The influence of surface segregation of oxygen or nitrogen on the decompositio of hydrocarbons on transition metals

Influence of oxygen and carbon on performance of superpermeable membranes

“…For example, the reaction coefficient of ethylene which was almost unity on a clean Ta surface was reduced to ca. 10 −4 at 1673 K by chemisorbed oxygen [21]. In addition, a major portion of deposited carbon can be transformed into metal carbides being permeable for hydrogen isotopes at elevated temperatures as described above.…”

“…By extrapolating the date obtained by other researchers at temperatures above 1400 K [19,20], the reaction coefficients of methane and ethane on clean Nb surface at 900 K were evaluated to be 2 × 10 −6 and of 3 × 10 −5 , respectively. It is also known for Ta that the presence of chemisorbed oxygen layer reduces the reaction coefficients by from 4 to 6 orders of magnitude [21]. Alkenes such as ethylene are much more reactive than alkanes.…”

Synthesis of Tantalum Carbide Using Purified Hexane by Titanium Powder

“…Tantalum carbide powders are mainly manufactured via three methods: (1) heat treatment in a non-oxidizing atmosphere using a mixture of tantalum metal and graphite powders, (2) solid carburization, such as self-propagating high-temperature synthesis (SHS) using the reaction heat between reactants by mixing tantalum and graphite powders [ 11 , 12 , 13 ], and (3) gaseous carburization using hydrocarbon gases such as methane, propane, and butane as the carburizing media for tantalum [ 14 , 15 ]. In addition, other methods such as reduction carburization, which employs a mixture of tantalum oxide (Ta 2 O 5 ) and graphite powders to simultaneously induce reduction and carburization reactions, are being studied for commercialization [ 16 ].…”