3D printed bioactive and antibacterial silicate glass-ceramic scaffold by fused filament fabrication.

The fused filament fabrication (FFF) technique was applied for the first time to fabricate novel 3D printed silicate bioactive and antibacterial Ag-doped glass-ceramic (Ag-BG) scaffolds. A novel filament consisting primarily of polyolefin and Ag-BG micro-sized particles was developed and its thermal properties characterized by thermogravimetric analysis (TGA) to define the optimum heat treatment with minimal macrostructural deformation during thermal debinding and sintering. Structural characteristics of the Ag-BG scaffolds were evaluated from macro- to nanoscale using microscopic and spectroscopic techniques.

Correlating results from high resolution EBSD with TEM- and ECCI-based dislocation microscopy: Approaching single dislocation sensitivity via noise reduction.

High resolution electron backscatter diffraction (HREBSD), an SEM-based diffraction technique, may be used to measure the lattice distortion of a crystalline material and to infer the geometrically necessary dislocation content. Uncertainty in the image correlation process used to compare diffraction patterns leads to an uneven distribution of measurement noise in terms of the lattice distortion, which results in erroneous identification of dislocation type and density. This work presents a method of reducing noise in HREBSD dislocation measurements by removing the effect of the most problematic components of the measured distortion.

Ultra-high spatial resolution selected area electron channeling patterns.

An approach for producing ultrahigh spatial resolution selected area electron channeling patterns (UHR-SACPs) using the FEI/Thermo Elstar electron column is presented. The approach uses free lens control to directly assign lens and deflector values to rock the beam about precise points on the sample surface and generate the UHR-SACPs. Modification of the lens parameters is done using a service application that is preinstalled on the microscope or using the iFast scripting interface to run a short program to assign lens and deflector currents.

Fabrication and multiscale characterization of 3D silver containing bioactive glass-ceramic scaffolds.

In this work, we fabricated and characterized bioactive 3D glass-ceramic scaffolds with inherent antibacterial properties. The sol-gel (solution-gelation) technique and the sacrificial template method were applied for the fabrication of 3D highly porous scaffolds in the 58.6SiO - 24.

Comparison of dislocation characterization by electron channeling contrast imaging and cross-correlation electron backscattered diffraction.

In this work, the relative capabilities and limitations of electron channeling contrast imaging (ECCI) and cross-correlation electron backscattered diffraction (CC-EBSD) have been assessed by studying the dislocation distributions resulting from nanoindentation in body centered cubic Ta. Qualitative comparison reveals very similar dislocation distributions between the CC-EBSD mapped GNDs and the ECC imaged dislocations. Approximate dislocation densities determined from ECC images compare well to those determined by CC-EBSD.

Sub-micron resolution selected area electron channeling patterns.

Collection of selected area channeling patterns (SACPs) on a high resolution FEG-SEM is essential to carry out quantitative electron channeling contrast imaging (ECCI) studies, as it facilitates accurate determination of the crystal plane normal with respect to the incident beam direction and thus allows control the electron channeling conditions. Unfortunately commercial SACP modes developed in the past were limited in spatial resolution and are often no longer offered. In this contribution we present a novel approach for collecting high resolution SACPs (HR-SACPs) developed on a Gemini column.

Growth mechanism and elemental distribution of beta-Ga2O3 crystalline nanowires synthesized by cobalt-assisted chemical vapor deposition.

Long beta-Ga2O3 crystalline nanowires are synthesized on patterned silicon substrates using chemical vapor deposition technique. Advanced electron microscopy indicates that the as-grown beta-Ga2O3 nanowires are consisted of poly-crystalline (Co, Ga)O tips and straight crystalline beta-Ga2O3 stems. The catalytic cobalt not only locates at the nanowire tips but diffuses into beta-Ga2O3 nanowire stems several ten nanometers.

Nanopipes in gallium nitride nanowires and rods.

Gallium nitride nanowires and rods synthesized by a catalyst-free vapor-solid growth method were analyzed with cross section high-resolution transmission electron microscopy. The cross section studies revealed hollow core screw dislocations, or nanopipes, in the nanowires and rods. The hollow cores were located at or near the center of the nanowires and rods, along the axis of a screw dislocation.

Internal structure of multiphase zinc-blende wurtzite gallium nitride nanowires.

In this paper, the internal structure of novel multiphase gallium nitride nanowires in which multiple zinc-blende and wurtzite crystalline domains grow simultaneously along the entire length of the nanowire is investigated. Orientation relationships within the multiphase nanowires are identified using high-resolution transmission electron microscopy of nanowire cross-sections fabricated with a focused ion beam system. A coherent interface between the zinc-blende and wurtzite phases is identified.

Physical factors that trigger cholesterol crystallization leading to plaque rupture.

Background: Triggers of plaque rupture have been elusive. Recently it was demonstrated that cholesterol expands when transforming from a liquid to a crystal state, disrupting overlying plaque. This study examined the effect of physical conditions including saturation, temperature, hydration, pH on cholesterol crystallization.

Electronic and structural characteristics of zinc-blende wurtzite biphasic homostructure GaN nanowires.

We report a new biphasic crystalline wurtzite/zinc-blende homostructure in gallium nitride nanowires. Cathodoluminescence was used to quantitatively measure the wurtzite and zinc-blende band gaps. High-resolution transmission electron microscopy was used to identify distinct wurtzite and zinc-blende crystalline phases within single nanowires through the use of selected area electron diffraction, electron dispersive spectroscopy, electron energy loss spectroscopy, and fast Fourier transform techniques.

Scanning electron microscopy imaging of dislocations in bulk materials, using electron channeling contrast.

The imaging and characterization of dislocations is commonly carried out by thin foil transmission electron microscopy (TEM) using diffraction contrast imaging. However, the thin foil approach is limited by difficult sample preparation, thin foil artifacts, relatively small viewable areas, and constraints on carrying out in situ studies. Electron channeling imaging of electron channeling contrast imaging (ECCI) offers an alternative approach for imaging crystalline defects, including dislocations.

New hetero silicon-carbon nanostructure formation mechanism.

We report the formation of silicon and carbon hetero-nanostructures in an inductively coupled plasma system by a simultaneous growth/etching mechanism. Multi-walled carbon nanotubes were grown during one, three and five hour depositions, while tapered silicon nanowires were progressively etched. The carbon and silicon nanostructures and the interfaces between them were studied by electron microscopies and micro Raman spectroscopies.

In vitro stability predictions for the bone/hydroxyapatite composite system.

Electroacoustic measurements of the zeta (zeta) potential as a function of pH were collected and used to probe the nature of the ionic contributions to the bond formed between synthetic hydroxyapatite (HA) and bone. HA powder and wet bone powder were dispersed into an electrolyte solution comprised of physiologic saline (0.154M NaCl), electroacoustic measurements collected, and the zeta potential calculated as a function of pH.