A facile top-down approach for constructing perovskite oxide nanostructure with abundant oxygen defects as highly efficient water oxidation electrocatalyst

Developing highly efficient electrocatalysts for oxygen evolution reaction (OER) is of significant importance for the application of many energy conversion and storage technologies. Perovskite oxides have attracted great attention as potential OER electro-catalysts. Their performance, however, are strongly limited by large particle size, owing to the high synthesis temperature. Herein, we report a facile top-down strategy for fabricating perovskite oxide nanostructures with large surface area and strongly improved intrinsic OER activity. SrNb_0.1Co_0.7Fe_0.2O_3-δ (SNCF) particles with micro size are treated by (NH₄)₂Fe(SO₄)₂ saturated solution for different time length at room temperature. The obtained catalysts exhibit significantly increased surface area with nanosheet structure in the outer layer. Furthermore, cobalt on the surface are reduced from Co³⁺ to Co²⁺, suggesting oxygen vacancy formation on the surface. The defective SNCF nanostructure exhibits significantly improved OER activity and good stability. The facile methodology reported in this work can be generally applied to other oxide electrocatalysts for energy applications.     

退火对Ge掺杂SiO2薄膜的影响

用等离子体增强化学气相淀积制备了Ge掺杂SiO2薄膜,并对薄膜进行了不同温度的退火处理。采用棱镜耦合仪、原子力显微镜和傅里叶变换红外光谱分析技术研究了不同退火温度对Ge掺杂SiO2薄膜性质的影响。通过1 100℃退火处理后,正的折射率变化量和负的体积变化量随着GeH4流量增加而增大,Ge-O-Ge键增多;而通过900℃退火处理后,折射率没有随着GeH4流量增加而增大;薄膜的表面粗糙度随着退火温度升高而降低。研究结果表明,SiO2薄膜中Ge掺杂过量,其折射率反常下降;通过1 100℃退火处理后,折射率随着GeH4流量增加而增大,折射率的增大主要是由于薄膜密实化和Ge-O-Ge键的形成。     

一种无线宽带收发机载波泄漏校准和补偿技术

A carrier leakage calibration and compensation technique based on digital baseband for a wideband wireless communication transceiver is proposed. The digital baseband transmits a calibration signal, samples the signal which passes through the transmitter path and the calibration loop in the RF chip, measures the carrier leakage by analyzing the sampled data and compensates it. Compared with a self-calibration technique in the RF chip, the proposed technique saves area and power consumption for the wireless local area network （WLAN） solution. This technique has been successfully used for 802.1 In system and satisfies the requirement of the standard by achieving over 50 dB carrier leakage suppression.     

一种低功耗高速空间光调制器驱动电路

本文描述了一种新型的多量子阱空间光调制器驱动电路的设计和测试。为了解决时钟同步问题并减少功耗,我们有别于前人,将所有电路模块集成在一块芯片上。因为传统的单斜坡数模转换器无法消除电容的失配,所以我们转而采用64个列共享8位电阻串数模转换器来提供输出电压,实现0.5V至3.8V的可编程电压调控。这些数模转换器被紧密放置于6464 驱动阵列的上方力求减小失配。每个转换器消耗80uA电流,在280ns内完成一次转换。为了更快的传输速率,系统采用2级缓存,工作时钟50MHz,真刷新率达到50K帧每秒,整片功耗302mW。芯片采用0.35um CMOS工艺,面积5.5 mm7 mm。     

Core-shell metallic alloy nanopillars-in-dielectric hybrid metamaterials with magneto-plasmonic coupling

Combining plasmonic and magnetic properties, namely magneto-plasmonic coupling, inspires great research interest and the search for magneto-plasmonic nanostructure becomes considerably critical. Here we designed a nanopillar-in-matrix structure with core–shell alloyed nanopillars for both BaTiO₃ (BTO)-Au_0.5Co_0.5 (AuCo) and BTO-Au_0.25Cu_0.25Co_0.25Ni_0.25 (AuCuCoNi) hybrid systems, i.e., ferromagnetic alloy cores (e.g., Co or CoNi) with plasmonic shells (e.g., Au or Au/Cu). These core–shell alloy nanopillars are uniformly embedded into a dielectric BTO matrix to form a vertically aligned nanocomposite (VAN) structure. Both hybrid systems present excellent epitaxial quality and interesting multi-functionality, e.g., high magnetic anisotropy, magneto-optical coupling response, tailorable plasmonic resonance wavelength, tunable hyperbolic properties and strong optical anisotropy. These alloyed nanopillars-in-matrix designs provide enormous potential for complex hybrid material designs with multi-functionality and demonstrate strong interface enabled magneto-plasmonic coupling along with plasmonic and magnetic performance.     

Conductive,self-cleaning,and short-circuit proof multi-functional graphene aerogel composite fibers

This work reports the superior properties of flexible multi-functional composite fibers based on graphene aerogel fibers. With the addition of phase change materials, the graphene aerogel fibers were synthesized by wet spinning and supercritical drying. The phase change materials can improve the structural uniformity and thermal stability of the composite fibers. The fibers coated with polydimethylsiloxane and fluorocarbon can respond to various external stimuli (e.g., electrons, photons, and heat), as well as have excellent properties of shape compliance, self-cleaning, and insulated surfaces. After coating fluorocarbon, the maximum water contact angle of graphene aerogel fibers increases from 132.18° to 151.77°. It is worth mentioning that adding an insulation layer of polydimethylsiloxane avoids the high-temperature problem caused by the short circuit of graphene aerogel fibers. The short-circuit temperature of graphene aerogel fibers is as high as 65 °C, while that of the composite fiber is only 41.5 °C after coating with polydimethylsiloxane. The temperature of graphene aerogel fibers with polyethylene glycol can increase to 39.3 °C under simulated sunlight. In addition, graphene aerogel fibers have excellent electrical conductivity (4.85?×?10³ S m^?1) at 300 K. After coating with polyethylene glycol, its electrical conductivity is still as high as 2.95?×?10³ S m^?1. The good electrical conductivity makes the aerogel fibers have promising application in advanced wearable systems.

     

Ferroelectric properties of neodymium-doped Bi4Ti3O12 thin films crystallized in different environments

Neodymium (Nd)-doped Bi₄Ti₃O₁₂ (Bi_3.15Nd_0.85Ti₃O₁₂, BNT) ferroelectric films have been deposited on Pt/Ti/SiO₂/Si substrates by a sol–gel process and crystallized in nitrogen, air and oxygen environments, respectively. The crystallization environment was found to be important in determining the crystallization and ferroelectric properties of the BNT films. The film crystallized in nitrogen at a relatively low temperature of 650 °C, and exhibits excellent crystallinity and ferroelectricity with a remanent polarization of 2P_r=63.6 μC/cm², a coercive field of 130 kV/cm and a fatigue-free characteristic. While the films annealed in air and oxygen, they did not show good crystallinity and ferroelectricity until they were annealed at 710 and 730 °C, respectively. A correlation between the remanent polarization and dielectric constants of the BNT films has been observed.     

Preparation of silver nanoparticles dispersed in polyacrylonitrile nanofiber film spun by electrospinning

Ag nanoparticles dispersed in polyacrylonitrile (PAN) nanofiber film spun by electrospinning were in situ prepared by reduction of silver ions in N₂H₅OH aqueous solution. The Ag/PAN nanocomposite film was characterized by UV absorption spectroscopy, transmission electron microscopy (TEM) and surface-enhanced Raman scattering (SERS) spectroscopy. UV spectrum and TEM image show that silver nanoparticles with average diameter of 10 nm were obtained and dispersed homogeneously in PAN nanofibers. SERS spectrum indicates that the structure of PAN has been changed after Ag nanoparticles are dispersed in PAN.