C₃N₄ as a Precursor for the Synthesis of NbC, TaC and WC Nanoparticles.

Abstract

Tantalum I 5200 C3N4 as a Precursor for the Synthesis of NbC, TaC and WC Nanoparticles. -Nanoparticles of NbC, TaC, and WC are prepared from mixtures of C 3 N 4 and Nb 2 O 5 , Ta2O5, and WO3, respectively (1150°C, 1 h). The samples are characterized by powder XRD, FE-SEM, EDX, TEM, and HRTEM. The metal oxides are completely converted into the corresponding carbides at 1150°C, which is significantly lower than the temperatures reported for the commercial preparation of the carbides, typically >1600°C. This novel route may provide new insights into the synthesis of other transition metal carbides. -(LI*, P. G.; LEI, M.; SUN, Z. B.; CAO, L. Z.; GUO, Y. F.; GUO, X.; TANG, W. H.; J.

A Solvothermal Approach for the Preparation of Nanostructured Carbide and Boride Ultra‐High‐Temperature Ceramics

“…T ransition metal carbides, such as tantalum carbide, are some of the most refractory ceramics known (having melting temperatures up to ∼4000 K). Besides being refractory, other beneficial properties include thermomechanical stability, thermochemical stability, corrosion and wear resistance, good creep and fatigue resistance, unique optical and electronic properties, high emissivity at elevated temperatures, and catalytic characteristics 1–8 . These materials are of particular interest in the aerospace industry, where reentry conditions and internal rocket conditions result in harsh environments with demanding specifications.…”

Facile route to prepare TaC, NbC and WC nanoparticles

“…According to the Refs. [10,13], a-C 3 N 4 can decompose into various carbon nitride species such as C 2 N 2 + , C 3 N 2 + , C 3 N 3 + and CN 2 2+ at high temperatures. It is deduced that these highly active carbon nitride species play crucial roles in the whole reaction.…”

“…In the standard synthesis [10] , firstly, 4 mmol as-synthesized a-C 3 N 4 and 1 mmol metal oxides Ta 2 O 5 were mixed and ground together, and then pressed to a pellet. The pellet was put into a silica ampoule with the volume of 20 cm 3 .…”

Low‐Temperature Formation of Ultra‐High‐Temperature Transition Metal Carbides from Salt–Polymer Precursors

“…The inefficient nature of heat transfer and the high incongruent melting temperatures causes these techniques to require high temperatures (above 1700°C) and long times to produce refractory carbides 16,17 . Other methods reported for processing transition metal carbides include carbothermal reduction of transition metal rapid metathesis reactions, 18,19 solid‐state reactions, 14,20 gas–solid reactions, 12,21–23 gas‐phase reactions, 24,25 carbothermal reaction assisted by microwaves, 13 electrochemical and solution state methods, 26,27 and high‐frequency plasma 28 . All of these methods, much like conventional techniques, are high‐temperature, high‐energy, and time consuming processes with relatively low yields that in many cases result in residual impurities such as free carbon, oxides, and subcarbides (e.g., Ta 2 C) 13,14 …”