Cleaner Materials最新文献

This paper analysed the possibility of using recycled powders (<75 µm) and recycling fine aggregates (<1.18 mm) obtained during the crushing and grinding of concrete waste (CoW), ceramic waste (CeW) and red clay brick waste (RCBW) when designing cementitious pastes and mortars for 3D printing. The effects of the type of powder (CoW-powder, CeW-powder and RCBW-powder) and of the liquid/solid (L/S) ratio on the mixture properties in the fresh and hardened states were studied. In the fresh state, the level of flowability (mini-slump), flow index (flow table), buildability and setting time characteristics of the cementitious pastes were evaluated. In addition, the rheological behaviour was analysed through a rotational rheometer. In the hardened state, the compressive strength was determined at 3, 7, 28 and 90 days. The effects of the type of recycled fine aggregate (RFA − CoW, RFA − CeW and RFA − RCBW) were evaluated for mortars with a cement:aggregate ratio of 1:0.5. Based on the results obtained, the most suitable mixtures were selected to carry out 3D printing tests on a laboratory scale. From the 3D printing of beam-type specimens, it was possible to determine the flexural and compressive strengths (28 days) of the selected mixtures. The results obtained validated the possibility of using recycled powders (CoW, CeW and RCBW) to replace 30 % of ordinary Portland cement (OPC) and to incorporate 100 % recycled fine aggregates in the design of cementitious materials (pastes and mortars) for 3D printing. In this regard, the recycled powders and recycled fine aggregates increase the buildability and thixotropy of cementitious mixtures. With an adjustment in the L/S (liquid/solids) ratio, their application in 3D printing becomes feasible. This alternative for the use of powders and fine aggregates from construction and demolition waste (CDW) could be considered a contribution towards the sustainability of the sector and the implementation of a circular economy.

The significance of Mg (alloy) extends to both the mechanical engineering and medical sectors. However, Mg is known for its high reactivity, posing significant challenges to its widespread utilization in large-scale lightweight applications. Research has shown that adding small amounts of reactive elements, such as Ca, can substantially improve the high-temperature oxidation resistance of numerous Mg alloys. This can diminish the reliance on greenhouse gases with high global warming potential, typically used as protective gases during processing. In a similar vein, the patented Environment-COnscious Mg technology offers distinct advantages by utilizing the cost-effective and more stable oxide form of the desired alloying element, notably alkaline earth metals like Ca, instead of their elemental forms, in the alloying of Mg. This development holds considerable importance in mitigating the carbon footprint throughout manufacturing. While the patents for Environment-COnscious production outline a method employing various versatile oxides, practical application has primarily relied on adding calcium oxide, as indicated by the literature. Therefore, this review brings to light the state of the art concerning the interaction between calcium oxide and molten Mg (alloy), and its influence on the technical properties, potential challenges, and areas requiring further investigation in this field. Until now, this issue has not been discussed from a critical and holistic approach.

Given the current growth in consumer environmental concerns, this study assessed green customers’ consumption value for mango waste-based vegan leather bags. The consumer values and market choices theories guided semi-structured interviews and grounded theory-based induction data gathering and analysis. The project provides lasting answers and theoretical insights for vegan leather bags and mango waste management. The five main values are functional, social, emotional, conditional, and epistemic. Ten consumption-related topics emerged. Vegan leather bags were valued for their durability and multifunctionality by green shoppers. The data also show that social media, family, and peers impact sustainable product selections. For sustainable vegan leather purses created from mango waste, beautiful design and customization, green behavior, convenience, and environmental and green experience were the emotional and conditional values. Green customers’ openness to experience and green information can drive them to buy sustainable vegan leather bags, the study revealed.

Production of zeolite-Y catalyst from natural substrate has been a research trend in the scientific community. Published articles revealed that zeolite-Y recovery from locally sourced metakaolin is confined to laboratory practice. Scale-up process design and its economic feasibility for zeolite-Y catalyst recovery are rarely found in the scientific bibliography. Therefore, this study presented conceptual scale-up process design, base-case techno-economics and Monte-Carlo simulation of zeolite Y recovery from Nigerian metakaoline. ASPEN Base Case Simulation (ABCS), scale-up design and economics were accomplished using inherent design and costing algorithms in ASPEN Batch Process Developer (ABPD) V10. Process economic parameters: Net Present Value (NPV), Internal Rate of Return (IRR), Return on Investment (ROI) and Payback Time (PBT), were modelled and optimized using Design Expert V13 software; while zeolite Unit Production Cost (UPC), Annual Production Cost (APC), Total Capital Investment (TCI) and interest/discount rate were considered as model inputs. Monte-Carlo Simulation (MCS) in Crystal Ball Oracle software was used to perform the sensitivity and uncertainty analyses. The base-case techno-economic results of process design of 600,000 kg/year zeolite production gave batch size 5000 kg/batch with 104 batches/year, batch time (4149 min), TCI ($15,930,306), APC ($147,145), NPV ($41,983,375), ROI (38.13 %) and PBT (2.14 years). The coefficient of determination (R²) of the economic models were 0.9978, 0.9989 and 0.9986 for NPV, ROI and IRR respectively. The optimum economic variables that maximized synthesis of 5000 kg/batch zeolite Y are UPC ($11.68), APC ($100,033) and TPC ($15,930,200). MCS uncertainty for NPV, IRR and ROI are negligible. Therefore, this study demonstrated that scale-up zeolite-Y production from the local substrate is economically feasible.

The utilization of marble waste powder (MWP) as a supplementary cementitious material in concrete, serving as a replacement for cement, holds the potential to enhance split tensile strength (STS) and flexural strength (FS), alongside offering environmental advantages. However, it is crucial to determine the optimal dosage of MWP, ensuring meticulous mix design and testing procedures to maximize the concrete's strength and overall performance. This research endeavor seeks to investigate a supervised data-driven approach for predicting STS and FS in concrete composites incorporating MWP, along with other cementitious materials such as silica fume (SF), granite powder (GP), and fly ash (FA), and their influence on the STS and FS of MWP-incorporated concrete. Ten distinct machine learning (ML) algorithms, including multivariate linear regression (MVLR), support vector regression (SVR), artificial neural networks (ANN), decision tree regressor (DT), random forest regressor (RF), adaptive boosting regressor (AdB), light gradient boosting machine (LGBM), gradient boosting regressor (GBR), extreme gradient boosting (XGB), and cat boost, are employed to assess the predictive capabilities of these models for FS and STS datasets. Statistical metrics like correlation coefficient (R2), root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) are used to evaluate the performance of each ML algorithm. To enhance model efficiency, hyperparameter tuning and a 5-fold cross-validation technique are implemented. Among the ML algorithms tested, the cat boost algorithm demonstrates superior performance in predicting STS, while the ANN algorithm excels in predicting FS. Additionally, SHAP dependency plots are utilized to ascertain the feature importance in the best-performing models. The analysis reveals that features such as curing age, water, and cement play a more significant role in predicting STS, whereas attributes like cement, concrete type, and sand hold greater importance in predicting FS.

Environmentally friendly technology is being used by industries all over the world, and engineers in the manufacturing and materials industry are embracing sustainable business models. In this paradigm, materials are processed using economically and environmentally sound methods. The use of microwave-absorbing materials (MAMs) in low-altitude observatory aircraft and the rise in electromagnetic pollution have brought them to light. The main aim of this study is to select an ideal MAM with excellent physical, electromagnetic, chemical, and thermal properties, which also fulfills sustainability aspects based on expert judgments. In this regard, we have proposed a new hybrid framework consisting of Modified Digital Logic (MDL), a subjective weighting method in combination with the measurement of alternatives and ranking according to compromise solution (MARCOS) under an interval-valued intuitionistic fuzzy (IVIF) environment to select an optimum MAM. Furthermore, this research work contributes to streamlining the selection process by consolidating the plethora of work available in the literature on the synthesis and characterization of MAMs. A database is created for 160 potential candidate materials in C, S, X, and Ku bands for carbon-based materials, including carbon nanotubes (CNT), graphene, reduced graphene oxide (rGO), carbon fibers, and biomass-derived materials. These materials are then passed through successive screening stages to shortlist 14 materials, which are ranked subsequently over a set of 15 crisp and ambiguous criteria. This comprehensive study simultaneously caters to quantitative and qualitative information extracted from experimental work, material resource packs, or expert evaluations. The findings highlight CNT/Fe (20 wt%, E) (Al1) as the most suitable candidate for MAM application with outstanding electromagnetic properties. Finally, the results are compared with extant approaches to check the reliability of the proposed framework. In addition, sensitivity analysis is carried out to establish the feasibility and robustness of the obtained results.

The foundry industry is responsible for consuming large quantities of lining materials and generating significant amounts of waste. Silico-aluminous linings are used in the production of cast iron due to their compatibility with molten metal and slag. However, after use, these materials are typically disposed of in industrial landfills, creating an environmental liability. This study demonstrated a feasible alternative approach to repurpose silico-aluminous refractory wastes from induction furnaces and casting ladles from the foundry industry to develop new materials for refractory hydraulic binders for lining (refractory patch). The wastes were characterized using X-ray Diffraction, X-ray Fluorescence Spectrometry, Thermal Analysis, Scanning Electron Microscopy, and particle size distribution. The behavior of the lining wastes was found to be compatible with the proposed application, despite the expected contamination. There is potential for cost savings of at least 25 % and promoting a culture of recycling.

At present, nearly 85 % all of the requirement for MWFs are satisfied by the use of mixtures of petroleum by-products and synthetic substances with supplementary additives to enhance their properties. The demand for easily biodegradable, environmental friendly MWFs is a current requirement. COCOTP, a novel biodegradable MWF based on white (refined) coconut oil, developed by authors, had previously shown promising tribological properties for machining mild steel (MS) and stainless steel (SS) when used with the flooding method, but had fallen short of the performance of commercially available, non-biodegradable alternatives with MQL. Therefore in the current investigation, nano-particles were added to improve the performance of novel COCOTP MWF to use it with MQL conditions. Two nanomaterials nano-graphite and nano-Al₂O₃ were separately added to the base fluid in different concentrations as a monodispersed suspension. These nano enhanced fluids (NEFs) were subsequently used in straight turning experiments of two work materials AISI304 and SS400. Both the nano-enhanced fluids show convincing improvements over both COCOTP and mineral-oil based fluids in terms of surface roughness of the specimens regardless of the material being turned. However when machining SS 400, NEFs perform better only in lower speeds in terms of temperature. SS400 has a much higher thermal conductivity than AISI304 means that the quantity of residual heat remaining at the point of material removal which can be absorbed by the cutting fluid is lower in SS400. During machining SS400 under MQL lubrication 9.8 %, 26.8 % and 24 % reduction of surface roughness values (with respect to soluble oil) and during machining AISI304 55.3 %, 73.7 % and 70.4 % reduction of surface roughness values were obtained at 1175 rpm with COCOTP, NEF A and NEF G respectively. Based on the experimental results, the best-performing nano-enhanced fluids under MQL are 0.3 % (w/w) Al₂O₃ and 0.3 % (w/w) graphite.

This study focuses on the development of eco and user-friendly mechanochemically-activated geopolymeric stabilizers, surpassing the limitations inherent in traditional geopolymerization methods. A comparative analysis was undertaken with conventionally activated geopolymer stabilizers to establish benchmarks for effectiveness in soil stabilization applications. Additionally, the research delves into the impact of granulated blast-furnace slag (GGBS) content on the mechanical and durability properties of stabilized soil samples. In addition, the investigation focuses on the influence of the activation method on soil effectiveness and strength post-exposure to sulfate attack. The durability performance is rigorously assessed through the immersion of specimens in a 1 % magnesium sulfate (MgSO₄) solution for 60 and 120 days. The comprehensive evaluation includes visual appearance, mass changes, Ultrasonic Pulse Velocity (UPV), Unconfined Compressive Strength (UCS), and Fourier-Transform Infrared (FTIR) spectra of geopolymer-stabilized soil specimens. The results showed that before the exposure to the MgSO₄ solution, the UCS of mechanochemically activated geopolymer (MAG) samples was higher (12–45 %) than that of conventionally activated geopolymer (CAG)-stabilized soil. Furthermore, the strength of the geopolymer-stabilized soil improved by 114 %, 247 %, and 361 %, at 50, 75, and 100 % GGBS content, respectively. On the other hand, after exposure to the MgSO₄ solution, the results showed that the mechanochemically activated geopolymer-stabilized soil has better resistance to sulfate erosion than the conventionally activated geopolymer-stabilized soil. The residual UCS for MAG and CAG samples were 93 % and 89 % when exposed to 1 % magnesium sulfate solution for 60 days, whereas they declined to 70 % and 58 %, respectively, after 120 days of immersion.

Recently, there has been considerable interest in utilizing various forms of graphene derivatives for producing high-strength concrete. Among these derivatives are superstructure of graphene quantum dots (GQDs), particularly in their assemblies of carbon dots, which is innovative in cement. This research investigates the impact of graphene derivatives known as supra-GQDs on the mechanical properties and microstructure analysis of cement composites, compared with the control mixture and GQDs solution. The results found that supra-GQDs exhibit enhanced mechanical characteristics. The composite containing 1.2 % supra-GQDs had higher compressive and flexural strengths than the control by 40 % and 108 %, respectively. The study also identified a microstructural bridging mechanism involving the seeding and crystal growth of the C-S-H phase, leading to refined pore structure and less nano-, meso-, and micro-pores. The measured total pore volume reduced by 30 % when compared to GQDs solution. This investigation provides novel insight into the potential of utilizing supra-GQDs in cement composites, opening promising possibilities for high-performance concrete in the construction industry.