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Dilatometric studies of C--Mn hypoeutectoid steel with an as-cast structure were carried out to study the effects of the heating or cooling rate, heating and cooling process on phase transformation, and the thermal expansion coefficient. As the heating or cooling rate (Vc) increased, the characteristic temperatures of Ac1, Acp, and Ac3 also rose, while Ar3, Ar1, and Arp fell. In addition, the phase transformation temperature range (Ac3-Ac1) rose, while (Ar3-Arp) fell as the heating or cooling rate increased. At the same time, the maximum thermal expansion coefficients |αT| between the heating and cooling processes during phase transformation showed significant differences, and the difference (|Δ αT|) in the maximum |αT| between these processes increased along with the heating or cooling rate, and this is because of the different phase transformation rates, with regard to the change from austenite to ferrite on cooling and ferrite to austenite on heating. During the heating process, the phase transformation rate of ferrite to austenite first decreases and then increases as the temperature rises, and the phase transformation rate of austenite to ferrite first increases and then decreases during the cooling process. The evolution of carbon and substitutional alloying elements (Si and Mn) in austenite during heating and cooling is also analyzed in this work. [ABSTRACT FROM AUTHOR]

Thermal behavior and phase transformation of ZrO 2 –10%SiO 2 precursor powder prepared by a co-precipitation route without adding stability agent has been studied using different thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED), high-resolution TEM (HRTEM) and energy-dispersive X-ray spectrometer (EDS). The TG results show that four weight loss regions were from 298 to 443 K, 443 to 743 K, 743 to 793 K and 793 to 1400 K. The DTA result shows that the ZrO 2 freeze-dried precursor powders crystallization at 1014 K. The activation energy of 993.7 kJ/mol was obtained for tetragonal ZrO 2 crystallization using a non-isothermal process. The XRD result shows that only a single phase of tetragonal ZrO 2 appears when the freeze-dried precursor powders after calcination between 1173 and 1373 K for 2 h. Moreover, when calcined at 1473 K for 2 h, the phase transformation from tetragonal ZrO 2 fully converted to monoclinic ZrO 2 occurred. [ABSTRACT FROM AUTHOR]

Abstract: The phase formation and microstructure of zinc titanate precursors prepared at pH 5 by hydrothermal routes using TiCl4 and Zn(NO3)2·6H2O as the initial materials were studied. When the zinc titanate precursors were calcined at 773K for 1h, only the single phase anatase TiO2 was obtained. The Zn2Ti3O8 phase first appeared at 873K and decomposition started at 1073K. After calcination at 1073K for 1h, only the Zn2TiO4 and rutile TiO2 appeared. The crystalline size of Zn2Ti3O8 increased from 11.9nm to 38.6nm with increasing the calcination temperature from 873K to 1173K. The crystalline size of anatase TiO2 also increased from 15.3nm to 50.8nm when the calcination temperature increased from 773K to 1173K. However, the crystalline size of rutile TiO2 stayed at about 57.5nm for calcination temperature between 1173K and 1273K. [Copyright &y& Elsevier]

This paper examines the phase transformation and microstructure of ZnTiO nanocrystallite powders prepared using the hydrothermal process that includes TiCl and Zn(NO)·6HO as the initial materials. Differential thermal analysis, X-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction, nanobeam electron diffraction, and high resolution TEM were utilized to characterize the transition behavior of zinc titanate precursor powders after calcination. Nanocrystalline ZnTiO powders with a size range of about 5.0 to 8.0 nm were obtained when the precursor powders were calcined at 773 K (500 °C) for 1 hour. When the zinc titanate precursor powders were calcined at 1073 K (800 °C) for 1 hour, the cubic crystal of ZnTiO with a = 0.8399 ± 0.0003 nm still remained the predominant crystalline phase and the crystallite size increased to 20.0 nm. In addition, ZnTiO phase first appeared because of the 13.8 pct of ZnTiO decomposition when the zinc titanate precursor powders were calcined at 1073 K (800 °C) for 1 hour. When the zinc titanate precursor powders were calcined at 1073 K (800 °C) for 9 hours, the ZnTiO crystallites grew continuously to 80.0 nm and enhanced the crystallinity. When the precursor powders were calcined at 1273 K (1000 °C) for 1 hour, ZnTiO crystallites with a = 0.8461 ± 0.0002 nm were the predominant crystalline phase. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of the magnetic phase upon aging at 300–520°C in a heavily cold-drawn AISI 316L austenitic stainless steel fiber was studied using thermomagnetic analysis (TMA) and magnetic force microscopy with a heating stage. An increasing trend of magnetization from 50°C to around 470°C in the heating curves of TMA in austenitic stainless steels after a cold-drawing process was observed. No significant Ms temperature signal in the TMA curve at cooling indicated an increase in magnetization upon cooling period without significant phase transformation. A series of in situ magnetic force microscopy observations reveal a growth of the magnetic domain structure after aging at 300°C for 2.5h. Results show that the ferromagnetic increase during aging at lower annealing temperature resulted from the growth of martensite. [Copyright &y& Elsevier]

Highlights: [•] The single phase of tetragonal ZrO2 formed when calcined at 1223K for 1h. [•] The tetragonal ZrO2 fully converted to ZrSiO4 when calcined at 1323–1473K for 1h. [•] The activation energy of t-ZrO2 formed is 399.9kJ/mol when 5mol% Fe2O3 added. [•] The activation energy of the Fe/ZrSiO4 formed is 257.7kJ/mol when 5mol% Fe2O3 added. [•] The growth morphology parameter and crystallization index are about 2.0 and 1.0. [Copyright &y& Elsevier]

The phase formation, growth kinetics and optical properties of 0.5ZnO-0.5CdO thin films have been investigated by X-ray diffraction (XRD) and UV–vis spectrophotometry. The XRD results show that all 0.5ZnO-0.5CdO thin films are composed of CdO as the major phase and ZnO as the secondary phase. Moreover, after annealing of the 0.5ZnO-0.5CdO thin films at 723 K for 45 min and 773 K for 30 min, the minor phase of CdSiO 3 also appeared. The average activation energy of CdO grain growth in 0.5ZnO-0.5CdO thin films by the isothermal method is 10.51±1.17 kJ/mol. The average optical transparency was nearly 80% for the wavelength range from 500 nm to 900 nm. The grain size of CdO on the band gap energy for 0.5ZnO-0.5CdO thin films after annealing has a critical value, namely 15.9 nm. When the grain size of CdO is smaller than 15.9 nm, the band gap energy decreases, showing a redshift effect. Conversely, the band gap energy increases when the grain size of CdO is greater than 15.9 nm, showing a blueshift effect. [ABSTRACT FROM AUTHOR]

Abstract: Two mol% Y2O3-PSZ precursor powders for dental applications were synthesized using ZrOCl2·8H2O and Y(NO3)3·6H2O by a co-precipitation process at pH 7 and 348K for 2h. The thermal properties and phase transformation of 2Y-PSZ nanocrystallite powder have been investigated using a thermogravimetric and difference scanning calorimeter (TG/DSC), Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction and dilatometric analysis. Two weaker broad exothermic peaks appear at around 618 and 718K were explored in DSC results. The TG analysis shows that minor weight loss occurs from 298 to 348K, followed by three major weight losses at 610, 630 and 773K. Calcinated at 773 and 1273K, the crystallized phases are composed of the major phase of tetragonal ZrO2 and minor phase of monoclinic ZrO2. TEM reveals that the tetragonal ZrO2 with an average size of less than 20.0nm is mainly aggregated into the secondary aggregates with a size of small than 30.0nm. The sintering curve of the compact pellet has a significant shrinkage with a linear rate of 18.5% at about 1341K. Maximum densification rate happened at 1473K, demonstrating the good low temperature sinterability for dental applications. [Copyright &y& Elsevier]

Abstract: In this work, quantitative crystalline phase analysis of 316L stainless steel from wire to fiber using a multi-pass cold drawing process was studied using the Rietveld whole XRD profile fitting technique. The different diameters of the fibers: 179, 112, 75, 50, 34, 20, and 8μm, were produced from an as-received wire with a diameter of 190μm. The crystalline phases were identified using MDI Jade 5.0 software. The volume fractions of crystalline phases were estimated using a Materials Analysis Using Diffraction software. XRD analysis revealed that the crystal structure of as-received wire is essentially a γ-austenite crystalline phase. The phase transformation occurred during the 316L stainless steel from wire to fiber. Three crystalline phases such as γ-austenite, α′-martensite, and sigma phase of the fine fiber were observed. A cold drawing accelerates the sigma phase precipitates, particularly during the heat treatment of the fiber. [Copyright &y& Elsevier]