نتایج جستجو برای: vanadium v oxide
تعداد نتایج: 478824 فیلتر نتایج به سال:
SnO2 nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization technique...
The information obtained from the characterization of vanadium oxide single crystal surfaces is related to the study of vanadia nanoparticles supported on silica and alumina thin films, model systems for the so-called ‘‘supported monolayer vanadia catalysts’’. It is found that these particles have properties similar to V2O3 surfaces, where the topmost V ions are involved in vanadyl groups and h...
The vanadium-vanadium interactions in the polygonal aggregates of d¹ vanadium(IV) atoms, with a total of 4k + 2 vanadium electrons (k an integer) imbedded in an electronically inactive borate matrix in certain vanadoborate structures are analogous to the ring carbon-carbon interactions in diamagnetic planar cyclic hydrocarbons. They thus represent a high-spin analogue of aromaticity. Thus, the ...
We report the synthesis and characterization of a molecular barium vanadium oxide cluster featuring high nuclearity and high symmetry. The tetrameric, 2.3 nm cluster H(5)[Ba(10)(NMP)(14)(H(2)O)(8)[V(12)O(33)](4)Br] is based on a bromide-centred, octahedral barium scaffold which is capped by four previously unknown [V(12)O(33)](6-) clusters in a tetrahedral fashion. The compound represents the l...
Vanadium dioxide (VO(2)) undergoes a sharp metal-insulator transition (MIT) in the vicinity of room temperature and there is great interest in exploiting this effect in novel electronic and photonic devices. We have measured the work function of vanadium dioxide thin films across the phase transition using variable temperature Kelvin force microscopy (KFM). The work function is estimated to be ...
The partial oxidation of methanol to formaldehyde was studied over highly dispersed vanadia supported on mesoporous silica SBA-15 (VOx/SBA-15). VOx/SBA-15 catalysts were prepared by a novel grafting/ion-exchange method and characterized using UV-VISand Raman spectroscopy. The resulting surface vanadium oxide species (0 – 2.3 V/nm), grafted on the inner pores of the SBA-15 silica matrix, consist...
the possibility of application of 4-nitrocatechol (4-nc) - tetrazolium salt - organic solventsystems for liquid-liquid extraction-spectrophotometric vanadium (iv and v) speciation wasstudied. six commercially available tetrazolium salts (2,3,5-triphenyltetrazolium chloride (ttc),3-(2-naphtyl)-2,5-diphenyltetrazolium chloride (tetrazolium violet, tv); 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyltetra...
A quadrupole-based mass spectrometer equipped with an electrospray ionization source was used to examine the gas-phase reactivity of various vanadium-oxide cations which mediate the oxidative dehydrogenation (ODH) of small alkenes and alkanes. For ion generation, a solution of V6O7(OMe)12 dissolved in deuterated methanol was subjected electrospray under very harsh conditions to obtain smaller v...
Vanadium silicates such as V-Al-analcime, V-analcime, V-magediite and V-ZSM-11 were synthesized using vanadium pentoxide or vanadyl sulfates. Vanadium silicates with analcime structure with and without aluminum (V-Al-analcime, V-analcime) were prepared as pure phase by hydrothermal crystallization from a gel with molar composition of (1 SiO2; 0.2 V2O5; 1 Na2O; 0.034 Al2O3; 35.7 H2O) and (1 SiO2...
Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micrometer-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulfides and hBN are f...
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