Chemical mechanical polishing (CMP) is a fundamental technology used in the semiconductor manufacturing industry to polish and planarize electronic materials. During the high shear (≥1,000,000 s
− 1
...) polishing process, it is hypothesized that individual slurry particles begin to interact and collide with one another forming large agglomerates (≥0.5 μm). These agglomerates are suspected of causing defects such as scratches or gouges during polishing, which costs the semiconductor industry billions of dollars annually. We have developed a method for investigating the shear thickening behavior of fumed silica slurries (20–34 wt.%) under high shear using a parallel-plate geometry in a conventional rotating rheometer. The CMP slurries displayed irreversible thickening at shear rates exceeding 10,000 s
− 1
. Viscous heating and sample evaporation are shown to be inconsequential to the witnessed shear thickening behavior. Also, the observed thickening is not a result of a critical rheometer speed, as the thickening was independent of the experimental gap height. In agreement with previous work, the slurries thickened at lower shear rates as silica concentration was increased. The shear thickening of the fumed silica slurries is truly shear-induced, and therefore, the thickening of CMP slurries can be examined using a rotational rheometer at small gap heights (≤100 μm).
High pressure rubber hose is in the lamination structure composed of pure rubbers and braided fabric composite layers to have the sufficient strength against the excessive radial expansion and the ...large deformation, in which the braided fabric layer is woven with wrap and fill tows inclined to each other with the predefined helix angle in the complex periodic pattern. The consideration of detailed geometry of braided fabric layer in the numerical analysis leads to a huge number of finite elements so that the braided fabric layer has been traditionally simplified as an isotropic cylindrical one with the homogeneous isotropic material properties of braid spun tread. However, this simple model leads to the numerical prediction and design with the questionable reliability. In this context, this paper addresses the development of an in-house module, which is able to be interfaced with commercial FEM code, for the reliable large deformation analysis of the reinforced rubber hose with the element number at the level of the traditional simple model. The in-house module is able to not only automatically generate 3-D unit cell (or RVE) model of the braided fabric layer but evaluate the homogenized orthotropic material properties by automatically performing a serious of unit cell finite element analyses based on the superposition method. The validity of the in-house module and the reliability of the homogenization method are verified through the illustrative numerical experiments.
Candidate coating materials for re-usable metallic nuclear fuel crucibles, HfN, TiC, ZrC, and Y
2O
3, were plasma-sprayed onto niobium substrates. The coating microstructure and the thermal cycling ...behavior were characterized, and U–Zr melt interaction studies carried out. The Y
2O
3 coating layer had a uniform thickness and was well consolidated with a few small pores scattered throughout. While the HfN coating was not well consolidated with a considerable amount of porosity, but showed somewhat uniform thickness. Thermal cycling tests on the HfN, TiC, ZrC, and Y
2O
3 coatings showed good cycling characteristics with no interconnected cracks forming even after 20 cycles. Interaction studies done on the coated samples by dipping into a U–20wt.%Zr melt indicated that HfN and Y
2O
3 did not form significant reaction layers between the melt and the coating while the TiC and the ZrC coatings were significantly degraded. Y
2O
3 exhibited the most promising performance among HfN, TiC, ZrC, and Y
2O
3 coatings.
As the result of a conventional wastewater treatment such as activated sludge process, an excess sludge is produced and must be disposed of safely. Recently, increased attention has been given to a ...minimization of waste sludge in a wastewater treatment process. In this study, hydrogen peroxide oxidation was applied for an excess activated sludge reduction and an alkaline pretreatment method was used to enhance the efficiency of hydrogen peroxide oxidation of sludge. Sludge particle disintegration by hydrogen peroxide oxidation was confirmed through the evaluations of total solid concentration and particle size distribution. The solubility (SCOD/TCOD) of sludge was increased, while the viscosity was decreased with hydrogen peroxide oxidation and alkaline hydrolysis. The settleability of sludge was improved. When alkaline hydrolysis was applied as a pretreatment for hydrogen peroxide oxidation, the sludge particle disintegration, viscosity decrease, and settleability improvement were accelerated. From the results of this experiment, it can be concluded that hydrogen peroxide oxidation combined with alkaline pretreatment was useful for an excess sludge reduction.
We numerically compute the density of states (DOS) of interacting disordered zigzag graphene nanoribbon (ZGNR) having midgap states showing e/2 fractional edge charges. The computed Hartree-Fock DOS ...is linear at the critical disorder strength where the gap vanishes. This implies an I-V curve of I∝V^{2}. Thus, I-V curve measurement may yield evidence of fractional charges in interacting disordered ZGNR. We show that even a weak disorder potential acts as a singular perturbation on zigzag edge electronic states, producing drastic changes in the energy spectrum. Spin-charge separation and fractional charges play a key role in the reconstruction of edge antiferromagnetism. Our results show that an interacting disordered ZGNR is a topologically ordered Mott-Anderson insulator.
A calcium molybdate (CaMoO 4 ) crystal scintillator, with molybdenum enriched in 100 Mo and calcium depleted in 48 Ca ( 40 Ca 100 MoO 4 ), was developed by the Advanced Molybdenum based Rare process ...Experiment (AMoRE) collaboration to search for a neutrinoless double beta (0 ν ββ) decay of 100 Mo. We are planning to use about 10 kg of 40 Ca 100 MoO 4 crystals as cryogenic bolometers for the first phase of the experiment (AMoRE-I) at the Yang Yang underground laboratory (Y2L) in Korea. This experiment calls for an extremely low level of radioactive contamination in detectors, particularly by thorium, uranium, and radium decay chains. We measured scintillation properties and radioactive contamination of CaMoO 4 and 40 Ca 100 MoO 4 crystals at the Y2L. We also estimated the acceptable level of internal radioactive background using Monte Carlo simulation for the AMoRE-I.
Field-flow fractionation Williams, S. Kim R.; Caldwell, Karin D.
Analytical and bioanalytical chemistry,
02/2014, Letnik:
406, Številka:
6
Journal Article
Recenzirano
Odprti dostop
In the middle of the last century, Martin and Synge 1 had developed a technique for separating small molecules, such as amino acids, by column liquid chromatography. Their work evoked strong ...attention and resulted in a Nobel Prize in chemistry in 1952. The young thermodynamicist, J Calvin Giddings, who had taken a special interest in separations, was attracted by their concept, but could not refrain from brooding over the inability to use their packed column approach for the separation of larger species such as macromolecules and colloids.
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