جستجوی مقالات مرتبط با کلیدواژه "metal-organic framework" در نشریات گروه "مواد و متالورژی"

The steel corrosion and the control of the damages caused by it is one of the challenging issues that has attracted the attention of many researchers and industrialists. Among corrosion control methods, protective coatings such as epoxy, vinyl ester, polyurethane, etc. are used more. Despite their wide applications, these coatings absorb water and corrosive species over time and cause the metal substrate to corrode and reduce the adhesion of the coating. Therefore, researchers are trying to find solutions to increase their lifespan and efficiency. In the present study, polyaniline (PANI) and its composite with copper metal-organic framework (Cu-MOF) were synthesized using in situ oxidation polymerization method. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray energy diffraction spectroscopy (EDX) were used for characterization. Then, 0.5 wt. % of PANI and PANI-Cu-MOF were added to vinyl ester (VE) resin based on bisphenol A and coated on mounted ST37 steel with a brush method. The protective performance of the prepared coatings was studied in 3.5 wt. % NaCl solution at ambient temperature using electrochemical impedance spectroscopy (EIS) and Tafel polarization for 240 hours. The EIS results showed that the corrosion resistance (Rcorr) of the VE/PANI-Cu-MOF coating at the end of immersion was 1.04 × 108 Ω cm2 , which compared to VE/PANI (1.31 × 105 Ω cm2 ) and VE (1.08 × 105 Ω cm2 ) is more. The results of Tafel polarization also indicate that the corrosion current density of VE coating is reduced in the presence of PANI-Cu-MOF composite.

In this research, the potential of using the carbonization of Zn based metal-organic framework under air atmosphere to synthesized C doped zinc oxide nanoparticles to create a fabric with UV protection was investigated. The results of X-ray diffraction spectroscopy, field emission scanning electron microscopy and elemental analysis showed that the coating of zinc oxide nanoparticles on the cotton fabric was successfully done. UV protection of the coated fabric were evaluated by changing the color of Methylene Blue exposed to UV light using a spectrophotometer. Compared to the raw fabric, the coated fabric showed higher UV protection. About 98% decomposition of Methylene blue was achieved in 45 min by ZnO doped with carbon. The results showed that the fabric coated with zinc oxide synthesized through the direct pyrolysis of metal-organic framework has the potential to provide protection against ultraviolet irradiation and can be used in advanced protective textiles. Also, synthesized zinc oxide nanoparticles can be effectively used in wastewater treatment and environmental applications.

In this research, the effect of hydrogen peroxide (H2O2) and benzoyl peroxide (BPO) on the structural properties, porosity, active pores, and surface area of the MOF-5 (Zn4O(BDC)3) metal-organic framework was studied. For this purpose, the metal-organic framework was synthesized by direct mixing and the molar ratios of the precursors to the ligand were modified to minimize the stoichiometric calculation error as well as the washing process to improve the properties of the synthesized MOF-5. In order to characterize the synthesized compounds and to investigate the effect of peroxides and washing process on the properties of the samples, X-ray diffraction (XRD), fourier Transform infrared spectroscopy (FTIR), and thermogravimetric/Differential scanning calorimetry (TG-DSC) analysis were performed. Structure, pore volume (1.212 cm3/g), and specific surface area (2307 m2/g) were compared to the sample synthesized with H2O2. DM-P-03 was selected as the optimal sample and prepared for thermal stability. According to TG-DSC analysis, the remaining zinc compounds in the sample were checked and the thermal stability of MOF-5 structure was confirmed up to 470°C.

In this study, chitosan composite nanofibers containing tannic acid and zinc-based metal-organic framework (ZIF-8) were produced for application as a hemostatic wound dressing. First, metal-organic framework named zeolite imidazolate framework (ZIF-8) was synthesized and chitosan composite nanofibers containing tannic acid and ZIF-8 were fabricated through electrospinning. The effect of tannic acid and metal-organic framework on the morphology and hemostatic properties of chitosan nanofibers was studied. Scanning electron microscopy, X-ray diffraction and blood coagulation tests were utilized. The study of the morphology of nanofibrous wound dressings shows the fabrication of uniform and bead-free nanofibers with an average diameter of 120 to 150 nm. The addition of tannic acid, due to the formation of hydrogen bonds and increasing the viscosity of the polymer solution, increased the diameter of chitosan nanofibers. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests, which check the performance of extrinsic and intrinsic pathway of blood coagulation, respectively, were used to evaluate the hemostatic activity of the fabricated wound dressings. The results show that the fabricated nanofibrous wound dressings significantly affect the extrinsic pathway of blood coagulation and factor VII, so that the blood coagulation time is reduced by 60% compared to the control sample. Due to the suitable structural and morphological properties of fabricated composite nanofibers, as well as their accelerated coagulation performance, they can be used as a suitable candidate in wound dressing applications.

Due to the severe and harmful effects of chemical pollutants on human health and the environment, researchers have always been looking for effective ways for detoxification of chemical pollutants. In this study, zirconium-based metal-organic framework (UiO-66) nanostructures were synthesized in two gel-based (xerogel) and solvothermal (aerogel) methods. Morphology, crystalline structure, porosity and specific surface area as well as their behavior against degradation of dimethyl methylphosphonate (DMMP) as nerve agent simulant were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption isotherms (BET) and gas chromatography-mass spectrometry (GC-MS). The results showed the synthesis of aerogel and xerogel UiO-66 with uniform size distribution and crystalline structure indicating the successful synthesis of these compounds. UiO-66 xerogel also showed higher specific surface area and pore volume than UiO-66 nanocrystals (aerogel). The degradation performance of the synthesized metal-organic framework nanostructures showed that the UiO-66 xerogel with a half-life of 28.6 min had better catalytic properties than the UiO-66 aerogel at 120 min and ambient temperature, as about 80% of DMMP is hydrolyzed.

Polyaniline metal organic framework (PAni-MOF) nanocomposite was synthesized via facile batch process in atmospheric pressure. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to determine the morphology and chemical structure of the synthesized samples, respectively. Synthesized nanocomposite was added to a 0.5 M hydrochloric acid solution and corrosion of carbon steel immersed in the solution, was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization corrosion testing. Results confirming the inhibition efficiency of PAni-MOF nanocomposite and its use reduce the rate of carbon steel corrosion in the environment of hydrochloric acid at a rate of 75 percent. Anodic protection mechanism of synthesize nanocomposite was confirmed via trend of open circuit potential changes and the analysis of electrochemical current noise data also showed a reduction in the probability of local corrosion in the presence of nanocomposite.

In this research, Zn/MWCNT porous nanocomposite and ZnO nanoparticles were prepared using Zn-based metal organic framework (MOF). Porous ZnO without MOF precursor was also synthesized. Structure, morphology and size of the films were analyzed by XRD and scanning electron microscope (SEM). Dye sensitized solar cells (DSSCs) were fabricated with ZnO/MWCNT nanocomposite and ZnO nanoparticles as photoanode. It was determined that ZnO based on MOF show higher surface area, more photon absorption and better short circuit current density compared with the reference ZnO without MOF precursor. Moreover, Effect of multiwall carbon nanotubes (MWCNT) on the porous structure of ZnO was studied and DSSC based on ZnO/MWCNT photoanode exhibited a short circuit current density of 23.89 mA cm-2, open circuit voltage of 0.68 V, and power conversion efficiency of 4.78%, which is almost 15% larger than that of the DSSC based on ZnO photoanode based on MOF (4.06%). The enhancement of efficiency in DSSCs made of ZnO/MWCNT nanocomposite can be attributed to the increase of the electrical conductivity of the photoanode, strong connection between conduction band of the anode with dye molecules and more contact surface of photoanode with electrolyte.

High conductivity and high level of electrolyte availability are the main requirements of active materials used in supercapacitors (SCs) to achieve high electrochemical efficiency. In recent years, metal-organic frameworks (MOFs) have been used as electrode materials for SCs due to their suitability of porosity and high surface area. However, using single-component MOFs in supercapacitors results in poor electrical conductivity, insufficient stability, and poor mechanical properties, and neutralize the effect of high capacity and efficient performance. In this paper, using a hydrothermal synthesis method, Cu-based MOFs were fabricated and graphene was added during synthesis to enhance the conductivity of these materials.  To investigate the structure of nanocomposites were used XRD, FTIR, and FESEM analyze. To investigate the electrochemical behavior of electrodes, cyclic voltammetry, electrochemical impedance and repeatability behavior were performed. The Cu based MOFs had a capacity of 372 F.g-1, while its composite capacity with graphene is 570 F.g-1. In these composites, graphene enhances electrical conductivity, porosity accessibility, and charge storage through a non-Faradic mechanism and metal-organic frameworks increase the total capacity with high porosity, porosity adjustable, and charge storage through the Faradic Mechanism.