Silīcija nitrīda pulverveida nanokompozītu saķepināšanas tehnoloģijas izstrāde

Promocijas darbs uzrakstīts latviešu valodā, satur ievadu, literatūras apskatu, metodisko daļu, eksperimentālo daļu, secinājumus un literatūras sarakstu, kas ietver 140 literatūras avotus. Darbs ietver 129 lappuses, 72 attēlus un 31 tabulu. Literatūras apskatā ir apkopoti svarīgākie pētījumi par silīcija nitrīdu saturošu keramiku. Darba eksperimentālajā daļā veikti plazmas strūklā sintezētu silīcija nitrīdu saturošu nanopulveru kompozīciju kompaktēšanas pētījumi ar dažādiem saķepināšanas paņēmieniem un noteikta iegūtās keramikas struktūra un īpašības. Noskaidrotas Si3N4-Al2O3-Y2O3 nanodaļiņu kompozīta saķepināšanas likumsakarības, izmantojot tradicionālo saķepināšanu, karsto presēšanu un saķepināšanu saules enerģijas krāsnī, salīdzinājumā ar rūpnieciskiem kompozītiem. Noskaidrota TiN, ZrO2 un SiC nanodaļiņu piedevu nozīme Si3N4-Al2O3-Y2O3 nanokompozītu materiālu mikrostruktūras veidošanā un mehānisko īpašību uzlabošanā. Noskaidrota saķepināšanas piedevu ievadīšanas veida ietekme uz Si3N4-SiC nanodaļiņu kompozīta mikrostruktūras veidošanos, izmantojot karsto presēšanu. Izstrādāts dažāda sastāva alfa-, beta- sialonu kompaktēšanas paņēmiens un noteiktas iegūto materiālu mehāniskās īpašības. Izdarīti secinājumi par silīcija nitrīdu saturošu nanopulveru izmantošanas iespējām nanostrukturētas keramikas izgatavošanā un nanopulveru pielietošanas priekšrocībām

Investigation of Production of Fine-grained SiAlON Ceramics from Nanopowders

Different sialons’ compositions were used to find the effect of material starting components on sintering and properties of sialon materials. The nanopowders (Si3N4, AlN, Al2O3, Y2O3 and Si3N4-27 wt.% AlN nanocomposite) were produced by the plasmachemical synthesis. The composite materials were sintered by the method of pressure-less sintering. Sintering temperature decreased significantly, if Si3N4-AlN nanocomposite was used as one of the components. The increased amount of a- sialon phase and higher hardness are characteristic for materials obtained from separate Si3N4, AlN, Al2O3, Y2O3 nanocomponents.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2439</p

The Effect of Raw Components on the Densification and Properties of Nanostructured Sialon Materials

Two sialon compositions (Y0,33Si10,5Al1,5O0,5N15,5 and Y0,5Si9,5Al2,5O1,0N15,0) were used to determine the effect of starting components on densification and properties of sialon materials. Plasma synthesized nanopowders (Si3N4, AlN, Al2O3, Y2O3 and 73 wt% Si3N4-27 wt%AlN nanocomposite) were used for the investigation. Materials were sintered using traditional or spark plasma sintering methods. Sintering temperature was reduced significantly, if Si3N4-AlN nanocomposite was used as one of the components. The increased amount of sialon phase and higher hardness were characteristic to materials obtained from individual Si3N4, AlN, Al2O3, Y2O3 components

Spark Plasma Sintering (SPS) to the Mullite-Zirconia Ceramics Development

This research is devoted to the investigation comparison of effect of SPS (spark plasma sintering) and conventional sintering for the mullite-ZrO2 ceramics development. Mullite-ZrO2 ceramics were produced from different time ball-milled powders. The effect of illite nanoparticles on the powder sintering promotion process was investigated and evaluated. The density and compressive strength as well as microstructure and crystalline phase development of ceramics were investigated in order to show the impact of SPS by comparing with conventional sintering. It is shown that SPS at 1250 °C produces samples with densities that are to 1.6 – 2.2 times higher than densities of samples obtained with conventional sintering at 1300 °C. Both compressive strength and Vicker's microhardness increase correlate well with the increase of density. The microstructure of the SPS samples is dense and consists of well-textured mullite and cubic ZrO2 particles, but conventionally sintered samples form mullite-corundum crystals with tetragonal ZrO2 inclusion. It is shown that illite clay additive is effective to increase density and compressive strength only when using conventional sintering