Analysis of the chemical and physical factors affecting reactive adsorption of ammonia on graphene/nanoporous carbon composites

Adsorption of ammonia was studied on composites of graphene and nanoporous carbon (5 and 20 wt.% graphene). The breakthrough curves were measured in three consequent adsorption–desorption runs in either dry or wet conditions. The mechanism of ammonia retention was evaluated from the point of view of either reactive or physical adsorption. The important finding is the insensitivity of the ammonia adsorption on the composites on the water content in the challenge gas. An about 50% decrease in the surface area and volume of micropores compared to nanoporous carbons does not affect the amount of physically adsorbed ammonia. It is governed by the volume of ultramicropores (pore width <0.7 nm), density of groups on the surface, hydrophobicity level, and the electronic conductivity. The surface acidity level and thus the amounts and strength of oxygen groups being able to react with ammonia at ambient conditions are of paramount importance for the reactive adsorption process.     

A correction method of color projection fringes in 3D contour measurement

In the three-dimensional (3D) contour measurement, the phase shift profilometry (PSP) method is the most widely used one. However, the measurement speed of PSP is very low because of the multiple projections. In order to improve the measurement speed, color grating stripes are used for measurement in this paper. During the measurement, only one color sinusoidal fringe is projected on the measured object. Therefore, the measurement speed is greatly improved. Since there is coupling or interference phenomenon between the adjacent color grating stripes, a color correction method is used to improve the measurement results. A method for correcting nonlinear error of measurement system is proposed in this paper, and the sinusoidal property of acquired image after correction is better than that before correction. Experimental results show that with these correction methods, the measurement errors can be reduced. Therefore, it can support a good foundation for the high-precision 3D reconstruction.     

永磁扰动检测有限元分析及优化设计

永磁扰动检测是一种新型无损检测技术,通过永磁扰动传感器在铁磁构件表面扫查并拾取受缺陷影响下静磁场变化情况来判别缺陷尺寸大小。本文深入分析了永磁体与缺陷的扰动机制,并针对传感器设计理论不足、永磁扰动检测信号微弱等问题,提出了采用环绕式体线圈探测永磁体内产生的磁扰动及采用螺旋线圈探测永磁体与缺陷间的外磁扰动,并在此基础上探究感应线圈及永磁体的几何参数对永磁扰动检测效率的影响。通过有限元模型多参数化扫描及正交试验设计方法对永磁扰动传感器进行了优化设计,该方法能够有效地提高永磁扰动内、外感应电压的幅值。     

Optimization of the incision size and cold-end temperature of a thermoelectric device

In order to optimize the performance of a thermoelectric device, an attempt is made to clarify the dependence on the temperature of its cold side and the size of the incisions made on its lateral faces. By means of experimental measurements and numerical simulations, the temperature difference between the hot and cold sides of the device is estimated, and the primary measures of performance, namely the electric power and the conversion efficiency, are examined for variations in the size of the incisions and in the cold-side temperature. The results of the simulations are in fairly good agreement with the experimental ones. Furthermore, the relationship between electrical power, conversion efficiency, and incision size were found to depend on the cold-side temperature.     

Effect of electrode structure on performance of Si anode in Li-ion batteries: Si particle size and conductive additive

The effects of Si particle size and the amount of carbon-based conductive additive (CA) on the performance of a Si anode in a Li-ion battery are investigated by adopting combinations of two different Si particle sizes (20 and 3 μm on average) and CA contents (15 and 30 wt.%), respectively. The CA contains graphitic flakes and nano-sized carbon black. Cyclic voltammetry, charge–discharge tests, scanning electron microscopy and X-ray diffraction establish that the CA content has a profound effect on the cycle-life and irreversible capacity of the Si anode. The former increases, while the latter decreases significantly with increasing CA content. Reducing the particle size of Si, on the other hand, facilitates the alloying/de-alloying kinetics. For instance a cycle-life of over 50 cycles with >96% capacity retention at a charge capacity of 600 mAh per g-Si has been demonstrated by adopting of 30 wt.% CA and 3 μm Si particles.     

Novel carbon-ceramic composite membranes with high cation exchange properties for use in microbial fuel cell and electricity generation

Actually, there are different configurations used in microbial fuel cells (MFCs) with presence or absence of an ion exchange membrane between their electrodes. Specifically, MFCs that use membranes have the objective of avoiding the diffusion of oxygen and substrate between the anodic and cathodic compartment, and to achieve a correct transfer of protons from one chamber to another. In this regard, the current study seeks to prepare and characterize new composite membranes using as precursors three types of carbonaceous materials such as bone char, coconut shell activated carbon and bituminous activated carbon and natural clay. The composite membranes of bituminous activated carbon and clay showed more promising specific conductivity (42%) than the one made with pure clay. The physicochemical properties of the membranes and their precursors were elucidated by SEM/EDX analysis, IR spectroscopy, nitrogen adsorption isotherms at 77 K and optical microscopy. Further, membranes performance was assessed using microbial fuel cells (MFCs) where the composite membranes prepared with clay-bituminous carbon reached the highest voltage values (0.95–1.02 V) in open circuits, while that reached a maximum power density of 0.699 W/m³ at a current density of 4.012 A/m³ in closed circuit. This behavior is associated with the high content of silicon and aluminum in bituminous activated carbon, which favored the proper functioning of membranes in the MFCs. Specifically, with this type of cells, energy recovery of 0.0057 kWh/m³ and 0.1322 kWh/kg chemical oxygen demand (COD) removed, which indicates an extra economic income of the order of $0.0025/kg COD. Finally, the produced power was demonstrated in prototypes to power LED and four digital clocks. This novel clay-bituminous activated carbon showed promising cost-effectiveness and sustainable energy generation, which may be suitable for wastewater treatment.     

Isothermal and thermal cycling oxidation of hot-dip aluminide coating on flake/spheroidal graphite cast iron

Two types of cast iron, flake graphite and spheroidal graphite cast iron, with ferrite matrix and similar composition, were aluminized by hot-dipping. As-coated aluminide layer consists of the outer Al topcoat, inner Fe–Al intermetallic layer and dispersed graphite. Isothermal and thermal cycling oxidation tests of aluminized specimens have been conducted. Cast irons with aluminide coating exhibit higher oxidation resistance than without the coating. However, different graphite structure results in diverse quality of aluminide coatings. Aluminide coating on flake graphite cast iron exhibits less oxidation resistance and adhesion to the substrate.     

电动汽车动态无线充电紧—强耦合模式分析

针对感应耦合结构近距离、弱偏移,以及谐振耦合式结构易受干扰的问题,提出紧—强耦合协同工作机构。通过建立动态无线充电系统的数学模型,研究其传输特性随品质因数和耦合系数的变化规律。基于有限元仿真,分析了系统的动态传输特性。为提高系统的抗偏移性、降低电磁辐射,在接收线圈装设铁氧体屏蔽结构。通过搭建实验平台对仿真过程进行实验验证,证明了所设计耦合机构的可行性。结果表明所设计的耦合机构具有较高的动态传输性能,并且在85kHz下获得了93.9%的传输效率。     

The enhancement of electrical and optical properties of PEDOT:PSS using one-step dynamic etching for flexible application

The conductivity enhancement of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) by dynamic etching process was investigated to introduce the outstanding and simplest method for soft electronics. Four different samples which were pristine PEDOT:PSS, PEDOT:PSS doped with 5 wt.% DMSO, PEDOT:PSS with dipping process, and PEDOT:PSS with dynamic etching process were prepared to compare the properties such as conductivity, morphology, relative atomic percentage, and topography. All samples were characterized by four point probe, current atomic force microscopy (C-AFM), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy. The conductivity of the sample with dynamic etching process showed the highest value as 1299 S/cm among four samples. We proved that the dynamic etching process is superior to remove PSS phase from PEDOT:PSS film, to flow strong current through entire surface of PEDOT:PSS, and to show the smoothest surface (RMS 2.28 nm). XPS analysis was conducted for accurate chemical and structural surface environments of four samples and the relative atomic percentage of PEDOT in the sample with dynamic etching was the highest as 29.5%. The device performance of the sample with the dynamic etching process was outstanding as 10.31 mA/cm² of J_sc, 0.75 eV of V_oc, 0.46 of FF, and 3.53% of PCE. All properties and the device performance for PEDOT:PSS film by dynamic etching process were the most excellent among the samples.