Positron studies of polycrystalline TiC

Abstract

The mean positron lifetime r. positron diffusion length L, and the positron and electron work functions (d+ and d -) for polycryst,alline Tic have been experimentally determined. The results were i = 160(2) ps. L+ = 138(27) nm and $-= 3.96(0.08) eV; 4+ w a shown to be almost certainly positive. These results svongly support the suggestion from recenl first-principles e l e m n i c StNCNre and positron state calcul~tions that positions are trapped by and annihilate in metal vacancies in this material. XPS measurements indicate that the trapping sites may be predominantly in thin carbon-rich layen between grains, a picture which may also explain the long near-surface diffusion length. may coexist and it is very hard to resolve their sometimes competing roles in the physical

Defect evolution in steels: Insights from positron studies

“…TiC has NaCl structure with Ti occupying fcc lattice position and carbon at edge centres with a lattice parameter of 0.4328 nm. Experimental positron lifetime in TiC is reported to be 160 ps [22] and based on detailed computation the positron annihilation site is assigned to Ti vacancies [23]. Our initial calculations are seen matching with these results as evident from Table 1.…”

A Systematic Density Functional Study of Molecular Oxygen Adsorption and Dissociation on the (001) Surface of Group IV−VI Transition Metal Carbides

“…This is their relatively easy oxidation, especially at high temperatures. , The oxidation process implies the removal of carbon atoms from the surface and ultimately the formation of oxycarbides, thus drastically modifying the chemical properties of these materials. ,,, For instance, some studies reveal that for ZrC and TiC a suboxide layer is formed while the carbide is exposed to oxygen at temperatures higher than 1000 °C. , The presence of oxygen affects the performance of metal−carbide coatings used in the fabrication of mechanical and electronic devices. ,− Nevertheless, oxycarbides thus formed have interesting properties on their own ,,, and can change the catalytic behavior of the carbide making it well suited for other purposes . Oxygen adsorption and surface inclusion is also important for the enhancement of these carbides as stable field electron emitters , and electron-injecting electrodes in organic light emitters. − …”

“…23 Oxygen adsorption and surface inclusion is also important for the enhancement of these carbides as stable field electron emitters 24,25 and electron-injecting electrodes in organic light emitters. [26][27][28][29] Many experimental studies have been carried out for oxygen adsorption on carbides and also to establish the properties of oxycarbides; most of them are based on the usual techniques ofsurfacesciencesLEED, 16,[30][31][32] ARPES, 17 HREED, 33 HREELS, 23,31 NEXAFS23, XPS, 23,26,[34][35][36] XAS, 30 AES 34,37 TDS, 38 UPS, 38 SEM, 37,39 XRD, 37,39,40 STM, 41 and AFM 16 sand essentially focus on few specific carbides: MoC; 23,[34][35][36]38,42,43 TiC; 19,37,40,41 ZrC. 18,16,30,39 Unfortunately, only few experimental articles focus on the (001) sur...…”

Synthesis and field emission properties of titanium carbide nanowires

“…Titanium carbide (TiC) is a high temperature ceramic material with a high melting point (3067 • C), high hardness, high thermal and electrical conductivity and high resistance to oxidation and corrosion, which is widely used for cutting tools, wear-resistant coatings and reinforcing components in composites [27,28]. Along with these good properties, TiC has a relatively low φ of about 3.6-4.1 eV [29][30][31][32], which is beneficial to FE. In fact, it was previously investigated as an environmentally tolerant field emitter for microelectronic devices [33][34][35].…”