (DA) and uric acid (UA).     

Effect of the thermal treatment on the magnetic and structural properties of cobalt ferrite particles

We herein report a study on the sol-gel synthesis of CoFe₂O₄ and the effect of thermal treatment on the product outcome. Xerogels treated at 750, 800 and 850 °C had their structural and magnetic properties thoroughly studied, in order to correlate their synthesis conditions to the positions in which the cations are inserted in the spinel structure. X-ray diffractograms exhibit reflections representative of the spinel structure and demonstrate that the thermal treatment does not affect the lattice parameters of the material. Mossbauer spectroscopy studies indicate a very low inversion degree in the synthesized spinels, which is very unusual for CoFe₂O₄. A maximum in coercivity of 1405.2 Oersted was achieved for the sample treated at 800 °C.     

Synthesis and properties of HA/ZnO/CNT nanocomposite

The goal of this study was to examine the tribomechanical properties of hydroxyapatite (HA)/ZnO and HA/ZnO/CNT composite ceramics (carbon nanotubes; with different ratios 0.5?wt%, 1.0?wt%, and 1.5?wt%). The composites were synthesized using the hydrothermal method in an autoclave. The structure and morphology of the composites were analyzed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX) and transmission electron microscope (TEM). The consolidation process was performed by sintering the compounds at 1150?°C under an argon gas atmosphere. The effects of ZnO and CNT on the mechanical properties and wear resistance of the HA-nanoparticle-based ceramic composites were investigated using a Vickers hardness tester, nanoindentation, and reciprocating wear tester equipment. The nanohardness and elastic modulus of the sintered samples increased and the friction coefficient of the sintered samples decreased as the fraction of CNTs increased compared to the pure HA and HA/ZnO compounds. Furthermore, the wear loss of HA/ZnO/CNT composites decreased with the increase in the CNT content compared to the HA and HA/ZnO samples.     

Sintering and mechanical properties of MgO-doped nanocrystalline hydroxyapatite

Hydroxyapatite (HA) has been extensively studied for its exceptional ability in promoting osseointegration as in bone graft substitute and biomimetic coating of prosthetic implants. However poor mechanical properties of HA, in particular its low fracture toughness, has made its widespread adaption in a number of biomedical applications challenging. Here we employ an optimized wet precipitation method to synthesize nanocrystalline HA with significantly improved mechanical properties. In addition doping by MgO is found to effectively suppress grain growth and enhance fracture toughness by nearly 50% while good densification and phase stability in all samples regardless of concentration of dopant are fully maintained. Microstructural analysis further suggests that the exceptionally superior mechanical properties can be explained by migration of MgO to grain boundaries where they transform the more common transgranular fracture into an intergranular mode. Our biodegradation tests also confirm that MgO-doped HA is indeed a suitable candidate for load bearing implants.     

Effect of fluoride additive on the mechanical properties of hydroxyapatite/alumina composites

The effect of fluoride additives on the mechanical properties of hydroxyapatite/alumina composites was investigated. When MgF₂ (5 vol%) was added to hydroxyapatite/alumina composites, the decomposition of hydroxyapatite was suppressed due to the substitution of F⁻ for OH⁻ in the crystal structure. Comparing two additives, such as MgF₂ and CaF₂, MgF₂ showed much more effective for the suppression of phase decomposition in the hydroxyapatite/alumina composites due to the enhanced substitution of F⁻ for OH⁻. In the case of MgF₂ addition, a relatively high-mechanical properties (flexural strength: ∼170 MPa; Vickers hardness: ∼7 GPa) was obtained compared to MgF₂-free composites.     

Synthesis and characterization of ceramic - polymer composites containing bioactive synthetic hydroxyapatite for biomedical applications

Presented research involved preparation of hydroxyapatite and synthesis of composites based on gelatin, albumin and polyvinylpyrrolidone (PVP) modified with the obtained compound. Hydroxyapatite was attained as a product of two-stage processing of pig bones. Applied procedure involved hydrolysis of the raw material in acidic environment and double calcination. Molar ratio Ca/P of hydroxyapatite has been determined and its chemical structure has been characterized using X-ray diffraction and FT-IR spectroscopy. Ratio Ca/P calculated on the basis of conducted research was 1.50?±?0.05. Thus prepared material met the ISO requirements, which assume that the Ca/P ratio should be in the range 1.5–2.0, which qualifies the material for further studies. Next, series of polymer matrix on the basis of gelatin, albumin and polyvinylpyrrolidone (PVP) has been synthesized and subjected to some analyzes. On the basis of the conducted studies, matrixes with the most favorable features such as desirable strength, flexibility and crosslinking degree were modified with previously prepared hydroxyapatite. Surface morphology and elemental composition of the composites have been analyzed using SEM-EDS method. Additionally, sorption capacity of modified composites and their behavior in simulated body fluids have been determined. Based on the conducted research it can be concluded that pig bones represent a good material for preparation of hydroxyapatite. Furthermore, composites based on proteins of natural origin modified with attained hydroxyapatite constitute a promising material that can be used for biomedical purposes.     

Investigation of the magnetic properties of nanometric SrSmCoNi ferrite/PST matrix

Y-type hexa-ferrite Sr_1.8Sm_0.2Co₂Ni_1.50Fe_10.50O₂₂ was synthesized via micro-emulsion route. Ferrite/PST composites were obtained by mixing the different ferrite ratio in the pure PST matrix. The microstructure was examined by scanning electron microscopy (SEM) and exhibited heterogonous distribution of grains. A keen observation of these SEM images revealed that the grain morphology changes noticeably with increasing ferrite filler contents. The electrical modulus, Cole–Cole plots and quality factor of ferrite polymer composites have been investigated in the frequency range (1 MHz to 3 GHz). The field dependent magnetic properties of the prepared samples were investigated at room temperature by using vibrating sample magnetometer (VSM). The shape of hysteresis loops and linearity of M_s, M_r, H_c values vs. ferrite contents unfold that the ferrite nanoparticles are evenly dispersed within the composite. The occurrence of resonance at high frequency suggests that the present investigated composite samples are best candidate for multilayer chip inductors.     

Optimized Zn-doped hydroxyapatite/doxorubicin bioceramics system for efficient drug delivery and tissue engineering application

The synthesis and fabrication of multifunctional nanostructures with enhanced biocompatibility are the most important characteristics for biomedical research. The goal of our present research is to study the optimum zinc (Zn)-loading on pure hydroxyapatite (HAp) bioceramics and its potential advantages in biomedical application. In this study, different mole concentrations (1, 2, 5 mol%) of Zn doped HAp (Zn-HAp) nanoparticles were synthesized through a facile co-precipitation technique using zinc nitrate as a source for Zn metal. The synthesized Zn-HAp nanoparticles were critically characterized for their structural and morphological changes by different spectroscopy and electron microscopy analysis. The potential advances of Zn-HAp nanoparticles in biological application was studied by using MG-63 cell line, drug model experiment and scaffold cell attachment, proliferation study. The cell cytotoxicity test (MTT assay and trypan blue) was first conducted to confirm the nontoxic characteristics of Zn-HAp with enhanced MG-63 cell proliferation activity. The drug loading experiment of Zn-HAp nanoparticles was then confirmed with 1 mol% Zn-HAp (which had the maximum drug loading efficiency with pH responsive drug interaction). Furthermore, the optimized 1 mol% Zn-HAp constructed biomimetic scaffold shows excellent cell attachment and proliferation behavior with MG-63 cells. The result suggests that the biomimetic 1 mol% Zn-HAp scaffolds may be of enormous potential in bone repair and regeneration. This research distinguishes from other research by showing an advanced analysis of the Zn-HAp and its enhanced physicochemical properties for tissue engineering and pH responsive drug delivery application.     

有序介孔TiO2材料的合成、表征与应用

有序介孔材料是近年来新兴起的一个研究热点,非硅基有序介孔材料在光催化、磁、电等诸多领域存在巨大的潜在应用价值.而TiO2以其特有的光催化活性、紫外光屏蔽效应等功能,以及化学性质稳定、毒性低、价格便宜和易于回收等特点,尤其值得关注.笔者综合阐述了有序介孔TiO2材料的合成过程、合成机理以及材料的表征和应用前景等情况.     

Synthesis of ultralong hydroxyapatite micro/nanoribbons and their application as reinforcement in collagen scaffolds for bone regeneration

Ultralong hydroxyapatite (HAp) micro/nanoribbons were successfully synthesized by a simple hydrothermal method without using any organic solvents and templates. The ultralong HAp micro/nanoribbons were up to several hundred micrometers in length and 100–400?nm in width. The growth process and mechanism of this micro/nanoribbons were also analyzed in this study. Moreover, the ultralong HAp micro/nanoribbons were used as reinforcement in collagen scaffolds and the HAp/collagen composite scaffolds were fabricated by freeze-drying process without cross-linking. The morphological results demonstrated homogeneous interconnected porous structure in 20?wt% and 35?wt% HAp reinforced scaffolds. The compressive modulus of the 35?wt% HAp/collagen composite was about 6 times that of the pure collagen scaffold. The ultralong HAp reinforced collagen scaffold possesses a porous structure, good flexibility as well as elasticity, and thus it is promising for used as bone repair material.     

Proteic sol-gel synthesis,structure and magnetic properties of Ni/NiO core-shell powders

Core-shell structured magnetic Ni/NiO powders were prepared by a proteic sol-gel route. Commercial gelatin and nickel nitrate were used as precursor materials. The synthesized material was calcined in air at 500 °C and further investigated by XRD, VSM and TEM. In order to investigate the effects of the structure on the magnetic properties, NiO powders were synthesized by three other methods for sake of comparison: citrate method, nitrate calcination and combustion method. XRD results revealed that the core-shell structured material is composed of 84.8 wt% NiO and 15.2 wt% Ni, while the samples from other methods are single phase. Hysteresis loop at room temperature showed a strong ferromagnetic behavior for samples prepared by proteic sol-gel and citrate methods. Powders from nitrate calcination and combustion showed weak ferromagnetic behavior most likely attributed to unpaired moments in their nanoparticles. The overall results showed that the proteic sol-gel method is a versatile chemical way to prepare Ni/NiO core-shell powders with high ferromagnetic signals.     

Hierarchical self-assembled hollow hydroxyapatite flower microspheres containing terpene functional groups for efficient drug loading and pH-responsive drug release

In this paper, we fabricated hierarchical self-assembled hollow rose-like flower microspheres (HRFM) and hollow burr-like flower microspheres (HBFM) hydroxyapatite (HAP) using dehydroabietyl phosphate tri-ester (DDPT) as an organic phosphorus source, a regulating agent, and a soft template simultaneously via a one-step solvothermal method. The HBFM and HRFM have been explored for their application in drug delivery, using doxorubicin (DOX) as a drug model. The formation mechanisms of HRFM and HBFM were proposed on the basis of the electrostatic potential diagrams and self-assembled behavior of DDPT organic molecule. After the rosin-based terpene functional groups were incorporated, both HRFM and HBFM exhibited low cytotoxicity against Hela cell, pH-dependent sustained drug release properties, and high drug loading capacity. The drug-loading capacities of HBFM and HRFM were 116.6?mg?g^?1 and 148.3?mg?g^?1, respectively. Thus, the as-prepared HRFM and HBFM are promising for the applications in drug delivery.     

Morphological and thermal characterization of zirconia/hydroxyapatite composites prepared via sol-gel for biomedical applications

The thermal behavior of pure ZrO₂ and hydroxyapatite (denoted as Z and HAp, respectively), as well as three composites with different content of Z and HAp (Z90HAp10, Z70HAp30 and Z50HAp50) prepared via sol-gel method has been studied by thermogravimetry (TG) and first-order derivative of TG up to 1200?°C under inert gas atmosphere. Dehydration, loss of alcohol and acetylacetone and a multi-step thermal decomposition processes has been identified by analyzing the gases evolved in each step by Fourier transform infrared spectroscopy (FTIR). Fresh samples of Z-rich composites undergo an abrupt ejection of material from the crucible around 200?°C with noticeable increase of the sample temperature. During the occurrence of this phenomenon FTIR spectra demonstrated the evolution of gases (CO, CO₂, acetone and ethylene) due to the simultaneous decomposition of acetylacetone and ethanol, not present in the samples calcined at 120?°C. As far as the structural study is concerned, pure Z crystallizes at 1000?°C in the monoclinic system, but the presence of HAp in the composite materials enables the crystallization of Z in the tetragonal phase. Finally, the amorphization degree increases with increasing the content of Z in all the composites treated at 600 and 1000?°C.     

Synthesis and rheological properties of polystyrene/layered silicate nanocomposite

Exfoliated polystyrene (PS)/organo-modified montmorillonite (MMT) nanocomposites were synthesized through in situ free radical bulk polymerization by dispersing a modified reactive organophilic MMT layered silicate in styrene monomer. The original MMT was modified by a mixture of two commercial cationic surfactants, [2-(acryloyloxy)ethyl](4-benzoylbenzyl)dimethylammonium bromide (ADAB) and cetyltrimethylammonium bromide (CTAB), with the former containing a polymerizable vinyl group. The exfoliating and intercalating structures were probed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Comparing with pure PS, the nanocomposites show much higher decomposition temperature, higher dynamic modulus, stronger shear thinning behavior and a smaller die swell ratio. The leveling-off of the storage modulus at low frequencies in the oscillatory shear measurements, as well as the observed yield like behavior, implies that the formation of a percolating nanoclay network is the origin of the enhanced viscoelasticity in these composites.     

Influence of silicon carbide on structural,optical and magnetic properties of Wollastonite/Fe2O3 nanocomposites

The influence of adding 10, 20 and 30% molar ratio of silicon carbide (SiC) separately to a composite of wollastonite (W) with a fixed content of 10%Fe₂O₃ prepared by wet precipitation method was studied. The crystal structure of the annealed composite powders was inspected by X-ray diffraction (XRD); revealing multi-phase structure. The highest estimated crystallite size investigated by Scherrer equation of W, SiC, WFe:SiC₁₀, WFe:SiC₂₀ and WFe:SiC₃₀ were 53.89, 54.6, 56.3, 48.5 and 54.6 nm respectively; demonstrating the formation of nanocomposites. Particles shape, size and crystallinity of the samples were studied using high resolution transmission electron microscope (HR-TEM). The band gap E_g values of the nanocomposites increased with SiC content having an intermediate value that lies between that of γ-Fe₂O₃ (maghemite) and SiC. Ferromagnetic and paramagnetic contributions were observed in the magnetic hysteresis loops for the composites. This study highlighted that the coercive field (H_ci) of the composites improved with increasing the SiC content. The innovative wollastonite/Fe₂O₃/SiC with amended magnetic properties elicited attention due to their promising application in bone filler and industrial purposes.