Sintering and Properties of Sintered ZnTiO3

Ultrаfini prаh cink-mеtаtitаnаtа vеličinе čеsticа 40 dо 80 nm pоdvrgnut је prilikоm sintеtskоg dеlа trеtmаnа uticајimа pritiskа i tеmpеrаturе kоrišćеnjеm prоcеsа prеsоvаnjа i rеаkciоnоg sintеrоvаnjа. S оbzirоm nа nеstаbilnоst prаhа pоsmаtrаn је оdgоvоr sistеmа nа оvа dvа trеtmаnа. Uslеd nаvеdеnih uticаја dоšlо је dо spеcifičnih prоmеnа svојstаvа isprеsаkа i sintеrоvаnih uzоrаkа. Štо sе prеsоvаnjа tičе urаđеn је sеt isprеsаkа kоmpаktirаnih nа rаzličitim pritiscimа uniаksiјаlnim dvоstrаnim nаčinоm prеsоvаnjа. Меtоdе kаrаktеrizаciје isprеsаkа kоје su kоrišćеnе su: mеrеnjе gustinе isprеsаkа, mеrеnjе spеcifičnе pоvršinе mеtоdоm аdsоrpciје аzоtа nа niskim tеmpеrаturаmа, оdrеđivаnjе pоrоznоsti mеtоdоm živinе pоrоzimеtriје. Zа оpisivаnjе fеnоmеnа prеsоvаnjа upоrеđеnе su еkspеrimеntаlnе vrеdnоsti gustinе isprеsаkа u zаvisnоsti оd pritiskа prеsоvаnjа sа јеdnаčinаmа kоmprеsibilnоsti. Pritisаk оd 98 MPa оdrеđеn је kао nајpоgоdniјi pri kоmpаktirаnju isprеsаkа zа nаrеdni prоcеs sintеrоvаnjа. Urаđеnа је rеndgеnоstrukturnа аnаlizа kао i аtоmskа mikrоskоpiја isprеskа cink-mеtаtitаnаtа ZnTiO3. Prоcеs sintеrоvаnjа prаćеn је tеhnikоm dilаtоmеtriје, оdnоsnо linеаrnоg skuplјаnjа uzоrаkа pri zаgrеvаnju. Rаđеnо је u dvа rеžimа rаdа dо 880°C i dо 1200°C. Zа rеžim rаdа pri zаgrеvаnju dо 880°C zа sintеrоvаnjе оdrеđеnа је еnеrgiја аktivаciје sintеrоvаnjа. Urаđеnа је rеndgеnоstrukturnа аnаlizа sintеrоvаnih uzоrаkа, i nа оsnоvu rаzličitоg fаznоg sаstаvа dоkаzаnо pоstојаnjе fаznоg prеlаzа u stаbilniјu fоrmu spinеlskе strukturе, cink-оrtоtitаnаt, Zn2TiO4. Dilаtоmеtriја kао оsnоvnа tеhnikа zа prаćеnjе prоcеsа sintеrоvаnjа је pоkаzаlа dа pri grејаnju nа višој tеmpеrаturi dоlаzi dо fаznоg prеlаzа. Strukturа sintеrоvаnih uzоrаkа оkаrаktеrisаnа је tаkоđе mеtоdоm аtоmskе mikrоskоpiје i uоčеnа rаzlikа u vеličini zrnа zа rаzličitе rеžimе grејаnjа.Zinc meta-titanate ZnTiO3 nano powder commercially available with particle size in a range from 40 nm to 80 nm was treated by conventional synthesis methods, namely, the compaction and the sintering. According to instability of the powder, response of the system to these two fundamental treatments was studied. Regarding used methods, changes in properties of the compacts and sintered specimens occurred. Uniaxial double sided compaction method produced set of green bodies obtained using different pressures. Employed characterization methods used were: density measurements, specific surface area measurements by nitrogen adsorption on low temperatures, porosity measurements with mercury porosimetry. For the compressibility phenomenon different compaction equations were used in order to mathematically describe compaction. Compacts obtained with 98 MPa pressure were determined as suitable for consequent sintering process. X-ray diffraction was conducted on green body of the commercial ZnTiO3 powder. Also, compact was characterized with atomic force microscopy. Sintering process was characterized with fundamental technique for following a linear change in dimensions, namely high temperature dilatometry. Experiments were conducted in two different isothermal temperatures: lower at 880°C and higher at 1200°C. For the lower temperature region of 880°C activation energy calculation was performed. Dilatometry as main technique for following of the sintering phenomenon registered at higher temperature region of 1200oC, phase transition to stabile zinc-orthotitanate spinel Zn2TiO4. Phase transition was justified with X-ray diffraction of specimens heated on 880°C showed characteristic perovskite ZnTiO3 structure diffractogram, while specimen heated at 1200°C gave spinel Zn2TiO4 characteristic diffraction patterns. Sintered specimens in two regimes were characterized with atomic force microscopy also, and significant difference between grain sizes was detected

Sinterovanje i svojstva sinterovanog ZnTiO3

PhD defence presentation. The thesis "Sintering and Properties of Sintered ZnTiO3" was defended at the University of Belgrade, Faculty of Physical Chemistry, in 2011.Prezentacija prikazana na odbrani doktorske teze "Sinterovanje i svojstva sinterovanog ZnTiO3", odbranjene na Fakultetu za fizičku hemiju Univerziteta u Beogradu 2011. godine

Structural and Electrical Properties of Sintered Zinc-titanate Ceramics

Poster presented at the ELECTROCERAMICS X, June 18-22, 2006, Toledo, Spai

Microstructure changes caused by thermal etching of sintered ZnTiO3

Polishing and thermal etching was performed on ZnTiO3sintered ceramic. Two set of specimens were recorded, on higher 1200oC/1100oC sintered/etched, and lower 900oC/800oC sintered/etched. Phase composition, crystallite sizes and grain size distributions before and after etching were compared. Grain size enlargement was noted.\ud \ud Poster presented at the 12th International Conference on Fundamental and Applied Aspects of Physical Chemistry - Physical Chemistry 2014, Belgrade, September 22-26, 201

Investigation of sintering kinetics of ZnO by observing reduction of the specific surface area

Reduction of the specific surface area of porous ZnO during the sintering process was studied. ZnO powder was sintered at temperatures from 673 K to 1173 K. The decrease in the specific surface area was observed as a function of temperature and sintering time. Two different models were involved in order to define the appropriate parameters. The Arrhenius equation was used to give information on the activation energy of sintering. The LSE method was applied for determining optimum parameter values

Reaction sintering of the 2ZnO-TiO2 system

Sintering kinetics of the mechanically activated ZnO-TiO2 system was studied. Mixtures of ZnO and TiO2 powders were mechanically activated using a high-energy ball mill for different time intervals from 0 to 300 minutes. Formal phenomenological analyses were performed in order to describe the specimen’s behavior during isothermal sintering at 1100oC. Non-isothermal sintering was investigated by dilatometer measurements up to 1100oC with a constant heating rate. The Dorn method was applied in order to give information on the activation energy

A phenomenological analysis of sintering kinetics from the viewpoint of activated volume

The sintering kinetics of real systems has been viewed as a process of transport of activated volume. Activated volume is a parameter that can be used to describe mass transport during the sintering process. It defines the movement of point defects and dislocations during the sintering process. A phenomenological equation has been defined using this parameter, which can be applied to analyze kinetics of the sintering process. It has been applied to analyze the sintering process of several disperse systems. Values obtained for parameters of the equation have also been analyzed

The Influence of Tribophysical Activation on Zn2TiO4 Synthesis

Poster presented at the Seventh Yugoslav Materials Research Society Conference - YUCOMAT 2005, Herceg Novi, Crna Gora, September 12-16, 2005

Influence of mechanical activation on synthesis and properties of the MgO-TiO2 system

Materials applied in electronics such as multilayer capacitors are an important field of ceramic materials. Magnesium titanate based dielectric materials are used for producing type-I capacitors. A common way of obtaining this material is a solid-state reaction during reaction sintering. The process of sintering can be enhanced if mechanical activation precedes. In this work starting powders of magnesium carbonate (MgCO3) and titanium dioxide (TiO2) with a rutile crystal modification were weighed to attain a 1:1 molar MgCO3:TiO2 ratio. Mechanical activation of the starting mixture was performed by high energy ball milling using ZrO balls and vessels with a ball to powder mass ratio of 40:1. The observed grinding times were 15, 30, 60 and 120 minutes. Powder characterization was conducted using X ray powder diffraction, DTA analysis up to 1000 o C and particle morphology changes were observed with Scanning Electron Microscopy. Isothermal sintering of compacted powders was conducted at 1100ºC during 30, 60 and 180 minutes. For specimens synthesized in such a manner, microwave dielectric properties were measured, quality factor Q, specific electrical resistivity (ρ) and the dielectric constant (Єr). In this work we explain the influence of mechanical activation on the MgCO3-TiO2 system leading to titanate formation during sintering, as well as induced changes in microwave dielectric properties

Modified glycine nitrate procedure synthesis and properties of nanostructured Ca1-xGdxMnO3 (x=0.05; 0.1; 0.15; 0.2)

Nanocrystalline manganites Ca1-xGdxMnO3(x=0.05, 0.1, 0.15, 0.2) were synthesized by a modified glycine-nitrate procedure. The subsequent studies were focused on the structural, microstructural and magnetic changes of the starting materials induced by calcination and sintering. Thermal treatments of the green bodies were carried out by conventional sintering method. Phase evolution, lattice parameters, chemical composition and magnetic properties were monitored by Differential thermal analysis (DTA), X-ray diffraction (XRD),Induction coupled Plasma Atomic Emission (ICPES), Scanning electron Microscopy with Energy Dispersive Spectroscopy SEM/EDS and magnetic measurements on Superconducting Quantum Interference Device (Squid).DTA revealed phase transition at ≈918ºC.Chemical analysis has been done by ICPES and EDSwhich confirmed that nominal composition has been attained for all samples. XRD data were analysed by Rietveld refinement which showed that orthorhombic perovskite structure, S.G. Pnma (62), persisted with the change of Gd content, while unit cell parameters depended on the composition. Magnetic measurements show that electron doping by Gd3+ ions substantially changes CaMnO3 antiferromagnetic behavior. After introduction of Gd3+ ions, significant ferromagnetic component appears due to an emergence of double exchange interaction between Mn3+-Mn4+ ions. This resulted in appearance of a low temperature plateau in field cooled magnetization diagram as well as in hysteresis loop with the relatively high coercivity up to 2300 Oe