Claudia Carrasco

• Professor
• University of Concepción

This study presents a novel approach to producing superficial micro- and nanostructures using a cold rolling process with rough rolls, followed by low-temperature annealing. The proposed technique attempts to recreate the superficial deformation occurring in the sandblasting process. It allows for the generation of an inhomogeneous network, or tang...

It is known that copper can be used as catalyst in photo-Fenton-like process; however, there is a lack of information related with its use in the treatment of landfill leachate (LL) in solar photo-Fenton-like processes. Here, we studied the effect of the mass of a copper sheet, the pH of the solution, and the concentration of LL in the removal of t...

The constant increment in human activity has generated an increase in solid waste deposited in landfills, which causes an increase in the production of landfill leachate (LL). Due to the...

Because of the massive increment in solar plants located in extreme environments, studying the association of climate parameters and soiling in natural conditions has been necessary. In this work, solar glass coupons were exposed to environmental conditions in Salvador solar plant, in the Atacama Desert, during summer and winter campaigns. The soil...

Comminution is the stage with the largest energy consumption in the mining process. Therefore, several pre-treatments have been proposed to reduce the energy requirements of this stage. This work analyzed the effect of a heating pre-treatment on the Bond index. A conventional heating pre-treatment was applied to a Chilean copper ore. The ore was he...

Thermal energy storage (TES) systems with molten salts involve different operating conditions causing corrosion problems in the materials due to the high operating temperature. In this work, the corrosion behavior was studied by means of flow accelerated corrosion (FAC) and static corrosion tests in contact with the ternary mixture (KLiNa)NO3 at 55...

The global water crisis limits the full implementation of purified water electrolysis across the world. Thus, seawater electrolysis has been identified as a powerful option to meet the requirements for sustainable production of green hydrogen without the constraint of using pure water. As in pure water electrolysis, seawater electrolysis research h...

In the context of Concentrated Solar Power (CSP), the metallic materials employed to build the critical components of the plant are exposed to severe conditions, Carbon and stainless steel have been used for this application. However, the technology CSP will evolve, so these materials will probably be replaced by superior performing and economicall...

Pb-Co anodes have been considered an attractive candidate for oxygen evolution reaction (OER) applications due to their low overpotential to catalyze the OER and its low cost. Despite these characteristics, their efficiency to produce oxygen at high current densities is low. In this work, we report a Pb-Co-Sn film with enhanced efficiency and impro...

The oxygen evolution reaction (OER) plays an important role in several industrial processes. However, the high overpotential that the OER requires to take place, has resulted in high costs associated with precious metals used in anodes that catalyze this reaction. Substitute elements, among them Co, have been investigated in order to decrease their...

A one-step electrodeposition process was used to obtain CuInS2 (CIS) films on a molybdenum substrate by varying the supporting electrolyte (lithium chloride, LiCl) concentration. The as-deposited samples were characterized by scanning electron microscopy, energy-dispersive spectroscopy, profilometry, and diffuse reflectance spectroscopy. From chara...

Pb-Co films have been studied due to the reduced oxygen overpotential at which they operate. However, the synthesis of these films is not trivial because Pb and Co are known to be immiscible metals. Thus, with the aim of understanding the process behind the formation of Pb-Co films, full structural characterization of such films is done. Moreover,...

ZnS thin films grown by the chemical bath deposition method have been under intense investigation due to their applications in solar cells. In this work, the early growth stages of ZnS thin films deposited by means of a non-toxic solution are studied by measuring the morphological, chemical and optical properties of the films obtained at different...

The aim of this paper was to study the effect of the grain size of lead-based anodes for copper electrowinning on their mechanical and anticorrosion properties. Aged anodes were cold rolled to different thicknesses, achieving reductions varying from their standard 50% up to 75%. The grain size, yield stress, and corrosion behavior of the different...

Electrodeposited lead (Pb)-cobalt (Co) coatings are an effective electrocatalyst in the oxygen-evolution reaction. We studied the effect of an electrolytic bath pH on the electrodeposition of Pb-Co coatings, and the coating properties were analyzed. The pH was varied from 1 to 6 for a solution without and with ascorbic acid as complexing agent. Cat...

In this work, we present the fundamentals of the estimation of the energy efficiency in an industrial coal boiler based in novel optical combustion diagnostics variables and several machine learning regression methods. The total radiation Radt and flame temperature Tf were considered. The inclusion of those variables allows to increase the overall...

Lead (Pb)–cobalt (Co) films have been studied by several researchers regarding their electrocatalytic activity when used as anodes in oxygen evolution reactions. Although several authors have suggested that the electrodeposition technique is the best alternative to Pb–Co film deposition, the process is complex. In many cases, the use of complexing...

The lead base anodes (Pb-0.07% Ca-1.3% Sn) of 6 mm thick have limited working life due to their loss of thickness and corrosion during the electrowinning process. If this loss of thickness is combined with a low yield stress of the anodes, these are much more likely to suffer premature deformations and distortions in cells. The aim of this study is...

A novel combustion diagnostics system based on flame radiation measurement and spectral emissions analysis is presented. The key aspect of this study is the proper estimation of the continuous component or baseline of spectral signals containing spurious discontinuities. We compare both, a PCA based method against an alternative method based on an...

Cd 1-x Zn x S thin films have been studied extensively as window layers for solar cell applications. However, a mismatch between the Cd 1-x Zn x S and copper-indium-gallium-selenide absorber layers increases with Zn film concentration, which reduces the device efficiency. In this work, Cd 1-x Zn x S thin films with low Zn concentrations were analyz...

This article reports the characterization and optical properties of (Ba,Ca)TiO3 thin films doped with Pr at different proportions (0–15 mol%). The films were deposited on Si (1 0 0) and quartz substrates using a photochemical method and post-annealed at 900 °C. The evaluation of photo-reactivity of the precursor complexes was monitored by UV–vis an...

In this work, the theoretical fundamentals and the experimental results of combustion control for a ladle furnace preheating process are presented, featured by a high fuel consumption and their subsequent high operational temperatures. The ladle furnace preheating process maximize the ladle's inner refractory temperature, via combustion. The highli...

The phase transformations of high carbon steel during quenching and equalizing were modelled using commercial computer packages based on the finite element method and the kinetic transformation of steel. The model was used to predict the temperature and microstructural changes taking place within balls of two different sizes that are used for grind...

Following standard heat treatment, steel grinding balls possess hardness values greater than 60 Rockwell C in the case of 3 inch diameter balls. The internal zone is also hard and therefore has low toughness, reducing the working life of the ball. The objective of the present study was to improve the quality of 3 inch diameter grinding balls by pro...

The collection of used beverage cans is limited in countries where they are not fabricated; their low value does not justify the extra charge of exporting them for further processing. To address this increasingly serious problem, here we optimize the properties of an aluminum metal matrix composite (Al-MMC) obtained through direct fusion of beverag...

(Ba, Ca, Sr)ZrO3−X thin films were prepared by a photochemical method using thin films of β-diketonate complexes as precursors. The photolysis of these films induces the fragmentation of the 2,2,6,6-tetramethyl-3,5-heptanedionate ligand and the partial reduction of metal ion together with volatile organic compounds as sub-products. When the metalli...

The carbon content in steel of the most produced grinding balls, 3 and 5 inch diameter, varies between 0.6% and 1.1% and, due to the presence of other addition elements, after their standard heat treatment, all the ball zones –external and central –reach high hardness values: over 60 RC in the case of the 3 inch diameter balls. The internal zone, h...

316L stainless steel plates of 5-mm thickness, normalized at 900 °C, were cold rolled with different reductions and number of passes using rolls with three different surface roughnesses: grain heights of 0.17 and 0.33 mm and rhomboid-shaped grains of 1.5-mm height. Subsequently, the rolled samples were annealed at 275 °C for 1 h in an effort to ach...

In this work different tests using electrolytic plasma (EP) on thin wires of stainless steel AISI 302 in an inert solution were performed. Tensile tests were carried out in order to measure changes in the mechanical strength of the samples; moreover, both the morphological and microstructural changes also were evaluated. It was found that after 10...

Films of poly(vinyl chloride)/copper (Cu) nanocomposites exhibiting reduced bacterial adhesion were prepared by film-casting method. Cu nanoparticles (NPs) synthesized using polyol method and stabilized with poly(N-vinyl-2-pyrrolidone) (PVP) at different Cu/PVP molar ratio were previously characterized using transmission electron microscopy (TEM),...

Starch isolated from pehuen seed (Araucaria araucana (Mol) K. Koch) was employed for producing thermoplastic starch (TPS). Pehuen starch was characterized, stating that the granules are rounded and small (12–21 μm), with an amylose content range 38–40%, a crystalline C-type structure and thermally stable, with decomposition temperature above 300 °C...

In this work we performed exploratory experiments aimed at understanding electrolytic plasma (EP), studying the variables that establish EP al low cell potential and / or low power. To do this we studied the effects of the relationship betwen electrode surfaces, conductivity and temperature of the electrolyte, resulting in conditions that allow the...

Pehuen cellulosic husk was characterized and employed as reinforcement for composite materials. In this research, thermoplastic pehuen starch (TPS) and TPS/poly(lactic acid) (PLA)/polyvinyl alcohol (PVA) composites, reinforced with 5 and 10% of pehuen husk, were prepared by melt-blending. Comparative samples of pehuen TPS and TPS/PLA/PVA blend were...

Samples from a hot rolled sheet of a tin and calcium bearing lead alloy were solution heat treated at 300 Degree-Sign C and cooled down to room temperature at different rates; these samples were left at room temperature to study natural precipitation of CaSn{sub 3} particles. The samples were aged for 45 days before analysing their microstructure,...

In the present study, the fabrication of an Al-based metal matrix composite material obtained directly from the melting of the aluminium used beverage cans in a modified rheocasting process is presented. The analysed operational condition is the shear rate applied to the bath and its influence on the properties of the obtained samples. Additionally...

The main characteristic of cathodic copper is the concentration of impurities because it depends on mechanical characteristics, i.e. ductility, of the derived copper wires. The standard mechanical tests that evaluate their ductility, are quick elongation and spiral elongation tests. The results of these essais shown that there is not a clear correl...

The main characteristic of cathodic copper is its concentration of impurities because this determines the mechanical properties, i.e., ductility, of the derived copper wires. However, the results of standard mechanical tests to evaluate ductility show that there is no clear correlation between the content of impurities in the cathodes and the ducti...

The influence of the semi-solid solidification production parameters (shear rate and agitation time) and the concentration of reinforcing particles on the microstructure formation and mechanical properties of a 520 aluminum alloy reinforced with Al2O3 particles was investigated. Depending on the content of reinforcing particles and the stirring con...

The influence of hot-deformation and tempering temperature on the microstructure evolution of a 12%Cr heat resistant steel during short-term creep at 80–250 MPa and 650 °C was investigated. Quantitative determination of dislocation density and sub-grain size in the initial microstructure and after creep was investigated by STEM-HAADF. A correlation...

The growth kinetics of Laves phase precipitates (type Fe2W) in the early stage of creep (650 °C for 10,000 h) in two 12% Cr ferrite–martensitic steels has been investigated. In one alloy the Laves phase formed on tempering, while in the second alloy the Laves phase precipitated during creep. Kinetic simulations were performed using the software DIC...

Coarsening of MX and M23C6 precipitates in two 12% Cr high alloyed steels have been investigated at creep conditions of 650 °C, 100 MPa up to 10,000 h. The evolution of precipitates at different creep times was determined experimentally using scanning transmission electron microscopy (STEM). Phase equilibria were calculated with Thermocalc and simu...

12% Cr heat resistant steels with a fine dispersion of nano precipitates were designed supported by thermodynamic modeling. A detailed characterization of the microstructure evolution at different creep times (100 MPa/650 °C/8000 h) was carried out by scanning transmission electron microscopy (STEM). The results of the microstructure analysis are c...

Thermal diffusivities of Al-Mg based metallic matrix composite reinforced with ceramic particles of Al2O3 are reported in this article. The samples were produced by rheocasting and the studied operational condition in this case is the shear rate: 800, 1400 and 2000 rpm. Additionally, the AlMg base alloy was tested. Measurements of thermal diffusivi...

Dental practitioners are instructed to avoid any type of contact with implant surfaces prior to their insertion. However, the probability of contaminating the surface is high, especially when placement of implants necessitates the use of precise surgical guides. The aim of this study was to evaluate the 2-year survival rate of splinted mini-implant...

A suitable yield stress for Pb anodes with 0.07% Ca and 1.3% Sn of 6 mm thickness for copper electrowinning is achieved by means of deformation and precipitation hardening processes, their useful life being dependent on this yield stress. The objective of the present work was to optimise the precipitation hardening, by finding the best cooling cond...

The suitable yield stress of Pb-0.07%Ca-1.3%Sn anodes of 6 mm thickness for copper electrowinning is achieved by means of deformation and precipitation hardening processes, being its useful life dependant of this yield stress. In such sense the objective of the present work is to optimize the precipitation hardening, finding for this purpose the be...

This work aimed to model the temperature distribution, phase transformation and residual stress induced during the heat treatment of grinding balls of 3 and 5in. diameter. The temperature model considered factors such as the heating of the water and the formation of a steam layer that surrounds the balls at the start of the quenching. The model of...

The goal of this work is to model the temperature distribution, phase transformation and residual stresses induced during the heat treatment of 3 and 5 inches diameter grinding balls. In the first step, the radial distribution of temperature inside the balls was calculated and validated experimentally. During the quenching, the model considers fact...

From the mechanical point of view, the successful cold drawing of wire-rods of low carbon steel requires a high ductility and a ratio between the yield stress and tensile strength as lowest as possible, both for diminish the fractures during the process. Small boron additions in the cast of this kind of steel produce an increase in the size of aust...

Contributing to the slight information about the Cu-Li alloys that is nowadays in scientific literature, this work reports the evolution with the temperature of the Cu - 2,5 wt % Li alloy. This alloy is obtained as powder by an electrodeposition process from salts. Powder samples, room temperature compacted tablets and the copper cathodes used in t...

This paper reports on the results of a study of the effect of static and dynamic stresses on hot dip galvanized coatings on SAE 1020 steel substrates. Galvanizing was performed using baths maintained at 450 °C, the zinc containing 0.16% Ti and 0.02% Fe and with Al and Ni in the ranges 0–0.20% and 0–0.30%, respectively. Static three-point bend tests...

Contributing to the slight information about the Cu-Li alloys that is nowadays in scientific literature, this work reports the evolution with the temperature of the Cu - 2,5 wt % Li alloy. This alloy is obtained as powder by an electrodeposition process from salts. Powder samples, room temperature compacted tablets and the copper cathodes used in t...

The theory of deposition of TiN by dc magnetron sputtering for wear protection of the surfaces is well known using different ferrous substrates. This theory apparently, is not so true for other non-ferrous materials. The present work shows the study of some characteristics of TiN deposition on a ternary copper alloy (Cu–3% Ti–1% Cr) with the purpos...

In the present work, copper powder (purity—99.7%, grain size—63 μm maximum) was mechanically alloyed with lithium (purity>99%) in a SPEX ball mill. The alloying process was carried out for 15 h under an argon atmosphere using WC containers and stainless steel balls. The alloyed powders were then hot-consolidated by uniaxial hot pressing at differen...

There is an interest in producing new materials with extreme combinations of mechanical properties such as high-hardness and low-friction coefficients. One example of such materials is crystalline C3N4, which has been predicted to have a bulk modulus higher than that of diamond. In this work we present the X-ray photoelectron spectroscopy analysis...

The goal of this study was the determination of the residual macroscopic stresses in titanium nitride (TiN) coatings deposited by DC planar magnetron sputtering (DCPMS) on a ternary copper alloy (Cu–3% Ti–1% Cr) under different conditions of applied current intensity, Ar/N2 flow ratio and bias voltage. The residual stresses were measured by X-ray d...

A proposal to reduce the batch stress relieving time in mill ball manufacturing industry is presented. It is proposed to change the last step of the production line of the 2 inch to 2.5 inch balls, sending them directly to storage, therefore eliminating the cooling of the balls in boxes, as presently done. It has been experimentally demonstrated th...