nan Widyastuti

Microstructure and Magnetic Properties of Barium Hexaferrite Produced by Sol Gel Auto Combustion for Radar Absorber Material (RAM) Application

Barium hexaferrite (BaFe12O19) with hexagonal structure has been known as the high performance magnetic for Radar Absorber Material (RAM). Barium hexaferrite (BaM) was synthesized by sol gel auto combustion to get an homogeneous nanoparticle of BaM. Barium hexaferrites obtained from solution mixture between barium nitrate and ferri nitrate nonahidrat with precipitation of ion barium (Ba2 +) and ferri (Fe3 +) by solution of sodium hydroxide. Sample prepared with mol ratio of Fe / Ba 11 then added ammoniac in order that pH varies become 7,5; 9; and 11. Citric acid added in order that happen process of combustion. The stirring time was varieties by 1, 2, 3 hours. The effect of pH, stirring time, microstructure, phase,and magnetic properties were investigated using X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and a vibrating sample magnetometer (VSM). The results showed that the highest coercivity was 0.6 Tesla and the smallest crystal size 414.409 nm was obtained for pH 7.5 and stirring time 2 hours. The largest magnetic saturation 55.54 emu /g was reached for pH 7.5 with stirring time 1 hour

Mechanical and Thermal Properties of Unsaturated Polyester/Vinyl Ester Blends Cured at Room Temperature

Unsaturated polyester (UP) resin containing aromatic ring was blended with vinyl ester (VE) at wide range composition (10, 20, 30, 40,and 80 wt.%) using mechanical blending method. The blends were cured at room temperature using methyl ethyl ketone peroxide (MEKP) (4 wt.%) as catalyst initiator without the presence of catalystaccelerator. The effect of vinyl ester composition on theenhancement of mechanical and thermal properties of unsaturated polyester/vinyl ester blends was investigated. The polymer blends were characterized by Fourier Transform Infra Red (FTIR)spectroscopy, tensile testing, hardness testing, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). IR spectra showed UP and VE peaks. The curing copolymerization reactionoccurred at vinyl (C=C) bonds. The addition of vinyl esters enhanced mechanical and thermal properties. The UP/VE blends showed homogeneous morphology, transparent and copolymer thermoset blend.

Improved Energy Saving for R22 Building Air Conditioning Retrofitted with Hydrocarbon Refrigerant, Study Case: Civil Engineering Department of ITS

Sepuluh November Institute of Technology (ITS) encourages the ECO Campus program. The program enables ITS to systematically identify, evaluate, manage and improve their environmental performance and practices. One of the program issue is energy saving in building. The energy saving effect of an air-conditioning system retrofit project is analyzed by Energy Conservation Opportunities (ECOs) Method. These ECOs are assessed in terms of their costs and benefits, and an economic comparison to rank the various refrigerants. Finally, an Action Plan is created where certain ECOs are selected for implementation. Civil Engineering Department has a responsibility to design infrastructure and green building concept planning. This department also has the largest energy consumption in this faculty comparing the other department. The energy consumption on this Department is 60829 kWh/month. The value of IKE is 13.39 per month with the largest electrical energy consumption in air-conditioning system is 57% from total consumption. The energy used of air-conditioning sytem is 523.692 kWh. The energy saving opportunities by CFC retrofitting with hydrocarbon can save its power consumption about 20%. It also saving cost and reducing the electricity bill of 1643871.838 IDR/month. The payback period of investment costs of retrofit R-22 to Hydrocarbonis about 13 month.

Al2O3 – SiO2 Coating by Flame Spray for Thermal Barrier Coating Application

Nozzle is one crucial part of rocket. In this research, the nozzle was made by AISI 4340 coated by termal barrier coating (TBC). The TBC material is Al2O3SiO2 composite, with different variation: Al2O3 20% SiO2; 70% Al2O3 30% SiO2; and 60% Al2O3 40% SiO2. The aim of this research to observe the composittion which will produce optimum adhesive strength and the most widely formed mullite phase. Mullite is an expected phase formed from composite and it has thermal resistance during 1300°C. Coating process was conducted by flame spray with variation of plies. The effect ratio, plies, microstructure, phase, and adhesive strength of TBC were investigated using Scanning Electron Microscope (SEM), X-ray diffraction (XRD),) and adhesion testing. The results showed that the highest adhesive strength was 16 MPa for 20%SiO2 with 2 plies. The highest mullite forming was TBC. After heat treatment, it was found that the mullite phases were most widely formed at a composition of TBC 30% SiO2-70% Al2O3.

Effect of Weight Fraction of Carbon Black and Number of Plies of E-Glass Fiber to Reflection Loss of E-Glass/Ripoxy Composite for Radar Absorbing Structure (RAS)

Nowadays, studies on investigating radar absorbing structure (RAS) using fiber reinforced polymeric (FRP) composite materials are becoming popular research field because the electromagnetic properties of FRP composites can be tailored effectively by just adding some electromagnetic powders, such as carbon black, ferrite, carbonyl iron, and etc., to the matrix of composites. The RAS works not only as a load bearing structure to hold the antenna system, but also has the important function of absorbing the in-band electromagnetic wave coming from the electromagnetic energy of tracking systems. In this study, E-glass fiber reinforced ripoxy resin composite was fabricated by blending the conductive carbon black (Ketjenblack EC300J) with the binder matrix of the composite material and maximizing the coefficient of absorption more than 90% (more than −10 dB) within the X-band frequency (8 – 12 GHz). It was measured by electrical conductivity (LCR meter) and vector network analyzer (VNA). Finally, the composite R...

Powder metallurgy process for manufacturing core projectile

Bullets are part of the defense equipment which the development is very rapid. There are a variety of forms but the bullet Lead is a metal that has always been used for applications projectiles. Lead core constituent materials are combined with antimony. In this research will be conducted by making the material for the core projectile with Tin Lead. The addition of Tin will increase the stiffness of Lead which is soft in nature. The Lead Tin composition variation was given in 10% weight of Sn. The manufacturing process using powder metallurgy using temperature and holding time variations of sintering at 100, 150, and 200°C for 1,2, and 3 hours. XRD samples will be tested to determine the form and phase morphology was observed using SEM-EDX. These results revealed that Pb-10%wtSn Composite which is sintered in temperature 200°C for 3 hours has the greatest density, 10.695 g/cm3 as well as the smallest porosity, 2.2%. In agreement with theoretical analysis that increasing higher temperature and longer holdi...

Study on PbSn Composites Produced by Powder Metallurgy as Core Bullet Projectile

PbSn composites have been prepared by powder metallurgy for Advance Energy Transfer Bullet Application. Sn compositions was variety 5, 10, 15wt%. The compacting pressure performed at 10, 15, and 20 MPa. Temperature and holding time of sintering constantly in 150OC for 2 hours. The microstructure and mechanical performance of PbSn composites are investigated by Scanning Electron microscope (SEM), and compression tests. The results show that the Pb-15%wtSn Composite which is compacted in 20 MPa has result greatest density which was 10.969 gr/cm3 and the smallest porosity (1.5%). Mechanical performance test of PbSn composite show the greatest hardness, compressive strength and modulus elasticity reach are 11.01 HV, 46.82 MPa and 34.96 GPa

Tensile and Thermal Properties of Bambusa arundinacea and Dendrocalamus asper Culm Fibers

Fibers from the culms of Bambusa arundinacea and Dendrocalamus asper were extracted mechanically and chemically treated using alkaline solution. Tensile and thermal properties of both bamboo fibers were examined. Tensile test on the bamboo fibers showed that Bambusa arundinacea fibers have higher strength and stiffness yet lower elongation than Dendrocalamus asper fibers. When the fibers were chemically treated, similar trend on tensile properties was observed but at lower magnitude compared to those shown by untreated fibers. Further characterization revealed that Bambusa arundinacea fibers are of higher fiber diameter and higher cellulose content compared to Dendrocalamus asper fibers. Thermogravimetric analysis showed that both fibers with same treatment have similar thermal stability, with chemically treated fibers are of higher thermal stability than untreated ones. The chemical treatment removed the lignin from the fiber structure, and affected tensile and thermal properties of both bamboos fibers.