Thermal synthesis of the CeO2-PrO2-La2O3 pigments

The synthesis of new compounds based on CeO₂-PrO₂-La₂O₃, which can be used as pigments for colouring of ceramic glazes, is investigated in our laboratory. The optimum conditions for the syntheses of these compounds have been estimated. The first information about the temperature region of the formation of the pigments investigated is provided by thermal analysis. The synthesis of these compounds is followed by thermal analysis using STA 449/C Jupiter (Netzsch, Germany). This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal synthesis of the (Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>)<Subscript>1–x</Subscript>(Er<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 environmentally friendly inorganic pigments. Chemical compounds of the (Bi₂O₃)_1–x(Er₂O₃)_x type were synthetized. The host lattice of these pigments is Bi2O3 that is doped by Er³⁺ ions. The incorporation of doped ions provides interesting colours and contributes to an increase in 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.     

Thermal behavior of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> mesoporous gels

Summary Titania-based photocatalytic materials were prepared by sol-gel method using Fe³⁺ and polyethyleneglycol (PEG₆₀₀) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe³⁺ containing titania gels. The microstructure development of the Fe₂O₃/TiO₂ gel samples with and without PEG₆₀₀ admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120&deg;C and the samples preheated for 1 h to 300 and 500&deg;C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600&deg;C.     

Effect of the modifier ion on the properties of MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> pigments

Magnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow- orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick color.     

Thermal oxide synthesis and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanowires

Fe₃O₄ nanorods and Fe₂O₃ nanowires have been synthesized through a simple thermal oxide reaction of Fe with C₂H₂O₄ solution at 200–600°C for 1 h in the air. The morphology and structure of Fe₃O₄ nanorods and Fe₂O₃ nanowires were detected with powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The influence of temperature on the morphology development was experimentally investigated. The results show that the polycrystals Fe₃O₄ nanorods with cubic structure and the average diameter of 0.5–0.8 μm grow after reaction at 200–500°C for 1 h in the air. When the temperature was 600°C, the samples completely became Fe₂O₃ nanowires with hexagonal structure. It was found that C₂H₂O₄ molecules had a significant effect on the formation of Fe₃O₄ nanorods. A possible mechanism was also proposed to account for the growth of these Fe₃O₄ nanorods. Supported by the Fund of Weinan Teacher’s University (Grant No. 08YKZ008), the National Natural Science Foundation of China (Grant No. 20573072) and the Doctoral Fund of Ministry of Education of China (Grant No. 20060718010)     

Thermal and structural investigation of SnO<Subscript>2</Subscript>/Sb<Subscript>2</Subscript>O<Subscript>3</Subscript> obtained by the polymeric precursor method

SnO₂-based materials are used as sensors, catalysts and in electro–optical devices. This work aims to synthesize and characterize the SnO₂/Sb₂O₃-based inorganic pigments, obtained by the polymeric precursor method, also known as Pechini method (based on the metallic citrate polymerization by means of ethylene glycol). The precursors were characterized by thermogravimetry (TG) and differential thermal analysis (DTA). After characterization, the precursors were heat-treated at different temperatures and characterized by X-ray diffraction. According to the TG/DTA curves basically two-step mass loss process was observed: the first one is related to the dehydration of the system; and the second one is representative to the combustion of the organic matter. Increase of the heat treatment temperature from 500 to 600°C and 700°C resulted higher crystallinity of the formed product.     

Phase equilibria in the Ce<Subscript>2</Subscript>O<Subscript>3</Subscript>-K<Subscript>2</Subscript>O-P<Subscript>2</Subscript>O<Subscript>5</Subscript> system

Ce₂O₃-K₂O-P₂O₅ ternary system has been investigated by thermoanalytical methods (DTA, DSC), powder X-ray diffraction, XPS and IR spectroscopy. The existence of three double potassium-cerium(III) phosphates has been confirmed and a new binary phosphate K₄Ce₂P₄O₁₅ has been found. Phase diagram and isothermal section at room temperature of the system Ce₂O₃-K₂O-P₂O₅ have been presented.     

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⁺.     

Effect of nucleating agents on the crystallization of Li<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system glass

The processes of nucleation of Li₂O-Al₂O₃-SiO₂ glasses with TiO₂ and TiO₂+ZrO₂ as nucleating agents were discussed. The DTA peak temperature and DTA peak height shown a strong dependence on the nucleation temperature in the glass with TiO₂, while in the glass with TiO₂+ZrO₂ this tendency was small. The optimum nucleation temperatures were 745 and 760°C for two glasses. It suggested that with TiO₂+ZrO₂ as nucleating agents, the crystallization had lower sensitivity for nucleation temperature, and the glass had higher nucleation efficiency than with TiO₂.     

Conductivity of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-NiO composites

The conductivity and transport number of oxygen ions of Bi₂O₃-(10, 30, 50) vol % NiO composites are measured using the four-probe and coulomb-volumetric methods at various temperatures. It is shown that the Bi₂O₃-50 vol % NiO composite exhibits a high mixed ionic-electronic conductivity in the temperature range from 730 to 800°C.     

Constant transformation rate thermal analysis of HGdP<Subscript>2</Subscript>O<Subscript>7</Subscript>·3H<Subscript>2</Subscript>O

Summary The aim of this work is the optimization of the preparation of anhydrous gadolinium hydrogen phosphate with good fluorescence properties. The products obtained by dehydration of gadolinium hydrogen phosphate trihydrate depend on the conditions chosen for the thermal treatment. For this reason, the dehydration was followed by Constant Rate Thermal Analysis whilst strictly controlling the water vapour pressure above the sample. Intermediate samples, obtained during dehydration were characterised by IR spectroscopy and X-ray diffraction. It has thus been shown that the thermal pathway taken for the dehydration depends on the water vapour pressure above the sample in the region from 10^-2to 5 mbar. Under the lowest water vapour pressure (5·10^-3mbar), the elimination of the crystallization water is carried out in a continuous way and produces a quasi-amorphous intermediate. Under higher water vapour pressure (5 mbar), well crystallized intermediate products are obtained. The results obtained suggest that the trihydrate contains zeolitic water which confirms a prior structural study.     

Hydrothermal synthesis and thermodynamic properties of 2CaO·3B<Subscript>2</Subscript>O<Subscript>3</Subscript>·H<Subscript>2</Subscript>O

2CaO·3B₂O₃·H₂O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B₂O₃·H₂O in HCl·54.572H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HCl·54.501H₂O and of CaO in (HCl+H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol⁻¹ of 2CaO·3B₂O₃·H₂O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.     

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.     

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.     

Phase diagram of the system KF-K<Subscript>2</Subscript>TaF<Subscript>7</Subscript>-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript>

As an asymmetric organic molecular crystal, p-N,N-dimethylaminobenzaldehyde (DAB) exhibits peculiar optical property. It was first grown by solution technique adopting slow evaporation method at room temperature using CCl₄ as growth medium. The solubility of DAB increases with temperature. Good quality transparent crystals of p-N,N-dimethylaminobenzaldehyde were carefully collected and subjected various characterization studies such as UV, FTIR, ¹H and ¹³CNMR spectral studies and thermal (TG-DTG) studies to determine the purity and application oriented properties of the grown crystals.     

Thermal behaviour and properties of Na<Subscript>2</Subscript>O-TiO<Subscript>2</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to study the thermal behaviour of (50-x)Na₂O-xTiO₂-50P₂O₅ and 45Na₂O-yTiO₂-(55-y)P₂O₅ glasses. The addition of TiO₂ to the starting glasses (x=0 and y=5 mol% TiO₂) resulted in a nonlinear increase of glass transition temperature and dilatation softening temperature, whereas the thermal expansion coefficient decreased. All prepared glasses crystallize under heating within the temperature range of 300–610°C. The contribution of the surface crystallization mechanism over the internal one increases with increasing TiO₂ content. With increasing TiO₂ content the temperature of maximum nucleation rate is also gradually shifted from a value close to the glass transition temperature towards the crystallization temperature. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were NaPO₃, TiP₂O₇ and NaTi₂(PO₄)₃. The chemical durability of the glasses without titanium oxide is very poor, but with the replacement of Na₂O or P₂O₅ by TiO₂, it increases sharply.     

Thermal analysis of pigments based on Bi2O3

The synthesis of new pigments based on Bi₂O₃ is investigated because they give interesting orange hues and can substitute the pigments problematic from the environmental point of view. Chemical compounds of the Bi_2–xZr_3x/4O₃ type were synthesized. The host lattice of these pigments is Bi₂O₃ that is doped by Zr⁴⁺ ions. The area of ZrO₂ solubility in Bi₂O₃ at 800°C forming solid solution of both oxides was studied. 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.     

Thermal synthesis and properties of the (Bi2O3)1–x(Ho2O3)x pigments

The synthesis of new compounds based on the Bi₂O₃–Ho₂O₃ system, which can be used as new ecological inorganic pigments, is investigated in our laboratory. The optimum conditions for the syntheses of these compounds have been followed by the methods of thermal analysis that can provide first information about the temperature region of the pigment formation. The synthesis of these compounds was followed by thermal analysis using STA 449/C Jupiter (Netzsch, Germany).     

Thermal stability of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of an α-Bi₂O₃ sample revealed staged phase transitions in the range 720–800°C (at 720, 780, and 800°C) and the elimination of oxygen to the composition Bi₂O_2.967 during heating to 895°C in air at 16 K/min. In dynamic vacuum (p = 1.33 Pa) at 780–800°C, Bi₂O₃ consecutively transforms to a phase with the cubic γ-Bi₂O₃ structure and tetragonal Bi₂O_2.3?2.4. In the latter, electron diffraction in a transmission electron microscope (ED/TEM) shows a superstructure with the superstructure vector q ₁₁₀ ≈ 1/9, which indicates an ordered arrangement of oxygen vacancies.