High-pressure phase transition in 3-D printed nanolamellar high-entropy alloy by imaging and simulation insights.

We report on the high-resolution imaging and molecular dynamics simulations of a 3D-printed eutectic high-entropy alloy (EHEA) NiCoFeCrAlW consisting of nanolamellar BCC and FCC phases. The direct lattice imaging of 3D-printed samples shows the Kurdjumov-Sachs (K-S) orientation relation {111} FCC parallel to {110} BCC planes in the dual-phase lamellae. Unlike traditional iron and steels, this alloy shows an irreversible BCC-to-FCC phase transformation under high pressures.

Synthesis and Thermal Oxidation Resistance of Boron-Rich Boron-Carbide Material.

A boron-rich boron-carbide material (BC) was synthesized by spark plasma sintering of a ball-milled mixture of high-purity boron powder and graphitic carbon at a pressure of 7 MPa and a temperature of 1930 °C. This high-pressure, high-temperature synthesized material was recovered and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Vickers hardness measurements, and thermal oxidation studies. The X-ray diffraction studies revealed a single-phase rhombohedral structure (space group R-3m) with lattice parameters in hexagonal representation as = 5.

Synthesis and Ultrahigh Pressure Compression of High-Entropy Boride (HfMoNbTaZr)B to 220 GPa.

The high-entropy boride (Hf0.2Mo0.2Nb0.

Creating superconductivity in WB through pressure-induced metastable planar defects.

High-pressure electrical resistivity measurements reveal that the mechanical deformation of ultra-hard WB during compression induces superconductivity above 50 GPa with a maximum superconducting critical temperature, Tof 17 K at 91 GPa. Upon further compression up to 187 GPa, the Tgradually decreases. Theoretical calculations show that electron-phonon mediated superconductivity originates from the formation of metastable stacking faults and twin boundaries that exhibit a local structure resembling MgB (hP3, space group 191, prototype AlB).

Plasma Electroless Reduction: A Green Process for Designing Metallic Nanostructure Interfaces onto Polymeric Surfaces and 3D Scaffolds.

The design of metal nanoparticle-modified polymer surfaces in a green and scalable way is both desirable and highly challenging. Herein, a new green low-temperature plasma-based surface reduction strategy termed plasma electroless reduction (PER) is reported for achieving metallic nanostructuring on polymer surfaces. Proof of concept for this new method was first demonstrated on hydrophilic cellulose papers.

Experimental and Computational Studies of Compression and Deformation Behavior of Hafnium Diboride to 208 GPa.

The compression behavior of the hexagonal AlB phase of Hafnium Diboride (HfB) was studied in a diamond anvil cell to a pressure of 208 GPa by axial X-ray diffraction employing platinum as an internal pressure standard. The deformation behavior of HfB was studied by radial X-ray diffraction technique to 50 GPa, which allows for measurement of maximum differential stress or compressive yield strength at high pressures. The hydrostatic compression curve deduced from radial X-ray diffraction measurements yielded an ambient-pressure volume V = 29.

Selective Deposition of Hard Boron-Carbon Microstructures on Silicon.

Boron-rich B-C compounds with high hardness have been recently synthesized by the chemical vapor deposition (CVD) method. In this paper, we present our successful efforts in the selective growth of microstructures of boron-carbon compounds on silicon substrates. This was achieved by combining microfabrication techniques such as maskless lithography and sputter deposition with the CVD technique.

HuBiogel incorporated fibro-porous hybrid nanomatrix graft for vascular tissue interfaces.

Native extracellular matrix (ECM) possesses the biochemical cues to promote cell survival. However, decellularized, the ECM loses its cell supporting mechanical integrity. We report, here, a novel biohybrid vascular graft of polycaprolactone (PCL), poliglecaprone (PGC) incorporated with human biomatrix as functional materials for vascular tissue interfacing by electrospinning, thus harnessing the biochemical cues from the ECM and the mechanical integrity of the polymer blends.

Electronic structure and anisotropic compression of OsBto 358 GPa.

High pressure study on ultra-hard transition-metal boride OsBwas carried out in a diamond anvil cell under isothermal and non-hydrostatic compression with platinum as an x-ray pressure standard. The ambient-pressure hexagonal phase of OsBis found to be stable with a volume compression/= 0.670 ± 0.

Experimental and Computational Studies on Superhard Material Rhenium Diboride under Ultrahigh Pressures.

An emerging class of superhard materials for extreme environment applications are compounds formed by heavy transition metals with light elements. In this work, ultrahigh pressure experiments on transition metal rhenium diboride () were carried out in a diamond anvil cell under isothermal and non-hydrostatic compression. Two independent high-pressure experiments were carried out on for the first time up to a pressure of 241 GPa (volume compression = 0.

Non-equilibrium organosilane plasma polymerization for modulating the surface of PTFE towards potential blood contact applications.

We report a novel and facile organosilane plasma polymerization method designed to improve the surface characteristics of poly(tetrafluoroethylene) (PTFE). We hypothesized that the polymerized silane coating would provide an adhesive surface for endothelial cell proliferation due to a large number of surface hydroxyl groups, while the large polymer networks on the surface of PTFE would hinder platelet attachment. The plasma polymerized PTFE surfaces were then systematically characterized via different analytical techniques such as FTIR, XPS, XRD, Contact angle, and SEM.

Room-temperature compression and equation of state of body-centered cubic zirconium.

Zirconium (Zr) has properties conducive to nuclear applications and exhibits complex behavior at high pressure with respect to the effects of impurities, deviatoric stress, kinetics, and grain growth which makes it scientifically interesting. Here, we present experimental results on the 300 K equation of state of ultra-high purity Zr obtained using the diamond-anvil cell coupled with synchrotron-based x-ray diffraction and electrical resistance measurements. Based on quasi-hydrostatic room-temperature compression in helium to pressure P  =  69.

Non-equilibrium hybrid organic plasma processing for superhydrophobic PTFE surface towards potential bio-interface applications.

Superhydrophobic surfaces have gained increased attention due to the high water-repellency and self-cleaning capabilities of these surfaces. In the present study, we explored a novel hybrid method of fabricating superhydrophobic poly(tetrafluoroethylene) (PTFE) surfaces by combining the physical etching capability of oxygen plasma with the plasma-induced polymerization of a organic monomer methyl methacrylate (MMA). This novel hybrid combination of oxygen-MMA plasma has resulted in the generation of superhydrophobic PTFE surfaces with contact angle of 154°.

Computational Predictions and Microwave Plasma Synthesis of Superhard Boron-Carbon Materials.

Superhard boron-carbon materials are of prime interest due to their non-oxidizing properties at high temperatures compared to diamond-based materials and their non-reactivity with ferrous metals under extreme conditions. In this work, evolutionary algorithms combined with density functional theory have been utilized to predict stable structures and properties for the boron-carbon system, including the elusive superhard BC₅ compound. We report on the microwave plasma chemical vapor deposition on a silicon substrate of a series of composite materials containing amorphous boron-doped graphitic carbon, boron-doped diamond, and a cubic hard-phase with a boron-content as high as 7.

Rapid Growth of Nanocrystalline Diamond on Single Crystal Diamond for Studies on Materials under Extreme Conditions.

Early stage nucleation morphologies of spatially localized nanocrystalline diamond (NCD) micro-anvils grown on (100)-oriented single crystal diamond (SCD) anvil surfaces were analyzed and investigated for applications in high pressure studies on materials. NCD was grown on SCD using Microwave Plasma Chemical Vapor Deposition (MPCVD) for brief time intervals ranging from 1-15 minutes. Early stage film morphologies were characterized using scanning electron microscopy (SEM) and Raman spectroscopy and were compared to films grown for several hours.

Pressure Induced Densification and Compression in a Reprocessed Borosilicate Glass.

Pressure induced densification and compression of a reprocessed sample of borosilicate glass has been studied by X-ray radiography and energy dispersive X-ray diffraction using a Paris-Edinburgh (PE) press at a synchrotron X-ray source. The reprocessing of a commercial borosilicate glass was carried out by cyclical melting and cooling. Gold foil pressure markers were used to obtain the sample pressure by X-ray diffraction using its known equation of state, while X-ray radiography provided a direct measure of the sample volume at high pressure.

Morphological Transition in Diamond Thin-Films Induced by Boron in a Microwave Plasma Deposition Process.

The purpose of this study is to understand the basic mechanisms responsible for the synthesis of nanostructured diamond films in a microwave plasma chemical vapor deposition (MPCVD) process and to identify plasma chemistry suitable for controlling the morphology and electrical properties of deposited films. The nanostructured diamond films were synthesized by MPCVD on Ti-6Al-4V alloy substrates using H₂/CH₄/N₂ precursor gases and the plasma chemistry was monitored by the optical emission spectroscopy (OES). The synthesized thin-films were characterized by -ray diffraction and scanning electron microscopy.

Pressure-induced superconductivity in the giant Rashba system BiTeI.

At ambient pressure, BiTeI exhibits a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur.

Magnetic transition temperatures follow crystallographic symmetry in samarium under high-pressures and low-temperatures.

Magnetic ordering temperatures in rare earth metal samarium (Sm) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to high-pressure up to 47 GPa and low-temperature to 10 K. The two magnetic transitions at 106 K and 14 K in the α-Sm phase, attributed to antiferromagnetic ordering on hexagonal and cubic layers respectively, collapse in to one magnetic transition near 10 GPa when Sm assumes a double hexagonal close packed (dhcp) phase. On further increase in pressure above 34 GPa, the magnetic transitions split again as Sm adopts a hexagonal-hP3 structure indicating different magnetic transition temperatures for different crystallographic sites.

High-pressure high-temperature phase diagram of organic crystal paracetamol.

High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped heating diamond anvil. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in five different experiments.