Monolithiation of 5,5′‐Dibromo‐2,2′‐bithiophene Using Flow Microreactors: Mechanistic Implications and Synthetic Applications

The lithiation of 5,5′‐dibromo‐2,2′‐bithiophene with one equivalent of an alkyllithium such as n‐BuLi or s‐BuLi was studied by varying the residence time in flow microreactors. With a short residence time, the product 2,2′‐bithiophene (3) derived from dilithiation was obtained preferentially and a significant amount of the starting material 5,5′‐dibromo‐2,2′‐bithiophene remained unchanged. An increase in the residence time caused a higher yield of the product 5‐bromo‐2,2′‐bithiophene derived from monolithiation with expense in the yields of 2,2′‐bithiophene and 5,5′‐dibromo‐2,2′‐bithiophene. The lithiation using MeLi gave the product 5‐bromo‐2,2′‐bithiophene preferentially even with a very short residence time.     

Application results of a prototype ultrasonic liquid film sensor to a 7 MPa steam–water two-phase flow experiment

A prototype ultrasonic liquid film sensor was applied to a high-temperature steam–water two-phase flow experiment. The liquid film sensor was vertically installed in a loop which was connected to HUSTLE, a multi-purpose steam source test facility. The hydraulic diameter of the measurement section was 9.4 mm. The output waveforms of the sensor were acquired with a digital oscilloscope. The fluid temperature and system pressure were kept at 288 °C and 7.2 MPa, respectively, during the experiment. The pulse-echo method was used to calculate the liquid film thickness. The cross-correlation calculation was utilized to determine the time difference between the pulse reflected at the sensor surface and the pulse reflected at the liquid film surface. The time-averaged liquid film thicknesses were less than 0.055 mm in the annular flow condition. The increase of the time-averaged thickness was small with the change of the gas momentum flux. The film thicknesses measured with the sensor were compared with the past experimental results; the former were smaller than one-fourth of the thickness estimated as the mean film thickness. The comparison results suggested that the continuous liquid sublayer thickness was measured with the liquid film sensor.     

Cathodic pulse breakdown of anodic films on aluminium in alkaline silicate electrolyte – Understanding the role of cathodic half-cycle in AC plasma electrolytic oxidation

Sequential anodic and cathodic pulse voltages were applied on anodised Al micro-electrodes in alkaline silicate electrolyte to explore the role of cathodic pulse in AC or bipolar plasma electrolytic oxidation (PEO) process. SEM observation was carried out to observe the sites of anodic and cathodic breakdown and their morphologies. The prior anodic breakdown accelerated the cathodic breakdown at ?50 V, and the acceleration was associated with the preferential cathodic breakdown at the anodic breakdown sites. However, the succeeding anodic breakdown during applying anodic pulse of 420 V for 2 ms was highly suppressed at the cathodic breakdown sites. This would randomise the anodic breakdown sites. Such role may contribute to the formation of rather uniform coatings on aluminium in this electrolyte without large discharge channels when larger cathodic current is applied with respect to the anodic current in AC PEO.     

Polyethylene–Carbon Nanotube Composite Film Deposited by Cold Spray Technique

Carbon nanotubes (CNTs) are high-performance materials because of their superior electrical conductivity, thermal conductivity, and self-lubrication, and they have been studied for application to polymer composite materials as fillers. However, the methods of fabricating polymer composites with CNTs, such as injection molding, are too complicated for industrial applications. We propose a simple cold spray (CS) technique to obtain a polymer composite of polyethylene (PE) and CNTs. The composite films were deposited by CS on polypropylene and nano-porous structured aluminum substrates. The maximum thickness of the composite film was approximately 1 mm. Peaks at G and D bands were observed in the Raman spectra of the films. Scanning electron microscopy images of the film surface revealed that PE particles were melted by the acceleration gas and CNTs were attached with melted PE. The PE particles solidified after contact with the substrate. These results indicate that PE–CNT composite films were successfully deposited on polypropylene and nano-porous structured aluminum substrates by CS.     

Influence of Cu metal on the domain structure and carrier mobility in single-layer graphene

We demonstrate that domain structure of single-layer graphene grown by ambient pressure chemical vapor deposition is strongly dependent on the crystallinity of the Cu catalyst. Low energy electron microscopy analysis reveals that graphene grown using a Cu foil gives small and mis-oriented graphene domains with a number of domain boundaries. On the other hand, no apparent domain boundaries are observed in graphene grown over a heteroepitaxial Cu(111) film deposited on sapphire due to unified orientation of graphene hexagons. The difference in the domain structures is correlated with the difference in the crystal plane and grain structure of the Cu metal. The graphene film grown on the heteroepitaxial Cu film exhibits much higher carrier mobility than that grown on the Cu foil.     

Chemical vapor deposition of boron- and nitrogen-containing graphene thin films

Boron and nitrogen-incorporated graphene thin films were grown on polycrystalline Ni substrates by thermal chemical vapor deposition using separate boron- and nitrogen-containing feedstocks. Boron and nitrogen atoms were incorporated in the film in almost equal amounts and the total content reached ∼28%. The film predominantly consisted of separate graphene and boron nitride domains. Carrier concentration in the graphene domains was estimated to be about 1 × 10⁻³ e/atom (3.8 × 10¹² cm⁻²) from G band shift in Raman spectra.     

Effect of α-substituents on molecular motion and wetting behaviors of poly(fluoroalkyl acrylate) thin films with short fluoroalkyl side chains

The effect of α-substituent on the molecular motion and wetting behavior of poly{2-(perfluorobutyl)ethyl acrylate} [PFA-C₄], poly{2-(perfluorobutyl)ethyl methacrylate} [PFMA-C₄], poly{2-(perfluorobutyl)ethyl α-fluoroacrylate} [PFFA-C₄], and poly{2-(perfluorobutyl)ethyl α-chloroacrylate} [PFClA-C₄] films were characterized by dynamic contact angle measurement, lateral force microscopy (LFM), wide angle X-ray diffraction (WAXD), and X-ray photoelectron spectroscopy (XPS). WAXD of oriented PFClA-C₄ fiber suggested the presence of rod-like chain due to the presence of bulky α-substituent. The glass transition temperature (T_g) of PFFA-C₄ and PFClA-C₄ were well above the room temperature. The water repellencies of PFFA-C₄ and PFClA-C₄ were as high as that of PFMA-C₄ and their oil repellency of PFFA-C₄ and PFClA-C₄ was higher than the PFMA-C_4. This result was originated from the low main chain mobility of PFFA-C₄ and PFClA-C₄ due to the presence of bulky α-substituents. The effect of molecular motion on water repellency was clarified by the results of temperature dependence studies of dynamic contact angle, LFM, and surface chemical composition measured by XPS.     

Thickness estimation of interface films formed on Li1−xCoO2 electrodes by hard X-ray photoelectron spectroscopy

Solid electrolyte interface (SEI) films formed on Li_1−xCoO₂ electrodes were observed with hard X-ray photoelectron spectroscopy (HX-PES). This paper particularly focuses on film thickness estimation using HX-PES with theoretical calculation. The validity of the calculation was proven by experiments using model SEI films. The native film formed on a LiCoO₂ composite electrode was estimated to be LiF with its thickness of 5 nm. Formation of Co (II) species on top of LiCoO₂ was also indicated. Storage of the electrode at 60 °C brought about considerable film growth (30-40 nm) with carbonate compounds formation. SEI film changes during charging of the LiCoO₂ electrode were also examined. The main component in the film was deduced to be LiF or a kind of fluorite, with its thickness decreased during charging. The SEI formation mechanisms are also elucidated.     

Effect of the atmosphere on chemical composition and electrochemical properties of solid electrolyte interface on electrodeposited Li metal

Many efforts have been paid to realize the superior anodes for future Li batteries in either the dry Ar atmosphere or the dry air atmosphere. In this work, in order to clarify the effects of such atmospheres, the most reactive anodes of Li were freshly electrodeposited under the dry Ar or under the dry air condition. The Solid Electrolyte Interface (SEI) formed during the electrodeposition of Li anodes is revealed to have a different chemical composition and protective feature. The Li deposited under the dry air was revealed to have longer cycle life in the electrolyte than that deposited in Ar, even in the electrolyte containing ionic liquid. From the XPS results, the SEI formed in dry air is proved to be different from that formed in Ar gas atmospheres, that is, the SEI formed in dry air consists of Li₂CO₃ and Li nitride. In order to improve the performance of the anodes, the atmosphere for the initial preparation of the anode/electrolyte interface should be tuned.