【作者】 张帆；

【导师】 杨明红；

【作者基本信息】 武汉理工大学 ， 材料科学与工程， 2024， 硕士

【摘要】 氢能源是一种易于获得且对环境无污染的新能源,但是氢气在使用过程中容易泄漏发生爆炸,因此为了更加安全的使用氢气,需要研发氢气检测技术,实现对氢气的泄漏的早期预警。而以光信号为传感信号的光纤氢气传感器具有本质安全的特点,其中基于布拉格光栅(FBG)的光纤氢气传感器是以FBG的中心波长的变化来表征氢气浓度。然而纯Pd膜吸收氢气容易开裂导致稳定性较差,并且FBG较大的带宽使其氢气传感精度难以得到提高,此外,环境温度变化导致的波长变化也会导致氢气检测的误差。基于上述问题,本文从材料和传感器结构两个角度出发,提出了基于Pd/Hf的多层复合薄膜和π相移光栅部分镀膜结构的光纤氢气传感器和基于Pd/Hf复合薄膜和光纤FP腔结构的光纤氢气传感器,本文的主要研究内容和成果如下:针对纯钯合金多次吸氢-释氢后易开裂的问题,采用磁控共溅射技术制备了Ni+Pd/Hf+Pd/Pt+PTFE多层复合薄膜。Hf原子的掺入还能抑制PdHx从α到β的不可逆相变,有效提高薄膜的稳定性,使其适用于氢气传感。针对FBG氢气传感器受温度影响的问题,设计制备了π相移光栅部分镀Pd/Hf复合薄膜氢气传感器。4 mm长的薄膜吸氢膨胀产生应力作用于10 mm长的光栅上,光栅各处受到应力不均匀使光栅的光谱不均匀移动。定义光谱反射率最低处的波长为波谷波长λnotch,光谱左侧反射率为50%处的波长为边带波长λflank。notch和λflank具有相同的温度灵敏度和不同的氢气灵敏度,使用λnotch和λflank之间的差值Δλ来表征氢气浓度实现了温度自补偿。此外,传感器在室温下工作稳定,重复性良好且具备较低的检测极限。针对部分镀膜结构灵敏度相对较低的问题,设计制备了基于双光栅FP结构的镀Pd/Hf复合薄膜氢气传感器。一种是双π相移光栅FP结构(PSFBG-PSFBG-FP),一种是π相移光栅普通光栅 FP 结构(FBG-PSFBG-FP),定义光谱中相移峰为λFBG,FP峰为λFP,λFBG与λFP之间的差值同样定义为Δλ。在两种FP结构上沉积Pd/Hf复合薄膜,实验表明,以Δλ作为氢气特征值也可以实现对温度的自补偿。两种结构的Δλ在20℃和10000 ppm的条件下的漂移分别达到8.79 pm和8.55 pm,相比于π相移光栅部分镀膜结构提升了 197%和186%。更多还原

【Abstract】 In order to reduce the air pollution caused by fossil energy and adjust the structure of world energy supply in the future,the whole world is actively exploring different new energy sources,among which hydrogen energy has become one of the important new energy sources because the product of hydrogen combustion is only water and renewable.However,hydrogen is easy to leak and explode during use,so in order to use hydrogen more safely,it is necessary to develop hydrogen detection technology to realize early warning of hydrogen leakage.The fiber-optic hydrogen sensor with optical signal as sensing signal is intrinsically safe.The fiber-optic hydrogen sensor based on Bragg grating(FBG)is characterized by the change of the central wavelength of FBG by depositing a hydrogen-sensitive film Pd on FBG,and the film absorbs hydrogen and expands to stretch FBG.However,the pure Pd film absorbs hydrogen easily,which leads to poor stability,and the large bandwidth of FBG makes it difficult to improve its hydrogen sensing accuracy.In addition,the wavelength change caused by environmental temperature change will also lead to the error of hydrogen detection.Based on the above problems,this paper puts forward an optical fiber hydrogen sensor based on Pd/Hf multilayer composite film and π phase shift grating partially coated structure,and an optical fiber hydrogen sensor based on Pd/Hf composite film and optical fiber FP cavity structure from the perspectives of materials and sensor structure.The main research contents and achievements of this paper are as follows:In order to solve the problem that pure palladium alloy is easy to crack after hydrogen absorption and hydrogen release for many times,Ni+Pd/Hf+Pd/Pt+PTFE multilayer composite films were prepared by magnetron co-sputtering technology.The doping of Hf atoms can also inhibit the irreversible phase transition of PdHx from α to β,effectively improve the stability of the thin film,and make it suitable for hydrogen sensing.Aiming at the problem that FBG hydrogen sensor is affected by temperature,a hydrogen sensor with π phase shift grating partially coated with Pd/Hf composite film is designed and fabricated.The 4 mm long film absorbs hydrogen and expands,resulting in stress acting on the 10 mm long grating,and the grating spectrum moves unevenly due to uneven stress everywhere.The wavelength at the lowest spectral reflectivity is defined as the trough wavelength,and the wavelength at the left side of the spectrum with a reflectivity of 50%is defined as the sideband wavelength.And have the same temperature sensitivity and different hydrogen sensitivity,and the temperature self-compensation is realized by using the difference between and to characterize the hydrogen concentration.In addition,the sensor works stably at room temperature,with good repeatability and low detection limit.Aiming at the problem that the sensitivity of some coating structures is relatively low,a Pd/Hf composite film coated hydrogen sensor based on double grating FP structure is designed and fabricated.One is the double π phase-shift grating FP structure(PSFBG-PSFBG-FP),and the other is the π phase-shift grating FP structure(FBG-PSFBG-FP).The phase shift peak in the spectrum is defined as,and the FP peak is defined as.Ni+Pd/Hf+Pd/Pt+PTFE composite films with a length of 4 mm were deposited on two FP structures.The experiments show that the temperature can also be self-compensated by taking hydrogen as the characteristic value.The drift of the two structures reached 8.79 pm and 8.55 pm at 20℃ and 10000 ppm,respectively,which was 197%and 186%higher than that of the π phase-shift grating partially coated structure.更多还原