Effects of Al2O3 Species and Particle Sizes on Properties of Al2O3-Cr2O3 Refractories

2013 ◽  
Vol 745-746 ◽  
pp. 610-615
Author(s):  
Hong Gang Sun ◽  
Peng Tao Li ◽  
Shuang Zhi Yan ◽  
Gang Wang ◽  
Jian Qiang Li ◽  
...  
Keyword(s):  
Pore Size ◽  
Bulk Density ◽  
Size Distribution ◽  
Modulus Of Rupture ◽  
Alumina Powder ◽  
Particle Sizes ◽  
Activated Alumina ◽  
Bimodal Size Distribution ◽  
Lower Porosity ◽  
Shock Resistance

The microstructure of Al2O3-Cr2O3 refractories is an important factor to affect its high temperature performance. The Al2O3-Cr2O3 green bodies were prepared by hot pressing using aluminum oxide and Cr2O3 powder mixture by adding a binder. And then the specimens were sintered at 1650 for 4h in the electric muffle furnace. Properties of specimens with different species of Al2O3 powders were studied, including α-Al2O3 powder, ρ-Al2O3 powder, and fused corundum powder. Moreover, three sizes of α-Al2O3 powder (D50=0.8 μm, 1.4 μm, 4.0 μm) were used as additive. Properties of specimens, including apparent porosity, bulk density, cold modulus of rupture, pore size distribution were tested. The morphology of sintered specimens was analyzed by the Scanning Electron Microscope. The results showed that the specimens adding α-Al2O3 powder had the better properties since α-Al2O3 powder has higher sintering activity, and it was more efficient for Al2O3-Cr2O3 solid solution. The specimens with α-Al2O3 had lower porosity, higher bulk density and cold modulus of rupture, and more uniform pore distribution. There were great differences in sintering activity for specimens with different particle size of α-Al2O3 powder. And the microstructure of Al2O3-Cr2O3 was significantly dissimilar. The specimen with the addition of the activated alumina powder of D50 with the size of 1.4 μm and bimodal size distribution showed the perfect performance, including high density and high flexural strength. The experimental results showed that the microstructure of this specimen was uniform and its pore size was homogeneous. This special microstructure is beneficial for improving the slag resistance and thermal shock resistance of Al2O3-Cr2O3 refractories.

Effect of MgO/CuO on the Microstructure and Thermal Properties of Cordierite–Alumina Ceramics

2012 ◽  
Vol 509 ◽  
pp. 240-244
Author(s):  
Li Ying Tang ◽  
Xi Cheng ◽  
Ping Lu ◽  
Fang Yue
Keyword(s):  
Thermal Conductivity ◽  
Bulk Density ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Raw Materials ◽  
Laser Flash ◽  
Alumina Powder ◽  
Alumina Ceramics ◽  
Conductivity Increase ◽  
Shock Resistance

Abstract: Cordierite–alumina ceramics were prepared with the raw materials of cordierite and α-alumina powder, and TiO2，CuO and MgO were added as composite additives. The effect of MgO/ CuO ratios on the microstructure, thermal conductivity and thermal shock resistance of cordierite–alumina ceramics were researched by X-ray diffraction, scanning electron microscopy and laser flash analyzer; the bulk density and the porosity of cordierite – alumina ceramics were measured. The results show that with increasing of MgO/CuO ratios, the bulk density and thermal conductivity increase firstly and then decrease, and have a minimum with 0.4wt% MgO and 0.667 MgO/CuO; and the porosity of ceramics decreases firstly and then increases and has a maximum with 0.4wt% MgO and 0.667 MgO/CuO;There are little changes in the size of the grain of the ceramics, and a small amount of magnesium aluminate spinel precipitate; the thermal shock resistance performance of the ceramics is developed with the increasing of MgO/CuO ratios.

Room-temperature synthesis of submicron platinum and palladium powders in glycols

1999 ◽  
Vol 14 (9) ◽  
pp. 3707-3712 ◽  
Author(s):  
K. Tekaia-Elhsissen ◽  
F. Bonet ◽  
S. Grugeon ◽  
S. Lambert ◽  
R. Herrera-Urbina
Keyword(s):  
Size Distribution ◽  
Room Temperature ◽  
Spherical Particles ◽  
Average Particle ◽  
Particle Sizes ◽  
Temperature Synthesis ◽  
Bimodal Size Distribution ◽  
Hydrazine Reduction ◽  
Average Size ◽  
Palladium Particles

Platinum and palladium powders with average particle sizes in the submicron range have been synthesized at room temperature by hydrazine reduction of and , respectively, in glycols. Platinum powders contain spherical particles with a bimodal size distribution. Palladium powders also contain spherical particles, but the size distribution is narrow. The effect of both ammonia and hydrazine concentration on the size distribution and average size of palladium particles was investigated.

scholarly journals Slip Casting of Alumina Powder Mixtures with Bimodal Size Distribution

1996 ◽  
Vol 104 (1209) ◽  
pp. 447-450 ◽  
Author(s):  
Seiichi TARUTA ◽  
Nobuo TAKUSAGAWA ◽  
Kiyoshi OKADA ◽  
Nozomu OTSUKA
Keyword(s):  
Size Distribution ◽  
Slip Casting ◽  
Alumina Powder ◽  
Bimodal Size Distribution ◽  
Powder Mixtures

Water retention of arctic zone soils (Spitsbergen)

2013 ◽  
Vol 27 (4) ◽  
pp. 439-444 ◽  
Author(s):  
J. Melke ◽  
B. Witkowska-Walczak ◽  
P. Bartmiński
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Bulk Density ◽  
Size Distribution ◽  
Water Retention ◽  
Total Porosity ◽  
The Arctic ◽  
Arctic Zone ◽  
Retention Characteristics

Abstract The water retention characteristics of the arctic zone soils ((TurbicCryosol (Skeletic), TurbicCryosols (Siltic, Skeletic) and BrunicTurbicCryosol (Arenic)) derived in different micro-relief forms were determined. Water retention curves were similar in their course for the mud boils, cell forms, and sorted circles ie for TurbicCryosols. For these forms, the mud boils showed the highest water retention ability, whereas the sorted circles - the lowest one. Water retention curves for the tundra polygons (Brunic TurbicCryosol, Arenic) were substantially different from these mentioned above. The tundra polygons were characterized by the lowest bulk density of 1.26 g cm-3, whereas the sorted circles (TurbicCryosol, Skeletic) - the highest: 1.88 g cm-3. Total porosity was the highest for the tundra polygons (52.4 and 55.5%) and the lowest - for the sorted circles (28.8 and 26.2%). Pore size distribution of the investigated soils showed that independently of depths, the highest content of large and medium pores was noticed for the tundra polygons ie 21.2-24.2 and 19.9-18.7%, respectively. The lowest content of large pores was observed for the cell forms (6.4-5.9%) whereas the mud boils exhibited the lowest amount of medium sized pores (12.2-10.4%) (both TurbicCryosols Siltic, Skeletic). The highest content of small pores was detected in the mud boils - 20.4 and 19.0%.

Defluoridation of water by chemical impregnated Artocarpus hirsutus sawdust

2016 ◽  
Vol 16 (5) ◽  
pp. 1297-1312 ◽  
Author(s):  
P. Dhanasekaran ◽  
P. M. Satya Sai ◽  
C. Anandbabu ◽  
K. K. Rajan
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Adsorption Capacity ◽  
Size Distribution ◽  
Surface Characterization ◽  
Ferric Hydroxide ◽  
Activated Alumina ◽  
Column Studies ◽  
Fluoride Adsorption ◽  
Defluoridation Of Water

Sawdust of Artocarpus hirsutus impregnated with ferric hydroxide and activated alumina (SFAA) has been studied for defluoridation of water. This paper presents a detailed surface characterization of the adsorbent by studying pore size distribution and surface morphology. By combining the constituents in the right proportion, an adsorbent with a well-developed pore size distribution could be synthesized. The effects of various parameters on fluoride adsorption by SFAA are investigated. The adsorption capacity of SFAA is considerably higher than that of many adsorbents including activated alumina. More importantly, the adsorption capacity remains unchanged for the pH range of 1 to 9, which also makes it attractive for wastewater treatment. Besides a higher efficiency supported by the results of column studies, this adsorbent is economic as the sawdust constitutes 40% by weight of the total adsorbent. Kinetic studies indicate that fluoride adsorption on SFAA follows pseudo second-order model. Breakthrough adsorption capacity of SFAA is 1.21 mg/g, as compared with 0.41 mg/g for activated alumina.

Temporal influence of fly ash on select soil physical properties

1997 ◽  
Vol 77 (4) ◽  
pp. 677-683 ◽  
Author(s):  
L. Y. Salé ◽  
D. S. Chanasyk ◽  
M. A. Naeth
Keyword(s):  
Fly Ash ◽  
Physical Properties ◽  
Bulk Density ◽  
Size Distribution ◽  
Aggregate Size ◽  
Penetration Resistance ◽  
Soil Physical Properties ◽  
Modulus Of Rupture ◽  
Soil Reclamation ◽  
Over Time

Fly ash, as a source of calcium, has potential for soil structure amendment. This potential was tested by examining the influence of fly ash on select soil physical properties of an easily clodded clay loam soil. Fly ash:soil mixtures were varied from 0 to 100% (vol/vol). Pots of these mixtures were placed into the soil of a reclaimed surface mine and sampled four times during a 15.5-mo period: upon mixing, after one summer, after one summer and a winter and after the second summer. Bulk density, dry aggregate size distribution, penetration resistance (PR) and modulus of rupture (MOR) were assessed on soils within the pots.Adding fly ash up to 25 to 50% generally increased bulk density; adding more decreased it. Bulk density decreased over time for most of the treatments. Adding 12.5 or 25% fly ash produced the greatest percentage of aggregates within the ideal range (0.5 to 4.0 mm). Blunt-end PR was a more sensitive parameter than cone resistance. Adding 25% fly ash resulted in lower MOR while maintaining a desirable level of aggregation, thus reducing cloddiness. In general most properties varied over time, indicating the need to consider the dynamic nature of them in reclamation. Key words: Fly ash, soil reclamation, bulk density, penetration resistance, particle size distribution

An approach to modelling soil structure dynamics and soil structure recovery due to earthworm bioturbation and root growth

2021 ◽  
Author(s):  
Katharina Meurer ◽  
Thomas Keller ◽  
Nicholas Jarvis
Keyword(s):  
Root Growth ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Bulk Density ◽  
Size Distribution ◽  
Soil Structure ◽  
Organic Matter Content ◽  
Matter Content ◽  
Structure Evolution ◽  
Static Properties

<p>The pore structure of soil is known to be dynamic at time scales ranging from seconds (e.g. compaction) to seasons (e.g. root growth, macro-faunal activity) and even decades to centuries (e.g. changes in organic matter content). Nevertheless, soil physical and hydraulic functions are generally treated as static properties in most soil-crop models. Some models account for seasonal variations in soil properties (e.g. bulk density) due to tillage loosening and post-tillage consolidation or soil sealing. However, no model can account for longer-term changes in soil structure due to biological agents and processes. The development of such a model remains a challenge due to the enormous complexity of the interactions in the soil-plant system. Here, we present a new concept for modelling soil structure evolution impacted by biological processes such as root growth and earthworm activity. In this preliminary test of the model, we compare simulations against field observations made at the Soil Structure Observatory (SSO) in Zürich, Switzerland, that was designed to provide information on soil structure recovery following a severe compaction event. In this simple application, we modelled changes in the pore size distribution in a bare soil treatment resulting from soil ingestion and egestion by earthworms and the loosening of compacted soil by casting at the soil surface. Following calibration, the model was able to reproduce the observed temporal development of total porosity, soil bulk density and pore size distribution during a four-year period following severe traffic compaction. The modelling approach presented here appears promising and could help support the development of cost-efficient strategies for sustainable soil management and the restoration of degraded soils.</p>

A new approach to modelling soil structure dynamics and a preliminary application to structure recovery by earthworm bioturbation after heavy compaction

2020 ◽  
Author(s):  
Katharina Meurer ◽  
Thomas Keller ◽  
Nick Jarvis
Keyword(s):  
Root Growth ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Bulk Density ◽  
Size Distribution ◽  
Soil Structure ◽  
Organic Matter Content ◽  
Matter Content ◽  
Structure Evolution ◽  
Static Properties

<p>The pore structure of soil is known to be dynamics at time scales ranging from seconds (e.g. compaction) to seasons (e.g. root growth, macro-faunal activity) and even decades to centuries (e.g. changes in organic matter content). Nevertheless, soil physical and hydraulic functions are generally treated as static properties in most soil-crop models. Some models account for seasonal variations in soil properties (e.g. bulk density) due to tillage loosening and post-tillage consolidation or soil sealing, but none can account for longer-term changes in soil structure due to biological agents and processes. Here, we present a new concept for modelling soil structure evolution impacted by biological processes such as root growth and earthworm activity. In this preliminary test of the model, we compare simulations against field observations made at the Soil Structure Observatory (SSO) in Zürich, Switzerland, that was designed to provide information on soil structure recovery following a severe compaction event. In this simple application, we modelled changes in the pore size distribution in a bare soil treatment resulting from soil ingestion and egestion by earthworms and the loosening of compacted soil by casting at the soil surface. Following calibration, the model was able to reproduce the observed temporal development of total porosity, soil bulk density and pore size distribution during a four-year period following severe traffic compaction. The modelling approach presented here appears promising and could help support the development of cost-efficient strategies for sustainable soil management and the restoration of degraded soils.</p>

Synthesis and Characterization of Double Pore Size Multiphase Materials from Waste Aluminum Slag and Activated Carbon

2012 ◽  
Vol 512-515 ◽  
pp. 626-630
Author(s):  
Yan Qing Chen ◽  
Ren Ping Wu
Keyword(s):  
Activated Carbon ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Benzene Adsorption ◽  
Activated Alumina ◽  
Multiphase Materials ◽  
New Material ◽  
Iodine Adsorption ◽  
Adsorption Capability

A new type of double pore size activated alumina/activated carbon multiphase material was made by using waste aluminum slag and activated carbon as main raw materials. The microstructures and pore size distribution of the new material were characterized by SEM and BET techniques. Iodine adsorption value was used to evaluate the adsorption performance of the multiphase materials, and the benzene adsorption capability was also measured. The results show that the specific surface area of the activated alumina/activated carbon multiphase materials is 261.95m2/g, pore volume can reach 0.25m3/g, and the iodine adsorption value is 381.97mg/g. BET pore size distribution shows that micropores and mesopores both exist in the composite material. The micropores range from 0.6 to 1.4nm, and the mesopores range from 3.0 to 7.0nm. The benzene adsorption capability of this new material is excellent, with a saturated adsorption capacity of 241.00 mg/g, much better than pure activated alumina or activated carbon.

Least limiting water range and soil pore-size distribution related to soil organic carbon dynamics following zero and conventional tillage of a black soil in Northeast China

2014 ◽  
Vol 153 (2) ◽  
pp. 270-281 ◽  
Author(s):  
X. W. CHEN ◽  
X. H. SHI ◽  
A. Z. LIANG ◽  
X. P. ZHANG ◽  
S. X. JIA ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Bulk Density ◽  
Size Distribution ◽  
Northeast China ◽  
Soil Bulk Density ◽  
Black Soil ◽  
Tillage Practices ◽  
Least Limiting Water Range ◽  
Soc Mineralization

SUMMARYThe present work built on a previous study of tillage trials, which found the effectiveness of least limiting water range (LLWR) as an indicator of soil organic carbon (SOC) mineralization under different tillage practices in a black soil of Northeast China in 2009. To improve the understanding of soil structure controls over SOC dynamics, a study was conducted to explore the relationship between LLWR, which was calculated based on soil bulk density and soil pore-size distribution, and the effects of LLWR, which was calculated based on soil bulk density and soil pore-size distribution on SOC mineralization following no tillage (NT) and mouldboard ploughing (MP). In contrast to MP, NT had a significantly greater volume of large macropores (>100 μm) at depths of 0–0·05 and 0·2–0·3 m, but a significantly lower volume of small macropores (30–100 μm) at depths of 0–0·05, 0·05–0·1, 0·1–0·2 and 0·2–0·3 m. The volume of meso- (0·2–30 μm) and micro-pores (<0·2 μm) at different depths under the two tillage practices were similar. Tillage-induced changes in soil bulk density and pore-size volumes affected the ability of soil to fulfil essential soil functions in relation to organic matter turnover. Soil pore-size distribution, especially small macropores greatly affected LLWR and there was a significant correlation between LLWR, which was calculated based on soil bulk density, and the proportion of small macropores. The proportion of small macropores were used to calculate LLWR instead of soil bulk density and the values for NT and MP soils ranged from 0·073 to 0·148 m3water/m3soil. Using the proportion of small macropores rather than bulk density in the calculation of LLWR resulted in more sensitive indications of SOC mineralization. Variation in the proportion of small macropores can help characterize the impacts of tillage practices on dynamics of LLWR and SOC sequestration.

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