An Acquisition Parameter Study for Machine-Learning-Enabled Electron Backscatter Diffraction.

Methods within the domain of artificial intelligence are gaining traction for solving a range of materials science objectives, notably the use of deep neural networks for computer vision for the analysis of electron diffraction patterns. An important component of deploying these models is an understanding of the performance as experimental diffraction conditions are varied. This knowledge can inspire confidence in the classifications over a range of operating conditions and identify where performance is degraded.

Efficient few-shot machine learning for classification of EBSD patterns.

Deep learning is quickly becoming a standard approach to solving a range of materials science objectives, particularly in the field of computer vision. However, labeled datasets large enough to train neural networks from scratch can be challenging to collect. One approach to accelerating the training of deep learning models such as convolutional neural networks is the transfer of weights from models trained on unrelated image classification problems, commonly referred to as transfer learning.

Bulk high-entropy nitrides and carbonitrides.

High-entropy ceramics have potential to improve the mechanical properties and high-temperature stability over traditional ceramics, and high entropy nitrides and carbonitrides (HENs and HECNs) are particularly attractive for high temperature and high hardness applications. The synthesis of 5 bulk HENs and 4 bulk HECNs forming single-phase materials is reported herein among 11 samples prepared. The hardness of HENs and HECNs increased by an average of 22% and 39%, respectively, over the rule-of-mixtures average of their monocarbide and mononitride precursors.

Deep Neural Network Enabled Space Group Identification in EBSD.

Electron backscatter diffraction (EBSD) is one of the primary tools in materials development and analysis. The technique can perform simultaneous analyses at multiple length scales, providing local sub-micron information mapped globally to centimeter scale. Recently, a series of technological revolutions simultaneously increased diffraction pattern quality and collection rate.

Phase Mapping in EBSD Using Convolutional Neural Networks.

The emergence of commercial electron backscatter diffraction (EBSD) equipment ushered in an era of information rich maps produced by determining the orientation of user-selected crystal structures. Since then, a technological revolution has occurred in the quality, rate detection, and analysis of these diffractions patterns. The next revolution in EBSD is the ability to directly utilize the information rich diffraction patterns in a high-throughput manner.

Crystal symmetry determination in electron diffraction using machine learning.

Electron backscatter diffraction (EBSD) is one of the primary tools for crystal structure determination. However, this method requires human input to select potential phases for Hough-based or dictionary pattern matching and is not well suited for phase identification. Automated phase identification is the first step in making EBSD into a high-throughput technique.

Novel remapping approach for HR-EBSD based on demons registration.

In this study, the possibility of utilizing a computer vision algorithm, i.e., demons registration, to accurately remap electron backscatter diffraction patterns for high resolution electron backscatter diffraction (HR-EBSD) applications is presented.

High-entropy high-hardness metal carbides discovered by entropy descriptors.

High-entropy materials have attracted considerable interest due to the combination of useful properties and promising applications. Predicting their formation remains the major hindrance to the discovery of new systems. Here we propose a descriptor-entropy forming ability-for addressing synthesizability from first principles.

Lightweight Open-Cell Scaffolds from Sea Urchin Spines with Superior Material Properties for Bone Defect Repair.

Sea urchin spines (Heterocentrotus mammillatus), with a hierarchical open-cell structure similar to that of human trabecular bone and superior mechanical property (compressive strength ∼43.4 MPa) suitable for machining to shape, were explored for potential applications of bone defect repair. Finite element analyses reveal that the compressive stress concentrates along the dense growth rings and dissipates through strut structures of the stereoms, indicating that the exquisite mesostructures play an important role in high strength-to-weight ratios.

Calcium phosphate-bearing matrices induce osteogenic differentiation of stem cells through adenosine signaling.

Synthetic matrices emulating the physicochemical properties of tissue-specific ECMs are being developed at a rapid pace to regulate stem cell fate. Biomaterials containing calcium phosphate (CaP) moieties have been shown to support osteogenic differentiation of stem and progenitor cells and bone tissue formation. By using a mineralized synthetic matrix mimicking a CaP-rich bone microenvironment, we examine a molecular mechanism through which CaP minerals induce osteogenesis of human mesenchymal stem cells with an emphasis on phosphate metabolism.

Cancer cell migration within 3D layer-by-layer microfabricated photocrosslinked PEG scaffolds with tunable stiffness.

Our current understanding of 3-dimensional (3D) cell migration is primarily based on results from fibrous scaffolds with randomly organized internal architecture. Manipulations that change the stiffness of these 3D scaffolds often alter other matrix parameters that can modulate cell motility independently or synergistically, making observations less predictive of how cells behave when migrating in 3D. In order to decouple microstructural influences and stiffness effects, we have designed and fabricated 3D polyethylene glycol (PEG) scaffolds that permit orthogonal tuning of both elastic moduli and microstructure.

Three-dimensional scaffolding to investigate neuronal derivatives of human embryonic stem cells.

Access to unlimited numbers of live human neurons derived from stem cells offers unique opportunities for in vitro modeling of neural development, disease-related cellular phenotypes, and drug testing and discovery. However, to develop informative cellular in vitro assays, it is important to consider the relevant in vivo environment of neural tissues. Biomimetic 3D scaffolds are tools to culture human neurons under defined mechanical and physico-chemical properties providing an interconnected porous structure that may potentially enable a higher or more complex organization than traditional two-dimensional monolayer conditions.

Evolution of iridium-based molecular catalysts during water oxidation with ceric ammonium nitrate.

Organometallic iridium complexes have been reported as water oxidation catalysts (WOCs) in the presence of ceric ammonium nitrate (CAN). One challenge for all WOCs regardless of the metal used is stability. Here we provide evidence for extensive modification of many Ir-based WOCs even after exposure to only 5 or 15 equiv of Ce(IV) (whereas typically 100-10000 equiv are employed during WOC testing).

Effects of age and loading rate on equine cortical bone failure.

Although clinical bone fractures occur predominantly under impact loading (as occurs during sporting accidents, falls, high-speed impacts or other catastrophic events), experimentally validated studies on the dynamic fracture behavior of bone, at the loading rates associated with such events, remain limited. In this study, a series of tests were performed on femoral specimens obtained post-mortem from equine donors ranging in age from 6 months to 28 years. Fracture toughness and compressive tests were performed under both quasi-static and dynamic loading conditions in order to determine the effects of loading rate and age on the mechanical behavior of the cortical bone.

Preparation, characterization and mechanical performance of dense beta-TCP ceramics with/without magnesium substitution.

Beta-tricalcium phosphate (beta-TCP) powder was prepared by a two-step process: wet precipitation of apatitic tricalcium phosphate [Ca(9)(HPO(4))(PO(4))(5)(OH)] (beta-TCP 'precursor') and calcination of the precursor at 800 degrees C for 3 h to produce beta-TCP. Magnesium-substituted tricalcium phosphate (beta-TCMP) was produced by adding Mg(NO(3))(2) . 6H(2)O into Ca(NO(3))(2) solution as Mg(2+) source before the precipitation step.

Conversion of bulk seashells to biocompatible hydroxyapatite for bone implants.

Strombus gigas (conch) shells and Tridacna gigas (Giant clam) shells have dense, tailored structures that impart excellent mechanical properties to these shells. In this investigation, conch and clam seashells were converted to hydroxyapatite (HAP) by a hydrothermal method at different temperatures and for different conversion durations. Dense HAP structures were created from these shells throughout the majority of the samples at the relative low temperature of approximately 200 degrees C.

Experimental investigation of dynamic effects in a two-bar/three-point bend fracture test.

A Hopkinson pressure bar has been modified to measure the dynamic fracture properties of materials at loading rates greater than approximately 10(6) MPa ms. Some fundamental dynamic effects associated with the incident stress pulse, such as stress wave propagation characteristics along the Hopkinson bar and within the cracked specimen, the specimen's dynamic response excited by the stress pulse, and the specimen contact situations with the impactor and supports, need to be understood. To better comprehend these fundamental issues, an experimental investigation of these dynamic effects with the emphasis on "loss of contact" was first performed on a two-bar/three-point dynamic bend fracture test setup using a voltage measurement circuit across the specimen/loading-pin interfaces and high-speed photographs.

Conversion of sea urchin spines to Mg-substituted tricalcium phosphate for bone implants.

The skeleton of sea urchin spines is composed of large single crystals of Mg-rich calcite, which have smooth, continuously curved surfaces and form a three-dimensional fenestrated mineral network. Spines of the echinoids Heterocentrotus trigonarius and Heterocentrotus mammillatus were converted by the hydrothermal reaction at 180 degrees C to bioresorbable Mg-substituted tricalcium phosphate (beta-TCMP). Due to the presence of Mg in the calcite lattice, conversion to beta-TCMP occurs preferentially to hydroxyapatite formation.

Growth of well-aligned carbon nanotube structures in successive layers.

Layered structures of well-aligned carbon nanotubes were grown using three variations of vapor-phase chemical vapor deposition growth processes. The reactants (typically ferrocene and benzene) were introduced either directly to a heated furnace or carried into the furnace by evaporation or spray pyrolysis in an argon flow. Thick mats of densely packed, well-aligned nanotubes were produced when the reactants were continuously introduced to the reaction; however, when the reactant flow was interrupted, the pauses allowed growth to stop and then restart as a new layer.

Local heating of discrete droplets using magnetic porous silicon-based photonic crystals.

This paper describes a method for local heating of discrete microliter-scale liquid droplets. The droplets are covered with magnetic porous Si microparticles, and heating is achieved by application of an external alternating electromagnetic field. The magnetic porous Si microparticles consist of two layers.

Thermogravimetric analysis of synthesis variation effects on CVD generated multiwalled carbon nanotubes.

Changes in the thermogravimetrically determined oxidation behaviors of CVD-grown multiwalled carbon nanotubes with varying synthesis conditions are examined. Catalyst type and synthesis temperature are found to have a measurable impact upon nanotube stability, suggesting differing levels of crystalline perfection in the resulting nanotubes. The results provide evidence showing the catalytic effects of nanotube catalyst particles and their oxides upon the oxidation of nanotube carbon and graphite.