In-situ fabrication of ZnO nanoparticles sensors based on gas-sensing electrode for ppb-level H_2S detection at room temperature

The zinc oxide(ZnO)nanoparticles(NPs)sensors were prepared in-situ on the gas-sensing electrodes by a one-step simple sol-gel method for the detection of hydrogen sulfide(H₂S)gas.The sphere-like ZnO NPs were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),x-ray diffraction(XRD),energy dispersive x-ray analysis(EDX),and their H₂S sensing performance were measured at room temperature.Testing results indicate that the ZnO NPs exhibit excellent response to H₂S gas at room temperature.The response value of the optimal sample to750 ppb H₂S is 73.3%,the detection limit reaches to 30 ppb,and the response value is 7.5%.Furthermore,the effects of the calcining time and thickness of the film on the gas-sensing performance were investigated.Both calcining time and film thickness show a negative correlation with the H₂S sensing performance.The corresponding reaction mechanism of H₂S detection was also discussed.     

Preparation and Characteristics of GaN Films on Freestanding CVD Thick Diamond Films

Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of the GaN films are characterized by x-ray diffraction, reflection high energy electron diffraction and atomic force microscopy. The results indicate that the structure and morphology of the films are strongly dependent on the deposition temperature. The most significant improvements in morphological and structural properties of GaN films are obtained under the proper deposition temperature of 400°C.     

Low-temperature synthesis of apatite-type La_(9.33)Ge_6O_(26) as electrolytes with high conductivity

In the present study,high-quality apatite-type La_(9.33)Ge_6O_(26) powders are successfully synthesized by a facile moltensalt synthesis method(MSSM) at low temperatures,using Li Cl,Li Cl/Na Cl mixture(mass ratio 1:1) as molten salt,respectively.Experimental results indicate that the optimal mass ratio between reactant and molten salt is 1:2,and Li Cl/Na Cl mixed molten-salt is more beneficial for forming high-quality La_(9.33)Ge_6O_(26) powders than Li Cl individual molten-salt.Comparing with the conventional solid-state reaction method(SSRM),the synthesis temperature of apatitetype La_(9.33)Ge_6O_(26) powders using the MSSM decreases more than 350?C,which can effectively avoid Ge loss in the preparation process of precursor powders.Furthermore,the powders obtained by the MSSM are homogeneous,nonagglomerated and well crystallized,which are very favorable for gaining dense pellets in the premise of avoiding Ge loss.On the basis of high-quality precursor powders,the dense and pure ceramic pellets of La_(9.33)Ge_6O_(26) are gained at a low temperature of 1100?C for 2 h,which exhibit higher conductivities(σ850?C(Li Cl)= 2.3 × 10~(-2) S·cm~(-1),σ850 ?C(Li Cl/Na Cl) = 4.9 × 10~(-2) S·cm~(-1)) and lower activation energies(Ea(Li Cl)= 1.02 e V,Ea(Li Cl/Na Cl)= 0.99 e V) than that synthesized by the SSRM.