Papers by Keyword: Scanning Electron Microscope (SEM)

Abstract: Mullite was synthesized by firing precursors prepared from kaolinite via a wet chemistry method at various temperatures. The acicular mullite grains were formed in samples with addition of AlF3 by this process. The phase evolution and morphology of the fired samples were investigated. For the samples without AlF3, the mullitization began to occur at 1300 and almost completed at 1550 , the grains formed were normal-shaped. For the samples with AlF3, acicular mullite was formed, and mullitization began to occur at 1100 and completed at 1250 . The growth of the acicular mullite was associated with a liquid phase. The formed acicular mullite was alumina-rich and had a composition of about 73.4 wt% Al2O3 and 26.6 wt% SiO2 (Al2O3/SiO2=1.65, molar ratio).

Abstract: The Shoushan Stone is one of the famous craft carving stones in China and the transparency is one of the decisive factors to appraise its value. The better the transparency is, the higher the value is. In this paper, the mineral compositions and morphology of some Shoushan Stone samples were investigated by XRD and SEM methods. Combining with the characterization of Shoushan Stone, the relationships between the morphology and the transparency of Shoushan Stone were studied. The results show that the transparency of Shoushan Stone samples was determined by their microstructures, such as the mineral particle sizes and its arrangement, the gaps and porosity. The Shoushan Stone samples with high transparency are those with good arrangement, bigger crystal particle and less porosity and gaps.

Abstract: SEM observations of coir fiber microstructure have been carried out. Uneven surface characteristics are conducive to the bonding between coir fibers and resin materials. The unique advantages of coir fiber have been verified. Doing orthogonal experiment design for coir fiberboard, the coir fiberboard can meet the mechanical properties of National Standards of China. The various factors optimization plan on the performance of coir fiberboard has been obtained. FFT nondestructive testing has been done for the coir fiberboard. Nondestructive testing results show that the good correlation exists between dynamic mechanical properties and the static test results.

Abstract: To improve the current efficient of Al-Zn-Sn alloy, the influence of different contents Ce on the microstructures and electrochemical properties of alloy was investigated. The results show that the appropriate amount of Ce was effective on improving the electrochemical properties of Al-Zn-Sn alloy. The corrosion potential shifted negatively and the current efficiency increased with the increasing of Ce contents. The optimal microstructure and electrochemical properties were obtained when the Ce content in the alloy was 0.5 wt.%. The good electrochemical properties of Al-7Zn-0.1Sn- 0.5Ce (wt.%) alloy is mainly attributed to the fine grains and the less segregation phases at grain boundary.

Abstract: Both a low and a high resistance stateｓ which were written by the voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the secondary electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.

Abstract: SiC Ceramic was joined to itself using active brazing Alloys, like Ti in shape of sheet filler of Ag-cu and Ti-6AI-4V. This operation is occurred in an inert gas furnace.Interfacial microstructure studied with Scanning electron microscopy and X-Ray diffraction. Variation of Electrical Specific Resistance measured by 4 pin astute multimeter and strength of these joint was measured by fracture shear loading. This Joint is happened at 900c and upper temperature with 90 minutes and upper time. Electrical specific Resistance goes upper with joint in low temperature & time but this variation is very little. The microstructure showed an excellent bonding at the interfaces. The data showed also that the joining of the SiC decreases with increasing temperature and time.

Abstract: Tetragonal zirconia in alumina matrix is known as Zirconia Toughened Alumina (ZTA). ZTA ceramics are attractive materials due to the combination of both ZrO2 (high strength and fracture toughness) and Al2O3 (high hardness and wear resistance) properties. This work reports the synthesis of ultra-fine Al2O3–ZrO2 powders (20–200 nm) through the wet chemical route. Hundred percent tetragonal ZrO2 can be found in the sintered body Al2O3(matrix)-30%Y0.1Zr0.9O2 at 16000 C/2 h with 98% densification. The fine ZrO2 (100–300 nm) has been homogeneously dispersed within the alumina matrix with a maximum grain size of 0.8 μm, which will increase the toughness of the alumina matrix. High fracture toughness of Al2O3-30%Y0.1Zr0.9O2 is attributed to the presence of a coupled mechanism of stress-induced transformation toughening and transformation-induced microcrack toughening, and high flexural strength of the ceramics is a coupled result of small-size flaw and high fracture toughness. Because of no amorphous phases and grain boundaries but clean and stable phase interfaces in the ceramic composite, the Al2O3(matrix)-30%ZrO2 and Al2O3(matrix)-30%Y0.1Zr0.9O2 obtained in the experiment are promised to have excellent strength retention and high creep resistance at high temperature, compared to ones prepared by powder sintering method.

Abstract: In the frame of a wide research program devoted to the matter recovery from waste by means of thermal processes, particular efforts have been put into the study of biomasses and waste residue of peculiar composition, which could be used as precursors of ceramic materials. Rice shells are waste biomasses coming from the purification process of rice, which show a high carbon and silica content. The exploitation of these peculiarity promoted a series of experimental activities, aimed at the production of ceramic materials through high temperature carbothermal synthesis reactions. The synthesis products were characterized by X Ray Diffraction (XRD) and scanning electron microscopy (SEM) and the data confirmed the production of ceramic silicon nitride (Si3N4) at high yield and purity, under the adopted process parameters.

Abstract: Nowadays, with increase amounts of sludge derived from the treatment of domestic sewage put pressure into research on systems for the adequate use of these materials. The aim of the present work is to study the use of sludge ash, from sintering and calcinated process, as a raw material for the ceramic industry. Using the sewage sludge ashes as ceramic raw material there will be no contamination of soil and underground water. Metals and toxic compounds like Al, Fe, Ba, Cr, Cu, Mn and Zn oxides were analyzed and characterized by X-ray fluorescence (XRF), scanning electron microscopy (SEM) and plasma emission spectroscopy (ICP-OES). The leached material was chemically analyzed where the integration of oxides into the ceramic matrix of sludge ash was observed. Residual decomposition was analyzed by TG, DTG and DTA curves.

Abstract: The present study suggests the use of high energy ball milling to mix (to dope) the phase MgB2 with the AlB2 crystalline structure compound, ZrB2, with the same C32 hexagonal structure than MgB2, in different concentrations, enabling the maintenance of the crystalline phase structures practically unaffected and the efficient mixture with the dopant. The high energy ball milling was performed with different ball-to-powder ratios. The analysis of the transformation and formation of phases was accomplished by X-ray diffractometry (XRD), using the Rietveld method, and scanning electron microscopy. As the high energy ball milling reduced the crystallinity of the milled compounds, also reducing the size of the particles, the XRD analysis were influenced, and they could be used as comparative and control method of the milling. Aiming the recovery of crystallinity, homogenization and final phase formation, heat treatments were performed, enabling that crystalline phases, changed during milling, could be obtained again in the final product.