Identification and analysis of factors affecting thermal shock resistance of ceramic materials in solar receivers

An analysis was conducted of the possible modes of thermal stress failure of brittle ceramics for potential use in point-focussing solar receivers. The pertinent materials properties which control thermal stress resistance were identified for conditions of steady-state and transient heat flow, convective and radiative heat transfer, thermal buckling and thermal fatigue as well as catastrophic crack propagation. Selection rules for materials with optimum thermal stress resistance for a particular thermal environment were identified. Recommendations for materials for particular components were made. The general requirements for a thermal shock testing program quantitatively meaningful for point-focussing solar receivers were outlined. Recommendations for follow-on theoretical analyses were made

Effect of Crystallization of the Grain-Boundary Phase on the Thermal Diffusivity of a Sialon Ceramic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65865/1/j.1151-2916.1984.tb19519.x.pd

The thermal diffusivity and conductivity of transformation-toughened solid solutions of alumina and chromia

The thermal diffusivity of a series of solid solutions of alumina and chromia transformation toughened with a dispersed phase of unstabilized zirconia was measured by means of the laser-flash method from room temperature to 1400° C. It was found, in general, that the thermal diffusivity could be decreased significantly by the combined effects of solid solution alloying, microcracking and by the presence of the low conductivity dispersed phase of zirconia. The decrease in thermal diffusivity by microcracking was found to be present in the solid solution with low chromia content which underwent extensive grain growth. The effectiveness of solid solution formation and microcracking on thermal diffusivity was found to be greatest at the lower and intermediate ranges of temperature. The decrease in the thermal diffusivity due to the zirconia inclusions was found to be effective over the total temperature range. A numerical example is presented for the thermal conductivity calculated from the thermal diffusivity multiplied by the volumetric heat capacity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44684/1/10853_2004_Article_BF00556087.pd

Thermal-Shock Resistance and Fracture-Strength Behavior of Two Tool Carbides

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66260/1/j.1151-2916.1976.tb09415.x.pd

Thermal-stress resistance and fracture toughness of two tool ceramics

The thermal-stress resistance and fracture strength behaviour of two oxide ceramics (a hot-pressed pure Al 2 O 3 and a composite ceramic NTK-HC2) subjected to severe thermal shocks have been investigated. The damage resistance parameter ( K IC / σ f ) 2 for both ceramics is also determined for a wide range of temperatures (25° to 800° C) and cross-head rates (10 −2 cm min −1 ∼ 2.5 m sec −1 ). Fracture strength behaviour of these two oxide ceramics is shown to follow Hasselman's model where the instantaneous strength loss at the critical quenching temperature may be calculated using appropriate ( K IC / σ f ) 2 values to give good agreement with experimental results. Repeated shocks show some further degradation in the retained strength for both ceramics so that these materials are susceptible to thermal fatigue. It is found that both materials possess similar resistance to crack initiation (i.e. similar Δ T c and retained strength after shocking through Δ T c ) but the pure oxide ceramic has higher resistance to crack propagation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44673/1/10853_2004_Article_BF00540875.pd

Stress-Biased Anisotropic Microcracking in Zirconia Polycrystals

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65263/1/j.1151-2916.1990.tb05152.x.pd

Mechanical properties and thermal expansion behaviour in leucite containing materials

The effect of a change in sodium content and thermal history on a leucite composition material produced by a coprecipitation process was studied. Five materials with formulae of (K( 1− x ),Na x ) 2 O-Al 2 O 3 -4SiO 2 ( x = 0.0, 0.2, 0.4, 0.6, 0.8) were investigated for differences in phases, thermal expansion, and strength. Strengths of up to 175 MPa were obtained for a leucite composition material ( x = 0.0). Sodium was effective in lowering the thermal expansion coefficients of these materials. Leucite was linked to higher flexural strengths, but was present only in those specimens which were sintered at 1200 °C. Leucite was not present in those specimens sintered at 1100 °C or lower. Porosity was present in all specimens sintered at 1000 °C or higher.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44726/1/10853_2004_Article_BF00356582.pd