Showing papers on "Sialon published in 2011"
TL;DR: In this article, a triplevalent Pr3+-doped oxynitirde red phosphors β-SiAlON with composition Si6−zAlzOzN8−z:Prx (z = 0-2.0, x = 0.016) were synthesized by gas pressure sintering (GPS) at 1950 °C for 2 h.
Abstract: Trivalent Pr3+-doped oxynitirde red phosphors β-SiAlON with composition Si6–zAlzOzN8–z:Prx (z = 0–2.0, x = 0.016) were synthesized by gas pressure sintering (GPS) at 1950 °C for 2 h. Red luminescence in the range 600–650 nm was detected upon excitation with 460 nm blue light, indicating that the phosphor can be excited by blue InGaN light-emitting diodes (LED). The crystallization and cell parameters of samples were investigated by powder X-ray diffraction (XRD), Rietveld refinement, and high-resolution transmission electron microscopy (HRTEM). Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) were further adopted to examine the effect of Al substitution on the microstructure. 27Al and 29Si solid-state nuclear magnetic resonance (NMR) data are consistent with SiN4–xOx and partially substituted AlN4–xOx tetrahedra. The temperature-dependent luminescence from the 1D2 and 3P0 states of Pr3+ were studied (10–573 K), and the integrated red emission from 600 to 650 nm increased w...
161 citations
TL;DR: The experimental results indicate that β-SiAlON:Yb2+ is a potential green phosphor for white light-emitting diodes (LEDs), which use blue LEDs as the primary light source.
58 citations
TL;DR: In this paper, a novel Eu 2+ activated Sr-SiAlON oxynitride phosphor, with the chemical composition of Sr 14 Si 68− s Al 6+ s O s N 106− s :Eu 2 + ( s ǫ ≥ 7), was synthesized by firing the powder mixture of SrO, SrSi 2, α-Si 3 N 4, AlN and Eu O 3 at 1900°C for 6h under 1MPa nitrogen atmosphere.
47 citations
TL;DR: In this paper, a mechanochemical activation route was proposed for the synthesis of fine Eu 2+ -doped Ca-α-SiAlON phosphors by using stoichiometric mixtures of β-Si 3 N 4, AlN, Al 2 O 3, CaO and Eu O 3.
41 citations
TL;DR: In this article, single-phase β-SiAlON compacts with z = 1 have been synthesized by reaction-bonded sintering using Si and Al2O3 as raw materials.
36 citations
TL;DR: In this paper, a review article covering various methods reported on synthesis of β-SiAlON based ceramic materials and on their net-shape consolidation into radome structures is presented.
Abstract: This paper is a review article covering various methods reported on synthesis of β-SiAlON based ceramic materials and on their net-shape consolidation into radome structures. It also identifies a composition out of a wide-range β-Si 6-z Al z O z N 8-z (where z = 0–4.1) solid solution suitable for radome applications and discusses about various efficient methods reported on fabrication of radome structures out of these compositions. This article also covers the literature pertaining to β-SiAlON-SiO 2 ceramic composites, which are considered to be materials of choice for certain high speed radome applications. Further, successful techniques employed for passivation of AlN powder against hydrolysis are also covered as this powder is one of the starting materials for both β-SiAlON and β-SiAlON-SiO 2 ceramic composites. Surface passivation of AlN is necessary as it decomposes into alumina and ammonia, when it comes into contact with water during aqueous processing of SiAlON based ceramics, thereby not permitting formation of desired SiAlON phase. Finally, the important properties of various commercial radome materials together with those of β-SiAlON and β-SiAlON-SiO 2 ceramic composites are also reviewed and presented in this article.
36 citations
34 citations
01 Jan 2011
TL;DR: The widespread interest in silicon nitride ceramics stems from their desirable physical and mechanical properties in many high temperature and pressure applications as mentioned in this paper, such as good resistance to oxidation and corrosive environments, low coefficient of friction and thermal expansion, negligible creep, and high decomposition temperature.
Abstract: The widespread interest in silicon nitride ceramics stems from their desirable physical and mechanical properties in many high temperature and pressure applications [1, 2, 3, 4, 5]. Good resistance to oxidation and corrosive environments, low coefficient of friction and thermal expansion, negligible creep, and high decomposition temperature are some of these important properties. Because of these, silicon nitride (especially its polymorph) is widely used in gas turbines, engine parts, bearings, dental drills and gauges, and cutting tools. In addition, thin films and coatings have been studied in relation to high-speed memory devices [6, 7, 8, 9, 10] and optical waveguide applications [11].
33 citations
TL;DR: In this paper, the effects of starting β-Si 3 N 4 particle sizes and post-sintering heat treatment on microstructure evolution and mechanical properties of prepared α-β SiAlON ceramics were reported.
Abstract: In the present study, we report the effects of starting β-Si 3 N 4 particle sizes and post-sintering heat treatment on microstructure evolution and mechanical properties of prepared α–β SiAlON ceramics. Three different β-Si 3 N 4 starting powders, with particle sizes of 2, 1 and 0.5 μm were used to prepare α–β SiAlON ceramics by gas-pressure sintering. Elongated β-SiAlON grain morphology was identified in the samples prepared using 0.5 μm particle size β-Si 3 N 4 powder. Low-aspect ratio grain morphology was observed in samples prepared from starting powders with coarse particles (2 μm and 1 μm). The sintered samples were further heat treated to develop desired microstructure with elongated grains. The hardness and indentation fracture toughness values of sintered and heat treated samples were found to lie in the range of 12.4–14.2 GPa and 5.1–6.4 MPa m 1/2 respectively. It was revealed that fracture toughness increases with decrease in particle size of starting β-Si 3 N 4 powder.
32 citations
TL;DR: In this paper, the effects of the activator concentration and the overall composition of host lattice on the phase evolution, morphology, and optical properties were investigated for single-phase Ca-α-Sialon:Ce3+,Li+ can be synthesized at x
30 citations
TL;DR: In this article, a large quantity of core-shell structured Sialon nanobelts containing amorphous carbon in the shell were synthesized by pressure enhanced CVD at 1450 °C without a catalyst.
Abstract: Large quantities of core–shell structured Sialon nanobelts containing amorphous carbon in the shell were synthesized by pressure enhanced CVD at 1450 °C without a catalyst. The products are high-quality nano single-crystalline with a uniform morphology. The yield and aspect ratio are systematically controlled by changing the growth temperature and chamber pressure. The nanostructures were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption isotherms and high-resolution transmission electron microscopy (HRTEM). A stepwise reaction model and luminescence characteristics were proposed based on the experimental results.
TL;DR: Sialon-Si3N4 graded nano-composite ceramic tool materials with five-layered symmetrical distribution were fabricated by using hot pressing technique as mentioned in this paper, and the residual stresses in the surface layer of the graded ceramic tool material were calculated by the indentation method.
Abstract: Sialon–Si3N4 graded nano-composite ceramic tool materials with five-layered symmetrical distribution were fabricated by using hot pressing technique. Mechanical property tests have been conducted to determine the optimal structural parameters and sintering parameters. The residual stresses in the surface layer of the graded ceramic tool materials were calculated by the indentation method. The experiment results showed that Sialon–Si3N4 graded ceramic tool materials with a thickness ratio of 0.3, which were sintered under a pressure of 35 MPa at a sintering temperature of 1700–1750 °C for 60 min, had optimum mechanical properties. And the graded structure can induce residual compressive stresses in the material surface layer. The characterization revealed a typical duplex distribution with small β-Si3N4 grains embedded in the matrix of large β-Si3N4 grains. This duplex microstructure can contribute to the improvement of flexural strength and fracture toughness. Additionally, a mix of intergranular and transgranular fracture, crack deflection and crack bridging in the material surface layer contributed to the strengthening and toughening mechanisms for Sialon–Si3N4 graded ceramic tool materials.
TL;DR: In this paper, the wear and mechanical properties of α- and α/β-SiAlON materials were compared related to the composition, additives and sintering processes, and the results showed that the hardness was not affected by the processing type whereas the toughness values were lower for spark plasma sintered materials than gas pressure sintering materials.
Abstract: In this study, α- and α/β-SiAlON materials, doped with Y 2 O 3 and Nd 2 O 3 , were sintered using two different sintering processes: spark plasma sintering (SPS) and gas pressure sintering (GPS). The wear and mechanical properties of the samples were compared related to the composition, additives and sintering processes. The results show that the hardness was not affected by the processing type whereas the toughness values were lower for spark plasma sintered materials than gas pressure sintered materials. This can be explained by the changed microstructure of the two different types of material. Additionally, α/β-SiAlON materials, sintered using gas pressure sintering, showed a lower wear than the spark plasma sintered materials. The results of the wear test were compared with β-Si 3 N 4 materials and it was observed that α/β-SiAlON, sintered by GPS, has better wear properties than the tested β-Si 3 N 4 materials.
TL;DR: SiAlON:Eu2+ green phosphor was successfully synthesized by solid-state synthesis for application to white-LED as mentioned in this paper, where phase development, microstructure, photoluminescence and thermal quenching properties were investigated.
Abstract: SiAlON:Eu2+ green phosphor was successfully synthesized by solid-state synthesis for application to white-LED. The phase development, microstructure, photoluminescence and thermal quenching properties were investigated in detail. The prepared SiAlON:Eu2+ green phosphor had a rod-like morphology with a uniform particle distribution in length. The SiAlON:Eu2+ green phosphor absorbed a broad UV–Vis spectral region and showed a single intense broadband emission near 540 nm. The prepared SiAlON:Eu2+ green phosphor showed superior thermal quenching properties compared to silicate green phosphor. The light emitting properties of white-LED prepared by SiAlON:Eu2+ as green phosphor was investigated. The white-LED using the prepared SiAlON:Eu2+ green phosphor exhibited good optical stability in high driving currents compared to silicate phosphor.
TL;DR: In this article, azeotropic solvent mixture of 60 MEK/40E, dispersant, binder, and plasticizer was used for tape casting by rheological measurements and tape properties.
Abstract: Suspensions consisting of precursor α/β SiAlON forming powders, azeotropic solvent mixture of 60 MEK/40E, dispersant, binder, and plasticizer were optimized for tape casting by rheological measurements and tape properties. Sodium tripolyphosphate (STPP) was introduced as a dispersant for low temperature applications of α/β-SiAlONs. Optimum STPP amount was determined as 0.012 g/m 2 (of the particle surface) for stable α/β-SiAlON suspensions. Different amounts of binder/plasticizer mixtures were added to the slurries and the effects on rheological and green tape properties were investigated. Green tapes with dibutyl phthalate (DBP), and plasticizer mixture, poly(ethylene glycol) (PEG) and DBP, exhibited centered cracks with high plasticity, on the other hand, polyvinyl butral (PVB) and PEG showed no crack but low plasticity. Therefore, many different parameters were found to be effective on final tape properties. In addition, tapes were prepared with 6 vol% PVB + PEG, sintered at 1800 °C for 2 h and exhibited almost 97%TD in room temperature applications of α/β SiAlONs.
TL;DR: In this paper, a single phase Ca-α-SiAlON:Yb2+ was synthesized by a spark plasma sintering (SPS) method without a reducing gas.
TL;DR: In this article, rapid nitridation was used to fabricate reaction-bonded and postsintered β-SiAlON ceramics with monoclinic ZrO2 added to the starting powder.
Abstract: Rapid nitridation was used to fabricate reaction-bonded and postsintered β-Si6−ZAlZOZN8−Z (Z=1) ceramics with monoclinic ZrO2 added to the starting powder. Thermo-gravimetric analysis revealed that the addition of ZrO2 reduced the starting temperature of the main nitridation reaction. Using a reaction-bonding route with heating rates of 5°, 10°, and 20°C/min, to fabricate β-SiAlON ceramics without ZrO2 resulted in unreacted silicon that bled out of the specimens and the Z=1 composition samples did not maintain the original green compact morphology. On the other hand, no such bleeding of melted silicon was observed for samples with ZrO2 additions and the samples following nitridation maintained the original green morphology. The microstructure and mechanical properties of samples produced by rapid reaction bonding and postsintering were comparable to those of samples produced by a conventional reaction-bonding and postsintering route.
TL;DR: In this paper, a continuous 3D network of conductive TiCN particles was successfully achieved by mechanically coating spray-dried SiAlON granules with varying amounts of nano sized TiCN (0 −10 vol.%) particles.
Abstract: Electrically conductive α–β SiAlON/TiCN composites were produced in the form of a segregated network in a ceramic matrix structure. A continuous 3D network of conductive TiCN particles was successfully achieved by mechanically coating spray-dried SiAlON granules with varying amounts of nano sized TiCN (0–10 vol.%) particles. For comparison, the same SiAlON matrix was incorporated with 25 vol.% micron sized TiCN particles to give a particle reinforced composite. Densification, together with mechanical and electrical properties of the composites produced were discussed in terms of conventional and novel approach. Fully dense composites were obtained by gas pressure sintering (GPS) under a nitrogen pressure of 100 bar at a peak temperature of 1990 °C. The electrical resistivity of the SiAlON (1 × 10 13 Ω m) matrix material was drastically reduced with the addition of only 5 vol.% TiCN (18 × 10 −4 Ω m) to the composites prepared by the coating method.
TL;DR: In this paper, the tribological properties of gas pressure sintered SiAlON and its composite with 18% silicon carbide (SiC) against two different mating materials, i.e., alumina and SiAlon are evaluated.
TL;DR: In this paper, a series of experiments have been performed using thermogravimetry (TG) and thermal field emission scanning electron microscope (FE-SEM) to investigate its oxidation resistance.
29 Oct 2011
TL;DR: In this paper, the authors successfully developed new hetero-modulus alumina matrix ceramic composite materials, reinforced with submicron and nanoparticles of α-Si3N4 β-Si 3N4, Si2ON2, SiAlON, AlN, and c-Si-3N 4 diamond sub-micron.
Abstract: Applying the well-known alumina powders for matrix, different oxide and non-oxide ceramic submicron and nano-particles as additive materials, and investigating the impact of nitrogen atmosphere on sintering; the authors successfully developed new hetero-modulus alumina matrix ceramic composite materials, reinforced with submicron and nanoparticles of α-Si3N4 β-Si3N4, Si2ON2, SiAlON and AlN. Thanks to the new compacting technology with high speed flying punches in vacuumed N2 atmosphere developed by authors, phase transformation of α-Si3N4 and β-Si3N4 into cubic c-Si3N4 can be observed, creating so-called Si3N4-diamond submicron and nanoparticles in alumina matrix. The α-Si3N4, β-Si3N4, Si2ON2, SiAlON, AlN and c-Si3N4 diamond submicron and nanoparticles reinforced alumina matrix hetero-modulus nanoceramics have excellent mechanical properties and extreme dynamic strength. The dynamic strength was tested through collision with high density metallic flying bodies, with speed higher than 900 m/sec. Analytical methods applied in this research were laser granulometry, scanning electron microscopy, X-ray diffraction and energy dispersive spectrometry. Digital image analysis was applied to microscopy results, to enhance the results of transformation.
TL;DR: In this paper, SiAlON nanopowder was synthesized from a PAM precursor by carbothermal reduction and nitridation processing (CRN) at different temperatures XRD, XRF, FTIR, RAMAN, STA, SEM, and LLS were used to characterize the phases, structures, and morphologies of the products.
TL;DR: In this paper, a detailed investigation of the properties in dependence on the processing route is performed, and the results show that the resulting corrosion and wear resistance depend not only on the processed method, but also on the incorporated hard phases in combination with the manufacturing method.
Abstract: Many industrial applications, e.g. processing of polymers, suffer from high costs caused by corrosion and wear. Particularly the combination of both increases the requirements for the materials used. Corrosion resistant cold work steels were developed to withstand the combined attack. Resistance is achieved by a sufficient content of chromium in the metal matrix and by carbides dispersed in a martensitic matrix. A further gain in wear resistance is possible by adding hard phases to the steel to produce a particulate reinforced metal matrix composite (MMC). The common consolidation process for such MMCs is hot isostatic pressing, but they can also be processed by solid state or liquid phase sintering. This work focuses on detailed investigations of the properties in dependence on the processing route. The results show that the resulting corrosion and wear resistance depend not only on the processing method, but also on the incorporated hard phases in combination with the manufacturing method. In addition, ...
TL;DR: In this article, the effect of ferric oxide impurities in coal gangue was investigated using isothermal thermogravimetry (TG) and field-emission scanning electron microscopy (FE-SEM).
Abstract: The oxidation behavior of different SiAlON phases (β-SiAlON, X-phase SiAlON and 12H powders) synthesized from coal gangue in air atmosphere was investigated using isothermal thermogravimetry (TG) and field-emission scanning electron microscopy (FE-SEM). The effect of ferric oxide impurities in coal gangue was studied. The results show that ferric oxide contributes to the growth of SiAlON crystalline during the synthesis process. In the oxidation experiment, the existence of ferric oxide decreases the oxidation resistance of SiAlON. The reason is that the impurity causes the formation of a liquid phase at a higher temperature. At 1423–1623 K, the oxidation of SiAlON powders is diffusion controlled and it can be described by Chou’s model. A fair agreement is found between theoretical calculations and the experimental data.
TL;DR: Doping structures of Ce(3+) into the refractory α-sialon crystal lattice have been examined via an atom-resolved Cs-corrected scanning transmission electron microscope and as-revealed structural information could be useful for understanding the luminescence properties of the promising rare-earth doped sialon materials.
Abstract: Doping structures of Ce3+ into the refractory α-sialon crystal lattice have been examined via an atom-resolved Cs-corrected scanning transmission electron microscope. The location and coordination ...
TL;DR: The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlon, and the emission color generated by irradiating doped glass with a blue LED at 450 nm depended on that concentration and the glass thickness, resulting in nearly white light.
25 Feb 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a new metal-Sialon-based ceramic composite of FeMo, FeSi2 and Mo has been processed using Si3N4, α-Al2O3 and FeMo70 alloy powders as main raw materials.
Abstract: A new metal–Sialon based ceramic composite of FeMo–Sialon has been processed using Si3N4, α-Al2O3 and FeMo70 alloy powders as the main raw materials. To explain why this composite has excellent mechanical properties, microstructure characterizations are carried out using the transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The results show that FeMo, FeSi2 and Mo have formed an alloy mixture of Mo–Fe–Si in the FeMo–Sialon ceramic composite. Elongated β-Sialon crystals, interlacing with each other, vary in size. The Y-SiAlON glass, as an inter-granular phase, surrounds the grain boundaries of β-Sialon crystals. Some of β-Sialon crystals are semi-surrounded by dumbbell-like Mo–Fe–Si particles. The good mechanical properties of FeMo–Sialon composite are greatly dependent on the elongated Sialon grains and Mo–Fe–Si particles with interlocking structures.
TL;DR: In this article, the possible incorporation of iron and chromium into the β-SiAlON structure was investigated by using analytical transmission electron microscopy (TEM) techniques, and it was found that transition metals (Cr and Fe) can enter into the crystal structure.
TL;DR: In this article, the effect of increasing the Al or Al2O3 precursor content, above the stoichiometric amount, on the formation of β-sialon by pressureless sintering of Al, Si and Al 2O3 powders in flowing nitrogen gas was investigated.
TL;DR: In this article, the relationship between the process, microstructure, and mechanical properties of Al2O3-Si3N4/ZrO2-Al 2O3 composites were determined.