Priyo Sardjono

Superhydrophobic surface as a fluid enhancement material in engineering applications

In this study, a superhydrophobic surface and its relation to the enhancement of the droplet fluid dynamics to the surface of the object materials was investigated. As the comparison, hydrophilic and uncoated surface of an object also investigated. The investigations used height of impact at 89 mm. The high quality speed camera is employed to investigate the droplet dynamic on a copper foil and a calcium fluoride surfaces. Both of the materials are coated with superhydrophobic and hydrophilic surfaces separately. The droplet diameter was analyzed using the program PHANTOM. The droplet contact angle was analyzed by the Goniometry method. The water was dropped on the calcium fluoride and the copper foil using a syringe (sharp tip) with initial droplet diameter of 1.9 mm. To record the droplet fluid shape, the photo micro sensor was placed inside the trigger box below the syringe. The results showed that the superhydrophobic surface both on copper foil and calcium fluoride enhanced the mobility of a droplet compared to the hydrophilic and the uncoated surfaces. The results showed that the maximum droplet diameter on the copper foil coated by the superhydrophobic, the hydrophilic and the uncoated surfaces are 4.7, 5.0, 5.2 mm, respectively; and for the calcium fluoride are 4.5, 5.1 and 5.5 mm, respectively. Meanwhile, the results for the droplet contact angle on the copper foil coated by the superhydrophobic, the hydrophilic and the uncoated surfaces are 20°, 90°, 160°, respectively; and for the calcium fluoride are 25°, 95°, 165°, respectively.

Effect of composition polymeric PVB binder on physical, magnetic properties and microstructure of bonded magnet NdFeB

The bonded magnet NdFeB has been made by using the hot press method and using Poly Vinyl Butiral (PVB) as a binder. The composition of polymeric binder was varied: 0, 2, 4, 6 and 7 % of weight. Both raw materials are weighed and mixed according to the composition of PVB, then formed by hot press with a pressure 30 MPa, a temperature of 160 ? C and holding time for 30 minutes. The bulk density was measured by using Archimedes method. SEM observation was done to determine the microstructure of bonded magnet NdFeB. The flux magnetic value was measured by using a Gauss meter and the measurement of hysteresis curves was done to know value of remanence Br, coercivity Hc and energy product BHmax by using VSM. According to the characterization results show that the best composition of PVB is 2 of weight. The properties of bonded magnet NdFeB of those compositions are the bulk density around 5.66 g/cm3. Flux Magnetic value: 1862 Gauss, Br value: 5000 kGauss, Hc value: 8.49 kOe and BHmax value : 5.10 MGOe. According of SEM observation results show that the polymer matrix of PVB appears to have covered on all surface grain and filled grain boundary.

Sinthesis and Characterization of Nd2Fe14B Powder from Nd-Fe-B Flakes by Wet Mechanical Milling and Heat Treatment

The Nyodimium-Iron-Boron (Nd-Fe-B) based materials are known as the best type of magnetic materials and it contains a magnetic phase Nd2Fe14B. The Nd-Fe-B alloy Flakes is one of the main raw material for producing of NdFeB-based permanent magnets and the size of Nd-Fe-B flakes are still coarse. Synthesis of Nd2Fe14B powder has been done by a wet mechanical milling method using the High Energy Milling (HEM) for 10 hrs and continued by heating at 600°C in vacuum condition (10-4 Pa). This process is used to produce a fine powder Nd2Fe14B for making of permanent magnets. The milling medium was used a toluene (pa-Emerck)) to protect of particle from oxidation during the milling process. After milling processes, the samples were measured distribution particle size by using Particle Size Analyzer (PSA). Microstructure analysis has been conducted by using X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM/EDX) for samples before milling and sample after heating. The characterization results show that after milling 10 hours, it was obtained fine powder with average size about 1.35 μm. According to SEM/EDX and XRD analysis show that the crystal structure of the sample before milling was different compared to the sample after heating. It is found new magnetic phase with formula Nd2Fe14B.

Preparation and Characterization of Hybrid Bonded Magnet Ba-Ferrite/NdFeB with Epoxy Resin

Hybrid bonded magnet Ba-Ferrite/NdFeB with 5% wt Epoxy Resin (ER) as polymer binder hsa been developed with variations in BaFe12O19 to NdFeB weight ratio. The variation of the BaO6Fe2O3 : Nd-Fe-B weight ratio are 90%:10%; 80%:20%; 70%:30% and 60%:40%. The magnetic particle consist of Ba-Ferrite and NdFeB were mixed until homogenize and compacted by using hydraulic press machine with 8 Tonf force to form a disc shape sample. The disc sample was dried using vacuum dryer with 10 mm bar pressure at 80°C for one hour before being magnetized using impulse magnetizer. The best %wt composition ratio of Ba-Ferrite/NdFeB is 70%/30% and 60%/40%. The hybrid bonded magnetic properties at the best %wt composition ratio are: bulk density = 4.28-4.43 g/cm3, FM = 1057-1121 Gauss, Br = 3.46-3.70 kG, Hc = 3.25-3.70 kOe, and BHmax = 1.60-1.70 MGOe.

Microstructure, Physical Properties, and Magnetic Flux Density Analysis of Permanent Magnet BaFe12O19 using Milling and Sintering Preparation Methods

The purpose of this experiment is to analyze the influence of sintering temperature to the microstructure, physical, and magnetic properties of BaFe12O19 materials. The permanent magnet BaFe12O19 was made by using milling and sintering method, BaFe12O19 commercial powder was used as the raw material in this experiment. The raw material was pulverized by using ball mill for 15 hours and compacted at 400 MPa pressure to obtain a 16mm diameter and 4mm thick pellet. The pellet was sintered with 10oC/minute heating rate at various temperature ranges of 1050, 1100, 1150, and 1200oC for 1 hour. The microstructure and particle size of the pellet was investigated using XRD, SEM, and Particle Size Analyzer (PSA). The result shows that the milled powder has hexagonal BaFe12O19 crystal structure as the dominant phase, inhomogeneous size and shape of the grains, and average particle size is 19.60 pm. The bulk density measurement, shrinkage, and magnetic properties of the sintered samples were being observed and analyzed. It was found through this experiment that the optimum sintering temperature is 1150oC to obtain optimum bulk density (4.71 g/cm3), constant shrinkage (12.07%), 550 Gauss magnetic flux density, 1.79 kGauss remanence Br, and 1.75 kOe coercivity.

Crystal structure and magnetic properties of Nd2Fe14B powder prepared by using high energy milling from elements metal Nd,Fe,B powders

The Nd2Fe14B powder has been made by using High Energy Milling (HEM) from mixed metal powders Iron (Fe), Neodymium (Nd) and Boron (B). The Nd, Fe and B powders were mixed according stoichiometric composition (atomic ratio Nd:Fe:B = 2: 14: 1) and milled and milling time was varied in 10, 20, and 40 hours by using HEM. Toluene liquid was used as milling media to protect of metal powders from oxygen. The measurement result of x- ray diffraction show that the optimum Nd2Fe14B phase already formed about 69,46% after milling 40 hours with crystallite size about 25.64 nm. The magnetic properties of milled powders were measured by using VSM at room temperature. The highest value of magnetic properties are obtained at powder milled in 40 hours, at this condition, it is obtained Ms = 122 emu/g, Mr = 81 emu/g, Hc = 5.54 kOe and BHmax = 11.01 MGOe.

Thermal Analysis and Magnetic Properties of Lanthanum Barium Manganite Perovskite

The lanthanum manganite is the family of magnetic materials which had the magnetic properties are varied depend on the composition. This study has been carried out synthesis and characterization of thermal and magnetic properties of the lanthanum barium manganite perovskite. The perovskite material is prepared by oxides, namely La2O3, BaCO3, and MnCO3. The mixture was milled for 10h and then sintered at temperature of 1000 °C for 10h. Thermal analysis and magnetic properties are measured by differential thermal analysis (TG-DTA) and vibrating sample magnetometer (VSM), respectively. Decomposition phase of MnCO3 become MnO occurred at temperatures around 390 °C with releasing in CO2. Since lanthanum manganite has a stable ion configuration, magnetic properties of these systems are built from MnO phase transformation become α-Mn2O3 is arrayed anti-ferromagnetic due to the presence of lanthanum in the system. And this anti-ferromagnetic behavior occurred due to magnetic interactions between Mn3+ adjacent ions through super-exchange mechanism. While lanthanum barium manganite had a less stable ion configuration, therefore magnetic properties of these systems are built from phase transformation MnO become α-Mn3O4 is arrayed ferromagnetic due to the presence of lanthanum and barium in this system. The presence of lanthanum and barium trigger in the emergence of mixed-valence Mn ions, so that occur to magnetic interaction between Mn3+ and Mn4+ through the double-exchange mechanism. We concluded that the characteristic of magnetic properties on the lanthanum barium manganite system perovskite is affected by thermal properties, fundamental properties of raw material and the result of reaction is formed.

Microstructural Studies of (Ba0.7Sr0.3Fe12O19)1-x - (Ba0.7Sr0.3TiO3)x with x = 0.2, x = 0.5 and x = 0.8 Composite System by Mechanical Alloying Process

In this paper, we report our investigation on material structure analysis of (Ba0.7Sr0.3Fe12O19)1-x-(Ba0.7Sr0.3TiO3)x with x = 0.2, x = 0.5 and x = 0.8 composite system prepared by a mechanical alloying process to promote feroic properties. It is shown that the x-ray diffraction patterns of each composition for the composite materials are the same. It consisted of the mixture for the two phases. The average of particle size for each respective phase in the composite materials was found initially increased, up to 18-20 μm after mechanically milled for 40 hours, then start to decreased to a smaller size ~ 8-10 μm after 80 hrs milling time. However, a plot of particle size against the milling time for each composite phase shown a trend of further reduction in the mean particle sizes. In addition, the x-ray traces of dense pellet samples after sintering the milled powders at a temperature of 1100 °C showed broadened diffracted peaks pattern due to fine crystallites in the samples. Results of mean crystallite size determination of respective phases in the composite samples showed the same trend, a decrease with milling time toward values about 10 nm at 80 hrs milling time. Hence, sintering to the milled particles has promoted the formation of nanocrystal containing particles. When compared between the mean particle size and mean crystallite size of respective phase in the composite samples, the mean crystallite size for magnetic phase (B7S3F) was found more than 100 times smaller than the mean particle size of composite particles. However, finer mean crystallite sizes were found in the ferroelectric phase (B7S3T) in which the mean was about 200 times smaller than the mean particle size.

Preparation and characterization of bonded NdFeB permanent magnet

Preparation and characterization of bonded NdFeB permanent magnets have been performed. NdFeB powder was milled by using the High Energy Milling (HEM) for 3 and 10 hours. The bonded magnets were prepared by NdFeB powder (50–200 mesh) and adhesive epoxy resin with composition variation of 93:7, 95:5, 90:10, 80:20, 70:30, 60:40, and 50:50 (% wt.), respectively. The mix powder was molded using a pressure of 100 kg/cm2 and then annealed at 150 °C for 4 hours. The result of particle size analysis by using PSA showed that the average particle size of NdFeB powder after milling time for 10 hours was 0.37 μm. Based on the differential thermal analysis (DTA) result, it was obtained that the optimal annealing temperature of the mixtures is at 150 °C. The result of the phase analysis by using XRD showed that the major phase is Nd2Fe14B and the minor phase is Fe. The surface morphology was observed by using SEM. The results of SEM showed that the particle shape disordered with the particle size within a range of 0.1–...

Effect of CeO{sub 2} addition on the properties of FeAl based alloy produced by mechanical alloying technique

Iron aluminides based on FeAl is notable for their low materials cost, ease of fabrication and good corrosion, suffixation and oxidation resistance. However, the application based on these unique properties still require the development of Fe-Al based alloy since it shows some drawbacks such as a lack of high temperature strength and low ductility. To improve the mechanical properties of FeAl based alloy, ceria (CeO2) will be added to this compound. FeAl based alloy produced by the mechanical alloying (MA) technique. The developed specimens then assessed with respect to oxidation behaviour in high temperature, scale microstructure and hardness. The surface morphologies of the alloy evaluated and observed using scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscopy (EDX). The phase structures of oxide scale formed on them were identified by X-ray diffraction (XRD). The results found that the FeAl intermetallic compound containing CeO2 0.5 wt.% is less pores and CeO2 1.0 wt.% is mor...