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The primary focus of this work is the study of different materials at extreme environment. These extreme environments include Atomic Oxygen (AO) impacts, ice cluster impacts, noble gas ions irradiation and electron irradiation on different materials. AO is the most abundant element in the low Earth orbit (LEO). It is the result of the dissociation of molecular oxygen by ultraviolet radiation from the sun. In the LEO, AO collides with the materials used on spacecraft surfaces and causes degradation of these materials. The degradation of the materials on the surface of spacecraft at LEO has been a significant problem for a long time. Kapton polyimide, polyhedral oligomeric silsesquioxane (POSS), silica, and Teflon are the materials used in spacecraft industry. Degradation caused by AO impact is an important issue in these materials applications on spacecraft surface. To investigate the surface chemistry of these materials in exposure to space AO, a computational chemical evaluation of the Kapton polyimide, POSS, amorphous silica, and Teflon was performed in separate simulations under similar conditions. For performing these simulations, the ReaxFF reactive force-field program was used, which provides the computational tool required to perform molecular dynamics (MD) simulations on system sizes sufficiently large to describe the full chemistry of the reactions. Using these simulations, the effects of AO impact on different materials and the role of impact energies, the content of material, and the temperature of material on their behavior are studied. The ReaxFF results indicate that Kapton is less resistant than Teflon against AO damage. These results are in good agreement with the MISSE experimental results. In the MISSE projects, the mass loss of different materials is studied during space missions. These simulations indicate that the amorphous silica shows the highest stability among these materials before the start of the highly exothermic silicon oxidation. We have verified that adding silicon to the bulk of the Kapton structure enhances the stability of the Kapton against AO impact. Our canonical MD simulations demonstrate that an increase in the heat transfer in materials during AO impact can provide a considerable decrease in the disintegration of the material. This effect is especially relevant in silica AO collision. During aircraft or spacecraft missions, ice accumulates on different parts of their surface. We studied the dynamics of the collisions between amorphous silica structures and amorphous and crystal ice clusters with impact velocities of 1, 4 and 7 km/s using the ReaxFF reactive molecular dynamics simulation method. The 1km/s and lower impact velocities can happen during aircraft missions and the impact velocities higher than 1 km/s can happen during spacecraft missions. The initial ice clusters consist of 150 water molecules for the amorphous ice cluster and 128 water molecules for the crystal ice cluster. The ice clusters are collided on the surface of amorphous fully oxidized and suboxide silica. These simulations show that at 1 km/s impact velocities, all the ice clusters accumulate on the surface and at 4 km/s and 7 km/s impact velocities, some of the ice cluster molecules bounce back from the surface. We also studied the effect of the second ice cluster impacts on the surfaces which are fully covered with ice, in particular their mass loss/accumulation. These studies show that at 1 km/s impacts, the entire ice cluster accumulates on the silica surface. At 7 km/s impact velocity some ice molecules, which are part of the ice layers accreted on the silica surface, will separate from the ice layers on the surface. At 4 km/s ice cluster impact, ice accumulation is observed for the crystal ice cluster impacts and ice separation is observed for the amorphous ice impacts. Observing the temperatures of the ice clusters during the collisions indicates that the possibility of electron excitation at impact velocities less than 10 km/s is minimal and ReaxFF reactive molecular dynamics simulation can predict the chemistry of these hypervelocity impacts.However, at impact velocities close to 10 km/s the average temperature of the impacting ice clusters increase to about 2000K, with individual molecules occasionally reaching temperatures of over 8000K and thus it will be prudent to consider the concept of electron excitation at these higher impact velocities, which goes beyond the current ReaxFF ability. An important parameter affecting the ability to remove this ice from the surface is the heat transfer characteristics of the accumulated ice. The ice heat transfer is related to the process of ice formation and its density and internal structure. We investigated the effects of ice and silica structure and the ice cluster attachment mechanism to the silica surface on the thermal conductivity (TC) of the attached ice cluster using the ReaxFF reactive molecular dynamics method. The purpose of this study is to investigate the thermal transport in amorphous and crystalline ice after deposition on the silica surfaces. A dual thermostat method was applied for the calculation of TC values. The validity of this method was verified by comparing the calculated values of TC for crystal and amorphous ice with available experimental values. Our calculations show that the TC value for both crystal and amorphous ice drop after deposition on the silica surfaces. This decrease in the TC is more significant for the ice deposition on suboxide silica surfaces. Furthermore, crystal ice shows higher TC values than amorphous ice after accumulation. However, when crystal ice impacts on the silica surface at 1 km/s impact speed, the crystalline shape of the ice cluster is lost to a considerable level and the TC values obtained for the ice clusters in such cases are closer to amorphous ice TC values. We observed a decrease in the TC values when ionic species are added inside the ice clusters. We studied Kr noble gas ions irradiations on graphene, and the subsequent annealing of the irradiated graphene. Different types of defects were generated in graphene after noble gas ion irradiations. Kr irradiation mostly caused mono vacancy defects in graphene while light noble v gas ions can mostly generate Stone-Wales defects in graphene. The irradiated graphene was annealed between 300K and 2000K and the reconstruction of the defects was studied. In order to study the electron beam irradiation on Kapton using molecular simulation, electron beams irradiation at random positions of Kapton are modeled. For changing the amount of energy transfer to Kapton, each electron beam is irradiated for 1fs or 2fs. The temperature evolution and chemical composition changes in Kapton during and after electron beam irradiation was studied. The changes in chemical composition of Kapton are compared to the experimental results. This study shows that the time of each electron beam irradiation has considerable effect on the amount of energy transferred to Kapton. Kapton decomposition takes place at different Kapton temperatures under different electron irradiation conditions. At the start of decomposition, small molecules separate from the surface and with continuing electron irradiation, larger molecules start to separate from the surface. As our simulations demonstrate, ReaxFF can provide a cost-effective screening tool for future material optimization for applications in extreme environments.
This is an open access book.2023 5th International Conference on Civil Engineering, Environment Resources and Energy Materials (CCESEM 2023), will be held during October 27–29, 2023 in Xiamen, China. The primary goal of the conference is to promote research and developmental activities in Civil Engineering, Environment Resources and Energy Materials and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an ideal platform for people to share views and experiences in Civil Engineering, Environment Resources and Energy Materials and related areas. A key aspect of this conference is the strong mixture of academia and industry. This allows for the free exchange of ideas and challenges faced by these two key stakeholders and encourage future collaboration between members of these groups.
The primary focus of this work was to study the chemistry and dynamics of hyperthermal collisions of oxygen atoms with carbon based materials of the kind witnessed in the Low Earth Orbit (LEO) environment and their pyrolysis through atomistic simulations using the ReaxFF reactive force field and to develop ReaxFF potentials for such applications. In particular, ReaxFF was used to study the oxidative erosion of graphene, graphite and diamond subjected to collisions with energetic oxygen atoms at elevated surface temperatures. Prior to these simulations, the ReaxFF C/H/O potential was validated against quantum chemical (QC) data for the energetics associated with the loss of a CO2 molecule from a model graphitic system and for various other chemical reactions occurring during the collision of a hyperthermal oxygen atom with a pristine and defective graphene sheet and a diamond slab. ReaxFF based simulations suggested that the breakup of a graphene sheet and graphite structure upon hyperthermal oxygen atom impact could be divided into distinct regimes. Graphene erosion proceeded through the formation of epoxides on the surface followed by the creation and growth of vacancy defects while the breakup of graphite occurred through the formation of epoxides on the top layer, creation and growth of vacancy defects on the top layer followed by epoxide formation on the bottom layer, creation of defects and their growth on the bottom layer. As such the breakup of graphite was observed to be a layer by layer event with the rate of growth of defects much larger along the basal plane directions compared to the axial direction. With increase in temperature, the rate of mass loss from graphite was observed to increase. While the impact of the oxygen atoms occurred at hyperthermal energies, the chemical reactions leading to mass loss from graphite were thermal in nature. Furthermore, molecular dynamics simulations of carbon loss from graphite at various surface temperatures upon hyperthermal oxygen atom collisions were used to obtain an Arrhenius type rate law for the carbon atom loss rate under such conditions. Further, the direction dependent etching properties of graphite exposed to hypothermal atomic oxygen collisions were also investigated. These simulations revealed that graphite basal planes are poorly resistant to energetic oxygen atom etching while the armchair and zigzag edge surfaces are an order of magnitude more resistant to energetic oxygen atom etching. To compare the response of diamond surfaces with graphite, energetic oxygen atom etching of low index diamond surfaces namely, diamond (100), diamond (111) and diamond (110) were carried out at various surface temperatures using the ReaxFF C/H/O potential. ReaxFF simulations on small oxygen terminated diamond slabs indicated that a variety of functional groups such as ethers, peroxides, oxy radicals and dioxetanes can form on the surface, in agreement with earlier experiments and first principles based calculations. Successive oxygen collisions on larger reconstructed diamond surfaces showed that all the low index surfaces can be etched by hyperthermal atomic oxygen with diamond (100) showing the lowest etching rate and diamond (110) presenting the largest etching rate. The erosion yield of these surfaces is in good agreement with experimental results. The simulations performed here have been used to obtain an Arrhenius type rate law for the mass loss from these surfaces under such conditions. Although diamond surfaces can be etched by energetic oxygen atoms, they were found to be more than two orders of magnitude more resistant to oxidative erosion as compared to graphite basal planes. These simulations suggest that diamond thin films are promising materials for the surface of space crafts exposed to LEO conditions and in general, the ability of ReaxFF to be used as an effective tool to screen or characterize materials for applications in extreme environments.In order to study the interaction of hyperthermal atomic oxygen with silica surfaces, a widely used material for the thermal protection system of high speed aircrafts, the ReaxFFSiO potential was extended to describe oxygen -- silica gas surface interactions by harvesting model clusters representative of a reconstructed (001) silica surface and surface defects on silica, obtaining density functional theory (DFT) based potential energy curves for the approach of an atomic and molecular oxygen to these clusters followed by re-parametrization of the ReaxFFSiO potential against this data. The new potential, ReaxFF-SiO/GSI, can be employed for accurate molecular dynamics simulations of oxygen -- silica gas surface interactions.The thermal fragmentation of a large fullerene molecule was studied through molecular dynamics simulations in order to understand the mechanisms underlying the pyrolysis of carbon based materials. While the performance of the ReaxFF C/H/O potential for the chemistry of graphite and diamond oxidation was very good, its description of the mechanical deformation of carbon condensed phases was not satisfactory. Thus ReaxFF C/H/O was re-parameterized against DFT data for the equation of state of graphite, diamond, the formation energies of defects in graphene and amorphous carbon phases from fullerenes. The newly developed ReaxFF potential (ReaxFFC-2013) was used in the molecular dynamics simulation of the thermal fragmentation of a C180 molecule. The simulations indicated that the thermal fragmentation of these giant fullerenes can be classified into two distinct regimes -- an exponential regime followed by a linear regime. In the initial exponential regime, the molecule shrinks in size but retains the cage like structure while in the final linear regime, the cage opens up into an amorphous phase, resulting in an acceleration of the decay process. Arrhenius parameters for the decay of the molecule in both the regimes were obtained by carrying out simulations at various temperatures. While the decay of the molecule occurred primarily via the loss of C2 units, with increase in temperature, the probability of loss of larger fragments was found to increase. The newly developed potential along with the methods used in this study can readily be extended towards the full computational chemical modeling of the high temperature erosion of graphitic rocket nozzles and ablation of carbon based spacecraft materials during atmospheric reentry. Finally, to explore the possibility of developing carbon based materials resistant to oxidative erosion through the impact of hyperthermal oxygen atoms, oxygen interaction with boron doped graphene was considered. Model clusters representative of boron doped graphene were used to obtain DFT based potential energy curves for the approach of an atomic oxygen to these clusters. This dataset can now be used to parameterize ReaxFF to describe oxygen -- boron doped graphene gas surface interactions.The research work reported in this dissertation lays out a clear strategy to develop a ReaxFF reactive potential and to apply it to study the oxidative degradation and pyrolysis of materials subjected to extreme conditions. Further it provides a straightforward way to extract Arrhenius type parameters from molecular dynamics simulations for the erosion of materials under such conditions. These parameters can be used directly in mesoscale simulation schemes such as Direct Simulation Monte Carlo (DSMC), thereby providing the vital link between atomic scale and macro scale in bottoms up materials design approach.
Chemistry at Extreme Conditions covers those chemical processes that occur in the pressure regime of 0.5–200 GPa and temperature range of 500–5000 K and includes such varied phenomena as comet collisions, synthesis of super-hard materials, detonation and combustion of energetic materials, and organic conversions in the interior of planets. The book provides an insight into this active and exciting field of research. Written by top researchers in the field, the book covers state of the art experimental advances in high-pressure technology, from shock physics to laser-heating techniques to study the nature of the chemical bond in transient processes. The chapters have been conventionally organised into four broad themes of applications: biological and bioinorganic systems; Experimental works on the transformations in small molecular systems; Theoretical methods and computational modeling of shock-compressed materials; and experimental and computational approaches in energetic materials research. * Extremely practical book containing up-to-date research in high-pressure science * Includes chapters on recent advances in computer modelling* Review articles can be used as reference guide
This book investigates the fundamental properties and response of materials in extreme environments such as static and dynamic high pressure, high strain and high strain-rates, high radiation and electromagnetic fields, high and low temperatures, corrosive conditions, environments causing embrittlement, and environments containing atomic oxygen. This is an extremely active and vibrant field of research, in particular because it is now possible to create laboratory conditions similar in pressure, temperature and radiation to those found in planetary interiors and in space. In addition, advanced simulation methods, coupled with high-performance computing platforms, now afford predictions - on a first-principles basis - of the properties of materials in extreme environments. Scientists from a broad spectrum of fields are represented, including space science, planetary science, high-pressure research, shock physics, ultrafast science, and energetic materials research.
High-temperature materials is a fast-moving research area with numerous practical applications. Materials that can withstand extremely high temperatures and extreme environments are generating considerable attention worldwide; however, designing materials that have low densities, elevated melting temperatures, oxidation resistance, creep resistance, and intrinsic toughness encompass some of the most challenging problems in materials science. The current search for high-temperature materials is largely based on traditional, trial-and-error experimental methods which are costly and time-consuming. An effective way to accelerate research in this field is to use recent advances in materials simulations and high performance computing and communications (HPCC) to guide experiments. This synergy between experiment and advanced materials modeling will significantly enhance the synthesis of novel high-temperature materials. This volume collects recent work from experimental and computational scientists on high-temperature materials and emphasizes the potential for collaboration. It features state-of-the-art materials modeling and recent experimental developments in high-temperature materials. Topics include fundamental phenomena and properties; measurements and modeling of interfacial phenomena, stresses, growth of defects, strain, and fracture; and electronic structure and molecular dynamics.
A student-oriented introduction to understanding mechanisms at the atomistic level controlling macroscopic materials phenomena through molecular dynamics simulations. Machine-learning-based computation in materials innovation, performance optimization, and sustainability offers exciting opportunities at the mesoscale research frontier. Molecular Mechanisms in Materials presents research findings and insights about material behavior at the molecular level and its impact on macroscopic properties. The book’s fifteen essays represent author Sidney Yip’s work in atomistic modeling and materials simulation over more than five decades. The phenomena are grouped into five basic types: fluctuations in simple fluids, crystal melting, plasticity and fracture, glassy relaxations, and amorphous rheology, all focused on molecular mechanisms in base materials. The organizing principle of Molecular Mechanisms in Materials is multiscale modeling and simulation, where conceptual models and simulation techniques are linked across the micro-to-macro length and time scales to control the outcome of specific materials processes. Each essay addresses a specific standalone topic of materials phenomena while also recognizing the larger context of materials science and technology. Individual case studies serve both as standalone essays and companion pieces to each other. Indeed, the global transformation of science and technology is well underway: in his epilogue, Yip discusses the potential of artificial intelligence and machine learning to enhance future materials for societal benefits in the face of global challenges such as climate change, energy sustainability, infrastructure renewal, and nuclear arms control.
Superseding Gardiner's "Combustion Chemistry", this is an updated, comprehensive coverage of those aspects of combustion chemistry relevant to gas-phase combustion of hydrocarbons. The book includes an extended discussion of air pollutant chemistry and aspects of combustion, and reviews elementary reactions of nitrogen, sulfur and chlorine compounds that are relevant to combustion. Methods of combustion modeling and rate coefficient estimation are presented, as well as access to databases for combustion thermochemistry and modeling.
This book presents recently developed computational approaches for the study of reactive materials under extreme physical and thermodynamic conditions. It delves into cutting edge developments in simulation methods for reactive materials, including quantum calculations spanning nanometer length scales and picosecond timescales, to reactive force fields, coarse-grained approaches, and machine learning methods spanning microns and nanoseconds and beyond. These methods are discussed in the context of a broad range of fields, including prebiotic chemistry in impacting comets, studies of planetary interiors, high pressure synthesis of new compounds, and detonations of energetic materials. The book presents a pedagogical approach for these state-of-the-art approaches, compiled into a single source for the first time. Ultimately, the volume aims to make valuable research tools accessible to experimentalists and theoreticians alike for any number of scientific efforts, spanning many different types of compounds and reactive conditions.
Molecular Modeling of the Sensitivities of Energetic Materials, Volume 22 introduces experimental aspects, explores the relationships between sensitivity, molecular structure and crystal structure, discusses insights from numerical simulations, and highlights applications of these approaches to the design of new materials. Providing practical guidelines for implementing predictive models and their application to the search for new compounds, this book is an authoritative guide to an exciting field of research that warrants a computer-aided approach for the investigation and design of safe and powerful explosives or propellants. Much recent effort has been put into modeling sensitivities, with most work focusing on impact sensitivity and leading to a lot of experimental data in this area. Models must therefore be developed to allow evaluation of significant properties from the structure of constitutive molecules. Highlights a range of approaches for computational simulation and the importance of combining them to accurately understand or estimate different parameters Provides an overview of experimental findings and knowledge in a quick and accessible format Presents guidelines to implement sensitivity models using open-source python-related software, thus supporting easy implementation of flexible models and allowing fast assessment of hypotheses