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The family of compounds with formula [NH4][M(HCOO)(3)], with M a divalent D-metal, is characterized by porous frameworks hosting NH4+ cations exhibiting at low temperature a spontaneous ferroelectric polarization. The presence of magnetically active divalent metal determines the occurrence of anti-ferromagnetic ordering below 30 K opening the avenue for a rational formulation of a new class of multiferroic materials. We demonstrate that this intriguing class of compounds can be synthetized with a mechanochemical approach. This novel route of synthesis was applied to the series [NH4][M(HCOO)(3)] with M = Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ using as reactants ammonium formate and the corresponding di-hydrated metal formates. The milling duration of the process correlates with the thermal stability of the dihydrated metal formates indicating that the first step of the mechanosynthesis process is represented by the removal of water molecules. The characterizations of the final products indicate the presence of single phase [NH4][M(HCOO)(3)] compounds with an excellent degree of crystallinity. (C) 2021 Elsevier B.V. All rights reserved.

This work presents a comparative study on the HITPERM type alloy prepared by wet and dry mechanical alloying. The chosen composition for this study was Fe38.5Co38.5Nb7B15Cu1. The powders were obtained via mechanical alloying starting from elemental Fe, Co, Cu powders and the ferroalloys of Nb and B. Mechanical alloying experiments were done using a high energy planetary ball mill Pulverizette 6 under Ar atmosphere. It was observed that for the powder milled in wet milling conditions, using benzene as process control agent, the alloy amorphisation occurs after 40 h of milling. X-ray diffraction patterns highlighted the alloy amorphisation. In the dry milled powder case, the amorphisation did not occur even after 100 h of milling. The thermal stability and the crystallisation kinetics of the amorphous powders were investigated via differential scanning calorimetry and in-situ high-temperature X-ray diffraction. The powders morphology and chemical homogeneity were studied by scanning electron microscopy and X-ray microanalysis. The saturation magnetisation also reveals a difference between wet and dry milled powders versus milling time. The obtained results concerning the alloy amorphisation and its thermal stability are compared with available data of the literature.

Fe3O4/Ni3Fe composite powder has been synthetized, starting from Fe, NiO and α-Fe2O3 precursors via mechanosynthesis and annealing, varying the alloy/ferrite ratio. The formation of Fe3O4 is noticed for the composite with low alloy content in the case of the samples milled for 10 h. Formation of Ni3Fe and Fe3O4 does not fully occur after milling for 10 h, in either of the cases and as a consequence, the presence of several intermediate phases can be observed. Annealing at 500 °C for 4 h led to an incomplete reaction between the precursors for the un-milled sample. For the milled and subsequently annealed samples, the complete formation of the composite Fe3O4/Ni3Fe occurs at the milling time of 10 h. The DSC measurements reveal a decrease of the temperature required for the Fe3O4 complete formation upon increasing milling time. The first magnetisation curves reveal a decrease of the magnetisation upon increasing milling time. The value of magnetisation after annealing is higher than the magnetisation value of the milled samples as a result of the complete formation of the ferrite phase and Ni3Fe intermetallic compound.

High-quality samples, in terms of phase purity and dielectric properties, of composition BiSmFeO (0.05 ≤ x ≤ 0.20) have for the first time been prepared by mechanosynthesis. Close inspection of the powder diffraction data, analysis via Rietveld refinement and TEM microscopy demonstrates that the BiSmFeO samples contain only perovskite phases. Additionally, by a combination of Rietveld analysis, TEM, DSC, temperature-dependent XRD and permittivity data a tentative phase diagram has been proposed where the high temperature paraelectric phase Pnma has been confirmed for samarium substituted BiFeO. Regarding the physical properties, the samples resulted to be electrically homogenous and highly insulating at room temperature, suggesting that other sources of conductivity, such as mixed valence of Fe associated with possible oxygen non-stoichiometry, have been avoided during the samples synthesis. In spite of the high quality of the samples, the dielectric and magnetic behaviour of the BiSmFeO samples change only modestly on Sm substitution, with neither a great change in the resistivity or remnant magnetisation of Sm substituted samples in comparison with BiFeO.

Both, microcrystalline LiFeSi 2 O 6 pyroxene and nanoglassy LiFeSi 2 O 6 −based composite are prepared via non-conventional mechanochemical/thermal processing and one-step mechanosynthesis, respectively. The structural state of the as-prepared materials on the long-range and local atomic scales is characterized by XRD and 57 Fe Mossbauer spectroscopy, respectively. The derived hyperfine interaction parameters indicate that the nanoglassy nature of the mechanosynthesized LiFeSi 2 O 6 −based composite is characterized, on the short-range scale, by a broadly distorted geometry of the constituent structural units, and on the long-range scale, by the raptured chains of the edge-sharing FeO 6 octahedra and of the corner-sharing SiO 4 tetrahedra.

Special features of the solid-phase transformations of the composites Cu–fullerite and Cu–graphite in process of their mechanoactivation (MA) and further heating have been studied. It was stated that the form of carbon (fullerite, C60/70; graphite, Cg) and its structural state in the composition of mechanocomposites Cu–С60/70 and Cu–Cg cause a dramatic effect on the oxidation of Cu. At the initial stage of mechanosynthesis (MS) (up to 2 h) copper oxide Cu2O was formed in the Cu–С60/70 mixture. The reduction of this oxide was only possible upon the destruction of fullerene molecules, the necessary condition for which was the increase of mechanosynthesis time (more than 4 h) and heating in the range of 230–330 °С. No copper oxide was formed in the case of Cu–Cg.

X-ray analysis, Mossbauer and Raman spectroscopies have been used to study mechanosynthesized iron-fullerite powders with the initial fullerite С60/70 content of 10, 25 and 75 at%. The structural changes of С60/70 in mechanocomposites have been studied. It has been shown that in conditions of high-energy mechanosynthesis of iron-fullerite powders the disordering of fullerite С60/70 crystalline structure takes place followed by the total fullerene molecules destruction with the formation of amorphous carbon. At content 75–90 at% iron serves as a catalyst of С60/70 destruction. It has been stated that the phase composition of mechanocomposites depends on the amount of fullerite and its structural state. Carbides formation takes place only after the destruction of fullerene molecules as a result of C–C and C C bonds disrupture. Amorphous carbon, Сam, amorphous phase, Am(Fe–C), carbides, Fe3C, Fe7C3 and a paramagnetic P-phase can be the end products of solid-phase reactions. At the initial stage of Fe–75C60/70 mechanosynthesis, while fullerene structure is preserved, it is possible to obtain iron-fullerene composite. The kinetics of carbide formation in the samples has been analyzed. It has been shown that the speed of solid-phase reactions at С60/70 content 25 at% is higher than at 75 at%.

The mechanosynthesis of hexagonal rhenium carbide (Re2C) from the elements is explored as a function of the balls to powder ratio (BPR). Burgios's equation has been used to calculate the accumulated energy ( Δ E a c c u m ) and the transferred energy per hit ( Δ E b ). To get the complete mechanosynthesis of Re2C several conditions have to be met: BPR > 115:1, Δ E a c c u m > 500 k J g , and Δ E b > 2.656 × 10−14 kJ. The reaction is completed after 30 min of milling if a BPR of 230:1 is used. The pressure dependence of the unit-cell volume and the lattice parameters have been evaluated by synchrotron radiation diffraction using a diamond anvil cell up to 61(2) GPa. A fit of a 2nd-order Birch-Murnaghan equation of state results in a bulk modulus of B 0 = 374(3) GPa.

We present a comparative study of synthesis of M-type strontium hexaferrite from strontium and iron single oxides mechanically activated by high-energy ball milling for 5 h, and assisted by two different methods: (a) conventional heat treatment and (b) Spark Plasma Sintering (SPS), both at relative low temperatures ( ⩽ 900 °C). Although it was found that both methods promoted the complete structural transformation of precursors to Sr-hexaferrite phase (S.G. Pmc21) for temperatures above 700 °C, higher saturation magnetization was found for SPS samples. X-ray diffraction analysis revealed that the structural transformation undergoes formation of an intermediate metastable structure (Fe2Sr2O5) in both methods, but with slight different kinetics. Maximum specific magnetization of 67 emu/g at 18 kOe and coercivity of 3.7 kOe were recorded from powder mixtures milled for 5 h, which were subsequently SPS-ed at 700 °C. By contrast, although magnetization values for the same milled samples after being annealed at 700 °C slightly decreased, it leads to a significant increase in the coercive field reaching 5.4 kOe. These results are explained on the basis of factors such as the complete formation of hexaferrite and the attained density of consolidated powders, in addition to particle and grain sizes also reported.

Solid solutions of yttrium–gadolinium orthoferrites Gd x Y 1− x FeO 3 (0 ⩽ x ⩽ 1) were prepared by high-energy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe 2 O 3 , Y 2 O 3 and Gd 2 O 3 , mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm ) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd 0.75 Y 0.25 FeO 3 . For Gd 0.5 Y 0.5 FeO 3 , the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments.

Aluminium and magnesium were used in the M/ZrSiO4/B 2O3/C (M = Al, Mg) system to induce a mechanically induced self-sustaining reaction (MSR). Aluminium was not able to reduce the system to the desired products, and the system became amorphous after 10 h milling. However, nanocomposite powder of ZrB2-SiC-ZrC was in situ synthesized by the magnesiothermic reduction with an ignition time of approximately 6 min. The mechanism for the formation of the product in this system was determined by studying the relevant sub-reactions. © 2013 Elsevier B.V. All rights reserved.

Nanocrystalline Ti 0.9 Si 0.1 C has been prepared by ball-milling the elemental stoichiometric mixture of Ti, Si and graphite powders at room temperature under argon atmosphere. Microstructure characterization and quantitative estimation of different phases present in the unmilled and ball milled samples are done by analyzing the XRD patterns employing the Rietveld’s powder structure refinement method. The results reveal that formation of Ti 0.9 Si 0.1 C is initiated just after 44 min of milling and full formation of stoichiometric Ti 0.9 Si 0.1 C without any contamination is achieved within 3 h. To study the effect of ball milling on different microstructure parameters milling is continued up to 12 h which results in a reduction of particle size to ∼9 nm. Direct microstructure characterization of 12 h milled sample by HRTEM corroborates the structural and microstructural evolution by indirect method using XRD data.

Cataloged from PDF version of article. Ti-41Ni-9Cu shape memory alloy was synthesized by mechanical alloying of pure elemental Ti, Ni, and Cu powders using high-energy ball milling. The qualitative and quantitative phase analyses of the as-milled powders were done by X-ray diffraction (XRD) using Rietveld refinement and the alloys microstructure was studied by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Concerning the results, by milling evolution, the dissolution of the primary materials occurred at different rates and a considerable amount of the amorphous phase as well as B19′-martensite and B2-austenite was created. The formation of Ni solid solution was also evidenced prior to its dissolution. It was found that at sufficient milling time, the mechano-crystallization of the amorphous phase occurred and at the end of milling, the B19′-martensite is the dominant phase of the structure. © 2012 Elsevier B.V. All rights reserved

The embedding of metal nanoparticles into an insulating ceramic matrix can provide encapsulation and prevent their oxidation and agglomeration. A nanoembedment powder with the Fe nanoparticles embedded into Al 2 O 3 matrix is prepared by high-energy ball milling. Starting from the highly exothermic reactant mixture of magnetite and aluminum, Fe nanoparticles were in situ formed in Al 2 O 3 matrix by mechanochemical reaction. It is found that a post-reaction milling significantly narrows the size distribution of Fe nanoparticles. The mechanism for the two-stage milling process was proposed. The microwave permeability of nanoembedments exhibited a multiresonance behavior, which was the evidence for monodispersed Fe nanoparticles. The Fe@Al 2 O 3 nanoembedments are potential candidates as microwave absorber and left-handed materials.

The formation processes and properties of the Fe-NbC nanocomposite produced by magnetic pulse compaction of the powder mechanically synthesized from (82 at.%) Fe and (18 at.%) Nb in toluene have been studied. Mechanosynthesis results in the formation of the powder of a complicated phase composition. The phases are presented as an X-ray amorphous phase based on carbide and NbC. The powder compaction leads to the formation of the Fe + NbC + Fe 3 C nanocomposite with high microhardness of 12 GPа.

CaFe 2 O 4 nanopowders were prepared via single-step mechanochemical processing of two various mixtures of precursors: simple oxides (CaO and α-Fe 2 O 3 ) and elemental metal and oxide powders (Ca and α-Fe 2 O 3 ). The mechanically induced evolution of the CaO/α-Fe 2 O 3 and Ca/α-Fe 2 O 3 mixtures was followed by 57 Fe Mossbauer spectroscopy, XRD, and HR-TEM. The mechanosynthesis of CaFe 2 O 4 proceeds very rapidly if starting from the metal/oxide system; after only 1 h of the mechanochemical treatment performed at room temperature, the synthesis of the complex oxide is almost completed. This is in a strong contrast to the conventional solid-state synthesis of CaFe 2 O 4 , which requires prolonged exposure (∼20 h) at considerably elevated temperatures (∼1400 K). It was revealed that mechanosynthesised CaFe 2 O 4 nanoparticles with an average size of about 15 nm possess the core–shell structure consisting of an ordered inner core surrounded by a disordered surface shell with the thickness of about 1.9 nm. The main structural features of the surface shell of nanoparticles are distorted oxygen octahedra.

Nanocrystalline stoichiometric TiN powder has been prepared by ball-milling the α-Ti powder under N 2 gas at room temperature. The α-Ti phase is partially transformed to the transient β-Ti phase and TiN phase is noticed to form after 3 h of milling and nanocrystalline TiN phase is formed after 9 h of milling. Microstructure characterization of unmilled and ball-milled samples characterized primarily by X-ray diffraction employing the Rietveld structure refinement clearly reveals the presence of TiN phase and inclusion of nitrogen atoms in the α-Ti lattice in the way to formation of nitride phase. Transmission electron microscopy image confirms the presence of TiN phase and the size of TiN particles obtained from both XRD and TEM methods of characterization are very close in value (∼13 nm).

Magnetic and structural investigation of Fe 80 Zn 20 systems shows that various methods of mechanosynthesis result in fine structures with crystallite sizes between 20 and 100 nm. All the systems studied exhibit strong magnetic ordering with Curie temperatures between 870 and 1000 K. The coercive fields and magnetic energy losses are compared for various milling conditions.

Experimental results concerning the mechanosynthesis (MSY), of PbTe from the PbO–Te powder system, at room temperature an atmospheric conditions are reported. XRD results for samples milled for and after 5.4 ks only show PbTe diffraction peaks; neither Te nor PbO or any other solid phase were detected. Particle size and morphology, was followed by SEM observations. Phase evolution and quantification was monitored by Rietveld refinements of the X-ray diffraction data. It was found that the use of lead oxide as a component of the mechanosynthesis system reduces milling time with respect to the Pb–Te metallic system with mechanical alloying.

Al 2 O 3 –Mo nanocomposites were synthesized by ball milling of aluminum and molybdenum oxide powder mixtures. The structural evaluation of powder particles after different milling times was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and measurement of vial temperature. The molybdenum oxide and aluminum reaction appeared to occur through a rapid combustion reaction process. As a result, an alumina matrix nanocomposite containing molybdenum particulate was formed. In final stage of milling, Mo and alumina had a crystallite size of about 28 nm and 60 nm, respectively. After annealing at 800 °C for 60 min, Mo crystallite size remained constant. However, α-alumina crystallite size increased to 120 nm. After annealing a partial transformation of α-Al 2 O 3 into different polymorphic, γ-Al 2 O 3 with a crystallite size of 50 nm was observed.

In this paper, synthesis, structural, microstructural and magnetic properties of high-energy ball milled BiFeO3 and Bi0.95Eu0.05FeO3 powders were thoroughly investigated through X-ray diffraction, scanning electron microscopy, Mossbauer spectroscopy and magnetization measurements. Single-phased compounds were processed by using both mechanosynthesis and post-milling annealing. The set of results did not indicate considerable alterations in the magnetic ordering of the powders, even though their ordering temperature, magnetization and coercivity were highly sensitive to the narrow grain sizes distribution of nanograins and substituting Eu ion. In addition, we have shown that enhanced magnetic properties of BiFeO3 could be achieved by a low degree of Eu substitution, yet preserving the structural and microstructural characteristics of the processed powders.

Different approaches have been investigated to synthesize Al(Zn)–4Cu/Al2O3 composites by displacement reactions involving Al, ZnO and CuO. The reactions have been performed either by mechanosynthesis, exothermic dispersion or a combined mechanical and thermal activation process. Differential thermal analysis, X-ray diffraction and scanning electron microscopy have been used to study the various reaction mechanisms and transformations. High-energy ball milling of the powder modifies the reactivity of the system. A milling treatment not only reduces the reaction temperature, but can also induces a different reaction path. It is reported here that an appropriate mechanical–thermal treatment leads to the synthesis of an Al(Zn)–4Cu/Al2O3 composite. The hardness and wear resistance of the in situ composites increase with the milling time.

β-Mo 2 C and high temperature phase η-Mo 3 C 2 were mechanosynthesised by ball milling mixtures (MoO 3 + 2Al + x C) with different molar graphite contents ( x = 0.5, 1.0, 1.25, 1.5, 1.75, 2.0) at room temperature. The experimental results and thermodynamic calculations reveal that the mechanosynthesis reactions were mechanically induced self-propagating reaction (MSR). The effects of graphite content on the phase constitution of the resultants were discussed. The structure and thermal stability of the molybdenum carbides were also studied.

In this work, the mechanosynthesis of zinc ferrite in WC vials is studied. Millings are performed under air, with a planetary ball-milling, starting from elemental oxides α-Fe2O3 and ZnO. As-milled powders are structurally and magnetically characterized by X-ray diffraction and Mossbauer spectroscopy. Milling parameters as rotational speeds of main disc and vials are particularly discussed in terms of influence on the obtaining of a pure zinc ferrite phase. These parameters have a strong influence on injected power, on radial and tangential components of the impact force. Friction phenomenon, associated with injected power, have been found to be the governing parameters of the end product.

Lanthanum manganite doped with calcium, Ca 1/3 La 2/3 MnO 3− δ , was prepared by a high-energy ball milling. The precursors used were Mn 2 O 3 , La 2 O 3 and CaO, mixed in the stoichiometric ratio to obtain this manganite. The mechano-chemical process was performed at room temperature in a SPEX 8000D mixer/mill, using hardened steel balls and stainless steel vials, in air atmosphere. X-ray diffraction was used to elucidate the phase transformation as a function of the milling time. The Rietveld refinement was used in order to characterize structurally the manganites. The morphology and particle size of powder compound obtained were characterized by scanning electron microscope. The particle size of this powder material was measured with zeta size analyzer, and selected area electron diffraction (SAED) from TEM was used to elucidate the crystalline structure of this powder compound. The results showed that it is possible to obtain calcium doped lanthanum manganite by mechano-synthesis, using a weight ratio of ball to powder of 12:1, after 3 h of milling. The evolution of the phase transformation during the milling time is reported. Increases in milling time produce exponential decrease in the particle size, up to 680 nm after 1 h of milling. After the milling process it is obtained a powder compound with an orthorhombic structure (S.G. Pbnm ). A prolonged milling time (>9 h) produce an important reduction in the particle size but this is accompanied with a high iron contamination caused by metallic residues originated from vial and balls and also, after 9 h of milling time, it was found an important distortion in orthorhombic structure, obtaining two types of parameters.

In situ formation of nanostructured composite materials consisting of intermetallic phases and ceramic oxide starting from two different mixtures of Cu 2 (OH) 2 CO 3 or CuO with Al was performed. Composites were synthesized by high-energy ball milling in a laboratory planetary mill. Formation of Cu(Al) solid solution and Al 2 O 3 composite was followed by X-ray diffraction and thermal analysis of milling products.

A novel mechanochemical activation route was applied in order to obtain the Ba 2 ANb 5 O 15 (A = K, Na, Li) ferroelectric materials. The evolution of the 4BaO 2 :A 2 CO 3 :5Nb 2 O 5 powder mixtures during mechanical treatment and subsequent annealings, was followed by X-ray powder diffraction (XRD), thermal analysis and scanning electron microscopy (SEM). The sought bronze-type phases were mechanosynthesized after 48 h of treatment in a planetary mill. Very crystalline phases can be obtained with very important decreases in the temperatures and reaction times as compared with the traditional ceramic method. Dense ceramics were processed from mechanosynthesized precursors at relative low temperature, by a conventional-sintering route, and their dielectric properties characterized.

Nanometric particles of elemental tungsten can be produced by solid state room temperature reduction of tungsten (VI) oxide with magnesium metal. The reaction is driven by high-energy ball milling powder mixtures of WO 3 and Mg and involves a thermite route that allows for very short reaction times (as small as 8 min) under the proper milling conditions. The evolution of the reaction was followed as a function of time by X-ray diffraction, showing a gradual decrease in crystallite size of the reactant WO 3 , with formation of intermediate reaction products, until a near-instantaneous reaction takes place leaving only MgO and elemental W as final products. MgO was removed by leaching in diluted HCl and high purity tungsten (purity >99%) was obtained with a typical molar yield of 84%. The W powders are formed of impact welded aggregates of small particles of homogeneous dimension of about 70–100 nm, the typical crystallite size is 19 nm.

X-ray diffraction and Mossbauer spectroscopy were used to study the structure and hyperfine interactions in Fe 80 Mo 20 and Fe 50 Mo 50 prepared by mechanical alloying. Two solid solutions, i.e. Fe(Mo) and Mo(Fe) with b.c.c. lattice were formed during milling of Fe 80 Mo 20 . Mossbauer spectra revealed different magnetic arrangements in these solid solutions. In the case of Fe 50 Mo 50 no amorphisation was observed, as literature data suggest. During mechanosynthesis of Fe 50 Mo 50 a paramagnetic Mo(Fe) solid solution was probably formed.

Metal hydrides (TiH1.9, δ-ZrH1.66 and MgH2) have been synthesized by mechanical alloying of metal powders in a hydrogen atmosphere at room temperature. The milling process was monitored using H2 pressure measurement. The sharp decrease in H2 pressure during milling indicates a high rate of H2 absorption into the metal powders. X-ray diffraction analysis of as-milled powders shows convertion to hydrides at short milling times (less than 6 h). Decomposition of the so-formed metal hydrides has been observed during thermal analysis. The results indicate that pulverization and deformation processes occurring during high energy ball impacts play a major role in the hydriding reaction.

The composites mechanically synthesized in immiscible Cu–Bi system, consist of nano-sized particles of copper coated with the bismuth layer 2–3 nm thick. Such mechanocomposites provide an extremely large surface and stabilize this nano-state. The interaction of mechanocomposites Cu 10 wt.% Bi with liquid gallium–indium and gallium tin eutectics was studied. It was shown that the nano-sized composite provides unusually high reaction rates with liquid eutectic phases.