scholarly journals A novel method to fabricate porous single phase O’-sialon ceramic and improve its mechanical property

2021 ◽  
Vol 53 (3) ◽  
pp. 387-395
Author(s):  
Haiqiang Ma ◽  
Chonggao Bao
Keyword(s):  
Mechanical Property ◽  
Pore Size ◽  
Single Phase ◽  
Bending Strength ◽  
Phase Evolution ◽  
Porous Ceramics ◽  
Si3n4 Powder ◽  
Novel Method ◽  
Gas Pressure Sintering ◽  
Sintering Method

Nowadays, the O?-sialon ceramics are synthesized by the reaction of Si3N4, SiO2 and Al2O3. However, it is difficult to achieve the single phase materials. Here, we have successfully developed porous single phase O?-sialon ceramics by pre-oxidation combined with gas-pressure sintering method. The effects of ?-Si3N4 powder on the microstructure, phase evolution, mechanical property were investigated. The result illustrated that the main crystal phase of the porous ceramics was composed of the single O?-sialon phase. The pores were well distributed and generated from the decomposition of Si2N2O. The elongated O?-sialon grains were found and formed around pore walls. Additionally, the addition of ?-Si3N4 powder was beneficial for improving the bending strength because of the reduction of porosity and pore size. The porous O?-sialon ceramics with uniform pores obtained the excellent bending strength when the ?-Si3N4 powder was 6 wt%.

Preparation of Porous Wollastonite Ceramics for Filtration

2007 ◽  
Vol 336-338 ◽  
pp. 1102-1104 ◽  
Author(s):  
Ming Sheng He ◽  
Jian Bao Li ◽  
Bo Wen Li ◽  
Hong Lin ◽  
Xiao Zhan Yang ◽  
...  
Keyword(s):  
Specific Surface ◽  
Pore Size ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sintering Temperature ◽  
Porous Ceramics ◽  
Holding Time ◽  
Starting Material ◽  
Sintering Method

Wollastonite powder was selected as a starting material with carbonate as pore-forming agent and binder added. The porous ceramics were prepared at different temperature by sintering method. The process includes batching, granulating, pressing molding, drying and sintering. It is discussed the influence of sintering temperature, dosage of binder, dosage of pore-forming agent, pressure of molding and holding time on the performance of porous ceramics. According to the principle of particles stack, the porous wollastonite ceramics for filtration with various diameters, shapes and porosity were fabricated by serial experiments. These products have 1 to 10 microns in pore size, 30.04 to 66.15% in porosity, 2.82 m2/g in specific surface area.

scholarly journals Effects of particle grading composition of SiC on properties of silicon-bonded SiC porous ceramics

2021 ◽  
Author(s):  
Changzhi Zhao ◽  
Huajian Hu ◽  
Meizhen Zhuo ◽  
Chunying Shen
Keyword(s):  
Silicon Carbide ◽  
Particle Size ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Single Particle ◽  
Packing Density ◽  
Bending Strength ◽  
Porous Ceramics ◽  
Argon Atmosphere ◽  
Coarse Powder

Abstract Silicon-bonded silicon carbide (SBSC) porous ceramics had been prepared by mixing two different particle size of SiC powder (coarse and fine) as aggregates for silicon carbide porous ceramics, adding metallic Si as the binder phase and firing at 1450 °C under argon atmosphere. Various combinations of SiC mixtures consisting of two different particle size and packing density were prepared, and the samples were investigated to understand apparent porosity, bending strength, pore size distribution, and microstructure. The result showed that mixing an appropriate proportion of SiC coarse and fine powders could not only improve the pore size distribution of SBSC porous ceramics but also significantly increase the bending strength compared with the single-particle size sample. The system had the highest free packing density when the ratio of coarse to fine SiC size was >2 and the coarse powder content was 60-70 wt%. The optimal bending strength, and apparent porosity were 37.53 MPa and 37.11% respectively when mixing 70 wt% of coarse powder (50.8 μm) and 30 wt% of fine powder (9.5 μm) and sintered at 1450 ℃ in an argon atmosphere. The material created had 100.3% increased bending strength, and 0.99% decreased porosity compared with the single-particle size sample (50.8 μm).

Fiber Dispersed Porous Alumina Sintered under Direct High Gas Pressure for High Thermal Shock Resistant Application

1991 ◽  
Vol 251 ◽  
Author(s):  
Toyokazu Kurushima ◽  
K. Ishizaki ◽  
S. Osaki
Keyword(s):  
Thermal Shock ◽  
Open Porosity ◽  
Thermal Shock Resistance ◽  
Bending Strength ◽  
Porous Alumina ◽  
Gas Pressure ◽  
Alumina Ceramics ◽  
Shock Resistance ◽  
Gas Pressure Sintering ◽  
Sintering Method

ABSTRACTFiber dispersed porous alumina ceramics were produced by a direct high gas pressure sintering method. The produced materials exhibited relative densities of 75–85%, high bending strength and good thermal shock resistance. The alumina ceramics were characterized by lower closed porosity and higher open porosity. These characters strengthen the thermal shock resistance of porous ceramics. This high gas pressure sintering by the direct high gas pressure sintering method densifies only bridge parts of alumina ceramics which support pores. This process is concluded to be effective to produce materials with higher strength, better thermal shock resistance and higher open porosity.

Mechanical Properties of Silicon Nitride Porous Ceramics with Bimodal Porosity

2012 ◽  
Vol 508 ◽  
pp. 69-75 ◽  
Author(s):  
Fei Chen ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Flexural Strength ◽  
Pore Size ◽  
Bending Strength ◽  
Porous Ceramics ◽  
Hierarchical Porosity ◽  
Continuous Reaction ◽  
The Difference ◽  
Macro Cellular

In this Paper, Silicon Nitride Porous Ceramics with Hierarchical Porosity Were Prepared Using Pressureless Sintering and their Mechanical Properties as a Function of Porosity and Pore Size Were Analyzed. In these Porous Ceramics, Macro-Pores with the Pore Size of 0.1 µm Were Formed by the Continuous Reaction of ZrP2O7 at ~250 °C and Macro-Cellular Pores with the Pore Size of 10~30μm Were Formed by the Burnout of Starch at ~550 °C or the Sublimation of Naphthalene at 80 °C. The Flexural Strength Decreased from 105 MPa to 6 MPa with the Porosity Increased from 35% to 65%. The Obtained Results Showed that the Flexural Strength Was Fit for the Equation of σ=σ0exp(-bP), where σ0 Is the Bending Strength of Nonporous Body of the same Material, P Is the Porosity and b Is the Factor Determines by Pore Structure. The Difference of Pore Size Was Determined by the Different Value of b and the Value of b Increased with the Increasing of Pore Size. Macro-Pores with the Pore Size of 0.1 µm Referred to a b Value of 4.3 and Macro-Cellular Pores with the Pore Size of 10 μm and 30 μm Referred to a b Value of 5.1 and 6.0 Respectively.

scholarly journals Electrical and mechanical properties of Cu-CNT nanocomposites sintered by microwave technique

2018 ◽  
Vol 23 (4) ◽  
pp. 303-317 ◽  
Author(s):  
Marjan Darabi ◽  
Masoud Rajabi
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Microwave Sintering ◽  
Multiwall Carbon Nanotubes ◽  
Physical And Mechanical Properties ◽  
Copper Matrix ◽  
Conventional Sintering ◽  
Novel Method ◽  
Sintering Method ◽  
Multiwall Carbon

In this research, multiwall carbon nanotubes were dispersed in a copper matrix using a planetary ball mill. The mixed powders were compacted using a uniaxial hydraulic presser. A novel method of microwave sintering was applied to consolidate Cu-CNT nanocomposites Conventional sintering method was also used to sinter samples to investigate the effects of applied methods on the properties of the sample. Sintering time was reduced to 20 min using microwave sintering method. The morphology and phase analysis of nanocomposites were studied by FESEM and XRD. The physical and mechanical properties of Cu-CNT nanocomposites were characterized using electrical conductivity, bending strength, and micro-hardness. The results show that the mechanical properties of Cu-CNT nanocomposites are improved significantly by microwave route. The optimum hardness and bending strength were obtained for 4 vol. % CNT as an optimum amount of reinforcement.

scholarly journals Preparation of high-entropy carbides by different sintering techniques

2021 ◽  
Vol 56 (19) ◽  
pp. 11237-11247 ◽  
Author(s):  
Johannes Pötschke ◽  
Manisha Dahal ◽  
Mathias Herrmann ◽  
Anne Vornberger ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Size ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
X Ray ◽  
High Entropy ◽  
Mean Grain Size ◽  
The Mean ◽  
Gas Pressure Sintering ◽  
Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

scholarly journals Effect of Sintering Temperature on Microstructure and Mechanical Properties of Hot-Pressed Fe/FeAl2O4 Composite

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 422
Author(s):  
Kuai Zhang ◽  
Yungang Li ◽  
Hongyan Yan ◽  
Chuang Wang ◽  
Hui Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Hot Press ◽  
Microstructure And Mechanical Properties ◽  
Powder Particles ◽  
Hot Press Sintering ◽  
Sintering Method

An Fe/FeAl2O4 composite was prepared with Fe-Fe2O3-Al2O3 powder by a hot press sintering method. The mass ratio was 6:1:2, sintering pressure was 30 MPa, and holding time was 120 min. The raw materials for the powder particles were respectively 1 µm (Fe), 0.5 µm (Fe2O3), and 1 µm (Al2O3) in diameter. The effect of sintering temperature on the microstructure and mechanical properties of Fe/FeAl2O4 composite was studied. The results showed that Fe/FeAl2O4 composite was formed by in situ reaction at 1300 °C–1500 °C. With the increased sintering temperature, the microstructure and mechanical properties of the Fe/FeAl2O4 composite showed a change law that initially became better and then became worse. The best microstructure and optimal mechanical properties were obtained at 1400 °C. At this temperature, the grain size of Fe and FeAl2O4 phases in Fe/FeAl2O4 composite was uniform, the relative density was 96.7%, and the Vickers hardness and bending strength were 1.88 GPa and 280.0 MPa, respectively. The wettability between Fe and FeAl2O4 was enhanced with increased sintering temperature. And then the densification process was accelerated. Finally, the microstructure and mechanical properties of the Fe/FeAl2O4 composite were improved.

Nanofiltration membranes with narrowed pore size distribution via pore wall modification

2016 ◽  
Vol 52 (55) ◽  
pp. 8589-8592 ◽  
Author(s):  
Yong Du ◽  
Yan Lv ◽  
Wen-Ze Qiu ◽  
Jian Wu ◽  
Zhi-Kang Xu
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Pore Wall ◽  
Nanofiltration Membranes ◽  
Novel Method

A novel method has been proposed to modify the pore wall of nanofiltration membranes (NFMs) by filtrating molecules that are reactive to the NFMs, leading to narrowed pore size distribution.

Mechanical Property of Phosphoaluminate Cement

2010 ◽  
Vol 150-151 ◽  
pp. 1754-1757 ◽  
Author(s):  
Peng Liu ◽  
Zhi Wu Yu ◽  
Ling Kun Chen ◽  
Zhu Ding
Keyword(s):  
Mechanical Property ◽  
Compressive Strength ◽  
Phase Composition ◽  
Electrical Properties ◽  
Pore Size Distribution ◽  
Pore Size ◽  
High Strength ◽  
Curing Time ◽  
Hydration Products ◽  
Resistance Value

The influence of curing time on the mechanical property of the phosphoaluminate cement (PAC) was investigated, and the mechanism was discussed as well. The phase composition and morphology of hydration products, electrical properties, porosity and pore size distribution of PAC cured different age were analyzed with XRD, EIS and MIP. The results showed PAC has the property of early-high strength, and the compressive strength of PAC cured for 1 day was about 70% of 28 days’. The main hydration products of PAC are micro-crystal phase and gel of phosphate and phosphoaluminate which formed compacter microstructure. In addition, there are no calcium hydroxide (CH) and ettringite (AFt) produced during the process of hydration. The compressive strength of PAC increased with age, which was due to more products continuously produced. The ac resistance analysis manifested as the change of the nyquist pattern and resistance value.

Development of α-β SiAlON Ceramics from Different Si3N4 Starting Powders

2008 ◽  
Vol 403 ◽  
pp. 107-108 ◽  
Author(s):  
Nurcan Calis Acikbas ◽  
Ferhat Kara ◽  
Hasan Mandal
Keyword(s):  
Fracture Toughness ◽  
Process Parameters ◽  
Gas Pressure ◽  
Economic Viability ◽  
Si3n4 Powder ◽  
Gas Pressure Sintering

- SiAlON ceramics were produced from different starting Si3N4 powders including β-Si3N4 and α-Si3N4 powders and mixtures of these powders. Gas pressure sintering was used for sintering. After sintering, resultant fracture toughness values were correlated with microstructure and starting powders. By optimizing chemistry and process parameters; - SiAlON ceramics with reasonable fracture toughness can be produced from rather coarse β-Si3N4 powder. This could improve the economic viability of SiAlON ceramics since -Si3N4 powders are less costly.

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