Sufficient Contact Research Articles

Synthesis of nitrogen-rich porous carbon nanotubes coated Co nanomaterials as efficient ORR electrocatalysts via MOFs as precursor

Transition metal-based nitrogen-doped carbon materials have been proved to be a promising low-cost electrocatalyst for oxygen reduction reaction (ORR), which is a critical step in systems such as fuel batteries and zinc-air batteries. In this paper, transition metal (cobalt) N-doped carbon nanomaterials derived from metal-organic framework (MOFs) were synthesized by calcination of ZIF-67 precursors at high temperature (Co@NCNTs). Nitrogen atoms were introduced into the carbon matrix by capturing volatile CNx from dicyandiamide, and porous carbon nanotube structures with N-doped and uniformly dispersed active sites were obtained. The effects of different carbonization temperatures and molar ratio of Co/2-MI on the catalytic activity of materials for ORR reaction were studied. It was found that the Co@NCNTs prepared at 700 ℃ with the ratio of cobalt metal to dimethylimidazole of 1: 8 shows excellent ORR activity in both acidic and alkaline electrolytes. In alkaline conditions, the half-wave potential E 1/2 = 0.81 V, initial potential E onset = 0.89 V, and limiting current density even reaching 7.4 mA cm −2 . And in acidic electrolytes, E 1/2 = 0.66 V, while the limiting current density is 6.4 mA cm −2 , which is still better than that of Pt/C. Its excellent ORR performance is due to the synergistic effect of the porous carbon nanotube structure, N-doped carbon and Co-Nx active sites. Meanwhile, the optimum catalyst also shows better stability and methanol resistance than Pt/C in both acidic and alkaline electrolytes. • N-doped porous carbon nanotubes coated Co material was used to enhance ORR activity in alkaline and acidic conditions. • Nanotube structure provides sufficient effective contact area and active sites. • Porous structure is conducive to mass diffusion and reduces electron transmission resistance. • N-doped carbon tube, Co-Nx and pyridine nitrogen jointly promote ORR activity.

Application of Pt loaded graphite felt in SO2-depolarized electrolyzer

The three-dimensional anodes for SO2 depolarized electrolysis (SDE) cells are prepared by loading Pt/C on high void content graphite felts, with the method of ultrasonic spray and vacuum suction. SEM results confirm the three-dimensional space distribution of Pt in graphite felts, which ensures sufficient contact between Pt/C and SO2 in anolyte. Comparing with the two-dimensional anodic catalyst layer loaded on the proton exchange membrane in a conventional SDE cell, the application of the three-dimensional anode decreases cell impedance greatly and improves the SDE performance significantly. In this study, 0.63 mg/cm2 Pt loading amount shows the best performance when Pt/C is double-side-sprayed on graphite felt, and the current density reaches 1.24 A/cm2 at cell voltage of 1.2 V, as operating at 60 °C and anolyte flow rate of 360 mL/min. The effects of the Pt loading amount, operating temperature and anolyte flow rate on the SDE performance are investigated.

Siphon-driven interfacial photocatalytic reactors enhanced by capillary flow for continuous wastewater treatment

Catalytic membrane reactors based on photo-Fenton reactions have been widely applied in organic wastewater treatment. Conventional porous membrane reactors require a multi-cycle operation to achieve a high degradation efficiency. To realize the continuous treatment of wastewater with high efficiency, we propose a novel siphon-driven interfacial photocatalytic reactor based on the β-FeOOH-coated fabrics in the current work, in which the feed transport is within the fabric rather than across the fabric. The liquid flow is driven by gravity without additional energy input and can be adjusted by the structural parameters to match the reaction rate. Moreover, the confined capillary flow ensures sufficient contact between the feed and catalysts, as well as sufficient sunlight utilization, leading to the high degradation efficiency (>99 %) for a variety of organic contaminants such as tetracycline and dyes. The relationship between the fabric structural parameters and degradation performance was also investigated to achieve an optimal design.

Laccase-functionalized magnetic framework composite enabled chlorophenols degradation, a potential remediation for fungicides residues in leather

Chlorophenols, used as the fungicides in leather, are strictly limited in leather products. In this work, a metal–organic framework material, zeolitic metal azolate framework-7 (MAF-7), was first used to encapsulate laccase (Lac) to prepare MAF-7/Lac bio-composites with 98.5% immobilization yield. Afterward, Lac/MNP@MOM was formed by introducing the magnetic nanoparticles (MNPs) into the Lac@MOM. MAF-7 with better hydrophilicity and stronger pH buffering ability, exhibits good compatibility with laccase, which can reserve the activity of laccase after immobilization. Moreover, the porous structure of MAF-7 is favorable for the sufficient contact between laccase and substrates. Lac/MNP@MOM exhibited excellent activity when exposed to high temperature, extreme pH, and organic solvents, which also simplified complex recovery steps. Furthermore, the degradation rate of 2,4-dichlorophenol (2,4-DCP) could reach as high as 97% within 24 h by immobilized laccase, and after nine consecutive cycles of operation, enzyme activity could remain over 80%, which gives it the potential for practical applications.Graphical abstract

Doping Sb into CuFe2O4 improved the catalytic performance in the electrochemically enhanced homogeneous peroxymonosulfate-heterogeneous catalytic system for the degradation of ciprofloxacin

In this study, the electrochemically enhanced homogeneous-heterogeneous catalytic system (EC/Sb-CuFe2O4/PMS and EC/Sn-CuFe2O4/PMS) was constructed by placing the heterogeneous CuFe2O4-based catalyst in parallel between the anode and the cathode, which was applied to activate PMS to remove ciprofloxacin (CIP). Sb and Sn were doped into CuFe2O4 nanosheets to improve its intrinsic catalytic performance. Under the optimal conditions (3.5 mM PMS, the catalyst area of 4 × 5 cm2, natural pH and the current density of 15 mA/cm2), 90.3 % of CIP was removed by the proposed EC/Sb-CuFe2O4/PMS system, which was much higher than that of the EC/CuFe2O4/PMS (71.56 %) and EC/Sn-CuFe2O4/PMS (77.71 %) systems. The enhanced degradation performance of EC/Sb-CuFe2O4/PMS system was mainly due to the increased species and content of low-valence metal ions (beneficial to the activation reaction of PMS) and the rougher surface for the sufficient contact between the Sb-CuFe2O4 heterogeneous catalyst and the homogeneous PMS, which in return promoted the activation of PMS and generated more ·OH and SO4·- for the degradation of CIP. The generated intermediates in the degradation process were analyzed and the possible degradation pathways were proposed. The developed EC/Sb-CuFe2O4/PMS system was a potential candidate for the degradation of CIP in the environment. In addition, improving the catalytic performance of heterogeneous spinel catalysts by moderate doping also provided new opportunities to develop more efficient catalytic materials.

Breathable and Waterproof Electronic Skin with Three-Dimensional Architecture for Pressure and Strain Sensing in Nonoverlapping Mode.

Wearable sensors have recently attracted extensive interest not only in the field of healthcare monitoring but also for convenient and intelligent human-machine interactions. However, challenges such as wearable comfort, multiple applicable conditions, and differentiation of mechanical stimuli are yet to be fully addressed. Herein, we developed a breathable and waterproof electronic skin (E-skin) that can perceive pressure/strain with nonoverlapping signals. The synergistic effect from magnetic attraction and nanoscaled aggregation renders the E-skin with microscaled pores for breathability and three-dimensional microcilia for superhydrophobicity. Upon applied pressure, the bending of conductive microcilia enables sufficient contacts for resistance decrease, while the stretching causes increased resistance due to the separation of conductive materials. The optimized E-skin exhibits a high gauge factor of 7.747 for small strain (0-80%) and a detection limit down to 0.04%. The three-dimensional microcilia also exhibit a sensitivity of -0.0198 kPa-1 (0-3 kPa) and a broad detection range up to 200 kPa with robustness. The E-skin can reliably and precisely distinguish kinds of the human joint motions, covering a broad spectrum including bending, stretching, and pressure. With the nonoverlapping readouts, ternary inputs "1", "0", and "-1" could be produced with different stimuli, which expands the command capacity for logic outputs such as effective Morse code and intuitive robotic control. Owing to the rapid response, long-term stability (10 000 cycles), breathability, and superhydrophobicity, we believe that the E-skin can be widely applied as wearable devices from body motion monitoring to human-machine interactions toward a more convenient and intelligent future.

Design of a specific two–dimensional layered V2C counter electrode for highly effective and stable rigid and flexible quasi–solid–state dye–sensitized solar cells

Exploring Pt–free counter electrode catalysts for quasi–solid–state DSCs (QSDSCs) is significant for overcoming the high cost of Pt counter electrodes and their insufficient contact with the electrolyte. Herein, a two–dimensional (2D) layered MXene, V2C, is synthesized via a simple etching method as a counter electrode in QSDSCs. The impact of the etching time on the catalytic activity toward the regeneration of the I–/I3– redox couple in a quasi–solid–state electrolyte is investigated. After optimization, the V2C etched for 48 h shows a high catalytic activity caused by the constructed unique 2D lamellar structure, which can provide smooth diffusion channels for the penetration of the quasi–solid–state electrolyte to form sufficient contact between the V2C counter electrode and the electrolyte. As a result, the QSDSCs using the 2D layered V2C counter electrode generate a power conversion efficiency (PCE) of 7.48%. Moreover, the catalytic behavior of V2C is further improved by K+ intercalation, and the PCE value of the corresponding QSDSCs is enhanced to 8.30% under standard illumination (1.0 Sun) and to 10.19% under weak illumination (0.1 Sun). Meanwhile, the K+–intercalated V2C shows excellent stability, and 87.9% of the initial PCE of the device is retained after 1050 h in a durability test. This research is expected to provide meaningful support for the exploration of new counter electrode materials and the improvement of the contact between the counter electrode and quasi–solid–state electrolyte for the pursuit of high–performance and low–cost QSDSCs.

Macroporous Hydrogel for High-Performance Atmospheric Water Harvesting.

Simple, low-cost, and high-performance atmospheric water harvesting (AWH) still remains challenging in the context of global water shortage. Here, we present a simple and low-cost macroporous hydrogel for high-performance AWH to address this challenge. We employed an innovative strategy of pore foaming and vacuum drying to rationally fabricate a macroporous hydrogel. The hydrogel is endowed with a macroporous structure and a high specific surface area, enabling sufficient contact of the inner sorbent with outside air and high-performance AWH. The experiments demonstrate that macroporous hydrogels can achieve high-performance AWH with a broad range of sorption humidity [relative humidity (RH) from 100% to even lower than 20%], high water sorption capacity (highest 433.72% of hydrogel's own weight at ∼98% RH, 25 °C within 60 h), rapid vapor capturing (the sorption efficiency is as high as 0.32 g g-1 h-1 in the first 3 h at 90% RH, 25 °C), unique durability, low desorption temperature (∼50 °C, lowest), and high water-releasing rate (release 99.38% of the sorbed water under 500 W m-2 light for 6 h). The results show that this macroporous hydrogel can sorb water more than 193.46% of its own weight overnight (13 h) at a RH of ∼90%, 25 °C and release as high as 99.38% of the sorbed water via the photothermal effect. It is estimated that the daily water yield can reach up to approximately 2.56 kg kg-1 day-1 in real outdoor conditions, enabling daily minimum water consumption of an adult. Our simple, affordable, and easy-to-scale-up macroporous hydrogel can not only unleash the unlimited possibilities for large-scale and high-performance AWH but also offer promising opportunities for functional materials, soft matter, flexible electronics, tissue engineering, and biomedical applications.

Mechanical Effects Occurring inside Large Format 94 Ah Prismatic Lithium-Ion Cells at Different Bracing during Aging

One of the biggest obstacles to the widespread adoption of fully electrified vehicles is the limited volumetric/gravimetric energy density of lithium-ion batteries to achieve driving ranges comparable to vehicles with internal combustion engines. Electrode thicknesses are being increased to enhance the energy density of the battery cells. Furthermore, the space within the confinements of the cell housing is utilized as much as possible. Today’s state-of-the-art (SoA) electrode materials exhibit volume and Young’s modulus change during formation and cycling, e.g. a volume change up to ~10% for graphite [1] and a threefold increase of the Young’s modulus of the graphite active particles [2]. This leads to a pressure build up within the cells due to reversible and irreversible volume changes, especially of the anode materials, during cycling. The optimized packing for SoA electrodes and the volume changes of the electrodes result in increased electrochemical/mechanical interactions that leads to stress inside the cells.In this work, the interactions between mechanical bracing and aging are studied for large format prismatic 94 Ah lithium-ion battery cells [3]. The impact of external bracing is shown for lithium-ion cells cycled up to over 7000 cycles with 100% depth of discharge (Figure 1 (a)), where the braced cells show an enhanced performance in the region of 80% state of health (SOH). The braced cells reach this threshold around 900 cycles later compared to the unbraced cells. Furthermore, the unbraced cells have a thickness change of around 17.5% after more than 7000 cycles (Figure 1 (b)). After cycling, the cells are examined with post-mortem analysis, showing significantly increased aging phenomena (e.g. lithium plating) in the unbraced cell compared to the braced cell. Inductively coupled plasma optical emission spectrometry (ICP-OES) analyses confirm these assumptions (Figure 1 (c) + (d)). In contrary to the enhanced lithium plating on the anode of the unbraced cell, X-Ray diffraction (XRD) show that bracing leads to an increased structural cathode degradation compared to the unbraced cells. Those ex-situ post-mortem experiments were also confirmed by electrochemical tests in laboratory cells, showing only small capacity fading of the aged anodes of the braced cell compared to unaged reference anode cells. Nevertheless the main factor for capacity loss inside the prismatic 94 Ah cells is the loss of lithium inventory.External pressure on cells is beneficial to guarantee sufficient contact of the components within an electrode stack and hence decreased aging phenomena mainly on the anode. The downside of the increased pressure on the cells are the significantly increased morphological and structural degradation of the cathode, which, however, plays a minor role in the overall cell degradation. The external bracing results in a more ‘homogeneous’ aging over the entire cell with only little locally different degradation characteristics.

Removal of air pollutant by a spike-tubular electrostatic device: Multi-stage direct current corona discharge enhanced electrostatic precipitation and oxidation ability

In this work, a spike-tubular electrostatic device was developed for effectively removing particulate matter (PM) and VOCs, based on multi-stage electric field enhancement and expanded arc interface ratio of corona discharge. In the experiment, it was equipped with a portable 12 V D.C. power supply module and a fan module; PM from moxa smoke, mainly composed of submicron particles with a high penetrate rate, and HCHO were employed to test its electrostatic precipitation and oxidation ability, respectively. Additionally, CFD numerical simulation was adopted to investigate the characteristics of the electric field, the flow field, and the ozone generation. Experimental results showed that the electrostatic device could remove 99% of the fine particles at 2 m/s. Meanwhile, it could also remove HCHO of 2.14 × 103-1.07 × 104 μg/m3 concentration with 100% efficiency. By comparison, its oxidation capacity could be about 80 times that of ozone oxidation, revealing the enhanced oxidation ability of other short-living reactive species. Simulation results proved that the promising purification performance resulted from the locally enhanced electric field strength, up to 2 × 107 V/m in the central region, and sufficient contact between pollutants and the corona discharge region. Finally, as verified by the airtight chamber cycle experiment and case comparison, the device owns feasible purification ability and promising energy yield (0.79 g/kWh) in the application. Moreover, prospects and strategies for the device's practical application in air purification and disinfection were proposed, which may provide helpful enlightenment for air purification.

Recent Advances in Bipolar Electrochemiluminescence for Analytical Application

Background: Bipolar electrode (BPE), as an immersed electrical conductor in the electrolyte, can be polarized into cathodic and anodic poles under a sufficient electric field without direct contact, which affords a unique way to promote asymmetrical reactions at two poles. Up to date, bipolar electrochemistry has been widely used in the preparation of Janus materials, the fabrication of sensing/screening platform, target focusing and microswimmers. However, the wireless feature of BPE makes monitoring the Faradaic current difficult. Electrochemiluminescence (ECL), the light emission via an electrochemical reaction, matches the feature of bipolar electrochemistry well and is widely adopted to achieve the record of the Faradaic current flowing through the BPE. The objective of the present review aims to demonstrate the most recent advances in analytical applications (2016-2020) in combination with the high sensitive ECL as the output. Methods: Due to the difficulty of the recording of the Faradaic current flowing the BPE, the ECL, as a simple, sensitive and detectable signal-out, has become a popular method for analytical application based on the BPE. This review mainly summarizes the recent research of BPE/ECL according to the configuration and sensing principle of BPE designed in the ECL analysis. Results: Various sensors based on the BPE/ECL have been proposed for the electroactive targets and the bio-relevant molecules without the electroactivity by different ingenious designs. Besides, the microelectrode array and ultra-microelectrode (UME) array have also been applied in the BPE/ECL field to achieve the high temporal-spatial resolution imaging of the sample molecules based on the BPE microelectrode array. Conclusion: The combination of BPE and ECL provides a simple, portable and versatile sensor strategy for various targets due to the unique advantages of BPE and ECL, and can be applied for the fast, accurate and point-of-care diagnostics of numerous diseases. Though the BPE/ECL analysis has many merits such as high-throughput, excellent sensitivity, and high spatial-temporal resolution, the sensitive and commercial ECL analysis based on the BPE is still difficult to realize and the analysis research of BPE/ECL is still in the early stage.

Use of the Electronic Health Record During Clinical Encounters: An Experience Survey.

Use of the electronic health record (EHR) during face-to-face clinical encounters affects communication, and prior research has been inconclusive regarding its effect. This survey study assessed health care practitioner use of EHR-specific communication skills and patient and practitioner experiences and attitudes regarding EHR use during clinical encounters. For this US-based study, we distributed previously validated surveys to practitioners and adult patients (aged >18 years) at academic primary care practices from July 1, 2018 through August 31, 2018. The electronic practitioner survey was completed first; a paper survey was administered to patients after appointments. Descriptive statistics were calculated, and the Cochran-Armitage test was used to assess for associations between key variables. The practitioner response was 72.9% (43/59); patient response, 45.2% (452/1,000). Practitioners reported maintaining less eye contact (79.1%), listening less carefully (53.5%), focusing less on patients (65.1%), and visits feeling less personal (62.8%). However, patients reported that practitioners provided sufficient eye contact (96.8%) and listened carefully (97.0%); they disagreed that practitioners focused less on them (86.7%) or that visits felt less personal (87.2%). Patients thought EHR use was positive (91.7%); only one-third of practitioners (37.2%) thought that patients would agree with that statement. Practitioners reported stress, burnout, and a lack of sufficient time for EHR documentation. A discrepancy existed in this study between patient and practitioner experiences and attitudes about EHR use, which appeared to negatively affect the experience of health care practitioners but not patients. Organizations should adopt formal strategies to improve practitioner experiences with EHR use.

Flower-shaped Fe–CoP@C composites derived from MOFs as an efficient electrocatalyst for oxygen evolution reaction

<p indent="0mm">Sluggish kinetics of oxygen evolution reaction (OER) dramatically hampers the large-scale application of electrochemical water splitting. It is of great importance to develop efficient and stable non-precious metal catalysts for OER. Using a hydrothermal-ion-exchange-high-temperature-phosphating approach, a novel 3D micron-flower-shaped composite (Fe–CoP@C) with strong coupling of iron-doped cobalt phosphide and carbon-based material was firstly prepared based on flower-like Co₃O₄@Co–MOF precursors. Fe–CoP nanoparticles loaded on functionalized carbon nanosheets can facilitate sufficient contact with the electrolyte and expose more catalytic active sites. The incorporation of Fe optimizes the electronic structure of the material and enables the material to exhibit excellent OER activity. In an alkaline electrolyte, Fe–CoP@C catalysts manifest superior electrocatalytic performance for OER with an overpotential of 259 mV at <sc>10 mA cm⁻²,</sc> a Tafel slope of 48.24 mV dec⁻¹. Benefiting from the strong coupling between nanoparticles and the carbon layer, the catalysts also exhibit faster reaction kinetics and higher structural stability. The composites display excellent long-term stability, with 108 h of continuous operation in alkaline solutions.

(Oxy)nitride heterojunction-strengthened separation of photogenerated carriers in g-C3N4 towards enhanced photocatalytic H2 evolution

The metal-free graphitic carbon nitride (g-C3N4) with a series of merits like low cost, favorable stability, and controllable two-dimensional graphite-like structure, has been extensively studied for photocatalytic H2 evolution. Composite engineering is regarded as one of effective strategies to adjust the kinetics of photogenerated carriers in g-C3N4 for elevating its photocatalytic performance. Herein, the composite system of g-C3N4 with oxynitride LaTiO2N was elaborately constructed for improving photocatalytic H2-evolution performance. With systematical characterizations, the partial cover of g-C3N4 nanosheets on LaTiO2N (LaTiO2N@g-C3N4) was verified and promoted the sufficient contact between g-C3N4 and LaTiO2N, accompanied by the formation of the (oxy)nitride heterojunction. Benefited by the well-matched band structures for g-C3N4 and LaTiO2N, the (oxy)nitride heterojunction strengthened the separation of photogenerated carriers and therefore enhanced the photocatalytic performance of g-C3N4. This work gives more insight in composite engineering on g-C3N4, and also provides feasible guidelines for designing g-C3N4-based photocatalysts towards improving photocatalytic performance.

Tertiary Treatment of Secondary Effluents from the East WWTP of Tizi-Ouzou (Algeria) with the Aqueous Extract of Ceratonia Siliqua Green Pod

The antibacterial action of the carob tree offers the possibility of using it for the disinfection of treated wastewater in biological process wastewater treatment plants. This paper reviews studies conducted to investigate the effect of carob tree on the reduction of indicator bacteria of fecal contamination that cannot be removed after the secondary stage of biological treatment. The aim is to use the wastewater safely in irrigation and expand the list of irrigable plants with this unexploited resource. Physico-chemical and bacteriological parameters were used to determine the optimal conditions and evaluate the treatment’s efficiency. A contact time of 1 h and a dose of 1 mL of disinfectant reduced E. coli and fecal coliforms from 5.105 CFU to 1 237 CFU (99.75%) and from 7.106 CFU to 1 505 CFU (99.98%), respectively. For the same contact time, the fecal streptococci were reduced from 4.105 CFU to 59 CFU (99.99%). According to WHO standards, this dose and contact time are sufficient to use this water for irrigation. A minimum contact time of 2 h with a dose of 1 mL of the aqueous extract of the green pod of the carob is required to obtain a reduction of E. coli and fecal coliforms from 5.105 CFU to 5 254 CFU (99.95%) and from 7.106 CFU to 340 CFU (99. 99%) to meet the Algerian standards of reuse of treated wastewater being more stringent. The results show that the same conditions reduce fecal streptococci from 4.105 CFU to 5 CFU (99.99%). This elimination level shows that green carob juice can be used for disinfection with the necessary doses for each bacterial load and sufficient contact time.

Engineering hierarchically ZnS/NiS/NiS2 hollow porous urchin-like composite towards exceptional lithium storage

Complex hollow structure nanostructure is regarded as the desired approach to alleviating the volume change of lithium-ion batteries (LIBs). In this work, ZnS/NiS/NiS2 composite with a distinctive hierarchical hollow porous urchin-like structure was prepared through pyrolysis of bimetal-organic frameworks obtained by one-step solvothermal and firstly used as anodes for LIBs. Varying the metal molar ratios allows the control of the surface area and pore size distribution of ZnS/NiS/NiS2. The obtained composite with a hollow porous urchin-like structure exhibits high porosity, large specific surface area, and strong synergetic interaction between ZnS and NiS/NiS2 can greatly buffer the volume expansion to keep the mechanical stability, ensure sufficient contact region between electrolyte and electrodes and shorten the Li+ transfer distance, meanwhile, the carbon derived from organic ligand of bimetal-organic frameworks also constructs the conductive matrix to accelerate electrons transfer. Based on the above outstanding properties, the obtained material delivers excellent rate capacity, superior reversible capacity, and long-cycle stability, especially disclosing a capacity of 615 mAh·g−1 after 300 cycles at 2 A·g−1. This work proposes a feasible strategy to obtain a unique hollow porous urchin-like structure through pyrolysis of bimetal organic frameworks, it can be extended to fabricate other mixed metal sulfides nanostructures with excellent electrochemical performances.

B, O and N Codoped Biomass-Derived Hierarchical Porous Carbon for High-Performance Electrochemical Energy Storage.

High specific surface area, reasonable pore structure and heteroatom doping are beneficial to enhance charge storage, which all depend on the selection of precursors, activators and reasonable preparation methods. Here, B, O and N codoped biomass-derived hierarchical porous carbon was synthesized by using KCl/ZnCl2 as a combined activator and porogen and H3BO3 as both boron source and porogen. Moreover, the cheap, environmentally friendly and heteroatom-rich laver was used as a precursor, and impregnation and freeze-drying methods were used to make the biological cells of laver have sufficient contact with the activator so that the layer was deeply activated. The as-prepared carbon materials exhibit high surface area (1514.3 m2 g−1), three-dimensional (3D) interconnected hierarchical porous structure and abundant heteroatom doping. The synergistic effects of these properties promote the obtained carbon materials with excellent specific capacitance (382.5 F g−1 at 1 A g−1). The symmetric supercapacitor exhibits a maximum energy density of 29.2 W h kg−1 at a power density of 250 W kg−1 in 1 M Na2SO4, and the maximum energy density can reach to 51.3 W h kg−1 at a power density of 250 W kg−1 in 1 M BMIMBF4/AN. Moreover, the as-prepared carbon materials as anode for lithium-ion batteries possess high reversible capacity of 1497 mA h g−1 at 1 A g−1 and outstanding cycling stability (no decay after 2000 cycles).

Numerical modelling of friction stir welding of pipes: Effect of tool shoulder on mechanical property and metallurgical characterization

One of the challenges during FSW of pipe is establishing sufficient contact between the tool shoulder and the pipes to be welded. With improper contact, the torque requirement increases, which thereby increases the power consumption. The present work focuses on the demonstration of a 3D thermo-mechanical model showing the influence of tool shoulder diameter on temperature rise, plastic strain development, spindle torque, material flow occurrence, and power consumption. The model showed a good correlation with experimentally observed temperature and maximum spindle torque for different rotational speeds. It was observed from the developed model that, an increase in the shoulder diameter increases the contact area and spread of maximum temperature resulting in a wider HAZ zone. Hence, optimization of the tool shoulder diameter was necessary, and it has been addressed considering its effect on contact area, heat generation, material flow, and spindle torque. The material flow behaviour has also been studied, and it was found that a larger shoulder diameter does not produce sufficient material stirring. The welded sample has been investigated by tensile strength and microstructure analysis. The optimum tool shoulder diameter of 16 mm resulted in joint strength efficiency of 90%.

Determination of the Coefficient of Friction in a Pulley Groove by the Indirect Method

In lifting systems used for the vertical transport of bulk materials and individual items or persons, so-called frictional force transmission between a steel cable and pulley is used. Due to the sufficient contact pressure between the pulley groove and the surface of the steel cable, the steel cable moves as a result of fibre friction. In general, it is possible to define fibre (also called belt) friction as the resistance that is imposed on a flexible steel cable sliding over the rounded surface of a pulley. The frictional transmission of the tractive force is considered safe if there is no slippage of the cable in the pulley groove. In the event of insufficient cable pressure against the pulley groove or insufficient friction, the transport process fails, and the lifting device is unable to perform its function. The purpose of the article and of the created measuring devices is to obtain by experimental measurements the most accurate true value possible of the coefficient of friction acting on the contact surface of the cable with the pulley groove. The values of the friction coefficients obtained by indirect measurements on laboratory equipment when the tractive force is transferred by friction differ in many cases and do not coincide with the values calculated using theoretical relationships. The aim of the paper is to present a method of measurement and to identify the magnitude of the forces acting on both sides of a cable belted in the V-groove of a cable drum. From the results obtained from the experimental measurements, to express the value of the random variable is based on the knowledge of the known values obtained from the measurements for their use in a failure analysis. This paper presents results that can be applied in the field of online monitoring of this type of lifting equipment for failure analysis, prediction and evaluation of their operational indicators.

Alternative measurement systems for recording cardiac activity in animals: a pilot study

Monitoring and assessing cardiac activity in animals, especially heart rate variability, has been gaining importance in the last few years as an indicator of animal health, well-being and physical condition. This pilot study tested the sensors based on ballistocardiography sensing the mechanical vibrations caused by the animal’s cardiovascular system, which have proved useful in measuring cardiac activity in humans. To verify the accuracy of these measurement systems, the conventional measurements based on electrocardiography were carried out and the outcomes were compared. The main objectives were to verify the suitability of these sensors in measuring cardiac activity in animals, to determine the advantages and disadvantages of these sensors, and to identify future challenges. Measurements were performed on various animals, specifically a goat, a cow, a horse, and a sheep. Electrocardiographic measurement, which has demonstrated high accuracy in procedures for animals, was used as the study’s gold standard. A disadvantage of this method, however, is the long time required to prepare animals and shear spots to attach electrodes. The accuracy of a ballistocardiographic sensor was compared to reference electrocardiographic signals based on Bland–Altman plots which analysed the current heart rate values. Unfortunately, the ballistocardiographic sensor was highly prone to poor adhesion to the animal’s body, sensor movement when the animal was restless, and motion artefacts. Ballistocardiographic sensors were shown only to be effective with larger animals, i.e., the horse and the cow, the size of these animals allowing sufficient contact of the sensor with the animal’s body. However, this method’s most significant advantage over the conventional method based on electrocardiography is lower preparation time, since there is no need for precise and time-demanding fixation of the sensor itself and the necessity of shaving the animal’s body.