Deposition of Nano-Size Titania—Silica Particles in a Hot-Wall CVD Process

The deposition of nano-size titania—silica particles is carried out in a hot-wall CVD reactor by using two premixed precursors, titanium tetraisopropoxide (TTIP) and tetraethyl orthosilicate (TEOS). The deposition occurs mostly in two regions, one near the reactor entrance and the other near the reactor exit. Deposits collected near the reactor entrance are densely packed micrometer-size aggregates/particles of good adhesion to the substrate, while those near the reactor exit are loosely packed nano-size particles with a poor adhesion to the substrate. It is conjectured that the more reactive TTIP reacts first and produces TiO₂ particles later covered by SiO₂ formed via a catalytic surface reaction of the less reactive TEOS on TiO₂ particle surfaces. The presence of surface SiO₂ retards the growth of TiO₂ particles, leading to deposits formed by micrometer-size aggregates containing nano-size primary particles of 30 to 40 nm in the first deposition region. With less or no SiO₂ present on TiO₂ particle surfaces, the deposits formed in the first deposition region are densely packed micrometer-size particles. The Ti/Si ratio of the produced particles, for a furnace temperature of 750°C, increases with increasing TTIP/TEOS concentration ratio, and is lower than the Ti/Si ratio of the incoming reactant stream. The Ti/Si ratio of the particles is also found to decrease with increasing furnace temperature.     

Preparation of Monolithic Silica Aerogel of Low Thermal Conductivity by Ambient Pressure Drying

Monolithic silica aerogels with thermal conductivity as low as 0.036 W·(m·K)⁻¹ and porosity as high as 97% were successfully prepared by ambient pressure drying through a multiple modification approach. This approach may replace the more costly and dangerous operation of supercritical drying. The tetraethoxysilane (TEOS)-derived wet gel was made hydrophobic with multiple treatments of trimethylchlorosilane and dried under ambient pressure. The multiple treatments were found to be necessary to achieve sufficient modification of the wet gel for reduction in drying-induced surface tension force to maintain product integrity and high porosity. Comparisons in nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy for surface bonding and contact angle measurement for hydrophobicity between the no, single, and multiple surface modification (MSM) samples were conducted to reveal the difference in the extent of the resulting surface modification. In conclusion, the MSM procedure reduced the volume shrinkage, increased the monolithicity and porosity, and lowered the thermal conductivity of the resulting aerogels.     

Rich photoluminescence emission of SnO2–SiO2 composite aerogels prepared with a co-fed precursor sol–gel process

Tin oxide–silica composite aerogels were successfully prepared with a co-fed precursor sol–gel process. The crystallinity of the tin oxide nanoparticles, embedded in the mesoporous SiO₂ network, was improved with increasing the post-reaction thermal treatment temperature. The composite aerogels exhibited a rich photoluminescence (PL) emission contributed by both SnO₂ and SiO₂. The PL peak of 346 nm was from the near band edge emission of the tin oxide nanoparticles, and the ones located at 310 and 476 nm were attributable to the oxygen deficiencies of the silica network. Three more emission peaks, 387, 432, and 522 nm, were observed, with the 387 nm peak contributed by the oxygen vacancies V_O⁺⁺, the 432 nm peak by the Sn interstitials, and the 522 nm peak by the oxygen vacancies V_O⁺, respectively, of the tin oxide nanoparticles. The intensities of these three defect level emissions were found decreased, as compared to that of the near band edge emission, with increasing the post-reaction thermal treatment temperature as the tin oxide crystallinity improved.     

Size Effects on Silica Polymorphism

In this study, we found that the polymorphism and sintering behavior of silica can be affected by the size of starting particles. The formation of the stable tridymite phase, which is metastable unless a flux or mineralizer is present, is achieved with sintering of very fine silica particles of about 10 nm without the presence of a flux or mineralizer. Cristobalite phase is obtained as an intermediate as the amorphous phase transforms into the stable tridymite phase.     

Inorganic Filler Enhanced Formation of Stable Inorganic-Rich Solid Electrolyte Interphase for High Performance Lithium Metal Batteries

Lithium metal (LM) is a promising anode material for next generation lithium ion based electrochemical energy storage devices. Critical issues of unstable solid electrolyte interphases (SEIs) and dendrite growth however still impede its practical applications. Herein, a composite gel polymer electrolyte (GPE), formed through in situ polymerization of pentaerythritol tetraacrylate with fumed silica fillers, is developed to achieve high performance lithium metal batteries (LMBs). As evidenced theoretically and experimentally, the presence of SiO₂ not only accelerates Li⁺ transport but also regulates Li⁺ solvation sheath structures, thus facilitating fast kinetics and formation of stable LiF-rich interphase and achieving uniform Li depositions to suppress Li dendrite growth. The composite GPE-based Li||Cu half-cells and Li||Li symmetrical cells display high Coulombic efficiency (CE) of 90.3% after 450 cycles and maintain stability over 960 h at 3 mA cm⁻² and 3 mAh cm⁻², respectively. In addition, Li||LiFePO₄ full-cells with a LM anode of limited Li supply of 4 mAh cm⁻² achieve capacity retention of 68.5% after 700 cycles at 0.5 C (1 C = 170 mA g⁻¹). Especially, when further applied in anode-free LMBs, the carbon cloth||LiFePO₄ full-cell exhibits excellent cycling stability with an average CE of 99.94% and capacity retention of 90.3% at the 160th cycle at 0.5 C.     

Fabrication of hydrogen electrode supported cell for utilized regenerative solid oxide fuel cell application

A utilized regenerative solid oxide fuel cell (URSOFC) provides the dual function of performing energy storage and power generation, all in one unit. When functioning as an energy storage device, the URSOFC acts like a solid oxide electrolyzer cell (SOEC) in water electrolysis mode; whereby the electric energy is stored as (electrolyzied) hydrogen and oxygen gases. While hydrogen is useful as a transportation fuel and in other industrial applications, the URSOFC also acts as a solid oxide fuel cell (SOFC) in power generation mode to produce electricity when needed. The URSOFC would be a competitive technology in the upcoming hydrogen economy on the basis of its low cost, simple structure, and high efficiency. This paper reports on the design and manufacturing of its anode support cell using commercially available materials. Also reported are the resulting performance, both in electrolysis and fuel cell modes, as a function of its operating parameters such as temperature and current density. We found that the URSOFC performance improved with increasing temperature and its fuel cell mode had a better performance than its electrolysis mode due to a limited humidity inlet causing concentration polarization. In addition, there were great improvements in performance for both the SOFC and SOEC modes after the first test and could be attributed to an increase in porosity within the oxygen electrode, which was beneficial for the oxygen reaction.     

Structural characterization and computer-aided optimization of a small-molecule inhibitor of the Arp2/3 complex, a key regulator of the actin cytoskeleton

CK-666 (1) is a recently discovered small-molecule inhibitor of the actin-related protein 2/3 (Arp2/3) complex, a key actin cytoskeleton regulator with roles in bacterial pathogenesis and cancer cell motility. Although 1 is commercially available, the crystal structure of Arp2/3 complex with 1 bound has not been reported, making its mechanism of action uncertain. Furthermore, its relatively low potency increases its potential for off-target effects in vivo, complicating interpretation of its influence in cell biological studies and precluding its clinical use. Herein we report the crystal structure of 1 bound to Arp2/3 complex, which reveals that 1 binds between the Arp2 and Arp3 subunits to stabilize the inactive conformation of the complex. Based on the crystal structure, we used computational docking and free-energy perturbation calculations of monosubstituted derivatives of 1 to guide optimization efforts. Biochemical assays of ten newly synthesized compounds led to the identification of compound 2, which exhibits a threefold increase in inhibitory activity in vitro relative to 1. In addition, our computational analyses unveiled a surface groove at the interface of the Arp2 and Arp3 subunits that can be exploited for additional structure-based optimization.     

Effect of the Spinning Deformation Processing on Mechanical Properties of Al-7Si-0.3Mg Alloys

This study investigates the mechanical properties of Al-7Si-0.3Mg (A356) alloy affected by the spinning deformation processing (SDP). The cast structure of the A356 alloy becomes elongated with increasing reduction in thickness. This leads to reduction of casting defects, and refines and distributes the eutectic silicon phase throughout the Al-matrix. The hardness tends to reach a steady value due to the uniformity of the microstructure with the reduction in thickness. The SDP leads to a re-arrangement in the eutectic region, which forces the propagation of cracks through the ductile ??-Al phase. The tensile strength and elongation increases accordingly. The improvement on tensile strength and elongation produces the best quality index for A356 alloy.     

A High-Speed Optical Multidrop Bus for Computer Interconnections

Signal integrity constraints of high-speed electronics have made multidrop electrical buses infeasible. This high-speed alternative uses hollow metal waveguides and pellicle beam splitters that interconnect modules attached to the bus. With 1 mW of laser power, the bus can interconnect eight modules at 10 Gbps per channel and achieves an aggregate bandwidth of more than 25 Gbytes per second with 10-bit-wide signaling paths.     

Surface acoustic wave gas monitor for ppm ammonia detection

A shear horizontal surface acoustic wave (SH-SAW) sensor coated with polyaniline (PANI) film was investigated in this study. The frequency shift of SH-SAW was measured to detect the presence of ammonia. In addition, an analysis of humidity interference with the ammonia was performed. The SH-SAW sensor in this study responded to the ammonia gas and could be recovered using dry nitrogen. Detecting at an ammonia concentration of 20.45 ppm, the frequency shift was 1.79 ppm and the signal-to-noise ratio was 25.06 dB. This sensor had a response time of less than 150 s. Also, the frequency shift increased as the humidity increased. The cross-sensitivity varied nonlinearly with the ammonia concentration.