Vorrada Loryuenyong

Preparation and Characterization of Reduced Graphene Oxide Sheets via Water-Based Exfoliation and Reduction Methods

This research studied the synthesis of graphene oxide and graphene via a low-cost manufacturing method. The process started with the chemical oxidation of commercial graphite powder into graphite oxide by modified Hummer’s method, followed by the exfoliation of graphite oxide in distilled water using the ultrasound frequency from a laboratory ultrasonic bath. Finally, the oxygen functional groups on exfoliated graphite oxide or graphene oxide were eliminated by stirring in hot distilled water at 95°C, as a replacement for highly toxic and dangerously unstable hydrazine. The results assured that stirring in hot distilled water could give the product of graphene or reduced graphene oxide. The samples were characterized by FTIR, XRD, TGA, Raman spectroscopy, SEM, and TEM methods.

Enhancement of (In,Ga)N light-emitting diode performance by laser liftoff and transfer from sapphire to silicon

(In,Ga)N light-emitting diodes (LEDs) fabricated on a sapphire growth substrate were successfully integrated onto Si substrates by a double-transfer technique using excimer laser liftoff and Pd-In transient-liquid-phase bonding. This transfer method resulted in a bonded LED heterostructure with the same orientation (p-side up) as the heterostructure before transfer from the sapphire growth substrate. Such a layer transfer approach enables a top and backside contact metallization scheme that reduces device series resistance, current crowding, and top electrode coverage area. Enhancement of the performance of the transferred LEDs was found in terms of the threshold voltage (at 20 mA) and the electroluminescence output from the front surface.

Effects of recycled glass substitution on the physical and mechanical properties of clay bricks.

In this study, wasted glasses from structural glass walls up to 45 wt.% were added into clay mixtures in brick manufacturing process. Physical and mechanical properties of clay bricks were investigated as functions of the wasted glass content and the firing temperature. The results indicated that with proper amount of wasted glasses and firing temperature, clay bricks with suitable physical and mechanical properties could be obtained. The compressive strength as high as 26-41 MPa and water absorption as low as 2-3% were achieved for bricks containing 15-30 wt.% of glass content and fired at 1100 degrees C. When the glass waste content was 45 wt.%, apparent porosity and water absorption was rapidly increased.

Calcium Oxide Derived from Waste Shells of Mussel, Cockle, and Scallop as the Heterogeneous Catalyst for Biodiesel Production

The waste shell was utilized as a bioresource of calcium oxide (CaO) in catalyzing a transesterification to produce biodiesel (methyl ester). The economic and environmen-friendly catalysts were prepared by a calcination method at 700–1,000°C for 4 h. The heterogeneous catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and the Brunauer-Emmett-Teller (BET) method. The effects of reaction variables such as reaction time, reaction temperature, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated. Reusability of waste shell catalyst was also examined. The results indicated that the CaO catalysts derived from waste shell showed good reusability and had high potential to be used as biodiesel production catalysts in transesterification of palm oil with methanol.

Oyster and Pyramidella Shells as Heterogeneous Catalysts for the Microwave-Assisted Biodiesel Production from Jatropha curcas Oil

Microwave-assisted biodiesel production via transesterification of Jatropha curcas oil with methanol using solid oxide catalyst derived from waste shells of oyster and Pyramidella was studied. The shells were calcined at 900°C for 2 h and calcium oxide (CaO) catalyst characterizations were carried out by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), and the Brunauer-Emmett-Teller (BET) surface area measurements. The effects of reaction variables such as reaction time, microwave power, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated. Reusability of waste shell catalyst was also examined. The results indicated that the economic and environmentally friendly catalysts derived from oyster and Pyramidella shells showed good reusability and had high potential to be used as biodiesel production catalysts under microwave-assisted transesterification of Jatropha curcas oil with methanol.

Rapid transesterification of Jatropha curcas oil to biodiesel using novel catalyst with a microwave heating system

We used a microwave heating system to increase Jatropha biodiesel yield, and to reduce both reaction time and energy consumption. The feasibility of converting natural and non-edible feedstocks including arcuate mussel shells and dolomitic rocks, into a novel high-performance, reusable, low-cost and heterogeneous catalyst for the synthesis of biodiesel was also explored. Arcuate mussel shells and dolomitic rocks were first ground and calcined at 900 °C for 2 h. After calcination, calcium oxide (CaO) or a mixed oxide of calcium and magnesium (CaO·MgO) was obtained as white powder, which was then chemically activated to improve the physical, chemical and surface properties, and catalytic activities of the catalysts. By heating CaO from waste shells in an excess dehydrated methanol under 65 °C at 8 h with nitrogen (N2) flow, calcium methoxide (Ca(OCH3)2) catalyst was prepared. The CaO from natural rocks was, however, turned into calcium glyceroxide complex, by combining with methanol and glycerol of the by-product. It was determined that calcium glyceroxide (Ca[O(OH)2C3H5]2) was formed during the transesterification and acted as the most active phase. Catalyst characterization was by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) surface area and basic strength measurements. The reaction parameters, including reaction time, microwave power, methanol/oil molar ratio, catalyst dosage and catalyst reusability, were studied for fatty acid methyl esters (FAME) yield. The results indicated that Ca(OCH3)2 and Ca[O(OH)2C3H5]2 catalysts derived from waste shells and natural rocks showed good reusability, high energy efficient, environmental-friendly, low cost and facile route for the synthesis of biodiesel.

Natural Hydroxyapatite (NHAp) Derived from Pork Bone as a Renewable Catalyst for Biodiesel Production via Microwave Irradiation

The use of waste materials for producing biodiesel via transesterification has been of recent interest. In this study, the pork bone was used as the raw materials for natural hydroxyapatite (NHAp) catalyst. The calcination of animal bone was conducted at 900 °C for 2 h. The raw material and the resulting heterogeneous catalyst were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method. The effects of reaction time, microwave power, methanol/oil molar ratio, catalyst loading and reusability of catalyst were systematically investigated. The optimum conditions, which yielded a conversion of oil of nearly 94%, were reaction time 5 min and microwave power 800 W. The results indicated that the NHAp catalysts derived from pork bone showed good reusability and had high potential to be used as biodiesel production catalysts under microwave-assisted transesterification of Jatropha Curcas oil with methanol.

The Photocatalytic Reduction of Hexavalent Chromium by Controllable Mesoporous Anatase TiO2 Nanoparticles

Titania (TiO2) nanoparticles with periodical mesopore size (up to 150 A) have successfully been synthesized by sol-gel template method, using titanium(IV) tetraisopropoxide as a starting precursor and isopropanol as a solvent. Different quantities of activated carbon (0%, 5%, and 10% by weight) were used as templates to control the porosity and particle size of titania nanoparticles. The templates were completely removed during the calcination in air at 500°C for 3 hr. The results showed that the specific surface area of titania is increased with increasing activated carbon content. The optical bandgap of synthesized titania exhibits a blue shift by 0.3–0.6 eV when compared to the reported value for the bulk anatase and rutile phases. The photocatalytic activity of porous titania is determined with its reduction efficiency of hexavalent chromium (Cr6

Synthesis of templated mesoporous silica nanoparticles under base catalysis

Abstract Abstract In this research, mesoporous silica nanoparticles were successfully prepared by a sol–gel process under base catalysis. The aim of this study is to control the size and distribution of porosities as well as to increase the specific surface area of the silica material using a template method. Tetraethoxysilane was employed as silica precursor with cetyltrimethyl ammonium bromide as template. The NH4OH solution was used as base catalyst. The as synthesised mesoporous silica was then calcined at different temperatures in the range of 300–600°C. The results indicated that the optimal adsorption capacity was achieved when the calcination temperature reached 600°C due to the complete removal of silanol groups. When the cetyltrimethyl ammonium bromide template was used, the specific surface area increased from 118 to 469 m2 g−1, enhancing the capability to adsorb the organic solution. The X-ray diffraction patterns demonstrated the amorphous nature of the sol–gel silica.

Utilization of Waste Enamel Venus Shell as Friendly Environmental Catalyst for Synthesis of Biodiesel

Calcium oxide (CaO) is one of the most promising heterogeneous alkali catalysts since it is cheap, abundantly available in nature, and some of the sources of this compound are renewable (waste material consisting of calcium carbonate (CaCO3)). In this study, the waste enamel venus shell was used as the raw material for CaO catalyst. The calcination of bio-waste was conducted at 900 °C for 2 h. The raw material and the resulting CaO catalyst were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method. The effects of reaction variables such as reaction time, microwave power, methanol/oil molar ratio, and catalyst loading on the yield of biodiesel were investigated by gas chromatograph-mass spectrometry (GC-MS). From the experimental results, it was found that the CaO catalysts derived from waste material showed good catalytic activity (the conversion of oil of nearly 93%, a very similar catalytic activity with laboratory CaO) and had high potential to be used as biodiesel production catalysts in transesterification of Jatropha Curcas oil with methanol.