Low Coefficient Research Articles

Investigation of mechanical and tribological properties of NiCrAlY/ZrO2-Y2O3 coatings obtained by detonation spraying

In this study, multilayer gradient NiCrAlY/ZrO2-Y2O3 coatings obtained by detonation spraying in 1D (spot sputtering) and 2D (full-surface scanning sputtering) modes were investigated. The structure of coatings was analyzed using scanning electron microscopy and electron dispersion analysis, mechanical properties (hard- ness, modulus of elasticity) were determined using various techniques. The tribological characteristics of the coatings including abrasion resistance and coefficient of friction were also studied. It was determined that the coatings consist of alternating layers of NiCrAlY and ZrO2-Y2O3, creating a multilayer gradient structure. It was found that the NiCrAlY layers act as a bonding element, providing interlayer adhesion, and the ceramic ZrO2-Y2O3 layer serves as a thermal barrier protecting the substrate from high temperature loads. It was found that the coatings in 2D mode have high microhardness compared to coatings in 1D mode. It was deter- mined that the hardness of coatings smoothly increases from the substrate to the surface layers due to the gra- dient increase in the content of ceramic materials. It was found that coatings obtained in 2D mode have better wear resistance and lower coefficient of friction compared to coatings in 1D mode, indicating the greater effi- ciency of coatings in dry friction conditions and their ability to prevent wear of the substrate material.

ASSESSING THE INFLUENCE OF CONTINUOUS PROFESSIONAL DEVELOPMENT PROGRAMMES ON THE TEACHING METHODOLOGIES OF HISTORY TEACHERS IN SENIOR SECONDARY SCHOOLS IN RIVERS STATE, NIGERIA

The study assessed the influence of continuous professional development programmes on the teaching methodologies of history teachers in senior secondary schools in Rivers State. Three research questions with corresponding three hypotheses guided the study. The study adopted descriptive survey designs. The population for the study consisted of 604 History teachers in public senior secondary schools in Rivers State. A retrieved sample was used for analysis, and there were 280 respondents. Stratified random sampling was used to stratify Rivers State into Rivers East, Rivers West and Rivers South East senatorial districts. Stage Quota sampling technique was applied to select History teachers from each senatorial district in Rivers State. The instrument constructed was a questionnaire titled “Influence of Continuous Professional Development Programmes on the Teaching Methodologies of History Teachers Questionnaire (ICPDPTMHTQ). The content and face validity instrument was validated by experts and History head teachers. Cronbach alpha was used to determine the reliability index of 0.80. Out of 302 copies of the instrument distributed to the respondents, 280 copies of the instruments were returned. Multiple Regression statistics method associated with ANOVA and t-test was used to answer research questions and test the hypotheses at 0.05 level of significance. The findings revealed that Continuous professional development significantly enhances teaching methods for history teachers in Rivers State. However, project-based learning, field trips, virtual tours, game-based learning, visual learning, and the Socratic method show no significant influence, indicated by high p-values and low coefficients. The study recommended that school administrators should be encouraged to offer CPD programmes that include training on innovative teaching strategies, like project-based learning and field trips, to enhance the overall effectiveness of history instruction.<p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/soc/0702/a.php" alt="Hit counter" /></p>

Influence of carbon ionization increment by adding ne on the bonding, electrical, and tribological properties of carbon thin films deposited by HiPIMS

In this work, we use mass quadrupole spectroscopy to analyze the ion energy distribution function for C+ ions from different gas composition discharges (20, 40, 60, 80, and 90% Ne) + Ar in a plasma sputtering process. Carbon films were obtained for each gas composition discharge. The carbon bonding structure of films was analyzed by Raman spectroscopy using deconvolution fitting of the G and D Raman peaks. The C-sp3 content was correlated with the electrical and tribological properties of the carbon films. Our results further corroborate the enhancement of carbon ionization in HiPIMS processes by adding neon in conventional argon gas during the deposition process. Furthermore, we found that excessive levels of carbon ionization were detrimental in the formation of C-sp3 decreasing the resistivity, and indicating the decrement of the elastic modulus of the samples. In addition, the use of neon in the gas working mixture increased the deposition rate significantly compared to argon-only processes from 1.7 to 3.22 nm/min for the highest deposition rate cases. Tribology showed that an intermediate C-sp3 content in the carbon films developed desirable tribological behaviors with lower friction coefficients and wear rates, revealing that higher values of C-sp3 content are not necessarily for robust solid lubricious and wear resistance.

A general strategy for developing eco-friendly, harsh condition adaptive, and friction tunable supramolecular gel lubricants via hydrogen bonding interaction

As green tribology and controllable lubrication technology progress, traditional lubricants fail to meet the evolving requirements of environmental sustainability, adaptability to extreme conditions, and precise friction coefficient control. In this work, a general strategy is proposed to obtain eco-friendly, harsh condition adaptive, and friction tunable polyol supramolecular gel lubricants. Molecular dynamics simulations reveal that the formation of supramolecular gels is induced by the hydrogen bond interaction between PVA, MXene, and polyols. Rheological tests demonstrate the excellent shear thinning and creep recovery properties of the prepared supramolecular gel at both room and low temperatures, positioning it as a promising new lubricant. Tribological tests further show that the supramolecular gel achieved a low friction coefficient of 0.056 and a wear rate as low as 1.88 × 10−9 mm3 N−1 m−1. Moreover, the tribological properties of various polyol supramolecular gels were compared and the viscosity-controlled friction lubrication behavior was observed. This research not only presents a novel strategy for developing environmentally friendly supramolecular gel lubricants that are adaptable to harsh conditions and tunable in friction, but also offers practical solutions to address challenges such as environmental pollution, lubrication failures in extreme environments, and precise friction control.

Comparing MLR and ANN models for school building electrical energy prediction in Osijek-Baranja County in Croatia

This paper presents a study conducted in Osijek-Baranja County, Croatia, to predict electrical energy consumption in school buildings. Data from the Energy Management Information System (EMIS) database for primary and secondary schools were analyzed using Multiple Linear Regression (MLR) and Artificial Neural Networks (ANN). The ANN model achieved a high R² of 0957 in the training set, with lower Mean Squared Error (MSE) and Root Mean Squared Error (RMSE) than the MLR model, which had an R² of 0950. On the validation set, the ANN model maintained an R² of 0954 and showed slightly better performance with a lower Coefficient of Variation of RMSE (CVRMSE) of 19,79 %, compared to the MLR model’s CVRMSE of 20,50 %. These results indicate that the ANN model generally provides more accurate and reliable predictions for energy consumption in school buildings. However, both models provided a robust positive correlation between the predicted and actual values.

Watermelon Derived Urease Immobilized Gold Nanoparticles-Graphene Oxide Transducer for Direct Detection of Urea in Milk Samples.

Urea contamination in milk poses significant health risks, including kidney failure, urinary tract obstruction, fluid loss, shock, and gastrointestinal bleeding. This highlights the need for sensitive, rapid, and reliable methods to detect traces amount of urea in milk. In this study, we designed an electrochemical transducer for urea detection by utilizing purified watermelon urease (Urs), gold nanoparticles (AuNPs), and graphene oxide (GO). The nanomaterials and biosensor probe were characterized using UV-vis spectroscopy, XPS, TEM, XRD, FTIR, AFM, CV, EIS, and DPV. The engineered probe (GCE/AuNPs/GO/Urs) demonstrated a broad linear detection range of 5 to 90 mg/dL and a low limit of detection (LOD) of 0.037 (±0.012) mg/dL (RSD < 3.7%). The biosensor was tested for potential interferents that may be present in adulterated milk and an exceptionally low coefficient of selectivity (ksel <0.1) was obtained. Evaluation of milk samples from a local dairy farm showed good recovery rates from 93.13% to. 98.79% (RSD < 4.28%, n = 3), indicating reliable detection capabilities. Stability tests confirmed the sensor's reproducibility and consistent performance. Additionally, a comparison study of the system was carried out using the purified watermelon urease and the commercially available urease. Herein, the results obtained using the sensor probe was finally validated with the gold standard method.

Enhanced wear resistance and strength synergy in Ti3AlC2 MAX through in-situ synthesis of nano TiB2 heterostructure

The rapid development of science and technology poses the core parts and techniques of industrial tribo-systems facing more stringent situations like high temperature exceeding 600 °C. For this case, solid lubrication materials are required to possess high strength, low friction coefficient and high wear resistance over a wide temperature range. However, achieving such “strong wearable yet lubricated” materials have proven challenging. Here we report a unique reinforced strategy for lubricated Ti3AlC2 MAX ceramic by in-situ synthesis of nano TiB2 heterostructure, which results in a superior high temperature strength and lubrication simultaneously excess other traditional solid-lubrication materials. Such TiB2/Ti3AlC2 composite employs a high level of compressive strength (1120 MPa ∼ 1368 MPa), wear resistance (<10‐5 mm3/(N∙m)) and low friction coefficient (<0.4) at even 800 °C. We show that its unusual properties stem from the introduction of TiB2 nanocrystalline densified and strengthened the Ti3AlC2 matrix thus to ensure the high strength. Meanwhile, the TiB2 also undergoes rapid oxidation along high temperatures friction, resulting in the formation of a continuous and smooth lubricative tribofilm containing solid lubricant B2O3, leading to exceptional solid lubrication effect at high temperature. Our finding provides a potential material portfolio and a new design strategy for high temperature solid-lubricative applications.

Frictional properties and environmental adaptability of Ti-MoS2/WC multilayer films

Magnetron-sputtered molybdenum disulfide films are extensively utilized as solid lubricating coatings in space applications as a result of their low friction coefficient and minimal contamination. However, MoS2-based films are sensitive to hygrothermal and oxidation environment, and are easily oxidized to form MoO3, which results in high friction and wear of the films, significantly reducing their operational lifespan. Especially when the spacecraft adopts the launching mode of coastal launch or ocean platform, the performance deterioration caused by oxidation of MoS2 films during transportation, storage and launch is more serious. Therefore, to enhance the frictional performance and oxidation resistance of the films in humid and salt spray environments, the Ti-MoS2/WC multilayer films with preferred (002) crystal plane orientation were prepared, achieving a friction coefficient of 0.009 in a vacuum environment and a wear rate of 1.1×10-7 mm3/N∗m. In particular, the film can maintain this extremely low coefficient of friction even after exposure to moisture or salt spray. These findings demonstrate that the dual doping of Ti and WC and the design of multilayer structures enable MoS2 films to achieve outstanding frictional performance and oxidation resistance. This is crucial for designing MoS2 films with excellent environmental adaptability.

Exploring aquaculture related traits of the grooved carpet shell (Ruditapes decussatus) in relation to other bivalve species using Dynamic Energy Budget theory

To assess the potential of the grooved carpet shell (Ruditapes decussatus) for aquaculture in Europe, we used Dynamic Energy Budget (DEB) theory to perform extensive parametrization on the species and compared its energy allocation strategy with those of commonly farmed bivalve species: mussels (Mytilus edulis and Mytilus galloprovincialis), oysters (Ostrea edulis and Magallana gigas), the common cockle (Cerastoderma edule), and great scallop (Pecten maximus). The comparison was based on DEB primary parameters relevant to aquaculture production, such as maximum assimilation rate and kappa, which represents the fraction of energy allocated to maintenance and growth, and compound parameters like the von Bertalanffy growth coefficient and maximum storage density. Furthermore, we evaluated the production efficiency at the population level, which represents the ratio of assimilated energy converted into biomass. Our results revealed notable differences in energy utilization strategies among species. However, uncertainties in parameter estimation and environmental factors challenge the direct translation of these parameters to real-world aquaculture, therefore our interpretation focuses on how these parameters might influence a species’ potential for aquaculture. The grooved carpet shell exhibits a balanced energy allocation strategy with a low growth coefficient and low maintenance costs, leading to high production efficiency. Similarly, the common mussel focuses on growth with significant biomass investment over reproduction, while the Pacific oyster and Mediterranean mussel prioritize reproductive development. The flat oyster and scallop demonstrate rapid growth at the cost of the low production efficiencies. The grooved carpet shell and mussels face constraints such as limited reserves, making them comparatively more susceptible to low food quality and quantity. In contrast, high storage densities in species like the common cockle, scallop, and Pacific oyster suggest resilience to fluctuating food conditions. These findings, along with both agreements and discrepancies with existing literature, highlight the need for further experimental research to refine DEB parameters and enhance their application in aquaculture. Overall, the DEB framework proves effective for exploring aquaculture traits across species and underscores the need for additional work on temperature-related processes, life-history events, and morphological variation.

Improved thermoelectric properties of metal ion doped aniline tetramer/carbon nanotube composite films

Carbon nanotubes and their composites have attracted much attention in the field of thermoelectric conversion for potential application in wearable electronics owing to their good electrical conductivity and excellent mechanical properties. However, low Seebeck coefficient of carbon nanotubes limit the improvement of their thermoelectric properties. In this work, metal ions (Mn+ = Fe3+, Ni2+, Cu2+) are used to further improve the thermoelectric properties of aniline tetramer (ANIT)/single-walled carbon nanotubes (SWCNT) composites, and Mn+@ANIT/SWCNT films are prepared by physical mixing and vacuum filtration method. The metal ions and concentrations for improving Mn+@ANIT/SWCNT thermoelectric films are optimized, and the metal ions doping optimizes carrier concentration and promotes carrier transport of the composites appropriately, which increased the Seebeck coefficient. Amone the prepared Mn+@ANIT/SWCNT films, the Cu2+@ANIT/SWCNT demonstrates the highest PF value of 145.3 ± 3.9 μW m−1 K−2 at the molar ratio of Cu2+/ANIT to being 5:100 with the σ of 560.1 ± 22.1 S cm−1, and the S of 51.0 ± 1.3 μV K−1 at room temperature. Finally, five pairs of p-type Cu2+@ANIT/SWCNT films and n-type copper sheets are connected in series to assemble a self-powered thermoelectric device, which demonstrates an actual output power of about 426 nW under a temperature difference of 50 K. Therefore, this work offers a metal ions doping strategy to improve the SWCNT composites with enhanced thermoelectric properties.

Influence of Fiber Volume Fraction on the Predictability of UD FRP Ply Behavior: A Validated Micromechanical Virtual Testing Approach.

Enhancing the understanding of the behavior, optimizing the design, and improving the predictability and reliability of manufactured unidirectional (UD) FRP plies, which serve as primary building blocks for structural FRP laminates and components, are crucial to achieving a safe and cost-effective design. This research investigated the influence of fiber volume fraction (vf) on the predictability and reliability of the homogenized elastic properties and damage initiation strengths of two different types of UD FRP plies using validated micromechanical virtual testing for representative volume element (RVE) models. Several sources of uncertainties were included in the RVE models. This study also proposed a modified algorithm for microstructure generation and explored the effect of vf on the optimal sizes of the RVE in terms of fiber number. Virtual tests were systematically conducted using full factorial DOE coupled with Monte Carlo simulation. The modified algorithm demonstrated exceptional performance in terms of convergence speed and jamming limit, significantly reducing the time required to generate microstructures. The developed RVE models accurately predicted failure modes, loci, homogenized elastic properties, and damage initiation strengths with a mean error of less than 5%. Also, it was found that increasing vf led to a concurrent increase in the optimal size of the RVE. While it was found that the vf had a direct influence on homogenized elastic properties and damage initiation strengths, it did not significantly affect the reliability and predictability of these properties, as indicated by low correlation coefficients and fluctuations in the coefficient of variation of normalized properties.

Establishment of a Sensitive and Reliable Droplet Digital PCR Assay for the Detection of Bursaphelenchus xylophilus.

Pine wilt disease (PWD), which poses a significant risk to pine plantations across the globe, is caused by the pathogenic agent Bursaphelenchus xylophilus, also referred to as the pine wood nematode (PWN). A droplet digital PCR (ddPCR) assay was developed for the quick identification of the PWN in order to improve detection sensitivity. The research findings indicate that the ddPCR assay demonstrated significantly higher analysis sensitivity and detection sensitivity in comparison to traditional quantitative PCR (qPCR). However, it had a more limited dynamic range. High specificity was shown by both the ddPCR and qPCR techniques in the diagnosis of the PWN. Assessments of reproducibility revealed that ddPCR had lower coefficients of variation at every template concentration. Inhibition tests showed that ddPCR was less susceptible to inhibitors. There was a strong linear association between standard template measurements obtained using ddPCR and qPCR (Pearson correlation = 0.9317; p < 0.001). Likewise, there was strong agreement (Pearson correlation = 0.9348; p < 0.001) between ddPCR and qPCR measurements in the evaluation of pine wood samples. Additionally, wood samples from symptomatic (100% versus 86.67%) and asymptomatic (31.43% versus 2.9%) pine trees were diagnosed with greater detection rates using ddPCR. This study's conclusions highlight the advantages of the ddPCR assay over qPCR for the quantitative detection of the PWN. This method has a lot of potential for ecological research on PWD and use in quarantines.

Cross-Modality Image Translation From Brain 18 F-FDG PET/CT Images to Fluid-Attenuated Inversion Recovery Images Using the CypixGAN Framework.

PET/CT and MRI can accurately diagnose dementia but are expensive and inconvenient for patients. Therefore, we aimed to generate synthetic fluid-attenuated inversion recovery (FLAIR) images from 18 F-FDG PET and CT images of the human brain using a generative adversarial network (GAN)-based deep learning framework called the CypixGAN, which combined the CycleGAN framework with the L1 loss function of the pix2pix. Data from 143 patients who underwent PET/CT and MRI were used for training (n = 79), validation (n = 20), and testing (n = 44) the deep learning frameworks. Synthetic FLAIR images were generated using the pix2pix, CycleGAN, and CypixGAN, and white matter hyperintensities (WMHs) were then segmented. The performance of CypixGAN was compared with that of the other frameworks. The CypixGAN outperformed the pix2pix and CycleGAN in generating synthetic FLAIR images with superior visual quality. Peak signal-to-noise ratio and structural similarity index (mean ± standard deviation) estimated using the CypixGAN (20.23 ± 1.31 and 0.80 ± 0.02, respectively) were significantly higher than those estimated using the pix2pix (19.35 ± 1.43 and 0.79 ± 0.02, respectively) and CycleGAN (18.74 ± 1.49 and 0.78 ± 0.02, respectively) ( P < 0.001). WMHs in synthetic FLAIR images generated using the CypixGAN closely resembled those in ground-truth images, as indicated by the low absolute percentage volume differences and high dice similarity coefficients. The CypixGAN generated high-quality FLAIR images owing to the preservation of spatial information despite using unpaired images. This framework may help improve diagnostic performance and cost-effectiveness of PET/CT when MRI scan is unavailable.

Triboelectric Nanogenerators Based on Transition Metal Carbo-Chalcogenide (Nb2S2C and Ta2S2C) for Energy Harvesting and Self-Powered Sensing.

With burgeoning considerations over energy issues and carbon emissions, energy harvesting devices such as triboelectric nanogenerators (TENGs) are developed to provide renewable and sustainable power. Enhancing electric output and other properties of TENGs during operation is the focus of research. Herein, two species (Nb2S2C and Ta2S2C) of a new family of 2D materials, Transition Metal Carbo-Chalcogenides (TMCCs), are first employed to develop TENGs with doping into Polydimethylsiloxane (PDMS). Compared with control samples, these two TMCC-based TENGs exhibit higher electric properties owing to the enhanced permittivity of PDMS composite, and the best performance is achieved at a concentration of 3wt. ‰ with open circuit voltage (Voc) of 112V, short circuit current (Isc) of 8.6µA and charge transfer (Qsc) of 175nC for Nb2S2C based TENG, and Voc of 127V, Isc of 9.6µA, and Qsc of 230nC for Ta2S2C based TENGs. These two TENGs show a maximum power density of 1360 and 911mWm-2 respectively. Moreover, the tribology performance is also evaluated with the same materials, revealing that the Ta2S2C/PDMS composite as the electronegative material presented a lower coefficient of friction (COF) than the Nb2S2C/PDMS composite. Their applications for energy harvesting and self-powered sensing are also demonstrated.

High-temperature thin-film strain sensors with low temperature coefficient of resistance and high sensitivity via direct ink writing

High-temperature thin-film strain sensors are advanced technological devices for monitoring stress and strain in extreme environments, but the coupling of temperature and strain at high temperature is a challenge for their use. Here, this issue is addressed by creating a composite ink that combines Pb2Ru2O6 and TiB2 using polysilazane (PSZ) as a binder. After direct writing and annealing the PSZ/Pb2Ru2O6/TiB2 film at 800 °C in air, the resulting thin film exhibits a low temperature coefficient of resistance (TCR) of only 281 ppm/°C over a wide temperature range from 100 °C to 700 °C, while also demonstrating high sensitivity with a gauge factor approaching 19.8. This exceptional performance is attributed to the intrinsic properties of Pb2Ru2O6, which has positive TCR at high temperature, and TiB2, which has negative TCR at high temperature. Combining these materials reduces the overall TCR of the film. Tests showed that the PSZ/Pb2Ru2O6/TiB2 film maintains stable strain responses and significant signal output even under varying temperature. These findings provide valuable insights for developing high-temperature strain sensors with low TCR and high sensitivity, highlighting their potential for applications in high-temperature strain measurements.

Tribological Properties of MoN (Ag‐W)‐MoS2 (W) Multilayer Films in Wide Temperature Range

In nitride films, an enhanced lubrication effect has been achieved through the incorporation of a soft metal element such as Ag. However, at medium and high temperatures, the favorable tribological properties cannot be sustained for an extended period due to the rapid depletion of Ag. To address this issue, a multilayer film design with W element doping is conceived to impede Ag depletion. MoN (Ag‐W)‐MoS2 (W) multilayer films with 4 different layers are prepared, and their tribological properties are systematically characterized across temperatures ranging from 25 to 800 °C. The results indicate that the tribological properties of four different multilayer films vary considerably at different temperatures. The 8‐layer multilayer film exhibits a relatively low friction coefficient that can be maintained at wide‐range temperatures. X‐ray diffractometer patterns are obtained before and after the friction test to elucidate the lubrication phases of different layers within the multilayer films at various temperatures. Additionally, 3D profiles of wear trajectory surfaces are generated, revealing enhanced wear resistance achieved by effectively inhibiting the migration of Ag. The low friction coefficient in multilayer films can be attributed to the oxidation of MoS2 and the generation of new lubrication phases, as confirmed by Raman spectra analysis.

Microstructure and high temperature tribological behavior of nickel-based superalloy with addition of revert

The recycling of revert plays a crucial role in cost-efficiency and green manufacturing of superalloy. In this study, optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, tensile test, and tribological analysis were employed to investigate the microstructure, mechanical properties, and tribological behaviors of vacuum induction melted superalloys of 100% original material (Sample 1) and 40% original material + 60% revert (Sample 2). Dry sliding tests were conducted at 300 and 730 °C. The addition of revert promotes microstructure refinement, hardness increase, and carbide formation, at the cost of 18.5% ductility loss. During the high-temperature dry sliding process, abrasive, adhesive, and oxidative wear mechanisms were observed on the contact surfaces. Sample 2 exhibited a lower wear rate and coefficient of friction at both 300 and 730 °C. Additionally, a more continuous and wear-resistant tribolayer was formed on the wear track of Sample 2, effectively mitigating matrix oxidation compared to Sample 1. At 730 °C, a thick tribolayer developed on the wear surface of Sample 2, characterized by a hard and wear-resistant glaze layer on the outermost surface. The continuous sliding induced matrix heating, which facilitates recrystallization in the subsurface of Sample 2, induced by increased inclusions and carbides from the revert. The analysis of wear debris further illustrated the variations of wear mechanism at different temperatures. These findings are meaningful for understanding the high-temperature behavior of superalloys and optimizing alloy recycling process.

Synovial fluid does not retard fluid exudation during stress-relaxation of immature bovine cartilage

Interstitial fluid load support (FLS) is a dominant mechanism of lubrication in cartilage, producing a low friction coefficient while enhancing the tissue’s load bearing capabilities. Due to its viscosity, synovial fluid (SF) may retard loss of FLS by slowing the exudation of interstitial fluid from the cartilage. This study tested this hypothesis by comparing the stress-relaxation (SRL) response of immature bovine articular cartilage immersed either in phosphate buffered saline (PBS) or in healthy mature bovine SF, under unconfined compression (fluid exudation across cut lateral tissue boundary) and indentation testing (fluid exudation across articular surface). To investigate the influence of diffusion of SF molecular constituents into cartilage, the effect of incubation time in SF on SRL was also investigated. The SRL response in unconfined compression was not significantly different in PBS versus SF when compared directly (p = 0.98) and had a slope ofm = 1.00 ± 0.04 (R2 = 0.989 ± 0.007). Samples tested in PBS exhibited characteristic relaxation times, τPBS=42.6 ± 5.3 s andτSF = 40.8 ± 4.7 s, that were not significantly different (p = 0.40). Incubation time of 24 h in SF resulted in no significant difference in the SRL response (p = 0.39, m=1.03 ± 0.12; R2=0.983 ± 0.011, andτPBS = 43.4 ± 10.7 s versusτSF = 41.5 ± 4.8 s, p = 0.59). Indentation testing showed some statistically significant, but functionally insignificant, difference in SRL responses in PBS versus SF with a slope ofm = 0.958 ± 0.060 (R2 = 0.957 ± 0.020, p = 0.029, andτPBS = 16.9 ± 2.6 s versusτSF = 19.4 ± 3.3 s, p = 0.073). Based on these results, we reject the hypothesis that healthy SF can retard the loss of FLS in cartilage due to its viscosity.

Femtosecond Pulsed Laser Machining of Fused Silica for Micro-Cavities with Sharp-Corners

Abstract Fused silica is the preferred material for applications requiring high temperature resistance, low thermal expansion coefficient and excellent optical properties. The machining of micro-cavities on fused silica surfaces is of particular interest for microfluidic manipulation, mechanical locking, and miniaturization of high-quality optical waveguides, but it still remains technically challenging via traditional manufacturing techniques especially for micro cavities with sharp corners. In the present study, the machining of micro-cavities in fused silica by a femtosecond laser-based method has been investigated numerically and experimentally. The effects of laser machining conditions, including laser power, laser scanning speed, laser incidence angle, and laser-off delay time, on the sidewall slope and bottom surface roughness of the micro-cavities were comprehensively investigated. The results indicated that laser power played a crucially important role in determining the sidewall slope of the micro-cavity, and the laser scanning speed had a significant influence on the bottom surface roughness. Furthermore, the sidewall slope of the micro-cavity was linearly increased as the laser incidence angle increases. By using a laser incidence angle of 10° and a laser-off delay time of 280 ms, a micro-cavity with sidewall slopes close to right angles (10°) was fabricated. This study confirms that femtosecond laser machining is an effective method for fabricating micro-cavities with sharp corners on fused silica surfaces, and the appropriate laser machining conditions should be considered based on practical application scenarios.

Investigation of microstructural, hardness, and wear properties of AlCrCuFeNi high entropy alloys produced by hot-pressing with the enhancement of manufacturability through electroless Ag incorporation

This study involves the production of HEA materials using low-temperature and high-pressure principles by mechanical-alloying AlCrCuFeNi high-entropy alloy powders, followed by electroless Ag coating for enhanced interface properties and hot-pressing without additional sintering. The Ag interface significantly improved the bonding of HEA powders. While increasing temperature causes a 10 % weight gain due to oxidation in HEA samples, this rate is only 1.5 % in those produced with Ag-coated HEA. The Ag interface improved the hardness of the HEAs by 50 %. The wear rate was reduced by more than twofold due to the Ag-interfaces. Ag exhibited a self-lubricating effect due to the Ag layers that repeatedly emerge during sliding, resulting in a low friction coefficient of 0.19 and excellent wear resistance.