Mechanical properties of silicon-doped diamond-like carbon films prepared by pulse-plasma chemical vapor deposition

Silicon-doped diamond-like carbon (Si-DLC) films were prepared by dc pulse-plasma chemical vapor deposition (CVD), using a mixture of acetylene (C₂H₂) and tetramethylsilane (TMS) as the material gas. The pulse voltage was varied from − 2 to − 5 kV, and the TMS flow ratio (TMS/(C₂H₂ + TMS)) was varied from 0 to 40%. At a pulse voltage of − 2 kV, an increase in TMS flow ratio leads to a decrease in hardness. In contrast, at a pulse voltage of − 5 kV, an increase in TMS flow ratio leads to a slight increase in hardness. The high hydrogen concentration in the films due to an increase in TMS flow ratio promotes the formation of polymeric sp³ C―H bonds, resulting in the fabrication of soft films at a low pulse voltage of − 2 kV. However, an increase in the effect of ion peening on the growth face results in the formation of hard films at a high pulse voltage of − 5 kV. Then, at a pulse voltage of − 5 kV fabricating hard Si-DLC films, an increase in TMS flow ratio leads to an increase in the silicon content in the films, resulting in a decrease in the friction coefficient. Therefore, it is clarified that Si-DLC films fabricated by dc pulse-plasma CVD under a high pulse voltage and high TMS flow ratio exhibit high hardness and a low friction coefficient. Moreover, to investigate the friction coefficient of Si-DLC films fabricated by dc pulse-plasma CVD, films deposited by dc plasma CVD were also evaluated. To obtain the same low friction coefficient, dc pulse-plasma CVD requires less TMS than dc plasma CVD. Hence, it is also clarified that Si-DLC films can be fabricated at a low cost by dc pulse-plasma CVD.     

Synthesis of CeO2-ZrO2 solid solution by glycothermal method and its oxygen release capacity

The glycothermal (GT) reaction of Ce acetate and Zr alkoxide directly yielded CeO₂-ZrO₂ solid solutions in a region of low Ce content ≤40 mol%. Of the CeO₂-ZrO₂ solid solutions obtained by the GT method and subsequent calcination at 500 or 800 °C, the sample with 20 mol% Ce content had the largest BET surface area. This sample exhibited the highest Ce-based oxygen release capacity in the whole Ce/Zr composition range. The oxygen release capacities of CeO₂-ZrO₂ solid solutions synthesized by the GT method were much larger than those of the samples prepared by a coprecipitation (CP) method. The Reitveld analysis and the repetitive reduction-oxidation experiment indicated that the CeO₂-ZrO₂ solid solution synthesized by the GT method has a homogeneous structure as compared with that prepared by the CP method.     

Surface and pore structure of alumina derived from xerogel/aerogel

The alkyl derivatives of boehmite were prepared by solvothermal reaction of aluminum isopropoxide in n-alcohols (ethanol, 1-butanol, 1-hexanol, 1-octanol and 1-dodecanol) and the products were recovered as aerogel/xerogel by the removal of the solvent at the end of reaction. Aerogel or xerogel can be obtained simply by using only a reaction vessel (autoclave) and the obtained products were composed of plate-like particles having a well-developed boehmite structure. The alumina powders obtained by calcination of these products had relatively large pore-volumes ranging from 1.35 to 2.56 cm³/g. Transformation into α-Al₂O₃ was retarded even after calcination at 1200 °C. The effect of n-alcohols used in the solvothermal reaction on the phase, morphology and pore-texture of the alumina samples are discussed.     

THREE‐DIMENSIONAL SEISMIC GEOMORPHOLOGY OF PALEOKARST IN THE CRETACEOUS MACAÉ GROUP CARBONATES,CAMPOS BASIN,BRAZIL

Three‐dimensional seismic data from an oilfield in the Campos Basin, SE Brazil, was used to characterize a karstified unconformity surface at the top of the Albian – Cenomanian Macaé Group. Macaé Group carbonates underwent intense karstification associated with subaerial exposure during a period of some 10 to 15 Ma resulting in the development of canyons, valleys, sinkholes and cave systems. The carbonates host commercial oil accumulations at a number of important oil fields. Understanding how the karstification process has affected the carbonates' reservoir properties is essential for future exploration, not only to improve recovery rates but also to avoid drilling‐related issues such as thief zones. In this context, this study aims to characterize the top‐Macaé Group paleokarst system by investigating the morphology of the associated reflectors recorded on seismic data, together with endokarst features in the underlying carbonate succession such as cave systems and collapse structures. The top‐Macaé Group seismic horizon can be divided into two principal geomorphological domains: highlands, characterized by abrupt relief with well‐developed erosional features; and lowlands, marked by a smoother topography. Collapse sinkholes occur in both domains and take the form of closed circular depressions. The study of endokarst features from an analysis of amplitude anomalies (bright spots) indicates the presence of heterogeneous cave systems. The interpreted data contributes to a better understanding of the spatial distribution of the paleokarst system in the Macaé Group carbonates and may assist with future hydrocarbon exploration in the Campos Basin.     

Present Status of the Nd:YAG Thomson Scattering System Development for Time Evolution Measurement of Plasma Profile on Heliotron J

A new high repetition rate Nd:YAG Thomson scattering system is developed for the Heliotron J helical device.A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma.The system has 25 spatial points with ～10mm resolution.Two high repetition Nd:YAG lasers (>550mJ@ 50Hz) realize the measurement of the time evolution of the plasma profile with ～10ms time intervals.Scattered light is collected by a large concave mirror (D=800 mm,f/2.25) with a solid angle of ～100 mstr and transferred to interference filter polychromators by optical fiber bundles in a staircase form.The signal is amplified by newly designed fast preamplifiers with DC and AC output,which reduces the low frequency background noise.The signals are digitized with a multi-event QDC,fast gated integrators.The data acquisition is performed by a VME-based system operated by the CINOS.     

On the separation in 2-period double round robin tournaments with minimum breaks

This paper considers the separation in 2-period double round robin tournaments (2P-DRRTs) with minimum breaks. The separation is a lower bound on the number of slots between the two games with the same opponents. None of known schemes provides 2P-DRRTs with minimum breaks and a positive separation. We first propose a new scheme to generate 2-separation 2P-DRRTs with minimum breaks, based on single round robin tournaments (SRRTs) with minimum breaks which have the last break in the third slot from the end. Our experiment results show that such SRRTs exist for 8-68 teams. Secondly, we consider maximizing the separation in general 2P-DRRTs with minimum breaks by integer programming and constraint programming, respectively. The two approaches of direct formulation and “first-break, then-schedule” decomposition are presented and compared. We obtain the maximum separation for up to 14 teams. Furthermore, we consider the application with place constraints to show the flexibility and efficiency of scheduling 2P-DRRTs with minimum breaks and a positive separation.     

Electrochemical analysis of perpendicular mesoporous Pt electrode filled with pure water for clarifying the active region in fuel cell catalyst layers

A perpendicular mesoporous platinum film is used as a model electrode to clarify the effectiveness of catalysts inside agglomerates of fuel cell catalyst layers on the basis of experimental facts. The analysis clarifies that: (i) Pt surface even apart from Nafion ionomer phase can be electrochemically active; (ii) its response is different from that of the surface covered with ionomer; and (iii) ionic resistance in pores filled with pure water is too high (ca. 0.18 MΩ cm) for fuel cell reactions to smoothly occur. We conclude that such catalysts in pores filled with pure water are ineffective for fuel cell reactions due to the high ionic resistance, though their catalytic activity is possibly higher than that of the catalysts covered with Nafion.