基于电纺丝法的In_2O_3/CdO复合材料的制备及甲醛气敏特性

Preparation of Electrospun In_2 O_3 /CdO Composite and Its Formaldehyde-Sensing Properties

用静电纺丝法制备了In(NO3)3/聚乙烯吡咯烷酮(PVP)纺丝前驱物,然后分别在500、600、700°C时烧结得到三种In2O3纳米纤维.通过X射线衍射(XRD)仪、热重差热分析(TG/DTA)、场发射扫描式电子显微镜(FE-SEM)表征结果得知,500°C时In2O3的晶相已经形成,且粒径为最小,约为24nm,纳米纤维呈介孔结构.将三种烧结温度的In2O3纤维制作成气敏元件,测试对比了三种元件对甲醛气体的敏感特性,结果表明,500°C烧结得到的In2O3纳米纤维在工作温度为240°C时响应最好,对浓度为10×10-6(体积分数,φ)甲醛的响应为7.用静电纺丝法合成了CdO纳米颗粒,通过XRD、SEM表征得知CdO呈粒径约为68nm的颗粒.将In2O3和CdO以不同摩尔比(1:1,10:1,20:1)复合,对比测试了纯In2O3及三种In2O3/CdO复合材料对应的气敏元件对甲醛的气敏特性,测试结果表明当In2O3纳米纤维与CdO纳米颗粒以摩尔比10:1复合时,元件的工作温度较低(200°C),且对甲醛表现出最佳的气敏特性,对浓度为10×10-6甲醛的响应为13.6,响应/恢复时间为140s/32s.最后对不同摩尔比复合的In2O3/CdO对甲醛的气敏机理进行了初步分析.

In（NO3）Jpolyvinyl pyrrolidone （PVP） nanofiber precursors were synthesized using a traditional electrospinning method, and were then annealed at 500, 600, and 700 ℃ to form In203 nanofibers. The as-prepared In203 nanofibers were characterized using X-ray diffraction （XRD）, thermal gravimetry and differential thermal analysis （TG/DTA）, and field-emission scanning electron microscopy （FE-SEM）. The results show that the In2O3 nanofibers crystallize well, with a small average grain size （about 24 nm） and a good mesoporous structure, when annealed at 500 ℃. The In203 nanofibers annealed at the three temperatures were further used to fabricate gas sensors. The test results show that the sensor based on In203 annealed at 500℃ has the highest response （about 7） to 10x 10-~ （volume fraction, ℃） formaldehyde （HCHO） at an operating temperature of 240 ℃. CdO nanoparticles were also prepared using the same method; XRD and FE-SEM show that the average grain size of CdO is about 68 nm. Finally, the as-prepared In203 nanofibers were mixed with the as-prepared CdO in molar ratios of 1：1, 10：1, and 20：1, and the mixtures were used to fabricate gas sensors. The HCHO-sensing properties of the sensors based on pure In2O3 and In2O3/CdO composites with different molar ratios were investigated at each optimum temperature. The results show that the In2O3/CdO composite with a molar ratio of 10：1 has excellent sensing properties： the response to 10x 10-6 HCHO is 13.6, the response/recovery time is 140 s/32 s, and the selectivity is better at a lower operating temperature of 200 ℃. In addition, the HCHO-sensing mechanism of the sensors based on the In2O3/CdO composites was briefly analyzed.