Mixed oxide

About: Mixed oxide is a research topic. Over the lifetime, 5224 publications have been published within this topic receiving 115567 citations.

V2O5/WO3 Mixed Oxide Films as pH-EGFET Sensor: Sequential Re-Usage and Fabrication Volume Analysis

Abstract: A vanadium and tungsten mixed oxide was deposited onto glassy carbon substrates and used as pH sensor in extended gate field effect transistor (EGFET) devices. WO3 at a molar ratio of about 5% was mixed with V2O5 by means of the sol-gel method. The main focus of this investigation was to determine the operation conditions for the best response of the device and to propose the mechanism involved in the sensor response. The use of either original or reused films were employed and the importance of the total volume of the starting solution was also examined. The time response of the V2O5/WO3-pH-EGFET sensor is due to a deprotonation mechanism of vanadium and tungsten oxide, similarly to a discharging capacitor. The loss of protons by the oxide film depends on the time it remains immersed in the buffer solution and this process is accelerated upon raising the pH value. The increase of the films fabrication volume reduces the importance of the changes of the surface charges compared to the charges of the bulk, leading to less sensitive and less stable sensor response. Therefore, the smaller the amount of material used, the better the sensing properties of the device.

Co-Al Mixed Oxides Prepared via LDH Route Using Microwaves or Ultrasound: Application for Catalytic Toluene Total Oxidation

Abstract: Co6Al2HT hydrotalcite-like compounds were synthesized by three different methods: co-precipitation, microwaves-assisted and ultrasound-assisted methods. The mixed oxides obtained after calcination were studied by several techniques: XRD, TEM, H2-TPR and XPS. They were also tested as catalysts in the reaction of total oxidation of toluene. The physico-chemical studies revealed a modification of the structural characteristics (surface area, morphology) as well as of the reducibility of the formed mixed oxides. The solid prepared by microwaves-assisted synthesis was the most active. Furthermore, a relationship between the ratio of Co2+ on the surface, the reducibility of the Co-Al mixed oxide and the T50 in toluene oxidation was demonstrated. This suggests a Mars Van Krevelen mechanism for toluene total oxidation on these catalysts.

Effects of noble metals doped on mesoporous LaAlNi mixed oxide catalyst and identification of carbon deposit for reforming CH4 with CO2

Abstract: BACKGROUND The effect of the B cation on the surface properties and catalytic activity in the dry reforming reaction over La0.4M0.6Al0.2Ni0.8O3 (M=noble metal) perovskite-type oxides with surface area 3.26–4.14 m2 g–1 and rhombohedral structure was studied. RESULTS Among LaAlxNi1-xO3 series, LaAl0.2Ni0.8O3 had the highest catalytic activity, but suffered a slow deactivation with time-on-stream (TOS). It is observed that all samples presented similar activity at low reaction temperatures (500–600°C), while at higher temperatures (600–850°C) the prepared solid was more active and perovskite phase was transformed into Ni0 or La2O2CO3. It was found that among the noble metal samples, La0.4Rh0.6Al0.2Ni0.8O3 possessed the highest surface area and surface oxygen concentration and the best low-temperature reducibility. For the Rh catalyst the CH4 and CO2 conversions were 89.1 and 86.2%, which were the most resistant against coke deposition and showed very high stability without decrease in reforming and remained constant during the 3000 min TOS. The following order of activity was observed: La0.4Rh0.6Al0.2Ni0.8O3 > La0.4Ru0.6Al0.2Ni0.8O3 > LaAl0.2Ni0.8O3> La0.4Ir0.6Al0.2Ni0.8O3 ≥La0.4Pt0.6Al0.2Ni0.8O3 > La0.4Pd0.6Al0.2Ni0.8O3. CONCLUSIONS It is believed that the high surface area and surface oxygen concentration and good low-temperature reducibility were responsible for the good catalytic performance of the La0.4Rh0.6Al0.2Ni0.8O3 sample. © 2013 Society of Chemical Industry

A versatile sol–gel synthesis route to metal–silicon mixed oxide nanocomposites that contain metal oxides as the major phase

Abstract: The general synthesis of metal–silicon mixed-oxide nanocomposite materials, including a variety of both main group and transition metals, in which the metal oxide is the major component is described. In a typical synthesis, the metal-oxide precursor, MClx · yH2O(x = 2–6, y = 0–7), was mixed with the silica precursor, tetramethoxysilane (TMOS), in ethanol and gelled using an organic epoxide. The successful preparation of homogeneous, monolithic materials depended on the oxidation state of the metal as well as the epoxide chosen for gelation. The composition of the resulting materials was varied from M/Si = 1–5 (mol/mol) by adjusting the amount of TMOS added to the initial metal-oxide precursor solution. Supercritical processing of the gels in CO2 resulted in monolithic, porous aerogel nanocomposite materials with surface areas ranging from 100–800 m2 g−1. The bulk materials are composed of metal oxide/silica particles that vary in size from 5–20 nm depending on the epoxide used for gelation. Metal oxide and silica dispersion throughout the bulk material is extremely uniform on the nanoscale. The versatility and control of the synthesis method will be discussed as well as the properties of the resulting metal–silicon mixed oxide nanocomposite materials.