Leander Michels
@lbl.gov
Chemical Sciences Division
Lawrence Berkeley National Laboratory / LBL
EDUCATION
2015 Physics/PhD Department of Physics, Norwegian University of Science and Technology, Norway
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Adam Götz, Leander Michels, and Jaakko Akola
Elsevier BV
Alexsandro Bobsin, Rodrigo Menezes Kerber, Iara Janaína Fernandes, Sandro Binsfeld Ferreira, Willyan Hasenkamp, Celso Renato Peter, Paulo Henrique Michels-Brito, Andrew Akanno, Leander Michels, Steinar Raaen,et al.
Elsevier BV
A. V. Bugten, P. Sanders, C. Hartung, R. Logan, M. Di Sabatino, and L. Michels
Springer Science and Business Media LLC
AbstractMost spheroidal graphite irons (SGIs) have a matrix consisting of ferrite, pearlite, or a mix of the two. To achieve the desired matrix composition, pearlite promoters such as Mn, Cu, or Sn, are added to the molten metal. Among these elements, Sn is the most potent pearlite promoter. However, each has a different impact on the solidification, graphite precipitation, eutectoid transformation, and ultimately the final structure of the material. Research has shown that B promotes ferrite in fully pearlitic grades where Cu and Mn were used to promote pearlite. The present work investigates the effect of B in SGI with additions of Sn, Cu, and Mn, and the effects of varying amounts of the different pearlite promoters on the matrix composition. The results show that Mn alone at levels of approximately 0.9 wt% is not enough to promote a fully pearlitic matrix, while 0.5 wt% Cu combined with 0.67 wt% Mn is sufficient. Likewise, a fully pearlitic microstructure can be obtained by alloying with 0.06 wt% Sn and 0.67 wt% Mn. B was found to promote ferrite in fully pearlitic SGI alloyed with Sn or Cu. However, in the absence of those elements, B promoted pearlite when alloyed with just Mn. Graphite protrusions were observed on the graphite nodule surface only for B-added alloys with Sn and Cu. In these cases, it is believed B promotes ferrite by changing the growth mechanism of graphite after solidification from spherical to lamellar. However, a different graphite morphology is observed when B is added with just Mn. Thermal analysis data is in agreement with the microstructural observations regarding the ferrite promoting effect of B.
Leander Michels, Bogdan Cygan, Miroslawa Pawlyta, Jan Jezierski, Adam Götz, and Jaakko Akola
Elsevier BV
Osvaldo Trigueiro Neto, Sabine Rosenfeldt, Paulo Henrique Michels-Brito, Konstanse Kvalem Seljelid, Andrew Akanno, Bruno Telli Ceccato, Rini Padinjakkara Ravindranathan, Tomás S. Plivelic, Leander Michels, Josef Breu,et al.
Springer Science and Business Media LLC
AbstractAqueous liquid suspensions of high aspect ratio 2D clay nanosheets were investigated using small angle X-ray scattering (SAXS). The high aspect ratio of synthetic fluorohectorite clays allows for investigation of liquid crystalline orientational order for relatively large nanosheet spacings, in the range which can produce structural coloration, thus providing two handles for determining the nanosheet spacings: SAXS and visible color. Various clay concentrations were investigated, and good agreement with previous work on structural coloration from such suspensions was obtained. Particular attention is given to the confinement caused by the container geometry, where both cylindrical and flat confinements were investigated. In both cases, the SAXS data suggest coherent regions that have a nematic inter-orientational distribution that surprisingly is linked to the container geometry, which apparently determines the efficiency of packing of the suspension. For both geometries, the analysis suggests that these coherent regions have a 1D lamellar periodic intra-structure with uniform nanosheet spacing determined by the clay concentration and a typical correlation length in the range of 200 to 500 nm. Graphical abstract
Cathrine Hartung, Matthew Liptak, Robert Logan, and Leander Michels
Springer Science and Business Media LLC
A. V. Bugten, L. Michels, R. B. Brurok, C. Hartung, E. Ott, L. Vines, Y. Li, L. Arnberg, and M. Di Sabatino
Springer Science and Business Media LLC
AbstractThe effects of boron at concentrations ranging from 5 to 525 ppm in low copper spheroidal graphite iron (SGI) has been studied. At 130 to 140 ppm, no particular effect of boron was observed on the size distributions, number densities, or morphologies of the microparticle populations in the material. Neither was there observed any effects on the size distributions or number densities of graphite nodules. However, boron was observed to lead to a rough surface morphology of the graphite nodules at concentrations as small as 24 ppm. Intercellular carbides were found to form in alloys containing more than 70 ppm boron. Additionally, the graphite shape began to degenerate in alloys with more than 300 ppm of boron. Mass spectrometry analyses revealed these carbides contain relatively high amounts of boron. In an alloy containing 74 ppm boron, it was inferred by using electron backscatter diffraction that these were of the type $${{\\hbox {M}}_{23}({\\hbox {C}},{\\hbox {B}})_{6}}$$ M 23 ( C , B ) 6 borocarbides, where M = Fe, Mn, V, or a combination of them. Mass spectrometry analyses also revealed elevated concentrations of boron in the surface layers of the graphite nodules.
António Pires, Sónia Simões, Leander Michels, Emmanuelle Ott, Cathrine Hartung, and Carlos Silva Ribeiro
MDPI AG
The effect of preconditioning treatments on the control and improvement of spheroidal graphite iron (SGI) microstructure was evaluated. In the melt, 0.15% of Zr-(Ca, Al) FeSi preconditioner was added into different conditions. Four samples were produced for this investigation: (1) in the first melt, there was no addition of a preconditioner for comparative purposes; (2) in the second melt, the preconditioner was added at the cold charge; (3) in the third melt, the preconditioner was added before the last cold charge; and (4) in the fourth melt, the preconditioner was added at tapping from the furnace. Microstructural characterization was conducted to understand the effect of the treatment on the SGI. Optical microscopy results show that preconditioning treatment increases graphite’s nodule density, ferrite content, and nodularity. Scanning electron microscopy (SEM), energy dispersive energy (EDS), and electron backscatter diffraction (EBSD) analysis were used to identify the types of microparticles present in the graphite nodules. Some complex microparticles were identified as AlMg2.5Si2.5N6, MgS, and CaS. The microstructural characteristics of the matrix, such as grain size, crystallographic orientation, and misorientation, were also evaluated by the EBSD. The addition of the preconditioning at tapping results in a higher ferrite fraction, smaller grain size, misorientation, and hardness values. This work suggests that the different preconditioning practice has a crucial effect on the microstructural characteristics of the SGI. This knowledge is vital, allowing the microstructure tailoring to enhance the mechanical properties of SGI to obtain the best performance of these materials.
L. Michels, A. J. F. Pires, C. A. S. Ribeiro, B. Kroka, E. G. Hoel, E. Ott, and C. Hartung
Springer Science and Business Media LLC
AbstractNon-metallic microparticles in spheroidal graphite irons are a product of the inoculation and the Mg-treatment of the liquid melt. Besides the influence on the mechanical properties of these iron–carbon–silicon alloys, they are also responsible for the nucleation and the morphology of the graphite phase. The present investigation is undertaken to study holding time effects of a (Ba, Ca, Al)–ferrosilicon (called Ba-inoculant) and (Ca, Al)–ferrosilicon (called Ca-inoculant) inoculants on the overall distribution of microparticles. Using the 2D to 3D conversions method, which is typically used for graphite nodules, the non-metallic microparticles’ statistical parameters, such as size distributions and number densities, are quantified. The total number of particles is similar after Mg-treatment and inoculation for Ca-inoculant but not for Ba-inoculated samples, which lose approximately 25 pct of microparticles after 1 minute of holding time. Iron treated with the Ca-inoculant loses about 37 pct of its nodules after 5 minutes, while the Ba-inoculated melts maintain their performance even after 10 minutes. Based on extrapolating the trend of the undercooling, Ba-inoculated samples would reach the uninoculated undercooling values in 48 minutes, while Ca-inoculated samples in only 11 minutes. By evaluating the size distributions of the non-metallic microparticles, the Ostwald ripening hypothesis or particle aggregation can be verified. The results suggest that sulfides are more critical for graphite nucleation since they can be correlated with the graphite number densities. However, due to the small difference in the microparticle population of the uninoculated sample with Ca-inoculated samples, other aspects of the fading mechanism need to be considered, such as transient metastable states, since the central hypothesis of loss of inclusions cannot alone explain the decrease in the nucleation frequency of graphite.
Paulo H. Michels-Brito, Volodymyr Dudko, Daniel Wagner, Paul Markus, Georg Papastavrou, Leander Michels, Josef Breu, and Jon Otto Fossum
American Association for the Advancement of Science (AAAS)
Structural colors originate by constructive interference following reflection and scattering of light from nanostructures with periodicity comparable to visible light wavelengths. Bright and noniridescent structural colorations are highly desirable. Here, we demonstrate that bright noniridescence structural coloration can be easily and rapidly achieved from suspended two-dimensional nanosheets of a clay mineral. We show that brightness is enormously improved by using double clay nanosheets, thus optimizing the clay refractive index that otherwise hampers structural coloration from such systems. Intralayer distances, and thus the structural colors, can be precisely and reproducibly controlled by clay concentration and ionic strength independently, and noniridescence is readily and effortlessly obtained in this system. Embedding such clay-designed nanosheets in recyclable solid matrices could provide tunable vivid coloration and mechanical strength and stability at the same time, thus opening a previously unknown venue for sustainable structural coloration.
Gustavo F. Perotti, Jéssica R. Bortotti, Filipe S. Lima, Leander Michels, Everton C. dos Santos, Mário A.S. Altoé, Giovanni Grassi, Geraldo J. Silva, Roosevelt Droppa-Jr, Jon O. Fossum,et al.
Applied Clay Science Elsevier BV
Leander Michels, Annika Richter, Rajesh K. Chellappan, Håkon I. Røst, Alenka Behsen, Kristin H. Wells, Luciano Leal, Vilany Santana, Rosana Blawid, Geraldo J. da Silva,et al.
Royal Society of Chemistry (RSC)
An optical, electronic and structural characterisation of three natural dyes potentially interesting for application in organic solar cells, curcumin (C21H20O6), bixin (C25H30O4) and indigo (C16H10N2O2), was performed.
L. Michels, C. L. S. da Fonseca, Y. Méheust, M. A. S. Altoé, E. C. dos Santos, G. Grassi, R. Droppa, K. D. Knudsen, L. P. Cavalcanti, K. W. B. Hunvik,et al.
American Chemical Society (ACS)
For applications benefitting from the swelling properties of nanolayered silicates (clay minerals), it is of paramount importance to understand the hysteresis in the clay–water interaction. In this...
Simon R. Larsen, Leander Michels, Éverton C. dos Santos, Marcella C. Berg, Will P. Gates, Laurie P. Aldridge, Tilo Seydel, Jacques Ollivier, Mark T.F. Telling, Jon Otto Fossum,et al.
Elsevier BV
A.S. Aguiar, L. Michels, F.G. da Silva, C. Kern, G. Gomide, C.M. Ferreira, J. Depeyrot, R. Aquino, and G.J. da Silva
Elsevier BV
Elvia A. Chavez Panduro, Benoît Cordonnier, Kamila Gawel, Ingrid Børve, Jaisree Iyer, Susan A. Carroll, Leander Michels, Melania Rogowska, Jessica Ann McBeck, Henning Osholm Sørensen,et al.
American Chemical Society (ACS)
Depleted oil reservoirs are considered a viable solution to the global challenge of CO2 storage. A key concern is whether the wells can be suitably sealed with cement to hinder the escape of CO2. Under reservoir conditions, CO2 is in its supercritical state, and the high pressures and temperatures involved make real-time microscopic observations of cement degradation experimentally challenging. Here, we present an in situ 3D dynamic X-ray micro computed tomography (μ-CT) study of well cement carbonation at realistic reservoir stress, pore-pressure, and temperature conditions. The high-resolution time-lapse 3D images allow monitoring the progress of reaction fronts in Portland cement, including density changes, sample deformation, and mineral precipitation and dissolution. By switching between flow and nonflow conditions of CO2-saturated water through cement, we were able to delineate regimes dominated by calcium carbonate precipitation and dissolution. For the first time, we demonstrate experimentally the impact of the flow history on CO2 leakage risk for cement plugging. In-situ μ-CT experiments combined with geochemical modeling provide unique insight into the interactions between CO2 and cement, potentially helping in assessing the risks of CO2 storage in geological reservoirs.
Nilesh Patil, Theyencheri Narayanan, Leander Michels, Eirik Torbjørn Bakken Skjønsfjell, Manuel Guizar-Sicairos, Niko Van den Brande, Raf Claessens, Bruno Van Mele, and Dag Werner Breiby
American Chemical Society (ACS)
An important and integral effort toward understanding the formation and reorganization of mesoscale structures in functional organic thin films, being of fundamental importance to the development of tomorrow’s green energy technologies, is the continuous sharpening of the experimental analytical tools used to observe and quantify these structures. In this study we present a combined investigation of organic thin films by small-angle X-ray scattering (SAXS) and the relatively new technique of high-resolution phase-contrast ptychographic coherent X-ray diffraction imaging (CXDI). Using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as a model system, we present the morphology development including phase separation in thermally annealed thin film blends. The state-of-the-art synchrotron SAXS measurements spanning a large q range from 2 × 10–3 to 6 nm–1 elucidate the multiscale structure within the material. Because the SAXS data in fact overlap with microscopy length sc...
Leander Michels, Yves Méheust, Mario A. S. Altoé, Éverton C. dos Santos, Henrik Hemmen, Roosevelt Droppa, Jon O. Fossum, and Geraldo J. da Silva
American Physical Society (APS)
The transport of chemical species in porous media is ubiquitous in subsurface processes, including contaminant transport, soil drying, and soil remediation. We study vapor transport in a multiscale porosity material, a smectite clay, in which water molecules travel in mesopores and macropores between the clay grains but can also intercalate inside the nanoporous grains, making them swell. The intercalation dynamics is known to be controlled by the type of cation that is present in the nanopores; in this case exchanging the cations from Na^{+} to Li^{+} accelerates the dynamics. By inferring spatial profiles of mesoporous humidity from a space-resolved measurement of grain swelling, and analyzing them with a fractional diffusion equation, we show that exchanging the cations changes mesoporous transport from Fickian to markedly subdiffusive. This results both from modifying the exchange dynamics between the mesoporous and nanoporous phases, and from the feedback of transport on the medium's permeability due to grain swelling. An important practical implication is a large difference in the time needed for vapor to permeate a given length of the clay depending on the type of intercalated cation.
E.C. dos Santos, W.P. Gates, L. Michels, F. Juranyi, A. Mikkelsen, G.J. da Silva, J.O. Fossum, and H.N. Bordallo
Elsevier BV
E. C. dos Santos, Z. Rozynek, E. L. Hansen, R. Hartmann-Petersen, R. N. Klitgaard, A. Løbner-Olesen, L. Michels, A. Mikkelsen, T. S. Plivelic, H. N. Bordallo,et al.
Royal Society of Chemistry (RSC)
We present the use of the synthetic clay fluorohectorite (Fh) as a drug delivery system of the antibiotic ciprofloxacin. The adsorption capacity is very high, and Fh promotes controlled drug release without changing drug effectiveness and toxicity.
M.A.S. Altoé, L. Michels, E.C. dos Santos, R. Droppa, G. Grassi, L. Ribeiro, K.D. Knudsen, H.N. Bordallo, J.O. Fossum, and G.J. da Silva
Elsevier BV
Jeane S. de Oliveira, Leander E. Michels, Marcelo Henrique Sousa, Jon Otto Fossum, Geraldo José da Silva, Kleber Carlos Mundim, and Luciano Ribeiro
Sociedade Brasileira de Quimica (SBQ)
No presente trabalho de difracao de raios X foi usada com o proposito de observar os estados de hidratacao estaveis da argila de niquel-fluorohectorita. Os padroes de difracao foram medidos em funcao da umidade relativa e da temperatura. As posicoes do pico de Bragg foram usadas para calcular o espacamento basal da argila (o espacamento ao longo da direcao de empilhamento) para cada temperatura. Os resultados mostram que o processo de intercalacao agua e mais dependente da umidade relativa do que a temperatura e tambem que o tamanho do cristalito da argila aumenta com a umidade relativa. Este estudo expoe a necessidade para mais experiencias em maior gama de temperaturas, a fim de alcancar outros estados de hidratacao. DOI: 10.5935/1984-6835.20160036
L. Michels, J. O. Fossum, Z. Rozynek, H. Hemmen, K. Rustenberg, P. A. Sobas, G. N. Kalantzopoulos, K. D. Knudsen, M. Janek, T. S. Plivelic,et al.
Springer Science and Business Media LLC
G. Grassi, L. Michels, Z. Rozynek, M. A. S. Altoé, E. C. dos Santos, C. L. S. da Fonseca, R. Droppa, A. Gholamipour-Shirazi, J. O. Fossum, and G. J. da Silva
Springer Science and Business Media LLC
Z. Rozynek, P. Dommersnes, A. Mikkelsen, L. Michels, and J. O. Fossum
Springer Science and Business Media LLC