Nitrogen Gas Flow Research Articles

Mechanisms of trace water vapor frosting on a cryogenic surface in nitrogen gas flow

Water vapor contamination control is currently one of the key technical issues faced in cryogenic wind tunnels. However, the behaviors and the underlying mechanisms of trace water vapor frosting under cryogenic conditions still remain unknown due to the extreme experimental conditions and difficulties in direct measurement. A computational fluid dynamics (CFD) model was developed for describing the frosting process of trace water vapor on a cryogenic surface in nitrogen gas flow. The calculated results were validated against published experimental data and showed good agreements. The macroscopic and local growth behaviors of the frost layer were further studied based on the validated model. The variation in the nitrogen gas density under cryogenic conditions and its impact on the frost layer properties were analyzed. The change in the nitrogen gas density displayed a major difference between the frosting under refrigeration temperature conditions and cryogenic conditions, and taking the nitrogen gas density as a constant like previous models would cause great deviations in the calculated frost layer properties. The influence of water vapor content on the frost properties was also investigated. The frost layer thickness showed less sensitivity to changes in the water vapor content compared to the frost weight deposited on per unit area of the cold surface and the frost layer density. The frost layer under extremely low water vapor content might still cause small levels of distributed roughness on the surfaces, thereby affecting the aerodynamic characteristics of the model in the cryogenic wind tunnel.

Modulation of thermoelectric properties of thermally evaporated copper nitride thin films by optimizing the growth parameters

In this paper, we have successfully controlled the thermoelectric properties of copper nitride (Cu3N) thin films by optimizing the post growth nitrogen gas flow time. During thermal evaporation growth of Cu3N thin films, pure copper power (0.12 g) was evaporated on soda lime glass substrate. The boat temperature and nitrogen gas flow rate were fixed at 1010 °C and 100 sccm respectively in horizontal glass tube furnace. In order to study the annealing time duration, all samples were annealed at 320 °C in tube furnace for 2–8 h with constant flow rate of 100 sccm. The formation of Cu3N phase was confirmed by X-Ray Diffraction (XRD) and it was found that crystallinity of grown thin films was improved with annealing time duration. The Seebeck data demonstrated that the value of Seebeck coefficient was increased form 87.59 μV/°C to 134.79 μV/°C as the annealing time duration was increased from 2 to 8 h. This improvement in Seebeck coefficient was associated with the enhancement of samples crystallinity which ultimately increase the mobility of charge carriers. The value of electrical conductivity was also increased from 26.04 S/cm to 33.49 S/cm, therefore we were able to achieve the highest value of power factor (6.08 × 10−5 Wm−1C−2) for sample annealed for maximum time duration. Raman spectroscopy and SEM measurements were additionally performed to strengthen our proposed argument.

Effect of nitrogen gas flowing continuously into the pyrolysis reactor for simultaneous production of charcoal and liquid smoke

Biomass waste such as sawdust or red fruit seed waste can be processed into charcoal (carbonized charcoal) and liquid smoke simultaneously by the pyrolysis method. The charcoal process using the pyrolysis method will be more perfect if the reactor is designed in such a way that oxygen from the air is not free to enter the reactor. The small amount of oxygen that is present and enters the reactor can be minimized by flowing inert nitrogen gas into the reactor continuously during pyrolysis. In this study, the effect of flowing nitrogen gas into the pyrolysis reactor was observed with a gas flow rate of 1 liter/minute using raw materials from wood sawdust biomass waste with a pyrolysis time of 2 hours and a pyrolysis temperature of 400 oC. The results showed that the quality of charcoal products was relatively better. The yield of liquid smoke was higher than the results of pyrolysis with nitrogen gas flow compared to without nitrogen gas flow. The calorific value of charcoal without and with nitrogen gas flow is 6828 cal/gram and 7109 cal/gram, respectively, the fixed carbon value is 68.37% and 70.40% respectively, and the yield of liquid smoke is 38.87% and 40.35%, respectively.

A high energy flexible symmetric supercapacitor fabricated using N-doped activated carbon derived from palm flowers.

Nitrogen doped activated carbons of high surface area are synthesized using palm flower biomaterial by KOH activation followed by pyrolysis. The concentration of the activating agent KOH and carbonization temperature are found to be crucial to obtain high surface area activated carbon. The optimal concentration of KOH and carbonization temperature for the synthesis of activated carbon, respectively, are 2 M and 800 °C in the flow of nitrogen gas. The optimized conditions have been employed to further prepare nitrogen doped activated carbon (NAC) by varying the weight ratio of palm flowers to melamine. All activated carbons are characterized by powder XRD, BET analysis, RAMAN spectroscopy, HR-SEM analysis, HR-TEM analysis and FT-IR analysis. With 2 wt% nitrogen doping, the BET surface area and pore diameter of the NAC-2 sample are 1054 m2 g−1 and 1.9 nm, respectively. The electrochemical charge storage performance of the nitrogen doped activated carbons has been evaluated in an aqueous acidic electrolyte medium. The results indicate that among the nitrogen doped activated carbons, the NAC-2 sample exhibits the highest electrochemical capacitance of 296 F g−1 at 0.5 A g−1. The performance of the NAC-2 electrode is further tested in aqueous, ionic liquid and solid polymer electrolytes by assembling a symmetric capacitor for real time application. By employing an ionic liquid as the electrolyte, the device delivers an energy density of 8.6 Wh kg−1 and a power density of 38.9 W kg−1 in the voltage window of 1.5 V and at an operating current density of 0.1 A g−1. Interestingly, the NAC-2 electrode shows good cycling performance in the ionic liquid electrolyte (up to 50k cycles). Furthermore, the symmetric device in 0.1 M H2SO4/PVA solid state electrolyte shows excellent electrochemical stability under various bending angles, demonstrating its potential in flexible electronic devices.

Adsorption enhancement of nitrogen gas by atomically heterogeneous nanospace of boron nitride.

In this study, porous boron nitride (p-BN) with hexagonal phase boron nitride (h-BN) pore walls was synthesized using high-temperature calcination. Negligible variation in pore-wall structure can be observed in powder X-ray diffraction (XRD) profiles and infrared (IR) spectra. However, a highly stable p-BN with a stable pore structure even at 973 K under the oxidative conditions is obtained when synthesized at higher than 1573 K under nitrogen gas flow. For p-BN, this stability is obtained by generating h-BN microcrystals. Nitrogen adsorption–desorption isotherms at 77 K provide type-IV features and typical adsorption–desorption hysteresis, which suggests micropore and mesopore formation. Moreover, adsorption–desorption isotherms of Ar at 87 K are measured and compared with those of nitrogen. The relative adsorbed amount of nitrogen (i.e., the amount of nitrogen normalized by that of Ar at each relative pressure or adsorption potential value) on p-BN is considerably larger than that on microporous carbon at low-pressure regions, which suggests the existence of strong adsorption sites on the p-BN surface. In fact, the relative number of adsorbed nitrogen molecules to that of Ar on p-BN is, at most, 150%–200% larger than that on microporous carbon for the same adsorption potential state. Furthermore, additional adsorption enhancement to nitrogen between P/P0 = 10−5 and 10−3 can be observed for p-BN treated at 1673 K, which suggests the uniformly adsorbed layer formation of nitrogen molecules in the vicinity of a basal planar surface. Thus, unlike typical nanoporous sp2 carbons, p-BN materials have the potential to enhance adsorption for certain gas species because of their unique surface state.

Propagation of shock wave of nitrogen gas in Titan stratosphere

Nitrogen gas is considered one of the significant standard gases in stratosphere of Titan, Saturn's largest moon, which represents almost 98.4% of Titan atmosphere chemical composites. Hydrodynamics fluid model has been constructed to describe the Nitrogen gas flows in the inner part of the Titan stratosphere. Using Fourier analysis, the linear dispersion relation of the fluid equations has been derived. Exploration of the resultant dispersion relation elucidated that two independent phenomena occurred simultaneously. Moreover, the reductive perturbation method has been utilized, yielding Burgers equation. A shock wave enveloped solution has been obtained using the computational F-expansion method. The different effects of thermal conductivity and kinematic viscosity on propagating wave have been studied. They have found to cause dissipation of envelope wave but don't affect the amplitude of envelope wave. Our investigations showed that the dissipation in the enveloped waves caused by thermal conductivity and kinematic viscosity.

Preparation and characterization of nanostructured TiCrN thin films deposited from Ti-Cr mosaic target by reactive DC magnetron sputtering

In this research work, nanostructured thin films of TiCrN have been deposited on Si by reactive DC magnetron sputtering from a mosaic Ti-Cr target. The effects of nitrogen gas flow rates on the structure of the as-deposited TiCrN thin films were examined. The crystal structure, microstructure, surface morphology, thickness, and composition were characterized by GI-XRD, FE-SEM and EDS technique, respectively. The results revealed that the thin films were formed as a (Ti, Cr)N solid solution. The as-deposited thin films showed a nanocrystalline structure of TiCrN with the crystal sizes less than 45 nm. The lattice constants were in the range of 4.144 to 4.181 Å. The thickness of the TiCrN films decreased from 379 to 276 nm with increasing of the nitrogen gas flow rates. The nitrogen content of the as-deposited films was increased with increasing of the nitrogen gas flow rates, while the titanium and chromium content in the films were decreased. Finally, the TiCrN thin films showed compact columnar and dense morphology as a result of various the nitrogen gas flow rate.

Influence of nitrogen gas flow ratio on gallium nitride film growth using high-density convergent plasma sputtering device at room temperature

The influence of the nitrogen gas ratio on the gallium nitride (GaN) film growth has been investigated using a high-density convergent plasma sputtering device at room temperature. To obtain a highly reactive environment for GaN film growth, the convergent magnetic field lines assist the high-density plasma transport near the target surface. An orthogonal array in the design of experiments was used to effectively investigate GaN film growth conditions. To optimize the GaN film growth conditions, we focus on four sputtering parameters: (1) the N2 gas flow ratio, (2) the inflowing ion current to the target, (3) the process gas pressure, and (4) the target-substrate distance. The N2 gas flow ratio mainly characterizes the growth condition of c-axis oriented wurtzite-structure GaN films on an unheated glass substrate. The full width at half maximum of the rocking curve for the GaN(0002) peak position decreases to 3.9° in the growth condition with 100% nitrogen at room temperature.

Atmospheric vapor-transport method for growth of VO2 single-crystalline nano- and microwires

The growth of high-quality single crystalline nano- and microwires of VO2 is necessary to study the Mott transition and to expand its applications. Here, we propose a modified vapor-transport method characterized by a one-step process that does not require a vacuum and can be performed at the atmospheric pressure conditions with a nitrogen gas flow. This, so called atmospheric vapor-transport (AVT) method, is simpler in terms of the growth procedure and the apparatus installation when compared to the widely used vacuum-based techniques. The crystalline wires obtained by AVT method show a sharp and large, up to five orders, change in the electrical resistance near TC ≈ 340 K, along with the M1–M2–R structural phase transition.

Optimization and characterization of detector and trigger system for a KAPAE design

The Kyungpook National University Advanced Positronium Annihilation Experiment (KAPAE) aims to study ortho-positronium annihilation including invisible and visible exotic decay processes. The detector for this experiment consists of two main parts: the trigger part and the γ-ray detection part. In this study, we focused on the development of the trigger and γ-ray detection setup for the KAPAE detector. In the trigger setup, the suitable thickness of the plastic scintillator for positrons trigger is determined. The aerogel and nitrogen gas environment in which ortho-positronium can reduce the pick-off effect for 3-γ annihilation is created. The γ-ray detection part consists of 196 bismuth germanate (BGO) crystals covered with reflectors. The light yield and energy resolution uniformity of BGO crystals and the best suitable reflector for better light collection are evaluated. The source position dependency test for the BGO crystals are also examined. Single layer of polyethylene naphthalate (PEN) film plastic scintillator and aerogel with the continuous flow of nitrogen gas are found well suited for positrons trigger and annihilation environment, respectively. The light yield and its uniformity of 196 BGO crystals confirm its application for γ-ray detection in the KAPAE detector. Moreover, the VM2000 are found the best suitable reflector due to the small thickness and good reflectivity as compared to Teflon reflector.

Stability Indicating LC-MS Method Development and Validation for the Study of the Forced Degradation Behavior of Pimobendan Drug

Objectives: Analytical methods are necessary for the field of pharmaceuticals to discover the drug, determination of drugs and metabolites in biological matrices. The present study aimed to develop liquid chromatography-tandem mass spectrometry (LC-MS) and validation for quantification of Pimobendan in the formulation. Methods: The mobile phase composition was methanol, acetonitrile and 0.1 M phosphate buffers in the ratio of 45:15:40 (v/v) mixtures with isocratic elution. Prontosil ODS C18 column (250 × 4.6 mm, 5μ) was selected for separation with 264nm of LC UV detector wavelength. Ionization mass spectrophotometer was analyzed at nitrogen gas flow at 300 Psi and 300°C of source temperature. Mass spectrometry analysis of Pimobendan drug fragments was performed by introducing column eluting into equipment for Q1 and MS scan. Results: The drug was eluted at 3.56 min retention and the calibration curve was achieved at 0.5-250 μg/ml standard concentration. Different parameters of validation (linearity, specificity, precision, accuracy, selectivity and robustness) were performed and results confirm that all the parameters are in the acceptable limit. In the electrospray ionization spectra of Pimobendan [M+H], positive ions were observed at an m/z value of 335.42. The product-ions of 335.42 were observed at m/z value of 319.18, 287.19, 277.09, 261.08, 250.16, 223.30, 111.47 and 86.05. Conclusion: The proposed method is successfully achieved the acceptance criteria of all validation parameters and stability studies.

Influence of Nanoparticles on Thermal, Mechanical and 3D Analysis of Hybrid Bamboo/Glass Fibre-Reinforced Polymer Composites

Thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG) are used to investigate the thermal degradation and thermal stability of the prepared bamboo/glass hybrid composites in a nitrogen atmosphere. The analysis is carried out in the temperature range of 0 °C to 800 °C at a heating rate of 20 °C min−1 with the nitrogen gas flow of 55 ml min−1. The hybrid glass/bamboo with coconut shell powder in micron and nano-size confirms a mass loss of 32.50% and 33.50%. Tensile and fatigue results confirm that the bamboo/glass hybrid composite added with coconut shell powder in micro- and nano-size exhibits good fatigue property and restrict crack initiation and crack propagation under cyclic loading. Fatigue analysis reveals that at 800 cycles, the hybrid bamboo/glass fibre-reinforced plastics (FRP) composite with nanoparticles posses 22.5% higher load compared to all other combinations. Finally, the fatigue life increases with decreasing the filler dimension of the hybrid composites. TGA/DTG analysis reveals that hybrid bamboo/glass FRP composite with nanoparticles has improved the thermal stability of the composites.

Ultrafast carbothermal reduction of silica to silicon using a CO2 laser beam

We report the extraction of silicon via a carbothermal reduction process using a CO2 laser beam as a heat source. The surface of a mixture of silica and carbon black powder became brown after laser beam irradiation for a few tens of seconds, and clear peaks of crystalline silicon were observed by Raman shift measurements, confirming the successful carbothermal reduction of silica. The influence of process parameters, including the laser beam intensity, radiation time, nitrogen gas flow in a reaction chamber, and the molar ratios of silica/carbon black of the mixture, on the carbothermal reduction process is explained in detail.

Physical Properties of Furfural Resin-Based Active Carbon for Improved Electric Double Layer Capacitor

Specific surface area, pore size distribution and surface functional group of carbonaceous material for electric double layer capacitor (EDLC) are controlling factors to improve energy density. High specific surface area would lead to high specific capacitance, however some micropores (smaller than 2 nm) may be inaccessible to electrolyte ions due to the narrow pore gate effect at the pore entrance, thereby resulting in specific capacity reduction. Surface functional groups also affect the wettability of the activated carbon electrode and pseudo-capacity was yielded due to redox reaction. The relationships between capacity and multiple factors (i.e., specific surface area, pore size distribution, and surface functional groups) are still unclear. In this study, the specific surface area was fixed at 1200 ± 100 m2/g to eliminate the influence of specific surface area on specific capacity. The influences of pore size distribution and surface functional groups on specific capacity were then evaluated.Furfural resin-based particles (1 µm in diameter) were carburized in a nitrogen atmosphere for 3 h at a temperature ramping rate of 1°C/min to 400°C. The carbonized particles were mixed with KOH at a KOH:carbonized particles ratio of 4:1; the mixture was then activated at 700–800°C for the prescribed holding time, ranging from 0 to 0.5 h, under flowing nitrogen gas at a temperature ramping rate of 10°C/min. After heat treatment had been performed, the active carbon was cooled to room temperature, washed with 1 M HCl, rinsed with distilled water, and dried in an oven at 150ºC for 24 h. Specific surface area/pore size distribution was evaluated by N2 adsorption method. Surface functional groups were evaluated by Boehm method. Active carbon, carbon black and polytetrafluoroethylene were mixed at a mass ratio of 8: 1: 1, then pellets (14 mm in diameter and 2 mm in thickness) were prepared and dried at 115ºC for 24 hours to obtain activated carbon electrodes. Constant current charge/discharge test (potential width: 0-1.0 V, current density: 20-500 mA/g) and was performed at room temperature by two-electrode cell using KOH aqueous solution (6 M) as an electrolytic solution.Table 1 shows the pore structure of 1-μm-diameter active carbon particles treated at 700–800°C for different holding times to set SBET at ca. 1200 m2/g, allowing elucidation of the factor controlling the specific capacity. For a holding time of 0.5 h, the specific surface area (SBET) and total pore volume (Vtot) increased with increasing activation temperature. We found that increasing the holding time led to higher Vmicro and lower Vmeso. The three experimental conditions (700°C-0.5 h, 750°C-0 h, and 800°C-0 h) yielded active carbons with an SBET of 1200 ± 100 m2/g; these are indicated by the orange squares in Table 1. Active carbon by 750°C-0 h or 800°C-0 h had 2 to 3 times larger Vmeso and 1.9 times larger mesopore ratio than the one with 700°C-0.5 h. Specific capacity per weight increases in the order of 750ºC-0 h (148 F/g), 800ºC-0 h (111 F/g), and 700ºC-0.5 h (66 F/g). Figure 1 shows pore size distribution of these active carbons. Although 750ºC-0 h, 800ºC-0 h have similar pore size distributions, specific capacity per weight are very different. This indicates that factors other than pore structure may have a great influence on specific capacity per weight.Figure 2 shows the quantitative results of acid-base surface functional group by acid-base back titration (Boehm method). The total amount of acidic groups increased from 700°C-0.5 h (2.48 mmol/g), 800°C-0 h (2.45 mmol/g) to 750°C-0 h (2.21 mmol/g) and correlates with the large of the capacity. The fractional order of carboxyl groups increased from 750°C-0 h (18.1%), 800°C-0 h (23.0%) to 700°C-0.5 h (31.4%). The increase of carboxyl would be one possible reason for better specific capacity. Carboxyl groups cause pseudo-capacity due to redox reaction and improve wettability, and contribute to high capacity. From these relationships, we assumed that the amount of surface functional groups has a larger influence on the capacity than the pore structure. Figure 1

Surface chemistry of oxidised pyrite during grinding: EDTA extraction analysis

This paper investigates the surface chemistry of oxidised pyrite under two different grinding conditions (forged steel grinding media and 30% chrome steel grinding media with nitrogen gas flow) using the ethylene diamine-tetra acetic acid (EDTA) extraction technique. The measurement of EDTA extractable iron and dissolved total sulfur (DTS) in the solid and aqueous phase of the grinding slurry enables us to decouple the relative intensity of the pyrite oxidation and galvanic interactions in the mill. It is found that the galvanic interaction predominates in the mill when pyrite samples are ground with forged steel media in the presence of sufficient dissolved oxygen. While the oxidation of pyrite becomes the predominant reaction when the concentration of dissolved oxygen is low in the mill. However, the oxidation of pyrite predominates in the mill when pyrite samples are ground with 30% chrome steel media regardless of the concentration of dissolved oxygen. Reducing the level of dissolved oxygen in the mill (e.g., purging the system with nitrogen gas) or applying less electrochemically active grinding media (e.g., high chrome steel) can reduce the hydrophilic species on the pyrite surface during grinding (e.g., iron hydroxides/oxyhydroxides). Hence, it would be expected to consequently increase the floatability of pyrite.

Thermal degradation characteristics, kinetics, thermodynamic, and reaction mechanism analysis of pistachio shell pyrolysis for its bioenergy potential

The research work aims to estimate the bioenergy potential of pistachio shell and study its degradation kinetics which is necessary for the efficient design and optimization of thermochemical processes for bioenergy generation. Initial characterizations (proximate, ultimate, higher heating value, and compositional analysis), kinetic study, and thermodynamic analysis accompanied by reaction mechanism are investigated. Physicochemical characterization results confirmed high volatile matter (~ 79.8 wt%) and high heating value (16.85 MJ/kg) of pistachio shell. Thermogravimetric analysis (TGA) is performed at four different heating rates of 10, 20, 30, and 40 °C/min under nitrogen gas flow rate from ambient temperature to 900 °C. TGA results show the three-stage pyrolysis reaction which involves removal of moisture and light volatiles, degradation of cellulose and hemicellulose, and decomposition of lignin. The result also reveals that maximum degradation occurred in the temperature range of 200–400 °C. For calculating the kinetic (activation energy and pre-exponential factor) and thermodynamic parameters (enthalpy, entropy, and Gibbs free energy), different iso-conversional models, i.e. Flynn-wall-Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Friedman, are employed which gives the average value of activation energy as 168.86, 165.80, 166.29, and 190.10 kJ/mol, respectively and the pre-exponential factor values lie in the range of 107-1021 s−1. The average values of Gibbs free energy calculated for FWO, KAS, Starink, and Friedman methods are 182.09, 182.15, 182.13, and 181.42 kJ/mol, respectively. Criado method and Z plot are showing complex reaction mechanism. The results of kinetics and thermodynamic study reveal pistachio shell is an efficient biomass for bioenergy production.

Dose-dependent x-ray sensing nature of nanocrystalline bismuth phosphate thick films

Bismuth and its compounds have been used in various optoelectronic devices because of their unique physical properties and non-toxic nature. In this present study, nanocrystalline bismuth phosphate (BiPO4) was synthesized by solid-state double exchange reaction and then processed at 150 °C for 30 min under nitrogen gas flow. The phase, morphology, purity and band gap of the sample were analyzed respectively using x-ray diffraction, scanning electron microscopy-energy dispersive x-ray, Fourier transform infrared, Raman and diffuse reflectance spectroscopy. The obtained results reveal that the sample exists in hexagonal phase with crystallites in sub-spherical morphology (∼84 nm) and having a direct transition band gap of 4.52 eV. Furthermore, the x-ray attenuating nature of nanocrystalline BiPO4 thick film was examined using an intra-oral diagnostic x-ray machine interfaced with a Suniray-2 radiography image sensor. A theoretical validation of the obtained x-ray attenuating nature was carried out using the NIST-XCOM online resource. Then, x-ray-induced photocurrent was measured for nanocrystalline BiPO4 thick (200 µm) film for four different doses (mGy) exposed under biased condition (2 V). A grain boundary double Schottky potential barrier height (ϕb) model was applied to explain the observed linear dose-dependent x-ray sensing nature.

Comparative study of oxidizing ambient infused with varying nitrogen flow rates for fabrication of ternary nitrided AlZrO based MOS capacitor

High dielectric constant nitrided aluminum zirconium oxide films were successfully fabricated on silicon substrate via an oxidation process infused with different nitrogen gas flow rates at 800°C. The presence of nitrogen piling up at the interface could control the thickness of interfacial layer formation. An increase in the nitrogen gas flow rate might be effective in controlling the overall thickness of the films, yet the nitrogen piling up at the interface impeded the diffusion of oxygen to the interface. Consequently, the interface quality was affected, leading to degradation in the interface-state density. In addition, the generation of oxygen vacancies in the films, as well as the presence of nitrogen at the interstitial sites, would create a lattice polarization, which decreased the k values. Corresponding effects were also discussed in corroboration with energy band gap, effective oxide charges, and slow trap density, as well as interface-state density calculated from capacitance and conductance methods.

Effect of using Palm Char and Coke as a Reductant in Production of Ferrosilicon

This research focused on the synthesis of ferrosilicon alloy by coke and palm char as a reductant. Raw materials which were iron ore, silica sand, coke and palm char mixed and compacted into pellets. The pellets were reduced at temperature of 1300°C using horizontal tube furnace with nitrogen gas flow. The pellets after reduction process were characterized by X-ray fluorescence (XRF), X- ray diffraction (XRD), Scanning electron microscope equipped with energy dispersive spectra (SEM/EDS). The results from XRD analysis indicated that the formation of FeSi, Fe3Si and SiC phases were appeared at 1300 °C for both reductants. The brighter phases were observed in SEM/EDS mapping analysis represents as iron and silicon. The EDX analysis showed the high amount silica developed for coke compared to palm char due to high content of silica and carbon. The results found that palm char as carbon reductant has the potential to produce ferrosilicon and silica carbide in sustainable way.

Modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films

This paper demonstrates an intrinsic modulation of the cutoff wavelength in the spectra for solar selective absorbing coating based on high-entropy films. The (NiCuCrFeSi)N ((NCCFS)N) films were deposited by a magnetron sputtering system. Rutherford backscattering spectroscopy analysis confirms the uniform composition and good homogeneity of these high-entropy films. The real and imaginary parts of the permittivity for the (NCCFS)N material are calculated on the basis of the reflectance spectral fitting results. A redshift cutoff wavelength of the reflectance spectrum with increasing nitrogen gas flow rate exists because of the different levels of dispersion when changing nitrogen content. To realize significant solar absorption, the film surface was reconstituted to match its impedance with air by designing a pyramid nanostructure metasurface. Compared with the absorptance of the as-deposited films, the designed metasurface obtains a significant improvement in solar absorption with the absorptance increasing from 0.74 to 0.99. The metasurfaces also show low mid-infrared emissions with thermal emittance that can be as low as 0.06. These results demonstrate a new idea in the design of solar selective absorbing surface with controllable absorptance and low infrared emission for high-efficiency photo-thermal conversion.