nan Fitrilawati

The optical band gap investigation of PVP-capped ZnO nanoparticles synthesized by sol-gel method

ZnO Nanoparticles (NPs) has unique natures on their crystal structure, direct band gap and high exciton binding energy, consequently applied in optoelectronic devices such as solar cells, optical wave guide and light emitting diodes (LED). However the drawback was ZnO NPs tend to agglomerate and turn to nano-structured materials with poor properties. Effort to avoid agglomerations generally resolved by surface modification of ZnO NPs to obtain well-dispersed suspension. However changes in the surface of ZnO NPs may change the electronic structure and density of states of ZnO NPs, in turn may change the optical band gap. Thus, the objective of current research is investigation of optical band gap of ZnO NPs due to surface modification by capping agent of poly-4-vinylpyrrolidone (PVP) molecules. Uncapped and PVP-capped ZnO nanoparticles were prepared by sol-gel method. The characteristics of surface modifications were investigated by UV-Vis and Photo Luminescence spectroscopy and Transmission Electron Micro...

Effect of Nb2O5 Addition to the Electrical Properties of Fe2TiO5 Ceramics-Based NTC Thermistor

The aims of this research is to identify the effect of Nb2O5 addition on the electrical properties of Fe2TiO5 ceramics-based NTC thermistor.The concentration of Fe2O3 and TiO2 was proportional to Fe2TiO5, whereas the concentration value of Nb2O5 were 0, 0.5 and 1.0 mole %, respectively. Within two hours, the mixed powder was pressed at 4 ton/cm2 to form pellets and sintered at 1300 °C in air. It can perceived from the XRD data that the sintered ceramics had single phase of Fe2TiO5, pseudobrookite. From SEM data, it is found that addition of Nb2O5 decreases the grain size. The addition of Nb2O5 increases thermistor constant, activation energy and electrical resistance of Fe2TiO5 ceramics. The values of thermistor constant of Nb2O5 added-Fe2TiO5 ceramics were relatively large, indicated that the ceramics were aplicable as the NTC thermistor.

Modification of Blue LED using Organic-Inorganic Hybrid Polymer Doped with Nile Red for Artificial Lighting of Photosynthesis

The photosynthesis process of chlorophyll absorbs only the light with wavelength in the blue and red ranges. The absorption peak of the chlorophyll-A is at 428 nm and 660 nm, while absorption peak of chlorophyll-B is at 453 nm and 643 nm. We report the modification of blue LED using hybrid polymer doped with Nile Red. In order to match the total absorption spectra of chlorophyll-A and chlorophyll-B, the emission spectrum of the modified blue LED was taken out by using the wavelength conversion material. We modified the blue LED by covering the blue LED of 450 nm as excitation source with precursor of red wavelength conversion material. The red wavelength conversion material was prepared by doped precursor of TMSPMA hybrid polymer with organic phosphor of Nile Red. The precursor of hybrid polymer was synthesized using sol-gel process and then it was doped with 0.1% Nile Red. In order to freeze the precursor of these conversion material, we employed UV photopolymerization process. The modified blue LED has two emission peaks, which are at 448 nm (blue emission) and at 651 nm (red emission). The optimum spectrum profile of the modified blue LED has similar range as the total absorption spectra of chlorophyll-A and chlorophyll-B that obtain using Nile Red with the mass of 2.9 μg and the driven current of 60 mA. This result has a potential application for the artificial lighting in the photosynthesis process of horticultures at indoor plantation.

Karakterisasi Poli(3-(Trimethoxysilyl)propyl methacrrylate)) yang dimodifikasi dengan Inhibitor Cerium Sebagai Bahan Proteksi Korosi Baja Karbon

Korosi merupakan peristiwa pengrusakan logam akibat bereaksi secara kimia dengan lingkungan sehingga menimbulkan kerugian. Dalam upaya mencegah terjadinya korosi pada material baja karbon API 5L X65, maka dilakukan proses pelapisan dengan menggunakan Poli(3-(Trimethoxysilyl)propyl methacrrylate)) . Poli (TMSPMA) merupakan bahan yang berpotensi untuk memproteksi material dari korosi. Untuk itu ditambahkan inhibitor Cerium Nitrate Hexahydrate , penambahan inhibitor ini bertujuan untuk membuat lapisan proteksi bersifat aktif dan pasif, sehingga ketika lapisan yang bersifat pasifnya rusak masih ada bagian aktifnya yang melindungi material. Bahan prekursor polimer hibrid dibuat dari monomer TMSPMA murni dan yang dicampur inhibitor dengan teknik sol-gel . Hasil yang didapat terbentuknya gel kental yang bening dan menghasilkan yield sebesar 89,58%. Prekursor polimer hibrid yang diperoleh kemudian dikarakterisasi dengan FTIR untuk melihat gugus fungsinya, dengan cara bahan prekursor tersebut dilapiskan pada substrat silikon, hasil karakterisasi FTIR menunjukkan adanya gugus anorganik dan organik yang mengalami polimerisasi. Selanjutnya prekursor polimer hibrid dilapiskan pada baja karbon kemudian dikarakterisasi dengan metoda Potensiostat untuk mengetahui arus korosinya, hasil yang diperoleh menunjukkan penurunan arus korosi dari 1,868 mm/th menjadi 0,02 mm/th

Reduction Kinetics of Thermally Reduced Graphene Oxide Thin Films

We report an experimentalstudy of thermal reduction of graphene oxide (GO) under nitrogen flow.Ultrathin films of GO were prepared on quartz glass substrates by spin-coatingfrom 3 mg/ml aqueous solutions of GO. These films were annealed at 50 °C under vacuum overnight before thermal reduction.The films were exposed to temperatures of 100 °C, 150 °C, 200 °C, 300 °C, 400 °C, 500 °C and 800 °C under nitrogen flowing. We used UV-Vis absorption spectroscopy tomonitor the change of absorption spectra caused by thermal reduction. We observed a significant change ofabsorption spectra due to formation of reduced graphene oxide (RGO). We found that thermal reduction startedalready at 100 °C, but proceeded significantly faster at heating temperatures higherthan 200 °C.

Conduction Properties of PTMSPMA-PEO and its Application as Polymer Electrolyte in LiFePO4 Batteries

The conduction properties of polymer composite PTMSPMA-PEO as electrolyte in lithium-ion batteries has been investigated. The gel polymer of PTMSPMA was synthesized by sol-gel method using 3-(Trimethoxysilyl)-propyl-methacrylate as monomer. The Composite of PTMSPMA-PEO with various composition (50:50, 60:40, 80:20; wt%) was made by solution method. The polymer electrolyte was composed of LiClO4 salt dissolved in propylene carbonate and mixed with PTMSPMA-PEO. The ionic conduction of polymer electrolyte was characterized by electrochemical impedance spectroscopy. The battery performance of polymer electrolyte was estimated with coin cell, where LiFePO4 was used as cathode and graphite was use as anode. The high ionic conductivity of 6.67 x10-3 S/cm has been observed for the composition of PTMSPMA : PEO 60:40 (wt%) in room temperature. The performance of cell battery was investigated by charge-discharge using constant current 0,1 mA/cm2. The operational voltage of cell battery is around 1 V until 2.2 Volt with Columbic efficiency around 60%.

The technique of Lloyd-Mirror interference for fabrication of 1D and 2D grating in hybrid polymer material

The grating is a periodic structure which commonly used in optical technology, such as frequency splitter, optical filter, spectrophotometer and laser resonator. In this paper, we reported the results of grating fabrication of hybrid polymer by use of Lloyd Mirror interference method. The grating with the shape of 1D, 2D square and 2D hexagonal was successfully fabricated. Various of the grating period is relatively easy to be fabricated by controlling the incident angle of laser. The surface profile of the grating was observed using Atomic Force Microscopy (AFM). The AFM measurements show the grating period vary in the range of 350 nm to 1000 nm for 1D grating and 390-410 nm for 2D grating. The analysis of the AFM image showed the depths of gratings were vary from 20 nm to 100 nm.