Residual Powder Research Articles

Phytochemical profiling and biological evaluation of the residues from industrial hemp (Cannabis sativa L.) inflorescences trimming: Focus on water extract

The study focused on investigating the phytochemical composition and bio-pharmacological properties of a water extract obtained from industrial hemp by-products, after trimming female inflorescences of Cannabis sativa L., cultivar Kompolti. The extract was found to be rich in phenolic compounds, particularly gallic acid, catechin, coumaric acid, ferulic acid, and benzoic acid. It also contained significant amounts of cannabidiolic acid and cannabigerolic acid as the main terpenophenols. To assess the biological potential of the extract, various ecotoxicological assays were conducted. The extract did not show significant phytotoxic effects on seedling germination in the allelopathic assay. In the brine shrimp (Artemia salina) lethality test, the LC50 value was 1.726 mg/mL, and in the Daphnia magna test, the extract showed no cardiotoxicity effects at the same concentration; thus, confirming its biocompatibility with these eukaryotic organisms. Additionally, the extract did not induce cytotoxicity in the murine C2C12 cell line till to the concentration of 1000 μg/mL. In isolated mouse prostate specimens, the extract (10–1000 μg/mL) also prevented LPS-induced gene expression of pro-inflammatory cytokines, namely tumor necrosis factor (TNF)α, interleukin (IL)-6, and IL-1β. Furthermore, the extract exhibited inhibitory effects on the growth of pathogenic bacterial, fungal, and dermatophyte species commonly associated with prostatitis. These results suggest that the residual powder from female inflorescence trimming can be considered an innovative plant material from the industrial hemp supply chain that deserves to be valorised in terms of recycling and upcycling; thus, reducing the environmental impact of the by-products and also opening the way for innovative health-promoting agents.

Towards bespoke gas permeability by functionally graded structures in laser-based powder bed fusion of metals

Permeable, media transporting, components are an integral part in numerous technical applications. In gas turbines combustors, for example, gaseous oxidizer and fuel are transported separately into the burner, where they are injected and mixed, and subsequently combusted. The mixture homogeneity strongly affects the combustion performance and emissions formation and is, amongst other, determined by the spatial distribution of fuel injection ports. In this context, porous media provide the limiting case for a spatial distribution of media-injecting pores, yet is typically associated with a high pressure drop that yields a loss in efficiency. In this study, possibilities of achieving gas permeability in additively manufactured porous structures are investigated. The objective is to selectively functionalize the permeable layers for gaseous media supply with low pressure loss and, when needed, enable a targeted mixing of different gas streams. For this purpose, a laser-based powder bed fusion process (PBF-LB/M) was used in this study. It offers the opportunity to manufacture varying porosities inside complex monolithic metal parts. To produce the porous structures and to achieve gas permeability, the effect of scan rotation angle, hatch distance, build-up direction and length of the porous specimen is investigated. Due to the high temperatures present in combustion systems, the present work utilizes Inconel 718 material. The AM gas permeable specimen are experimentally characterized by means of surface topography, micro X-ray computed tomography (µXRCT) as well as flow and pressure loss test. The results show, that the AM process parameter provide effective control parameters to adjust the permeability. The strongest effect originates from the hatch distance for a given build-up direction. Depending on the scan rotation, the flow transitions from a turbulent pipe flow to a Darcy flow as present in conventional porous media. A structured alignment and connectivity of pores can be realized as evident in the µXRCT results, surface topography and the flow measurements. Residual powder, powder adhering to the pore walls and stochastic closure of pores or channels lead to deviations and need to be considered when designing respective parts. Nonetheless, the results further show that a directional dependence of the permeability and the build-up direction can be realized and controlled. Consequently, when considering the AM build-strategy in the design of components, this directed permeability can be functionalized in the generation of gas transporting and gas mixing layers separately by adjusting the AM processing parameter.

Reactive formation of C3N4 as a by-product of AISI 1070 parts produced by laser powder bed fusion in N2 atmosphere

AbstractIn metal additive manufacturing (AM), inert gases are traditionally used to achieve a controlled atmosphere and mitigate the effects of residual reactive gases. However, the interaction between gases and laser processes, particularly in reactive laser powder bed fusion (RL-PBF) technology, offers the possibility of opening up new avenues for material synthesis. In this experimental work, the authors observed the presence of C3N4 in the residual powder during the manufacture of AISI 1070 steel parts by L-PBF, indicating a reactive process occurred during parts production. This investigation revealed the formation in the working chamber of a waste product containing C3N4 carbon nitride, due to the reaction between the carbon released from the steel and the nitrogen in the chamber. Remarkably, despite carbon depletion, the final product of AISI 1070 steel complies with the specifications of use. Hence, the L-PBF machine was modified to allow black powder sampling from various locations in the chamber. Authors attempted to enhance the production of the C3N4 material by increasing the SED up to 7143 J/mm2 to sublimate a pure graphite rod and concurrently manufacture parts in AISI 1070, in a nitrogen atmosphere. The results obtained at higher SED values showed that in both cases (graphite rod or AISI 1070 steel) a C3N4 compound in the black powder is formed in the investigated atmosphere by reaction of nitrogen atoms with the carbon atoms vaporized by the laser beam. Thus, the study highlights the novel achievement of synthesizing carbon nitride as a high-value by-product while producing functional AISI 1070 steel parts via L-PBF through reaction with nitrogen atmosphere.

Intrasample osmium isotope disequilibrium in young volcanic rocks: Insights from a new progressive digestion procedure

Some young volcanic rocks have been found to possess intrasample Os-isotope heterogeneity. This has important implications for source tracing and dating. Here, we use a new procedure through which it is possible to sequentially extract, from a single aliquot, the 187Os/188Os ratio of: i) the surface contaminant(s) (hydrobromic acid leachate); ii) the residual bulk rock powder (Step I) and iii) the Os-bearing phases entrapped within silicates (Step II). We applied this technique to two young basaltic reference materials (RMs), USGS BHVO-2 and EN026 10D-3. The former samples the 1919 lava from the Kīlauea summit crater (Hawaii) and the latter is a basalt sample dredged from Mohns Ridge (Greenland Sea). Both rock standards have previously been shown to display large intrasample Os isotope heterogeneity. In addition to analyzing these RMs, we also analyzed the RM USGS BHVO-1 for comparison, as well as another sample from the Kīlauea 1919 summit eruption (Kil 1919-6) along with a picritic tholeiite from the Kīlauea Iki 1959 eruption.Our leaching results show that BHVO-2 is contaminated with a highly radiogenic and labile contaminant with 187Os/188Os ratio of 0.525 ± 0.021. Without leaching, the Step I 187Os/188Os ratios varied from 0.1399 ± 0.0013 to 0.1568 ± 0.0014 while those for Step II were uniform (average = 0.1286 ± 0.0006, N = 5). A comparison of Re, Mo concentrations and 187Os/188Os ratio of the leachates of BHVO-2 and its predecessor (BHVO-1) indicates that BHVO-2 was contaminated during preparation. After leaching, the Step I and Step II 187Os/188Os ratios of BHVO-1 and another sample (Kīlauea 1919-6) from the same lava flow are identical within error to that of the Step II ratio of BHVO-2. A picrite from the 1959 Kīlauea Iki eruption also analyzed using the new technique gives homogenous results for both the steps with an average 187Os/188Os ratio of 0.1302 ± 0.0005. The 187Os/188Os ratio of recent Kīlauea lavas is identical within error to that of the primitive upper mantle (=0.1296). The Kīlauea Os-isotope composition could represent a “common component” that occurs globally in many plumes. The Step I 187Os/188Os ratio of EN026 10D-3 is 0.136 with Step II ratio being 0.131 (N = 2). The Step II 187Os/188Os ratios are more radiogenic than the nearby Jan Mayen lavas (187Os/188Os = 0.124–0.129) that have been argued to influence the chemistry of the Western section of the Mohns Ridge basalt but fall within the range of the Primitive Upper Mantle. We also discovered that BHVO-1, KIL 1919-6, 1959 Kīlauea Iki picrite, and EN026 10D-3 show Os-isotope disequilibrium between the leachate and Step I, suggesting wall rock assimilation during magma ascent. The data set presented here indicates a need for re-evaluating the extent to which mantle heterogeneities influence the Os isotope composition of ocean basalts.

Residual mass prediction of powder discharged from hopper at non-gravity directions

Residual powder often occurs when the hopper is inclined, which leads to material waste and reduces utilization efficiency. This paper carried out hopper discharge experiments of fine glass beads at non-gravity directions with hopper tilted from vertical to horizontal. The powder residual mass at different discharge directions was first analyzed. The criterion equation of powder residue was established in combination of experimental observation and force analysis, based on which the effect of the operation conditions on the utilization rate of powder was discussed. Second, based on the morphological characteristics of residual powder, the integral equation for calculating volume was established. Meanwhile, the error caused by the slip phenomenon was corrected. Finally, the residual mass prediction model was established. The model demonstrates precise prediction outcomes This study provides a reference for improving the utilization rate of powder in the aspects of hopper structure setting, powder flow properties, and discharge directions matching.

Ionic Liquid Processing of Residual Wood Powder into Additive-Free Wood Composites

AbstractThis work presents a novel process for production of additive-free wood composites by ionic liquid treatment of wood powder involving extraction of lignin followed by precipitation onto particle surfaces, and hot pressing to form a cellulose-reinforced lignin biocomposite. Physicochemical properties of lignin-coated wood powders, as well as their degree of fusion upon hot pressing, were evaluated with the aim of optimising ionic liquid treatment and hot-pressing conditions. Optimal conditions to achieve complete fusion while minimising process energy demand were determined using response surface methodology, and mechanisms of process parameter effects investigated using gas pycnometry, electron microscopy, image analysis, thermogravimetry, and calorimetry. These novel materials, derived solely from waste with only reusable reagents, represent a sustainable alternative to existing engineered wood products, which rely on petrochemical additives that release toxic volatile compounds, offering a means to reduce environmental and health hazards associated with production and use of composites from wood waste.

Mechanical properties and energy absorption capabilities of plate-based AlSi10Mg metamaterials produced by laser powder bed fusion

Plate-based lattice structures are an emerging category of mechanical metamaterials with exceptional mechanical performance. In this work, plate-based SCFCC metamaterials of AlSi10Mg with various relative densities are fabricated by laser powder bed fusion (LPBF). Circular holes are strategically designed and placed at the center of each non-load-bearing face for residual powder removal. Quasi-static compression experiments and numerical simulations are performed to investigate their mechanical performance and deformation mechanisms. Results indicate that the elastic modulus of SCFCC metamaterials decreases by 3.5% with the presence of 0.9 mm diameter holes, while increasing the hole size shows negligible impact on the elastic modulus. The novel plate-based SCFCC structure exhibits superior mechanical properties and enhanced energy absorption capacity concerning conventional high-stiffness truss-based and shell-based counterparts. The improvement, at the relative density of 0.2, can be observed in terms of elastic modulus (around 50%), peak compressive strength (around 300%), energy absorption capacity (around 400% or 200%). When increasing the relative density from 0.2 to 0.5, plate-based SCFCC metamaterial still maintains superior mechanical performance while the gaps between SCFCC and its counterparts narrow down gradually owing to the loss of structural features. Moreover, mechanical characteristics and coefficients of three Gibson and Ashby analytical equations are determined. This work proposes a novel type of plate-based structure with both exceptional mechanical performance and good additive manufacturability, which opens a new avenue for the design of lightweight mechanical metamaterials.

The pinhole method as a novel approach to remove residual hyaluronidase powder: a case report

The pinhole method as a novel approach to remove residual hyaluronidase powder: a case report

New spinel‐structured high‐entropy oxides with high‐ and stable‐infrared radiation properties

AbstractSpinel‐structured high‐entropy oxides (HEOs), the novel materials, have recently attracted great attention for their unexpected properties and extensive applications. In this work, employing a facile scalability process of solid‐state reaction method, we synthesized a new kind of non‐equimolar (Co2/11Mn2/11Fe2/11Cr2/11Ni2/11Cu1/11)3O4 HEOs powder. However, under the same condition, the raw mixed oxide powders, with equimolar cations and higher configuration entropy, cannot form single‐phase HEOs powder but with the mixture of (Co,Mn,Fe,Cr,Ni,Cu)3O4 and residual CuO powders, ruling out the crucial role of entropy effect in forming single‐phase spinel‐structured HEOs. In addition to (Co2/11Mn2/11Fe2/11Cr2/11Ni2/11Cu1/11)3O4 powder, various (Co,Mn,Fe,Cr,Ni,Cu)3O4 HEOs powders can be obtained by controlling the Cu cation content in an appropriate range. To explore the application of the spinel‐structured HEOs in high‐temperature infrared field, the infrared radiation properties of the (Co2/11Mn2/11Fe2/11Cr2/11Ni2/11Cu1/11)3O4 powder were evaluated and exhibited a high‐infrared radiation emissivity of 0.880 in the near‐infrared wavelength range (0.78–2.5 µm) and superior thermal stability. Notably, the infrared radiation emissivity of the HEOs powder was maintained at 0.855 with a slight loss of 2.8% after high‐temperature treatment. This work not only provides a valuable strategy for fabricating high‐ and stable‐infrared radiation properties materials but also expands the great potential application of spinel‐structured HEOs to high‐temperature infrared field, such as energy saving in industrial high‐temperature furnaces.

High‐pressure processing‐assisted in‐situ extraction of caffeine, chlorogenic acid, phenolic content, and antioxidant properties of green coffee bean

AbstractThis research aimed to efficiently extract valuable bioactive compounds from green coffee beans (GCBs), meeting the rising demand for natural compounds in the pharmaceutical and food industries. The study sought to overcome the limitations of conventional extraction techniques, such as low efficiency, prolonged processing, and heat‐sensitive compound degradation, by employing an eco‐friendly solvent and high‐pressure assisted extraction. Experiments were conducted at different pressure levels (300, 400, and 500 MPa), treatment times (10, 20, and 30 min), and using water, ethanol, and their combination (1:1) as solvents. The study evaluated the impact of these variables on radical scavenging activity (RSA), caffeine content, chlorogenic acid (CGA) levels, total phenolic content (TPC), pH, cyclic voltammetry, and scanning electron microscopy (SEM) analysis. Results were compared with conventional extraction and untreated extracts. High‐pressure processing (HPP) significantly enhanced RSA, reaching a maximum of 94.872 ± 0.290%, except for ethanol extracts. CGA content decreased with increasing pressure, correlating with improved antioxidant activity. Caffeine content remained higher even at shorter treatment times (1.170 ± 0.131 mg/mL). The ethanolic extract at the lowest pressure and time yielded the highest TPC (74.130 ± 1.141 mg of GAE/mL). Importantly, pH showed no significant variations. SEM analysis revealed a denser microstructure in the residual green coffee powder. Voltammetric tests confirm potent antioxidant properties due to its polyphenolics oxidizing within the potential range. This study demonstrates HPP as an eco‐friendly method for extracting bioactive compounds from GCBs. It effectively addresses the limitations of conventional extraction techniques, offering a sustainable and efficient alternative.Practical applicationsHigh‐pressure‐assisted extraction is a novel method of extracting bioactives from natural products. The current study proposes the innovative approach to optimize the processing parameters for extracting the bioactives (total phenols, CGA, and caffeine) from the GCB under HPP with improved antioxidant properties. This greener approach of high‐pressure‐assisted extraction is an alternative method to conventional extraction. This can be achieved with limited time of extraction using water or ethanol:water as a prospective alternative solvent devoid of harmful chemicals to extract with higher natural antioxidant capacity. Also, extensive research on green coffee extracts has demonstrated that extracted bioactives find applications as functional ingredients, natural preservatives, and potential natural antioxidants in the pharmaceutical and food industries.

Impact of Electron Beam Melting process recycling on defects and microstructure of Ti-6Al-4V powders

Metal powders are used as the feedstock material during the Electron Beam Melting processes. The process involves using an electron beam as the energy source to produce intricate parts with complex shapes in a layer-by-layer production system. The electron beam is directed by information from an STL file, and the process takes place in a pre-heated chamber that is maintained under vacuum. Once the production cycle is complete, the process yields the desired components along with a certain amount of residual powders that were not melted.To improve process efficiency and reduce costs associated with powder atomization, it is feasible to reuse the excess powder for subsequent production cycles. Prior to starting a new cycle, the excess powder is initially sieved to ensure a more uniform powder batch, and subsequently, the sieved powder can be mixed with other virgin powder to decrease oxygen content.This study examines the microstructure and defects present in a batch of virgin powders produced through plasma atomization and a batch of powders that were reused five times and mixed with Ti-6Al-4V grade 23 (ELI powders) at each cycle. The ELI powders are characterized by a low oxygen content.The results of the analysis indicate a connection between the powder atomization process and the formation of porosities in virgin powders resulting from trapped gas, as well as surface irregularities, including the presence of satellites. With an increase in the number of reuses, there is a reduction in the number of satellites, potentially due to surface partial melting due to the pre-heating of the EBM chamber, leading to rougher surfaces on the recycled particles.The microstructure of virgin powders is predominantly characterized by a fine acicular α’ phase, known as martensitic, formed due to the rapid cooling rate during the atomization process. Conversely, recycled powder tends to exhibit a coarser grain microstructure due to lower cooling rates. However, it is common to observe particles with a microstructure similar to that of newly manufactured powders, indicating that each individual particle has undergone a distinct thermal history.

Mill Scale - Biomass Pellet as a Charged Material for EAF Steelmaking

With an aim to utilize the local-based waste materials, this research investigated the production of mill scale - biomass pellet (MBP) as an alternative charged material for EAF steelmaking. Rubber tree bark (RTB) is one of the major biomasses in Thailand, consisting of carbon and hydrogen as the main compositions. The carbon derived from RTB was mixed with coal into five different ratios. Pure coal and RTB were employed for comparison. Seven carbonaceous samples were blended with mill scale at a C/O molar ratio of 1:1 to produce MBP, namely Coal, blend#1 – blend#5 and RTB. The reduction of MBP was investigated in a horizontal tube furnace under argon atmosphere at 1550°C for 15 and 30 minutes. The obtained products were iron droplets and residual black powder of unreacted oxides. Quantities of reduced iron from the MBP of blend#1 – blend#5 was about 58 – 61 wt% after 30 minutes, while it was 62 wt% and 57 wt% for coal and RTB, respectively. Degree of metallization (DOM) for blend#1 – blend#5 was between 78.1 – 81.7%, while it was 82.7% and 83.3% for coal and RTB. This research offers the possible method to utilize mill scale and RTB biomass toward circular economy.

Effect of high-dose electron beam irradiation on thermal decomposition behavior of polytetrafluoroethylene (PTFE)

In this study, we investigated the effect of high-dose (>10.0 MGy) irradiation on polytetrafluoroethylene (PTFE) decomposition in the presence of oxygen. To this end, we analyzed the chemical structures of PTFE residues after irradiation and thermal treatment as well as the outgas components during thermal treatment at 50 °C intervals. Thermogravimetric analyses indicated that the residual PTFE powder exhibited an initial decomposition (5% weight loss) at 159 °C, which is 365 °C lower than that of the original unirradiated sample. The initial decomposition temperature decreased at up to 5 MGy and gradually leveled off at above 140 °C. Fourier transform infrared (FT-IR) spectroscopy analysis of the residual PTFE powders indicated that the contents of thermal decomposition at lower temperature ranges were qualitatively related to the extent of the formation of oxidizable PTFE components, such as carbonyl groups. The formation of these components increased as the absorbed doses increased. The oxidized components gradually decreased with increasing thermal treatment temperature and tended to disappear at 470 °C. This demonstrated the effect of the oxidized compounds in the irradiated PTFE on lower temperature decomposition. The analysis of the gas components resulting from the thermal decomposition of the PTFE residuals revealed more detailed chemical information concerning the oxidative components of the irradiated PTFE. At temperatures below 420 °C, approximately 30% of the PTFE residue underwent pyrolysis to yield oxidized fluorocarbon products (CxFyOz) and further decomposed products (CO2). The remaining 70% of the residue thermally decomposed at temperatures above 420 °C, yielding monomer-related products such as C2F4, C3F6, and C4F8. These were identical to the gas products resulting from the thermal degradation of the original PTFE in the same temperature range. These results are indicative of the possibility of recycling and reusing fluorocarbons during irradiation.

Efficacy of bone defect therapy involving various surface treatments of titanium alloy implants: an in vivo and in vitro study

Multiple surface treatment methods for titanium alloy prostheses, widely used in orthopedics, are available; however, these can affect bone integration and regeneration efficiency. In this study, through cell and animal experiments, we devised seven bone implant categories of Ti6Al4V based on surface preparation and post-processing technology (polishing, grit-blasting, fine titanium spraying, coarse titanium spraying, electron beam melting [EBM] printing, selective laser melting [SLM] printing, and post-processed SLM printing) and imaged each microscopic surface structure with a scanning electron microscope (SEM). Mechanical testing revealed excessive post-processing damaged the mechanical properties of the implants. In vitro, human bone marrow mesenchymal stem cells (hBMSCs) were cultured with implants, and the morphology of the cells adhering to the implant surface was observed using SEM and confocal laser scanning microscopy. Cell Counting Kit-8 (CCK-8) semi-quantitatively determined cell activity, indirectly reflecting the proliferation of hBMSCs. Alizarin red and alkaline phosphatase experiments assessed osteogenic differentiation. In vivo, experiments utilized the New Zealand rabbit femoral condyle bone defect model to assess bone regeneration and integration using micro-computed tomography, Van Giesen staining, and Masson staining. We found that 3D-printed implants with regular pore structures were more conducive to hBMSC osteogenic differentiation, while the presence of metal powder on NPT-SLM-printed implants hindered such differentiation. The post-treatment SLM scaffold surface may have some residual semi-melted powder; however, these powder residues have no significant effect on cell activity and differentiation. Surface treatment (grit-blasting and titanium spraying) of planar structures can enhance hBMSC adhesion but does not necessarily promote their differentiation. The framework structure of 3D printing may affect the osteogenic differentiation of hBMSCs, and for SLM-printed implants, excessive pursuit of a “powderless” state will damage the mechanical properties of the implant.

Characterization and Application in Natural Rubber of Leucaena Leaf and Its Extracted Products.

Leucaena is a fast-growing tree in the legume family. Its leaf contains a significant amount of protein and is thus widely used as fodder for cattle. To broaden its application in the rubber field, the effects of Leucaena leaf powder and its extracted products on the cure characteristics and mechanical properties of natural rubber were investigated. The extraction of Leucaena leaf was carried out by using a proteolytic enzyme at 60 °C. The digested protein was separated from the residue by centrifugation. Both digested protein and residue were then dried and ground into powder, namely digested protein powder and residual powder, respectively, before being characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction, particle size determination, and protein analysis. After being added to natural rubber at 3 parts per hundred rubber, they significantly reduced both the scorch time and the optimum cure time of the rubber compounds, probably due to the presence of nitrogen-containing substances, without a significant sacrifice of the mechanical properties. For instance, the optimum cure time decreased by approximately 25.5, 35.4, and 54.9% for Leucaena leaf powder, residual powder, and digested protein powder, respectively. Thus, they can be used as green and sustainable fillers with a cure-activation effect in rubber compounding.

Properties study of artificial aggregate with high-content recycled concrete powder

With the need for urban development, there is a trend towards constructing large-span and super high-rise buildings. People have placed higher performance requirements on building materials. Therefore, the development of high-strength materials has become one of the current research focuses. Recycled concrete powder (RCP) is the residual powder generated while crushing waste concrete into a recycled aggregate. In order to achieve the low energy consumption resource utilization of RCP solid waste, a large amount of RCP with slag (a by-product of the blast furnace ironmaking process) addition was activated under an alkaline environment to prepare a cementitious material. The effects of RCP/Slag, liquid-solid ratio, Na2O content, and Na2SiO3 modulus on the setting time, compressive strength, and microstructure of alkali-activated high-content RCP-slag cementitious materials (AARCPS) were determined. The results showed that AARCPS had good compressive strength and microstructure; as the RCP content increased, the setting time of the cementitious material gradually prolonged. Based on the research of AARCPS, the mixing ratio was improved, and alkali-activated high-content RCP-slag aggregates (AARCPSA) were prepared. The results showed that with the increase in RCP content, the material fast setting speed and the sticky surface of material balls phenomenon during the aggregate preparation process was improved, and increasing the RCP content from 0% to 50% increased the ball-forming rate by about 14.36%. AARCPSA has good early strength performance, with the compressive strength at 3d reaching 75.18%–90.15% of that at 28d and the compressive strength at 7d reaching 93.85%–99.51% at 28d. The maximum compressive strength at 28d was 8.2 MPa. Increasing the slag and Na2O content in AARCPSA increased aggregate strength and density and decreased water absorption. The increase in RCP content and the decrease in Na2O content increased the peak strain of single particle compression of the aggregate and improved the deformation performance of the aggregate.

Critical considerations and effective assessment of extraction and recovery processes of RAP

With the increasing shortage of resources, the reuse of recycled asphalt pavements (RAP) in pavement engineering is considered as a sustainable technology. Challenges posed by common extraction and recovery methods may result in misjudgment of asphalt pavement performance. In this study, we investigate the optimization of extraction and recovery processes in recycled asphalt pavement (RAP) recycling, aiming to promote sustainable development within the pavement engineering sector. We prepared eleven asphalt samples to simulate common extraction and recovery scenarios, using virgin SBS-modified asphalt as a reference. Employing Fourier Transform Infrared (FTIR) analysis, thermogravimetric analysis (TGA), and Dynamic Shear Rheometer (DSR) testing, we assessed the samples' rheological and chemical properties. We pointed out three common but easily overlooked problems in the extraction and recovery process, namely residual mineral powder, residual trichloroethylene, and incomplete extraction. Residual mineral powder and trichloroethylene greatly influence extraction recovery accuracy; high-speed centrifugation effectively addresses trichloroethylene, but completely removing mineral powder remains challenging. Accurate evaluation of residual substances in recycled asphalt is achievable through FTIR, TGA, and rheological tests, providing valuable insights for material selection and processing. Additionally, it is crucial to fully recover the binder from RAP for precise performance evaluation, as the binder's interior exhibits lower aging levels compared to the surface. This aging heterogeneity should be considered when assessing RAP performance and developing effective rehabilitation strategies. Our findings hold significant implications for enhancing the efficiency and effectiveness of extraction and recovery processes in RAP recycling, ultimately contributing to sustainable development in pavement engineering.

Laser Beam Polishing of PA12 Parts Manufactured by Powder Bed Fusion

PurposeMulti Jet Fusion™ (MJF) is a powder bed fusion technology that fuses material locally with infrared radiation. Fabricated parts show high mechanical strength, low porosity and good dimensional accuracy, even for challenging geometries. They do, however, have a distinctive grainy surface with a roughness of Ra > 5 μm limiting possible applications. A fairly recent technology for the smoothing and polishing of polymer surfaces is the surface re-melting by laser beam polishing (LBP). The objective of this study is to characterize the LBP-process of MJF-manufactured Nylon PA12 parts and evaluate it in relation to state-of-the-art finishing methods.MethodsPA12 samples produced using the Multi Jet Fusion™ process are laser beam polished with a 30 W CO2-laser system. A numerical model is applied in order to estimate the effects of different processing parameters and laser scanning strategies. Calculated temperature progressions are validated experimentally with thermographic measurements. The laser beam polished surfaces are subsequently characterised by surface topography, tensile strength, surface energy and hardness.ResultsA re-melting and concurrent smoothing of PA12 surfaces was demonstrated for a number of different processing strategies. The use of a line-focus resulted in the best combination of processing speed, flexibility and surface quality with a reduction in roughness of up to 91%.ConclusionLaser beam polishing is applicable to parts manufactured by Multi Jet Fusion™. Depending on the case of application, it can be preferable to conventional post-processing strategies for fusing residual powder and improving tribological properties.

Direct ink writing of porous Fe scaffolds for bone implants: Pore size evolution and effect on degradation and mechanical properties

Existing research suggested 300∼600 μm as the optimal pore size range for metallic bone implants. The human bones, however, have numerous pores smaller than 300 μm for bone ingrowth, cell growth and migration, fluid flow, and so forth. The bone implant with such small-sized pores has been rarely manufactured and its property is unclear. In the paper, biodegradable Fe scaffolds of different pore sizes (50 μm, 100 μm, 150 μm, 200 μm, and 300 μm) were fabricated by direct ink writing (DIW) with subsequent sintering. The interconnected pores of all scaffolds are highly precise and have no residual powders. The in-vitro degradation and compression tests were conducted on the scaffolds to evaluate the effect of pore size on degradation and mechanical behaviors, respectively. The results indicate that a decrease in pore size leads to an increase in degradation rate, from 0.0423 ± 0.0014 to 0.0433 ± 0.0035 mm/year, with the exception of the 50 μm scaffolds which exhibit the lowest value of 0.0052 ± 0.0018 mm/year due to clogging by degradation products; meanwhile, both elastic modulus and yield strength rise from 344.8 ± 18.6 MPa to 625.0 ± 52.5 MPa and from 9.5 ± 0.9 MPa to 15.1 ± 0.8 MPa, respectively. The pore size of 100 μm shows the most significant potential for use in Fe bone implants regarding its good degradation and mechanical behaviors. Our work provides new insight into the preferable pore size of metallic bone implants produced by additive manufacturing.

Geometrical features and mechanical properties of the sheet-based gyroid scaffolds with functionally graded porosity manufactured by electron beam melting

Functionally graded porous scaffolds (FGPS) constructed with pores of different size arranged as spatially continuous structure based on sheet-based gyroid with three different scaling factors of 0.05, 0.1 and 0.2 were produced by electron beam powder bed fusion. The pore dimensions of the obtained scaffolds satisfy the values required for optimal bone tissue ingrowth. Agglomerates of residual powder were found inside all structures, which required post-manufacturing treatment. Using X-ray Computed Tomography powder agglomerations were visualized and average wall thickness, wall-to-wall distances, micro- and macro-porosities were evaluated. The initial cleaning by powder recovery system (PRS) was insufficient for complete powder removal. Additional treatment by dry ultrasonic vibration (USV) was applied and was found successful for gyroids with the scaling factors of 0.05 and 0.1. Mechanical properties of the samples, including quasi-elastic gradients and first maximum compressive strengths of the structures before and after USV were evaluated to prove that additional treatment does not produce structural damage. The estimated quasi-elastic gradients for gyroids with different scaling factors lie in a range between 2.5 and 2.9 GPa, while the first maximum compressive strength vary from 52.5 for to 59.8 MPa, compressive offset stress vary from 46.2 for to 53.2 MPa.