Fracture Toughness of Liquid Phase Sintered SiC by Using Indentation Fracture Method

2005 ◽  
Vol 297-300 ◽  
pp. 137-142
Author(s):  
Hun Chae Jung ◽  
Han Ki Yoon ◽  
Bu Ahn Kim ◽  
Joon Soo Park ◽  
Akira Kohyama
Keyword(s):  
Fracture Toughness ◽  
Liquid Phase ◽  
Coefficient Of Thermal Expansion ◽  
Average Particle Size ◽  
Chemical Vapor Deposition Method ◽  
High Temperature Strength ◽  
Average Particle ◽  
Indentation Fracture ◽  
Pressing Method ◽  
Sintering Additives

SiC materials have excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. Therefore, in the interests of safety, we are required to measure fracture toughness of materials. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method under 20MPa using sintering additives at different temperature such as 1760oC, 1780oC, 1800oC and 1820oC. The starting powder was high purity β-SiC nano-powder with an average particle size of 30nm. Compositions of sintering additives were Al2O3 / Y2O3 = 0.7 and 1.5 (wt. %). Monolithic LPS-SiC was evaluated in terms of sintering density, hardness and fracture toughness through indentation fracture method by the Vickers hardness tester. Sintered density, hardness and fracture toughness of fabricated LPS-SiC increased with the increase of sintering temperature. They are higher than those of fabricated SiC by the chemical vapor deposition method.

Tribological Characteristics Manufactures SiC by Liquid Phase Sintered Method

2006 ◽  
Vol 324-325 ◽  
pp. 1177-1180
Author(s):  
Won Jo Park ◽  
Sun Chul Huh ◽  
Sung Ho Park ◽  
Hong Tae Song
Keyword(s):  
Wear Resistance ◽  
Liquid Phase ◽  
Coefficient Of Thermal Expansion ◽  
Average Particle Size ◽  
High Temperature Strength ◽  
Average Particle ◽  
Pressing Method ◽  
Sintering Additives ◽  
Resistance To Oxidation ◽  
Sic Composites

SiC materials have excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. In this study, monolithic liquid phase sintered SiC (LPS-SiC) was made by hot pressing method with nano-SiC powder an average particle size is 30nm and less. Alumina (Al2O3), yttria (Y2O3) and silica (SiO2) particles were used for sintering additives. To investigate effects of SiO2, Al2O3/Y2O3 composition was fixed and then ratios of SiO2 were changed as seven kinds. Materials have been sintered for 1 hour at 1760, 1780 and 1800 under the pressure of 20MPa. The system of sintering additives which affects a property of sintering as well as the influence depending on compositions of sintering additives were investigated by measurement of density, mechanical properties such as Vickers hardness and sliding wear resistance were investigated to make sure of the optimum condition which is about matrix of SiCf/SiC composites. The abrasion test condition applies to load of 20N at 100rpm for 20min. Sintered density, abrasion property of fabricated LPS-SiC increased with increasing the sintering temperature. In case of LPS-SiC with low SiO2 content, has very excellent wear resistance.

Effect of Sintering Additives on Fabrication Properties of Liquid Phase Sintered SiC

2005 ◽  
Vol 297-300 ◽  
pp. 2539-2544 ◽  
Author(s):  
Han Ki Yoon ◽  
Yi Hyun Park ◽  
Joon Soo Park ◽  
Akira Kohyama
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Liquid Phase ◽  
Hot Pressing ◽  
Bending Test ◽  
Average Particle ◽  
Pressing Method ◽  
Sintering Additives ◽  
Temperature And Pressure ◽  
Sic Composites

SiC has been extensively studied for high temperature components in advanced energy system and gas turbine because of its excellent high temperature mechanical properties and good thermal-chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiCf/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiCf/SiC composites by hot pressing method. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method in Ar atmosphere at 1800oC under 20MPa using Al2O3, Y2O3 and SiO2 as sintering additives. The starting powder was high purity β-SiC nano-powder with an average particle size of 30nm. The characterization of LPS-SiC was investigated by means of SEM and three point bending test. Base on the composition of sintering additives-, microstructure- and mechanical property correlation, the compositions of sintering additives are discussed.

Application of nanocrystalline structure modifi ed layers on coldworking tool

2021 ◽  
pp. 37-43
Author(s):  
S.S. Samotugin ◽  
V.I. Lavrinenko ◽  
Yu.S. Samotugina ◽  
O.A. Khristenko ◽  
O.N. Shicheva ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Particle Size ◽  
Surface Modification ◽  
Structure Formation ◽  
Cold Working ◽  
Average Particle Size ◽  
Nanocrystalline Structure ◽  
Cutting Edge ◽  
Average Particle ◽  
Plasma Surface

The regularities of the structure formation and changes in the fracture toughness parameters of the Kh12M steel are studied for various technological variants of plasma surface modification. The possibility for the formation of nanocrystalline martensite-carbide structure with average particle size of 50...150 nm in the surface volumes at the cutting edge of cold-working tool is shown.

Fabrication and Strength Properties of LPS-SiC Ceramics

2005 ◽  
Vol 287 ◽  
pp. 183-188 ◽  
Author(s):  
Yi Hyun Park ◽  
Dong Hyun Kim ◽  
Han Ki Yoon ◽  
Akira Kohyama
Keyword(s):  
Elastic Modulus ◽  
High Temperature ◽  
Flexural Strength ◽  
Hot Pressing ◽  
Average Particle Size ◽  
Process Temperature ◽  
Average Particle ◽  
Pressing Method ◽  
Temperature And Pressure ◽  
Sic Composites

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. SiCf/SiC composites are promising for various structural materials. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of the process temperature and pressure is key requirements for the fabrication of SiCf/SiC composites by hot pressing method. In the present work, monolithic LPS-SiC was fabricated by hot pressing method at various temperatures. The starting powder was high purity β-SiC nano-powder with an average particle size of 30nm. Compositions of sintering additives were Al2O3 / Y2O3 = 0.7 and 1.5 (wt.%). Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the process temperature. Particularly, relative density of LPS-SiC fabricated at 1820oC with additive composition of Al2O3/Y2O3=1.5(wt.%) was 95%. Also, flexural strength and elastic modulus were 900MPa and 220GPa, respectively. In the fracture surface of this specimen, the size and shape of SiC grains grew up and changed. Also, tortuous crack paths and occurrence of interfacial debonding were observed.

Influence of Second Phase Particles on Fracture Toughness in AZ31 Magnesium Alloys

2004 ◽  
Vol 261-263 ◽  
pp. 369-374 ◽  
Author(s):  
Taisuke Sasaki ◽  
Hidetoshi Somekawa ◽  
Akira Takara ◽  
Yukio Nishikawa ◽  
Kenji Higashi
Keyword(s):  
Fracture Toughness ◽  
Particle Size ◽  
Magnesium Alloys ◽  
Average Particle Size ◽  
Second Phase ◽  
Average Particle ◽  
Particle Spacing ◽  
Strain Fracture ◽  
Second Phase Particles ◽  
Good Agreement

Three kinds of thin AZ31 wrought magnesium alloys sheets were used in order to investigate the influence of the second phase particles on fracture toughness. From the theoretical model, the ratio of λp/dp would be estimated 5~ 6. On the other hand, from the microstructural observation, average particle spacing on each material was sample A: 13.1µm, sample B: 14.1, and sample C: 12 µ. In addition, average particle size on each sample was sample A: 2.1, sample B: 1.9, and sample C: 2.3 µm. Therefore, the ratio of λp/dp calculated from fracture surface observation would be predicted 6 ~ 7. In comparison with the result of the prediction by theoretical analysis was in good agreement with the result of fracture toughness observation. It was found that the variation in plane-strain fracture toughness on AZ31 were affected by both of particle spacing and particle size.

Fracture Toughness of Si3N4 Based Ceramics with Rare-Earth Oxide Sintering Additives

2009 ◽  
Vol 409 ◽  
pp. 377-381 ◽  
Author(s):  
Peter Tatarko ◽  
Štefánia Lojanová ◽  
Ján Dusza ◽  
Pavol Šajgalík
Keyword(s):  
Fracture Toughness ◽  
Rare Earth ◽  
Silicon Nitride ◽  
Aspect Ratio ◽  
Rare Earth Oxide ◽  
Rare Earth Oxides ◽  
Crack Deflection ◽  
Indentation Fracture ◽  
Toughening Mechanisms ◽  
Sintering Additives

Fracture toughness of hot-pressed silicon nitride and Si3N4+SiC nanocomposites prepared with different rare-earth oxides (La2O3, Sm2O3, Y2O3, Yb2O3, Lu2O3) sintering additives have been investigated by Chevron Notched Beam, Indentation Strength and Indentation Fracture techniques. The fracture toughness values of composites were lower due to the finer microstructures and the lack of toughening mechanisms. In the Si3N4 with higher aspect ratio (Lu or Yb additives) crack deflection occurred more frequently compared to the Si3N4 doped with La or Y, which was responsible for the higher fracture toughness.

Modification of Epoxy Resin Using Liquid Natural Rubber

2006 ◽  
Vol 517 ◽  
pp. 272-274 ◽  
Author(s):  
Ismail Zainol ◽  
Mohamad Ibrahim Ahmad ◽  
Fadzil Ayad Zakaria ◽  
Anita Ramli ◽  
Haslan Fadli Ahmad Marzuki ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Natural Rubber ◽  
Epoxy Resin ◽  
Average Particle Size ◽  
Sem Analysis ◽  
Average Particle ◽  
Uniform Dispersion ◽  
Liquid Natural Rubber ◽  
The Impact ◽  
Modified Epoxy

The cure process and the mechanical properties of liquid polymethylmethacrylate grafted natural rubber (LMG30) modified epoxy have been studied. Addition of LMG30 significantly increased the fracture toughness and the impact strength of the epoxy resin. The fracture toughness increased up to 22 fold (17.3 MNm-3/2) when modified with 5 phr LMG30. The glass transition temperature however, decreases as the rubber content increases. The SEM analysis shows uniform dispersion of rubber particles within the epoxy matrix with average particle size between 0.4 to 0.8 0m in diameter.

Mechanical Properties and Fabrication of Silicon Carbide Ceramic by NITE Method

2007 ◽  
Vol 124-126 ◽  
pp. 699-702
Author(s):  
Han Ki Yoon ◽  
Young Ju Lee ◽  
Yi Hyun Park ◽  
Joon Soo Park ◽  
Akira Kohyama
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Average Particle Size ◽  
Bending Test ◽  
Average Particle ◽  
Pressing Method ◽  
Three Point Bending ◽  
Nano Powder ◽  
Strength Characterization ◽  
Sintered Temperature

Nano infiltration transient eutectic ceramic (NITE-SiC) was fabricated by hot pressing method using Al2O3 and Y2O3 as sintering additives. The ratio of the Al2O3/Y2O3 additives was changed between 6:4 and 4:6. The densification and mechanical properties were investigated for the sintered temperature. The starting powder was high purity β -SiC nano-powder with an average particle size of 30nm. The bending strength characterization and densification of NITE-SiC was investigated by the FE-SEM and three point bending test.

Fracture Toughness of Liquid Phase Sintered SiC by Using Indentation Fracture Method

2005 ◽  
pp. 137-142
Author(s):  
Hun Chae Jung ◽  
Han Ki Yoon ◽  
Bu Ahn Kim ◽  
Joon Soo Park ◽  
Akira Kohyama
Keyword(s):  
Fracture Toughness ◽  
Liquid Phase ◽  
Indentation Fracture

scholarly journals Passage kinetics of digesta in horses fed with coastcross hay ground to different degrees

2014 ◽  
Vol 38 (5) ◽  
pp. 506-514 ◽  
Author(s):  
Vinicius Pimentel Silva ◽  
Fernando Queiroz de Almeida ◽  
Róbson Ricardo Moreira Pimentel ◽  
Fernanda Nascimento de Godoi ◽  
Tiago Marques dos Santos ◽  
...  
Keyword(s):  
Particle Size ◽  
Liquid Phase ◽  
Transit Time ◽  
Solid Phase ◽  
Average Particle Size ◽  
Neutral Detergent Fiber ◽  
Average Particle ◽  
Passage Rate ◽  
The Right ◽  
Kinetics Of

This study was conducted to evaluate the kinetics, physicochemical characteristics and particle size of digesta in the right ventral colon (RVC) of horses fed coastcross hay ground to different degrees. Four horses fitted with cannulae in the RVC were used and were fed the following forms of hay: long, chopped, ground to 5 mm and ground to 3 mm. A Latin Square 4x4 study design was used. Each experimental period included 10 days for diet adaptation, four days for feces collection and one day for digesta collection. The kinetics of the particulate and solute phases of digesta were evaluated based on the mean retention time (MRT), passage rate (k) and transit time (TT) using two external markers: Cr-NDF and Co-EDTA. The TT of solid phase digesta was 3 hours longer (P<0.05) for ground hay than with the other physical forms of hay. There was no difference (P>0.05) in k or MRT in either the liquid or solid phase of digesta as a function of the different degrees of hay grinding. However, the liquid phase of digesta presented a higher k than the solid phase, with values of 3.28 and 2.73 h-1 being obtained, respectively. The smallest particle size and the lowest neutral detergent fiber contents in colon digesta were observed when hay ground to 3 mm was offered, leading to values of 0.51 mm and 53.46%, respectively. Grinding the hay increased the transit time of the liquid phase in the digestive tract of the horses, whereas no change in the kinetics of the solid phase digesta was observed. The grinding of hay reduced the NDF and the average particle size in the right ventral colon.

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