Preparation and characterization of nanofluids: Influence of variables on its stability, agglomeration state and physical properties

In recent years it has spread the use of suspensions containing nanometre sized particles, known as nanofluids, in many applications owing the good properties having nanocrystalline materials. One of the main advantages of using nanofluids is its high stability, which causes the particles do not settle over long periods of time. This stability depends on the preparation conditions such as pH, the presence of electrolytes or the solids content. Moreover, there are a number of physical properties which are influenced and altered by agglomeration of the particles. This article will analyze all the variables that affect agglomeration of the particles, nanofluids stability and properties from which it can obtain information on the state of suspension. It then lays out the different methods of dispersion of nanoparticles and their effectiveness.

Path-dependency and path-making in the energy system in the spanish ceramic tile cluster

This paper analyses how energy consumption and energy efficiency evolved in the Spanish ceramic tile industry in the 20th century and explores the emerging possibilities in the 21st century. In the last century, the tile industry undertook three radical transitions by switching from traditional biomass fuels to liquid hydrocarbon fuels (fuel oil and gas oil), and subsequently to gas fuels, mainly involving natural gas. Although it is difficult to obtain the information that enable the real energy efficiency in manufacturing plants to be reliably evaluated, the available data indicate that a high degree of efficiency has been achieved with current manufacturing technologies. Consequently, significant developments in this sense are not expected, even though efforts are still being made to reduce energy consumption in the production process. However, environmental regulations and impacts, and the emerging new energy sources based on agricultural biomass could open up new avenues for energy supply in the Spanish ceramic tile cluster.

Solid state reaction synthesis of Ba0.75Sr0.25AlSi2O8 - Al2O3 ceramic composites from mechanically activated precursor mixtures

Ceramic composites with Ba0.75Sr0.25AlSi2O8 (SBAS)/Al2O3 mass ratios of: 1) 90/10, 2) 70/30, and 3) 50/50, were in situ synthesized at 900-1500 °C/5 h from mixtures of fly ash, BaCO3, SrCO3 and Al2O3. The green mixtures were mechanically activated for 0, 4 and 8 h in an attrition mill. As a result, the solid state reactions were faster and occurred at lower temperatures. Only the SBAS and Al2O3 phases were obtained at 1300-1500°C, with the SBAS present in composition 1 achieving full conversion from its hexagonal (Hexacelsian) into its monoclinic (Celsian) form, with or without milling. The higher nominal SBAS content of composition 1 facilitated in it the mentioned conversion, in comparison with the other two studied compositions, which required to be mechanically activated for times that increased with increasing Al2O3 content, in order to attain in them similarly high Hexacelsian to Celsian conversions. The mechanical properties of the synthesized materials increased with increasing milling time, sintering temperature and Al2O3 content. Thus, the best mechanical properties were obtained for composition 3 milled for 8 h and sintered at 1500 °C.

Mechanical properties and coefficient of thermal expansion of β-eucryptite sintered by microwave technique

Microwave non-conventional sintering technique allows obtaining fully dense glass-free β-eucryptite bulk material (∼99 %). A considerable difference in the densification, microstructure, coefficient of thermal expansion behaviour and mechanical properties, between conventional and non-conventional sintered specimens was observed. The hardness and Young’s modulus values obtained by microwaves at 1200 °C-5min have been relatively high, 6.8 GPa and 101 GPa, respectively, compared to conventional sintering (3.9 GPa and 58 GPa, respectively). Very low thermal expansion materials have been obtained in a wide temperature range including cryogenic temperatures (from -150 ºC to 150 ºC). The high heating rate along with the lower energy consumption makes microwave technique a clear alternative to other types of sintering methods.

Terra-cotta figurines from the Roman theatre of Malaga (Spain): An archaeometric study

A series of 22 figured Phoeno-Punic and Roman terra-cottas, of high relevant archaeological and patrimonial values, have been studied. The samples were recovered in the Roman Theatre of Malaga (Spain). A thorough analysis including stereomicroscopy, elemental analysis by WDXRF, mineralogical analysis by XRPD coupled with the Rietveld method, and SEM, has been carried out. Highly diluted fused glass beads probed to be enough for the X-ray fluorescence analyses, minimizing the damage to the samples. For selected samples, in addition to the classical use of the Rietveld method, the G-factor external-standard approach has been employed to get full quantitative crystalline and amorphous phase analysis. The analytical results allow proposing a local/regional provenance for the main part of the samples, being a relevant data for several artifacts, not contextualized due to stratigraphic alterations in the site. In addition, some relevant samples, for instance a theatrical mask fragment (TRC005), are likely foreign. The overall amorphous is not negligible in phase quantification, accounting for up to 50 wt %. Technologically, all terra-cotta samples are similar, made of calcareous clays, fired at ~700-950 ºC.

The Spanish ceramic industry: a business opportunity for ERP consultant services enterprises

The ceramic industry is a strategic sector in Spain, which is losing market share to the production of emerging countries. To gain competitive advantage over other countries competing in cost , one of the opportunities for improvement of the ceramic industry in Spain , is to increase and optimize the use of ICT. However, there is currently no developed systems that provide appropriate to the specific problems of the ceramic sector solution.
Therefore, a business opportunity arises for companies that provide consulting services for the implementation of information systems, such as Enterprise Resource Planning System (ERP). To do this, first we need to know the industry and its specific problems, with the goal of developing a suitable ERP. This paper identifies such business opportunity and presents one of the more specific problems of the sector, which is not implemented in any ERP system. Then, ERP consulting services companies will have the knowledge of the problem and they will be able to develop an appropriate solution.

Ceramics in the world of biology

Research in biomaterials and nanostructures is inspired by the search of a common goal, that is, to remedy the pain, disease, and deterioration of our bodies.
Manufacture of spare parts for the human body, bothby traditional methods and using tissue engineering and cell therapy, is a major challenge in this research field. Additionally, the design of nanoparticles for drug delivery to direct a highly toxic drug dosage directly to tumors minimizing theeffect to healthy cells and ensuring the death of tumor cells without affecting healthy tissues,is also a great challenge nowadays.
The incessant progress in the preparation of nanosystems with applications in the medical field in the last few years have led to new challenges in the design of smart materials able to meet clinical requirements.

Synthesis, characterization and electric evaluation of barium zirconate doped with trivalent lanthanides

Barium zirconate is an oxidic material having perovskite structure that exhibits high chemical stability in both oxidizing and reducing environments, such as in the presence of water and carbon dioxide, its conductivity has led to consider it as a electrolyte for solid oxide fuel cell finding good results, with the limitation of operating at temperatures above 800 °C.
Several researchers have proposed that it is possible to improve their electrical conductivity by changes in chemical composition, particularly for doping with trivalent cations that replace the zirconium in B site of perovskite. In this study, barium zirconate was synthetized by the amorphous citrate method to examine the possibility of obtaining in more favorable conditions than those made by the conventional method of synthesis (ceramic method or solid state reaction) conditions are synthesized.
Barium zirconate doped with europium, gadolinium, holmium, lanthanum, neodymium and praseodymium was prepared, the present phase identification was verified by X-ray diffraction (XRD), the electrical properties were examined by impedance spectroscopy (IS) at temperatures between 480 and 680 °C in order to evaluate its potential use as a fuel cell electrolyte in solid oxide.
The contributions of this research has focused on the synthesis method, in the production of ceramic powders of barium zirconate at temperatures lower than those required by the ceramic method, in obtaining chemical, structural, morphological and electrical information of material synthesized.
The desired phase synthesis conditions set found, also, a significant increase is seen in the solid conductivity of doped lanthanum, holmium and europium zirconate of barium in relation to the material without doping.

The influence of green microstructure and sintering parameters on precipitation process during copper-nickel-zinc ferrites sintering

Microstructural changes that occur during heat treatment of copper-nickel-zinc ferrites have been studied. The process of precipitation of the two types of crystals that occur during the sintering process has been analyzed. It is found that this process depends on dry relative density of the press specimens and on the following sintering parameters: sintering temperature, sintering time and cooling rate of the thermal cycle. Crystal precipitates characterization have been done by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These techniques have allowed to determine the nature of these crystals, which in this case correspond to zinc and copper oxides. It has been used two chemical reactions to explain the bulk precipitation and subsequent re-dissolution of these crystal precipitates during sintering. 

Synthesis of nanocomposites NTC-13 %ZrO2 – (87-x)Al2O3-xFe

Carbon nanotubes (CNT) in a ceramic matrix – Fe, NTC-13%ZrO2 – (87-x)Al2O3-xFe, (x = 1.9, 4.6 y 6.4%), were obtained using a combustion synthesis urea-nitrate, calcination treatment and  chemical vapor deposition (CCVD) in H2–CH4 atmosphere. The effect of the addition of Fe ions on the ceramic matrix was studied and presented. The ceramic powder obtained was calcined at 1200 °C for 2 h to modify the phases present in the solid solution. Subsequently it was introduced in a H2-CH4 reducing atmosphere at 1000 °C in order to promote the formation of CNT in the matrix. Both, the solid solution obtained and the composite materials were characterized by X-ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). Carbon content and specific surface also were determined. The quality and quantity of CNT present in the nanocomposite powder were related to the concentration of Fe, which significantly modifies their carbon content and specific surface.

Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

Concentrated ceramic inks based on β-SiC powders, with different amounts of Y2O3 and Al2O3 as sintering aids, are developed for the adequate production of SiC scaffolds, with different patterned morphologies, by the Robocasting technique. The densification of the as-produced 3D structures, previously heat treated in air at 600 ºC for the organics burn-out, is achieved with a Spark Plasma Sintering (SPS) furnace. The effects of the amount of sintering additives (7 - 20 wt. %) and the size of the SiC powders (50 nm and 0.5 µm) on the processing of the inks, microstructure, hardness and elastic modulus of the sintered scaffolds, are studied. The use of nano-sized β-SiC powders significantly restricts the attainable maximum solids volume fraction of the ink (0.32 compared to 0.44 of the submicron-sized powders-based ink), involving a much larger porosity of the green ceramic bodies. Furthermore, reduced amounts of additives improve the mechanical properties of the ceramic skeleton; particularly, the stiffness. The grain size and specific surface area of the starting powders, the ink solids content, green porosity, amount of sintering additives and SPS temperatures are the main parameters to be taken into account for the production of these SiC cellular ceramics.

“Noble” metallic effects obtained by means of the development of water-based inkjet inks using traditional ceramic raw materials

Coloronda, S.L. has tackled the technical viability of developing water-based inkjet inks (containing up to 5-µm particle sizes) so as to obtain noble metallic effects by means of different raw materials traditionally used in the ceramic tile manufacturing process. In this context, several parameters and working conditions (i.e. heat treatment, temperature, particle size, chemical composition, etc.) have been studied in order to examine their influence on the nucleation and crystallization mechanisms which are responsible for the physical-optical phenomena obtained on single-firing ceramic tiles.

Densexplorer is the first device for industrial manufacturing plant capable of determining the distribution of bulk density of large ceramic tiles in a non-destructively way, which is not harmful to health, respectful with the environment and that increases the productivity of the process regarding to existing equipment. The system is based on the X-ray absorption technique, in which a material absorbs an amount of radiation depending on its thickness and density.

Synthesis, microstructure and properties of BiFeO3-based multiferroic materials: A review

BiFeO3-based materials are currently one of the most studied multiferroics due to their possible applications at room temperature. However, among the large number of published papers there is much controversy. For example, possibility of synthesizing a pure BiFeO3 phase is still source of discussion in literature. Not even the nature of the binary Bi2O3-Fe2O3 diagram has been clarified yet. The difficulty in controlling the formation of parasite phases reaches the consolidation step. Accordingly, the sintering conditions must be carefully determined both to get dense materials and to avoid bismuth ferrite decomposition. However, the precise conditions to attain dense bismuth ferrite materials are frequently contradictory among different works. As a consequence, the reported properties habitually result opposed and highly irreproducible hampering the preparation of BiFeO3 materials suitable for practical applications. In this context, the purpose of the present review is to summarize the main researches regarding BiFeO3 synthesis, microstructure and properties in order to provide an easier understanding of these materials.

Electric behavior of functional glasses based on TeO2

In this paper we study the structural and electrical behavior of glass-ceramic material of general formula: xMgO (1-x)(0.5V2O5.0.5MoO3)2TeO2 (0≤x≤0.9) through measurements of density, molar volume, oxygen packing density (OPD), differential scanning calorimetry (DSC) and Raman spectroscopy: electric behavior was studied by impedance spectroscopy. We found that magnesium cation induces the growth of slightly crystallized areas inside the material. Those nanocrystallizations were detected to a greater extent by atomic force microscopy (AFM) and in lesser extent by X-ray diffraction (XRD). Regarding the electrical measurements, it can be established that magnesium cation does not act as good ionic conductor in this material.

Evolution of the crystalline structure in (Bi0.5Na0.5)1-xBaxTiO3 thin films around the Morphotropic Phase Boundary

(Bi0.5Na0.5)1-xBaxTiO3 (BNBT), which exhibits compositions for the morphotropic phase boundary (MPB) where exist an intimate coexistence of the rhombohedral and tetragonal structures, is being considered as promising lead-free alternative to the well known Pb(Zrx,Ti1-x)O3 (PZT). In this work, BNBT thin films were fabricated by chemical solution deposition (CSD) with a wide range of compositions (x~0.050-0.150) onto Pt/TiO2/SiO2/(100)Si substrates. Structural studies by X-ray diffraction (λCu~1.5406 Å) using a four-circle goniometer were carried out to determine the crystalline structure of the films. Rietveld analysis of the experimental X-ray patterns showed different volume fractions of the rhombohedral and tetragonal phases as a function of the Ba2+ content and the coexistence of both phases, characteristic of a MPB region, for x∼0.055-0.080. Finally, Rutherford backscattering experiments (RBS) were performed to determine the compositional profile of the films. This study revealed a homogenous composition of the BNBT films with abrupt film/substrate interfaces.

Study of processing conditions of Bi0.5(Na0.8K0.2)0.5TiO3

In this paper, the improvement of the ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 ceramics through the implementation of different processing conditions is studied. Ceramic powders were obtained by solid state reaction, after mechanochemical activation of the starting reagents. Thermal evolution of starting powders was analyzed by differential thermal analysis and thermogravimetry (DTA-TGA). Crystalline phases of powders, thermally treated at temperatures ranging between 550 and 800 ºC, were characterized by X-ray diffraction (XRD). The influence of the sintering temperature on the BNKT-system was characterized by Raman microspectroscopy, and impedance spectroscopy. It was found that samples sintered at 1100 ºC showed the highest density and the lowest dielectric loss values. Moreover, in these samples, secondary phases were not detected by XRD.

Application of the electrical characterization to the study of the hydrated phases of the cement with coal bottom ash

The present paper investigates the influence of using Bottom and Fly Ash as partial replacement of cement in the hydration process. Through measurements of electrical impedance spectroscopy (EIS) and X -ray diffraction (XRD), we analyze from the early stages to the hydration process to the end. Values of EIS, XRD and its relation, are used to determine transformation of hydrated phases, and for each of the substitutions, is indicated as modified the hydrated phase as a function of time and compared it with the reference material. It also proves the relevance of using EIS measures in real time, and as non–destructive testing to characterize the hydration process of these materials.

Influence of Ca substitution by Mg on the Ca3Co4O9 performances

Ca3-xMgxCo4O9 polycrystalline thermoelectric ceramics with small amounts of Mg have been synthesized by the classical solid state method. Microstructural characterizations have shown that all the Mg has been incorporated into the Ca3Co4O9 structure and no Mg-based secondary phases have been identified. Apparent density measurements have shown that samples do not modify their density until 0.05 Mg content, decreasing for higher contents. Electrical resistivity decreases and Seebeck coefficient slightly raises when Mg content increases until 0.05 Mg addition. The improvement in both parameters leads to higher power factor values than the usually obtained in samples prepared by the conventional solid state routes and close to those obtained in textured materials.

Ferroelectric and Piezoelectric Characterization of Porous (K,Na,Li)(Nb,Ta,Sb)O3

KNL-NTS powder with (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 stoichiometry was prepared following the conventional ceramic method of mixing carbonates and oxides. KNL-NTS powder synthesis is carried out in solid state at 700 ºC for 3h. To obtain ceramic samples with different porosity the sintering of pellets is carried out in air at different temperatures between 1088 and 1125 ºC for 2h. Structural and microstructural characterizations are performed by XRD and SEM and the degree and type of porosity is determined by mercury intrusion porosimetry. The influence of sintering temperature on the porosity and its consequence on both the ferroelectric hysteresis loops and the piezoelectric response was evaluated. The maximum densification is achieved at 1125 ºC and the best ferroelectric response is achieved in sintered pellets at 1125 ºC. Meanwhile, it was observed that pellets sintered in a lower temperature range (1094-1100 ºC) where porosity reaches values up to 15 % have good ferroelectric piezoelectric response, similar to that found in the sintered pellets to 1125 ºC.

Chemical analysis of chalcolithic pottery from Arlanzón river middle basin (Burgos): a way to examine the origin and exchange

The study is aimed on pottery that it is recovered in Chalcolithic contexts from Arlanzón River Middle Basin. Within these sets of pottery there are similarities and differences —morpho-typological and technical—, which it is necessary to study in order to understand its significance in archaeological terms. To doing so, we need to use a different method than typology. In fact, we used chemical analysis of ceramic as a way to obtain less subjective observations. The results allow discussing about origin and exchange of Chalcolithic pottery in this zone of the Spanish North Plateau. Data show a mainly local origin of ceramics with some exchanged artifacts. In archaeological terms, the pattern may be related to a domestic model of production.