Electron spin resonance study on Mo-SiO₂ and Mo-TiO₂ with adsorbed benzene

The study is devoted to ESR-investigation of the primary processes upon chemisorption of benzene molecules onto the molybdenum supported on dispersed SiO₂ and TiO₂ samples. It has been confirmed that benzene chemisorption onto the Mo⁶⁺ species results in one-electron transfer in the ground state and paramagnetic species formation, namely reduced molybdenum species (Mo⁵⁺ species) and radicals of benzene. Computer treatment of ESR experimental data revealed that there are several types of Mo⁵⁺ species and benzene radicals, the assignment of which is proposed

Investigation by X-ray photoelectron spectroscopy of the process of TiC synthesis during annealing of ТiН2/ТiО2/С in vacuum

Small dimensional transition metal carbides (MXenes) are promising materials for the development of photocatalysts and are highly efficient cocatalysts for industrial TiO_2 (P25). Thus, in the Ti_3C_2@TiО_2 nanocomposite obtained by layering Ti_3C_2 nanoplates, the ability to separate charge carriers increases due to the high electrical conductivity of TiC_{1-х}. The task of forming the TiC_{1-х}@TiО_{2-х} nanocomposite by direct synthesis with n-TiO_2 is promising, which allows to increase the quality of contact between the shell and the nanocomposite core and to reduce the number of intermediate stages of synthesis. In addition, highly dispersed TiC has high values of hardness, melting point, modulus of elasticity and shear and has the prospect of use in materials science in plasma spraying coatings. In work ТіС was synthesized on the surface of TiO_2 - the shell of the modified micropowder TiH_2/TiO_2/С during reductive annealing in vacuum using TiH_2 as a source of atomic hydrogen. After a series of annealing at 535 ºС - 600 ºС, the Ti2p- C1s- and O1s- spectra of surface atoms were obtained. The main stages of TiC synthesis in the TiO_2/С conversion reaction were established by the XPS method. The use of TiH_2 as a source of atomic hydrogen in nanosystems of the «core/shell» type is proposed for local synthesis on the surface of nanoobjects in a vacuum or inert atmosphere.Key words: X-ray photoelectron spectroscopy, XPS, titanium carbide, TiC, TiO_2, nanopowders.Pages of the article in the issue: 85 - 94Language of the article: Ukrainia

Radioluminescent, thermoluminescent and dosimetric properties of X-ray phosphors

Time-resolved radioluminescence (RL) of X-ray phosphors: BaFCl:Eu, ZnS.CdS:Ag and Y₂О₃:Еu, which exhibited ultraviolet (lmax = 390 nm), yellow-green, (lmax = 530 nm) and red (lmax=620 nm) luminescence respectively, have been measured. For tested phosphors a good proportionality between the light output of the radioluminescence and the dose rate in the region of dose rates from 3 to 45 MGy/s has been obtained. It was also revealed that the emitting properties of all phosphors are preserved after high-dose (10⁴ Gy) and high temperature (500°C) annealing the samples. Thermoluminescent (TL) characterization of Sr₃(PO₄)₂:Eu and BaFCl:Eu under X-ray, beta and gamma irradiation have been performed. Linear TL dose dependence under irradiation dose in the mGy - Gy region was revealed, which makes these phosphors suitable also for luminescence dosimetry in the low doses region. Thus, the main characteristics of phosphors: i) the high conversion efficiency, ii) the good dose-rate proportionality, iii) the radiation stability allow to consider these materials as promising for high-energy and high dose rate dosimetry

Synthesis of Carbon-Silica Nanomaterials by Carbonization of Cellulose Acetate and Polyisocyanate Copolymer

Cellulose acetate and polyisocyanate copolymer synthesized by mechanical mixing of cellulose acetate, polyisocyanate and fumed silicon dioxide in the presence of nickel chloride was carbonized in silicon dioxide template. Copolymer and silicon dioxide template were formed simultaneously. Composite structure and composition was studied with SEM and EDS. SEM showed that porous carbonaceous nanomaterial was synthesized. Formed carbon is represented by coating on silicon dioxide, layered ribbon-like and fibrous structures in template pores with size from several nm (thickness) to several microns (length). Metallic nickel crystals up to 200 nm in size were fabricated in composite pores from Nickel chloride by reduction of Ni2 with products of pyrolysis of organic compounds. Key words: carbon-silica nanomaterials, polyisocyanate, cellulosr acetate, fumed silica, nickel chloride, carbonization.</p

Synthesis of Carbon-Silica Nanomaterials by Carbonization of Cellulose Acetate and Polyisocyanate Copolymer

Cellulose acetate and polyisocyanate copolymer synthesized by mechanical mixing of cellulose acetate, polyisocyanate and fumed silicon dioxide in the presence of nickel chloride was carbonized in silicon dioxide template. Copolymer and silicon dioxide template were formed simultaneously. Composite structure and composition was studied with SEM and EDS. SEM showed that porous carbonaceous nanomaterial was synthesized. Formed carbon is represented by coating on silicon dioxide, layered ribbon-like and fibrous structures in template pores with size from several nm (thickness) to several microns (length). Metallic nickel crystals up to 200 nm in size were fabricated in composite pores from Nickel chloride by reduction of Ni2 with products of pyrolysis of organic compounds. Key words: carbon-silica nanomaterials, polyisocyanate, cellulosr acetate, fumed silica, nickel chloride, carbonization.</p

Carbon-Silica Composites with Cellulose Acetate, Polyisocyanate and Copper Chloride

Cellulose acetate and polyisocyanate copolymer synthesized by simultaneous mixing of cellulose acetate and polyisocyanate with acetone solution of Copper chloride and fumed silicon dioxide was carbonized in a silicon dioxide template. The composite structure and composition was studied with SEM, EDS and XRD. It was shown that the porous carbonaceous nanomaterial was synthesized where formed carbon was represented by coating on silicon dioxide and consisted of graphite, graphene and amorphous nonstructured carbon. Crystals of metallic copper with the size up to few µm were formed from Copper chloride after reduction of Cu&lt;sup&gt;2+&lt;/sup&gt; with products of organic compounds pyrolisis.Key words: carbon-silica nanomaterials, polyisocyanate, cellulosr acetate, fumed silica, copper chloride, carbonization.</p

Ni/C/SiO2 nanostructured composites synthesized by carbonization of carboxymethyl cellulose

Ni/C/SiO2 porous composites were synthesized by one-pot approach by carbonization of sodium carboxymethyl cellulose/SiO2 xerogels containing NiCl2. Synthesized composites are mesoporous materials (average pore size 11.8 -15.1 nm) with the surface area 72.1 – 91.1 m2. Ni nanoparticles of 30-90 nm in diameter are evenly distributed within the volume of composites. The hydrogen sorption capacity at -196\ub0C and 20 bar measured for as-synthesized samples was up to 0,32%