The difference between self compacting concrete (SCC) and conventional concrete (CC) is in fresh state, is the high fluidity at first and the need for vibration at second, but in hardened state, both concretes must comply with the resistance specified, in addition to securing the safety and functionality for which it was designed. This article describes the tests and results for shrinkage and creep at some medium strength Self Compacting Concrete with added sand (SCC-MSs) and two types of cement. The research was conducted at the
Laboratorio de Tecnología de Estructuras (LTE) of the Universitat Politécnica de Catalunya (UPC), in dosages of 200 liters; with the idea of evaluating the effectiveness of implementation of these new concretes at elements designed with conventional concrete (CCs).
Cornado, C.; Garcia-Almirall, Pilar; Vima-Grau, S.; Vilà, G.; Uzqueda, A.L. IOP Conference Series: Materials Science and Engineering num. 245, p. 1-11 DOI: 10.1088/1757-899X/245/4/042062 Data de publicació: 2017 Article en revista
In a context of a shifting environmental, economic and social paradigm, European cities face a situation that is at the same time challenge and opportunity: the need for urban rehabilitation of the vulnerable degraded socio residential fabric. Public administrations in big
cities and metropolitan areas are confronted with both the undercurrent need of actualization of the built stock and the rise of urban residential vulnerability. The city of Barcelona, as many
others, is the result of multiple phenomena with high urban and social consequences. The socio spatial integration of immigrant population, the touristic rise and gentrification processes are current situations simultaneously taking place in the city. In parallel, a framework of economic crisis in which public investments in urban and social matters decrease, provides a temporal juncture that results into an increase of social polarization and socio economic inequality that becomes evident and expressed in the territory. This research focuses in the case of Barcelona, and presents a methodology based on a system of indicators elaborated through the exploitation of statistical data complemented with very specific data supplied by the Barcelona City Council. The accurate knowledge of socio demographic, socioeconomic and residential and urban characteristics is crucial in order to define the very complex urban dynamics that describe in the city neighbourhoods and areas. Residential vulnerability is defined as an assembly of objective conditions that relate to residential space and indicate situations of social discrimination and structural disadvantage of the population, related to a specific time and context. Thus, it is
relevant to analyse the concentration of certain indicators of vulnerability in specific places or neighbourhoods, to contrast its effect on the socio-residential situation and its temporal evolution
in order to identify tendencies. The present study contributes to the identification of data sources and a system to calculate the purposed indicators, the elaboration of a GIS analysis in order to
determine the characterization of neighbourhoods and census sections according to each indicator, and the identification of areas with a higher degree of problematic based on synthetic analysis. A very relevant knowledge basis that can be used by public policy makers in order to establish measures that define vulnerable areas where to carry out actions that foster urban equality.
Corso, J.M.; Garcia-Almirall, Pilar; Lopez, D.; Casals, J. IOP Conference Series: Materials Science and Engineering num. 245, p. 1-11 DOI: 10.1088/1757-899X/245/5/052092 Data de publicació: 2017 Article en revista
In a context of web application in the field of the dissemination of cultural heritage, this article advances in a methodology for the optimization of points clouds obtained through the technology of Laser Scanner (TLS). Identifying the potential of TLS surveys as interactive models that allow the cultural heritage to be perpetuated over time.
This point cloud optimization is developed with free software, focusing its exploitation on an interactive web application, which has made it possible to convert two temporary museum exhibitions into permanent exhibitions in virtual format. Developed in conjunction with the Museu d’Història de la Ciutat de Barcelona. The case study focuses on the Palau Reial Major, Gothic style, formed by the chapel of Santa Àgata (built in 1302, on the Roman wall) and Saló del Tinell (built between 1359 and 1370, on the Roman remains). Located in the Plaça del Rei, in the old town of Barcelona. In this application is very important the visual impact, it requires to represent a faithful model of the interior of the building, from the point of view of color and lighting, avoiding the
transparencies of the model through a dense cloud of dots, without occlusions, this requires a great quantity of positions. This implies a clear methodology, using different techniques such as photographic proyection, given the complexity of lighting of the building, as much for the artificial lighting as for the lighting of the stained glass. In this process, there were 84 positions that provide greater density of points, which are optimized with free programs. The temporary exhibitions of the case studies, elaborated by the MUHBA in the Saló del Tinell are: "Indianas, 1736-1847. The origins of industrial Barcelona" exposed from May 19, 2012 to March 3, 2013 and "El Món del 1714"exposed from December 20 to September 28, 2014. Both are based on a tour with showcases and exhibitors where different objects of a museum character are shown, such as looms, cloths, dresses, books, among others, accompanied by panels with texts and images that contain the information that each exhibition shows. Virtual applications allow such temporary exposures to become an interactive model, in which information can be permanently consulted. A virtual tour where the user can interact with the information panels and observe in detail the different objects of the exhibition. The results of this work manage to generate a powerful mechanism of diffusion and approximation to the society of the cultural heritage that, otherwise, as a whole as exhibition would disappear.
Corso, J.M.; Garcia-Almirall, Pilar; Marco, A. IOP Conference Series: Materials Science and Engineering num. 245, p. 1-11 DOI: 10.1088/1757-899X/245/5/052091 Data de publicació: 2017 Article en revista
This article intends to explore the limits of scanning with the technology of 3D Laser Scanner and the 3D printing, as an approximation to its application for the survey and the study
of singular elements of the architectural heritage. The case study we developed is the Porta del Drac, in the Pavelló Güell, designed by Antoni Gaudí. We divided the process in two parts, one about how to scan and optimize the survey with the Laser Scanner Technology, made with a Faro Forus3D x330 scanner. The second one, about the optimization of the survey as a highresolution mesh to have a scaled 3D model to be printed in 3D, for the musealization of the Verdaguer House of Literature in Vil.la Joana (Barcelona), a project developed by the Museum of History of Barcelona, in tribute to Jacint Verdaguer. In the first place, we propose a methodology for the survey of this atypical model, which is of special interest for several factors:
the geometric complexity in relation to the occlusions, the thickness of the metallic surfaces, the hidden internal structure partially seen from the outside, the produced noise in its interior, and the instrumental errors. These factors make the survey process complex from the data collection, having to perform several scans from different positions to cover the entire sculpture, which has a geometry composed of a variety of folds that cause occlusions. Also, the union of the positions
and the average of the surfaces is of great relevance, since the elements of the sculpture are constructed by a metal plate of 2mm, therefore, the error in the union of all these many positions
must be smaller than this. Moreover, optimization of the cloud has a great difficulty because of the noise created by the instrumental error as it is a metal sculpture and because of noise point clouds that are generated inside the internal folds of the wings, which are made with a welded wire mesh with little spaces between them. Finally, the added difficulty that there is an internal structure between elements of the parts of the Drac that are partially hidden and therefore cannot
be recorded. Secondly, we expose the procedures performed to move from a point cloud to an optimal high-resolution mesh to be printed in 3D, adapting it to all the limitations that this printing technique entails. On the one hand, for the meshing process, a previous classification of
the point cloud by pieces (wings, chains, mosaics, head ...) is made and an internal structure is re-assembled to avoid floating parts. On the other hand, the selection of the 3D printing technique, in this case FDM (Fused Deposition Modelling), limits the size of the model so it
needs to be cut by determined maximum dimension, and also it limits the minimum thickness of the model’s surface, that is to say, the model cannot be directly scaled to the desired size because the 2mm surfaces would be too thin to be printed. This research intends to advance the knowledge of data acquisition, optimization, modelling and 3D printing, with a case study of great complexity. A process that can be systematized and applied to other models.
Tibaduiza, D.A.; Anaya, M.; Forero, E.; Castro, R.; Pozo, F. IOP Conference Series: Materials Science and Engineering Vol. 138, p. 1-8 DOI: 10.1088/1757-899X/138/1/012016 Data de publicació: 2016 Article en revista
Benito, J.; Cabrera, J.; Casas, C.; Gregoire, V. IOP Conference Series: Materials Science and Engineering Vol. 63, p. 1-7 DOI: 10.1088/1757-899X/63/1/012024 Data de publicació: 2014-07 Article en revista
In this paper iron powders with two oxygen content (0.2 and 0.6% wt.) have been mechanically milled and consolidated by hot static pressing at different temperatures to obtain different grain sizes. At lower temperatures the grain size was in the nanostructured and ultrafine range and with increasing temperature abnormal grain growth was observed for both compositions. This led to the development of bimodal grain size distributions. In the samples with lower oxygen content the grain size and the percentage of coarse grain areas were larger than in the case of high oxygen content.
The strength and ductility have been determined by tensile tests. For low oxygen content, the presence of large coarse grains allowed plastic strain in some cases, and for the samples consolidated at higher temperatures, yield strength of 865 MPa with a 8% total strain were obtained. For the samples with high oxygen content plastic deformation was no possible in any case.
The observed stress for both compositions was analysed by two approaches, one based exclusively in grain boundary strengthening and the other one based in two effects acting at the same time: grain boundary and particle strengthening. Whereas grain boundary strengthening seems to fit with the strength of the samples in the nanostructured range, when coarse ferrite grains appear the addition of particle strengthening help to get better results. This indicates that the presence of oxides dissolved inside the large grains reinforce the structure of ball-milled iron.
The strain hardening behavior of an ARMCO iron processed by ECAP at room temperature up to sixteen passes following route Bc was investigated through Hollomon and differential Crussard-Jaoul models. Results indicate that the Hollomon analysis shows some deviations from the experimentally determined true stress – true strain curves while the differential Crussard-Jaoul analysis based on the Ludwik equation and the modified Crussard- Jaoul analysis based on the Swift equation fit better when two work hardening exponents are considered. As expected, the strength of the material increased with the number of ECAP passes. Indeed the ultimate tensile stress reached a maximum of ~900MPa after 16 passes, which is more than three times higher than the UTS of the annealed material. Nevertheless, the strain hardening capacity of the material was reduced in comparison with the material without severe plastic deformation. For that reason the tensile ductility was also reduced at increasing ECAP passes. The increase in strength was attributed to the reduction of the grain size through refined sub-grains with high density of dislocations. After sixteenth passes the original grain size (namely 70 mm) was reduced down to 300 to 400 nm observing a good correspondence with the Hall-Petch relationship. The microstructural analysis, carried out by EBSD, showed an increasing amount in the fraction of high Angle Grain Boundaries (HAGB) after 1 pass due to the regeneration of the microstructure with a smaller grain size
Mateo, A.; Zapata, A.; Fargas, G. IOP Conference Series: Materials Science and Engineering Vol. 48, num. 012001, p. 1-7 DOI: 10.1088/1757-899X/48/1/012001 Data de publicació: 2013-03-21 Article en revista
AISI 301LN is a metastable austenitic stainless steel that offers an excellent combination of high strength and ductility. This stainless grade is currently used in applications where severe forming operations are required, such as automotive bodies. When these
metastable steels are plastically deformed at room temperature, for example by cold rolling, austenite transforms to martensite and, as a
result, yield strength increases but ductility is reduced. Grain refinement is the only method that allows improving strength and ductility simultaneously. Several researchers have demonstrated that fine grain AISI 301LN can be obtained by heat treatment after cold rolling. This heat treatment is called reversion because it provokes the reversion of strain induced martens ite to austenite. In the present work, sheets of AISI 301LN previously subjected to 20% of cold rolling reduction were treated and a refined grain austenitic microstructure was obtained. Mechanical properties, including fatigue limit, were determined and compared with those corresponding to the steel both before and after the cold rolling.
AISI 301LN is a metastable austenitic stainless steel that offers an excellent
combination of high strength and ductility. This stainless grade is currently used in applications
where severe forming operations are required, such as automotive bodies. When these
metastable steels are plastically deformed at room temperature, for example by cold rolling,
austenite transforms to martensite and, as a
result, yield strength increases but ductility is
reduced. Grain refinement is the only method that allows improving strength and ductility
simultaneously. Several researchers have demonstrated that fine grain AISI 301LN can be
obtained by heat treatment after cold rolling. This heat treatment is called reversion because it
provokes the reversion of strain induced martens
ite to austenite. In the
present work, sheets of
AISI 301LN previously subjected
to 20% of cold rolling reduction were treated and a refined
grain austenitic microstructure was obtained. M
echanical properties, including fatigue limit,
were determined and compared with those corres
ponding to the steel both before and after the
Mateo, A.; Fargas, G.; Mauricio, A. IOP Conference Series: Materials Science and Engineering Vol. 31, num. 1, p. 1-8 DOI: 10.1088/1757-899X/31/1/012010 Data de publicació: 2012-01-08 Article en revista
The plastic deformation accumulated during fatigue testing can induce the transformation of austenite to martensite in metastable austenitic stainless steels. To analyze this issue, a metastable austenitic stainless steel grade AISI 301 LN was studied in two different conditions, i.e. annealed and cold rolled. In the first case, the steel was fully austenitic, whereas cold rolled material had almost 30% of martensite. High cycle fatigue tests at a stress ratio of 0.8 were carried out on flat specimens from both steel conditions. Several characterization techniques, including optical microscopy, X-ray diffraction (XRD) and electron back scattered diffraction (EBSD), were used to detect and quantify the martensite induced by the cyclic deformation
The plastic deformation accumulated during fatigue testing can induce the
transformation of austenite to martensite in metastable austenitic stainless steels. To analyze
this issue, a metastable austenitic stainless steel grade AISI 301 LN was studied in two
different conditions, i.e. annealed and cold rolled. In the first case, the steel was fully
austenitic, whereas cold rolled material had almost 30% of martensite. High cycle fatigue tests
at a stress ratio of 0.8 were carried out on flat specimens from both steel conditions. Several
characterization techniques, including optical microscopy, X-ray diffraction (XRD) and
electron back scattered diffraction (EBSD), were used to detect and quantify the martensite
induced by the cyclic deformation.
García-Álvarez, J.; Rosell, C.M.; Garcia, M.; Chavez-Dominguez, J. A.; Turo, A.; Salazar, J. IOP Conference Series: Materials Science and Engineering Vol. 42, p. 1-4 DOI: 10.1088/1757-899X/42/1/012042 Data de publicació: 2012 Article en revista
Many varieties of bread are prepared using flour coming from wheat. However, there are other types of flours milled from rice, legumes and some fruits and vegetables that are also suitable for baking purposes, used alone or in combination with wheat flour. The type of flour employed strongly influences the dough consistency, which is a relevant property for determining the dough potential for breadmaking purposes. Traditional methods for dough testing are relatively expensive, time-consuming, off-line and often require skilled operators. In this work, ultrasonic analysis are performed in order to obtain acoustic properties of bread dough samples prepared using two different types of flour, wheat flour and rice flour. The dough acoustic properties can be related to its viscoelastic characteristics, which in turn determine the dough feasibility for baking. The main advantages of the ultrasonic dough testing can be, among others, its low cost, fast, hygienic and on-line performance. The obtained results point out the potential of the ultrasonic analysis to discriminate doughs of different types of flour.
Novoa-Díaz, D.F.; Puig-Pujol, A.; García-Álvarez, J.; Chavez-Dominguez, J. A.; Turo, A.; Mínguez, S.; Garcia, M.; Bertrán, E.; Salazar, J. IOP Conference Series: Materials Science and Engineering Vol. 42, p. 1-4 DOI: 10.1088/1757-899X/42/1/012045 Data de publicació: 2012 Article en revista
n the winemaking process, the malolactic fermentation is an essential process in the production of high quality red wines which concerns the conversion of malate into lactate. In this work, the ultrasonic velocity through wine samples with different concentrations of malate
and lactate was measured using the pulse echo technique with 1 MHz tone burst signals. The evolution of these concentrations during malolactic fermentation was taken into account in order to determine the ratio between concentrations of malate and lactate of the different
samples. These preliminary results have revealed that the ultrasonic velocity increases during the conversion of malate to lactate. In addition, measurements have been conducted to quantify
the influence of variations in turbidity and temperature on test samples. Therefore, these results show the possibility of using ultrasonic velocity measurements for on-line monitoring the
malolactic fermentation of red wine and may help to improve and contribute to the development of the winemaking process.
Gedler, G.; De Sousa Pais, M.; De Redondo, V.; Velasco J.I. IOP Conference Series: Materials Science and Engineering Vol. 31, num. 1 DOI: 10.1088/1757-899X/31/1/012008 Data de publicació: 2012 Article en revista
Originally published as "IOP Conference Series: Materials Science and Engineering", vol. 31, no 1, 2012. DOI:10.1088/1757-899X/31/1/012008. .
Polycarbonate foams reinforced with 0,5 wt% of graphene were obtained by firstly melt-mixing the polycarbonate and graphene in an internal mixer, compression-moulding the melt-compounded grinded material and lastly dissolving CO2 inside a high pressure vessel. The CO2 desorption behaviour in the unfilled polycarbonate and nanocomposite was studied in terms of the CO2 saturation concentration and desorption diffusion coefficient, with the graphene-filled nanocomposite displaying a higher CO2 loss rate when compared to the neat polycarbonate. The cellular structure of the foams was found to be highly dependent on the saturation/foaming temperature, with smaller cell sizes being obtained with decreasing the temperature. Another parameter that had an important influence was the residual pressure, with higher residual pressure values resulting in foams with more uniform and regular cells.
De Armas, Z.; Jimenez-Pique, E.; Mestra, A.; Anglada, M. IOP Conference Series: Materials Science and Engineering Vol. 27, p. 51-56 DOI: 10.1088/1757-899X/5/1/012013 Data de publicació: 2010 Article en revista
The behaviour of hydrothermal degraded 3 % molar yttria stabilised zirconia under
monotonic spherical indentation has been studied. The investigation is focused mainly on analysing the response under spherical indentation in terms of the transformed monoclinic surface layer that appears after hydrothermal degradation. The mechanisms of damage are ring and cone cracking, similarly as in as sintered specimens. The permanent damage induced in degraded specimens is always larger than in the as sintered specimens. The "plastic" damage measured by the value of the indentation strain in degraded specimens is larger than in as
sintered specimens at the same indentation pressure. The critical contact load to induce ring cracking is determined and it is found that in degraded specimens its value is lower than in as sintered specimens. The results are discussed in terms of elastic properties and microstructure of the degraded layer.
Lee, D.S.; Gonzalez, L.F.; Walker, R.; Périaux, J.; Oñate, E. IOP Conference Series: Materials Science and Engineering Vol. 10, num. 1, p. 1-10 DOI: 10.1088/1757-899X/10/1/012197 Data de publicació: 2010 Article en revista
Fargas, G.; Zapata, A.; Anglada, M.; Mateo, A. IOP Conference Series: Materials Science and Engineering Vol. 5, num. 1, p. 012008- DOI: 10.1088/1757-899X/5/1/012008 Data de publicació: 2009-11-04 Article en revista
Metastable austenitic stainless steels are currently used in applications where severe
forming operations are required, such as automotive bodies, due to its excellent ductility. They
are also gaining interest for its combination of high strength and formability after forming. The
biggest disadvantage is the difficulty to predict the mechanical response, which depends
heavily on the amount of martensite formed. The martensitic transformation in metastable
stainless steels can be induced by plastic deformation at room temperature. In this research, the
martensitic transformation was provoked by means of torsion testing. Several torsion angles
were selected to achieve different percentages of martensite at the surface of the specimens.
The next step was to evaluate their effect on the fatigue life of the steel. Fatigue testing in the
high cycle regime was done at different levels of mean stress. As a conclusion, the presence of
martensite in the surface of the specimen led to an increase of the fatigue life when high mean
stress was imposed. By contrast, at lower values of mean stress, martensitic transformation has
no positive effect on the fatigue life.
Fargas, G.; Mestra, A.; Anglada, M.; Mateo, A. IOP Conference Series: Materials Science and Engineering Vol. 5, num. 1, p. 012009- DOI: 10.1088/1757-899X/5/1/012009 Data de publicació: 2009-11-04 Article en revista
Duplex stainless steel (DSS) is a family of steels characterized by two-phase
microstructure with similar percentages of ferrite (α) and austenite (y).Their attractive
combination of mechanical properties and corrosion resistance has increased its use in last
decades in the marine and petrochemical industries. Nevertheless, an inappropriate heat
treatment can induce the precipitation of secondary phases which affect directly their
mechanical properties and corrosion resistance. There are few works dealing with the influence
of heat treatments on wear behaviour of these steels in the literature. For instances, this paper
aims to determine wear kinetic and sliding wear volume developed as a function of heat
treatment conditions. Therefore, the samples were heat treated from 850 ° C to 975 º C before
sliding wear tests. These wear tests were carried out using ball on disk technique at constant
sliding velocity and different sliding distances. Two methodologies were used to calculate the
wear volume: weight loss and area measurement using a simplified contact model.
Microstructural observations showed the presence of sigma phase for all studied conditions.
The formation kinetics of this phase is faster at 875 ºC and decrease at higher temperatures.
Results related to wear showed that the hardness introduced due to the presence of sigma phase
plays an important role on wear behaviour for this steel. It was observed also that wear rates
decreased when increasing the percentage of sigma phase on the microstructure.
De Sousa Pais, M.; Arencon, D.; De Redondo, V.; Velasco J.I. IOP Conference Series: Materials Science and Engineering Vol. 5, p. 1-11 DOI: 10.1088/1757.899x/5/1/012001 Data de publicació: 2009-11 Article en revista
The use of polyolefin flexible foams with typical thicknesses between 1 and 3 mm
produced by a physical foaming extrusion process is nowadays quite widespread in the
packaging sector. Their high flexibility and closed-cell structure allows them to show good
energy absorption properties under low loading conditions. Although the compressive response
of these materials is well known, the inner microstructure developed during processing induce
a high anisotropy that is responsible for their direction-dependent tensile and fracture
behaviours. In this work, two different polyolefin-based foams, with densities ranging from 20
to 45 kg/m3, were studied. The induced microstructure anisotropy was characterized by micro-
Raman. With this technique, the relative orientations of both crystalline and amorphous phases
in the foam’s base polymer could be determined and thus related to their mechanical properties
measured in the different directions.
Franco, M.; Puiggali, J.; Ricart, A.; Morales, L.; Soto, D. IOP Conference Series: Materials Science and Engineering Vol. 14, p. 1-7 DOI: 10.1088/1757-899X/14/1/012006 Data de publicació: 2009-09-08 Article en revista
Aliphatic polyamides derived from odd diamine or odd dicarboxylic acid units cannot adopt a conventional sheet structure when molecular chains have an all trans conformation. However, typical fiber diffraction patterns of this sheet structure were observed in several polyamides derived from odd units such as nylons 65 and 56. Consequently, a new structure based on the establishment of intermolecular hydrogen bonds along two different directions was postulated. Real-time temperature dependence of X-ray diffraction patterns for nylons 65 and 56 was studied by synchrotron radiation to gain understanding of the Brill transition usually occurring in polyamides. Significant differences were found between the temperature dependence of both nylons, although a transition towards a monoclinic structure characterized by a single equatorial reflection around 0.425-0.420 nm was observed to occur at high temperatures. This transition was reversible for nylon 65 only. In this case, a characteristic hysteresis effect was found.
Marro, F.G.; De Armas, Z.; Horwat, D.; Anglada, M. IOP Conference Series: Materials Science and Engineering Vol. 5, num. 1, p. 1-8 DOI: 10.1088/1757-899X/5/1/012023 Data de publicació: 2009 Article en revista
A method is present for estimating the thickness of monoclinic layer formed by hydrothermal degradation of zirconia doped with 3 mol % of yttria (3Y-TZP) by means of X-ray diffraction at different incidence angles. The method is based on: a) determining the monoclinic concentration in the degraded layer by X-ray diffraction at angles for which the beam penetration depth is smaller than the layer thickness; b) calculating and using the ratio between intensities of the same main tetragonal peak in the degraded and in the as sintered specimens at angles for which the contribution of the same tetragonal peak form the layer and from the underneath non-degraded material are significant. In order to compare with experimental results, 3Y-TZP has been subjected to degradation in an autoclave at temperatures of 131ºC in water vapour at a pressure of 0.2MPa. The method may be useful when the thickness of the degraded layer is in the range between a few hundred nanometres and a few microns.
Marro, F.G.; Valle, J.; Mestra, A.; Anglada, M. IOP Conference Series: Materials Science and Engineering Vol. 5, num. 1, p. 1-8 DOI: 10.1088/1757-899X/5/1/012015 Data de publicació: 2009 Article en revista
Surface modification with cerium oxide of tetragonal zirconia polycrystals stabilised with 3 % molar yttria (3Y-TZP) has been investigated in order to avoid low
temperature degradation. The surface modification was performed by annealing 3YTZP
with surface coated CeO2 powder at temperatures of 1400 ºC and 1500 ºC for
periods of time up to 10 hours. These heat-treatments diffused cerium up to about 10 mm depth. The bulk fracture toughness, Vickers hardness and Young modulus of the
surface modified specimens showed no significant deviation as compared to the nontreated original material. Even the surface mechanical properties measured by
penetration curves corresponding to nanoindentations of up to 2 mm depth, did not show significant differences after surface modification. All heat-treatments produced an increase in the surface grain size and a large increase in resistance to degradation.
Chitapalli, R.; Marro, F.G.; Valle, J.; Yan, H.; Reece, M.; Anglada, M. IOP Conference Series: Materials Science and Engineering Vol. 5, num. 1, p. 1-8 DOI: 10.1088/1757-899X/5/1/012014 Data de publicació: 2009 Article en revista
Commercially available tetragonal zirconia powder doped with 3 mol% of yttria has been sintered using spark plasma sintering (SPS) and has been investigated for its resistance to hydrothermal degradation. Samples were sintered at 1100, 1150, 1175 and 1600ºC at constant pressure of 100 MPa and soaking for 5 minutes, and the grain sizes obtained were 65, 90, 120 and 800 nm, respectively. Samples sintered conventionally with a grain size of 300 nm were also compared with samples sintered using SPS. Finely polished samples were subjected to artificial degradation at 131 0C for 60 hours in vapour in auto clave under a pressure of 2 bars.
The XRD studies show no phase transformation in samples with low density and small grain
size (<200 nm), but significant phase transformation is seen in dense samples with larger grain size (>300 nm). Results are discussed in terms of present theories of hydrothermal degradation.