Microstructural Design by Selective Grain Growth of β-Si3N4

1992 ◽  
Vol 287 ◽  
Author(s):  
Naoto Hirosaki ◽  
Yoshio Akimune ◽  
Mamoru Mitomo
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Material Properties ◽  
Weibull Modulus ◽  
Sintered Material ◽  
High Reliability ◽  
Uniform Size ◽  
Microstructural Design ◽  
Sintering Conditions

ABSTRACTRaw β-Si3N4 powder was gas-pressure sintered with Y2 O3-Nd2O3additives at > 1700ºC. Graingrowth behavior was investigated in relation to sintering conditions. Selective growth of large grains was accomplished by sintering the powder at high temperatures with small amounts of additives. As a result, in-situ composites were obtained from β-powder.The desired material properties have been attained by controlling the microstructural design using large grains. Materials with high reliability, having a Weibull modulus of about 50, were fabricated by maintaining a uniform size and distribution of elongated grains. Tough materials, having fracture toughness of, were developed by increasing the diameter of elongated grains. This method was applied to the sintering of refractory grade powder with the aim of lowering sintered material cost. Fairly good mechanical properties have been obtained even with impure powders.

Mechanical Properties of Zirconia Toughened Alumina Composites with TZP Partially Nanostructured Sintered by Liquid Fase

2008 ◽  
Vol 591-593 ◽  
pp. 436-440
Author(s):  
João Marcos K. Assis ◽  
Francisco Piorino Neto ◽  
Francisco Cristóvão Lourenço de Melo ◽  
Maria do Carmo de Andrade Nono
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Weibull Modulus ◽  
Bending Test ◽  
Sintering Aid ◽  
Zirconia Composites ◽  
Alumina Composites ◽  
Grain Size And Shape ◽  
Zirconia Toughened Alumina ◽  
Zirconia Powders

A comparative study between alumina added niobia ceramics and two alumina zirconia composites from nanostructured TZP (7% and 14% weight) was made. On this composites the zirconia were yttria stabilized and the alumina were submicron structured. As sintering aid a mixture of magnesia, niobia and talc were used on all samples. The sintering was performed at 1450 oC during 60 minutes. The characteristic grain size and shape of an alumina and zirconia powders, aggregates and agglomerates were characterized. The sintering ceramics were evaluated through hardness, fracture toughness and 4 point bending test. Weibull statistic was applied on the flexural results. Although the fracture toughness result from ZTA were lower, and seems to be affected by the liquid fase, the hardness and Weibull modulus were higher than alumina niobia. The grains size and the homogeneity of its distributions on the microstructure of this ceramics was correlated to these higher values. The results from these alumina zirconia composites showed a potential to apply as a ballistic armor material.

In Situ Preparation and Mechanical Properties of (ZrB2+ZrC)/Zr3[Al(Si)]4C6 Composites

2014 ◽  
Vol 602-603 ◽  
pp. 438-442
Author(s):  
Lei Yu ◽  
Jian Yang ◽  
Tai Qiu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Bending Strength ◽  
Coefficient Of Thermal Expansion ◽  
Raw Materials ◽  
Linear Increase ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Uniform Microstructure

Fully dense (ZrB2+ZrC)/Zr3[Al (Si)]4C6 composites with ZrB2 content varying from 0 to 15 vol.% and fixed ZrC content of 10 vol.% were successfully prepared by in situ hot-pressing in Ar atmosphere using ZrH2, Al, Si, C and B4C as raw materials. With the increase of ZrB2 content, both the bending strength and fracture toughness of the composites increase and then decrease. The synergistic action of ZrB2 and ZrC as reinforcements shows significant strengthening and toughing effect to the Zr3[Al (Si)]4C6 matrix. The composite with 10 vol.% ZrB2 shows the optimal mechanical properties: 516 MPa for bending strength and 6.52 MPa·m1/2 for fracture toughness. With the increase of ZrB2 content, the Vickers hardness of the composites shows a near-linear increase from 15.3 GPa to 16.7 GPa. The strengthening and toughening effect can be ascribed to the unique mechanical properties of ZrB2 and ZrC reinforcements, the differences in coefficient of thermal expansion and modulus between them and Zr3[Al (Si)]4C6 matrix, fine grain strengthening and uniform microstructure derived by the in situ synthesis reaction.

Mechanical properties of NiAl-Mo composites produced by specially controlled directional solidification

2012 ◽  
Vol 1516 ◽  
pp. 255-260 ◽  
Author(s):  
G. Zhang ◽  
L. Hu ◽  
W. Hu ◽  
G. Gottstein ◽  
S. Bogner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Directional Solidification ◽  
Creep Resistance ◽  
Room Temperature ◽  
Growth Direction ◽  
Nominal Composition ◽  
Potential Candidate ◽  
In Situ Composites

ABSTRACTMo fiber reinforced NiAl in-situ composites with a nominal composition Ni-43.8Al-9.5Mo (at.%) were produced by specially controlled directional solidification (DS) using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. In these composites, single crystalline Mo fibers were precipitated out through eutectic reaction and aligned parallel to the growth direction of the ingot. Mechanical properties, i.e. the creep resistance at high temperatures (HT, between 900 °C and 1200 °C) and the fracture toughness at room temperature (RT) of in-situ NiAl-Mo composites, were characterized by tensile creep (along the growth direction) and flexure (four-point bending, vertical to the growth direction) tests, respectively. In the current study, a steady creep rate of 10-6s-1 at 1100 °C under an initial applied tensile stress of 150MPa was measured. The flexure tests sustained a fracture toughness of 14.5 MPa·m1/2at room temperature. Compared to binary NiAl and other NiAl alloys, these properties showed a remarkably improvement in creep resistance at HT and fracture toughness at RT that makes this composite a potential candidate material for structural application at the temperatures above 1000 °C. The mechanisms responsible for the improvement of the mechanical properties in NiAl-Mo in-situ composites were discussed based on the investigation results.

scholarly journals Fabrication and mechanical properties of Al2O3/TiAl in situ composites doped with Nb2O5

2015 ◽  
Vol 47 (3) ◽  
pp. 311-317 ◽  
Author(s):  
F. Wang ◽  
N. Fan ◽  
J. Zhu ◽  
H. Jiang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Hot Press ◽  
Dispersion Method ◽  
Powder Mixtures ◽  
In Situ Composites ◽  
Microstructures And Mechanical Properties

Al2O3/TiAl composites were successfully fabricated from powder mixtures of Ti, Al, TiO2, Cr2O3 and Nb2O5 by a hot-press-assisted exothermic dispersion method. The effect of the Cr2O3 and Nb2O5 addition on the microstructures and mechanical properties of Al2O3/TiAl composites was characterized. The results showed that the specimens are mainly composed of TiAl, Ti3Al, Al2O3, NbAl3 and Cr2Al. The Vicker-hardness and density of Al2O3/TiAl composites increase gradually with the increase of Nb2O5 content. When the Nb2O5 content was 6.54 wt %, the flexural strength and fracture toughness of the composites have a maximum values of 789.79 MPa and 9.69 MPa?m1/2, respectively. The improvement of mechanical properties is discussed in detail.

scholarly journals Synthesis of "in situ" reinforced silicon nitride composites

2004 ◽  
Vol 69 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Aleksandra Vuckovic ◽  
Snezana Boskovic ◽  
Ljiljana Zivkovic
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Nitride ◽  
Pressureless Sintering ◽  
Sintering Additives ◽  
Sintering Time

The objective of this work was to investigate the effect of two different sintering additives (CeO2 and Y2O3 + Al2O3), sintering time and amount of ?-Si3N4 seeds on the densification, mechanical properties and microstructure of self-reinforced Si3N4 based composites obtained by pressureless sintering. Preparation of ?-Si3N4 seeds, also obtained by a pressureless sintering procedure, is described. Samples without seeds were prepared for comparison. The results imply that self-reinforced silicon nitride based composites with densities close to the theoretical values and with fracture toughness of 9.3MPa m1/2 can be obtained using a presureless sintering procedure.

Microstructure Development and Mechanical Properties of Ce-TZP/La- β-Alumina Composites

1992 ◽  
Vol 274 ◽  
Author(s):  
Takashi Fujii ◽  
Hironobu Muragaki ◽  
Hiraku Hatano ◽  
Shin-Ichi Hirano
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Hydrothermal Treatment ◽  
Fracture Strength ◽  
Sintered Body ◽  
Microstructure Development ◽  
Lanthanum Aluminate ◽  
Alumina Composites ◽  
In Situ Formation

ABSTRACTSimultaneous additions of lanthanum aluminate(LAL) and Al2O3 to Ce-TZP (12mol% CeO2-ZrO2) lead to the in-situ formation of lanthanum- β-alumina(LBA) platelets (∼1.0.μ m in width and 5 ∼10 μ m in length) in the Ce-TZP matrix during sintering. The composites showed a fracture toughness(SEPB method) of 9.5 MPa · m0.5 and fracture strength of 960 MPa. which are remarkably improved from Ce-TZP sintered body (8.5 MPa · m0.5 and 560 MPa).The composites also exhibit the no degradation by hydrothermal treatment.

Damage of T300 Carbon Fiber during Precursor Pyrolysis

2008 ◽  
Vol 368-372 ◽  
pp. 1019-1021
Author(s):  
Song Wang ◽  
Zhao Hui Chen
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Carbon Fiber ◽  
Flexural Strength ◽  
Phenolic Resin ◽  
Poor Performance ◽  
Precursor Polymers

C/SiC, C/Si-O-C and C/C composites reinforced with T300 carbon fiber were fabricated via polycarbosilane (PCS), polysiloxane (PSO), and phenolic resin precursor polymers infiltration/pyrolysis, respectively. Flexural strength and fracture toughness of the composites were evaluated. The results showed that all the composites had poor mechanical properties, less than 160 MPa in flexural strength and 5 MPa•m1/2 in fracture toughness. Deep investigation illuminated that the fiber was damaged severely during the preparation of the composites, especially in the first cycle of precursor pyrolysis. Great degradation of the fiber has relationship with coarsening of the microstructure. Bad in-situ strength of the fiber resulted in poor performance of the composites.

Influence of Sintering Conditions on Mechanical Properties of Ag-Nano Sintered Material

2017 ◽  
Vol 741 ◽  
pp. 7-12
Author(s):  
Shota Okuno ◽  
Qiang Yu ◽  
Yusuke Nakata
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Cross Section ◽  
Sintered Material ◽  
Sintering Process ◽  
Effect Of Pressure ◽  
Sintering Conditions ◽  
Sintering Processes ◽  
Joint Method

Recently, sintering joint using Ag-nanohas been attracting attention as a new joint method to replace the solder. However, the joint layer would contain a lot of voids after sintering processes. Since the voids affect mechanical property, the proper sintering conditions have to be selected in order to reduce these voids. In this research, the authors focus on the effect of pressure conditions at sintering process. Then, by creating FEM models including voids from cross section image of the joint layer and carrying out tensile analysis, the mechanical property of the joint layer has been acquired. Using this approach, the influence of pressure conditions on the mechanical properties is revealed.

scholarly journals Bending strength and reliability of porcelains used in all-ceramic dental restorations

Cerâmica ◽  
2018 ◽  
Vol 64 (372) ◽  
pp. 491-497
Author(s):  
A. A. de Almeida Junior ◽  
G. L. Adabo ◽  
B. R. Galvão ◽  
D. Longhini ◽  
B. G. Simba ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Weibull Modulus ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Weibull Analysis ◽  
Specific Group ◽  
Dental Restorations ◽  
Residual Amorphous Phase ◽  
All Ceramic

Abstract Four dental porcelains for covering zirconia were sintered (fired) at 910-960 °C and characterized, focusing in analyzing reliability, physical and mechanical properties. Samples with relative density close to 99% presented leucite crystallization apart from residual amorphous phase. Hardness between 491±23 and 575±32 HV was different among all ceramics. Fracture toughness between 1.13±0.11 and 1.42±0.25 MPa.m1/2 was statistically different. Bending strength results were not different for three porcelain groups (73±9 to 75±12 MPa), with the exception of one specific group (62±4 MPa). Weibull analysis indicated bending strength between 73 and 75 MPa, Weibull modulus (m) between 5.7 and 7.1, while the ceramic with strength of 60 MPa presented m=13.6. The use of classical theory of fracture mechanics associated to the results of properties obtained in this work indicated the critical failure size in these ceramics lays between 65 and 90 μm and the theoretical fracture energy of porcelains is approximately from 10.5 to 16.3 J/m. It was concluded that the porcelains had different behavior, and it seems that there is no clear relationship among the studied properties.

Nickel-Alumina Composites: In Situ Synthesis by a Displacement Reaction, and Mechanical Properties

1994 ◽  
Vol 365 ◽  
Author(s):  
Steven A. Jones ◽  
James M. Burlitch ◽  
Ersan Üstündag ◽  
Jeannie Yoo ◽  
Alan T. Zehnder
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Constants ◽  
High Performance ◽  
In Situ Synthesis ◽  
Displacement Reaction ◽  
Ductile Phase ◽  
Flexure Strength ◽  
Alumina Composites

ABSTRACTNickel-alumina composites have the potential to be high performance materials. Alumina, with its excellent oxidation resistance, combined with a ductile phase such as nickel may provide a tough material with a lower density and higher Young's modulus, overall, a higher specific modulus than typical Superalloys. Dense, interpenetrating Ni-Al2O3 composites were synthesized using a displacement reaction between NiO and aluminum. The resulting composites were characterized in terms of their mechanical properties such as hardness, flexure strength, fracture toughness and elastic constants. The synthesis, characterization, and mechanical properties, as well as the effect of the interpenetrating microstructure on the toughening mechanisms and other properties will be discussed.

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