Papers by Keyword: Thermolysis

Abstract: Globally, the adverse environmental impact of waste plastics is of increasing concern. Most plastics are naturally non-degradable, thus imposes serious environmental threats, especially, to marine life. Upcycling such waste into valuable contents is an effective approach to managing waste plastics. In this study, graphene is synthesized from waste polystyrene (PS) by thermal decomposition at different temperatures (500, 600, 700, 800, 900 and 1000 °C) for two hours reaction time in a stainless steel autoclave. The synthesized materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy-disperse X-ray analysis (EDS) and surface area by using Brunauer–Emmett–Teller (BET). The yield of the product materials was investigated and optimized against the temperature. The synthesized graphene is considered a promising material for many applications, especially in environmental applications.

Abstract: The paper overviews the process of thermolysis of fire-retardants based on melamine, ammonium polyphosphate and pentaerythtritol and containing titanium dioxide of different trademarks. The role of titanium dioxide as a component of fire-retardants is revised. Titanium dioxide was perceived only as white pigment, but this paper states that the properties of a charred layer forming from an intumescent coating depend on the properties of titanium dioxide's species, such as surface treatment and crystalline structure. This statement is proven by using thermal analysis of intumescents with different titanium dioxide's trademarks; it shows that rutile titanium dioxide helps forming a charred layer with the highest thermal stability thus fire retardant efficiency grows up. It means that the knowledge of processes which occur in intumescents based on primary products with different qualities helps to create fire-protective compositions which will perform more reliable in case of fire.

Abstract: In this work we propose a new method for synthesis of ultrafine powders of tungsten, titanium and vanadium carbides combining two methods – liquid-phase precipitation on carbon substrate and low-temperature microwave heat treatment in argon stream. An entire spectrum of intermediates obtained by thermolysis, reduction and carbonization of precursors, as well as the final products has been presented. As a result of sample assessment, the phase composition, structure, morphology and particle size, as well as the size of specific surface areas have been determined.

Abstract: Ammonia borane (NH3BH3, AB) is an excellent source of hydrogen(19.6 wt %) for fuel cell applications. In this paper, pure ammonia borane is successfully prepared by using amino complex for ammonia complex Ag(NH3)2Cl as new ammonia source, and sodium borohydride (NaBH4) as boron source. The composition and constitution of the products are measured by XRD and FT-IR. The thermolysis of ammonia borane is significant for its practical application. Boric acid plays a role in improving ammonia borane hydrogen performance. The effects of different mass ratio of boric acid and ammonia borane on dehydrogenation are tested by XRD, TG/DTA and TPD-MS. The results show that boric acid can decrease the first level dehydrogenation temperature of ammonia borane decrease to about 85°C (working temperature of PEMFC). What’s more, the onset temperature of AB’s thermolysis can decrease to about 60°C when the mass ratio of ammonia borane and boric acid is equal to 3:1. This makes ammonia borane be more suitable for the application in on-board hydrogen storage system.

Abstract: Novokuibyshevsk refinery vacuum gasoil (VG) with a high sulfur content (2.02 % wt.) thermocracking results are represented in abstract. Its density is 909.8 kg/m³. Material balance and fractional composition of liquid products cracking and reduction of sulfur containing in every component of it was established. Based on experimentally measured parameters we calculated gas, liquid, coke yields depending on process conditions. The amount of hydrocarbons and resins-asphaltens components increased in the vacuum gasoil cracking products, but these products have lower molecular weight in comparison to initial object. Cracking liquid products composition, which were gained after vacuum gasoil benzoyl peroxide (BP) oxidation pretreatment, specific differences from VG thermolysis products with BP used as radical forming addition were established.

Abstract: Incomplete binder removal may introduce severe defects during ceramic processing. This work presents a new method to eliminate polyethylene glycol used as a binder in pre-sintering steps of alumina parts. The effectiveness of the proposed method was evaluated by density and pore size measurements, as well as thermogravimetry (TG), differential thermal analysis (DTA), volumetric physical adsorption analyzer (BET), and Fourier transformed infrared spectroscopy (FTIR). The results show that the new method, although relatively slow in comparison with traditional procedures, yields smaller pore sizes and better mechanical properties of the final products.

Abstract: Diethyl dithiocarbamate [Cd (S₂CN Et₂)₂] complex is used to deposit the cadmium sulphide thin film at much lower temperature by Aerosol Assisted Chemical Vapour deposition (AACVD) and same precursor is used to synthesize the nanocrystals in Oleylamine at elevated temperature. Thermogravimetric analysis shows that precursor [Cd (S₂CN Et₂)₂] decomposes in the single stage, losing 62% of total weight. Deposition of thin films at 300 ^°C and 400 ^°C showed the growth of CdS clusters which were made of granular crystallites. These results are confirmed by SEM analysis. Thermolysis of the precursor in oleylamine at 240 ^°C gave the nanoparticles most of them are monodispersed spherical shape, few having mono and dipod structures. TEM images confirm the structures. XRD results show the thin films and nanoparticles have hexagonal phase of CdS.

Abstract: A novel approach for synthesis of CdS-intercalated nanocomposites was investigated by thermal decomposition of cadmium thiourea complex embedded in the interlayer of montmorillonite. XRD results indicated that the incorporation of CdS into the interlayer of montmorillonite led to expansion of the layer spacing. The diffuse reflectance UV-visible spectra showed that the absorption edge of nanocomposites of CdS and montmorillonite was blue-shifted as compared with pure CdS due to quantum size effect. The photoelectric performance of nanocomposites was evaluated by photocatalytic water-splitting for production of hydrogen and the nanocomposites displayed much higher photocatalytic activities of H2 production than that of pure CdS owing to the synergistic effects between CdS and montmorillonite. A probable photocatalytic mechanism was proposed.

Abstract: With the ultraviolet-visible spectrophotometry, we have investigated the effects of red laser (633 nm) and green laser (532 nm) irradiations on the optical absorption of the ethyl alcohol solutions of an azo-containing bent-core liquid crystal. As the irradiation duration increases, the optical absorptions at about 360 nm of the bent-core compound exhibit concentration dependent and irradiation-time dependent features. The absorptions of dilute solutions (~2.2 mg/litter) are not sensitive to the laser irradiation duration whereas the absorptions of higher concentrations (~10 mg/litter) decrease as the laser irradiation continues. Our results have demonstrated that laser irradiation induced thermolysis is responsible for the dissociation of the azo-linkages in azo-containing bent-core compound. The mechanisms on the red and green light irradiations are discussed.

Abstract: Three copolymers containing isobutyl p-styrenesulfonate (IBSS) and carboxyl units, i.e. methyl methacrylate (MMA) and methacrylic acid (MAA), were synthesized and their chemical structures and thermal behaviors were investigated by using TGA, DSC, FTIR and other methods. Films were prepared by using the synthesized copolymers in combination with a bisvinyl ether compound, i.e. 2,2-bis(4-(2-(vinyloxy)ethoxy)phenyl)propane (BVPP), to applied onto an aluminum plate. Crosslinking and de-crosslinking reactions would readily take place when the polymer films were baking treated at 100 oC and 200 oC for a short period of time, respectively. Along with the chemical structural changes during thermal treatments, an affinity change was achieved from being insoluble to completely soluble in neutral water. A positive-working and neutral water-developable imaging material was proposed and preliminary studies on the imaging properties were conducted.