As the operating environment in semiconductor processes becomes demanding, research is being conducted to manufacture dense alumina substrates without defects after sintering to ensure high durability of electrostatic chucks, which are critical components in semiconductor equipment. Therefore, in this study, in order to manufacture green sheets with a high filling ratio for implementing a high-density substrate, alumina powders with average particle sizes of 2.07 μm (L) and 0.37 μm (S) were mixed in ratios of 9:1, 8:2, 7:3, and 6:4, respectively, and green sheets were manufactured and the filling ratio and sintering behavior were observed. Green sheets were fabricated by preparing a slurry using organic materials in Al2O3 powders of different particle sizes. The packing density of the green sheet mixed with L and S alumina powders with different average particle sizes in a ratio of 7:3 before and after binder burn-out showed the highest values of 3.19 g/cm3 and 2.87 g/cm3, respectively. As a result of observing the sintered density based on the mixing ratio of alumina powders revealed that the alumina sheet mixed at a 6:4 ratio of L and S powders, sintered at 1,700℃, exhibited the best sintering characteristics with a density of 3.96 g/cm³.
Recently, active research has been conducted to enhance the power characteristics and thermal stability of lithiumion batteries (LiBs) by modifying separators using a ceramic coating method. However, since the thermal properties and surface features of the separator vary depending on the characteristics of the ceramic powders applied to the separator, it is crucial to manufacture ceramic powders optimized for the separator’s performance. In this study, we evaluated the characteristics of three types of α-alumina (A-1, A-2, and A-3) produced with varying dispersant contents and milling times, in addition to commercial α-alumina (AES-11). Subsequently, the optimized powders (A-3) were coated onto the separator using an aqueous binder for comparison with the characteristics of an AES-11 coated separator and an uncoated PE separator. The A-3 coated separator improved electrolyte wettability with a low contact angle (44.69°) and increased puncture strength (538 gf). Furthermore, it exhibited excellent thermal stability, with a shrinkage value of 5.64% when exposed to 140℃ for 1 hour, compared to the AES- 11 coated separator (6.09%) and the bare PE separator (69.64%).
Aluminum is a lightweight metal and has excellent properties with regard to conductivity, workability, and strength. It has been used in various industries owing to its economic benefits. To improve upon the mechanical properties and processability by adding various alloying elements to aluminum, improving the corrosion resistance and heat resistance by electrochemically forming a porous anodic film having a thickness and hardness on the surface of the aluminum alloy is crucial. In this study, the aluminum 6061 alloy was controlled by an anodization process in a 0.3M oxalic acid electrolyte at room temperature to investigate the oxide film parameters such as porosity and thickness depending on the modulating applied voltage and time. The anodizing experiment was performed by increasing the time from 1 h to 9 h at 2-h intervals at applied voltages of 50 V and 60 V.
In this study, we introduce a Na β″-alumina composite thick film as a solid electrolyte, to reduce the resistance of electrolyte for a Na/S battery. An alumina/zirconia composite material was used to enhance the mechanical properties of the electrolyte. A solid electrolyte of about 40 μm thick was successfully fabricated through the conversion and tape-casting methods. In order to investigate the effect of the surface treatment process of the solid electrolyte on the battery performance, the electrolyte was polished by dry and wet processes, respectively, and then the Na/S batteries were prepared for analyzing the battery characteristics. The battery with the dry process performed much better than the battery made with the wet process. As a result, the battery manufactured by the dry process showed excellent performance. Therefore, it is confirmed that the surface treatment process of the solid electrolyte has an important effect on the battery capacity and coulombic efficiency, as well as the interface reaction.
An 80 nm thick zinc aluminate thin film was deposited on a glass substrate via radio-frequency (rf) magnetron sputtering and heat treated to analyze changes in the wetting angles due to a surface modification. The thin films were modified from hydrophilic to hydrophobic by a simple thermal treatment. The surface modification from a heat treatment increased the wetting angles up to 111°, which was explained by the relationship with the excess surface area. The wetting angles of the annealed thin films decreased with increasing exposure time under ambient conditions, which was attributed to the oxygen vacancies in the films that were introduced during deposition. The annealed thin films were treated by ionized oxygen via oxygen plasma. After the oxygen plasma treatment, the decreased wetting angles were maintained at ~95° for 11 days.
The effects of compaction methods on the sintering density, microstructures, and mechanical properties were investigated in α-alumina ceramics. α-Alumina powders were granulated with a 10% aqueous solution of polyvinyl alcohol (PVA). Uniaxially pressed (UAP) and cold isostatic-pressed (CIP) samples were prepared by pressing uniaxially at a pressure of 1 ton for 1 min, and isostatically at 200 MPa for 15 min, respectively. Subsequently, both types of samples were sintered at 1,200℃, 1,300℃, 1,400℃, 1,450℃, 1,500℃, 1,550℃, and 1,600℃ at a rate of 5℃/min for 2 h. The CIP samples were better than the UAP samples for all properties measured, such as the sintering density, Vicker’s hardness, and toughness. The CIP sample sintered at 1,400℃ showed the maximum Vicker’s hardness and toughness; this may be attributed to the competing effects of a decrease in porosity and the growth of grains with increasing sintering temperature.
In order to develop an electrical insulation material for gas GIS (insulation switch gear) spacer, 4 types of epoxy/micro-alumina (40, 50, 60, 70 wt%) composites and 9 types of epoxy/nano-alumina (1, 3, 5 g)/micro-alumina (40, 50, 60, 70 wt%) composites were prepared and tensile test was carried out. In here, nano-alumina was previously surface-treated with GDE (glycerol diglycidyl ether). As micro-alumina and GDE-treated nano-alumina contents increased, tensile strength increased and the highest value was shown in the system with 3 g GDE-treated nano-alumina.
The aim of this study is to improve of dielectric properties using epoxy/nano alumina composites with adding glycerol diglycidyl ether (GDE:1,2 g). This paper deals with the effects of dielectric properties(□´ and tan δ) for epoxy/nano alumina contents (1,3 phr) and GDE addition (1,2 g)composites. 5 kinds specimen were prepared with containing epoxy resins, epoxy nano alumina composites. Average particle size of nano used were 30 nm. The nano alumina used were gamma phase particles of spherical shape. The suppression of epoxy chain motion by addition of nano alumina+GDE decreased dielectric loss and relative permittivity magnitude.
Alumina added with Mn3O4 up to 7.5 cat% of Mn was prepared by conventional ceramic processing, and the sintering behavior and the optical properties of which were studied as functions of Mn content. Densification and grain growth of alumina were enhanced by Mn addition up to 0.75 cat% but was leveled off at higher concentrations. XRD revealed that Al2MnO4(galaxite) was formed as a second phase in the specimens with more than 0.75 cat% of Mn. Thus it is believed that either the solid solution effect of Mn or the Zener effect of Al2MnO4 becomes predominant in the sintering of Mn-added Al2O3 according to the additive concentration. UV-VIS reflectivity(SCI) spectra of Mn-added Al2O3 consisted of smooth bottoms in 300~550 nm wavelength range and plateaus at wavelengths longer than 650 nm. The reflectivity spectrum continuously moved downward, and the specimen color became darker and thicker with increasing Mn content. The CIELAB color change with respect to standard white was also dependent on the amount of Mn added: TRIANGLE L^{*} (D65) negatively increased and TRIANGLE E _{ab} ^{*} (D65) positively increased with increasing Mn content, probably due to Mn substitution to Al and/or the mixing effect of black Al2MnO4 as a second phase.
In this work, the complex permittivity of epoxy resins is measured. Epoxy resins, epoxy with micro size fillers and epoxy with micro+nano alumina composites have been evaluated for dielectric properties according to frequency variation. The dielectric spectroscopy measurement and analyses are carried out in the frequency range of 10-2 Hz to 1MHz and constant to room temperature. The results of dielectric loss suggest that significant improvement in the electrical performance can be expected by using samples containing nano and micro fillers mixture when compared to materials containing only microfillers. As the result, we verified the specific characteristics of dielectric permittivity and dielectric loss namely, relative permittivity become low with improving dispersibility of nano+micro mixture composites and become rise with agglomerate of nano particles.
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