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Influence of mechanical surface treatments on the indentation fracture toughness of glass infiltrated zirconia toughened alumina "GI-ZTA" disks
Silva, Flavio T. da;Zacché, Marcio A.N.;Amorim, Helio Salim de;
Matéria (Rio de Janeiro) , 2007, DOI: 10.1590/S1517-70762007000200020
Abstract: the main objective of this study was to evaluate the influence of mechanical surface treatments for excess glass removal on the fracture toughness of a glass infiltrated zirconia toughened alumina "gi-zta" disks (in-ceram? zirconia). the gi-zta disks were submitted to three different mechanical surface treatments after glass infiltration (grinding, sandblasting and grinding/sandblasting/annealing). fracture toughness was evaluated through indentation fracture (if) test. reliability of tests results was accessed through weibull statistics. results: indentation fracture tests (if) of gi-zta disks have shown that grinding was the surface treatment that presented the lowest kic and reliability. an annealing treatment after grinding and sandblasting promoted an increase in kic, mainly due to monoclinic-tetragonal reverse transformation recovering the tetragonal zirconia lost during the different mechanical surface treatments. the highest kic values were observed after sandblasting and grinding/sandblasting/annealing. significance: the proposed mechanical surface treatments played an important role on the metastability of tetragonal zirconia and strongly influenced the mechanical performance of gi-zta. kruskhall-wallis test indicated that kic values of the three mechanical surface treatments were statistically distinct.
Fracture simulation for zirconia toughened alumina microstructure  [PDF]
Kyungmok Kim,Jean Geringer,Bernard Forest
Physics , 2013, DOI: 10.1108/EC-08-2013-0163
Abstract: Purpose - The purpose of this paper is to describe finite element modelling for fracture and fatigue behaviour of zirconia toughened alumina microstructures. Design/methodology/approach - A two-dimensional finite element model is developed with an actual $Al{_2}O{_3}$ - 10 vol% $ZrO{_2}$ microstructure. A bilinear, time-independent cohesive zone law is implemented for describing fracture behaviour of grain boundaries. Simulation conditions are similar to those found at contact between a head and a cup of hip prosthesis. Residual stresses arisen from the mismatch of thermal coefficient between grains are determined. Then, effects of a micro-void and contact stress magnitude are investigated with models containing residual stresses. For the purpose of simulating fatigue behaviour, cyclic loadings are applied to the models. Findings - Results show that crack density is gradually increased with increasing magnitude of contact stress or number of fatigue cycles. It is also identified that a micro-void brings about the increase of crack density rate. Social implications - This paper is the first step for predicting the lifetime of ceramic implants. The social implications would appear in the next few years about health issues. Originality/value - This proposed finite element method allows describing fracture and fatigue behaviours of alumina-zirconia microstructures for hip prosthesis, provided that a microstructure image is available.
Degradation of alumina and zirconia toughened alumina (ZTA) hip prostheses tested under microseparation conditions in a shock device  [PDF]
Juliana Uribe,Jean Geringer,Laurent Gremillard,Bruno Reynard
Physics , 2013, DOI: 10.1016/j.triboint.2012.10.002
Abstract: This paper considers the degradation of alumina and zirconia toughened alumina vs. alumina for hip implants. The materials are as assumed to be load bearing surfaces subjected to shocks in wet conditions. The load is a peak of force; 9 kN was applied over 15 ms at 2 Hz for 800,000 cycles. The volumetric wear and roughness are lower for ZTA than for alumina. The long ZTA ageing did not seem to have a direct influence on the roughness. The ageing increased the wear volumes of ZTA and it was found to have a higher wear resistance compared to alumina.
International Journal of Engineering Science and Technology , 2011,
Abstract: Alumina has got some excellent properties like chemical inertness, thermal and mechanical strength against hazardous environment. Alumina is a good ceramic material which is being used for structuralapplications. To enhance the toughness and strength of the body some Zirconia is also used with it. The use of Zirconia in alumina is known as toughening of alumina. One difficulty arises, when alumina and alumina toughened composite are sintered , because the low sinterability of Alumina-Zirconia forced the compact to give very low density body. To overcome this problem alumina and alumina composites are made from slurry method which gives nearly theoretical density. The combined effect of alumina and Zirconia on the phase transformation and microstructure development of heat-treated Alumina-Zirconia composites has been studied. Slurry is prepared by adding water, dispersant, binder and anti-foaming agent. In the present study, Sintering schedule is optimized and kept constant for all samples. After sintering, mechanical behaviour of the composite has been studied.
Microstructural features of alumina refractories with mullite-zirconia aggregates  [cached]
Ferrari, C. R.,Rodrigues, J. A.
Boletín de la Sociedad Espa?ola de Cerámica y Vidrio , 2003,
Abstract: Refractory materials are often subjected to high temperatures and loads and their performance depends on their microstructural evolution during use. In this context, microstructural changes were monitored in alumina-based refractories containing mullite-zirconia aggregates and heat-treated at 1400°C and 1500°C for 2, 6, and 18 days. With the purpose of inducing in situ mullite formation, bricks containing microsilica were also prepared and heat-treated at 1500°C for 6 days for the sake of comparison. These heat treatments allowed for an evaluation of the use of refractories from the standpoint of temperature and time. In this work, scanning electron microscopy and X-ray diffraction analyses were made to identify the phases in the materials. The Rietveld method was also used for quantitative phase analyses. Interfacial reactions occurred between alumina and aggregates and between alumina and microsilica, causing the system to become mullitized. The effect of in situ-formed mullite was particularly evident in the results of the modulus of rupture of the materials containing microsilica. Creep tests revealed a reduction in the creep rate of materials treated at 1500°C for 18 days. El comportamiento de los materiales refractarios, cuando sometidos a altas temperaturas y a grandes esfuerzos mecánicos, está íntimamente relacionado con la evolución microestuctural, durante su uso. En este contexto, fue realizado un estudio de la evolución microestructural de los materiales refractarios de alumina conteniendo diferentes porcentajes de agregado de mullita–circona, sometidos a tratamientos térmicos por 2, 6 y 18 días, en temperaturas de 1400 y 1500oC. Fueron confeccionados, algunos ladrillos conteniendo microsílice, con la idea de se introducir la formación de mullita en situ. Para la comparación de los ladrillos, fueron realizados tratamientos térmicos por un periodo de 6 días en 1500oC. Estos tratamientos térmicos permitieron una aproximación del refractario en uso, considerando apenas el efecto del tiempo y la temperatura. En este trabajo, fueron utilizados, la microscopia electrónica de barrido y la difracción de rayos-X para identificación y caracterización de las fases presentes. Se aplicó el método de Rietveld para el análisis cuantitativo de las fases. Ocurrieron reacciones interfaciales entre la alúmina y los agregados, y entre la alúmina y la microsílice, como resultado de la mullitización del sistema. El efecto de la formación en situ de la mulita fue notado especialmente en los resultados del modulo de ruptura para los materiales que contienen microsí
Correlation between fracture toughness, work of fracture and fractal dimensions of Alumina-mullite-zirconia composites
Santos, Sérgio Francisco dos;Rodrigues, José de Anchieta;
Materials Research , 2003, DOI: 10.1590/S1516-14392003000200017
Abstract: the purpose of this work is to show the correlation between the fractal dimension, d, and mechanical properties such as work of fracture, gwof, and fracture toughness, kic. alumina-mullite-zirconia composites were characterized by the slit-island method, sim, to obtain values of d and its fractional part, d*. the fracture surface roughness was also evaluated using a cyclic voltametric method. it will be shown that there is a positive experimental dependency of gwof on d* and that there is not an evident correlation between kic and d*.
Correlation between fracture toughness, work of fracture and fractal dimensions of Alumina-mullite-zirconia composites
Santos Sérgio Francisco dos,Rodrigues José de Anchieta
Materials Research , 2003,
Abstract: The purpose of this work is to show the correlation between the fractal dimension, D, and mechanical properties such as work of fracture, gammawof, and fracture toughness, K Ic. Alumina-mullite-zirconia composites were characterized by the slit-island method, SIM, to obtain values of D and its fractional part, D*. The fracture surface roughness was also evaluated using a cyclic voltametric method. It will be shown that there is a positive experimental dependency of gammawof on D* and that there is not an evident correlation between K Ic and D*.
Effect of 3 mol% Yttria Stabilized Zirconia Addition on Structural and Mechanical Properties of Alumina-Zirconia Composites  [PDF]
M. A. Gafur, Md. Saifur Rahman Sarker, Md. Zahangir Alam, M. R. Qadir
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.87041
Abstract: Alumina-Zirconia (Al2O3-ZrO2) composites especially Zirconia Toughened Alumina (ZTA) shows better mechanical properties over alumina. Al2O3-ZrO2 composites were prepared by powder compaction method varying 3 mol% yttria stabilized zirconia (3Y-ZrO2) content from 0 to 20 vol% using small amount of MgO as sintering aid. The composites were sintered for two hours in air at 1580°C. At this temperature maximum density was achieved 99.31% of theoretical density for composite containing 20 vol% 3Y-ZrO2. Density measurement of sintered composites was carried out using Archimedes’s method. Hardness and fracture toughness measurement was carried out using Vickers indentation. Phase content and t-ZrO2 retention were detected by means of X-ray diffraction (XRD). Microstructure of the composites and grain size of alumina and zirconia was determined by Scanning Electron Microscopic (SEM) analysis. Maximum microhardness (17.46 GPa) was achieved for composite containing 5 vol% ZrO2 and maximum flexural strength (684.32 MPa) and fracture toughness (10.33 MPam0.5) was achieved for composite containing 20 vol% of 3Y-ZrO2. The aim of the present work is to investigate the optimum 3Y-ZrO2 content for obtaining maximum density, microhardness, flexural strength and fracture toughness of Al2O3-ZrO2 composites.
Influence of different surface treatments on the fracture toughness of a commercial ZTA dental ceramic
Silva, Flavio Teixeira da;Zacché, Marcio Alessandro Negrelly;Amorim, Helio Salim de;
Materials Research , 2007, DOI: 10.1590/S1516-14392007000100014
Abstract: the objective of this study was to investigate how mechanical surface treatments performed for removal of excess of molten glass, influence the fracture toughness of a dental zirconia toughened alumina (in-ceram? zirconia). infiltrated zta disks were submitted to three different surface treatments (grinding, sandblasting and grinding + sandblasting + annealing). fracture toughness was accessed through indentation strength test (is). x ray diffraction was used to investigate the metastability of tetragonal zirconia particles under all treatments proposed. kruskall-wallis non-parametrical test and weibull statistics were used to analyze the results. grinding (group 1) introduced defects which decreased the fracture toughness and reliability, presenting the lowest kic. on the other hand, grinding followed by sandblasting and annealing (group 3) presented the highest kic. sandblasting (group 2) presented the highest reliability but lower kic compared to group 3.
Wear Characteristics of Zirconia Toughened Ceramic Drawing Dies
Zhigang CHEN,

材料科学技术学报 , 1995,
Abstract: Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic CoWC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service life. Excellent wear resistance of ceramic die is obtained with a very high hardness (19 GPa). The service life is nearly three times that of Co-WC die. SEM observation on wear surfaces showed that material removal is mainly caused by plastic flow and ploughing process. But when the ceramic is composed of zirconia, alumina and some titanium carbide, micro-chipping and tribochemical reaction take place, and wear rate increases. Wear and friction induced martensite was detected by XRD. The T-M (tetragonal to monoclinic) phase transformation has a contribution to inhibiting microfracture.
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