Nanometer materials of rare earth mixed oxides REFeO3 (RE=Eu, Gd) with the structure of perovskite type were synthesized by sol–gel method in the citric acid system. The structure and crystal phase of the powders were characterized on an X-ray diffractometer. The shape and size were analyzed with the help of JEM-100X Transmission electron microscopy. The results show that the morphologies of the two perovskite-type oxides are spherical with the mean grain size of 20 and 21 nm, respectively. Their crystal structures show a certain amount of lattice distortion due to the decrease of grain size and the increase of surface area. Gas sensitivities of these two kinds of materials to C2H5OH, H2S, gasoline and H2 were tested. The studies of gas-sensing characteristics show the sensitivities of EuFeO3 and GdFeO3 nanometer materials to gasoline are 39 and 45 at 340 °C, respectively, and both of them have appropriate selectivity. So they are promising candidates for the detection of gasoline in monitoring environment.

Preparation, characterization and gas-sensing properties of rare earth mixed oxides

This paper presents the sensing model and scheme for utilizing thermoplastic polyimide-coated fiber Bragg grating (FBG) to measure the relative humidity (RH) on the basis of the application of FBG in chemical sensing. The volume expansion and shrinkage of the polyimide moisture sensitive material after water absorption and desorption have direct effects on the FBG and result in the shift of the Bragg wavelength. The low-cost coarse wavelength division multiplexing (CWDM) is used to interrogate the Bragg wavelength through converting the wavelength signals into the optical intensity ones. Experimental results show that the applicable low-cost relative humidity sensor has a linear, reproducible and reversible response over a wide RH range from 11% to 98%. The thickness and the length of the thermoplastic polyimide coating considered as a moisture sensitive polymer material are 8 μm and 2.5 cm, respectively. The sensitivity of the sensor is −0.000266V/%RH, and the response time is approximately 5 s.

Low-cost relative humidity sensor based on thermoplastic polyimide-coated fiber Bragg grating

One of the largest movers of the world economy is the oil and gas industry. The industry generates billions of barrels of oil to match more than half the world’s energy demands. Production of energ...

https://journals.sagepub.com/doi/pdf/10.1177/1475921719837718

F.J.Mendieta Jiménez

Papers

Fiber Bragg grating sensor for petroleum hydrocarbon leak detection