WorldCat Identities

Blomqvist, Andreas

Overview
Works: 11 works in 11 publications in 1 language and 11 library holdings
Roles: Author, opp
Publication Timeline
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Most widely held works by Andreas Blomqvist
ICME guided modeling of surface gradient formation in cemented carbides( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Abstract: Structural gradients are of great interest for state-of-the-art cemented carbides used in metal cutting applications. The gradient growth during sintering is controlled by the fundamental aspects of diffusion, thermodynamics and phase equilibria in systems with multiple components and phases. With the demand for binder alternatives to Co, there is a need for understanding the diffusion and thermodynamics in new materials systems. Materials development guided by ICME (Integrated Computational Materials Engineering) is a new approach that accelerates the design of tailor-made materials, assisting us to find and optimize prospective binder candidates using computational tools. The role of the thermodynamic descriptions will be briefly discussed but this work focuses on a better kinetic description. Models based on cemented carbide microstructures and fundamental understanding of kinetics will allow for a more general use of simulations of gradient formation. The diffusion of elements during sintering mainly occurs in the liquid binder phase, with the solid WC and gamma phases acting as an effective labyrinth, hindering diffusion. In this work, the liquid mobilities and the effective labyrinth factor is studied for traditional and alternative binders by combing ab initio molecular dynamics and diffusion couple experiments with CALPHAD modeling. Highlights: Presentation of the ICME framework for the surface gradient formation Combination of Ab initio liquid diffusion data and upper scale DICTRA simulations Presentation of experimental methods for a detailed investigation of the labyrinth factor
Cemented carbides based on WC pre-alloyed with Cr or Ta( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Abstract: WC powder pre-alloyed with Ta or Cr was used to produce WC-Co based cemented carbides and these were compared with materials produced from pure WC. Atom probe tomography analysis of the pre-alloyed as-sintered materials showed that a high, non-uniform, concentration of Ta or Cr remained in the WC lattice after sintering. The hexagonal (W, Ta)C partially decomposes during sintering leading to the formation of a fcc MC phase. Similarly, the (W, Cr)C partially decomposes, but no Cr-rich precipitates were observed in either of the Cr containing samples. The hardness of the crystallites of the doped materials was significantly lower than the undoped WC, as measured by nano-indentation. The Young's moduli of the doped crystals were significantly lower than the undoped WC in agreement with the lowering of the elastic constants, from ab initio calculations. The microhardness (HV) reflected what would be expected from the average WC grain size giving that the grain boundary surface area is more important for the material hardness than the hardness of the WC crystals themselves in the investigated grain size range. Highlights: WC powder pre-alloyed with Ta or Cr was used to produce cemented carbides. High concentration of Ta and Cr remained in the WC lattice also after sintering. Pre-doped WC powder causes WC crystallites with lower hardness. Grain size is more important than crystallite hardness for the matrix hardness
Ab initio Investigation of Al-doped CrMnFeCoNi High-Entropy Alloys by Xun Sun( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

High-entropy alloys (HEAs) represent a special group of solid solutions containing five or more principal elements. The new design strategy has attracted extensive attention from the materials science community. The design and development of HEAs with desired properties have become an important subject in materials science and technology. For understanding the basic properties of HEAs, here we investigate the magnetic properties, Curie temperatures, electronic structures, phase stabilities, and elastic properties of paramagnetic (PM) body-centered cubic (bcc) and face-centered cubic (fcc) Al x CrMnFeCoNi (0 ≤ x ≤ 5, in molar fraction) HEAs using the first-principles exact muffin-tin orbitals (EMTO) method in combination with the coherent potential approximation (CPA) for dealing with the chemical and magnetic disorder. Whenever possible, we compare the theoretical predictions to the available experimental data in order to verify our methodology. In addition, we make use of the previous theoretical investigations carried out on Al x CrFeCoNi HEAs to reveal and understand the role of Mn in the present HEAs. The theoretical lattice constants are found to increase with increasing x , which is in good agreement with the available experimental data. The magnetic transition temperature for the bcc structure strongly decreases with x , whereas that for the fcc structure shows a weak composition dependence. Within their own stability fields, both structures are predicted to be PM at ambient conditions. Upon Al addition, the crystal structure changes from fcc to bcc with a broad two-phase field region, in line with the observations. Bain path calculations suggest that within the duplex region both phases are dynamically stable. Comparison with available experimental data demonstrates that the employed approach describes accurately the elastic moduli of the present HEAs. The elastic parameters exhibit complex composition dependences, although the predicted lattice constants increase monotonously with Al addition. The elastic anisotropy is unusually high for both phases. The brittle/ductile transitions formulated in terms of Cauchy pressure and Pugh ratio become consistent only when the strong elastic anisotropy is accounted for. The negative Cauchy pressure of CrMnFeCoNi is found to be due to the relatively low bulk modulus and C 12 elastic constant, which in turn are consistent with the relatively low cohesive energy. Our findings in combination with the experimental data suggest anomalous metallic character for the present HEAs system. The work and results presented in this thesis give a good background to go further and study the plasticity of Al x CrMnFeCoNi type of HEAs as a function of chemistry and temperature. This is a very challenging task and only a very careful pre-study concerning the phase stability, magnetism and elasticity can provide enough information to turn my plan regarding ab initio description of the thermo-plastic deformation mechanisms in Al x CrMnFeCoNi HEAs into a successful research
Paracetamol analogues conjugated by FAAH induce TRPV1-mediated antinociception without causing acute liver toxicity by Johan L. A Nilsson( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

Paracetamol, one of the most widely used pain-relieving drugs, is deacetylated to 4-aminophenol (4-AP) that undergoes fatty acid amide hydrolase (FAAH)-dependent biotransformation into N-arachidonoylphenolamine (AM404), which mediates TRPV1-dependent antinociception in the brain of rodents. However, paracetamol is also converted to the liver-toxic metabolite N-acetyl-p-benzoquinone imine already at therapeutic doses, urging for safer paracetamol analogues. Primary amine analogues with chemical structures similar to paracetamol were evaluated for their propensity to undergo FAAH-dependent N-arachidonoyl conjugation into TRPV1 activators both in vitro and in vivo in rodents. The antinociceptive and antipyretic activity of paracetamol and primary amine analogues was examined with regard to FAAH and TRPV1 as well as if these analogues produced acute liver toxicity. 5-Amino-2-methoxyphenol (2) and 5-aminoindazole (3) displayed efficient target protein interactions with a dose-dependent antinociceptive effect in the mice formalin test, which in the second phase was dependent on FAAH and TRPV1. No hepatotoxicity of the FAAH substrates transformed into TRPV1 activators was observed. While paracetamol attenuates pyrexia via inhibition of brain cyclooxygenase, its antinociceptive FAAH substrate 4-AP was not antipyretic, suggesting separate mechanisms for the antipyretic and antinociceptive effect of paracetamol. Furthermore, compound 3 reduced fever without a brain cyclooxygenase inhibitory action. The data support our view that analgesics and antipyretics without liver toxicity can be derived from paracetamol. Thus, research into the molecular actions of paracetamol could pave the way for the discovery of analgesics and antipyretics with a better benefit-to-risk ratio. (C) 2020 The Author(s). Published by Elsevier Masson SAS
Insights into Materials Properties from Ab Initio Theory Diffusion, Adsorption, Catalysis & Structure by Andreas Blomqvist( )

1 edition published in 2010 in English and held by 1 WorldCat member library worldwide

Utility of single-item questions to assess physical inactivity in patients with chronic heart failure by Andreas Blomqvist( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Aim The purpose of this study was to explore the utility of two single-item self-report (SR) questions to assess physical inactivity in patients with heart failure (HF). Methods and results This is a cross-sectional study using data from 106 patients with HF equipped with accelerometers for 1 week each. Two SR items relating to physical activity were also collected. Correlations between accelerometer activity counts and the SR items were analysed. Patients were classified as physically active or inactive on the basis of accelerometer counts, and the SR items were used to try to predict that classification. Finally, patients were classified as having high self-reported physical activity or low self-reported physical activity, on the basis of the SR items, and the resulting groups were analysed for differences in actual physical activity. There were significant but weak correlations between the SR items and accelerometer counts: rho = 0.24, P = 0.016 for SR1 and rho = 0.21, P = 0.033 for SR2. Using SR items to predict whether a patient was physically active or inactive produced an area under the curve of 0.62 for SR1, with a specificity of 92% and a sensitivity of 30%. When dividing patients into groups on the basis of SR1, there was a significant difference of 1583 steps per day, or 49% more steps in the high self-reported physical activity group (P < 0.001). Conclusions There might be utility in the single SR question for high-specificity screening of large populations to identify physically inactive patients in order to assign therapeutic interventions efficiently where resources are limited
Large-Scale Screening of Interface Parameters in the WC/W System Using Classical Force Field and First-Principles Calculations by Emil Edin( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

To understand the observed wear in WC/Co tools during machining of Ti-alloys, it is important to know which interfaces are present in the tool-workpiece contact zone. It has been shown that WC grains in contact with the workpiece form a C depleted layer consisting of BCC W, and as such, knowledge of which WC/W interfaces can be expected and which interfaces can be used as starting points for further computations are of great importance. Here, this is studied by the systematic construction of interfaces and evaluation of the work of adhesion and interfacial energies of 60,000 unique interfaces spread across six different interface systems made up of the basal and prismatic surfaces of WC and the low index surfaces of BCC W. Calculations are made using a classical approach in LAMMPS as well as subset analysis using first principles in VASP (Vienna Ab Initio Simulation Package). The results show trends as functions of strain and system size giving a large-scale overview of this system and finding the energetically preferred interface combination to be the type-I, W-terminated prismatic WC surface against the [110] surface of BCC W
Microstructure evolution during phase separation in Ti-Zr-C( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Abstract: (Ti, Zr)C powder was synthesized by carbothermal reduction and subsequently aged at 1150-2000 °C. The phase composition and microstructure was investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and electron backscatter diffraction. It was found that the as-synthesized (Ti, Zr)C particles have a concentration gradient with a higher concentration of Ti at the surface of the particles. Furthermore, during aging the (Ti, Zr)C decomposes into Ti-rich and Zr-rich lamellae. During aging at 1400 and 1800 °C for 10 h, most Zr-rich and Ti-rich domains precipitate at grain boundaries, inheriting the crystal orientation of the parent grain behind the growth front. When the precipitate grows into another (Ti, Zr)C grain, that grain adopts the same crystal orientation as the parent grain. The crystallographic misorientation between adjacent lamellae is 0-5°. Based on these microstructural observations it is hypothesized that the mechanism of decomposition is discontinuous precipitation. Highlights: Ti-Zr-C, synthesized at 2200 °C, demixes into nanostructure at lower temperatures. Demixing initiates discontinuously at grain boundaries. Demixing further proceeds by migrating parent grain boundaries. Demixed nanostructure inherits orientation of parent grains. The mechanism of demixing is most likely to be discontinuous precipitation
High resolution STEM investigation of interface layers in cemented carbides( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Abstract: Cemented carbides with sub-micron grain size have increased the need to restrict grain growth during sintering. Commonly used inhibitors like V, Ti, and Cr have been observed to form interface layers in the interfaces between WC grains and the Co binder. Atomistic modeling has predicted the composition and thickness of the interface layers. Earlier, the interface layers have been characterized qualitatively using high resolution transmission electron microscopy (TEM). To get more information about the structure and composition of the interface layers in a Ti containing cemented carbide in this work, Z contrast imaging and spectroscopy using scanning transmission electron microscopy (STEM) have been combined. Elemental maps revealing the structure of the interface layers will be presented. Highlights: Ti selectively segregates to basal WC planes only despite Ti-saturated Co binder. Two interfacial monolayers between the WC and Co binder were verified by STEM HAADF. STEM-EDXS proved the stacking order to be a Ti-rich followed by a W-rich monolayer
Surface gradients in cemented carbides from first-principles-based multiscale modeling: Atomic diffusion in liquid Co( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Abstract: The kinetic modeling of cemented carbides, where Co is used as binder element, requires a detailed diffusion description. Up to now, no experimental self- or impurity diffusion data for the liquid Co system have been available. Here we use the fundamental approach based on ab initio molecular dynamics simulations to assess diffusion coefficients for the liquid Co system, including six solute elements. Our calculated Co self-diffusion coefficients show good agreement with the estimates that have been obtained using scaling laws from the available literature data. To validate the modeling method, we performed one set of calculations for liquid Ni self-diffusion, where experimental data are available, showing good agreement between theory and experiments. The computed diffusion data were used in subsequent DICTRA simulations to model the gradient formation in cemented carbide systems. The results based on the new diffusion data allows for correct predictions of the gradient thickness. Graphical abstract: Highlights: Multiscale modeling of diffusion in the binder phase of cemented carbide systems. Combining ab initio molecular dynamics (AIMD) and kinetic DICTRA simulations. Diffusion data for liquid Co and liquid Co-X alloys (X = W, C, N, Ti, Ta, Nb) are computed using AIMD. Obtained diffusion data are used as input to DICTRA simulations to model the gradient formation during sintering
Self-organizing nanostructured lamellar (Ti, Zr)C -- A superhard mixed carbide( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Abstract: A nanoindentation and first-principles calculation study of a self-organizing nanostructured lamellar (Ti, Zr)C powder has been performed. The nanoindentation measurements reveal that the hardness of the carbide is comparable to the hardest transition metal carbides that have been reported previously. The origin of the super-high hardness is postulated to be due to the inherent bond strength and the large coherency strains that are generated when the carbide demixes within the miscibility gap. The high hardness is maintained at a high level even after 500 h aging treatment at 1300 °C. Therefore, it is believed that the new superhard mixed carbide has a high potential in various engineering applications such as in bulk cemented carbide and cermet cutting tools, and in surface coatings. Highlights: Nanoindentation measurements on (Ti, Zr)C aged inside the miscibility gap show very high hardness values (~ 41 GPa). The state-of-the-art bond strength model cannot account for the increase in hardness
 
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Audience level: 0.92 (from 0.88 for ICME guide ... to 0.96 for Ab initio ...)

Alternative Names
Andreas Blomqvist ceoltóir Sualannach

Andreas Blomqvist músic suec

Andreas Blomqvist musicien suédois

Andreas Blomqvist músico sueco

Andreas Blomqvist músicu suecu

Andreas Blomqvist muzikant suedez

Andreas Blomqvist Swedish musician

Andreas Blomqvist Zweeds muzikant

Languages
English (11)