Gustavo Suarez

• Dr.
• Researcher at Centro de Tecnología de Recursos Minerales y Cerámica

Ti-doped lithium zirconate (LZTO) sheets were successfully made by aqueous tape casting, by starting from an innovative colloidal synthesis route and optimizing the colloidal processing parameters. Zeta potential and particles size measurements, together with rheological characterization, were performed to adjust the slip composition. Then, the sus...

In the context of the current global environmental paradigm, lithium zirconate-based materials (LZOs) are of great technological interest in the reduction of the carbon footprint. Due to their exceptional mechanical, thermal and chemical stability, high lithium atom density and outstanding tritium release behavior, LZOs have been studied as tritium...

Zircon (ZrSiO4) is a refractory structural ceramic material difficult to consolidate because of its thermal dissociation into ZrO2 and SiO2. Addition of sintering aids can improve its densification, but with detrimental effects on high temperature mechanical properties and corrosion resistance. In this work, zircon was consolidated by employing the...

Novel 1:1 Yttria partially stabilized zirconia (PSZ) - aluminum borate (AB: Al11B4O33) ceramic composites were prepared and characterized by a simple direct sintering process of PSZ-mixtures. Sintering was performed below 1300°C to minimize the decomposition of borate. Phases were corroborated by XRD. SEM permitted to characterize the microstructur...

The effect of the TiO2 addition in the ceramic processing of dense zircon materials from zircon fine powders was established. The addition of TiO2 (5-10 wt%) permitted to obtain dense ceramics at lower temperatures (100-150 oC below), with comparable mechanical behavior. The thermochemical processes were described after a multi-technique experiment...

Aluminum titanate Al2TiO5 materials were successfully processed from different fine commercial powders and characterized. Particularly, two calcined aluminas were compared through a multitechnique approach including differential thermal analysis and dilatometry together with structural, microestructural, and mechanical characterization. This allowe...

A processing strategy for obtaining alumina-spodumene ceramics from fine commercial powders is presented. In this work, a spodumene addition to calcined alumina powder was performed and their proportion was explored between 15 and 45 wt%. The industrial spodumene presented secondary phases, mainly albite and quartz. Mechanical properties were evalu...

Ceramic materials were satisfactorily processed through a dry scalable process from binary clay–boric acid (H3BO3) mixtures. Relevant thermal parameters were established by a multitechnique approach that included thermogravimetric, differential thermal analysis, dilatometric analysis and structural and microstructural characterization of fired samp...

Reinforcement of ceramic composites using carbon nanotubes (CNT) has been extensively studied for materials such as Al2O3, Si3N4 and tetragonal ZrO2. Knowledge concerning CNT composites based on a matrix of cubic zirconia (8YZ) is in short supply, however. This paper presents a study on the addition of 1 wt% CNT to an 8YZ matrix. CNT was functional...

Dense aluminum borate (Al18B4O33) materials were processed by simple milling-sintering of aluminum borate powders obtained by reacting calcined alumina and fine boric acid at temperatures of around 600- 800ºC. The effect of milling on the grain size and sintering behavior of the aluminum borate powders was also determined. Sintering began at around...

Aluminum titanate (Al2TiO5) materials and aluminum titanate - mullite- zirconium titanate (Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO4) addition to stoichiometric alumina - titania mixtures. Zircon addition was the principal proc...

Although yttria-stabilized zirconia (YSZ) is prevalent as ceramic electrolyte in solid oxide fuel cells (SOFCs), a trend to switch to lower operating temperatures requires the replacement of YSZ. Lanthanum silicate oxyapatite (LSO) is one of encouraging materials for satisfying this requirement. The design of SOFCs and SOFC stacks demands the knowl...

The results of qualitative and quantitative properties of clay based ceramic are presented in this work. Four different shaping methods and sintering temperatures were used to understand their influence in the final properties of a ceramic material formulated using kaolinite clay and calcined alumina. This material can be used as a structural ceram...

In this work, a simple milling sintering route (pressure less) to process dense zircon ceramics from fine (D50 0.8 μm) zircon powders is explored. Particularly, the milling time effect (0-120 min) and the maximum sintering temperature (1400-1600°C) were studied. The sintering grade developed microstructure and Vickers hardness (Hv) were evaluated a...

We present a study of sulfonitric treatment and its effect on MWCNTs at different temperatures (90, 110, 130 and 150°C) using DRX, XPS, FTIR, Raman spectroscopy, TEM and zeta potential. It was found that oxidation starts with the C-C and C-H bonds generating different oxidized groups from alcohol to carboxylic acid, following a sequential oxidation...

In this article we assess and compare the complex mechanical behavior of two complex microstructure ceramics material formed within the reaction sintering framework. Two comparable pairs of materials with respectively similar microstructures were obtained by reaction sintering from boric acid and alumina. Two single phase porous ceramics were compa...

By means of Perturbed Angular Correlation (PAC) analysis the resulting phases during mechano-chemical activation process on zircon (ZrSiO4) commercial fine powder (D50 ≅ 0.8μm) were accurately identified and characterized.A high energy planetary mill was employed with 850. rpm up to 120. min. The phenomenological macroscopic confirmation of the str...

The formation of aluminum borates (Al18B4O33 and Al4B2O9) from alumina and boron oxide occurs between 600 and 800°C. These materials have refractory properties and corrosion resistance. The objective of this work is to develop materials from the Al2O3-B2O3 system, employing alumina and boric acid as starting powders, to study the critical processin...

Lanthanum silicate oxyapatite ((LSO, La9.33+2x(SiO4)6O2+3x)(0<x<0.33)) is an oxygen-ion conductor that offers some advantages over the typical yttria-stabilized zirconia (YSZ) used in SOFCs. LSO has higher oxygen-ion conductivity than YSZ at temperatures below 873K.The powder was synthesized from reagent grade La2O3 and SiO2 powders. Presents an av...

Carbon nanotubes are widely used for electronic, mechanical, and optical devices due to their unique structural and quantum characteristics. The species generated by oxidation on the surface of these materials permit binding new reaction chains, which improves the dispersibility, processing and compatibility with other materials. Even though differ...

In the current paper we present a study of the sinterability of two zirconia (ZrO2) nanopowders with different content of yttrium oxide (Y2O3) 3 and 8 % tetragonal and cubic zirconia, respectively. After sintering between 900-1500ºC, the samples were characterized in terms of their density and porosity using Archimedes technique. Their grain size w...

Composites based on ZrO2 stabilized with CaO and CaAl4O7 were sintered via two different techniques: Conventional Sintering route and Spark Plasma Sintering (SPS) between 1200 and 1400 °C. The effectiveness of sintering technique applied on the stabilization degree of ZrO2 (conversion to c-ZrO2, Ca0.15Zr0.85O1.85), microstructure, densification and...

In the present work we attempt to describe the results of the thermal behavior analysis of a commercial glaze obtained in a thermal microscope developed by the research group. At the same time, the density and the wetting angle of the glaze with an alumina surface was evaluated. Particularly the sintering temperature, the sphere, semi-sphere and fu...

The use of industrial waste (by-products) as raw materials in the ceramic industry has been under study for decades due to the economical, energy, tax and environmental advantages. The specificity of the waste requires a basic characterization and technology thereof. The applicability of rice husk ash (RHA), as silica (SiO2) source, in refractory a...

Materials from the Al2O3-SiO2-ZrO2 and the Al2O3-SiO2-ZrO2-TiO2 systems have several high temperature applications because they present the good refractoriness, chemical inertness, adequate mechanical and thermo-mechanical behaviors with a relatively good cost: performance ratio. In this work stoichiometric (3:2:1) molar incompatible mixtures of al...

The study of possible incorporation of nontraditional starting powders is a contribution to the rational utilization of raw materials in the ceramic industry. The technological properties of solid waste problems (both urban and industrial) in many cases are not correctly studied and reported. The main objective of the present work is to study and d...

Dense Zircon ceramics were prepared from a commercial Zircon powder via the colloidal route, and critical processing variables were explored. To achieve highly dispersed suspensions, the zeta potential of Zircon was evaluated by adding different concentrations of a dispersant (ammonium polyacrylate). Zircon suspensions with high solid loading were...

The phase quantification in ceramic nanopowders presents technological interest for studying and design purposes. Especially in zirconia ceramics where the mechanical and transport properties are strongly affected by the crystalline composition. In this work we present the comparison XRD based methods and differential thermal analysis methods for p...

Spark Plasma sintering (SPS) was applied for the densification of Calcia stabilized ZrO2 based composites obtained from mixtures of pure zirconia (m-ZrO2) and calcium aluminate cement (HAC). Two commercial powders of pure zirconia were employed as reactants. One of these powders had a coarse mean particle size (d(50) = 8 mu m) and the other was a s...

Computer assisted designing (CAD) is well known for several decades and employed for ceramic manufacturing almost since the beginning, but usually employed in the first part of the projectual ideation processes, neither in the prototyping nor in the manufacturing stages. The rapid prototyping machines, also known as 3D printers, have the capacity t...

As transformações de queima de cerâmicas tradicionais (à base de argila) são de interesse tecnológico e arqueológico, e são geralmente reportadas qualitativa ou semi-qualitativamente. Estes tipos de sistemas apresentam uma importante complexidade, especialmente para técnicas de difração de raios X, devido à presença de fases totalmente cristalinas,...

Aluminum titanate (Al2 TiO5) is a high refractoriness material with excellent thermal shock resistance. Hence it is suitable for several applications at elevated temperatures where insulation and thermal shock resistance are required. Such as components of internal combustion engines, exhaust port liners, metallurgy, and thermal barriers. The therm...

The main objective of this article is to obtain dense (porosity under 0.5%) polyphasic ceramics belonging to the Al2O3-SiO2-ZrO2 system by SPS sintering of high energy powders milled drily; the stoichiometric (54.45:45.54 zircon-alumina, weight basis) mixture was explored in this work. Particularly the principal sintering variables sintering temper...

Calcareous earthenware is used very frequently for tableware, and fired twice between 980 degrees C and 1040 degrees C. Before firing it mostly consists in a kaolinitic clay accompanied by quartz and approximate to 7 wt% of carbonates (Ca and Mg) as fluxing fraction. In this article the firing temperature correlation with the textural, structural a...

Highly concentrated zirconia-carbon nanotube (CNT) water suspensions were prepared using an advanced milling technique. The bead-milling operation parameters were optimized for this system and used to prepare zirconia-stabilized water-based suspensions with different CNT contents. The effects of different milling conditions were studied. The partic...

The mechanochemical activation process has proved to be an effective technique to enhance a solid-state reaction at relatively low temperatures. In such a process, the mechanical effects of milling, such as reduction of particle size and mixture homogenization, are accompanied by chemical effects. The actual chemical phases during the mechanical tr...

Mineralogical transformations caused by firing are usually studied by XRD methods only semi-quantitatively. In this work the original mineral disappearance and the neo-mineralization were evaluated quantitatively. Furthermore an indirect non crystalline phase quantification was performed under 1100 ºC was also carried out using the quartz content a...

We have studied the sintering kinetic of 3 and 8 mol% of yttria stabilized zirconia under isothermal conditions. Sintering was performed in the temperature range between 1200 and 1450 °C. The sintering kinetic process was followed by measuring density as a function of sintering time. A model was applied to the first stage of densification. Sinterin...

Plasma dissociated zircon (PDZ) has attractive applications in ceramic colouring, as well as the preparation of fine ZrO2 crystals, coatings and refractory materials. Generally the PDZ is obtained from different natural or synthetic zircon powders, if the cooling rate is high enough a complete dissociation is achieved, with rounded (dendritic) zirc...

Triaxial ceramics (clay-quartz-feldspar) represents a significant proportion of traditional ceramic production; art, craft and/or industrial. The use of flux is widely used in order to modify the range of maturation of ceramic pastes. The objective of the present study is to establish the influence of the addition of different secondary fluxes in t...

The addition of sintering additives has always been detrimental to the mechanical properties of sintered ceramics; therefore, methods to reduce or, as in this case, eliminate sintering additives are usually relevant. In this paper, dense zircon ceramics were obtained starting from mechanically activated powder compacted by spark plasma sintering wi...

Dense reinforced zircon (ZrSiO4)–20vol.% zirconia (ZrO2) ceramic composites were obtained by spark plasma sintering (SPS) starting from high energy milled commercially available powders. The sintering temperature and holding time resulted in two different microstructural configurations.In the first configuration, the nano sized zirconia nanoparticl...

During a heating–cooling cycle, zirconia (ZrO2) undergoes a martensitic transformation from monoclinic to tetragonal structure phases, which presents special hysteresis loop in the dilatometry curve at temperatures between 800 and 1100°C. Monoclinic zirconia (m-ZrO2) particles reinforced ceramic matrix composites not always present this behavior. I...

The mechanochemical activation processing has proved to be an effective technique to enhance a solid-state reaction at relatively low temperatures. In such a process, the mechanical effects of milling, such as reduction of particle size and mixture homogenization, are accompanied by chemical effects, such as partial decomposition of salts or hydrox...

RESUMEN La cerámica triaxial (Arcilla-Cuarzo-Feldespato) representa una importante proporción de la producción cerámica tradicional, artística, artesanal y/o industrial. En las mismas la utilización de fundentes secundarios es ampliamente utilizada con el objeto de modificar el intervalo de maduración de las pastas cerámicas. El objetivo del presen...

In service refractory materials are submitted to local temperature gradients that originate thermal stresses causing a thermal shock (TS) damage to the material. Practical tests for evaluating the thermal shock resistance (TSR) determine the variation or change of some characteristic property of the test sample like E (elastic module) or the streng...

A 2.7 mol% yttria stabilizing tetragonal zirconia (2.7Y-TZP) nanopowder was synthesized and stored for five years. Humidity and unsatisfactory storage conditions gradually caused heavy agglomeration. Within a few months, 2.7Y-TZP nanopowder became useless for any technological application. A bead-milling deagglomeration technique was applied to rec...

RESUMEN Dentro de los productos usuales de la cerámica tradicional podemos encontrar a las cerámicas blancas de mesa, pavimentos, revestimiento, sanitarios, porcelanas, etc. La loza calcárea es la cerámica blanca de menor complejidad tecnológica, sus materias primas son naturales y presentan una importante fracción de impurezas que determinan las p...

The effect of 0–10wt% alumina addition on the initial sintering of 8mol% Y2O3 cubic ZrO2 (8YSZ) was studied. Activation energy and initial stage of sintering mechanism were analyzed in order to understand the effect of the alumina in the sintering process. The analysis was carried out using the analytical method for constant rate heating (CRH). The...

Dense bulk ZrB2 ceramic was synthesized by mechanical alloying (MA) and followed spark plasma sintering (SPS) using zirconium and boron as initial materials. It was found that MA process was effective to fragment the coarse metal zirconium particles from 45 m to less than 1 m within 20 hours. In comparison with the commercial ZrB2 powder, the as-...

We have developed a method of forming textured tetragonal zirconia. A suspension containing 10vol% solid loading of monoclinic ZrO2 mixed with 3mol% Y2O3 was prepared, and then a bead-milling process was performed using 50μm diameter zirconia beads resulting in a well-dispersed suspension. The mixture suspension of monoclinic zirconia and yttria na...

The advantages of a good colloidal processing of tetragonal zirconia for achieving a full densification and a small grain size were determined in this study. The optimization of slurry preparation was studied to obtain well-dispersed suspensions. A deagglomeration technique was applied by bead-milling using grinding media of 50 mu m diameter and in...

The effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The prepa...

Zirconia ceramics, mainly of cubic phase, are used in different applications because of their particular electrical and structural properties.After the forming stage, sintering leads to a material with suitable microstructural characteristics. The sintering process mainly depends on thermal cycle and on starting particle size and its distribution;...

The dispersion of concentrated 0.53 μm yttria stabilized zirconia (YSZ) aqueous slip to achieve sintered compacts with high and uniform microstructure was investigated. 78 wt.% (37.5 vol%) and 83 wt.% (45.3 vol%) slips were prepared by dispersing the powder in water with ammonium polyacrylate (NH4PA) at pH values in a range of 8–9.5. The influences...

The photolysis of folic acid (=N-(4-{[(2-amino-1,4-dihydro-4-oxopteridin-6-yl)methyl]amino}benzoyl)-L-glutamic acid) in alkaline aqueous solution (pH 10.0–11.0) was carried out at 350 nm at room temperature and monitored by UV/VIS spectrophotometry, anal. and prep. thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC, H...

6-formylpterin solutions at pH 11 were photolyzed at 350 nm at room temperature. The photochemical reactions were followed by UV/VIS spectrophotometry, thin layer chromatography (TLC), and high-performance liquid chromatography (HPLC). In the presence of oxygen, 6-carboxypterin is the only photoproduct detected by the analytical techniques mentione...

Folic acid and 6-formylpterin solutions of pH in the range 4.5–6.0 were photolysed at 350nm at room temperature. The photochemical reactions were followed by UV–VIS spectrophotometry, thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). In the presence of oxygen, folic acid is photochemically cleavaged yielding 6-formy...

6-Carboxypterin was photolyzed at 350nm in aqueous acid and alkaline solutions at room temperature. The photochemical reaction was followed by UV–Vis spectrophotometry, thin layer chromatography (TLC) and HPLC. Changes in the absorption spectrum of the irradiated solution, TLC and HPLC, show the formation of pterin as one of the photoproducts. The...