Synthesis and characterization of magnesium–carbon compounds for hydrogen storage

Magnesium (Mg) and carbon (C) compounds were synthesized by ball-milling a mixture of Mg and different graphites with different crystallinities. The materials were characterized by X-ray diffraction, X-ray absorption spectroscopy, and X-ray total scattering techniques. Hydrogen storage properties were also investigated. In the case of the material using low-crystalline graphite, a Mg and C compound was formed as main phase, and its chemical bonding state was similar to that of magnesium carbide (Mg₂C₃). The hydrogen absorption reaction of the Mg–C compound occurred at around 400 °C under 3 MPa of hydrogen pressure to form magnesium hydride (MgH₂) and the C–H bonds in the carbon material. The hydrogenated Mg–C material desorbed about 3.7 mass% of hydrogen below 420 °C with two processes, which were the decomposition of MgH₂ and the subsequent reaction of the generated Mg and the C–H bonds. From the results, it is concluded that the Mg–C compound absorb and desorb about 3.7 mass% of hydrogen below 420 °C.     

Fabrication and characterization of hybrid coating on Mg–Zn–Ca Mg alloy for enhanced corrosion and degradation resistance as medical implant

Magnesium (Mg)-based alloys have appealing properties as promising implants for medical applications. However, their clinical applications are hindered due to the rapid corrosion and degradation rate in the physiological environment. In this investigation, we reported a novel interfacial engineering approach for the fabrication of polymer/ceramic hybrid coating on Mg–Zn–Ca Mg alloy. Firstly, hydroxyapatite (HA) coating was fabricated on the Mg–Zn–Ca sample followed by an alkali treatment that was performed in 1 M NaOH solution at 60 °C. Finally, polycaprolactone (PCL) coating was synthesized using a dip-coating approach on the top of the HA-coated Mg–Zn–Ca specimen. Microhardness test and adhesion test revealed that PCL/HA hybrid coating significantly improved mechanical properties and enhanced biointerface property between the substrate and coating. The immersion tests showed that the hybrid coating considerably slowed down the degradation in the simulated body fluid (SBF) solution. In addition, in vitro electrochemical investigations confirmed that PCL/HA coating significantly improved corrosion resistance and greatly reduced corrosion rate by about 10 times compared to HA coating and about 900 times to untreated Mg–Zn–Ca sample. Moreover, cytotoxicity assessment exhibited PCL/HA hybrid coating enhanced biocompatibility and bioactivity due to adopting a suitable interfacial engineering approach.     

Synthesis and characterization of corrosion-resistant and biocompatible Al2O3–TiB2 nanocomposite films on pure titanium

Alumina is widely used as a coating on a metal implant due to its favorable mechanical and biological properties. In this research, in order to improve mechanical and biological properties of alumina, a composition of nanoparticles of alumina (instead of microparticles) and titanium diboride micro powder is introduced. The atmospheric plasma spray (APS) technique was applied to deposit Al₂O₃–TiB₂ on the pure titanium substrate. The properties of Al₂O₃–TiB₂ nanocomposite coatings with various weight percent of TiB₂ (20, 30 and 40 wt%) were experimentally studied. The characteristics of nanocomposite films of TiB₂ (20, 30 and 40 wt%) were analyzed using Field Emission Scanning Electron Microscopy (FE-SEM), energy dispersive electron spectroscopy (EDX) and X-Ray Diffraction (XRD) tests. The XRD spectra exhibited that in addition to alumina and titanium diboride, the films contained titania. Thickness and morphology of the films were calculated from FE-SEM images and the thickness of the optimized coating (Al₂O₃-30 wt% TiB₂) was about 30–45 μm. Also, the roughness, corrosion resistance, hardness and cytotoxicity (MTT) tests were studied. The highest of hardness and roughness of the samples were obtained from Al₂O₃-30 wt% TiB₂. According to the obtained results from the polarization test, Al₂O₃-30 wt% TiB₂ coating had the highest corrosion resistance (222558.9962 Ω cm²). Therefore, the toxicity of Al₂O₃-30 wt% TiB₂ was investigated as the optimized coating and the results confirmed its non-toxicity and biocompatibility.     

Processing and characterization of elastomeric polycaprolactone triol–citrate coatings for biomedical applications

In this paper we describe the synthesis, processing and characterization of a novel elastic polyester coating created by carrying out catalyst-free polyesterification between biocompatible and non-toxic multifunctional reactants, namely polycaprolactone triol and citric acid. The physico-chemical and surface properties of the resulting polyester coatings and films have been investigated. This new material has been characterized by matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infra-red spectroscopy (FTIR), water-in-air contact angle measurements, scanning electron microscopy (SEM), thermal analysis (DSC), mechanical tests and swelling experiments. The polymer structure, surface properties (morphology and chemistry), mechanical integrity and hydration of the elastomer can be controlled by simple variation of the initial citric acid concentration in the polymer formation. This feature of the novel polyester material presents a significant development in the production of advanced coatings for biomedical applications.     

Adhesion evaluation of different bioceramic coatings on Mg–Ca alloys for biomedical applications

The aim of this study was to evaluate the adhesion of different bioceramic coatings deposited by radio frequency magnetron sputtering on the biodegradable implant-type magnesium–calcium (MgCa) alloys. Hydroxyapatite (HA) and bioactive glass (BG) were chosen as coating materials, due to their remarkable biological potential. The morphology, composition, structure and adhesion of the deposited thin coatings was characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy and pull-out adherence measurements. A variation of the coating-to-substrate adhesion has been recorded and correlated with the physico-chemical results. The bonding strength values of the coatings were promising (being superior to the ISO13779-2:2008 fabrication standard for load-bearing biomedical coatings), and thus, encourage us to further proceed with the biological evaluation of the HA or BG coatings-MgCa substrate couples.     

Synthesis of CaCO3–P(MMA–BA) nanocomposite and its application in water based alkyd emulsion coating

As part of broader effort to synthesize a new class of water-based composite, hybrid emulsion polymerization was carried out with acrylic monomers [methyl methacrylate (MMA), n-butyl acrylate (BA)]. Nanocomposite of P(MMA–BA)/nano CaCO₃ was synthesized by in situ emulsion polymerization. Water-based alkyd coating with various proportions nano CaCO₃, P(MMA–BA) and its nanocomposite was formulated. Extent of polymerization with and without nano CaCO₃ was measured using gravimetric method. Thermal properties of neat polymer, nanocomposite and coating films were evaluated by TGA and DSC, DTA analysis. Uniform dispersion of nano CaCO₃ in polymer matrix was ensured from SEM/TEM images. Incorporation of nanoparticles to hybrid polymer and nanocomposite to alkyd emulsion showed significant enhancement in mechanical and thermal properties. Dual role of nanocomposite in coating; as a partial binder and a filler to improve property profile of neat coating has been reported.     

Synthesis and characterization of new Mg–O–F system and its application as catalytic support

The Mg–O–F system (MgF₂–MgO) with different contents of MgF₂ (100–0%) and MgO is tested as support of iridium catalysts in the hydrogenation of toluene as a function of the MgF₂/MgO ratio. Mg–O–F samples have been prepared by the reaction of magnesium carbonate with hydrofluoric acid. The MgF₂–MgO supports, after calcination at 500 °C, are classified as mesoporous of surface area (34–135 m²·g^− 1) depending on the amount of MgO introduced. The Ir/Mg–O–F catalysts have been tested in the hydrogenation of toluene. The highest activity, expressed as TOF, min^− 1, was obtained for the catalyst supported on Mg–O–F containing 75 mol%MgF₂.     

Preparation and characterization of hydroxyapatite coating by magnetron sputtering on Mg–Zn–Ag alloys for orthopaedic trauma implants

The aim of the present paper was to evaluate the effect of hydroxyapatite coatings on the two types of Mg–Zn–Ag alloys as a possible solution to control magnesium alloy degradation. The coatings were prepared by the radio frequency magnetron sputtering method at a deposition temperature of 300 °C. To perform this evaluation, the coated alloys were immersed in a simulated body fluid solution at body temperature (37 ± 0.5 °C) to determine the corrosion resistance through electrochemical and immersion tests. Moreover, the investigation also consisted of the evaluation of microchemical, mechanical, and morphological properties. The deposition temperature of 300 °C was enough to obtain a crystalline hydroxyapatite structure with a Ca/P ratio close to the stochiometric one. The adhesion of coatings was not influenced by the nature of Mg–Zn–Ag alloys, so similar values for both coated alloys were found. The results showed that the coating was homogonous deposited on the Mg–Zn–Ag alloys and the corrosion resistance of uncoated magnesium alloys was improved.     

Synthesis and characterization of nano-sized calcium zincate powder and its application to Ni–Zn batteries

Nano-sized calcium zincate powders used as active materials for a secondary Zn electrode were prepared by a chemical co-precipitation method. The properties were studied by thermal gravimetric analysis (TGA), micro-Raman spectroscopy and nitrogen adsorption–desorption experiments. The secondary Zn electrodes using chemical co-precipitation calcium zincate powders (CP-ZnCa) and ball-milled calcium zincate powders (BM-ZnCa), were examined and compared. The electrochemical performance of the secondary Zn electrodes was systematically investigated by cyclic voltammetry and galvanostatic charge/discharge measurements. It was demonstrated that the electrochemical properties of the secondary Zn-pasted electrode using CP-ZnCa powders were greatly improved, as compared with conventional secondary ZnO electrodes. The results indicated that secondary Ni-Zn batteries using CP-ZnCa powders exhibited a better charge/discharge property and a longer life-cycle performance, compared with those based on ball-milled ZnO + Ca(OH)₂ (BM-ZnCa) powders.     

Electrodeposition and characterization of Zn–Ni alloys as sublayers for epoxy coating deposition

The chemical composition and phase structure of Zn–Ni alloys obtained by electrodeposition under various conditions were investigated. The influence of the deposition solution and deposition current density on the composition, phase structure, current efficiency and corrosion properties of Zn–Ni alloys were examined. It was shown that the chemical composition and phase structure affect the anticorrosive properties of Zn–Ni alloys. A Zn–Ni alloy electrodeposited from a chloride solution at 20 mA cm^–2 exhibited the best corrosion properties, so this alloy was chosen for further examination. Epoxy coatings were formed by cathodic electrodeposition of an epoxy resin on steel and steel modified with a Zn–Ni alloy. From the time dependence of the pore resistance, coating capacitance and relative permittivity of the epoxy coating, the diffusion coefficient of water through the epoxy coating, D(H₂O), and its thermal stability, it was shown that the Zn–Ni sublayer significantly affects the electrochemical and transport properties, as well as the thermal stability of epoxy coatings. On the basis of the experimental results it can be concluded that modification of a steel surface by a Zn–Ni alloy improves the corrosion protection of epoxy coatings.     

Electrodeposition and characterization of nickel–copper metallic foams for application as electrodes for supercapacitors

Nickel–copper metallic foams were electrodeposited from an acidic electrolyte, using hydrogen bubble evolution as a dynamic template. Their morphology and chemical composition was studied by scanning electron microscopy and related to the deposition parameters (applied current density and deposition time). For high currents densities (above 1 A cm^?2) the nickel–copper deposits have a three-dimensional foam-like morphology with randomly distributed nearly-circular pores whose walls present an open dendritic structure. The nickel–copper foams are crystalline and composed of pure nickel and a copper-rich phase containing nickel in solid solution. The electrochemical behaviour of the material was studied by cyclic voltammetry and chronopotentiometry (charge–discharge curves) aiming at its application as a positive electrode for supercapacitors. Cyclic voltammograms showed that the Ni–Cu foams have a pseudocapacitive behaviour. The specific capacitance was calculated from charge–discharge data and the best value (105 F g^?1 at 1 mA cm^?2) was obtained for nickel–copper foams deposited at 1.8 A cm^?2 for 180 s. Cycling stability of these foams was also assessed and they present a 90 % capacitance retention after 10,000 cycles at 10 mA cm^?2.     

Synthesis and characterization of microporous silica–alumina membranes

The development of microporous ceramic thin layers is of prime interest for sensors or gas separation membranes working at high temperature. Microporous silica membranes can be easily prepared by the sol–gel process. However the microporosity of pure silica is rapidly modified by steam at high temperature. One way to improve hydrothermal stability is to use mixed-oxide membranes. In this work, microporous silica–alumina membranes were prepared by a simple and robust sol–gel method. Tetraethoxysilane was mixed with an acidic alumina hydrosol. Urea was added for preparing the alumina hydrosol, for controlling the mixed-oxide network polycondensation and also as porogen agent. FTIR and ²⁷Al NMR spectroscopic analyses showed that for Si/Al molar ratios up to 6/1, homogeneous mixed oxides were obtained with a random distribution of Al and Si atoms in the oxide lattice based on tetrahedral units. The derived supported layers were crack-free as demonstrated by scanning electron microscopy (SEM) observations. Their microporosity was investigated using ellipsoporosimetry (EP) with films supported on flat dense substrates. He, N₂ and CO₂ permeance measurements were performed for membranes deposited on porous tubular substrates. The measured values of He/N₂ and He/CO₂ ideal selectivities are in agreement with the microporous nature of the prepared layers.     

Synthesis and characterization of chlorapatite–ZnO composite nanopowders

The influence of zinc oxide content on the formation of chlorapatite-based composite nanopowders in the mechanically alloyed CaO–CaCl₂–P₂O₅–ZnO system was studied. To mechanosynthesize composite nanopowders, different amounts of hydrothermally synthesized zinc oxide nanoparticles (0–10 wt%) were mixed with ingredients and then were mechanically activated for 5 h. Results showed that in the absence of zinc oxide, high crystalline chlorapatite nanopowder was obtained after 5 h of milling. In the presence of 4 and 7 wt% zinc oxide, the main product of milling for 5 h was chlorapatite–zinc oxide composite nanopowder. On increasing the zinc oxide content to 10 wt%, composite nanopowder was not formed due to improper stoichiometric ratio of the reactants. The crystallite size, lattice strain, volume fraction of grain boundary, and crystallinity degree of the samples fluctuated significantly during the milling process. In the presence of 7 wt% zinc oxide, the crystallite size and crystallinity degree reached 51±2 nm and 79±2%, respectively. During annealing at 900 °C for 1 h, the crystallization of composite nanopowder occurred and as a result the crystallinity degree rose sharply to 96±3%. In addition, the crystallite size increased to 77±2 nm after annealing at 900 °C. According to SEM and TEM images, the composite nanopowder was composed of both ellipse-like and polygonal particles with a mean size of about 98 nm.     

Microstructures,mechanical properties and corrosion resistance of sprayed Ca–P coating for micropatterning carbon/carbon substrate surface

Carbon/carbon (C/C) surface micropatterning is a method of modifying the surface into the complete and regular geometry. In this work, we introduce a positive effect on bonding strength between sprayed Ca–P coating and surface micropatterning C/C substrate. Interestingly, C/C substrate coated by Ca–P coating provides textured surface for a new bone ingrowth. The sprayed Ca–P coating is then subjected to microwave-hydrothermal (MH) treatment with the aim of eliminating surface defects and obtaining a uniform purity phase. These objectives were achieved in our previous study by the MH method. The molar ratio of Ca/P in the coatings is nearly close to 1, which is far below that of Ca/P for hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA, 1.67). The purpose of this article is to transform the phases in the sprayed Ca–P coating, which owns the better bioactivity and high corrosion resistance. In order to raise the molar ratio of Ca/P, the coatings are treated under high-temperature (around 700 °C). They are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and a fourier transform infrared spectra (FTIR). The bonding strength (coating/substrate), biological activity and corrosion resistance of the coatings are investigated. The resulting coatings own the different microstructures and phase compositions from the original sprayed Ca–P coating. Especially, results show that the shear strength of the sprayed Ca–P coating deposited on surface micropatterning C/C substrate increases by 61% which is more than that of the coating on non-surface micropatterning C/C substrate. Additionally, high-temperature treated coating presents a good biological activity and an excellent corrosion resistance of current density (1.3078 × 10^-6 A/cm²) and potential (−0.17 V_SCE).     

Synthesis and characterization of hybrid organic–inorganic materials based on sulphonated polyamideimide and silica

The preparation of hybrid organic–inorganic membrane materials based on a sulphonated polyamideimide resin and silica filler has been studied. The method allows the sol–gel process to proceed in the presence of a high molecular weight polyamideimide, resulting in well dispersed silica nanoparticles (<50 nm) within the polymer matrix with chemical bonding between the organic and inorganic phases. Tetraethoxysilane (TEOS) was used as the silica precursor and the organosilicate networks were bonded to the polymer matrix via a coupling agent aminopropyltriethoxysilane (APTrEOS). The structure and properties of these hybrid materials were characterized via a range of techniques including FTIR, TGA, DSC, SEM and contact angle analysis. It was found that the compatibility between organic and inorganic phases has been greatly enhanced by the incorporation of APTrEOS. The thermal stability and hydrophilic properties of hybrid materials have also been significantly improved.     

Synthesis and characterization of epoxy–silicone–polythiophene interpenetrating polymer network for corrosion protection of steel

Polymer alloys, particularly interpenetrating polymer networks (IPNs) exhibit excellent coating properties. Often combination of polymers result in IPNs with controlled morphologies and synergistic behavior. In this study, corrosion-resistant IPNs were prepared from immiscible resins (epoxy, silicone and thiophene) using a cross-linking agent and a catalyst. GPC, FTIR, NMR, TG, DTA and SEM studies used to fix the best performing IPN. Surface morphology studies using SEM confirm the incorporation of silicone and polythiophene in to the epoxy polymer to form homogeneously micro structured IPN. The heat-resistance of the IPN was determined as per ASTM 2485. The improved corrosion resistance of the IPN was evaluated by AC impedance measurements.     

Synthesis and structural characterization of urea–isobutyraldehyde–formaldehyde resins

Urea–isobutyraldehyde–formaldehyde (UIF) resins were synthesized using urea, isobutyraldehyde, and formaldehyde; sulfuric acid was used as a catalyst. The effects of molar ratio of urea/isobutyraldehyde/formaldehyde (U/I/F) on the properties of resins were investigated, and the structures of the resins were characterized by FTIR, ¹H-NMR, and ¹³C-NMR. When U/I/F was 1.0/3.6/2.4, the yield of the resin was 76.5%. The softening point and hydroxyl value were 90°C and 32 mg KOH/g, respectively. The FTIR, ¹H-NMR, and ¹³C-NMR results showed that an α-ureidoalkylation reaction occurred between urea and isobutyraldehyde to form a lactam. The UIF resins also contained hydroxyl groups and aldehyde groups; the content of aldehyde groups in the resin increased as the amount of isobutyraldehyde increased.     

Cellulose acetate–silica fume membrane: characterization and application for separation of starch and maltose

Maltose is one of the starch derivatives. Maltose can be produced by starch hydrolysis using any kind of hydrolytic process. One of the methods to separate a mixture of both compounds is using porous membrane. In this research, a novel type of hybrid membrane was prepared from a mixture of cellulose acetate and silica fume. Silica fume is widely used in the domain of construction as cement material, whereas in this research silica fume was successfully used as membrane material. Various compositions of membrane dope solutions were prepared for obtaining the membranes used for separation of starch and maltose. Such synthesized membranes demonstrate a good performance in separation processes. The best performance is achieved when the composition of cellulose acetate in membrane dope solution is 15 % (w/w) in N,N-dimethylacetamide solvent and the mass ratio between cellulose acetate and silica fume is 4:1. For this composition, the rejection of membranes towards starch and maltose is 87 and 2 %, respectively, at working pressure of 3 bar and compaction time of 2 h. Infrared spectrum indicates no new peaks are found compared to raw materials’ spectral peaks. Thus, it can be concluded that the interaction between the cellulose acetate and silica fume is merely a physical type. From the observation of cross-sectional SEM images, we can remark that the morphology of such a membrane is porous. X-ray diffractogram indicates that the synthesized membranes are amorphous.