Synthesis and characterization of LnFeO<Subscript>3</Subscript> pigments

This work is focused on determination of the optimum firing temperature which leads to formation of the compounds LnFeO₃ with good pigment-application properties (Ln=Gd, La, Yb, Tm, Lu). Based on results of thermal analysis the compounds were prepared by the solid-state reaction at temperature 900 and 1000°C. Colours of pigments vary depending on type of used lanthanoid (from light sienna to dark brown) and also on the type of precursor. Generally, the compounds prepared from iron oxide have more interesting color properties. Colour of these compounds is brighter and deeper. Increasing of the calcination temperature from 900 to 1000°C causes the darkening of colour. The most problably, the darkening is connected with partial reduction of Fe³⁺ to Fe²⁺.     

Transient thermal response of phase change material embedded with graphene nanoplatelets in an energy storage unit

This research was focused on the preparation of mixed metal oxide pigments doped with terbium ions with the general formula of Sn_0.752Co_0.08P_0.16Tb_0.008O₂. These pigments were synthesised by solid-state reactions at high calcination temperatures. The temperature range was chosen from 1350 to 1500 °C. The goal was to develop conditions for the synthesis of this type of pigments and to determine the influence of terbium ions on the colour properties of these compounds. All prepared pigments were applied into the organic matrix and into the ceramic glaze. Thermal behaviours of the reaction mixtures were investigated using differential thermal and thermogravimetric analysis. Synthesised Sn_0.752Co_0.08P_0.16Tb_0.008O₂ pigments were compared with concurrently prepared pigment Sn_0.760Co_0.08P_0.16O₂ depending on the calcination temperature with respect to the colour properties in CIE L*a*b* colour space, furthermore from the point of particle size distribution and phase composition. All compounds provided blue–violet hues that are stable in ceramic glazes.     

Synthesis and study of mixed oxide inorganic pigment from Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO–CeO<Subscript>2</Subscript> system

Novel environment-friendly yellow mixed oxide inorganic pigment from Bi₂O₃–ZnO–CeO₂ system with the composition 23 mol% Bi₂O₃, 15 mol% ZnO and 62 mol% CeO₂ was successfully synthesized by a conventional solid-state reaction method. Comprehensive analyses were carried out to characterize the develop pigment powder including simultaneous TG–DTA thermal analysis, colour properties and particle size distribution. The results demonstrated that the optimum calcination for pigment synthesis was located at a range 800–950 °C. The colour of the studied mixed oxide pigment is connected with the calcination condition. The substitution of Zn²⁺ changes the colour from orange to yellow. The colour of the obtained samples was dependent on the calcination condition and the particle size distribution. The most saturated yellow hue was obtained at the calcination temperature of 950 °C for 2 h in a furnace of pure air and after its application into organic binder in mass tone. The value C of this sample was approx. 65. The mixed oxide pigments were also evaluated from the standpoint of their particle size distribution. Bi₂Ce₂O₇ is considered to be a non-toxic compound, and the other component (Zn²⁺ ions) is also the safe element. Therefore, the present mixed oxide could be an attractive candidate as a novel environment-friendly inorganic yellow pigment.     

Thermal analysis of the Bi2O3-Y2O3-ZrO2 pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new colour inorganic pigments. Chemical compounds of the Bi_2-xY_x/2Zr_3x/₈O₃ type were synthetised. The host lattice of these pigments is Bi₂O₃ that is doped by Y³⁺ and Zr⁴⁺ ions. The incorporation of doped ions provides interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray powder diffraction and their colour properties.     

Structural changes in Fe-doped SrSnO3 perovskites during thermal analysis

Perovskite-type strontium stannate, SrSnO₃, is of technological interest because of its potential applications. In the present work, Fe(III)-doped SrSnO₃ perovskites were synthesized using Sn metal and the polymeric precursor method, derived from the Pechini method. Thermogravimetric evaluations in N₂ and O₂ atmospheres were performed to evaluate the possible formation of oxygen vacancies resulting from Fe(III) doping. The X-ray diffraction patterns showed the formation of an orthorhombic structure with high crystallinity after calcination at 1,073 K. The first thermal analysis, in a N₂ atmosphere, led to the partial elimination of strontium carbonate and hydroxyl groups, while the thermal analysis in an O₂ atmosphere led to an increase in the mass, indicating O₂ adsorption on the lattice, which could be related to the presence of Fe(III) and Fe(IV) in the perovskite structure. Moreover, the thermal analysis changed the symmetry of the iron-doped perovskites.     

Study of Bi2O3 doped by rare-earth element

A series of novel environmentally inorganic pigments based on Bi₂O₃ doped by metal ion Dy³⁺ has been developed and characterized using methods of thermal analysis, X-ray powder diffraction and by reflectance spectral data. The new pigments have been synthesized from mixtures containing Bi₂O₃ and Dy₂O₃ by traditional solid-state route. The incorporation of Dy³⁺ into crystal lattice Bi₂O₃ changes the colour from yellow-orange to orange. The band gap of phases with formula Bi_2?xDy_xO₃, where x = 0.8, increases from 2.30 to 2.38 eV with growth of calcination temperature. The pigment Bi_1.2Dy_0.8O₃ was also evaluated from the standpoint of influence of milling time on the colour properties and particle size. The simultaneous TG–DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. The results confirm the positive effect of lanthanide ions into Bi₂O₃ on thermal stability of prepared phases.     

Crystallization study of SrSnO3:Fe

Alkaline earth stannates have recently become important materials in ceramic technology due to its application as humidity sensor. In this work, alkaline earth stannates doped with Fe³⁺ were synthesized by the polymeric precursor method, with calcination at 300 °C/7 h and between 400 and 1100 °C/4 h. The powder precursors were characterized by TG/DTA after partial elimination of carbon. Characterization after the second calcination step was done by X-ray diffraction, infrared spectroscopy, and UV?Cvis spectroscopy. Results confirmed the formation of the SrSnO₃:Fe with orthorhombic perovskite structure, besides SrCO₃ as secondary phase. Crystallization occurred at 600 °C, being much lower than the crystallization temperature of perovskites synthesized by solid state reaction. The analysis of TG curves indicated that the phase crystallization was preceded by two thermal decomposition steps. Carbonate elimination occurred at two different temperatures, around 800 °C and above 1000 °C.     

Effect of variation of metal and non-metal elements on various properties of rare-earth-based inverse perovskites Gd3XY (X = Ga,In and Y = B,N)

Ferromagnetic rare-earth-based inverse perovskites Gd₃AlX (X = B, N) are studied using hybrid functionals in the framework of density functional theory. Different exchange correlation potentials are employed to analyze the structural parameters and geometry of the materials. The spin polarization and band structure explain the metallic behavior of these materials with high values of magnetic moment. The calculated elastic constants specify all materials are ordered perovskite compounds, among which Gd₃GaB, Gd₃GaN, Gd₃InN are brittle in nature while as Gd₃InB is ductile in nature. The quasi-harmonic Debye model was used to predict the thermodynamic properties of the material. The analysis of thermoelectric properties viz. Seebeck coefficient, electronic and thermal conductivities at higher temperature has been carried out. To check the optoelectronic response of the material various optical properties have been calculated up to 14 eV photon energy range. The competent thermoelectric and optoelectronic properties with high value of magnetic moment and ductile character suggests the application in thermoelectric and electro-optic devices.     

Synthesis and description of SrSn0.6Ln0.4O3 perovskite pigments

Inorganic pigments containing lanthanides based on pseudo cubic structure of SrSnO₃ have been prepared by solid state reaction between SrCO₃, SnO₂ and lanthanide oxides (Tb₄O₇, Pr₆O₁₁, CeO₂) in the temperature range 1300–1550°C. The resultant materials were characterised by XRD, TG-DTA and colourimetric techniques were used. The most interesting colour properties were provided by SrTb_0.4Sn_0.6O₃ prepared by firing at temperature 1500°C which has light yellow-green colour hue. The increase of temperature 1300–1500°C caused the creation of pigments with deeper and brighter colour hue. Colour properties of the samples prepared by calcination at 1550°C were of inferior quality due to structural changes from pseudo cubic to orthorhombic system.     

Thermal analysis of the (Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1−x</Subscript>(Y<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>x</Subscript> pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new ecological inorganic pigments. Chemical compounds of the (Bi₂O₃)_1−x(Y₂O₃)_x type were synthesized. The host lattice of these pigments is Bi₂O₃ that is doped by Y³⁺ ions. The incorporation of doped ions provides the interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray powder diffraction and their colour properties.     

Thermal analysis of the Bi2O3-Er2O3-Zro2 pigments

The synthesis of new compounds based on Bi₂O₃ is investigated because they can be used as new ecological inorganic pigments. Chemical compounds of the Bi_2−xEr_x/2Zr_3x/8O₃ type were synthetized. The host lattice of these pigments is Bi₂O₃ that is doped by Er³⁺ and Zr⁴⁺ ions. The incorporation of doped ions provides interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments. This paper also contains the results of the pigment characterization by X-ray powder diffraction and their colour properties.     

Yellow pigments based on Fe2TiO5 and TiO2

The aim of our research was to prepare yellow pigments based on structure of pseudobrookite Fe₂TiO₅. Part of Fe was substituted with Li and Ti from Fe₂TiO₅ to Li_0.05Fe_0.07Ti_2.44O₅. Synthesis and pigmentary-application properties in the Li₂O–Fe₂O₃–TiO₂ system were studied for 800 and 900°C using classical ceramic method of preparation. The main attention was aimed to usage of four different sources of titanium compounds as raw materials. We studied the influence of different sources of titanium compounds on the structural and the colour properties of the prepared pigments. The thermal analysis was used for characterization of titanium compounds and determination of their thermal stability.     

Study of ceramic pigments based on Er2Ce2?x Mo x O7

This contribution is focused on the synthesis, characterization and optical properties of new inorganic pigments which are environment friendly and can substitute some toxic metals in interesting colour compounds. Pyrochlores belong to the group of high-temperature pigments, and are a variety of actual and potential applications for several materials. Examples include catalysts, thermal barrier coatings, solid electrolytes, nuclear waste forms and host materials for luminescence centers. The pigments were prepared by the solid state reaction and also by method of suspension mixing of materials in the series with increasing content of molybdenum. The pigments were applied into organic matrix and ceramic glaze. The colour properties of these applications were investigated depending on content of Mo, method of preparation and temperature of calcination (1350?C1550?°C after step 50?°C). The optimum conditions for their synthesis were determined. The pigments were evaluated from standpoint of their structure, colour and particle sizes. Characterization of Er₂Ce_2?x Mo _x O₇ pigments (x?=?0.1, 0.3, 0.5 and 0.7) suggests that they have a potential to be alternative yellow or orange colourants for paints, plastics, ceramics and building materials.     

The photocatalytic properties of Ti–Mo oxides prepared by a simple sol–gel route

Powders containing mixtures of titania and molybdite in different ratios were prepared by sol–gel processing. The sols were dried and subsequently calcined at 300, 500 and 700 °C. Depending on the ratio of Ti and Mo in the initial sol and the calcination temperature, Ti-doped MoO₃, TiO₂/MoO₃ or Mo-doped TiO₂ have been formed. The as prepared samples were characterised by scanning electron microscopy with attached X-ray dispersive energy analysis, X-ray diffractometry, Raman spectroscopy, gas adsorption and optical characterisation by ultraviolet/visible spectroscopy. The latter was used for the analysis of the photocatalytic properties on the decolourisation of methylene blue solutions under visible light irradiation. The phase composition, the specific surface and the photocatalytic activity were influenced by the molybdenum content and the calcination temperature. The final molybdenum content in the samples additionally depends on the calcination temperature. The optimum photocatalytic properties were observed or Ti-doped MoO₃.     

The influence of trehalose–maltodextrin and lactose–maltodextrin matrices on thermal and sorption properties of spray-dried β-lactoglobulin–vitamin D3 complexes

In the study, the effect of lactose–maltodextrin and trehalose–maltodextrin matrices on the glass transition temperatures and moisture sorption characteristics of spray-dried β-lactoglobulin–vitamin D₃ complexes was investigated. Incorporation of sugars into complexes can influence the thermal properties and moisture sorption characteristics of powders. The glass transition temperature as an important physiochemical parameter that determines the processing conditions, product quality and stability of the final product was studied with the use of modulated differential scanning calorimetry method. Moisture sorption isotherms, water activity and moisture content as parameters related to sorption properties, were also investigated. Additionally, particle size, wettability and insolubility index were studied to characterise newly synthesized products. For the samples tested, two well-separated glass transitions were found. The dominant effect of maltodextrin on the glass transition temperatures was observed. An increase in the percentage of maltodextrin added resulted in increasing T _g value of studied complexes. At low water activity all powdered complexes showed typical sorption behaviour of food systems. Trehalose as a carbohydrate component of powdered complexes, in comparison to lactose, delayed the occurrence of crystallization.     

Microwave synthesis of LaBO3 (B = Co,Fe) perovskites using graphite and citric acid additions

We studied the effects of graphite and citric acid additions on the formation of LaFeO₃ and LaCoO₃ perovskites upon microwave treatment of crystalline hydrates or nitrate solutions, respectively. The addition of graphite was shown to increase the yield of LaCoO₃ perovskite and to result in the formation of crystalline LaFeO₃ perovskite even at the microwave treatment stage. Subsequent thermal treatment at 800°C yields single-phase lanthanum ferrite with a high specific surface area (11 m²/g). Due to the addition of citric acid to nitrate solutions, a highly viscous gel forms, which allows preparation of single-phase perovskites with a high specific surface area (up to 34 m²/g) after microwave treatment and calcination. The samples obtained using the admixtures are characterized by a high catalytic activity in methane oxidation. No single-phase oxides form without introduction of these admixtures.     

Effect of sulfadiazine on biological model membranes

Summary In this paper the optimization of the kaolin calcination is studied, aiming at using the produced metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of metakaolins and finally by strength development analysis of cement-metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO₃. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive metakaolins.     

Temperature-Responsive Photoluminescence and Elastic Properties of 1D Lead Halide Perovskites R- and S-(Methylbenzylamine)PbBr3

Low-dimensional metal halide perovskites (MHPs) have received much attention due to their striking semiconducting properties tunable at a molecular level, which hold great potential in the development of next-generation optoelectronic devices. However, the insufficient understanding of their stimulus-responsiveness and elastic properties hinders future practical applications. Here, the thermally responsive emissions and elastic properties of one-dimensional lead halide perovskites R- and S-MBAPbBr₃ (MBA⁺ = methylbenzylamine) were systematically investigated via temperature-dependent photoluminescence (PL) experiments and first-principles calculations. The PL peak positions of both perovskites were redshifted by about 20 nm, and the corresponding full width at half maximum was reduced by about 40 nm, from ambient temperature to about 150 K. This kind of temperature-responsive self-trapped exciton emission could be attributed to the synergistic effect of electron–phonon coupling and thermal expansion due to the alteration of hydrogen bonding. Moreover, the elastic properties of S-MBAPbBr₃ were calculated using density functional theory, revealing that its Young’s and shear moduli are in the range of 6.5–33.2 and 2.8–19.5 GPa, respectively, even smaller than those of two-dimensional MHPs. Our work demonstrates that the temperature-responsive emissions and low elastic moduli of these 1D MHPs could find use in flexible devices.     

Study of thermal behaviour and stability of Co-doped malayaite ceramic pigments

This contribution deals with the preparation and characterization of Co-doped malayaite pigments. Pigment samples were prepared by solid-state reaction at different firing temperatures (1200–1400 °C). For characterization of thermal behaviour, pigment formation and thermal stability were studied by the methods of thermal analyses. The compounds were evaluated from standpoint of their phase composition and particle size distribution. The XRD analysis of samples prepared at 1,300–1,400 °C indicates the occurrence of two-phase compounds, i.e. the malayaite and the cassiterite. Average value of mean particle size of tested malayaites is moved ~10 μm. The great attention was focused on determination of impact of firing temperature on the pigment-application properties. Because the malayaite compounds belong into ceramic pigments, the pigment-application properties were observed after application into organic matrix in mass tone and middle-temperature glaze in different pigment amounts. Generally, the colour appearance of tested malayaites is dependent on the firing temperature and it moves in different shades of blue colour. From pigmentary point of view, it is possible to recommend 15 % of mass pigment for sufficient colouring of middle-temperature glaze. The higher firing temperature provides the formation of pigment samples with the higher saturation and the higher values of hue angle. For preparation of Co-doped malayaite pigments with the excellent colour properties, the firing temperature 1,350 °C is necessary.     

基于纳米ZnO/聚氯乙烯的复合材料光催化性能研究

本文采用纳米氧化锌与聚氯乙烯溶液共混制备了复合材料前驱体，运用TG-DTA联机分析得到了其分解温度及相关热分解数据；经适当温度煅烧后得到复合材料光催化剂，并用TEM、XRD、FTIR、UV-Vis、ESR对复合材料进行分析表征。在室内普通照明用荧光灯作用下，以甲基橙溶液为催化对象，对复合材料的光催化性能进行了检测，并在相同条件下，与纳米氧化锌、纳米氧化钛及聚氯乙烯直接煅烧产物的光催化性能进行了比对分析；同时研究了pH值对复合材料光催化性能的影响。研究结果表明，复合材料对甲基橙催化降解8 min后，甲基橙溶