Material Process Research Articles

A coupled data-physics computational framework for temperature, residual stress, and distortion modeling in autoclave process of composite materials

It is challenging to obtain the full-field temperature profile during autoclave processes to control the temperature uniformity and minimize the residual stress and distortion of cured composite structures. This paper proposes a coupled data-physics computational framework for full-field temperature reconstruction and the subsequent residual stress/distortion modeling by using limited monitoring temperature data. Firstly, a Long Short-Term Memory (LSTM) model is developed for full field temperature reconstruction. In this LSTM model, a cross-recombination method is proposed to maximize the value of monitored temperature data. The method effectively cuts through the bottleneck of neural network training with limited labeled data. The LSTM model’s prediction stability is enhanced based on the mean-teacher and ensemble learning strategy. To train and validate the proposed method, we perform experiments using an autoclave at the National Institute for Aviation Research (NIAR). The LSTM model’s accuracy is assessed by comparing its predicted results with the thermocouple (TC) data from measurements and high-fidelity simulation data from computational fluid dynamics (CFD). The study shows that the proposed LSTM model can effectively reconstruct the full-field temperature using limited monitoring data and significantly improve accuracy and efficiency compared with the CFD-based counterpart. Then, we create a coupled data-physics computational framework by embedding the data-driven LSTM model into a physics-based thermo-mechanical finite element model to predict residual stress and distortion. The simulation results show that the coupled data-physics framework provides an effective way for process-to-performance modeling and simulation of autoclave curing processes.

The effect of processing/curing temperature and viscosity of epoxy resins on the flexural/tensile properties of GNP-epoxy resin nanocomposites

Despite the problem of graphene aggregation in cured epoxy resin, no studies have clarified the tendency of graphene aggregation in a wide variety of material systems and process. We hypothesized that the use of epoxy resins at high temperatures leads to an extreme decrease in resin surface tension and viscosity of epoxy, which would cause re-aggregation of graphene once dispersed. So, we examined process/material with/without high temperature treatment and epoxy resins of different viscosities, and properties of nanocomposites were evaluated by flexural/tensile test. Experiments revealed that the process not including high temperature treatment suppressed graphene re-aggregation and maintained the high mechanical properties of nanocomposites. In particular, the increased tensile modulus by 18.44% and flexural strength by 2.81% (@ 1 wt% graphene loading), which were quite high for non-functionalized graphene, were recorded when epoxy was treated and cured at 20 ˚C at all times to keep the surface tension of epoxy desirable.

The anisotropic sublimation induces rhombohedral to rock-salt phase transformation of chalcogenide SnSb2Te4 two-dimensional nanomaterial

We report the sublimation and phase transformation mechanisms of a two-dimensional (2D) chalcogenide SnSb2Te4 using a lab-developed in-situ electro-thermal testing system on a Cs-corrected transmission electron microscope. It reveals that the sublimation process is primarily governed by the surface energy mechanism, following an anisotropic route. The van der Waals (vdW) layers ending with Te atoms lead to the preferential sublimation on (003) plane, with the (1 1‾ 4) and (117) planes accommodating the sublimation. It is uncovered for the first time, that the preferential and accommodated sublimation of Te and Sb atoms along the vdW planes results in short-range diffusion inducing a phase transition from rhombohedral SnSb2Te4 to rock-salt (Sn1-xSbx)Te. These results highlight complex physics processes of 2D materials under service conditions and the route of atomic-resolved electro-thermal research platforms for investigations of complex atomistic mechanisms of 2D materials by thermal-electric external fields.

OPTIMIZATION OF THE PERFORMANCE OF THE SANDSTONE CRUSHING PLANT UNIT AT PT PULAU LEMON

The process of processing sandstone material at the PT Pulau Lemon crushing unit is not yet optimal. This is due to differences in the amount of material entering and leaving the crushing unit. To optimize the performance of the processing unit, it is necessary to conduct research on the causes of material loss. Furthermore, the research aims to: 1) calculate material loss; 2) assess the causes of material loss and determine efforts to minimize material loss. The research was carried out using mathematical calculations using mass balance equations for material entering and leaving the processing unit, field observations and interviews. The research results showed that the amount of incoming material was 16.66 tons/day and outgoing material was 14.85 tons/day, so the material lost was 1.81 tons/day. or 10.80%. Material loss is caused by the slope of the conveyor belt being less than gentle and some parts being torn, wind, rain and mechanical problems. Efforts to optimize the performance of processing units include reducing waiting times, regularly checking and repairing equipment, and installing roofs.

Enhancing layered perovskite ferrites with ultra-high-density nanoparticles via cobalt doping for ceramic fuel cell anode

Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural configuration. Herein, we employ controlled Co doping to effectively enhance the nanoparticle exsolution process in layered perovskite ferrites materials. CoFe alloy nanoparticles with ultra-high-density are exsolved on the (PrBa)0.95(Fe0.8Co0.1Nb0.1)2O5+δ (PBFCN0.1) surface under reducing atmosphere, providing significant amounts of reaction sites and good durability for hydrocarbon catalysis. Under a reducing atmosphere, cobalt facilitates the reduction of iron cations within PBFCN0.1, leading to the formation of CoFe alloy nanoparticles. This formation is accompanied by a cation exchange process, wherein, with the increase in temperature, partial cobalt ions are substituted by iron. Meanwhile, Co doping significantly enhance the electrical conductivity due to the stronger covalency of the CoO bond compared with FeO bond. A single cell with the configuration of PBFCN0.1-Sm0.2Ce0.8O1.9 (SDC)|SDC|Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF)-SDC achieves an extremely low polarization resistance of 0.0163 Ω cm2 and a high peak power density of 740 mW cm−2 at 800 °C. The cell also shows stable operation for 120 h in H2 with a constant current density of 285 mA cm−2. Furthermore, employing wet C2H6 as fuel, the cell demonstrates remarkable performance, achieving peak power densities of 455 mW cm−2 at 800 °C and 320 mW cm−2 at 750 °C, marking improvements of 36% and 70% over the cell with (PrBa)0.95(Fe0.9Nb0.1)2O5+δ (PBFN)-SDC at these respective temperatures. This discovery emphasizes how temperature influences alloy nanoparticles exsolution within doped layered perovskite ferrites materials, paving the way for the development of high-performance ceramic fuel cell anodes.

Natural Death and Teleology in Aristotle’s Science of Living Beings

Abstract According to most interpreters, Aristotle explains death as the result of material processes of the body going against the nature of the living being. Yet, this description is incomplete, for it does not clarify the relationship between the process of decay and the teleological system in which it occurs: this makes it impossible to distinguish between natural and violent death. In this paper, I try to fill this gap by looking at his so-called ‘biological works’ and mainly at the De Juventute. I first introduce the specific concept of life at play in this treatise and prove its complementarity with the framework of the De Anima. Then, I illustrate in detail the process of dying and the reasons why a merely material description is insufficient to account for the distinction between natural and violent death. Finally, I show that for Aristotle natural death is a by-product of teleologically directed life activities: only against the background of this teleological structure is natural death fully explained in terms of essence and causes. To support this claim, I compare death to two analogous cases in Aristotle’s biology, namely dreams and the features of GA V.

Temperature damage assessment of mass concrete based on the coupling mechanism of hydration-temperature-humidity-constraint factors

Temperature cracking of mass concrete is an important issue affecting the safety of concrete foundations in civil engineering. This problem extends from the construction process of concrete foundations to the operation stage. This study uses low-temperature-rising (LTR) polymers to regulate the hydration process of cementitious materials, and prepares LTR mass concrete. Taking the hydration degree of concrete-cement system as the basic state variable, the multi-factor effects of actual hydration process, temperature, humidity changes, and constraints on mass concrete are comprehensively considered. A concrete temperature-damage model based on the coupling mechanism of “hydration-temperature-humidity-constraints” is established, and the temperature, stress, and temperature damage evolution laws of LTR mass concrete and ordinary mass concrete are calculated. The reliability of the model is verified through field tests. The results show that the finite element method can effectively simulate the development of concrete temperature, stress, and damage degree based on actual working conditions under multi-factor coupling.

Ship Emergency Material Allocation Model Based on NSGA-II Algorithm

The process of ship material resupply is studied to illustrate the importance of the material resupply process; the common emergency material scheduling problem is compared with the material resupply problem to analyze the similarities and differences; analogous to the part of the emergency material scheduling problem to design the material resupply algorithm, and finally, a material resupply mission is taken as an example to use this paper's algorithm for solving the model and verifying the feasibility of the algorithm.

The hydrometallurgical recovery of critical and valuable elements from WEEE shredding dust: Process effectiveness in a life cycle perspective

Waste electrical and electronic equipment (WEEE) recycling stands as a crucial opportunity to get critical resources while managing a waste stream in accordance with the circular economy principles. Recently, a two-step hydrometallurgical process has been successfully investigated to treat the dust originating from the mechanical processing of WEEE. The best operating conditions selected in this study were used to further investigate the recovery of precious metals and critical elements, achieving extraction yields of approximately 77.7 % and 53.1 %, respectively; base metals (i.e. aluminum, zinc, copper, ..) were also leached from dust up to 96 %. A life cycle approach was also applied to preliminary assess and compare the potential environmental impact of the proposed process with respect to the manufacturing process of the virgin material. The analysis focused on standard environmental indicators (i.e. global warming potential, acidification, …), human toxicity and eco-toxicty and a set of five different characterisation models for abiotic depletion of resources. Four scenarios, differing for allocation criteria (mass/economic) and the possible recovery of metals along with REEs, were compared. Among the recovered products, the greates potential benefits were found in the case of rare earth elements, in the scenario considering the complete recovery of base and precious metals and performing an economic allocation. Impacts on abiotic depletion and toxicity account for the highest benefits from maerial recovery. Nevertheless, the recovery of sulphuric acid would allow a further reduction also in other impacts, strengthening the potential competitiveness of REE recovery against the manufacturing of virgin materials.

THE DEVELOPMENT OF A PIEZOELECTRIC DEFECT DETECTION DEVICE THROUGH MATHEMATICAL MODELING APPLIED TO POLYMER COMPOSITE MATERIALS

In this research article, the focus is on examining the strength characteristics of polymer composite materials under various stress states. The investigation into the material dissolution process is conducted in two distinct stages. Initially, the article employs a criterion approach to derive explicit formulas for the latent decay time (incubation period) of materials, considering singular, exponential and Abelian kernels of the damage operator. In the subsequent stage, the classical strength condition is applied to establish a Volterra type integral equation, which characterizes the damage process for hereditary materials. These resulting differential equations are then solved with appropriate initial conditions. The study utilizes the obtained results to create time-dependent graphs of the damage parameter and performs comparisons. A piezoelectric defect detection device for polymer composite materials has been proposed through the application of mathematical modeling.

Cooperative competition between melt-phase and void during micro-spallation and recompression

Dynamic tensile (micro-spallation) fracture and subsequent recompression in a molten state is the key physical process for metallic materials undergoing multiple intense dynamic loadings. However, there still lacks in-depth analysis of the complete evolution process from damage accumulation to recompression, as well as the influence of damage history on subsequent deformation and fracture. In the present work, the mechanism of cooperative competition evolution between the melt-phase and voids has been proposed as a new perspective to investigate damage evolution. Various important physical phenomena discovered in larger-scale MD simulations of molten aluminum can be self-consistently explained according to the proposed mechanism, such as the rate-dependence of spall strength and the pressure oscillation. The recompression-after-damage and second fracture process are discussed in detail to analyze the damage history effect. Under the present framework, two theoretical models have been proposed from the perspective of void and melt-phase evolution, respectively. The proposed models agree well with the simulation results and provide a comprehensive understanding of the damage evolutionary characteristics.

Influence of the solvent removal method on the morphology of polystyrene porous structures prepared via thermally induced phase separation

Thermally induced phase separation (TIPS) allows preparation of nano and micro-porous structured materials for various applications. The literature thoroughly examines the impact of initial polymer solution concentration and cooling rate on the products morphology. On the contrary, the influence of the solvent removal methods was so far researched scarcely. Hence, we compare both qualitatively and quantitatively the effects of the solvent removal method on pore size distribution, structure, porosity, and thermal conductivity. Our study was carried out with samples prepared by TIPS from polystyrene/cyclohexane solutions employing either extraction agent or lyophilization at different solvent removal temperatures. Materials exhibited interconnected pore structure, implying good sound insulation properties, and had low thermal conductivity, offering the combination of thermal and sound insulation in one layer of material. Pore sizes after lyophilization were up to two times larger than after solvent removal by an extraction agent. On the other hand, the use of extraction agent led up to 10% porosity decrease with average porosity after lyophilization being above 82%. Our findings demonstrate that the solvent removal method is an important parameter during TIPS and that pros and cons of both methods should be carefully considered to obtain optimal material and TIPS process economy.

Recent progress on charge transfer engineering in reticular framework for efficient electrochemiluminescence.

Electrochemiluminescence (ECL) is a luminescence production technique triggered by electrochemistry, which has emerged as a powerful analytical technique in bioanalysis and clinical diagnosis. During ECL, charge transfer (CT) is an important process between electrochemical excitation and luminescent emission, and dramatically affects the efficiency of exciton generation, playing a pivotal role in the light-emitting properties of nanomaterials. Reticular framework materials with intramolecular/intermolecular interactions offer a promising platform for regulating CT pathways and enhancing luminescence efficiency. Deciphering the role of intramolecular/intermolecular CT processes in reticular framework materials allows for the targeted design and synthesis of emitters with precisely controlled CT properties. This sheds light on the microscopic mechanisms of electro-optical conversion in ECL, propelling advancements in their efficiency and breakthrough applications. This mini-review focuses on recent advancements in engineering CT within reticular frameworks to boost ECL efficiency. We summarized strategies including intra-reticular charge transfer, CT between the metal and ligands, and CT between guest molecules and frameworks within reticular frameworks, which holds promise for developing next-generation ECL devices with enhanced sensitivity and light emission.

Towards automated characterisation of fatigue damage in composites using thermoelastic stress analysis

Composite materials demonstrate complicated fatigue behaviour due to their microstructure and the varied types of defects that can occur during loading. This necessitates experimentation to determine their performance under loading. In this study an algorithm is introduced for identifying and categorising different defects forming during fatigue tests. Thermoelastic stress analysis was used to obtain high spatial and temporal resolution stress information from the surface of notched composite specimens. Specimens with three different geometries were loaded in tension–tension fatigue to failure. An algorithm was used to identify when and where matrix cracking and delaminations formed within the specimens as well as quantify how this changed over time. By improving how damage events are identified and characterised, the algorithm reduces the amount of time needed to process experimental fatigue data and helps to provide greater understanding of fatigue processes in new materials from early small-scale cracking all the way to final failure.

THEORETICAL AND EXPERIMENTAL ANALYSIS OF DRYING KINETICS OF COLLOID CAPILLARY-POROUS MATERIALS AS DRYING OBJECTS

Considering the current situation in the energy sector of Ukraine, the urgent need to improve and develop energy-efficient thermal technologies for dehydration of plant raw materials is urgent and timely, which would ensure minimal energy consumption and high quality of the final product. The processing of vegetable raw materials into dried products is important for the sustainable development of the food industry. Cultivated Pleurotus eryngii mushrooms, which are valued for their high content of protein, carbohydrates, unsaturated fatty acids, vitamins and other nutrients, etc., are increasingly relevant in the mushroom industry on the world food market. It is important, in order to optimize energy consumption during dehydration and to select rational equipment, in addition to experimental studies, to perform theoretical calculation analysis of heat and mass transfer based on mathematical models. The article provides a theoretical and experimental analysis of the drying kinetics of colloidal capillary-porous materials. To determine the characteristics of the convective drying process, in addition to experimental studies, numerical modeling of this process was performed, which is performed on the basis of the numerical solution of the system of heat and mass transfer equations in colloidal capillary-porous materials. The calculation model can be used for the approximate determination of the main characteristics of the drying process of colloidal capillary-porous materials.

Phase field modeling of crack propagation in three-dimensional quasi-brittle materials under thermal shock

Quasi-brittle materials create intricate crack patterns on their surface and internal three-dimensional crack networks when exposed to thermal shock conditions. Their cracking behavior is notably impacted by their quenching temperature and size. In this paper, a coupled three-dimensional phase field-cohesive zone model that accounts for thermoelastic fracture is developed to reproduce the quenching and cracking experiments of ceramic balls. The accuracy of the phase field model is demonstrated by simulating the phase field of a single-element cooling process and comparing it with the analytical solution. The quench fracture process of the 3D ceramic ball is then simulated. The phase field simulations show that the surface crack morphology during the quenching process is somewhat random. Still, the crack distribution density is determined by the quenching temperature difference and ceramic ball size. Furthermore, a threshold size is present during the quenching process. When the ceramic ball's radius falls below this threshold, the surface crack pattern no longer appears during quenching. Consequently, the phase-field-cohesive zone model represents an effective means of predicting three-dimensional fracture processes in quasi-brittle materials subjected to thermodynamically coupled loading.

STUDY OF THE PROCESS OF PLANT RAW MATERIAL EXTRACTION IN A STATIC-TYPE CAVITATION INLINE MIXER

Abstract. The flowering heads of calendula have a significant content of biologically active substances (BAS) with a wide range of pharmacological activities. Traditional methods for obtaining their aqueous extracts include maceration or percolation. However, these methods have significant drawbacks. The rational choice of equipment and the study of the influence of thermophysical conditions on the extraction process of specific plant raw materials to intensify mass transfer processes are relevant. The aim of the study is to investigate the transition of solid substances of calendula flowers into a soluble state in a flow cavitation mixer of a static type to intensify mass transfer processes in obtaining aqueous extracts. For the research, previously ground dry calendula flower heads, swollen in distilled water at a hydro module of 1:15 and reduced to 0,1-2 mm, were used. The work was carried out on an experimental cavitation mixer of the Venturi tube type with a variable cavitation reactor with a nozzle throat diameter ranging from 0,006 m to 0,12 m. The efficiency of extraction was determined by the amount of water-soluble substances, and the cavitation phenomenon was characterized by the cavitation number. Results: The overall design of the cavitation apparatus, the profile and geometric parameters of the nozzle, the flow parameters, as well as the properties of the plant material, significantly affect the hydrodynamic conditions and the development of cavitation effects during processing. The Venturi-type flow cavitation mixer used in the research showed high efficiency in processing mass transfer processes during the extraction of a water suspension of calendula flower heads. The results obtained indicate that the most significant impact of cavitation effects is observed at nozzle throat diameters of 0,08 m and 0,10 m, with cavitation numbers χ = 0,53 and χ = 0,84, respectively. In this case, the process duration can be limited to 60 seconds. The obtained conclusions are confirmed by microstructure studies.

Thermally Prolonged NIR-II Luminescence Lifetimes by Cross-Relaxation.

Temperature regulates nonradiative processes in luminescent materials, fundamental to luminescence nanothermometry. However, elevated temperatures often suppress the radiative process, limiting the sensitivity of thermometers. Here, we introduce an approach to populating the excited state of lanthanides at elevated temperatures, resulting in a sizable lifetime lengthening and intensity increase of the near-infrared (NIR)-II emission. The key is to create a five-energy-level system and use a pair of lanthanides to leverage the cross-relaxation process. We observed the lifetime of NIR-II emission of Er3+ has been remarkably increased from 3.85 to 7.54 ms by codoping only 0.5 mol % Ce3+ at 20 °C and further increased to 7.80 ms when increasing the temperature to 40 °C. Moreover, this concept is universal across four ion pairs and remains stable within aqueous nanoparticles. Our findings emphasize the need to design energy transfer systems that overcome the constraint of thermal quenching, enabling efficient imaging and sensing.

Identifying the Active Sites in MoSi2@MoO3 Heterojunctions for Enhanced Hydrogen Evolution.

Developing Two-dimensional (2D) Mo-based heterogeneous nanomaterials is of great significance for energy conversion, especially in alkaline hydrogen evolution reaction (HER), however, it remains a challenge to identify the active sites at the interface due to the structure complexity. Herein, the real active sites are systematically explored during the HER process in varied Mo-based 2D materials by theoretical computational and magnetron sputtering approaches first to filtrate the candidates, then successfully combined the MoSi2 and MoO3 together through Oxygen doping to construct heterojunctions. Benefiting from the synergistic effects between the MoSi2 and MoO3, the obtained MoSi2@MoO3 exhibits an unprecedented overpotential of 72mV at a current density of 10mA cm-2. Density functional theory calculations uncover the different Gibbs free energy of hydrogen adsorption (ΔGH*) values achieved at the interfaces with different sites as adsorption sites. The results can facilitate the optimization of heterojunction electrocatalyst design principles for the Mo-based 2D materials.

Formation of Highly Robust Superhydrophobic Nanocomposite Coatings via Dual Spraying Technique

The development of materials that repel water, known as superhydrophobic materials, has been hindered by their vulnerability to mechanical abrasion. This issue is particularly pronounced for superhydrophobic nanocomposite coatings fabricated using a simple blend of resin and nanoparticles (NPs) through uncomplicated methods such as spraying or brushing, where an excessive amount of NPs can deteriorate the mechanical property. Moreover, the limitation of thickness puts forward a request for a high retention rate of the coatings. In response to these challenges, this study presents an innovative approach aimed at enhancing the robustness of superhydrophobic nanocomposite coatings through the utilization of a straightforward dual spraying technique. The results demonstrate that the particles with hierarchical micro/nanostructures fabricated by the primary spraying process provide abundant roughness feedstocks for the secondary‐sprayed coatings, in which superhydrophobicity properties can be achieved with less NP content. Additionally, the mechanical durability of the coatings can be reinforced by the addition of appropriate amounts of aluminum oxide (Al2O3) NPs and the continuous‐distributed particles fabricated by the primary‐spraying process, exhibiting a longer abrasion distance and a higher retention rate. Also, the prepared sample shows comprehensive robustness in adhesion, abrasion, and dynamic impact tests. By offering insights into material selection and process optimization, this study paves the way for creating resilient superhydrophobic coatings using a streamlined and convenient approach.