Abstract
The use of niobium containing materials' has gained much attention of the scientific community in the late years due its various applications in diverse fields. NbC is a highly versatile material. Copper addition may alter several of its properties, such as morphology, crystal structure etc. as well as enhance its catalytic behavior. Nanostructured NbC with copper addition synthesis' presented here had the precursor [(NH4 )3[NbO(C2O4)3]xH2O] as starting material, which was doped with Cu(NO3)2at 5% and 10% (molar) ratios. Doped NbC was obtained via gas solid reaction in fixed bed reactor at lower temperature (980°C) and with shorter reaction time (2h) than traditional methods. Reaction products' were characterized by XRD, crystal sizes were estimated according to HWL method, and SEM, XRF, BET and laser particle size analysis were performed. XRD indicated the formation of NbC and Cu phases with cubic crystal structure of ~20nm. SEM showed slight morphological change upon increasing copper content, indicating a less porous structure, which is consistent with BET data (43.7m2/g for 5%Cu-NbC and 37m 2/g for the 10% Cu-NbC). Crystal size calculations showed that increasing dopant content particle sizes were also increased, probably due to the presence of the dopant, in some extent, in the crystal structure
Highlights
The development of materials with various applications has become a major industrial interest; in that sense, researches have been developed considering and aiming to change synthesis conditions or parameters, so that time and energy requirements can be minimized and, ideally, more versatile materials can be obtained
The process was studied in two compositional levels with both materials being produced via gas solid reaction in a fixed bed reactor with a methane/hydrogen gas atmosphere
Copper doped niobium carbide (Cu-NbC) was synthesized via gas solid reaction in a fixed bed reactor using as a starting material finely grained precursor ammoniobium (V) oxalate [(NH4)3[NbO(C2O4) 3]xH2O] doped with copper nitrate (Cu(NO3)[2], Sigma Aldrich, 99,99%)
Summary
The development of materials with various applications has become a major industrial interest; in that sense, researches have been developed considering and aiming to change synthesis conditions or parameters, so that time and energy requirements can be minimized and, ideally, more versatile materials can be obtained. Niobium based catalysts are effective in different processes, such as hydrogenation, oxidation, esterification, polymerization, and condensation reactions[13] In those catalytic reactions a promoting metal is used[14]. For the synthesis of niobium carbide with the copper addition high energy milling followed by sintering is the traditional route In this process metallic copper and graphite are used as starting materials[17,18,19]. Niobium carbide with copper addition was synthesized by gas solid reaction from a niobium oxalic precursor and copper nitrate in a fixed bed reactor This precursor's use for the synthesis of niobium powders has been proved feasible and interesting as it presents higher reactivity than the commercial niobium pentoxide[21]. The process was studied in two compositional levels with both materials being produced via gas solid reaction in a fixed bed reactor with a methane/hydrogen gas atmosphere
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