Papers by Keyword: SiO₂

Abstract: A systematic capacitance-voltage (C-V) and time-dependent dielectric breakdown (TDDB) study on silicon carbide (SiC) metal-oxide-semiconductor capacitors (MOSCAPs) that use silicon dioxide (SiO₂) is shown in this paper. Oxides were formed using atomic layer deposition (ALD), low-pressure chemical vapour deposition (LPCVD) or direct thermal growth in nitrous oxide (N₂O) ambient, where both deposited oxides were post-deposition annealed in N₂O ambient, too. The electrical characterisation results reveal that the ALD-deposited and N₂O-annealed oxides show the best capacitance-voltage (C-V) characteristics, with flatband and hysteresis voltages (V_FB) averaging 1.44 V and 0.41 V, respectively. When measuring the leakage current levels at 175°C, the ALD-deposited MOSCAPs’ breakdown electric fields are averaging similar to their counterparts at 9.71 MV/cm. MOSCAPs which utilized ALD-deposited SiO₂ also showed 29% and 345% increased average injected charge-to 63% failure (Q_BD,63%) at 9 MV/cm and 9.6 MV/cm, respectively, when comparing these devices to their direct thermally grown SiO2 counterparts.

Abstract: Reinforcement of both fibrous and particulate materials can improve composite properties for various applications, such as biomedical applications. The alkali-treated kenaf fibers and (SiO2, bentonite, and CaCO3) microparticles 400 mesh in size reinforce the epoxy matrix for hybrid composites. The bending and impact properties of hybrid composites, as well as their water absorption, are compared. The hybrid composites were prepared in a compression mold using a hand lay-up technique at 100°C for 20 – 50 minutes consisting of 28 vol.% of short kenaf fibers ~5 mm in length, 2 vol.% of each type of microparticle, and 70 vol.% the epoxy resin. The flexural and impact properties of kenaf/silica/epoxy composite indicated the highest flexural strength (58.37±3.9 MPa), flexural modulus (4.68 ± 0.17 MPa), and impact strength (7.49 kJ/m²⁾. The addition of the microparticles reduced water absorption in the composites. The water absorption of kenaf/silica/epoxy composite appeared to be stable for immersion time near 216 hours. Other microparticle-filled composites did not show this pattern. The incorporation of silica microparticles to the kenaf/epoxy composite potentially enhanced the mechanical properties of the composite, with the expectation of using it to be developed for biomedical composite material.

Abstract: In this paper, the sol-gel method was used for in-situ synthesis of SiO₂ nanoparticles (NPs) on cotton fabrics with tetraethyl orthosilicate (TEOS) in the presence of acid and alkaline indicators. The samples were characterized using by (X-ray diffraction) XRD, (scanning electron Microscopy) SEM, (Inductively coupled plasma) ICP, water drop test and also the flame retardant properties were studied by char yield. The SEM images showed that the nanoparticles are spherical in shape and the acidity or alkalinity of the medium has an effect on the formation of particles. The XRD patterns showed the typical diffraction of amorphous SiO₂ (Si-O short-order structure), also ICP analysis showed that by washing the fabrics, the nanoparticles are still present on the fabric, and this indicated the stability of the washing of the fabrics impregnated with the nanoparticles. By in-situ synthesis of SiO₂ nanoparticles, the flame retardant properties have been improved significantly and the amount of residual char was increased and samples were observed to be hydrophilic.

Abstract: The article analyses the influence of SiO₂ and Al₂O₃ nanopowders on properties of ceramics consisting of fly ash from thermal power plants, glass waste, and clay binder. Based on studies of physical and mechanical properties of the obtained ceramics (ultimate compressive strength, ultimate three-point bending strength, wear resistance, and water absorption), the paper shows the positive influence of the nanoadditives. The optimal number of SiO₂ and Al₂O₃ nanopowders in the formulation is 0.5 wt. % that has the strongest effect on ultimate compressive strength and water absorption of the fly ash ceramics samples. The direction of further research on improving the properties of ceramic products is an application of the Al₂O₃ nanopowder as more perspective nanoadditive using clay dispersant.

Abstract: Calcium-looping technology is defined as one of the most desirable methods of carbon capture, utilization and storage (CCUS). However, because of sintering, rapid deactivation of CaO-sorbents is currently a major barrier to this technology. The stability of calcium based sorbent may be enhance by incorporating them with inert support materials such as MgO, Al₂O_2, ZrO₂ and SiO₂. For this study, calcium based sorbent has been incorporate with silica obtained from rice husk ash. CaO-SiO₂ sorbents are prepared using physical dry mixing method which is much simpler compared to other available methods. The prepared CaO-SiO₂ sorbents were then characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). New crystalline phase, larnite (Ca₂SiO₄) was detected in XRD patterns and this phase possess good chemical durability and may help to prevent sintering effect of calcium based sorbents and enhance their cyclic capability. CaO-SiO₂ sorbent calcined at 700 oC with different grinding times have highest intensity of XRD peak at (104) with element of calcite. Sorbents with different weight composition of CaCO₃-RHA were observed to have different surface morphology. SEM images of the sorbent (90wt% CaCO₃-RHA) before calcination showed bigger particle size with irregular shape and more porosity. Then, SEM analysis was conducted for samples with different grinding times after calcination. CaO-SiO₂ sorbents with 20minutes grinding time exhibited small size of particles with some porosity. Besides that, the particles are well distributed without agglomeration occured. The CaO-SiO₂ sorbent calcined at 700 oC sorbents were tested for 20 consecutive carbonation and calcination cycles using Thermogravimetric Analysis (TGA). CaO-SiO₂ sorbent treated with 700 oC calcination temperature and 20 minutes of grinding shows better cyclic CO₂ sorption capacity.

Abstract: A systematic post-deposition annealing study on Silicon Carbide (SiC) metal-oxide-semiconductor capacitors (MOSCAPs) using atomic layer deposition (ALD)-deposited silicon dioxide (SiO₂) layers was carried out. Anneals were done in oxidising (N₂O), inert (Ar) and reducing (H₂:N₂) ambients at elevated temperatures from 900°C to 1300°C for 1 hour. Electrical characterisation results show that the forming gas treatment at 1100°C reduces the flatband voltage to 0.23 V from 10 V for as-deposited SiO2 layers. The density of interface traps (D_IT) was also reduced by one order of magnitude to 2×10¹¹ cm^-2 eV^-1 at E_C-E_T = 0.2 eV. As an indicator of the improvement, characterisation by x-ray photoelectron spectroscopy (XPS) showed that silicon enrichment present in as-deposited layers was largely reduced by the forming gas anneal, improving the stoichiometry. Time-dependent dielectric breakdown (TDDB) results showed that the majority of forming gas annealed samples broke down at breakdown fields of 12.5 MV × cm^-1, which is about 2.5 MV × cm^-1 higher than for thermally oxidised samples.

Abstract: One of the important characteristics of magnetic materials is the measurement of magnetic characteristics through Superconducting Quantum Interference Device (SQUID) especially magnetization temperature dependence M(T)_ZFC and MT_FC measurement. In this work, we reported magnetization temperature dependence measurements of magnetite nanoparticles without SiO₂ encapsulation (Fe₃O₄) and magnetite nanoparticles with SiO₂ encapsulation (Fe₃O₄.SiO₂) at the application of magnetic fields of 100 Oe. The nanoparticles magnetite was synthesized by co-precipitation method. It was calculated that the blocking temperature of magnetite nanoparticles Fe₃O₄ without and with SiO₂ encapsulation is 118.38 K and 209.03 K, respectively. The blocking temperatures of magnetic nanoparticles increase by SiO₂ encapsulation.

Abstract: In this work, hydrophobic of modified SiO₂ coating for self cleaning material were prepared by dip-coating methods and solvothermal manual. SiO₂ was successfully prepared from silica sand by purified followed sol-gel methods. Tetraetoxysilane (TEOS) and Hexamethyldisilanze (HMDS) were used as surface chemical modification agents with varied mass of SiO₂, which were 1, 2, 3, and 4 g. X-ray fluorescence spectrometer (XRF) , X-ray powder diffraction (XRD), Particle size analyzer (PSA), Ultraviolet–visible spectrophotometer (UV-Vis), and Water contact angle (WCA) were employed to investigate the element composition, crystal structure, size of particles, transparency, and hydrophobicity of coating. The results indicated that modified SiO₂ coatings has hydrophobic feature as self cleaning material (WCA > 90˚) for indium tin oxide (ITO) glass.

Abstract: Bio jet fuel becomes one of the feasible solutions for jet fuel inadequate supply in Indonesia. However, study in this field by far has been limited. In this study, bio jet fuel was synthesized from Crude Palm Oil (CPO) by Hydroprocessed Esters and Fatty Acid (HEFA) facilitated by Ni-Mo/SiO₂ catalyst, in which the support was derived from rice husk ash. The study focused on investigating the influence of catalyst-CPO mass ratio and temperature of the catalytic process. Experimental works consisted of silica-based catalyst preparation via impregnation method, followed by sample assessments. Catalytic reactions were conducted at 20-50 bars, with temperature of reaction 300°C and 400°C. Catalyst performance were evaluated from crystallinity, composition, and activity in the reaction. Catalyst characterization shows an amorphous structured with high dispersion of Ni-Mo in rice husk ash have been produced. The HEFA process successfully obtained bio jet fuel (C₁₀-C₁₅ hydrocarbons) with yield and selectivity of 45.17% and 45.46%, respectively. Overall, a systematic approach shows rice husk ash has potential to be developed as a catalyst support for bio jet fuel production from crude palm oil.

Abstract: Charge trapping at 4H-SiC/dielectric interfaces in 4H-SiC MOS capacitors has been investigated using constant capacitance deep level transient spectroscopy (CCDLTS). The experiments were focused on further understanding of the following aspects related to 4H-SiC/SiO₂ interfaces: (i) Origin of near interface oxide traps (NITs), (ii) Effect of interfacial impurity/passivation methods and (iii) Characterization of near-interface oxide traps for different SiC wafer orientations. For the (0001) Si-face 4H-SiC/ SiO₂ interface, two types of NITs are typically detected by CCDLTS, named ‘O1’ and ‘O2’ traps with emission activation energies of about 0.15±0.05 eV and 0.39±0.1 eV respectively below the 4H-SiC conduction band. Based on comparison with previous ab initio calculations, the physical identities of these defects have been suggested to be carbon dimers substituted for O dimers (‘O1’) and interstitial silicon atoms (‘O2’) in the near interfacial SiO₂ respectively. In this work, it is shown for the first time that such traps are not observed for 4H-SiC/ Al₂O₃ interfaces, proving that these traps are inherent to the near-interfacial SiO₂. In addition, the summary of CCDLTS results for Si-face with different interface trap passivation methods are included in this study. Finally, a comparison is presented for NO annealed (0001) Si-face, (11-20) a-face and (000-1) C-face interfaces that highlight the difference of CCDLTS signatures for the different crystal faces.