جستجوی مقالات مرتبط با کلیدواژه « Sintering » در نشریات گروه « فنی و مهندسی »

The purpose of this research was to fabricate and investigate the properties of SiC-5TiB2 nano composites reinforced by gaphene quantum dot nanoparticles via pressure less sintering method. In this way, SiC, TiB2, and graphene quantum dot raw materials were used in nanometer dimensions. First, before performing any laboratory operations, experimental samples were designed using Minitab 14 software. The design was done by the Taguchi method according to the L9 array and the parameters of the amount of gaphene quantum dot amplification in three levels were set at 0.2, 0.6, and 1 wt.% and sintering temperatures were defined as 2000, 2100, and 2200°C. The sintering process was carried out at certain temperatures in argon atmosphere for 2 h. XRD, FESEM, FTIR and Raman spectroscopy were performed. Density, micro hardness, and fracture toughness measurements were used for further investigations of physical and mechanical properties. The microstructure of the samples was also observed to determine the fracture toughness mechanisms. The results showed that the parameter of the amount of reinforcement was in the first rank of influence and the sintering temperature was in the second rank, and the best results were obtained in the sample with the amount of 0.6 wt.% of gaphene quantum dot and the sintering temperature of 2100 °C, where hardness and fracture toughness values were obtained to be 27.7 GPa and 3.3 MPa.m1/2, respectively.

In this research, PZT fibers were fabricated using PZT-5A commercial powder, polymeric additives and deionized water as solvent. The rheological behavior of different pastes with various amounts of solids and additives was investigated and the best paste was selected for syringe injection (extrusion process). Meanwhile, the paste containing 85wt% solid content and 1wt% glycerol, which was prepared using a 15wt% PVA solution, showed the best rheological behavior. The obtained fibers were dried at 100°C and the burnout process was carried out at 600°C with heating rate of 1°C/min for 2 hours. The sintering process was carried out in the temperature range of 1220-1270 ͦC for 2.5-4 hours. The phase investigations conducted by X-ray diffraction analysis showed that the fibers sintered at 1220°C have a single-phase perovskite structure and peak splitting confirms the ferroelectric nature of fiber. However, at higher sintering temperature, secondary peaks related to zirconium and titanium oxides were observed in the fiber diffraction patterns. Scanning electron microscope (SEM) images from the surface of the fibers showed that the fibers sintered at 1220°C for 2 hours were free of any cracks and had an acceptable density. In addition, based on the SEM images from the fracture surface of the fibers, the microstructure of this sample consisted of cuboid grains with average size of 1.5 μm, which is half of the average grain size of bulk PZT with spherical grains at its optimum sintering temperature.

MAX phases are an attractive class of layered solids that have recently attracted a great deal of attention due to their unusual and unique composition. The ternary compound Ti3SiC2 is an example of a material that combines the properties of ceramics and metals. As a ceramic, they are high stiff. Some of them are resistant to oxidation, creep, fatigue, corrosion. They are extremely refractory and have a high melting temperature. Also, their strength remains stable with temperature. When considered as a metal, this compound is a conductor of electricity and thermal and is not prone to thermal shock, has easy machining with a variety of modern tools, is relatively soft and also has high chemical resistance. Combining SiC with Ti3SiC2 for fabrication the composite is an effective way to improve the high temperature properties, because SiC as a reinforcing phase has good oxidation resistance, high hardness, abrasion resistance, and in addition, it is compatible with Ti3SiC2 at high temperatures. Fully-dense Ti3SiC2 –SiC composites were in-situ synthesized and sintered through a reactive hot-pressing process using TiC and Si powders with different molar ratios of 3TiC:3Si, 3TiC:2Si (stoichiometric composition), and 3TiC:1.5Si. Phase characterization of the hot-pressed specimens was performed by X-ray diffraction (XRD) analysis, and the microstructures were studied by scanning electron microscope (SEM). The mechanical properties of the hot-pressed composites were investigated in terms of Vickers hardness, fracture toughness, and flexural strength. It was found that the in-situ synthesized SiC particles, with platelet morphology, have been distributed in the in-situ formed Ti3SiC2 matrix. The highest Vickers hardness belonged to the 3TiC:1.5Si sample with a value of 14.2 GPa, related to the presence of SiC and residual TiC phase in the microstructure. The flexural strength enhanced with increasing the molar value of Si, due to the presence of the free Si phase in the sample and the further formation of the SiC phase. The 3TiC:3Si sample achieved the highest fracture toughness of 10.1 MPa.m1/2 and the highest flexural strength of 576 MPa.

Amorphous slag from the electric arc furnace of Mobarakeh Steel Company, and soda ash flute glass waste (window, mixed with equal weight ratio and sintered with foaming agents and used to prepare glass-ceramic foam. Five types of foaming agents including silicon carbide, calcium carbonate, chromium oxide, graphite and barium carbonate were added to the base composition in five amounts and sintered at 1200 ° C.The crystalline phase crystallized in the composite was at a low weight percentage of foaming agent wollastonite and with increasing weight percentage by 5% Pesudo wollastonite-.The highest volume increase is related to the sample with 5% by weight of barium carbonate and the highest porosity is related to silicon carbide with 1% by weight.The highest compressive strength among the three approved compounds reaches 4.8 MPa in terms of microstructural content of the sample with a weight percentage of calcium carbonate.Also, the distribution of porosity in all foam foams used is non-uniform and only chromium oxide has a better distribution than others.

In this study, the solution combustion method was used to synthesize a bioactive borate compound. XRD, FTIR, PSA analyses have been used to identify phase composition, bond determination, and particle size, respectively. In addition, MTT and cell migration 3assay were utilized to measure the biocompatibility of the particles. The synthesized particles not only were nano in size along with amorphous structure, but also showed positive effects on cell proliferation and migration. To attain bioactive compositional scaffolds, the borate amorphous compound was combined with hydroxyapatite nanoparticles at different weight percentages. Afterward, mixtures were sintered at 600, 650, and 700 oC for 0.5 and 1 h. XRD and DTS analyses were operated to evaluate the phase composition and mechanical strength. FESEM micrograph was evaluated to observe the crack path in addition to porosity andthe effect of borate glass on the sintering process. The sample sintered at 700 oC for 1h containing 20% borate glass and 80% of hydroxyapatite, accounted for the highest mechanical strength at 4.87 ± 0.02 MPa. ICP-OES analysis of the sample containing 20% hydroxyapatite, which was sintered at 700 oC for 1 h, showed an increase in ion release compared to pure sintered hydroxyapatite after immersing in SBF for 7 days. Also, ion release of the borate glass has considerably been controlled and diminished by virtue of combining and sintering with hydroxyapatite nanoparticles. Furthermore, the mentioned composition is able to bond with soft tissue as well as hard tissue.

The one forming method in powder engineering is the injection molding method of metal powders. The combination of conventional molding methods in plastic injection and using metal powders has led to significant improvements in the quality of production of sensitive and complex parts in various industries. In this method, the metal powder is mixed with a set of polymeric materials and an injectable mass is formed, which is called feedstock. The resulting feedstock is injected by metal injection machines and the binder part is removed. The de-adhesive part is subjected to a sintering process by controlled atmosphere furnaces to increase its strength and mechanical properties. In this research, first, the optimal binder composition for the production of industrial parts is created. In this research de-binding of a polymeric component at low temperatures is applied to reduce the total production costs of synthesis and after injection of the properties of the final part was discussed. The most important feature of industrial binder composition in the production of various parts is its high ability to remove quickly and without creating cracks and blisters in the final part, while the components of the optimal binder must be available and show good sintering behavior. Based on the results, a four-component binder based on polyethylene oxide has been synthesized, while reducing the final price of the parts, it has been removed well during the solvent and thermal descaling process and its slow release rate during cracking have prevented cracks and blisters in the final parts.

Recovery of machined filings in the form of powder used in the metallurgy industry has a very favorable economic advantage. In order to optimize this process and maximize the efficiency of recovering gray cast iron filings by spray mill method, the experimental design techniques are used in conjunction with the sensitivity analysis in this paper. By Design of experiments based on the response procedure, four main factors were extracted as input variables including cast iron powder, compression pressure, sintering temperature and sintering time. These input variables are investigated on three important outputs of machining capabilities including axial force, drilling torque and surface roughness based on sensitivity analysis. The sensitivity analysis method, which is based on the analysis of variance, is E-fast. The sensitivity analysis is a statistical method results in describing the quantitative and qualitative changes of the input variables on the output factors. For the axial force, the effect of the input variables was obtained with 37%,31%,27%,5% for cast iron powder, sintering temperature, compression pressure and sintering time, respectively. Also for drill torque, parameter impressment is 44% cast iron powder, 38% compression pressure, 15% sintering temperature and 3% sintering time, respectively. Cast iron powder percentage, compression pressure, sintering temperature and time have impressed on surface roughness, respectively with 26 %, 49 %, 19%, 6%.

Powder metallurgy involves forming processing of metal powders into useful metallic parts. In fact this process is a unique method which can produce porous parts so that its porosities, distribution and pour size are controllable. Stainless steel filters are commonly made from steel or alloy powder via pressing and sintering. In this research, ST.ST.316L and ST.ST. 316Lt + 2%wt Sn powders have been used to from filter by using uniaxial press to forming powder and then sintered. When Tin powder added sinterability showed improved. Tin addition affected microstructure so that grain growth was obvious evidence, also pore size expansion occurred. Grain coarsing in the sintered tin added stainless steel samples may indicate that liquid tin accelerates atomic diffusion related processes occurring during heating of powder compacts. Also, some pores created by Tin particle disappearance, were observed in addition to those initiated by original voids in the green compacts. The remained porosity was between 46 to 38 %.