nan Triwikantoro

XRD line‐broadening characteristics of M‐oxides (M = Mg,Mg‐Al, Y, Fe) nanoparticles produced by coprecipitation method

Simple coprecipitation method has been used to produce nanoparticles of MgO (magnesia), MgO⋅Al2O3 (spinel), Y2O3 (yttria) and Fe3O4 (ferrite). The raw materials were, in respective, magnesium powder, magnesium and aluminium powders, ytrria powder, and natural sand. The coprecipitation included the use of suitable acid and base to dissolve the powders or sand and to produce precipitates, as well as the use of water to wash and purify the precipitates, and drying at relatively low temperatures, namely lower than 100° C, followed by heating at 450° C, 750° C, 600° C and 200° C to produce magnesia, spinel, yttria and ferrite nanopowders, respectively. X‐ray diffractometry was used to characterise the purity and nanocrystallinity of the final powders. It was found qualitatively that the powders were of high purity. Further line‐broadening analysis using single‐line and Rietveld‐based softwares was performed to reveal the nanocrystallinity of the powders. Different line breadth values were found for the powders...

Synthesis of SiO2 nanopowders containing quartz and cristobalite phases from silica sands

Abstract In this study, extraction and synthesis of SiO2 nanoparticles from silica sands have been conducted by means of two different methods, i.e. dry method (method 1) and hydrothermal process (method 2). The basic difference between the two methods is in the extraction step. The two methods were compared in terms of being more efficient, economical, and superior in obtaining SiO2 nanoparticles. The SiO2 nanoparticles were characterized in terms of phase purity, crystallinity, Si-O functional bonding as well as particles size and morphology. The most interesting fact in this study was the formation of both quartz and cristobalite phases within all prepared SiO2 nanoparticles.

Small-Angle X-Ray Scattering Study on PVA/Fe3O4 Magnetic Hydrogels

A synchrotron small-angle X-ray scattering (SAXS) study on PVA/Fe3O4 magnetic hydrogels has been performed to investigate the effect of clustering on their magnetic properties. The hydrogels were prepared through freezing–thawing (F–T) processes. The structure, morphology and magnetic properties of magnetite (Fe3O4) nanoparticles (NPs) were investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and a superconducting quantum interference device (SQUID) magnetometer, respectively. In this study, SAXS data were used to reveal the structural dimensions of the magnetite and its distribution in the polymer-rich PVA and magnetic hydrogels. As calculated using the Beaucage and Teubner–Strey models, the average of the structural dimensions of the PVA hydrogels was 3.9nm (crystallites), while the average distance between crystallites was approximately 18nm. Further analysis by applying a two-lognormal distribution showed that the magnetite NPs comprised secondary particles with a diameter of 9.6nm that were structured by primary particles (∼3.2nm). A two-lognormal distribution function has also been used in describing the size distributions of magnetite NPs in magnetic hydrogels. The clusters of magnetite NPs in the magnetic hydrogels are significantly reduced from 30.4nm to 12.8nm with decreasing concentration of the NPs magnetite from 15wt.% to 1wt.%. The saturation magnetization values of the magnetite NPs, the 15% and 1% magnetic hydrogels were 34.67emu/g, 6.52emu/g and 0.37emu/g, respectively.

Various Magnetic Properties of Magnetite Nanoparticles Synthesized from Iron-sands by Coprecipitation Method at Room Temperature

Natural sand-based magnetite nanoparticles have been succesfully synthesized by coprecipitation method at room temperature. Magnetite nanoparticles were investigated by X-ray Diffractometer (XRD) and Vibrating Sample Magnetometer (VSM). The morphology of magnetite nanoparticles has been evaluated by Transmission Electron Microscopy (TEM). Qualitative analysis of XRD data reveals that the structure of magnetite nanoparticles have the same phase of ICSD No. 82237. On the other hand, quantitative analysis shows that the crystallite size of magnetite nanoparticles have ranges between 8.89 nm to 12.49 nm. The average diameter of magnetite nanoparticles increase with the increase the stirring rate of reaction when the stirring rate is lower than 1000 rpm, while the crystallite size of magnetite particles decrease with the increase the stirring rate when the stirring rate is higher than 1000 rpm. The stirring rate of reaction influence the the magnetic properties of magnetite nanoparticles. The results of the best magnetic respon are revealed for the stirring rate of 1000 rpm with the larger the crystallite size of magnetite nanoparticles due to its stronger saturation magnetization.

Preparing Fe3O4 Nanoparticles from Fe2+ Ions Source by Co‐precipitation Process in Various pH

Magnetite ( Fe 3 O 4 ) nanoparticles were synthesized from the Fe 2+ ions in the form of ferrous chloride tetrahydrate ( FeCl 2 .4 H 2 O ) by coprecipitation method at low temperature (⩽70 ° C ). During the precipitation process pH was kept constant at 7.37, 8.07, 9.12, 10.37 and 10.55 respectively. It was found that the magnetite nanoparticles was formed as a result of the dehydration reaction of ferrous hydroxide and ferric oxyhydroxide, in which the latter compound was produced by the partial oxidation of ferrous hydroxide by O 2 in dissolved air during the synthesis. The X‐ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to characterize these resulted particles. The average crystalline size of Fe 3 O 4 was obtained in the range between 18–55 nm for the corresponding range of pH used in the process. These results show that the pH of precipitation and the valence of the metal salt used in the synthesis have played an important role in influencing the particle size.

Spinel‐Structured Nanoparticles for Magnetic and Mechanical Applications

Nanoparticles of Fe3O4 have been successfully synthesized using a simple coprecipita‐ tion technique from natural iron sands, employing HNO3 and NH4OH as dispersing and precipitating agents, respectively. The substitution of Fe with Mn to result in Fe3‐ xMnxO4 (0 ≤ x ≤ 3) was conducted to control the magnetic strength of this nano‐sized spinel powder. It is shown that magnetic properties depend not only on the particle size and Mn doping but also on the particles clustering. The applications for magnetic fluids, gels, and coating are extensively described. Meanwhile, the spinel MgAl2O4 nanoparti‐ cles have also been prepared by the same simple method from commercial starting materials. This powder was used as a nano‐reinforcer of Al‐matrix composites. In addition, MgAl2O4 micro‐sized powder forming a thick layer was successfully grown by electroless plating on the interface of matrix‐filler in Al/SiC composites. The strengthening of mechanical properties with respect to the varying uses of these MgAl2O4 powders is discussed.

Synthesis of microforsterite using derived-amorphous-silica of silica sands

Synthesis of microforsterite (Mg2SiO4) has been successfully done by a simple method benefiting of the local silica sands from Tanah Laut, Indonesia. The starting material was amorphous silica powder which was processed using coprecipitation method from the sands. The silica powder was obtained from a series of stages of the purification process of the sands, namely magnetic separation, grinding and soaking with HCl. The microforsterite synthesis followed the reaction of stoichiometric mole ratio mixing of 1:2 of the amorphous silica and MgO powders with 3 wt% addion of PVA as a catalyst.The mixture was calcined at temperatures between 1150-1400°C with 4 hours holding time. XRD data showed that calcination at a temperature of 1150°C for 4 hours was optimum where the weight fraction of forsterite can reach as much as 93 wt% with MgO as the secondary phase and without MgSiO3. SEM photograph of the microforsterite showed tapered morphology with a relatively homogeneous distribution.

Synthesis of nano-sized ZnO particles by co-precipitation method with variation of heating time

Zinc oxide powders have been synthesized by a co-precipitation method at low temperature (85 °C), using zinc acetate dihydrate, ammonia, hydrochloric acid solutions as the reactants. A number of process parameters such as reaction temperature, solution basicity or pH and heating time are the main factors affecting the morphology and physical properties of the ZnO nanostructures. In this work the effect of heating time on the morphology and particles size were studied. The as-synthesized ZnO powders were characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The samples were also analyzed using Fourier transform infrared (FTIR). Rietveld refinement of XRD data confirms that ZnO crystallizes in the hexagonal wurtzite structure with high degree of purity and the (101) plane predominant. The XRD results show that the average crystallite sizes were about 66, 27 and 12 nm for 3, 4 and 5 h of heating times, respectively. The XRD analysis indicated that a fraction of nano-sized ZnO powders were in the form of aggregates, which was also verified by TEM image. The TEM photograph demonstrated that the nano-sized ZnO particles were a pseudo-spherical shape.

Precipitated CaCO3 with Unique Crystalline Morphology Prepared from Limestone

A carbonation method has been applied to induce the precipitation reaction of calcium carbonate powders with unique morphology. The reaction was strongly influenced by temperature, pH, CO2 gas flow rate and flow duration. Characterization of the as-prepared CaCO3 by XRD and SEM demonstrated that the vaterite phase was mostly formed at low temperature and CO2 gas flow rate. Phase transformation from vaterite to calcite phases at room temperature was initiated by the formation of calcite structure in ¼ spherical shapes and was followed by transformation to the rhombic structure. The highest growth of calcite structure, resulting in purity up to 98.6%, occurred at the CO2 gas flow rate of 5 SCFH in 36 s. Aragonite particles were produced at CO2 gas flow rate of 0.5 and 5 SCFH to yield 99.2% and 72.3% phase purities, respectively, with needle-like morphology at a higher temperature of 85oC. Furthermore, the reaction with lower CO2 gas flow rate (2 SCFH) led to the formation of aragonite with a flower-like morphology.

Thermal expansion coefficient prediction of fuel-cell seal materials from silica sand

This study is focused on the prediction of coefficient of thermal expansion (CTE) of silica-sand-based fuel-cell seal materials (FcSMs) which in principle require a CTE value in the range of 9.5–12 ppm/°C. A semi-quantitative theoretical method to predict the CTE value is proposed by applying the analyzed phase compositions from XRD data and characterized density-porosity behavior. A typical silica sand was milled at 150 rpm for 1 hour followed by heating at 1000 °C for another hour. The sand and heated samples were characterized by means of XRD to perceive the phase composition correlation between them. Rietveld refinement was executed to investigate the weight fraction of the phase contained in the samples, and then converted to volume fraction for composite CTE calculations. The result was applied to predict their potential physical properties for FcSM. Porosity was taken into account in the calculation after which it was directly measured by the Archimedes method.