Search Results (45)

Micro-structured SAE H13 tool steel inserts for polymer injection molding require accurate replication of sub-millimeter features while retaining adequate densification and heat-treatment response. This study compared two powder-based routes on the same hemispherical insert containing pyramidal features of approximately 0.145 mm base width: hot embossing (HE) of water-atomized SAE H13 powder (supplier d50 = 5.7 µm, irregular morphology) compounded with a commercial M1 binder, and material extrusion (MEX) of a commercial gas-atomized SAE H13 filament processed on a Markforged Metal X. Rheological screening selected a 57:43 vol% powder-to-binder ratio for the in-house HE feedstock, and DSC/TGA measurements defined two-step debinding windows. The best HE conditions were 220 °C, 8 MPa, and 45 min for the in-house mixture, and 210 °C, 8 MPa, and 30 min for the granulated commercial filament; the latter showed a 0.15% linear deviation from the silicone replica diameter among the best-rated samples. Under the tested commercial MEX configuration, the pyramidal features were not resolved because the 0.40 mm deposition line width exceeded the target feature base width, causing the slicer to omit the sub-line-width geometry. The defect populations differed qualitatively: HE specimens showed porosity and local cracking associated with powder morphology and pressureless sintering, whereas MEX specimens showed build-direction-aligned inter-raster voids associated with the toolpath. Microhardness and tensile data are therefore interpreted as process-history-specific results rather than as a direct route ranking, because sintering conditions were not uniform across all specimens. The study defines an experimentally bound process-selection limit for SAE H13 micro-tooling: HE remains preferable for sub-nozzle surface features, whereas MEX remains attractive for macro-scale geometric freedom, if resolution, densification, and post-sintering consolidation are addressed. Full article

Within a waste biorefinery framework, integrating agro-industrial by-products into the circular economy requires a detailed understanding of the thermochemical conversion behaviour of low-grade carbonaceous materials. This study evaluates the co-pyrolysis characteristics of Soma lignite (SL) and pectin-rich sugar beet pulp (SBP) as a sustainable route for upgrading these resources into clean energy carriers. Interactions between the two feedstocks were analysed by thermogravimetric measurements, triple-region kinetic modelling, and quantitative synergy indices at six mixing ratios, including the pure samples (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wt% SL:SBP). The Reactivity Index ($R_{\mathrm{m}}$) increased from 0.97 × 10⁻⁴ s⁻¹K⁻¹ for pure SL to 8.65 × 10⁻⁴ s⁻¹K⁻¹ for the 20:80 blend, showing that SBP acts as a highly reactive biomass component that accelerates devolatilisation in the main pyrolysis region. Synergy analysis indicated a shift from inhibitory behaviour in coal-rich blends to slightly positive synergy in SBP-rich mixtures, with the onset of positive $\Delta TC$ around 60 wt% SBP under the present single-heating-rate, non-replicated TGA conditions. This tentative threshold-like behaviour suggests that a critical level of literature-supported, hypothesised hydrogen-donating biomass radicals may be required to overcome the structural resistance of the coal matrix. Within these experimental limitations, the apparent macro-kinetic deviations and first-order Arrhenius parameters suggest that SL/SBP co-pyrolysis follows a complex, non-additive pathway that should be further validated by multi-heating-rate and product characterisation studies in future work. The primary contribution of this work lies in proposing this distinct threshold-like biomass fraction at the macro-kinetic level that governs the transition from heat-transfer-limited antagonism to radical-influenced synergy in low-rank coal and pectin-rich biomass blends. Overall, the combined $\Delta TC$, $\Delta E$ and $R_{\mathrm{m}}$ descriptors provide useful macro-kinetic benchmarks for guiding the optimisation of thermochemical processes for low-grade carbonaceous resources. Full article

The increasing demand for sustainable materials has accelerated the development of environmentally friendly filaments for fused deposition modeling (FDM). In this study, the surface roughness and thermal degradation behavior of sustainable PLA-based filaments, including PLA, recycled PLA (Re–PLA), and wood-filled PLA (Wood–PLA), were systematically investigated under different FDM printing conditions. A full factorial experimental design was employed to identify the dominant processing parameters and optimize surface quality. Surface roughness was evaluated using values Ra, Rz, and Rq parameters measured on three different surface orientations (top surface at 0°, top surface at 45°, and side surface). Scanning electron microscopy (SEM) was used to examine the relationship between roughness measurements and surface morphology, while thermogravimetric analysis (TGA) was performed to evaluate the thermal degradation behavior of the filaments in relation to printing temperature. The results have shown that filament material is the most important parameter affecting surface roughness. While Wood–PLA exhibited the highest roughness due to fiber-induced surface heterogeneity, recycled Re–PLA showed moderate surface irregularities resulting from degradation compared to pure PLA. Despite a rougher filament surface prior to production, recycled PLA exhibited a surface morphology similar to that of pure PLA after printing, influenced by the processing parameters. Furthermore, SEM findings indicated that the Ra parameter predominantly reflects macro-scale surface topography, while local microstructural heterogeneity can be better characterized by complementary roughness parameters such as Rz. These findings support optimizing printing conditions to improve surface quality and more widespread use of sustainable FDM filaments in applications where surface roughness is critical. Full article

The expanding insect farming industry generates up to 67,000 tons of frass per year. Its potential use as fertilizer is promising, but has not yet been widely studied. This study aimed to characterize the chemical composition, organic matter structure, ecotoxicity, and phytotoxicity of frass from four insect species in order to evaluate its potential as a fertilizer. We compared four types of insect frass (IF) (Tenebrio molitor, Galleria mellonella, Hermetia illucens, and Acheta domesticus) to Eisenia fetida vermicompost (EFV). We used physicochemical analyses (pH, electrical conductivity (EC), macro-micronutrients and dissolved organic carbon (DOC), spectroscopy (solid-state ¹³C nuclear magnetic resonance (NMR), and Fourier-transform infrared spectroscopy (FTIR)) and thermogravimetry/differential scanning calorimetry (TGA/DSC: R₁, R₂, Tmax), together with phytotoxicity (germination index, %GI) and ecotoxicity (toxicity units, TU) bioassays. Composition was species-dependent: A. domesticus showed the highest levels of nitrogen (N), phosphorus (P), and potassium (K); the concentration of DOC was higher in insect frass (IF) than in EFV, with the highest concentration found in IF of T. molitor. ¹³C NMR/FTIR profiles distinguished between frass (carbohydrates/proteins and chitin signals) and EFV (humified, oxidized matrix). Thermal stability followed: G. mellonella (R₁ ≈ 0.88) ≥ A. domesticus (0.79) > H. illucens (0.73) > EFV (0.67) > T. molitor (0.50). In bioassays, T. molitor and A. domesticus exhibited phytotoxicity (%GI < 30), whereas G. mellonella and H. illucens did not. EFV exhibited the highest %GI. Dilution increased %GI in all materials, especially in T. molitor and A. domesticus, and reduced acute risk (TU). Frass is not a uniform input: its agronomic performance emerges from the interaction between EC (ionic stress), the availability of labile C (DOC, C/N and low-temperature exotherms), and structural stability (R₁/R₂ and aromaticity). In terms of formulation, IF can provide nutrients that mineralize rapidly, whereas EFV contributes stability. Controlling the inclusion and dilution of materials (e.g., limiting the amount of T. molitor in blends) and considering the mixing matrix helps to manage phytotoxicity and ecotoxicity, and realize the fertilizer value of the product. Full article

This study aimed to assess the physical, chemical, and combustion properties of pellets made from corncob and rice husk residues sourced in Sucre, Colombia, and to evaluate the performance of different blending ratios. Before pelletization, the residues were ground and processed using a small-scale flat die pellet mill equipped with a 6 mm die. Physical properties were evaluated according to ISO standards for particle density, bulk density, and impact resistance assessment. Proximate and ultimate analyses, as well as heating values, were determined and compared against the ISO 17225-6:2021 classification for herbaceous biomass. The 70:30 corncob-to-rice husk blend (CC70:RH30) showed good quality, with 7.23% ash, 9.18% moisture, and an LHV of 15.19 MJ/kg, meeting the criteria for Class B pellets. Combustion performance was assessed using a custom-designed macro-TGA, revealing that co-pelletized blends exhibited improved ignition temperatures and comprehensive combustion indices compared to the individual feedstocks. Additionally, calorific values were proportional to the blending ratios. In summary, controlling the blending ratio of corncob and rice husk residues during pellet production allows modulation of both the total ash content and the lower heating value of the resulting solid biofuels, making them more suitable for thermochemical conversion routes such as combustion and/or gasification. Full article

Hemp (Cannabis sativa L.) is a high-yielding crop cultivated for fiber and seed production, generating substantial lignocellulosic residues such as hurds. These byproducts can be valorized through pyro-gasification, a thermochemical process that offers a sustainable alternative to combustion and produces biochar—a promising soil amendment due to its ability to enhance soil quality and mitigate drought stress. This research explores the viability of utilizing industrial hemp hurds as a direct feedstock for biochar production within the context of agricultural exploitation. The study specifically focuses on assessing the feasibility of converting raw, unprocessed hemp hurds into biochar through pyrolysis. A comprehensive characterization of the resulting biochar is conducted to evaluate its properties and potential applications in agriculture, establishing a foundational understanding for future agronomic use. Specific analysis included proximate and ultimate analysis, thermogravimetric analysis (TGA), SEM-EDS, and phytotoxicity testing. The biochar exhibited an alkaline pH (≥9), a low H/C ratio (0.37), and suitable macro- and micronutrient levels. Microstructural analysis revealed a porous architecture favorable for nutrient retention and water absorption. Germination tests with corn (Zea mays L.) showed a germination index above 90% for substrates containing 0.5–1% biochar. These findings establish a foundation for future research aimed at thoroughly exploring the agricultural potential of this material. Full article

This study presents a detailed and comprehensive investigation into the macro-scale performance, strength gain mechanisms, environment and economic performance of graphene oxide (GO)-enhanced low-emission concrete. A comprehensive experimental program evaluated fresh and hardened properties, including slump retention, bleeding, air content, compressive, flexural, and tensile strength, drying shrinkage, and elastic modulus. Scanning Electron Microscopy (SEM), energy-dispersive spectroscopy (EDS), Thermogravimetric analysis (TGA) and proton nuclear magnetic resonance (¹H-NMR) was employed to examine microstructural evolution and early age water retention, confirming GO’s role in accelerating cement hydration and promoting C-S-H formation. Optimal performance was achieved at 0.05% GO (by binder weight), resulting in a 25% increase in 28-day compressive strength without compromising workability. This outcome is attributed to a tailored, non-invasive mixing strategy, wherein GO was pre-dispersed during synthesis and subsequently blended without the use of invasive mixing methods such as high shear mixing or ultrasonication. Fourier-transform infrared (FTIR) spectroscopy further validated the chemical compatibility of GO and PCE and confirmed the compatibility and efficiency of the admixture. Sustainability metrics, including embodied carbon and strength-normalized cost indices (USD/MPa), indicated that, although GO increased material cost, the overall cost-performance ratio remained competitive at breakeven GO prices. Enhanced efficiency also led to lower net embodied CO₂ emissions. By integrating mechanical, microstructural, and environmental analyses, this study demonstrates GO’s multifunctional benefits and provides a robust basis for its industrial implementation in sustainable infrastructure. Full article

This study aimed to evaluate the potential of beetroot powder (BP) as a functional ingredient in biscuits by investigating its effects on nutritional composition, sensory properties, and glycemic response. The primary goal was to determine whether BP could serve as a natural alternative to synthetic additives while maintaining product stability and consumer acceptability. Biscuits were formulated by replacing spelt flour with 15, 20, and 25% BP. The functional impact of the BP was assessed based on betaine content, macro- and microelements, glycemic index (GI), and acrylamide concentration. Thermal analysis (DSC and TGA) and water activity measurements confirmed the BP’s stability during six months of storage. Increased BP content led to higher betaine levels and mineral enrichment, particularly with potassium and phosphorus among the macroelements and zinc among the microelements. Sensory analysis identified biscuits with 20% BP as the most preferred, maintaining acceptable ratings even after six months. Hardness initially increased with BP incorporation but decreased over time (p < 0.05). The acrylamide content in the BP-enriched biscuits was significantly lower than in control samples and well below the reference safety threshold. Notably, consuming beetroot biscuits did not trigger a sharp postprandial glucose spike, with the GI of the most acceptable sample (20% BP) measured at 49 ± 11. These findings confirm that BP improves the nutritional and sensory characteristics of biscuits while ensuring product safety and stability, supporting its application as a natural functional ingredient in confectionery products. Full article

This study investigates the root causes of substandard concrete quality in a newly constructed residential complex, addressing the critical issue of compressive strength failure in structural elements. To tackle this problem, twelve core samples were extracted from affected areas and analyzed using a combination of macro-scale techniques (high-temperature heating, acid-immersion tests) and advanced microscopic methods (SEM-EDS, XRF, XRD, FTIR, TGA). The results revealed that while material proportions generally met specifications, uneven aggregate gradation and excessive use of mineral admixtures were key factors compromising strength. Microscopic analysis further identified harmful phases and chemical corrosion products, such as sulfates, which weakened the concrete matrix. These findings underscore the necessity of stringent quality control in raw material selection, aggregate gradation, and admixture dosage. The research demonstrates that integrating macro- and microanalytical methods can significantly optimize concrete mix designs, enhance durability, and prevent premature deterioration in reinforced concrete structures. This approach has broad implications for improving construction quality and ensuring the longevity of residential and infrastructure projects. Full article

The pyrolysis of municipal solid waste (MSW) is an efficient, cost-effective, and environmentally beneficial thermochemical treatment method. A macro thermogravimetric analyzer (Macro TGA) was used to study the pyrolysis behavior of cedar and polyethylene (PE) at slow (10 K/min) and fast (700, 800, and 900 °C) heating rates. For cedar, the pyrolysis rate curve showed multi-peak characteristics at the slow heating rate and single-peak characteristics at the fast heating rate. Conversely, PE exhibited the opposite behavior. At fast heating rate of 700 °C, the pyrolysis rate for cedar increased from 0.685 to 0.847 min⁻¹ as the sample temperature rose by over 100 °C, from 351 to 455 °C. By contrast, for PE, the rate increased from 0.217 to 1.008 min⁻¹ with a smaller temperature rise of less than 30 °C, from 630 to 656 °C. According to the International Confederation for Thermal Analysis and Calorimetry (ICTAC) guidelines for analyzing pyrolysis thermogravimetric data, cedar pyrolysis primarily followed a single-step parallel reaction pathway, while PE exhibited some multi-step parallel reactions. A newly developed discrete distributed activation energy model (DDAEM), along with the traditional iso-conversional model (ICM) and distributed activation energy model (DAEM), were applied to predict pyrolysis characteristics at fast heating rates. For cedar, both DDAEM and ICM provide accurate predictions, with average activation energies calculated by these two models being 48.08 and 66.37 kJ/mol, respectively. For PE, DDAEM demonstrates significantly higher predictive accuracy than ICM, particularly when the conversion is below 0.2. As the pyrolysis conversion of PE increases from 0.25 to 0.65, the average activation energy calculated using ICM was found to be 58.32 kJ/mol. By contrast, for DDAEM, the activation energies for the first and second step reactions were 110 and 60 kJ/mol, respectively. This indicates that ICM can only calculate the activation energy for the final step and not for the rate-limiting step. For both cedar and PE, DAEM fails to provide accurate predictions due to the unsteady heating rate. Full article

Most of the therapeutic systems developed for managing chronic skin wounds lack adequate mechanical and hydration properties, primarily because they rely on a single component. This study addresses this issue by combining organic and inorganic materials to obtain hybrid films with enhanced mechanical behavior, adhesion, and fluid absorption properties. To that aim, chitosan/hydrolyzed collagen blends were mixed with halloysite/antimicrobial nanohybrids at 10% and 20% (w/w) using glycerin or glycerin/polyethylene glycol-1500 as plasticizers. The films were characterized through the use of Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and electron microscopy. The mechanical properties were evaluated macroscopically using tensile tests, and at a nanoscale through atomic force microscopy (AFM) and nanoindentation. Thermodynamic studies were conducted to assess their hydrophilic or hydrophobic character. Additionally, in vitro cytocompatibility tests were performed on human keratinocytes. Results from FTIR, TGA, AFM and electron microscopy confirmed the hybrid nature of the films. Both tensile tests and nanomechanical measurements postulated that the nanohybrids improved the films’ toughness and adhesion and optimized the nanoindentation properties. All nanohybrid-loaded films were hydrophilic and non-cytotoxic, showcasing their potential for skin wound applications given their enhanced performance at the macro- and nanoscale. Full article

Amphiphilic block copolymers of N-vinyl pyrrolidone (NVP) and various vinyl esters (VEs), PNVP-b-PVEs, namely vinyl butyrate (VBu), vinyl decanoate (VDc), and vinyl stearate (VSt), were synthesized through RAFT polymerization techniques. The sequential addition of the monomers methodology was employed starting from the polymerization of NVP followed by the polymerization of the Ves’ monomer. The polymerization of NVP was conducted at 60 °C in benzene solution using AIBN as the initiator and O-ethyl S-(phthalimidylmethyl) xanthate as the CTA. The resulting PNVP macro-CTA was further applied for the polymerization of the vinyl ester in dioxane solution at 80 °C using, again, AIBN as the initiator. The block copolymers were characterized through size-exclusion chromatography (SEC) and NMR spectroscopy. The thermal behavior of the copolymers was studied by Differential Scanning Calorimetry (DSC), whereas their thermal stability via Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG). Full article

During biomass combustion in a grate-fired boiler, each particle undergoes a sequence of different reactions, and the phenomena differ from the conversion of a single, thermally thin, particle. Hence, this paper aims to deepen the understanding of biomass conversion processes and provides valuable insights for advancing biomass-based energy systems. Firstly, the weight loss characteristics of the larger particles of eucalyptus, pine, acacia, and olive samples were investigated at different isothermal temperatures in a purpose-built reactor that simulates the devolatilization process in a controllable manner. As opposed to the thermogravimetric analysis using thermally thin particles, it was concluded that all fuels show that the combustion of large particles does not exhibit separate consecutive conversion stages, due to internal diffusion resistance. Furthermore, it was verified that the devolatilization rate depends mainly on the reactor temperature, and, consequently, the mass-loss profile is independent of the biomass type. In addition to these experiments, the composition of the gases over the devolatilization period was analyzed for the main fuel used in power plants, eucalyptus. Once again, a strong correlation to the reactor temperature was observed, with CO₂ and CO always being the main devolatilization products. The temperature dependence of both compounds presented an increase from 8 to 13% between 600 and 800 °C for CO, while the CO₂ yield only slightly increased from 11 to 12%. These observations were essential to identify the transport phenomena effect and the gaseous products released during the biomass combustion. Full article

High-viscosity modified asphalt binder (HVMA) is used widely as a polymer-modified binder in porous asphalt pavement because it can improve the cohesiveness of the asphalt mixture. However, because of the high voidage in the mixture, HVMA is vulnerable to aging induced by temperature, oxygen, water, sunlight, and other climatic conditions, which degrades the performance of pavement. The properties of asphalt binder are affected adversely by the effects of hygrothermal environments in megathermal and rainy areas. Therefore, it is essential to study the aging characteristics of HVMA under the influence of hygrothermal environments to promote its application as a high-viscosity modifier. A hygrothermal cycle aging test (HCAT) was designed to simulate the aging of HVMA when rainwater was kept inside of the pavement after rainfall in megathermal areas. One kind of base bitumen and three kinds of HVMA (referred to as SBS, A, and B, respectively) were selected in this study. Short-term aging tests, hygrothermal cycling aging tests, and long-term aging tests were performed on the base bitumen and three kinds of modified asphalt binder. Fourier-transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and dynamic shear rheological (DSR) tests were used to evaluate the properties of the binders on the micro and macro scales. By comparing the index variations of the four binders before and after aging, the effects of the hygrothermal environment on the properties of HVMA were studied. It was found that the effects of the hygrothermal environment expedited the decomposition of the polymer and the formation of carbonyl groups compared with the TFOT and PAV test, which TGA confirmed further. Moreover, the thermal stability of the samples was improved after HCAT. In addition, the master curves of the complex modulus showed that hygrothermal cycles made the high-temperature rutting resistance of asphalt binder increase significantly. All of the results above verified that the effect of hygrothermal cycling could accelerate the aging of HVMA and shorten its service life. Full article

This study addresses the co-pyrogasification of municipal solid waste (MSW) from the Environmental Technology Park, San Juan, Argentina. This process involves heating waste at high temperatures in a low-oxygen or oxygen-free atmosphere as a sustainable strategy for waste management and energy generation. The principal objective is to focus on understanding the MSW co-pyrogasification kinetics to enhance performance in reactor design. A representative sample of MSW collected over a month was analyzed, focusing on the variation in mass proportions of plastic, organic matter, and paper. The empirical methodology included the deconvolution of macro-TGA curves and deep learning algorithms to predict and validate macro-TG data during co-pyrogasification. The findings reveal that MSW is a solid matrix more easily treated on thermochemical platforms, with kinetic and thermodynamic parameters favoring its processing. This approach suggests that MSW co-pyrogasification may represent a feasible alternative for resource recovery and bioenergy production, supporting the policies for the transition to a cleaner future and a circular economy. Full article