Synthesis of bulk reactive Ni-Al composites using high pressure torsion

17 USC 105 interim-entered record; under review.The article of record as published may be found at http://dx.doi.org/10.1016/j.jallcom.2020.157503Self-propagating exothermic reactions, for instance in the nickel-aluminum (Ni-Al) system, have been widely studied to create high performance intermetallic compounds or for in-situ welding. Their easy ignition once the phase spacing is reduced below the micron scale, makes top-down methods like high energy ball milling, ideal to fabricate such reactive nanostructures. A major drawback of ball milling is the need of a sintering step to form bulk pieces of the reactive material. However, this is not possible, as the targeted reactions would already proceed. Therefore, we investigate the ability of high pressure torsion as an alternative process, capable to produce bulk nanocomposites from powder mixtures. Severe straining of powder mixtures with a composition of 50 wt% Ni and 50 wt% Al enables fabrication of self reactive bulk samples with microstructures similar to those obtained from ball milling or magnetron sputtering. Samples deformed at ambient temperature are highly reactive and can be ignited signifi cantly below the Al melting point, finally predominantly consisting of Al3Ni2 and Al3Ni, independent of the applied strain. Although the reaction proceeds first at the edge of the disk, the strain gradient present in the disks does not prevent reaction of the whole sample.COMETAustrian Federal MinistriesDepartment of Energy National Nuclear Security AdministrationERC Advanced Grant INTELHYBCOMET programERC-2013-ADG-340025DENA0002377Project No 859480DE-AC02-06CH1135

The Roles of Impurities and Surface Area on Thermal Stability and Oxidation Resistance of BN Nanoplatelets

This study considers the influence of purity and surface area on the thermal and oxidation properties of hexagonal boron nitride (h-BN) nanoplatelets, which represent crucial factors in hightemperature oxidizing environments. Three h-BN nanoplatelet-based materials, synthesized with different purity levels and surface areas (~3, ~56, and ~140 m2/g), were compared, including a commercial BN reference. All materials were systematically analyzed by various characterization techniques, including gas pycnometry, scanning electron microscopy, X-ray diffraction, Fouriertransform infrared radiation, X-ray photoelectron spectroscopy, gas sorption analysis, and thermal gravimetric analysis coupled with differential scanning calorimetry. Results indicated that the thermal stability and oxidation resistance of the synthesized materials were improved by up to ~13.5% (or by 120 ◦C) with an increase in purity. Furthermore, the reference material with its high purity and low surface area (~4 m2/g) showed superior performance, which was attributed to the minimized reactive sites for oxygen diffusion due to lower surface area availability and fewer possible defects, highlighting the critical roles of both sample purity and accessible surface area in h-BN thermooxidative stability. These findings highlight the importance of focusing on purity and surface area control in developing BN-based nanomaterials, offering a path to enhance their performance in extreme thermal and oxidative conditions

Boron nitride nanotubes versus carbon nanotubes: A thermal stability and oxidation behavior study

Program and book of abstracts / 2nd International Conference on Innovative Materials in Extreme Conditions i. e. (IMEC2024), 20-22 March 2024 Belgrade, Serbia

Effect of Pt nanoparticle decoration on the H2 storage performance of plasma-derived nanoporous graphene

A nanoporous and large surface area (∼800 m2/g) graphene-based material was produced by plasma treatment of natural flake graphite and was subsequently surface decorated with platinum (Pt) nano-sized particles via thermal reduction of a Pt precursor (chloroplatinic acid). The carbon-metal nanocomposite showed a ∼2 wt% loading of well-dispersed Pt nanoparticles (<2 nm) across its porous graphene surface, while neither a significant surface chemistry alteration nor a pore structure degradation was observed due to the Pt decoration procedure. The presence of Pt seems to slightly promote the hydrogen sorption behavior at room temperature with respect to the pure graphene, thus implying the rise of “weak” chemisorption phenomena, including a potential hydrogen “spillover” effect. The findings of this experimental study provide insights for the development of novel graphene-based nanocomposites for hydrogen storage applications at ambient conditions

Purity and surface area: Key factors on thermal stability and oxidation resistance of BN nanoplatelets

Program and book of abstracts / 2nd International Conference on Innovative Materials in Extreme Conditions i. e. (IMEC2024), 20-22 March 2024 Belgrade, Serbia

Development of Computational Tools for Noise Studies in the LHC

Noise can have a significant impact on the beam dynamics in the LHC, enhancing diffusion processes and leading to emittance blowup. In order to study the details of such effects with computer simulations, a new set of tools is being developed. In particular, a demonstrator GPU-based particle tracker has been built profiting from the technology provided by the NVRTC Cuda library. Its performances for short term beam dynamic simulations in presence of many macro particles are highly promising. In addition, the Numerical Analysis of Fundamental Frequencies (NAFF) algorithm has been thoroughly inspected. Several alternatives to its fundamental steps have been investigated in a modern C++ implementation. The method was also used to produce Frequency Maps and benchmark these tools with other simulations

Analysis on bunch-by-bunch beam losses at 6.5 TeV in the Large Hadron Collider

In 2018, a large fraction of the physics data taking at the Large Hadron Collider has been performed with a beam energy of 6.5 TeV, the nominal bunch spacing of 25 ns and beta functions at the high luminosity interaction points of 30 cm. In order to maximize the integrated luminosity, the crossing angles are gradually reduced as the beam intensity reduces due to luminosity burn-off. In these conditions the beam lifetime is visibly affected by collective effects and in particular by beam-beam interaction and electron cloud effects. By analysing the beam losses at a bunch-by-bunch level, it is possible to disentangle the contributions from different effects and to assess the impact on the losses of changes applied to the machine configuration