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Sialon-SiC composite powders were synthesized from kyanite tailings through the carbothermal reduction nitridation (CRN) technique. Using Sialon-SiC composites to substitute Si3N4 composites via the CRN technique synthesize Sialon/Si3N4-SiC composite refractories. The phase composition, cross section morphology, and the substituent amount of Sialon-SiC composites impact on refractories mechanical properties were investigated, respectively. The optimized synthesis temperature for the CRN reaction was found to be 1550 °C for 4 h with the excess carbon 20%. The substituent amount of Sialon-SiC was 25%, the mechanical properties of Sialon/Si3N4-SiC composite refractories reached optimal performance, which bending strength value was 41.8 MPa and compression strength value was 61.6 MPa.

Super-grade bauxite, pure silicon carbide, andalusite and metal silicon were used as the raw materials to produce plastic phase mullite-SiC bricks. By analysis of the microstructure, physical and chemical properties, it proves that the introduction of metal plastic phase can improve the properties of bricks, such as lower porosity, higher cold crush strength, and wearing resistance. It also can improve the toughness, and effectively relieve the thermal and mechanical stress when using in cement kilns. By analysis of the comparison with MA spinel bricks and ordinary mullite-SiC bricks, the plastic phase mullite-SiC bricks have good thermal shock resistance and lower thermal conductivity. The result shows that the bricks can replace MA spinel bricks using in the transition zone of cement kilns and realizes the aim of saving energy and a long service life.

Cordierite samples were prepared using quartz sand tailings, industrial alumina and magnesite tailings as raw materials by high-temperature reaction. The influence of mineral composition and sintering temperature on the final phase composition and physical properties of cordierite were studied. The results shown that a large number of cordierite generated at 1300 °C. When the ratio of Al2O3/SiO2 equals to 1.08, the flexural strength of samples increased to 27.66 MPa.

Mullite material was prepared from quartz (SiO2) and industrial alumina (γ-Al2O3). The effects of mineral composition and sintering temperature on the final phase composition and physical properties of mullite were investigated. The results shown that a large number of mullite phase was emerged in samples when the ratio of alumina to silica (A/S) was 2.55. At 1500 oC and 1600 oC, the flexural strength of the samples reached to 87.13 MPa and 89.50 MPa, respectively. Consider the environmental protection and energy saving, the optimal sintering temperature was 1500 °C.

The performance and phase behavior of Quartz - Aluminum Matrix Composites at different temperatures were studied. Quartz aluminum matrix composites were prepared by powder metallurgy method. At the temperature that was less than 660.4°C(the melting point of aluminum), a portion of quartz was happened decomposition and revivification to silicon, most aluminum still existed in the form of metal aluminum. All quartz were happened at the temperature that was higher than 660.4°C. When the temperature is 700°C, the compressive strength of S5(added 40% quartz) is up to 46.02MP. The higher the value of compressive strength was, the less the amount of quartz were happened decomposition. At the temperature more than the melting point of aluminum, Quartz was revivification to silicon, aluminum is oxidized to Al2O3. When the amount of silica exceeded 10%, the mechanical properties of composites declined consequently.

The total bauxite reserves of China are about 3.7 billion tons, however the principal and the first-class bauxite reserves account for only about 20%. A large number of coal gangue was accumulated on the surface of earth, which not only encroaches land but also pollutes the environment. In this study, low-grade bauxite with alumina content of 53.18 wt.% originating from Shanxi Yangquan and coal gangue with alumina content of 38.07 wt.% originating from Shanxi Datong were used to synthesize mullite materials. Bauxite and gangue were mixed by the ratio of 1 to 1. The ingredients were prepared according to the alumina content of 45.63 wt.% and 70 wt.%, by adding a certain amount of industrial alumina, respectively. The samples were sintered at 1350°C to 1600°C after being milled, dried and formed. The influence of alumina content and sintering temperature on the phase, microscopic morphology and properties of samples were discussed. The results show that, the main phases of the sample with the alumina content of 70 wt.% were mullite (more than 60 %) and corundum after being sintered for 4h at 1600 °C. The phenomenon of columnar mullite and granular corundum staggering had been observed. The bulk density and the bending strength of sample is 3.21 g/cm3and of 220.73 MPa respectively.

Alumina from sericite phyllite was extracted by the way of limestone self-pulverization sintering technique. The key technical processes, including self-pulverization sintering, clinker leaching reaction and the carbonation decomposition, were investigated systematically. The results showed that the main phases of pulverized clinker consisted of γ-C2S and C12A7, and the self-pulverization rate was 95% . The dissolution rate of Al2O3 clinker could reach 86.7% when the concentration of Na2CO3 solution was 7% and the solid-liquid ratio was 1:3. The Al(OH)3 prepared at 80°C carbonation temperature and pH=10.5 was relatively pure, with hexagonal plate-like crystals. The α-alumina could be acquired by calcination at 1200°C with the content of 99.71% Al2O3 and 0.02% Na2O. This work provided optimal technological parameters for effectively extracting alumina from the sericite and other inexpensive non-bauxite mineral resources with A/S ratio lower than 1.

In this study, β-Sialon/Al2O3/TiN diphase powder was synthesized using low-grade bauxite and rutile via carbothermal reduction-nitridation. The phase transitions of low-grade bauxite and rutile in the carbothermal reduction and nitridation process were analyzed by XRD, SEM and EDS. The effects of different reaction parameters such as reaction temperature, rutile addition on the phase composition and microstructure of products were analyzed. The results showed that β-Sialon/Al2O3/TiN powder was prepared using low-grade bauxite and rutile as raw materials and coke as reducing agent by carbothermal reduction-nitridation reaction in flowing nitrogen atmosphere of 0.03 MPa at 1350-1375 °C, for 4 h.

β-Sialon/Ti(C,N) composites were prepared using low and middle grade bauxite and ilmenite as raw material,while coke as reducing agent in high purity nitrogen atmosphere through carbothermal reducrion-nitridation(CRN).The main phases of low and middle grade bauxite are kaolinire(Al2O3•2SiO2•2H2O) and (Al2O3•H2O)2 and ilmenite mainly contain ilmenite(FeTiO3) and rutile(TiO2).The reaction products of bauxite are the β-Sialon(Z=3,Si3Al3O3N5) while those of ilmenite are TiC and Fe.The results showed that the main phases are β-Sialon,Ti(C,N),Al2O3 and Fe when the reaction temperature is at 1400°C holding for 4 hours(10wt% ilmenite and 90wt% bauxite as raw material).However,β-Sialon decomposes into 21R at 1450°C and into 15R and AlN at 1500°C.So 1400°C is selected as the proper temperature to synthesize β-Sialon/Ti(C,N) composites.At 1400°C,the β-Sialon crystals with the largest quantity grow well and show long column in shape.With the increase of the reacrion temperature β-Sialon begin to decompose,the β-Sialon crystals change to short columnar,with the number decreasing quickly.

Mullite with puncheon-like grains was synthesized by sintering the mixtures of coal gangue and γ-Al2O3 at 1400 °C~1550 °C for 4 h. The phase and microstructure evolution of the mullitization behavior were investigated by XRD, SEM and EDS. Phases of the sintered specimens were mullite, corundum and cristobalite at 1400 °C to 1450 °C. Arise of temperature would enhance mullitization, and total consumption of cristobalite occurred from 1500 °C upward. The in-situ produced primary mullite from gangue upon heating may be seeds for the growth of enenly dispersed mullite puncheons. Specimen sintered at 1550 °C consists of puncheons with an aspect ratio of 2~4, regionally forming an interlocking structure.

In this paper, the mineral composition and main mineral morphology of bauxite were studied from ZhongXiang deposit, HuBei province. Through Electron Microscope Identification, there are two main rock types, oolitic, bean-like and aphanitic or fine crystalline structure of bauxite. The main mineral morphology is micro-crystalline or flake, crumby forms. The mineral and chemical compositions of samples were investigated by XRD, EPMA analysis tests. The EPMA results showed that Al2O3 content is 47.95% ~ 75.04%, in association with other isomorphous impurities, such as Si, Fe, Ti and Mg in varying proportions. The mineral compositions of bauxite ore are mainly aluminum, iron, silicon minerals, which totally account for from 83.01% to 86.40%. The XRD revealed that diaspore, hematite and kaolinite are the major mineral components in the bauxite ores. The bauxite from ZhongXiang deposits is a type of high diaspore bauxite, partly with clay minerals. Furthermore, the function of bauxite as a good fire-resistant material was discussed.

Ti(C,N) powder was prepared via carbothermal reduction nitridation (CRN) using rutile and carbon black as the raw material. The phase evolution and the reaction mechanism during the CRN synthesis of Ti(C,N) were investigated, and the effect of reaction temperature and C/TiO2molar ratio on the phase composition and x value in TiC1–xNxwas analyzed. The XRD and SEM results show that: Ti(C,N) powder was synthesized at 1500°C for 4h with the C/TiO2molar ratio of 2.2, under the nitrogen pressure of 0.2MPa. Irregular granular structure and the growth stripes were observed in the final products. The growth of Ti(C,N) grains in CRN process was followed by the gas-solid mechanism.The phase compositions of the products were quite dependent on the reaction temperature and the C/TiO2molar ratio. The TiN content in Ti(C,N) decreased with the increase of reaction temperature. TiC1–xNxpowder with different x values can be synthesized by optimizing the experiment conditions including the synthesis temperature and the C/TiO2molar ratio.

Calcium hexaluminate (CA6) because of its high stability, high melting point and low thermal conductivity properties make it as a new high-temperature insulation materials are valued. In this paper, chemical analysis and XRD were used to investigate the composition of the white beach sand mineral from Perth coast of Western Australia. The main composition of it was carbonate. White beach sand as calcium source respectively, and industrial alumina as aluminum source synthesized CA6 at 1550°C-1650°C for 3h. The results showed that: synthetic CA6 shapes in platelet crystalline. Influence of different amounts of alumina and sintering temperature on synthesis of calcium hexaluminate are studied.The main phase of the samples with different amounts of alumina which decrease or increase 5%, 10% and 15% alumina around theory are CA6. The porosity of the samples obtained is about 53%. The bending strength of Sample S-0 of theoretical ratio values up to 7.73Mpa. Sintering temperature from 1500°C to 1650°C is not conductive to the improvement of apparent porosity of CA6 materials.

The erosion wear resistance of YSZ ceramics is worth studying because solid particle erosion is one of the main causes of destroying the materials and apparatuses. In this paper, 8YSZ ceramics reinforced by NiCr alloy and Al2O3 particles were pressureless sintered at an optimized sintering condition. The facture toughness reached a maximum value of 4.6 MPa•m 1/2 when the addition of NiCr alloy is 12 vol.%, which was much higher than that of the pure 8YSZ ceramic (2.0 MPa•m 1/2) fabricated in the same condition. Solid particle erosion wear behavior of NiCr-Al2O3-ZrO2 (8Y) ceramics composites was performed by self-designed sand blasting type solid particle erosion wear equipment, using 36# SiC particles as abrasive particles with the 90o erosion angle. The effect of the volume addition of NiCr alloy on the erosion wear of NiCr-Al2O3-ZrO2 (8Y) ceramic composites at room temperature was investigated. The results show that the volume erosion rate of the ceramic composites decreased as the volume addition of the NiCr alloy increasing. Crossing cracks, plastic deformation and minor chipping are the major erosion mechanisms.

Solid particle erosion wear behavior of 3YSZ ceramics were performed by self-designed sand blasting type high-temperature solid particle erosion wear equipment, using 36#corundum as abrasive particles. 3YSZ ceramics were pressureless sintered in air atmosphere at 1500°C for 3h. The fracture toughness and Vickers hardness could achieve 10.3 MPa•m1/2and 12.8 GPa, respectively. The effect of temperature (25°C, 400°C, 600°C, 800°C, 1000°C) and the total weight of the abrasive particles (300g, 900g, 1800g) at room temperature on the erosion wear of 3YSZ ceramic were investigated. The volume erosion rate raised and developed a nonlinear dependence on the weight of corundum abrasive particles at room temperature. The slope of the curve decreased gradually. At elevated temperature, volume erosion rate increased as the temperature went up. Nonlinear fitting presents the relationship between the volume erosion rate of 3YSZ ceramics and the corresponding temperature. Plastic deformation is the major erosion mechanism at room temperature when the weight of corundum particles was 300g and 900g. Minor chipping instead of it when the temperature grew up to 400 and 600°C or the corundum particles was as much as 1800g at 25°C. When 3YSZ targets were eroded at 800°C and 1000°C, the material removal are mainly attributed to lateral cracks for an ideally brittle material. Crack propagation is the controlling factor of volume erosion rate.

By using the industrial waste boron mud as raw material, graphite as reductant, coke particles as burying materials. During carbothermal reduction process, the Mg-Fe forsterite phase in boron mud row materials can transformed into forsterite and Fe2O3 at 1550°C and 1600°C for 3 h, and the Fe3C can be generated from the partial reduction of Fe2O3 with graphite, The main phase in samples calcined under 1650°C for 3 h contained forsterite, Fe2O3, Fe3C and β-SiC. The compound powder of Mg2SiO4 and β-SiC was prepared through the carbothermal reduction process. The effects of different graphite proportion (theoretical proportion, exceeding 10%, 50% and 100%) and firing temperature (1550°C, 1600°C and 1650°C) on the phase transformation and microstructure of the products were investigated by XRD, SEM and EDS. The results show that β-SiC powders were obtained at 1650°C for 3 h when graphite content was theoretical.

A WTi(C,N)-06 cemented carbide with TaC and NbC is studied as the research objective in this paper. The phase composition of the cemented carbide was analyzed by using XRD method, and the microstructure of the cemented carbide was studied and evaluated by using optical microscopy and scanning electron microscopy. According to the comparison with a general-grained cemented carbide, the addition of TaC and NbC can suppress the grain growth of WC crystal, and it is also good for improving mechanism performance. The average grain size of WTi(C,N)-06 cemented carbide is 2.1μm, density 12.9g/cm3, hardness 74HRC, and bending strength 2378MPa.

In this study we observed the phase behavior of silica brick used in the process of carbothermal reduction. At 1550°C, there are liner β-SiC in clumps huddled together; At 1550°C, short line clumps changed into filamentous, mixed together. There are many particles and some β-SiC lines and few filamentous β-SiC at 1600°C . Different ratio of carbon coke also effect the phase behavior. From the results we obtained SiC powders. SiC refractory powders were prepared via carbothermal reduction method using used silica bricks as raw materials. The effects of carbon content, temperature and holding time on the phase composition and microstructure were analyzed. XRD and SEM analyses show that: β-SiC refractory powders were synthesized at 1600°C for 6 h with100 wt% excessive of carbon content. With the increase of carbon content, the reaction temperature and holding time, content of β-SiC gradually increased while that of cristobalite decreased.

The effect of elements such as Ti, Al, Hf, Zr and B on hot tearing susceptibility during directional solidification was explored by tube-like samples with thickness of 1.0 mm, 1.5mm and 2.0mm in wall. Results of SEM of elements on solidification of casting Ni-based superalloys were presented. The influential extent among the investigated elements is found to be: the largest is Ti, then Zr, B and Al, and Hf is the smallest. Titanium promotes the formation of (γ+γ´) eutectic, increases sizes of the eutectic. Increasing Al content results in the size of γ+γ´ eutectic and the number of γ´. Increasing Zr content promotes γ+γ´ eutectic.Varying B content shows little microstructural evolution.

Two MCrAlY overlay coatings (NiCrAlYSi and NiCoCrAlYHf) were deposited on a DS superalloy of Ni-Al-Cr-Co-W-Mo-Ta-Hf system by vacuum arc deposition method. The two coatings show a good protection for the DS superalloy during the isothermal oxidation test at 1150 for 100 h. A continuous alumina-based scale was formed at the surfaces of the coated specimens after oxidation. Y2O3, NiO and SiO2 are also detectable in the oxide scale. For the Hf-bearing coating, some HfO2 particles exist at the interface between the coating and the substrate. But after the cyclic thermal oxidation at 1100°C, the Hf-free coating exhibited better oxidation resisitance than the Hf-bearing coating. The HfO2 blocks between the coat and the substrate may be the crack initiation which leads to the failure of the coating.

Transformation of the microstructure of molybdenum disilicide heating unit in nitrogen atmosphere at 1700°C was investigated by XRD, SEM and EDS. The results showed that MoSi2 was transformed to polyhedral Si3N4 crystals groups distributed across in the matrix with irregular geometry Mo5Si3 and Mo3Si crystals, and the Si3N4 crystal groups were dense areas, while the Mo5Si3 and Mo3Si groups were loose areas after being heated in nitrogen atmosphere at 1700°C for 3h. The thickness of conversion zone of MoSi2 matrix was about 30μm and the loose Mo5Si3 and Mo3Si areas can damage the dense structure of MoSi2 matrix.

Single phase YIG powders were synthesized successfully using Fe2O3 and Y2O3 as starting materials by solid state reaction, and YIG ceramics were prepared by pressureless sintering. The influence of synthesizing temperature and Fe2O3 content on the final production were studied The effect of Fe2O3 content on volume density and microstructure of the sintered YIG was also investigated. The results showed that single phase YIG powders were synthesized by solid state reaction at 1400°C for 3h. When Fe2O3 content was excessive 3 wt%, YIG ceramics with a density of 5.294g·cm-3 was fabricated by sintering at 1480°C for 2.5h.

The phase transformation of Tangshan ironstone-tailings between 900°C ~1200°C in air was investigated by DTA-TG. XRD and SEM analyses indicated that the ironstone-tailings, sintered at 900° and 1000°C respectively, mainly were composed of α-quartz, anorthite [(Na0.45Ca0.55)(Al1.55Si2.45O8)], tremolite and a little of hematite. For the sample sintered at 1100°C, augite appeared and tremolite disappeared. Fayalite formed in the sample sintered at 1200°C. The two samples both exhibited contraction character in the range of experimental temperature.

High pressure die casting is the most common method in making magnesium alloys for both auto parts and 3C products. Pressure variations in the mold during mold filling and solidification process have direct influences on the quality and properties of die castings. In this paper, a cylinder head cover was produced to experimentally study pressure variations in the mold during magnesium alloy die-casting process in real time for the first time. Pressure varies at different positions in the mold during die casting process. This study indicates that mold filling and solidification process of magnesium alloy die castings can be described by pressure curves obtained by pressure measurement at different test positions in the cavity in real time.

Ni/Al-Al2O3 gradient ceramic coating was prepared on Q235 steel by plasma spraying. Microstructure and corrosion behavior in boiling 5%HCl solution of the samples sprayed with this coating were investigated. The results showed that thickness of Al2O3 ceramic coating was increased greatly and almost no connected pores formed in the gradient coating due to the existent of Ni/Al-Al2O3 transition interlayer coatings. The corrosion resistance of Q235 steel with Ni/Al-Al2O3 gradient composite ceramic coating in boiling 5%HCl solution was greatly improved.

A new environment friendly method to synthesize sialon composites using fly ash with high content of Al2O3 by carbon-thermal reduction-nitridation was presented. The results showed that sintering temperature and the pressure of N2 gas are in favor of the nitrification synthesis of Sialon composites. When Samples wear buried in silicon powder and sintered at 1400°C under N2 atmosphere, Sialon (Si4Al2O2N6) had been synthesized.

The corrosion behavior of BF slag to sialon bonded corundum refractories using reaction nitriding technology at 1500°C was investigated by crucible test method. The results show that the reaction products of slag corrosion are anorthite, magnalium-spinel and glass phases. The corundum grains can react with MgO in the slag to produce magnalium-spinel, accompanying by expansion and liquating stepwise by slag. Erosion mechanism is oxidation-erosion-dissolving. This study is very necessary and useful to improve the property of BF slag resistance and to yield better overall properties of sialon bonded corundum refractories.

Wear-resistant ceramics were prepared successfully with Tangshan Ironstone-tailings. The effects of additives and sintering temperature on their mechanical property were studied. The erosive wear performance of ceramics was evaluated in liquid-solid flow. The erosive wear mechanism was also analyzed. The results showed that the wear-resistant ceramic prepared at 1200°C using 50wt% Tangshan Ironstone-tailings 10wt%, mild-clay and 40wt% high aluminum fly ash as the starting materials had high strength and good erosive wear resistance. The erosive wear mechanisms were washout particles’ micro-cutting and liquid washing.