Flash spark plasma sintering of UHTCs

During the five year XMat research project supported by EPSRC (Engineering and Physical Sciences Research Council, UK) at Queen Mary we developed a novel sintering technique called Flash Spark Plasma Sintering (FSPS[1]) which is particularly suitable for the ultrarapid (a few seconds) consolidation of UHTCs. As in the case of incandescent lamps, flash sintering techniques use localized Joule heating developed within the consolidating particles using typically a die-less configuration. Heating rates are extreme (104–106 °C/min), and the sintering temperature is therefore reached extremely rapidly. The research covered mostly metallic conductors (ZrB2[2], HfB2,TiB2) and semiconductors (B4C, SiC and their composites). The talk will summarize the joint XMat team efforts to: -Identify the FSPS consolidation mechanism using modelling and transmission electron microscopy, -Characterise the structural properties for the bulk materials and redefine the structure-property relationships of FSPSed materials Please click Additional Files below to see the full abstract

Fabrication and characterization of high entropy pyrochlore ceramics

High-entropy rare-earth (RE) zirconates with pyrochlore structure were successfully fabricated by pressureless and spark plasma sintering. RE2Zr2O7 compound with nominal composition (La0.2Y0.2Gd0.2Nd0.2Sm0.2)Zr2O7 was prepared by simple glycine nitrate procedure (GNP). GNP process yielded powders with low crystallinity and after subsequent calcination, well crystalline ceramics were formed. During calcination defective fluorite (F-RE2Zr2O7) and crystal pyrochlore (Py-RE2Zr2O7) structures coexist. Formation of pure crystalline pyrochlore occurs after sintering at 1450°C. High-density ceramics, free of any additives, were obtained after powders compaction and pressureless (PS), as well as field assisted sintering technique (FAST) at 1450°C. Theoretical investigations of the high-entropy RE2Zr2O7 pyrochlore systems were performed. Unit cell parameter of the obtained Py-RE2Zr2O7 is 10.5892(2)Å and 10.5999(2)Å for PS and FAST sintering, respectively, which is in good agreement with the results of Density Functional Theory (DFT) calculations. The thermal diffusivity of sintered samples at room temperature was ∼0.7mm2/s for both sintering methods.ResumenSe fabricaron con éxito, mediante sinterización por plasma sin presión y por chispa, los circonatos de tierras raras (RE) de alta entropía con estructura de pirocloro. El compuesto RE2Zr2O7 con composición nominal (La0,2Y0,2Gd0,2Nd0,2Sm0,2)Zr2O7 se preparó mediante un procedimiento simple de nitrato de glicina (GNP). El proceso GNP produjo polvos con baja cristalinidad y después de la posterior calcinación, se formaron cerámicas bien cristalinas. Durante la calcinación coexisten estructuras defectuosas de fluorita (F-RE2Zr2O7) y pirocloro cristalino (Py-RE2Zr2O7). La formación de pirocloro cristalino puro se produce después de la sinterización a 1.450°C. Después de la compactación de polvos y sin presión (PS), así como por la técnica de sinterización asistida en campo (FAST) a 1.450 oC, se obtuvieron cerámicas de alta densidad, libres de aditivos. Se realizaron investigaciones teóricas de los sistemas de pirocloro RE2Zr2O7 de alta entropía. El parámetro de celda unitaria del Py-RE2Zr2O7 obtenido es 105.892(2) Å y 105.999(2) Å para la sinterización PS y FAST, respectivamente, lo que está de acuerdo con los resultados de los cálculos de la teoría funcional de la densidad (DFT). La difusividad térmica de las muestras sinterizadas a temperatura ambiente fue de ∼ 0,7 mm2/s para ambos métodos de sinterización

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Small-Scale Mechanical Testing of Cemented Carbides from the Micro- to the Nano-Level: A Review

In this overview, we summarize the results published to date concerning the small-scale mechanical testing of WC−Co cemented carbides and similar hardmetals, describing the clear trend in the research towards ever-smaller scales (currently at the nano-level). The load-size effect during micro/nanohardness testing of hardmetals and their constituents and the influence of the WC grain orientation on their deformation, hardness, indentation modulus, fracture toughness, and fatigue characteristics are discussed. The effect of the WC grain size/orientation, cobalt content, and testing environment on damage accumulation, wear mechanisms, and wear parameters are summarized. The deformation and fracture characteristics and mechanical properties, such as the yield and compression strength, of WC−Co composites and their individual WC grains at different orientations during micropillar compression tests are described. The mechanical and fracture properties of micro-cantilevers milled from WC−Co hardmetals, single WC grains, and cantilevers containing WC/WC boundaries with differently-oriented WC grains are discussed. The physical background of the deformation and damage mechanisms in cemented carbides at the micro/nano-levels is descri and potential directions for future research in this field are outlined

Micro/Nano Indentation Testing of Spark Plasma Sintered Al2O3 + ZrO2 + cBN Ceramics

Al2O3 + 30 vol% ZrO2 matrix composites with 20 and 30 vol% cBN have been prepared with the optimized processing route, using spark plasma sintering (SPS) at temperatures of 1400 °C and 1250 °C. The influence of cBN addition on the microstructure characteristics, micro/nanohardness, elastic modulus, and crack-extension resistance of the composites and their constitutions have been investigated using scanning electron microscopy (SEM), statistical analyses of the individual grain size and micro/nanoindentation methods. The matrix consists of alumina and zirconia grains with grain sizes/diameter of approximately 220 and 160 nm with approximately 1.9 μm cBN grains in the Al2O3 + ZrO2 + cBN composites. The microhardness is slightly increasing with cBN addition from 16.2 to 17.1 GPa and the crack-extension resistance from 3.72 to 4.29 MPa.m1/2. The toughening mechanisms are in the form of crack deflection, crack branching, and crack bridging. The nanohardness and indentation modulus of the matrix are approximately 30 and 420 GPa, and the cBN grains 70 and 777 GPa, respectively

Micro/Nano Indentation Testing of Spark Plasma Sintered Al₂O₃ + ZrO₂ + cBN Ceramics

Al2O3 + 30 vol% ZrO2 matrix composites with 20 and 30 vol% cBN have been prepared with the optimized processing route, using spark plasma sintering (SPS) at temperatures of 1400 °C and 1250 °C. The influence of cBN addition on the microstructure characteristics, micro/nanohardness, elastic modulus, and crack-extension resistance of the composites and their constitutions have been investigated using scanning electron microscopy (SEM), statistical analyses of the individual grain size and micro/nanoindentation methods. The matrix consists of alumina and zirconia grains with grain sizes/diameter of approximately 220 and 160 nm with approximately 1.9 μm cBN grains in the Al2O3 + ZrO2 + cBN composites. The microhardness is slightly increasing with cBN addition from 16.2 to 17.1 GPa and the crack-extension resistance from 3.72 to 4.29 MPa.m1/2. The toughening mechanisms are in the form of crack deflection, crack branching, and crack bridging. The nanohardness and indentation modulus of the matrix are approximately 30 and 420 GPa, and the cBN grains 70 and 777 GPa, respectively