共查询到20条相似文献,搜索用时 78 毫秒
1.
A complete review, critical evaluation, and thermodynamic optimization of phase equilibrium and thermodynamic properties of the MnO–SiO2–“ TiO2”–“ Ti2O3” systems at 1 bar pressure are presented. The molten oxide phase was described by the Modified Quasichemical Model. The Gibbs energies of the manganosite, spinel, pyrophanite and pseudobrookite and rutile solid solutions were taken from the previous study. A set of optimized model parameters for the molten oxide phase was obtained which reproduces all available reliable thermodynamic and phase equilibrium data within experimental error limits from 25 °C to above the liquidus temperatures over the entire range of compositions and oxygen partial pressure in the range of pO2 from 10−20 bar to 10−7 bar. Complex phase relationships in these systems have been elucidated, and discrepancies among the data have been resolved. The database of model parameters can be used along with software for Gibbs energy minimization in order to calculate any phase diagram section or thermodynamic properties. 相似文献
2.
A complete review, critical evaluation, and thermodynamic optimization of the phase equilibrium and thermodynamic properties of the MnO–“ TiO2”–“ Ti2O3” systems at 1 bar pressure are presented. The molten oxide phase was described by the Modified Quasichemical Model. The Gibbs energy of spinel, pyrophanite and pseudobrookite solid solutions were modeled using the Compound Energy Formalism, and rutile solid solution was treated as a simple Henrian solution. Manganosite solid solution was assumed to dissolve both Ti4+ and Ti3+. A set of optimized model parameters for all phases was obtained which reproduces all available reliable thermodynamic and phase equilibrium data within experimental error limits from 25 °C to above the liquidus temperatures over the entire composition ranges and in the range of pO2 from 10−20 to 10−7 bar. Complex phase relationships in these systems have been elucidated, and discrepancies among the data have been resolved. The database of model parameters can be used along with software for Gibbs energy minimization in order to calculate any phase diagram section or thermodynamic properties. 相似文献
3.
Shiwei LinAuthor VitaeDongrong LiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(2):505-509
A new gas sensor using TiO2 nanotube arrays was fabricated and explored for formaldehyde detection at room temperature. Highly ordered vertically grown TiO2 nanotube arrays were synthesized by using the conventional electrochemical anodization process. The sensor using the fabricated nanotube arrays as the sensing elements demonstrated a good response to different concentrations of formaldehyde from 10 to 50 ppm and a very good selectivity over other reducing gas species such as ethanol and ammonia at room temperature. While the exact sensing mechanism is unclear, some possibilities are briefly discussed. 相似文献
4.
Yu-Jin ChenAuthor Vitae Gang XiaoAuthor VitaeTie-Shi WangAuthor Vitae Fan ZhangAuthor VitaeYang MaAuthor Vitae Peng GaoAuthor Vitae Chun-Ling ZhuAuthor VitaeEndi ZhangAuthor Vitae Zhi XuAuthor VitaeQiu-hong LiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):270-277
Crystalline α-MoO3/TiO2 core/shell nanorods are fabricated by a hydrothermal method and subsequent annealing processes under H2/Ar flow and in the ambient atmosphere. The shell layer is composed of crystalline TiO2 particles with a diameter of 2-6 nm, and its thickness can be easily controlled in the range of 15-45 nm. The core/shell nanorods show enhanced sensing properties to ethanol vapor compared to bare α-MoO3 nanorods. The sensing mechanism is different from that of other one-dimensional metal oxide core/shell nanostructures due to very weak response of TiO2 nanoparticles to ethanol. The enhanced sensing properties can be explained by the change of type II heterojunction barrier formed at the interface between α-MoO3 and TiO2 in the different gas atmosphere. The present results demonstrate a novel sensing mechanism available for gas sensors with high performance. 相似文献
5.
Ju Wu Xucheng Fu Chenggen Xie Mei Yang Wei Fang Shan GaoAuthor vitae 《Sensors and actuators. B, Chemical》2011,160(1):511
This paper reports a surface molecular self-assembly strategy for chlorpyrifos (CPF) imprinting of polymer membranes at the surface of TiO2 nanoparticles for flow injection chemiluminescence (CL) detection of pesticide CPF which using the character of TiO2 enhance the chemiluminescence of the luminol–H2O2 system. The CL signals produced by the reaction between luminol and H2O2, were increased in the presence of CPF imprinting of polymer membranes at the surface of TiO2 which were eluted from the column through luminol and H2O2 injection. The CL enhancement by TiO2 nanoparticles of the luminol–H2O2 system was supposed to originate from the catalysis of TiO2 nanoparticles and CPF. The CL intensity was linear over the logarithm of concentration of chlorpyrifos ranging from 1.0 × 10−10 to 5.0 × 10−7 mol/L (r2 = 0.996), and the limit of detection was 1.0 × 10−11 mol/L (3σ). The detection limit for CPF is lower than other methods. An excellent CL selectivity for CPF over other pesticides was also achieved. The combination of surface molecular self-assembly with polymer molecular imprinting on larger surface area of TiO2 nanoparticles produce a high ratio of imprinted sites and, thus, provide an ultrasensitive CL detection of CPF. 相似文献
6.
K.O. RochaAuthor VitaeS.M. ZanettiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(2):654-661
Nanocrystalline WO3/TiO2-based powders have been prepared by the high energy activation method with WO3 concentration ranging from 1 to 10 mol%. The samples were thermal treated in a microwave oven at 600 °C for 20 min and their structural and micro-structural characteristics were evaluated by X-ray diffraction, Raman spectroscopy, EXAFS measurements at the Ti K-edge, and transmission electron microscopy. Nitrogen adsorption isotherms and H2 Temperature Programmed Reduction were also carried out for physical characterization. The crystallite and particle mean sizes ranged from 30 to 40 nm and from 100 to 190 nm, respectively. Good sensor response was obtained for samples with at least 5 mol% WO3 activated for at least 80 min. Ceramics heat-treated in microwave oven for 20 min have shown similar sensor response as those prepared in conventional oven for 120 min, which is highly cost effective. These results indicate that WO3/TiO2 ceramics can be used as a humidity sensor element. 相似文献
7.
Yu-Jin ChenAuthor Vitae Gang XiaoAuthor VitaeTie-Shi WangAuthor Vitae Fan ZhangAuthor VitaeYang MaAuthor Vitae Peng GaoAuthor VitaeEndi ZhangAuthor Vitae Zhi XuAuthor VitaeQiu-hong LiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(2):867-874
Crystalline CeO2/TiO2 core/shell nanorods were fabricated by a hydrothermal method and a subsequent annealing process under the hydrogen and air atmosphere. The thickness of the outer shell composed of crystal TiO2 nanoparticles can be tuned in the range of 5-11 nm. The crystal core/shell nanorods exhibited enhanced gas-sensing properties to ethanol vapor in terms of sensor response and selectivity. The calculated sensor response based on the change of the heterojunction barrier formed at the interface between CeO2 and TiO2 is agreed with the experimental results, and thus the change of the heterojunction barrier at different gas atmosphere can be used to explain the enhanced ethanol sensing properties. 相似文献
8.
A compact tubular sensor based on NASICON (sodium super ionic conductor) and V2O5-doped TiO2 sensing electrode was designed for the detection of SO2. In order to reduce the size of the sensor, a thick-film of NASICON was formed on the outer surface of a small Al2O3 tube; furthermore, a thin layer of V2O5-doped TiO2 with nanometer size was attached on the NASICON as a sensing electrode. This paper investigated the influence of V2O5 doping and sintering temperature on the characteristics of the sensor. The sensor attached with 5 wt% V2O5-doped TiO2 sintered at 600 °C exhibited excellent sensing properties to 1–50 ppm SO2 in air at 200–400 °C. The EMF value of the sensor was almost proportional to the logarithm of SO2 concentration and the sensitivity (slope) was −78 mV/decade at 300 °C. It was also seen that the sensor showed a good selectivity to SO2 against NO, NO2, CH4, CO, NH3 and CO2. Moreover, the sensor had speedy response kinetics to SO2 too, the 90% response time to 50 ppm SO2 was 10 s, and the recovery time was 35 s. On the basis of XPS analysis for the SO2-adsorbed sensing electrode, a sensing mechanism involving the mixed potential at the sensing electrode was proposed. 相似文献
9.
Phase equilibria and thermodynamic properties at 1 bar in the Y 2O3–Al2O3–SiO2 ternary system and its constituent binaries Y 2O3–Al2O3 and Y 2O3–SiO2 have been reevaluated using the CALPHAD approach. The liquid phase is described by the ionic two-sublattice model with the formula (Al+3,Y +3)P(AlO2−1,O−2,SiO4−4,SiO20)Q. The SiO2 solubility in the YAM phase was described using a compound energy model. Two datasets of self-consistent model parameters are presented. However, the rather meagre and scattered experimental data imply that the present assessments should be regarded as provisional. Some critical experiments are suggested for this system. 相似文献
10.
Ya-Hui HoAuthor VitaeArun Prakash PeriasamyAuthor Vitae Shen-Ming ChenAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(1):84-94
Herein we report the photoelectrocatalytic regeneration of NADH at poly(4,4′-diaminodiphenyl sulfone)/nano TiO2 (PDDS/TiO2) composite modified indium tin oxide (ITO) electrode. The PDDS film growth was confirmed through in situ electrochemical quartz crystal microbalance (EQCM) studies. The prepared PDDS/TiO2 composite was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) studies. SEM and AFM results confirmed that TiO2 nanoparticles size is between 130 and 180 nm. XRD results showed that TiO2 nanoparticles are crystalline and belong to anatase phase. Electrochemical impedance spectroscopy (EIS) and light induced EIS results substantiate a rapid electron transfer process at PDDS/TiO2 composite surface. Cyclic voltammetry (CV) results demonstrated that composite film showed excellent response to the photoelectrocatalytic regeneration of NADH. The photoelectrocatalytic oxidation of NADH at composite film surface irradiated for 5 min (optimized irradiation time) produced a notable enhancement in anodic peak current and it was 18-fold higher than that of PDDS film and several folds higher than that of TiO2 and bare ITO electrodes. Further, composite film showed higher sensitivity of 124.1 μA μM−1 for NADH. From Square wave voltammetry (SWV) results, sensitivity of the irradiated composite film was obtained as 0.252 μA nM−1 of NADH. The linear concentration range was between 23 and 39 nM NADH respectively. Further, the composite film exhibits good selectivity towards NADH and no significant interference effect was observed even when 200-fold excess of ascorbic acid (AA), dopamine (DA) and uric acid (UA) coexist in the same supporting electrolyte solution. 相似文献
11.
Chander ShekharAuthor VitaeK.I. GnanasekarAuthor Vitae E. PrabhuAuthor VitaeV. JayaramanAuthor Vitae T. GnanasekaranAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(1):19-27
Indium oxide (In2O3) doped with 0.5-5 at.% of Ba was examined for their response towards trace levels of NOx in the ambient. Crystallographic phase studies, electrical conductivity and sensor studies for NOx with cross interference for hydrogen, petroleum gas (PG) and ammonia were carried out. Bulk compositions with x ≤ 1 at.% of Ba exhibited high response towards NOx with extremely low cross interference for hydrogen, PG and ammonia, offering high selectivity. Thin films of 0.5 at.% Ba doped In2O3 were deposited using pulsed laser deposition technique using an excimer laser (KrF) operating at a wavelength of (λ) 248 nm with a fluence of ∼3 J/cm2 and pulsed at 10 Hz. Thin film sensors exhibited better response towards 3 ppm NOx quite reliably and reproducibly and offer the potential to develop NOx sensors (Threshold limit value of NO2 and NO is 3 and 25 ppm, respectively). 相似文献
12.
Hi Gyu MoonAuthor Vitae Ho Won JangAuthor Vitae Jin-Sang KimAuthor VitaeHyung-Ho ParkAuthor Vitae Soek-Jin YoonAuthor Vitae 《Sensors and actuators. B, Chemical》2011,153(1):37-43
We report a novel route for the fabrication of highly sensitive and rapidly responding Nb2O5-based thin film gas sensors. TiO2 doping of Nb2O5 films is carried out by co-sputtering without the formation of secondary phases and the surface area of TiO2-doped Nb2O5 films is increased via the use of colloidal templates composed of sacrificial polystyrene beads. The gas sensitivity of Nb2O5 films is enhanced through both the TiO2 doping and the surface embossing. An additional enhancement on the gas sensitivity is obtained by the optimization of the bias voltage applied between interdigitated electrodes beneath Nb2O5-based film. More excitingly, such a voltage optimization leads to a substantial decrease in response time. Upon exposure to 50 ppm CO at 350 °C, a gas sensor based on TiO2-doped Nb2O5 film with embossed surface morphology exhibits a very high sensitivity of 475% change in resistance and a rapid response time of 8 s under 3 V, whereas a sensor based on plain Nb2O5 film shows a 70% resistance change and a response time of 65 s under 1 V. Thermal stability tests of our Nb2O5-based sensor reveal excellent reliability which is of particular importance for application as resistive sensors for a variety gases. 相似文献
13.
Nupur BahadurAuthor Vitae Kiran JainAuthor VitaeRenu PasrichaAuthor Vitae GovindAuthor VitaeSuresh ChandAuthor Vitae 《Sensors and actuators. B, Chemical》2011,159(1):112-120
Bare and Ag loaded TiO2 (0.05, 0.5, and 5.0 mol% Ag) powders prepared by sol-gel process have been used for the detection of ethanol, LPG, acetone and toluene gases. These materials were well characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) specific surface area analysis techniques. Specific surface area increased with increasing Ag loading in these mesoporous materials. A thorough TEM/HRTEM investigation with X-ray maps of the modified particles shows the extent of TiO2 surface coverage by Ag nanoparticles. From the comparative study of the sensor response of Ag-TiO2 powders for various gases, it is observed that each Ag loading resulted in the highest response towards a particular gas or in other words, every gas responded best towards a particular Ag loading of the sensor material, i.e. 0.05 mol% Ag-TiO2 sensor showed highest response towards ethanol, 0.5 mol% Ag-TiO2 sensor showed best response towards toluene, whereas, bare TiO2 proved to be the best sensor for both acetone and LPG gases. This establishes that Ag loading is not required for detection of acetone and LPG gases. On the basis of detailed materials characterization, a mechanism for the gas sensing response of each analyte has been discussed. 相似文献
14.
Wen Zeng Tianmo Liu DeJun Liu ErJing HanAuthor vitae 《Sensors and actuators. B, Chemical》2011,160(1):455
The microstructure of M-doped SnO2 (M = Cr3+, Cu2+ and Pd2+) prepared by the sol–gel method and their gas-sensing performance were investigated. In particular, we focus on the effects of metallic ions on the hydrogen sensing behavior of the SnO2-based sensor. It is found that hydrogen gas response of SnO2 can be enhanced evidently by adding Pd2+, while such effect from Cr3+ and Cu2+ exhibits somewhat slight. A theoretical study based on first principles calculation shows that SnO2–Pd (1 1 0) surface enable adsorb more H2 gas and receive larger electrons from adsorbed H2 molecule, thereby holding the potential for the improvement of gas response to hydrogen. 相似文献
15.
16.
This paper presents the ability of electrostatic sprayed tin oxide (SnO2) and tin oxide doped with copper oxide (1, 2, and 4 at.% Cu) films to detect different pollutant gases, i.e., H2S, SO2, and NO2. The influence of a copper oxide dopant on the SnO2 morphology is studied using scanning electron microscopy (SEM) technique, which reveals a small decrease in the porosity and particle size when the amount of dopant is increased. The sensing properties of the SnO2 films are greatly improved by doping, i.e., the Cu-doped SnO2 films have large response to low concentration (10 ppm) of H2S at low operating temperature (100 °C). Furthermore, no cross-sensitivity to 1 ppm NO2 and 20 ppm SO2 is observed. Among the studied films, the 1 at.% Cu-doped SnO2 layer is the most sensitive in the detection of all the studied gases. 相似文献
17.
Hui Wang Shuhua Zhong Yu He Gongwu SongAuthor vitae 《Sensors and actuators. B, Chemical》2011,160(1):189
The nanocomposite TiO2/molecular sieve 4A as photocatalyst was fabricated and employed to develop an effective, rapid, simple and environmental friendly method for chemical oxygen demand (COD) detection. This new approach overcomes the problems with direct use of TiO2 for COD detection techniques such as photo-decay and difficulties in recycling. Here, the COD value was calculated from the changed absorbance of Cr(VI) and the mechanism of the photocatalytic oxidation was discussed. Under the optimal condition, the COD sensor gave a detection limit of 0.24 mg l−1 and a linear range from 3.0 to 15 mg l−1. With the recoveries from 97 to 103% and without any pretreatments for complicated samples, the developed sensor was successfully applied to the determination of COD in real samples. 相似文献
18.
Yongping PuAuthor VitaeHaidong WuAuthor Vitae Jifeng WeiAuthor Vitae 《Sensors and actuators. A, Physical》2012,173(1):158-162
Nb2O5-doped (1 − x)Ba0.96Ca0.04TiO3-xBiYO3 (where x = 0.01, 0.02, 0.03 and 0.04) lead-free PTC thermistor ceramics were prepared by a conventional solid state reaction method. X-ray diffraction, scanning electron microscope, Agilent E4980A and resistivity-temperature measurement instrument, were used to characteristic the lattice distortion, microstructure, temperature dependence of permittivity and resitivity-temperature dependence. It was revealed that the tetragonality c/a of the perovskite lattice, the microstructure and the Curie temperature changed with the BiYO3 content. In order to decrease the room temperature resistivity, the effect of Nb2O5 on the room temperature resistivity was also studied, and its optimal doping content was finally chosen as 0.2 mol%. The 0.97Ba0.96Ca0.04TiO3-0.03BiYO3-0.002Nb2O5 thermistor ceramic exhibited a low ρRT of 3.98 × 103 Ω cm, a typical PTCR effect of ρmax/ρmin > 103 and a Tc of 153 °C. 相似文献
19.
A thermally oxidized TiO2 or Nb2O5 film equipped with a top Pd film electrode and a bottom Ti or Nb plate electrode (Pd/MO(n)/M, MO: oxide film, M: metal plate, n: annealing temperature (°C)) has been investigated as a diode-type H2 sensor under air or N2 atmosphere. Pd/TiO2(n)/Ti sensors showed relatively poor H2 sensing properties in air, in comparison with Pd/anodic-TiO2(n)/Ti sensors constructed with an anodized TiO2 film equipped with a top Pd film electrode and a bottom Ti plate electrode, which were reported in our previous studies. On the other hand, Pd/Nb2O5(n)/Nb sensors showed relatively larger H2 response with fast response and recovery speeds than Pd/TiO2(n)/Ti sensors in air under high forward bias conditions. A Pd/Nb2O5(450)/Ti sensor, which was fabricated by radio-frequency magnetron sputtering of Nb metal on a Ti substrate followed by thermal oxidation at 450 °C, showed the largest H2 response and relatively fast response and recovery speeds in air, among the sensors tested. In addition, H2 response of the Pd/Nb2O5(450)/Ti sensor in air was much lower than that in N2, but the logarithm of H2 response was almost proportional to the logarithm of H2 concentration in a wide range of H2 concentration (10–8000 ppm) in air, and the H2 sensitivity in air was much higher than that in N2. 相似文献
20.