Physical Behavior Research Articles

Sex Differences in Physical Activity Levels and Sitting Time in Patients With Atrial Fibrillation.

While research demonstrates low levels of physical activity (PA) among adults living with atrial fibrillation (AF), there is limited evidence investigating sex differences in moderate to vigorous intensity physical activity (MVPA) and sedentary time in this population. The primary aim was to examine sex differences in MVPA levels and sitting time between women and men with AF. Secondary aims explored sex differences in sociodemographic factors, outcome expectations, and task self-efficacy toward PA levels. This was a subanalysis of the CHAMPLAIN-AF cohort study. Women and men with AF completed a survey, including the Short-Form International Physical Activity Questionnaire. A total of 210 women (median = 66.0 yr: 95% CI, 63.5-68.0) and 409 men (median = 66.0 yr: 95% CI, 64.0-67.0) were included. No sex differences were observed in median weekly MVPA (60 min/wk: 95% CI, 0-120 in women vs 120 min/wk: 95% CI, 85-150 in men) and daily sitting time (5.5 hr/d: 95% CI, 5.0-6.0 in women vs 6.0 hr/d: 95% CI, 5.0-6.0 in men). Women engaged in significantly less vigorous-intensity PA than men (P = .03) and demonstrated significantly lower task self-efficacy (P < .01). Significant positive correlations in PA levels with outcome expectations (mostly weak) and task self-efficacy (mostly strong) were observed in both sexes. Most women and men with AF did not meet the global MVPA guidelines but met the sitting time recommendation. Women presented with lower vigorous-intensity physical activity levels and confidence than men. Strategies to increase physical activity behavior, considering sociodemographic factors and task self-efficacy, are needed and may differ between sexes.

On the overall properties of young neutron stars: an application to the Crab pulsar

In this brief report, we present a model that complements the well-established canonical model for the spin evolution of rotation-powered pulsars, which is typically used to estimate ages, spin-down luminosity, and surface magnetic fields of middle-aged pulsars. We analytically explore the growth of the magnetic field during a pulsar’s early history, a period shortly after supernova explosion from which the neutron star forms, encompassing the hypercritical phase and subsequent reemergence of the magnetic field. We analyze the impact of such growth on the early dynamics of the pulsar. Investigations into a pulsar’s magnetic evolution are not new, and we expand the knowledge in this area by examining the evolutionary implications in a scenario governed by growth functions. The proposed growth functions, calibrated with data from the Crab pulsar, exhibit satisfactory physical behaviors.

Data Evaluation Framework for Refining PFAS Conceptual Site Models

AbstractContaminated sites with per‐ and polyfluoroalkyl substances (PFASs) are the cause of environmental, health, and financial concerns. Understanding and addressing PFASs at their source areas is important for effective characterization, risk assessment, and remediation. This paper introduces a framework that relies on commonly available PFAS data to assist in identifying PFAS source areas and assess PFAS fate and transport considerations along flowpaths. Currently accepted PFAS physical and chemical behaviors have been incorporated into metrics that can be evaluated geospatially, and/or over time, to build a weight‐of‐evidence approach to refine conceptual site models (CSMs). Graphical representation of data according to a PFAS “family tree” is also proposed for more consistent interpretation and pattern recognition. Combined, these tools create a PFAS data evaluation framework (PFAS Framework) that consists of a tiered analysis approach based on data availability and site complexity. Case studies from real sites are presented to demonstrate the capabilities of the PFAS Framework in identifying source areas.

Effect of partial substitution of K2O by MgO on the structure, and thermal, physical, optical properties and crystallization behaviour of K2O–MgO–B2O3–P2O5 glasses

In this work, a series of K2O–MgO–B2O3–P2O5 (KMBP) glasses were prepared by the melt-quenching method and the glass-ceramics were prepared by the one-step heat treatment. The thermal, structural, physical and optical properties, as well as the crystallization behaviour of the KMBP system, were investigated in detail using characterization techniques such as DSC, XRD, SEM, FTIR, transmittance spectroscopy and microhardness. As indicated by DSC, the thermostability and glass-forming ability were gradually enhanced through the partial substitution of K2O by MgO. XRD showed that the main crystalline phases of the glass-ceramics (GC) were gradually converted from the P–Mg–K–O based crystalline phases to the P–Mg–O based and the P–Al–O based crystalline phases. The SEM results indicated that tiny grain-like crystals were successfully precipitated from the parent glasses after heat treatment. The deconvoluted FTIR spectra results showed a gradual conversion of the [BO3] and [PO3] units towards the [BO4] and [PO4] units with the increase of the MgO contents. The increase in the degree of glass network polymerization was the essential reason for the increment in the microhardness of the parent glasses. The microhardness of GC featured a trend concordant with the crystallinity of the crystalline phases. The values of metallization criteria (MC) between 0.34 and 0.45, as well as the higher values of third-order nonlinear polarizability (χ(3)) and nonlinear refractive index (nnl) are indicative of the good suitability of the KMBP glasses for the nonlinear optical applications.

Impact of a Nyakaza Move-for-Health Intervention Programme among Adolescents in a Resource-Constrained South African Community

Adolescents in resource-constrained environments face increasing sedentary lifestyles and obesity rates, necessitating effective interventions for promoting physical activity and combating non-communicable diseases. This study evaluates the impact of a 12 week Nyakaza Move-for-Health intervention on physical activity, anthropometry, cardiorespiratory fitness, and behaviour change among adolescents in KwaZulu-Natal, South Africa. One hundred twenty-eight adolescents participated, with assessments including self-reported physical activity, anthropometric indices, and cardiorespiratory fitness measures. The intervention significantly increased physical activity levels. The treatment group’s mean score was 2.2 (0.4) at baseline and 2.6 (0.4) (F (14, 79) = 4.884, p = &lt;0.001, η2 = 0.156) at the endline. The body mass index decreased (mean = 22.4 (4.6) at baseline and 21.9 (4.2) at endline; p = 0.025, partial eta squared = 0.025, η2 = 0.004). The intervention programme significantly affected the WHR (mean = 0.80 (0.10) at baseline and 0.76 (0.9) at endline; p &lt; 0.001, partial eta squared = 0.327, η2 = 0.100) and the predicted maximal oxygen uptake (VO2 max) for the treatment group (mean = 42.4 (8.7) at baseline and mean = 43.6 (8.7) at endline; p &lt; 0.711, partial eta squared = 0.017, η2 = 0.033). Focus group discussions indicated shifts in knowledge, attitudes, and motivation towards physical activity. Power analysis revealed strong observed power (PA: 0.983, BMI: 0.098, WHR: 0.887), indicating the robustness of the intervention’s effects. These findings underscore the effectiveness of the intervention in improving physical health outcomes. It is recommended that longitudinal studies be conducted to assess the long-term sustainability and impact of such interventions on adolescents’ health outcomes, thereby informing the development of comprehensive public health policies and programmes to promote physical activity and combat non-communicable diseases in similar settings.

Impact of Tolman–Kuchowicz potentials on Gauss–Bonnet gravity and isotropic stellar structures

In this manuscript, we study the behavior of charged isotropic compact stellar objects within the framework of modified f(G) theory of gravity by considering the Tolman–Kuchowicz spacetime. We use some matching condition of spherically symmetric space–time with Bardeen’s model as an exterior geometry and examine the physical behavior of stellar structures. In the current analysis, we discuss the energy conditions to check the viability of our model. Many physical aspects have been examined, such as energy density, pressure evolution, equation of state parameter, and causality condition. Furthermore, an equilibrium condition can be visualized through the modified Tolman–Oppenheimer–Volkov equation. Further, we study mass–radius function, compactness and redshift function, which are some essential features of charged compact star model. It is worthwhile to mention here for the current study that our stellar structure in the background of Bardeen’s model is more viable and stable.

Device-assessed physical activity and sleep quality of post-COVID patients undergoing a rehabilitation program

BackgroundAn infection with SARS-CoV-2 can lead to persistent symptoms more than three months after the acute infection and has also an impact on patients’ physical activity behaviour and sleep quality. There is evidence, that inpatient post-COVID rehabilitation can improve physical capacity and mental health impairments, but less is known about the change in physical behaviour and sleep quality.MethodsThis longitudinal observational study used accelerometery to assess the level of physical activity and sleep quality before and after an inpatient rehabilitation program. The study sample consists of 100 post-COVID patients who acquired COVID-19 in the workplace. Group differences related to sex, age, COVID-19 severity, and pre-existing diseases were also analysed.ResultsLevel of physical activity and sleep quality didn’t increase after rehabilitation. Overall, there is a high extent of inactivity time and poor sleep quality at both measurement points. Regarding group differences, male patients showed a significantly higher inactivity time before rehabilitation, and younger patients (< 55 years) spend significant more time in vigorous physical activity than older patients. Post-COVID patients with pre-existing cardiovascular, respiratory, and metabolic disease show slightly less physical activity than post-COVID patients without these comorbidities. Female patients and younger patients showed better sleep quality in some sleep parameters at both measurement points. However, no differences could be detected related to COVID-19 severity.ConclusionsOngoing strategies should be implemented to address the high amount of inactivity time and the poor sleep quality in post-COVID patients.

Physical, mechanical and tribological behavior of metal matrix hybrid composite fabricated via friction stir consolidation process: an integrated DEM simulation with optimization and validation

Physical, mechanical and tribological behavior of metal matrix hybrid composite fabricated via friction stir consolidation process: an integrated DEM simulation with optimization and validation

The relationships between emerging adults self-efficacy and motivation levels and physical activity: a cross-sectional study based on the self-determination theory.

The study aims to examine the associations between exercise self-efficacy, motivation, physical activity, and body composition among emerging adults. Cross-sectional. A convenience sample of 147 emerging adults participated in the Releasing Weight (RELEW) project. The InBody720 analyzer was used to measure body composition, and the International Physical Activity Questionnaire-Short, the Shortened Physical Activity Self-Efficacy Scale, and the Treatment Self-Regulation Questionnaire were used to measure self-reported physical activity, self-efficacy, and motivation. Structural Equation Modeling was used to exam the complex relationships among multiple variables. in this study. The Partial least squares structural equation modeling analysis with bootstrapping in Smart PLS 3 was employed to explore the path coefficients and t-values for the relationships that were thought to exist. Significance was determined using a threshold of p < 0.05. The mean age of 147 participants was 18.5 ± 1.87, of whom 51.7% were female, recruited for this study. Exercise self-efficacy has a significant positive correlation with exercise motivation (r = 0.220, p = 0.008) and physical activity (r = 0.279, p < 0.001). Exercise motivation does not demonstrate significant associations with physical activity (r = 0.094, p = 0.298). Utilizing SEM, the model explained 9.2% of exercise self-efficacy, 11.8% of physical activity, and 68.3% of body composition variance. Mediation analysis revealed that exercise self-efficacy partially mediated the relationship between exercise motivation and physical activity (β = 0.106, t = 2.538, p < 0.05), and physical activity partially mediated the relationship between exercise self-efficacy and body composition (β = -0.296, t = 4.280, p < 0.001). This study sheds light on the complex relationships among motivation, self-efficacy, physical activity and body composition during emerging adulthood. Our results highlight the mediating role of self-efficacy and its impact on physical activity behaviors, offering valuable insights for targeted interventions and policy development to improve health outcomes in this demographic.

Preparation of biomass carbon dots/carboxymethyl cellulose-based fluorescent hydrogel: Combines selective detection and visual adsorption for Copper(II)

Abstract In this study, we used nitrogen-doped carbon dots (NCDs), which were synthesized via the hydrothermal method of corn-stover biomass as raw material and polyethyleneimine (PEI) as the nitrogen source, introduced them into the carboxymethyl cellulose-based hydrogel to prepare an environmentally friendly fluorescent cellulose-based hydrogel (NCDs/CMC-PAM). NCDs/CMC-PAM was also used for simultaneous fluorescence monitoring and removal of Cu (II) in aqueous solution. The chemical and physical structures, adsorption behaviors and fluorescent properties of NCDs/CMC-PAM were investigated. The results showed that NCDs/CMC-PAM exhibited a well-linear response range of fluorescence response for Cu (II) (0∼100 μM, detection limit of 3.42 μM). NCDs/CMC-PAM showed maximum adsorption capacities of 237.71 mg/g for Cu (II), the adsorption process followed the Langmuir isotherm model and pseudo-second-order kinetic model, which is an exothermic spontaneous reaction with an increase in entropy. It can still maintain 79.03% of the original adsorption capacity after six cycles (pH=6). The adsorption mechanisms of NCDs/CMC-PAM for Cu (II) are intraparticle diffusion, electrostatic attraction, ion exchange, and ligand interaction. Hence, the present study provides a new green way to synthesize an adsorbent that can be applied for the adsorption and detection of heavy metal ions.

Relationship between skeletal mitochondrial function and digital markers of free-living physical activity in older adults.

This study examined the association between in vivo skeletal mitochondrial function and digital free-living physical activity patterns-a measure that summarizes biological, phenotypic, functional, and environmental effects on mobility. Among 459 participants (mean age 68years; 55% women) in the Baltimore Longitudinal Study of Aging, mitochondrial function was quantified as skeletal muscle oxidative capacity via post-exercise phosphocreatine recovery rate (τPCr) in the vastus lateralis muscle of the left thigh, using 31P magnetic resonance spectroscopy. Accelerometry was collected using a 7-day, 24-h wrist-worn protocol and summarized into activity amount, intensity, endurance, and accumulation patterning metrics. Linear regression, two-part linear and logistic (bout analyses), and linear mixed effects models (time-of-day analyses) were used to estimate associations between τPCr and each physical activity metric. Interactions by age, sex, and gait speed were tested. After covariate adjustment, higher τPCr (or poorer mitochondrial function) was associated with lower activity counts/day (β = - 6593.7, SE = 2406.0; p = 0.006) and activity intensity (- 81.5 counts, SE = 12.9; p < 0.001). For activity intensity, the magnitude of association was greater for men and those with slower gait speed (interaction p < 0.02 for both). Conversely, τPCr was not associated with daily active minutes/day (p = 0.15), activity fragmentation (p = 0.13), or endurance at any bout length (p > 0.05 for all). Time-of-day analyses show participants with high τPCr were less active from 6:00 a.m. to 12:00 a.m. than those with low τPCr. Results indicate that poorer skeletal mitochondrial function is primarily associated with lower engagement in high intensity activities. Our findings help define the connection between laboratory-measured mitochondrial function and real-world physical activity behavior.

Tribological and Chemical–Physical Behavior of a Novel Palm Grease Blended with Zinc Oxide and Reduced Graphene Oxide Nano-Additives

The role of industrial lubricants in machinery is to reduce friction and wear between moving components. Due to the United Nations’ tendency to reduce dependency on fossil fuel, a general awareness is strongly driven towards developing more eco-friendly lubricants. Palm oil possesses promising properties, which promote it to be a competitive alternative to the hostile mineral oils. Still, marginal oxidation stability, viscosity, and tribological properties remain critical issues for performance improvement. This paper presents an improved palm grease using reduced graphene oxide (rGO) and zinc oxide (ZnO) nano-additives at different concentrations. Oil and grease samples were tested for viscosity, oxidation stability, pour point, penetration, roll stability, dropping point, churned grease-oil release, copper corrosion, friction, and wear. ZnO additives enhanced the oxidation stability by 60% and shifted the pour point to 6 °C. Adding ZnO and rGO to the palm grease increased the load-carrying capacity between 30% and 60%, respectively, and reduced the friction coefficient by up to 60%. From the wear scar morphologies, it is believed that graphene 2D nanoparticles formed absorption layers which contributed to the increase in load-carrying capacity, while ZnO chemically reacted with the metallic surface layer, forming zinc compounds that resulted in a protective boundary lubricating film.

Treatment efficiency and recovery in sand filters for on-site wastewater treatment: Column studies and reactive modelling

This study examined the adsorption capacity and treatment efficiency of sand filters in on-site treatment systems for cold climate regions. The effects of different operating conditions, porosity and kinetics parameters were investigated in column experiments and COMSOL Multiphysics® modelling, to comprehensively reveal the mechanisms and optimize treatment efficiency of nitrogen (N) and phosphorus (P) removal in a field tidal flow constructed wetland (TFCW), treating effluent from a package treatment plant with P filter material. The results from column experiments with sand showed that Total-P adsorption rate was dependent on feed water quality (Septic tank >0.77 ± 0.06 g kg−1; Biotreatment >0.41 ± 0.07 g kg−1; Reactive material Polonite® <0.18 ± 0.07 g kg−1). In the field TFCW trial, Total-P adsorption in the top layer (>1.42 ± 0.55 g kg−1) and middle layer (>1.06 ± 0.51 g kg−1) was twice that in laboratory columns, due to strong interaction with the air-water interface and use of fluctuated domestic wastewater solutions. The breakthrough curve (BTCs) of the coarse sand matched the physical behaviour of tracer electrical conductivity (EC) in effluent from the sand column experiments. The modelling results demonstrated that high filter porosity and low hydraulic load were significant factors for optimal removal of NH4–N, Total-N, PO4–P, Total- P in the top layer (>99.95 ± 0.03 %, 44.37 ± 28.75%, 70.89 ± 28.30%, 76.18 ± 20.3%), middle layer (>98.94 ± 1.77%, 18.23 ± 23.04%, 76.62 ± 28.73%, 65.40 ± 31.85%) and deep layer (>99.99 ± 0.02%, 65.50 ± 20.64%, 75.53 ± 23.16%, 41.54 ± 28.81%) in the TFCW system, respectively. The results show that on-site wastewater treatment in cold climate TFCW can be applied as a technology to polish effluent from a three-step pretreatment system. However, hydraulic optimization is an important factor for the design of the TFCW to receive a successful long-term operating system.

Lay perceptions of mental health among Afghan forced migrants residing in Finland

ABSTRACT This study explores lay perceptions of mental health among Afghan forced migrants in Finland. Semi-structured interviews were conducted with 25 participants. Reflexive thematic analysis was used as the method of analysis. The analysis produced two main themes: external symptoms (changes in physical appearance and behavior) and internal symptoms (burdensome feelings and sensations). Participants rarely used explicit mental health terminology, preferring nuanced culture-specific, individual expressions, and indirect communication about stress and trauma. This study contributes to the understanding of Afghan forced migrants’ lay perceptions of mental health and calls for culturally-safe approaches in social work and mental health services for forced migrants.

Deep embedded clustering of physical behaviour in patients with an implanted cardioverter-defibrillator identifies high and low risk profiles

Abstract Introduction Patients at high risk of sudden cardiac death are treated with an implantable cardioverter-defibrillator (ICD). Patterns in physical behaviour may be prognostic for clinical deterioration. Deep embedded clustering (DEC) employs deep neural networks to learn compact and meaningful representations from high-dimensional data, on which an unsupervised clustering then operates. Purpose The objectives of this study were to use DEC to identify and describe behavioural profiles in a prospective ICD cohort and assess their risk of clinical outcomes. Methods Data from the multicenter, prospective SafeHeart study conducted at our 2 centers, was used. Patients received an implantable cardioverter defibrillator (ICD) between May 2021 and September 2022, who then wore wearable devices during 6 months that capture physical behaviour. Latent representations were extracted from the time-series behavioural data using a variational autoencoder, and used as input to an unsupervised machine learning algorithm (Figure 1). Kaplan-Meier survival curves were used to visualise the annual risk of appropriate ICD-therapy, and the composite of all ICD-therapy and death. Results A total of 272 patients (mean age of 63.1 ±10.2 years, 81% male) were eligible, with a total of 37478 days of behavioural data (138 ±47 days per patient). DEC identified five distinct behavioural profiles: Cluster A (n=70) had high activity levels, mainly at light-to-moderate intensity. Cluster B (n=51) showed above-average sleep efficiency. Cluster C (n=63) exhibited a high-intensity activity profile. Cluster D (n=42) had frequent waking episodes and poor sleep. Cluster E (n=46) had very low physical activity levels and an impaired sleep architecture. Significantly differences were observed between clusters A-E in ICD-therapy and mortality (log-rank p-value 0.04) (Figure 2). Clusters B and D exhibited a threefold decrease in the annual risk of appropriate ICD therapy compared to cluster E. Conclusion DEC reveals distinct behavioural profiles in a prospective ICD cohort, with their inherent risk on outcomes. Wearable accelerometer devices enable behavioural monitoring that may provide opportunities for improved personalised risk prediction in a notoriously heterogeneous high-risk patient population.Deep embedded clustering of behaviourEvent rates stratified for clusters

Physical, chemical, and thermal behaviour of date palm leaflet as potential reinforcement material for green composites

Physical, chemical, and thermal behaviour of date palm leaflet as potential reinforcement material for green composites

Effect of Chemical Corrosion on Rock Fracture Behavior in Coastal Deep Mines: Insights from Mechanical and Acoustic Characteristics

The demand for critical minerals has increased extraction activities in coastal deep mines where challenges such as high stresses, chemical corrosion, and mining disturbance impacts are present. This study investigated the effects of chemical corrosion and confining pressure on the mechanical and fracture behaviors of granite specimens, which are crucial for ensuring the stability of surrounding rock in coastal deep mines. Triaxial compression tests were conducted on uncorroded specimens and corroded specimens immersed in acid and alkali solutions under varying confining pressures, with real-time acoustic emission (AE) monitoring. Based on the test results, the strength and deformation properties, progressive fracture, and failure processes, as well as the AE response characteristics of the specimens under chemical corrosion and confining pressure were analyzed. Additionally, the influence of confining pressure on the chemical damage and brittle–ductile transition behavior of specimens was discussed, and the mechanism of chemical corrosion on the physical and mechanical behavior of specimens was revealed based on mineralogical analysis. These findings underscore the importance of understanding the interplay between chemical corrosion, confining pressure, and rock fracture behavior in coastal deep mining and contribute to evaluating the stability of underground surrounding rocks under corrosion environments.

Feasibility and acceptability of a cohort study baseline data collection of device-measured physical behaviors and cardiometabolic health in Saudi Arabia: expanding the Prospective Physical Activity, Sitting and Sleep consortium (ProPASS) in the Middle East.

Physical behaviors such physical activity, sedentary behavior, and sleep are associated with mortality, but there is a lack of epidemiological data and knowledge using device-measured physical behaviors. To assess the feasibility of baseline data collection using the Prospective Physical Activity, Sitting, and Sleep consortium (ProPASS) protocols in the specific context of Saudi Arabia. ProPASS is a recently developed global platform for collaborative research that aims to harmonize retrospective and prospective data on device-measured behaviors and health. Using ProPASS methods for collecting data to perform such studies in Saudi Arabia will provide standardized data from underrepresented countries. This study explored the feasibility of baseline data collection in Saudi Arabia between November and December 2022 with a target recruitment of 50 participants aged ≥ 30 years. Established ProPASS methods were used to measure anthropometrics, measure blood pressure, collect blood samples, carry out physical function test, and measure health status and context of physical behaviors using questionnaires. The ActivPal™ device was used to assess physical behaviors and the participants were asked to attend two sessions at (LHRC). The feasibility of the current study was assessed by evaluating recruitment capability, acceptability, suitability of study procedures, and resources and abilities to manage and implement the study. Exit interviews were conducted with all participants. A total of 75 participants expressed an interest in the study, out of whom 54 initially agreed to participate. Ultimately, 48 participants were recruited in the study (recruitment rate: 64%). The study completion rate was 87.5% of the recruited participants; 95% participants were satisfied with their participation in the study and 90% reported no negative feelings related to participating in the study. One participant reported experiencing moderate skin irritation related to placement of the accelerometer. Additionally, 96% of participants expressed their willingness to participate in the study again. Based on successful methodology, data collection results, and participants' acceptability, the ProPASS protocols are feasible to administer in Saudi Arabia. These findings are promising for establishing a prospective cohort in Saudi Arabia.

Laboratory investigation on physical and mechanical behaviors of granite after heating and different cooling rates

As an important formation of geothermal reservoirs, granite has very complex microstructure and strong heterogeneity which play an important role in the damage and failure mechanical behavior of granite under different temperatures and cooling rates. In order to better understand the influence of microstructure on the multiscale physical and mechanical properties of granite at evaluated temperatures and cooling rates, this paper conducted a series of macroscopic and microscopic experimental investigations on the granite samples after a heating with two cooling rates treatment. The results show that the failure mode changes from brittle to ductile at 400 °C which is the critical temperature for both macroscopic and microscopic properties. The physical and mechanical properties of specimen after air cooling treatment increase at 200 °C due to the transition of macropores into micropores. Transgranular cracks take place in feldspar at 400 °C and numbers of intergranular cracks develop inside all minerals at 500 °C. The number and width of microcracks in water-cooled samples are much greater than those of air-cooled simples. Based on these experimental investigations, a cross-scale characterization method of Young’s modulus is proposed by introducing a thermal damage factor into the Mori–Tanaka method to consider the thermal damage induced by the thermal treatment.

Effect of cryogenic duration on the tribological properties of sintered polycrystalline c-BN during sliding mating materials in vacuum

The service performance of polycrystalline cubic boron nitride (PcBN) tools undergoes significant changes due to the deep space environment to the structure and wear behaviors of PcBN. In this paper, the effect of cryogenic treatment (CT) was studied to investigate the physical and tribological behaviors of PcBN. The hardness and wear resistance of PcBN are improved but wear forms are not affected, which are abrasive wear. The shedding of cBN played the role of micro-cutting edges, carving furrows on surfaces. As the CT duration increases, the wear rate of PcBN decreases from 2.56 × 10−8 mm3/N mm to 1.61 × 10−8 mm3/N mm for sliding against Si3N4. When PcBN slid Al2O3, the lowest wear rate is 1 × 10−8 mm3/N mm which the decline reached 34 %. Due to discrepancies in physical and mechanical properties, Si3N4 and YG8 balls exhibit abrasive and adhesive wear, and Al2O3 shows fatigue wear. Until the fatigue failure appeared, Al2O3 exhibited the lowest wear rate of 2.30 × 10−9 mm3/N mm. Among three materials, the wear rate of Si3N4 was the highest. By calculating the wear rate ratio of the materials, it was concluded that the optimal removal efficiency was achieved for Si3N4 and YG8 when CT duration is 24 and 48 h, respectively.