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1.
A mesoscopic study of natural convection due to MWCNT-Fe 3O 4/Water hybrid nanofluid is conducted utilizing the Lattice Boltzmann Method. The test fluid is filled in a differentially heated rectangular enclosure. Effects of aspect ratio in the range of 0.5–2.0, Rayleigh number varying from 10 3 to 10 5 and nanocomposite volume fraction on heat and fluid flow characteristics and entropy generation have been illustrated. It is observed that the mean Nusselt number rises with the increase in Rayleigh number, while it falls as the aspect ratio increases. However, the mean Nusselt number enhances with the increase in MWCNT-Fe 3O 4 volume fraction up to 0.001. On further increasing the volume fraction, the mean Nusselt number shows either no significant rise or deterioration for the case of MWCNT-Fe 3O 4 nanocomposite. The dimensionless entropy generation number rises with the increase in the Rayleigh number. However, it falls with an increase in aspect ratio and dimensionless temperature difference. Interestingly in the case of increasing nanoparticle loading fraction, entropy generation number augments first, attains a maximum at 0.001 ?vol fraction of nanocomposite, and then it decreases. Nevertheless, at the low Rayleigh number, it keeps on rising with an increase in nanocomposite volume fraction. The best thermal performance is obtained for the cavity of 0.5 aspect ratio. A correlation for the mean Nusselt number is proposed. 相似文献
2.
In this research, three different volume concentrations (??=?0.05, 0.1 and 0.2%) of Al2O3/water, CuO/water and Al2O3–CuO/water (50:50) nanofluids are prepared by adopting a two-step nanofluid preparation method. Al2O3 and CuO nanoparticles with the average diameter of 50 nm and 27 nm were dispersed in distilled water. The thermal conductivity and viscosity of prepared nanofluids are measured for different temperatures by using KD2 Pro thermal property analyzed and Brookfield viscometer, respectively. The effects of nanofluids on the thermal, electrical and overall efficiency of photovoltaic thermal (PVT) solar collector are also studied. The experimental results revealed that the thermal conductivity and viscosity increase with the increase in percentage volume concentration and viscosity decreases with the increase in temperature. Furthermore, the obtained maximum thermal and electrical efficiencies of a PVT solar collector for 0.2% volume concentration of hybrid nanofluids are 82% and 15%, respectively, at peak solar radiation. The highest overall efficiency of a PVT collector with .2% volume concentration of hybrid nanofluid was 97% at peak solar radiation. Results recommend that nanofluids can be used as a heat transfer in PVT solar collector. 相似文献
3.
To obtain a recyclable surface-enhanced Raman scattering (SERS) material, we developed a composite of Fe 3O 4\SiO 2\Ag with core\shell\particles structure. The designed particles were synthesized via an ultrasonic route. The Raman scattering signal of Fe 3O 4 could be shielded by increasing the thickness of the SiO 2 layer to 60 nm. Dye rhodamine B (RB) was chosen as probe molecule to test the SERS effect of the synthesized Fe 3O 4\SiO 2\Ag particles. On the synthesized Fe 3O 4\SiO 2\Ag particles, the characteristic Raman bands of RB could be observed when the RB solution was diluted to 5 ppm (1×10 −5 M). Furthermore, the synthesized particles could keep their efficiency till four cycles. 相似文献
4.
In this work we prepare high contact Poly Ethylene Terephthalate (PET) fabric surface from low contact angle materials. Superhydrophobic
PET fabric is prepared by coating the fabric with hybrid Al 2O 3–SiO 2 sol. In this case, the high contact angle Al 2O 3–SiO 2 hybrid is created from low contact angle Al 2O 3 and SiO 2 precursors. PET treated with hybrid Al 2O 3–SiO 2 exhibit Water Contact Angle (WCA) as 150°, while PET treated with individual Al 2O 3 sol or SiO 2 sol exhibits lower WCA, (Al 2O 3 WCA = 137°; SiO 2 WCA = 141°). FESEM and AFM investigations show that the hybrid Al 2O 3–SiO 2 sol and individual Al 2O 3 or SiO 2 sol imparted different roughness geometry on the PET fabric surface. We observe surface structure of fish fin-like, particle-like
and hybrid fin-particle for treated PET fabric with; Al 2O 3, SiO 2 and hybrid Al 2O 3–SiO 2 sol, under FESEM and AFM observations.AFM observations show the evolution of roughness (Ra) dimension of different surface
structures with the order of: SiO 2 < Al 2O 3 < Al 2O 3–SiO 2 (Ra = 31, 63 and 273 nm). We believe that the disparity of the surface geometries lead into different surface WCA. FTIR spectra
of Hybrid Al 2O 3–SiO 2 shows additional peak at 902, 850, 557, and 408 cm −1 which can be ascribed to the hybridization structure. 相似文献
5.
Fe 2O 3/SiO 2 nanocomposites based on fumed silica A-300 ( SBET = 337 m 2/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac) 3) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac) 3 then oxidized in air at 400–900 °C. Samples with Fe(acac) 3 adsorbed onto nanosilica and samples with Fe 2O 3/SiO 2 including 6–17 wt% of Fe 2O 3 were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe 2O 3 deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac) 3 solution in isopropanol) treated at 500–600 °C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac) 3 solution in carbon tetrachloride only α-Fe 2O 3 phase is formed in addition to amorphous Fe 2O 3. The Fe 2O 3/SiO 2 materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12–0.15 g/cm 3 and SBET = 265–310 m 2/g. 相似文献
6.
Samples of 40SiO 2·30Na 2O·1Al 2O 3·(29 − x)B 2O 3· xFe 2O 3 (mol%), with 0.0 ≤ x ≤ 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe 3+ ion complexes ( g = 4.27 and g = 6.4) and Fe 3+-based clusters ( g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe 3+-based clusters built in from two sources of isolated ions, namely Fe 2+ and Fe 3+; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe 2+ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed 5E g– 5T 2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe 2+ and Fe 3+ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO 4 complex resulting from replacing silicon in non-bridging oxygen (SiO 3O −) sites whereas ferric ions are incorporated as FeO 4 complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO 4). 相似文献
7.
The thermal performance of a flat-plate solar collector (FPSC) is investigated experimentally and analytically. The studied nanofluid is SiO2/deionized water with volumetric concentration up to 0.6% and nanoparticles diameter of 20–30 nm. The tests and also the modeling are performed based on ASHRAE standard and compared with each other to validate the developed model. The dynamic model is based on the energy balance in a control volume. The system of derived equations is solved by employing an implicit finite difference scheme. Moreover, the thermal conductivity and viscosity of SiO2 nanofluid have been investigated thoroughly. The measurement findings indicate that silica nanoparticles, despite their low thermal conductivity, have a great potential for improving the thermal performance of FPSC. Analyzing the characteristic parameters of solar collector efficiency reveals that the effect of nanoparticles on the performance improvement is more pronounced at higher values of reduced temperature. The thermal efficiency, working fluid outlet temperature and also absorber plate temperature of the modeling have been confirmed with experimental verification. A satisfactory agreement has been achieved between the results. The maximum percentage of deviation for working fluid outlet temperature and collector absorber plate temperature is 0.7% and 3.7%, respectively. 相似文献
8.
Reduced graphene nanosheets/Fe 2O 3 nanorods (GNS/Fe 2O 3) composite has been fabricated by a hydrothermal route for supercapacitor electrode materials. The obtained GNS/Fe 2O 3 composite formed a uniform structure with the Fe 2O 3 nanorods grew on the graphene surface and/or filled between the graphene sheets. The electrochemical performances of the GNS/Fe 2O 3 hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests in 6 M KOH electrolyte. Comparing with the pure Fe 2O 3 electrode, GNS/Fe 2O 3 composite electrode exhibits an enhanced specific capacitance of 320 F g −1 at 10 mA cm −2 and an excellent cycle-ability with capacity retention of about 97% after 500 cycles. The simple and cost-effective preparation technique of this composite with good capacitive behavior encourages its potential commercial application. 相似文献
9.
The heat transfer performance and entropy analysis are done in a compact loop heat pipe (CLHP) with Al2O3/water and Ag/water nanofluid. A compact loop heat pipe having a flat square evaporator with dimensions of 34 mm (L)?×?34 mm (W)?×?19 mm (H) has been fabricated and tested for the heat load ranging from 30 to 500 W. The experimental tests are conducted by keeping the CLHP in the vertical orientation with distilled water, silver (Ag)/water and aluminium oxide (Al2O3)/water nanofluid having low volume concentrations of (0.09% and 0.12%). The effect of wall and vapour temperature, evaporator and condenser heat transfer coefficient, thermal resistance on the applied heat loads is experimentally investigated and compared. The experimental results showed that the evaporator thermal resistance is reduced by 34.70% and 20.21%, respectively, for 0.12 vol% of Ag, Al2O3 nanoparticles when compared with that of the distilled water. For the same volume concentrations of Ag, Al2O3 nanoparticles, an enhancement of 34.52%, 23.7%, 39.27% and 30.8%, respectively, observed for the convective heat transfer coefficients at the evaporator and condenser. The entropy is also reduced by 19.08% and 11.58% when Ag and Al2O3 nanofluids are used as the operating fluid. From the experimental tests, it is found that the addition of small amount of Ag nanoparticles in the working fluid enhanced the operating range by 15% when compared with that of Al2O3/water nanofluid without the occurrence of any dry-out conditions. 相似文献
10.
Sensitive fluorescent probes for the determination of hydrogen peroxide and glucose were developed by immobilizing enzyme
horseradish peroxidase (HRP) on Fe 3O 4/SiO 2 magnetic core–shell nanoparticles in the presence of glutaraldehyde. Besides its excellent catalytic activity, the immobilized
enzyme could be easily and completely recovered by a magnetic separation, and the recovered HRP-immobilized Fe 3O 4/SiO 2 nanoparticles were able to be used repeatedly as catalysts without deactivation. The HRP-immobilized nanoparticles were able
to activate hydrogen peroxide (H 2O 2), which oxidized non-fluorescent 3-(4-hydroxyphenyl)propionic acid to a fluorescent product with an emission maximum at 409 nm.
Under optimized conditions, a linear calibration curve was obtained over the H 2O 2 concentrations ranging from 5.0 × 10 −9 to 1.0 × 10 −5 mol L −1, with a detection limit of 2.1 × 10 −9 mol L −1. By simultaneously using glucose oxidase and HRP-immobilized Fe 3O 4/SiO 2 nanoparticles, a sensitive and selective analytical method for the glucose detection was established. The fluorescence intensity
of the product responded well linearly to glucose concentration in the range from 5.0 × 10 −8 to 5.0 × 10 −5 mol L −1 with a detection limit of 1.8 × 10 −8 mol L −1. The proposed method was successfully applied for the determination of glucose in human serum sample. 相似文献
11.
The vibrational (infrared and Raman) spectroscopy is used in order to identify and characterize the following amphibole minerals with general formula W 0–1X 2Y 5Z 8O 22(OH) 2 (W = Na, K; X = Na, Ca; Y = Mg, Fe 2+, Fe 3+, Al; Z = Si, Al) originating from the localities in the Republic of Macedonia: glaucophane, Na 2(Mg,Fe 2+) 3(Fe 3+,Al) 2Si 8O 22(OH) 2; tremolite–actinolite, Ca 2(Mg,Fe 2+) 5Si 8O 22(OH) 2; hornblende (Na,K) 0–1Ca 2(Mg,Fe 2+,Fe 3+,Al) 5(Si,Al) 8 O 22(OH) 2 and arfvedsonite, NaNa 2(Mg,Fe 2+) 4(Fe 3+,Al)Si 8O 22(OH) 2. The chemical composition of these minerals is not necessarily fixed. It is due to the possibility to form solid solution series with other minerals being their end-members (for example, tremolite–ferro-actinolite series, Ca 2Mg 5Si 8O 22(OH) 2–Ca 2Fe 2+5Si 8O 22(OH) 2). In this context, it is shown that the intensity and especially the number of the IR bands in the ν(OH) region could serve as a tool for exact mineral identification. Namely, it is based on the presence of different Y cations in various octahedral sites (M1 and M3), which is manifested by different spectral view. On the other hand, the expressed similarities in the 1300–370 cm −1 (IR) and 1200–100 cm −1 regions (Raman) of the spectra are observed due to their common structural characteristics (double chains of SiO 4 tetrahedra). Thus, the bands in this region are tentatively prescribed mostly to the vibrations of the SiO 4 tetrahedra. The results of our study are compared with the corresponding literature data for the analogous mineral species originating all over the world. 相似文献
12.
On‐surface degradation of sildenafil (an adequate substrate as it contains assorted functional groups in its structure) promoted by the Fenton (Fe 2+/H 2O 2) and Fenton‐like (M n+/H 2O 2; M n+ = Fe 3+, Co 2+, Cu 2+, Mn 2+) systems was investigated by using paper spray ionization mass spectrometry (PS‐MS). The performance of each system was compared by measuring the ratio between the relative intensities of the ions of m/z 475 (protonated sildenafil) and m/z 235 (protonated lidocaine, used as a convenient internal standard and added to the paper just before the PS‐MS analyzes). The results indicated the following order in the rates of such reactions: Fe 2+/H 2O 2 ≫ H 2O 2 ≫ Cu 2+/H 2O 2 > M n+/H 2O 2 (M n+ = Fe 3+, Co 2+, Mn 2+) ~ M n+ (M n+ = Fe 2+, Fe 3+, Co 2+, Cu 2+, Mn 2). The superior capability of Fe 2+/H 2O 2 in causing the degradation of sildenafil indicates that Fe 2+ efficiently decomposes H 2O 2 to yield hydroxyl radicals, quite reactive species that cause the substrate oxidation. The results also indicate that H 2O 2 can spontaneously decompose likely to yield hydroxyl radicals, although in a much smaller extension than the Fenton system. This effect, however, is strongly inhibited by the presence of the other cations, ie, Fe 3+, Co 2+, Cu 2+, and Mn 2+. A unique oxidation by‐product was detected in the reaction between Fe 2+/H 2O 2 with sildenafil, and a possible structure for it was proposed based on the MS/MS data. The on‐surface reaction of other substrates (trimethoprim and tamoxifen) with the Fenton system was also investigated. In conclusion, PS‐MS shows to be a convenient platform to promptly monitor on‐surface oxidation reactions. 相似文献
13.
The degradation of nitro aromatics like trinitrotoluene (TNT) released in the waste water from explosive process plants is
the serious problem due to toxic and explosive nature of TNT. The poor response of TNT to biodegradation enhanced the gravity
of the problem. We have demonstrated that high specific surface area TiO 2–SiO 2 nano-composite aerogel is promising photo catalyst in successful treating of TNT contaminated aqueous solution. The TiO 2–SiO 2 composite aerogel with nominal content of 20 and 50% TiO 2, used as catalyst, were prepared by co-precursor sol–gel method using titanium isopropaxide and tetramethylorthosilicate
as source of titania and silica, respectively. The XRD studies confirmed formation of anatase phase of crystalline TiO 2 with nano sized crystallites. The TiO 2–SiO 2 aerogel showed specific surface area of 1,107 and 485 m 2/g for the aerogels containing 20 and 50% TiO 2, respectively. The 100 ppm TNT solution was treated, in 700 ml capacity reaction vessel, using H 2O 2 oxidizer and TiO 2–SiO 2 aerogel catalyst in presence of UV light (8 W UV lamp). Using TiO 2–SiO 2 (50/50) aerogel with surface area of 485 m 2/g, we succeeded to reduce the TOC to 1 ppm within 3.5 h where as using TiO 2/SiO 2 (20/80) aerogel with surface area of 1,107 m 2/g, the TOC was reduced to about only 7 ppm in the same time. It revealed that the combination of high TiO 2 content and high specific surface area is an important factor to achieve effective and faster degradation of TNT for complete
mineralization. 相似文献
14.
Tri-layer magnetite/silica/poly(divinylbenzene) (Fe 3O 4/SiO 2/PDVB) core-shell hybrid microspheres were prepared by distillation precipitation polymerization of divinylbenzene (DVB) in the presence of magnetite/3-(methacryloxyl)propyl trimethoxysilane (MPS) modified silica core-shell particles as seeds. The polymerization of DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat magnetite/MPS-modified silica particles through the capture of DVB oligomers with the aid of vinyl groups on the surface of inorganic seeds in absence of any stabilizer or surfactant. Other magnetite/silica/polymer tri-layer hybrid particles, such as magnetite/silica/poly(ethyleneglycol dimethacrylate) (Fe 3O 4/SiO 2/PEGDMA) and magnetite/silica/poly(ethyleneglycol dimethacrylate- co-methacrylic acid) (Fe 3O 4/SiO 2/P(EGDMA- co-MAA)) with various polarity and functionality, were also prepared by this procedure. Magnetite/silica/poly( N,N′-methylenebisacrylamide- co-methacrylic acid) (Fe 3O 4/SiO 2/P(MBAAm- co-MAA)) were synthesized with unmodified magnetite/silica particles as seeds. The resultant tri-layer hybrid particles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), dynamic light scattering, and vibrating sample magnetometer (VSM). 相似文献
15.
In this work, magnetic nanoparticles (Fe 3O 4) were prepared by simple co‐precipitation method in aqueous medium and then subsequently modified with tetraethyl orthosilicate and 3‐aminopropyl triethylenesilane. The properties of the particles were characterized by FTIR spectroscopy X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. The SiO 2‐NH 2@Fe 3O 4 particles were successfully applied to simultaneously enrich and separate diclofenac from water, urine, and plasma samples. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid some of the time‐consuming experimental procedures related to the traditional solid phase extraction. The main parameters affecting extraction and desorption efficiency such as pH, amount of SiO 2‐NH 2@Fe 3O 4, volume of desorption solvent, and extraction time were screened. The significant variables were optimized by using central composite design. At optimum conditions values of variables set as pH = 4, 10 mg SiO 2‐NH 2@Fe 3O 4, 0.5 mL methanol, and 15 min extraction time and then the extracted diclofenac were injected to HPLC for analysis. The linear response ( r2 > 0.9992) was obtained in the range of 0.004–15 µg/mL with detection limit 0.0012 µg/mL and extraction recovery was in the range of 92–96% with RSD < 5% ( n = 6). 相似文献
16.
A magnetic hybrid material (Fe 3O 4‐COOH/HKUST‐1) was easily synthesized via a two‐step simple solvothermal method. Through adding sodium acrylate directly into the synthesis of Fe 3O 4 spheres, the surface has more carboxyl groups. It is notable that the reactions proceed without use of organic surfactants. The magnetic hybrid material was characterized using various techniques. The magnetic hybrid material has a high specific surface area (430.15 m 2 g −1) and excellent magnetism (23.65 emu g −1). It is an efficient adsorbent for removing organic dyes like methylene blue (MB) from aqueous solution. It also can be easily recovered from liquid media using an external magnetic field. Adsorption experiment shows the magnetic hybrid material possesses a high adsorption capacity (118.6 mg g −1), and has high adsorption efficiency (94.3%) after five adsorption cycles with ethanol (0.2% HCl) as eluent. The sorption kinetics and isotherm analysis indicate these sorption processes are better fitted to the pseudo‐second‐order and Langmuir equations. Thermodynamic study shows the sorption processes are spontaneous and endothermic. 相似文献
17.
Materials having both magnetic and catalytic properties have shown great potential for practical applications. Here, a reduced graphene oxide/iron oxide/silver nanohybrid (rGO/Fe 3O 4/Ag NH) ternary material was prepared by green synthesis of Ag on pre‐synthesized rGO/Fe 3O 4. The as‐prepared rGO/Fe 3O 4/Ag NH was characterized using Fourier transform infrared spectroscopy, X‐ray diffractometry, Raman spectroscopy, vibrating sample magnetometry, transmission electron microscopy and energy‐dispersive X‐ray spectroscopy. rGO sheets were covered with Fe 3O 4 (8–16 nm) and Ag (18–40 nm) nanoparticles at high densities. The mass percentages were 13.47% (rGO), 62.52% (Fe 3O 4) and 24.01% (Ag). rGO/Fe 3O 4/Ag NH exhibited superparamagnetic behavior with high saturated magnetization (29 emu g −1 at 12 kOe), and efficiently catalyzed the reduction of 4‐nitrophenol (4‐NP) with a rate constant of 0.37 min −1, comparable to those of Ag‐based nanocatalysts. The half‐life of 4‐NP in the presence of rGO/Fe 3O 4/Ag NH was ca 1.86 min. rGO/Fe 3O 4/Ag NH could be magnetically collected and reused, and retained a high conversion efficiency of 94.4% after the fourth cycle. rGO/Fe 3O 4/Ag NH could potentially be used as a magnetically recoverable catalyst in the reduction of 4‐NP and environmental remediation. 相似文献
18.
The phase relations in the Fe-rich part of the pseudo-binary system SrO–Fe 2O 3 (>33 mol% Fe 2O 3) were reinvestigated between 800 and 1500 °C in air. A combination of microscopy, electron probe micro-analysis, powder X-ray diffraction and thermal analysis was used to determine phase relations, crystal structure parameters and phase transition temperatures. M-type hexagonal ferrite SrFe 12O 19 (85.71 mol% Fe 2O 3) is stable up to 1410 °C. No indication of a significant phase width was found; Sr 4Fe 6O 13±δ appears as a second phase in compositions with <85.71±0.2 mol% Fe 2O 3. Sr 4Fe 6O 13±δ itself is stable between 800 and 1250 °C. Two other hexagonal ferrites were found to exist at high temperatures only: W-type SrFe 2+2Fe 3+16O 27 is stable between 1350 and 1440 °C and X-type ferrite Sr 2Fe 2+2Fe 3+28O 46 between 1350 and 1420 °C, respectively, which is shown here for the first time. These findings in combination with previously published data were used to derive a corrected phase diagram of the Fe-rich part of the pseudo-binary system SrO–Fe 2O 3. 相似文献
19.
In this paper, the effects of pure water, SiO2/water nanofluid, and a phase-change material (PCM) as coolants on the performance of a photovoltaic thermal (PVT) system are numerically investigated. The simulations are performed on two modules of PVT with PCM (PVT/PCM module) and without (PVT module). Parameters including PV surface temperature, thermal, and electrical efficiencies of the systems are studied and compared with each other. Moreover, the results of nanofluid as a working fluid is compared with those obtained using pure water. The results show that in the water-based PVT/PCM, the average PV cell temperature is decreased by 16 °C compared to that of the PVT system. This results in an increase of 8% in the electrical efficiency and 25% in the thermal efficiency. In addition, using nanofluid (SiO2 with 1 and 3 mass% mass fraction) as a coolant in the PVT/PCM system increases the thermal efficiency by 3.51% and 10.40%, for 1 and 3 mass%, respectively, compared to that of the PVT/PCM with pure water as a coolant. This study shows that increasing the melting temperature of the phase-change material leads to an increase in the thermal efficiency of the PVT/PCM system. 相似文献
20.
A boronate-decorated nanomagnetic organic-inorganic hybrid material was facilely synthesized by utilizing the nanomagnetic polyhedral oligomeric silsesquioxanes (POSS) composite (Fe 3O 4@POSS) as the base platform. A simple copolymerization occurred between 3-acrylamidophenylboronic acid (AAPBA) and the residual end vinyl groups supplied by the substrate. Here the special emphasis was placed on the octavinyl POSS, which not only acted as the building blocks for a hybrid architecture but also facilitated the process of grafting boronate groups onto the surface of POSS based nanomagnetic composite (Fe 3O 4@POSS). The successful immobilization of affinity ligand-AAPBA on the Fe 3O 4@POSS was confirmed by Fourier transform infrared (FT-IR), elemental analysis, inductively coupled plasma atomic emission spectrometer (ICP-AES), field emission scanning electron microscope. A magnetic solid-phase extraction (MSPE) for cis-diols enrichment was developed using the as-prepared Fe 3O 4@POSS-AAPBA material as an affinity sorbent and three catecholamines (CAs), namely noradrenaline, epinephrine and isoprenaline, as model analytes. Under the optimal extraction conditions, sensitive and simultaneous analysis of three CAs from the urine sample was achieved by high-performance liquid chromatography with UV detection (HPLC-UV). The limits of detection (LOD, S/N = 3) and the limits of quantitation (LOQ, S/N = 10) for the target analytes were 0.81–1.32 ng mL −1 and 2.70–4.40 ng mL −1, respectively. Also good recoveries (85.5–101.7%) and repeatability (RSD≤10.1%) were obtained by this method. This work not only showed a facility for the utilization of Fe 3O 4@POSS as a substrate for constructing a boronate functionalized nanomagnetic sorbent, but also demonstrated the capability of the derived material for recognition of trace amount of cis-diols biomolecules presented in complicated biological matrices. 相似文献
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