【作者】 刘繄；

【导师】 陈幼平； 张冈；

【作者基本信息】 华中科技大学 ， 机械电子工程， 2013， 博士

【摘要】 随着工业化的发展，氢气传感器在国防、军事及民用中均表现出强烈的需求。但是目前的各种氢气传感器都还存在着这样或者那样的缺点，无法满足各种实际需求。光纤传感器以其特有高安全性和高抗干扰性成为氢气传感器领域中最具应用前景的一类传感器。本论文针对光纤氢气传感器的研究现状以及存在的问题，主要以钯基薄膜反射式光纤氢气传感器为对象，在传感器机理、传感器关键技术、高重复性氢气传感器样机研制、快速型氢气传感器样机研制等方面进行了以下研究：（1）提出了基于光学矩阵的薄膜反射模型。该模型解决了薄膜折射率、薄膜厚度、基底材料折射率、入射光波波长等因素对薄膜反射率的影响。（2）提出了钯基合金薄膜中氢原子扩散模型。该模型建立了薄膜中氢原子浓度与扩散时间、薄膜厚度等因素的关系。通过仿真分析得出传感器的响应时间与薄膜厚度的平方呈正比。（3）基于对现有薄膜微观实验现象的观察，提出了用于解释薄膜失效的氢气泡模型。该模型阐明了脱层高度，薄膜折射率、薄膜厚度、基底材料折射率、入射光波波长等因素对传感器重复性的影响。（4）建立了光纤束的反射耦合模型，通过仿真计算研究了发送光纤芯径，接收光纤芯径，反射距离，光纤数值孔径等参数对薄膜反射率的影响。讨论了适合光纤氢气传感器的最佳反射距离。（5）为了提高氢气传感器的精度，本文分析了光电二极管工作原理，设计了基于T型网络的前置放大电路，减小了输出偏置电压。采用小波变换方法设计了基于Matlab的滤波程序，有效地消除噪声的影响，提高了传感器的信噪比。（6）在对钯基薄膜型传感器失效机理深入分析的基础上，首次阐明了掺杂抑制破裂的原理。并以密度泛函理论作为工具，提出了面向氢气传感器的钯基合金掺杂方法。通过该方法设计了高重复性的PdY合金薄膜材料并制作了传感器样机。样机试验结果表明，钯钇合金薄膜的确能够提高传感器的重复性。同时，实验还表明，新制薄膜的通氢老化处理有利于提高传感器的重复性。老化后的传感器零点漂移和氢气点漂移均小于0.2%，具有较好的实用价值。（7）最后，根据钯基合金薄膜中氢原子扩散模型的分析结果，提出了基于超薄纳米膜的快速型氢气传感器。实验结果表明，10nm的Pd/PdY的复合膜氢气传感器具有良好的时间特性。最快响应时间和恢复时间分别只有6秒和8秒（4%H2）。一个通、放氢循环时间不超过16秒。这和目前报道的其他类型光纤氢气传感器相比，具有明显的优越性。更多还原

【Abstract】 With the industrial development, hydrogen sensors become very popular in the defense,military and civilian field. Unfortunately, existing hydrogen sensors have some disadvantageand can not satisfy actual demand. Due to the high safty and anti-interference, the fiberoptic sensor is a most application prospect sensor type in the hydrogen detecting field.Considering the problems in the research of hydrogen sensors, this thesis focuses on thesensing mechanism of the material, sensor design, the development of the high repeatabilityhydrogen sensor and the fast hydrogen sensor. The main work as follows:(1) A reflected model of films basd on optic matrix is proposed. It shows how therefractive index, thickness, substrate material and the wavelength of the incident lightinfluence the reflectivity of the film.(2) A hydrogen atomic diffusion model in the films is proposed. It shows therelationships between the concentration of hydrogen atoms and the diffusion time, the filmthickness.The response time of sensors is proportional to the square of the film thicknessaccording to the results of the simulation analysis.(3) A hydrogen bubble model is proposed to explaim the failure of films, according tothe micro-observation to the film. It shows how the delamination height, refractive index,thickness, substrate material, the incident light wavelength influence the repeatability of thefilm.(4)A reflection coupled model of the optical fiber bundle is proposed. The simulationstudy shows the influence of the transmission fiber core diameter, receiver fiber core diameter,reflective distance and numerical aperture on the reflectivity of films. Coupling model isverified by experiments. The optimum reflection distance is discussed for the reflected-typedfiber hydrogen sensor.(5) To improve the accuracy of the hydrogen sensor, this thesis analyzes the principle ofphotodiodes, designs a preamplifier circuit based on the T-network to eliminate the outputoffset voltage, a matlab filtering procedures based on wavelet transform method to eliminatethe influence of noise and improve the SNR of sensors.(6)According to the deeply analysis of films failure mechanism, the thesis first-ly explain the principle of the crack inhibited by doping in Pd and proposes a doping methodof the Pd-based alloy film based on DFT theory for hydrogen sensing. By using this method, ahigh repeatability hydrogen sensor prototype is fabricated and tested.The experimental resultsshow that the PdY alloy film can improve the repeatability of hydrogen sensors and theH-induce aging treatment can imporove the repeatability of new films. The drifts of the zeropoints and hydrogen points are smaller than0.2%after aging treatment. The sensors have ahigh practical value. (7)According to the analysis results of hydrogen atoms diffusion model in films, a fasthydrogen sensor based on ultrathin nano-film is proposed and tested. The experimental resultsshow that the10nm Pd/PdY composite film has a fast response performance. The shortestresponse time and recovery time is6s and8s for4%H2. A loading/unloading cycle is notmore than16s. Compared with other fiber hydrogen sensors reported, it possesses obviouslysuperiority.更多还原