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Experimental manufacturing of multiphase Ni-Si based layers
Rončák, Ján ; Moravčík, Igor (referee) ; Jan, Vít (advisor)
The diploma thesis deals with the preparation of the composite material based on the NiSi system using powder metallurgy supplemented by the sintering with the usage of SPS method (spark plasma sintering). Theoretical part contains general information about the mechanical-chemical process and sintering, while materials and methods used for experimental observation are explained in a separate chapter. Experimental part explains the procedure of the experiment and selected parameters of individual processes. In the experiment, two powder mixtures were created in order to form the NiSi phase in the maximum possible amount of powder material. After successfully reaching presence of the NiSi phase in the range of 87 to 89 wt. %, both mixtures were used to produce sintered samples at temperatures from 700 to 900 °C. Experiments showed the best results for sample number 2, which was sintered at 900 °C for 4 minutes. Resulting porosity was 0.9 % and hardness reached a maximum value of 718 HV 1. However, all sintered samples show cracks at room temperature associated with increased brittleness of the material.
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Multiphase Ti-Ni layer on Ti6Al4V substrate by local nickel alloying
Barančíková, Miriama ; Havlík, Petr (referee) ; Jan, Vít (advisor)
This bachelor's thesis comprises two main parts. The first part consists of a theoretical study on the Ti6Al4V alpha-beta titanium alloy and on the possibilities of adjusting its tribological properties. The second part deals with experimental work with the aim of improving tribological properties of Ti6Al4V by alloying nickel into its surface, creating a hard and homogeneous surface layer with superior tribological properties. In order to achieve these goals, a nickel layer was created on a Ti6Al4V substrate by electrical deposition. The layer was later melted with an electron beam, thus creating a Ti-Ni alloy. Several different parameters of the electron beam were used to create a homogeneous surface layer. This layer was then tested for its mechanical properties. The evaluation of its microstructure was conducted as well. The experiment resulted in the creation of a surface layer with hardness and tribological properties superior to the base material.
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Determination of heavy metals in soils and sediments in the region Revúce
Kováč, Lukáš ; Vávrová, Milada (referee) ; Doležalová Weissmannová, Helena (advisor)
This thesis aims to assess the extent of contamination of soil and sediment with risk metals in Jelšava. The main polluter of the environment in this area is the magnetize factory. Sampling of soils and sediments were made in three seasons. Sampling times were staggered to represent different seasons and to take into account the impact of the seasons on the obtained values of the concentrations in soil and sediment. Sampling sites were selected according according to the different distances from the factory and according to the different loading of roads. In each of the collected samples were determined concentrations of the elements copper, lead, zinc, nickel, manganese, mercury, cadmium and vanadium. Copper, lead, zinc, nickel and manganese were analyzed by atomic absorption spectrometry with atomization in a flame (F AAS), cadmium and vanadium were determined by atomic absorption spectrometry with electrothermal atomization (ET AAS). For the determination of mercury was used mercury analyzer (AMA).
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Experimental manufacturing of multiphase Ni-Si based layers
Rončák, Ján ; Moravčík, Igor (referee) ; Jan, Vít (advisor)
The diploma thesis deals with the preparation of the composite material based on the NiSi system using powder metallurgy supplemented by the sintering with the usage of SPS method (spark plasma sintering). Theoretical part contains general information about the mechanical-chemical process and sintering, while materials and methods used for experimental observation are explained in a separate chapter. Experimental part explains the procedure of the experiment and selected parameters of individual processes. In the experiment, two powder mixtures were created in order to form the NiSi phase in the maximum possible amount of powder material. After successfully reaching presence of the NiSi phase in the range of 87 to 89 wt. %, both mixtures were used to produce sintered samples at temperatures from 700 to 900 °C. Experiments showed the best results for sample number 2, which was sintered at 900 °C for 4 minutes. Resulting porosity was 0.9 % and hardness reached a maximum value of 718 HV 1. However, all sintered samples show cracks at room temperature associated with increased brittleness of the material.
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Multiphase Ti-Ni layer on Ti6Al4V substrate by local nickel alloying
Barančíková, Miriama ; Havlík, Petr (referee) ; Jan, Vít (advisor)
This bachelor's thesis comprises two main parts. The first part consists of a theoretical study on the Ti6Al4V alpha-beta titanium alloy and on the possibilities of adjusting its tribological properties. The second part deals with experimental work with the aim of improving tribological properties of Ti6Al4V by alloying nickel into its surface, creating a hard and homogeneous surface layer with superior tribological properties. In order to achieve these goals, a nickel layer was created on a Ti6Al4V substrate by electrical deposition. The layer was later melted with an electron beam, thus creating a Ti-Ni alloy. Several different parameters of the electron beam were used to create a homogeneous surface layer. This layer was then tested for its mechanical properties. The evaluation of its microstructure was conducted as well. The experiment resulted in the creation of a surface layer with hardness and tribological properties superior to the base material.
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Determination of heavy metals in soils and sediments in the region Revúce
Kováč, Lukáš ; Vávrová, Milada (referee) ; Doležalová Weissmannová, Helena (advisor)
This thesis aims to assess the extent of contamination of soil and sediment with risk metals in Jelšava. The main polluter of the environment in this area is the magnetize factory. Sampling of soils and sediments were made in three seasons. Sampling times were staggered to represent different seasons and to take into account the impact of the seasons on the obtained values of the concentrations in soil and sediment. Sampling sites were selected according according to the different distances from the factory and according to the different loading of roads. In each of the collected samples were determined concentrations of the elements copper, lead, zinc, nickel, manganese, mercury, cadmium and vanadium. Copper, lead, zinc, nickel and manganese were analyzed by atomic absorption spectrometry with atomization in a flame (F AAS), cadmium and vanadium were determined by atomic absorption spectrometry with electrothermal atomization (ET AAS). For the determination of mercury was used mercury analyzer (AMA).
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Structure and magnetism of clean and impurity-decorated grain boundaries in nickel from first principles
Všianská, Monika ; Šob, Mojmír
We present a detailed theoretical study of segregation of sp-elements from the 3rd-5th period (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) in fcc FM Ni. Whereas there is a slight enhancement of magnetization at the clean GB and FS with respect to bulk nickel (3–7% and 24%, respectively), the studied impurities entirely kill or strongly reduce ferromagnetism at the GB so that magnetically dead layers are formed. We determine the preferred segregation sites at the GB for the impurities studied, their segregation enthalpies and strengthening/embrittling energies. We find interstitially segregated Si and P and substitutionally segregated Al as a GB cohesion enhancer, and interstitially segregated S, Ge, As, Se and substitutionally segregated Ga, In, Sn, Sb and Te as GB embrittlers in Ni. As there is very little experimental information on GB segregation in nickel most of the present results are theoretical predictions which may motivate future experimental work.
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