Bambang Mukti Wibawa

Synthesis and Dispersion of Nanoparticles, and Indonesian Graphite Processing

Synthesis of nanoparticles and processing of nanocomposites are the essential steps in the application of nanotechnology in various industrial fields including environmental remediation and renewable energy conversion. It is very important to develop their synthesis methods in which nanoparticles having controlled characteristics including size distribution, morphologies, and compositions. Thus, the process needs to be simple, low in cost, and have both continuous operation and high production rate to meet the industrial requirements. The synthesis method for nanoparticles and the development of nanoparticles dispersion technology will be reviewed; nanoparticles synthesis by pulse combustion spray pyrolysis to improve production rate and dispersion of nanoparticles by bead mill method. Furthermore, the availability of the raw materials are also very important to produce the end products economically. The current development on the graphite processing and the future development on the end product in Indonesia will be reviewed.At the request of the authors and Proceedings Editor an updated version of this article was published on 24 September 2013. All changes are restricted to minor updating and editing of references: the scientific content of the paper remains unchanged.Synthesis of nanoparticles and processing of nanocomposites are the essential steps in the application of nanotechnology in various industrial fields including environmental remediation and renewable energy conversion. It is very important to develop their synthesis methods in which nanoparticles having controlled characteristics including size distribution, morphologies, and compositions. Thus, the process needs to be simple, low in cost, and have both continuous operation and high production rate to meet the industrial requirements. The synthesis method for nanoparticles and the development of nanoparticles dispersion technology will be reviewed; nanoparticles synthesis by pulse combustion spray pyrolysis to improve production rate and dispersion of nanoparticles by bead mill method. Furthermore, the availability of the raw materials are also very important to produce the end products economically. The current development on the graphite processing and the future development on the end product in Indone...

Blue Luminescent of ZnO:Zn Nanocrystal Prepared by One Step Spray Pyrolysis Method

A blue luminescent of ZnO:Zn nanocrystal has been successfully prepared by one step spray pyrolysis method without reducing gas atmosphere. Zinc acetate dihydrate aqueous solutions (0.05 M) were atomized by ultrasonic atomizer. The atomizer used an air as carrier gas with 1, 3 and 5 L/min flowrate. The tubular reactor was set at 500, 600 and 700oC. As prepared samples were characterized by means of x-ray diffraction spectroscopy and scanning electron microscope-energy dispersive x-ray spectroscopy (SEM-EDS). The crystal size of as prepared particles calculated by Scherrer’s equation give 10-20 nm. The luminescent properties of as prepared particles were measured using spectrofluorophotometer. The highest photoluminescent intensity of particles irradiated with excited wavelength of 250 nm was obtained from samples prepared using 5 L/min carrier gas with temperature of tubular reactor 700oC. High intensity of blue luminescent was obtained due to oxygen vacancy in ZnO:Zn.

Development and characterization of integrating sphere for photometry and radiometry measurement

Integrating Sphere (IS) is an instrument formed a cavity sphere with its inner surface act as a Lambertian reflector. IS is needed in many optical measurements which involves a high diffused reflection. In addition, IS very essential in photometry and radiometry measurement system. However, currently, IS is still an imported product which considered very expensive. The material for the sphere and inner surface coating affect the performance of the IS systems. Therefore, the main challenges in designing IS are the material engineering for the sphere and the procedure for the inner surface coating. The inner surface was coated using BaSO4 which has a low absorption and high diffuse reflection. Spectral responses of the IS system was characterized using USB2000+ and calibrated using a standard Spectralon from ocean optic. The obtained IS system used an inner surface coating from a mixed 80% Barium Sulfate (BaSO4) and 20% Nippon Elastex paint which yield a reflection factor ρ = 0.955 and amplification factor ...

MOSFET-based high voltage short pulse generator for ultrasonic transducer excitation

This paper presents the generation of a high-voltage short pulse for the excitation of high frequency ultrasonic transducers. This is highly required in the purpose of various ultrasonic-based evaluations, particularly when high resolution measurement is necessary. A high voltage (+760 V) DC voltage source was pulsated by an ultrafast switching MOSFET which was driven by a pulse generator circuit consisting of an astable multivibrator, a one-shot multivibrator with Schmitt trigger input and a high current MOSFET driver. The generated pulses excited a 200-kHz and a 1-MHz ultrasonic transducers and tested in the transmission mode propagation to evaluate the performances of the generated pulse. The test results showed the generator were able to produce negative spike pulses up to -760 V voltage with the shortest time-width of 107.1 nanosecond. The transmission-received ultrasonic waves show frequency oscillation at 200 and 961 kHz and their amplitudes varied with the voltage of excitation pulse. These result...

Integrating sphere design for characterization of LED efficacy

The integrating sphere (IS) is one of the most important device in characterization of illuminance of a light source, such as CFL, LED etc. to obtain their efficacy. IS is a hollowed sphere with its interior covered with a diffuse white reflective coating where its accuracy of the measurement is highly affected by reflectance of its interior coating. This paper report the preparation of inner surface coating of the IS with inner diameter of 25 cm attempt to create a durable and highly reflective interior coating by combining BaSO4 with a binding material (either Polyethylene Glycol (PEG) or white paint). The various inner surface coating mixture vary in weight % ratio of BaSO4:PEG or BaSO4:white paint were investigated. The results show that the inner surface coating mixture of BaSO4:PEG (99.8:0.2) has highest reflectance compared to others mixture. The IS with best mixture was calibrated with white LED and resulted an average sphere multiplier (M) was 8.7, and average reflectance (ρ) was 0.90. The result...

Development of Indonesia corncob and rice husk biobriquette as alternative energy source

Facing the increasing of fuel price and lacking of world oil resource, research for biobriquette as alternative energy for fossil fuel is conducted. Indonesia has considerable amount of biomass and it is still remain unused that can be used as biobriquette. As the initial research, Garut, Ciamis, and Sumedang district, West Java are selected which have rice husk and corncob commodities. In these disrticts, rice husk and corncob potency are respectively 4,460.73 tons and 3,222.85 tons and potentially result 57,572.86 GJ from husk and 60,911.86 GJ from corncob. To optimize mechanical properties and calorie value of biobriquette, research for calorie content and combination of rice husk and corncob are being conducted with various adhesive content and mixture. The best result of shatter index, durability, and calorie test on the corncob biobriquette is from biobriquette with 6% adhesive with calorie content as 5,516.85 kkal/kg. While the best calorie content for husk biobriquette is 6% adhesive with calorie ...

Optical properties of amorphous silicon quantum dots (a-Si QDs) with various dot size using extended Hückel theory

A high quality amorphous silicon (a-Si) nanostructures has grown experimentally to study the origin of light emission and the quantum confinement effect in a-Si. The quantum confinement effect increases the band gap of material as the size of quantum structure decreases, which results in a blue shift in optical luminescence and energy absorption. Here we demonstrate this effect using extended Huckel method to calculate fundamental band gap and optical absorption energy of a-Si samples with various dot sizes. As result, when the dot size was decreased from 2.2 to 1.0 nm, the absorption spectra peak shifted toward higher energy from 2.278 eV to 3.856 eV.