Dry State Research Articles

Understanding the drying mechanism of straw substrate culture block: Physicochemical properties, pore structure, and drying optimization

As a new type of agricultural waste block substrate utilization, the initial wet base state of the substrate culture block needs to be dried. Therefore, studying the drying mechanism of substrate culture block is critical. In this study, the substrate culture block in a dry state was taken as the research object. Based on physical and chemical properties, the internal section of the substrate culture block was characterized by scanning electron microscopy and the pore condition of the particles was quantified. The results showed that the internal pore structure was uniform and favorable for plant root growth. Based on the pore structure, pore channel modeling was constructed to investigate the distribution of the internal multiphase medium and to distinguish between channels and pore-blind channels. The applicability of the modeling was verified and discussed. By measuring the drying rate of the substrate culture block and classifying its drying stages as fast speed, constant speed, and slow speed, it is clarified that the forms of moisture existence are bound-state water and free-state water, and the moisture migration is prioritized as surface adsorption water, interparticle water, particle attached water, and capillary water. Innovate a method to quantify the change of pore space in the drying process by pore coefficient ratio to evaluate the drying quality. The results show that when the pore coefficient ratio is about 40 %, its moisture content is 20 %∼30 %, and the drying effect is best at this time. The physical drying test further confirmed the correctness of the conclusion of the drying stage division and water loss law. This study can provide a theoretical reference for the modeling study of the pore structure of the block matrix and the exploration of its drying mechanism.

Applicability of Single-Layer Graphene as a Hydrogen-Blocking Interlayer in Low-Temperature PEMFCs.

Gas crossover is critical in proton exchange membrane (PEM)-based electrochemical systems. Recently, single-layer graphene (SLG) has gained great research interest due to its outstanding properties as a barrier layer for small molecules like hydrogen. However, the applicability of SLG as a gas-blocking interlayer in PEMs has yet to be fully understood. In this work, two different approaches for transferring SLG from a copper or a polymeric substrate onto PEMs are compared regarding their application in low-temperature PEM fuel cells. The SLG is sandwiched between two Nafion XL membranes to form a stable composite membrane. The successful transfer is confirmed by Raman spectroscopy and in ex situ hydrogen permeation experiments in the dry state, where a reduction of 50% upon SLG incorporation is achieved. The SLG composite membranes are characterized by their performance and hydrogen-blocking ability in a fuel cell setup at typical operating conditions of 80 °C and with fully humidified gases. The performance of the fuel cell incorporating an SLG composite membrane is equal to that of the reference cell when avoiding the direct etching process from a copper substrate, as remnants from copper etching deteriorate the performance of the fuel cell. For both transfer processes, the hydrogen crossover reduction of SLG composite membranes is only 15-19% (1.5 barabs) in the operating fuel cell. Further, hydrogen pumping experiments suggest that the barrier function of SLG impairs the water transport through the membrane, which may affect water management in electrochemical applications. In summary, this work shows the successful transfer of SLG into a PEM and confirms the effective hydrogen-blocking capability of the SLG interlayer. However, the hydrogen-blocking ability is significantly reduced when running the cell at the typical humidified operating conditions of PEM fuel cells, which follows from a combination of reversible interlayer alteration upon humidification and irreversible defect formation upon PEM fuel cell operation.

Effects of freeze-drying bovine pericardium using a combination of polyethylene glycol and trehalose

The freeze-drying is a technology that preserves biological samples in a dry state, which is beneficial for storage, transportation, and cost saving. In this study, the bovine pericardium was treated with a freeze-drying protectant composed of polyethylene glycol (PEG) and trehalose (Tre), and then freeze-dried. The results demonstrated that the mechanical properties of the pericardium treated with PEG + 10% w/v Tre were superior to those of the pericardium fixed with glutaraldehyde (GA). The wet state water content of the rehydrated pericardium, determined using the Karl Fischer method, was (74.81 ± 1.44)%, which was comparable to that of the GA-fixed pericardium. The dry state water content was significantly reduced to (8.64 ± 1.52)%, indicating effective dehydration during the freeze-drying process. Differential scanning calorimetry (DSC) testing revealed that the thermal shrinkage temperature of the pericardium was (84.96 ± 0.49) ℃, higher than that of the GA-fixed pericardium (83.14 ± 0.11) ℃, indicating greater thermal stability. Fourier transform infrared spectroscopy (FTIR) results showed no damage to the protein structure during freeze-drying. Hematoxylin and eosin (HE) staining demonstrated that the freeze-drying process reduced pore formation, prevented ice crystal growth, and resulted in a tighter arrangement of tissue fibers. The frozen-dried bovine pericardium was subjected to tests for cell viability and hemolysis rate. The results revealed a cell proliferation rate of (77.87 ± 0.49)%, corresponding to a toxicity grade of 1. Additionally, the hemolysis rate was (0.17 ± 0.02)%, which is below the standard of 5%. These findings indicated that the frozen-dried bovine pericardium exhibited satisfactory performance in terms of cytotoxicity and hemolysis, thus meeting the relevant standards. In summary, the performance of the bovine pericardium treated with PEG + 10% w/v Tre and subjected to freeze-drying could meet the required standards.

Robust Enhancement of Direct Air Capture of CO2 Efficiency Using Micro-Sized Anion Exchange Resin Particles

In the quest to mitigate carbon dioxide emissions, it becomes essential to address the existing atmospheric CO2. Effective and economical methodologies, particularly those without additional energy consumption, are crucial. Currently, a leading method is the direct capture of CO2 using ion exchange resins, which achieve the adsorption and desorption of carbon dioxide simply by using the humidity variations. This technology, though minimizing additional energy cost, still needs improvement in its efficiency in CO2 capture capacity and compared to other methods. In this work, we develop low-cost techniques to reduce the AmberLite™ IRA900 Cl (IRA-900) anion exchange resin to micro size, and observe significant performance enhancement on CO2 capture efficiency contingent on reducing the particle diameters. This performance disparity is attributed to the differential water adsorption capacities inherent in particles of diverse diameters. Our results reveal that smaller resin particles outperform their larger counterparts, exhibiting accelerated adsorption rates and expedited transitions from wet to dry states. Notably, these smaller particles display a quintupled enhancement in adsorption efficacy relative to non-treated particles and a marked increase in relative adsorption capacity. Upon treatment, IRA-900 demonstrates robust CO2 processing efficiency, achieving a peak adsorption rate of 1.28 g/mol·h and a maximum desorption rate of 1.18 g/mol·h. Also, the material is subjected to almost 100 cycles of testing, and even after 100 cycles, the resin particles maintain a capacity of 100%. Moreover, our material can be fully regenerated to 100% efficiency by simply immersing it in water. Simultaneously, storing it in water allows for the long-term maintenance of its performance without other treatment methods. A key observation is the resin’s sustained performance stability post extended exposure to humid conditions. These outcomes offer substantial practical implications, emphasizing the relevance of our study in practical environmental applications.

A flexible and deep peak shaving scheme for combined heat and power plant under full operating conditions

Improving the flexible and deep peak shaving capacity of combined heat and power (CHP) plant under full operating conditions to facilitate renewable energy consumption is the main choice of novel power system. Accordingly, a dry/wet state automatic conversion control scheme fuses the precise mechanism structure, reinforcement learning and multi-objective model predictive control (MPC) algorithms is designed to promote the deep peak shaving ability of CHP plant in this paper. Firstly, the detailed mechanism models of once-through boiler at dry and wet state are presented by analyzing the dynamic characteristics of steam-water flow. Secondly, the large-scale unknown parameters in mechanism models are identified via the Takagi-Sugeno fuzzy modeling, reinforcement learning algorithms and actual dry/wet state conversion data. Thanks to the proposed hybrid modeling strategy, the high-precision boiler-steam unit models at dry and wet state are rapid obtained. Then, to meet different peak shaving demands, the multi-objective MPC algorithm is respectively constructed under dry and wet state with the comprehensive consideration of operational constraints, load tracking error, algorithm stability, power generation cost, CO2 and NOx emission costs. Aiming at maximizing the peak shaving efficiency and flexible operation ability of plant, a dry/wet automatic control scheme combined the designed multi-objective MPC algorithms and identified dry/wet state models is proposed. Finally, the load variation rate of 5 % and 2 % RCM/min is respectively achieved in the dry/wet state conversion tests on a 350 MW CHP plant based on the proposed control scheme. Thus, the rapid and thorough dry/wet state conversion performance of once-through boiler has successfully improved the operational flexibility of CHP plant under full operating conditions.

Twisted integration of high-efficiency photothermal/water-transported yarns for boosting solar-powered fabric evaporator

Positioned as high-efficiency low-cost desalination technology, solar interfacial vapor generation still remains challenging in precisely managing interfacial photothermal behaviors. Here, an integral solar-heating yarn twisted by both carbon nanotube (CNT) fibers and cotton yarns processed via carbon black slurry is developed for architecting high-efficiency fabric evaporators, where modified CNT and cotton serve as the solar-heating unit and water-supply unit, respectively. The unique structure of hybrid yarns features pronounced gradient photothermal difference of 5 °C between CNT and cotton regions in dry state, and meanwhile enables robust Marangoni vapor flows and weak hydration state. As a result, the crafted fabric evaporator has a superior evaporation rate of 2.83 kg m−2 h−1, which is the highest value reported among 2D fabric evaporators. This work introduces an innovative strategy for high-efficiency interfacial solar heating, significantly boosting evaporation performance of flexible and portable evaporators.

A Meta-Analysis of the Effect of Moisture Content of Recycled Concrete Aggregate on the Compressive Strength of Concrete

To reduce the environmental impact of concrete, recycled aggregates are of significant interest. Recycled concrete aggregate (RCA) presents a significant resource opportunity, although its performance as an aggregate in concrete is variable. This study presents a meta-analysis of the published literature to refine the understanding of how the moisture content of RCA, as well as other parameters, affects the compressive strength of concrete. Seven machine learning models were used to predict the compressive strength of concrete with RCA, including linear regression, support vector regression (SVR), and k-nearest neighbors (KNN) as single models, and decision tree, random forest, XGBoost, and LightGBM as ensemble models. The results of this study demonstrate that ensemble models, particularly the LightGBM model, exhibited superior prediction accuracy compared to single models. The LightGBM model yielded the highest prediction accuracy with R2 = 0.94, RMSE = 4.16 MPa, MAE = 3.03 MPa, and Delta RMSE = 1.4 MPa, making it the selected final model. The study, employing feature importance with LightGBM as the final model, identified age, water/cement ratio, and fine RCA aggregate content as key factors influencing compressive strength in concrete with RCA. In an interaction plot analysis using the final model, lowering the water–cement ratio consistently improved compressive strength, especially between 0.3 and 0.4, while increasing the fine RCA ratio decreased compressive strength, particularly in the range of 0.4 to 0.6. Additionally, it was found that maintaining moisture conditions of RCA typically between 0.0 and 0.8 was crucial for maximizing strength, whereas extreme moisture conditions, like fully saturated surface dry (SSD) state, negatively impacted strength.

Fungal Diversity in Wet and Dry Ripe Plantains: Isolation, Identification, and Implications for Public Health

The persistent inadequacy of storage facilities in in globally and more prevalent in developing nations leads to substantial annual losses of harvested agricultural produce, severely impacting the economic stability of local farmers. This investigation focuses on the critical public health implications arising from the fungal contamination of stored plantain chips, a delicacy snack in Nigeria, West Africa. Notably, the fungal species isolated, which are Aspergillus flavus, Aspergillus niger, Penicillium chrysogenum, Saccharomyces cerevisiae, Aspergillus fumigatus, Fusarium spp., Rhizopus stolonifer, and Mucor spp. are critical from a public health perspective. Species such as Aspergillus flavus and Aspergillus niger are particularly concerning due to their capacity to produce aflatoxins, which are among the most carcinogenic substances known and have been linked to liver cancer and immune system suppression. The prevalence of these mycotoxins not only compromises the nutritional integrity and safety of the plantain chips but poses severe risks to consumers, highlighting a broader issue of food security and safety. This study brings to the fore the pressing need for interventions that enhance the storage conditions and decrease fungal contamination, thereby reducing the exposure of the population to mycotoxins. The implications of this research extend beyond the economic damage to encompass significant public health concerns, emphasizing the critical need for regulatory, technical, and infrastructural developments to uphold the microbial quality of plantain both in wet and dry states, ensuring safe consumption.

PA 10.10 and PA 6 composites with glass or basalt fibre: mechanical properties in dry and wet state

The effect of basalt and glass fibres and moisture on the impact strength, tensile mechanical properties and heat resistance of PA 10.10 and PA 6 was examined. It was shown that PA 10.10 composites can compete with PA 6 composites in terms of mechanical properties, in a humid environment. Their heat resistance was lower than that of PA 6 composites. Regardless of the type of polyamide, composites with glass fibre had better properties than those with basalt fibre.

The Use of Lightweight Aggregates in Geopolymeric Mortars: The Effect of Liquid Absorption on the Physical/Mechanical Properties of the Mortar.

Geopolymers have been proposed as a green alternative to Portland cement with lowered carbon footprints. In this work, a geopolymeric mortar obtained using waste materials is studied. Fly ash, a waste generated by coal combustion, is used as one of the precursors, and waste glass as lightweight aggregates (LWAs) to improve the thermal performance of the mortar. The experimental study investigates the effect of varying the alkali activating solution (AAS) amount on the workability, compressive strength, and thermal conductivity of the mortar. Indeed, AAS represents the most expensive component in geopolymer production and is the highest contributor to the environmental footprint of these materials. This research starts by observing that LWA absorbs part of the activating solution during mixing, suggesting that only a portion of the solution effectively causes the geopolymerization reactions, the remaining part wetting the aggregates. Three mixes were investigated to clarify these aspects: a reference mix with a solution content calibrated to have a plastic consistency and two others with the activating solution reduced by the amount absorbed by aggregates. In these cases, the reduced workability was solved by adding the aggregates in a saturated surface dry state in one mix and free water in the other. The experimental results evidenced that free water addiction in place of a certain amount of the solution may be an efficient way to improve thermal performance without compromising the resistance of the mortar. The maximum compressive strength reached by the mortars was about 10 MPa at 48 days, a value in line with those of repair mortars. Another finding of the experimental research is that UPV was used to follow the curing stages of materials. Indeed, the instrument was sensitive to microstructural changes in the mortars with time. The field of reference of the research is the rehabilitation of existing buildings, as the geopolymeric mortars were designed for thermal and structural retrofitting.

Upscaling earth formworks: 3D printing strategies for material optimised reinforced concrete structures

There is a growing need to understand how locally sourced earthen materials can be processed to build more efficiently and sustainably. Earthen formworks combined with 3D printing technologies present a unique opportunity for the concrete construction sector to address the wastefulness and complexity of custom formworks. The current state-of-the-art projects in academia and industry demonstrate that earthen formwork strategies effectively address this challenge, but remain burdened by upscaling issues such as production speed. This research bridges the gap by exploring strategies for 3D Printed earth formworks to efficiently produce structural elements using custom self-compacting and set-on-demand concrete mixtures. A first base earth mix is developed for reduced shrinkage and later modified via a plasticizer for increased green strength, forming the final mix. Two mix iterations are deployed in two corresponding strategies where concrete is cast into the earth formwork in a dry or plastic state. The methods highlighting the setups for 3D printing and procedures for appropriate material processing such as slump flow, shrinkage and rheology are presented. The results are explored via two column prototypes leading to a final demonstrator for a 2 m high reinforced concrete column. Conclusions are drawn on the implications of the two casting strategies, the current persisting challenges and the crucial next steps for development. Thus, the research provides a foundation for how clay formworks can be upscaled effectively for more sustainable production of complex concrete structures.

Highly water-resistant paper via infiltration with polymeric microspheres from nanocellulose-stabilized plant oil-derived monomer

Sustainable strategies to improve the water resistance of cellulose paper are actively sought. In this work, polymeric microspheres (PMs), prepared through emulsion polymerization of cellulose nanofibers stabilized rubber seed oil-derived monomer, were investigated as coatings on corrugated medium paper (CMP). After infiltrating porous paper with PMs, the water-resistant corrugated papers (WRCPn) with enhanced mechanical properties were obtained. When 30 wt% PMs were introduced, WRCP30 turned out to be highly compacted with an increased water contact angle of 106.3° and a low water vapor transmission rate of 81 g/(m2 d) at 23 °C. Meanwhile, the tensile strength of WRCP30 increased to 22.2 MPa, a 4-fold increase from CMP. When tested in a well-hydrated state, 71% of its mechanical strength in the dry state was maintained. Even with a low content of 10 wt% PMs, WRCP10 also exhibited stable tensile strength and water wettability during the cyclic soaking-drying process. Thus, the plant oil based sustainable emulsion polymers provide a convenient route for enhancing the overall performance of cellulose paper.

Evolution And Its Misinterpretation By The Scientific Community

Allah has created the heavens and the earth in stages as he declares in the Holy Quran. It is Allah Who creates, develops and sustains life, and ensures harmony and diversity in all things, living and non-living. The verses from the Quran make it obvious that the conditions required for God’s ultimate creation to exist and survive are only possible if the universe contains matter, energy, water, and other entities as they are. The total measure of these entities cannot be altered, which means the total energy and matter in the universe is constant. These values are actually the result of the fine-tuned universe, where any deviation from it will lead to its instability and hence its extinction. This balance is maintained by the eternal and extremely intelligent being through His commands, and these commands, by observers, are conceived as laws of nature or scientific laws. This universe is solely meant for the trial of the ultimate creation, hence puzzling, brain-teasing, and other sorts of entangled phenomena in the observable universe are inevitable. This kind of nature is intentionally imparted to the universe by God to test mankind (God’s ultimate creation). The definition of biological evolution in modern science is actually an illusion and hence a trial for humans, since God calls this universe by the word "Garoor," meaning illusion or unreal. In conclusion, the misinterpretation of evolution by the scientific community can be attributed to the lack of understanding of the true nature of human existence and the purpose of life on Earth. By examining religious scriptures, we can see that humans are sent on Earth for minor and major trials by God, with minor trials such as evolutionary theory and other incomplete sciences being part of this category. It is evident that God initially formed the shape of a human from stagnant dark mud and then preserved it in a dry state. He did not breathe life into the mould until all the necessary conditions for human existence on Earth were ensured. After God infused life or spirit into the mould of Adam (AW), He taught Adam (AW) the names of things. Thus, it can be inferred that life on Earth was created by God in stages, and these stages are designed in a way that life and the species on Earth may appear to disbelievers as a result of natural selection or random evolution. However, as Muslims, it is important to remember that everything we observe in the universe is intended to test us by God, so it is best to avoid engaging in vague discussions on this matter. Know well that the life of this world is but an amusement and diversion, and adornment and boasting to one another, and competition in increase of wealth and children. This worldly life is no more than play and amusement. But the Hereafter is indeed the real life, if only they knew.(The Quran 29:64)

High pressure salt water and low temperature effects on the material performance characteristics of additive manufacturing polymers

The effects of salt water exposure at deep ocean depth pressures when coupled with low temperatures on the material characteristics of three unique additively manufactured polymers has been investigated through a detailed experimental approach. The polymers in the study were manufactured utilizing both Vat Photopolymerization and Material Extrusion printing techniques. The Material Extrusion process was utilized to produce material specimens of Stratasys ULTEM 9085 and Markforged Onyx while the Vat Photopolymerization process was used to produce specimens of Accura ClearVue. The ULTEM 9085 and Markforged Onyx are filament based polymers and the ClearVue is a liquid based resin. The specimens were first submerged in a high pressure, salt water bath of 3.5% NaCl solution at 34.5 MPa (5000 lb/in2) for a total exposure time of 60 days to determine the water absorption characteristics. Subsequent to the salt water exposure at high pressure, the specimens were evaluated to determine changes in tension, compression, flexure, and in-plane fracture properties. To determine the effects of water saturation and low temperature coupling, the mechanical testing was performed at temperatures of 20 °C, 0 °C and −20 °C in both dry and saturated conditions. Additionally, non-destructive testing in the form of TeraHertz and FIRT imaging was conducted to analyze the physical material changes through the thickness of the material due to the saline water absorption. To quantify the change in material storage and loss moduli properties, Dynamic Mechanical Analysis (DMA) characterization was performed on each of the AM polymers in dry and saturated states. The DMA testing also quantified changes in the Glass Transition Temperature because of salt water exposure. In summary, The current study investigates the effects of coupled long term/high pressure salt water exposure with low temperatures on the mechanical and material characteristics of three unique AM polymers by: (1) immersing the materials in a salt water solution at 34.5 MPa for 60 days, (2) Conducting post exposure mechanical testing on the materials at 0 °C and −20 °C with comparisons to 20 °C testing on dry specimens, and quantifies changes in material properties through DMA experiments. The results from all testing in the study show that high pressure salt water exposure when coupled with low temperatures has unique effects on each of the materials considered in the study and careful consideration to each parameter must be given based on the material type when components will be employed in marine operations.

Use of synthetic calcium hydrosilicate in Portland cement compositions

We investigated the patterns of the synthesis of calcium hydrosilicate of tobermorite composition in the "amorphous silica–calcium hydroxide–water" system. The gradual interaction of calcium hydroxide and amorphous silicon(IV) oxide leading to the formation of synthetic tobermorite was confirmed by X-ray diffraction analysis. It was determined that the optimal duration of the synthesis of calcium hydrosilicate was 5 days, which, according to electron microscopic studies, ensured the production of grains with a size of 0.4–4 m. The influence of the synthesized tobermorite on the change in strength characteristics of cement stone during setting was studied using cement-sand mortar mixtures with sands of different particle size distribution. A comparative analysis of the effect of storage conditions of the synthesized product on the structure-forming processes of cement stone was carried out. It was established that the modifying effect of synthetic tobermorite was observed when it was dried after synthesis and stored in a dry state. Conversely, prolonged storage of calcium hydrosilicate in a wet state led to a loss of its activity and a decrease in the strength characteristics of cement stone. The mechanism of the influence of calcium hydrosilicate additive was studied by measuring the change in the rate of heat release of cement dough at the initial stage of hydration. It was shown that the addition of dry calcium hydrosilicate accelerated the physicochemical processes of hydration of clinker minerals, while the addition stored in wet conditions slowed down hydration. Electron microscopic studies of cement stone after 28 days of setting confirmed that the introduction of dry calcium hydrosilicate contributed to the formation of a structure characterized by a higher degree of crystallization and an increase in the strength of the samples.

Microscopic occurrence and distribution of oil and water in situ shale: Evidence from nuclear magnetic resonance

Characterizing the microscopic occurrence and distribution of in-situ pore water and oil is crucial for resource estimation and development method selection of shale oil. In this paper, a series of nuclear magnetic resonance (NMR) experiments were conducted on shales from the Gulong Sag, Songliao Basin, China, at AR, WR-AR, WOR-AR, Dry, SO, and WR states. In-situ pore water and oil were reconstructed after WOR-AR. An improved T1–T2 pattern for shale oil reservoirs comprising water and oil was proposed to classify and quantitatively detect pore fluids at different occurrence states. The total and free oil contents derived from NMR T1–T2 spectra at AR states were found to correlate well with those from multistage Rock-Eval. Moreover, the NMR-calculated total and free oil are generally larger than those measured from multistage Rock-Eval, whereas adsorbed oil is the opposite, which implies that adsorbed, bound, and movable oils in shale pores can be accurately and quantitatively detected via NMR, without absorbed hydrocarbons in kerogen. As per the NMR T2 and T1–T2 spectra at WOR-AR state, the microdistributions of in-situ pore water and oil were clearly demonstrated. Adsorbed, bound, and movable oils primarily occur in the micropores (<100 nm), mesopores (100–1000 nm), and macropores (>1000 nm), respectively, whereas capillary-bound water is primarily correlated with micropores. Thus, the microscopic occurrence and distribution of adsorbed oil are remarkably affected by pore water, followed by bound oil, and movable oil is hardly affected. This study would be helpful in further understanding the microscopic occurrence characteristics of pore fluids in-situ shale oil reservoirs.

Effects of Lubricating Conditions on Wear Performance of U77MnCrH Rail

With the rapid development of railway towards being high speed and having heavy load capacity, the wheel–rail wear and rolling contact fatigue in the curve section with a small radius of freight have become the key problems in urban railways, which need to be solved urgently. The aims of this study were to compare the wear resistance with three different lubricating conditions on wheel–rail wear based on the wheel–rail rolling contact simulation tests. The wear loss, microhardness, and microstructure of the contacted surface of the rail were detected systematically. The results showed that the wear rates of rail were reduced by 71% for grease lubrication and 55% for solid lubrication, compared to those without lubrication. At the same time, the thickness of plastic deformation layer of rail samples were about 167 μm for the dry state, 138 μm for the solid lubrication state, and 128 μm for the oil lubrication state, respectively. It indicates that the thickness of the plastic deformation layer was significantly reduced under both grease and/or solid lubricating conditions. In addition, the microstructure of the deformation layer with two kinds of lubricated states was coarser and denser than that without lubricants. The average grain size of the deformation layer was approximately 0.22 μm under dry conditions and 0.32 μm under lubricated conditions. It also indicated that the changes in lubricants did not have a significant effect on the average grain size of the deformation layer. The results of the present study could provide theoretical reference for the development and design of lubricants used as rail materials.

Study on stress–strain relationship and constitutive model of recycled aggregate concrete under axial cyclic compression

AbstractThe effects of dry or saturated state, water–cement ratio, coarse aggregate type and steel fiber on the stress–strain relationship of RAC under cyclic loading were studied. What is more, the characteristics of stress–strain curve, plastic strain, stress degradation and stiffness degradation of RAC under cyclic loading were analyzed. The microstructure of RAC was analyzed. Based on the principle of surface energy, the reason for the decrease in compressive strength of wet concrete was analyzed. In addition, the envelope equation of stress–strain curve under cyclic loading, unloading and reloading curve was established. The test results showed that the peak stress of the envelope line of RAC under cyclic loading was affected by dry or saturated state, water–cement ratio and coarse aggregate type, but the addition of steel fiber could reduce the degradation rate of stress and stiffness of RAC after peak strain. The plastic strain accumulation of RAC before and after the peak stress was quite different, but dry or saturated state, water–cement ratio, coarse aggregate type and steel fiber have no obvious influence on the plastic strain accumulation of RAC. The pores and cracks of RAC provide space and channels for the moisture absorption and water absorption. The Weibull–Lognormal statistical distribution envelope model, unloading curve model and reloading curve model established were in good agreement with the experimental curves. The research results provided a reference for the study of the full curve constitutive model of RAC under cyclic loading.

Tribological properties of titanium alloy with micro-nano multiscale texturing against bone under simulated implant contact conditions

The stability of a titanium alloy screw implant in a spinal internal fixation system is primarily influenced by its tribological properties. We integrated laser texturing and anodic oxidation technology to fabricate surface micro/nanostructures on titanium alloys. The tribological properties of titanium alloys against bone were investigated by mimicking the progress of screw implantation. The results demonstrated that surface structure reduced the dynamic friction of the titanium alloy under dry conditions and increased the static friction under wet conditions. The low sliding friction in the dry state facilitated the initial implantation of the titanium alloy screws. Conversely, the high static friction in the wet state prevents post-implantation loosening of the titanium alloy screw and enhances its stability within bone tissue.

Biobased Composites of Poly(Lactic Acid) Melt Compounded with Bacterial and Vegetal Nanocelluloses Incorporated through Different Strategies.

In the current contribution, bacterial nanocellulose obtained from a by-product of Kombucha tea production and vegetal nanocellulose isolated from milled rice husks were employed as fillers of PLA-based composites prepared by intensive mixing followed by compression molding. Given the challenges associated with the incorporation of nanocelluloses-initially obtained as aqueous suspensions-into melt compounding processes, and also with achieving a proper dispersion of the hydrophilic nanofillers within PLA, three different nanofibrils incorporation strategies were studied: i.e., direct mixing of dried milled nanocelluloses and PLA; masterbatching by solvent casting of native nanocelluloses followed by melt compounding; and masterbatching by solvent casting of acetylated nanocelluloses followed by melt compounding. Composites with varying filler content (from 0.5 wt.% to 7 wt.%) were characterized in terms of morphology, optical properties, and mechanical performance. Results revealed the relative suitability of each strategy employed to promote nanocelluloses dispersion within the PLA matrix. PLA/nanocellulose masterbatches prepared by solvent casting proved to be particularly useful for feeding the nanocelluloses into the processing equipment in a dry state with limited hornification. Acetylation also contributed to a better dispersion of both nanocelluloses within the PLA matrix, although no clear positive impact on the mechanical properties of the films was observed. Finally, filler loading played an important role in the films' properties by increasing their stiffness while reducing their translucency.