Release behavior and kinetic evaluation of berberine hydrochloride from ethyl cellulose/chitosan microspheres

Novel ethyl cellulose/chitosan microspheres （ECCMs） were prepared by the method of w/o/w emulsion and solvent evaporation. The microspheres were spherical, adhesive, and aggregated loosely with a size not bigger than 5 pm. The drug loading efficiency of berberine hydrochloride （BH） loaded in microspheres were affected by chitosan （CS） concentration, EC concentration and the volume ratio of V（CS）/V（EC）. ECCMs prepared had sustained release efficiency on BH which was changed with different preparation parameters. In addition, the pH value of release media had obvious effect on the release character of ECCMs. The release rate of BH from sample B was only a little more than 30% in diluted hydrochloric acid （dHCl） and that was almost 90% in PBS during 24 h. Furthermore, the drug release data were fitted to different kinetic models to analyze the release kinetics and the mechanism from the microspheres. The released results of BH indicated that ECCMs exhibited non-Fickian diffusion mechanism in dHCI and diffusion-controlled drug release based on Fickian diffusion in PBS. So the ECCMs might be an ideal sustained release system especially in dHCl and the drug release was governed by both diffusion of the drug and dissolution of the polymeric network.     

Thermal and Oxygen Barrier Properties of Chitosan Bionanocomposites by Reinforcement of Calcium Carbonate Nanopowder

Chitosan and calcium carbonate nanopowder（chitosan/CaCO3） bionanocomposites were prepared by solution method.Interaction between chitosan and CaCO3 was studied by Fourier transform infrared spectroscopy（FTIR）.Structure and surface morphology of chitosan/CaCO3 bionanocomposites were investigated by X-ray diffraction（XRD） and field emission scanning electron microscopy（FESEM）,respectively.The energy dispersive X-ray spectroscopy（EDS） of chitosan/CaCO3 bionanocomposites was studied in order to establish the elements of composition.Thermal stability of prepared bionanocomposites was studied by thermogravimetric analysis（TGA） and a substantial increase of thermal stability of virgin chitosan was noticed due to incorporation of CaCO3 nanopowder.The oxygen permeability was reduced by three times as compared to the raw chitosan due to the dispersion of nano CaCO3 filler.Biodegradability and resistance towards dilute acid and alkali of the prepared bionanocomposite were investigated.The bionanocomposite having gas barrier and thermal stable property may be suitable for packaging and biomedical applications.     

Effect of corrosion on mechanical behaviors of Mg-Zn-Zr alloy in simulated body fluid

The main purpose of this paper is to investigate the effect of corrosion on mechanical behaviors of the Mg-Zn-Zr alloy immersed in simulated body fluid （SBF） with different immersion times. The corrosion behavior of the materials in SBF was determined by immersion tests. The surfaces of the corroded alloys were examined by SEM. The tensile samples of the extruded Mg-2Zn-0.8Zr magnesium alloy were immersed in the SBF for 0, 4, 7, 10, 14, 21 and 28 d. The tensile mechanical behaviors of test samples were performed on an electronic tensile testing machine. SEM was used to observe the fracture morphology. It was found that with extension of the immersion time, the ultimate tensile strength （UTS）, yield strength （YS） and elongation （EL） of the Mg-2Zn-0.8Zr samples decreased rapidly at first and then decreased slowly. The main fracture mechanism of the alloy transformed from ductile fracture to cleavage fracture with the increasing immersion times, which can be attributed to stress concentration and embrittlement caused by pit corrosion.     

Hierarchical TiO2/ZnO Nanostructure as Novel Non-precious Electrocatalyst for Ethanol Electrooxidation

Metal oxides have a higher chemical stability in comparison to metals,so they can be utilized as electrocatalysts if the activity could be enhanced.Besides the composition,the morphology of the nanostructures has a considerable impact on the electrocatalytic activity.In this work,zinc oxide nano branches-attached titanium dioxide nanofibers were investigated as an economic and stable catalyst for ethanol electrooxidation in the alkaline media.The introduced material has been synthesized by electrospinning process followed by hydrothermal technique.Briefly,electrospinning of colloidal solution consisting of titanium isopropoxide,poly(vinyl acetate) and zinc nanoparticles was performed to produce nanofibers embedding solid nanoparticles.In order to produce TiO_2 nanofibers containing ZnO nanoparticles,the obtained electrospun nanofiber mats were calcined in air at 600 °C.The formed ZnO nanoparticles were exploited as seeds to outgrow ZnO branches around the TiO_2 nanofibers using the hydrothermal technique at sub-critical water conditions in the presence of zinc nitrate and bis-hexamethylene triamine.The morphology of the final product,as well as the electrochemical measurements indicated that zinc nanoparticles content in the original electrospun nanofibers has a significant influence on the electrocatalytic activity as the best performance was observed with the nanofibers synthesized from electrospun solution containing 0.1 g Zn,and the corresponding current density was 37 mA/cm~2.Overall,this study paves a way to titanium dioxide to be exploited to synthesize effective and stable metal oxide-based electrocatalysts.     

Processing of Ceramic Based Nanocomposite Using α-Al2O3 Powder and FeCl2 Solution as Starting Materials

Alumina-iron nanocomposite powders were prepared by a two-step process. In the first step, α-Al2O3-FeCl2 powder mixture was formed by mixing α-Al2O3 powders with FeCl2 solution followed by drying. In the second step, the FeCl2 in the dry power mixture was selectively reduced to iron particles. A reduction temperature of 750℃ for 15 min in dry H2 was chosen based on the thermodynamic calculations. The concentration of iron in FeCl2 solution was calculated to be 20 vol. pct in the final composite. Two techniques were used to produce composite bulk materials. The Al2O3 nanocomposite powders were divided to two batches. The first batch of the produced mixture was hot pressed at 1400℃ and 27 MPa for 30 min in a graphite die. To study the effect of oxygen on the Al2O3/Fe interface bonding and mechanical properties of the composite, the second batch was heat treated in air at 700℃ for 20 min to partially oxidize the iron particles before hot pressing. Characterization of the composites was undertaken by conventional density measurements, X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electron probe micro analysis （EPMA）. The suggested processing route （mixing, reduction and hot pressing） produces ceramic-metal nanocomposite much tougher than the pure Al2O3. The fracture strength of the produced Al2O3/Fe nanocomposite is nearly twice that of the pure Al2O3. The presence of spinel phase, FeAl204, as thick layer around the Fe particles in the Al2O3 matrix has a detrimental effect on interfacial bonding between Fe and AI203 and the fracture properties of the composite.     

Effects of Cure Pressure Induced Voids on the Mechanical Strength of Carbon/Epoxy Laminates

This work aims at designing a set of curing pressure routes to produce laminates with various void contents. The effects of various consolidation pressures resulting in different void contents on mechanical strength of carbon/epoxy laminates have been examined. Characterization of the voids, in terms of void volume fraction, void distribution, size, and shape, was performed by standard test, ultrasonic inspection and metallographic analysis. The interlaminar shear strength was measured by the short-beam method. An empirical model was used to predict the strength vs porosity. The predicted strengths conform well with the experimental data and voids were found to be uniformly distributed throughout the laminate.     

Poly（Vinyl Chloride） Nanocomposites Prepared in the Suspension Polymerization Process,Part II,PVC Filled with Silica Nanofiller

Silica/PVC nanocomposites were prepared by VCM suspension polymerization in the presence of nanosilica （0.2-2.0 wt.% /VCM）. Unmodified nanosilica prepared by sol-gel method was used. The process of VCM polymerization in the nanofiller presence was carried out without disturbances. SEM and TEM analyses confirmed the presence of nanofiller both on the surface and in cross-sections of PVC grains. The filler distribution in polymer grains was uniform. TEM observations showed that nanosilica content in amount 〈_ 2.0% led to formation of crystalline phase. The base properties of PVC nanocomposites differed from neat PVC. An improvement in mechanical properties of PVC/nanosilica composites in comparison with commercial PVC has been found. The use of the nanofiller in an amount equal to 1.0 wt.%/VCM resulted in the largest increase in tensile strength with simultaneous highest elongation at break. An addition of 0.5 wt.% ofnanosilica improved impact strength of polymer nearly 40% in comparison with neat PVC.     

Binary Co–Ni oxide nanoparticle-loaded hierarchical graphitic porous carbon for high-performance supercapacitors

Heteroatom doped graphitic porous carbon is highly desirable for electrochemical applications because of its excellent conductivity and high surface area. In this study, highly uniform Co-Ni oxide nanoparticleloaded B, N-doped hierarchical graphitic porous carbon was prepared through a dual pyrolysis process.Graphene dispersed chitosan hydrogel was first used as a precursor to fabricate the porous carbon(GCS–C)at 700℃. Co and Ni oxide nanoparticles were further anchored on the porous carbon through chemical reduction and calcined at high temperature. The structure of the porous carbon was optimized by the introduction of graphene to the chitosan hydrogel. The graphitic degree of the porous carbon was significantly improved by the Co and Ni species. The heteroatom B and N were found to be well doped in the composite. These features enable the composite to be an excellent candidate for supercapacitor electrodes. The composite demonstrates a high capacitance(1266.7 F g~(-1) at 1 A g~(-1)) and excellent stability.     

Effect of δ Phase on Hydrogen Embrittlement of Inconel 718 by Notch Tensile Tests

The effect of δ phase on the hydrogen embrittlement (HE) sensitivity of Inconel 718 was investigated by conducting notch tensile tests. Notch tensile specimens with various precipitation morphologies of δ phase were prepared with different heat treatments, and hydrogen was charged into the tensile specimens before tensile tests via a cathodic charging process. The loss of notch tensile strength (NTS) due to the charged hydrogen was used to evaluate the hydrogen embrittlement sensitivity. The results show that δ phase has deleterious effect on NTSs, and the fracture of hydrogen-charged specimens initiated near the notch surfaces. The loss of NTS caused by precharged hydrogen can be greatly decreased by dissolving δ phase. δ-free Inconel 718 alloy is proposed for the applications in hydrogen environments.     

An Innovative Approach for Improving the Reliability of Reticulated Porous Ceramics

An innovative approach has been developed to fabricate reticulated porous ceramics (RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates. In this approach, the coating process comprises of two stages. In the first stage, the thicker slurry was used to coat: uniformly the sponge substrate. The green body was preheated to produce a reticulated preform with enough handling strength after the sponge was burned out. In the second stage, the thinner slurry was used to coat uniformly the preform. The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process. A few filled cells and cell faces occur in the fabrication and the struts were thickened. A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively. The result shows that the mechanical reliability of RPCs is improved by the innovative approach     

High-strength mineralized collagen artificial bone

Mineralized collagen （MC） is a biomimetic material that mimics natural bone matrix in terms of both chemical composition and microstructure. The biomimetic MC possesses good biocompatibility and osteogenic activity, and is capable of guiding bone regeneration as being used for bone defect repair. However, mechanical strength of existing MC artificial bone is too low to provide effective support at human load-bearing sites, so it can only be used for the repair at non-load-bearing sites, such as bone defect filling, bone graft augmentation, and so on. In the present study, a high strength MC artificial bone material was developed by using collagen as the template for the biomimetic mineralization of the calcium phosphate, and then followed by a cold compression molding process with a certain pressure. The appearance and density of the dense MC were similar to those of natural cortical bone, and the phase composition was in conformity with that of animal＇s cortical bone demonstrated by XRD. Mechanical properties were tested and results showed that the compressive strength was comparable to human cortical bone, while the compressive modulus was as low as human cancellous bone. Such high strength was able to provide effective mechanical support for bone defect repair at human load-bearing sites, and the low compressive modulus can help avoid stress shielding in the application of bone regeneration. Both in vitro cell experiments and in v/vo implantation assay demonstrated good biocompatibility of the material, and in v/vo stability evaluation indicated that this high-strength MC artificial bone could provide long-term effective mechanical support at human load- bearing sites.     

Synthesis and Room Temperature d~o Ferromagnetic Properties of α-MoO_3 Nanofibers

Herein,we report the magnetic properties of α-MoO_3 nanofibers synthesized via a hydrothermal method.X-ray photoelectron and Raman spectroscopic studies have been employed to evidence the presence of oxygen vacancy defects in the α-MoO_3 nanofibers.To elucidate the oxygen vacancy related ferromagnetism,post-thermal annealing in oxygen and vacuum was performed.The UV emission band of α-MoO_3 nanofibers reveals a red shift from oxygen annealed to vacuum annealed,indicating a bandedge reduction.The saturation magnetization of oxygen annealed nanofibers decreases while that of vacuum annealed nanofibers increases.These results strongly confirm that the oxygen vacancies play a significant role in inducing ferromagnetism.The origin of ferromagnetism may be due to the exchange interactions among localized electron spin moments resulting from oxygen vacancies of α-MoO_3 nanofibers.The presence of such defects was further supported by the photoluminescence measurements.     

Immobilization of Co(Ⅱ) Ions in Cement Pastes and Their Effects on the Hydration Characteristics

The immobilization of Co(Ⅱ) in various cement matrices was investigated by using the solidification/stabilization(S/S) technique.The different cement pastes used in this study were ordinary Portland cement in absence and presence of water reducing-and water repelling-admixtures as well as blended cement with kaolin.Two ratios of Co(Ⅱ) were used(0.5% and 1.0% by weight of the solid binder).The hydration characteristics of the used cement pastes were tested via the determination of the combined water content,phase composition and compressive strength at different time intervals up to 180 d.The degree of immobilization of the added heavy metal ions was evaluated by determining the leached ion concentration after time intervals extended up to 180 d.The leachability experiments were carried out by using two modes:the static and the semi-dynamic leaching processes.It was noticed that the concentration of the leached Co2+ ions in the static mode of leachability was lower than the solubility of its hydroxide in all the investigated cement pastes.     

Sol-Gel Coating with 3-Mercaptopropyltrimethoxysilane as Precursor for Corrosion Protection of Aluminium Metal

Sol—gel coatings offer a number of advantages over other methods of protection for metallic materials.In the present work,3-mercaptopropyltrimethoxysilane（MPTS） was used as the precursor for sol—gel coating on aluminium metal.The gelation of MPTS sol—gel was characterized by Fourier transform infrared spectroscopy（FT-IR） studies.The formed film was found to be stable up to 350 ℃ as evident from thermogravimetric analysis.X-ray diffraction study and scanning electron microscopy supported the formation of MPTS coating on aluminium surface while the characterization of the coating was done by FT-IR studies.The corrosion inhibition potential of the sol—gel coatings on metal in 3.5%（w/v） of NaCI solution was assessed as a function of different concentrations of MPTS using electrochemical polarization and impedance measurements.The corrosion inhibition efficiency was found to increase with increasing MPTS concentration.The results of the study unravel the use of MPTS as a precursor in the formation of sol—gel coating over aluminium surface so as to protect the metallic surface from corrosion in neutral environment.     

Mechanical Properties of V-, Nb-, and Ti-bearing As-cast Microalloyed Steels

The influence of microalloying additions on the mechanical properties of a low-carbon cast steel containing combinations of V, Nb, and Ti in the as-cast condition was evaluated. Tensile and hardness test results indicated that good combinations of strength and ductility could be achieved by V and Nb additions. While the yield strength and UTS （ultimate tensile strength） increased up to the range of 378-435 MPa and 579- 590 MPa, respectively in the microalloyed heats, their total elongation ranged from 18% to 23%. The presence of Ti, however, led to some reduction in the strength. Microstructural studies including scanning electron microscopy （SEM） and optical microscopy revealed that coarse TiN particles were responsible for this behavior. The Charpy impact values of all compositions indicated that microalloying additions significantly decreased the impact energy and led to the dominance of cleavage facets on the fracture surfaces. It seems that the increase in the hardness of coarse ferrite grains due to the precipitation hardening is the main reason for brittle fracture.     

Electrospinning nanofibers to ID,2D,and 3D scaffolds and their biomedical applications

Electrospinning is a popular and effective method of producing porous nanofibers with a large surface area,superior physical and chemical properties,and a controllable pore size.Owing to these properties,electrospun nanofibers can mimic the extracellular matrix and some human tissue structures,based on the fiber configuration.Consequently,the application of electrospun nanofibers as biomaterials,varying from two-dimensional(2D)wound dressings to three-dimensional(3D)tissue engineering scaffolds,has increased rapidly in recent years.Nanofibers can either be uniform fiber strands or coaxial drug carriers,and their overall structure varies from random mesh-like mats to aligned or gradient scaffolds.In addition,the pore size of the fibers can be adjusted or the fibers can be loaded with disparate medicines to provide different functions.This review discusses the various structures and applications of 2D fiber mats and 3D nanofibrous scaffolds made up of different one-dimensional(1D)fibers in tissue engineering.In particular,we focus on the improvements made in recent years,especially in the fields of wound healing,angiogenesis,and tissue regeneration.     

An Innovative Approach fro Improving the Reliability of Reticulated Porous Cermaics

An innovative approach has been developed to fabricate reticulated porous ceramics(RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates.In this approach,the coating process comprises of two stages.In the first stage,the thicker slurry was used to coat uniformly the sponge substrate.The green body was preheated to produce a reticulated perform with enough handling strength after the sponge was burned out.In the second stage,the thinner slurry was used to coat uniformly the perform .The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process.A few filled cells and cell faces occur in the fabrication and the struts were thickened.A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively.The result shows that the mechanical reliability of RPCs is improved by the innovative approach.This innovative approach is very simple and controlled easily,and will open up new technological applications for RPCs.     

Dielectric and Ferroelectric Properties of BaTiO3 Nanofibers Prepared via Electrospinning

BaTiO3 nanofibers of about 400 nm in diameter were synthesized via electrospinning.The evolution of the morphology and phase composition of the BaTiO3 nanofibers was studied by scanning electron microscopy and X-ray diffraction within the annealing temperature of 750-1050 ℃.Higher annealing temperature led to rougher surface and better crystallization of the BaTiO3 nanofibers.Below 1050 ℃,the BaTiO3 nanofibers maintained its large aspect ratios and could still be regarded as individual nanofiber.The dielectric permittivities of the BaTiO3 nanofibers（εr 820） were calculated with the MG equation by considering the porous bulk specimens as composites of BaTiO3 nanofibers and air.The ferroelectric properties of the BaTiO3nanofibers were measured by using a ferroelectric analyzer coupled with an atomic force microscope.P-E loop measured for the BaTiO3 nanofiber exhibits small hysteresis.     

Effect of Sn on the Microstructure and Mechanical Properties of Mg-5Al-2Si Alloys

The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.     

Catalytic Reduction of Coomassie Brilliant Blue R-250 by Silver Nanomagnetic Clusters

The research work represents the synthesis of silver nanoparticles(AgNPs)coated on magnetic iron oxide nanoparticles by chemical reduction and co-precipitation method,respectively.AgNPs were coated on magnetic ironoxide nanoparticles to form Ag@Fe3O4.AgNPs were characterized by UV-Visible spectroscopy.The magnetic nanoparticles(MNPs)and magnetic nanoclusters(MNC)were characterized by Fourier transform infra red(FTIR)spectroscopy.Bulk density,moisture content and ash content were also determined.These MNCs were used for the reduction of 4-nitrophenol(4-NP)and coomassie Brilliant Blue R-250(CBBR-250).The parameters such as effect of time,catalyst dosage,concentration of sodium borohydride and concentration of 4-NP and dye were studied.It was found that the catalytic reduction of 4-NP and dye were in 20 minutes by MNCs.Kinetic analysis shows that the pseudo-first-order was found to be linear.It revealed that the use of these MNCs can be considered as a reliable method for the catalytic reduction studies.