•Thermal radiative properties of Al2O3-paraffin nanofluid were investigated.•Influences of volume concentration, nanoparticle size, temperature, and optical path were investigated.•Absorption ...coefficient of nanofluid at 0.01 vol% is 15.5 times higher compared to that of paraffin.•Nanoparticle size has more influence on reflectivity than on absorption coefficient.
The thermal radiative properties of nanofluids have considerable contribution to the effectiveness of harvesting solar energy. In this work, the thermal radiative properties of Al2O3-paraffin nanofluid were experimentally investigated in terms of the influence of volume concentration, nanoparticle size, temperature and optical path. The transmittance spectrums of Al2O3-paraffin nanofluid were measured by a TU-19 FTIR spectrometer which was used for the calculation for the absorption coefficient and reflectivity of nanofluid. The experimental results show that Al2O3-paraffin nanofluid performs excellent ability to absorb solar energy compared to pure paraffin, with higher absorption coefficients increased up to 15.5 times at volume concentration 0.01%. The reflectivity of nanofluid is sensitive to nanoparticle size. When the nanoparticle size decreases from 30 to 10 nm the reflectivity of Al2O3-paraffin nanofluid reduces about 37.04%. With increasing temperature, the absorption coefficient of Al2O3-paraffin nanofluid increases and the reflectivity accordingly decreases.
In this paper, we have studied the influence of Ce3+on the structural, magnetic and Mossbauer properties of Sr1-xCexFe12O19 (x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.25). We have synthesized Sr1- ...xCexFe12O19 using the sol – gel technique. We have investigated the structural and magnetic properties of the grown samples using X-ray diffractometer and Vibrating sample magnetometer. We have used Scanning electron microscope, FTIR and Raman spectrometer to study the morphological properties. We have also focused on the Mossbauer spectroscopy analysis. The XRD studies confirm the hexagonal with M-type magnetoplumbhite structure. The SEM image confirms the coarseness in the sample with porosity which decreases with increasing Ce3+ in SrFe12O19. The FTIR spectrum confirms the formation of single phase ferrite in the grown sample. Raman spectrum reveals the formation of different vibrations of FeO bonds is observed at different peaks. The VSM studies confirm the hard nature of strontium ferrite as the cerium content is increased. The saturation magnetization and remnant magnetization of all doped strontium ferrite decrease as and when the cerium is increased. Mossbauer spectrum analysis reveals that the iron ions exist in Fe3+ state. Mossbauer study confirms that all the five sextets are attributed to the Fe3+ions. The obtained results with Ce3+ doping of SrFe12O19 demonstrate the usefulness for magnetic recording and memory devices.
•X-ray diffraction studies have confirmed the single magneto-plumbite hexagonal phase for the three samples.•Fourier transform infrared spectroscopy confirmed the formation of the single phase of ferrites.•Raman spectrum reveals that A1g vibrations of FeO bonds have been observed at the peaks of 724 cm−1 and 689 cm−1 in octahedral site.•Magnetic properties confirmed cerium doped strontium ferrite exhibits hard magnetic nature.•Due to the doping of Ce3+ in Sr-Hexa ferrite matrix, Mossbauer spectra revealed that the crystallite size has been reduced.
The hygroscopicity and phase transition of the mixed aerosol particles are significantly dependent upon relative humidity (RH) and interactions between particle components. Although the efflorescence ...behavior of particles has been studied widely, the crystallization behavior of each component in the particles is still poorly understood. Here, we study the hygroscopicity and crystallization behaviors of internally mixed ammonium sulfate (AS)/glutaric acid (GA) aerosols by a vacuum FTIR spectrometer coupled with a RH-controlling system. The mixed AS/GA aerosols in two different RH control processes (equilibrium and RH pulsed processes) show the fractional crystallization upon dehydration with AS crystallizing prior to GA in mixed particles with varying organic to inorganic molar ratios (OIRs). The initial efflorescence relative humidity (ERH) of AS decreased from ~43% for pure AS particles to ~41%, ~36% and ~34% for mixed AS/GA particles with OIRs of 2:1, 1:1 and 1:2, respectively. Compared to the ERH of 35% for pure GA, the initial ERHs of GA in mixed AS/GA particles were determined to be 31%, 30% and 28% for OIRs of 2:1, 1:1 and 1:2, respectively, indicating that the presence of AS decreased the crystallization RH of GA instead of inducing the heterogeneous nucleation of GA. When the AS fractions first crystallized at around 36% RH in the 1:1 mixed particles, GA remained noncrystalline until 30% RH. For the first time, the crystallization ratios of AS and GA are obtained for the internally mixed particles during the rapid downward RH pulsed process. The crystallization ratio of AS can reach around 100% at around 24% RH for both pure AS and the 1:1 mixed particles, consistent with the equilibrium RH process. It is clear that the RH downward rate did not influence efflorescence behavior of AS in pure AS and AS in mixed particles. In contrast, the crystallization ratio of GA can reach about 90% at 15.4% RH for pure GA particles in excellent agreement with the equilibrium RH process, whereas it is only up to 50% at 16.0% RH in the 1:1 mixed particles during the rapid downward pulsed process lower than that of the equilibrium RH process. Our results reveal that the rapid RH downward rate could inhibit the efflorescence of GA in the mixed droplets.
Fractional crystallization with AS crystallizing prior to GA in mixed particles during rapid downward RH pulsed process. Display omitted
•The mixed AS/GA aerosols show the fractional crystallization upon dehydration with AS crystallizing prior to GA.•The presence of AS decreased the crystallization RH of GA instead of inducing the heterogeneous nucleation of GA.•The crystallization ratios of AS and GA are obtained for the mixed particles during the rapid downward RH pulsed process.
Fourier transform spectrometers (FTS), mostly working in infrared (IR) or near infrared (NIR) range, provide a variety of chemical or material analysis with high sensitivity and accuracy and are ...widely used in public safety, environmental monitoring and national border security, such as explosive detection. However, because of being bulky and expensive, they are usually used in test centers and research laboratories. Miniaturized FTS have been developed rapidly in recent years, due to the increasing demands. Using micro-electromechanical system (MEMS) micromirrors to replace the movable mirror in a conventional FTS system becomes a new realm. This paper first introduces the principles and common applications of conventional FTS, and then reviews various MEMS based FTS devices.
•An extensive study on Silver - Ge20Se70Te10 film system as a substrate for SEIRA spectroscopy is carried out.•SEIRA response of the system was analyzed by recording FTIR transmission spectra of ...analyte Hexa Decane Thiol (HDT).•Silver structures were developed on Ge20Se70Te10 film via oblique angle deposition and ideal Ag thickness for maximum SEIRA enhancement is found.•The response of the system to variations in the analyte concentration is also explored.
Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful tool for characterizing and identifying chemical/biological species. Though SEIRA technique has enabled detection up to few molecule levels with sophisticated device structures, there is still room for improvement (can extend to detect down to a single molecule). Superior sensor platforms can be developed by incorporating advanced substrate material, so as to be actively employed in trace analysis, forensic sciences etc. In this work, chalcogenide glass of composition Ge20Se70Te10 is characterized to probe its usability as a SEIRA substrate. Silver island structures were developed on Ge20Se70Te10 film via oblique angle deposition and its SEIRA response was recorded using FTIR spectrometer with Hexa Decane Thiol (HDT) as the analyte. Investigations reveal an optimum silver thickness at which maximum absorption enhancement is obtained. The response of the system to variations in the analyte concentration is also explored. Studies prove them to be a promising candidate as an IR substrate which can be used to develop integrated optical waveguide for highly sensitive SEIRA spectroscopy.
Sodium nitrate as an important inorganic component can be chemically formed from the reactions of nitrogen oxides and nitric acid (HNO3) with sea salt in atmosphere. Organic acids contribute a ...significant fraction of photochemical formed secondary organics that can condense on the preexisting nitrate-containing particles. Atmospheric particles often include a complex mixture of nitrate and secondary organic materials accumulated within the same individual particles. Here we studied the hygroscopicity of aerosol particles composed of sodium nitrate and glutaric acid (GA) by using a pulsed RH controlling system and a rapid scan vacuum FTIR spectrometer (PRHCS-RSVFTIR). The water content in the particles and efflorescence ratios of both NaNO3 and GA at ambient relative humidity (RH) as a function of time were obtained from the rapid-scan infrared spectra with a sub-second time resolution. Our study showed that both NaNO3 and GA crystallized at 44.1% RH during two different RH control processes (stepwise and pulsed processes). It was found that the addition of GA could suppress the efflorescence of NaNO3 during the dehumidifying process. In addition, the mixed NaNO3/GA particles release HNO3 during the dehumidifying and humidifying cycles. These findings are important in further understanding the role of interactions between water-soluble dicarboxylic acids and nitrates on hygroscopicity and environmental effects of atmospheric particles.
Fractional crystallization with AS crystallizing prior to GA in mixed particles during rapid downward RH pulsed process. Display omitted
•NaNO3 and GA crystallized at 44.1% RH during both stepwise and pulsed RH control processes in the mixed NaNO3/GA particles.•The addition of GA could suppress the efflorescence of NaNO3 during the dehumidifying process.•The mixed NaNO3/GA particles release HNO3 during the dehumidifying and humidifying cycles.
•A three-layer structure model is adopted to consider the effect of edge in foams.•Extinction coefficients are compared between traditional and the three-layer model.•Radiative properties of nickel ...foam are obtained in the near infrared band.•Temperature influence on the radiative properties is analyzed in 1.3–2.2 μm.
Considering the existence of edge effect caused by the cut surface of struts or sintering points will affect the actual radiative transfer process in metallic foams, a three-layer structure model is constructed to obtain their spectral radiative properties. Using the double-thickness model for reference, the real spectral radiative properties of metallic foams are calculated based on transmittance spectra. To verify the feasibility of this method, transmittance spectra of nickel foams with different cell sizes and thicknesses are measured by FTIR spectrometer system in the near infrared band. Through comparing extinction coefficients obtained by traditional single-layer structure model and the three-layer structure model proposed in this paper, it is found that extinction coefficient will be underestimated by the latter method, while the deviation can reach 13% for 20ppi nickel foam and 8% for 40ppi nickel foam. Then absorption coefficient and scattering coefficient are calculated by a prediction model with parameters corrected. Based on this method, temperature influence on extinction coefficient of nickel foam is studied from 293 K to 773 K and it is found that extinction coefficient decreases with temperature in the researched band while the maximum changing rate is 2.1% in the researched band.
•Decomposition products in the gas are correlated to interactions in the precipitate.•For Cu2+ and Fe3+, both metal xanthate and dixanthogen affect CS2 generation.•For Cu2+, decrease of CS2 is ...accompanied by the decrease of Cu2X2 and X2.•For Fe3+, increases of CS2 is accompanied by the increase of FeX3 and X2.
An earlier study (Part I) indicated that Cu2+ ion suppresses while Fe3+ ion promotes xanthate decomposition into CS2. The main factor responsible for the disparate effects was proposed to be the differences in interactions between xanthate and metal ions in solution. UV–vis and FTIR spectrometers were used to examine the products of such interactions in the liquid and precipitate phases, respectively. For both metal ions, it was found that metal xanthate (i.e. cupric xanthate Cu2X2 and ferric xanthate FeX3) and dixanthogen (X2) are formed. Although for different metal ions metal xanthate and dixanthogen are formed by different mechanisms, generation of CS2 in the gas phase can be correlated to the formation and decomposition of the metal xanthate and dixanthogen. It was found that metal xanthate and dixanthogen both are responsible for the effects of metal ions on SIBX decomposition: with the increase of Cu/SIBX ratio, decrease of CS2 is accompanied by the decrease of Cu2X2 and X2; with the increase of Fe/SIBX ratio, increases of CS2 are accompanied by the increase of FeX3 and X2. Which compound, metal xanthate or dixanthogen, play a more important role in affecting the decomposition could not be determined yet. Further studies is also required to elucidate the mechanisms how Cu2X2, FeX3 and X2 are quantitatively determining the overall decomposition kinetics.
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