Primary Crystallization Phase Research Articles

Experimental investigation and thermodynamic modeling of the Al–Dy–Zr system

The Al–Dy–Zr ternary system has been experimentally studied and thermodynamically assessed to contribute to the development of novel heat-resistant aluminum alloys. Using equilibrated alloys, the isothermal section of this ternary system at 873 K has been established by means of scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). Experimental information on vertical sections was obtained by performing differential scanning calorimetry (DSC) analysis on selected annealed samples and that on liquidus projection was extracted from the as-cast samples by observing the primary crystallization phases. In addition, the first-principles method was employed to calculate the enthalpy of formation of metastable compounds involved in the sublattice model. Based on the experimental data and first-principles calculation results in this work, the Al–Dy–Zr system was optimized within the framework of the calculation of phase diagram (CALPHAD) method. Good agreement was found between the experimental data and the thermodynamic calculation results, which indicates that the thermodynamic description developed in this work is reliable.

Phase equilibria in the Tl–TlI–Se system and thermodynamic properties of the ternary phases

By using differential thermal analysis (DTA), X-ray analysis and electromotive force (EMF) methods the Tl–Se–I system was investigated in the Tl–TlI–Se composition range. Several polythermal sections, the isothermal section at 300K and the projection of the liquidus surface of the system were constructed. The fields of primary crystallization of phases as well as types and coordinates of non- and monovariant equilibria were determined. Formation of two congruently melting ternary compounds (Tl5Se2I at 720K, and Tl6SeI4 at 705K) was observed. The system is characterized by the existence of wide areas of solid solutions on the base of Tl2Se (α-phase) and Tl5Se2I (δ-phase). The partial molar thermodynamic functions (ΔG‾,ΔH‾,ΔS‾) of thallium as well as the standard integral thermodynamic functions of Tl6SeI4 and Tl5Se2I compounds and Tl5Se3−xIx solid solution (for x=0.2, 0.4, 0.5, and 0.8) were calculated based on the EMF data.

Nucleation control for fine nano crystallization of Fe-based amorphous alloy by high-magnetic-field annealing

The magnetization measurements for an Fe83.3Si4.2B12.5 amorphous alloy were carried out to investigate the magnetic field effect on the crystallization kinetics. From the isochronal measurements, the gain of the Zeeman energy was estimated from the increase of magnetization at the crystallization temperature. By the isothermal measurements, the growth curve of bcc-Fe(Si), which is the primary crystal phase of this material, was obtained. The growth curve at 10T shows more abrupt time evolution, compared with that at 0.5T. However, the growth curves as a function of the scaled time converge to a universal sigmoidal curve, regardless of the applied magnetic field strength. These behaviors indicate that the rate of this crystallization reaction is increased, whereas the crystallization process is not changed by applying the high magnetic field.

Thermodynamic Modeling of Crustal Melting Using Xenolith Analogs from the Cortlandt Complex, New York, USA

Emplacement of gabbroic magmas of the Cortlandt Complex, New York, induced rapid (less than 5 years) heating of pelitic schist protoliths (up to ∼1200°C at ∼0·9 GPa). Xenoliths entrained within the mafic melt experienced significant melting and melt-segregation, now represented as a series of complex fabrics and structures comprising Si-rich veins and an Al-rich, Si-poor residuum (a typical assemblage is spinel–magnetite–ilmeno-hematite–sillimanite ± sapphirine ± corundum). Subtle microscopic textures in the residuum include corundum–magnetite symplectites, which are interpreted to be a result of oxidative breakdown of the hercynite component in spinel during cooling. Aluminous orthopyroxene selvages in veins have typically grown along the contact between the residuum and quartzofeldspathic ‘melt’. Hybrid monzonorite and monzodiorite crop out near the xenoliths and are interpreted to represent assimilation by the mafic magma of some of the partial melt produced from the pelitic xenoliths. Equilibrium-melting and batch-melting thermodynamic models track the evolution of the pelitic schist, its partial melt upon heating, and the residuum from melting and melt extraction. We introduce a ‘filter-pressing’ cooling calculation to simulate the crystallization of the quartzofeldspathic veins. Modeling results yield the following: (1) an initial partial melt that, when mixed with the estimated composition of the mafic melt, produces a hybrid igneous rock consistent with the monzonorite found near the xenolith; (2) a high- T melt that upon ‘filter-pressing’ crystallization produces a mineral assemblage that texturally and compositionally corresponds to the quartzofeldspathic veinlets retained in the samples within xenolith interiors; (3) a residual material that, when oxidized, resembles the aluminous assemblages in the residuum. Modeling of crystallization of the high- T melt predicts early orthopyroxene formation, with the Al content of orthopyroxene consistent with that of analyzed selvage pyroxene. We propose that this pyroxene reflects a primary melt crystallization phase rather than reaction-rim margins of the veins against residual matrix.

Synthesis and Characteristics of Al2O3-doped α-CaSiO3 Ceramics

Calcium silicate ceramics with pseudo-wollastonite phase (α-CaSiO3) were synthesized by solid state reaction method with different additions of Al2O3. The X-ray diffraction patterns show that the primary crystal phase of obtained samples is α-CaSiO3. The addition of Al2O3 will induce a secondary phase of Ca2Al2SiO7. The accounts of added Al2O3 and calcining temperatures have obvious influence on bulk densities, dielectric constants, and quality factors of α-CaSiO3 ceramics. The α-CaSiO3 ceramic with 3wt% addition of Al2O3 calcined at 1225°C has the best properties.

鋳造法によって作製された ZrC 添加 Mo-Si-B 合金のミクロ組織と機械的性質

ZrC-added Mo-Si-B alloys were prepared by arc-melting. After heat-treatment at 1800℃ for 24 h, their density and elastic moduli were measured, and their microstructure was evaluated. Moreover, high-temperature compression tests at 1400℃ and four-point bending tests with a Chevron notch at room temperature were conducted to investigate their mechanical properties. The primary phase was Mo solid solution (Moss) or ZrC depending on Mo/ZrC compositional ratio. After the primary phase crystallization, Mo2B, Mo5SiB2 (T2), Moss+ZrC eutectic, Moss+T2 eutectic and/or Moss+Mo3Si+T2 eutectic were crystallized out during solidification. Mo2B and/or Mo3Si dissolved during the heat treatment in some alloys. The ZrC-added Mo-Si-B alloys had higher high-temperature strength compared with the ternary Mo-Si-B alloys even though ZrC-added Mo-Si-B alloys contained less volume fraction of the T2. Besides, the ZrC-added Mo-Si-B alloys exhibited better fracture toughness than that of ternary Mo-Si-B alloys, reaching 20.2 MPa(m)1/2. Therefore, this study found that ZrC plays a significant role in improving high-temperature strength and fracture toughness in Mo-Si-B alloys.

Influence of TiO2 nanoparticle synthesis on the properties of thin coatings

Three different types of titania nanoparticles were used to fabricate coatings on glass substrates, comprising of two commercial products obtained from pyrolysis and precipitation as well as self-synthesized particles from a sol–gel-synthesis. The effect of different particle properties on the coating properties like film thickness, roughness, transparency and photocatalytic activity was investigated. Thereby, not only the primary particle size and crystal phase being the main differences of the chosen TiO2 particles but especially the secondary particle size and morphology were found to affect the coating characteristics, first of all the photocatalytic activity. Furthermore, we were able to synthesize titania nanoparticles showing consistent properties independent of the agglomerate size, outperforming the commercial products in most investigated attributes.

Experimental study and thermodynamic assessment of the Cu–Ni–Ti system

The Cu–Ni–Ti ternary system has been systematically investigated combining experimental measurements with thermodynamic modeling. With selected equilibrated alloys, the equilibrium phase relations in the Cu–Ni–Ti system at 850°C were obtained by means of SEM/EDS (Scanning Electron Microscopy/Energy Dispersive Spectrum), EPMA (Electron Probe Micro-Analysis) and XRD (X-ray Diffractometry). Phase transformation temperatures were measured by DSC (Differential Scanning Calorimetry) analysis in order to construct various vertical sections in the Cu–Ni–Ti system. The liquidus projection of the ternary system was determined by the identifying primary crystallization phases in the as-cast alloys and from the liquidus temperatures obtained from the DSC analyses. Based on the available data of the binary systems Cu–Ni, Cu–Ti, Ni–Ti and the ternary system Cu–Ni–Ti from the literature and the present work, thermodynamic modeling of the Cu–Ni–Ti ternary system was performed using the CALculation of PHAse Diagram (CALPHAD) approach. A new set of self-consistent thermodynamic parameters for the Cu–Ni–Ti ternary system was obtained with an overall good agreement between experimental and calculated results.

Influence of Si Content on Microstructure and Erosion Properties of Al-Based Alloy

In order to develop new protective materials for magnesium alloy, Al-based alloys with different Si-content were fabricated by copper mold casting. Microstructure, erosion properties of the ingot samples were characterized or tested by using spectrum analysis, optical imcroscope, salt testing machine etc, respectively. The results indicated that the microstructure of Al-1.9Si-1.32Mg-0.40Mn was mostly dendritic crystal. That of Al-13Si consisted of α-Al, flaky eutectic silicon and primary crystal silicon. That of Al-18Si-0.01%P was consistent of a large proporation of primary crystal silicon phase, a part of eutectic silicon phase and a little of α-Al phase. With Si-content increasing, anti-corrosion properties of Al-based alloy gradually improved, which could provide theoretical principle to determine chemical elements of protective materials for magnesium alloy.

Milling, Sintering and Crystallization of 11BaO‐25CaO‐64SiO2 Glass Powder

The crystallization of 11BaO‐25CaO‐64SiO2 mol% glass powders and related effects of glass powder milling have been studied by X‐ray diffraction (XRD), light and scanning electron microscopy (SEM) and differential thermal analysis (DTA). Glass powders were made by ZrO2 crushing with subsequent sieving or sedimentation or alternatively made by milling with agate, corundum and tungsten carbide. Although surface crystallization was detectable during late sintering, all powders fully sintered. Wollastonite was found as primary crystal phase followed by cristobalite and sanbornite precipitation. The latter crystallization steps caused a second DTA‐peak for fine powders. DTA‐peak temperatures shifted to lower temperature with decreasing particle size in any case. No significant effects of milling materials on DTA‐peak temperatures were evident. As an exception, however, milling in agate caused strongly decreased temperatures of the second DTA‐peak. This observation can be explained by the progressive mechanical damaging, which results from the required prolonged milling time with agate due to its small materials density, and the fact that diamond made scratches did promote surface crystallization of cristobalite. The present study thus shows that even for glass powders with excellent sinterability, milling can affect microstructure evolution.

Effect on P-Element Modification on Microstructure of Al-Based Alloy

To develop high wear-resistant protective materials for magnesium alloy, high-silica Al-based alloy modified via P-element was fabricated by DC casting method. Microstructure of ingot samples was observed by using optical microscopy (OM), etc. The results demonstrated that Al-Si-0.01%P alloy with unique microstructure and without defects such as voids and rarefaction might be generated by processing control. Owing to modification by Al-P interalloy, primary crystal silicon phase in hypereutectic Al-Si alloy were refined effectively. Its size in Al-18Si-0.01%P alloy decreased from 50μm to 20μm, and distributed uniquely than that in Al-18Si alloy. Al-P acted as heterogeneous core of primary crystal silicon phase, which was the main mechanism for Al-P interalloy to modify primary crystal silicon in Al-Si alloy.

Pb-Sb-S ternary system

The Pb-Sb-S ternary system was studied by physicochemical analysis methods (differential thermal, X-ray powder diffraction, and microstructural analyses and microhardness measurements), and a projection of the liquidus surface was constructed. The regions of primary crystallization of phases were determined. It was established that the ternary system has seven invariant equilibrium points. Near Sb2S3 and PbS, narrow solubility ranges were found.

The effect of high-level waste glass composition on spinel liquidus temperature

Spinel crystals precipitate in high-level waste glasses containing Fe, Cr, Ni, Mn, Zn, and Ru. The liquidus temperature (TL) of spinel as the primary crystallization phase is a function of glass composition, and the spinel solubility (c0) is a function of both glass composition and temperature (T). Previously reported models of TL as a function of composition are based on TL measured directly, which requires laborious experimental procedures. Viewing the curve of c0 versus T as the liquidus line allows a significant broadening of the composition region for model fitting. This paper estimates TL as a function of composition based on c0 data obtained with the X-ray diffraction technique.

Experimental study and thermodynamic assessment of the Cu–Fe–Ti system

The Cu–Fe–Ti ternary system has been systematically studied through experimental investigation and thermodynamic modeling. Combining diffusion multiple technique with selected equilibrated alloys, equilibrium phase relations in the Cu–Fe–Ti system at 800°C have been established by means of SEM/EDS (Scanning Electron Microscopy/Energy Dispersive Spectrum) and EPMA (Electron Probe Micro-Analysis). DSC (Differential Scanning Calorimetry) analysis has been also employed to measure phase transformation temperatures in order to construct various vertical sections of the Cu–Fe–Ti system. Liquidus projection of the ternary system has been determined by identifying primary crystallization phases in as-cast alloys. Based on all available experimental information from literatures and this work, the Cu–Fe–Ti ternary system was modeled with the aid of the CALPHAD (CALculation of PHAse Diagram) method. Comprehensive comparisons made between experimental and calculated results shed light on reliability of the current thermodynamic description.

Crystallization Behavior of the CaO-Al2O3-MgO System Studied with a Confocal Laser Scanning Microscope

The crystallization behavior of a calcium-aluminate system with various MgO content from 2.5 to 7.5 wt pct and CaO/Al2O3 ratios between 0.8 and 1.2 has been examined using a confocal laser scanning microscope (CLSM). CCT (continuous cooling transformation) and time temperature transformation (TTT) diagrams were constructed to identify the primary crystal phase of slag at different compositions and at cooling rates between 25 and 800 K/minutes. In the slag at a CaO/Al2O3 ratio of 1.0, crystallization temperature increased during isothermal and continuous cooling with higher MgO content, and the shortest incubation time was observed at 5 wt pct MgO. When MgO content was fixed to be 5 wt pct, crystallization temperature increased with lower CaO/Al2O3 ratio. According to the slag composition, cooling rates and temperature, the primary phase could be CA, or C5A3, or C3A, or C3MA2, or MgO, and the crystal morphology changes from dendrites to faceted crystals to columnar crystals in this composition range.

Phase equilibria in the Cu-Cu2S-As system

Phase equilibria in the Cu-Cu2S-Assystem have been studied by DTA and X-ray powder diffraction. Cu0.667S0.333-As, Cu0.667S0.333-Cu0.735As0.265, and Cu0.8S0.2-As polythermal sections, an isothermal section at 300 K, and the liquidus projection have been constructed. Our data differ from reported data in the extents of primary crystallization phase fields and the coordinates of some invariant equilibrium points.

Cytotoxicity and Genotoxicity of Nanosized and Microsized Titanium Dioxide and Iron Oxide Particles in Syrian Hamster Embryo Cells

Potential differences in the toxicological properties of nanosized and non-nanosized particles have been notably pointed out for titanium dioxide (TiO(2)) particles, which are currently widely produced and used in many industrial areas. Nanoparticles of the iron oxides magnetite (Fe(3)O(4)) and hematite (Fe(2)O(3)) also have many industrial applications but their toxicological properties are less documented than those of TiO(2). In the present study, the in vitro cytotoxicity and genotoxicity of commercially available nanosized and microsized anatase TiO(2), rutile TiO(2), Fe(3)O(4), and Fe(2)O(3) particles were compared in Syrian hamster embryo (SHE) cells. Samples were characterized for chemical composition, primary particle size, crystal phase, shape, and specific surface area. In acellular assays, TiO(2) and iron oxide particles were able to generate reactive oxygen species (ROS). At the same mass dose, all nanoparticles produced higher levels of ROS than their microsized counterparts. Measurement of particle size in the SHE culture medium showed that primary nanoparticles and microparticles are present in the form of micrometric agglomerates of highly poly-dispersed size. Uptake of primary particles and agglomerates by SHE exposed for 24 h was observed for all samples. TiO(2) samples were found to be more cytotoxic than iron oxide samples. Concerning primary size effects, anatase TiO(2), rutile TiO(2), and Fe(2)O(3) nanoparticles induced higher cytotoxicity than their microsized counterparts after 72 h of exposure. Over this treatment time, anatase TiO(2) and Fe(2)O(3) nanoparticles also produced more intracellular ROS compared to the microsized particles. However, similar levels of DNA damage were observed in the comet assay after 24 h of exposure to anatase nanoparticles and microparticles. Rutile microparticles were found to induce more DNA damage than the nanosized particles. However, no significant increase in DNA damage was detected from nanosized and microsized iron oxides. None of the samples tested showed significant induction of micronuclei formation after 24 h of exposure. In agreement with previous size-comparison studies, we suggest that in vitro cytotoxicity and genotoxicity induced by metal oxide nanoparticles are not always higher than those induced by their bulk counterparts.

Contribution to the Study of the Relation between Microstructure and Electrochemical Behavior of Iron-Based FeCoC Ternary Alloys

This work deals with the relation between microstructure and electrochemical behavior of four iron-based FeCoC ternary alloys. First, the arc-melted studied alloys were characterized using differential thermal analyses and scanning electron microscopy. The established solidification sequences of these alloys show the presence of two primary crystallization phases (δ(Fe) and graphite) as well as two univariante lines : peritectic L + δ(Fe)↔γ(Fe) and eutectic L↔γ(Fe) + Cgraphite. The ternary alloys were thereafter studied in nondeaerated solution of 10−3 M NaHCO3 + 10−3 M Na2SO4, at 25°C, by means of the potentiodynamic technique. The results indicate that the corrosion resistance of the FeCoC alloys depends on the carbon amount and the morphology of the phases present in the studied alloys.

Reinforcement of Hydroxyapatite with Multi-Walled Carbon Nanotubes

Multi-walled carbon nanotubes (MWNTs) reinforced hydroxyapatite (HA) composite was fabricated by in-situ method and followed by hot-pressing sintering; the influence of MWNTs’ content on the mechanical and microstructure properties was explored. The results show that adding MWNTs within a certain range could enhance the mechanical properties of HA matrix significantly. The maximal increment of the bending strength and fracture toughness of the composites, compared with the pure HA, were 157% and 171% respectively. XRD and TEM showed that the primary crystal phase of the composite was HA together with the diffraction peaks of carbon nanotube. By SEM, we found that MWNTs are homogeneously dispersed within grains or at grain boundaries of the HA matrix in composites which MWNTs’ content was not more than 15vol%, otherwise MWNTs tended to be agglomerated. The reinforcement mechanism was discussed based on the microstructure investigation. The broken nanotubes and pullout of MWNTs at interfaces were efficient in transferring the load from the HA matrix to the nanotubes, leading to the improvement of the mechanical properties.

Projection of the liquidus surface of the Co – Sb – Pb ternary intermetallic system

Methods of physicochemical analysis are used to plot the phase diagram of the Co0.745Sb0.255 – Sb0.8Pb0.2 section and the projection of the liquidus surface of the Co – Sb – Pb system. Triangulation secants are used to cut the system into two secondary ternary subsystems consisting of six fields of primary crystallization of phases and a splitting field. The boundaries of monotectic transformations, the development of single-variant processes, and the coordinates of nonvariant equilibrium compositions are determined.