Non-destructive evaluations of water uptake in epoxy coating

A commercial epoxy coating was studied on steel panels and as free films to investigate water uptake using non-destructive techniques (gravimetric analysis, Electrochemical Impedance Spectroscopy [EIS], Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy [ATR-FTIR], and Scanning Acoustic Microscopy [SAM]) after immersion in 3.5 wt% NaCl solution. In epoxy free films, water uptake showed rapid absorption initially, slowing down due to the counteracting process between water uptake and leachable content. Later, a mass decrease indicated leaching dominance. On coated steel, EIS revealed rapid water absorption within 72 h, followed by slower uptake up to 336 h. The continuous increase in water content resulted from observed coating layer swelling, confirmed by SAM. ATR-FTIR analysis indicated hydrogen bonding of most absorbed water molecules to the epoxy matrix. By combining non-destructive techniques, water uptake mechanisms into the epoxy coating film were proposed.     

模具设计中动态干涉检查方法

基于汽车模具企业广泛使用的CATIA、UG软件,介绍了3种汽车模具设计时的动态干涉检查方法,并详细叙述了SAM专业检测干涉软件的使用,同时列举了模具设计过程中常见的动态干涉检查类型,为以后的模具设计及制造提供必要的帮助。     

基于单片机的煤矿瓦斯小型智能监控系统设计

由于技术资金的限制,我国中小型煤矿在瓦斯监测体系建设上存在诸多问题。为了破解这些难题,面向中小型煤矿的实际应用设计了一种基于单片机AT91SAM9261的小型瓦斯智能监控系统。整个设计具有简单实用、便于在现有设备技术上升级改造的特点,具有一定的应用前景。     

Adsorption of Alkanethiols on Gold Surfaces: PM-IRRAS Study of the Influence of Terminal Functionality on Alkyl Chain Orientation

The present paper focuses on a simplified method to study the orientation and the anisotropy of two different alkanethiols self-assembled monolayers on gold surfaces. The alkanethiols of interest vary only by their terminal functionalities (COOH and COOCH₃), thus allowing one to highlight the influence of these ending chemical groups on the final orientation of the adsorbed molecules. 11-Mercaptoundecanoic acid [HS-(CH₂)₁₀-COOH] and the methyl-11-mercaptoundecanoate [HS-(CH₂)₁₀-COOCH₃] were grafted under adequate conditions to obtain a high grafting density on gold substrates. These latter, before and after the alkanethiol adsorption, were analyzed mainly by the polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) technique to access orientation angles, and by atomic force microscopy (AFM) to check the homogeneity of the grafted layer.

By applying an original PM-IRRAS simplified method, the results showed an orientation closer to the normal of the surface plane in the case of the acid thiol compared with the ester one, which is probably because of the lateral hydrogen bonds established between the adjacent COOH functions. This method offers a direct and simple way to quantify the orientation angles in the alkanethiol nanofilms.     

A review of self-assembled monolayers as potential terahertz frequency tunnel diodes

In this review, we describe the principles of the tunnel junction, self-assembled monolayer （SAM） application techniques, experimental testbed fabrication, and characterization of the films and devices. In addition, techniques for directed application, removal, and functionalization of the monolayers are discussed. Bottom-up fabrication techniques have seen increased attention because of their versatility and ease of use. These films see mechanical uses as surface modifiers and micro-scale lubricants. Advances in nanowatt electronics and ultra-low power sensors have opened up an energy harvesting niche for solutions which would have proven ineffective just some years ago. The focus of this study is the two- terminal junction which has potential applications in THz rectification for energy harvesting, medical imaging, and defense sensing. The quantum theory of operation behind these devices is touched on briefly---describing tunneling through the organic monolayers. Commentary on trends in research and potential future work are presented as well.     

1 Volt organic transistors with mixed self-assembled monolayer/Al2O3 gate dielectrics

Control of the threshold voltage and the subthreshold swing is critical for low voltage transistor operation. In this contribution, organic field-effect transistors (OFETs) operating at 1 V using ultra-thin (∼4 nm), self-assembled monolayer (SAM) modified aluminium oxide layers as the gate dielectric are demonstrated. A solution-processed donor–acceptor semiconducting polymer poly(3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione)thieno[3,2-b]thiophene) (PDPP2TTT) is used as the active layer. It is shown that the threshold voltage of the fabricated transistors can be simply tuned by carefully controlling the composition of the applied SAM. The optimised OFETs display threshold voltages around 0 V, low subthreshold slopes (150 ± 5 mV/dec), operate with negligible hysteresis and show average saturated field-effect mobilities in excess of 0.1 cm²/V s at 1 V.     

基于AT91SAM9263的嵌入式系统启动过程分析

以Atmel公司的AT91SAM9263为例分析研究了它的bootloader启动过程.对从系统上电后的第一条指令到加载Linux kernel的过程进行了分析,主要阐述了bootstrap和uboot的启动过程.掌握嵌入式开发的启动过程,对后续的开发至关重要.     

SAM扫描器件芯/焊结合空洞的失效分析

超声无损检测是70种无损探伤技术的最热点。扫描声学显微镜(SAM)的原理是声阻抗成像,要求缺陷尺度大于超声波的波长。结合SAM技术中的A-扫描波形分析和C-扫描特征成像,针对由封装引入的分层和空洞缺陷进行失效分析。研究发现:分层定位的关键是A-扫描波形分析中对各界面处反射波的时间位置的判断;基于分层定位的芯/焊结合空洞缺陷的判别,关键是C-扫描图像中灰阶色带的区分(反射率差值)。     

智能保密柜嵌入式控制系统的设计与实现

为了提高保密柜管理的保密性和自动管理物品的能力,基于工业级AT91SAM9260处理器设计了一个智能保密柜嵌入式控制系统。该系统具有指纹识别开启柜门、摄像记录、RFID读写器采集柜内物品ID以及保密柜所有操作的文件记录等功能。对开源的μC/OS-Ⅱ与Linux操作系统进行了分析比较,选择Linux作为嵌入式操作系统,在进程调度、文件系统管理等方面提供了很好的支持。应用结果表明,该系统具有较好的实时处理能力,可以满足用户的应用需求。     

基于WinCE5.0下WM8731音频驱动器设计

讨论了在WinCE5.0操作系统下,基于AT91SAM9260 ARM平台,控制WM8731音频芯片的音频驱动设计,在驱动设计中利用AT91SAM9260的SPI和SSC实现对WM8731的控制和音频数据传输,并在驱动中设立多缓冲有效地提高了语音数据的实时处理,设计的驱动器可以支持同时录放音,并在实际应用中取得了很好的效果.