Ti2AlC and Ti3SiC2 MAX phase foams: processing, porosity characterization and connection between processing parameters and porosity

Proceeding of: World PM2016 Congress Proceedings. New materials and applications, biomedical applicationsMAX phases Ti2AlC and Ti3SiC2 foams with controlled porosity and pore size were produced using the space holder method. The foams were processed using water-leachable crystalline carbohydrate as space holder that involves: mixing, cold isostatic pressing, dissolution and sintering. Three combinations of volume percentage (20%-60%) and size distribution (250-1000 mum) of space holder were introduced during mixing. The foams were characterized and compared with the material without space holder. The characterization included: morphology (overall, open and closed porosity by Archimedes method) and gas permeability. Foams with porosity up to about 60 vol% and pore size distribution ranging from about 250 to 1000 mum were produced. Experimental porosity was compared to the theoretical expected porosity. The results show a bimodal porosity that can be customized by the sintering and the space holder. This study connects the processing parameters to the porosity created and allows control of porosity and pore size to produce tailor-made properties.The authors would like to thank the funding provided for this research by the Regional Government of Madrid- Dir. Gral. Universidades e Investigación, through the project S2013/MIT-2862 (MULTIMAT-CHALLENGE-CM), and by Spanish Government through Ramón y Cajal contract RYC-2014-15014 and the project MAT2012/38650-C02-0

The High-Acceptance Dielectron Spectrometer HADES

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from 18 to 85 degree, a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system

Labile Soil Carbon Inputs Mediate the Soil Microbial Community Composition and Plant Residue Decomposition Rates

• Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? • In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g soil) to soils amended with and without 13C-labeled plant residue. We measured CO2 respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). • Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g-1) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g-1) had no impact on plant residue decomposition, while greater concentrations of C (\u3e 7.2 mg C g-1) reduced decomposition -50%). Concurrently, high exudate concentrations (\u3e 3.6 mg C g-1) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (\u3c 3.6 mg C g-1) increased metabolic activity rather than gene copy numbers. • These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria

The HADES-at-FAIR project

After the completion of the experimental program at SIS18 the HADES setup will migrate to FAIR, where it will deliver high-quality data for heavy-ion collisions in an unexplored energy range of up to 8 A GeV. In this contribution, we briefly present the physics case, relevant detector characteristics and discuss the recently completed upgrade of HADES. © 2012 Pleiades Publishing, Ltd. 75 5 589 593 Cited By :

Silver/diamond composite material - powder metallurgical route and thermo-physical properties

To meet the need of high-performance thermal management materials in the field of electronic applications, heat sink materials reinforced with synthetic diamonds have been prepared via powder metallurgy. A matrix of a silver alloy with a silicon content of 0.45 wt.% was chosen out of the prediction of the thickness of a final carbide layer of about 180 nm. The volume content of the diamonds and the diamond size were kept constant. The mixed powders were consolidated by Spark Plasma Sintering (SPS) using different sintering temperatures between 800 and 870 °C with a holding time of 30 min. The maximum thermal conductivity of 680 W/(mK) measured at room temperature and 620 W/(mK) at 275 °C was obtained at 810 °C sintering temperature. The degradation of the most promising sample after one thermal cycle up to 275 °C was determined below 1 percent of the value after sintering

Properties and reliability of molybdenum-copper-composites for thermal management applications

Multilayered composites made of molybdenum and copper combine a low coefficient of thermal expansion with a high thermal conductivity. By varying the layer structure, both properties can be tailored to the application requirements. Therefore, these composites are interesting candidates for the thermal management of electronics in general and especially for thermal management of GaN based devices. In this work reliability tests were performed on a three layered structure (Cu-Mo-Cu) with 63 wt% copper according to EN 60068-2-14. The results show that the interface is not degrading by thermal cycling between -40 °C and +125 °C after 2000 cycles. Moreover, no change in thermal conductivity or flatness of the samples was observed. The molybdenum-copper-interface was found to be stable up to the melting point of copper

TFP reinforced metal - one way to increase the specific strength

The integration of fibers, especially tailor fiber placement (TFP), in metal matrices offers one way to generate composite materials with increased specific strength compared to the unreinforced metal matrix. The TFP can be adapted according to the final load paths through the component and can be covered partially or fully with the metal. Following this approach load transfer elements can be built, transferring much load and having low mass. First fields of application are identified in building and automotive industry. This work includes the powder metallurgical manufacturing process using Spark Plasma Sintering (SPS) technique, the characterization of the microstructure and the tensile test of different specimens (sintered copper, TFP (as received) and TFP (Cu covered) reinforced copper). Experimental result on 19.5 vol.% TFP (Cu covered) reinforced copper shows an increase of specific strength around a factor of 2.2 compared to pure copper

Novel approach for thermal diffusivity measurements in inert atmosphere using the flash method

Determining the thermal conductivity is crucial whenever heat transfer issues are considered which play a major role in many technological applications. However, various materials are sensitive to oxygen or moisture and, therefore, cannot be examined with commonly used equipment under ambient conditions. Here, we present a novel approach which combines the inert requirements of ambient-sensitive specimens with the flash method in which the apparatus, a Netzsch LFA 447 NanoFlash®, is placed under ambient conditions. A new measuring cell with flash-transparent windows was constructed which resembles a gas-tight specimen chamber. This device can be easily adapted to other apparatuses based on the flash method. The thermal conductivities of reference materials in inert and ambient conditions were examined in a temperature range from 25 to 275 °C. In general an excellent agreement was found. Further, the usability of this special sample cell is demonstrated for the investiga tion of the thermal conductivities of two complex hydride systems which are important for solid-state hydrogen storage applications