Manish Jugroot

Optimising the platinum–carbon bond in nitrogen-doped single-walled carbon nanotubes

The durability, high surface area and metallic properties demonstrated by single-walled carbon nanotubes (SWCNTs) show potential as a catalyst support. In this work, the effects of nitrogen doping of SWCNTs are examined using density functional theory. It will be shown that by adding nitrogen, the durability of a platinum catalyst, measured by the binding energy it has with the surface, increases with the number and proximity of N atoms to the carbon–platinum bond. A twofold increase in binding energy is measured and is due to the disruption that the N atoms cause locally in the surface at the C–Pt bond.

Investigation of a Dual Electrostatic Colloid Micropropulsion System for Space Applications

Electric propulsion is an advanced form of spacecraft propulsion with many advantages compared to chemical propulsion. It can be considered for operations such as stationkeeping, attitude control, and possibly de-orbiting of small satellites at end-of-life. An electrostatic colloid thruster is investigated in the present paper via numerical and experimental studies. The objective is to test the concept of a dual colloid system with a positively and a negatively charged beam thereby operating without the use of a neutralizer. Dual and multiplexed configurations are also investigated and a laboratory model has been designed and tested with the aid of simulation results. Both simulation and experimental results are assisting in the understanding of dual beam effects and the testing of doped propellants.

Biomimetic Soft Polymer Nanomaterials for Efficient Chemical Processes

Nanostructured soft materials combine structure and function to produce effects inspired by natural systems. Recent innovations in polymer science and supramolecular chemistry have led to the development of materials that can respond to and control their microenvironment, allowing them to increase the efficiency of chemical processes while decreasing their ecological impact. Size effects are profound at the nanoscale, allowing for a broad range of applications. This chapter features synthetic biomimetic nanosystems at different size regimes and match them with biological counterparts from tissues through cell walls to vesicles and proteins. The application of soft, bioinspired nanomaterials in fields ranging from medicine to sustainable energy represents a fundamental advancement in science and technology.

Plasma-based thrusters: Electrostatic and electromagnetic coupling

Summary form only given. Electric propulsion for spacecraft offers many advantages compared to other traditional counterparts such as chemical propulsion. Plasma-based propulsion devices can be useful for satellites for the purpose of station-keeping, attitude control, formation-flying and possibly end-of-life de-orbiting for space debris mitigation. There is a growing interest to have a propulsion system for small satellites (microsatellites and nanosatellites) as their mission capabilities can drastically be increased. Satellites with masses of a few kilograms approximately require only tens of micronewtons of thrust for station-keeping and attitude control, implying that electric propulsion could be an excellent candidate. There are three main types of electric propulsion: electrostatic, electromagnetic and electrothermal, each with its own advantages and characteristics [1,2] depending on the application and space mission. In the present work, the different types of thrusters will be presented with an aim to design a hybrid thruster coupling the advantages of the three modes of electric thrusters. The simulations will detail the plasma evolution within the thrusters and help optimize the governing parameters such as electric and magnetic field profiles.

Surface and volume effects in micro-scale plasma evolution

Micro-scale plasmas are extremely interesting due to the spectrum of applications potentially feasible for these small scale plasmas. Due to the small physical size and short temporal scales, simulations can provide complementary and insightful tools to help understand the underlying physical processes. The present paper discusses a numerical model coupling the plasma, metastable species and gas dynamics in atmospheric microcavities in helium at atmospheric pressure. The self-consistent and time-dependant model is described with emphasis on terms involved in the close coupling among species (plasma, metastable and gas) and the applied field – both electric and magnetic fields. The microplasmas are studied from an initial cloud and transients are particularly important in the evolution. Gas heating, neutral depletion initiation and electrohydrodynamic effects are observed, highlighting the interaction between neutral gas and plasma species in governing the microplasmas. The crucial effects of the applied magnetic field and secondary emission are discussed – and surface and volume effects are compared in terms of spatial and temporal evolutions of the plasma and gas dynamics in atmospheric microplasmas.

Study of an electrospray-based electric propulsion system for small satellites

Summary form only given. Electric propulsion is highly efficient for both deep-space and near-earth applications and it is an excellent candidate for small satellites due to its inherent small size and high specific impulse. A colloid electrostatic thruster for small spacecrafts is investigated in the present work. The study aims to gain an increased understanding of complex underlying physical processes. A simulation approach was previously used to investigate the beam trajectories and have helped to design a laboratory model of the electrospray-based micro-thruster which has been characterized experimentally1. Interestingly, simulations can offer insights into the flows within the electrospray and offer critical local information difficult to measure experimentally due to the small scales. Thus, an electrohydrodynamic modeling of the transition of a charged liquid interface into a cone is described via a coupled formalism. The governing factors are accessed in order to precisely predict the initiation of the electrospray as well as capture the cone-jet mode of a focused beam of droplets or ions. Furthermore, in order to build a matrix of multiple emitters for use in a nano-satellite, the phenomena governing the transition in the electrospray has to be clearly understood. The competing processes in the cone-jet mode essential for optimization of a large-scale micro-thruster are fully discussed and compared. Moreover, interesting mixed modes comprising charged droplets as well as ions are explored in order to increase thrust or specific impulse.