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•FeCo-MCM-41 exhibits excellent performance for MO degradation by activating PMS.•FeCo-MCM-41 has good stability and low metal leaching amount.•1O2 plays a dominant role for MO ...degradation in FeCo-MCM-41/PMS system.•The degradation pathways of MO are proposed.
Cobalt-mediated activation of peroxymonosulfate (PMS) has been widely investigated for the effective oxidation of organic contaminants in wastewater. Herein, monometal- and bimetal-doped MCM-41 catalysts (Fe-MCM-41, Co-MCM-41, and FeCo-MCM-41) were synthesized by using one-pot hydrothermal method and attempted to degrade artificial methyl orange (MO) dye wastewater via PMS activation. The influences of initial PMS concentration, pH, catalyst dosage and reaction temperature on the degradation efficiency of MO were systematically examined. Compared with the contrasting catalysts, FeCo-MCM-41 exhibited extremely higher activity and lower amount of metal leaching in the degradation process. The excellent catalytic activity of FeCo-MCM-41 was ascribed to the high dispersion of metals and the synergistic effects of Co2+/Co3+ and Fe2+/Fe3+ redox cycles. A series of radical inhibition and electron paramagnetic resonance experiments revealed that both radical and non-radical pathways were involved in the degradation of MO. Singlet oxygen (1O2) was unveiled to be the dominant reactive oxygen species in the FeCo-MCM-41/PMS system. The possible degradation pathways were proposed based on the identification of intermediate products generated in the degradation process by LC-MS analyses.
Flow boiling in microchannels is a promising technique to achieve large cooling rates and high heat transfer coefficients for electronic cooling. This work reports an effective approach to enhance ...flow boiling heat transfer in microchannels through expansion areas. Flow boiling experiments were conducted on plain microchannels and microchannels with single and three expansion areas for comparison. Experimental results show that the flow boiling heat transfer coefficient can be effectively enhanced by up to 43.3% through adding three expansion areas in microchannels, while the pressure drop variation is within 3 kPa. Expansion areas significantly reduce the inlet temperature fluctuation, indicating the suppression of flow boiling instability in microchannels. As disclosed by the visualization of flow patterns, the improved heat transfer coefficient can be attributed to the enhanced bubble nucleation and formation of a nonuniform liquid layer near the corners of expansion areas.
•Report an effective approach to improve flow boiling heat transfer in microchannels.•Enhance the HTC by 43.3% through adding expansion areas in microchannels.•Expansion areas effectively suppress flow reversal in microchannels.•The increase in pressure drop is less than 3 kPa.
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•Co@C catalyst was prepared by carbonizing Co-MOF particles.•Cobalt nanoparticles are highly dispersed and encapsulated in porous carbon.•MOF-derived Co@C exhibits high and stable ...catalytic performance.•Co@C combines the advantage of uniform Co nanocrystals and stable carbon matrix.
Metal–organic frameworks (MOFs) have gained significant attention as precursors for the fabrication of porous hybrid materials. However, a systematic investigation into the preparation of MOF-derived composites with high catalytic performance for hydrolysis of NaBH4 is very limited. In this work, we report the fabrication of Co@C composites using Co-MOF as the starting precursor. Physicochemical properties of the as-prepared Co@C catalysts are well characterized by XRD, BET, SEM, XPS, and HRTEM. The results of catalytic performance tests show that the Co@C-700 catalyst exhibits optimal activity among the Co@C catalysts prepared at different carbonization temperatures and retains 93.1% of its initial catalytic activity after five cycles. The cobalt nanoparticles are found to be highly dispersed and encapsulated in porous carbon, which might be responsible to the good stability of Co@C catalyst.
Core–shell nanoparticles (NPs) with lipid shells and varying water content and rigidity but with the same chemical composition, size, and surface properties are assembled using a microfluidic ...platform. Rigidity can dramatically alter the cellular uptake efficiency, with more‐rigid NPs able to pass more easily through cell membranes. The mechanism accounting for this rigidity‐dependent cellular uptake is revealed through atomistic‐level simulations.
In this paper, we report a high power density cross-plane micro-thermoelectric generator (TEG) fabricated by integrating pulsed electroplating with micro-fabrication processes. The TEG consists of a ...total of 127 pairs of n-type Bi 2 Te 3 and p-type Sb 2 Te 3 thermoelectric pillars embedded in a SU-8 matrix in order to enhance the overall mechanical strength of the device. Both bottom and top electrical connections are formed by electroplating, which is advantageous because of facile and low cost fabrication and low parasitic electrical resistances. The device demonstrates a maximum power of 2990 μW at a temperature difference of 52.5 K, corresponding to a power density as high as 9.2 mW · cm -2 . The power density of our device is more than two times the highest value reported for the electroplated micro-TEGs in the literature, which can be attributed to the low internal resistance and high packing density of thermoelectric pillars.
An attapulgite clay-supported cobalt-boride (Co-B) catalyst used in portable fuel cell fields is prepared in this paper by impregnation–chemical reduction method. The cost of attapulgite clay is much ...lower compared with some other inert carriers, such as activated carbon and carbon nanotube. Its microstructure and catalytic activity are analyzed in this paper. The effects of NaOH concentration, NaBH
4 concentration, reacting temperature, catalyst loadings and recycle times on the performance of the catalysts in hydrogen production from alkaline NaBH
4 solutions are investigated. Furthermore, characteristics of these catalysts are carried out in SEM, XRD and TEM analysis. The high catalytic activity of the catalyst indicates that it is a promising and practical catalyst. Activation energy of hydrogen generation using such catalysts is estimated to be 56.32
kJ
mol
−1. In the cycle test, from the 1st cycle to the 9th cycle, the average hydrogen generation rate decreases gradually from 1.27
l
min
−1
g
−1 Co-B to 0.87
l
min
−1
g
−1 Co-B.
Low-grade heat exists ubiquitously in the environment. Thermogalvanic cells (TGCs) are promising for converting the widespread low-grade heat directly into electricity owing to relatively high ...thermopowers of redox reactions. This work reports polarized electrolytes with ultrahigh thermopowers of -8.18 mV K
for n-type and 9.62 mV K
for p-type. The electrolyte consists of I
/I
redox couple, methylcellulose, and KCl. Thermoresponsive methylcellulose leads to polarization switching from n-type to p-type above a transition temperature due to the strong hydrophobic interaction between methylcellulose and I
ions. The giant thermopowers can be attributed to the simultaneously enhanced entropy change and concentration difference of redox couple enabled by the gelation of methylcellulose and KCl-induced complexation. The p-type TGC with the optimized electrolyte achieves a normalized maximum power density of 0.36 mW m
K
, which is far superior to other reported I
/I
-based TGCs. This work demonstrates cost-effective, high-thermopower polarized electrolytes for low-grade heat harvesting.
Low cost transition metal catalysts with high performance are attractive for the development of on-board hydrogen generation systems by catalytic hydrolysis of sodium borohydride (NaBH
4) in fuel ...cell fields. In this study, hydrogen production from alkaline NaBH
4 via hydrolysis process over carbon-supported cobalt catalysts was studied. The catalytic activity of the supported cobalt catalyst was found to be highly dependent on the calcination temperatures. The hydrogen generation rate increases with calcination temperatures in the range of 200–400
°C, but a high calcination temperature above 500
°C led to markedly decreased activity. X-ray diffraction patterns reveal that the catalysts experience phase transition from amorphous Co–B to crystalline cobalt hydroxide with increase in calcination temperatures. The reaction performance is also dependent on the concentration of NaBH
4, and the hydrogen generation rate increases for lower NaBH
4 concentrations and decreases after reaching a maximum at 10
wt.% of NaBH
4.
To investigate the effect of combined repetitive peripheral magnetic stimulation and transcranial magnetic stimulation on upper extremity function in subacute stroke patients.
Pilot study.
Subacute ...stroke patients.
Included patients were randomized into 3 groups: a central-associated peripheral stimulation (CPS) group, a central-stimulation-only (CS) group, and a control (C) group. The CPS group underwent a new paired associative stimulation (combined repetitive peripheral magnetic stimulation and transcranial magnetic stimulation), the CS group underwent repetitive transcranial magnetic stimulation, and the C group underwent sham stimulation. All 3 groups received physiotherapy after the stimulation or sham stimulation. The treatment comprised 20 once-daily sessions. Primary outcome was the Fugl-Meyer Assessment Upper Extremity (FMA-UE) score, and secondary outcomes were the Barthel Index and Comprehensive Functional Assessment scores, and neurophysiological assessments were mainly short-interval intracortical inhibition. A 3-group (CPS, CS, C) × 2-time (before, after intervention) repeated measures analysis of variance was conducted to determine whether changes in scores were significantly different between the 3 groups.
A total of 45 patients were included in the analysis. Between-group comparisons on the FMA-UE demonstrated a significant improvement (group × time interaction, F2,42 = 4.86; p = 0.013; C vs CS, p = 0.020; C vs CPS, p = 0.016; CS vs CPS, p = 0.955). Correlation analysis did not find any substantial positive correlation between changes in FMA-UE and short-interval intracortical inhibition variables (C, r = -0.196, p = 0.483; CS, r = -0.169, p = 0.546; CPS, r = -0.424, p = 0.115).
This study suggests that the real-stimulus (CS and CPS) groups had better outcomes than the control (C) group. In addition, the CPS group showed a better trend in clinical and neurophysiological assessments compared with the CS group.
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