노화 및 열화학적 특성 변화가 금속 기반 고에너지 물질의 화학 반응 역학에 미치는 영향에 대한 실험적 연구

학위논문(박사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2023. 2. 여재익.This thesis has conducted an in-depth study on aging of the metal-based energetic materials and identification of the fundamental cause of thermal runaway of the energy storage system (ESS). For the aging-related research, the energetic materials composed of titanium, zirconium, tungsten, and magnesium respectively were utilized while for the ESS research, the latent thermal energy storage (TES) materials and lithium-ion batteries (LIB) were adopted. The current study has enabled the expansion of their effective utilization via various experimental techniques. From conducted aging research, it was discovered the general aging effects on the chemical compositions of the energetic materials such as pre-oxidation of metals and a priori decomposition of oxidizer. Also, hygrothermal aging effects on the chemical reaction kinetics and the aging mechanism were described for the first time. For the ESS-related research, compatibility between the phase change materials (PCM) and the heat transfer fluids (HTF) was confirmed, and it was first suggested that a thermal reaction analogous to gunpowder can occur under a certain condition, resulting in thermal runaway. In addition, it was revealed that when high-nickel LIBs were heated to 50℃ during charging, the exothermic reaction between the anode materials and the electrolyte can act as a trigger reaction for thermal runaway. Aging Analysis on Titanium-based Energetic Materials: Titanium Hydride Potassium Perchlorate (THPP) Titanium hydride potassium perchlorate (THPP), which is one of the most commonly utilized pyrotechnic initiators, can fail or deviate from the desired performance when subjected to aging. The aging process is known to change its composition as well as its thermochemical kinetics; however, the variation in the performance of THPP regarding its combustion behavior has not been addressed. This experimental thesis reports new correlations between the ignition and combustion characteristics of THPP. A thermal analysis, along with morphological observations, conducted on aged samples revealed that aging causes progressive oxidation of the fuels and subsequent decomposition of the oxidants. The reaction kinetics extracted using Friedman isoconversional method showed a decrease in the activation energy due to thermal aging while the opposite was noted under hygrothermal aging conditions. As a result, increased activation energy limited the range of ignition temperature and decreased the reactivity, thereby both the ignition delay time and burn time were extended. Such altered characteristics by aging could lead to inconsistent performance of the pyrotechnic initiators. Aging Analysis on Zirconium-based Energetic Materials: Zirconium Potassium Perchlorate (ZPP) Aging of pyrotechnic substances, primarily fuel oxidization, can cause changes in composition that degrade their performance. This study investigates the effect of aging on zirconium potassium perchlorate (ZPP), a widely used NASA standard initiator. Although prior studies have investigated the effects of accelerated aging on ZPP, this is the first to conduct kinetic analyses at different relative humidity (RH) levels. Here, both thermal and kinetic analyses are conducted for a variety of hygrothermal aging cases in order to replicate the natural aging process. X-ray photoelectron spectroscopy (XPS) results reveal that oxidant levels drop and zirconium dioxide levels rise as ZPP ages. Lower heats of reaction and increases in activation energy were also observed under the RH conditions. Calculations using vant Hoff equation indicate that moisture shortened the lifespan of the unaged ZPP up to about 85% under extreme RH conditions, while significantly deteriorating the heat of reaction, and sensitivity, thus increasing the risk of a misfire. Aging Analysis on Tungsten-based Energetic Materials: Tungsten Pyrotechnic Delay Mixtures Although exact predictions of the performance of aged pyrotechnic compositions intended to produce non-detonative self-sustaining exothermic chemical reactions remain unsolved, progress has been made to determine the reaction kinetics of aging compositions. The present study investigates the key factors that govern the reaction kinetics of hygrothermally aged mixtures that utilize metal powders of tungsten (W) as fuels and potassium perchlorate (KClO4) as a common oxidizer. It is shown that Gaussian distribution of activation energy for aged mixtures can be correlated to the thickness of the oxide layer on the metal particle as the mean value and the number of intermediate processes of reaction as the standard deviation. Here, the mean value of activation energy tended to increase in proportion to the oxide thickness as the oxide layer obstructs the reaction between metal fuels and oxidizer. Meanwhile, the changes in the standard deviation are directly correlated to the electronegativity between metal and oxygen. In other words, the metals with low percent ionic characters to the oxygen can give rise to decreased standard deviation as they can strongly combine with oxygen having a higher covalent bond, which then reduces the intermediate steps of a chemical reaction. Therefore, the key factors viz. the oxide thickness and the electronegativity of the metal component are shown responsible for defining the chemical reaction kinetics of the aging pyrotechnic compositions. Aging Analysis on Magnesium Metal Particles as a Renewable Energy Carrier Magnesium is regarded as one of the promising metal energy carriers because it contains a considerable energy density comparable to fossil fuels. Also, the element is nontoxic and abundant on earth. With the advantages, Mg has been utilized for various energy-related fields such as the battery cathode, additives in propellants, pyrotechnics, hydrogen carriers, etc. The most appreciable point of Mg particles is that they can release intense heat energy via an oxidation process that never produces any carbon dioxide. The oxidation process of Mg, however, proceeds through very complex procedures as the element is known to be very reactive to moisture as well as oxygen. The analysis of chemical kinetics for Mg oxidation has been studied and it was found that the chemical reaction kinetics of Mg particles are highly dependent on morphological properties such as particle size and shape. The current study newly found that hygrothermal aging of Mg particles can give rise to severe changes in the shape of particles by agglomeration. In addition, the aging products were dependent on the aging duration: Mg(OH)2 (short-term aging) and MgO (long-term aging). The accompanied aging effects on Mg particles finally appeared as changed reaction kinetics. Thermal aging led to 55% decrease in activation energy and hygrothermal aging created additional intermediate sub-reactions involving products of pre-oxidation such as Mg(OH)2, H2O, and H2. Thermal Runaway Reaction: Thermal Runaway Mechanism of a Thermal Energy Storage System based on KNO3/NaNO3/Graphite Exposed to a Heat Transfer Fluid An application of latent-type thermal energy storage (TES) system and its issues associated with the safe operation for TES composite materials (i.e., solar salts (KNO3/NaNO3) and expanded graphite (EG) are investigated. This work is aimed to present the compatibility of various compositions of TES materials with a HTF to provide a guideline for safe and reliable system usage. The thermochemical characteristics and chemical kinetic mechanism for HTF-diluted TES samples were measured using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). In addition, additional numerical analysis for validation of the constructed reaction kinetics was provided. Amongst the amount of HTF dilutions, 20 wt. % HTF diluted case showed the strongest exothermic runaway reaction. For instance, with a decrease in the onset temperature, the time to reach runaway was reduced, while the change in the heat of reaction was not significant. The numerical simulations calculated based on the results of chemical reaction kinetics revealed that the reaction runway characteristics of HTF-diluted TES materials show a similar detonative behavior as of gunpowder. Moreover, the function of HTF in TES system appeared to be identical to that of sulfur in gunpower as its specific percent composition was responsible for accelerating an exothermic chemical reaction. Thermal Runaway Reaction: The Fundamental Cause of Thermal Runaway of High-nickel/silicon-graphite Lithium-ion Batteries During Charging Recently, the global Lithium (Li)-ion battery market has been focusing on improving energy density by increasing the nickel (Ni) content in the cathode material. High-nickel battery indicates a Li-ion battery in which the Ni content in the cathode active materials is increased to 70-90%, and has strong points such as an enhanced energy density and lightweight. However, Ni metals are highly reactive to oxygen and other solvents, so they can give rise to thermal runaway when the battery is overheated, increasing the risk of an explosion. Also, considerable cases of fire accidents in electric vehicles using Li-ion batteries have been reported during or after the charging process lately. To identify the fundamental cause of the unexpected exothermic events while charging of electric vehicles (EV), the current study has carried out the thermal analysis in detail to high-nickel LIBs. The combinations of five different states of charge (0%, 25%, 50%, 75%, and 100%) and mixtures of the battery components (i.e., anode, cathode, anode+electrolyte, cathode +electrolyte, anode+cathode+electrolyrte+separator, etc.) were employed in the DSC experiments. Comprehensively, it was confirmed that when the electrolyte coexists with the active materials of the cathode and the anode, the exothermic characteristics were remarkably intensified. Meanwhile, the solid electrolyte interface (SEI) layer decomposition from the anode materials and thermal reactions with the electrolyte occurred at around 50℃. The corresponding reaction can trigger a breakdown of the structure of the cathode materials which can release substantial heat of enthalpy. Eventually, the reaction can develop into a thermal runaway reaction by leading to the separator collapse and the internal short circuit in the battery cells after all.본 논문은 다양한 금속 물질을 바탕으로 하는 고에너지 물질의 노화와 더불어 에너지저장물질의 열폭주 현상 원인 파악에 대한 심도있는 연구를 진행하였습니다. 우선, 노화관련 연구의 경우 티타늄, 지르코늄, 텅스텐, 마그네슘과 같이 다양한 금속 원료를 포함하는 고에너지 물질을 활용하였으며, 에너지저장물질의 경우 가정 및 산업환경에서 보편적으로 사용되는 잠열축열재와 리튬이온배터리에 집중하여 다양한 실험적 기법을 적용시켜 연구를 확장시켰습니다. 노화 연구를 통해 금속의 산화와 산화제의 사전분해라는 공통적인 노화 효과를 발견하였으며, 이를 바탕으로 수분 및 열이 각각의 고에너지 물질의 연소과정에 있어서 화학 반응 역학에 미치는 효과와 노화 메커니즘을 최초로 제공하였습니다. 그리고 에너지 저장물질의 경우 잠열축열재 시스템내 상변화물질과 열매유간의 호환성을 열분석 바탕의 실험을 통해 최초로 파악하였습니다. 그 결과, 특정 조건에서 축열재가 화약의 열폭주와 유사한 반응을 발현할 수 있음을 최초로 제시하였습니다. 또한, 하이니켈 리튬이온배터리의 경우 충전 중에 배터리 셀 내부가 약 50℃의 온도상승이 나타나게 되면, 음극재와 전해액간의 발열 반응이 열폭주의 촉발반응으로 작용할 수 있음을 파악하였습니다.Chapter 1. Introduction 1 1.1 Study Background 1 1.2 Purpose of Research 3 Chapter 2. Aging Analysis on Ti-based Energetic Materials 8 2.1 Study Background 8 2.2 Utilized Materials and Experimental Setup 10 2.3 Results 14 2.4 Discussion 31 Chapter 3. Aging Analysis on Zr-based Energetic Materials 34 3.1 Study Background 34 3.2 Utilized Materials and Experimental Setup 36 3.3 Results 41 3.4 Discussion 57 Chapter 4. Aging Analysis on W-based Energetic Materials 59 4.1 Study Background 59 4.2 Utilized Materials and Experimental Setup 62 4.3 Results 67 4.4 Discussion 97 Chapter 5. Aging Analysis on Magnesium Metal Particles as a Renewable Energy Carrier 99 5.1 Study Background 99 5.2 Utilized Materials and Experimental Setup 102 5.3 Results 106 5.4 Discussion 122 5.5 A Comprehensive Summary: Aging of Metal-based Energetic Materials (Ti, Zr, W, and Mg) 124 Chapter 6. Thermal Runaway Mechanism of a Thermal Energy Storage System Based on KNO3/NaNO3/Graphite Exposed to a Heat Transfer Fluid 131 6.1 Study Background 131 6.2 Utilized Materials and Experimental Setup 135 6.3 Numerical Formulation for Simulation of Thermochemical Reaction 138 6.4 Results 141 6.5 Discussion 162 Chapter 7. The Fundamental Cause of Thermal Runaway of High-nickel/silicon-graphite Lithium-ion Batteries during the Charging 165 7.1 Study Background 165 7.2 Reported Accidents with the Lithium-ion Battery Failure during Charging 169 7.3 Utilized Materials and Experimental Setup 171 7.4 Results 175 7.5 Discussion 192 Chapter 8. Conclusion 193 Bibliography 199 Abstract in Korean 215박

Thermography to assess grapevine status and traits opportunities and limitations in crop monitoring and phenotyping – a review

Mestrado em Engenharia de Viticultura e Enologia (Double degree) / Instituto Superior de Agronomia. Universidade de Lisboa / Faculdade de Ciências. Universidade do PortoClimate change and the increasing water shortage pose increasing challenges to agriculture and viticulture, especially in typically dry and hot areas such as the Mediterranean and demand for solutions to use water resources more effectively. For this reason, new tools are needed to precisely monitor water stress in crops such as grapevine in order to save irrigation water, while guaranteeing yield. Imaging technologies and remote sensing tools are becoming more common in agriculture and plant/crop science research namely to perform phenotyping/selection or for crop stress monitoring purposes. Thermography emerged as important tool for the industry and agriculture. It allows detection of the emitted infrared thermal radiation and conversion of infrared radiation into temperature distribution maps. Considering that leaf temperature is a feasible indicator of stress and/or stomatal behavior, thermography showed to be capable to support characterization of novel genotypes and/or monitor crop’s stress. However, there are still limitations in the use of the technique that need to be minimized such as the accuracy of thermal data due to variable weather conditions, limitations due to the high costs of the equipment/platforms and limitations related to image analysis and processing to extract meaningful thermal data. This work revises the role of remote sensing and imaging in modern viticulture as well as the advantages and disadvantages of thermography and future developments, focusing on viticultureN/

Power Consumption Analysis, Measurement, Management, and Issues:A State-of-the-Art Review of Smartphone Battery and Energy Usage

The advancement and popularity of smartphones have made it an essential and all-purpose device. But lack of advancement in battery technology has held back its optimum potential. Therefore, considering its scarcity, optimal use and efficient management of energy are crucial in a smartphone. For that, a fair understanding of a smartphone's energy consumption factors is necessary for both users and device manufacturers, along with other stakeholders in the smartphone ecosystem. It is important to assess how much of the device's energy is consumed by which components and under what circumstances. This paper provides a generalized, but detailed analysis of the power consumption causes (internal and external) of a smartphone and also offers suggestive measures to minimize the consumption for each factor. The main contribution of this paper is four comprehensive literature reviews on: 1) smartphone's power consumption assessment and estimation (including power consumption analysis and modelling); 2) power consumption management for smartphones (including energy-saving methods and techniques); 3) state-of-the-art of the research and commercial developments of smartphone batteries (including alternative power sources); and 4) mitigating the hazardous issues of smartphones' batteries (with a details explanation of the issues). The research works are further subcategorized based on different research and solution approaches. A good number of recent empirical research works are considered for this comprehensive review, and each of them is succinctly analysed and discussed

Advanced Technologies for Biomass

The use of biomass and organic waste material as a primary resource for the production of fuels, chemicals, and electric power is of growing significance in light of the environmental issues associated with the use of fossil fuels. For this reason, it is vital that new and more efficient technologies for the conversion of biomass are investigated and developed. Today, various advanced methods can be used for the conversion of biomass. These methods are broadly classified into thermochemical conversion, biochemical conversion, and electrochemical conversion. This book collects papers that consider various aspects of sustainability in the conversion of biomass into valuable products, covering all the technical stages from biomass production to residue management. In particular, it focuses on experimental and simulation studies aiming to investigate new processes and technologies on the industrial, pilot, and bench scales

2013 Oklahoma Research Day Full Program

This document contains all abstracts from the 2013 Oklahoma Research Day held at the University of Central Oklahoma

PP/clay nanocomposites: compounding and thin-wall injection moulding

This research investigates formulation, compounding and thin-wall injection moulding of Polypropylene/clay nanocomposites (PPCNs) prepared using conventional melt-state processes. An independent study on single screw extrusion dynamics using Design of Experiments (DoE) was performed first. Then the optimum formulation of PPCNs and compounding conditions were determined using this strategy. The outcomes from the DoE study were then applied to produce PPCN compounds for the subsequent study of thin-wall injection moulding, for which a novel four-cavity injection moulding system was designed using CAD software and a new moulding tool was constructed based upon this design. Subsequently, the effects of moulding conditions, nanoclay concentration and wall thickness on the injection moulded PPCN parts were investigated. Moreover, simulation of the injection moulding process was carried out to compare the predicted performance with that obtained in practice by measurement of real-time data using an in-cavity pressure sensor. For the selected materials, the optimum formulation is 4 wt% organoclay (DK4), 4 wt% compatibiliser (Polybond 3200, PPgMA) and 1.5 wt% co-intercalant (erucamide), as the maximum interlayer spacing of clay can be achieved in the selected experimental range. Furthermore, DoE investigations determined that a screw speed of 159 rpm and a feed rate of 5.4 kg/h are the optimum compounding conditions for the twin screw extruder used to obtain the highest tensile modulus and yield strength from the PPCN compounds. The optimised formulation of PPCNs and compounding conditions were adopted to manufacture PPCN materials for the study of thin-wall injection moulding. In the selected processing window, tensile modulus and yield strength increase significantly with decreasing injection speed, due to shear-induced orientation effects, exemplified by a significantly increased frozen layer thickness observed by optical microscopy (OM) and Moldflow® simulation. Furthermore, the TEM images indicate a strong orientation of clay particles in the flow direction, so the PPCN test pieces cut parallel to the flow direction have 36.4% higher tensile modulus and 13.6 % higher yield strength than those cut perpendicular to the flow direction, demonstrating the effects of shear induced orientation on the tensile properties of thin-wall injection moulded PPCN parts. In comparison to injection speed, mould temperature has very limited effects in the selected range investigated (25-55 °C), in this study. The changes in moulding conditions show no distinctive effects on PP crystallinity and intercalation behaviour of clay. Impact toughness of thin wall injection moulded PPCN parts is not significantly affected by either the changes in moulding conditions or clay concentration (1-5 %). The SEM images show no clear difference between the fracture surfaces of PPCN samples with different clay concentrations. TEM and XRD results suggest that higher intercalation but lower exfoliation is achieved in PPCN parts with higher clay content. The composites in the thin sections (at the end of flow) have 34 % higher tensile modulus and 11 % higher yield strength than in the thicker sections, although the thin sections show reduced d001 values. This is attributed to the significantly enhanced shear-induced particle/molecular orientation and more highly oriented frozen layer, according to TEM, OM and process simulation results. In terms of the reduced d001 values in the thin sections, it is proposed that the extreme shear conditions in the thin sections stretch the PP chains in the clay galleries to a much higher level, compaction of clay stacks occurs as less interspacing is needed to accommodate the stretched chains, but rapid cooling allows no time for the chains to relax and expand the galleries back. Overall, data obtained from both actual moulding and simulation indicate that injection speed is of utmost importance to the thin-wall injection moulding process, development of microstructure, and thus the resulting properties of the moulded PPCN parts, in the selected experimental ranges of this research

Fire performance of residential shipping containers designed with a shaft wall system

seven story building made of shipping containers is planned to be built in Barcelona, Spain. This study mainly aimed to evaluate the fire performance of one of these residential shipping containers whose walls and ceiling will have a shaft wall system installed. The default assembly consisted of three fire resistant gypsum boards for vertical panels and a mineral wool layer within the framing system. This work aimed to assess if system variants (e.g. less gypsum boards, no mineral wool layer) could still be adequate considering fire resistance purposes. To determine if steel temperatures would attain a predetermined temperature of 300-350ºC (a temperature value above which mechanical properties of steel start to change significantly) the temperature evolution within the shaft wall system and the corrugated steel profile of the container was analysed under different fire conditions. Diamonds simulator (v. 2020; Buildsoft) was used to perform the heat transfer analysis from the inside surface of the container (where the fire source was present) and within the shaft wall and the corrugated profile. To do so gas temperatures near the walls and the ceiling were required, so these temperatures were obtained from two sources: (1) The standard fire curve ISO834; (2) CFD simulations performed using the Fire Dynamics Simulator (FDS). Post-flashover fire scenarios were modelled in FDS taking into account the type of fuel present in residential buildings according to international standards. The results obtained indicate that temperatures lower than 350ºC were attained on the ribbed steel sheet under all the tested heat exposure conditions. When changing the assembly by removing the mineral wool layer, fire resistance was found to still be adequate. Therefore, under the tested conditions, the structural response of the containers would comply with fire protection standards, even in the case where insulation was reduced.Postprint (published version

Vat photopolymerisation 3D printing of controlled drug delivery devices

Pharmaceutical three-dimensional (3D) printing has led to a paradigm shift in the way medicines are designed and manufactured, moving away from the traditional ‘one-size-fits-all’ approaches and advancing towards personalised medicines. Among different 3D printing techniques, vat photopolymerisation 3D printing affords superior printing resolution, which in turn enables fabrication of micro-structures and smooth finishes. This thesis aims to investigate different vat photopolymerisation 3D printing techniques for the fabrication of personalised drug delivery devices for different routes of administration. Stereolithography (SLA) and digital light processing (DLP) 3D printing was used to manufacture devices with flexible materials for localised delivery of a single drug in the bladder and at the anterior segment of the eye. In vitro release studies demonstrated drug releases from these devices were sustained over weeks. Subsequently, to investigate the feasibility of loading more than one drug in a single dosage form, clinically relevant multi-layer antihypertensive polypills were fabricated using SLA 3D printing. A drug-photopolymer interaction was observed from these polypills, and Michael’s addition reaction was confirmed to have occurred. Despite these studies demonstrating the viable use of vat photopolymerization 3D printing for fabricating drug delivery devices, the bulky nature of current printers could be a barrier to clinical integration. As such, a smartphone-enabled DLP 3D printing system was developed to fabricate personalised oral dosage forms and patient-specific drug delivery devices. The portability of this printer could secure exciting opportunities for manufacturing personalised medicines at point-of-care settings. Overall, this thesis showed the potential of vat photopolymerisation 3D printing in preparing different patient-centric drug delivery devices with tuneable and sustained release profiles as well as advancing traditional treatments towards digital healthcare