Malik Anjelh Baqiya

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...

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.

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.

Magnetic properties of superconductors Bi-2212 and (Bi,Pb)-2212 nanoparticles synthesized by dissolved method

The Pb-free and partially Pb-substituted Bi2−xPbxSr2CaCu2O8+δ(x = 0;0.4) powders have been synthesized by using dissolved method followed by short period of sintering. The XRD spectra showed that the 2212 phase of Bi-based system was the dominant phase. It means that Pb-free and partially Pb-doped superconductors can successfully be formed by this route of synthesis. From the TEM observations, it was shown that the particle size of Pb-free powder is in the nano-scaled range. The vibrating sample magnetometer (VSM) measurements showed that samples B3, B4, and BP3 exhibited soft ferromagnetic with a thin magnetic hysteretic curve at the room temperature. This soft magnetism may possibly be due to the oxygen deficiency on the surface of nano-scaled samples.

Ferromagnetism in 2212 phase Bi-Sr-Ca-Cu-O nano-superconductors

Superconductors are characterized by zero resistance and Meissner effect. At below critical temperature (Tc), these materials exhibit diamagnetic properties. On the other hand, materials in nano-crystal size have specific properties that differ from bulk state. Nanomaterials are characterized by surface effect which influences physical and chemical properties of the materials. Combining these two mayor fields, it can be obtained superconductors in nano-crystal size (below 200 nm) using simple method (called as nano-superconductors). Generally, ceramic-oxides in nano-crystal size, even in cuprate-superconductors, may have ferromagnetic behavior at room temperature. In this research, Bi and Bi, Pb-based nano-superconductors synthesized by wet mixing technique have Tc ∼80 K for 2212 (Bi2Sr2CaCu2O8−δ and Bi1,6Pb0,4Sr2CaCu2O8−δ) phases. They also exhibit ferromagnetism effect and hysteresis curve although at well above Tc. This is unusual phenomenon because superconductor materials are generally diamagnetic at...

Epoxy Resin Matrix Nanocomposites with Core‐Shell Structure of NiZnFerrite/Ag and NiZnFerrite/PANi as Fillers for Microwave Absorber in Ka‐band

The core‐shell NiZnFerrite/Ag and NiZnFerrite/PANi (7:1 %wt) with epoxy resin forming a nanocomposite structure were synthesized by blending at 70 %vol content and introduced it into epoxy resin to be a microwave absorber. The phase and morphology characterization of the formation processes of NiZnFerrite/Ag and NiZnFerrite/PANi core‐shell structure were studied using X‐ray diffraction, transmission electron microscopy and scanning electron microscopy respectively. Microwave absorbing properties were investigated by reflectivity measurements in Ka‐band (18–26 GHz). The reflection losses were calculated based on the model of a single layered plane wave absorber backed by a perfect conductor. The composite epoxy resin‐NiZnFerrite/Ag shows matching frequency (fm1 = 20.7GHz and fm2 = 23.2GHz), maximum reflection loss (RLm1 = −20.8dB and RLm2 = −29.8dB) and bandwith (Δf1 = 18.6–21.7GHz and Δf2 = 21.7–25.0GHz ) Further, the composite epoxy resin‐NiZnFerrite/PANi shows matching frequency (fm1 = 20.7GHz and fm2 =...

Synthesis of amorphous carbon from bio-products by drying method

Amorphous carbon (a-C) has extensively been studied in the last two decades due to many superior properties. Amorphous carbon was successfully prepared by carbonization of organic compounds exposed up to 200°C. Organic compounds that used in this research were coconut sap, lontar palm sap and their derivatives. The X-ray diffraction pattern shows that carbonization of organic compounds produce amorphous carbon phase at 2θ =20°. The infrared absorption in the region from 500 to 4000 cm-1 were resolved into several peaks, which were assigned to C-H, C=C, C-O, C=O and O-H. Four point probe method was also used to measure the conductivity and band gap of each material, resulting in 1.73 – 29.6 S/m and 0.08 – 0.49 eV respectively.Amorphous carbon (a-C) has extensively been studied in the last two decades due to many superior properties. Amorphous carbon was successfully prepared by carbonization of organic compounds exposed up to 200°C. Organic compounds that used in this research were coconut sap, lontar palm sap and their derivatives. The X-ray diffraction pattern shows that carbonization of organic compounds produce amorphous carbon phase at 2θ =20°. The infrared absorption in the region from 500 to 4000 cm-1 were resolved into several peaks, which were assigned to C-H, C=C, C-O, C=O and O-H. Four point probe method was also used to measure the conductivity and band gap of each material, resulting in 1.73 – 29.6 S/m and 0.08 – 0.49 eV respectively.

Protected Vacuum Annealing Effect on Single Crystals of Pr1-x LaCe x CuO4 in the Overdoped Regime

We report the effect of protected vacuum annealing on the superconducting (SC) and magnetic properties of Pr1-x LaCe x CuO4 (PLCCO) single crystals in the overdoped regime (x = 0.13 – 0.20). The powders and single crystals of PLCCO with all x were synthesized by the solid state reaction and grown by the travelling solvent floating zone (TSFZ) method, respectively. The powder x-ray diffraction (XRD) results analyzed by the Rietveld method have shown that there is a systematic decrease in the c-axis length with increasing x, suggesting the proper substitution of Ce for Pr in overdoped PLCCO up to x = 0.20. The so-called two-step annealing performed in the overdoped regime was essential for increasing the SC volume fraction estimated from the magnetic susceptibility measurements. Furthermore, the temperature dependence of the normal-state magnetic susceptibility for reduced crystals of PLCCO with all x has exhibited a Curie-Weiss-like behavior regardless of various steps of the protected vacuum annealing process.

Photoluminescence of Reduced Graphene Oxide Prepared from Old Coconut Shell with Carbonization Process at Varying Temperatures

Reduced graphene oxide (rGO) powder has been prepared from coconut shells by carbonization process at 400°C, 600°C, 800°C and 1000°C for 5 hours at ambient air. In this study the exfoliation rGO was added into distilled water with variation of concentration solution using the sonication process for 3 hours and centrifugation at 4000 rpm for 20 minutes. The characterization were performed by using XRD and photoluminescence (PL) spectroscopy. The photoluminescence or rGO showed the peak of excitation and emission at wavelengths ranging from 340 nm to 800 nm. The PL emission spectra are at wavelength ranging from UV to visible region approaching red. Observation showed that the photoluminescence intensity was significantly increased by the increasing content of rGO in the solution. The influence of the varying temperature on the PL spectra will also be discussed in this study.