The PAN/TiO 2 /Ag nanofibers membrane for air filtration media was successfully synthesized with electrospinning method. The morphology, size, and element percentage of the nanofiber were characterized by a scanning electron microscopy–energy dispersive spectroscopy, while X-ray fluorescence and FTIR were used to observe the chemical composition. The water contact angle and UV–vis absorption were measured for physical properties. Performance for air filtration media was measured by pressure drop, efficiency, and quality factor test. TiO 2 and Ag have been successfully deposited in nonuniform 570 nm PAN/TiO 2 /Ag nanofibers. The nanofiber membrane had hydrophilic surface after TiO 2 and Ag addition with a water contact angle of 34.58°. UV–vis data showed the shifting of absorbance and band gap energy of nanofibers membrane to visible light from 3.8 to 1.8 eV. The 60 min spun PAN/TiO 2 /Ag nanofibers membrane had a 96.9% efficiency of PM 2.5 , comparable to results reported in previous studies. These properties were suitable to be applied on air filtration media with photocatalytic activity for self-cleaning performance.

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Yttrium aluminum garnet (YAG) is an important material which require high temperature of 1600°C in its solid-state reaction. To lower this temperature, mechanical activation process has applied to the system which make the crystal arrangement broken thus make it more reactive. This process results in homogeneous and fine particle distribution of Al2O3 and Y2O3 compared to manually mixed powders. Moreover, milling process also reduce the particle size of the Al2O3 and Y2O3 from 4694 nm and 349 nm down to 274 nm. This also lessen the crystallite size of Al2O3 and Y2O3 from 1010 and 164 Å to 310 and 50 Å respectively. Then, after calcination at 1100°C, the milled powders form YAG phase in the opposite of manually mixed powders which form YAM phase. YAG formed have nearly round shape with finer grain compared to manually mixed powders which still has large grain of Al2O3 and Y2O3. This formation temperature is much lower than the require conventional solid-state reaction.

Photoelectrochemical cell (PEC) has the same working principle as solar cell which convert solar energy into electricity. PEC consists of photoanode, electrolyte, and counter electrode, where electrolyte plays an important role in determining PEC performance. Yttria-stabilized zirconia (YSZ) is the most suitable electrolyte used due to its high ionic conductivity and chemically stable. In this study, YSZ was deposited to ZnO Nanorods (NRs) by doctor blade method with thickness variation of 100 μm (PEC10) and 120 μm (PEC12). X-ray diffraction (XRD), scanning electron microscope (SEM), and UV-Vis spectroscopy were used to distinguish the phase, morphology, and band gap of the formed materials, respectively. Moreover, I-V test was also conducted to evaluate the performance of the fabricated PEC with different YSZ thickness. SEM image confirmed the deposition thickness of YSZ layer on NRs which formed rough and irregular interface due to grain boundary fusion of YSZ and NRs. In addition, there is little difference XRD pattern from PEC10 and PEC12 which shows ZnO and YSZ peaks with peak shifting observed. Meanwhile, slightly difference noticed on band gap value where PEC10 has 3.25 eV and PEC12 has 3.58 eV. Even though, the characteristic of PEC10 and PEC12 is similar, the I-V test shown a significant difference of solar efficiency where PEC10 has higher efficiency of about 0.328% than PEC12. This difference is contributed by smaller grain size which has higher specific surface area and porosity. Based on this study, the thickness of electrolyte layer YSZ doesn’t affect the basic characteristic of PEC but affect the efficiency of PEC significantly.

Dense monolithic silicon carbide (SiC) was successfully sintered by hot-pressing at 1750 ?C for 1 h under an applied pressure of 20 MPa with the addition of a nitrate-based additive. A relative density of more than 98% were obtained with the addition of MgO-Y2O3 and Al2O3-Y2O3 in nitrate form, while in the oxide form they were 85.0 and 96.0%, respectively. Indeed, MgO-Y2O3 showed poor densification due to the eutectic temperature of 2110?C, however, the addition of nitrate form of MgO-Y2O3 enhanced the densification greatly. The sintering mechanism in the nitrate-based additive is liquid phase sintering, which is identified by the presence of an oxide phase, i.e., Y2O3 in the SiC with the addition of Al2O3-Y2O3 in nitrate form. Moreover, the addition of nitrate form suppressed the grain growth of SiC, which was believed to be due to the adequate rearrangement stage during sintering.