Исследование процесса сушки продуктов обогащения в вихревых аппаратах

Проаналізовані особливості кінематики високотемпературних теплоносіїв, які використовують при сушці вологих концентратів, на основі чого була складена математична модель руху гетерогенного потоку в вихровому апараті та приведені кількісні показники її рішення.Проанализированы особенности кинематики высокотемпературных теплоносителей, используемых при сушке влажных концентратов, на основе чего была составлена математическая модель движения гетерогенного потока в вихревом аппарате и приведены количественные показатели ее решения

Influence of the plasma chemistry and energetics of an Al cathodic arc discharge on the composition and structure of Alumina thin films

In this thesis the relationship between plasma chemistry and energetics and thin film properties was investigated for an Al cathodic arc discharge. A virtually monoenergetic beam of single charged Al ions was generated at pressure distance products higher than 128 Pa.cm. In the literature Al cathodic arc discharges always contained a high energy tail which made it difficult to analyse the influence of plasma parameters on thin film properties. Thermalization of the cathodic arc discharge is expected at high pressure distance products. What made this work particularly interesting is that the thermalization effect was observed at conditions where the deposition rates were still high (about 1nm/s). It was shown that crystalline films containing alpha- and gamma-Al2O3 phases could be grown using cathodic arc discharges containing monoenergetic single charged Al ions. This is a prerequisite for a meaningful study of the influence of plasma parameters (such as ion flux and energy) on film formation and properties. The plasma chemistry and energetics of an Al cathodic arc discharge was studied as a function of the filter current. At filter currents 94%). At filter currents > 17 A Ar and oxygen ion populations increase and dominate the plasma composition. The average energy of the Al+ ions does not vary significantly. The total as well as Al+ ion flux, however, decreases for one order of magnitude as the filter current is increased from 10 to 20 A. According to XRD and SAED data, the films grown at 10, 17, and 20 A are gamma-Al2O3. The films grown at 12 and 15 A contain a phase mixture of alpha-Al2O3 and gamma-Al2O3. The alpha-Al2O3 phase may have been formed due to additional energy that was added to the substrate via higher ion flux. At 10 A the film thickness was about vi 200nm which corresponds to earlier reports suggesting that alpha-Al2O3 formation succeeds a thin gamma-Al2O3 film of about 200 nm. The grain size was calculated to be in the range from 20 to 30 nm. The average Young’s modulus values of gamma-Al2O3 films were 7-20% lower than literature values. SEM and TEM investigations show that dense films can be deposited with columnar as well as equiaxed grains. Thin films were deposited at substrate bias potentials ranging from -8 V to -300 V on TiAlN coated Si wafers at a filter current of 20 A. All films exhibited an O/Al ratio of 1.5 ± 1% and are hence close to stoichiometric alumina. XRD data indicate the formation of gamma-Al2O3 in all films. There was no evidence for the presence of other phases. The Young’s modulus values of the films grown from -50 to -250 V deviated up to 14% from the Young’s modulus values of gamma-Al2O3 from literature (350 Gpa). It is found that the films grown from -50 to -250 V are dense with equiaxed grains. TEM analysis of films grown at -200 V show dense, phase pure gamma-Al2O3 with equiaxed grains of about 20 nm size. The application temperature of gamma-Al2O3 coated cutting inserts containing a TiAlN interlayer is limited to temperatures below 1000°C based on our annealing experiments in air

Influence of the plasma chemistry and energetics of an Al cathodic arc discharge on the composition and structure of Alumina thin films

In this thesis the relationship between plasma chemistry and energetics and thin film properties was investigated for an Al cathodic arc discharge. A virtually monoenergetic beam of single charged Al ions was generated at pressure distance products higher than 128 Pa.cm. In the literature Al cathodic arc discharges always contained a high energy tail which made it difficult to analyse the influence of plasma parameters on thin film properties. Thermalization of the cathodic arc discharge is expected at high pressure distance products. What made this work particularly interesting is that the thermalization effect was observed at conditions where the deposition rates were still high (about 1nm/s). It was shown that crystalline films containing alpha- and gamma-Al2O3 phases could be grown using cathodic arc discharges containing monoenergetic single charged Al ions. This is a prerequisite for a meaningful study of the influence of plasma parameters (such as ion flux and energy) on film formation and properties. The plasma chemistry and energetics of an Al cathodic arc discharge was studied as a function of the filter current. At filter currents 94%). At filter currents > 17 A Ar and oxygen ion populations increase and dominate the plasma composition. The average energy of the Al+ ions does not vary significantly. The total as well as Al+ ion flux, however, decreases for one order of magnitude as the filter current is increased from 10 to 20 A. According to XRD and SAED data, the films grown at 10, 17, and 20 A are gamma-Al2O3. The films grown at 12 and 15 A contain a phase mixture of alpha-Al2O3 and gamma-Al2O3. The alpha-Al2O3 phase may have been formed due to additional energy that was added to the substrate via higher ion flux. At 10 A the film thickness was about vi 200nm which corresponds to earlier reports suggesting that alpha-Al2O3 formation succeeds a thin gamma-Al2O3 film of about 200 nm. The grain size was calculated to be in the range from 20 to 30 nm. The average Young’s modulus values of gamma-Al2O3 films were 7-20% lower than literature values. SEM and TEM investigations show that dense films can be deposited with columnar as well as equiaxed grains. Thin films were deposited at substrate bias potentials ranging from -8 V to -300 V on TiAlN coated Si wafers at a filter current of 20 A. All films exhibited an O/Al ratio of 1.5 ± 1% and are hence close to stoichiometric alumina. XRD data indicate the formation of gamma-Al2O3 in all films. There was no evidence for the presence of other phases. The Young’s modulus values of the films grown from -50 to -250 V deviated up to 14% from the Young’s modulus values of gamma-Al2O3 from literature (350 Gpa). It is found that the films grown from -50 to -250 V are dense with equiaxed grains. TEM analysis of films grown at -200 V show dense, phase pure gamma-Al2O3 with equiaxed grains of about 20 nm size. The application temperature of gamma-Al2O3 coated cutting inserts containing a TiAlN interlayer is limited to temperatures below 1000°C based on our annealing experiments in air