Relative Phase Content Research Articles

Innovative microstructures in SmCo5-based ribbons regulated by Fe-Ni-Al-Ti alloy

We proposed a new measure to optimize the comprehensive magnetic properties of SmCo5 alloy. By compounding Fe-15Ni-3Al-1Ti (FNAT) alloy with high saturation magnetization and Sm(Co, Cu)5 matrix alloy in the liquid state, an innovative two-phase separation microstructure or cellular microstructure is formed after melt-spinning using the phase separation effect of the two alloys. At the same time, the element concentration, relative phase content, and microstructure are adjusted by adding different contents of FNAT alloy. The results show that FNAT addition promotes the as-spun ribbons phase separation (or spinodal decomposition) into Co-rich SmCo5- and Sm-Ni-rich CeCo5- or Sm2Co7-type phases. Adding 3 wt.% FNAT increases the coercivity, saturation magnetization, and remanence of the ribbons by 320.6 %, 39.8 %, and 82.8 %, respectively. Adding 5 wt.% FNAT promotes forming the Sm2(Co, M)7 cell-wall phase and increases the coercivity and remanence by 272.7 % and 48.1 %, respectively. Finally, the corresponding microstructure evolution models, magnetization, and demagnetization mechanisms are proposed.

A structure formation in Ti-Ni powder after high-energy mechanical treatment

In this work a structure formation in Ti-Ni powder after high-energy mechanical treatment in a planetary ball mill with an acceleration of 60g are presented. Mechanical treatment time of powder was 5-300 seconds. It was shown the powder in initial state consists of phase mixture TiN (B2, B19`), Ti2Ni (E93) and TiNi3 (D024). The lattice parameters of powders not significantly change at mechanical treatment and correspond in good agreement with literature data. The quasi-amorphous phase is formed after mechanical treatment and the relative content of phases change so that the relative content of quasi-amorphous phase increases steeply from 0 % to 45 % in first 10 second of treatment mechanical treatment and not significantly changes at more prolong milling. The full widths at half maximum of peaks not significantly change to 10 second mechanical treatment, but the more prolong milling leads to them increasing due to forming of dislocation in all phases, wherein the value of the dislocation density of Ti2Ni phase is more than of TiNi and Ni3Ti phases and corresponds to 1013 cm−2 at 60 second of mechanical treatment.

Effect of sol–gel pH on XRD peak broadening, lattice strain, ferroelectric domain orientation, and optical bandgap of nanocrystalline Pb1.1(Zr0.52Ti0.48)O3

Nanocrystalline Pb1.1(Zr0.52Ti0.48)O3 (PZT) samples were prepared using a citrate–nitrate sol–gel process near the morphotropic phase boundary. The effect of pH on the lattice parameters (tetragonality and lattice constants), crystal structure [strain broadening, relative phase content, ferroelectric domain (FD) orientation and nanocrystallite size], microstructure (grain size and particle morphology) and optical bandgap was investigated. The samples were characterized using X-ray diffraction (XRD), the size strain plot (SSP) method, Fourier-transform infrared spectroscopy, and the classical Tauc relation. The particle morphology was investigated using field-emission scanning electron microscopy. The XRD results revealed a perovskite structure and coexisting tetragonal and rhombohedral phases for all PZT samples. Lattice strain and peak broadening were determined from SSP and XRD results. The behavior of these parameters was in agreement for all pH values. The optical bandgap for PZT was estimated from UV-vis absorption spectra. We found that for PZT the maximum relative tetragonal phase content, c/a ratio, and FD orientation along the a-axis occurred at pH 4.

Phase content controlled TiO 2 nanoparticles using the MicroJetReactor technology

In this paper, a method for the continuous preparation of nanoscaled titania with controlled phase content is presented. The method bases on the MicroJetReactor technology. The synthesis process was carried out by using the hydrolysis of titanium tetraethylate (TET). Synthesis with flow rates to 14 ml/min are implemented, and temperatures are varied between 20 and 210 °C. Particle size distribution measurements by dynamic light scattering (DLS) show monomodal particle size distributions from 1 to 10 nm, stable for more than 24 h. There is no correlation between hydrolysis temperature and the particle size distributions. XRD (X-ray diffractometry) investigations showed, that crystal structures of anatase, brookite, rutile and an amorphous content can be detected in all samples. Quantitative analysis using the Rietveld refinement shows a significant effect of the synthesis temperature on the phase content. The relative phase content of anatase can be raised from 40 wt% up to 75 wt%, accompanied by a loss of all other phases.

Martensitic transformation of Ti50Ni30Cu20 alloy prepared by powder metallurgy

Phase transformation behavior of Ti50Ni30Cu20 shape memory alloys prepared by powder metallurgy is analyzed with respect to the duration of mechanical alloying. The processed blends were studied by differential scanning calorimetry and room temperature X-ray diffraction. The martensitic transformations evidenced by thermal scans are discussed in correlation with the relative phase content obtained from the refinement of the X-ray diffraction patterns.

Structural macrokinetics of synthesizing ZnFe 2O 4 by mechanical ball milling

Powder mixtures of Fe 2O 3 and ZnO were milled in a high-energy planetary ball mill to synthesize ZnFe 2O 4 and X-ray powder diffractometry was used to obtain the relative content of phases, crystallite size and microstrain of both Fe 2O 3 and ZnFe 2O 4. The lattice constants of Fe 2O 3 were obtained by cell refinement method. The macrokinetics and the structure evolution of matters were studied and the results show that the dynamics process of mechanochemical synthesis of ZnFe 2O 4 fits Avrami-Erofe'ev model and is controlled by a nucleation-growth mechanism, and the structural macrokinetics theory in combustion synthesis research area could be used to describe the kinetic process as well.

Mössbauer study of formation of iron oxides and carbonate by dissimilatory alkaliphilic bacterium

The process of amorphous Fe(III)-hydroxide (AFH) reduction by anaerobic alkaliphilic bacterium – Geoalkalibacter ferrihydriticus (strain Z-0531) was investigated by Mössbauer spectroscopy methods. Strain Z-0531 was isolated from the sediments of soda Lake Khadyn (Tuva, Russian Federation). The influence of AFH concentration and the concentration of anthraquinone-2,6-disulfonate added to the cultivation medium as well as the incubation time influence on the reducing process were studied. It was found that increase in the time of cultivation of bacteria led to an increase in the relative content of phases containing ferrous atoms that could be explained by the adaptation of bacterium to the cultivation medium.

Mössbauer studies of the thermal stability of layered metallic systems

Methods of Mossbauer spectroscopy at 57Fe nuclei and X-ray diffraction analysis have been used to investigate layered systems Fe (5 μm)-Zr (2 μm) and Fe0.966Ti0.034(13 μm)-Ti (1 μ)-57Fe(0.8 μm) obtained by the method of ion-plasma deposition and subjected to sequential isothermal annealings at T = 900 and 650°C, respectively. The relative content of phases that are formed in the systems at each stage of annealing has been established and the sequence of transformations and their kinetics have been determined. For both systems, thermal stabilization of the structural and phase state, which is inhomogeneous in depth, has been observed.

Studying refractoriness of silicon-carbide materials fabricated in a big solar furnace

The dependence of the refractoriness value of a silicon-carbide material on the phase component ratio in it has been obtained. We demonstrate the possibility of determining the refractoriness value and/or the relative phase content in silicon-carbide materials by the procedure proposed using the refractoriness value-phase composition curve.

Structure–performance relations in nanocomposite coatings

Properties of hard nanocomposite coatings, especially hardness, can be explained by their nanostructure. Hardness maxima are found for different nanocrystalline/amorphous materials deposited by different techniques at typically 20% of the amorphous phase. A zone model is proposed which correlates the hardness to the relative phase content. The hardness of nanocomposite coatings peaks at the common minimum of the grain size of the crystalline phase and the grain separation. For an adequate description of the performance of a coating, the thermal stability, oxidation behavior and frictional behavior should be included in addition to hardness. In a friction situation involving at least two friction partners, the overall behavior of the system is determined by many-body interactions. While thermal stability and oxidation properties as inherent material properties can be directly linked to the nanostructure of the coating, the frictional behavior of a coating cannot be generalized independent of the friction conditions.

Ion channeling studies on mixed phases formed in metalorganic chemical vapor deposition grown Mg-doped GaN on Al2O3(0001)

Rutherford backscattering spectrometry and ion channeling were used to determine the relative quantities of wurtzite and zinc-blende phases in metalorganic chemical vapor deposition grown Mg-doped GaN(0001) on an Al2O3(0001) substrate with a GaN buffer layer. Offnormal axial channeling scans were used. High-resolution x-ray diffraction measurements also confirmed the presence of mixed phases. The in-plane orientation was found to be GaN[11̄0]‖GaN[112̄0]‖Al2O3[112̄0]. The effects of rapid thermal annealing on the relative phase content, thickness and crystalline quality of the GaN epilayer were also studied.

Evaluation of the degree of texturing and relative phase content in hot-pressed Bi(Pb)SrCaCuO superconductors

Peak intensities from (001) planes of the 2223 phase was measured to receive information on the c-axis orientation, while the ratio of (0 0 10) and (0 0 14) peaks intensities of the high- T c 2223 phase to the (0 0 8) and (0 0 12) peaks of the low- T c phase gave information on the relative content of the high- T c phase. Sintering prior to hot press3ng has shown strong effect on the resulting structure and physical properties with the optimum for 26MPa and 850°C between 96h and 120h. the highest value of J c for the uniaxially hot pressed pellet was ∼11,500Acm −2 at 77K and OT.

Microstructure and composition of plasma-nitrided Ti-6Al-4V layers

Nitriding of titanium alloys was performed in an r.f. plasma of nitrogen, hydrogen and argon at a substrate temperature of about 500 °C. The microstructure and the composition of the nitrided layers obtained were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). Three phases were identified: (a) a solid solution of nitrogen in titanium, α-(Ti, N), (b) tetragonal ϵ-Ti 2N and (c) cubic δ-TiN (NaCl-type structure). Two distinct layers were formed on top of the plasma-nitrided Ti-6Al-4V alloy, followed by a solid solution of nitrogen in the titanium alloy. The outer layer was identified as δ-TiN while the inner layer was identified as a mixture of δ-TiN and ϵ-Ti 2N. The ϵ-Ti 2N was found to be highly oriented (002) while the δ-TiN was obtained as a randomly oriented polycrystalline layer. The outer δ-TiN was found to have a fine structure, while the inner δ-TiN plus ϵ-Ti 2N comprised large and oriented grains. TEM studies showed that the crystallite size in the upper layer was tens to hundreds of ångstroms, while in the inner layer it was one tenth to about half a micrometre. Energy-dispersive analysis performed with the TEM system and AES shows a variation in the bulk composition along the nitride layer. The microstructures and the relative phase content are presented and discussed in relation to the gas feed composition in the plasma.