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1.
To explore the potential application of industrial waste, steel slag powder in combination with melamine pyrophosphate (MPP) was adopted to improve the flame retardancy of rigid polyurethane foam (RPUF). The incorporation of steel slag slightly reduced the thermal conductivity of the resulting flame-retardant RPUF samples. The addition of MPP and/or steel slag did not significantly alter the thermal stability in terms of T-10% and Tmax but did obviously increase the T-50% value, suggesting the improved thermal resistance of the residues. The coaddition of MPP and steel slag into RPUF resulted in higher LOI values and lower peak heat release rates than the samples incorporating either MPP or steel slag alone. The superior flame retardancy could be attributed to MPP promoting char formation, which then acted as a barrier at the beginning of RPUF thermal decomposition; simultaneously, the thermally stable inorganics in the steel slag powder strengthened the thermal resistance of this char layer.  相似文献   

2.
Carbon nanotubes (CNTs) have been proposed as new candidate particles to enhance the utilization efficiency of solar energy in solar fluidized bed receiver (SFBR) for solar air heating in low- and mid-temperature ranges. Heat absorption characteristics of the CNTs have been determined in a SFBR (50 mm i.d. X 150 mm high). Two types of experimental particles were used which consisted of multi-walled CNTs with different nanotube shapes, such as entangled CNTs (ENCNTs) and vertically aligned CNTs (VACNTs). The particle dynamics and heat absorption characteristics of CNTs were studied and compared with those of silicon carbide (SiC), a conventional particle. CNTs showed lower pressure fluctuation with relatively uniform particle behavior in the freeboard compared to SiC. The outlet gas temperatures of the receiver with CNTs were higher than those inside the fluidized bed above 0.10 m/s of gas velocity. The temperature increment of gas per irradiance (ΔT/IDNI) decreased with increasing gas velocity. VACNTs, which are characterized by the coexistence of aggregates and nanotubes in the freeboard, showed a higher value of ΔT/IDNI than ENCNTs for the same gas velocity. The relative heat absorption temperature (T*) decreased with increasing gas velocity, and dropped below 1.0 at the solid holdup of 0.04, indicating that the freeboard region’s contribution to the receiver’s heat absorption increased. VACNTs and ENCNTs showed maximum thermal efficiencies of 26.7 % and 30.5 % at gas velocities of 0.12 and 0.16 m/s, respectively, which was 33 % higher than that of SiC. Considering the particle properties and particle dynamics, the obtained thermal efficiencies in the present and previous studies were correlated with the Reynolds, Archimedes and Prandtl numbers and the ratios of the specific heat capacities of the particles to the gas.  相似文献   

3.
Despite a good understanding of the filtration properties of various face and nose coverings during aerosol inhalation, their effectiveness in reducing aerosol emitted by infected individuals during exhalation or coughing is not fully characterized. This paper presents experiments conducted using a silicone model of a standardized face for controlled flow patterns (steady flow, typical exhalation or flow pulses associated with coughing/sneezing) used to push test aerosols (0.5–20 μm) through valved or non-valved respirators, surgical masks and cloth masks. The aerosol characteristics determined during experiments allowed quantitative comparison of size-dependent aerosol penetration for different flow conditions. The results showed that only aerosols smaller than 8.5–10 μm more easily penetrated beyond the face coverings tested but their concentrations outside were significantly reduced. Calculations based on experimental data showed that the amount of emitted airborne particles that can be inhaled into the lower respiratory tract of bystanders was reduced 1.3–5.7 times compared to the case when the spreader does not use a mask. These results bring additional quantitative information on the role of selected masks and respirators in reducing aerosol emission that potentially contribute to the transmission of viral diseases, including COVID.  相似文献   

4.
The objective of the present study was to investigate whether mixing ratio of maize and soybean meal (SBM) affects the breaking behaviour during hammer-milling in terms of the nutrient properties and in vitro digestibility of fractionated particles. Mixtures of maize and SBM with different proportions (% Maize:SBM; 0:100, 25:75, 50:50, 75:25, 100:0) were hammer milled using a 2-mm screen. The obtained powder was sieved into seven fractions with size ranges from 0.149 to 1.190 mm. Results show that energy consumption of grinding mixtures increased from 3.8 to 48.4 kJ/kg with the maize proportion increasing from zero to 100%. Mixing proportion of maize and SBM showed significant effects on nutrient content of fractionated material. For hammer milled material <595 µm, the in vitro digestibility of crude protein (CP) and organic matter (OM) of fractionated material decreased with increasing particle size. Additionally grinding fractionated particles ≥595 µm over a 1-mm sized screen before in vitro digestion analysis increased the digestibility of OM and CP. Equivalent particle size (EPS) and geometric standard deviation (GSD) of hammer milled maize and SBM and their mixtures correlated better than geometric mean diameter (GMD) to OM and CP in vitro digestibility in a linear regression model. In summary, the mixing ratio of maize and SBM had a significant effect on the breaking behaviour of ingredients and in vitro digestibility of CP and OM of the isolated fractions. Mixing ingredients before grinding is suggested in terms of saving energy consumption. The GSD/EPS of ground material should be considered while studying the effects of particle size distribution on the in vitro digestibility of nutrients.  相似文献   

5.
A novel approach for preparing drug-containing particles (DCPs) with controlled size distribution and high drug loading was developed using melt granulation. This approach comprises two steps. First, melting component adsorbed particles (MAs) were prepared by mixing and heating the melting components with a porous carrier using a high shear granulator. Second, DCPs were prepared by layering the drug on MAs using a fluidized bed rotor granulator. The time taken for both steps was within 30 min. Adding the polymer in the second step remarkably increased the viscosity of the mixture of melting components and the polymer. Therefore, DCPs could be successfully loaded with a high amount of drug (70% w/w). The particle size distribution of the DCPs was narrow, and it depended on that of the MAs. The flowability of the DCPs was excellent, and the sphericity was close to 1. A unique particle formulation mechanism was suggested based on the observation of DCPs using scanning electron microscopy. The manufacturing time and DCP characteristics were not affected by the manufacturing scale. In conclusion, we have successfully developed a highly efficient novel approach for preparing optimal DCPs through melt granulation, named “Melt Adsorption and Layering with Porosity Core” (MALCORE®).  相似文献   

6.
A cobalt-based metal–organic framework was used as a precursor to synthesize Co3O4 catalysts exhibiting a hexagonal layered morphology by calcination at varying temperatures. Various characterization techniques, such as XRD, SEM, Raman, H2-TPR, O2-TPD and N2 adsorption–desorption, were used to study the effects of calcination temperature on the grain size, surface area, and pore volume of the catalysts. The Co3O4 catalyst obtained by calcination at 350 °C (Co3O4-350) exhibited the highest catalytic activity for the total oxidation of propane. Furthermore, the small grain size and layered structure of Co3O4-350 allowed it to possess a high specific surface area, a highly exposed {1 1 2} facets, and abundant oxygen defects that facilitated a favorable low-temperature reducibility and oxygen mobility, thereby improving catalytic activity. This research offers a simple strategy for synthesis of Co3O4 with layered structure, highly exposed {1 1 2} facets and rich oxygen defects.  相似文献   

7.
This study mainly investigated the physicochemical characteristics of ethylene glycol/ water (EG/W) based hydroxyl-functionalized boron nitride (BN-OH) and graphite (G) hybrid nanofluids. A novel simple and efficient annealing method was proposed to have hexagonal boron nitride (h-BN) nanoparticles functionalized to improve the synergistic role between hybrid G/BN-OH nanoparticles. Meanwhile, the dispersion stability, thermal stability, and rheological behavior of diverse nanofluids (h-BN, BN-OH, G, G/BN and G/BH-OH) were comprehensively evaluated. The results showed that the G/BN-OH hybrid nanofluids demonstrate both better dispersion stability and thermal stability, as well as a lower increase in viscosity. In addition, the thermal conductivity of G/BN-OH hybrid nanofluids was increased by up to 18.05% with a concentration of 0.2 wt% when compared to the base fluid. Ultimately, the complicated theoretical mechanism of thermophysical performance augment for G/BH-OH hybrid nanofluids was reliably presented. The enhanced thermal conductivity of nanofluids may be attributed to the formation of adsorption layers and the synergistic effect of the thermal conductivity network.  相似文献   

8.
《Advanced Powder Technology》2020,31(3):1114-1124
The prefabrication of Mo-Nb composite powders is an effective way of improving the homogeneity of Mo-10Nb targets, which have broad application prospects in the photoelectric sensor industry. However, this aspect has been rarely addressed so far. Therefore, we prepared Mo-10Nb composite powders by mechanical alloying (MA), and investigated the effects of the experimental parameters such as the milling speed and duration on the particle morphology, size distribution, compositional homogeneity, crystallite size, inner strain, and oxygen content. High-quality Mo-10Nb composite powders with 3-μm spherical particles of narrow size distribution, homogeneous elemental distribution, and nanometric crystalline structure were obtained by implementing optimum MA parameters, viz., a milling speed of 250 rpm and duration of 36 h using an MITR QM-QX-4L omnidirectional ball mill. The mechanically alloyed Mo-10Nb composite powders were prone to oxidation when exposed to air, which led to a sharp increase in the oxygen content to ~5400 ppm. X-ray photoelectron spectroscopic analysis revealed the presence of Nb2O5, MoO2, and MoO3 on the surface of the Mo-10Nb particle. We believe that this study demonstrates an interesting strategy for the fabrication of high-quality Mo-10Nb targets.  相似文献   

9.
The current electrowetting mechanisms show a low efficiency, although manipulating liquid droplets is essential to biological and chemical fields. Herein, we propose a highly efficient droplet manipulating method using direct charge injection (DCI) via human motion induced triboelectricity. A triboelectric nanogenerator (TENG) is used to provide both the charges and strong electric fields to drive the movement of liquid droplets. Using this method, the charge quantity and average velocity of the droplet (10 μL) reach 0.25 nC and 255 mm s−1, respectively, over 6 times higher than those of traditional methods (0.03 nC and 43.2 mm s−1). Alternative charge injection was demonstrated to enable both reciprocating and jumping motions of the droplet. Finally, we also successfully devised and demonstrated a platform with versatile system-level functions including droplets transportation, positioning, merging, and cleaning. This work advances the current droplet manipulation field via introducing a compelling approach using human-motion-induced direct charge injection.  相似文献   

10.
《Advanced Powder Technology》2020,31(5):2092-2100
Tapered wire coil insert is proposed as a novel enhancer in the double tube heat exchanger and experimental studies on Al2O3 + MgO hybrid nanofluid flowing under the turbulent condition are performed to investigate the hydrothermal characteristics. Effects of using tapered wire coil turbulator and hybrid nanofluid on the hydrothermal behaviors are examined for different coil configurations (Converging (C) type, Diverging (D) type and Conversing-Diverging (C-D) type) and hybrid nanofluid inlet temperatures and volume flow rates. Results show that D-type wire coil insert promotes better hydrothermal performance as compared to C-type and C-D type. Nusselt number and friction factor of hybrid nanofluid using D-type, C-D type and C-type wire coil inserts enhance up to 84%, 71% and 47%, and 68%, 57% and 46%, respectively than that of water in tube without insert. The entropy generation of hybrid nanofluid is lower than that of base fluid in all cases. The thermal performance factor for hybrid nanofluid is found more than one with all inserts. The thermal performance factor is observed a maximum of 1.69 for D-type coil. The study reveals that the hybrid nanofluid and tapered wire coil combination is promising option for improving the hydrothermal characteristics of double pipe heat exchanger.  相似文献   

11.
《Advanced Powder Technology》2020,31(5):2161-2177
The present research work has concentrated to synthesize nanocrystalline (NC) Cr0.26Fe0.24Al0.5 (medium entropy alloy, 3E-MEA) and Cr0.15Fe0.14Al0.30Cu0.13Si0.28 (high-entropy alloy, 5E-HEA) non-equiatomic (equal weight fraction) alloys through mechanical alloying (MA); which studied the influence of entropy effect on structural properties, microstructural characterization, and mechanical behaviour. Further, the same non-equiatomic ratio of two coarse grain alloys (CGAs) was manufactured by conventional powder metallurgy (PM) route (blending method, 3E-CGA, 5E-CGA) for comparison. All synthesized powders were hot-pressed (HPed) at 723 k for 30 min subsequently mechanical properties in terms of compressive stress-strain and hardness were examined. The samples of as-milled powders, HPed, and fractured were investigated using X-ray diffraction (XRD) and advanced electron microscopes. The HPed sample of 3E-MEA of Cr0.26Fe0.24Al0.5 produced 94% BCC and 6% FCC crystal structures due to more dissolution of Al atoms in the stronger bonding atoms of Cr-Fe lattice. Whereas 5E-HEA of Cr0.15Fe0.14Al0.30Cu0.13Si0.28 sample has exhibited 72.1% FCC phase and 27.9% BCC phase due to balance between the dissolution of FCC elements (Al, Cu, Si) and BCC elements (Cr, Fe). Further, 3E-MEA and 5E-HEA have exhibited the ultimate compressive strength (UCS) of 1278 ± 6.75 MPa and 2060 ± 2.8 MPa respectively whereas the corresponding conventionally blended alloys produced 268 ± 5 MPa and 615 ± 3 MPa for 3E-CGA and 6E-CGA respectively. Vicker’s hardness strength (VHS) of 5E-HEA of Cr0.15Fe0.14Al0.30Cu0.13Si0.28 has exhibited 68% more when compared to 3E-MEA of Cr0.26Fe0.24Al0.5, 3.26 times higher compared to blended alloys. Further, several strengthening mechanisms on the mechanical behaviour of MEA and HEA were investigated in which dislocation strengthening mechanisms followed by solid solution strengthening mechanisms have influenced more as compared to grain boundary strengthening mechanisms.  相似文献   

12.
《Advanced Powder Technology》2019,30(10):2422-2429
Carrier-free method is an alternative approach for dry powder inhaler (DPI) formulations, which overcome poor drug mobility and distribution. Here we investigated the properties of an active pharmaceutical ingredient (API) within composite particles. We used highly-branched cyclic dextrin (HBCD) as the excipient matrix that was prepared using a spray-drying technique. 4-Aminosalicylic acid (4-ASA) and 4-dimethylaminobenzonitrile (DMABN) were selected as a hydrophilic second-line antitubercular agent and a surrogate for 4-ASA as a model compound, respectively. The spray-dried particles (SDPs) containing 4-ASA or DMABN with HBCD had geometric median diameters (D50) of 2.34 ± 0.07 μm and 2.26 ± 0.10 μm, respectively. Further, the in vitro aerodynamic properties were similar for SDPs containing 4-ASA and DMABN with HBCD. To determine the properties of APIs within composite particles, we performed solid-state fluorescence spectroscopy of DMABN. As a candidate excipient, hydroxypropyl methylcellulose (HPMC) was compared to HBCD. We determined the intensity ratio of twisted intramolecular charge transfer (TICT) emission to locally excited emission within the excipient matrix environment. The HBCD matrix environment was better than HPMC to trigger a more robust TICT reaction of DMABN. A potent state-changing interaction of APIs occurred in the HBCD matrix environment versus another excipient environment.  相似文献   

13.
Naringin (NAR), a major flavanone (FVA) glycoside, is a component of food mainly obtained from grapefruit. We used NAR as a food additive to improve the solubility and permeability of hydrophobic polyphenols used as supplements in the food industry. The spray-dried particles (SDPs) of NAR alone show an amorphous state with a glass transition temperature (Tg) at 93.2 °C. SDPs of hydrophobic polyphenols, such as flavone (FVO), quercetin (QCT), naringenin (NRG), and resveratrol (RVT) were prepared by adding varying amounts of NAR. All SDPs of hydrophobic polyphenols with added NAR were in an amorphous state with a single Tg, but SDPs of hydrophobic polyphenols without added NAR showed diffraction peaks derived from each crystal. The SDPs with NAR could keep an amorphous state after storage at a high humidity condition for one month, except for SDPs of RVT/NAR. SDPs with NAR enhanced the solubility of hydrophobic polyphenols, especially NRG solubility, which was enhanced more than 9 times compared to NRG crystal. The enhanced solubility resulted in the increased membrane permeability of NRG. The antioxidant effect of the hydrophobic NRG was also enhanced by the synergetic effect of NAR. The findings demonstrated that NAR could be used as a food additive to enhance the solubility and membrane permeability of hydrophobic polyphenols.  相似文献   

14.
The purpose of this study was to develop a site targeting montelukast sodium (MTK) microparticles as a respiratory drug delivery system using the spray freeze drying (SFD) process. A range of sugars and cyclodextrins (CDs) were screened as carrier in order to find compatible excipients for the preparation of dry powder inhalers (DPIs). The physical characteristics of collected powders were studied by scanning electron microscopy (SEM), laser light scattering, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The aerodynamic behavior of the particles was also assessed using twin stage impinge (TSI). In the presence of simple sugars as carriers, highly porous particles in irregular shapes were produced. The use of CDs resulted in the formation of spherical particles with high porosity. Among all carriers that were used during the preparation of powders, raffinose had the best aerodynamic behavior with a fine particle fraction (FPF) of 60 % in sugar groups, while the lowest FPF was related to trehalose as carrier. Powders containing CDs mostly showed proper aerodynamic behavior, especially in formulations containing alfa-cyclodextrin (A-CD), beta-cyclodextrin (β-CD), and highly branched cyclic dextrin (HBCD). Overall, data indicated that the CDs were excellent excipients for use with MTK for respiratory drug delivery.  相似文献   

15.
Although curcumin is considered to have various therapeutic effects, its use as a functional food or supplement is restricted owing to its low water solubility and bioavailability. To increase the solubility of curcumin in water, the use of polyvinylpyrrolidone (PVP) and vinylpyrrolidone-vinyl acetate copolymers with a pyrrolidone skeleton was noted to be promising. In particular, the bi-component formulations of curcumin/PVP prepared through spray drying exhibited an amorphous state in powder X-ray diffraction observations and temporally increased the apparent solubility of curcumin to over 5000 times that of untreated curcumin; nevertheless, after 24 h, the solubility decreased owing to the unstable supersaturated state of curcumin. The addition of α-cyclodextrin (α-CyD) in the bi-component curcumin/PVP formulation helped maintain the supersaturated state of curcumin, whereas the addition of β- and γ-CyD led to the collapse of the supersaturated state. The addition of α-CyD can likely help inhibit the nucleation and crystal growth of curcumin, through the interaction among the solubilized units of curcumin/PVP and α-CyD.  相似文献   

16.
In recent years, electrochemical technologies have been widely used to remove contaminants at lab-scale and semi-pilot scale. Boron-doped diamond (BDD) electrodes have been considered as efficient materials for the abatement of persistent organic pollutants owing to their outstanding properties, such as rapid rates of electron-transfer for soluble redox systems, wide electrochemical potential window for water discharge reactions in aqueous and non-aqueous electrolytes, and high stability. Similar to other applications of electrochemical technology, wastes display medium to high ionic conductivity. Therefore, one of the applications highlighted for the electrolysis with these new electrodes is the treatment of soil-washing fluids, because in the polluted streams, washing of polluted soils provides a suitable conductivity to the effluent. In this context, this review summarizes the application of conductive diamond anodes for the electrochemical treatment of soil-washing effluents contaminated with different persistent organic pollutant such as pesticides, hydrocarbons, dyes, and organochlorine compounds, in single anodic oxidation processes and in other more complex processes such as electro-Fenton, photoelectrolysis, or sonoelectrolysis. Finally, the challenges and future research directions of electrochemical technology are discussed and outlined at pilot and prototype scale.  相似文献   

17.
Corncob is one of the main components of corn ears. Because the mechanical properties of different parts of corncob are very different, and there is a lack of research on the simulation and calibration of corncob parameters at present, the established corn ear or corncob simulation model has low accuracy and poor reliability. In this study, the simulation tests of corncob calibration parameters are carried out based on DEM. Firstly, a modelling method of corncob is proposed to establish sample models of corncob. Then, the DEM simulation parameters that restitution coefficient, static friction coefficient, and rolling friction coefficient of “particle–particle” and “particle-geometry”, and Poisson’s ratio of particle are determined by the Plackett-Burman test and Box-Behnken test. Next, the simulated bending test of corncob is carried out using the calibrated parameters. Finally, by comparing the physical and simulated bending test results, it shows the anti-destructive forces of corncob are 204.52 N and 197.3 N, respectively, with a relative error of 3.53%. This study verifies the reliability of parameter calibration for the discrete element model of corncob and provides a new method for establishing simulation models of corn ear and other materials.  相似文献   

18.
Thermal safety is one of the most pressing issues facing lithium batteries development, particularly in large-scale battery packs with high power densities. However, traditional external strategies fail to respond immediately to the internal increased heat and pressure. Therefore, it is of great urgency to develop internal control strategies to confer innate thermally self-protective intelligence onto lithium batteries. This paper reviews the research progress of internal intelligent thermal protection methods to improve the thermal safety of lithium batteries. Firstly, through phase separation/transition of electrolytes and thermoregulating separators with phase-change materials or flame retardants, thermal runway could be largely alleviated. However, continuous electrochemical reactions still go on and further heat-generation still exists, thus this kind of strategies can only delay but not eliminate the onset of thermal runaway. Hence, on the other hand, strategies by insulating ionic or current transport to switch off cell reactions have also been developed to avoid heat-generation and eradicate possible thermal runaway. Finally, insights into the future development of smart safer lithium batteries to avoid thermal runaway in terms of consistency, reversibility and adjustability are discussed, offering avenues in the rational design of smart thermally self-protective lithium batteries in the near future.  相似文献   

19.
Many older adults find it difficult to accept new forms of information and communication technology (ICT), despite its advantages such as convenience and efficiency. It is necessary to identify the reasons for low ICT use among older people—even among those with positive attitudes toward ICT—to help older adults cope with social changes and bridge the digital divide. This study explored technology acceptance and related factors among older Korean adults living in rural areas. Based on an existing model (the senior technology acceptance model), a new conceptual framework for technology acceptance was proposed, and the framework was tested using pathway analysis. Semi-structured interviews were conducted in three focus groups (n = 15), and a survey questionnaire was administered to older Korean adults living in a rural area (n = 233) from 17 January 2021 to 18 February 2021. Qualitative data were analyzed using directed content analysis, and quantitative data were analyzed using pathway analysis. Four categories, 11 subcategories, and 18 codes were identified, and a new conceptual framework was proposed based on the qualitative findings. The results of the model revealed significant positive direct paths from external controls (β = 0.45, p < .001), attitudinal beliefs (β = 0.33, p < .001), and cognitive health (β = 0.10, p = .040) to internal abilities. It is necessary to develop and apply a targeted and tailored ICT education program to improve self-efficacy and reduce anxiety regarding technology use among older Korean adults living in rural areas.  相似文献   

20.
The solution of instrumented indentation inverse problems by physically-based models still represents a complex challenge yet to be solved in metallurgy and materials science. In recent years, Machine Learning (ML) tools have emerged as a feasible and more efficient alternative to extract complex microstructure-property correlations from instrumented indentation data in advanced materials. On this basis, the main objective of this review article is to summarize the extent to which different ML tools have been recently employed in the analysis of both numerical and experimental data obtained by instrumented indentation testing, either using spherical or sharp indenters, particularly by nanoindentation. Also, the impact of using ML could have in better understanding the microstructure-mechanical properties-performance relationships of a wide range of materials tested at this length scale has been addressed.The analysis of the recent literature indicates that a combination of advanced nanomechanical/microstructural characterization with finite element simulation and different ML algorithms constitutes a powerful tool to bring ground-breaking innovation in materials science. These research means can be employed not only for extracting mechanical properties of both homogeneous and heterogeneous materials at multiple length scales, but also could assist in understanding how these properties change with the compositional and microstructural in-service modifications. Furthermore, they can be used for design and synthesis of novel multi-phase materials.  相似文献   

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