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In this study, the utilization of an electric field generated by the high voltage discharge plasma over a liquid water surface containing glycine compound to synthesize titanium dioxide (TiO2) nanoparticles was demonstrated. The experiments were conducted in a batch-type system with applied voltages ranging from 18.6 − 23.4 kV under various pressurized gases at room temperature. The results indicated that the applied voltages, applied pulse numbers, and pulsed repetition rates had a significant influence on the decomposition reaction of glycine compounds and titanium rod electrode erosion. The ultraviolet − visible (UV − vis) spectra showed that titanium dioxide nanoparticles could be observed in each solution product, and most of them were brookite-type structures. According to the HRTEM images, TiC was also produced as a nanoparticle product. Based on the experimental results, this process is applicable and could result in advanced metal-based nanoparticle synthesis technology.

Bimetallic nanoparticle formation by applying pulsed laser ablation on the gold (Au) - titanium (TiO2) film was demonstrated. Experiments were conducted at room temperature. Au and TiO2 nanoparticles were mixed in different ratios and deposited as the starting material on silicon wafer plates, which were dried and placed in a beaker with distilled water. After a pulsed laser beam was applied, the collected aqueous solution products were analysed by ultraviolet–visible (UV–vis) spectrophotometry and characterised by scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS). The UV spectra indicated that the Au, TiO2, and Au–TiO2 nanoparticles were dispersed in the aqueous solution product. STEM-EDS images showed that spherical bimetallic nanoparticles containing gold and titanium were generated. A core of TiO2 nanoparticles was found to be well surrounded by a shell of Au nanoparticles when colloidal Au and TiO2 nanoparticles at a 1:1 ratio was used as the starting materials. The technique described here is simple and innovative, and this study enhances our understanding of bimetallic nanoparticle synthesis using a pulsed laser beam in a liquid environment.

In this study, ethanolic extracts of Curcuma mangga (C. mangga) were micronized using the supercritical antisolvent (SAS) method. Acetone, ethyl acetate, and dichloromethane were used as solvents to study the effects of solvent selection on the obtained particles. Supercritical carbon dioxide (CO2) was used as the antisolvent. The effects of nozzle geometry (cross nozzle and T-nozzle) on particle size and morphology were also evaluated. Microparticles and submicron particles were successfully produced with particle sizes ranging from 0.202 ± 0.05 μm to 1.653 ± 0.89 μm. Of the three solvents, ethyl acetate produced smaller particle sizes with a narrow particle size distribution. For all the types of solvents used, micronized particles prepared with the cross-nozzle had smaller average particle sizes than with the T-nozzle. The smallest particles of mean size 0.202 ± 0.05 μm were achieved at 16 MPa and 313 K using ethyl acetate as the solvent and a cross-nozzle. Computational fluid dynamics simulations were successfully performed on the internal flow to study the turbulent flow and volume fraction inside the nozzle. The results of this are expected to help improve the applications of the active ingredients of C. mangga rhizomes in the pharmaceutical industry.

Gold nanoparticle (AuNP) formation by applying pulsed discharge plasma in the slug flow reactor system was demonstrated. Experiments were carried out continuously at room temperature. The argon gas as a gas phase and the hydrogen tetrachloroaurate(III) tetra hydrate solution containing lysine as a liquid phase simultaneously flowed in the slug flow reactor system. The flow rates of the feed solution and argon gas were kept at 1.5 and 0.2 mL/min, respectively. To generate discharge plasma, the AC power supply with a bipolar pulsed output at 10 kV was applied. The purple color solution product was obtained, and the ultraviolet–visible (UV–vis) spectrophotometer showed that this possessed the absorption light from 510 to 550 nm associated with the existence of gold nanoparticles in each collected sample. Transmission electron microscopy (TEM) revealed that the lysine-capped AuNPs were produced in a spherical morphology and dispersed in aqueous solution products with a diameter of less than 20 nm.

Laser ablation in liquid (LAL) is known to be a promising method for synthesizing metal nanoparticles. In this study, gold and silver nanoparticles were fabricated by ultrasonic-assisted LAL. Gold ...

Nanomaterials that comprise titanium dioxide (TiO2) nanoparticles have received much attention owing to their wide applications; presently, the green synthesis of TiO2 nanoparticles is a developing research area. In this study, the TiO2 nanoparticles were synthesized through a DC-pulsed discharge plasma over an aqueous solution surface under a high-pressure argon environment. The titanium-rod electrode was utilized as the material source for the TiO2 nanoparticle generation. Experiments were performed at room temperature with pressurized argon at 1–4 MPa. To generate a pulse electrical discharge plasma, a DC power supply of 18.6 kV was applied. The Raman spectroscopy showed that the TiO2 nanoparticle with a brookite structure was formed dominantly. The scanning transmission electron microscopy equipped with energy dispersion spectroscopy (STEM coupled with EDS) indicated that TiO2 coated with carbon and that without carbon coating were successfully produced at the nanoscale. The process presented here is an innovative process and can update the existing information regarding the synthesis of metal-based nanoparticles using pulsed discharge plasma under an argon environment.

The production of fine particles via the supercritical carbon dioxide (SC–CO2) antisolvent process was carried out. The experiments were conducted at temperatures of 40–60 °C and pressures of 8–12 MPa with a 15 mL min–1 carbon dioxide (CO2) and 0.5 mL min–1 feed solution flow rate. As a feed solution, the curcumin and the polyvinylpyrrolidone (PVP) powder were dissolved in acetone and ethanol at concentrations of 1.0 mg mL–1 and 2.0–4.0% in weight, respectively. Scanning electron microscopy (SEM) images described that most of the precipitated particle products have spherical morphologies with a size of less than 1 μm. The Fourier transform infrared spectroscopy (FT-IR) spectra exhibited that the curcumin structural properties did not shift after the SC–CO2 antisolvent process. Moreover, the PVP addition in the curcumin particle products can enhance the curcumin dissolution in distilled water significantly.

Non-equilibrium pulsed discharge plasma using a gas–liquid slug flow in a glass column as a plasma reactor is developed and applied to methylene blue (MB) dye decolorization in aqueous wastewater. By flowing the solution and gas simultaneously in the slug flow system, the interval of the bubbles could be controlled and adjusted for each flow rate. After the slug flow became steady, an electrical discharge was introduced into the system using an AC power supply with a bipolar pulsed output voltage to generate plasma in the bubbles between the electrodes with a high applied voltage. The decolorization rate of the MB dye was determined by UV–Vis absorption spectroscopy. Based on the experimental results, it was determined that approximately 90% of the MB dye was decolorized for one-time treatment in oxygen and argon in a gaseous phase. This suggests that the oxygen-based reactive species derived from oxygen gas were effective as oxidizing agents, whereas short lifetime OH radicals were mainly produced and decolorized the MB dye in the case of argon and helium gas.

Fabrication of polyvinylpyrrolidone (PVP) particles by an electrospraying process under pressurized carbon dioxide (CO2) used as an anti-solvent was studied. The process was carried out at a constant temperature with CO2 pressures ranging from 1 to 6 MPa. A fixed applied voltage (17 kV) was employed to generate electric field. PVP powder dissolved in dichloromethane (DCM) at concentrations of 4, 6, and 8 wt% was used as the starting material. Scanning electron microscopy observations indicated that the electrosprayed PVP particles produced at 1–3 MPa using 8 wt% PVP solutions have spherical morphologies. At a similar concentration, increasing the CO2 pressure up to 6 MPa resulted in particle strings and strings as major products. Interestingly, hollow core particles formed when ethanol was added as a secondary solvent for controlling the evaporation rate of DCM during the electrospraying process under pressurized CO2. The FT–IR spectra revealed that the structural properties of PVP did not change after the electrospraying process. This work demonstrates that electrohydrodynamic processes under pressurized CO2 are likely to be fruitful for the fabrication of organic polymers with hollow cores.

The study of interaction between microwave radiation and minerals is gaining increasing interest in the field of minerals and material processing. Further studies are, however, still required to deepen the understanding of such microwave heating mechanisms in order to develop innovative techniques for mineral treatment using microwave heating. In this paper, effects of sample shapes and thickness on the distribution of temperature inside the mineral ilmenite (FeTiO3) due to microwave heating were numerically studied using the finite element (FE) method. The analysis was carried out in such a way that the flux of microwave energy was converted into an equivalent amount of heat generation in the mineral through the Poynting theorem of conservation of energy for the electromagnetic field. In this study, as a first attempt, the cylinder and slab of ilmenite were modeled to be irradiated from top and bottom surfaces with the variation of cylinder and slab thicknesses. Temperature-dependent material properties of ilmenite were taken into account in the FE simulation. Corresponding boundary conditions were then applied accordingly to the cylinder and slab of ilmenite with comparable characteristic length. Numerical results showed that, in terms of temperature differences between locations having maximum and minimum temperatures, slab geometries tended to produce higher values in comparison to those of cylinder geometries with the thickness variation, while the profiles of temperature inside the ilmenite samples were similar for both geometries. For the same duration of microwave heating, the slab geometry, hence, induced greater non-uniformity of temperature inside the ilmenite. It was also observed that, for the ilmenite samples with thickness value greater than 1.5 cm, the hotspot locations were not in the center of the sample, but on the surface of sample. Moreover, from several thickness values considered in this study, the ilmenite sample with thickness value of 3 cm gave a good trade-off between the maximum temperature value attained and temperature differences inside the sample, for both geometries. Thus, the shape and thickness of ilmenite samples affect the effectiveness of microwave heating of ilmenite, in terms of maximum temperature attained, temperature differences, and uniformity of temperature.

Biogas is produced when certain kinds of bacteria digest organic substances in an anaerobic environment. Typical raw biogas consists of about two thirds of methane (CH4) and one third of carbon dioxide (CO2). Even though raw biogas can be used directly to generate power, but the large volume of CO2 reduces the heating value of the gas, increasing compression and transportation costs and limiting economic feasibility. In this work, the raw biogas from small scale digester was upgraded by counter-current contacting it with a saturated Ca(OH)2 solution in a bubble column contactor to capture CO2. The bubble column comprises of a cylindrical column 7.3 cm in diameter and 100 cm high and is equipped with a perforated plate gas distributor. The CO2 content in upgraded biogas exit from top bubble column was sampled and measured using Gas Chromatography. The effect of ratio raw biogas to Ca(OH)2 solution flow rate with different liquid height and concentration of Ca(OH)2 solution on CO2 removal were investigated. The results showed that CO2 removal depends on the superficial velocity of the biogas, the flow rate of the Ca(OH)2 solution, the liquid height. The absorption of CO2 increases as the absorbent flow rate increases and decreases as the gas flow rate increases. The use of Ca(OH)2 above the solubility shown in the continuous process showed higher absorption of CO2. However, the increasing CO2 absorption is not significant with increasing Ca(OH)2 concentration. The highest absorption of CO2 obtained in the continuous process is 79.34 %.

A side from being a raw material for agar, Eucheuma cottonii algae have many other benefits because they contain various phytochemical compounds. The phytochemical compounds in Eucheuma cottonii have many benefits in the industrial and pharmaceutical fields. A method to get phytochemical compounds is through the extraction process. In the traditional method, the extraction is using organic solvents that dangerous to the environment. Therefore, this study used an environmentally friendly hydrothermal extraction method. Extraction was carried out at 160oC and a pressure of 7 MPa. The extraction results were then micronized using electrospraying. The electrospraying process was carried out with precursor solution concentration of 4 and 6% w/v, the applied voltage of 12, 14 and 16 kV, and the distance between tip and collector of 6.8 and 10 cm. The particles produced was characterized by Scanning Electron Microscope (SEM), Thermal Gravimetry Analysis (TGA), and antioxidant efficiency (AE) analysis. The morphological form of particles were spheres with a diameter below 3 μm. The largest AE value was 0.1818 obtained at operating conditions of 6% precursor solution, 10 cm tip distance, 16 kV applied voltage. The Operating conditions did not affect the TGA results.

The crystallization of b-carotene through supercritical antisolvent process with carbon dioxide (CO2) as an antisolvent has been demonstrated. The experiments were conducted at temperatures of 40 - 60oC and pressures of 10 - 14 MPa at a constant CO2 flow rate. As a starting material, b-carotene powder was dissolved in dichloromethane (DCM). Results of UV-vis spectrophotometry analysis showed that there was no remaining DCM solvent in the b-carotene particles products. It showed that CO2 has successfully removed DCM from b-carotene particles products. The product characterization by using fourier transform infrared spectroscopy (FT-IR) showed that the CO2 solvent did not impregnate to the b-carotene particles products. Results from scanning electron microscope (SEM) images showed that the b-carotene particles products were successfully prepared in plate-like shape morphologies with size around 1 mm.

Electrospinning is an electrostatic process for formation of polymer fibers with nano/microscale diameter from solution. In this study, poly(vinyl pyrrolidone) (PVP) dissolved at 4 wt% concentration in dichloromethane (DCM) containing titanium oxide (TiO2) nanoparticles was used as polymer feed solution for electrospinning under pressurized carbon dioxide (CO2) at temperature of 30 °C, pressure of 5 MPa, and applied voltage of 10–14 kV. Scanning electron microscopy (SEM) revealed that the PVP fibers electrospun with and without TiO2 nanoparticles exhibited the same morphology with hollow structure and average pore diameter of 2–7 μm. Fourier-transform infrared (FT-IR) spectroscopy revealed that the electrospun PVP fibers had properties similar to the PVP starting material. X-ray photoelectron spectroscopy (XPS) revealed that the TiO2 nanoparticles were present in the residue after thermogravimetric (TG) analysis of electrospun fibers., ファイル公開：2019/04/01

Zinc oxide (ZnO) is one of the most commonly used semiconductor materials for various applications, namely as photocatalysts, gas sensors, antimicrobial substances, and photovoltaic cells. The performance of the particles is greatly influenced by the morphology and the optical properties of the particles itself. To improve the performance of ZnO, one method which can be applied is by doping support with other semiconductor materials, such as TiO2. This is caused by electron transfers between ZnO and TiO2 which are able to enhance the stability of ZnO and the electron mobility of TiO2. Therefore, the electron-hole recombination can be inhibited by this mechanism. Fabrication of ZnO-TiO2 can be prepared by several methods, which is gas or liquid phases and solid phase. Spray pyrolysis, chemical vapor deposition, micro-arc oxidation, electrospinning and electron beam evaporation are preparation method for gas-phase synthesis, while sol-gel, hydrothermal, precipitation, solution combustion, pulse plating, and wet impregnation are for liquid phases. In this study, the fabrication methods of ZnO-TiO2 and its application have been reviewed as well as the factors that affect the morphology, performance, and the stability of ZnO-TiO2 nanocomposite. This review is conducted by comparing the analysis results with their performances. It is clearly found that there is an optimum condition for obtaining the best photocatalytic performance by adjusting the ratio of ZnO to TiO2. Furthermore, ratio of ZnO:TiO2 concentration on antimicrobial activity shows a linear performance, and it is obviously observed that the ZnO- TiO2 nanocomposite shows a better performance compared to the pristine ZnO or TiO2 in various applications. We believe that this review will provide valuable information and new insights into possible fabrication methods of ZnO-TiO2 nanocomposite materials, which can be used in many applications.

Nanostructured zinc oxide (ZnO) was synthesized via a sonochemical method. The effect of the duration of ultrasonic irradiation in a continuous mode on the generated particles was investigated. Additionally, the effect of flowing either air or nitrogen during the sonication process was investigated. Zinc nitrate and ammonia water-based solutions were selected as chemicals without the addition of other surfactants. The generated particles indicated that a wurtzite structure of ZnO in a hexagonal phase was formed with a crystalline size that increased as the ultrasound irradiation time increased. The morphology of the generated ZnO particles could be changed from flowerlike to needlelike structures via continuous ultrasound irradiation over one to two hours, resulting in increases in the particle lengths and decreases in the particle diameters from 200 to 80 nm. Photoluminescence intensity was also increased with increases in the ultrasonic irradiation times. Photoluminescence spectra were also influenced by the atmospheric environment. Two bands centered at 390 and 500 nm were generated under a nitrogen environment. On the other hand, a single wide band with a peak at around 430 nm was found for particles generated under an air environment. It can be applied for light emitting diodes (LED) or laser fabrication with a controlled emitting band.

Electrospinning is one of the simple techniques for the production of polymer nano-microfibers. In this study, hollow fibers from poly(methyl methacrylate) (PMMA) were formed by electrospinning under pressurized carbon dioxide (CO2) in a single processing step. The experiments were conducted at temperatures and pressures in the range 27–37°C and 4–6 MPa, respectively. At 5 MPa, CO2 seemed to have enough affinity to dissolve a portion of dichloromethane (DCM) to assist its evaporation. Under subcritical CO2, electrospun products with hollow core fibers having diameters of 4–16 μm were generated. The results confirmed that the change of operating parameters had a strong influence on the morphologies (crack or hollows) of the electrospun products. This study demonstrated that this process offers the possibility that electrospinning under pressurized CO2 will become an essential and useful method for the generation of polymer structures with hollow interiors. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Porous zirconia particles were synthesized through a low-temperature hydrothermal synthesis process. Under hydrothermal conditions, water can control the direction of crystal growth, morphology, particle size, and size distribution because thermodynamics and transport properties can be controlled by pressure and temperature. In a batch process, the hydrothermal synthesis was conducted at 200–300 °C and 30 MPa with an SUS-304 tube as the reactor. At the same reaction pressure, experiments were also performed for a flow process with temperatures of 180–200 °C. The synthesized products were calcined and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results showed that the macroporous zirconia particles that were formed had pore diameters around 419 nm. The XRD pattern indicated that the products were composed of zirconium oxide particles with monoclinic, tetragonal, and cubic structures.

The drying process of droplets into particles on a spray dryer is influenced by several factors, including the temperature and the flow rate of inlet air as a carrier gas and a drying media. The effects of temperature of the inlet air in the spray dryer system was elucidated in this study. A solution containing 35 w% polysaccharide extract and water as the solvent was injected into a spray dryer. The inlet air temperatures were varied at 135, 170, and 200 °C with 3 L/min. The geometry of spray dryer consisted of the tubular-conical with a length of 48.8 cm and 15.2 cm diameter cylinder. The spray dryer unit was simulated using CFD code, Fluent Ansys R15.0 with the second phase of droplets/particles was modelled by the Lagrangian discrete phase model (DPM). The inlet air temperature also affected the size of the particles. The increase of the air temperature led to the increase of the average particle diameter leaving the chamber with the smaller standard deviation. The air flow rate affected the particle size. The higher the air flow rate, the smaller the size of the average diameter of the particles and smaller standard deviation would be. The evaporation rate increased with the increase of the flow rate and inlet air temperature. The resulting particles had an average size of 1.28∼1.9 μm diameter to drying with hot air that flowed continuously. The simulation result was validated by the experimental work with discrepancy less than 20%.

Metal−based nanoparticles have been used in diverse industrial applications owing to their physicochemical properties. Here, the electric field produced by pulsed high−voltage discharge plasma over an aqueous solution surface that was generated under high−pressure argon environment would be employed to synthesis and to modify metal materials. The plasma reactor was made of stainless steel and contained two sapphire windows to monitor the plasma performance. The experiments were conducted at room temperature (25 − 28 °C) with argon environment at a pressure of 3.0 MPa and the DC power supply at 18.6 kV was introduced into the reactor through the electrode to generate pulse electrical discharge plasma. The metal rod electrode which was used as a material source for nanoparticles generation was placed over an aqueous solution containing glycine, as carbon source, to introduce electrical discharge plasma. The scanning transmission electron microscopy which was equipped with energy dispersion spectroscopy (STEM coupled with EDS) indicated that titanium dioxide and iron oxide with and without carbon covered were successfully produced in nano−scale (

In this work, Ganoderma lucidum (G. lucidum) extract was produced in microparticles form by electrospraying. G. lucidum was extracted hydrothermally at temperature of 160oC and pressure of 7 MPa. The extract solution was subsequently mixed with 6% of Polyvinyl pyrrolidone (PVP) and formed into microparticles by electrospraying process. The electrospraying was carried out at applied voltage of 12, 14, and 16 kV, and the distance between syringe tip and electrospun collector of 8, 10, and 12 cm. The microparticles formed was analyzed using scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectroscopy, and UV-Vis spectrofotometer. The antioxidant efficiency of particles was also analyzed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Based on the SEM analysis, the G. lucidum extract (GLE) – PVP spherical particles were formed by electrospraying. The finer fibres were clearly formed with the increasing applied voltage. The results showed that applied voltage and distance of tip to electrospun collector significantly influence the antioxidant efficiency and the diameter size of particles. The antioxidant efficiency increased with the rising applied voltage and gap of tip to electrospun collector, while the particle diameter decreased with the rising applied voltage and gap of tip to electrospun collector due to fast mass transfer and evaporation. The largest antioxidant efficiency of particles was 0.377/min obtained at 16 kV and 12 cm. It indicated that electrospraying is an effective process to produce pharmaceutical compounds in powder form.

Flame pyrolysis is widely used for the fabrication of particles because of great crystallinity and fine size distribution of the products. In this research, ZnO-Ag particle materials have been favourably made by flame pyrolysis. The impacts of Ag loading varying from 0 to 20 wt% on the photocatalytic activity of ZnO-Ag particle under ultraviolet (UV) and sunlight irradiations were studied. ZnO-Ag particles were fabricated based on zinc acetate dihydrate (Zn(CH3COO)2.2H2O) 0.1 M and silver nitrate (AgNO3) as a precursor inside a flame reactor. Crystallinity and morphology of ZnO-Ag particles were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. SEM analysis showed that the particles had irregular sphere-like shapes. The XRD patterns showed that the produced ZnO had a wurtzite structure with different crystallite sizes. XRD analysis also confirmed the existence of Ag particles in ZnO-Ag particles after the addition of Ag greater or equal to 5 wt%. The existence of Ag was indicated by the appearance of the XRD peak at 38.1°. The peak at 38.1° increased with the increase of Ag loading. Finally, the photocatalytic activity was evaluated by estimating the degradation of methylene blue aqueous solution under UV and sunlight irradiations. It noted that the most excellent photocatalytic performance was achieved at 5 wt% Ag loading for both irradiations.

Ceria oxide (CeO2) is widely used as catalyst with high oxygen storage capacity at low temperature. The addition of zirconia oxide (ZrO2) to CeO2 can enhance oxygen storage capacity as well as thermal stability. In this work, ceria zirconia oxides has been synthesized via a low temperature solvothermal treatment in order to produce ceria zirconia oxides composite with high oxygen storage capacity as electrolyte of solid oxide fuel cells (SOFC). Under solvothermal conditions, solvent may control the direction of crystal growth, morphology, particle size and size distribution, because of the controllability of thermodynamics and transport properties by pressure and temperature. Water, mixed of water and ethanol (70/30 vol/vol), and mixed of water and ethylene glycol (70/30 vol/vol) were used as solvent, while Ce(NO3)3 and ZrO(NO3)2 with 0.06 M concentration were used as precursor. The experiments were conducted at temperature of 150 °C and pressure for 2 h in a Teflon-lined autoclave of 100 mL volume. The synthesized products were dried at 60 °C for 6 and 12 h and then calcined at 900 °C for 6 h. The particle products were characterized using SEM, XRD, TG/DTA, and Potentiostat. The results showed that the morphology of particles formed were affected by the solvent. Solid plate shaped particles were produced in water, and tend to be pore with the addition of ethylene glycol. The addition of ethanol decreased the size of particles with sphere shaped. The XRD pattern indicated that ceria-zirconia oxides particles are uniformly distributed in the structure to form a homogeneous solid solution. Based on the electrochemical analysis, ceria zirconia oxides produced via solvothermal synthesis had high conductivity ion of 0.5594 S/cm, which is higher than minimum conductivity ion requirement of 0.01 S/cm for SOFC electrolyte. It indicated that ceria zirconia oxides produced via solvothermal synthesis is suitable for SOFC electrolyte.

Nickel nanoparticles with various structures were synthesized by a pulsed laser ablation process in liquid CO2 at 17 °C and 5.2 MPa. A nickel plate immersed in liquid CO2 was used as a target. This was irradiated by a laser beam with a fundamental wavelength of 1064 nm at 2.46 mJ for 15 min. The generated particles were deposited on a silicon wafer after natural evaporation of the liquid CO2, and analyzed by field emission scanning electron microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Nickel and carbon particles with sphere-like structures or apple-shaped structures were observed. Furthermore, characteristic nickel/carbon particles with core/shell structures were also produced. The generated particles ranged in size between 5 and 350 nm in diameter, with dominant sizes under 50 nm.

Here, ZnO particles and ZnO-SiO2nanocomposites synthesized by sonochemical method under continuous ultrasound irradiation were reported. For an hour ultrasound irradiated by ultrasonic horn at atmospheric condition, nanorods and spherical structures with crystalline sizes 33 and 17 nm were obtained for ZnO and ZnO-SiO2, respectively, revealed that silica inhibited the particles and crystal growth. FTIR analysis also indicated that silica covered the ZnO particles. In addition, photocatalytic activity was also inhibited by silica in which ZnO without and with silica had degradation rate 69% and 48%, respectively, to degrade methylene blue solution under direct sunlight irradiation for an hour. The addition of SiO2to ZnO gives an advantage in some application to avoid excessive degradation by controlling their photocatalytic activity.

The purpose of this work was to investigate the mechanism of macroporous zirconia particles formation by hydrothermal synthesis. Hydrothermal synthesis of zirconia was prepared from precursor solution of Zr(NO3)2 with a concentration of 0.3 M at temperatures of 300 and 200°C carried out in a batch and a continuous reactor, respectively. Hydrothermally synthesized colloid subsequently was mixed with polystyrene template to form macroporous zirconia particles, and then was synthesized hydrothermally for 1 hour at temperature of 150°C and 200°C. Once the synthesis was complete, the particles were then dried at temperature of 60°C for 6 hours. In order to eliminate polystyrene template from the particles, the dried particles were calcined at temperature of 600°C and 900°C for 6 hours. The morphology of particles formed were characterized by scanning electron microscope (SEM) and Particle Size Analyzer (PSA). The analytical result showed that macroporous particles were formed at all experimental condition, and the mechanism of macroporous particles formation could be observed clearly. Based on the XRD analysis, the crystal zirconia consisted of monoclinic and tetragonal phase.

Magnetite film was successfully prepared on the mild steel surface in alkaline environment by hydrothermal electrolysis treatment. The principle of hydrothermal electrolysis is applying current directly to electrolyte solution at hydrothermal conditions. The anodizing of mild steel was conducted at temperatures of 100–200 °C and applied current densities of 0.1–0.4 A/cm2 for 5–60 min reaction time with sodium hydroxide (NaOH) as an electrolyte solution (5–15%). Magnetite film on the mild steel surface was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and cyclic voltammetry. The patterns of XRD showed that magnetite was formed dominantly in the surface of mild steel with black color. Cyclic voltammetry analysis showed that the magnetite films produced on the mild steel surface could prevent or minimize the corrosion on its surface.

ZnO-SiO2 nanocomposite particles were prepared by sonochemical method under continuous ultrasound irradiation for an hour. Zinc nitrate and sodium silicate were used as zinc oxide and silica sources, respectively. Silica concentration was varied to investigate the effect of silica on the characteristics of the generated composite particles and they were also compared to ZnO particles. Morphology, crystallinity, chemical bonding analysis, photoluminescence spectra, and photocatalytic activity were characterized by scanning electron microscopy (SEM), X-Ray diffraction, Fourier Transform Infrared (FTIR), luminescence spectrophotometer, and UV-Vis spectrophotometer, respectively. Nanorod structures were observed for pure ZnO, ZnO-SiO2 particles with 250 ppm and 750 ppm silica addition during synthesis. Spherical agglomerated particles were found for particle with 0.1 M silica addition. The crystalline size and photocalytic activity decreased with the silica addition. A strongest chemical bonding for ZnO and SiO2 was also observed for particle with 0.1 M silica addition based on FTIR spectra. However, the highest photoluminescence emission by excitation wavelength at 250 nm, was observed for ZnO-SiO2 particles with 750 ppm silica addition with emission peak at 515 nm wavelength.

ZnO/SiO 2 nanocomposites were prepared using consecutive sol–gel and flame-assisted spray-drying methods. Zinc oxide and silica sols were prepared individually from zinc acetate and water glass, respectively, via a sol–gel method. Subsequently, zinc oxide sol, silica sol, and a mixture of both were spray dried in a flame reactor to generate powder of pure zinc oxide, pure silica, and a ZnO/SiO 2 nanocomposite, respectively, in order to compare the characteristics. The generated particles were characterized via luminescence spectrophotometer, Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to obtain the photoluminescence spectra, chemical bonding, crystallinity, and morphology of the particles, respectively. The photoluminescence emission recorded at 250 nm excitation showed a peak at approximately 400 nm that was characterized by a violet band. The highest intensity was shown by a 75 mol% ZnO sample followed, in order, by 50 mol% ZnO, 25 mol% ZnO, and pure ZnO.

It was well known that electrospinning is one of the simple technical methods for the production of polymer nanoparticles and nanofibers. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years mostly in solvent solution and some in melt form. In this work, hollow fibers with walls made of organic polymer composites have been formed by electrospinning in a single processing step under pressurized carbon dioxide (CO2). The experiments were conducted at 313 K and ∼8 MPa. The capability and feasibility of this technique was demonstrated by the production of polyvinylpyrrolidone (PVP) fibers whose size and wall thickness could be independently varied by controlling a set of experimental parameters. The PVP fibers had an average pore diameter 2–4 μm. At low pressures (

Magnetite particles were successfully generated by hydrothermal synthesis using water at subcritical conditions. By changing the temperature and pressure at subcritical water conditions, the thermodynamics and transport properties of the water can be controlled, thus enabling to manage the way of crystal formation, morphology, and particle size. In this work, the experiments were carried out at temperatures of 250 °C and 290 °C and a pressure of 10 MPa with a reactor made of SUS 316 in a batch system. The synthesized particles were dried in vacuum condition and characterized by SEM and XRD. The XRD patterns showed that magnetite particles were dominantly formed in the particle products with a black color. The results showed that the magnetite particles formed had diameters of around 60 nm in all experiments with irregular polyhedral shaped morphologies.

Carbon fibres are important materials due to their excellent properties. Carbon fibres were formed by blending Poly(vinyl alcohol) (PVA) and a high conductivity material of Acetylene black (AB). Electrospinning technique was used to fabricate PVA and AB solutions in demineralized water. Electrospinning is an efficient technique for the formation of polymer nanofibers. The effects of solution concentration and AB contents on morphological appearance and diameter of those as-spun fibres were investigated by scanning electron microscopy (SEM). Iodine treatment on the fabricated PVA/AB composite was successfully achieved in order to build up the carbonization process and retained their original fibrous structure. The mass of iodinated nanofibers at 80 °C for 24 h increased about 130 %. The mechanism of iodine uptake by electrospun PVA/AB fibres have been obtained by thermal behaviour and its morphological characteristics. It was found that iodine treatment played an important role in changing the morphological structure during the carbonization process. With the iodine treatment of PVA/AB precursor fibres successfully converted into thin carbon fibres and SEM analysis confirmed that the diameter of fibres was about 290 nm. The resulted pure fibres and iodine treatments show guarantee for production carbon fibres.

Cerium oxide (CeO2) is a rare earth metal oxide that has high oxygen storage capacity at low temperature. In order to enhance this capacity, as well as its thermal stability, it is necessary to combine CeO2 with zirconium oxide (ZrO2). This work focuses on the synthesis of cerium-zirconium oxides by hydrothermal and solvothermal treatment at low temperature to obtain ones suitable for catalyst applications. The possibility of the application of ceria-zirconia oxide to the delignification reaction was investigated. The experiments were conducted at a constant pressure of 5 MPa, constant temperature of 150oC, and constant synthesis time of 2 h, in an autoclave reactor made of SUS 316 with an internal volume of 100 mL. Precursor was prepared from Ce(NO3)3 and ZrO(NO3)2 at 0.06 M concentration, dissolved in various solvents. The solvents used were water, water/ethanol (70:30 vol/vol), and water/ethylene glycol (70:30 vol/vol). After hydrothermal and solvothermal synthesis, the colloid products were dried at 60oC for 6 h and then calcined at 500oC for 6 h. The characterizations of the particle products were analyzed using SEM and XRD. Furthermore, these products were used for the hydrothermal delignification process of wood biomass. The addition of ceria-zirconia particles dramatically increased the percentage of lignin removal from rapeseed wood up to 97.58%. Based on the results, ceria-zirconia oxide particles are effective for the pre-treatment of wood biomass in bio-refinery applications. Moreover, ceria-zirconia oxides may reduce the use of chemical compounds in the delignification process.

The degradation of organic pollutants using photocatalysis is more effective than conventional methods, with ZnO being the most widely used of the various semiconductor materials for application in photocatalysis. Unfortunately, degradation efficiency is inhibited by the electron-hole recombination. The photocatalytic activity of ZnO can be enhanced by adding noble metals, such as Ag nanoparticles. However, the fabrication of ZnO?Ag using liquid-phase processes is complicated and often requires multiple steps. In this study, the effects of Ag content, ranging from 0 to 20 wt%, in the photocatalytic activity of ZnO?Ag nanocomposites are investigated. The nanocomposites were fabricated by a one-step process using flame pyrolysis and with zinc acetate and AgNO3 as the precursors. The nanocomposites were collected using an electrostatic precipitator and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption-desorption of the Brunauer-Emmett-Teller (BET) specific surface area. The XRD results confirm the existence of Ag nanoparticles in the prepared nanocomposites, whose crystallite size was not significantly influenced by the presence of the nanoparticles. The SEM indicated that the morphology of the nanocomposites produced was spherical, with some aggregates. Particle size distribution of the nanocomposites increased with higher Ag content. The photocatalytic activity of the produced nanocomposites, estimated by evaluating the degradation of the methylene blue aqueous solution under UV irradiation, showed that the highest photocatalytic performance was attained when the concentration of Ag was equal to 5 wt%.

With a view to promoting dispersion of lycopene in water, the precipitation of an inclusion complex of lycopene and β -cyclodextrin was investigated using the solution-enhanced dispersion by supercritical fluids (SEDS) process. The inclusion complex, which was prepared in N,N -dimethylformamide (DMF), was dissolved in the same solvent and then micronized by SEDS, using carbon dioxide (CO 2 ) as a supercritical antisolvent. The effects of the initial concentrations of lycopene and β -cyclodextrin, the CO 2 flow rate, the solution flow rate, and the pressure and temperature at which the process was conducted were examined. The morphologies of the resulting particles were observed by scanning electron microscopy (SEM) and field emission-scanning electron microscopy (FE-SEM). Small spherical particles were obtained at all operating conditions. At high pressure, high temperature, high CO 2 flow rate and low solution flow rate, particles with an average particle size of about 40 nm were obtained.

Flame assisted spray dryer are widely uses for large-scale production of nanoparticles because of it ability. Numerical approach is needed to predict combustion and particles production in scale up and optimization process due to difficulty in experimental observation and relatively high cost. Computational Fluid Dynamics (CFD) can provide the momentum, energy and mass transfer, so that CFD more efficient than experiment due to time and cost. Here, two turbulence models, k-e and Large Eddy Simulation were compared and applied in flame assisted spray dryer system. The energy sources for particle drying was obtained from combustion between LPG as fuel and air as oxidizer and carrier gas that modelled by non-premixed combustion in simulation. Silica particles was used to particle modelling from sol silica solution precursor. From the several comparison result, i.e. flame contour, temperature distribution and particle size distribution, Large Eddy Simulation turbulence model can provide the closest data to th...

Pulsed laser ablation (PLA) has been widely employed in industrial and biological applications and in other fields. The environmental conditions in which PLA is conducted are important parameters that affect both the solid particle cloud and the deposition produced by the plume. In this work, the generation of nanoparticles (NPs) has been developed by performing PLA of silver (Ag) plates in a supercritical CO2 medium. Ag NPs were successfully generated by allowing the selective generation of clusters. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures and temperatures of CO2 medium. On the basis of the experimental result, both surface of the irradiated Ag plate and structure of Ag NPs were significantly affected by the changes in supercritical CO2 pressure and temperature. With increasing irradiation pressure, plume deposited in the surrounding crater created by the ablation was clearly observed. In Field Emission Scanning Electron Microscopy (FE-SEM) the image o...

Electrospinning is one of the simple technical methods for the production of polymer nanoparticles and nanofibers. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years mostly in solvent solution and some in melt form. In this work, near- and supercritical CO2 were used as media for this process. At these conditions, the solubility can be tuned by controlling the temperature and pressure. Therefore, it is possible to form particles and fibers within a thermodynamic window where the biopolymer has been softened, but not dissolved. The experiments were conducted by using electrospinning under pressurized CO2 system at pressures of ∼ 8.0 MPa and temperature of 313 K to produce several polymers fibers. Polyvinylpyrrolidone was used as the starting material. During the electrospinning process, the applied voltage was 10–17 kV and the distance of nozzle and collector was 8 cm. The concentration of polymer solution was 4 wt%. The morphology- and structure-produce...

An advanced method for producing nano-structured materials has been developed by performing pulsed laser ablation of gold plate in supercritical CO2 (SCCO2). The method successfully generated gold nano-structured particles with allowing the selective generation of clusters. Laser ablation was performed with an excitation wavelength of 532 nm. Generated gold nano-structured particles collected in the silicon (Si) wafer and the ablated gold plate were analyzed by field emission gun scanning electron microscopy (FE-SEM), scanning electron microscopy (SEM), and 3D laser scanning microscopy. Absorption spectrum of generated gold nano-structured particles collected in the glass slide was also evaluated by UV-Vis spectrophotometer. Gold plate was ablated at various SCCO2 densities and irradiation time at constant temperature of 40 and 60 °C. Both surface of ablated gold plate and amount of gold nano-structured particles were significantly affected by the changes in SCCO2 density and the surrounding environment. Surface morphology of ablated gold plate was significantly affected by irradiation time. As increasing irradiation time, plume deposited in the crater vicinity of ablated gold plate was clearly observed. The depth of crater increased with increasing pressure or SCCO2 density and temperature due to heat transfer properties of CO2 change in the system. The deepest crater was observed at 10 MPa and 60 °C. The spectra of generated gold nano-structured particles in a glass slide contain bands near 530 nm. The peak near 530 nm has been known to correspond to the plasmon band of gold nanospheres with diameters

Nanosecond pulsed laser ablation (PLA) of gold plate with an excitation wavelength of 532 nm was carried out in supercritical CO2 (scCO2) to fabricate gold nanoparticles. Surface morphology of the gold plate after irradiation and the crater depth after PLA were observed by scanning electron microscopy and laser scanning microscopy, while extinction spectra of gold nanoparticles collected in the glass slide was measured by UV–Vis spectrophotometer. The gold plate was ablated at various scCO2 densities and irradiation times at constant temperature of 40°C. The ablation was also conducted at atmospheric condition with air to evaluate the environmental dependence of ablation. Both surface morphology of the irradiated gold plate and crater depth formation were significantly affected by the changes in scCO2 density, the surrounding environment, and irradiation time. As expected, the increasing scCO2 density resulted in a deeper ablation crater, however, the deepest crater was obtained at a density of 0.63 g/cm3 or pressure of 10 MPa. Gold nanoparticles generated by PLA in scCO2 have been confirmed at the spectra band near 530 nm.

Japanese rice straw, an agricultural by-product, was utilized for the extraction of lignin by hot compressed water at temperatures of 443 - 503 K and a pressure of 4.0 MPa using a flow-through system, a simple and environmentally friendly extraction method requiring no chemicals other than water. Under these conditions, thermal softening of the Japanese rice straw occurred, allowing the removal of lignin via depolymerization reactions. Lignin as an extraction product was analyzed using utraviolet-visible (UV-vis) spectrophotometry. Lignin recovery approached 85% when the extraction was performed at 443 and 473 K with a flow rate of 4.67 ml min-1. At a constant residence time, recovery amounts increased with increasing flow rate at each temperature. The results suggested that this process may result in an advanced plant biomass components extraction technology.

Electrospinning technique is feasible in some applications, it has attracted more attention in recent years. Various polymers have been successfully electrospun into ultrafine fibers in solvent solution and some in melt form. In this work, polyvinylpyrrolidone (PVP) as a hydrophilic polymer would be synthesized by electrospinning under dense carbon dioxide (CO2). The experiments were performed at 40 °C and ∼ 5 MPa. During the electrospinning process, the applied voltage was 10–17 kV and the distance of nozzle and collector was 8 cm. The concentration of PVP solution as a major component was 4 wt%. The results showed that the fibers surface morphology from PVP which blended with poly L-lactide acid (PLLA) were smooth with hollow core fibers at 5 MPa. At the same conditions, PVP-carbon nanotube was also successfully generated into electrospun fiber products with diameter ∼ 2 μm.

Nanostructured ZnO was synthesized by a sonochemical reaction. Ultrasonic irradiation were set up in continuous, pulse in 3 seconds on and a second off (on:off=3:1), and pulse in 2 seconds on and a second off (on:off=2:1) wave modes for 1.5 hours. The characteristics of particles generated by these modes such as morphology, crystallinity, FTIR, photoluminescence, and photocatalytic activity to degrade methylene blue were compared. Zinc nitrate and ammonia water-based solutions were selected as chemicals without the addition of other surfactants. The morphology of the generated ZnO particles could be tuned from flower-like, needle- or hairy-like, and spherical structures by changing the mode of ultrasonic irradiation from continuous, on:off=3:1, and on:off=2:1 modes, respectively. The generated particles indicated that a wurtzite structure of ZnO in a hexagonal phase was formed. The crystalline sizes of particles generated in continuous, on:off=3:1, and on:off=2:1 modes were 28, 27, 24 nm. A similar position of reduction peak of FTIR in all samples indicated that no differences in particles chemical bonding characteristics. Photoluminescence intensity was also decreased with changes the wave mode from continuous to pulse. Photocatalytic activity was also evaluated resulting in particles synthesized by continuous mode had the highest methylene blue degradation degree following by on:off=3:1, and on:off=2:1 modes.

This paper highlights the conversion of oil palm mesocarp fiber into bio-oil via SFE. Effects of extraction temperature which are temperature within 60-90°C are investigated for two hours of extraction time. The yield is diluted in 10ml dichloromethane (DCM) for analysis of gas chromatography-mass spectrometry (GC-MS). The extracted bio-oil is found to contain fatty acid, esters and other long chain hydrocarbon. The concentration of these compounds is determined based on chromatogram peak area. The analysis indicates that fatty acid such as 6-octadecanoic acid (stearic acid), n-hexadecanoic acid (palmitic acid) and dodecanoic acid, 1,2, 3-propanetryl ester (glycerol trilaurate), are the major compounds of the extracted bio-oil. The extraction yield increased from 16.7% to 19.8% once the temperature was increased from 60 to 90°C. Concentration of palmitic acid constantly decreased with temperature. Inversely, myristic acid concentration constantly increased with temperature. However, concentration of glycerol trylaurate, stearic acid and lauric acid was not significantly affected by temperature. Concentration of stearic acid and lauric acid was first reduced once temperature increased from 60 to 70°C yet increased at 90°C and vice versa observation for glycerol trilaurate.

Electrospinning is a simple technique that has gained much attention because of its capability and feasibility in the fabrication of large quantities of fibers from polymer with diameters ranging in nano-microscale. These fibers provided high surface area to volume ratios, and it was of considerable interest for many applications, such as nanoparticle carriers in controlled release, scaffolds in tissue engineering, wound dressings, military wear with chemical and biological toxin-resistance, nanofibrous membranes or filters, and electronic sensors. Recently there has been a great deal of progress in the potential applications of hollow fibers in microfluids, photonics, and energy storage. In this work, electrospinning was conducted under high-pressure carbon dioxide (CO{sub 2}) to reduce the viscosity of polymer solution. The experiments were conducted at 313 K and ∼8.0 MPa. Polymer solution containing 5 wt% polymers which prepared in dichloromethane (DCM) with polyvinylpyrrolidone (PVP) to poly-L-lactic acid (PLLA) ratio 80:20 was used as a feed solution. The applied voltage was 15 kV and the distance of nozzle and collector was 8 cm. The morphology and structure of the fibers produced were observed using scanning electron microscopy (SEM). Under pressurized CO{sub 2}, PVP electrospun was produced without bead formation with diameter ranges of 608.50more » - 7943.19 nm. These behaviors hold the potential to considerably improve devolatilization electrospinning processes.« less