James P. Best

Max Planck Institute for Sustainable Materials

Grain boundary hardening and precipitation hardening are important mechanisms for enhancing the strength of metals. Here, we show that these two effects can be amplified simultaneously in nanocrystalline compositionally complex alloys (CCAs), leading to near-theoretical strength and large deformability. We develop a model nanograined (TiZrNbHf)98Ni...

Face‐centered cubic (fcc) metals deposited onto crystalline substrates grow heteroepitaxially with specific orientation relationships (ORs). The ORs depend on a number of factors including lattice mismatch, bonding and the relative symmetry between the surface and the film. Less explored factors include defects like growth and annealing twins. In t...

The effects of thermal treatments on metallic glass nanolaminates (NLs), with a composition of Zr$_{24}$Cu$_{76}$ and Zr$_{61}$Cu$_{39}$ and a bilayer period of 50 nm, were explored to control their mechanical properties through annealing-induced atomic structure modifications, structural relaxation, and partial crystallisation. Annealing treatment...

The cubic C15 CaAl2 Laves phase is an important brittle intermetallic precipitate in ternary Mg–Al–Ca structural alloys. Although knowledge of the mechanical properties of the co-existing phases is essential for the design of improved alloys, the fracture toughness of the C15 CaAl2 intermetallic has not yet been studied experimentally due to limita...

[This corrects the article DOI: 10.1371/journal.pone.0281703.].

The design of high‐performance structural thin films consistently seeks to achieve a delicate equilibrium by balancing outstanding mechanical properties like yield strength, ductility, and substrate adhesion, which are often mutually exclusive. Metallic glasses (MGs) with their amorphous structure have superior strength, but usually poor ductility...

Wüstite, Fe 1-x O, is a crucial phase for the transition to CO 2 -free steel manufacturing as well as promising for electrochemical applications such as water splitting and ammonia synthesis. To study the effect of interfaces in these applications, thin-film model systems with defined interfaces are ideal. Previous studies lack a description of the...

Differentiation of granular bainite and polygonal ferrite in high-strength low-alloy (HSLA) steels possesses a significant challenge, where both nanoindentation and chemical analyses do not achieve an adequate phase classification due to the similar mechanical and chemical properties of both constituents. Here, the kernel average misorientation fro...

The role of a ∑3{112} incoherent twin boundary (ITB) on the shear stress of Cu at the micron scale has been investigated through microcompression of bi-crystalline pillars containing ITB, as well as single-crystalline pillars, in two different compression directions. The Cu sample containing ITBs was synthesized using magnetron sputtering on a sapp...

Interest in the technique of low temperature environmental nanoindentation has gained momentum in recent years. Low temperature indentation apparatuses can, for instance, be used for systematic measurements of the mechanical properties of ice in the laboratory, in order to accurately determine the inputs for the constitutive equations describing th...

Bulk‐scale (2¯$\bar{2}$01)‐oriented monoclinic beta‐phase gallium oxide (β‐Ga2O3) single crystals are brittle and fracture at low compressive strains. Here, it is reported that submicron β‐Ga2O3 pillars exhibit an exceptional room temperature plastic strain of up to ≈22% under compression. Deformation is observed in transition from brittle to super...

Laser powder bed fusion is an established and viable method to produce large and complex bulk metallic glass geometries. However, the thermal gradients and cooling rates during processing are affected by geometric features, in particular close to the part-powder bed interface, which may impair vitrification and mechanical properties. As such, the p...

Recent experimental and computational studies at different scales reveal an apparent flow-induced anisotropy of the inelastic deformation behaviour in metallic glasses (MGs). However, the anisotropic damage behaviour accompanied by the formation of shear bands is not adequately described in the previous constitutive modelling work. In this study, w...

The Mg-Al-Ca system has been shown to be a promising alloy system since it combines the low density of Mg with a high creep resistance at high alloying contents and a high ductility for dilute alloys, while simultaneously avoiding the requirement of alloying with costly rare earth elements. Nevertheless, the adequate preparation of the alloy system...

Additive manufacturing of bulk metallic glasses (BMGs) has opened this material class to an exciting new range of potential applications, as bulk-scale, net-shaped amorphous components can be fabricated in a single step. However, there exists a critical need to understand the structural details of additive manufactured BMGs and how the glassy struc...

Thin film metallic glasses (TFMGs) are a novel class of materials showing a mutual combination of large plastic deformation in tension (>10% strain) and superior yield strength up to ∼3.5 GPa, which make them ideal candidates for applications such as flexible electronics. Nevertheless, a clear relationship between the atomic structure and mechanica...

Experimental differentiation of individual strengthening effects from the nanoscale precipitates in Alloy 718 remains challenging due to co-precipitation of γ′ and γ′′. Here, we examine a region adjacent to the δ-phase consisting of γ-matrix containing γ′-precipitates only. The width and compositional profile of this γ′′-free zone is uncovered via...

Interstitials, e.g., C, N, and O, are attractive alloying elements as small atoms on interstitial sites create strong lattice distortions and hence substantially strengthen metals. However, brittle ceramics such as oxides and carbides usually form, instead of solid solutions, when the interstitial content exceeds a critical yet low value (e.g., 2 a...

The impact of a coherent twin boundary (CTB) on the size scaling of the shear stress in micropillar compression tests has been investigated through microcompression of bi-crystalline pillars containing a vertical CTB, as well as single-crystalline pillars in three different nominal diameters of 1, 3 and 5 µm. While both, single- and bi-crystalline...

Dislocation-enhanced electrical conductivity is an emerging topic for ceramic oxides. In contrast to the majority of present studies which focus on large-scale crystal deformation or thin film fabrication to introduce dislocations, we use a nanoindentation “pop-in stop” method to locally generate 〈011〉 edge-type dislocations at room temperature, wi...

Science-driven design of future thermoelectric materials requires a deep understanding of the fundamental relationships between microstructure and transport properties. Grain boundaries in polycrystalline materials influence the thermoelectric performance through the scattering of phonons or the trapping of electrons due to space-charge effects. Ye...

Science-driven design of future thermoelectric materials requires a deep understanding of the fundamental relationships between microstructure and transport properties. Grain boundaries in polycrystalline materials influence the thermoelectric performance through the scattering of phonons or the trapping of electrons due to space-charge effects. Ye...

High strain rate micromechanical testing can assist researchers in elucidating complex deformation mechanisms in advanced material systems. In this work, the interactions of atomic-scale chemistry and strain rate in affecting the deformation response of a Zr-based metallic glass was studied by varying the concentration of oxygen dissolved into the...

The combination of refined microstructures (induced by rapid cooling) and melt pool-induced mesostructures in AlSi10Mg fabricated using laser powder bed fusion (LPBF) – a widely used additive manufacturing technique – impart high strength and fracture toughness. Further exploitation of such property combinations requires a detailed understanding of...

In this paper, a novel approach is presented to tailor the stress properties of diamond thin films via boron doping and micro-fabrication of bridges using focused ion beam milling. The experimental data, based on detailed confocal micro-Raman investigations, are supported and interpreted through finite element method calculations of the stress dist...

Selective laser melting (SLM) is a promising powder bed based additive manufacturing technique for the near-net-shape production of large-scale bulk metallic glasses (i.e. 3D-printed BMGs). Initial defects such as pores inherent to the SLM process are regarded as key factors for the mechanical integrity of BMGs. Here the structural defects in the f...

Laser additive manufacturing of bulk metallic glass (BMG) provides an effective bypassing of the critical casting thickness constraints that limit the size of components that can be produced; however, open questions remain regarding the resulting mechanical properties. In this work, a Zr-based glass with composition Zr59.3Cu28.8Nb1.5Al10.4 was prin...

This work considers the resulting material structural effects of laser-processing chemical vapor deposited (CVD) diamond. The utilized 532 nm wavelength laser had a pulse duration of 40 ns together with a spot diameter of ca. 40 μm. The effect of cutting fluence on the CVD diamond microstructure was investigated using both Raman and transmission el...

Recently, fabrication of bulk metallic glasses (BMGs) components with complex shapes has been realized using laser powder bed fusion (PBF). Initial defects such as porosity inherent to the PBF process can significantly degrade the mechanical integrity of the BMGs components. In spite of intensive studies on pore structures in 3D-printed crystalline...

A Zr-based bulk metallic glass produced using selective laser melting (SLM) was compared to the same alloy fabricated using traditional suction-casting. Analysis of the fracture toughness and mechanism through single edge notched beam bending experiments show a significantly reduced damage tolerance for the laser-processed material (KQ ~ 138.0 ± 13...

Microfabrication of synthetic single crystal diamond using accelerated helium ions beams has significant potential for functional applications such as high precision optical devices, through tailoring of the optical properties via diamond graphitization. The use of helium ion microscopes (HIM) with nano-scaled focused ion beam spot sizes also allow...

Additive manufacturing of bulk metallic glasses (BMGs) allows for effective bypassing of critical casting thickness constraints for glassy alloys, opening this exciting materials class up to new applications. An open question is how the laser processing of such materials affects the short-range structural order; a critical mediating parameter for g...

Titanium diboride (TiB 2 ) is a hard coating with a hexagonal crystal structure that maintains its high hardness and inertness at elevated temperatures, even in contact with aluminum and its alloys. Therefore, titanium diboride coatings are often used in cutting, forming, injection molding and tribological applications. While there are multiple dep...

Additive manufactured Sc‐modified aluminum alloys hold great promise for aerospace components under high and/or complex loads. While the thermal patterns formed in the melt pool during selective laser melting (SLM) of the powdered material result in a complex microstructure featuring a bimodal grain size distribution, such alloys show an isotropic...

Micro-pillar splitting at temperatures up to 500 °C was used to evaluate the toughness for a series of thin physical vapour deposited ceramic-nitride coatings. When compared to ion beam notched geometries, this testing ap- proach reduces the likelihood of ion impregnation within a material volume where fracture may initiate. A tough- ness increase...

Effective strategies to improve the tarnishing resistance of the 18 K (karat) gold-based bulk glass-forming composition Au49Ag5.5Pd2.3Cu26.9Si16.3 were recently found, with the addition of Ga at the expense of Cu and a sufficient reduction of Si. However, the modification of the alloy is accompanied by a reduction of the glass-forming ability (GFA)...

Optimally, hard protective coatings should effectively absorb impact energy to reduce the likelihood of failure events. In this work, an arc-PVD approach was utilised for the deposition of thick ceramic multilayer AlCrTiN/CrN-based coatings containing a distribution of metallic nickel inclusions throughout sequential CrN-based interlayers. The aim...

The effect of extracellular polymeric substances (EPS) on the meso-scale physical structure and hydraulic resistance of membrane biofilms during gravity driven membrane (GDM) filtration was investigated. Biofilms were developed on the surface of ultrafiltration membranes during dead-end filtration at ultra-low pressure (70 mbar). Biofilm EPS compos...

Experiments and theory are employed to investigate the thermal damage induced by infra-red nanosecond pulses in atmospheric air into a boron-doped diamond target. Micro-Raman spectroscopy, Transmission Electron Microscopy (TEM) analysis and surface topography measurement are used to investigate the carbon phase created during the rapid heating and...

High-impact applications such as forging, punching or fine blanking often utilise hard-coating systems to improve wear and lifetime performance. For rational design of such systems, evaluation after repeated impacts at the application temperature is critical. However, such investigations are time-consuming and costly to perform in-line on an indust...

Skeletal diseases such as osteoporosis constitute a seri-ous socio-economic burden in aging societies. Patient specific tissue strength estimation could be helpful for personalised treatment strategies. Reference point in-dentation (RPI) [1] that derives from instrumented in-dentation [2] has been proposed. With imprints of sev-eral 100 μm at inden...

Direct writing utilizing a focused electron beam constitutes an interesting alternative to resist based techniques, as it allows for precise and flexible growth onto any conductive substrate in a single-step process. One important challenge, however, is the identification of appropriate precursors which allow for deposition of the material of choic...

Melt spinning and drawing of amorphous cyclo-olefin and co-polyamide polymeric materials were performed to develop mono-component continuous filaments. Raman spectroscopy was employed to assess the effect of a static bending deformation on the microstructure of the filaments. Spectra stemming from the fiber regions under tensile and compressive loa...

An effective post growth electrical tuning, via an oxygen releasing-method, to enhance the content of non-noble metals in deposits directly written with gas-assisted focused-electron-beam-induced deposition (FEBID) is presented. It represents a novel and reproducible method for improving the electrical transport properties of Co-C deposits. The met...

The micro-mechanical fracture behavior of single crystalline silicon was investigated as a function of temperature in situ in the scanning electron microscope equipped with a nanoindenter. A gradual but continuous increase in KC was observed with increasing temperature above 300 °C, in contrast to the sharp transitions observed in earlier works. No...

In a recent commentary to our manuscript "Mechanical properties of cortical bone and their relationships with age, gender, composition and microindentation properties in the elderly" Thurner [1] discusses several points that should be regarded in investigations of extra-cellular matrix properties with respect to age and gender. Thurner specifically...

Highly ordered anodic aluminum oxide (AAO) films were fabricated using a two-step anodization process in oxalic acid, sulfuric acid, or ethylene glycol containing sulfuric acid, which are important in design of nanostructured optical devices. The morphology and UV-Vis reflectance spectroscopy of these films were analyzed. The morphological paramete...

Hard coatings are used extensively to protect tools in forming, forging and milling operations. While modern deposition of hard coatings using plasma methodologies has opened industry up to a new range of potential coating systems, challenges remain regarding coating optimization under specific conditions and environments. In the presented work a p...

For the implementation of thin ceramic hard coatings into intensive application environments, the fracture toughness is a particularly important material design parameter. Characterisation of the fracture toughness of small-scale specimens has been a topic of great debate, due to size effects, plasticity, residual stress effects and the influence o...

The growing incidence of skeletal fractures poses a significant challenge to ageing societies. Since a major part of physiological loading in the lower limbs is carried by cortical bone, it would be desirable to better understand the structure-mechanical property relationships and scale effects in this tissue. This study aimed at assessing whether...

Thin-film multilayer stacks of mechanically hard magnetron sputtered indium tin oxide (ITO) and mechanically soft highly porous surface anchored metal-organic framework (SURMOF) HKUST-1 were studied using nanoindentation. Crystalline, continuous, and monolithic surface anchored MOF thin films were fabricated using a liquid-phase epitaxial growth me...

While small-scale fracture toughness measurements provide an extremely useful material parameter, notch preparation and ion-beam damage continue to be contentious issues. Herein we utilize a conventional gallium source for notching ceramic cantilevers, and compare against notches fabricated using xenon and helium ions from commercial focused ion mi...