Milling Annealing Research Articles

High-performance lithium storage in Li2SnO3-graphite composite enabled by Ag3Sn nanoparticles and oxygen vacancies

With high capacity (653 mAh g−1) and low voltage (0.6 V), Li2SnO3 is considered as a prospective anode material for Li-ion batteries (LIBs). Nevertheless, its practical uses are restricted by inferior electrochemical kinetics and fast capacity decay. Herein, a novel ternary composite of Ag3Sn alloy-lithium stannate-graphite (denoted as Ag3Sn-Li2SnO3-x-G) is designed and fabricated by ball milling and vacuum annealing. In this ternary composite, oxygen vacancy-containing Li2SnO3 and Ag3Sn alloy nanoparticles are homogeneously dispersed in the exfoliated graphite nanosheets. The introduction of Ag3Sn nanoparticles and oxygen vacancies into Li2SnO3-graphite can significantly enhance charge transport kinetics and structure stability of composite during the lithiation and delithiation processes. Benefiting from these merits, the Ag3Sn-Li2SnO3-x-G composite presents excellent cycling stability (782.4 mAh g−1 at 0.2 A g−1 after 200 cycles) and impressive rate capability (251.5 mAh g−1 at 2 A g−1). Broadly, this design strategy can provide an effective and reliable route for constructing advanced metal oxide-based anode materials for high-energy LIBs.

Sulfur-doped g-C3N4/V2C MXene Schottky junctions for superior photocatalytic H2 evolution

An advanced sulfur-doped g-C3N4/V2C MXene (SCN/V2C) Schottky junction HER photocatalyst was prepared via vacuum ball milling and subsequent annealing.

Annealing Heat Treatment for Homogenizing the Microstructure and Mechanical Properties of Electron-Beam-Welded Thick Plate of Ti-6Al-4V Alloy

In the application of Ti-6Al-4V to aerospace structural components, when welding thick plates similar of the thickness of the components, microstructure and hardness gradients emerge between the base material (BM) and the joint. This leads to the issue of significant stress concentration in the BM under tensile stress. To address this problem through post-welding heat treatment, this study conducted heat treatments at temperatures both below (mill annealing, MA) and above the beta-transus temperature (beta annealing, BA) on electron-beam weldments of 18 mm thickness Ti-6Al-4V plates. Subsequently, microstructures and hardness were analyzed at different depths from the upper surface and areas (fusion zone (FZ), heat-affected zone (HAZ), and BM), and tensile properties were measured at various depths. The results indicated that α′ observed in FZ and HAZ was resolved through both MA and BA. Particularly after BA, the microstructural gradient that persisted even after MA completely disappeared, resulting in the homogenization of widmanstätten α + β. Consequently, after BA, the hardness gradient in each zone also disappeared, and the tensile strength was higher than in just-welded and MA heat-treated plates.

Synthesis-Controlled Polymorphism and Anion Solubility in the Sodium-Ion Conductor Na3InCl6-xBrx (0 ≤ x ≤ 2).

Motivated by the significant transport property improvement of the anion-substituted lithium metal halides, a series of anion mixed solid solutions of Na3InCl6-xBrx (0 ≤ x ≤ 2) are successfully synthesized by ball milling and subsequent annealing. By milling, the Na3InCl6-xBrx solid solution series crystallizes in a monoclinic P21/n phase, while the subsequently annealed Na3InCl6-xBrx series transforms into a trigonal P3̅1c phase. Through annealing and changes of the structure type, greater anion solubility can be achieved. The halide substitution slightly improves the ionic conductivity in the Na3InCl6-xBrx series, indicating that mixed halide compositions and their structural changes affect the ionic transport albeit less strongly than in the lithium analogues such as Li3YCl6-xBrx and Li3InCl6-xBrx.

Structure, electrical and thermal transport properties of Sn reinforcedAl-Cu-Fe quasicrystalline matrix composite prepared by mechanical milling and subsequent annealing

The present work deals with the structure, electrical and thermal transport properties of Al-Cu-Fe quasicrystal (IQC) reinforced with soft Sn phase (10–30 vol%) processed by mechanical milling and subsequent annealing. The 40 h milled powder of IQC-Sn nanocomposite contains IQC phase along with other crystalline phases i.e. B2-Al(Cu, Fe) (a = 0.29 nm; cP2) and monoclinic Al13Fe4 (a = 1.549 nm, b = 0.808 nm, c = 1.248 nm; α = γ = 90°, β = 107.72°; mC102). The IQC phase was also found to be ordered from the existence (311111) superlattice reflection of IQC. The phase fraction of IQC phase increased (in comparison with the crystalline phases) on annealing of IQC-Sn powder milled powder at 800 °C. The nano quasi-crystalline and nano-crystalline nature of these IQC and crystalline phases in milled and annealed powders were observed through transmission electron microscopy. The nano-beam diffraction (NBD) of the annealed samples confirmed the presence of nearer to 5-fold symmetry corresponding to the IQC phase. The electrical and thermal transport properties of milled and annealed samples were studied. The electrical and thermal transport properties of annealed sample was higher than that of the milled IQC-Sn nanocomposite powders. The ratio of electrical and thermal conductivity for IQC-20Sn annealed sample was found to be the highest (σ/ κ ∼4704 SK/W). These findings suggest the possibility of using IQC-Sn annealed nanocomposites for potential application as thermoelectric materials.

Effect of different carbon sources on the conversion of ilmenite into synthetic rutile via ball milling induced carbothermic reduction

Carbothermic reduction reduces ilmenite into TiO2 or acid-soluble intermediates. This method gained more attention due to several industrial applications of TiO2 and metal Ti. However, the efficiency of carbothermic reduction of ilmenite into synthetic rutile is poorly investigated for different carbon sources. In this study, several advanced characterization techniques were used to examine the effect of carbon on the carbothermic reduction of ilmenite via ball milling and isothermal annealing. Fourier transform infrared spectroscopic (FTIR) analysis showed new broad bands appearing in ball milled mixtures (ranging from ∼650 cm−1 to 1200 cm−1), due to temporary bonding of Ti–O–C overlapped with Ti–O–Ti bonding. Scanning electron microscopic (SEM) analysis also suggested that carbon was incorporated in the crystal lattice of ilmenite during ball milling. However, no new phases were observed in the X-ray diffraction (XRD) patterns of ball milled ilmenite-carbon mixtures. Therefore, the energy transferred during ball milling is not sufficient to overcome the activation energy of carbothermic reduction of ilmenite. Phase transformation of ilmenite occurred after annealing at 1000 °C by forming new phases such as rutile, pseudorutile, and pseudobrookite. Intermediate phases such as pseudorutile and pseudobrookite decreased with the use of carbon. Consequently, the efficiency of carbothermic reduction decreased in the order of coconut shells (amorphous)> activated carbon> vein graphite (crystalline). The absence of temporary bonding of Ti–O–C in annealed samples further confirmed the phase transformation of ilmenite. This study also showed that ball milled, and annealed samples resulted in highly crystalline rutile. Thermodynamic behavior of carbothermic reduction was finally simulated using the calculated enthalpy, entropy, and the Gibb’s free energy for each reaction.

Structural evolution of mechanically alloyed ODS steel powders during ball milling and subsequent annealing treatment

In the present work, a novel 9Cr oxide-dispersion strengthened (ODS) steel powders with Y2O3 (0.5 wt%) dispersoids were synthesized by high planetary ball milling at different time intervals (2, 8, and 16 hours). The structural and crystallographical evolution of the produced powders during the ball milling and post-annealing treatment were evaluated by SEM, XRD, and micro-Vickers hardness analyses. The SEM results showed that the fine dispersions of powders were achieved with the extending milling time. When milling time was 8h, it was observed that the mean size of powders increased maximum level of 101 μm and then dramatically reduced to 5 μm at latest milling time (16h). The XRD data revealed that the crystallite size of ODS powders diminished gradually with increasing milling time. Plus, all reflection peaks of the Fe, Cr, W, Mo expanded and the diffraction peaks of the Y2O3, W progressively disappeared with the increasing milling time. The hardness results revealed that the increasing milling time was beneficial for hardness improvement, due to dominant strain hardening mechanism and it developed from 160 to 334 Hv after 16h of milling protocol. To understand high temperatures characteristics such as grain growth, phase transformation, and hardness of produced powders, 16h milled powders subjected to post-annealing treatments at 700 oC and 900 oC for 1 h. When pure Fe and Cr peaks were observed in the non-annealed powders, no evident reflection peak of Y2O3 was observed. However, all pure Fe and Cr reflection peaks became narrower and Y2O3 reflection exhibited more sharper tendency with increased annealing temperatures, which resulted in increased grain growth and formation of Fe-based oxide structures.

PHASE FORMATION BEHAVIOR ON MECHANICALLY ACTIVATED ANNEALING OF Al-RICH PERITECTIC Al-Cr COMPOSITIONS

The formation of phases in the Al rich peritectic compositions of Al - Cr system was investigated under mechanical milling (MM) and subsequent annealing. MM led to the formation of nanocrystalline Al (Cr) solid solution and also caused carbon contamination originating from the organic process control agent (PCA). Al11Cr4 and AlCr2 phases were formed on annealing instead of the equilibrium peritectic compounds. Additionally, AlCr2C phase was also detected after annealing of Al-16 to 33Cr whereas Al-13Cr did not produce any intermetallic compound. The generation of the intermetallic phases was attributed to classical theories of nucleation and growth.

Combined Mössbauer Spectrometry and Atom Probe Tomography Investigation of Mechanically Milled Rare Earth / Transition Metal Powders

"The microstructure of mechanically milled Nd2Fe14B, SmCo5/Fe and SmCo3Cu2/-Fe alloys has been investigated by Mössbauer spectrometry and atom probe tomography. The structural changes that occur upon milling and subsequent annealing were characterised at a nanometer scale. Milling promotes intermixing of the elements and the formation of nanograins. In Nd-Fe-B powders, the Nd2Fe14B phase is transformed into -Fe and an amorphous Nd-Fe-B phase. In SmCo5/Fe powders, Fe/Co intermixing occurs, leading to the formation of Sm(Co,Fe)5 and -Fe(Co) phases. In SmCo3Cu2/Fe powders, although Sm is partly oxidised, Fe/Co intermixing occurs as well, leading to the formation of -Fe(Co) nanograins surrounded by Sm(Co,Cu,Fe)5 intergranular regions. The combined Mössbauer and atom probe tomography investigation of rare earth / transition metal powders thus allows revealing the effect of mechanical milling and subsequent annealing on the nanostructure of the powders. These results are helpful for the understanding of the magnetic properties of the powders. Keywords: rare earths-transition metals powders, Mössbauer spectrometry, atom probe tomography "

Revival of Smooth MgO(100) Surface: Ar Ion‐Beam Milling and Postvacuum Annealing in Oxygen Atmosphere

A recreation procedure for achieving the smooth and clean surface morphology of the degraded MgO(100) substrates is presented. The surfaces of the degraded MgO(100) substrates are treated with Ar ion‐beam milling (IBM) and annealing in O2 atmosphere. After each treatment, the changes in the MgO(100) substrate surface morphology are characterized using X‐ray diffraction (XRD), a 3D optical profilometer, atomic force microscopy, and Fourier‐transform infrared (FTIR) spectroscopy and compared with a fresh MgO substrate. It is shown that before any treatment, XRD and FTIR spectra show peaks corresponding to hydroxyl and carbonate groups in the degraded samples, whereas after treatment, XRD and FTIR spectra are comparable with the fresh sample. Further, after treatment, the surface roughness Rav value for two used/degraded samples reduces from 129 and 186 nm to 3.96 and 7.91 nm, respectively, after combined Ar IBM and annealing treatment. It is shown that the surface quality of the treated MgO(100) substrate improves in comparison with as it was before any treatment and can be reused for the good quality thin‐film deposition.

Predicting Strength of Titanium Alloys Using Aluminum and Molybdenum Equivalents at Operating Temperatures

This study contains the results of statistical studies of strength of sheeted products and bars made from α-, near α-, and α+β titanium alloys based on their composition. Based on summarizing the literature data, we have studied the ultimate tensile strength after mill annealing of 30 serial and experimental alloys at testing temperatures between 20 and 600°C. We have also substantiated the possibility to evaluate the tensile strength of semi-finished products using the strength equivalents (such as aluminum and molybdenum) of alloying elements and impurities at various temperatures. We have put forth models that help to predict the ultimate strength of titanium alloys based on their composition and the operating temperature with a confidence level of 0.95 and statistical errors comparable with the regulated spread.

Modified Li7P3S11 Glass-Ceramic Electrolyte and Its Characterization.

Li7P3S11 glass ceramics have high conductivities competitive with liquid electrolytes, making them good candidates as solid-state electrolytes for all-solid-state lithium-ion batteries. However, the metastable nature and performance of Li7P3S11 glass ceramics remain mysterious. Herein, modified Li7P3S11 glass ceramics with compositions of 70Li2S-30P2S5 were prepared via two-step mechanical milling and thermal annealing. Li7P3S11 glass ceramics synthesized using the conventional method (mechanical milling and thermal annealing) were again ball-milled to obtain amorphous 70Li2S-30P2S5 with a peculiar glass structure. Further thermal annealing was carried out to crystallize the glass. The obtained crystalline phase was analogous to the original Li7P3S11 phase, but the conductivity was enhanced by a factor of 1.7. Based on 31P solid-state nuclear magnetic resonance (NMR) spectroscopy, the Li7P3S11 phase contained an additional PS43- unit. A rational deconvolution procedure for the 31P solid-state NMR spectra based on crystalline Li7P3S11 was developed and applied to the samples. The analysis can resolve the additional crystalline PS43- unit in the Li7P3S11 structure. Based on two-dimensional double-quantum 31P NMR spectroscopy, the additional PS43- unit is located adjacent to the P2S74- unit, suggesting that P2S74- is divided into two PS43- units in the Li7P3S11 phase. The flip motion of Li+ was also investigated based on the 7Li spin-lattice relaxation time. The independent activation energy of spin-lattice relaxation with respect to temperature in the Li7P3S11 phase was attributed to a conduction path between the two PS43- units. The findings provide a synthetic route that can be used to develop metastable solid-state electrolytes.

Improvement of high‐temperature stability of PIP SiCf/SiC material through in situ grown BNNTs

AbstractIn this paper, the effect of in situ grown boron nitride nanotubes (BNNTs) and preparation temperature on mechanical behavior of PIP (Precursor Infiltration and Pyrolysis) SiCf/SiC minicomposites under monotonic and compliance tensile is investigated. In situ BNNTs are grown on the surface of SiC fibers using ball milling–annealing process. Composite elastic modulus, tensile strength, fracture strain, tangent modulus, and loading/unloading inverse tangent modulus (ITM) are obtained and adopted to characterize the mechanical properties of the composites. Microstructures of in situ grown BNNTs and tensile fracture surfaces are observed under scanning electronic microscopic (SEM). For SiCf/SiC minicomposites with BNNTs, the elastic modulus, tensile strength, and fracture strain are all lower than those of SiCf/SiC minicomposites without BNNTs, mainly due to high preparation temperature and the oxidation of the PyC interphase during the annealing process. Tensile stress–strain curves of SiCf/SiC minicomposites with and without BNNTs are predicted using the developed micromechanical constitutive model. The predicted results agreed with experimental data. This work will provide guidance for predicting the service life of SiCf/SiC composite materials and may enable these materials to become a backbone for thermal structure systems in aerospace applications.

The improved electro-chemical performance of β-LiVOPO4 by relieved strain via a post ball milling annealing process as a cathode material for lithium ion batteries

Electro-active lithium vanadyl phosphate, β-LiVOPO4, was synthesized by solid-state method and post ball milling annealing treatment. SEM/TEM showed diminished particle size and thin amorphous surface layer after high energy ball milling. Deconvolution analysis based on Rietveld refinement revealed significantly relieved lattice strain. These factors contributed to the significantly improved electro-chemical performance of strain-relief β-LiVOPO4 (S-LVOP). The initial discharge specific capacity of S-LVOP was 154.5 mAh g−1 at the current density of 16 mA g−1, ca. 93% of the theoretical capacity of 166 mAh g−1, and that was only 61.6 mAh g−1 for pristine LVOP. It also remained 106.4 mAh g−1 after 80 cycles. Better rate performance was also observed. Moving boundary model based GITT method showed that the lithium ion diffusion coefficients in the two phase region varied in the range of 1.5 × 10−11 cm2 s−1 - 6.0 × 10−11 cm2 s−1, 2–4 orders of magnitude higher than that obtained by traditional GITT method.

Suppression and Recovery of Martensitic Transformation and Magnetism in Mechanically and Thermally Treated Magnetic Shape‐Memory Ni−Mn−Ga Melt‐Spun Ribbons

As‐melt‐spun Ni50.2Mn28.3Ga21.5 ribbons are subjected to milling and subsequent annealing for various times. With progressing milling time, the martensitic transformation is gradually suppressed, magnetic moment deteriorates, whereas the crystal structure undergoes a body centered tetragonal (bct) into face centered cubic (fcc) change. High‐resolution transmission electron microscopy demonstrates a twin‐deformed zone in fcc powder particles, which works to improve circularity of as‐produced powders. Subsequent annealing of as‐milled powders restores martensitic transformation and magnetism, as well as it reverts the fcc into the original 5M structure. It is hence showcased that due to an allotropic transformation, brittle Heusler alloys are mechanically optimized for 3D printing without loss of their functional properties.

Facilitated Synthesis of Mg2Ni Based Composites with Attractive Hydrogen Sorption Properties.

Composites based on Mg2Ni with 5% activated carbon from apricot stones (ACAP) have been prepared by ball milling and subsequent annealing in hydrogen atmosphere. The purpose of the primary metal (Mg, Ni, and V) milling was to reduce the particle size and achieve a good contact between them, without forming intermetallic compounds. During hydriding/dehydriding at 300 °C the amount of the Mg2Ni phase progressively increased, and after 10 cycles about 50% Mg2(Ni,V) was achieved. The hydrogenation produced mainly Mg2NiH4, but small amounts of MgH2 and VHx were also detected in the powder mixture. Relatively high hydrogen storage capacity and fast hydriding/dehydriding kinetics of the Mg2.1Ni0.7V0.3—5 wt.% ACAP composite were determined both from hydrogen gas phase and electrochemically.

Effect of HfC addition on the microstructure and properties of W–4.9Ni–2.1Fe heavy alloys

In this study, W–4.9Ni–2.1Fe-xHfC mixed alloy powders were prepared by secondary high-energy ball milling and secondary hydrogen annealing, and then sintered and consolidated by spark plasma sintering (SPS) techniques. The microstructure, mechanical properties, wear resistance and corrosion behavior of alloy were obtained by Vickers hardness tester, X-ray diffraction, scanning electron microscopy, reciprocating frictional wear testing machine, CHI 660 E electrochemical workstation and electronic universal testing machine. The results showed that a certain amount of Hafnium carbide (HfC) could effectively inhibit the growth of W particles during sintering process, make the bonding phase disperse more evenly, and effectively improve the hardness, relative density, compression strength, friction and wear properties as well as corrosion resistance of alloy. When the content of HfC was excessive, the inhibition effect of particle growth would be weakened and the bonding phase tended to agglomerate, affecting the strength and hardness, and reducing the abrasion performance and corrosion resistance of alloy. By comparison, the alloy with 0.4 wt% HfC showed the best comprehension performance.

Investigation of Possible Uniaxial Anisotropy in Co11Zr2 Magnetic Phase

"The Co11Zr2 magnetic phase was obtained by a combination of melting, mechanical milling and high temperature annealing. The structure and magnetic properties of the obtained material were investigated. Even though the samples possessed low coercivity, it was shown that they possess uniaxial anisotropy. Keywords: hard magnetic materials, magnetic anisotropy, mechanical milling, high temperature annealing "

Short-route synthesis method of N-doped exfoliated graphite whit catalytic activity for the oxygen reduction reaction

AbstractWe report the synthesis of metal-free nitrogen-doped electrocatalysts obtained from graphite and urea as carbon and nitrogen precursor, respectively. High-energy milling and thermal annealing were carried out to obtain low cost electrocatalysts. Additionally, this method has shorter synthesis times, is environmentally friendly and use high-availability raw materials. A short-route synthesis consisted in the partial exfoliation of graphite by mechanical milling with urea. Afterwards, nitrogen was integrated into the exfoliated graphite lattice by thermal annealing at 500°C. XPS analyses shows up to 1.7 at. % was incorporated to the graphitic lattice. Scanning Electron Microscopy, X-ray diffraction and Raman Spectroscopy were used to analyse the morphology and structural features. The catalytic activity for the oxygen reduction reaction in basic media was evaluated by the rotating disk electrode technique.

Phase structure and magnetic properties of La/Ce substituted nanocomposite SmCo5/α-Fe magnets prepared by high energy ball milling and subsequent annealing

The phase structures and magnetic properties of isotropic nanocomposite permanent magnetic materials with the nominal composition of (Sm1-xRx)Co5 (x = 0, 0.25, 0.5, 0.75, 1; R = La, Ce) + 25 wt% α-Fe prepared by high-energy ball milling and subsequent annealing have been investigated systematically. It is found that the phase structure of La-doped nanocomposite magnets is quite different from that of the Ce- doped. The hard phase of Ce-doped nanocomposite magnet is 2:7 phase and unchangeable with increasing the Ce content and annealing temperatures (≤650 °C), while that of La-doped nanocomposite magnets undergoes a phase transition from 2:7 phase to 1:7 and 2:17 hard phases with increasing the La content and annealing temperatures. Both magnetic performance of La and Ce doped nanocomposite magnets shows a tendency to decrease as La or Ce content increases. The analysis of hysteresis loop reveals that both La and Ce doped nanocomposite magnets exhibit the strong ferromagnetic exchange coupling between hard and soft magnetic phases. Surprisingly, the magnetic performance of La-doped SmCo5/a-Fe is much superior to that of the Ce-doped although the Ce-doped Sm-Co hard phase has a relatively higher intrinsic magnetic property. The mechanism behind is found to be related to the change of Fe soft phase after adding La. Our results demonstrate that the substitution of Sm by La instead of Ce can produce the high-performance and low-cost SmCo5/a-Fe nanocomposite magnets. Our study is of significance to balance the utilization of the rare-earth resource.