Fibrous Carbon Materials Research Articles

Fiber-Reinforced Flexible Self-Healing Strain Sensor with Failure-Improving Sensitivity Recovery.

In this work, we address the inherent limitations of porous, flexible, fibrous, and self-healing strain sensors. Specifically, we tackle issues such as the fatigue failure of carbon-fibrous materials and the long-term flow and low mechanical stability of self-healing materials. We achieve this by combining self-healing carbon/PBS blends with fibrous materials, creating a fiber-reinforced self-healing composite. The self-healing carbon/PBS blends provide strain sensitivity and the ability to recover after fatigue and impact failure, while the fibers prevent the long-term flow of material and the scattering of pieces during impact and fatigue failure within the elastic deformation regime, enabling shape recovery. We fabricated composite wearable strain sensors with a viscoelastic functional layer composed of two continuous phases: (i) a self-healing polymer-carbon blend and (ii) long electrospun fibers of commercial polyurethane. This setup also eliminates the other drawbacks of bulk materials, such as nonlinearity of volt-ampere characteristics, irreversibility of deformation, and a low working factor, and allows improvement of the working factor after failure and healing. Most importantly, we discovered that hindered self-healing, like in the case of the MWCNT/PBS system, enables improvement of sensor sensitivity after large strains and failure, which is due to partial failure of the network formed by conductive particles.

Micro-CT image-based computation of effective thermal and mechanical properties of fibrous porous materials

Fibrous porous materials are extensively employed as heat shielding material for space vehicles and capsules. To predict the performance of these materials using computational modeling at the vehicle/capsule scale, the effective material properties are needed. In this work, the effective thermal conductivity and elastic constants of a carbon fibrous porous material called FiberForm (precursor of PICA) were calculated using a direct image-based approach. In this image-based approach, the microstructures obtained using X-ray computed tomography technique are represented as binary voxel data. Nonlocal interactions are introduced between neighboring voxels. Integro-differential equations, with respect to spatial and temporal dimensions respectively, are developed to govern material thermal and mechanical behaviors. Using this approach, energy-based computational procedures were developed to calculate the effective material properties of fibrous and porous materials irrespective of the periodicity of underlying microstructures. The size of representative volume element was determined by convergence of effective properties with respect to microstructure size.

Conversion of CO2 into fibrous carbon materials using Ga-based liquid alloys

This study investigates the catalytic reduction of CO2 using various ratios of Ga-based liquid alloys under different conditions. We explored the alloying of liquid gallium with metals like indium (In) and magnesium (Mg) through mechanical stirring and heating. The alloys, once prepared, were exposed to CO2 in a reactor, with the Ga-In-Mg alloy demonstrating optimal reaction effects. In an exemplary synthesis, 1 g of Ga was combined with 30 wt% In and 7 wt% Mg, yielding a 7 wt% Ga-In-Mg alloy. This alloy, when reacted with CO2 for 10 h, exhibited a maximum weight gain of 445 mg. Elemental analysis showed a carbon content increase from 4.56 % to 72.56 % post-reaction. The reacted alloy, post-acid washing and electron microscopy examination, revealed the production of fibrous carbon materials approximately 7 μm wide. The primary objectives of this research were to identify the optimal temperature for CO2 reduction by the alloy and to determine the most efficient alloy catalyst using orthogonal experimental methods. Furthermore, we aimed to elucidate the catalytic mechanism of gallium-based liquid metal in CO2 reduction. The study also involved analyzing the adsorption and reaction processes by fitting the adsorption and reaction kinetic curves of the liquid metal with CO2. Achieving these objectives could enable the conversion of CO2 into solid carbon products, aligning with current environmental and sustainable development goals. This research offers new insights and innovative approaches to tackling energy-related challenges, highlighting the potential of liquid metal alloys in carbon capture and reduction applications.

Scaling up Electrode Manufacturing with Non-Solvent Induced Phase Separation Technology

Grid-scale energy storage technologies must be deployed at a massive scale to balance the mismatch between energy generation using renewable technologies and demand. Redox flow batteries are an emerging technological option for large-scale and multi-hour electrochemical energy storage thanks to their ability to decouple energy and power1. Despite their intrinsic advantages, the current elevated costs of this technology hinders commercialization2. To improve cost competitiveness, research efforts have focused on developing novel electrolyte chemistries and optimized reactor concepts. To the latter, optimizing the porous electrode microstructure and surface chemistry offers a promising pathway to increase the performance of flow batteries. However, porous electrodes design is challenging as they must fulfil contradictory requirements such as providing high surface area for electrochemical reactions, facilitating mass transport of reactive species, and maintaining low operational pressure drop. Furthermore, state-of-the-art porous electrodes have been repurposed from other mature electrochemical technologies but have not been tailored for the unique requirements of redox flow batteries3.Non-solvent induced phase separation (NIPS) has been recently introduced as a versatile method to synthesize porous structures suitable for RFBs with unique properties, which are unattainable with current fibrous materials4,5. Drawing inspiration from membrane fabrication techniques, we reengineered the method for the synthesis of porous electrodes for use in redox flow batteries. The porous electrodes synthesized with NIPS were tested in a single-electrolyte cell configuration and then in an all-vanadium redox flow battery, showing promising electrochemical performance in comparison with existing commercial fibrous carbon materials. In this presentation, I will discuss our current efforts to scale up the NIPS method to manufacture electrodes at industrial scale. We believe that non-solvent induced phase separation is a cost-effective alternative to traditional carbon fibrous materials thanks to the few simpler steps required for the electrode preparation. Based on technoeconomic modeling, we estimate that the production cost of the NIPS electrodes can be less than half of the production costs of traditional carbon fibrous electrodes6. Moreover, the phase separated electrodes do not require post-manufacturing heat treatment to increase the surface area and wettability, which further translates into savings on energy costs. In this project, we aspire to scale-up the NIPS materials to a final size, after carbonization, of 30·30 cm2 while retaining similar microstructural and electrochemical performance properties as in laboratory scale. We perform a suite of microscopy, spectroscopic and flow cell diagnostics to correlate the electrode microstructure, surface chemistry and device performance. In this presentation, I will discuss the scalability of the method, reproducibility based on statistical analysis of sample properties and performance, and finally electrochemical performance on two flow battery chemistries.References Markard, J. (2018). The next phase of the energy transition and its implications for research and policy. Nature Energy, 3(8), 628-633.Darling, R. M. (2022). Techno-economic analyses of several redox flow batteries using levelized cost of energy storage. Current Opinion in Chemical Engineering, 37, 100855.Forner-Cuenca, A., and Brushett, F. R. (2019). Engineering porous electrodes for next-generation redox flow batteries: recent progress and opportunities. Current Opinion in Electrochemistry, 18, 113-122.Wan, C. T. C., Jacquemond, R. R., Chiang, Y. M., Nijmeijer, K., Brushett, F. R., & Forner‐Cuenca, A. (2021). Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes. Advanced Materials, 33(16), 2006716.Jacquemond, R. R., Wan, C. T. C., Chiang, Y. M., Borneman, Z., Brushett, F. R., Nijmeijer, K., & Forner-Cuenca, A. (2022). Microstructural engineering of high-power redox flow battery electrodes via non-solvent induced phase separation. Cell Reports Physical Science, 3(7), 100943.Minke, Christine, Ulrich Kunz, and Thomas Turek. "Carbon felt and carbon fiber-A techno-economic assessment of felt electrodes for redox flow battery applications." Journal of Power Sources342 (2017): 116-124.

Theoretical and experimental study on a compound insulation system for high temperature applications

• Designed a test setup for determining high temperature thermal performance of CFMLI. • Measured the temperature profile and effective thermal conductivity of CFMLI at 800–1325 K. • Discussed CFMLI thermal performance with gas pressure, spacing materials and foil numbers. • Validated the accuracy of experimental data by comparison with theoretical predictions. High temperature thermal insulation performance plays a crucial role in the application of thermal contact resistance precision measurement to reduce systematic heat loss and ensure 1D axial heat flow. In this paper, a compound insulation system composed of carbon fibrous materials and multilayer insulation (CFMLI) with non-interlayer-contact space was proposed in terms of high temperature sustainability, low thermal conductivity and thermal performance stability. An experimental set-up was designed and fabricated to measure the temperature distribution and the effective thermal conductivity of CFMLI as a function of temperature (800 K−1325 K). The experimental results showed that the temperature gradually decreases from inner to external radius of CFMLI, and a temperature jump of 40 K−80 K appears at the interface between two segments under vacuum conditions. It also reveals that the thermal performance of CFMLI is strongly dependent on the gas pressure and the number of reflective layers, while it is hardly affected by the filling materials when the temperature is above 1050 K. Meanwhile, the effective thermal conductivity of CFMLI varies around 0.2 W/m/K for two levels of pressure (10 -4 Pa and 0.1 MPa), and it decreases by 14.7% when the number of reflective layers increases from 6 to 21 at 1325 K. Additionally, a theoretical model with thermal resistance network was developed for heat transfer analysis of CFMLI. The model could predict the external temperature of CFMLI with high accuracy so that the difference between the theoretical results and experimental data was less than 2.61%.

Изучение электрохимических свойств углеродных волокнистых материалов для отрицательного электрода гибридного суперконденсатора с кислотным электролитом

The electrochemical characteristics of electrodes based on various fibrous carbon materials (manufactured by OOO NPTs Uvikom) for hybrid supercapacitors C/PbO2 with an acid electrolyte have been investigated. It is shown that the highest values of the capacitive characteristics of the electrodes were obtained using carbon activated felt UVIS-AK-V-170, characterized by capacities up to 400 F/g.

Gas–surface interactions in lightweight fibrous carbon materials

We investigate reactive and non-reactive scattering of hyperthermal beam of gas particles within highly porous carbon-fiber preform using particle-based numerical simulations. High-resolution X-ray tomography images of the microstructure is used to resolve its complex fiber network. The gas–surface interaction is studied at material temperatures up to 2000 K, typical of hypersonic aero-thermal environments. We extended a detailed surface chemistry model for oxidation of vitreous carbon to carbon-fiber materials. The model agrees well with experiments and predicts increasing oxidation product flux with larger porosities. Higher porosities lead to a larger fraction of thermalized argon atoms and greater mole fraction of CO for the oxygen beam due to greater penetration of the beam into the microstructure. It is found that a 6% porosity increase results in higher mole fractions of CO and lower amounts of O, with differences of around 10% of the total product flux. Furthermore, we construct an effective oxidation model with porosity-dependent rates that inherently accounts for the characteristics of the material microstructure and its varying porosity. Comparison of full microstructure simulation results and the effective model applied to a flat surface showed excellent agreement, thus suggesting that the model can be used directly in computational fluid dynamics codes.

Pulmonary toxicity, cytotoxicity, and genotoxicity of submicron-diameter carbon fibers with different diameters and lengths

Submicron-diameter carbon fibers (SCFs) are a type of fine-diameter fibrous carbon material that can be used in various applications. To accelerate their practical application, a hazard assessment of SCFs must be undertaken. This study demonstrated the pulmonary toxicity, cytotoxicity, and genotoxicity of three types of SCFs with different diameters and lengths. The average diameter and length of SCFs were 259.2 nm and 11.7 μm in SCF1 suspensions, 248.5 nm and 6.7 μm in SCF2 suspensions, and 183.0 nm and 13.7 μm in SCF3 suspensions, respectively. The results of pulmonary inflammation and recovery following intratracheal instillation with SCFs at doses of 0.25, 0.5, or 1.0 mg/kg showed that the pulmonary toxicity of SCFs was SCF3 > SCF1 > SCF2. These results suggest that SCF diameter and length are most likely important contributing factors associated with lung SCF clearance, pulmonary inflammation, and recovery. Furthermore, SCFs are less pulmonary toxic than bent multi-walled carbon nanotubes. Cell viability, pro-inflammatory cytokine and intracellular reactive oxygen species productions, morphological changes, gene expression profiling in NR8383 rat alveolar macrophage cells showed that the cytotoxic potency of SCFs is: SCF3 > SCF1 > SCF2. These results showed that SCFs with small diameters had high cytotoxicity, and SCFs with short lengths had low cytotoxicity. We conclude that pulmonary toxicity and cytotoxicity are associated with the diameter and length distributions of SCFs. In addition, a standard battery for genotoxicity testing, namely the Ames test, an in vitro chromosomal aberration test, and a mammalian erythrocyte micronucleus test, demonstrated that the three types of SCFs did not induce genotoxicity. Our findings provide new evidence for evaluating the potential toxicity of not only SCFs used in this study but also various SCFs which differ depending on the manufacturing processes or physicochemical properties.

A Flexible Multi-Channel Hollow CNT/Carbon Nanofiber Composites with S/N Co-Doping for Sodium/Potassium Ion Energy Storage.

Carbon fibrous materials are the promising candidate for the anode of flexible sodium-ion batteries and potassium-ion batteries due to the structural advantages. However, the progress of mechanically robust anode materials with high electrochemical properties is still unsatisfactory for the flexible electrodes. Herein, the comprehensive design of the morphology with unique multi-channel hollow 1D/1D carbon nanotube/carbon nanofiber network and the lattice structure of carbon with S/N co-doping has been proposed. Benefiting from the enlarged interlayer spacing and the flexible fibrous network, the S/N doped carbon nanotube/carbon nanofiber composites (CNT/SNCF) possess not only high conductivity but also good structural stability during sodiation and potassiation processes. When used as anode materials in SIBs and PIBs, the free-standing CNT/SNCF electrodes exhibit high discharge capacities (274.1 and 212.5 mA h g-1 at 1 A/g after 1000 cycles, respectively), superior cycle stability (150.4 and 100.1 mA h g-1 at 5 A/g after 5000 cycles, respectively) and rate performance (109.3 mA h g-1 at 10 A/g and 108.7 mA h g-1 at 5 A/g, respectively), showing great prospects in flexible energy storage devices.

Mechanical and Thermal Behavior of Fibrous Carbon Materials.

The ability of various commercial fibrous carbon materials to withstand stress and conduct heat has been evaluated through experimental and analytical studies. The combined effects of different micro/macro-structural characteristics were discussed and compared. Large differences in mechanical behavior were observed between the different groups or subgroups of fibrous materials, due to the different types of fibers and the mechanical and/or chemical bonds between them. The application of the Mooney–Rivlin model made it possible to determine the elastic modulus of soft felts, with a few exceptions, which were studied in-depth. The possible use of two different mechanical test methods allowed a comparison of the results in terms of elastic modulus obtained under different deformation regimes. The effective thermal conductivity of the same fibrous materials was also studied and found to be much lower than that of a single carbon fiber due to the high porosity, and varied with the bulk density and the fiber organization involving more or less thermal contact resistances. The thermal conductivity of most materials is highly anisotropic, with higher values in the direction of preferential fiber orientation. Finally, the combination of compression and transient thermal conductivity measurement techniques allowed the heat conduction properties of the commercial fibrous carbons to be investigated experimentally when compressed. It was observed that thermal conductivity is strongly affected under compression, especially perpendicular to the main fiber orientation.

Characterization of carbon fibrous material from platanus achenes as platinum catalysts support

Carbon materials with developed porosity are usually used as supports for platinum catalysts. Physico-chemical characteristics of the support influence the properties of platinum deposited and its catalytic activity. In our studies, we deposited platinum on carbon fibrous like materials obtained from platanus seeds - achenes. The precursor was chemically activated with different reagents: NaOH, pyrogallol, and H2O2, before the carbonization process. Platinum was deposited on all substrates to study the influence of the substrate properties on the activity of the catalyst. Carbon materials were characterized by nitrogen adsorption/desorption isotherms measurements, X-ray diffraction, and scanning electron microscopy. It was noticed that the adsorption characteristics of carbon support affected the structure of platinum deposits and thus their activity.

Enhancement of charge transport in interconnected lignin-derived carbon fibrous network for flexible battery-supercapacitor hybrid device

Self-supporting and flexible carbon fibrous mats are promising electrode materials for wearable devices. The contact resistance between adjacent fibers is still a limit for further improvement of energy storage performance. Herein, an activated interconnected lignin-derived carbon fibrous network (AILCFN) is fabricated by electrospinning followed by heat treatment. The unique interconnected structure between fibers in AILCFN is designed by controlling the ratio of soft Kraft lignin fractions with different thermal mobility. While the interconnected fibers are benefited for the electron transport and conductive property of the carbon networks, the high specific surface area is synergistically conduced to the direct channels for the fast ion transfer. The as-prepared AILCFN-3 exhibits an excellent specific capacitance and a high rate capability (69% from the current density from 1 to 20 mA cm−2). Further, AILCFN-3 can act as the scaffold to support the electrodeposited Ni-Co-S nanosheets. The AILCFN/Ni-Co-S composite electrode displays a high specific capacity of 1140.0 C g−1 at a current density of 10 A g−1. The assembled AILCFN/Ni-Co-S//AILCFN-3 BSH exhibits a high energy density of 30.8 Wh kg−1 with a power density of 0.8 kW kg−1 and demonstrates both excellent cyclability and flexibility, attributed to the high effective specific surface area and advantageous interconnected structure. The self-powered system assembled onto a lab coat can continuously power for the electronic watch under sunlight illumination and dark environment, demonstrating the promising potential of AILCFN in future wearable electronics. This work represents a “waste into wealth” direction of conversion strategy from biomass waste lignin to value-added energy storage materials, which conversely turns different thermal property of lignin fractions to good account, and breaks through the application limits caused by the heterogeneity.

Insight into the performance of the mesoporous structure SiOx nanoparticles anchored on carbon fibers as anode material of lithium-ion batteries

SiO x has aroused great attractions as a promising substitute for the anode materials of high-performance lithium-ion batteries (LIBs) because of the high specific capacity and the longer cycle life as well as relatively low volume expansion compared to Si. However, the unstable structure and poor conductivity of the SiO x lead to unideal electrochemical properties in LIBs, and thus hindering the widespread application of the SiO x anode. Herein, a facile approach has been put forward to prepare the high-performance mesoporous structure SiO x /carbon (m-SiO x /C) composites by electrospinning technique and sintering processes. The spherical SiO x nanoparticles are well anchored on the carbon fibers, and the reserved space can accommodate large volume expansion of the SiO x materials. Besides, the fibrous carbon materials can significantly enhance the conductivity for the SiO x anodes. Therefore, the resultant m-SiO x /C composites exhibit high discharge specific capacity of 1434 mAh g −1 at 500 mA g −1 with 67.5% capacity retention after 500 cycles and the good rate properties of 410 mAh g −1 at 2000 mA g −1 . In consequence, the reasonable structural design and innovative fabrication technique can facilitate the practical application for the m-SiO x /C composites and further promote the comprehensive electrochemical performance of LIBs.

Electrochemical properties of kenaf-derived activated carbon electrodes under different activation time durations for supercapacitor application

<span>The electrochemical properties of supercapacitors with kenaf-derived activated carbon electrodes under different activation time durations were evaluated. The study aims to determine the optimum activation time required that contributes to highest supercapacitor’s perfomance. Kenaf fibre was firstly carbonized at 400 °C to remove its water content and any volatile substances. The resulted kenaf-derived carbon was then impregnated in potassium hydroxide (KOH) with 4:1 impregnation ratio and left overnight. After the impregnation process, the carbon sample was activated at 600 °C with different heating time durations of 1, 2, 3 and 4 hours and named as A600-1, A600-2, A600-3 and A600-4, repectively. Four supercapacitors with the kenaf-derived activated carbon samples as the electrodes were fabricated based on two-electrode symmetrical test cell system. Specific capacitances of 108, 189, 242, and 126 F/g for supercapacitors with activated carbon A600-1, A600-2, A600-3 and A600-4 electrodes, respectively were achieved. These were much higher than previously reported values of only up to 37 F/g. </span><span>The finding suggests that an inexpensive fibrous carbon material derived from kenaf by a facile pyrolysis process may be a remarkable choice to construct high performance supercapacitor.</span>

Electrolysis with Fibrous Carbon Electrodes in Recovery of Platinum Metals from Mineral and Secondary Raw Materials

Electrolytic recovery of platinum metals onto electrodes of fibrous carbon materials from solutions formed by processing of copper–nickel ores, gold- and silver-containing concentrates (gold and silver refining), platinum–rhenium catalysts, and simulated solutions from spent nuclear fuel reprocessing was studied. Combined flowsheets including electrolysis with fibrous carbon electrodes, anodic labilization of platinum metal compounds, extraction, and ion exchange were used. Platinum metals were recovered to low residual concentrations from sulfuric acid, hydrochloric acid, hydrochloric acid + thiourea, ammonia–ammonium, nitric–nitrous acid, and nitric acid solutions. The following processes were used: electrolysis at constant and varied current density, deposition–anodic dissolution, and deposition–dissolution in the short-circuited electrochemical system fibrous carbon material–metal alloy–electrolyte solution. Some processes were successfully trialed on the semicommercial and commercial scales. Trials were performed using semicommercial electrolyzers with fibrous carbon electrodes, developed in cooperation with the special designing bureau of mining and dressing equipment.

Разработка технологии плазменной обработки волокнистых углеродных материалов перед их металлизацией

Разработка технологии плазменной обработки волокнистых углеродных материалов перед их металлизацией

Highly Chlorinated Polyvinyl Chloride as a Novel Precursor for Fibrous Carbon Material.

Pure, highly chlorinated polyvinyl chloride (CPVC), with a 63 wt % of chlorine, showed a unique-thermal-pyrolytic-phenomenon that meant it could be converted to carbon material through solid-phase carbonisation rather than liquid-phase carbonisation. The CPVC began to decompose at 270 °C, with a rapid loss in mass due to dehydrochlorination and novel aromatisation and polycondensation up to 400 °C. In this study, we attempted to prepare carbon fibre (CF) without oxidative stabilisation, using the aforementioned CPVC as a novel precursor. Through the processes of solution spinning and solid-state carbonisation, the spun CPVC fibre was directly converted to CF, with a carbonisation yield of 26.2 wt %. The CPVC-derived CF exhibited a relatively smooth surface; however, it still demonstrated a low mechanical performance. This was because the spun fibre was not stretched during the heat treatment. Tensile strength, Young’s modulus and elongation values of 590 ± 84 MPa, 50 ± 8 GPa, and 1.2 ± 0.2%, respectively, were obtained from the CPVC spun fibre, with an average diameter of 19.4 μm, following carbonisation at 1600 °C for 5 min.

Study of the structure of fibrous carbon materials using X-ray diffractometry

New possibilities for diagnosing the structure of carbon materials by X-ray diffraction analysis are described. The studies were performed on an X-ray diffractometer D8 ADVANCE (filtered Cu K α radiation) using carbon fibers (CF) differed in the mode of heat treatment (~2300 to ~3000°C). It is shown that when studying the structure of fibrous carbon materials characterized by a large depth of X-rays penetration, it is necessary to limit the thickness of the object under study to ~0.1 mm to provide the self-focusing condition for the entire sample volume engaged in formation of the diffracted beam. The material of high modulus carbon fibers can be heterogeneous and contain coherent scattering regions wherein the crystal structure parameters are somewhat different and experimentally observed diffraction peaks 002, 004, and 006 become asymmetric and are not described by the Gauss, Lorentz, or Voigt functions. Thus, the standard method used for determination of the average value of the interplanar spacing and the size of coherent scattering regions does provide reliable information on the real structure of the material. The profile of the asymmetric diffraction peak 002 was analyzed using the Origin program thus providing information about fine (heterogeneous) structure of the carbon fiber material which largely determines the physicomechanical properties. The data on 002 diffraction peak profiles of carbon fibers before and after removal of the Cu K α 2 component are presented. The data on decomposition of the experimentally observed asymmetric 002 diffraction peaks into symmetric peaks described by the Gaussian, Lorentz, and Voigt functions are compared. The most preferable is the decomposition into the components described by the Gaussian or Voigt functions.

Low thermal conductivity carbon material from electrospinning and subsequent chemical activation

Low thermal conductivity carbon fibers from polyacrylonitrile (PAN) are currently being explored as an alternative for traditional rayon-based carbon fibers with a thermal conductivity of 4 W/m K. Compared to multiple component electrospinning, this research demonstrated another feasible way to make low thermal conductivity carbon fibrous material by electrospinning PAN followed by carbonization and alkali activation. The effects of activation condition on microstructure, pore formation, and thermal conductivity of the resultant carbon nanofibrous material were investigated. The processing-structure-thermal conductivity relationship was revealed and mechanism of thermal conductivity reduction was discussed. The overall thermal conductivity of the prepared carbon nanofibrous material is a result of combined effects from factors of carbon structure and number of pores rather than volume of pores or specific surface area. The activated carbon nanofibrous materials showed thermal conductivity as low as 0.12 W/m K, which is a reduction of ~ 99% when compared to that of solid carbon film and a reduction of ~ 95% when compared to that of carbon nanofibrous material before activation.

2019 Academy Proceedings

2019 Academy Proceedings