JOURNAL OF ADVANCED MATERIALS AND TECHNOLOGIES
Year:2019 | Volume:7 | Issue:4 |Papers Count:8

The Current investigation was designed to study different steps of powder injection molding of Stainless Steel/TiC Composite. So a multi-component binder was selected and its melting, recrystallization and degradation temperatures were evaluated via DSC and TGA experiments. In order to study the rheological behavior of feedstock, a capillary rheometer was incorporated and the effects of shear rate, TiC content, temperature and solid loading on rheological behavior of feedstock were investigated and based on the results the best feedstock and processing temperature were selected. In the next step, some samples were injection molded at two temperatures (93 and 115 oC) and two pressures (5 and 10 MPa). Results showed that by increasing temperature from 60oC to 70oc the viscosity decreased 20% but will be stable in higher temperature. The viscosity of all sample was below 1000 Pa. s. the calculated solid loading was 64%. By adding TiC particles, the green density of samples decreased from 4. 85 gr/cm3 to 4. 7 gr/cm3.

Cr2O3, YSZ and SiC nano-powders were prepared by ball milling and subsequently mixed and agglomerated to reach the proper composition and size for spraying. Morphological investigations and particle size analysis showed that powder particles after 5h of milling time reached to an ultrafine/nano size. The powder mixtures were then deposited onto 304L steel substrates using Atmospheric Plasma Spray (APS) to deposit Cr2O3-20vol%YSZ-10vol%SiC composite coating. Microstructure and morphology of the elemental/milled powders and plasma sprayed coatings were characterized using Field Emission scanning electron microscopy (FESEM) equipped by EDS. X-ray diffraction (XRD) patterns of powder particles and coatings included only the elemental peaks without any traces of impurities and new appearance peaks. Using image analysis method, the coatings porosity content increased from 8. 7 to 12. 8 through formation of composite coating. Also mechanical properties of the coatings including bonding strength, micro hardness and fracture toughness were evaluated. The results showed that coatings have high bonding strength of 40-49 MPa. Regarding hardness and toughness results, adding reinforcements to Cr2O3 coating increased hardness and toughness to 910 HV and 8. 1 MPam1/2, respectively.

Carbide free bainitic steel, so called supper bainitic or nano-structured bainitic steel has attracted considerable attentions due to its remarkable combination of strength and ductility. Unfortunately, the effect of prior austenite grain size has not been investigated for the low carbon nano-structured bainitic steels. In this research, attempts were made to understand the effect of prior austenite grain size effect on the microstructure of carbide free medium carbon bainitic steel. The steel was cast by using induction furnace under argon gas atmosphere. The ingot was electro-slag-remelted (ESR) to obtain clean steel followed by hot rolling.

Inconel 718 is precipitation strengthened Ni-base superalloy that is strengthened by γ ″ precipitate with the Ni3Nb chemical composition, widely used for medium and high temperature applications in different industries. Despite high resistance to strain aging cracking for Inconel 718, this alloy is more sensitive to solidification and liquation cracking. The main purpose of this investigation is to compare the effect of Nd: YAG pulsed laser and fiber continuous laser on the Microstructure, Connection Geometry and Hot cracking Mechanism in Inconel 718. For this purpose, an Nd: YAG pulsed laser device and a continuous wave fiber laser device were used. To determine the percentage of the elements, using the quantum test and an electron microscope and optical microscope (OM) was used to investigate the microstructure and electron microscopy (SEM) equipped with EDS also used for chemical analysis.

This article reports a simple and novel method to synthesize magnetic nanoparticles embedded into thermosensitive copolymers. To form a stabilized suspended core, Co-Zn ferrite nanoparticles synthesized through thermal decomposition method. Oleylamine as a surfactant used as hydrophobic agent at the surface of nanoparticles. Amphiphilic thermo-sensitive copolymer linked with magnetic nanoparticles. Composite of magnetic nanoparticles and polymers can be suspended in hydrophobic media. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) used as structural analysis to confirm spinel structure. Crystallite size of magnetic nanoparticles estimated by Rietveld refinement from XRD patterns. The particle diameters measured approximately 9± 1 nm with TEM micrograph. Also, UV-visible used as a method to determine LCST temperature of nanoparticles. These novel magnetic thermo-responsive composite have potential applications in biomedical applications, such as, protein immobilization, hyperthermia cancer therapy and target drug delivery systems.

In this research work, the effects of nano-diamond addition on densification and mechanical properties of 25 vol% SiC reinforced ZrB2-based ultra-high temperature composites were studied. In this way, a ZrB2– SiC composite (as the baseline) and three ZrB2– SiC-based composites doped with different amounts of nano-diamond additive (1, 2 and 3 wt% of matrix phase) were fabricated by spark plasma sintering route. The sintering process was carried out at 1900 ° C for 7 min under 40 MPa. The addition of nano-diamond, up to 2 wt%, has not significantly affected the densification process because the 0-2 wt% nano-diamond reinforced samples reached their theoretical densities but the relative density of sample reinforced with 3 wt% diamond was less than 99%. The hardness of 0, 1, 2 and 3 wt% diamond reinforced ceramics were 19. 5, 23. 4, 24. 7 and 22. 2 GPa, respectively. All diamond reinforced samples were harder than the diamondfree one but the hardness slightly decreased by the addition of 3 wt% diamond. The fracture toughness linearly increased from 4. 3 MPa. m1/2 for diamond-free ceramic to 5. 8 MPa. m1/2 for3 wt% diamond reinforced sample. The sintering route was a reactive process as the nano-diamond was transformed to the graphite during the sintering and/or converted to the in-situ formed ZrC and B4C phases through the removal of oxide impurities from the surfaces of raw materials.

In this study, the effect of yttria and benzotriazole doping on corrosion behavior and activation of self-healing mechanism in Alumina-based nanostructured coatings was investigated. Single-component Alumina, double-component Alumina-Ytteria, and triple-component Alumina-Ytteria-benzotriazole ceramic-based coatings have been layer-deposited over St52 steel surface by the sol-gel process in order to improve the abrasion and corrosion behaviour of this steel. Afterwards, phase analysis, morphology, and topography of these coatings have been carried out respectively by Grazing Incidence X-ray Diffraction (GIXRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Atomic Force Microscopy (AFM). Moreover, in order to investigate elemental distribution in layer-deposited coatings, Energy Dispersive Spectroscopy (EDS) was performed. Also, the corrosion behaviour of under-investigation coatings and substrate were studied using electrochemical impedance spectroscopy and potentiodynamic polarization for 1, 48, and 96 hours of immersion in 3. 5wt%NaCl solution. GIXRD results revealed the amorphous nature of the coatings and the absence of formation of crystalline structure. AFM and FE-SEM observations revealed intactness of double-component Alumina-Ytteria and Alumina-Ytteria-benzotriazole coatings in comparison with single component Alumina coating.

The poly (ɛ-caprolactone)/gelatin nanofibrous scaffolds with weight ratio of 70: 30 and PCL/gelatin 70: 30 nanocomposite scaffold containing 0. 5%wt. MWNTs (PCL-gelatin/0. 5%wt. MWNT) were fabricated through electrospinning. The morphology, physical and mechanical property of the scaffolds was evaluated through SEM, FTIRATR, water contact angle and tensile strength test. The scaffold containing 0. 5%wt. MWNTs had the best average and distribution of fibers diameter in comparison with PCL/gelatin scaffold due to the increased conductivity of the solution and the alignment of the MWNTs in the nanofibers. The presence of MWNTs did not have any reverse effect on the porosity of the scaffolds and the porosity percentage of the scaffolds was more than 80%. According to FTIR spectra there was a connection between gelatin amine group and MWNTs carboxylic group that could affect the mechanical properties directly. Adding 0. 5%wt. MWNTs to the PCL/gelatin scaffold decreased contact angle and lead to an increase in mean tensile strength about 7 times in comparison with scaffold without MWNTs. The enhancement of the mechanical properties of the scaffold can be seen due to the inherent strength of MWNTs, the position of the MWNTs in the polymer nanofibers and the optimal dispersion in the polymer matrix. PCL-gelatin/0. 5%wt. MWNT scaffold can be an appropriate scaffold for tissue engineering applications.