Predictions regarding the HEA phase formation rules of the alloy system require subsequent empirical confirmation. Microstructural and phase analyses of the HEA powder were performed across various milling times and speeds, along with diverse process control agents and sintering temperatures of the pre-milled HEA block. Milling time and speed have no effect on the alloying process of the powder; nevertheless, faster milling speeds produce smaller powder particles. Ethanol, used as the processing chemical agent in a 50-hour milling process, produced a powder with a dual-phase FCC+BCC structure. Concurrently, the inclusion of stearic acid as a processing chemical agent limited the powder's ability to alloy. The HEA, subjected to a SPS temperature of 950°C, undergoes a change in its structural arrangement from dual-phase to a single FCC structure, and as temperature increases, the alloy's mechanical properties exhibit a gradual amelioration. When subjected to 1150 degrees Celsius, the HEA shows a density of 792 grams per cubic centimeter, a relative density of 987 percent, and a hardness of 1050 on the Vickers hardness scale. The brittle fracture mechanism, marked by typical cleavage, demonstrates a maximum compressive strength of 2363 MPa, with no yield point present.
Materials that have undergone welding procedures often benefit from post-weld heat treatment, or PWHT, which improves their mechanical properties. Several publications have explored the effects of the PWHT process, employing experimental designs to achieve their findings. Nonetheless, the integration of machine learning (ML) and metaheuristics for modeling and optimization remains unreported, a crucial prerequisite for intelligent manufacturing applications. This research's novel contribution lies in the application of machine learning and metaheuristic optimization for adjusting the parameters of the PWHT process. click here The objective is to pinpoint the optimal PWHT parameters, encompassing both singular and multifaceted viewpoints. Within this research, a relationship model between PWHT parameters and the mechanical properties ultimate tensile strength (UTS) and elongation percentage (EL) was developed via the application of four machine learning techniques: support vector regression (SVR), K-nearest neighbors (KNN), decision trees (DT), and random forests (RF). The results showcase the superior performance of the SVR algorithm relative to other machine learning techniques, specifically within the contexts of UTS and EL models. Subsequently, the Support Vector Regression (SVR) model is employed alongside metaheuristic optimization techniques, including differential evolution (DE), particle swarm optimization (PSO), and genetic algorithms (GA). The fastest convergence among the different combinations is demonstrably achieved by SVR-PSO. This research contributed final solutions to the fields of single-objective and Pareto optimization.
This research focused on silicon nitride ceramics (Si3N4) and silicon nitride composites reinforced with nano silicon carbide particles (Si3N4-nSiC), containing 1-10 weight percent of the reinforcement. Materials were sourced using two sintering regimes, operating within the constraints of ambient and high isostatic pressures respectively. Research explored how sintering conditions and the amount of nano-silicon carbide particles impacted thermal and mechanical properties. The presence of highly conductive silicon carbide particles led to a rise in thermal conductivity exclusively within composites containing 1 wt.% of the carbide (156 Wm⁻¹K⁻¹), outperforming silicon nitride ceramics (114 Wm⁻¹K⁻¹) created under the same conditions. As the carbide phase increased, the sintering densification rate diminished, causing a reduction in both the thermal and mechanical performance. Improvements in mechanical properties were observed following the sintering process using a hot isostatic press (HIP). The process of high-pressure assisted sintering, carried out in a single step within hot isostatic pressing (HIP), minimizes the creation of surface imperfections within the sample.
Geotechnical testing utilizing a direct shear box forms the basis of this paper's examination of coarse sand's micro and macro-scale behavior. In a 3D discrete element method (DEM) model, sphere particles were used to simulate the direct shear of sand, thereby evaluating the capability of the rolling resistance linear contact model to reproduce this standard test involving particles of real-world size. A crucial focus was placed on the effect of the main contact model parameters' interaction with particle size on maximum shear stress, residual shear stress, and the change in sand volume. Following calibration and validation with experimental data, the performed model underwent sensitive analyses. An appropriate replication of the stress path has been observed. The prominent impact of increasing the rolling resistance coefficient was seen in the peak shear stress and volume change during the shearing process, particularly when the coefficient of friction was high. Nevertheless, when the coefficient of friction was low, the rolling resistance coefficient had a negligible influence on shear stress and volume change. The influence of varying friction and rolling resistance coefficients on the residual shear stress, as anticipated, was comparatively small.
The combination of x-weight percentage of Spark plasma sintering (SPS) was the method used to achieve titanium matrix reinforcement with TiB2. Evaluation of the mechanical properties of the sintered bulk samples followed their characterization. A near-full density was achieved, the sintered specimen exhibiting the lowest relative density at 975%. The SPS process's effectiveness is evident in its contribution to excellent sinterability. The consolidated samples exhibited a Vickers hardness increase, from 1881 HV1 to 3048 HV1, a result demonstrably linked to the exceptional hardness of the TiB2. click here The sintered samples' tensile strength and elongation were inversely proportional to the concentration of TiB2. By incorporating TiB2, the nano hardness and reduced elastic modulus of the consolidated samples were improved, with the highest values of 9841 MPa and 188 GPa, respectively, seen in the Ti-75 wt.% TiB2 sample. click here Whiskers and in-situ particles are dispersed throughout the microstructures, as confirmed by X-ray diffraction (XRD) analysis, which detected new phases. The TiB2 particles, when incorporated into the composites, brought about a substantial improvement in wear resistance compared to the control sample of unreinforced titanium. Sintered composite material displayed both ductile and brittle fracture patterns, owing to the presence of dimples and considerable cracks.
Various types of polymers, including naphthalene formaldehyde, polycarboxylate, and lignosulfonate, are examined in this paper to assess their effectiveness as superplasticizers for concrete mixtures utilizing low-clinker slag Portland cement. Utilizing a mathematical experimental design and statistical models of water demand in concrete mixtures containing polymer superplasticizers, alongside concrete strength measurements at various ages and differing curing treatments (conventional and steam curing), were obtained. Superplasticizers, according to the models, led to alterations in both water content and concrete's strength. Evaluating the efficacy and integration of superplasticizers within cement relies upon a proposed criterion that factors in their water-reducing capacity and the resultant alteration in concrete's relative strength. The results highlight the substantial strength gain in concrete when using the examined superplasticizer types and low-clinker slag Portland cement. The inherent characteristics of different polymer types have been found to facilitate concrete strength development, with values spanning 50 MPa to 80 MPa.
The surface characteristics of drug containers need to reduce drug adsorption and avoid unwanted interactions between the container surface and the drug, especially with biologically-produced pharmaceuticals. Our study, utilizing a combination of Differential Scanning Calorimetry (DSC), Atomic Force Microscopy (AFM), Contact Angle (CA), Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), and X-ray Photoemission Spectroscopy (XPS), explored the nature of rhNGF's interactions with various pharmacopeial polymer materials. Polypropylene (PP)/polyethylene (PE) copolymers and PP homopolymers, examined as both spin-coated films and injection-molded specimens, were analyzed for their degree of crystallinity and protein adsorption capabilities. Our study demonstrated that copolymers exhibit a lower degree of crystallinity and reduced roughness in comparison to PP homopolymers. PP/PE copolymers, in accordance with this trend, demonstrate higher contact angles, thereby indicating a lower wettability of their surface by rhNGF solution compared to PP homopolymers. Our results reveal a direct correlation between the chemical composition of the polymer and its surface roughness, and how proteins interact with it, showing that copolymers could offer an advantage in terms of protein interaction/adsorption. Protein adsorption, as evidenced by the combined QCM-D and XPS data, proved a self-limiting process, effectively passivating the surface after the deposition of roughly one molecular layer, thereby hindering any long-term subsequent protein adsorption.
Biochar derived from walnut, pistachio, and peanut shells underwent analysis to determine its potential utility as a fuel or soil enhancer. At five distinct temperatures—250°C, 300°C, 350°C, 450°C, and 550°C—all samples were pyrolyzed. Following this, proximate and elemental analysis, calorific value assessments, and stoichiometric calculations were performed on all the samples. With a view to its use as a soil amendment, phytotoxicity testing was carried out to determine the quantities of phenolics, flavonoids, tannins, juglone, and antioxidant activity. To define the chemical composition of the shells of walnuts, pistachios, and peanuts, the levels of lignin, cellulose, holocellulose, hemicellulose, and extractives were determined. The pyrolytic process demonstrated that walnut and pistachio shells yielded the best results at 300 degrees Celsius, and peanut shells at 550 degrees Celsius, thereby establishing them as suitable substitutes for conventional fuels.