Through Thermogravimetric Analysis Research Articles

Formulation and Characterization of Chitosan-Based Mixed-Matrix Scaffold for Tissue Engineering

The use of scaffolds, three-dimensional porous, biodegradable and biocompatible structures, that can be produced from natural polymers, synthetics, ceramics and metals is crucial in the tissue engineering field. Chitosan is a polysaccharide of natural origin, found in the exoskeleton of marine arthropods and in the cell wall of fungi, with enormous popularity in the production of three-dimensional materials for Tissue Engineering, in particular bone repair. This polymer has several advantages in the production of these structures in bone regeneration and repair: biodegradability, biocompatibility, non-toxicity and antimicrobial properties. This study aimed to prepare porous scaffolds, for bone repair of degenerative diseases in the spine with better performance and less secondary effects, based on chitosan and another biopolymer (sodium alginate) with the incorporation of calcium phosphates (hydroxyapatite and β-tricalcium phosphate), for tissue engineering application. The obtained scaffolds were object of a detailed characterization, namely with regard to their porosity through the ethanol method, degradation, positron annihilation spectroscopy (PAS), mechanical properties, scanning electronic microscope (SEM), thermal stability through thermogravimetric analysis (TGA), chemical composition through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results obtained showed that the different scaffolds presented pores able to support osteoid matrix growth. The crosslinking of scaffolds was also evaluated and resulted in pores with smaller dimensions and higher regularity in the chitosan-sodium alginate polymer without calcium phosphate scaffold. It was also possible to observe the effect of inorganics on mixed-matrix scaffolds, both morphologically and chemically. These scaffolds showed promising results in terms of mechanical and chemical properties, along with promising porosity for tissue regeneration applications.

Preparation of amine functionalized micro-mesoporous silicon adsorbent from fly ash and its kinetic characteristics of CO2 adsorption/desorption process

Micro-mesoporous silicon materials were prepared using silicate filtrate produced from fly ash as a silicon source. Then, the micro-mesoporous silica material was used as the carrier and amine compounds as modifiers to prepare a micro-mesoporous CO2 adsorbent. Afterwards, the structural properties, surface groups, thermal stability of micro-mesoporous silicon materials and micro-mesoporous CO2 adsorbent were studied. The results reveal that the micro-mesoporous CO2 adsorbent maintains the same micro-mesoporous structure as the micro-mesoporous silica material. And the thermal stability temperatures of adsorbent is below 383 K. Later, the CO2 adsorption performance and kinetic characteristics of adsorption process were studied through thermogravimetric analysis (TGA) and adsorption column experiments. The results indicated that the optimal CO2 adsorption capacity of 2.31 mmol/g-adsorbent was achieved at 343 K, and the adsorption capacity remained basically unchanged after 10 adsorption/desorption cycles. Dynamics studies have shown that the Avrami fraction model fits the CO2 isothermal adsorption curve very well, and the fitting results reveal that the intra-particle diffusion dominates the speed of the adsorption process. Additionally, the Yasyerli deactivation model can perfectly fit the CO2 adsorption breakthrough curve, and the fitting results indicate that the CO2 adsorption process is the deactivation process of the adsorbent. Finally, the adsorption/desorption kinetic simulation parameters can be used for the design and optimization of CO2 adsorption and desorption processes in industry.

Controlled release of foam from mesoporous silica-surfactant nanocomposite for enhanced natural gas production

Foam generated from solid foam sticks plays a crucial role in enhancing natural gas production by mitigating liquid accumulation in gas wells. Traditional solid foam sticks dissolve rapidly, releasing foam instantly, particularly at high downhole temperatures in gas wells. This necessitates frequent addition of surfactants to sustain foam generation. To address this issue, this study investigates the use of mesoporous silica nanocomposite to encapsulate the surfactant, cetyltrimethylammonium bromide (CTAB), as foam sticks, allowing for extended foam release. Mesoporous silica was synthesized through a sol–gel process involving a silica precursor and surfactant, utilizing alkali-acid catalysts in two steps. The resulting nanocomposite solid sticks were formed through aging and drying in a mold. The silica-surfactant nanocomposite was characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and small angle X-ray diffraction (SAXD). Experimental results demonstrated the successful encapsulation of 68.2 % surfactant into an average size of 50 nm nanosized silica capsules with a mesoporous structure. Quantitative determination of surfactant release over time in brine at a high temperature (130 °C) was determined through thermogravimetric analysis (TGA), which showed 6.3 % surfactant remained in nanocomposite after 3 days. Foam performance from the released surfactants was evaluated using a dynamic foam apparatus and blender test. The study showed that foam could be control-released over a period of 7 days through surfactant diffusion from mesoporous nanoparticles. The release of CTAB follows the first-order release kinetic model. This research provides a sustainable solution by utilizing mesoporous silica nanoparticles as carriers for surfactants, resulting in longer-lasting foam for the gas well deliquification and the enhancement of gas production.

Form-stable oleic acid based polyHIPE/nanoclay framework supported composite phase change materials for low‐temperature latent heat storage

Latent heat storage, one of the promising methods in energy storage, is an important option for the sustainable use of energy and is attracting more attention day by day. Phase change materials (PCMs) produced for this purpose allow the storage/release of latent heat due to the temperature of the medium and can be obtained using various methods. In this work, the preparation of a new fatty acid based composite phase change material was accomplished by applying simple two-step approach. Here, oleic acid (OA) was employed as PCM, and emulsion templated macroporous polymers (polyHIPEs) as supporting matrices. Furthermore, macroporous supports were also fabricated in the presence of surface modified montmorillonite nanoclay to enhance thermal properties of the targeted composite PCMs. In this respect, a neat macroporous support and surface modified nanoclay enhanced macroporous support were synthesized. Then, the composite PCMs were prepared by filling the macropores of the obtained polymer foams with OA via a solvent-assisted impregnation approach for cold energy storage. The examinations on the thermal characteristics of the composite PCMs were performed through Differential Scanning Calorimetry (DSC), while the chemical structure was analyzed with FT-IR. Besides, polarizing optical microscopy (POM) was used to monitor the loading of OA to macroporous polymer supports. Additionally, the thermal behaviors of composite PCMs were investigated by the temperature-history (T-history) method and the findings were also found to be compatible with DSC. Furthermore, thermal stability of the composite PCMs was investigated through thermogravimetric analysis (TGA). According to DSC results, the prepared composite PCMs are candidates for utilizing cold thermal energy storage such as building cooling, cold protection and cold chain transportation applications with their proper melting temperatures (7.08 °C and 7.40 °C) and moderate latent heat capacities.

Co-Pyrolysis of Woody Biomass and Oil Shale—A Kinetics and Modelling Study

The co-pyrolysis of biomass and fossil fuels has been the subject of studies on sustainable energy. Co-feeding oil shale with woody biomass can contribute to a transition into carbon neutrality. The present study analysed the thermal decomposition behaviour of oil shale and biomass blends (0:1, 3:7, 1:1, 7:3, 9:1, and 1:0) through thermogravimetric analysis (TGA) at 80–630 °C with a heating rate of 10 °C/min in CO2 and N2 atmospheres. A comparison of theoretical and experimental residual mass yields of oil shale–biomass mixtures indicated no significant interactions between the fuels. The blends contributed to a decrease of up to 34.4 wt% in solid residues compared to individual pyrolysis of oil shale, and the TGA curves were shifted from up to 10 °C to a lower temperature when the biomass ratio increased. The use of a CO2 atmosphere resulted in the production of solid residues, comparable to the one obtained with the N2 atmosphere. CO2 atmosphere can be used in oil shale–biomass co-pyrolysis, without affecting the decomposition process or increasing the yield of residues. A kinetic model method is proposed based on TGA data at 10, 20, and 30 °C/min. The apparent activation energies for a temperature range of 200–520 °C were in the order of 139, 155, 164, 197, 154, and 167 kJ/mol for oil shale–biomass 0:1, 3:7, 1:1, 7:3, 9:1, and 1:0 blends, respectively. From the isoconversional kinetic analysis, a two-stage pyrolysis was observed, which separated biomass and oil shale pyrolysis. A simulation of biomass and oil shale co-pyrolysis was conducted in Aspen Plus® using TGA-derived kinetic data. The model prediction resulted in a close match with the experimental thermogravimetric data with absolute errors from 1.75 to 3.78%, which highlights the relevance of TGA analysis in simulating co-pyrolysis processes.

Hollow Hafnium Oxide (HfO2) Fibers: Using an Effective Combination of Sol-Gel, Electrospinning, and Thermal Degradation Pathway.

In recent years, hafnium oxide (HfO2) has gained increasing interest because of its high dielectric constant, excellent thermal stability, and high band gap. Although HfO2 bulk and film materials have been prepared and well-studied, HfO2 fibers, especially hollow fibers, have been less investigated. In this study, we present a facile preparation method for HfO2 hollow fibers through a unique integration of the sol-gel process and electrospinning technique. Initially, polystyrene (PS) fibers are fabricated by using electrospinning, followed by dipping in a HfO2 precursor solution, resulting in HfO2-coated PS fibers. Subsequent thermal treatment at 800 °C ensures the selective pyrolysis of the PS fibers and complete condensation of the HfO2 precursors, forming HfO2 hollow fibers. Scanning electron microscopy (SEM) characterizations reveal HfO2 hollow fibers with rough surfaces and diminished diameters, a transformation attributed to the removal of the PS fibers and the condensation of the HfO2 precursors. Our study also delves into the influence of precursor solution molar ratios, showcasing the ability to achieve smaller HfO2 fiber diameters with reduced precursor quantities. Validation of the material composition is achieved through thermogravimetric analysis (TGA) and energy-dispersive spectroscopy (EDS) mapping. Additionally, X-ray diffraction (XRD) analysis provides insights into the crystallinity of the HfO2 hollow fibers, highlighting a higher crystallinity in fibers annealed at 800 °C compared with those treated at 400 °C. Notably, the HfO2 hollow fibers demonstrate a water contact angle (WCA) of 38.70 ± 5.24°, underscoring the transformation from hydrophobic to hydrophilic properties after the removal of the PS fibers. Looking forward, this work paves the way for extensive research on the surface properties and potential applications of HfO2 hollow fibers in areas such as filtration, energy storage, and memory devices.

Synthesis of multilayer graphene and its graphene derivatives from coal

In our study, we selected three prevalent coal types from Xinjiang: Dahuangshan coal (referred to as Y-coal), Black Mountain coal (B-coal), and Kuche coal (K-coal). Initially, we assessed their morphological differences using electron microscopy. Subsequently, we evaluated the superiority of Y-coal through Thermogravimetric Analysis (TGA). Furthermore, we compared their performances using various electrochemical tests, including the J-V curve, dark current curve, open-circuit voltage curve, and Electrochemical Impedance Spectroscopy (EIS) curve. Ultimately, we investigated the potential of synthesizing graphene from Y-coal and its derivatives. The first step was the preparation of multilayer graphene (MG) by treating Y-coal with acid to obtain demineralized coal, followed by treatment in a tube furnace to obtain ultrafine powdered MG. The second step was then followed by successive oxidation and ultrasonication of the already obtained MG to obtain graphene oxide (GO). Finally, ascorbic acid (VC) was selected to treat GO to prepare an aqueous suspension of reduced graphene oxide (rGO). MG (2θ = 26.2°), GO (2θ = 12.4°) and rGO (2θ = 25.5°) were obtained by XRD analysis. C 1s and O 1S were analyzed by XPS spectra. The functional groups −OH, C=O, and −C=C–, which are unique to graphene and its derivatives, were comparatively analyzed using infrared spectroscopy. The change of π→π* was analyzed by the UV–vis method. The absorbance was further found in combination with PL spectra. Immediately after, the morphology of graphite and its derivatives was analyzed by SEM, HRTEM, the physical properties by contact angle and BET, and finally the content of elements C and O by EDS. The successful demonstration of the superiority of the synthesized MG and its derivatives was achieved.

Determination of the property evolution in rock after laser irradiation by nanoindentation and nuclear magnetic resonance

Laser technology, as a novel approach to rock breaking, holds great promise for accessing resources in deep, hard rock layers. Therefore, it is crucial to conduct microscopic testing and analysis of rocks following laser irradiation. In this study, the changes in minerals and elements of the rocks after laser irradiation are clarified using X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). Additionally, the primary temperature range for rock weight loss is determined through thermogravimetric analysis (TGA). The rocks' microscopic features after irradiation are observed using a scanning electron microscope (SEM) and nuclear magnetic resonance (NMR), while the micromechanical properties of the rocks after irradiation are analyzed using nanoindentation techniques. New components such as Ca(OH)2 and CaO are generated in the laser irradiation zone. There is a decrease in the mass percentage of carbon (C), from 10.10 % without laser irradiation to 9.70 % with irradiation, and a decrease in the mass percentage of oxygen (O), from 46.38 % without irradiation to 43.99 % with irradiation. The percentage of large and medium-sized pores is evenly distributed, accounting for more than 50 % of the total after laser irradiation. The small pores occupy 18.85 % and 18.08 % within the size range of 0.0025–0.01 μm and 0.01–0.025 μm, respectively, accounting for a combined total percentage of slightly over 35 %. In the nanoindentation test, the laser irradiation area exhibits more significant deformation, with an average maximum indentation depth increase of 139.4 % compared to non-irradiated areas. The average microscopic modulus of elasticity of the rocks decreases from 36.69 GPa without laser irradiation to 10.06 GPa with laser irradiation, representing a reduction of 72.58 %. Moreover, the average hardness of the rocks decreases from 1.67 GPa without laser irradiation to 0.47 GPa with laser irradiation, indicating a decrease of 71.86 %. This study provides valuable foundational data for potential engineering applications.

Modifying the manufacturing process of high-graphite content polylactic acid filament for advanced energy and sensing applications in 3D printing

This research paper introduces an innovative method for tailoring polylactic acid/graphite (PLA/GPT) filament, specifically designed for 3D printing applications. The main achievement is the seamless incorporation of 30 % graphite without the need for a reflux system, elevated temperatures, or additional additives. The filament is thoroughly characterized through Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The electrochemical performance of 3D-printed electrodes is assessed using cyclic voltammetry and a dual-stage activation process, while surface properties are analyzed via roughness examination. The results highlight the successful fabrication of a PLA/GPT filament with uniformly dispersed graphite within the PLA matrix. Additionally, the study confirms the presence of graphite on the surface of the printed electrode, underscoring the vital role and effectiveness of the activation process in enhancing electrochemical responses. These findings have the potential to significantly impact materials in the fields of 3D printing and electrochemistry, offering new possibilities for advanced technological applications.

Application of used engine oil as a hydrogen-rich substance in co-pyrolysis with pine wood for reduction its environmental hazards and produced diesel-like fuel: Thermal behavior, kinetic and thermodynamic analysis

This study introduced co-pyrolysis process as effective way for convert used engine oil (UEO) into useful product and reduced its environmentally hazardous. The co-pyrolysis of acid-washed pine wood (APW) and used engine oil was investigated through thermogravimetric analysis (TGA) within the temperature range of 30 to 700 °C, employing heating rates of 5, 10, and 20 °C/min. Among the blends studied, a blend containing an equal ratio of two feeds exhibited the highest synergism. The study of the oil composition obtained from the co-pyrolysis of APW and UEO in the fixed-bed reactor showed that the simultaneous use of UEO as a feedstock reduced the yield of oxygenated compounds from 82.69 % to 25.06 %, while significantly increasing the yield of hydrocarbons from 17.31 % to 74.93 % compared to APW alone. 51.25 % of these hydrocarbons were in the range of diesel fuel. The kinetic parameters were determined using three iso-conversional methods: Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), and Starink. The obtained average activation energy was 162.65, 161.39, and 161.66 kJ/mol for FWO, KAS, and Starink, respectively. The pre-exponential factors, determined by the Kissinger method, varied from 1.98 × 108 to 9.12 × 1018. Also, the use of master plots in combination with iso-conversional methods showed that the reaction order model, f(α)= (1-α)n, with n between 2 and 3, provides the best description for the co-pyrolysis of APW and UEO in the applied heating rate range. Furthermore, with increasing conversion from 0.2 to 0.8, the thermodynamic parameters including ΔH, ΔG, and ΔS, changed in the range of 125.09–234.59 KJ/mol, 159.02–155.92 KJ/mol, and −0.06 to 0.13 KJ/mol, respectively.

Facile synthesis of mesoporous active carbon from the valorisation of biomass waste and assessment of sequester efficiency of arsenic (As) from water

In this study, Phoenix dactylifera frond active carbons (PDFACs) were prepared using a low-cost biomass source through zinc chloride (ZnCl2) activation for the efficient elimination at batch scale, of the environmentally hazardous component arsenic (As) from polluted water. The influence of different factors including activation temperature, impregnation ratio, and impregnation time on the pore volumes, surface areas, and carbon yields of PDFACs were investigated. The PDF, PDF charcoal (PDFC) and PDFACs were characterized through thermogravimetric analysis (TGA), BET surface area (N2 adsorption-desorption), pore size distributions (PSD), SEM, FTIR, Energy-dispersive X-ray spectroscopy (EDX), and Transmission electron microscopy (TEM) analysis demonstrated successful modification in porosity and surface morphology. The maximum BET surface area of 1677 m2/g (1666 m2/g mesopore, 11 m2/g micropore surface area) and 0.665 cm3/g total pore volume were achieved at optimum synthesis condition of 4:5 impregnation ratio, 400 °C activation temperature, and 24 h soaking time. The impregnating ratio, impregnation time and activating temperature were found to have an inverse relationship with the yield of PDFACs. The impact of pH, sorbent dosage, As(V) concentration, contact time, temperature and agitation speed were inspected in batch experiments for As(V) adsorption efficiency by PDFAC. A maximum extraction efficiency 97% of As(V) was attained at optimal working conditions of 1.5 g dosage of PDFAC, initial concentration of As(V) 10 mg L−1, 120 min contact time, pH 6.0 and agitation speed 200 rpm at temperature 25 °C. The adsorption kinetic data fit the pseudo second order kinetic model well and the sorption data fit both Langmuir and Freundlich equations with little deviation in the r2 values. Research indicated that PDFAC derived from biomass wastes by ZnCl2 activation was found to be promising and feasible material for the elimination of As(V) from the aquatic environment.

Molecular dynamics simulation and experiment study on technology and mechanism of removing oil and water from aluminum chips

The processes and mechanism of removing oil and water from aluminum chips were clarified through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), response surface method (RSM) and molecular dynamics (MD). The results indicate that the cutting fluid loses mass obviously at 200–300 °C and is carbonized above 400 °C. A layered arrangement of water–surfactant–oil is formed. There are strong hydrogen bonds, strong and weak van der Waals (vdW) forces between O—H in surfactant and O atom in water at 1.63, 3.27 and 5.05 Å, respectively. With the increase of temperature, the weak interaction vdW force is vanished, and the hydrogen bond is reduced. The strong vdW force and hydrogen bonds are broken and the layered arrangement of water–surfactant–oil interface is unstable and destroyed above 277 °C. The removal rate of water and oil is up to 99.7% when the chips are heated at 370 °C for 70 min with 3 cm loading thickness.

Synthesis and comprehensive characterization of bio-based polyamide 56/6 Copolymer: Mechanical, Thermal, and processing properties

In this study, nylon 56/6 copolymers with different biobased contents were synthesized using biobased pentylenediamine, adipic acid, and caprolactam as the main raw materials. The structure of the synthesized copolymers was characterized using nuclear magnetic analysis (NMR) and infrared analysis (IR). The crystal structure and crystalline properties were investigated using X-ray diffraction (XRD) and differential scanning calorimeter (DSC), while the thermodynamic properties were studied through thermogravimetric analysis (TGA). Furthermore, the mechanical and rheological properties of the copolymers were investigated. The results showed that PA56/6 copolymers exhibited excellent mechanical properties. They displayed tensile strength similar to that of pure PA56 and PA6 but with improved toughness. Moreover, PA56/6 copolymers demonstrated higher thermal stability, lower melting points, and enhanced processing properties. Rheological investigations revealed that compared to PA56 and PA6, PA56/6 copolymers exhibited reduced viscous flow activation energy. As a result, they offered a wider temperature processing range in practical production. Given the numerous benefits offered by bio-based polyamide 56/6 (PA56/6), this versatile material finds extensive utility across diverse applications, including but not limited to automotive engineering, specialty clothing fabrics, and packaging engineering. Exploiting its unique properties, PA56/6 exhibits remarkable potential in addressing various industry-specific challenges, thereby contributing to sustainable and innovative solutions.

Effect of the Pulsed Electric Field Treatment on Physical, Chemical and Structural Changes of Vacuum Impregnated Apple Tissue in Aloe Vera Juices

Vacuum impregnation (VI) stands as a diffusion-driven food processing method that has found recent application within the food industry, particularly for the cold formulation of fortified food products. Pulsed electric field (PEF) treatment can affect the food structure, influencing therefore the mass transfer phenomena during the further processing. Thus, the study aimed at investigating the effect of PEF treatment on selected physicochemical properties of vacuum-impregnated apples. Apple slices were vacuum impregnated with aloe vera juice solution with or PEF treatment at different intensities (125, 212.5 or 300 V/cm). The PEF was applied as a pretreatment—applied before the VI process as well as posttreatment—applied after the VI process. The VI process with aloe vera juice resulted in a sample weight increase of over 24% as well as structural changes, partial cell viability loss and color alteration. In addition, the decrease of bioactive compounds was observed, while antioxidant activity remained at a similar level as in raw material. PEF treatment adversely affected vacuum impregnation efficiency, causing microstructural changes and cell viability loss. Additionally, chemical composition modifications were evident through thermogravimetric analysis (TGA) and Fourier Infrared Spectroscopy (FTIR) analyses. Tissue hardness decreased significantly due to structural damage and caused high leakage from plant tissue, which resulted in hindering saturation with aloe vera juice during the VI process. Additionally, reduced bioactive substance content after PEF treatment was observed and the VI process did not restore apple samples of the bioactive compounds from aloe vera juice.

Comprehensive investigation on fast pyrolysis of waste Lotus shells to produce valuable products: Pyrolysis characteristics, reaction mechanism and economic analysis

Lotus shells (LS) represent an abundant, underutilized renewable resource with significant potential for producing bio-based fuels and chemicals. Pyrolysis emerges as an effective means to maximize the value derived from LS waste. This study assessed the behavior, kinetics of LS pyrolysis for bioenergy production through thermogravimetric analysis (TGA), model-free and model methods. The product distribution resulting from LS fast pyrolysis and the physicochemical properties of the derived products were comprehensively investigated. A plausible reaction mechanism for LS pyrolysis was proposed, followed by an estimation of the associated costs for bioenergy production through pyrolysis. The activation energy (Eα) for LS calculated through Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Friedman (FR) methods was 197.36 kJ/mol, 193.66 kJ/mol, and 197.16 kJ/mol, respectively. The kinetic reaction model for LS pyrolysis was represented by the equation f(α) = α−26.59(1-α)12.35[-ln(1-α)]−27.26, indicating the dominance of a diffusion model and nucleation mechanism in the LS pyrolysis process. Notably, the fast pyrolysis bio-oil derived from LS mainly comprised phenols (34.73 % at 300 °C), acids (42.33 % at 600 °C), and nitrogenous compounds (27.40 % at 800 °C), and the gaseous products primarily consisted of H2, CH4, CxHy, CO, and CO2. Biochar derived from LS exhibited abundant functional groups and mesoporous structure, and its moderate C/N ratio and low H/C ratio indicated potential for soil remediation. Furthermore, the high heating value (21.55–27.01 MJ/kg) of LS biochar exceeded that of Zhaotong lignite, demonstrating its favorable combustion characteristics. This study lays the theoretical foundation for the efficient treatment and high-value utilization of Lotus shells.

Experimental study on the factors affecting smouldering behaviour of CCA-treated wood

Waterborne chromated copper arsenate (CCA) is a highly effective, widely used wood preservative. While it does not appear to markedly alter the flaming behaviour of treated wood, there are significant concerns regarding post-fire smouldering. Our understanding of the mechanisms and factors affecting smouldering behaviour is currently insufficiently developed. This study used a multiscale approach to better understand smouldering in slash pine treated to different CCA retentions and investigated reaction kinetics through thermogravimetric analysis (TGA) in addition to Cone Calorimeter smouldering tests. Derivative thermogravimetry (DTG) showed that the temperatures at the onset of pyrolysis and oxidation, and where the maximum rate of decomposition occurred were both lowered by CCA treatment, and effects became more pronounced as CCA retention increased. Bench-scale smouldering tests showed that the smouldering mass loss rate increased with higher CCA retention, lower wood density, and prolonged heat exposure. Smouldering mode changed from a steady to an unsteady pattern as CCA retentions decreased to a threshold from combined pyrolysis and oxidation to isolated char-to-ash oxidation. Once initiated, the reaction can be self-sustaining until all the mass has been consumed regardless of the initial smouldering rate.

Field study of the dielectric constant of concrete: A parameter less sensitive to environmental variations than electrical resistivity

In this work, a field study was conducted to evaluate the curing effectiveness of concrete slabs cured by air and compound. Two non-destructive testing methods including ground penetrating radar (GPR) and electrical resistivity measurement were used. The dielectric constant value developments of air and compound cured concrete slabs were determined by GPR measurement. The compressive strength development was tested by concrete cylinders. The hydration degrees of air and compound cured slabs were determined by Ca(OH)2 (CH) content through thermogravimetric analysis (TGA) by a modified calculation method. The microstructure development of air and compound cured concrete slabs were characterized by mercury intrusion porosimetry measurement (MIP). It has found that the dielectric constant value of compound cured concrete slab was always higher than air cured concrete slab. The second reflected pulse peak amplitude of GPR waveform was less influenced by weather conditions, making it a reliable indicator of the dielectric constant value. On the other hand, the dielectric constant value determined by the first reflected pulse peak amplitude was greatly influenced by the weather conditions. The dielectric constant value determined by the two-way travel time method exhibited strong correlations with compressive strength, CH content and porosity. However, the electrical resistivity development of air and compound cured concrete slabs were not consistent with compressive strength, CH content and microstructure development. Our findings suggested that the GPR measurement can be practically used to evaluate the curing effectiveness of concrete and can be a good indicator of “hydration potential” from a development perspective.

Fired brick production using phosphogypsum and phosphate mining waste

The main objective of this study is to propose advanced solutions for recycling phosphogypsum (PG) in the construction industry. In Morocco, PG has been produced in large quantities (around 20 million tons) by a series of phosphoric acid manufacturing plants for many years. To address this issue, fired bricks were created using PG and red clay (RC), a waste material from Moroccan phosphate mines. The pressed brick samples were dried at 105 °C and then fired at temperatures between 900 and 1100 °C for 2–5 h. The PG, RC, and sintered briquettes were characterized and analyzed through thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), physical properties and response surface methodology (RSM). The Toxicity characteristic leaching procedure test (TCLP) was also conducted on the raw materials and the fired brick samples to assess contamination risk. At all temperatures, the addition of PG results in a microstructure with high porosity that significantly impacts the mechanical characteristics. Despite this, the mechanical and physical performance of the fired brick samples meet the required standards. The TCLP test results did not detect any release of contaminants. The samples fired at 1056 °C for 4.5 h with a PG content of 40% demonstrate optimal conditions, exhibiting a notable bending strength of 13.15 MPa, a moderate density, and minimal water absorption. These findings indicate a promising and sustainable future trend in the construction industry by incorporating PG in fired brick production, providing a viable solution for waste management. Furthermore, comparing the results with previous works highlights the significant improvements achieved in terms of meeting industry standards and minimizing contamination risks associated with the utilization of mine wastes in fired bricks.

Non-isothermal kinetics of cellulose, hemicellulose, and lignin degradation during cocoa bean shell pyrolysis

The waste generated by the cocoa industry consists of lignocellulosic material that can be used as a source of energy. To investigate this potential, the pyrolysis of cacao bean shell (CBS) was analyzed through thermogravimetric analysis (TGA) using nitrogen as the carrier gas. The process was performed at four different heating rates (β1 = 20 °C min−1, β2 = 30 °C min−1, β3 = 40 °C min−1, and β4 = 50 °C min−1) from 40 to 600 °C. The CBS degradation process was found to be similar to lignocellulosic biowaste, and the Friedman, Osawa-Flynn-Wall (OFW), and Kissinger-Akahira-Sunose (KAS) isoconversion methods were used to obtain kinetic parameters. The Friedman model had the best fit for the experimental data, and the activation energy (Ea) of the overall process increased with the conversion ratio due to changes from the broken bond reaction in the early stages to the secondary cracking response in the later stages. Due to the complexity of the thermal degradation of CBS, a detailed analysis was made by Fourier deconvolution to analyze the process in each stage of its pseudocomponents. The drying Ea (26.8–58.6 kJ/mol) was determined, along with the Ea of P-extractives (38.2–81.9 kJ/mol), P-hemicellulose (59.5–128.6 kJ/mol), P-cellulose (74.2–159.4 kJ/mol), P-lignin (79.8–173.4 kJ/mol), and carbonaceous degradation (102.2–186.2 kJ/mol). FTIR analysis showed that compounds such as CO2, esters, hydrocarbons, and phenols are released in the gas fraction during CBS pyrolysis. These results are useful for developing phenomenological models of the process and designing reactors to exploit the energetic potential of CBS through pyrolysis.

(Digital Presentation) The Utilization of Platinum Catalysts Deposited on Carbon Support Synthesized from Coffee Grounds in a Polymer Electrolyte Membrane Fuel Cell

Exploring alternative sources for platinum catalyst carbon support material is vital for the further development of polymer electrolyte membrane fuel cells (PEMFC).1 The support material and the method of depositing Pt nanoparticles are crucial for defining the catalytic properties of the catalyst. In this study, carbon support material, derived from coffee grounds was used in the preparation of Pt catalysts for PEMFC application. The carbon material was synthesized using ZnCl2 activated pyrolysis method2 and the Pt nanoparticles were deposited onto carbon support by two methods: using ethylene glycol3 or hydrogen4 as a reducing agent.The physical properties of the support material, as well as catalysts were analysed through thermogravimetric analysis (TGA), dynamic light scattering, X-ray diffraction (XRD), N2 sorption analysis and high-resolution scanning electron microscopy (HR-SEM) methods. The electrochemical activity, as well as the electrochemically active surface area (ECSA) of the catalysts were determined in a completed PEMFC. The properties and performance of catalysts synthesised were compared with the catalyst which was deposited onto commercial carbon (Ketjenblack, EC-300J).TGA displayed that carbon derived from coffee grounds contained 6.9 % of impurities by mass in the form of metal oxides and that the coffee carbon Pt catalyst contained 60 wt% of Pt. The Pt crystallite size was determined through XRD and it was 1.4 nm. HR-SEM analysis displayed that the average particle size of Pt nanoparticles on the coffee carbon catalyst was 4.7±2.5 nm. Results from N2 sorption analysis showed that all materials were micro-mesoporous, with coffee ground carbon having a specific surface area of 590 m2 g-1. The coffee carbon Pt catalyst produced smaller results of 370 m2 g-1 compared to the carbon support, due to the Pt nanoparticles depositing in the micropores, however still had a larger specific surface area than the commercial carbon catalyst with a specific surface area of 300 m2 g-1.Catalysts deposited on coffee ground carbon produced comparable electrochemical results to catalysts deposited on commercially available carbon. The coffee carbon catalyst produced a higher ECSA of 64 mPt 2 gPt -1, compared to the commercial carbon catalyst with an ECSA of 51 mPt 2 gPt -1. The current density of the Pt catalyst deposited onto coffee carbon was 0.68 A cm-2 at 670 mV, whilst in the same conditions commercial carbon peaked at 0.70 A cm-2. Both coffee and commercial carbon Pt catalysts produced similar power density maximums with the coffee Pt catalyst producing 0.56 W cm-2 and the commercial Pt catalyst producing 0.60 W cm-2.Physical and electrochemical characterizations displayed that higher ECSA values were strongly correlated to smaller Pt crystallite size. Other techniques to increase fuel cell performance were also experimented with, such as covering the gas diffusion layer with catalyst instead of Nafion membrane and adding additional Nafion layers, with both methods producing promising results.This study displays that there is a lot of potential in improving the catalytic performance of Pt catalysts by depositing on support materials derived from alternative sources. The methods of boosting PEMFC performance could be further investigated for catalysts deposited on different carbon supports. Acknowledgements This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), Personal Research Grant PRG676 and by private limited company AuVe Tech LLTKT20148 “Production of Polymer Electrolyte Membrane Fuel Cells”. The SEM measurements were conducted using the NAMUR+ core facility funded by the Estonian Research Council (TT 13). References S. Shahgaldi and J. Hamelin, Carbon, 94, 705-728 (2015). M. Härmas, PhD thesis, University of Tartu, Tartu, Estonia (2020). Y. Shao, S. Zhang, R. Kou, X. Wang, C. Wang, S. Dai, V. Viswanathan, J. Liu, Y. Wang, Y. Lin, J. Power Sources 195, 1805-1811 (2010). Y. Zheng, Z. Dou, Y. Fang, M. Li, X. Wu, J. Zeng, Z. Hou, S. Liao, J. Power Sources, 306, 448-453 (2015).