Effect of underpotential deposition of lead on polarization behavior of nickel in acidic perchlorate solutions at room temperature

The effect of Pb²⁺ on polarization behavior of nickel has been investigated in 0.1 M NaClO₄ + 10⁻² M HClO₄ + x M PbO solutions (x = 0, 10⁻⁵, 10⁻⁴, 10⁻³) at room temperature. The cyclic voltammogram has suggested that Pb²⁺ degrades the stability of the passive film on Ni. The corrosion potential of Ni shifted to the more noble direction and the anodic current peak of Ni dissolution decreased with increasing Pb²⁺ concentration in solution, indicating that Pb²⁺ suppresses significantly the anodic dissolution. The underpotential deposition (UPD) of lead on Ni in the potential range more noble than −0.215 V (SHE) corresponding to the equilibrium potential of the Pb²⁺ (10⁻³ M)/Pb electrode was confirmed by XPS and GDOES analyses. The anodic Tafel slope, b⁺, of Ni dissolution changed from b⁺ = 40 mV decade⁻¹ in the absence of Pb²⁺ to b⁺ = 17 mV decade⁻¹ in the presence of 10⁻⁴ or 10⁻³ M Pb²⁺, which was ascribed to the increase in active sites of Ni surface emerged as a result of electrodesorption of Pb adatoms. The roles of Pb adatoms in active dissolution and active/passive transition of Ni were discussed from the above results.     

不同pH条件下几种铜缓蚀剂的比较研究

采用交流阻抗法研究了在不同ｐＨ条件下的３％ＮａＣｌ溶液中３种缓蚀剂４ＣＢＴＡ,５ＣＢＴＡ,ＣＢＴ－１在浓度为４０ｍｇ／ｋｇ时对铜电极的缓蚀行为并与ＢＴＡ进行了比较,实验结果表明在ｐＨ＝６及ｐＨ＝９时这３种缓蚀剂均无缓蚀作用,而在ｐＨ＝３时它们的缓蚀作用比较明显,缓蚀效果均比ＢＴＡ好,尤以４ＣＢＴ缓蚀效果最佳。     

Diffusion coefficient analysis method using data statistical processing to reduce interference fringe noise effects

We proposed a simple statistical analysis method of minute concentration changes for measuring diffusion coefficient with reduced interference fringe noise effect. In the “Soret-Facet Mission,” the one-dimensional diffusion equation discretized by the finite difference method was applied for temporal homogenization processes of the minute concentration gradient induced by the Soret effect with random noises. Measured diffusion coefficient D_exp was determined by evaluating the obtained apparent diffusion coefficient distributions D. The measured value D_exp obtained by the proposed processes was found to be valid because the measured value D_exp was close to the theoretical one D_th calculated by the Darken equation and the reference one D_ref calculated in” Facet Mission” in the same solution system, respectively. In addition, by analyzing about 1/16th of the total field of view, it was possible to obtain a diffusion coefficient that are more than 95% convergent for the measured value D_exp obtained from the full field of view analysis.     

Disturbance suppression beyond Nyquist frequency in hard disk drives

In conventional hard disk drives, a control system compensates for vibration in which the frequency is higher than the Nyquist frequency by using a multi-rate filter that decreases the gain above the Nyquist frequency. However, such a control system can only avoid instability and cannot suppress disturbances above the Nyquist frequency. To overcome this problem, a control system design method that suppresses disturbances beyond the Nyquist frequency is proposed. This method uses frequency responses of a controlled object and a digital controller to calculate the gain of the sensitivity function in a sampled-data system without requiring complex calculations involving matrices, and realizes a stable resonant filter that decreases the gain of the sensitivity function above the Nyquist frequency. Significant suppression of the vibrations caused by the disturbances beyond the Nyquist frequency is demonstrated by implementing this method in the head-positioning system of a hard disk drive.     

Mechanical and thermal properties of the hybrid composites of vinylester resin and methacryl‐substituted polysilsesquioxane

Vinylester resin (VER) composed of bisphenol‐A‐based epoxy methacrylate and styrene was cured finally at 120°C with methacryl‐substituted polysilsesquioxane (ME‐PSQ) prepared from 3‐(trimethoxysilyl)propyl methacrylate and tetramethylammonium hydroxide. The dynamic mechanical and thermal properties of the VER/ME‐PSQ 90/10–60/40 hybrid composites were investigated when compared with crosslinked‐VER (C‐VER) and VER/phenyl‐substituted polysilsesquioxane (Ph‐PSQ) 80/20 composite cured at the same condition. As a result, the VER/ME‐PSQ hybrid composites showed much higher storage modulus (E′) at rubbery state than C‐VER and the VER/Ph‐PSQ composite. The E′ of the hybrid composites increased with increasing ME‐PSQ content. Also, coefficient of thermal expansion of the hybrid composites decreased with increasing ME‐PSQ content. The glass transition temperatures and 5% weight loss temperatures of the VER/ME‐PSQ hybrid composites were almost the same as those of C‐VER and the VER/Ph‐PSQ composite. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Attractive performance of a Gifford–McMahon cryocooler by co-axial layout of regenerator materials

A novel filling method of regenerator materials, which we name a co-axial layout, is experimentally investigated. The 2nd stage regenerator of a Gifford–McMahon cryocooler was packed with 50% by volume of the co-axial layout (low temperature side) that consisted of 20% Gd₂O₂S and 30% HoCu₂ spheres. The warm temperature side was packed with 50% lead spheres as a single layer. The experimental results show that the cooling power of co-axial layout is almost the same as that of a three-layer layout, 20% Gd₂O₂S, 30% HoCu₂ and 50% lead, at temperatures between the ultimate low temperature (3.0 K) and 6 K. Moreover, at the temperatures above 10 K, the co-axial layout has 1.7–2.0 times the cooling power of the three-layer layout. Thus the co-axial layout produces a major improvement in cooling power. In this paper, the performance of five types of material assortments is discussed.     

Structure and properties of Ti(IV)-doped zinc hydroxychloride rusts formed at various temperatures

To simulate the atmospheric corrosion of steels galvanized with Ti–Zn alloys under different atmospheric temperatures, Ti(IV)-doped zinc hydroxychloride (Zn₅(OH)₈Cl₂·H₂O: ZHC) was prepared at various aging temperatures of 6–120 °C. Adding the Ti(IV) inhibited the crystallization and particle growth of ZHC, showing a minimum at 50 °C. Higher aging temperature promoted the formation of TiO₂ nano-particles. Elevating the aging temperature suppressed the adsorption of H₂O and CO₂ on Ti(IV)-doped ZHC. These results suggest that the alloying Ti in galvanized steel forms compact zinc rust layer at various atmospheric temperatures in marine environment, which would lead to the enhancement of corrosion resistance.     

Numerical modeling on a reciprocating active magnetic regenerator refrigeration in room temperature

Considering the unignorable factors in practice, a new time independent, 2-dimensional porous media model of room-temperature Active Magnetic Regenerative Refrigeration (AMRR) has been proposed. The 2-D model improved the existing 1-dimensional model by introducing the influence of heat transfer effect though the regenerator wall and conduction for y-axis inside the regenerator. This study compared the previous 1-D model with the 2-D model and concluded that the system can lose 22% of cooling capacity caused by air convection and the conduction loss in y can reach to 10% of cooling capacity. It is concluded that the new model will be useful to predict the performance of room AMRR for more practical conditions.     

Compensation for position‐dependent mechanical resonances in head‐positioning control of hard disk drives

We propose a compensation method for position‐dependent mechanical resonances in head‐positioning control system of hard disk drives (HDDs). To realize high‐accuracy head‐positioning control, it is important to compensate for the mechanical resonances in the head‐positioning control system. The some mechanical resonance characteristics depend on the magnetic head's location. In conventional design method, a notch filter must be designed to compensate for the mechanical resonances at any magnetic head location. The disadvantage is that phase lag caused by the notch filter worsens the stability of the head‐positioning control system. To overcome this disadvantage, we propose a magnetic head‐position‐dependent notch filter to compensate for the position‐dependent mechanical resonances in the head‐positioning control system. The simulation results in HDD benchmark model show that the proposed method can decrease the phase lag caused by the notch filter. That is, the proposed method can improve the stability compared to the conventional method. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Setting time and formability of calcium phosphate cements prepared using modified dicalcium phosphate anhydrous powders

Calcium phosphate cements (CPCs) were prepared using Ca₄(PO₄)₂O (TeCP) and modified CaHPO₄ (DCPA) to evaluate the effects of the powder properties for DCPA particles on the setting time and formability of the resulting CPCs. Two types of modified DCPA were prepared by milling commercially available DCPA with ethanol (to produce E-DCPA) or distilled water (to produce W-DCPA). The E-DCPA samples consisted of well-dispersed, fine primary particles, while the W-DCPA samples contained agglomerated particles, and had a smaller specific surface area. The mean particle size decreased with increased milling time in both cases. The raw CPC powders prepared using W-DCPA had a higher packing density than those prepared using E-DCPA, regardless of the mean particle size. The setting time of the CPC paste after mixing with distilled water decreased with decreases in the mean particle size and specific surface area, for both types of DCPA. The CPCs prepared using W-DCPA showed larger plasticity values compared with those prepared using E-DCPA, which contributed to the superior formability of the W-DCPA samples. The CPCs prepared using W-DCPA showed a short setting time and large plasticity values, despite the fact that only a small amount of liquid was used for the mixing of the raw CPC powders (a liquid-to-powder ratio of 0.25 g g^?1 was used). It is likely that the higher packing density of the raw CPC powders prepared using W-DCPA was responsible for the higher performance of the resulting CPCs.