Porosity dependence of elastic constants in aluminum nitride ceramics

Yoshimura, Humberto Naoyuki; Molisani, André Luiz; Narita, N. E.; César, Paulo Francisco; Goldenstein, Hélio

doi:10.1590/s1516-14392007000200006

Cited by 68 publications

(54 citation statements)

References 26 publications

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“…The time of flight of the ultrasonic pulse was measured with an oscilloscope (TDS 1002, Tektronix, USA) and the thickness of the sample was measured with a digital micrometer (Mitutoyo, Brazil). Sonic velocities were calculated by: 2 t/a, where t is the specimen thickness and a is the time of flight 16 . The density of the specimens was determined by the Archimedes' principle, using water as the immersion liquid.…”

Section: Methodsmentioning

confidence: 99%

Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

et al. 2008

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The objective of this work was to evaluate biaxial-flexural-strength (σ f ), Vickers hardness (HV), fracture toughness (K Ic ), Young's modulus (E), Poisson's ratio (ν) and porosity (P) of two commercial glass-ceramics, Empress (E1) and Empress 2 (E2), as a function of the hot-pressing temperature. Ten disks were hot-pressed at 1065, 1070, 1075 and 1080 °C for E1; and at 910, 915, 920 and 925 °C for E2. The porosity was measured by an image analyzer software and σ f was determined using the piston-on-three-balls method. K Ic and HV were determined by an indentation method. Elastic constants were determined by the pulse-echo method. For E1 samples treated at different temperatures, there were no statistical differences among the values of all evaluated properties. For E2 samples treated at different temperatures, there were no statistical differences among the values of σ f , E, and ν, however HV and K Ic were significantly higher for 910 and 915 °C, respectively. Regarding P, the mean value obtained for E2 for 925 °C was significantly higher compared to other temperatures.

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Section: Methodsmentioning

confidence: 99%

Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

et al. 2008

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“…The porosity dependence of elastic moduli can be estimated by a simple linear model at very low porosities, while over a broad range of porosities the relationship is non-linear. A great number of models have been proposed to describe the variation in elastic moduli with porosity [113][114][115][116], notably including those of Hasselman [117] and Knudsen [118]. However, variation of elastic moduli is dependent not only on the volume of porosity but also its morphology, precluding use of one model to describe the variation for all materials [119].…”

Section: Young's Bulk and Shear Modulimentioning

confidence: 99%

A review of the processing, composition, and temperature-dependent mechanical and thermal properties of dielectric technical ceramics

et al. 2011

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The current review uses the material requirements of a new space propulsion device, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR ® ) as a basis for presenting the temperature dependent properties of a range of dielectric ceramics, but data presented could be used in the engineering design of any ceramic component with complementary material requirements. A material is required for the gas containment tube (GCT) of VASIMR ® to allow it to operate at higher power levels. The GCT's operating conditions place severe constraints on the choice of material. A dielectric is required with a high thermal conductivity, low dielectric loss factor, and high thermal shock resistance. There is a lack of a representative set of temperature-dependent material property data for materials considered for this application and these are required for accurate thermo-structural modelling. This modelling would facilitate the selection of an optimum material for this component. The goal of this paper is to determine the best material property data values for use in the materials selection and design of such components. A review of both experimentally and theoretically-determined temperature-dependent & room temperature properties of several materials has been undertaken. Data extracted are presented by property. Properties reviewed are density, Young's, bulk and shear moduli, Poisson's ratio, tensile, flexural and compressive strength, thermal conductivity, specific heat capacity, thermal expansion coefficient and the factors affecting maximum service temperature. Materials reviewed are alumina, aluminium nitride, beryllia, fused quartz, sialon and silicon nitride.

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“…The Poisson's ratio (ν) and Young's modulus (E) were determined using a 200 MHz ultrasonic pulser-receiver (Panametrics, USA, 5900 PR), 20 MHz longitudinal pulses, as described by Yoshimura et al 28 The measured bulk density, longitudinal velocity and shear velocity were used as the parameters. Ten measurements at both velocities were made on polished samples with composition corresponding to the different mixtures.…”

Section: Methodsmentioning

confidence: 99%

Influence of additive system (Al2O3-RE2O3 , RE = Y, La, Nd, Dy, Yb) on microstructure and mechanical properties of silicon nitride-based ceramics

Marchi

Silva²,

Silva

et al. 2009

Mat. Res.

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Silicon nitride based ceramics have been widely used as structural ceramics, due mainly to their thermomechanical properties such as high density, high thermal shock resistance, corrosion resistance and chemical stability. The aim of this study was to determine the influence of rare earth and aluminum oxide additions as sintering aids on densification, microstructure and mechanical properties of silicon nitride. Silicon nitride mixtures with 91 wt. (%) Si 3 N 4 and 9% wt. (%) additives were prepared and sintered. The density, microstructure and mechanical properties of the sintered specimens of these mixtures were determined. In most specimens, scanning electron microscopic examination and X ray diffraction analysis revealed elongated grains of β-Si 3 N 4 with aspect ratio of about 2.0 and dispersed in a glassy phase. The density of the sintered specimens was higher than 94% of the theoretical density (td) and specimens with La 2 O 3 and Al 2 O 3 additions exhibited the highest value. The results of this investigation indicate that the rare earth ion size influences densification of silicon nitride, but this correlation was not observed in specimens containing two different rare earth oxides. The hardness values varied in direct proportion to the density of the specimens and the fracture toughness values were influenced by the composition of the intergranular glassy phase.

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Porosity dependence of elastic constants in aluminum nitride ceramics

Cited by 68 publications

References 26 publications

Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

A review of the processing, composition, and temperature-dependent mechanical and thermal properties of dielectric technical ceramics

Influence of additive system (Al2O3-RE2O3 , RE = Y, La, Nd, Dy, Yb) on microstructure and mechanical properties of silicon nitride-based ceramics

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