Phase transformation from initially α-MnO2 to R-MnO2 due to Fe-doping cause modification of interatomic distances affects to the electrical properties.
In this study, extraction and synthesis of SiO 2 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 SiO 2 nanoparticles. The SiO 2 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 SiO 2 nanoparticles.
Polyethylene glycol (PEG)/quartz (denoted as BP/Q) composites have been investigated as candidates of phase change materials (PCMs) due to their thermomechanical properties around the glass transition temperature as well as thermal properties between 30 and 600 C. Quartz (q-SiO 2 ) powders were extracted from local sand in Tanah Laut, Pelaihari, South Kalimantan, Indonesia. The composites were prepared by dispersing q-SiO 2 powders in the PEG matrix followed by the wet mixing process. The thermal properties of the composites were characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), while the thermomechanical properties were examined using a dynamic mechanical analyzer (DMA) in a three-point bending mode around the PEG glass transition temperature range (−100-50 C). The morphology and interface bonding were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From the DSC measurement, the endothermic peak of the composites showed a shift of approximately 7-12 C toward higher temperatures than that of the pure polymer. The melting enthalpy values (ΔH m ) of the BP/Q composites covered the required PCM application range, that is, between 139 and 182 J/g. The TGA of the composites showed that thermal degradation occurs in the range of 250-450 C. We found that solid-solid PCMs (ssPCMs) were successfully fabricated with the addition of 10 and 20 wt% q-SiO 2 . From DMA characterization, the BP/Q 20 wt% composite exhibited the maximum E' and the minimum energy dissipation (E"). Its E' value was approximately 250 MPa more than that of the pure PEG. The glass transition (T g ) temperatures of PEG and BP/Q composites (5, 10, and 20 wt%) were around −24.5, −19.1, −17.1, and − 5.3 C, respectively. In addition, the E" and tan δ values decreased with q-SiO 2 filler content. Furthermore, the Cole-Cole plots of the BP/Q composites revealed a better interfacial bonding between the q-SiO 2 and the PEG matrix in the composites with higher silica content. A compact morphology was shown by the BP/Q 20 wt% composite due to high silica concentration.
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 3.9[Formula: see text]nm (crystallites), while the average distance between crystallites was approximately 18[Formula: see text]nm. Further analysis by applying a two-lognormal distribution showed that the magnetite NPs comprised secondary particles with a diameter of 9.6[Formula: see text]nm that were structured by primary particles ([Formula: see text][Formula: see text]3.2[Formula: see text]nm). 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 30.4[Formula: see text]nm to 12.8[Formula: see text]nm with decreasing concentration of the NPs magnetite from 15[Formula: see text]wt.% to 1[Formula: see text]wt.%. The saturation magnetization values of the magnetite NPs, the 15% and 1% magnetic hydrogels were 34.67[Formula: see text]emu/g, 6.52[Formula: see text]emu/g and 0.37[Formula: see text]emu/g, respectively.
Indonesia adalah negara dengan potensi alam yang melimpah, khususnya bahan tambang (mineral), diantaranya material-material dengan kandungan oksida yang mempunyai prospek aplikasi sebagai material cerdas (misalnya SiO2, CaCO3, Al2O3,TiO2, dsb). Tujuan dari penelitian ini adalah mencari atau mengidentifikasi kandungan unsur oksida didalam bahan alam jenis batuan atau pasir kuarsa dengan kemurnian tinggi (> 50%), khususnya sebagai sumber oksida SiO2 (silica) dan CaCO3 (calsite). Selanjutnya bahan-bahan tersebut akan diproses dengan milling proses serbuk (ukuran mikron) untuk, peningkatan kemurnian tinggi dan pengecilan ukuran pada orde nanometer. Identifikasi awal adalah melakukan uji difraksi Sinar-X (XRD) dan analisisnya (kualitatif) serta uji flouresensi sinar-X (XRF). Telah dilakukan uji XRD dan XRF pada sampel batuan yang diambil dari daerah Tulungagung, onik dari pulau Bawean-Gresik, dan pasir dari Tuban dan Sumenep. Hasil difraksi sinar X (XRD) bahan alam (batuan dan pasir) yang diambil sebagai sampel yang diambil dari beberapa daerah tersebut, diperoleh bahwa Batu_1(onik) dan Batu_2(putih) menunjukan bahwa sampel tersebut mempunyai fase dominan struktur kristal Calsite (CaCO3), dan untuk pasir dari Tuban dan Sumenep mempunyai fase dominan quartz (SiO2), demikian. Dan hasil XRF menunjukan kandungan CaCO3 pada sampel batuan (onik) cukup tinggi (98,23%), dan untuk sampel pasir (Tuban dan Sumenep) menunjukan kandungan oksida quartz (SiO2) dengan kemurnian yang tinggi (65,9 -76,8 %), dengan impuritas terbanyak CaO dan Fe2O3 (20-28%).
Proses sintesis silika (SiO2) berbasis bahan alam telah dilakukan dengan metode kopresipitasi menggunakan NaOH. Bahan dasar pasir alam yang digunakan berasal dari pasir pantai Bancar, Tuban, Jawa Timur, Indonesia. Penelitian ini bertujuan untuk mengetahui SiO2 berbasis bahan alam menggunakan uji XRF dan XRD. Penelitian dilakukan dengan perlakuan yang berbeda. Kajian awal dari analisis X-ray Fluorescence (XRF) menunjukkan bahwa pasir alam pantai Bancar yang digunakan mengandung unsur Si 81,7 wt%. Berdasarkan pola X-ray Diffraction (XRD) mengindikasikan bahwa SiO2 hasil sintesis yang terbentuk adalah silika kuarsa dengan background amorf. Kandungan SiO2 yang didapatkan menunjukkan kesesuaian yang baik dilakukan dengan analisis menggunakan software Rietica diperoleh GoF < 4% dan menggunakan software MAUD diperoleh estimasi ukuran kristal silika hasil kopresipitasi ∼52,7 ± 21,9 nm. Diharapkan kandungan SiO2 yang diperoleh memiliki potensi yang menjanjikan sebagai aplikasi material teknologi tinggi.
A cathode Lithium Ferro Phospate (LFP) composite material with variation doping ion Silicon (Si) with x = 0; 0,01; 0,03; 0.06 and carbon coating (LiFeSixP1-xO4/C) as lithium ion battery cathode were synthesized by a solid state reaction and wet milling methods. X-Ray Diffraction (XRD) pattern showed that the of olivine phase formed, and analysis characterization of Scanning Electron Microscopy (SEM) have shown average dimension particle of cathode in orde 1 micron. Analysis by Cyclic Voltammetry (CV) doping ion Si x = 0,03 have the best reversible electrochemical process than the other concentration, and have the highest charge and discharge capacity (78,745 mAh/g).
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