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A materials discovery algorithm geared towards exploring high-performance candidates in new chemical spaces. https://github.com/sparks-baird/mat_discover/blob/main/README.md

Raw RBS data for article Investigation of matrix independent calibration of oxygen in glow discharge optical emission spectrometry. All raw data as well as simulation files (SIMNRA) are included.

Here we highlight 35 researchers approximately under the age of 35. Age, of course, is just a number—our target was emerging early-career academics. Contributors were recruited in a self-propagating “pay-it-forward” manner, with each invitee being suggested by a peer who had already contributed. The final collection is an inspiring look at the challenges the current generation of materials researchers are tackling.

Electron Backscatter Diffraction (EBSD) in Scanning Electron Microscope (SEM) has been one of the most popular tools for characterizing microstructures of materials and in particular alloys made by additive manufacturing (AM) in recent years. This characterization technique can provide abundant microstructural data, including phase distribution, grain size, grain boundary character, crystallographic orientation, and texture. However, it has recently been noticed that there are several challenges in the characterization of AM alloys by EBSD, causing the misunderstanding of material microstructures. This presentation discusses two challenges associated with the grain size determination by EBSD. Grain size is an important parameter used in understanding the relationship between the mechanical property and microstructure of a 3D-printed alloy, and is usually measured by optical microscope (OM) and EBSD. However, a common issue is that the grain size determined by EBSD sometimes is inconsistent with that from OM. Here We measured the grain size from the same areas in a Ti64 sample by OM and EBSD, respectively, and compared the results, in order to correlate two techniques. The result shows that when the grain size is greater than 10um, the data from OM and EBSD can completely match. When the grain size is in the range of 4~10um, there is a significant deviation between the size distributions. For fine grains, e.g. <4um, the EBSD measurement is more reliable. This indicates that OM and EBSD are equivalent for analyzing grains which sizes are bigger than 10um, but EBSD is more suitable for measuring fine grains due to the higher spatial resolution than OM. Further analysis reveals that the accuracy of grain size measurement especially for the fine grains is strongly related to the threshold angle of grain boundary used in the EBSD data process. Step size is another important parameter to determine the grain size. Another usual challenge in the EBSD analysis is how to choose the step size to obtain a high-quality EBSD map with high spatial resolution and high hit rate [1]. As the typical AM alloy has two different microstructural features in terms of grain size, melt pools with large columnar grains and fine-grained regions between the melt pools, researchers like to choose a small step size to map the sample. This is a conventional EBSD strategy used in the characterization of heterogeneous microstructures in materials. However, the recent characterization in Al printed alloys shows that such a strategy doesn���t work well at low magnification even a very small step size is used. Normally, grains in melt pools are visualized and measured well, but the fine grains at the melt pool boundaries are invisible at the low magnification due to the low hit rate. To improve EBSD map quality and grain size measurement at the fine-grained regions, higher magnification with a smaller step size has been used, but this condition limits the size of the mapping area. Compromising the magnification and grain size determination, a new EBSD strategy that includes two steps of mapping AM samples is recommended, firstly scanning a big area to show the domain microstructures of melt pools, and secondly mapping with higher magnification to show the typical fine-grained region in detail.

Chiral materials, similarly to human hands, have distinguishable right-handed and left-handed enantiomers which may behave differently in response to external stimuli. Here, we use for the first time an approach based on the density functional theory (DFT)+PAOFLOW calculations to quantitatively estimate the so-called collinear Rashba-Edelstein effect (REE) that generates spin accumulation parallel to charge current and can manifest as chirality-dependent charge-to-spin con- version in chiral crystals. Importantly, we reveal that the spin accumulation induced in the bulk by an electric current is intrinsically protected by the quasi-persistent spin helix arising from the crystal symmetries present in chiral systems with the Weyl spin-orbit coupling. In contrast to con- ventional REE, the spin transport can be preserved over large distances, in agreement with the recent observations for some chiral materials. This allows, for example, generation of spin currents from spin accumulation, opening novel routes for the design of solid-state spintronics devices. Quantum Espresso, 6.6 PAOFLOW, 2.0

Phenolic materials are naturally occurring molecules present in a wide range of organisms, from fungi to bacterium, and from plants to animals. Their unique structural and chemical features can form covalent or non-covalent interactions with diverse materials including inorganic (e.g., metal ion, metal oxide, silica, gold, silver), organic (e.g., small molecule, polymers), and biomaterials (e.g., proteins, peptides). As phenolic-based material can establish multiple physicochemical interactions such as metal coordination, hydrogen bonding, interactions, hydrophobic interactions, electrostatic interactions, and covalent bonding, diverse phenolic-enabled nanostructures have been developed for biomedical applications such as phenolic nanoparticles, phenolic surface coating, and secondary growth on phenolic surface. In this dissertation, I will explain how phenolic materials can benefit nanomaterials and their role in bioimaging and biosensing applications. First chapter reviews the hybrid gold nanorod-polydopamine nanoparticles which enhance photoacoustic performance more than bare gold nanorod both in in vitro and in vivo. The role of polydopamine shell in protection for gold nanorod is largely described. Second chapter describes the impact of nanoparticle size in photoacoustic and photothermal therapy. Two different-sized gold nanorods were synthesized and coated with polydopamine. These two different sizes of polydopamine-coated gold nanorod show same extinction peak (i.e., 1064 nm); however, the small size of gold nanorod exhibits remarkable photoacoustic and photothermal performance compared to large sized particles. Third chapter studies the polydopamine nanocapsule coated with organic dyes to detect heparin in whole human blood and plasma. The dye-coated polydopamine nanocapsule showed increased photoacoustic signal as a function of heparin concentration due to particle aggregation. In this chapter, tannic acid-mediated di thiol nanoparticles were also introduced to synthesize polydopamine nanocapsules. Fourth chapter investigates the impact of skin tone on biomedical optics. Darker skin tones (i.e., phototype) absorb and scatter more incident light before it reaches to target of interest. To understand the impact of skin tone, we mimic human skin using gelatin-based hydrogel and polydopamine nanoparticles (referred as synthetic melanin) in which they have similar chemical and optical properties compared to real melanin. Using 3D-bioprinted skin phantoms, multiple biomedical optics (photoacoustic, fluorescence, and photothermal) were extensively examined. Fifth chapter includes peptide-driven particle dissociation of gold nanoparticle aggregates for protease detection. Gold nanoparticle aggregation is often hindered by protein corona formation in biofluid, and undesired aggregation can produce false positives. In this chapter, diverse peptide structures were investigated for a matrix-insensitive dissociation platform.

The shrinkage during solidification of aluminium and iron based alloys has been studied experimentally and theoretically. The determined shrinkage behaviour has been used in theoretical evaluation of shrinkage related phenomena during solidification. Air gap formation was experimentally studied in cylindrical moulds. Aluminium based alloys were cast in a cast iron mould while iron based alloys were cast in a water-cooled copper mould. Displacements and temperatures were measured throughout the solidification process. The modelling work shows that the effect of vacancy incorporation during the solidification has to be taken into account in order to accurately describe the shrinkage. Crack formation was studied during continuous casting of steel. A model for prediction of crack locations has been developed and extended to consider non-equilibrium solidification. The model demonstrates that the shrinkage due to vacancy condensation is an important parameter to regard when predicting crack formation. The centreline segregation was studied, where the contributions from thermal and solidification shrinkage were analysed theoretically and compared with experimental findings. In order to compare macrosegregation in continuous casting and ingot casting, ingots cast with the same steel grade was analysed. However, the macrosegregation due to A-segregation is driven by the density difference due to segregation. This is also analysed experimentally as well as theoretically.

Molybdenum disulfide, as a transition metal dichalcogenide, has attracted huge attention for its good optical properties. However, to produce corresponding arrays of nano/microscale devices, resist-based lithography and etching generate permanent contaminations and damages. Here, we report a method capable of generating arbitrary MoS2 patterns without additional lithography or etching processes.

Ion irradiation is capable of modifying the structure of materials. By changing the structure in a controlled fashion, it is possible to tune the material properties to create new devices. One of the most exciting applications of ion irradiation can be found in the semiconductor industry, where this technique is used to manufacture electronic components. Swift Heavy Ions (SHI) are a specific type of ion irradiation characterized by their high mass, and elevated energies (> 1 MeV/amu). These ions interact mainly with the electrons in the material, and often leave traces of cylindrical defected regions known as ion tracks. These defects are few nanometers wide but can be up to several microns long. SHI irradiation can be used to produce ion tracks of tunable size, making it a suitable technique for several promising applications. By analyzing the abundance of tracks one can estimate the age of geological and archaeological samples. The etched ion tracks in silica (a-SiO2) serve as excellent templates to grow arrays of metallic nanowires. On the other hand, SHI irradiation of graphene allows also the engineering of high efficiency water desallinators. Experimental measurements have shown that SHIs can produce defects in graphene, and that their size grows with the ion energies. Previous reports have identified a core-shell structure within the ion tracks of several amorphous materials: a-SiO2, a-Si3N4 and a-Si. Nevertheless, current experimental techniques are not able to resolve the structure of these defects, nor the mechanism of their formation. In this study, we use Molecular Dynamics, augmented by the two-temperature model and a Monte Carlo-based electronic cascade model to study the formation mechanism and structure of defects at the atomic level, as well as to investigate the early electron dynamics after the ion impact in these materials. Our simulations show that SHI irradiation can create pore-like defects in graphene; even when a considerable amount of the energy initially deposited by the ion is removed via electron emission during the development of the electron cascade. Moreover, we attribute the formation of the core-shell structure in a-SiO2, a-Si3N4 and a-Si to the different transient pressure levels at the time when the core and the shell of the track solidify; higher (lower) pressures leading to higher (lower) densities, respectively. This work constitutes a step forward at modeling the interaction of SHI in 2D and amorphous materials, and sheds light on the mechanisms how defects form in these type of materials under extreme conditions of high-energy ion irradiation. Ionisäteily voi aiheuttaa muutoksia materiaalien rakenteessa. Muuttamalla rakennetta hallitusti pystyy säätämään materiaalin ominaisuuksia uusien laitteiden luomiseksi. Yksi jännittävimmistä ionisäteilyn sovelluksista löytyy puolijohdeteollisuudessa, jossa tätä tekniikkaa käytetään elektronisten komponenttien valmistukseen. Ripeät raskas-ionit ovat tietyntyyppinen ionisäteily, jolle on ominaista niiden iso massa ja suuret energiat (> 1 MeV per nukleoni). Nämä ionit vuorovaikuttavat pääasiassa materiaalin elektronien kanssa ja indusoivat usein sylinterinmuotoisen defektiä, joita kutsutaan ionin jäljeksi. Nämä jäljet ovat muutaman nanometrin levyisiä, mutta voivat olla jopa useita mikroneja pitkiä. Ripeät raskas-ionit voidaan käyttää tuottamaan erikokoisia ionin jälkiä, mikä tekee siitä sopivan tekniikan useisiin lupaaviin sovelluksiin. Analysoimalla jälkien määrä voidaan arvioida geologisten ja arkeologisten näytteiden ikä. Piidioksidin (a-SiO2) etsattyt ionin jäljet toimivat erinomaisina malleina metallisten nanolankojen tuottamiseen. Toisaalta, ripeät raskas-ionisäteilytys voi käyttää valmistamaan grafeenista tehokkaan veden desallinaattorin. Kokeelliset mittaukset ovat osoittaneet, tämä ionisäteilytys voi aiheuttaa defektiä grafeenissa ja että niiden koko kasvaa ionienergioiden myötä. Aiemmissa raporteissa on tunnistettu ydin-kuori rakenne useiden amorfisten materiaalien: a-SiO2: n, a-Si3N4: n ja a-Si: n ionin jäljissä. Nykyiset kokeelliset tekniikat eivät kuitenkaan pysty ratkaisemaan näiden vikojen rakennetta eikä niiden muodostumismekanismia. Tässä tutkimuksessa käytämme molecular dynamicsia, kahden lämpötilan malli ja Monte Carlo -pohjainen elektroninen kaskadimalli, tutkiaksemme defekti muodostumismekanismia ja rakennetta atomitasolla sekä tutkiaksemme varhaista elektronidynamiikkaa näiden materiaalien ionivaikutuksen jälkeen. Simulaatiomme osoittavat, että ripeät raskas-ionisäteilytys voi aiheuttaa huokosmaisia defektiä grafeenissa; silloinkin, kun huomattava määrä ionin alun perin sijoittamaa energiaa poistetaan elektronipäästöjen kautta elektronikaskadin kehittämisen aikana. Lisäksi annamme ydin-kuoren rakenteen muodostumisen a-SiO2: ssa, a-Si3N4: ssä ja a-Si: ssä eri ohimenevistä painetasoista silloin, kun ionin jäljen ydin ja kuori kiinteytyvät; suuremmat (alemmat) paineet, jotka johtavat suurempaan (pienempään) tiheyteen. Tämä työ on askel eteenpäin ripeät raskas-ionisäteilytyksen vuorovaikutuksen mallintamisessa 2D- ja amorfisissa materiaaleissa ja paljastaa mekanismeja, miten defektiä muodostuvat tämäntyyppisissä materiaaleissa äärimmäisessä korkean energian ionisäteilyssä.