1,721,081 research outputs found
Nanocellulose Aerogel-based Solar Steam Generator
No full textWe have developed a new method to fabricate environmentally friendly cellulose nanofiber (CNF)-based aerogel. CNF was obtained by TEMPO-mediated oxidation of bleached pulp. Whereas the conventional fabrication method of CNF aerogel was based on freeze-drying or supercritical drying of a CNF suspension, our method allowed to obtain CNF aerogel under atmospheric conditions. In order to demonstrate the applicability of the CNF aerogel, it was used as a solar steam generator (SSG).2
Photomultiplication-type Organic Photodetectors with Fast Response Enabled by The Controlled Charge Trapping Dynamics of Quantum Dot Interlayer
No full text1
Regeneration of an electret filter by contact electrification
No full textA facile and efficient method for the regeneration of electrostatic potential in electret filters by contact electrification (i.e., triboelectrification) was developed herein. The efficiency of a commercial polypropylene (PP) electret filter (PEF) for face masks was evaluated for filtration of particulate matter (PM) composed of fine solid dust and liquid droplets containing airborne bacteria (bioaerosol). The efficiency of pristine PEF for filtration of fine dust was 72.4%; however, this decreased to 62.7% following the removal of electrostatic charges in PEF by ethanol treatment. In contrast to fine dust, the bioaerosol (BA) removal efficiency of the filter was not affected by ethanol treatment because micro-sized liquid droplets could not penetrate the hydrophobic PEF surface. The electrostatic potential of PEF was restored or even enhanced by rubbing with Teflon, which exhibited a large triboelectric charge density. The PM removal efficiency of the resulting filter was higher than that of pristine PEF. Importantly, no performance degradation was observed even after 10 regenerations, demonstrating that the disposable filter can be reused to reduce the environmental problems associated with accumulation of waste.11Ysciescopu
One-dimensional model of manifold microchannels for embedded cooling: Prediction of thermal performance and flow non-uniformity
No full textA one-dimensional model has been developed to accurately predict the thermal performance and flow nonuniformity of the manifold microchannels (MMC) for embedded liquid cooling. The model consists of onedimensional governing equations derived from the integral relations of momentum and energy over appropriately-defined two separate control volumes. To validate the model, a series of 3-D numerical simulation is conducted over the wide ranges of the Reynolds number (Rem,in) at the manifold inlet from 560 to 3190, the dimensionless hydraulic flow length (x+) from 0.012 to 0.123, and the dimensionless thermal flow length (x*) from 0.002 to 0.023. It is shown that the model provides accurate predictions of the thermal performance and flow non-uniformity (CV) of MMC heat sinks within the root mean square percentage error (RMSPE) of 6% and 26% for 50 data points, respectively. The significant improvement of the prediction accuracy is made over the earlier models with an error reduction of 82%. Finally, a design guideline for the uniform flow distribution is suggested for the first time based on a newly proposed explicit correlation for predicting the flow non-uniformity: the dynamic pressure at the manifold inlet should be kept smaller than the pressure drop across the microchannels.
Synthetization of hybrid nanocellulose aerogels for the removal of heavy metal ions
No full textThis study aims to explore heavy metal ion adsorbents with excellent removal performance. For this, chitosan and gelatin-based hydrogel beads (Hyb) were prepared and crosslinked with a nanocellulose structure using ammonium zirconium carbonate (AZC) and calcium chloride (Ca). The prepared hybrid aerogels, HybAZC and HybCa, were characterized by using various techniques to investigate their respective morphologies and functional groups for a better understanding of their capacity for heavy metal ion adsorption. Then, we systematically investigated the difference in removal and adsorption capacities of heavy metal ions for single and multiple ion cases using the prepared aerogels-HybAZC and HybCa. The tested heavy metal ions were Hg(II), Pb(II), Cd(II), and Cr(III) ions. For the adsorption systems with single ion (S-HybAZC and S-HybCa) cases, every single metal ionic solution was studied in the presence of the aerogels; but for the multiple ion (M-HybAZC and M-HybCa) adsorption systems, mixed metal ionic solutions with predetermined concentrations of four heavy metal ions were studied. In a single system using S-HybAZC and S-HybCa aerogels, the removal efficiencies of all metal ions except the Cd(II) ion (using S-HybCa) were calculated to be above 65%. In multiple systems, regardless of the quality or quantity of aerogels or metal ions, the removal efficiencies were calculated to be above 85%. Overall, results suggest the prepared aerogels HybAZC and HybCa can be employed as effective adsorbents for single and multiple systems. Thus, hybrid nanocellulose aerogels have great potential for practical applications in the removal of heavy metal ions.11Nsciescopu
van der Waals Epitaxy of Organic Semiconductor Thin Films on Atomically Thin Graphene Templates for Optoelectronic Applications
No full textOrganic semiconductors (OSCs) offer unique advantages with respect to mechanical flexibility, low-cost processing, and tunable properties. The optical and electrical properties of devices based on OSCs can be greatly improved when an OSC is coupled with graphene in a certain manner. Our research group has focused on using graphene as a growth template for OSCs and incorporating such high-quality heterostructures into optoelectronic devices. The idea is that graphene's atomically flat surface with a uniform sp(2) carbon network can serve as a perfect quasi-epitaxial template for the growth of OSCs. In addition, OSC-graphene heterostructures benefit from graphene's unique characteristics, such as its high charge-carrier mobility, excellent optical transparency, and fascinating mechanical durability and flexibility. However, we have often found that OSC molecules assemble on graphene in unpredictable manners that vary from batch to batch. From observations of numerous research systems, we elucidated the mechanism underlying such poor repeatability and set out a framework to actually control the template effect of graphene on OSCs. In this Account, we not only present our scientific findings in this spectrum of areas but also convey our research scheme to the readers so that similar heterostructure complexes can be systematically studied. We began with experiments showing that the growth of OSCs on a graphene surface was driven by van der Waals interactions and is therefore sensitive to the cleanliness of the graphene surface. Nonetheless, we noted that, even on similarly clean graphene surfaces, the OSC thin film still varied with the underlying substrate. Thanks to the graphene-transfer method and in situ gating methods that we developed, we discovered that the decisive parameter for molecule-graphene interaction (and, hence, for the growth of OSCs on graphene) is the charge density in the graphene. Thus, to prepare a graphene template for high-quality graphene-OSC heterostructures, we controlled the charge density in the graphene to minimize the molecule-graphene interaction. Moreover, the possible charge transfer between OSC molecules and graphene, which induces additional molecule-graphene interactions, should also be taken into account. Eventually, we demonstrated a wide range of optoelectronic applications that benefitted from high-quality OSC-graphene heterostructures fabricated using our proof-of-concept systems.11Nsciescopu
Unraveling the efficiency-limiting morphological issues of the perylene diimide-based non-fullerene organic solar cells
Full text linkHerein we report a comparative morphological analysis of the perylene diimide (PDI)-and fullerene-based organic solar cells (OSCs) to identify the factors responsible for low performance of PDI-based devices. A PDI derivative, bis-PDI, and a fullerene derivative, PC70BM, are mixed with an efficient polymer donor, PffBT4T-2OD. The large disparity in power conversion efficiencies (PCEs) of OSCs composed of PffBT4T-2OD: bis-PDI (PCE = 5.18%) and PffBT4T-2OD: PC70BM (PCE = 10.19%) observed are attributed to differences in the nanostructural motif of bulk heterojunction (BHJ) morphologies of these blend systems. The X-ray scattering and surface energy characterizations revealed that the structurally dissimilar bis-PDI and PC70BM molecules determine the variation in blend film morphologies, and in particular, the molecular packing features of the donor PffBT4T-2OD polymer. In addition, high-resolution transmission electron microscopy (HRTEM) images explore the BHJ morphologies and presence of longer polymer fibrils in PffBT4T-2OD: bis-PDI system, justifying the unbalanced charge transport and high hole mobility. The low performance of PffBT4T-2OD: bis-PDI devices was further investigated by studying charge carrier recombination dynamics by using lightintensity- dependent and transient photovoltage (TPV) experiments. Furthermore, the temperature-dependent experiments showed the photovoltaic properties, including charge recombination losses, are strongly affected by energetic disorder present in bis-PDI-based system.112Ysciescopu
Conversion of a lipid-rich microalga Nannochloropsis oceanica to biocrude via hydrothermal liquefaction
No full textHighly efficient evaporative cooling by all-day water evaporation using hierarchically porous biomass
No full textAbstract We developed a 3D solar steam generator with the highest evaporation rate reported so far using a carbonized luffa sponge (CLS). The luffa sponge consisted of entangled fibers with a hierarchically porous structure; macropores between fibers, micro-sized pores in the fiber-thickness direction, and microchannels in the fiber-length direction. This structure remained after carbonization and played an important role in water transport. When the CLS was placed in the water, the microchannels in the fiber-length direction transported water to the top surface of the CLS by capillary action, and the micro-sized pores in the fiber-thickness direction delivered water to the entire fiber surface. The water evaporation rate under 1-sun illumination was 3.7 kg/m2/h, which increased to 14.5 kg/m2/h under 2 m/s wind that corresponded to the highest evaporation rate ever reported under the same condition. The high evaporation performance of the CLS was attributed to its hierarchically porous structure. In addition, it was found that the air temperature dropped by 3.6 °C when the wind passed through the CLS because of the absorption of the latent heat of vaporization. The heat absorbed by the CLS during water evaporation was calculated to be 9.7 kW/m2 under 1-sun illumination and 2 m/s wind, which was 10 times higher than the solar energy irradiated on the same area (1 kW/m2)
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