氧化锌气敏传感器性能的改善及在民航系统的应用

氧化锌是多功能N型半导体材料,具有优良的气敏性能,在气体传感器方面具有广泛的用途。氧化锌气敏材料及测试方法进一步优化后,传感器具有更高的灵敏度和更广泛的适用性。对纳米氧化锌传感器的气敏机理、改善气敏性能的主要方法以及传感器在民用航空方面的应用做了详细的综述。     

半导体陶瓷型薄膜气敏传感器的研究进展

半导体陶瓷型薄膜气敏传感器,具有灵敏度高、与气体反应快、制备成本较低等优点,已经成为近年传感器研究和开发的重点．是未来气敏传感器的发展方向之一。本文介绍了陶瓷型半导体薄膜气敏传感器常见的器件结构、薄膜材料的主要制备方法．部分主要的半导体金属氧化物薄膜气敏材料．以及近期相关的研究进展,并扼要分析了今后的发展方向。     

纳米ZnO气敏传感器研究进展

半导体金属氧化物气敏传感器被广泛应用于有毒性气体、可燃性气体等的检测.ZnO是一种重要的半导体气敏材料,特别是纳米ZnO,由于其粒子尺寸小,比表面积大,成为被广泛研究的气敏响应材料之一.简要介绍了纳米ZnO气敏传感器的气敏机理、主要特性,综述了通过新型纳米形貌、结构制备以及元素掺杂改性提升纳米ZnO气敏性能等方面的研究进展,并进一步指出了纳米ZnO气敏传感器研究中存在的问题和未来的研究方向.     

碳纳米管及其掺杂氧化物半导体气敏传感器

碳纳米管气敏传感器以其工作温度低和最低检出限较低等优点而备受关注,而碳纳米管掺杂氧化物半导体气敏传感器兼备了氧化物半导体气敏传感器和碳纳米管气敏传感器二者的优点,具有灵敏度较高、最低检出限低和工作温度低等特性。综述了这两类传感器的研究进展,介绍了其气敏机理,并对相应存在的问题及今后的发展趋势进行了概述。     

气敏材料及传感器特性检测系统

讨论了在气敏材料及气敏传感器检测中遇到的问题和解决方法，并设计实现了新型检测系统，通过采用动态配气技术，结合计算机软硬件技术，采用按需设计测试流程的方法实现气敏传感器和气敏材料多方面性能的灵活检测，满足科研、生产中的不同检测需要。     

微结构气敏传感器敏感薄膜制备方法的研究

随着微结构气敏传感器的出现,金属氧化物半导体薄膜因具有灵敏度高、热质量小、批量制备一致性好等特点受到日益广泛的重视,本比较了在微结构气敏传感器中三种方法制备的ＳｎＯ２敏感薄膜的结构和气敏响应特性。结果表明,用液涎生长和热氧化技术制备Ｓｎ２薄膜虽然能采用Ｌｉｆｔ－ｏｆｆ技术成形,但由于膜中晶粒结构和Ｓｎ／Ｏ比不合适使得它的气敏响应特性很差;室温混合气氛（Ａｒ／Ｏ２比为８：２）下射频溅射ＳｎＯ２靶然     

微结构气敏传感器敏感薄膜制备方法的研究

随着微结构气敏传感器的出现 ,金属氧化物半导体薄膜因具有灵敏度高、热质量小、批量制备一致性好等特点受到日益广泛的重视。本文比较了在微结构气敏传感器中三种方法制备的SnO2 敏感薄膜的结构和气敏响应特性。结果表明 ,用液涎生长和热氧化技术制备的SnO2 薄膜灵敏度高、稳定性好 ,但这种方法与lift off技术不兼容 ;室温直流溅射Sn然后热氧化方法制备的SnO2 薄膜虽然能采用lift off技术成形 ,但由于膜中晶粒结构和Sn/O比不合适使得它的气敏响应特性很差 ;室温混合气氛 (Ar/O2 比为 8∶2 )下射频溅射SnO2 靶然后退火制备的SnO2 薄膜 ,不仅对有机分子十分灵敏 ,而且与微电子工艺相容。室温射频溅射是制备微结构气敏传感器敏感薄膜较理想的方法     

γ-Al2O3基纳米陶瓷气敏元件稳定性研究

报道对采用纳米粉料制作的γ-Al2O3基气敏元件的稳定性的研究结果。分别采用纳米粉料和微米级粉料制备了γ-Al2O3基气敏元件,该气敏元件对碳氢化合物还原性气体敏感;连续17个月测定了这些气敏元件对甲烷的气敏特性;通过XPS等技术分别在3个阶段对这两种元件的表面化学元素含量进行了表征。结果表明,元件失效的原因之一是由于在气敏反应过程中由于部分反应产物在表面沉积造成表面活性位减少,并导致吸附能力下降所致;而元件失效或不稳定与使用过程中元件表面有沉积物有关。通过以上研究工作,找出了利用纳米粉料制备气敏元件失效快和长期工作稳定性差的部分原因,为该类材料的进一步发展提供实验依据。     

苯系物(BTEX)检测气敏材料研究进展

金属氧化物半导体传感器因具有体积小、成本低廉、使用方便等优点,越来越受到研究者的关注并被用于有毒有害气体的监测。传感材料是气敏传感器的核心,本文综述了近年来氧化物半导体BTEX气敏传感材料的研究进展,对传感材料的微结构、负载/掺杂改性、气敏性能、气敏机理及存在的问题进行了分析,并探讨了其下一步发展趋势。     

掺杂对金属半导体氧化物气敏性能影响的研究

综述了金属氧化物半导体气敏元件的掺杂技术，探讨了掺杂作用的机理，列举了对最典型半导体气敏元件的掺杂以及掺杂对气敏元件灵敏度和选择性的影响作用。     

声障板对圆柱换能器轴向波束抑制技术研究

文章研究了声障板对圆柱换能器轴向波束抑制特性。利用有限元仿真方法建立了带轴向反声障板的圆柱形换能器的水中模型,通过改变障板距离圆柱形换能器的相对距离、直径等参数,探索了障板对圆柱形换能器轴向波束的抑制效果,并实际制作了带轴向障板的圆柱形换能器。结果表明:有限元仿真计算结果与试验测试结果吻合较好,利用障板技术可以有效地抑制圆柱换能器轴向声压。     

收缩包装对香皂失水性的影响

针对香皂容易失水的问题做了香皂收缩包装的研究.研究了不同材料对香皂包装失水性的影响,以及不同形状香皂的裹包与收缩包装对其失水性的影响.经实验分析,用POF薄膜收缩包装后再放入纸盒中的包装方法阻湿效果最好.     

Determination of temperature corrections for the dimensions of machine details

Conclusions The above semiconductor thermometer with a special transducer is convenient for measuring the temperature of flat, spherical, and fashioned outer and inner surfaces.The special transducer provides temperature measurements lasting not more than 10 sec. The error in measuring temperature does not exceed ±0.3°.The above technique for determining corrections of temperature deviations from the normal of the article and the measuring instrument by means of a semiconductor thermometer and special graphs raises the accuracy of measurement and productivity in manufacturing precision articles on metal-working machines, and reduces the percentage of rejects due to inaccurate measurements.The above technique and instrument can be used under workshop conditions at the bench, in the Technical Control Division (OTK), inspection and test points, in factory test laboratories, and in GKLs for measuring equipment of the State Committee of Standards, Measures, and Measuring Instruments of the USSR.     

Modeling of transient ultrasonic wave propagation using the distributed point

Transient ultrasonic waves in a fluid medium generated by a flat circular and a point-focused transducer of finite size are modeled by the distributed point source method (DPSM). DPSM is a Green's-function-based semi-analytical mesh-free technique which is modified here to incorporate the transient loading from a finite-sized acoustic transducer. Conventional DPSM solves acoustic problems in steady-state frequency domain. Here, DPSM is extended to the time domain without the fast Fourier transform (FFT) but using the Green's function in the time domain. This modified method is denoted t-DPSM. Harmonic point sources of DPSM are replaced by time-dependent point sources in t-DPSM. Generated t-DPSM results are compared with the finite element (FE) results for both focused and flat circular transducers. The developed method is used to solve the transient problem of wave scattering by an air bubble in a fluid as the bubble is moved horizontally or vertically from the focal point of the focused transducer. The received energy signal is compared for different eccentricities.     

Sensing a buried resonant object by single-channel time reversal

Scaled laboratory experiments are conducted to assess the efficacy of iterative, single-channel time reversal for enhancement of monostatic returns from resonant spheres in the free field and buried in a sediment phantom. Experiments are performed in a water tank using a broad-band piston transducer operating between 0.4 and 1.5 MHz and calibrated using free surface reflections. Solid and hollow metallic spheres, 6.35 mm in diameter, are buried in a consolidation of 128-μm-mean- diameter spherical glass beads. The procedure consists of exciting the target object with a broadband pulse, sampling the return using a finite time window, reversing the signal in time, and using this reversed signal as the source waveform for the next interrogation. Results indicate that the spectrum of the returns rapidly converges to the dominant mode in the backscattering response of the target. Signal-to-noise enhancement of the target echo is demonstrated for a target at several burial depths. Images generated by scanning the transducer over the location of multiple buried targets demonstrate the ability of the technique to distinguish between targets of differing type and to yield an enhancement of different modes within the response of a single target as a function of transducer position and processing bandwidth.     

Sizing Cracks in Power Plant Components Using Array Based Ultrasonic Techniques

New techniques developed using the array transducer, to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components are discussed. Three studies are reported here including (a) Optimal beam steering angle for focused and unfocused inspection using phased array method for bottom-surface crack sizing. (b) A front wall correction algorithm for sizing of near-through-wall crack-like defects. (c) A small aperture technique for sizing of near-through-wall crack-like defects. A Finite Difference Time Domain (FDTD) based simulation was used to study and verify the experimental observations. The application of time domain scheme relative arrival time technique (RATT), to measure the size of the near-through wall crack-like defects for the leak before break (LBB) criterion, was also investigated and found to be insufficient. A conventional SAFT algorithm was used for improving the sizing using the small aperture technique.     

应用半导体制冷的冷藏链用储藏箱性能实验研究

半导体制冷片因其体积小、制冷速度快的优点在冷藏链运输领域具有很强的应用潜力。为测试半导体制冷箱的制冷效率,本文搭建了制冷储藏箱性能测试实验台,对应用两片TEC1-12706型及TEC1-12712型半导体制冷片的制冷储藏箱的工作性能进行实验研究。实验中分别在储藏箱中加入2 000 m L冰块开始实验及应用1 500 mL冰块与3 kg食材及3瓶500 mL矿泉水的组合开始实验,两次实验中同时改变热端散热方式及冷端风扇吹风方式。结果表明:对于同型号半导体制冷片,水冷方式时制冷效果更好,但持久性不强;同型号半导体制冷片冷端风扇下吹方式与侧吹方式相比气流组织更好。当容积为0. 1 m^3的储藏箱面向冷藏需求时,可应用两片采取热端风冷方式的TEC1-12706型半导体制冷片,此时10 h内箱体中心温度最大约为6℃,最小约为0℃;当容积为0. 1 m^3的储藏箱面向冷冻需求时,可应用两片TEC1-12712型半导体制冷片结合水冷式热端和风扇下吹式冷端,能维持3 h箱体内温度不高于0℃。     

Two-step preparation of Ag/tetrapod-like ZnO with photocatalytic activity by thermal evaporation and sputtering

A two-step method to synthesize metal–semiconductor heterostructure photocatalyst is presented in this research. Based on the tetrapod-like zinc oxide (T-ZnO) deposited by thermal evaporation, Ag/T-ZnO heterostructure is synthesized by RF magnetron sputtering method in this two-step preparation technique. The structure and the photocatalytic properties of the Ag/T-ZnO were studied in detail. The Ag/T-ZnO heterostructure exhibits better photocatalytic activity than that of the pure T-ZnO and there is an optimum sputtering time and sputtering power for the heterostructure's photocatalytic activity. The essential photocatalytic mechanism of this heterostructure have been discussed and the enhanced photocatalytic activity indicates the feasibility of this novel two-step method which may be developed to a promising synthesis technique.     

缺陷形貌的超声成像方法

传统超声成像方法如合成孔径聚焦技术、超声衍射时差法,只能确定缺陷的位置,无法对整个缺陷形貌进行成像。逆时偏移方法基于波动方程、有限元或有限差分等方法计算声源的正延拓声场分布和接收回波的逆时延拓声场分布,并对其采用互相关等成像条件,可以成像缺陷的形貌。针对平底狭缝铝块试样,采用多阵元超声换能器扫描,将接收数据用于成像,并与合成孔径聚焦技术的成像比较,结果很好验证了逆时偏移成像方法的优越性。     

Optoelectronic transmitters for medical ultrasound transducers

Optoelectronics and fiber optics can be used to miniaturize and improve the flexibility of the transducer cable and transducer handle of medical diagnostic ultrasound scanners. The reduction in size has gained importance as 2-D array transducers with up to 1000 independent channels become accepted to improve diagnostic ultrasound images. The authors describe the analysis, design, fabrication and testing of a prototype silicon photoconductive semiconductor switch (PCSS). The monolithic silicon PCSS was used in combination with an infrared semiconductor diode laser with a fiber optic “pigtail” to shock excite and burst excite a 2-D array transducer element resonant at 2.5 MHz. Optically controlled voltage, current, and ultrasound pulses are compared to those from conventional electronic shock excitation and narrow band Doppler pulses. The optically triggered ultrasound pulse for single shock excitation produced 30 V spikes at the 2-D array element with a fall time of 200 nsec and a rise time of 2 μsec with a peak current through the transducer element of 34 mA. An optically produced burst of eight pulses at a frequency of 2.5 MHz produced 11 V spikes at the transducer with a fall time under 100 nsec and a rise time of approximately 300 nsec. The peak current per pulse was 25 mA through the transducer element. These results show the feasibility of applying optoelectronic technology to replace conventional electronic transmitter technology