جستجوی مقالات مرتبط با کلیدواژه « microwave sintering » در نشریات گروه « مواد و متالورژی »

In this research, Li2TiO3 ceramic was sintered via heating procedures of conventional and microwave sintering. The maximum density of 3.08 g/cm3 at 1200˚C with 3 h holding time and 3.12 g/cm3 at 1300˚C without any holding time was achieved through conventional and microwave sintering, respectively. The thermal behavior was investigated using DTA-TG, phase analysis was performed by XRD technique, and microstructures were observed by FE-SEM. Also microwave measurements were performed using Network Analyser. XRD investigations showed a higher intensity of (002) peak located at 2θ=18.46˚ in microwave sintered part attributed to higher degree of cation ordering and superlattice formation. Microstructural investigations by SEM revealed the finer microstructures of microwave rather than conventionally sintered parts. The maximum microwave characteristics were measured εr= 20.29 and Q×f = 26191 GHz for parts sintered in a conventional furnace at 1200˚C and εr= 20.86 and Q×f = 25610 GHz for parts sintered in microwave at 1300˚C.

In this research, aluminum-tungsten carbide metal-base composites were fabricated by microwave and conventional sintering methods and compared. Three-point bending strength specimens were prepared with uniaxial press at 250 MPa and then were sintered in graphite bed at 650 °C and 750 °C in microwave and conventional furnaces for 1 minute and 1hour, respectively. Density and mechanical properties (bending and compressive strength and microhardness) of samples were calculated. The highest bending strength of conventional andmicrowave sintered samples were 143 and 231 MPa at 750 °C, respectively. XRD patterns showed the decomposition of WC particles and formation of Al5W interfacial reaction product phases in microwave heating method processes. SEM studies showed that WC reinforcement particles had uniform distribution in Al matrix.

The work evaluates the effect of Al2O3 nanopowder addition on microstructure, tribological and corrosion properties of CuNi-Al2O3 nanocomposites. The elemental powders of Cu and Ni contains 0, 10 and 20 vol. % of Al2O3 nanopowder were mixed in a high-energy ball mill in Ar atmosphere for 30 h. Phase transformation of the alloyed powders obtained were characterized by X-ray diffraction (XRD). The results show that CuNi solid solution alloy was formed during mechanical alloying (MA) process through milling-induced interdiffusion of the elements. Mechanically alloyed powders compacted under cold pressure at 350 MPa. The green compacts were sintered in microwave furnaces (2.45 GHz) for 90 min at 600 W radiation powers. The microstructural analysis of the cross section of the sintered samples was made using scanning electron microscopy (SEM). The sintered sample show fully dense microstructure without any radial cracks. Tribological properties of sintered nanocomposites were evaluated by ball-on-disk wear test. Increasing the Al2O3 content in the nanocomposite decreased the wear rate and coefficient of friction. These results showed that the addition of Al2O3 nanopowder in the NiCu matrix caused improves its wear behavior. The corrosion performances of nanocomposites were evaluated by potentiodynamic polarization in 1 M NaOH solution. Corrosion experiments show that addition of Al2O3 nanopowder is not effective on the corrosion behavior.

Al-SiC-TiC composites have been produced via conventional and microwave sintering. The initial composition as: SiC 15 wt%، TiC 1، 3، 5 and 7 wt% and Al balance، were compacted with uniaxial press at 240 MPa. Green samples were subjected to sintering at 650، 750، 850 and 950°C for 1 h and 1 min in a conventional sintering method and a microwave، respectively. Results indicated that the optimum bending strength corresponded to the sintering at 950°C for samples with 7 wt% and were 140 MPa and 215MPa for conventional and microwave sintered samples، respectively. The microwave sintered specimens showed more uniform distribution of reinforcement particles and higher density than conventional sintered ones concurrent time and energy saving. SEM studies revealed a homogeneous distribution of carbide phases within the Al matrix.