Bambang Soegijono

Microstructural and Magnetic Properties of Ti2+-Mn4+ Substituted Barium Hexaferrite

In this paper we report the microstructure and magnetic properties of Ti4+-Mn4+ ions substitued barium hexaferrites (BHF) with formula of BaFe12-2xMnxTixO19 (x = 0.2, 0.4, 0.6 and 0.8) which prepared by mechanical alloying and successive sintering at 1100 °C. Ti4+-Mn4+ ions were obtained from TiO2 and MnO precursors which were mechanically alloyed together with BaCO3 and Fe2O3 precursors. X-ray diffraction patterns for sintered samples confirmed that the materials are consisted with single phase BHF structure. Unit cell volume and crystallite size was found increase with increasing x. The crystallite size for all samples was below 70 nm, but microstructure observation shown that the particle size is in range of 200 - 400 nm, which concluded that the grains are polycrystalline. The saturation magnetization is increases up to x = 0.4 and decrease for higher x values, while the coercivity remain decreases monotonically. These results were interpreted in terms of the site preferential occupation of Ti2+ and Mn4+ at low level substitution.

The Carbon Black Sonofication Effects on Vulcanisate Properties of Natural Rubber

The mechanical properties of natural rubber can be enhanced by the addition of carbon black. The mechanical properties change is highly affected by particle size and carbon black structure used. A modification of N660 carbon black was conducted in the research by sonoficating the carbon black for 3 and 5 hours (N600-M3; M5). The results of adding modified carbon black were characterised by Particle Size Analysis (PSA), Scanning Electron Microscopes - Energy Dispersive Spectrometry (SEM-EDS) and Thermogravimetric Analysis (TGA). The addition of modified carbon black shows bound rubber, thermal properties, and mechanical properties such as tensile strength, elongation at break and modulus 300% on the vulcanisate produced were increased from the vulcanisate that had been filled with N660 natural (N660-N). Keywords: natural rubber, carbon black, particle size, sonofication, characterisation

Simple Recipe to Synthesize BaTiO3-BaFe12O19 Nanocomposite Bulk System with High Magnetization

Barium titanate BaTiO3 (BTO) - barium hexaferrite BaFe12O19 (BHF) nanocomposite could be as a raw material of multiferroic. Multiferroic is a class of materials with coupled electric, magnetic and structural order parameters that yield simultaneous effects of ferroelectric, ferromagnetism and ferroelasticity in the same material. This material has potential applications in such as spintronic devices and sensors. This work was an earlier research towards formation of multiferroic material. Knowing magnetic properties that will lead to a better understanding of magnetoelectric coupling in multiferroic material is the objective of this research.The samples were BTO and BHF prepared by sol-gel and then were mixed to synthesize composite in bulk system by a conventional techniques in various of weight fraction between BTO : BHF = 1:1 ; 1:2 and 1:3, then samples were sintered at 925°C for 5, 10 and 15 hours for each fraction respectively. Composite phase study was carried out using X-Ray Diffraction (XRD). MPS Magnet Physik EP3 Permagraph L was used to characterize magnetic properties. No residual phases were identified in the XRD analysis for all parameters. The peaks can be only indexed to BaTiO3 and BaFe12O19 phases for all parameters respectively confirming the formation of a BaTiO3-BaFe12O19 composite system. Barium titanate retains its tetragonal structure while barium hexaferrite exhibits hexagonal structure. For weight fraction of BaFe12O19 until 2 parts there is an increase of intrinsic coersive and saturation magnetization value. The maximum values of intrinsic coersive for samples with 5, 10 and 15 hours sintering are of 361.3 kA/m, 359.0 kA/m and 391.6 kA/m respectively and the maximum values of saturation are of 0.1515 T, 0.1516 T and 0.1414 T respectively leading to good characteristics of multiferroic materials.

Boron Carbide B25C and B8C18 Synthesized Using Boric Acid-Glucose and Boric Acid-Active Carbon at Low Temperature without Coreductor Materials

This study examines the formation of Boron carbide with a wide homogeneity range B8C18 and B25C, from boric acid-glucose and boric acid-active carbon as precursor materials. The samples was analysed by means of X-ray diffraction and Fourier Transform Infrared spectrometer. X-ray diffraction pattern was analysed by GSAS software. X ray diffraction pattern of B8C18 shows peaks at 27o, 39o, 45o, 65o and 79o, orthorhombic crystal system and lattice parameters a = 13.640 Ǻ, b = 7.8500 Ǻ and c = 12.910 Ǻ and space group P212121, whereas for B25C sample show peaks at 2θ angle 28o and 40o, tetragonal crystal system, and the lattice parameters a = b = 8.753 Ǻ and c = 5.093 Ǻ and space group P-4 2 m. FTIR results show that for B8C18 have absorption bands with B-C bond at 1196.5 cm-1, 0-H 3216.7 cm-1 and B-O at 1477.1 cm-1, whereas the formation B25C have absorption bands with B-C bond at 1195.1 cm-1, O-H 3216.7 cm-1 and B-O 1460.8 cm-1.

Magnetic Behaviors of BaTiO3-BaFe12O19 Nanocomposite Prepared by Sol-Gel Process Based on Differences in Volume Fraction

Barium titanate BaTiO3 (BTO) - barium hexaferrite BaFe12O19 (BHF) nanocomposite could be as a raw material of multiferroic. Multiferroic is a class of materials with coupled electric, magnetic and structural order parameters that yield simultaneous effects of ferroelectric, ferromagnetism and ferroelasticity in the same material. This material has potential applications in such as spintronic devices and sensors. This work was an earlier research towards formation of multiferroic material. Knowing magnetic properties that will lead to a better understanding of magnetoelectric coupling in multiferroic material is the objective of this research.The samples were BTO and BHF prepared by sol-gel and then were mixed in bulk system by a conventional techniques in various of volume fraction between BTO : BHF = 1:1 ; 1:2 and 2:1, then samples were sintered at 925°C for 5, 10 and 15 hours. Composite phase study was carried out using X-Ray Diffraction (XRD). MPS Magnet Physik EP3 Permagraph L was used to characterize magnetic properties. XRD results confirm that composite with volume fraction of BTO : BHF = 1:1 with sintering at 925°C for 5 hours consists only of 2 phases BTO and BHF. There is impurity phase BaFe2O4 beside BTO and BHF phases at samples with volume fraction BTO:BHF = 1:2 and 2:1 for longer sintering. Composite with volume fraction of BTO:BHF = 1:1 for 5 hours sintering has a high value of remanent magnetization 0.081 T and the lowest value of intrinsic coersive 333.6 kA/m leading to good characteristics of multiferroic materials.

Influence of Ba/Fe mole ratios on magnetic properties, crystallite size and shifting of X-ray diffraction peaks of nanocrystalline BaFe12O19 powder, prepared by sol gel auto combu

Barium hexaferrite BaFe12O19 (BFO) is of great importance as permanent magnets, particularly for magnetic recording as well as in microwave devices. Nano-crystalline BFO powders were prepared by sol gel auto combustion method in citric acid - metal nitrates system. Hence the mole ratios of Ba/Fe were variated at 1:12; 1:11.5 and 1:11. Ratio of cation to fuel was fixed at 1:1. An appropriate amount of amonia solution was added dropwise to this solution with constant stirring until the PH reached 7 in all cases. Heating at 850oC for 10 hours for each sample to get final formation of BFO nanocrystalline. The data from XRD showing the lattice parameters a,c and the unit-cell volume V, confirm that BFO with ratio 1:12 has same crystall parameters with ratio 1:11. Ratio of Ba/Fe 1:12 and 1:11 have diffraction pattern similarly at almost each 2 θ for each samples. Ratio of Ba/Fe 1: 11.5 has the finest crystallite size 22 nm. Almost diffraction pattern peaks of Ba/Fe 1:11.5 move to the left from of Ba/Fe 1:12 the...

Effects of the geometry factor on the reflection loss characteristics of the modified lanthanum manganite

The synthesis and characterization of modified lanthanum manganite materials by using mechanical milling technique have been performed. This magnetic material is prepared by oxides, namely lanthanum oxide, barium carbonate, iron oxide, titanium dioxide, and manganese carbonate. The mixture was milled for 10h, compacted at 5000 psi into pellets with three kinds of different thickness (d = 1.5, 2.0 and 4.0 mm, respectively) and then sintered at temperature of 1000 °C for 10h. The refinement results of x-ray diffraction pattern showed that the sample is single phase. The sample had composition in accordance to stochiometry composition. The geometry factor consists of the particle morphology observed using scanning electron microscope and thickness measured millimeter device. The microstructure analyses shows that the particle shapes was aggregates with the particle sizes distributed homogeneously on the surface of the sample. The results of the microwave absorption indicated that there were three of absorption peak frequency at 9.9 GHz, 12.0 GHz, and 14.1 GHz. The microwave absorption of the sample increases with increasing thickness of absorption area. We concluded that the increasing thickness of absorption region resulted new resonance frequencies, and the new resonance frequencies are joined to each other to form a wider resonance frequency and it is known as a broadband absorber. The first section in your paper.

Critical exponent analysis of lightly germanium-doped La0.7Ca0.3Mn1-xGexO3 (x = 0.05 and x = 0.07)

We have used a critical behavior study of La0.7Ca0.3MnO3 (LCMO) manganite perovskites whose Mn sites have been doped with Ge to explore magnetic interactions. Light Ge doping of 5 or 7 percent tended to produce LCMOs with second order magnetic transitions. The critical parameters of 5- and 7-percent Ge-doped LCMO were determined to be TC = 185 K, β = 0.331 ± 0.019, and γ = 1.15 ± 0.017; and TC = 153 K, β = 0.496 ± 0.011, and γ = 1.03 ± 0.046, respectively, via the modified Arrott plot method. Isothermal magnetization data collected near the Curie temperature (TC) was split into a universal function with two branches M(H,e) = |e|βf±(H/|e|β+γ), where e=(T–TC)/TC is the reduced temperature. f+ is used when T>TC, while f is used when T<TC. Such results demonstrate the existence of ferromagnetic short-range order in lightly Ge-doped LCMOs. Notably, doping with Ge at high concentrations tends to generate long-range ferromagnetic order.

Effect of expanded organoclay by stearic acid to curing, mechanical and swelling properties of natural rubber nanocomposites

The interlayer basal spacing of organoclay (OC) could be increased with stearic acid (SA) added, thus OC changed into expanded organoclay by SA (OCSA). The effect of various loadings of OCSA on the curing, mechanical and swelling properties of natural rubber (NR) nanocomposites were studied. The natural rubber/expanded organoclay (NR/OCSA) nanocomposites were prepared by melt intercalation using a laboratory open mill. The curing characteristics of NR compounds were determined using a Moving Die Rheometer (MDR). The X-ray Diffraction (XRD), Attenuated Total Reflectance Infrared (ATR-IR) Spectroscopy and Field Emission Scanning Electron Microscopy (FESEM) were used to study the dispersion of OCSA in the NR matrix. The mechanical properties of NR/OCSA nanocomposites such as tensile strength, elongation at break and hardness were determined using ISO standard and swelling of NR/OCSA nanocomposites in toluene were determined using ISO 1817. The results showed that the SA intercalated into the gallery of OC and reacted with the hydroxyl groups in OC. It was indicated with the shifting of the negative peak 1,700 to 1,723 cm-1 in the ATR-IR spectrum and increase the d-spacing of OC. The adding of various loadings of OCSA into NR could increase the torque and accelerate the curing of nanocomposites and it also could increase the mechanical and swelling properties of nanocomposites. The change in modulus at 100% elongation significantly increased with increasing the OCSA load until maximum loading at 10 phr. This trend was same with the hardness and modulus at 300% elongation. Meanwhile, the improvement of tensile strength and elongation at break was higher at 4 phr OCSA compared with the other loading. The increase of mechanical and swelling properties of NR/OCSA nanocomposites was due to intercalation/exfoliation of OCSA in NR matrix. It was revealed by appearing of the out-of-plane Si-O-(Al) stretch with peak value 1080 cm-1 in the ATR-IR spectrum and the peaks of OCSA in the XRD pattern was disappeared until the loading of OCSA 8 phr and the thickness of morphology of OCSA below 100 nm.

Pengamatan In-Situ Tekanan dan Temperatur pada Pembentukan MgH2/Ni melalui Metode Reactive Mechanical Alloying (RMA) untuk Aplikasi Material Penyimpan Hidrogen

The observation on reactive mechanical alloying (RMA) process had been done to form MgH2 material with adding Ni nanoparticles as catalist for hydrogen storage material applications. Pressure and temperature of material forming were recorded by microcontroller set for 30 minutes. Mg with adding Ni 5 wt % was milled by High Energy Ball Mill (HEBM) at H2 atmosphere in 1 atm of pressure. The measurement results showed that the pressure had been changed and temperature also changes up to 38oC. This process proves that the alloying betwen Mg and H2 had been formed. The X-ray diffraction pattern identify MgH2 phase. SEM image showed the morphology of MgH2 particles.