3N Phase Research Articles

Structural and magnetic properties of nanocrystalline Fe–N thin films and their thermal stability

The nanocrystalline Fe–N films with a mixture of ɛ-Fe 3N and α-Fe phase synthesized on NaCl (1 0 0) substrate by dc magnetron sputtering were annealed at different temperatures in order to investigate their thermal stability and magnetic properties. The structure, morphology, and magnetic properties of the samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID). The results showed that the release of nitrogen from nanocrystalline ɛ-Fe 3N phase during annealing led to the formation of γ′-Fe 4N phase. At annealing temperature of 350 °C, nanocrystalline γ′-Fe 4N phase tended to decompose to the more stable phase α-Fe. This transition deposition temperature was lower than what had been reported that the single-phase γ′-Fe 4N was still stable at 400 °C. As the annealing temperature increased, the saturation magnetization (Ms) for the films with a mixture of ɛ-Fe 3N and α-Fe phase did not change significantly, but decreased drastically for the films with a mixture nanocrystalline γ′-Fe 4N and α-Fe phase. It was also found that both the relief of the stress and an increase in grain size during annealing had significant influences on the coercivity for the films with mixed ɛ-Fe 3N and α-Fe phases. The coercivity of the films decreased when the phase transformation from nanocrystalline ɛ-Fe 3N phase to γ′-Fe 4N phase occurred.

Study of the S phase formed on plasma-nitrided AISI 316L stainless steel

Some tribological and corrosion resistance properties of austenitic stainless steels are enhanced by the formation of the S phase, also called expanded austenite. This phase is formed on the surfaces of austenitic stainless steels nitrided under certain conditions. In this work, AISI 316L steel was plasma-nitrided at 350, 400, 450, and 500 °C, and the samples were characterized by X-ray diffraction (XRD), conversion electron Mössbauer spectroscopy (CEMS), and wavelength dispersive spectroscopy (WDS) in order to investigate the S phase. XRD analysis identified the presence of a distorted cubic structure phase. The modified layer consists of an austenitic phase with different content of nitrogen, ranging from approximately 10 to 40 at%, and also γ′-Fe 4N and ɛ-Fe 2–3N phases. A diminution in the S phase occurs with the increase in nitriding temperature, and this decrease is related to the transformation of the S phase to the γ′-Fe 4N phase.

Discrimination between γ′‐Fe4N and ε‐Fe2–3N iron nitride compounds using PCA of Auger electron spectra

AbstractAES offers high spatial resolution that is useful when analysing cross sections of nitrided steels. To discriminate between different iron nitride compounds in such an analysis, so‐called factor analysis (FA) can be applied. This requires acquisition of Auger electron spectra which are associated with either the γ′‐Fe4N or the ε‐Fe2–3N phases as principal components. In this study, the N KLL and Fe LMM Auger electron spectral lines of γ′‐Fe4N and ε‐Fe2–3N phases were acquired in great detail from the pure γ′‐Fe4N and ε‐Fe2–3N phases obtained by gaseous nitriding of pure iron. To this end, two different samples of known composition were analysed. Firstly, Auger electron spectra were recorded from a nitrided layer with large γ′‐Fe4N grains (∼30 µm) on top of an iron substrate. Secondly, Auger electron spectra were recorded from an ε‐Fe2–3N outer layer (∼6 µm) with 26 at.% N, on a γ′‐Fe4N layer (∼4 µm) with 20 at.% N, created on top of an iron substrate. The latter sample was also used for FA. It is shown that principal component analysis of a series of N KLL Auger electron spectra recorded from the iron nitride double layer could be represented by three contributions. These principal components are associated with γ′‐Fe4N, ε‐Fe2–3N and the background. On the other hand, when a background subtraction was applied to the acquired N KLL Auger electron spectra, it was not possible to discriminate between the two iron nitride phases. Copyright © 2006 John Wiley & Sons, Ltd.

Effects of various nitriding parameters on active screen plasma nitriding behavior of a low-alloy steel

Active screen plasma nitriding (ASPN) is a novel surface modification technique that has many capabilities over the conventional DC plasma nitriding (CPN). In this study, 30CrNiMo8 low-alloy steel was active screen plasma-nitrided under various nitriding parameters such as active screen set-up parameters (different screen hole sizes, mesh sheet and plate top lids) and treatment temperature (520, 550 and 580 °C), in the gas mixture of 75% N 2+25% H 2 and chamber pressure of 500 Pa for 5 h. The properties of the nitrided specimens have been assessed by evaluating composition of phases, surface hardness, compound layer thickness and case depth using X-ray diffraction (XRD), microhardness measurements and scanning electron microscopy (SEM). It was found that the screen hole size and top lid type (mesh or plate) play an important role in transition of active species (nitrogen ions and neutrals) toward the sample surface, which in turn can affect the nitrided layer hardness and thickness. Treatment at higher temperature with bigger screen hole size resulted in a thicker compound layer and higher layer hardness. The compound layers developed on the samples treated under different conditions were dual phase consisting of γ′-Fe 4N and ε-Fe 2–3N phases.

Improvements in the understanding and application of duplex coating systems using arc plasma technology

There has been interest for some years now in the development of duplex treatments involving plasma nitriding coupled with the deposition of a hard coating. Although this coating system has in service use for various applications, there are still however many underlying uncertainties with regard to how treatment parameters affect coating performance, for example the deposition temperature and the related substrate softening. Different duplex treatments are applied to SKH 51 and SKH 2 steel by changing the nitriding atmosphere and TiN deposition temperature. The nitride layers with the ε-Fe 3N phase are more prone to denitriding than those consisting of either an α or γ′-Fe 4N phase during deposition of the hard coating. The black layer formed through denitriding of the SKH 51 alloy is thinner than that of the SKH 2 alloy. This is considered to be a result of the presence of nitride forming elements. Regardless of the nitride phases that are formed, the diffusion of nitrogen atoms is enhanced at increased substrate temperatures, induced by ion bombardment characteristics during coating growth, causing a significant decrease in the nitrogen content of the original prenitrided layer. The composite surface hardness of the treated specimens is found to be most dependent on substrate softening effects, as opposed to factors such as black layer formation. The adhesion of the TiN coating to the underlying nitrided layer again appears to be influenced more by softening of the substrate during higher temperature deposition as opposed to the formation of a black layer. This is indicated by the fact that the adhesion to the samples with an initial ε-Fe 3N nitrided surface is greater than those with an α phase, even though the black layer is only present for the former. These studies reveal that avoiding substrate softening is essential in producing high performance hard coating/nitride duplex coatings.

Subnitride chemistry: A first-principles study of the NaBa 3N, Na 5Ba 3N, and Na 16Ba 6N phases

An ab initio study on the electronic structure of the subnitrides NaBa 3N, Na 5Ba 3N, and Na 16Ba 6N is performed for the first time. The NaBa 3N and Na 5Ba 3N phases consist of infinite 1 ∞[NBa 6/2] strands composed of face-sharing NBa 6 octahedra surrounded by a “sea” of sodium atoms. The Na 16Ba 6N phase consist of discrete [NBa 6] octahedra arranged in a body-cubic fashion, surrounded by a “sea” of sodium atoms. Our calculations suggest that the title subnitrides are metals. Analysis of the electronic structure shows partial interaction of N ( 2 s ) with Ba(5 p) electrons in the lower energy region for NaBa 3N and Na 5Ba 3N. However, no dispersion is observed for the N ( 2 s ) and Ba(5 p) bands in the cubic phase Na 16Ba 6N. The metallic band below the Fermi level shows a strong mixing of N ( 2 p ) , Ba(6 s), Ba(5 d), Ba(6 p), Na(3 s) and Na(3 p) orbitals. The metallic character in these nitrides stems from delocalized electrons corresponding to hybridized 5 d l 6 s m 6 p n barium orbitals which interact with hybridized 3 s n 3 p m sodium orbitals. Analysis of the electron density and electronic structure in these nitrides shows two different regions: a metallic matrix corresponding to the sodium atoms and the regions around them and heteropolar bonding between nitrogen and barium within the infinite 1 ∞[NBa 6/2] strands of the NaBa 3N and Na 5Ba 3N phases, and within the isolated [NBa 6] octahedra of the Na 16Ba 6N phase. The nitrogen atoms inside the strands and octahedra are negatively charged, the anionic character of nitrogens being larger in the isolated octahedra of the cubic phase Na 16Ba 6N, due to the lack of electron delocalization along one direction as opposed to the other phases. The sodium and barium atoms appear to be slightly negatively and positively charged, the latter to a larger extent. From the computed Ba–N overlap populations as well as the analysis of the contour maps of differences between total density and superposition of atomic densities, we suggest partial covalent bonding between nitrogen and barium atoms along the infinite 1 ∞[NBa 6/2] strands and within isolated [NBa 6] octahedra.

Plasma-based ion implantation: a valuable industrial route for the elaboration of innovative materials

Plasma-based ion implantation is used to modify the magnetic properties of a thin film of nickel first deposited by microwave plasma assisted sputtering. Implantation of nitrogen in the Ni layer produces the metastable phase Ni 3N that does not exhibit magnetic properties. Ni and Ni 3N phases are determined by X-ray characterization and the magnetic properties measured using the SQUID technique. The perspectives offered by PBII processing for the elaboration of magnetic micro-and nanostructure are briefly discussed.

Characterization of plasma-nitrided iron by XRD, SEM and XPS

The plasma nitriding technique has been used to improve the tribological and mechanical properties of materials, especially iron-based alloys. In this work, the pulsed glow discharge (PGD) technique was used for nitriding pure iron. Three samples were nitrided in a gas mixture of 80 vol.% H2 and 20 vol.% N2 under a pressure of 400 Pa, discharge frequency of 9 kHz, and temperature of 580 °C. Samples A, B and C were nitrided for 30 min, 60 min and 90 min, respectively. The nitrided iron samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM micrographs showed differences in the surface morphologies among the samples. XRD identified the γ′-Fe4N and ε-Fe2–3N phases in all samples. The Rietveld analysis was performed in order to investigate the concentration variations of the phases as a function of nitriding time. XPS was employed to obtain chemical-state and semi-quantitative information, and revealed a thin film of Fe2O3 covering a Fe3O4 layer formed on top of the Fe2–3N and Fe4N layers.

Characterization of plasma-nitrided iron by XRD, SEM and XPS

The plasma nitriding technique has been used to improve the tribological and mechanical properties of materials, especially iron-based alloys. In this work, the pulsed glow discharge (PGD) technique was used for nitriding pure iron. Three samples were nitrided in a gas mixture of 80 vol.% H 2 and 20 vol.% N 2 under a pressure of 400 Pa, discharge frequency of 9 kHz, and temperature of 580 °C. Samples A, B and C were nitrided for 30 min, 60 min and 90 min, respectively. The nitrided iron samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM micrographs showed differences in the surface morphologies among the samples. XRD identified the γ′-Fe 4N and ε-Fe 2–3N phases in all samples. The Rietveld analysis was performed in order to investigate the concentration variations of the phases as a function of nitriding time. XPS was employed to obtain chemical-state and semi-quantitative information, and revealed a thin film of Fe 2O 3 covering a Fe 3O 4 layer formed on top of the Fe 2–3N and Fe 4N layers.

Growth, structural and optical properties of Cu 3N films

Thin films of Cu 3N were grown on (0 0 1) MgO and (0 0 1) Cu substrates by molecular beam epitaxy of copper in the presence of nitrogen obtained from a radio frequency atomic source. The different aspects of the growth and the properties of the copper nitride films were investigated in relation with growth parameters such as: substrate temperature, growth rate and flux of nitrogen. On MgO substrates, despite a mismatch as high as ∼10%, the Cu 3N films grow as epitaxial layers even at room temperature. The upper temperature limit for growth was found to be ∼250 °C. It is likely that the growth mechanism proceeds in a layer-by-layer fashion similar to the growth of γ ′-Fe 4N layers on MgO substrates using the same growth method. This results in the growth of smooth layers of Cu 3N. The films, grown as a pure phase, have a behavior typical for an insulator with an optical gap of 1.65 eV. If a low amount of Cu impurities is present in the Cu 3N insulating matrix, the films still have the overall behavior of an insulator, but with a reduced optical band gap. For higher amounts of metal impurities, seen as Cu crystallites in the epitaxial Cu 3N phase, the optical band gap reduces even further, and additionally, an extra absorption peak due to Cu appears. The films grown on (0 0 1) Cu substrates, despite the better lattice match, did not show a striking improvement of the crystal quality.

Mechanochemical nitridation by ball milling iron with m-phenylene diamine

The solid state synthesis reactions between elemental α-Fe powder and m-phenylene diamine (C 6H 4(NH 2) 2) have been studied. The different phase transformations are found in the course of milling and during subsequent thermal annealing. The single ε-Fe 2–3N phase with nitrogen concentration up to 11.53 wt% was obtained after 250 h ball milling. Owing to the local inhomogeneity of N content, the ε-Fe 2–3N phase can be formed by ball milling at room temperature, even though the sample has a low average N content. The saturation magnetization M S and coercivity H C of ε-Fe 2–3N are 81.4 A m 2/kg and 16.28 kA/m. Thermal analysis experiments show structural stability of the ε-Fe 2–3N phase up to 512.0°C. On comparison with α-Fe ball milled in NH 3 atmosphere, it is evident that the nitridation process in our experiment occurs more rapidly because more active nitrogen-containing radicals can be maintained during the milling process. It illustrates that the solid–solid reaction is more efficient than the solid–gas reaction.

Magnetic properties and structure of the α″-Fe 16N 2 films

Single-phase α″-Fe 16N 2 films have been grown epitaxially on Al 2O 3 single crystal substrates by using the thermalized plasma DC-sputtering process at a high sputtering pressure of 250 mTorr. α″-Fe 16N 2 films can be grown at room temperature (RT) as a single crystal phase and have one very intense peak in their X-ray diffraction pattern (XRD), with orientation (1 1 2), and d-spacing=2.4771 Å, and another minor peak with orientation (2 2 4), and d-spacing=1.2388 Å. This phase was reproducible at different nitrogen flow rates (NF) from 1.5 to 3 sccm. The annealing of these films at different temperatures for 3 h lead to the decomposition of the α″-Fe 16N 2 phase. At the annealing temperature T ann=435°C, the structure of the films changes completely to the Fe 3N phase. Increasing the sputtering temperature T s up to 300°C, and using NF=3 sccm leads to other orientations of the α″-Fe 16N 2 phase. At lower nitrogen flows, NF=1.5, 2, and 2.5 sccm, other phases like Fe 2N, Fe 3N and γ-Fe austenite were found in the XRD patterns as phases mixed with the α″-Fe 16N 2 phase. The magnetic properties of the α″-Fe 16N 2 single crystal films which were sputtered at RT were very surprising: they have a very low magnetic moment 4 πM s which varies between 0.097 kG for 1 μm thick films to 0.31 kG for 6 μm thick films. M s was measured using a vibrating reed magnetometer in a magnetizing field of 10 kOe at RT. By using a SQUID magnetometer and magnetizing field up to 50 kOe the 4 πM s at 5 K showed a small increase, 4 πM s=0.35 kG, for the 6 μm thick films. After annealing these films for 3 h at 435°C, 4 πM s increased to 10 kG, which is due to the change of the film crystal structure from the α″-Fe 16N 2 phase to the Fe 3N phase. Also, the hot (300°C) sputtered α″-Fe 16N 2 films under NF=3 sccm have a low 4 πM s equal to the value of the cold sputtered films. The hot sputtered films at lower NF=1.5, 2 and 2.5 sccm showed a small increase of its 4 πM s up to 2 kG depending on the amount of the secondary phases of Fe 2N and Fe 3N which were found in its XRD patterns.

A study of martensitic stainless steel AISI 420 modified using plasma nitriding

We studied martensitic stainless steel AISI 420, modified using glow discharge plasma nitriding. Microhardness measurements, X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to investigate the surface microhardness, crystal structure, microstructure and chemical bonding in the modified surfaces. High surface microhardness (∼1300 HV) over a case depth of about 60 microns is obtained. Glancing incidence X-ray diffraction (GIXRD) indicates the presence of a predominantly Fe 3N phase with dispersed CrN within 2–5 microns on the surface. In addition, using Bragg–Brentano geometry, we measured the presence of a minor phase of Fe 4N in the case depth. SEM confirms that the microstructure within 2–5 microns of the surface is different from that of the bulk. XPS shows nitride phase formation on the surface. AES measured over the cross-section of the case depth shows a direct relation of the increased surface microhardness to the high nitrogen content.

TEM and simulation studies of Ti 3N ordered superstructure formed in intensified plasma assisted nitrided Ti–6Al–4V alloy

We have used transmission electron microscopy (TEM) and image simulation techniques to systematically investigate the surface microstructures evolved in Ti–6Al–4V alloy after nitriding by intensified plasma assisted processing (IPAP). Cross-sectional TEM and X-ray energy-dispersive spectroscopy studies demonstrated that the surface layer in the IPAP-treated Ti–6Al–4V has a N composition of approximately 25 at.%. By using electron diffraction analysis, the nitride layer was found to be composed of an ordered superstructure Ti 3N (ϑ-phase) that can be identified as a trigonal structure with a space group of P3 and lattice parameters a=6.04 Å and c=4.82 Å (hexagonal setting). The 3( d)-( 1 2 0 0) and 3( d)- 1 3 1 6 1 2 positions in the unit cell are occupied by metallic (Ti, Al, V) atoms, whereas the 1( a)- 0 0 0 and 1( c)- 1 3 2 3 1 2 positions are occupied by N atoms. The N content at the surface layer gradually decreases with depth, producing a composition gradient structure. This composition gradient layer is accomplished by gradually reducing the amount of Ti 3N phase and increasing that of the α-Ti structure.

Cobalt molybdenum bimetallic nitride catalysts for ammonia synthesis: Part 3. Reactant gas treatment

Co 3Mo 3N catalyst was found to be more active than the doubly-promoted iron catalyst for ammonia synthesis. The precursor CoMoO 4· nH 2O was heated under a 160 ml min −1 flow of NH 3 gas at 5.0 K min −1 to 973 K and kept at 973 K for 6 h. The sample was quenched during the nitridation process and we examined how the Co 3Mo 3N phase was formed. This Co 3Mo 3N phase was formed at the last stage of NH 3 treatment when the sample was kept at 973 K for 6 h. However, Mo 2N and Co phases still remained at this stage. The formation of Co 3Mo 3N bimetallic nitride phase became much slower after caesium addition to CoMoO 4· nH 2O. The ammonia activity of Co 3Mo 3N catalyst was found to be promoted by the treatment with N 2+3H 2 reactant gas at 873 or 973 K. Co 3Mo 3N catalysts once treated with diluted oxygen were treated with the reactant gas (N 2+3H 2, 60 ml min −1) at 873 or 973 K for various times. The rates were increased by this treatment, although the surface areas were decreased. By keeping the sample at 873 K for 12 h or at 973 K for 3 h in the reactant gas, the activities of Co 3Mo 3N catalysts reached the maximum. XRD, elemental analyses, and TEM measurements revealed that the complete Co 3Mo 3N phase was achieved by the reactant gas treatment. The rate at 673 K under 3.1 MPa with a flow rate of 60 ml min −1 of N 2+3H 2 over 2 mol% Cs-promoted catalyst reached even 40% of the equilibrium yield.

Effect of substrate temperature on the physical properties of copper nitride films by r.f. reactive sputtering

Deposition of copper nitride films are of significant interest because of their low thermal stability and semiconducting characteristics resulting in emerging applications in optical memories and laser writing. Copper nitride films are deposited by 13.56 MHz r.f. reactive sputtering (in the nitrogen plasma environment), keeping the substrates at 30°C (no deliberate heating of the substrate), 75°C and 150°C. Crystalline phases of the films are identified by grazing angle X-ray diffraction (GAXRD) technique. With an increase in substrate temperature, the film orients strongly towards the (100) plane of the Cu 3N phase. Surface morphology of the films studied by atomic force microscopy (AFM) indicates an increase in grain size and a decrease in surface roughness in the films with increasing substrate temperature. Agglomeration effect of grains are observed at the substrate temperature corresponding to 75°C. The bandgap of the films are found by UV-VIS absorption spectroscopy varying from 1.3 to 1.76 eV. Stoichiometry of the films is determined by heavy ion elastic recoil detection analysis (ERDA) technique with a Δ E– E detector telescope. This study provides insight into the importance of substrate temperature on the characteristics of copper nitride films.

Formation process of Ni–N films by reactive sputtering at different substrate temperatures

Ni–N thin films are prepared by reactive sputtering in an rf diode sputtering system. Deposition parameters, such as nitrogen flow ratio, substrate temperature and substrate holder potential were changed and their effects were investigated. When the substrate was heated at 220°C, Ni and Ni 3N phases were observed by XRD. In the case of substrate temperature being room temperature (RT), Ni 2N phase also appeared and characteristic nitrogen incorporation into Ni lattice was seen. In addition, when the substrate holder was set to the float potential, nitrogen content of the film which is thought to be lower than the case of ground potential, caused stronger resputtering effect. Because it was observed that the formation phase and nitrogen content of the film depend on the substrate temperature, the nitrogenizing reaction on the deposit surface was considered to rule the film formation. This was also supported by the results on the target surface analysis after sputtering and plasma emission spectroscopy measurements.

Pion absorptionon4He into theppdfinal state

Results from a 4π solid angle measurement of the reaction π++4He→ppd at incident pion energies of Tπ+=70, 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the final states with energetic deuterons (ppd) and (pd)p. The differential cross sections are described by a complete set of five independent variables and various other kinematic variables and compared to cascade and phase space models where deuterons were formed by a semiclassical pickup model. The data are investigated for signatures of initial and final state interactions: it is found that more than half of the (ppd) yield cannot be explained by these mechanisms. The remaining strength is reasonably well reproduced by 3N phase space models followed by pickup.Received 7 October 1999DOI:https://doi.org/10.1103/PhysRevC.61.054604©2000 American Physical Society

Surface characterisation of plasma-nitrided iron by X-ray photoelectron spectroscopy

The nitriding by plasma has the potential to improve the tribological and mechanical properties on a number of substrates, and offers various advantages as compared with other methods used in the modification of surfaces. We prepared four samples by nitriding the iron substrates in a gas mixture (80% H 2 and 20% N 2) under a pressure of 9.0 mbar, discharge frequency of 10 kHz and temperature of 773 K, for periods of 1, 2, 4 and 6 h. We characterised the samples by scanning electron microscopy (SEM), X-ray diffraction (XRD) and microhardness techniques, and detected the presence of Fe 4N and Fe 2–3N phases. We employed X-ray photoelectron spectroscopy (XPS) to obtain chemical-state and quantitative information of the plasma-nitrided iron surfaces. In situ cleaning was carried out by argon ion bombardment. The Fe 2p 3/2 photoelectron peaks for all samples presented three components, associated with Fe 0, Fe 2+ and Fe 3+, while the N 1s lines showed two components, the main one due to iron nitride and the other is connected with oxidised nitrogen.

Structure change in Fe 4N powders by mechanical milling: a new aspect and correction of our previous reports

We have prepared impurity-free Fe x N powders ( x=3.6) and re-examined their structure change by mechanical milling and subsequent annealing. X-ray diffraction and Mössbauer spectroscopic studies of the milled powders indicate that the initial fcc (γ′-) Fe 4N phase is mechanically deformed and changes to the hcp (ϵ-Fe 3N type) phase, even though the Fe content is much higher than the stoichiometry of the latter compound. This phase transformation is due to the local structure similarity of Fe atoms in γ′-Fe 4N and ϵ-Fe 3N, and introduction of hcp type stacking faults along the most dense crystalline plane of (111) in the fcc lattice by shear force. The ϵ-Fe 3N phase is maintained after annealing at 230°C and it almost returns to the γ′-Fe 4N phase after annealing at 420°C. These results indicate that our previous reports for Fe x N powders ( x≥4) are not correct: the γ′-Fe 4N phase does not martensitically transform to the bct (α′-) Fe–N phase by mechanical milling and the milled Fe x N powders do not become α″-Fe 16N 2 by subsequent annealing. The previous results were confused by the coexistence of bcc (α)-Fe, the oxidation in the powder specimens, and the very broad structure-less X-ray diffraction patterns of the powder specimens milled for less than 300 h.