水热法制备石墨烯-镓酸锌复合物及其气敏性能的研究

通过水热法制备了一系列的石墨烯-镓酸锌复合物。所制备的材料用XRD,SEM,TEM,拉曼和XPS进行表征。同时,探究了复合物的气敏性能。结果表明,石墨烯的含量对复合材料的气敏响应值和选择性有着很大的影响,并且当石墨烯的含量在0.1%时,复合材料的性能最好。当操作温度在203摄氏度时,0.1%石墨烯-镓酸锌复合材料对1000ppm的甲醛的响应值达32.2倍,最低检测限度为1ppm。同时,该材料的选择性也比较优越,对1000ppm甲醛和1000ppm丙酮的响应值的比值为26.8。该材料对1000ppm甲醛的响应和恢复时间分别为11秒和5秒,对1ppm甲醛的响应和恢复时间分别为6秒和5秒.     

DyFeO3纳米材料的制备及H2S敏感特性

采用柠檬酸溶胶-凝胶法制备了具有钙钛矿结构的稀土复合氧化物DyFeO3，X射线粉末衍射和透射电镜观察表明该材料为粒径约26nm的纳米颗粒，由于粒径的减小、表面积的增大而造成其晶体结构中呈现出一定的晶格畸变率。将材料制成气敏元件并测试了其对H2S，乙醇，CO，H2等多种气体的气敏特性，结果发现该材料对H2S有较高的灵敏度和选择性，因而有较高的实用价值。     

共沉淀法制备金、镍掺杂氧化锌的丙酮气敏性能探究（英文）

利用共沉淀法制备了纯氧化锌和镍掺杂氧化锌。比较了不同Ni掺杂浓度对ZnO丙酮气敏传感器性能的影响。结果表明,1 mol%Ni掺杂ZnO具有最高的丙酮传感性能,其对20μg/g丙酮的响应值达到12。在此基础上,添加金作为异质结进一步激活氧化锌传感材料。实验结果表明,0.03 mol%Au活化1 mol%Ni掺杂的ZnO表现出最高的丙酮气敏响应,对20μg/g丙酮的响应值达到17。同时,该气敏材料保持了对乙醇、甲醛及苯的高选择性,以及对丙酮的快速响应恢复时间(10 s)。     

（Al，Sb）／ZnO复合氧化物对乙醇气体气敏功能特性的影响

用可溶性无机盐法制备了较宽工作温度范围的纳米(Al，Sb)/ZnO气敏材料。该材料主相属于ZnO纤锌矿结构，并同时存在Sb2O5、Sb6O132种微量杂相。该复合氧化物的平均晶粒为86nm。用制备的氧化物纳米粉做成气敏元件，测试了不同铝含量的纳米材料在2000μg/g浓度乙醇气体下的敏感特性。当铝含量为Al/ZnO=1．5％(mol比，下同)时，对2000μg的乙醇气体的灵敏度最大可达到26。固定Al/ZnO=3％时，掺入不同量锑得到对乙醇气体有更大工作温度范围的纳米复合氧化物材料。同时讨论了掺铝掺锑复合氧化物对敏感气体的物理吸附和化学吸附及其气敏机理。     

纳米晶La_(0.7)Pb_(0.3)FeO_3的制备 及其对CO敏感特性的研究

利用溶胶-凝胶法制备了纳米晶La0.7Pb0.3FeO3气敏材料,并对其相组成、电导及其对CO气敏性能进行了研究。XRD结果表明:掺铅固溶体La0.7Pb0.3FeO3仍为正交晶系钙钛矿结构,粒径约为17nm,低于纯相LaFeO3的粒径31nm。电导测量显示:该材料呈p型半导体导电行为,电导大于同温度下纯相LaFeO3的电导,且电导突变温度有所降低。气敏性能研究表明:Pb掺杂对其CO气敏性能有了明显改善。     

纳米晶La0.7Pb0.3FeO3的制备及其对CO敏感特性的研究

利用溶胶-凝胶法制备了纳米晶La0.7Pb0.3FeO3气敏材料,并对其相组成、电导及其对CO气敏性能进行了研究.XRD结果表明：掺铅固溶体La0.7Pb0.3FeO3仍为正交晶系钙钛矿结构,粒径约为17nm,低于纯相LaFeO3的粒径31nm。电导测鼍显示：该材料足P型半导体导电行为，电导大于同温度下纯相LaFeO3的电导，且电导突变温度有所降低。气敏性能研究表明：Pb掺杂对其CO气敏性能有了明显改善。     

单晶型锂离子正极材料用Ni0.65Co0.15Mn0.20(OH)2前驱体的合成过程

采用共沉淀制备了形貌均一、振实密度高的Ni_(0.65)Co_(0.15)Mn_(0.20)(OH)_2前驱体。结果表明,在固含量高于80 g·L~(-1)的条件下,可调节pH值来控制前驱体的成核及长大过程,即成核的籽晶小颗粒数量增加后可降低前驱体生长速率。当满足0.015μm·h~(-1)的粒度生长速率时,前驱体振实密度可达到1.83 g·cm~(-3)。烧结制备成正极后测试,在0.2C倍率下克容量为186.3 mAh·g~(-1),1C循环50周容量保持率达到96.3%。对比市售商业化样品测试结果表明,可通过烧结过程优化和掺杂工艺来进一步提升正极材料循环性能。     

多孔ITO负载贵金属的制备和气敏性能表征

采用等体积浸渍法分别将Ag、Pd、Pt三种贵金属负载到用固相烧结法制备的多孔ITO材料上,并通过XRD、SEM和EDS等手段对相应的物相和显微组织进行了分析。结果表明:由于多孔ITO孔径较小,以及盐溶液对ITO表面结构的破坏和腐蚀,造成浸渍液难以进入到样品内部,使负载的贵金属在多孔ITO表面集聚,导致贵金属的实际负载量高于理论负载量。通过对乙醇的气敏性能测试结果表明:Pd的负载能提高多孔ITO气敏材料的灵敏度;Pt的负载对多孔ITO气敏材料的灵敏度影响不大;而Ag的负载则降低了多孔ITO气敏材料的灵敏度。     

固相燃烧法快速合成LiNi0.03Mg0.10Mn1.87O4正极材料及电性能研究

采用固相燃烧法在500℃反应1 h然后再650℃二次焙烧6 h,快速合成了Ni、Mg共掺杂的LiNi_(0.03)Mg_(0.10)Mn_(1.87)O_4正极材料。借助X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱仪(XPS)和电化学测试等对材料的结构、形貌、物相和电化学性能进行测试。结果表明:LiNi_(0.03)Mg_(0.10)Mn_(1.87)O_4正极材料为立方尖晶石型结构,颗粒尺寸在100～200nm之间,为多面体形貌。合成的LiNi_(0.03)Mg_(0.10)Mn_(1.87)O_4材料有良好的电化学性能,在1C时首次放电比容量为107.6 mAh·g~(-1),10 C首次放电比容量有68.7 mAh·g~(-1),在55℃、1 C首次放电比容量有103.7 mAh·g~(-1),CV和EIS测试得出该材料有较大的锂离子扩散系数1.038×10~(-11) cm~2·s~(-1)和较小的活化能32.69 kJ·mol~(-1),对循环1000次后的极片进行剖面分析,该材料的晶体结构和颗粒形貌基本没有变化,适量Ni、Mg共掺杂能够有效提高尖晶石型LiMn_2O_4在循环过程中的容量衰减和结构稳定性,抑制了Jahn-Teller效应。     

GNP-SnO_2纳米气敏元件的气敏性能（英文）

合成了不同金属纳米颗粒含量的SnO_2纳米颗粒,并研究了其CO气敏性能。采用溶胶-凝胶法制备初始溶液,通过SEM、TEM、XRD、DLS和分光光度法表征纳米颗粒。在340°C操作温度下,纯SnO_2纳米气敏元件对(20-80)×10~(-6)CO的响应值为4~12.8;在50×10~(-6)CO浓度下,其响应和恢复时间分别为10和14 s。当m(Au)/m(Sn)=3.7663×10~(-4)时,GNP-SnO_2气敏元件具有良好的性能,在260°C优化操作温度下,对(20-80)×10~(-6)CO的响应值为8.3~29.5。     

Nd: Bi4Ge3O12 crystal growth by czochralski method

Nd-doped Bi₄Ge₃O₁₂ (Nd:BGO) crystals were successfully grown in the auto-diameter control system equipped with a frequency weighing sensor with the Czochralski method. The Nd³⁺ ion doping level was varied from 0.25 to 2.5 at.%. The crystals were transparent and of light purple color, with a typical size of about 20 mm in diameter and 50 mm in length. The effective distribution coefficient (k_eff) of Nd³⁺ ion was about 0.957 irrespective of concentration, and the Nd³⁺ ions were distributed homogeneously throughout the crystal. The doping concentration (p_i) of active ion in Nd:BGO crystal was 2.54x10²⁰ ions/cm³, which is higher than that in the Nd:YAG crystal. Therefore, the Nd:BGO crystal was judged to be more suitable for the laser diode pumping microchip laser material where size reduction was desirable.     

Investigation on transverse defect and cavitation depth in ferrous pipe using melt spun FeSiB ribbon as magnetostrictive sensing element

The investigation addresses the scope of rapidly quenched Fe₈₀Si₈B₁₂ ribbons as magnetostrictive sensor (MsS) material to generate guided waves in galvanised iron pipe and evaluation of defects with different geometries and dimensions. Enhancement in the effective defect size (EDS) of transverse and pit type defects increased the MsS signal. However, the backwall echo showed opposing trend (transverse: reduced and pit: increased) with increase in dimensions of these defects. Such behaviour of backwall intensities has been correlated to different type of guided wave strain field distributions around these defects and reflection coefficients.     

Hydrogen sensors based on carbon nanotubes thin films

Single-walled carbon nanotubes (SWNTs) produced by arc-discharge have been researched as resistive gas sensors for H₂ detection. Raw as well as modified single-walled carbon nanotubes were utilised as sensor material. Two types of modification treatments were carried out on the as grown SWNT material; chemical functionalization with palladium and doping with palladium by sputtering.CNTs were deposited on alumina substrates by airbrush. Two different alumina substrates (with and without heater element) were used to obtain the sensor devices.Conductance measurements were carried out in a N₂ constant flow for H₂ detection. The results demonstrate that the CNTs are p-type semiconductor materials, increasing their resistance with reducing gases. SWNTs functionalized with Pd show the best response when exposed to H₂ at room temperature.     

Gas sensing properties of nano-crystalline SnO<Subscript>2</Subscript>-CuO compounds

We fabricated a micro gas sensor for hydrogen sulfide (H₂S) gas using MEMS technology and the sol-gel process, and synthesized SnO₂-CuO as a sensing material by the sol-gel method. Synthesized particles of SnO₂-CuO were characterized with an average particle size of about 40 nm as measured by FE-SEM imagery and XRD peaks. The sensing material was coated on the micro platform and annealed at 400 °C. The maximum gas sensitivity (R_s= R_g/R_a) was 0.005 at 300 °C for 1.0 ppm — H₂S. The gas sensitivity showed linear behavior with increasing H₂S concentration.     

Facile synthesis of NiO nanowires and their gas sensing performance

The NiO nanowires were prepared by a facile PEG assisted hydrothermal method using NiC₂O₄·2H₂O as a precursor compound. The microstructure of the samples was characterized by SEM and XRD. The gas sensing properties of the NiO nanowires toward ethanol was also investigated. The results show that PEG plays a key role in the synthesis of wire-like NiO. The NiO nanowires show excellent sensing performances to ethanol gas. This morphology holds substantial promise for applying NiO as a potential gas sensing material for future sensor application.     

Magnetic image detection of the stainless-steel welding part inside a multi-layered tube structure

The stainless-steel welding part inside a multi-layered tube was successfully detected using low-frequency magnetic imaging. The magnetic images were obtained by the developed measurement system, consisting of an exposure coil, magnetoresistive (MR) sensor, lock-in amplifier, x–y stage, revolving stage with a horizontal level stage and personal computer. To expose the magnetic field to a wide area of the stainless-steel sample, the radius of the exposure coil was made comparable to the sample size. The MR sensor measured the vector components of the magnetic field generated from the sample within the range of low frequencies between 50 Hz and 1 kHz. A cylindrical stainless-steel sample was fabricated as a tube by rolling a stainless-steel sheet and welding each edge using arc welding with argon as shielding gas. The normal components (B_z) and tangential components (B_x and B_y) to the sample surface were measured by scanning the MR sensor on the sample surface and the magnetic characteristics of each of the component images were documented. As a result, the difference in permeability between the weld area and the base material was successfully visualized as magnetic images.     

碳纳米管修饰的空心多孔NiO/SnO2纳米复合材料对丙酮传感性能的优化

通过静电纺丝法制备中空多孔的NiO/SnO2复合纳米纤维,在复合纤维表面装饰碳纳米管,在此基础上制备气敏传感器器件。利用TGA确定了复合材料热分解温度,得到热处理工艺;利用SEM、XRD、TEM、XPS分别对复合材料的形貌、结构、尺寸、表面成分进行了表征。使用WS-30A气敏元件测试仪对气敏元件响应进行测试,结果表明CNTs装饰的NiO/SnO2复合纳米材料制备的气敏传感器降低了丙酮检测最佳工作温度,为160℃,提高了检测灵敏度,对50 ppm丙酮的响应达到25.25,对检测丙酮有快速的响应(~8.2 s)以及恢复性能(~10.5 s),同时在30天的长期稳定性测试中也体现了良好的稳定性。证明了装饰CNTs 的 NiO/SnO₂复合材料在检测丙酮方面的潜在价值,同时本文也进一步讨论了CNTs, 中空多孔结构的NiO/SnO₂提高检测性能的作用机理。     

Fundamental study of welding with a 1 kW YAG laser beam transmitted by optical fibre

Summary

This paper describes an in-process monitoring system developed to monitor the quality of CO₂ laser welding. It incorporates two photo sensors aligned at different angles to detect the long-term power stability as well as underfill and pitting defects and has been used on a production line for tailored blank welding of automotive parts since 1993. The laser power stability can be monitored by long-term recording of the average plasma emission intensity. Underfills can be sensitively recognised by a decrease in the light emission intensity detected by the low angle sensor, since the hot core of the plasma plume is hidden by the surrounding material. Small pits can be detected by a sharp decrease in the light emission intensity recorded by the high angle sensor.     

An anti-oxidation coating for WMo and ZrO2 composite in a wide range from room temperature to 1200 °C

WMo and ZrO₂ composite has been used for molten steel temperature sensor. The sensor has an additional potential to measure the baking temperature of tundish. However, its oxidation during the baking (room temperature ~ 1200 °C) restricts this potential. Thus, an anti-oxidation coating has been developed. Raw materials of 20 wt% borax, 20 wt% potash feldspar and 60 wt% fused silica that had suitable melting temperature and low volatility were obtained and fused at 1200 °C to prepare borosilicate glass. Then, the glass powders were brushed on sensor surface through the slurry method, which was fused at 1200 °C to form the coating. The coating exhibited low volatility (weight loss: <0.5%), good compactness, continuity and adhesion to the matrix. Whether it was in solid or molten state (1000 °C or 1200 °C), it showed excellent oxidation resistance. Based on application test, it protected the sensor against oxidation during the baking. As a result, the sensor could be used to measure the baking temperature.     

Unusual spectroscopic properties of PPE/TiO2 composite and its sensor response to TNT

A composite from a broad bandgap polymer, poly(phenylene ethylene) (PPE), and nano-sized TiO₂ particles was found to be able to sense 2,4,6-trinitrotoluene (TNT) for TNT sensor. Fluorescence quenching induced by charge transfer from PPE to nano-sized TiO₂ was observed in toluene solution. At high TiO₂ composition, a strong exciplex band occurred at 550 nm. Under prolonged light irradiation at 400 nm, unusual fluorescence gains took place at 460 nm, companied with a very small change in the UV–vis absorbance. After 30 min light irradiation, the fluorescence at 460 nm reached a maximum, but the peak at 550 nm disappeared. This composite showed amplified sensor response to TNT compared to the pristine PPE film, which can be potentially used as sensing material for detecting TNT based explosives.