Slow Crack Growth by Grain Boundary Dissolution of Hydroxyapatite in Water

2011 ◽  
Vol 488-489 ◽  
pp. 428-431
Author(s):  
Dong Seok Seo ◽  
Kyu Hong Hwang ◽  
Jong Kook Lee
Keyword(s):  
Surface Roughness ◽  
Grain Boundary ◽  
Crack Growth ◽  
Immersion Time ◽  
Slow Crack Growth ◽  
Mechanical Degradation ◽  
Liquid Environment ◽  
Hydroxyapatite Ceramics ◽  
Initial Stage ◽  
Boundary Dissolution

Mechanical degradation of hydroxyapatite ceramics due to the slow crack growth was observed in water. Microstructural crack on the surface of hydroxyapatite initiated by grain boundary dissolution in liquid environment resulting in particle loosening and microstructural-level degradation, followed by a drastic decrease of mechanical properties. In this study, slow crack growth by the dissolution behavior of hydroxyapatite ceramics was investigated based on microstructural observation by field emission microscopy. The crack growth and morphological change of hydroxyapatite surface, especially at the initial stage of dissolution and related surface roughness were observed with immersion time. The surface dissolution occurred from the initial stage of immersion showing increase in surface roughness. Following certain period of immersion time, the surface dissolution initiated at grain boundaries and generated many separated grains.

AFM Study on the Surface Dissolution of Hydroxyapatite

2007 ◽  
Vol 336-338 ◽  
pp. 1553-1555 ◽  
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Jong Kook Lee
Keyword(s):  
Surface Roughness ◽  
Immersion Time ◽  
Distilled Water ◽  
Force Microscopy ◽  
Atomic Force ◽  
Hydroxyapatite Powder ◽  
Hydroxyapatite Ceramics ◽  
Initial Stage ◽  
Moisture Protection ◽  
Scanning Electron

The surface dissolution of hydroxyapatite ceramics in distilled water was investigated by using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The disks made of hydroxyapatite powder were sintered at 1200oC for 2 h in air with under moisture protection. After sintering, the disks were polished to smoothness using 1 μm diamond and they were soaked in 40 ml of pH 7.4 distilled water at 37oC for certain period of time. The morphological change of hydroxyapatite surface, specifically at the initial stage of immersion, and related surface roughness were observed with immersion time. The present study suggested that an artificial fact like surface scratch in this case initiated to be eliminated prior to the surface dissolution along grain boundary. That is, the surface roughness decreased at the initial stage of immersion, and then increased due to the surface dissolution.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Slow crack growth behaviour of hydroxyapatite ceramics

Biomaterials ◽  
2005 ◽  
Vol 26 (31) ◽  
pp. 6106-6112 ◽  
Author(s):  
Chahid Benaqqa ◽  
Jerome Chevalier ◽  
Malika Saädaoui ◽  
Gilbert Fantozzi
Keyword(s):  
Crack Growth ◽  
Slow Crack Growth ◽  
Growth Behaviour ◽  
Crack Growth Behaviour ◽  
Hydroxyapatite Ceramics

Assessment of Mechanical Degradation in Pressure Vessel Steel by Morphological Analysis of Carbides

2006 ◽  
Vol 321-323 ◽  
pp. 561-564
Author(s):  
Jai Won Byeon ◽  
S.I. Kwun ◽  
Kae Myung Kang
Keyword(s):  
Grain Boundary ◽  
Morphological Analysis ◽  
Mechanical Degradation ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Carbide Morphology ◽  
Initial Stage ◽  
Mean Size ◽  
Degradation Time ◽  
Quantitative Morphological Analysis

In this study, mechanical degradations in 2.25Cr-1Mo steel were evaluated by quantitative morphological analysis of carbides. Based on the morphology, carbides were classified as globular, fine acicular, rod, and grain boundary one. Mean size of carbides were determined as a function of morphology and thermal degradation time at 630°C. Area fraction of grain boundary carbides and fraction of grain boundary M6C carbides were observed to increase rapidly in the initial stage of degradation and then gradually afterwards. Both mean size of globular carbide and fraction of grain boundary M6C carbides were linearly correlated with strength. Potentials of carbide morphology analysis as a health monitoring technique were discussed, in term of correlation coefficient with strength.

Dissolution Resistance of Bovine Teeth-Derived Hydroxyapatite

2010 ◽  
Vol 97-101 ◽  
pp. 2257-2260
Author(s):  
Dong Seok Seo ◽  
Kyu Hong Hwang ◽  
Hwan Kim ◽  
Jong Kook Lee
Keyword(s):  
Immersion Time ◽  
Dwell Time ◽  
Sintered Density ◽  
Sintered Specimen ◽  
Liquid Environment ◽  
Peak Intensity ◽  
Hydroxyapatite Ceramics ◽  
Immersion Period

Dissolving behavior of hydroxyapatite ceramics prepared from bovine teeth (BTHA) was investigated. The bovine teeth were soaked in 0.1 M of NaOH at 80°C for 1 h. After soaking, the teeth were calcined at 800°C for 1 h, and then they were attritor-milled for 24 h. BTHA powder consisted of mainly HA and small amount of MgO. The powders obtained were cold isostatically pressed and sintered at 1200°C with a dwell time of 1 h. Sintered density of BTHA was about 70%. After polishing the surface of sintered specimen, BTHA was immersed in buffered water at 37°C for 3 and 7 days. After immersion period, there is no evidence of dissolution for BTHA at the end of the immersion time. In addition, there is no change of peak intensity in XRD after immersion time. It was found that hydroxyapatite from bovine teeth was more stable than commercial HA in liquid environment.

Grain-Boundary Engineering for Aging and Slow-Crack-Growth Resistant Zirconia

2017 ◽  
Vol 96 (7) ◽  
pp. 774-779 ◽  
Author(s):  
F. Zhang ◽  
J. Chevalier ◽  
C. Olagnon ◽  
M. Batuk ◽  
J. Hadermann ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Crack Growth ◽  
Slow Crack Growth ◽  
Grain Boundary Engineering

Slow Crack Growth Analyses of Oxygen Transport Ceramic Membranes

2007 ◽  
Vol 1023 ◽  
Author(s):  
Nagendra Nagabhushana ◽  
Jing Zhang ◽  
Thangamani Nithyanantham ◽  
Sukumar Bandopadhyay
Keyword(s):  
Flexural Strength ◽  
Crack Growth ◽  
Oxygen Transport ◽  
Room Temperature ◽  
Loading Rate ◽  
Slow Crack Growth ◽  
Ceramic Membranes ◽  
Effect Of Temperature ◽  
Mechanical Degradation ◽  
Specific Chemical

AbstractPerovskite-type oxides are promising materials with potential use as dense membranes for oxygen separations. We herein report slow crack growth (SCG) studies of La0.2Sr0.8Fe0.8Cr0.2O3-δ (LSFCO) perovskite membranes as Oxygen Transport Membranes (OTM). Two sample batches of perovskite were tested to investigate the effect of temperature, specific chemical environments, and loading rate on flexure strengths, using four-point bending tests. The first batch was examined at room temperature in air. The second batch was soaked in a N2/air atmosphere at 1000°C for 1 hour prior to application of load. Loading rates varied from 0.00005 mm/s to 0.01 mm/s. Flexural strength data indicate that the examined OTM material showed little susceptibility to SCG at room temperature in air. However, the sample is susceptible to SCG in a N2/air environment at 1000°C. Also, the experiments demonstrate flexural-strength rate dependency, with strength increasing with the loading rate. The observed phenomena are explained by the decomposition and microstructural transitions in the perovskite. The results provide important information about OTM mechanical degradation, which is valuable for future OTM design applications.

Sign in / Sign up

Export Citation Format

Share Document