Morphology control of aluminum nitride(AlN)for a novel high-temperature hydrogen sensor

Hydrogen is a promising renewable energy source for fossil-free transportation and electrical energy generation.However,leaking hydrogen in high-temperature production processes can cause an explosion,which endangers production workers and surrounding areas.To detect leaks early,we used a sensor material based on a wide bandgap aluminum nitride(AlN)that can withstand a high-temperature environment.Three unique AlN morphologies(rod-like,nest-like,and hexagonal plate-like)were synthesized by a direct nitridation method at 1400℃usingγ-AlOOH as a precursor.The gas-sensing performance shows that a hexagonal plate-like morphology exhibited p-type sensing behavior and showed good repeatability as well as the highest response(S=58.7)toward a 750 ppm leak of H2 gas at high temperature(500°C)compared with the rod-like and nest-like morphologies.Furthermore,the hexagonal plate-like morphology showed fast response and recovery times of 40 and 82 s,respectively.The surface facet of the hexagonal morphology of AlN might be energetically favorable for gas adsorption–desorption for enhanced hydrogen detection.

Micro Hydrogen Sensor Based on Pd-Ag Nanofilm

In this paper,palladium-silver (Pd-Ag) system was studied for hydrogen sensing.Nanofilm of Pd-Ag was fabricated on a porous ceramic substrate through a combination of microfabrication techniques.The electric resistance of the zigzag-shaped microstructure was measured toward hydrogen concentration change.The sensing element demonstrates high sensitivity,fast response and fast recovery to hydrogen.The Pd-Ag film was characterized by scanning electron microscopy (SEM) equipped with X probe to correlate its physical and chemical properties to its sensing performance.The present sensor is very promising for room temperature hydrogen leakage detection and related applications.The temperature effect on the sensing performance of the metal film was also investigated.

New Applications of the Noise Spectroscopy for Hydrogen Sensors

Peculiarities of the low-frequency noise spectroscopy of hydrogen gas sensors made on MgFeO4 n-type porous semiconductor covered by the palladium catalytic nanosize particles are investigated. Behavior of the low-frequency noise spectral density and its exponent value from sensitive layer thickness in the frequency range 2 - 300 Hz are analyzed. Sensitivity of the sensor calculated by the noise method is several tenth times higher as compared with the resistive method. It is shown that besides of the well-known applications, noise spectroscopy can be also used for definition of the unknown thickness of gas sensitive layer, for definition of the sensitive layer subsurface role in the formation of the low-frequency noises and for definition of the intensity of trapping-detrapping processes of the gas molecules.

Low-Temperature Formation of a WO₃Thin Film by the Sol-Gel Method Using Photo-Irradiation and Fabrication of a Flexible Hydrogen Sensor

Hydrogen has been recently attracted much attention with respect to high energy-conversion efficiency and low environmental burden. However, hydrogen gas is dangerous due to an explosive gas and a fast combustion rate. Therefore, the development of hydrogen sensor with high accuracy and reliability that can detect hydrogen easily is required. Especially, a flexible hydrogen sensor is useful because it has a high degree of freedom with respect to the shape of location in which the sensor is to be located. A flexible hydrogen sensor—namely, a WO3 thin film formed on a PET film by the sol-gel method using photo irradiation—based on gasochromism of WO3 was developed. By irradiating a thin film, which was prepared by using WO3 precursor solution synthesized by the sol-gel method, with ultraviolet rays, a high-purity WO3 film could be prepared on PET at low temperature. The sensor was structured as a polystyrene (PS) film containing palladium (Pd) laminated on a WO3 film. The WO3 layer was porous, so the PS containing Pd atoms solution penetrated the WO3 layer. WO3 reacted with hydrogen gas and instantly turned blue as the transmittance of the WO3 layer changed. The sensor showed high reactivity even for hydrogen concentration below 4% (1%, 0.5%, 0.25%, and 0.1%), which was the lower limit of hydrogen ignition, and a linear relationship between hydrogen concentration and change in transmittance was found. Moreover, the resistance of the WO3 film significantly and instantaneously changed due to hydrogen-gas exposure, and the hydrogen concentration and resistance change showed a linear relationship. It is therefore possible to quantitatively detect low concentrations of hydrogen by using changes in transmittance and resistance as indices. Since these changes occur selectively under hydrogen at room temperature and normal pressure, they form the basis of a highly sensitive hydrogen sensor. Since the developed sensor is flexible, it has a high degree of freedom with respect to the shape of location in which the sensor is to be

A Hydrogen Sensor Using SrCe_(0.95)Yb_(0.05)O_(3-α) as Proton Conductor and YH_x+YH_(2-z) as Reference Electrode for Determining Hydrogen Pressure in Solid Steel

The steel contains a small amount of hydrogen which will escape during the heat treatment.The hydrogen pressure in 16MnRE steel was investigated with a hydrogen sensor,which used SrCe0.95Yb0.05O3-α proton conductor as a solid electrolyte,YHx＋YH2z as a solid state reference electrode and Ni wire as electrode constructing a hydrogen concentration cell,shown as Ni｜YHx＋YH2z ｜SrCe0.95Yb0.05O3-α ｜[H] steel ｜Ni.The response time of sensor is less than 10s.The relational expression of hydrogen partial pressure with temperatures was determined using two shape proton conductors.The results showed the regularity in experimental temperature range,and the hydrogen partial pressure increased as its temperature was raised.

Performance of Amperometric and Potentiometric Hydrogen Sensors

The principle, design, construction and performance of the amperometric and potentiometric sensors for measuring the permeation rate of hydrogen through the wall of metal equipment were investigated in order to develop a new type of hydrogen sensor with high accuracy. The transient curves of hydrogen permeation under a given charging condition were employed to evaluate the performance of two types of hydrogen sensors. The relative deviation of the hydrogen concentration detected with two types of sensors under the same condition varied from 3.0% to 13%. The accuracy, response time, reproducibility, and installation were discussed and compared. Response time of the potentiometric sensor （E-sensor） was shorter than that of the amperometric sensor （I-sensor）. Both types of sensors exhibited good reproducibility. Development of I-sensor composed of a kind of proton conductor adhesives or non-fluid electrolytes which contain two functions of high electrical conductivity and a strong adhesion will be a promising prospect in order to measure hydrogen permeation at high temperature.

Hydrogen Gas Sensor Based on Nanocrystalline SnO_2 Thin Film Grown on Bare Si Substrates

In this paper, high-quality nanocrystalline SnO_2 thin film was grown on bare Si(100) substrates by a sol–gel method. A metal–semiconductor–metal gas sensor was fabricated using nanocrystalline SnO_2 thin film and palladium(Pd)metal. The contact between Pd and nanocrystalline SnO_2 film is tunable. Ohmic barrier contact was formed without addition of glycerin, while Schottky contact formed by adding glycerin. Two kinds of sensor devices with Schottky contact were fabricated(Device 1: 8 h, 500 °C; Device 2: 10 h, 400 °C). The room temperature sensitivity for hydrogen(H_2) was120 and 95 % in 1000 ppm H_2, and the low power consumption was 65 and 86 l W for two devices, respectively. At higher temperature of 125 °C, the sensitivity was increased to 195 and 160 %, respectively. The sensing measurements were repeatable at various temperatures(room temperature, 75, 125 °C) for over 50 min. It was found that Device 1 has better sensitivity than Device 2 due to its better crystallinity. These findings indicate that the sensors fabricated on bare Si by adding glycerin to the sol solution have strong ability to detect H_2 gas under different concentrations and temperatures.

Fiber-Optic Fabry-Perot Hydrogen Sensor Coated With Pd-Y Film

一个光纤的 Fabry-Perot 氢传感器被在不同的氢集中测量穗对比变化开发。试验性的结果显示有 Pd-Y 电影的察觉到的表演与 Pd 电影比那好。有 0.5 dB 的减少的一个穗对比从 0% ～ 5.5% 与一个氢集中变化被检测。传感器的温度反应也被测量。

Research Surveys of Electrochemical Sensors for in-situ Determining Hydrogen in Steels

The principle, construction and application of two types of electrochemical sensors-amperometric and potentiometric are surveyed. Both types of sensors are very sensitive to changes in temperature. The accuracy of hydrogen measurement depends on both the precision of sensors developed and the reliable technique of installation and security of sensors. The two types of sensors have been used for in-situ determining hydrogen permeated in steels owing to a corrosive reaction, a hydrogen gas circumstance at elevated temperatures and high pressure or also a pretreatment process such as pickling and plating process, etc.

Electrodeposited Cobalt-Iron Alloy Thin-Film for Potentiometric Hydrogen Phosphate-Ion Sensor

A cobalt-iron alloy thin-film electrode-based electrochemical hydrogen-phosphate-ion sensor was prepared by electrodepositing on an Au-coated Al2O3 substrate from an aqueous solution of metal-salts. The use of a cobalt-iron alloy electrode greatly improved the hydrogen-ion sensor response performance, i.e., the sensor worked stably for more than 7 weeks and showed a quick response time of several seconds. Among the cobalt and iron alloy systems tested, the electrodeposited Co58Fe42 thin-film electrode showed the best EMF response characteristics, i.e., the sensor exhibited a linear potentiometric response to hydrogen-phosphate ion at the concentration range between 1.0 × 10–5 and 1.0 × 10–2 M with the slope of –43 mV/decade at pH 5.0 and at 30℃. A sensing mechanism of the Co-based potentiometric hydrogen-phosphate ion sensor was proposed on the basis of results of instrumental analysis.

Simple Planar Structure Hydrogen Gas Sensor Device with Large Response

Hydrogen gas sensor device with simple planar structure based on p^+ silicon substrate with n-type epi-layer was fabricated only by using a lift-off technique of an evaporated metal film.The device consists of Ohmic source and drain electrodes and platinum Schottky gate electrode.This sensor device has a little similar property as FET.Current-voltage characteristics between the source and drain of the device are sensitive to hydrogen gas.The voltage difference between in hydrogen ambient and oxygen ambient is about 2.3 volts for a constant current of 0.9 mA.The device can detect 0.4% hydrogen gas in air.Based on oxidation reaction of hydrogen on the surface of the platinum gate,hydrogen sensitivity of the device changes by the coexisting oxygen concentration.Electrons flow in the buried channel formed between the gate electrode and the p^+n junction.It was confirmed that the gate bias influences the properties.The current-voltage property changes also depending on the wiring method.

Fiber Optic Hydrogen Sensors： a Review

氢以后是下一代精力之一，它在太空和化学工业显示出有希望的应用。氢漏监视因为它的低点火精力，高燃烧效率，和最小的分子很危险、重要。这份报纸考察纤维的 state-of-art 发展眼的氢察觉到技术。纤维的主要发展中趋势眼的氢传感器基于二种氢敏感材料，即钯合金薄电影和做磅的 WO < 潜水艇 class= “ a-plus-plus ” > 3 涂层。在这个评论工作，这些二种察觉到的技术的优点和劣势将被评估。

Amperometric Sensors for Determination of Hydrogen Peroxide Based on Electron Transfer Between Horseradish Peroxidase and 1，1＇－Dimethylferrocene

hydrogen peroxide electrode with 1,1'-dimethylferrocene(DMFc)used as an electron transfer mediator has been described.Using Nafion, DMFc was modified on a glassy carbon electrode(GCE)surface,and horseradish peroxidase(HRP)was then immobiliged on the DMFc-Nafion film,forming a HRp-DMFc-Nafion modi- fied electrode. The chracteristics of the sensor has been shown by cyclic voltam- metry and constant potential measurements,The sensor responds fastly to hydro- gen peroxide,the time required to reach 95%of the steady-state current is less than 50s. The sensor displays a sensitive catalytic current response to hydrogen peroxide and can be operated at a potential range in which the oxidation of common interfering species,such as ascorbic acid and uric acid,does not occur. The sensor is stable for 20 days and its detection limit is 1 μmol/L.

Calibration of Hydrogen Peroxide Vapour Sensor

Hydrogen Peroxide vapour is becoming more popular to use as a method of decontamination, particularly for medical equipment and enclosures. It is highly effective in terms of microbiological kill rates and has a variety of uses in healthcare. Although it is environmentally acceptable as it spontaneously decomposes into water and oxygen, concentration of hydrogen peroxide in the air needs to be monitored and controlled. A method of calibrating hydrogen peroxide vapor sensors is described which is based on the concentration of hydrogen peroxide in saturated vapour over a solution in water at a defined temperature. The saturated vapour is generated by bubbling dry air into a solution of hydrogen peroxide at a defined concentration and temperature. A vapour at a concentration of 0.7 ppm was produced and used to successfully calibrate a hydrogen peroxide sensor.

Optical fiber hydrogen sensor based on light reflection and a palladium-sliver thin film

Thin alloy films of palladium(Pd) and silver(Ag) are deposited onto glass substrates via the direct current(DC) magnetron technique.The hydrogen sensor probe consists of optical fiber bundle and Pd/Ag optical thin film.when the sensor is exposed to hydrogen,the refractive index of Pd/Ag optical thin layer will diminish and cause attenuation changes of the reflective light.It is observed that the thickness of Pd/Ag alloy layer can affect the hydrogen sensor signal.Under different substrate temperatures,several Pd/Ag samples are coated with different thicknesses of Pd/Ag alloy,and the results of a hydrogen sensor based on reflective light from the Pd/Ag alloy thin film are discussed.

氢气传感器在电解制氧系统中的应用研究

针对电解制氧系统中氢气浓度测量受环境因素影响大、测量准确性低等问题,选取了半导体型、催化燃烧型、热导型三类不同原理的氢气传感器,对其在电解制氧系统中的应用进行了试验验证,并对试验结果进行了讨论,分析了各类氢气传感器的使用局限性。

基于钯纳米颗粒导电沟道的室温型氢气传感器的研究

随着氢能的广泛应用,检测氢气(H_(2))泄漏十分必要。采用溶剂热法合成钯(Pd)纳米颗粒,结合旋涂法从极大程度上简化了覆盖敏感层工艺,在利用微机电系统(MEMS)工艺制备的硅基金(Au)叉指电极上研究了基于“氢致Pd晶格膨胀效应(HILE)”的裂结式H_(2)传感器的敏感特性,为低成本批量化制备室温型氢气传感器提供了可行性研究。结果表明该传感器对H_(2)的响应值与Pd纳米颗粒在基底上的覆盖率密切相关:覆盖率在一定范围内越大,响应值越小。在室温下,该类传感器对500×10^(-6)~2500×10^(-6)H_(2)表现出了较快的响应速度:响应时间在5 s左右,恢复时间在25 s左右,具有较高的响应值:在2500×10^(-6)H_(2)气氛下高达83%,有较好的选择性和稳定性。

Pd/Ga_(2)O_(3)/AlGaN/GaN HEMT基氢气传感器研究

氢气易燃易爆,因此需要海量快速响应的氢气传感器对加氢站、运输车及氢能源汽车等氢能源各个环节进行预警预报。本文研究了基于贵金属钯(Pd)为栅极的高速二维电子气晶体管(HEMT)型氢气传感器,金属Pd栅极为敏感电极,Ti/Al/Ti/Au为源漏极。结果表明:该晶体管开关比为3.58×10^(7)。实验研究了不同厚度Ga_(2)O_(3)插入层对氢气响应特性的影响规律。随着Ga_(2)O_(3)插入层的厚度增大,传感器的饱和体积分数明显增大,从1×10^(-3)提高到7×10^(-3)。对于Ga_(2)O_(3)插入层厚度为10 nm的器件,其综合性能最好,饱和浓度为5×10^(-3),且具有很高的响应度,1×10^(-3)时的响应度为4300%。特别地,其响应速度非常快,最快可以2 s内完成氢气检测。

燃料电池汽车用氢气浓度传感器技术现状及发展趋势

对燃料电池汽车用氢气传感器的技术要求进行分析,并对各类车载氢气传感器的工作原理和特点进行研究,对比了现阶段主流氢气浓度传感器的性能和参数,对氢气浓度传感器的发展现状进行了综述和分析,并结合行业发展需求对氢气浓度传感器的技术发展趋势进行了展望。

薄膜氢气传感器改进型PID控温方法研究

为满足航天、航空、船舶等领域对氢气高精度测量的需求,针对电阻式薄膜氢气传感器的响应时间和测量精度易受温度波动影响的问题,该文提出了一种改进型数字PID控温方法,缩短了传感器温度进入稳态的时间,降低了超调幅度,提高了温度控制精度。试验结果表明,采用传统PID算法氢气传感器的调节时间为68 s,控温精度为±0.25℃,采用改进型PID算法其调节时间缩短至35 s,控温精度为±0.1℃,使氢气传感器响应时间缩短,信噪比得到提升,具备工程应用价值。