Evaluation of a Lightly Scratched Amorphous Carbon Surface by Contact Resistance of a Conductive Diamond Tip and the Carbon Surface

An electron-cyclotron-resonance-sputtered amorphous carbon film is scratch-scanned by an AFM and a conductive diamond tip at small contact loads (2N). The electrical contact resistance between the tip and the scratched carbon surface increases upon increasing the scratching load and the number of scratching scans and decreases with increasing scratching velocity. The wear depth is less than 0.6 nm in all scratching experiments and is almost independent of the scratching load, the number of scratching scans and the scratching velocity. The change in contact resistance caused by the scratching is affected by environmental humidity. The magnitude of the change in the contact resistance is almost the same at 20 and 50% RH and increases with increasing relative humidity at humidities higher than 50% RH. The contact resistance also increases upon scratching in vacuum. The change in contact resistance is thought to be caused by tribochemical oxidation of the rubbed surface by humid air and also destruction of the graphite structure of the ECR-sputtered carbon surface.     

Secondary electron emission of TiN-coated alumina ceramics

TiN film is often coated on alumina rf windows to suppress multipactor due to high secondary electron emission (SEE) coefficients. In this paper, SEE coefficients of alumina ceramics and sapphire coated with TiN films of various thicknesses are investigated. The SEE coefficients were measured using a scanning electron microscope with a single-pulse electron beam (100 pA, 1 ms). The SEE coefficients of TiN-coated alumina ceramics were lower than those of uncoated ones and nearly unity for TiN thickness of more than 1 nm, even with incident energy of 1 keV. To emulate multipactor-induced surface heating, the SEE coefficients were also measured at high temperature. The results showed a decrease in the SEE coefficients with temperature for TiN thickness of more than 0.5 nm. TiN coating on an rf window should be as thin as possible, and 0.5-1 nm may be the optimum thickness for suppressing multipactor.     

High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics

Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.     

Development of method for estimation of world industrial energy consumption and its application

The energy balances published by the International Energy Agency (IEA) are one of the most valuable sources of energy statistics covering world energy supply and demand. However, some issues arise when these data are analyzed or used directly. Even when industrial energy consumption alone is examined, at least three types of issues are encountered: missing data, large amounts of misallocated data in some countries, and numerous unrealistic outliers in the time-series variations. When we deal with only a few regions, we can look at data one by one and modify them. In this case, we are going to overcome these issues with a systematic method because the data covers world including more than a hundred regions.This paper proposes a data reconciliation method to treat these issues, and describes its application to world industrial energy consumption. As a result of its application, we found that the three issues mentioned above seemed to be overcome. The degree of the reconciliation by region showed that OECD countries' degree tends to be smaller than those of non-OECD countries. However, not all of the OECD countries have low values and some countries, such as the United States, have high values.     

Origin of Surface Coating Effect for MgO on LiCoO2 to Improve the Interfacial Reaction between Electrode and Electrolyte

Surface coating on lithium‐ion battery cathodes improves their durability at high potentials, which is a well‐known practical application. However, the mechanism is still unclear because the coating influences the electrode/electrolyte interface at a few nanometer‐scale and direct observation of the interface under real operating conditions of a battery is challenging. This study reveals the mechanism of the surface coating effect on lithium‐ion battery cathodes by using in operando X‐ray absorption spectroscopy (XAS) on well‐defined MgO‐coated LiCoO₂ thin‐film electrodes prepared via pulsed laser deposition. Total‐reflection in operando XAS measurements reveal that LiCoO₂ forms a reductive phase at the interface between the uncoated‐LiCoO₂ electrode and the electrolyte, while the MgO coating layer inhibits the redox process, leading to an improvement in the cycle performance of the battery. Depth‐resolved in operando XAS measurements indicate that a solid solution of the magnesium phase forms at the LiCoO₂ surface upon MgO coating. Magnesium ions function as pillars to stabilize the layered structure at the interface between the LiCoO₂ electrode and the electrolyte for delithiated states upon cycling at potentials.     

Investigation of the cause of peculiar irradiation behavior of 9Cr-ODS steel in BOR-60 irradiation tests

Four experimental fuel assemblies (EFAs) containing 9Cr-ODS steel cladding fuel pins were previously irradiated in the BOR-60 to demonstrate the in-reactor performance of 9Cr-ODS steel for use as fuel cladding tubes. One of the EFAs achieved the best data, a peak burn-up of 11.9at% and a neutron dose of 51 dpa, without any microstructure instability or any fuel pin rupture. On the other hand, in another EFA (peak burn-up, 10.5at%; peak neutron dose, 44 dpa), peculiar irradiation behaviors, such as microstructure instability and fuel pin rupture, occurred. Investigations of the cause of these peculiar irradiation behaviors were carried out. The detection sensitivity in an ultrasonic inspection test was shown to be low for the metallic Cr and metallic Fe inclusions. The peculiar microstructure change reappeared with high-temperature thermal-aging of the 9Cr-ODS steel containing metallic Cr inclusions. The strength and ductility of the defective part containing metallic Cr inclusions were appreciably lower than those of a standard part without the inclusions. The combined effects of matrix Cr heterogeneity (presence of metallic Cr inclusions) and high-temperature irradiation were concluded to be the main cause of the peculiar microstructure change in 9Cr-ODS steel cladding tubes in the BOR-60 irradiation tests. They contributed to the fuel pin rupture.     

Surface characteristics and electrical breakdown of alumina materials

The electrical breakdown of alumina materials is one of the difficulties in higher electric field applications. This breakdown takes place due to localized excess heating, which is induced by surface defects, multipactor, and surface discharge. These factors were evaluated for several commercial alumina ceramics using a scanning electron microscope and comparing these observations with high-power rf transmission tests. The results indicate that alumina ceramics without F-center defects and lower surface charging are feasible for higher electric field operation.