Low Apparent Porosity Research Articles

Application of Reclaimed Ladle Bricks in Magnesium Aluminate Spinel Based Castables

The way of producing ladle used MgO-Al2O3 castables using reclaimed bricks of ladle as aggregate is researched by structure analysis, XRD and phase diagram analysis. Influence on structure and physical properties of castables added different percentage of reclaimed bricks is discussed. The following conclusions are got: Adding suitable reclaimed ladle bricks won’t decrease the strength of the specimens, all the specimens have high bulk density(≥2.98g/cm3) and low apparent porosity(≤14%); Suitable addition of reclaimed ladle bricks as aggregate can improve the thermal shock resistance of MgO-Al2O3 castables, however, over-addition will weaken its thermal shock resitance; Slag erosion resistance increases with the addition of reclaimed ladle bricks. To sum up, reclaimed ladle bricks can be used in MgO-Al2O3 castables and castables with excellent comprehensive properties can be got when 12.5% reclaimed ladle bricks are added as aggregate.

Influence of Nano-Yb<sub>2</sub>O<sub>3</sub>, Nano-Nd<sub>2</sub>O<sub>3</sub> and Nano-Dy<sub>2</sub>O<sub>3</sub> on Sintering and Crystallization of Fused Quartz Ceramic Materials

Fused quartz powder (d50=19μm) was used as raw material, nano-Yb2O3, nano-Nd2O3 and nano-Dy2O3 were dividedly used as additive with dosages of 3% each. Fused quartz ceramic materials were sintered in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h. The influence of rare earth nanooxides on sintering and crystallization of the fused quartz ceramic were researched by measurements of apparent porosity, bending strength and thermal expansion ratios, and analyses of XRD and SEM. The results showed that samples added nano-Yb2O3 and nano-Nd2O3 have lower apparent porosity, higher bending strength and lower thermal expansion rate. It can be deduced that additives nano-Yb2O3 and nano-Nd2O3 have obvious effect on facilitating sintering and inhibiting crystallization of fused quartz materials at experimental temperatures.

Study on the slag corrosion resistance of unfired Al2O3–SiC/β-Sialon/Ti(C, N)–C refractories

Al2O3–SiC–C refractories are widely used in the steelmaking process due to their outstanding properties, and in order to improve their slag corrosion resistance, the erosion resistant materials have often been used. β-Sialon and Ti(C, N) are point out as novel additives that present suitable properties to increase the corrosion resistance of refractories. In this study, unfired Al2O3–SiC/β-Sialon/Ti(C, N)–C refractories were prepared using Ti(C, N)/β-Sialon powders, brown alumina, SiC, micro α-Al2O3 powder, silica fume, ball pitch, calcium aluminate cement, aluminum and silicon as the starting materials. The effect of the Ti(C, N)/β-Sialon powders and SiC on the slag penetration and corrosion resistance of the refractories was investigated, and the slag resistance mechanisms of the Al2O3–SiC/β-Sialon/Ti(C, N)–C refractories were also discussed. Fractal theory, scanning electron microscopy (SEM) and energy dispersive spectroscope (EDS) were carried out in order to better understand the slag resistance effects and reaction mechanisms. The results showed that all samples made with Ti(C, N)/β-Sialon powders had excellent slag corrosion resistance. The slag corrosion resistance of the samples was based on their low apparent porosity and high volume density. The β-Sialon and SiC powders contributed to the improved slag corrosion resistance performance of the composite refractories.

Effects of Enthalpy-Enhancing Gas on Ionic Conductivity of Atmospheric Plasma-Sprayed 3.9YSZ Electrolyte for 45-75 μm Particles

Enthalpy-enhancing gas is used to optimize the ionic conductivity of atmospheric plasma-sprayed 3.9 mol% yttria-stabilized zirconia (3.9YSZ) electrolyte. In the experiment, three hydrogen gas-flow rates were used to control the plasma energy. The size of the 3.9YSZ feedstock powder was sieved to be set in the range of 45-75 μm. When the hydrogen gas-flow rate was increased, the electrolyte became harder, and the sprayed surfaces became smoother. However, the lowest apparent porosity and the highest bulk density of the electrolyte were obtained at a hydrogen gas-flow rate of 7 L/min. A 3.9YSZ electrolyte with an ionic conductivity of 2860 µ(S/cm) and the lowest dissociation energy was obtained at 800 °C with a hydrogen gas-flow rate of 12 L/min. It was controlled by the intragrain conductivities. A higher hydrogen gas-flow rate enhanced the growth of columnar grains and suppressed the appearance of the monoclinic phase, which led to the greater intragrain conductivities. The increase in grain-boundary conductivities is closely related to the decrease in grain size.

A novel polymer concrete made with recycled glass aggregates, fly ash and metakaolin

A novel polymer concrete (PC) was synthesized by mixing epoxy resins and waste glass as aggregates. In this study, metakaolin (MK) and fly ash (FA) were used as filler and compositions with 0%, 10% and 15% by weight of recycled glass sand (<2.36mm) were prepared to investigate the mechanical and durability properties of the PC. The results indicated that all compositions assessed in this study display high strength and modulus of elasticity values. MK and FA have a significant effect on the compressive strength, the flexural strength and the modulus of elasticity of the PC. Moreover, the PC made with recycled glass aggregate, MK and FA has good chemical resistance for 20% Na2CO3, 10% NaOH, tap water, and sea water. Besides the acceptable chemical resistance, the prepared waste glass PC shows low apparent porosity and low water absorption.

Effects of Vacuum Sintering, HIP and HP Treatments on the Microstructure, Mechanical and Electrical Properties of Cr70Cu30 Alloys

The aim of this paper is to study and produce Cr70Cu30 alloys via vacuum sintering, hot isostatic pressing (HIP) and hot pressing (HP) of powder metallurgy technology. The experimental results show that a lower density of Cr70Cu30 alloys is produced after vacuum sintering, owing to the many pores existing in the sintered Cr70Cu30 alloys, which are not completely removed by HIP treatment. Conversely, the HP treatment of Cr70Cu30 alloys at 1000°C 60MPa for 1h achieves the optimal density (97.82%), lower apparent porosity (0.65%) and higher international annealed copper standard (IACS) value (22.78%). Moreover, it also obtains the highest hardness (HRB 68.7) and transverse rupture strength (TRS) value (843MPa). The results indicate that the closed pores can be effectively eliminated and that the mechanical properties of Cr70Cu30 alloys are obviously improved by HP treatment. Meanwhile, the Cr70Cu30 alloys also have an improved microstructure and electrical conductivity. [doi:10.2320/matertrans.M2013173]

Effect of Nano-Nd&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; on Sintering and Crystallization of Fused Quartz Ceramic Materials

Fused quartz powder (d50=19μm) was used as raw material, and nano-Nd2O3 was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. The effects of nano-Nd2O3 on crystallization and sintering behavior of the materials at various temperatures (1300 °C/1h, 1350 °C /1h and 1400°C /1h) were studied by measurements of apparent porosity, bending strength and thermal expansion ratios (RT~1200°C), and analyses of XRD and SEM. The results of XRD and thermal expansion ratios analysis showed that 3% nano-Nd2O3 additive had excellent effect on inhibiting crystallization of the samples sintered at 1350 °C and 1400°C. The results showed that the samples sintered at various temperatures with 3% nano-Nd2O3 had the lowest apparent porosity and more compact microstructure. This indicated that 3% nano-Nd2O3 had better effect on facilitating sintering of fused quartz materials.

Influence of Grain Composition and Sintering Temperature on Performance of Silicon Carbide Refractory Material

Silicon carbide with diffierent granularity and three grain composition was used as raw material. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C, 1450 °C and 1500 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples sintered at 1400 °C have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that (1.0-0.5mm) / (0.5-0.1mm) / (45μm) / (5μm) = 50 / 17/ 20/ 13 is the best grain composition to improve integrated performance of silicon carbide refractory material.

Petrophysical and geochemical properties of Columbia River flood basalt: Implications for carbon sequestration

This study presents borehole geophysical data and sidewall core chemistry from the Wallula Pilot Sequestration Project in the Columbia River flood basalt. The wireline logging data were reprocessed, core‐calibrated and interpreted in the framework of reservoir and seal characterization for carbon dioxide storage. Particular attention is paid to the capabilities and limitations of borehole spectroscopy for chemical characterization of basalt. Neutron capture spectroscopy logging is shown to provide accurate concentrations for up to 8 major and minor elements but has limited sensitivity to natural alteration in fresh‐water basaltic reservoirs. The Wallula borehole intersected 26 flows from 7 members of the Grande Ronde formation. The logging data demonstrate a cyclic pattern of sequential basalt flows with alternating porous flow tops (potential reservoirs) and massive flow interiors (potential caprock). The log‐derived apparent porosity is extremely high in the flow tops (20–45%), and considerably overestimates effective porosity obtained from hydraulic testing. The flow interiors are characterized by low apparent porosity (0–8%) but appear pervasively fractured in borehole images. Electrical resistivity images show diverse volcanic textures and provide an excellent tool for fracture analysis, but neither fracture density nor log‐derived porosity uniquely correlate with hydraulic properties of the Grande Ronde formation. While porous flow tops in these deep flood basalts may offer reservoirs with high mineralization rates, long leakage migration paths, and thick sections of caprock for CO2 storage, a more extensive multiwell characterization would be necessary to assess lateral variations and establish sequestration capacity in this reservoir.

Fabrication and Properties of CaAl&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;19&lt;/sub&gt;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Composite Ceramics

CaAl12O19-Al2O3 composite ceramics were synthesized by in situ solid state reaction using CaCO3 and industrial α-Al2O3 powders. The effects of sintering temperature and ratio of CA6 (CaAl12O19) content on phases and microstructure of the final composite ceramics were studied by XRD and SEM. The result showed that sheet-like CA6 appeared in the materials when sintering temperature was higher than 1400°C and grew up with the increased of the sintering temperature. The optimum sintering temperature was 1600°C, when the sample containing 20wt% CA6 was sintered at 1600°C, the bulk density was 3.21g/cm3, the apparent porosity achieved 9.94% and the bending strength gained 149.88MPa. With the increasing of CA6 content in the final composite ceramics, the bulk density and the bending strength increased firstly and then decreased. The lowest apparent porosity 1.42%, a density of 3.60g/cm3 and the highest bending strength of 265.10MPa were achieved for the sample containing 10wt% CA6 sintered at 1600°C.

The Influence of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-AlN Compound Additive on the Crystallization Characteristics and Properties of Fused Quartz Ceramic Materials

Fused quartz granule (d50=10μm) was used as raw material, and Al2O3-AlN (1:1, in mass) was used as additive with dosages of 1 wt%, 2 wt% and 3 wt%. The crystallization characteristics of fused quartz ceramic fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h has been investigated by thermal expansion ratio and XRD. The results showed that the crystallization characteristics were markedly improved by 1 wt% AI2O3-AIN compound additive. 1 wt% Al2O3-AIN had obvious effect on inhibiting crystallization of the samples sintered at various temperatures. The apparent porosity, bending strength and SEM of the samples were also examined. The results showed that the samples with 1 wt% AI2O3-AIN had the lowest apparent porosity among the samples containing Al2O3-AlN, the highest bending strength, and the sample AA1 sintered at 1350°C had more compact microstructure, which indicated that 1 wt% Al2O3-AlN was conducive to sintering of fused quartz ceramic materials. It can be deduced that the 1 wt% Al2O3-AIN compound additive plays the excellent role on inhibiting crystallization and promoting sintering of fused quartz ceramic materials.

Influence of Additives on Performance of Silicon Carbide Refractory

Silicon carbide with diffierent granularity was used as raw material, quartz, silica fume, aluminum powder or alumina was used as additive with dosages of 1% (in mass, similarly hereinafter), 3% and 5%. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples added silica fume have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that 5% silica fume plays the excellent role to improve integrated performance of silicon carbide refractory material.

The Study on Nano-Silica Modified Phenolic Resin Used as the Magnesite-Carbon Brick Binder

The modified phenolic resin was synthesized by sol-gel process using in-situ formed nanosized silica. The improved phenolic resin was characterized by IR and TG-DTA analyses .The results show that the interaction between SiO2 nanoparticles and phenolic resin lead to the decrease of concentration of phenolic hydroxyl groups, and introduce the impurity atom Si to the phenolic resin molecule chain, which promotes the heat resistance and stability of phenolic resin. The physicochemical property analyses show that the magnesite-carbon brick using this modified phenolic resin as binder possesses a low apparent porosity and a high bulk density and compression strength.

Effects of Enthalpy‐Enhancing Gas on Ionic Conductivity of Atmospheric Plasma‐Sprayed 3.9YSZ Electrolyte for 20–45 μm Particles

Enthalpy‐enhancing gas is used to optimize the ionic conductivity of atmospheric plasma‐sprayed 3.9 mol% yttria‐stabilized zirconia (3.9YSZ) electrolyte. In the experiment, three hydrogen gas flow rates were used to control the plasma energy. The size of the 3.9YSZ feedstock powder was sieved to be in the range of 20–45 μm. When the hydrogen gas flow rate increased, the sprayed surfaces became rougher. Nevertheless, the lowest apparent porosity, the highest bulk density, and the hardest electrolyte were obtained at the hydrogen gas flow rate at 7 L/min. A 3.9YSZ electrolyte with an ionic conductivity of 1480 μ (Ω cm)‐1 was obtained at 800°C, when the hydrogen gas flow rate was at 12 L/min. It was controlled by the grain‐boundary conductivity, which was closely related to the lowest migration energy, the highest density of the columnar grains, and the closest bonding between lamellar layers. The increase in the hydrogen gas could diminish the amount of the migration energy and increase the grain‐boundary conductivity. On the other hand, a larger cubic lattice constant and a less amount of the monoclinic phase in the as‐sprayed electrolyte helped obtain greater intragrain conductivity.

Research on Carbon-Free Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Composite Sliding Gate Performance

The Al-Al2O3 specimens of the carbon-free sliding gate are made from sintered corundum, white fused corundum, activated alumina powder and aluminum. The Al contents of the metal Al-Al2O3 composite sliding gate are 3%, 6%, 9%, 12% and 15% respectively. The specimens are treated with three different processes (200°C drying, Nitriding and CO atmosphere). The results show that, the specimen of Nitriding has the best performance. Especially, the specimen, whose Al content is 9% and is treated with Nitriding, has relative lower apparent porosity, higher cold crushing strength and hot modulus of rupture, which makes it posses the superior combination property.

Carbonization Rate and Impregnating Methods on the Tribological Behavior of Carbon/Carbon Composites

This study compares two different impregnating methods to investigate the influence of carbonization rate on the tribological properties of carbon/carbon (C/C) composites. The experimental results indicate that the bulk density, hardness, infiltration efficiency and friction coefficient of pressure impregnating specimens are higher than those of vacuum impregnating specimens. In comparison with the vacuum impregnating specimens, the pressure impregnating specimens also show the lower apparent porosity and weight loss. Studies on the tribological properties of the specimens with different carbonization rate show that the specimens with the higher carbonization rate exhibit the lower bulk density and infiltration efficiency, but the higher porosity and friction coefficient. These results are attributed by the defect induced by the thermal stress during the higher carbonization rate process. In addition, the pressure impregnating method produces a more notable effect on the properties of C/C composites than that of the carbonization rate.

Effects of enthalpy-enhancing gas on ionic conductivity of atmospheric plasma-sprayed 3.9 mol % yttria-stabilized zirconia electrolyte for 75–106 micron particles

Enthalpy-enhancing gas is used to optimize the ionic conductivity of atmospheric plasma-sprayed 3.9 mol % yttria-stabilized zirconia (3.9YSZ) electrolyte. In the experiment, three hydrogen gas flow rates are used to control the plasma energy. The 3.9YSZ feedstock powder is sieved to obtain particles with sizes in the range of 75–106 µm. The electrolyte has the highest hardness and lowest roughness when sprayed at hydrogen gas flow rates of 12 and 7 Lmin−1, respectively. The electrolyte bulk density increases and the apparent porosity decreases with increasing hydrogen gas flow rate. A 3.9YSZ electrolyte with an ionic conductivity of 1789 µ(Ω cm)−1 is obtained at 800°C with a hydrogen gas flow rate of 12 Lmin−1. It is controlled by the grain-boundary conductivity. The increase in grain-boundary conductivity is closely related to a low apparent porosity, low migration energy, and a decrease in grain size. Hydrogen gas enhances the growth of columnar grains and suppresses the formation of the monoclinic phase, which is attributed to increased intragrain conductivity.

Preparation and Performance of β-Sialon Bonded ZrO&lt;sub&gt;2&lt;/sub&gt; Composites

β-Sialon bonded ZrO2 composites were prepared by reaction sintering process using β-Sialon and CaO stabilized ZrO2 powders as raw materials.The effect of β-Sialon powder additions on the properties of the composites was investigated. The results show that the samples with 10 wt% of β-Sialon addition had the lowest apparent porosity (29.80%) and the highest of flexural strength (68.70MPa). The thermal shock resistance in carbon addition of the composites could be improved by addtion of 5wt% β-Sialon. It may be relative with that the sample had the lowest thermal expansion coefficient in vacuum.

Influence of CeO&lt;sub&gt;2&lt;/sub&gt; Nanopowder on Crystallization Behavior and Sintering Performance of Fused Quartz Ceramic Materials

Fused quartz granule was used as raw material, and CeO2 nanopowder was used as additive with dosages of 1wt %, 2 wt % and 3 wt %. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h, respectively. The properties of samples including apparent porosity, bending strength and thermal expansion ratio were measured. The results show that the sample with 1 wt % CeO2 nanopowder has the lowest apparent porosity, the highest bending strength and the lowest thermal expansion ratio. The XRD and SEM results show that through the CeO2 nanopowder adding, the diffraction peak intensity of quartz phase in the fused quartz ceramics decrease, and the microstructure of the samples become more compact. It can be deduced that CeO2 nanopowder plays the excellent role as the crystallization inhibitor and sintering assistant to fused quartz materials sintered at various temperatures.

Influence of La&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Nanopowder on Crystallization Behavior and Sintering Performance of Fused Quartz Ceramic Materials

Fused quartz granule was used as raw material, and La2O3 nanopowder was used as additive with dosages of 1wt %, 2 wt % and 3 wt %. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h, respectively. The properties of samples including apparent porosity, bending strength and thermal expansion ratio were measured. The results show that the sample with 2 wt % La2O3 nanopowder has the lowest apparent porosity and the highest bending strength, and sample added 1% nano-La2O3 has the best inhibiting effect on crystallization of fused quartz. The samples with La2O3 nanopowder adding have lower thermal expansion ratio than blank sample. The XRD and SEM results show that the diffraction peak intensity of quartz phase decrease and the microstructure of the samples become more compact, after the La2O3 nanopowder was added into fused quartz ceramics. It indicated that La2O3 nanopowder has excellent inhibiting effect on crystallization of fused quartz and facilitating effect on sintering of fused quartz ceramics.