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Photocatalytic treatment of palm oil mill effluent by visible light-active calcium ferrite: Effects of catalyst preparation technique
摘要： Palm oil mill effluent (POME) is a serious and expensive environmental problem in Malaysia. In this paper, CaFe2O4 is introduced as a novel photocatalyst for the degradation of POME under visible light irradiation. Two synthesis routes, auto-combustion and co-precipitation, and two calcination temperatures 550 °C and 700 °C were used to produce four CaFe2O4 catalysts AC550, AC700, CP550 and CP700. CP550 exhibited the greatest photocatalytic degradation at 56% chemical-oxygen-demand (COD) removal after 8 h of irradiation which dropped to 49% after three consecutive cycles indicating reasonable conversion and high recyclability. BET analysis indicated CP550 had the highest SBET (27.28 m2/g) and pore volume (0.077 cm3/g) which dropped precipitously for CP700 upon increasing the calcination temperature to an SBET of 9.73 m2/g and pore volume of 0.025 cm3/g due to annealing which created a smoother surface area as evidenced by the SEM images. UV–Vis DRS indicated CP550 had the highest band-gap (1.52 eV) which is likely due to the presence of a highly crystalline pure CaFe2O4 phase compared to the other products which existed as a mixture of Fe oxidation states evidenced by the XRD data. The PL spectra for all catalysts indicated significantly lower recombination rate for both CP550 and CP700. Introduction of IPA into the reaction mixture to eliminate hydroxyl radicals resulted in a diminishing of COD removal from 56% to 7% proving hydroxyl radicals to be the primary reactive species responsible for photodegradation of POME.
关键词： Co-precipitation,POME,Photocatalysis,Visible light,Calcium ferrite,Auto-combustion
更新于2025-09-23 15:23:52
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Evolution of shapes and identification of level II and III features of fingerprints using CaZrO3:Sm3+ fluorescent markers prepared via solution combustion route
摘要： Simple solution combustion route is used for the fabrication of CaZrO3: Sm3+ (1–11 mol %) nanophosphors using Aloe Vera gel as a fuel. The powder X-ray diffraction profiles confirm the pure orthorhombic phase. The granular type particles with non-uniformity in the size is observed. Photoluminescence emission spectra exhibit intense peaks at ～571, 603, 651 and 708 nm, which are attributed to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2 and 4G5/2 → 6H11/2 transitions of Sm3+ ions, respectively. The photometric properties evident that the prepared samples emit bright orange - red light with 79% color purity. The average correlated color temperature value is found to be ～3100 K. Thermoluminescence glow curves exhibit a broad, intense peak at ～148 °C. The highest thermoluminescence intensity is recorded for 5 mol % of Sm3+ doped sample. The thermoluminescence intensity at ～148 °C is found to increase with increase of γ-dose. The optimized CaZrO3:Sm3+ (5 mol %) nanophosphors used as a luminescent labeling agent for visualization latent fingerprints on various porous and non-porous surfaces under ultraviolet 254 nm and normal light. The obtained results exhibits well defined ridge details with high sensitivity, selectivity, and low background hindrance which showed greater advantages. Extensive fingerprint details, namely level II and III features are clearly revealed. Hence, aforementioned results evident that the optimized sample endorse wide spread of applications, namely solid state lighting, high temperature dosimetry and advanced forensic science fields.
关键词： Thermoluminescence,Photoluminescence,Sweat pore visualization,Solution combustion,Photometric properties
更新于2025-09-23 15:23:52
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Preparation and photocatalytic performance of Cu-doped CeO <sub/>2</sub> by citrate combustion method
摘要： Cu-doped cerium oxides were successfully prepared by nitrate combustion method. The crysatlline phase evolution, micro morphology and photocatalytic performance of the products are systematically studied by XRD, SEM/EDX and degradation rate of methylene blue. The results show that at relative low temperature (<600°C), 20 mol% copper can be dissolved into CeO2 fluorite type cubic structure, however, at high temperature of 700°C, CuO phase desolution from CeO2 solid solution is detected by XRD, and confirmed by DTA for 5% Cu-doped sample. The as prepared photocatalysts show agglomeration of ultra fine particles with porous structure. Degradation results of methylene blue indicate that better photocatalytic performance is obtained for 5% Cu-doped CeO2 under the stimulated visible light than UV light irradiation (both 254 nm and 365 nm), even the power of former is half of the later. The loss of photocatalytic activity for higher doping samples (>5% Cu) is believed to be the serious agglomeration of the particles and desolution of CuO from CeO2 solid solution.
关键词： doping,citrate combustion method,copper,photocatalytic,Ceria
更新于2025-09-23 15:23:52
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Effects of Heat-Treatment on Photoluminescence Spectra and Photocatalytic Properties of Solution-Combusted ZnO Nanopowders
摘要： ZnO nanopowders were prepared by a solution combustion method (SCM). The SCM ZnO nanopowders were heat-treated at 200, 400, 500, or 700 °C for 30 min in air and the photoluminescence (PL) of the nanopowders was evaluated. Two strong PL emission peaks are generally recognized as the unique PL signature of ZnO, one is from the band-edge emission and the other corresponds to green emission. The green emission is derived from crystalline defects, and is a critical obstacle for the electrooptical applications of ZnO. Surprisingly, the PL spectra of the SCM ZnO powders showed a single sharp peak near 390 nm. Furthermore, the intensity of this blue emission doubled when the synthesized ZnO powder was heat-treated at 400 °C. The green emission appeared for the sample treated at 500 °C, and was the highest for that treated at 700 °C. To confirm the photocatalytic activity of the ZnO powder heat-treated at 400 °C, the removal of Ag ions from a used photofilm developer was evaluated, with complete removal within 10 min. The removal of the Ag ions by the ZnO powder heat-treated at 400 °C was more than two orders of magnitude faster than that achieved with the SCM ZnO powder. The relation between PL and photocatalytic activity was explained in terms of recombination of the photogenerated electrons. These results might be very useful for highly efficient photocatalyst applications.
关键词： Heat-Treatment,ZnO Nanopowder,PL Spectra,Solution Combustion Method
更新于2025-09-23 15:22:29
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Effect of grain size and temperature on DC electrical conductivity of tin oxide nanoparticles synthesized by gel combustion method
摘要： Tin oxide (SnO2) nanomaterials of different grain size have been prepared using gel combustion method by varying the fuel (C6H8O7) to oxidizer (HNO3) molar ratio as a process parameter. The prepared samples were characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Analysis X-ray Spectroscope (EDAX). The XRD patterns showed the formation of single phase Tetragonal rutile structure. The average particle size is found to be in the range of 19–34 nm. SEM images show high porosity in the material. The DC electrical conductivity of SnO2 thick film increases with the temperature significantly from 308K to 670K. The DC electrical conductivity of SnO2 thick film decreases with decrease in grain size due to the effect of surface to volume ratio while activation energy increases with decrease of grain size.
关键词： Thick film,Tin oxide,Activation energy,DC conductivity,Combustion synthesis
更新于2025-09-23 15:22:29
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Evolution of volatile cloud in pulverized coal combustion with high-speed digital inline holographic visualization
摘要： The coal devolatilization plays a significant role in the combustion of pulverized coal particles. The evolution of volatile cloud during devolatilization of pulverized coal particles (105–125 μm) is studied in a high-temperature flat-flame burner by combining high-speed photography with high-speed digital inline holography (DIH). By the high-speed holographic visualization, the evolution of volatile cloud of pulverized coal from volatile release to soot aggregation generation can be divided into four stages. Effects of coal type on volatile cloud evolution are investigated using three different coals, i.e., Shanxi bituminous coal, Ximeng lignite and Yinni lignite. The results show that both the Shanxi bituminous coal and Ximeng lignite produce soot aggregation during devolatilization, which is rarely observed for Yinni lignite. Moreover, Shanxi bituminous coal has a higher potential in soot cluster formation for its higher coal rank than Ximeng lignite. The high-speed reconstructed image sequences are analyzed to measure the velocity slip between the parent particle and volatile cloud. Compared with Shanxi bituminous coal, Ximeng lignite exhibits a larger slip velocity. This work also demonstrates that high-speed DIH has the powerful capacity of directly observing the evolution of volatile cloud, and helps to gain a deep understanding of pulverized coal combustion.
关键词： Volatile cloud,Coal combustion,High-speed digital inline holography,Soot aggregation,High-speed photography
更新于2025-09-23 15:22:29
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Optical analysis of flame inception and propagation in a lean-burn natural-gas spark-ignition engine with a bowl-in-piston geometry
摘要： Heavy-duty diesel engines can convert to lean-burn natural-gas spark-ignition operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector to initiate and control combustion. However, the combustion phenomena in such converted engines usually consist of two distinct stages: a fast-burning stage inside the piston bowl followed by a slow-burning stage inside the squish area. This study used flame luminosity data and in-cylinder pressure measurements to analyze flame propagation inside a bowl-in-piston geometry. The experimental results showed a low coefficient of variation and standard deviation of peak cylinder pressure, moderate rate of pressure rise, and no knocking for the lean-burn (equivalence ratio 0.66), low-speed (900 r/min), and medium-load (6.6 bar IMEP) operating condition. Flame inception had a strong effect on the flame expansion velocity, which increased fast once the flame kernel established, but it reduced near the bowl edge and the entrance of the narrow squish region. However, the burn inside the bowl was very fast. In addition, the long duration of burn inside the squish indicated a much lower flame propagation speed for the outside-the-bowl combustion, which contributed to a long decreasing tail in the apparent heat release rate. Furthermore, cycles with fast flame inception and fast burn inside the bowl had a similar end of combustion with cycles with delayed flame inception and then a retarded burn inside the bowl, which indicated that the combustion inside the squish region determined the combustion duration. Overall, the results suggested that the spark event, the flame development inside the piston bowl, and the start of the second combustion stage affected the phasing and duration of the two combustion stages, which (subsequently) can affect engine efficiency and emissions of diesel engines converted to a lean-burn natural-gas spark-ignition operation.
关键词： spark ignition,Optical engine,combustion,bowl-in-piston,natural gas
更新于2025-09-23 15:22:29
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Investigation of photocatalytic, electrochemical, optical and magnetic behaviors of rare-earth double perovskites using combustion synthesized Gd2NiMnO6 nanostructures in the presence of different saccharides
摘要： This paper reports combustion synthesis of Gd2NiMnO6 nanostructures (GNMO NSs), for the ?rst time, through reaction between metal nitrates in the presence of different saccharides, as capping and reducing agents. Analysis of XRD, FT-IR, EDS, along with TEM and SEM images and also VSM and DRS spectra were applied to study the NSs. The VSM showed an antiferromagnetic behavior. The DRS spectroscopy ascertained semiconducting behavior of GNMO NSs with Eg ? 3.05 eV for optimum sample prepared in the presence of glucose at 1000 (cid:2)C. The CV was used to investigation of electrochemical property of the NSs. For the ?rst time, the photocatalytic behavior of the GNMO NSs was evaluated, using the degradation of organic dyes under UV irradiation. The photodegradation of EDT was almost similar to that of ES, except for initial times of the irradiation. The degradation percentage of EBT and ES in the presence of GNMO NSs was large, whereas that of MV was little in the time range.
关键词： Direct band gap,Photocatalysis,Antiferromagnetism,Gd2NiMnO6,Combustion,Nanostructures
更新于2025-09-23 15:21:21
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Green Synthesis Approach for Nano sized CoFe2O4 through Aloe Vera Mediated Sol-gel Auto Combustion Method for High Frequency Devices
摘要： Nanosized CoFe2O4 was synthesized by Aloe vera-mediated sol-gel auto-combustion method. The yielded nanoparticles were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) to investigate the phase formation and morphology of the obtained powders. FTIR, XRD and Raman spectra revealed the formation of single phase CoFe2O4. FESEM micrographs showed the formation of some bud like structure and the particle size obtained is around 50-65?nm. Investigation of magnetic properties viz. saturation magnetization (Ms), remenant magnetization (Mr) and coercivity (Hc) were studied from the M-H loop and were found to be 72.23 emu/gm, 31.29 emu/gm, 1519 Oe respectively. In addition, the massive dielectric constant, low dielectric loss, and AC conductivity of the CoFe2O4 nanoparticles were dependent on the frequency (100 Hz-1 MHz), method of preparation and grain size. Room temperature ferroelectric measurement reveals a partially unsaturated P-E loop due to the high coercive field and influence of leakage current.
关键词： Aloe vera plant extract,magnetism,nanostructured materials,Dielectric properties,sol-gel auto combustion
更新于2025-09-23 15:21:21
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Two dimensional temperature measurement characteristics in pulverized coal combustion field by computed tomography-tunable diode laser absorption spectroscopy
摘要： Two dimensional temperature and concentration distributions are important parameters for pulverized coal combustion used for power plant to understand the combustion field and develop the high efficient combustion technologies. However, it is difficult to measure two dimensional temperature and concentration in pulverized coal combustion field using conventional measurement technologies because pulverized coal combustion produces lots of dust and strong emission from its flame. This paper focused on the application of two dimensional temperature measurement method based on the combination of computed tomography and tunable diode laser absorption spectroscopy using absorption spectra of water vapor at 1388nm and 1343nm for each laser scanning using direct absorption spectroscopy, which show the better characteristics of spatial-temporal resolution, fast response, high sensitivity, self-calibration and optical accessibility. Accuracy of temperature measurement using tunable diode laser absorption spectroscopy was improved by applying the corrected spectroscopic database. Computed tomography reconstruction accuracy of 16 laser-paths configuration was evaluated using sum of squared difference (0.001) and zero-mean normalized cross-correlation (over 0.991), which presented the consistent temperature between assumed and reconstructed distributions. This developed computed tomography-tunable diode laser absorption spectroscopy was successfully applied to pulverized coal flame for two dimensional temperature measurement with 1 ms temporal resolution for time-series two dimensional temperature measurement in the range of 300K-2500K. The rationality was demonstrated by comparison of pulverized coal flame and Methane-Air flame temperature distributions due to the main heat release produced by methane fuel. Its applicability to pulverized coal combustion field will be benefit for optimal operation control and combustion efficiency improvement by combustion organization or new design of combustion system.
关键词： Power plant,Pulverized coal combustion,Computed tomography (CT),Tunable diode laser absorption spectroscopy (TDLAS),Two dimensional temperature measurement
更新于2025-09-23 15:21:01