Initial Contact Angle Research Articles

Soccer and volleyball players do not land differently: implications for anterior cruciate ligament injury risk.

Non-contact anterior cruciate ligament injuries are common in soccer and volleyball, occurring during changes of direction and landings. This study aimed to investigate kinematic differences between soccer and volleyball players in single-planar and multiplanar landing tasks, simulating sport-specific injury mechanisms. Since the anterior cruciate ligament injury rate in soccer is higher than in volleyball, we hypothesized that volleyball players would adopt safer landing strategies, especially in single-planar landing tasks. Twenty-two soccer and 19 volleyball players performed single-leg drop landing, drop jump in vertical, 45°-medial and 45°-lateral directions. Box height and jump length were adapted to the subject's height and performance level, respectively. A 9-camera motion capture system provided lower limb kinematics. Two mixed multivariate analyses of covariance (sport, task, sex as covariate) were used to compare soccer and volleyball players' initial contact and peak kinematics (α=0.05). Task had significant effects on lower limb initial contact and peak angles, as expected. Sport and task × sport interaction had no significant effects on kinematics. Soccer and volleyball players' landing strategies were thus similar in each task, in opposition to initial hypotheses. We might speculate that the higher anterior cruciate ligament injury rate in soccer may be more related to non-predictable factors than the isolated landing kinematics.

Wettability Characteristics of Nanoporous Carbon Bricks Incorporated with Al2O3 Phase and Molten Iron in Sustainable and Low‐Carbon Blast Furnace

Analyzing the wetting behavior between carbon brick and molten iron in a blast furnace is crucial for understanding prolonging the furnace's lifespan. This study investigates the wetting behavior between microporous carbon brick and molten iron. The contact angle between the carbon brick and molten iron is measured at various temperatures and carbon saturation conditions, while the microscopic morphology of the reacted interface is examined. Furthermore, the wetting mechanism of molten iron on the carbon brick surface is elucidated. The findings reveal that both the microporous carbon brick and molten iron remain in a never‐wetting state within the furnace. As the temperature rises from 1150 to 1450 °C, the contact angle decreases from 138° to 128°, whereas the initial carbon content in the molten iron increases from 2.6 wt% to 4.1 wt%. Additionally, the initial contact angles gradually increase from 128.3° to 133.6°, with final equilibrium contact angles of 119.2° to 127.0°, indicating a nonwetting state. The carbon dissolution reaction occurs within the carbon matrix region of the microporous carbon brick prior to carbon saturation in the molten iron. Conversely, the presence of a ceramic phase in the ceramic area hampers both chemical erosion and physical penetration of the molten iron.

Preparation and performance evaluation of a novel temperature-resistant anionic/nonionic surfactant

Aiming at oil extraction from a tight reservoir, the Jilin oil field was selected as the research object of this study. Based on the molecular structures of conventional long-chain alkyl anionic surfactants, a new temperature-resistant anionic/nonionic surfactant (C8P10E5C) was prepared by introducing polyoxyethylene and polyoxypropylene units into double-chain alcohols. The resulting structures were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H-NMR), and electrospray ionization mass spectrometry (ESI–MS). Then, based on surface tension, interfacial tension, adsorption resistance, wettability, and emulsification performance tests, the performance of C8P10E5C was evaluated. The FT-IR, ESI–MS, and NMR spectra confirmed that C8P10E5C was successfully prepared. The critical micelle concentration (CMC) of C8P10E5C in water was 2.9510 × 10−4 mol/L (the corresponding mass concentration is 0.26%), and the surface tension of the aqueous C8P10E5C solution at this concentration was 30.5728 mN/m. At 0.3% concentration, the contact angle of the C8P10E5C solution was 31.4°, which is 60.75% lower than the initial contact angle. Under high-temperature conditions, C8P10E5C can still reduce the oil–water interfacial tension to 10−2 mN/m, exhibiting good temperature resistance. At 110 °C, upon adsorption to oil sand, the C8P10E5C solution could reduce the oil–water interfacial tension to 0.0276 mN/m, and the interfacial tension can still reach the order of 10−2 mN/m, indicating that C8P10E5C has strong anti-adsorption capability. Additionally, it has good emulsifying performance; upon forming an emulsion with crude oil, the highest drainage rate was only 50%. The forced imbibition oil recovery of C8P10E5C is 65.8%, which is 38.54, 24.22, and 27.25% higher than those of sodium dodecyl benzene sulfonate, alkyl polyoxyethylene ether carboxylate, and alkyl ether carboxylate, respectively.

The influence of women’s age and fall history on foot and lower limb kinematics during transition step descent

Falls are a major public health concern, with older women being at the greatest risk to experience a fall. Step descent increases the likelihood of a fall injury, yet the influence of age and fall history on lower extremity kinematics have not been extensively studied. The purpose of this study was to examine lower extremity and foot kinematics of women with and without a fall history during single step descent. Hip, knee, and foot kinematics of young women (n = 15, age = 22.6 ± 3.2 years), older women with no recent falls (n = 15, age = 71.6 ± 4.4 years), and older women with a fall history (n = 15, age = 71.5 ± 5.0 years) as they descended a 17 cm step were examined. Differences in initial contact angles and ROM during landing were examined with between group MANOVA tests. Distal foot initial contact angles were not significant between groups. For range of motion, both older groups went through greater hip extension (p = 0.003, partial η2 = 0.25), but less hip adduction (p = 0.002, partial η2 = 0.27) and less lateral midfoot dorsiflexion (p = 0.001, partial η2 = 0.28) than the younger women. The older fall group had reduced knee flexion (p = 0.004, partial η2 = 0.23) than the younger group, and the older non-fallers slightly plantarflexed at the medial midfoot (p = 0.005, partial η2 = 0.23) while the young women dorsiflexed. Thelanding phase ROMdifferences exhibited by the older adult groupsmayincrease the likelihood of a misstep, which may result in a fall.

Enhanced hydrophilicity of low melting point polylactic acid by butenediol vinyl alcohol copolymer via melt blending

In order to solve the poor hydrophilicity of low melting point polylactic acid (LMPLA) limiting its application in absorbent sanitary products. LMPLA/butenediol vinyl alcohol copolymer (BVOH) blends with different ratios were manufactured by simple melt blending. The BVOH exhibited good compatibility and dispersity in LMPLA matrix without chemical reaction, and LMPLA/BVOH blends showed sea-island structure. The introduction of BVOH could promote the crystallization of LMPLA and improve the crystallinity, whereas the crystallization of BVOH were limited. Furthermore, the introduction of BVOH could also decrease the thermal stability of LMPLA without affecting its application, but the tensile stress of LMPLA could be significantly increased. The tensile stress of LMPLA/BVOH blends could reach 78.59 MPa (increased by 10.9%) when he BVOH content was 3 wt%. Most importantly, the introduction of BVOH could significantly improve the hydrophilicity of LMPLA. The initial water contact angle decreased from 68.5° to 51.4° with the increase of BVOH content, and the contact angle decreased from 63.7° to 44.6° at 60 s. Moreover, the contact angle change rate of LMPLA/BVOH blends increased with the increase of BVOH content at different contact time, which also indicated adding BVOH could sharply improve the hydrophilicity of LMPLA.

Effects of water-based SiO2 nanofluids on the wettability of coal dust and particle deposition characteristics

Coal wettability plays a crucial role in the prevention of coal mine dust and associated disasters such as coal and gas outbursts. Water-based SiO2 nanofluids have emerged as promising wetting agents because of their sustainable wetting effects on coal. However, the current research on the wetting characteristics of nanofluids has predominantly focused on small coal fragments, with limited studies on coal dust. This study aims to investigate the influence of water-based SiO2 nanofluids with varying particle concentrations on the wettability of coal dust via physical experiments. The findings revealed that the modification by nanofluids significantly reduced the contact angles of the coal dust particles with the particle size ranges of 60–80, 80–100, and 100–150 mesh, compared to the initial contact angles. Moreover, higher particle concentrations resulted in smaller contact angles. Notably, the wetting effects of the nanofluid modification on coal dust were particularly prominent for larger particles. Furthermore, compared with water immersion, nanofluid modification demonstrated a significantly more positive impact on the wettability of coal dust. Notably, the SiO2 nanoparticles exhibited a wide distribution and substantial adsorption capacity on the coal surface, enabling the formation of a hydrophilic structure coverage. This study contributes to a comprehensive understanding of the wetting behavior of coal dust when exposed to water-based SiO2 nanofluids. These findings underscore the potential of nanofluids to enhance coal dust prevention and control, and provide valuable insights for future research in this field.

Comparative analysis of angular contact bearing stiffness calculated by Hertz contact and thermo-elastohydrodynamic lubrication

Stiffness is the key dynamic parameter of the angular contact ball bearing. This work established a dynamic bearing model based on Hertz theory and thermo-elastohydrodynamic lubrication (TEHL) and compared the contact angle, inner race position, and stiffness. In most cases, the stiffness calculated via Hertz was higher than when using TEHL. The axial stiffness values determined via the two theories were close, while the radial stiffness calculated via the Hertz theory was smaller than that determined by TEHL under light load and high speed. Considering the elastic deformation of the races and the initial contact angle, the results obtained by TEHL displayed a lower error rate in the experiment than Hertz.

New Insights Optimize Landing Strategies to Reduce Lower Limb Injury Risk.

Single-leg landing (SL) is often associated with a high injury risk, especially anterior cruciate ligament (ACL) injuries and lateral ankle sprain. This work investigates the relationship between ankle motion patterns (ankle initial contact angle [AICA] and ankle range of motion [AROM]) and the lower limb injury risk during SL, and proposes an optimized landing strategy that can reduce the injury risk. To more realistically revert and simulate the ACL injury mechanics, we developed a knee musculoskeletal model that reverts the ACL ligament to a nonlinear short-term viscoelastic mechanical mechanism (strain rate-dependent) generated by the dense connective tissue as a function of strain. Sixty healthy male subjects were recruited to collect biomechanics data during SL. The correlation analysis was conducted to explore the relationship between AICA, AROM, and peak vertical ground reaction force (PVGRF), joint total energy dissipation (TED), peak ankle knee hip sagittal moment, peak ankle inversion angle (PAIA), and peak ACL force (PAF). AICA exhibits a negative correlation with PVGRF (r = -0.591) and PAF (r = -0.554), and a positive correlation with TED (r = 0.490) and PAIA (r = 0.502). AROM exhibits a positive correlation with TED (r = 0.687) and PAIA (r = 0.600). The results suggested that the appropriate increases in AICA (30° to 40°) and AROM (50° to 70°) may reduce the lower limb injury risk. This study has the potential to offer novel perspectives on the optimized application of landing strategies, thus giving the crucial theoretical basis for decreasing injury risk.

Study on liquid dielectrophoresis based on double flexible electrodes simulating interdigitated pattern electrodes

Dielectrophoresis affects the surface wettability by applying a non-uniform electric field to dipoles inside dielectric liquid, achieving adjustable droplet contact angle and overcoming the saturation limitation of contact angle caused by the electrowettability effect. However, it is difficult to realize useful three-dimensional tunable optical devices because most of the driving electrodes need to be patterned. In this work, a model of double flexible electrodes simulating planar interdigitated pattern electrodes is proposed based on the dielectrophoresis. Double flexible electrodes, which are wrapped with an insulating dielectric layer and are not conductive to each other are arranged at close intervals and wound along the plane substrate to form a two-dimensional planar line wall. A hydrophobic layer is used to fill the gap and increase the initial contact angle. Ultimately, the “droplet-interdigitated planar line wall” dielectrophoresis driven-droplet model is formed after the dielectric droplets have been deposited on the line wall surface. Firstly, considering the influence of penetration depth and electrode gap area, Young’s equation is theoretically modified to adapt to this model. Then, the finite element algorithm simulation is used to used to comparatively analyze the potential distribution of this model and the planar interdigitated pattern electrode model. The field strength distributions of the electrodes with different wire diameters and insulating layer thickness values are analyzed. It can be found that with the increase of the diameter of the electrode wire and the thickness of the insulating layer, the morphology of the model changes from the tip electrode into the planar electrode, the surface field strength attenuates exponentially and the peak value decreases. This shows that the structure of this electrode in this model is superior to that of the planar electrode. After that, the contact angle of the model is measured experimentally in a range of 58°－90° under 0–250 <i>V</i><sub>rms</sub> voltage, which is in line with the theoretical expectation. At the same time, neither obvious contact angle lag nor saturation is observed in the experiment. Finally, the new electrophoretic driving droplet model constructed in this paper transforms the dielectric electrophoretic driving mode from a two-dimensional planar electrode to a one-dimensional flexible linear electrode. Because of its flexibility and plasticity, it is convenient to form a three-dimensional cavity and can be applied to more complex device structures.

A simple approach to produce hydrophobic biobased coatings using methylcellulose and organosolv lignin.

Substituting plastics with circular and sustainable alternatives has increasingly become a priority. Protective coatings, crucial components in numerous industries, are now in demand for biodegradable options to replace their plastic-based counterparts. Being one of nature's most abundant components, lignin remains underutilized, and this study focuses on investigating its potential for the production of biobased coatings. The method used here involved formulating coating suspensions by mixing methylcellulose and organosolv lignin powders and adding water to the mixture. Glass wafers were coated with the formulated suspensions using spin-coating. The morphology of the coated surfaces was assessed using optical and scanning electron microscopy. In addition, the wettability of the surfaces was examined through water contact angle experiments, and a numerical model was introduced to predict the water contact angle evolution over time. The results revealed that the sample coated with a 2.5 wt% lignin suspension exhibited the highest initial contact angle (114°), with a decreasing trend as the lignin fraction increases. Moreover, coatings with 3.5 wt% lignin and above exhibited lower surface coverage due to lignin particle aggregation and surface defects. By approximating the water droplet on the surface as a spherical cap, the introduced numerical model successfully predicted the time-dependent evolution of the water contact angle by showing strong alignment with experimental results. Taken altogether, we have showcased here a method for modifying coating properties-in a practical sense from water-absorbent to splash-proof-using readily available forest-based materials. This advancement is paving the way for sustainable protective packaging, aiming to replace styrofoam in the electronics and food industries.

An engineering approach to assess friction torque in generally loaded four-point contact slewing bearings

This manuscript presents a tool for the estimation of the friction torque in four-point contact slewing bearings. A normalised expression for the friction torque is obtained that depends on three design parameters (osculation ratio, initial contact angle and preload of the balls) and the external loading system defined by three components (axial force, radial force and tilting moment). The authors perform normalised friction torque simulations for combinations of those six variables established upon a DoE. The load distribution problem is solved prior to the friction torque calculation, which considers rigid rings. The simulations do not consider the effects coming from the seals, the spacers or the cage. By interpolating friction torque results from the simulations, a sufficiently populated number of data points is obtained to generate friction torque maps. Assuming some simplifications, the friction torque maps allow both customers and manufacturers to estimate the friction torque in a practical way.

Approximate symplectic approach for mistuned bladed disk dynamic problem

A blade disk system plays a crucial role in the energy conversion efficiency of turbomachinery. Generally, a bladed disk is designed as a tuned system, which implies that the dynamic behaviors of all the blades are identical. In practice, there are some differences between the blades, known as mistuning, that can result in localized vibration. Thus, in this study, an approximate symplectic method developed to reproduce the vibration localization in a mistuned bladed disk system, that can provide guidance for designing vibration control strategies for the system. Considering the morphological characteristics of the interface roughness and the dynamic/stickiness characteristics of the sliding joint surface, an improved dry friction model is established to describe the coupling effects between the blades. Considering the micro-dynamic behaviors of the multi-joint surfaces, the dynamic problem of the entire bladed disk system is formulated as a set of ordinary differential equations (ODEs). An approximate symplectic method is developed in the Hamiltonian framework to simulate the vibration of each blade in the mistuned bladed disk system. From the numerical results reported, the phenomenon of vibration localization in the mistuned bladed disk system is reproduced in the comparison with the results in the tuned bladed disk system. In addition, the influences of the initial positive pressure, contact angle, and roughness of the surfaces on the strength of the vibration localization are revealed in detail in the numerical simulations.

Influence of Si, Ti, and Cu as alloying elements on the wettability and reactivity of an Al/B4C system

The wettability and reactivity of Al alloys and B4C are of vital importance in the production of B4C-reinforced Al-matrix composites. However, previous research has primarily focused on pure Al/B4C systems, with little focus on alloying elements. In this paper, we investigated the influence of Si, Ti and Cu as alloying elements on the wettability and interfacial reactivity of an Al/B4C system using improved sessile drop methods. The B4C substrate was not wetted by molten Al at 700−1000 °C, with initial contact angles higher than 100°. However, rapid spreading was observed in the initial stages due to the formation of Al3BC and Al4C3. Si had a noticeable effect on the interfacial wettability only at levels of 15 wt% or above, with the interfacial products changing from Al3BC and AlB2 to SiC-dominated phases. The addition of Ti to Al led to the formation of TiB2-dominated interfacial products, which replaced the Al3BC and AlB2 phases, with the spreading kinetics mainly controlled by interfacial reactions in the early stages and the diffusion of Ti from the bulk of the drop to the triple line in the later stages. The addition of Cu had a negligible effect on the wettability but slightly weakened the formation of AlB2 by promoting substrate dissolution.

Recyclable oil resistant paper with enhanced water resistance based on alkyl ketene dimer modified sodium alginate

Abstract Sustainable coatings exhibit potential in enhancing oil resistance of packaging paper. Alkyl ketone dimer (AKD) was used to esterify sodium alginate (SA) to prepare water and oil resistant agent SAD. As SAD was coated on paper, it reduced the surface energy and blocked the fiber pores of paper, thus improving the barrier performance of paper. The oil resistance grade can reach grade 6 at coating amount of 2.13 ± 0.26 g/m2, which is qualified for food packaging. The coated paper also showed good barrier to hot castor oil. Resistance to organic solvent and water were also enhanced with initial water contact angle (WCA) increased to 69.2°. Compared with base paper, SAD coated paper had better mechanical properties and more importantly, coated paper can be effectively recycled to achieve green recycling.

Simulation of a sessile nanofluid droplet freezing with an immersed boundary-lattice Boltzmann model

The freezing process of a sessile nanofluid droplet has been reported to behave differently from a pure sessile water droplet in terms of freezing dynamics and the final shape of the ice droplet. When nanoparticles are added to the water droplet, instead of forming a pointed tip on the top, the completely frozen droplet exhibits a flat plateau shape. To investigate this unique scenario, we developed a lattice Boltzmann (LB) model that combines the multiphase solidification model (MSM) with the immersed boundary method (IBM). The MSM is based on our previous work of simulating the freezing of a pure droplet, while the IBM is used to handle the interaction forces between the suspended particles and the different phases in the freezing droplet. Using this LB model, we succeeded in simulating the formation process of the frozen plateau shape. The simulation takes into account the dynamics of the dispersed particles, including their expulsion from the propagation freezing front and their segregation, which brings the liquid water to the edge. We compared the simulated freezing shape profiles with the experimental images and found that the shape forms in a similar manner. We then used the developed model to explore more cases, considering the effects of droplet contact angles and particle volume concentration. Results show that the distribution of particles and final droplet height depend on the surface wettability, as the freezing front exhibits a concave/convex shape on hydrophilic/hydrophobic surfaces, resulting in different particle separation distributions on the freezing front interface. Furthermore, our simulation results confirm the experimental conclusion that the plateau size on the frozen top increases with particle concentration and appears to be independent of the initial droplet contact angle.

Wetting and pressureless infiltration behavior of Cu/316L system at 1100°C

It is still one of the great challenges to fully understand the coupling of reactive infiltration kinetics and wetting mechanism in the pressureless infiltration processes. We studied the wetting and pressureless infiltration behavior of Cu on 316L substrate with different pore sizes and porosity at 1100 °C under high vacuum by using the sessile drop method. The initial contact angle of Cu/316L system is ∼ 26 °, and rapid spreading (in ∼1.35 s) occurs under the action of capillary force due to the dissolutive wetting mechanism. The passivated film (Cr2O3) on the surface of 316L stainless-steel removed by self-cleaning reaction and interface reaction accompanying CrO gas phase release. Further, the obstacles of wetting and infiltration were eliminated. The reactive infiltration kinetics of Cu/316L cannot be predicted by the Washburn equation, preferring to an exponential variation. The infiltration kinetics is consistent with the wetting kinetics of melt on the smooth substrate surface, that is, the infiltration kinetics is limited by the dissolution kinetics.

Accurately and effectively predict the ACL force: Utilizing biomechanical landing pattern before and after-fatigue

Background and ObjectiveAs a fundamental exercise technique, landing can commonly be associated with anterior cruciate ligament (ACL) injury, especially during after-fatigue single-leg landing (SL). Presently, the inability to accurately detect ACL loading makes it difficult to recognize the risk degree of ACL injury, which reduces the effectiveness of injury prevention and sports monitoring. Increased risk of ACL injury during after-fatigue SL may be related to changes in ankle motion patterns. Therefore, this study aims to develop a highly accurate and easily implemented ACL force prediction model by combining deep learning and the explored relationship between ACL force and ankle motion pattern. MethodsFirst, 56 subjects' during before and after-fatigue SL data were collected to explore the relationship between the ankle initial contact angle (AIC), ankle range of motion (AROM) and peak ACL force (PAF). Then, the musculoskeletal model was developed to simulate and calculate the ACL force. Finally, the ACL force prediction model was constructed by combining the explored relationship and sparrow search algorithm (SSA) to optimize the extreme learning machine (ELM) and long short-term memory (LSTM). ResultsThere was almost a stronger linear relationship between the PAF and AIC (R = −0.70), AROM (R2 = −0.61). By substituting AIC and AROM as independent variables in the SSA-ELM prediction model, the model shows excellent prediction performance because of very strong correlation (R2 = 0.9992, MSE = 0.0023, RMSE = 0.0474). Based on the equal scaling by combining results of SSA-ELM and SSA-LSTM, the prediction model achieves excellent performance in ACL force prediction of the overall waveform (R2 = 0.9947, MSE = 0.0076, RMSE = 0.0873). ConclusionBy increasing the AIC and AROM during SL, the lower limb joint energy dissipation can be increased and the PAF reduced, thus reducing the impact loads on the lower limb joints and reducing ACL injuries. The proposed ACL dynamic load force prediction model has low input variable demands (sagittal joint angles), excellent generalization capabilities and superior performance in terms of high accuracy. In the future, we plan to use it as an accurate ACL injury risk assessment tool to promote and apply it to a wider range of sports training and injury monitoring.

Gluing Characteristics of Giant Bamboo Using Four Commercial Adhesives

The study aimed to determine the bonding performance of laminated giant bamboo[Dendrocalamus asper (Schult.) Backer] glued with four commercial adhesives (PVAc-D3, PUR, UF, PF) at different surface pairings (pith-pith, pith-skin, and skin-skin) and glue spread rates(100, 150, and 200 g/m2). Kiln-dried giant bamboo poles were ripsawn, planed, and cut to length to produce slats for lamination. Slats for surface roughness and wettability tests were sanded with 180-grit sandpaper on both skin and pith surfaces. Surface roughness of the skin and pith was measured using Mitutoyo SJ–210 Surftest unit, whereas wettability was determined via the sessile drop method. Giant bamboo slats were bonded using specific lamination parameters for each adhesive. Tensile shear tests at dry and wet conditions were performed on the laminates to determine bond strength. The results showed that the bamboo pith had a rougher texture than the skin but with insignificant contact angle differences. Moreover, PVAc-D3 and PUR gave the highest and lowest initial contact angles on both sides, respectively, with PUR maintaining the smallest values throughout the contact duration. Adhesive, surface pairing, and some interactions (adhesive x glue spread and adhesive x surface pairing) significantly affected the dry shear strength, whereas adhesive and adhesive x surface pairing influenced wet shear strength. PUR-bonded laminates had the highest dry shear strength, followed by PF, PVAc-D3, and UF. In terms of wet shear strength, only PVAc-D3 did not conform to the minimum glue bond strength requirement of more than 1 MPa and cohesive bamboo failure of at least 40% (PNS 2099:2015). Skin-skin and pith-pith surface pairing yielded the highest and lowest dry shear strengths, respectively. Increasing the amount of glue did not translate to a stronger bond. PUR, UF, and PF are feasible alternatives to PVAc-D3 in engineered bamboo production for various end-uses.

Wetting of FeCoCrNiTi0.2 high entropy alloy on the (HfZrTiTaNb)C high entropy ceramic

To clarify the unique interfacial interaction of heterogeneous system under high entropy effect, the wettability of the liquid FeCoCrNiTi0.2 high entropy alloy (HEA) on the (HfZrTiTaNb)C high entropy ceramic (HEC) was studied at 1370–1430 °C. The dissolved HEC contributed Hf and Zr atoms to the liquid HEA, and their adsorption at the triple line promoted the rapid reduction of the initial contact angle. Meanwhile, the active Ti in liquid HEA diffused into the HEC, which induced a phase transition from HEC to HEC' with the unaltered lattice structure. The spreading of liquid HEA depended on the formation of HEC' judged by the linear relationship between ln(cosθe−cosθd) and time. The calculated high wetting activation energies revealed sluggish spreading for the HEA/HEC system. Based on the good wettability of HEA/HEC system, the HEC brazed joints with high shear strengths above 245 MPa were constructed using HEA fillers at a wide temperature interval of 1400–1490 °C.

An inorganic hydrophobic layer connected by rivets endows the bamboo with high fire retardant, mechanical, and mold-proof properties

This study investigated the mineralization process of calcium carbonate on bamboo surfaces using aqueous solutions of calcium propionate and sodium carbonate as precursors. The mineralization process was carried out once, three times, and five times, and its effects on fire-retardant, mechanical, and mold-proof properties were examined. Scanning electron microscopy revealed that calcium carbonate bonded with bamboo cells through a rivet structure, resulting in a pronounced roughness of the mineralized layer. Mineralized bamboo exhibited improved fire-retardant properties, with decreases of the maximum heat release rate and total heat release rate by 20–32 % and 8–13 %, respectively. Additionally, mineralized bamboo displayed enhanced mechanical properties, increase of modulus of elasticity (MOE) and modulus of rupture (MOR) by 1–3 % and 3–10 %, respectively. After five cycles of deposition, the initial contact angle of the mineralized bamboo became 159°, and the infestation value of Aspergillus niger mold was almost zero, indicating satisfactory hydrophobicity and mold-proof properties. Mineralization of bamboo surfaces with calcium carbonate substantially improved the properties of bamboo and extended its application in various fields.