Mkhitar Hobosyan | University of Texas at San Antonio (original) (raw)

Papers by Mkhitar Hobosyan

Chemical Engineering Journal, 2011

In this work the feasibility of synthesizing MoSi2/Al cermet foam under the combustion mode was s... more In this work the feasibility of synthesizing MoSi2/Al cermet foam under the combustion mode was studied. A halogen containing organic polymer, namely, polytetrafluoroethylene (PTFE) was used as foaming agent. It was shown that the target product reached the maximum porosity, up to 70%, when amount of the foaming agent was 0.04mol. SEM analyses have shown there are two types of

Applied Physics Letters, 2017

Twisted laminar composite structures for high power and large-stroke actuators based on coiled Mu... more Twisted laminar composite structures for high power and large-stroke actuators based on coiled Multi Wall Carbon Nanotube (MWNT) composite yarns were crafted by integrating high-density Nanoenergetic Gas Generators (NGG) into carbon nanotube sheets. The linear actuation force, resulting from the pneumatic force caused by expanding gases confined within the pores of laminar structure and twisted carbon nanotube yarns, can be further amplified by increasing NGG loading and yarns twist density, as well as selecting NGG compositions with high energy density and largevolume gas generation. Moreover, the actuation force and power can be tuned by the surrounding environment, such as to increase the actuation by combustion in ambient air. A single 300-μm-diameter integrated MWNT/NGG coiled yarn produced 0.7 MPa stress and a contractile specific work power of up to 4.7 kW/kg while combustion front propagated along the yarn at velocity up to 10 m/s. Such powerful yarn actuators can also be operated in vacuum, enabling their potential use for deploying heavy loads in outer space, such as to unfold solar panels and solar sails.

Energy, Environment, and Sustainability, 2018

There is a growing interest in novel energetic materials called nano-energetic gas generators (NG... more There is a growing interest in novel energetic materials called nano-energetic gas generators (NGGs) which are potential alternatives to traditional energetic materials including pyrotechnics, propellants, primers, and solid rocket fuels. NGGs are formulations that utilize metal powders as a fuel and oxides or hydroxides as oxidizers that can rapidly release a large amount of heat and gaseous products to generate shock waves. The heat and pressure discharge, impact sensitivity, long-term stability, and other critical properties depend on the particle size and shape, as well as assembling procedure and intermixing degree between the components. The extremely high energy density and the ability to tune the dynamic properties of the energetic system makes NGGs ideal candidates to dilute or replace traditional energetic materials for emerging applications. In terms of energy density, performance, and controllability of dynamic properties, the energetic materials based on bismuth and iod...

Bulletin of the American Physical Society, 2011

The risk of bioterrorism events involving the intentional airborne release of contagious agents h... more The risk of bioterrorism events involving the intentional airborne release of contagious agents has led to development of new approaches for bio agent defeat technologies both indoors and outdoors. The spore-forming bacteria, in particular Bacillus anthracis is one of the biologic agents most likely to be used as a bio-weapon. Novel approaches to defeat harmful biological agents have generated a strong demand for new active materials, including nanostructured high density energetic composites. This report describes nanoenergetic gas generators (NGG) system that exhibit long term stability and superior release of biocidal substances for destruction of spore forming bacteria. By using nano-thermite reactions, with energy release up to 25 kJ/cc, based on I 2 O 5 /Al nanoparticles we intend to generate high quantity of vaporized iodine for spatial deposition onto harmful bacteria for their destruction. The study has shown that I 2 O 5 /Al nanosystem is extremely effective to sterilize potentially harmful biological agents in seconds.

Nanomechanics Science and Technology: An International Journal, 2015

Materials Chemistry and Physics

IEEE Nanotechnology Magazine

Propellants, Explosives, Pyrotechnics

We report the first study of gas generation and thermal wave behavior during the performance of a... more We report the first study of gas generation and thermal wave behavior during the performance of a novel nano-energetic system based on aluminum and bismuth hydroxide Al–Bi(OH) 3. Thermodynamic calculations demonstrate that this system is comparable to one of the most powerful known nano-thermite systems, Al–Bi 2 O 3 , in terms of energy capacity per initial charge mass, and may generate more than twice the gaseous products: 0.0087 mol g À1. Differential scanning calorimetry analysis shows that homogenization of the as-received powder using mechanical activation is an essential step to reduce the decomposition energy of bismuth hydroxide by 30%. This results in nano-thermite with higher pressure discharge abilities. The mechanical activation with energy of 450–750 kJ g À1 is enough to transform micro-meter sized particles to sub-micro and nano-sized particles. The resulting nano-thermite generated a significant pressure discharge with a value of up to 5.6 kPa m 3 g À1 .

Aluminum diboride was chosen as an initial reagent to obtain BN/AlN composites with high homogene... more Aluminum diboride was chosen as an initial reagent to obtain BN/AlN composites with high homogeneity. By comparing the specific surface area of products, it was established that this parameter can be increased (up to 10-24 m 2 /g) by increasing the amount of boron nitride. The gasifying compounds have essential influence on the formation of submicron particles in products. Even at their negligible amounts the specific surface area can increase by a factor of 2, and at higher amounts (close to the combustion limit) by 4 times. The maximum value for specific surface area (86 m 2 /g) was obtained for the 80%BN+20%AlN composite. It was established that it is impossible to obtain BN-B4C composite by direct interaction between elements (B, C and N2). Therefore another way was developed aimed at synthesizing BN-B4C composite under the activated combustion mode. Organic nitrogen containing compounds (ONCC) were used as sources for both the carbon and nitrogen.

MRS Proceedings, 2013

The dynamic features of Al 2 O 3 -polytetrafluoroethylene (PTFE) and Al -PTFE reactions in noniso... more The dynamic features of Al 2 O 3 -polytetrafluoroethylene (PTFE) and Al -PTFE reactions in nonisothermal conditions are presented. The Differential Scanning Calorimetry (DSC) and High-Speed Temperature Scanner (HSTS) were used to characterize the Al 2 O 3 /Al -PTFE reactions at different heating rates. The study shows that the HSTS instrument can give more information about the reaction mechanism and kinetics than the conventional DSC measurements. In this work we show that high heating rates may reveal exothermic reaction between Al 2 O 3 and PTFE that were previously unidentified. The PTFE can potentially remove the oxide layer from aluminum in the initial period of the reaction and increase the direct contact area between oxygen and aluminum, which increases the reaction velocity and improves the energy release abilities of the system. *

2012 12th IEEE International Conference on Nanotechnology (IEEE-NANO), 2012

The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.

Journal of Thermal Analysis and Calorimetry, 2014

Differential scanning calorimetry and a highspeed temperature scanner were used to characterize d... more Differential scanning calorimetry and a highspeed temperature scanner were used to characterize dynamic features of the reaction between polytetrafluoroethylene (PTFE) and Al 2 O 3 under heating rates ranging between 20 and 780°C min -1 . Exothermic reaction behavior between PTFE and Al 2 O 3 was observed at heating rates of 150°C min -1 and higher. Thermodynamic calculations predicted an adiabatic temperature of 1,425 K for the PTFE/Al 2 O 3 stoichiometric ratio. At lower heating rates, endothermic decomposition of PTFE dominated the interaction, where PTFE decomposes into gaseous products that escape the system without interacting with alumina. The enthalpy of the PTFE-Al 2 O 3 exothermic reaction was estimated to be -103 kJ mol -1 with activation energy of 21 kJ mol -1 . This study shows that, for energetic formulation of Al-PTFE, the Al 2 O 3 layer on the aluminum particles can exothermically react with PTFE, producing AlF 3 and carbon monoxide.

Nanoscale research letters, 2014

The specific energy of the existing lithium ion battery cells is limited because intercalation el... more The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source...

14th IEEE International Conference on Nanotechnology, 2014

International Journal of Self-Propagating High-Temperature Synthesis, 2011

A feasibility of combustion synthesis of lithium cobaltate powders using oxide sources was inves ... more A feasibility of combustion synthesis of lithium cobaltate powders using oxide sources was inves tigated. Cobalt oxide Co 3 O 4 and lithium carbonate Li 2 CO 3 were used as starting reactants. Two different oxi dizers were explored: (i) ammonia nitrate NH 4 NO 3 and (ii) lithium nitrate LiNO 3 . Some organic reducers (ORs)-such as CH polymers, melamine, urotropine, etc.-were used as a fuel. Investigated was the effect of green composition/density and inert gas pressure on combustion parameters (burning velocity and com bustion temperature) and product micro structure/composition. Best results were obtained for LiNO 3 -Co 3 O 4 -OR blends. Relative green density ρ was found to have a crucial effect: good results might be obtained only for ρ > 65%. XRD data testified that the combustion products obtained in optimized conditions con tained pure lithium cobaltate LiCoO 2 . According to SEM data, the obtained powders had a mean particle size of 20 μm.