Gaida Maruta Sedmale

Application of chemical trated illite clay for development of ceramics products

The chemically treatment by alkali solutions of illite clay, so-called geopolymer method, were studied to show the impact on changes of structure and crystalline phases composition of treated not dehydroxylated illite Quarternary clay, as well as ceramic properties and compressive strength of sintered respective ceramic samples. The degree of activating process were followed by FTIR-spectra, X-ray diffraction and differencial thermal analysis. The low temperature ceramic product was achieved by sintering of alkali solution (KOH or NaOH 1M, 3M, 4M and 6M) activated clay samples in temperature range from 100°C to 700°C . Sintered ceramic samples were characterized by compressive strength, total porosity, bulk density and shrinkage. It is shown that treatment of the illite Quarternary clay by KOH changes illite structure, but not destroyed. Main changes could be connected with changes of O-Al-OH grouping where O is associated with neighbour Si- layer That results into lowering of sintering temperature and development of amorphous (glassy) phase of sintered at 600–700 °C ceramic samples together with growing of total porosity. Consolidated at 600°C ceramic samples have the compressive strength ranged from 16–23 N.mm2. These values increases with growing of concentration of used alkali solution as well as with temperature for NaOH treated samples and is comparable with compressive strength for the respective ceramic products sintered at 900 °C.

Characterisation of mullite – ZrO2 ceramics prepared by various methods

Mullite – ZrO2 ceramics was sintered from variously prepared powder mixtures -different time milled and hydrothermal synthesized. As sintering aid 8 wt. % illite clay for one part of starting mixtures was added. Two sintering routes was applied for consolidation of powder – spark plasma sintering (SPS) technique and conventional sintering reactions in air. It is shown that the structure of sintered samples for SPS was completed at 1250°C and by conventional - at 1300°C. The developed microstructure both conventional and SPS can be characterized by mullite matrix with evenly distributed ZrO2 grains. For conventionally prepared and sintered samples corundum and ZrO2 tetragonal grains are observed, but for SPS dominates ZrO2 cubic. The microstructure of ceramic samples from hydrothermal synthesized powders and consolidated by SPS is amorphous like, with xenomorfic crystals of mullite and inclusions of ZrO2 cubic grains. It is stated that additive of illite clay promotes the densification. At conventional sintering clay prevents the transformation of ZrO2 tetragonal to ZrO2 monoclinic by cooling of samples, but for SPS promotes formation of ZrO2 cubic. SPS sintered samples processed from conventionally milled powder mixture are characterized by pressure strength.

Ceramic of the Mullite–ZrO2–SiAlON System During Spark Plasma Sintering

Results are provided for a study of ceramic of the mullite–ZrO2–SiAlON system formed from oxide mixtures with addition of SiAlON nanopowder during spark plasma sintering (SPS) compared with properties of similar ceramic prepared by traditional sintering. It is shown that ceramic prepared by the SPS-process (compared with traditional sintering) has high indices for density (3.10 – 3.32 g/cm3), ultimate strength in compression (295 – 305 MPa), and also a high elasticity modulus (170 – 180 MPa) after ten thermal shock cycles. This is due to the packing density of mullite formations within sintered specimen microstructure, including ZrO2 inclusions of cubic modification.

Comparative study of illite clay and illite-based geopolymer products

Quaternary (Q-clay) clayey deposits are one of the dominating parts of mineral raw materials of the sedimentary cover at present area of Latvia. These clays can be characterised by illite content up to 75-80 %. Two ways for use of illite clays were studied: conventional and geopolymers method. Purpose of the second mentioned method was showing the influence of alkali (KOH) on the transformation of Q-clay/illite structure. Obtained products were investigated by IR–spectroscopy, DTA and XRD, pore size distribution was determined as well. Some ceramic properties and compressive strength were determined and compared. IR-spectrum showed the effect of alkali on the transformation of Q-clay/illite structure in three main absorption bands: 3620-3415 cm−1 which is related to the vibrational modes of adsorbed water between SiO4 and AlO6 layers; new stronger absorption bands at 1635 cm−1 and 1435 cm−1 indicate on the appearance of vibrations in Q-KOH and are related to the K-O-Si bonds; the most essential changes are vibrations at 850 cm−1 showing the changes in the coordination number of Al from 6 to 4 for Q-KOH. Investigations of the bulk density in dependence on temperature showed the small increase of bulk density for Q-clay while - the relatively remarkable decrease for Q-clay/KOH. Mentioned values correlate with the compressive strength of Q-clay and Q-KOH products.

Phase Formation and Structure of Mullite-Alumina-Zirconia and Spinel-Enstatite Ceramics Developed from Synthetic and Mineral Raw Materials

New dense and porous ceramics are developed using two formulation approaches. These are ceramics with remarkable content of mullite, corundum and ZrO2 - tetragonal and monoclinic in crystalline phase and porous (average size of pores up to 150-350μm) spinel-enstatite/forsterite ceramics. To promote the phase development by high-temperature synthesis of these ceramics the mineral raw materials – illite clay and illite clay together with dolomite are used. Bulk density for mullite (corundum) – zirconia ceramics is increased by equal addition of illite clay (8.2 wt.%) as well as ZrO2 and especially ZrO2 +Y2O3 to starting mullite mixtures. Contrary the addition of different kind and amount of illite clay together with dolomite trends to formation of spinel – enstatite (forsterite) ceramics and decrease the bulk density to the value up to 0.35 g/cm3. The XRD results indicate that ZrO2 monoclinic/tetragonal incorporation in mullite (corundum) structure realizes through the liquid phase. Development of the spinel MgAl2O4 and enstatite MgSiO3 crystalline phases along with the sufficient amount of glassy phase in microstructure and even distributed pores are proper for spinel-enstatite (forsterite) ceramic samples.

Influence of Technological Parameters on Thermal Properties of Cordierite Ceramics

Porous cordierite ceramic samples have been prepared by using 33% of two carbonate-containing illite clays as substitutes for the necessary synthetic ingredients. The changes of thermal (CTE) and mechanical properties (compressive strength, modulus of elasticity), as well as phase content, apparent porosity and bulk density have been investigated in regards to gradual changes in maximum sintering temperature. It can be affirmed that these properties strongly depend on the thermal parameters of sintering as well as slightly upon differences in chemical composition of composition substitutes.

Effect of Illite Clay Additive on Sintering, Phase Composition and Properties of Mullite-ZrO2 Ceramics / Illītu mālu piedevas ietekme uz mullīta-ZrO2 keramikas saķepšanu, fāžu sastāvu un īpašībām.

Abstract This study focuses on the influence of illite clay on changes of ZrO2 modifications after sintering and consolidation of mullite-ZrO2 ceramics with or without Y2O3 additive. It was found that mullite-ZrO2 ceramics both with 4.5 % Y2O3 additive or without it in presence of illite clay tend to have increased densification and compression strength after sintering. Presence of illite clay also promotes change of ZrO2 monoclinic phase to tetragonal phase and the presence of Y2O3 promotes change to ZrO2 cubic phase. Mullīts ir viena no svarīgākajām augsttemperatūras kristāliskajām fāzēm. Mullīta veidošanās keramikā, tajā skaitā arī keramikā, kas satur ZrO2, nodrošina tai augstas mehāniskās, ķīmiskās un termiskās īpašības, arī pie paaugstinātām temperatūrām. Lai gan mullīta fāze sāk veidoties jau ~ 1000 °C temperatūrā, blīvu mullīta keramikas materiālu parasti iegūst viena cikla saķepināšanas procesā pie paaugstinātas temperatūras (≥ 1400 °C). Lai veicinātu šīs keramikas saķepšanu un saķepšanas temperatūras pazemināšanu, pielieto piedevas vai arī aktīvus pulverus, piemēram, γ-Al2O3 nanopulveri, kvarca smiltis, u.c. Dotajā darbā ir pētīta illīta nanopulvera ietekme uz mullīta-ZrO2 keramikas (ar Y2O3 piedevu un bez tās) sablīvēšanos saķepšanas procesā, iegūtā keramikas materiāla kristālisko fāžu sastāvu un īpašībām. Darbā ir pielietoti divu veidu pulveru maisījumi, kas sastāv no γ-Al2O3, SiO2, ZrO2 (monoklīns), ar Y2O3 piedevu vai bez tās. Katrai maisījumu grupai pievienots illīts 5 %, 10 % vai 15 % (masas daļas). Izejas pulveru morfoloģijas izpētei pielietots elektronmikroskops Hitachi-TM3000 un diferenciāli termiskai analīzes iekārta Setaram, Setsys Evolution 1750. Paraugi formēti disku un cilindru veidā. Saķepināšana veikta divās maksimālajās temperatūrās - 1400 °C vai 1500 °C. Keramikas fāžu sastāvs noteikts pielietojot Rentgena staru difraktometriju (D8 Advance Bruker). Raksturīgās keramikas īpašības (relatīvais blīvums, sarukums) noteiktas izmantojot EN, spiedes izturība noteikta pielietojot iekārtu Toni-Technic. Ir iegūti rezultāti, kas parāda, ka saķepināto keramikas paraugu sablīvēšanās (relatīvais blīvums un sarukums) pakāpe pieaug ar illīta mālu piedevu līdz 10%. Pie lielākas piedevas (15 %) ir vērojama iekšējo poru veidošanās tendece. Savukārt Y2O3 piedeva, it sevišķi illītu mālu klātienē veicina sablīvēšanos saķepināšanas procesā, it seviķi pie 1500 ºC. Ir jāatzīmē arī, ka mālu klātiene veicina ZrO2 monoklīnās modifikācijas transformāciju tetragonālā, bet vienlaicīga mālu un Y2O3 piedevu klātiene savukārt ZrO2 monoklīno modifikāciju tranformē kubiskā modifikācijā.

Use of Differential Treatment of Illite to Modify Their Structure and Properties / Diferencētas apstrādes pielietojums illītu struktūras un īpašību modificēšanai

Abstract Influence of chemical, mechanical and thermal treatment on structure and properties of illite and impact on development of high-temperature ceramics was investigated. The object of this study was illite from Quartenary glacio-limnic clay of state importance deposit Apriki. Treated clay fractions were subjected to X-ray diffraction, SEM and differential thermal analysis. It was found that thermal and chemical treatment is effective. Thermally treated illite with Al(OH)3 additive was used for sintering a new dense ceramic compositions. Ceramics were characterized by bulk density, shrinkage and compressive strength 150−165 N/mm2. Pētīta ķīmiskas, mehāniskas un termiskas apstrādes ietekme uz illītu struktūras un īpašību izmaiņām, kā arī šīs apstrādes nozīme blīvu augsttemperatūras keramiko materiālu izstrādē. Par izpētes objektu bija izvēlēti kvartāra māli no Apriķu atradnes, kas ir valsts nozīmes māla atradne. Māli no šīs atradnes ir pieskaitāmi pie karbonātus mazsaturošiem māliem un tiem ir relatīvi augsts mālainās frakcijas saturs (daļiņas ar izmēru < 0,005 μm). Mālu frakciju (illīti/kaolinīts) izdalīja no māliem, pielietojot sedimentācijas un ķīmisko metodi. Pētījumiem pielietota ķīmiski izdalītā mālu frakcija. Šīs frakcijas ķīmiskai apstrādei ir pielietots 3 M un 6 M NaOH ūdens šķīdums, mehāniskai apstrāde bija 24 hilga intensīva malšana planetārajās dzirnaviņās, termiskā - izkarsēšana 600 °C temperatūrā 30 min. Neapstrādāto un apstrādāto illītu raksturojumam pielietoja rentgena fāžu analīzi (XRD modelis Rigaku, Japāna un D8 Advance Bruker AXS). Elelementu/oksīdu analīzi veica ar XRD spektrometru (S4 PIONEER Bruker AXS). Daļiņu morfoloģijas un sastāva izmaiņu izpētei pielietoja skenējošo elektronmikroskopu Nova- Nano 650 (FEI Netherlands). Diferenciāli termiskā fāžu pāreju analīzi veica ar iekārtu Setaram, SETSYS Evolution-1750. Ir parādīts, ka sedimentāri un ķīmiski izdalīto illītu/kaolonīta fāžu sastāvs, kā arī oksīdu analīze ir nedaudz nobīdīti. Bija vērojamas arī daļiņu morfoloģijas atšķirības - sedimentēto illītu plākšņveida morfoloģija bija izteiktāka nekā ķīmiski iegūto. Rentgena fāžu analīze rāda, ka saistībā ar intensīvi malto un ar 3 M NaOH šķīdumu apstrādāto illītu/ kaolinīta fāžu difrakcijas maksimumu izmaiņas ir niecīgas. Maz izmaiņu novēroja arī DTA rezultātos. Savukārt, termiski apstrādātie illīti ir daļēji destrukturēti, pie ~ 600 °C izdalījās struktūras OH- grupas. Izmaiņas pēc apstrādes ar 6 M NaOH šķīdumu arī ir attiecināmas uz illītu struktūras izmaiņām, veidojoties nātrija alumosilikāta hidrātam Na(AlSiO4)6·H2O, kurš, cauraužot illītus, tos “sacementē”. Termiski apstrādātie illīti ir aprobēti kā saķepšanu veicinošs komponents jaunu keramikas kompozīciju izveidošanai ar Al(OH)3. Ir parādīts, ka 60 masas % termiski apstrādātu illītu piedeva pie Al(OH)3 apdedzināšanas temperatūrā > 1050 °C veido blīvu keramikas materiālu ar augstu spiedes izturības vērtību - 168 N/mm2.

Influence of Bacteria Pseudomonas Fluorescens on the Properties of Latvian Clay

Wide varieties of bacteria are able to produce extracellular polymeric substances (EPS) which are mostly composed of polysaccharides. It is suggested that EPS substances can alter certain clay soil properties due to their ability to adhere to the surface of mineral particles. Most common used microorganisms by the researchers for this purpose are of either genus Bacillus or genus Pseudomonas. In this study growth of bacteria P. fluorescens AM PS11 culture in locally obtained clay is studied for the purpose of establishing their influence on rheological properties of clay. An attempt to evaluate it has been made using FT-IR and XRD. Change in plasticity of clay using Atterberg limits method and coefficient of drying sensitivity has also been determined.

Different Treatment Application of Illite Clay for Low Temperature Ceramics

Impact of chemical treatment by alkali of raw, dehydroxylated at 600 °C and intensively milled illite clay on structure, phase composition and some properties of sintered at lower temperatures ceramic materials were studied using DTA, X-ray diffraction (XRD), as well as scanning electron microscopy (SEM) and mercury intrusion porosimetry. DTA and XRD results show that alkaline activation of illite clay by sodium hydroxide leads to the slight structural changes of illite characterized by structural water losses showed from DTA and negligible decrease of illite and kaolinite, as well dolomite diffraction peaks on XRD. Additional treatment, intensive milling and in particular dehydroxylation, contributes to the considerable changes in intensities of all effects on DTA-curves, especially for dehydroxylation endo-peak. It is shown that chemical treatment promotes the formation of rather amorphous and homogenous structure of sintered at 600°C respective ceramic samples and leads to the growth of the compressive strength.