Journal of Advanced Materials in Engineering (Esteghlal)

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In recent years many different ways have been investigated by steel producers to increase ductility, impact strength and formability of steels. More important ways are steels with very low amounts of inclusion, small size inclusions and modified inclusions. In this study, experiments have been performed on the API-X42 steel produced by the electric arc furnace in Mobarekeh Steel Co. After the preparation of the melt in the electric arc furnace, it is taped in a 200-ton ladle and ladle treatment was preformed in a ladle furnace (LF) in the steelmaking shop. In this study the effects of amount and the rate of CaSi wire addition on the shape and structure of inclusion were investigated. The optimum conditions for adding CaSi for inclusion shape control were also determined. Scanning electron microscope (SEM) and chemical energy analysis dispersive system (EDS) showed that adding calcium to the melt affects the chemical composition of inclusions present in steel melt. The effects of CaSi wire injection treatment, injection amount and inclusion shape control on the impact property and formability of steel were shown using charpy impact test. Keywords: Inclusion shape control, calcium treatment, ladle furnace and inclusion modification

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Nanowire is a cylindrical nano-structure with nanometer dimensions. In this research, the studied nanowire was made from the magnetic triple Ni-Fe-Co alloy. We utilized ordered porous anodic aluminum oxide as a template for the nanowire deposition. The nanowire arrays were electrodeposited in the cylindrical pores of the oxide layer by AC potential in a simple sulfate bath. Then the relation of shape and composition of the nanowires with their fabrication parameters was investigated. The results showed that the barrier layer modification had an essential role in the deposition process and a composition gradient was detected in a single nanowire.

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The formation of microporosity in modified Al-Si alloys has been reviewed in the present study. A major concern in modification is the increased tendency to form microporosity in the macro-shrinkage free Al-Si alloy castings. It has also been demonstrated that at low hydrogen contents (0.1cc/ 100g, Al), where only shrinkage porosity should occur, the effect of Sr-modification on porosity content is not considerable, indicating that the increase in porosity is due to an increase in gas porosity. Modification treatment, however, does not add hydrogen to the melt, nor does it increase the rate of regassing of the liquid, revealing that it can not enhance pore formation by increasing the melt hydrogen content. Modification treatment raises the freezing range (4-10 oC), but this increased freezing range exerts only a very small effect on microporosity formation, which cannot, by itself, explain the increased tendency to microporosity formation observed in modified alloys. The presence of modifiers slightly decreases the surface tension of the melt (5%), although this decrease in surface tension is not sufficiently high to considerably enhance pore formation in modified alloys. Many researchers have reported that modification treatment might favour the formation of porosity due to its effect on oxide use in the heterogeneous pore formation although the systematic observation of pores has shown that SrO does not take part in pore fomation in Sr-modified alloys. Strontium and other modifiers which increase pore formation (Na and Ca) in Al-Si alloys have a high chemical affinity to form complex intermetallic compounds with Si and Al. Systematic observation of pores have shown that Sr-rich intermetallics take part in pore formation. Thus, Sr-modification may increase the porosity content through the formation of Sr-rich compounds during solidification.

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Polypropylene (PP) has poor adhesion to metals and other surfaces for its chemical structure. Hence, chemical modification of PP is necessary for metal surface coating application. In this research, grafting of maleic anhydride (MA) onto co(propylene-b-ethylene) in the presence of a dicumyl peroxide (DCP) was accomplished in a single screw extruder. Characteristics of the modified polymer were determined by Infra-red Spectroscopy (IR), Scanning Electron Microscopy (SEM), and adhesion test. Maximum grafting of MA was found to be 1.2832% for 1.5 pph of MA. Adhesion test showed that the samples containing 1 pph of MA (degree of grafting is 0.5816%) had better adhesion to steel surface (17.25 kgf).

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The osseointegration of oral implants is related to the early interactions between osteoblastic cells and titanium surface. Chemical surface modification of titanium (Ti) implants is used to improve peri-implant bone growth, bone-to-implant contact, and adhesion strength. Thus, in this study, the surface topography, chemistry, and biocompatibility of polished titanium surface treated with mixed solution of three acids containing hydrochloric acid (HCl)- hydrofluoric acid (HF)- phosphoric acid (H3PO4) were studied under different concentration conditions. Moreover, Osteoblast cell (MG-63) was cultured on the and treated polished titanium surface. Also, in order to investigate titanium surface, SEM, AFM and EDS analyses were carried out. The results revealed that the surface of titanium treated with mixed solution containing the aforesaid acids had higher roughness, cell attachment, and proliferation than the controls

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Employing direct and alternative electric currents at the time of casting and solidification modified grains of Al and Si. The highest wear resistance was obtained in the direct current, and for alternative current the wear resistance corresponded to the electric current. The change of polarity in the pure Al did not influence the wear resistance, but for the Al-Si alloy the highest wear resistance was obtained when the mold was connected to the positive and the molten metal to the negative pole. Direct current used in the Al-Si alloy brought about three different microstructures including the stretched clusters of Si in the electrons' direction near the negative pole, fine clusters of Si in the intermediate zones that surrounded the oval shape of α-Al, and broken Si clusters near the positive pole.

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In this study, NBG was successfully achieved through a sol-gel technique, and to further improve its dispersibility, a crylate coupling agent was coupled onto the surface of the NBG. The 3-(Trimethoxysilyl)Propylmethacrylate coupling agent was used to the surface modification of the synthesized NBG by a wet-chemical method in a dynamic inert nitrogen atmosphere. The surface properties of the biomaterials before and after modification were characterized and compared using FTIR and AFM techniques. The characteristic peaks in FTIR spectra indicated that –CH2, –CH3 and C=O groups appeared on the surface of modified NBG, and also, AFM analysis revealed that the dispersibility of surface modified NBG was improved, significantly. The above results proved that the desired groups of 3-(Trimethoxysilyl)Propyl methacrylate had been covalently bonded onto the surface of NBG. Besides, a nanocomposite scaffold was synthesized using the synthesized NBG and polyurethane foam as raw materials. The morphology of pores, porosity contents, compress strength and bioactivity of the scaffold were studied. The results showed that the biological scaffolds for use in bone tissue engineering with the basic requirements (90% porosity and 200-600 μm pore diameter) were successfully prepared. The polymer component had no effect on the relationship between the scaffold pores and bioactivity of bioglass nanoparticles. Improvement of compressive strength and proper bioactivity of the resulted scaffold showed that it is an acceptable candidate for biomaterials applications.

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