Microstructural and XRD analysis and study of the properties of the system Ti-TiAl-B4C processed under different operational conditions

High specific modulus materials are considered excellent for the aerospace industry. The system Ti-TiAl-B4C is presented herein as an alternative material. Secondary phases formed in situ during fabrication vary depending on the processing conditions and composition of the starting materials. The final behaviors of these materials are therefore difficult to predict. This research focuses on the study of the system Ti-TiAl-B4C, whereby relations between microstructure and properties can be predicted in terms of the processing parameters of the titanium matrix composites (TMCs). The powder metallurgy technique employed to fabricate the TMCs was that of inductive hot pressing (iHP) since it offers versatility and flexibility. The short processing time employed (5 min) was set in order to test the temperature as a major factor of influence in the secondary reactions. The pressure was also varied. In order to perform this research, not only were X-Ray Diffraction (XRD) analyses performed, but also microstructural characterization through Scanning Electron Microscopy (SEM). Significant results showed that there was an inflection temperature from which the trend to form secondary compounds depended on the starting material used. Hence, the addition of TiAl as an elementary blend or as prealloyed powder played a significant role in the final behavior of the TMCs fabricated, where the prealloyed TiAl provides a better precursor of the formation of the reinforcement phases from 1100 °C regardless of the pressur

Supervivencia de los pacientes con coinfección VIH-tuberculosis en Pereira, Colombia enero 2014 y marzo 2016

La tuberculosis es un problema de salud pública mundial, con 8 millones de casos nuevos y 2 millones de muertes cada año.La coinfección con VIH asociada a la reactivación y diseminación incrementa la mortalidad. La actual prevalencia de coinfección VIH-tuberculosis en Latinoamérica no se conoce exactamente, se ha estimado 5,9% y las muertes atribuibles al VIH en 6,5%. Los estudios en Colombia han mostrado que la frecuencia de la infección por Mycobacterium tuberculosis en pacientes con VIH fluctúa entre el 8 y 30%. Por lo que se hace necesario conocer las características de los pacientes con coinfección VIH-tuberculosis y los factores asociados a la mortalidad en la ciudad de Pereira, Colombia

Fabricación mediante innovadoras técnicas pulvimetalúrgicas de materiales compuestos de matriz ligera

Hoy en día el interés por desarrollar nuevos materiales que satisfagan las necesidades tecnológicas, conlleva a un estudio continuo en la innovación de los procesos de fabricación. La ventaja que ofrecen las técnicas pulvimetalúrgicas de procesado en caliente convencional (HP) y directa (dHP), suponen un ahorro en tiempo que puede favorecer la viabilidad de nuevos materiales fabricados por estas técnicas El potencial que presentan en cuanto a sus propiedades los materiales compuestos de matriz de titanio (TMCs), es muy valorado por el sector aeroespacial. La gran limitación de uso de estos materiales en su aplicación en otros sectores se debe en gran medida al alto coste. La línea de investigación creada por este grupo en colaboración con la empresa austríaca RHP-Technology, promueve el estudiofabricación-caracterización de TMCs fabricados mediante técnicas pulvimetalúrgicas avanzadas de compactación en caliente. Esta colaboración ofrece la posibilidad de producir materiales a la carta desde un punto de vista pulvimetalúrgico. Los materiales estudiados principalmente son materiales compuestos de matriz titanio (TMCs) reforzados con partículas cerámicas como son el boro amorfo (B), el carburo de boro (B4C) y el diboruro de titanio (TiB2), con el objetivo de promover reacciones entre la matriz de titanio y las partículas de cerámicos que consoliden nuevos compuestos que actúan reforzando la matriz in situ.Nowadays, the interest in developing novel materials to achieve the technological needs, leads to an ongoing study on innovation of manufacturing processes. The advantages of conventional Hot Pressing technique (HP) and direct Hot Pressing (dHP) involve savings in time in order to promote the viability of new materials manufactured by hot consolidation processes. Titanium Metal matrix Composites (TMCs) offer interesting properties, which are highly valued by the aerospace sector. However, there are some use limitations of these materials in other sectors due to their high cost. The research created by this group in collaboration with the Austrian research-company RHP-Technology, promotes the study-manufacturingcharacterization of these TMCs. This collaboration provides the possibility of manufacturing materials “à la carte” from a point of view of Powder Metallurgy (PM). The materials studied are primarily TMCs reinforced with ceramic particles as boron amorphous (B), boron carbide (B4C) and titanium diboride (TiB2). By the addition of these ceramic materials to the matrix, in situ reactions between the matrix and the ceramic reinforcement are expected. In this respect, the titanium matrix becomes reinforced

In Situ Titanium Composites: XRD Study of Secondary Phases Tied to the Processing Conditions and Starting Materials

Nowadays, the development of high specific modulus materials involves studies of new materials and novel manufacturing routes. From the point of view of composite materials, titanium composites (TMCs) have been long studied for their interesting properties, as a result of the conjunction of low-density and high mechanical properties, as well as corrosion resistance. Among various processing techniques, the in situ reinforced method shows many advantages above the rest. The reactions between matrix and reinforcement drive up the final properties of TMCs. Varying the processing conditions, in addition to reinforcement type and content, significant variations are expected in TMCs’ behaviour. In this regard, the present study draws on previous author works. The specimens studied were manufactured by hot consolidation processes, inductive hot pressing (iHP) and direct hot pressing (DHP), at different operational parameters and compositions. X-ray powder diffraction (XRD) investigations tied formations of secondary phases to substantive changes in TMC behaviour under the influence of the fabrication parameters

Influence of sintering temperature on the microstructure and mechanical properties of in situ reinforced titanium composites by inductive hot pressing

This research is focused on the influence of processing temperature on titanium matrix composites reinforced through Ti, Al, and B4C reactions. In order to investigate the effect of Ti-Al based intermetallic compounds on the properties of the composites, aluminum powder was incorporated into the starting materials. In this way, in situ TixAly were expected to form as well as TiB and TiC. The specimens were fabricated by the powder metallurgy technique known as inductive hot pressing (iHP), using a temperature range between 900 °C and 1400 °C, at 40 MPa for 5 min. Raising the inductive hot pressing temperature may affect the microstructure and properties of the composites. Consequently, the variations of the reinforcing phases were investigated. X-ray diffraction, microstructural analysis, and mechanical properties (Young’s modulus and hardness) of the specimens were carried out to evaluate and determine the significant influence of the processing temperature on the behavior of the compositesJunta de Andalucía. TIC-752

Analysis of the Influence of Starting Materials and Processing Conditions on the Properties of W/Cu Alloys

In this work, a study of the influence of the starting materials and the processing time used to developW/Cu alloys is carried out. Regarding powder metallurgy as a promising fabrication route, the difficulties in producingW/Cu alloys motivated us to investigate the influential factors on the final properties of the most industrially demanding alloys: 85-W/15-Cu, 80-W/20-Cu, and 75-W/25-Cu alloys. Two different tungsten powders with large variation among their particle size—fine (Wf) and coarse (Wc) powders—were used for the preparation ofW/Cu alloys. Three weight ratios of fine and coarse (Wf:Wc) tungsten particles were analyzed. These powders were labelled as “tungsten bimodal powders”. The powder blends were consolidated by rapid sinter pressing (RSP) at 900 C and 150MPa, and were thus sintered and compacted simultaneously. The elemental powders andW/Cu alloys were studied by optical microscopy (OM) and scanning electron microscopy (SEM). Thermal conductivity, hardness, and densification were measured. Results showed that the synthesis ofW/Cu using bimodal tungsten powders significantly affects the final alloy properties. The higher the tungsten content, the more noticeable the effect of the bimodal powder. The best bimodalWpowder was the blend with 10 wt % of fine tungsten particles (10-Wf:90-Wc). These specimens present good values of densification and hardness, and higher values of thermal conductivity than other bimodal mixtures.Junta de Andalucía TIC-752

Porous Titanium for Biomedical Applications: Evaluation of the Conventional Powder Metallurgy Frontier and Space-Holder Technique

Titanium and its alloys are reference materials in biomedical applications because of their desirable properties. However, one of the most important concerns in long-term prostheses is bone resorption as a result of the stress-shielding phenomena. Development of porous titanium for implants with a low Young’s modulus has accomplished increasing scientific and technological attention. The aim of this study is to evaluate the viability, industrial implementation and potential technology transfer of different powder-metallurgy techniques to obtain porous titanium with stiffness values similar to that exhibited by cortical bone. Porous samples of commercial pure titanium grade-4 were obtained by following both conventional powder metallurgy (PM) and space-holder technique. The conventional PM frontier (Loose-Sintering) was evaluated. Additionally, the technical feasibility of two different space holders (NH4HCO3 and NaCl) was investigated. The microstructural and mechanical properties were assessed. Furthermore, the mechanical properties of titanium porous structures with porosities of 40% were studied by Finite Element Method (FEM) and compared with the experimental results. Some important findings are: (i) the optimal parameters for processing routes used to obtain low Young’s modulus values, retaining suitable mechanical strength; (ii) better mechanical response was obtained by using NH4HCO3 as space holder; and (iii) Ti matrix hardening when the interconnected porosity was 36–45% of total porosity. Finally, the advantages and limitations of the PM techniques employed, towards an industrial implementation, were discussed.Ministry of Economy and Competitiveness of Spain Grant MAT2015-71284-PJunta de Andalucía Grant P12-TEP-1401Comisión Nacional de Investigación, Científica y Tecnológica (CONICYT) of the Chilean government project FONDECYT 1116086

Development of chiral methodologies by Capillary Electrophoresis with ultraviolet and Mass Spectrometry detection for duloxetine analysis in pharmaceutical formulations

Two chiral methodologies were developed by capillary electrophoresis (CE) with UV and mass spectrometry (MS) detection to ensure the quality control of the drug duloxetine, commercialized as a pure enantiomer. Both methods were optimized to achieve a high baseline enantioresolution (Rs > 2) and an acceptable precision (RSD values 0.05). (C) 2014 Elsevier B.V. All rights reserved

Recent contributions of Capillary Electrophoresis to neuroscience

Contributions to neuroscience are necessary to understand the behavior of the brain. Powerful analytical techniques are needed to monitor neuroactive molecules and their concentrations in biological samples (fluids, cells, and brain tissues). Capillary electrophoresis (CE) is well known for its high resolution power, short analysis times, and low consumption of reagents and samples. It presents analytical advantages for the determination of neuroactive molecules not easily determined by other analytical techniques. CE also offers the possibility of controlling more than one neuroactive molecule at a time, making it interesting to detect changes as a result of a stimulus. CE is well established to accomplish enantioseparations, contributing a better understanding of the properties of a neuroactive chiral molecule. This review focuses on the most relevant articles published from January 2008 to July 2014, based on the determination in biological samples of potentially interesting molecules in neuroscience using CE and microchip-CE. (C) 2014 Elsevier B.V. All rights reserved

Analysis of the microstructure and mechanical properties of Titanium-based composites reinforced by secondary phases and B4C particles produced via direct hot pressing

In the last decade, titanium metal matrix composites (TMCs) have received considerable attention thanks to their interesting properties as a consequence of the clear interface between the matrix and the reinforcing phases formed. In this work, TMCs with 30 vol % of B4C are consolidated by hot pressing. This technique is a powder metallurgy rapid process. Incorporation of the intermetallic to the matrix, 20 vol % (Ti-Al), is also evaluated. Here, the reinforcing phases formed by the reaction between the titanium matrix and the ceramic particles, as well as the intermetallic addition, promote substantial variations to the microstructure and to the properties of the fabricated composites. The influences of the starting materials and the consolidation temperature (900 C and 1000 C) are investigated. By X-ray diffraction, scanning and transmission electron microscopy analysis, the in-situ-formed phases in the matrix and the residual ceramic particles were studied. Furthermore, mechanical properties are studied through tensile and bending tests in addition to other properties, such as Young’s modulus, hardness, and densification of the composites. The results show the significant effect of temperature on the microstructure and on the mechanical properties from the same starting powder. Moreover, the Ti-Al addition causes variation in the interface between the reinforcement and the matrix, thereby affecting the behaviour of the TMCs produced at the same temperature.Junta de Andalucía TIC-752