مجله مواد و فناوری های پیشرفته
سال دهم شماره 4 (زمستان 1400)

Specific properties such as pore tunability, structural variety as well as chemical, mechanical, and thermal stability, make zeolitic imidazolate frameworks (ZIFs) suitable and of high importance for practical applications. Optical and chemical sensors and supercapacitors are among these applications which necessitate the detailed study of optical and dielectric properties of ZIFs. Therefore, ZIF-8 as a zinc-based mesoporous material was studied by reflection electron energy loss spectroscopy (REELS) applying the Yubero-Tougaard algorithm which is based on dielectric response theory. The band gap energy (Eg) of ZIF-8 was determined to be 4.2 eV using an extrapolation procedure applied to an experimental REELS spectrum. Its bulk and surface energy loss functions were also determined. Inelastic mean free path (IMFP) values of electrons of different energies transported in ZIF-8 were determined and their large differences with values calculated from the Tanuma-Powell-Penn (TPP) formula were discussed. In addition, the obtained ELF was used to apply the Kramers-Kronig transformation to obtain the real part (ε1) and imaginary part (ε2) of the dielectric function (ε), refractive index (n), extinction coefficient (k), reflection coefficient (R) and absorption coefficient (µ) of ZIF-8 as important optical properties of this widely applicable material.

One of the overlooked topics in classical wetting, which is the main subject of numerous recent researches, is the concept of the triple-phase contact line (TPCL). In this article, after defining the TPCL and emphasizing its significance in wetting studies, this concept and its characterization methods using experimental techniques and molecular dynamics simulations are reviewed and investigated. First, the ideal Young’s model was revised based on the generalized theory of capillarity, and line tension, Γ, was assigned to TPCL as a defining physical parameter. Because ideal models cannot correctly determine the sign and value of Γ, real and non-ideal surfaces were used. Furthermore, the width of the TPCL was investigated by the obtained data from structural analysis of the droplet’s edge using optical and environmental-scanning electron microscopy. The corresponding scaling law from the former lead to a power greater than 0.66, whereas the latter high-resolution method resulted in a value of ~ 0.62. Conversely, MD simulations have illustrated that it is possible to locally use the minimum particle distance for the Lennard-Jones potential as the effective width of the TPCL. In the final section, the most important interaction of the TPCL with its vicinity, known as pinning, was discussed. From the experimental perspective, the focus is on the adhesion force measurements which results in the force-based characterization of the pinning phenomenon. However, on the nanoscale, due to the available kinetic energy, this phenomenon is defined as the drastic slow-down of the motion of the TPCL, directly contradicting the macroscopic view.

The aim of this study was to fabricate and characterize silk fibroin scaffold containing chitosan nanoparticle loaded with ascorbic acid. Therefore, ascorbic acid- chitosan nanoparticles were fabricated using the ionic gelation method. Scanning Electron Microscopy (SEM) images and Dynamic Light Scattering (DLS) results showed that the nanoparticles are spherical with the average size of 200 nm. Then, different amounts of nanoparticles were placed in the silk fibroin solution, and finally, the scaffolds were prepared by the freeze-drying method. The effect of nanoparticle concentrations on various properties such as morphology, structural changes, water absorption, drug release, toxicity, adhesion, and alkaline phosphatase activity of MG63 cells were studied. The results of Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of nanoparticles in the scaffold. Morphological examinations of the cross-section of the scaffold showed that all scaffolds have a porous structure with interconnected pores. The mean size of the pores and porosity percentages reduced as the nanoparticle content rose. The release of ascorbic acid in all samples started with the burst release in the first 24 hours and then continued with a controlled release for up to 14 days. Higher amounts of ascorbic acid were released from the scaffold containing more nanoparticles. Cellular studies showed that the scaffold was non-toxic and that MG63 cells adhered well onto the surface of the scaffold and the pores’ wall. Also, the proliferation and alkaline phosphatase activity of MG63 cells increased with increasing ascorbic acid amounts.

2D materials are a class of materials with only one dimension in nanoscale. Due to the increase in the number of surface atoms in two-dimensional materials, the physical and chemical reactivity compared to the bulk counterpart significantly increased. 2D materials characteristics such as high anisotropy, high surface area, unique morphology, and tunable mechanical, optical, electrical, and magnetic functionalities come out to be a fascinating candidate for application in electro-optical and electronic devices, energy and environmental fields, as well as biomedical and drug delivery in medicine. 2D materials are divided into ten major groups, including carbon-based 2D materials (includes graphene, graphene oxide, reduced graphene oxide, graphane, fluorographene, graphyne, graphdiyne, graphone), hexagonal boron nitride (hBN), graphitic C3N4, elemental 2D materials (elements groups 14 and 15), transition metal dichalcogenides (TMDs), transition metal oxides (TMOs), MXenes, 2D perovskite materials, 2D metal materials, and 2D clay materials (silicate clays and layered double hydroxides (LDHs)). In this paper, after the classification of these materials, the introduction, application, and related properties are investigated. So far, more studies have been done on graphene than other 2D materials. These materials are expected to have a similar capacity to graphene in terms of properties and applications, while ongoing research will increase the diversities of this category and depth of knowledge on these groups of materials.

In this study, the effect of superheat temperature of cooling slope process on the microstructure and electrochemical behavior of Al-Zn-In sacrificial anode has been investigated. Cooling slope Semisolid Casting was performed at three different temperatures of 660, 680, and 700 °C and the microstructure investigated by optical microscopy, electron microscopy and image analysis software. The electrochemical behavior of the alloy was determined by electrochemical impedance and polarization tests. According to the results, the sample produced by cooling slope at a temperature of 680 °C with a sphericity number of 0.68 and grain size of 45 microns had the maximum sphericity and minimum grain size. Also, the mentioned sample had the corrosion rate of 0.086 mm/year, which was the highest corrosion rate compared to other samples, and the results of the electrochemical impedance test confirmed the better behavior of its. Increasing the superheat temperature to 700 °C has led to a decrease in the electrochemical and microstructural properties of the sample.

Tissue engineering creates a suitable substrate for the regeneration and repair of damaged bone tissue by providing scaffolds with the ability to stimulate bone formation. In this study, polycaprolactone (PCL) scaffold (scaffold A), PCL/keratin (Kr) scaffold (scaffold B), and PCL/Kr scaffold reinforced with carboxylated multi-walled carbon nanotubes (MWCNT-COOH) (scaffold C) were fabricated by electrospinning method and rapid osteogenic differentiation of mesenchymal stem cells and biomineralization on the scaffolds surface were evaluated. The bioactivity of scaffolds was investigated using energy dispersive x-ray spectroscopy (EDS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) and extracellular matrix proteins adsorption on the surface of scaffolds were also evaluated by BCA assay kit. Moreover, the effect of MWCNT-COOH on calcium deposition in the scaffolds were studied on days 7 and 14 of culture. The formation of hydroxyapatite layer on the scaffold C indicated the excellent osteoproductivity and bioactivity of scaffold. The amount of protein adsorption on the surface of scaffolds B and C was measured to be 32 μg/mm3 and 43 μg/mm3, respectively, which showed an increase in mesenchymal stem cells proliferation on the surface of scaffold C compared to the scaffold B. Also, high calcium deposition on the surface of scaffold C indicated mesenchymal stem cells differentiate into osteoblasts on the surface of scaffold. Therefore, the results of this study demonstrated that the PCL/Kr scaffold reinforced with MWCNT-COOH with excellent bioactivity, high protein adsorption, and osteogenic differentiation of mesenchymal stem cells can be a suitable candidate for bone tissue engineering applications.

Nickel-Copper ferromagnetic core is used for interstitial local thermotherapy techniques to treat deep-seated tumors such as brain tumors and prostatic tumors. In the present study, the effective parameters on the amount of induction heating in the ferromagnetic core and determining the optimal conditions before performing laboratory processes was investigated by the Comsol Multiphysics 5.4 software. The model consisted of a single Nickel-Copper ferromagnetic core (29.6-70.4 wt %) in the two different size that placed in the central region of a cylindrical water phantom with different radius between 20 mm up to 60 mm. For the study of the thermal distribution due to the electromagnetic induction was used from a finite-element analysis method. The temperature profiles of the ferromagnetic core in the electromagnetic field with a frequency of 75- 350 kHz and the magnetic field of strength (H0) with 200-500 Oe up to 30 minutes showed the possibility of temperature control at the thermo-seed for producing the desired temperature in the thermotherapy process. The decreased phantom radius, as well as increase in the volume of the ferromagnetic core led to a rise in the induction temperature of the core due to the increase in the amount of induced field at the center of the phantom in the constant current and frequency. The results showed that the induced temperature in the core was increased due to the rise of the magnetic field in the fixed frequency or the increase of the frequency in the fixed magnetic field type, which is within most of us interested.

Titanium carbide (TiC) and zirconium carbide (ZrC) are among well-known transition-metal carbide ceramics which have received great attention in the past decades. This comes from their excellent properties including high melting temperature, extraordinary strength at high temperatures, chemical and mechanical stability, low density and, good resistance to corrosion and oxidation. All these unique and extraordinary features lead to the widespread applications of these compounds, including in cutting tools, information storage technology, hard and thin coatings as protectors of electronic surfaces protector, and optoelectronic devices. In this paper, the structural and thermodynamic properties of titanium carbide and zirconium carbide as a function of temperature and pressure were investigated, by using the density functional theory method and quasi-harmonic Debye model. The obtained structural results by using different equations of state showed that the structural parameters are in good agreement with the experimental results. The investigation of temperature and pressure effects on the bulk modulus indicated that zirconium carbide and titanium carbide have good strength at high temperatures and pressure, respectively. Also, the Gibbs free energy result showed that zirconium carbide remained stable up to high temperatures and this justifies its high melting temperature. Calculations of thermodynamic properties such as Debye temperature, specific heat capacity at constant volume and pressure, and thermal expansion coefficient also represent the good performance of zirconium carbide and titanium carbide compounds at high temperatures and pressures.