Proton incorporation in yttria-stabilized zirconia during atomic layer deposition

This work elucidated the proton-incorporation mechanism in ALD YSZ¹. Isotope ²H₂O was used as an oxidant to trace proton incorporation. The ratio of ZrO₂ to Y₂O₃ ALD cycles was varied from 1:1 to 5:1. TEM confirmed that the ALD YSZ films grew as fully crystallized columnar grains in the cubic ZrO₂ phase. SIMS indicated that the Y³⁺ and ²H⁺ concentrations were linearly correlated, indicating yttria-deposition-induced proton incorporation. XPS confirmed an appreciable amount of Y(OH)₃ proportional to the ²H⁺ content in the ALD YSZ, as was also detected by SIMS. Oxide ion vacancies created by the replacement of ZrO₂ with relatively small amounts of Y₂O₃ provided additional vacancies for proton incorporation, resulting in steeper [²H⁺]/[Y³⁺] slopes.     

Direct stamping of silver nanoparticles toward residue-free thick electrode

Direct stamping of functional materials has been developed for cost-effective and process-effective manufacturing of nano/micro patterns. However, there remain several challenging issues like the perfect removal of the residual layer and realization of high aspect ratio. We have demonstrated facile fabrication of flexible strain sensors that have microscale thick interdigitated capacitors with no residual layer by a simple direct stamping with silver nanoparticles (AgNPs). Polyurethane (PU) prepolymer was utilized as an adhesive layer to transfer AgNPs more efficiently during the separation step of the flexible stamp from directly stamped AgNPs. Scanning electron microscopy images and energy dispersive x-ray spectroscopy analysis revealed residue-free transfer of microscale thick interdigitated electrodes onto two different flexible substrates (elastomeric and brittle) for the application to highly sensitive strain sensors.     

Development of a press-forming technology of the pressboard for a 154 kV transformer

A pressboard consisting of an angle ring and a cap is installed at the primary and secondary coil windings of a transformer. This pressboard is related to transformer durability. Since transformer capacities are increasing, it is necessary to develop a pressboard of high voltage grade (above 150 kV). In this study, a press-forming technology was developed for the pressboard of a 154 kV transformer. To determine the optimum shape of the pressboard, the press-forming factors were experimentally evaluated through the mechanical tensile strength and AC withstand voltage tests under wet conditions. From the results, the optimum size and shape of the pressboard was found to be R15??R20 mm under a forming pressure of 10 MPa. When the relative humidity (RH) was less than 50%, the moisture absorption rate in oil decreased by 25??40% compared to that in air. However, when RH exceeded 50%, the difference in the moisture absorption rate between the cases of oil and air was just 8??10%. The AC withstand voltage of the pressboard was weak against moisture. The average AC withstand voltage at 40°C and RH of less than 50% decreased by about 15% compared to the dried condition, and the maximum value decreased by 30% at 40°C and RH of more than 50%.     

Assessment of the crack growth characteristics at the low fatigue limit of a multi-pass welded Ni-based alloy 617

It has become known that the most effective methodology for green power plant systems is to increase the generating efficiency of steam power plants. Among the materials developed to improve the performance, it is known that the most practical and applicable materials are Ni-based Alloys. However, it is necessary to first guarantee mechanical reliability of the weld for applying these Ni-based Alloys. In this study, firstly, the fatigue strength of multi-pass welded Ni-based Alloy 617 in as-welded and post weld heat-treated conditions were assessed. And then the crack growth characteristics at the low fatigue limit of them were assessed. From the results, fatigue strength of the welds those were post weld heat treated did not show large difference compare to not heat-treated ones. These results mean that the weld of Ni-based Alloy 617 is not influenced remarkably by post weld heat treatment in the metallurgical and mechanical changes. However, it was found that the fatigue crack grew at the low fatigue limit, which was about 48.4% (327 MPa) of the static tensile strength (675.1 MPa) of the weld, and 43.1% of the base material (759.4 MPa).     

Thermal stabilities and flame retardancies of phloroglucinol‐based organo phosphates when applied to polycarbonate

A series of organo phosphorus flame retardants (FRs) based on aromatic phosphate and cyclic phosphate were synthesized in an attempt to develop an efficient FR for polycarbonate. Their successful synthesis was confirmed by FT‐IR and ¹ H and ³¹P NMR. Their thermal stability and flame retarding efficiency as a single‐component additive were investigated and compared with the commercial FR, resorcinol bis(diphenyl phosphate). The thermogravimetric analysis results revealed that the aromatic phosphate synthesized in this study, phloroglucinol diphenyl phosphate (PDP), shows a higher thermal degradation temperature and better flame retardancy even though it has a lower P content than cyclic phosphate‐based FRs. The flame retarding efficiency was evaluated by the UL‐94 test method. The V‐0 rating was achieved at a PDP loading of 2 wt% in polycarbonate in the presence of an anti‐dripping agent (1 wt%), which is better than that of resorcinol bis(diphenyl phosphate) and cyclic phosphate‐based FRs. The high thermal stability and P–OH generation tendency is responsible for the better flame‐retarding performance of PDP. The degradation path of PDP is also discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Predicting the Lifespan and Retweet Times of Tweets Based on Multiple Feature Analysis

In social network services, such as Facebook, Google+, Twitter, and certain postings attract more people than others. In this paper, we propose a novel method for predicting the lifespan and retweet times of tweets, the latter being a proxy for measuring the popularity of a tweet. We extract information from retweet graphs, such as posting times; and social, local, and content features, so as to construct prediction knowledge bases. Tweets with a similar topic, retweet pattern, and properties are sequentially extracted from the knowledge base and then used to make a prediction. To evaluate the performance of our model, we collected tweets on Twitter from June 2012 to October 2012. We compared our model with conventional models according to the prediction goal. For the lifespan prediction of a tweet, our model can reduce the time tolerance of a tweet lifespan by about four hours, compared with conventional models. In terms of prediction of the retweet times, our model achieved a significantly outstanding precision of about 50%, which is much higher than two of the conventional models showing a precision of around 30% and 20%, respectively.     

Conductive adhesive with transient liquid‐phase sintering technology for high‐power device applications

A highly reliable conductive adhesive obtained by transient liquid‐phase sintering (TLPS) technologies is studied for use in high‐power device packaging. TLPS involves the low‐temperature reaction of a low‐melting metal or alloy with a high‐melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag‐coated Cu, a Sn96.5‐Ag3.0‐Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 °C, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.     

Optimal replacement strategy for stochastic deteriorating system with random wear limit under periodic inspections

In this paper, we examine the preventive maintenance policies for systems/items which are degraded continuously in time and the degree of deterioration that can be observed through periodic inspection. The items will be replaced preventively if the wear process exceeds a limit at periodic inspection or replaced immediately on failure. The limit is assumed to be random in taking individual variation to withstand damages or unmeasurable variables latent to failure into account. Continuous wear process is modeled via a gamma process. We derive an optimal wear limit for preventive replacement so that the long-run total expected cost per unit time is minimized. The proposed method is applied to a problem of block mat inspection for the barrier’s seabed protection.