August 2024
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27 Reads
Ceramics International
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August 2024
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27 Reads
Ceramics International
September 2023
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49 Reads
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10 Citations
Journal of the European Ceramic Society
October 2022
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17 Reads
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1 Citation
Journal of Machinery Manufacture and Reliability
Abstract—This study aims to evaluate the mechanical behavior of nanostructured and conventional alumina–titania coatings by means of combining four-point bend tests monitored with acoustic emission. Determination of bending strength, along with information received from acoustic emission signal, such as quantity, amplitude, energy and length of events gives a better understanding of failure mechanisms in coatings. This information has been complemented with optical analysis of fracture surfaces. Failure of coatings has been observed to follow four stages that are clearly defined in the acoustic emission data. This fracture behavior has been observed for all three types of coating tested, but the nanostructured coating presented the best combination of hardness and strength, due to its duplex microstructure. Keywords: atmospheric plasma spraying, nanostructured coatings, alumina–titania acoustic emission, four-point bend test DOI: 10.3103/S1052618822050065
August 2022
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31 Reads
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2 Citations
Ceramics International
This paper analyses the effect of the starting composition on the humidity regulating capacity of a gibbsite-based composition successfully tested for the manufacture of ceramic tiles. For this purpose, the proportion of gibbsite and quartz has been varied and the effect of these two ingredients of the composition on the moisture regulating capacity and on the kinetics of adsorption-desorption of sintered tiles has been studied. To explain the effect, the microstructure of the sintered bodies has been also characterised. It has been found that increasing the proportion of gibbsite in the starting composition produces a significant increase in the moisture regulating capacity as a consequence of the higher proportion of transition alumina in the sintered bodies that provide a larger mesopore reservoir. In contrast, the addition of quartz does not affect the moisture regulating capacity but does affect the rate at which moisture adsorption and desorption phenomena take place by increasing the fraction of larger pores in the structure. In both cases, the kinetic model tested corroborates the observed relationship between microstructure and moisture regulating capacity.
May 2022
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16 Reads
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3 Citations
Journal of the European Ceramic Society
The effect of sintering temperature on the humidity regulating capacity of a ceramic composition based on the mineral gibbsite has been studied. The humidity self-regulation functionality is due to the presence of mesopores in the material. In this work, it has been found that the adsorption-desorption capacity decreases drastically with sintering temperature, preserving a certain regulating activity up to temperatures as high as 1200 ºC. The variation of the regulating capacity with temperature is consistent with the transformation of gibbsite from transition alumina to alpha alumina, which leads to a sharp decrease of the mesopore volume which can be determined from mercury porosimetry and especially nitrogen gas adsorption. The adsorption-desorption curves fit well to a pseudo-second order kinetic model and it is found that the equilibrium moisture is proportional to the specific surface area while the sorption rate constant depends on permeability for water diffusion through the porous structure.
March 2022
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67 Reads
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14 Citations
Journal of the European Ceramic Society
Zircon is a ceramic material that decomposes at high temperature, limiting its use by conventional thermal spraying. In this work, it is intended to use thermal spraying from concentrated aqueous suspensions to evaluate the possibility of obtaining coatings in which a significant proportion of zircon could be preserved. For this purpose, stable concentrated suspensions of zircon have been prepared, which have been subsequently sprayed at two different spraying distances. The coatings were characterised in terms of microstructural features and the amount of zircon present in the coatings was quantified. All the coatings obtained display the typical microstructure derived from the deposition of liquid feedstocks by plasma spraying. In all cases, the XRD analysis demonstrates the partial decomposition of zircon into zirconia and residual silica, but also that a significant percentage (about 20%) is preserved without decomposing, which marks a strong difference with respect to reported data for atmospheric plasma spraying.
October 2021
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65 Reads
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8 Citations
Journal of the European Ceramic Society
The development of ceramic tiles with humidity regulating capacity is a topic of great interest for the comfort of interior spaces. The humidity regulating capacity of fired specimens from five compositions used for porous ceramic products has been assessed and their microstructure has been characterised. The main novelty of the work consists of obtaining pieces with regulating functionality from common ceramic raw materials used in industrial practice, establishing a kinetic model and confirming the role of porosity and microstructure. The results have shown that moisture adsorption and desorption curves fit very well to a pseudo-second order model. Additionally, it has been found that the humidity regulating capacity is not related to the total porosity, but it depends on the presence of mesopores in the structure of the pieces. Concerning the tested compositions, those containing gibbsite present higher regulating capacity as a consequence of their greater amount of mesopores.
June 2021
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54 Reads
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6 Citations
Ceramics International
This study aims to demonstrate the feasibility of developing zirconia ceramic coatings with the incorporation of silica aerogel particles, which exhibit outstanding insulating properties. Thus, the research aims to find a suitable methodology to disperse aerogel particles, which are strongly hydrophobic, in an aqueous medium. In the study, a double rheological characterisation was carried out, firstly, to adapt the dispersion of the aerogel particles and, secondly, to characterise the different suspensions made up of silica aerogel and zirconia to be atomised. Aerogel additions ranging from 2% to 98% in volume were addressed. Spray-dried powders were characterised in terms of flowability. Finally, coatings microstructure was examined, and their thermal conductivity determined. The results showed that it is possible to disperse aerogel particles in an aqueous medium and to obtain stable suspensions together with the addition of zirconia. Suitable spray-dried powders were then produced in all the cases. On the other hand, coatings obtained by atmospheric plasma spraying showed appreciable microstructural differences with the addition of aerogel particles and their insulating effect is evident in the thermal tests, with their improved (decreased) thermal conductivity.
January 2021
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33 Reads
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4 Citations
Surface and Coatings Technology
Plasma-sprayed 45S5 bioactive glass coatings were manufactured using two types of powder feedstocks (commercial and lab-made 45S5 glass) and two plasma torches (single and triple cathode) to analyse their influence on the microstructure and bioactivity of the coatings. Besides, the volatilisation of glass oxides such as Na2O and P2O5 during the deposition was studied. All coatings were microstructurally characterised by scanning electron microscopy, X-ray diffraction and X-ray dispersive energy analysis. Moreover, the bioactivity of the sprayed coatings was studied by immersing the coatings in Simulated Body Fluid until 14 days. The coatings obtained using the triple cathode torch showed similar thickness, less total porosity and greater microstructural homogeneity than the coating deposited with the single cathode torch. X-ray dispersive energy analysis revealed lower amounts of sodium and phosphorus at the surrounding of the lamellae, due to its volatilisation during the formation of the coatings. The volatilisation of these elements varied depending on the type of feedstock and plasma jet enthalpy. Concerning the bioactivity of the coatings, all of them have developed a hydroxycarbonate apatite layer on their surface.
December 2020
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8,675 Reads
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42 Citations
Open Ceramics
This paper describes the operation principles of a micro-scale rheometry equipment based on the technology of microchannels on a chip and compares it with a conventional macro-scale rotational rheometer. Both techniques are used for the study of different solutions and suspensions of ceramic particles with different saccharides, which are subjected to a wide variety of shear rates from their preparation to their processing and injection in plasma spraying processes. The results have shown a clear difference between the rheological values obtained between both equipment, clearly influenced by the different measurement method. However, the microfluidic technique has higher accuracy to characterise fluids at high shear rates and low viscosities, and the apparent shear thickening observed in rotational rheometry for low viscosity samples due to wall slippage is not observed. In contrast, the fine microchannels of are easily clogged in concentrated suspensions.
... Zircon (ZrSiO 4 ) has become a widely used material in the steel, glass, aerospace, and nuclear industries due to its advantageous physical and chemical properties. These include a relatively low linear thermal expansion (4.10 − 6 / • C from room temperature to 1400 • C), low thermal conductivity coefficient (5.1 W/m • C at room temperature and 3.5 W/ m • C at 1000 • C), chemical inertness and good compatibility with multivalent nuclides [1][2][3][4][5]. It has also attracted considerable interest in many fields and has been extensively studied, such as semiconductor heterojunctions, microwave integrated circuits, gate dielectrics, and sensors [6][7][8][9]. ...
Reference:
Low-toxic gelcasting of zircon ceramics
September 2023
Journal of the European Ceramic Society
... Because of their moisture-regulating capabilities, zeolites have been investigated as building material additives [46,47]. In construction materials, research has shown that they have the ability to improve insulation, reduce humidity, and increase energy efficiency. ...
August 2022
Ceramics International
... It is sometimes described as an alchemical process of transforming earthy ingredients to strong and sturdy works of art. It is a process in which an apparently common composition of clay and minerals is exposed to the tremendous heat of transformation, resulting in a product of utility as well as aesthetics [5,6]. One of the most important technological processes in conventional ceramic manufacture is sintering. ...
May 2022
Journal of the European Ceramic Society
... In a highly viscous suspension, due to the presence of more solid particles, the interaction between the particles would be increased, and agglomeration occurs. An efficient method for decreasing the viscosity of the suspension involves using an appropriate dispersing agent in relation to the mixture [23]. An alternative approach chosen for this experiment entails increasing the temperature of the suspension until it reaches a su- In this research, nano titanium dioxide powder was chosen for its long-term sustainability, accessibility and cost-effectiveness. ...
March 2022
Journal of the European Ceramic Society
... In order to promote its recycling, SiC sludge and GS should be manufactured into high value-added products, such as novel humidity control material. Recent research on preparing humidity control material [6,7] has led to a proliferation of relevant studies on improving comfort and saving energy in buildings [8]. The humidity regulating material has the capability of absorbing water vapor to lower the humidity once the indoor RH is more than 70%, and vice versa, it can release the adsorbed water vapor to raise the humidity when the humidity falls under RH 40% [6]. ...
October 2021
Journal of the European Ceramic Society
... There are different approaches to the methods of film formation, from common, conventional methods like dip coating, spin coating, spray methods, chemical vapor deposition, and tape casting [8] to more advanced methods like 3d printing [9,10], inkjet printing [9], and plasma spraying [11]. Chemical structure is one of the most important ...
June 2021
Ceramics International
... The asymmetric vibration noted at 941 and 1072 cm −1 was attributed to two Si-O and one nonbridging oxygen atom, respectively. The P-O bending vibrations are made evident with dual peaks at 517 and 649 cm −1 [21][22][23]. A band at 1597 cm −1 is related to the presence of residual carbonate groups from the precursors [15,24]. ...
January 2021
Surface and Coatings Technology
... These shear rates fall within the range suitable for high-shear processes, such as those encountered in a 3D food printer [31]. This corresponds to the extrusion region within the typical ranges of shear rates for common industrial processes, as shown by Carnicer et al. [32]. This indicates that the selected shear rates are appropriate for studying the dough's behavior under conditions similar to those in a 3D printing nozzle. ...
December 2020
Open Ceramics
... Introduction. During the last decade, the new group of promising technologies of surface engineering sector have been actively developing in a number of countries [1][2][3][4][5][6] for electric arc spraying (at atmospheric pressure, APS) and for melting/spheroidizing of ceramic (refractory oxides and carbides) and metal (copper and nickel alloys) powder materials, as with the use of hydrocarbon based gas combinations (including "liquefied petroleum gas (LPG) + air" and "methane + CO 2 " mixtures) to enhance plasma jet parameters in order to intensify the material melting in them, as well as with carbonaceous additives injection into the jets for improved control of the structure of sprayed coatings [7][8][9][10][11]. ...
June 2020
Ceramics International
... Los resultados son prometedores, pero existen problemáticas que deben atenderse antes de llegar a su aplicación y comercialización. Una de ellas es su comportamiento mecánico y baja durabilidad derivado del compromiso entre la capacidad para generar enlaces biológicos y la falla del recubrimiento antes de alcanzar su objetivo, producto de la disolución de este [57,69,77,[79][80][81]. Esta problemática puede verse desde el punto de vista de las técnicas usadas para el depósito de los recubrimientos, pero también debe considerarse la composición de los vidrios usados como materia prima, ya que las que se han explorado hasta el momento, han limitado su uso como recubrimientos confiables. ...
September 2020
Journal of Non-Crystalline Solids