Curing Methods Research Articles

Development of an Electroactive and Thermo-Reversible Diels-Alder Epoxy Nanocomposite Doped with Carbon Nanotubes.

The manufacturing of Diels-Alder (D-A) crosslinked epoxy nanocomposites is an emerging field with several challenges to overcome: the synthesis is complex due to side reactions, the mechanical properties are hindered by the brittleness of these bonds, and the content of carbon nanotubes (CNT) added to achieve electroactivity is much higher than the percolation thresholds of other conventional resins. In this work, we develop nanocomposites with different D-A crosslinking ratios (0, 0.6, and 1.0) and CNT contents (0.1, 0.3, 0.5, 0.7, and 0.9 wt.%), achieving a simplified route and avoiding the use of solvents and side reactions by selecting a two-step curing method (100 °C-6 h + 60 °C-12 h) that generates the thermo-reversible resins. These reversible nanocomposites show ohmic behavior and effective Joule heating, reaching the dissociation temperatures of the D-A bonds. The fully reversible nanocomposites (ratio 1.0) present more homogeneous CNT dispersion compared to the partially reversible nanocomposites (ratio 0.6), showing higher electrical conductivity, as well as higher brittleness. For this study, the nanocomposite with a partially reversible matrix (ratio 0.6) doped with 0.7 CNT wt.% was selected to allow us to study its new smart functionalities and performance due to its reversible network by analyzing self-healing and thermoforming.

Ultra‐fast curing of benzoxazine with surface modified fly ash‐assisted microwave: Achieving excellent comprehensive performances

AbstractBenzoxazine has aroused a lot of research interest because of its high mechanical performance and excellent thermal stability in polybenzoxazines. However, it suffers from its high curing temperature and long curing time, which necessitate resolution. This study addresses this issue by employing a surface‐modified fly ash‐assisted microwave curing method to achieve ultra‐fast benzoxazine curing within 15 min. The impact strength of the resulting cured product displayed an increasing‐then‐decreasing trend with the addition of fly ash, reaching a maximum impact strength of 18.71 ± 1.20 kJ/m2 at a 3% fly ash content. This value is 113.3% higher than the impact strength of pure PBA‐a. Additionally, when using the same amount of fly ash, the microwave‐cured product exhibited a flexural strength of up to 135.9 MPa and a flexural modulus of up to 6.71 GPa, surpassing those of pure PBA‐a by 28.7% and 33.1%, respectively. Moreover, the glass transition temperature (Tg) increased by 19.56°C. Furthermore, there was a slight improvement in flexural strength compared to the heat‐cured product, and no significant loss in thermal properties was observed. The method demonstrated in this study presents a novel approach for the rapid molding and preparation of benzoxazine in composites.

Elemental and structural evolution of polymer-derived SiC fibers fabricated via solution blend and iodine curing methods

Elemental and structural evolution of polymer-derived SiC fibers fabricated via solution blend and iodine curing methods

Biodegradation of malathion and chlorpyrifos by some microorganisms isolated from agricultural drainage water in Egypt

ABSTRACT Malathion and chlorpyrifos are pesticides used excessively for agricultural purposes in Egypt to fight insects. The presence of such toxic compounds in watercourses exhibits harmful threats to the environment. The technology of bio-removal (or biodegradation) is nowadays the alternate method for environmental curing. The present study aimed to isolate and identify microbial strains (fungi and bacteria) with strong capabilities of biodegrading such pesticides, and to evaluate their abilities to uptake both pesticides at the same time. Agricultural drainage water samples were collected from four different drains in Egypt, named; El-Rahawi drain, Giza Governorate; Sabal drain, Minufiya Governorate; Ketshiner drain, Kafr El-Shiekh Governorate and Genag drain, Gharbiya Governorate. Water quality studies were carried out for water samples including organophosphorus (OP) pesticide contamination using Gas Chromatography-Mass Spectrometry (GC-MS). Malathion and chlorpyrifos was detected in slightly high concentration in Genag drain. So, Genag drainage water was used as enrichment to isolate the microorganisms having pesticide-biodegrading abilities. A total of four fungal and two bacterial strains were isolated, all of which showed a high ability to biodegrade one or both of the pesticides. The identification of the fungal isolates was carried out by 18S rRNA sequence analysis as Aspergillus fumigatus, Aspergillus niger, Penicillium chrysogenum and Aspergillus flavus. The bacterial isolates were identified as Acinetobacter boumnnii and Pseudomonas putida using 16S rRNA sequence analysis. The results of the biodegradation – capabilities experiments indicated the promising efficiency of A. niger, P. chrysogenum and P. putida where they could remove 90.5%, 95% and 64.4% of malathion and 85.8%, 85% and 88.2% of chlorpyrifos, respectively. Also, they exhibited potential abilities in biodegrading both pesticides at once, so, we recommend the use of such microorganisms as tools for bioremediation of agricultural drainage water contaminated with pesticides.

Multiscale performance and environmental impact assessment of slag and Portland blended cement for optimum carbonation curing

This article presents an investigation into the potential use of ground granulated blast-furnace slag (addressed as Slag cement or ‘SC’) as a replacement to Ordinary Portland Cement (OPC) in hybrid (carbonation and hydration) cured cement-based materials. To investigate the effects of carbonation on mechanical performances and microstructures, 0 %–100 % OPC was replaced with slag cement (SC). Thermogravimetric analysis (TGA) and Fourier transformed infrared (FTIR) spectra were utilized to investigate the carbonation reaction extent, rate, and microstructural phase formations. Slag cement was found to improve the efficiency and rate of carbonation. This study revealed that a minimum of 72 h of carbonation in a CO2-containing environment yields better mechanical performance compared to the traditional curing method. Specifically, the incorporation of 72 h of carbonation curing was observed to increase the strength of concrete up to 30 % after 28 days of total curing duration (carbonation and hydration). The chloride permeability of the carbonation cured samples was observed to reduce by 80 % due to the addition of SC. Finally, it was observed that, the carbonated concrete sample with slag has nearly 60 % lower global warming potential compared to the carbonated and non-carbonated concrete sample with 100 % OPC binder.

Hydrophobic modified melamine sponge for highly effective remediation of crude oil in water and soil

Crude oil pollution in water and soil has resulted in considerable environmental damage. The utilization of hydrophobic and oleophilic sponge materials for the treatment of crude oil pollution has garnered significant interest, owing to their excellent selective adsorption performance. In this paper, superhydrophobic and superoleophilic sponges (SMF) are prepared by a simple silane hydrolysis-thermal curing method, which is low-cost, environmentally friendly, large-scale preparation, acid and alkali-resistant, and mechanically stable. They can be used for the remediation of oil pollutants in water and soil simultaneously, and show high efficiency, excellent stability, and biosafety. Under appropriate circumstances, SMF is capable of adsorbing up to 82.7 g/g of crude oil in water and eliminating over 70.0 % of crude oil in soil, while exhibiting exceptional recycling performance. Notably, this study introduces a novel technique that alters soil viscosity by controlling soil water content, in conjunction with SMF, for the removal of crude oil in soil. Consequently, SMF shows great promise for practical application in the remediation of oil pollutants in both water and soil.

Impact of the Smoking Process on Biogenic Amine Levels in Traditional Dry-Cured Chorizo

This study aimed to investigate the influence of various production stages on the quality and spoilage conditions of traditionally dry-cured chorizo. To accomplish this, we employed an experimental design that examined three key production parameters: the batch, the filling stage, and the food smoking process. The study was conducted in collaboration with a local producer who adheres to traditional curing methods utilizing oak wood smoke and heat. Biogenic amine levels were closely monitored throughout the process. This involved their extraction and derivatization through the salting-out technique, followed by identification and quantification using LC-ESI/MSn and HPLC-DAD, respectively. The findings suggest that both raw materials and the production process are well controlled during the filling stage. However, it became evident that the 14-day oak wood smoking period had a significant impact on biogenic amine formation, whose total mean values increased from 126 to 1385 mg kg−1, particularly with respect to putrescine (PUT), cadaverine (CAD), and tyramine (TYR), although these levels remained below the oral toxicity limit (2000 mg kg−1). Consequently, the concentration of these compounds can influence the quality and safety of traditionally dry-cured chorizos. Therefore, the combined levels of PUT, CAD, and TYR can serve as a valuable quality indicator for these products.

Effects of GBFS content and curing methods on the working performance and microstructure of ternary geopolymers based on high-content steel slag

Aimed to address the low utilization rate of steel slag (SS) and its challenge in resource utilization in China, this study developed ternary geopolymers made by high-content (50%) SS together with fly ash (FA) and granulated blast furnace slag (GBFS). The effects of GBFS content (0–40%) and curing methods (water curing, standard curing, sealed curing, and heat curing) on the working performance and microstructure of geopolymers were investigated. Microscopic analysis such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG), and scanning electron microscopy (SEM) were utilized to investigate the hydration process and products of geopolymers under different curing conditions and GBFS content. The results indicated that when the GBFS content increased from 0% to 40%, the fluidity of the mixture decreased by 11.7%, the initial setting time of the geopolymer slurry decreased by 76%, and the geopolymer mortar’s 28d compressive strength increased from 31.9 MPa to 60.6 MPa. At room temperature, the geopolymer mortar’s 28d compressive strength was higher under standard curing (70.8 MPa) compared to water curing (57.5 MPa) and sealed curing (68 MPa). The geopolymer mortar cured at 60 °C for 24 h exhibited the highest 28d compressive strength (76.3 MPa). However, excessively high curing temperatures or prolonged durations led to more shrinkage cracks and reduced the compressive strength. The microscopic analysis revealed that the main gel products of ternary geopolymer were C-(A)-S-H gel. The amount of gel products is directly related to the strength of geopolymers. The developed ternary geopolymer has the potential to promote the large-scale utilization of SS in the concrete industry, making a significant contribution to sustainable development.

Highly Sensitive Flexible Capacitive Pressure Sensor with Porous Hierarchical Structure Realized by a Microwave Curing Method

The introduction of porous hierarchical microstructures effectively improves the sensitivity of flexible pressure sensors. However, it is difficult to achieve porous hierarchical microstructures for pressure sensors through inexpensive, efficient, and simple preparation methods. Herein, a hemispherical array with porous hierarchical microstructure is prepared on polydimethylsiloxane substrate using a simple one‐step microwave curing process with glucose as porogen. Furthermore, the flexible electrode based on the polydimethylsiloxane substrate is combined with an ionic liquid polymeric gel membrane to obtain a flexible capacitive pressure sensor. Thanks to the deformability of porous hierarchical microstructure and the double‐dielectric layer effect of ionic liquid polymeric gel membrane, the sensor displays an ultrahigh sensitivity of 131.21 kPa−1 within 0–1 kPa. Meanwhile, the sensor has short response time, excellent dynamic loading stability, as well as excellent long‐term stability (>3000 cycles). In application testing, the sensor effectively monitors various physiological activities like pulse, breathe, speech, and swallowing, demonstrating its good prospects in the field of health electronics. Most importantly, the proposed microwave curing method can realize the preparation of porous hierarchical structure on flexible substrate through a one‐step process, which offers a fresh way for the economical, green, and efficient preparation of high‐sensitivity capacitive pressure sensors.

Multivariate Regression and Variance in Concrete Curing Methods: Strength Prediction with Experiments

Because concrete strengths and quality are affected by various factors, multivariate regression models are often used to analyze the differences between predicted and target outputs. However, the variableness of a predicted output and how individual input parameters affect prediction reliabilities are still uncertain in practical applications, especially for the prediction of compressive strengths of concrete. This study aims to develop multivariate models for predicting concrete strengths and providing the variance analysis of prediction results by comparisons with experiment outcomes. First, this paper provides an in-depth examination of established variance analysis methods in the context of commonly used multivariate regression models. Then, based on Gaussian process regression, this study melds principal component analysis (PCA), linear discriminant analysis (LDA), and multivariate analysis of variance (MANOVA) to assess the variability in concrete strength prediction using different curing methods. This innovative approach proves effective in evaluating the precision of the correlation and regression models (R-squared values ≥ 0.9049). The comparison between prediction results and experiment outcomes shows that retaining heat in cylinders can make them become too hot and overestimate in-place concrete strength. This study improves the methodologies of regression modeling for variance analysis and improves the reliability of concrete strength prediction. Additionally, the outcomes of this research can help save a substantial amount of financial resources and time that are required to obtain experimental data on the strengths of concrete components.

Experimental study on the development mode and evolution mechanism of sodium silicate solidified sand under different temperatures and curing paths

Water glass, which can be cured by rapid dehydration, is an ideal environmentally friendly material for engineering grouting solidification and ecological environment restoration. The curing efficiency of water glass at room temperature was low, the curing mechanism and strength characteristics at high temperature were not clear, and the engineering applicability and optimal curing methods were to be explored. In this paper, 10 curing paths were designed within 100 °C. The mechanical and acoustic characteristics of water glass-cured sandy soils were tested by uniaxial compressive tests and acoustic emission (AE). The relationship between strength, wave velocity and curing age was established based on the “logistics” model. The characteristic parameter “Q” value was proposed based on the AE characteristic value. Combined with the results of scanning electron microscopy (SEM), the solidification evolution process was revealed in terms of gel structure, crystal morphology and pore space. The process of water glass curing sandy soil was divided into a “strength rising period” and a “strength deterioration period”. The enhancement and weakening effects of high temperature on the gel layer were stronger than those at room temperature. The longer the room temperature curing time is, the weaker the effect of high temperature on the specimen. After high-temperature curing, the maximum strength of the specimens increased by 107.85 %, and the strength growth rate and strength deterioration rate increased by 586.34 % and 3738.79 %, respectively. The conversion rate of the gel under high temperature conditions determined the strength of the specimen. The rate of strength deterioration of the specimen was determined by the hardening effect of the undehydrated gel and the excessive dehydration effect of the rigid gel.

Investigation of the effect of different curing conditions on the mechanical performance of calcium aluminate cement concrete at elevated temperatures

Research on improving the performance of concrete at elevated temperatures has been increasing in recent years. In this context, Calcium Aluminate Cement (CAC) can be used in concrete mixes to increase the performance of concrete at elevated temperatures. However, the use of CAC has not yet become widespread in structural applications due to the unstable nature of CAC, which is highly affected by curing temperature and humidity. Therefore, it is of great importance to investigate the curing conditions that directly affect the unstable nature of CAC. In the present study, different curing methods were applied to calcium aluminate cement concretes (CACC) and their performance at elevated temperatures (300 °C, 600 °C, 900 °C) was investigated. In this framework, compressive strength, modulus of elasticity and flexural strength of the samples were determined, load–displacement relations and microstructural changes were evaluated. As a result of the study, it has been determined that CACC samples have better mechanical performance than normal concrete at elevated temperatures and especially the mechanical performance of CACC samples cured at high temperature (CACCH) is better than CACC samples cured under normal conditions (CACCN).

Preparation of high performance dense Al2O3 ceramics by digital light processing 3D printing technology

The incorporation of a significant amount of organic materials in the fabrication process of Al2O3 ceramics using digital light processing (DLP) 3D printing technology leads to a noticeable reduction in mechanical properties compared to those prepared using traditional methods. To enhance its mechanical performance of Al2O3 ceramics, the addition of MgO and MgO-Y2O3 sintering additives, along with a three-step curing method, has resulted in significant improvements. Al2O3 ceramics fabricated with the addition of MgO exhibited a flexural strength of 454.2 MPa, Vickers hardness of 20.24 GPa and apparent porosity of 0.15 %. Similarly, the addition of MgO-Y2O3 yielded Al2O3 ceramics with a flexural strength of 491.6 MPa, Vickers hardness of 20.91 GPa, and apparent porosity of 0.11 %. These values exceed the typical flexural strength of Al2O3 ceramics prepared using traditional methods. This research provides a fundamental basis for the production of high performance, dense, and complex shaped Al2O3 ceramics using DLP 3D printing technology.

Preparation of geopolymer concrete with Bayer red mud and its reaction mechanism

Red mud (RM) is a hazardous waste product resulting from alumina production in the aluminum industry. In China, the alumina industry generates a significant amount of solid waste RM annually. The accumulation of RM not only occupies a large area of land but also leads to environmental pollution. Currently, Bayer red mud (BRM) constitutes the majority of the piled-up RM in China. Due to its high alkalinity and low activity, BRM cannot be directly used in the cement industry, and its comprehensive utilization is severely limited. Thus, finding a bulk, safe, and cost-effective utilization method is crucial in tackling the massive accumulation of BRM. This study primarily focuses on the reactivity and reaction mechanisms of BRM in cement-based and geopolymer material. Firstly, it was demonstrated through compressive strength, chemical bound water content, SEM microstructures, and flowability that BRM exhibits relatively low reactivity in cement-based material. Experimental investigations were conducted to study the impact of the BRM addition and curing methods on the mechanical properties of BRM based geopolymer materials. The dosage range of BRM under different conditions was given. Through SEM-EDS analysis, the influence of BRM with its high-temperature activation on the early hydration products in geopolymer material was investigated. The reaction mechanism of BRM in geopolymers was analyzed, and a reliable, affordable, and efficient way to use BRM on a large scale was developed.

The utilization of natural eco-benign sources for sustainable management to preserve hides and docking analysis of identified potential phytochemicals.

The industrial leather sector is one of the most ancient industries globally and continues to influence the global economic system in contemporary times significantly. Regardless of income, the leather sector is widely recognized as a significant environmentally detrimental sector because of the utilization of materials involved in preserving and processing leather. Raw hides, the primary ingredient in the leather industry, are highly susceptible to microbial attack once they have been flayed from animals. The current review provides information about the diverse operational processes employed in the beam house to produce leather goods. This paper primarily focuses on the preservation of various types of hides, including those derived from goats, cows, sheeps, deers, pigs, and other species, with particular emphasis on bio-based preservation methods. It also discusses various salt and salt-free curing methods along with their limitations. Furthermore, it reviews a viable and economically advantageous option for preserving animal hides using plant and microbial sources. Moreover, it focuses on investigating the molecular docking interactions between three critical enzymes in the phytochemical synthesis pathway, namely phenylalanine ammonia-lyase, phosphomevalonate kinase, and dihydroflavonol 4-reductase, and a set of specific modulators, followed by ADMET analyses. The objective was to determine the optimal binding affinity score for these enzyme-modulator complexes through virtual screening. The depiction of protein-ligand interactions offers potential benefits for future research endeavours, as well as valuable insights into the identification of modulators and the evaluation of the potency and efficacy of phytochemicals in the preservation of hides.

Early Mechanical and Microstructure Evolution Characteristics of Concrete in Steam Curing Condition

In order to study the effect of steam curing on early mechanical properties of concrete, the strength, dynamic elastic modulus, and microstructure characteristics of concrete under different curing methods were tested. The results show that the early strength growth rate of steam curing concrete is obviously higher than that of standard curing. The strength development of concrete during steam curing can be divided into three stages. Stage I and stage II (0 h-30 h) are critical periods for concrete strength growth. The dynamic elastic modulus of steam-curing concrete is mainly formed in the early stage and shows a linear rapid growth characteristic. The growth rate of the dynamic elastic modulus of concrete under standard curing condition is relatively slow, but in the later curing period (30 h-48 h), the growth rate of dynamic elastic modulus of concrete is significantly higher than that of steam curing concrete. Steam curing can accelerate the production of cement hydration products which rapidly increases the early strength of concrete. Under the standard curing condition, the hydration product structure of concrete is more compact, which is conducive to the growth of dynamic elastic modulus in a later period. This study provides a theoretical reference for the application of steam curing in engineering, which is important to ensure the production efficiency and quality of concrete in engineering.

Thickness, Adhesion and Microscopic Analysis of the Surface Structure of Single-Layer and Multi-Layer Metakaolin-Based Geopolymer Coatings

This work is focused on creating coating layers made of a metakaolin-based geopolymer suspensions (GP)-formed Al matrix modified using H3PO4 acid with Al(OH)3 in isopropyl alcohol, named GP suspension I, and H3PO4 acid with nano Al2O3 in isopropyl alcohol, named GP suspension J. The selected GP suspensions were applied on aluminum and steel underlying substrates as single-layer coatings and multi-layer coatings, where multi-layer coatings included three and five layers that were polymerized by a curing process. Curing was divided into two types with every layer curing process and final layer curing process. For both GP suspensions I and J, the effect of the number of layers and the type of substrate on adhesion was investigated. The prepared samples on underlying substrates were characterized on the microscopy analysis including SEM for high-resolution images and 3D laser confocal microscopy (CLSM) for the 3D visualization of the coatings structure. Microscopy analysis showed structural defects such as porosity, cracks and peeling, which increase with a greater number of applied layers. However, these defects were only evident on a micro scale and did not seem to be fatal for the performance of the surface stability. The EDS mapping of the prepared layer showed inhomogeneity in the distribution of elements caused by the brush application. A grid test and thickness measurement were performed to complete the microscopy analysis. The grid test confirmed a very high adhesion of GP coatings on the aluminum substrate with a rating of one (only in one case was there a rating of two) and a lower adhesion on the steel substrate with the most frequent rating of three (in one case, there were ratings of two and one). The thickness measurement proved a noticeably thicker thickness of the prepared layer on the Fe substrate compared to the Al substrate by 20%–30% in the case of suspension I and by 70%–10% in the case of suspension J. The thickness of the layer also showed a dependence on the method of application and curing, as a thicker layer was always achieved when curing after the final layer of the GP suspension, compared to curing after each applied layer. The resulting single-layer and multi-layer thicknesses ranged from approx. 7 to 30 µm for suspension I and from approx. 3 to 11 µm for suspension J. A non-linear increase in thickness was also evident from the thickness measurement data.

The influence of microwave curing on the strength of silica fume-added fly ash-based geopolymer mortars

Geopolymer concretes a substitute for traditional Portland cement as a more environmentally sustainable alternative. In addition, one of the most significant advantages of geopolymer concrete is the high setting speed that can be achieved with thermal curing, that is, the short curing period. Research on geopolymer concrete has focused on curing, where curing is usually done with conventional ovens. Microwave curing initiates heat generation at the molecular level, which results in a minimal heat increase on the surface of the specimens compared to traditional thermal curing methods. In addition, it provides internal, rapid, and homogeneous heating and rapid strength development. This study is based on research that examined the effect of microwave cure on the compressive strength of silica füme-modified geopolymer mortar. In the study, sodium silicate and sodium hydroxide were used for activation, and first of all, fly ash substituted geopolymer mortar specimens were subjected to conventional thermal curing in an oven. On the other hand, the mortar specimens with the same composition were subjected to short-duration (10 minutes) microwave curing at power levels of between 200-600 W. When the results were compared regarding compressive strength, void and percent water absorption, UPV, and SEM-internal structure examination, it was revealed that microwave curing could be used faster than the conventional oven curing method in silica füme-added fly ash-based geopolymer mortars. This research can be considered an essential step for further optimizing and popularising geopolymer concrete and microwave curing and proposes a method that should be considered in the future development of more sustainable construction materials.

Lamination curing method for silver nanoparticle inkjet printed flexible electronics: design, uncertainty and performance analysis

Lamination curing method for silver nanoparticle inkjet printed flexible electronics: design, uncertainty and performance analysis

Integrating Curing Experience and Fluctuating Leaf Quality in an Intelligent End-Cloud Collaboration

Automated tobacco curing systems have been widely deployed to meet the demand of large-scale production of high-quality tobacco. Existing tobacco curing systems control the process based on a fixed standard curing curve to increase the production of high-quality tobacco and reduce the cost. However, it is difficult to adapt the standard curing curve to the various qualities of tobacco leaves and different experience of operators. In this paper, we propose an end-cloud collaborative intelligent curing technique which can continuously extract and integrate curing experience by using clustering and regression analysis method. At the terminal, we use a microcontroller to receive sensor data collected and exchange the information with servers through a 4G communication module. On the server side, we use a clustering-based method to separate the data of high-quality tobacco, and use regression analysis and kalman filtering for data fusion. Compared with the existing automatic curing method, our proposed method can continuously extract curing experience and optimize curing curves.