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• Mechanosynthesis as new route to synthesize [NH4][M(HCOO) 3 ] compounds • Dehydration process of metal formate as first step of the synthesis • XRD and Raman spectroscopy indicate single phase product for all the compositions explored [Display omitted] The family of compounds with formula [NH 4 ][M(HCOO) 3 ], with M a divalent d -metal, is characterized by porous frameworks hosting NH 4 + cations exhibiting at low temperature a spontaneous ferroelectric polarization. The presence of magnetically active divalent metal determines the occurrence of antiferromagnetic 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 [NH 4 ][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 di-hydrated 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 [NH 4 ][M(HCOO) 3 ] compounds with an excellent degree of crystallinity. [ABSTRACT FROM AUTHOR]

Abstract: An efficient strategy for the mechanosynthesis of γ-nitro dicarbonyl esters has been developed. A CaCl2-catalyzed Michael reaction, conducted at room temperature, afforded nitroalkenes from malonates in a short reaction time and in high yields. In most cases, polymerized side-reactions are eliminated or minimized. [Copyright &y& Elsevier]

Abstract: The influence of zirconia content on the mechanosynthesis of fluorapatite–zirconia composite nanopowders was investigated. The structural features of the specimens with different amounts of monoclinic zirconia (0–20wt%) were examined after 5h of mechanical activation. Results indicated that the formation of fluorapatite–zirconia composite was strongly influenced by the zirconia content. In the presence of 5–10wt% monoclinic zirconia, fluorapatite–zirconia composite nanopowders were produced after 5h of milling. With increasing zirconia content to 20wt%, there was no trace of fluorapatite–zirconia composite. In the absence of zirconia, the average crystallite size, lattice strain and the volume fraction of grain boundary of fluorapatite were about 34nm, 0.469% and 8.38%, respectively. These values reached 24nm, 0.754% and 11.71% with the addition of 10wt% monoclinic zirconia. In the presence of 10wt% monoclinic zirconia, the fraction of crystalline phase considerably decreased after 5h of milling. Results revealed that the lattice parameter deviations were affected by the zirconia content. Based on SEM observations, no significant differences in the size distribution and morphology of the agglomerates were observed. [Copyright &y& Elsevier]

Abstract: This paper addresses the potential of mechanochemical activation of MgO and α-Fe2O3 precursor powders to obtain Fe2.3Mg0.7O4 ceramics with enhanced redox stability and electrical conductivity. X-ray diffraction (XRD) and Mössbauer spectroscopy suggest the initial formation of the spinel phase after 5h of high-energy milling in inert gas, but after 10h of mechanoactivation, the precursor still comprised hematite as a major phase with minor amounts of magnesiowustite as by-product. The activated mixtures can be nearly completely converted to spinel solid solution by heating to 1173K, whereas single-phase, dense spinel ceramics can be prepared by sintering at 1773K in inert atmosphere. These ceramics demonstrated redox stability under mildly reducing conditions (p(O2)∼10Pa), as confirmed by XRD, thermogravimetry and electrical measurements. The electrical conductivity of Fe2.3Mg0.7O4 at this oxygen partial pressure is lower compared to magnetite, but it is still as high as 60S/cm at 1073K and 15S/cm at room temperature. Cooling below 1473K in air results in a drop of conductivity due to segregation of hematite phase at the grain boundaries. However, the phase separation is kinetically stagnated at 1073K, and, after slight initial degradation, the retained electrical conductivity is more than 3 orders of magnitude higher compared to hematite and MgFe2O4 spinel. [Copyright &y& Elsevier]

The shock-induced structural and morphological transformations in petrurgical materials are studied. Synthetic minerals serve as an example of petrurgical materials. An analogy is drawn between shock metamorphism in nature and shock action on synthetic material. The data obtained make it possible to study shock action as a new kind of synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Complete solid-solution cermets based on titanium–tantalum carbonitride using a starting nominal composition with 80wt.% of (Ti0.8Ta0.2)(C0.5N0.5) and 20wt.% of Co were performed by pressure-less sintering at 1550°C for different times (from 0 to 180min) in an inert atmosphere. Chemical and phase analyses were conducted using X-ray diffraction (XRD), elemental analysis and energy dispersive X-ray spectrometry (EDX). The binder mean free path and the contiguity of the carbonitride particles were used to rationalise the microstructural effects of the mechanical behaviour. Mechanical characterisation included determining the Vickers hardness, the fracture toughness (conventional indentation microfractures, IM), the dynamic Young''s modulus (ultrasonic technique), the biaxial strength (ball on three ball) and a detailed fractographic examination. Finally, the experimental findings were combined with a theoretical fracture mechanics analysis to estimate the critical processing flaw sizes. Binder-less carbonitride clusters, pores and coarse carbonitride grains were the main defects observed and were responsible for the fractures. [Copyright &y& Elsevier]

Nanometric tungsten carbide for the formation of functional nanocomposite materials promising for making cutting tools and anodic electrodes is obtained by the methods of mechanosynthesis and mechanical activation. The structure formation of nanometric tungsten carbide is investigated and the interaction regularities in the metal-nonmetal system are investigated. [ABSTRACT FROM AUTHOR]

Rational synthesis of hydrogen-bonded organic frameworks (HOFs) with predicted structure has been a long-term challenge. Herein, by using the efficient, simple, low-cost, and scalable mechanosynthesis, we demonstrate that reticular chemistry is applicable to HOF assemblies based on building blocks with different geometry, connectivity, and functionality. The obtained crystalline HOFs show uniform nano-sized morphology, which is challenging or unachievable for conventional solution-based methods. Furthermore, the one-pot mechanosynthesis generated a series of Pd@HOF composites with noticeably different CO oxidation activities. In situ DRIFTS studies indicate that the most efficient composite, counterintuitively, shows the weakest CO affinity to Pd sites while the strongest CO affinity to HOF matrix, revealing the vital role of porous matrix to the catalytic performance. This work paves a new avenue for rational synthesis of HOF and HOF-based composites for broad application potential., (© 2022 Wiley-VCH GmbH.)

Mechanochemistry uses mechanical force to break, form, and manipulate chemical bonds to achieve functional transformations and syntheses. Over the last years, many innovative applications of mechanochemistry have been developed. Specifically for the synthesis and activation of carbon-rich π-conjugated materials, mechanochemistry offers reaction pathways that either are inaccessible with other stimuli, such as light and heat, or improve reaction yields, energy consumption, and substrate scope. Therefore, this review summarizes the recent advances in this research field combining the viewpoints of polymer and trituration mechanochemistry. The highlighted mechanochemical transformations include π-conjugated materials as optical force probes, the force-induced release of small dye molecules, and the mechanochemical synthesis of polyacetylene, carbon allotropes, and other π-conjugated materials., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Abstract: (Ti,Ta)(C,N) solid solution-based cermets with cobalt as the binder phase were synthesised by a two-step milling process. The titanium–tantalum carbonitride solid solution (the ceramic phase) was obtained via a mechanically induced self-sustaining reaction (MSR) process from stoichiometric elemental Ti, Ta, and graphite powder blends in a nitrogen atmosphere. Elemental Co (the binder phase) was added to the ceramic phase, and the mixture was homogenised by mechanical milling (MM). The powdered cermet was then sintered in a tubular furnace at temperatures ranging from 1400°C to 1600°C in an inert atmosphere. The chemical composition and microstructure of the sintered cermets were characterised as ceramic particles grown via a coalescence process and embedded in a complex (Ti,Ta)–Co intermetallic matrix. The absence of the typical core–rim microstructure was confirmed. [Copyright &y& Elsevier]

Abstract: The room temperature mechanosynthesis of La1−x Sr x Ga1−y−z Mg y Al z O3−δ nanopowders is successfully demonstrated for a broad compositional range (x ≤ 0.1; y ≤ 0.2, z ≤ 0.4) by resorting to a nearly amorphous alumina precursor with enhanced reactivity. It is shown that ceramics with one single phase and free from open porosity can be obtained by sintering these nanopowders at 1350–1450 °C. Microstructural data show that the substitution of Ga by Al hinders densification and decreases the grain size of ceramics. This is explained assuming the segregation of aluminum cations to the grain boundaries as a result of the decrease of the cationic diffusion coefficients. [Copyright &y& Elsevier]

Abstract: The aim of this work was to study the relationship between the crystalline structure, the mixed ionic–electronic conductivity and the calcium content in calcium-doped lanthanum manganites (CLM, La1−x Ca x MnO3) synthesized by reactive ball milling. Mechanosynthesis was employed to produce nanocrystalline CLM with varying calcium content (x =0–0.8 in increments of 0.1). Powders of Mn2O3, La2O3 and CaO mixed in the stoichiometric ratio were used as raw materials. The mechanosynthesis was carried out using a high-energy shaker mixer/mill. X-ray powder diffraction and Rietveld refinement were used to determine the crystalline structure as a function of calcium content. The four-point probe resistivity test was used to measure the electrical resistivity of the compacted and sintered powders using a DC milli-ohm meter. The results showed that the substitution of the La3+ ion by the Ca2+ ion during mechanosynthesis only changed the lattice parameters but not the orthorhombic Pnma structure. The mixed ionic–electronic conductivity increased with the Ca2+ content. The best conductivity was observed for the composition of La0.2Ca0.8MnO3. [Copyright &y& Elsevier]

Ferrites of composition MCoZnFeO with M = Cu, Mn and Ni were prepared by citrate complex method. Later, their composites with silica have also been obtained by a simple route. The citrate complex precursors of multielement ferrites were characterized by FTIR spectroscopy and thermal analysis, been found a similar behavior for the three systems. The thermal treatment (at 400, 600 and 800 °C) of precursors gives, as result, the spinel type cubic ferrite pure when the ions substituted were copper and nickel; when manganese was used an hematite phase was obtained as contaminant at 800 °C. The presence of all ions involved and the particle size was corroborated by EDX analysis and measured from a TEM micrograph, respectively. The magnetic parameters related to magnetic properties, magnetization and coercivity, were different depending of the chemical composition of the ferrite and the thermal treatment temperature, as it was expected. At room temperature, the values obtained were near to those reported for Co-ferrite in bulk. The synthesis route of the composites MCoZnFeO-SiO, proposed in this work, gives as result magnetic nanoparticles in an amorphous silica matrix. Their magnetic properties were depending on weight percentage of the magnetic phase in the composite. [ABSTRACT FROM AUTHOR]

Abstract: Mechanochemical methods have been demonstrated to be an effective means of synthesizing nanocrystalline high sensitivity piezoelectric low tolerance factor perovskites capable of providing enough material to carry out systematic studies on the processing of ceramics and on their properties. Here BiScO3–PbTiO3 is used as a model system of general BiMO3–PbTiO3 perovskite solid solutions with ferroelectric morphotropic phase boundaries and a high Curie temperature to describe mechanochemical effects on the properties of the ceramic materials. These effects are shown to be the consequence of perovskite crystalline strain accumulated during milling and of accidental doping from the medium, and cause no significant degradation of the electrical and piezoelectric properties of ceramics that are fully functional. The high temperature actuation characteristics of morphotropic phase boundary BiScO3–PbTiO3 ceramics are described for the first time. The room temperature response is highly linear, with an effective piezoelectric coefficient of 380pCN−1, and materials maintain the high piezoelectric response up to 400°C. Hysteresis and effective coefficients significantly increase at 300°C up to values above 1000pCN−1, which is shown to be associated with the onset of large extrinsic contributions. [Copyright &y& Elsevier]

Abstract: Chemical potential phase stability diagrams were calculated from relevant thermodynamic properties and used to predict the thermodynamic driving force under prospective conditions of room temperature mechanosynthesis. One analysed the dependence of chemical potential diagrams on temperature and partial pressure of evolving gases such as oxygen or carbon dioxide, as expected on using strontium peroxide or strontium carbonate as precursor reactants for the alkali earth component. Thermodynamic calculations were also obtained for changes in titania precursor reactants, including thermodynamic predictions for reactivity of strontium carbonate with amorphous titania. Experimental evidence showed that strontium titanate can be obtained by mechanosynthesis of strontium carbonate+anatase mixtures, due to previous amorphization under high energy milling. Ability to perform mechanosynthesis with less energetic milling depends on the suitable choice of alternative precursor reactants, which meet the thermodynamic requirements without previous amorphization; this was demonstrated by mechanosynthesis from anatase+strontium peroxide mixtures. [Copyright &y& Elsevier]

Abstract: In the present manuscript the authors have systematically investigated the composition and microstructure of a series of ternary nitrides (Ti x V1−x N y ) (0.0≤ x ≤1.0) prepared by mechanosynthesis, using XRD, SEM, EELS, XAS and TGA. The ternary titanium–vanadium nitride (Ti x V1−x N y ) has been obtained in all range of compositions by the mechanical treatment of the two metals under nitrogen pressure in a planetary mill with a maximum milling time of 3h and without any post-heating treatment. The materials’ microhardnesses were measured after sinterisation and compared to those reported in the literature for these types of materials. When compared with the previously reported data for bulk samples, these values are similar or higher for compositions within the range x =0.5 to x =0.77 (Ti x V1−x N). [Copyright &y& Elsevier]

The methods of X-ray diffraction analysis, Mögsbauer spectroscopy, and measurement of dynamic magnetic susceptibility have been used to study stationary phase states that develop at the later stages of mechanical alloying in a planetary ball mill. In the Fe(100 − x)C( x), Fe(75)C(25 − x)Si( x), and Fe(75 − x)C(25)Si( x) ( x ≤ 25) systems, the processes of phase formation are determined by the dynamic equilibrium between the crystalline and amorphous phases. Depending on the composition of the alloys, the conditions of this equilibrium are changed, which is reflected in the sets of the crystalline phases that are formed. [ABSTRACT FROM AUTHOR]

Abstract: High energetic milling of the corresponding oxides and carbonates mixture was employed to obtain highly dense ceramics with Ce0.80Sm0.20−x Ca x O1.9 (x =0, 0.02) compositions at low sintering temperature. After 17h of milling, the samarium and calcium have entered in the ceria fluorite-type structure, indicating that the mechanosynthesis of the material has occurred. Densities in the order of 97–98% were obtained at temperatures as low as 1250–1300°C in a single thermal treatment. Besides, the addition of Ca is shown as a clear aid to sinter high-density ceramics with improved grain size for the increase of the ionic conductivity. The high homogeneity of the mixture allows Ca not only to partially incorporate to the structure, but also to react to the glassy siliceous phase located at the grain boundary. This effective cleaning process, together with the additional grain growth promoted by Ca doping, increases the grain boundary conductivity, and thus, the total conductivity of the ceramics. The influence of the microstructure on the electrical properties of the ceramics is discussed. [Copyright &y& Elsevier]

In this article, we present the results of a solvent-free synthesis of iridium(0) nanoparticles, both water washed and unwashed. IrCl and NaBH, as starting materials, are mixed using an agate mortar and milled for 15 min until a black powder is obtained, which is heated in a nitrogen-controlled atmosphere oven at 200 °C for 2 h. If the product of the reaction is not washed before heating, NaBH and IrO impurities are observed. On the other hand, if the reaction product is washed before the heating, the obtained powder is free of impurities. We study the effect of the variation in reducing agent concentration and the annealing temperature used after the reaction. In all cases, the calculated particle size is less than 10 nm. [ABSTRACT FROM AUTHOR]

The synthesis of single phase tin-ferrite, SnFeO, from tin (II) oxide or stannous oxide (SnO), and hematite (α-FeO) solid precursors was carried out via high energy ball milling (HEBM) under wet condition involving the addition of controlled amounts of acetone. The stoichiometric amounts of the precursor materials were ball milled continuously for up to 22 h in a Spex-8000D mill using a ball-to-powder ratio of 40:1, with hardened stainless steel balls in WC-lined jars. The time-dependent formation of the SnFeO based on combined X-ray diffraction and room temperature Mössbauer spectroscopy (MS) measurements revealed reaction enhancements associated with particles size reduction. The 22 h milled material indicated that synthesized SnFeO had a particle size of 10.91 nm, coercivity of 4.44 mT, magnetic saturation/remanent ratio ( M/ M) of 0.085, while its superparamagnetic behavior was confirmed based on the combined MS and vibrating sample magnetometer measurements. [ABSTRACT FROM AUTHOR]

Piezoelectric oxides are currently being considered in combination with magnetic materials for the development of magnetoelectric composites, in which stress transfer across the interface is a key issue. In this context, we report here a detailed study of the mechanochemical activation processes of the ferroelectric perovskite BiScO-PbTiO and of the ferrimagnetic spinel NiFeO. Highly sinterable, single-phase nanopowders of both ferroic oxides are synthesised, and used for the preparation of high-density materials and two-phase composites by hot pressing. Emphasis is put on studying chemical reactions at and interdiffusion across the interface between the two phases using high spatial resolution techniques such as micro X-ray diffraction and piezoresponse force microscopy. The feasibility of preparing magnetoelectric composites by this approach is demonstrated, for which the necessity of controlling physicochemical processes at the interface is key to obtain functionality. [ABSTRACT FROM AUTHOR]

Abstract: Mechanochemical synthesis was used to prepare BaTa2O6 powders from BaCO3 and Ta2O5 precursors in a planetary ball mill. Effect of milling time and heat treatment temperature on the formation of BaTa2O6 and on the microstructure was investigated. Intensive milling of starting materials resulted in crystallization of BaTa2O6 even after 1h of milling time and single phase BaTa2O6 was obtained after 10h of milling under optimal conditions. The powder derived from 10h of mechanical activation had crystallite size of 22nm. But the increase in milling time did not decrease the crystallite size further. High energy milling activated the powders that although 1h of milling led to formation of single phase BaTa2O6 at 1200°C, this temperature decreased to 900°C after 5h of milling. No significant grain growth was observed when the milled powders were heat treated below 900°C. However, annealing at 1100 and 1200°C gave an average BaTa2O6 grain size of 180 and 650nm, respectively. An unidentified phase started to form at 1100°C increasing to high amounts at 1200°C and they had different shapes and sizes than BaTa2O6 grains. These elongated large grains were thought to be due to liquid phase formation caused by iron contamination. [Copyright &y& Elsevier]

Abstract: Multiferroic ceramics based on BiFeO3 and Sr-doped BiFeO3 have been processed by high energetic milling and later thermal treatments at reduced temperatures to synthesize the perovskite structure. Single phase materials are obtained at 800°C, reducing the temperature needed to complete the reaction in solid state method. Ceramics with densities higher than 94% were obtained at 1000°C, and up to 98% at 1050°C. All the ceramics were obtained in a single thermal treatment, where synthesis, grain growth and densification take place. The addition of Sr stabilizes the BiFeO3 perovskite structure, avoiding its decomposition. Ceramics with higher dielectric permittivity and conductivity than non-doped materials are obtained, due to the increase of the amount of oxygen vacancies. It is shown for the first time that the grain boundary conductivity is increased in BiFeO3 by doping with Sr. [Copyright &y& Elsevier]

Copyright of Superficies y Vacío is the property of Sociedad Mexicana de Ciencia y Tecnologia de Superficies y Materiales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Three different methods - melt quenching, twin rollers and mechanosynthesis - were used for preparation of the 50AgI·30Ag2O·20V2O5 glass – a good amorphous superionic conductor. It was demonstrated that physical properties of the final amorphous material depend to some extent on the preparation method. As-received samples were characterized by: X-ray diffractometry (XRD), differential scanning calorimetry (DSC), infrared absorption (FTIR), Raman scattering and impedance spectroscopy (IS) in a wide temperature range from -150 to 20°C. Main conclusion of the results of these studies is that substantially different synthetic routes can be used to produce amorphous materials of very similar but not identical properties. [Copyright &y& Elsevier]

Abstract: The work studies the effect of selected milling variables on mechanosynthesis of the materials formed in the AgI–Ag2O–WO3 system. These variables were: a rotation speed, a milling time, a ball-to-powder mass ratio, a process control agent and a level of preliminary grinding of the reactant powders. The mechanosynthesis was carried out using Fritsch Pulverisette 7 and Fritsch Pulverisette Premium Line planetary mills. The X-ray diffraction method was applied for phase identification in the final product and for determination of their relative contents. It has been found out that: the synthesis leads to amorphous products and its efficiency is enhanced when: i) rotation speed and milling time are increased, ii) ball-to-powder mass ratio decreased and iii) starting powders are pre-ground. When the substrates are milled too long or applied milling speed is too fast, exceeding 600rpm, then the process of amorphisation is impeded. The limit values of rotation speed and milling time are interrelated. Additionally they depend on the type of mill and applied mode of work. Preliminary grinding of the starting compounds enhances the milling efficiency. Addition of acetone, a control agent, to the milling batch reduces efficiency of production of amorphous phase. [Copyright &y& Elsevier]

Abstract: Composite ionic conductors for fuel cells were produced by combination of one ceria-based ceramic electrolyte and various mixtures of Na and Li carbonates, using several processing routes. These materials were characterized by impedance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy with attenuated total reflectance. The chemical composition of the mixed carbonates and the processing route were influential in the development of impressive conductivity levels (close to 0.1 S/cm) at modest temperatures (below 600 °C), suggesting a complex role of chemical composition (Na/Li ratio), phase composition (solid/liquid ratio), processing route (mechanothermal history) and microstructure. Furthermore, exposure to humidity showed formation of OH groups. Such hydrogenated species are believed to increase the complexity of the global surface processes and charge transport mechanisms where several native and foreign species may play a significant role. [Copyright &y& Elsevier]

composite material (CM) based on titanium carbosilicide with a titanium carbide content of 50% possessing a microcrystalline structure is obtained by mechanosynthesis in a planetary mill with subsequent hot pressing. The highly nonequilibrium structure of the powder material, which forms due to the high-energy treatment, makes it possible to obtain material with a relative density of 96% at a hot-pressing temperature of 1400°C and a pressure of 20 MPa. Comparative tests of the CM and silicon carbide for wear resistance under different conditions are carried out. The CM based on titanium carbosilicide showed less wear of the counterbody and a lower friction coefficient in all cases. However, in tests using an abrasive medium, wear of the composite material itself is observed. [ABSTRACT FROM AUTHOR]

Abstract: Complex ternary hydrides based in Mg and transition metals are very attractive materials for hydrogen and energy storage due to their large volumetric capacity, up to 150 kgH2/m3 in Mg2FeH6 and their high dissociation enthalpies. These compounds may be produced at room temperature by mechanical milling of the constituents in H2 atmosphere. This technique has also served to explore the synthesis of quaternary hydrides Mg2T1−zT’zHy, combining two transition metals to optimize the properties of the resulting hydride. In the present work we analyze the mechanical synthesis of the compounds Mg2Fe1−zCozHy (z = 0, ¼, ½, ¾, 1) by mechanical alloying at room temperature Mg–Fe–Co powder mixtures in adequate proportion, at 0.3 MPa H2. We follow the mechanosynthesis process trough the analysis of the hydrogen absorption kinetic curves. Samples obtained after a steady state was reached were characterized by X ray diffraction and Mössbauer spectroscopy. The different stages in the mechanosynthesis of these complex hydrides are discussed in terms of the composition and initial state of the powder mixture. [Copyright &y& Elsevier]

The combination of non-conventional methods of synthesis (mechanosynthesis) and sintering (SPS) has been used for the preparation of nanostructured BiScO3–PbTiO3 ceramics with tailored grain size. The key to control grain growth in the nanoscale is to achieve a significant densification during initial stages of the SPS, mainly by particle rearrangement under pressure, before thermally activated processes are triggered. The temperature dependence of dielectric permittivity suggests that the ferroelectric transition might have vanished for the material with the smallest grain size. [ABSTRACT FROM AUTHOR]

Abstract: Vanadium nitride (VN) has been prepared by mechanosynthesis from vanadium metal under a pressurized nitrogen atmosphere in a short milling time. The characterization of the final product by X-ray diffraction, scanning electron microscopy, electron energy loss (EELS), and X-ray absorption spectroscopy (XAS) is presented. The final product, VN with 96% of purity, is obtained at room temperature with nanometric particle size and a very high microhardness after sintering. A relationship between microstructure and microhardness as well as a comparison between the VN obtained mechanical and thermal method is also presented. [Copyright &y& Elsevier]

Copyright of Superficies y Vacío is the property of Sociedad Mexicana de Ciencia y Tecnologia de Superficies y Materiales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: The synthesis of saponites with Mg2+ as octahedral cation by using microwave radiation and their modification by mechanical grinding as a new way of synthesis of these materials were studied. The effect of time of irradiation during the microwave-assisted synthesis, and of the time of grinding during the further mechanical treatments was considered. Microwave radiation allowed obtaining saponites with structural formulae very close to the theoretical one and good ordering and properties employing short times of irradiation. Mechanical grinding induced the breakage of particles and the ordering of the layers, that is, smaller particles were formed, but they became much better oriented along the c direction than those existing in the as-synthesized saponites. [Copyright &y& Elsevier]

Abstract: Magnetic and structural investigation of Fe80Zn20 systems shows that various methods of mechanosynthesis result in fine structures with crystallite sizes between 20 and 100nm. All the systems studied exhibit strong magnetic ordering with Curie temperatures between 870 and 1000K. The coercive fields and magnetic energy losses are compared for various milling conditions. [Copyright &y& Elsevier]

Abstract: Ceramic precursors with LaGaO3 composition have been obtained by mechanosynthesis of a stoichiometric mixture of La2O3 and Ga2O3 after 34h of milling. Single and crystalline phase powders can be obtained at a temperature as low as 800°C; while by classical solid state reaction the La4Ga2O9 secondary phase still appears after calcination at 1200°C. The influence of the mechanosynthesis route on the sintering of the ceramics has also been studied. The reduction of the particle size by prolonged milling and the higher reactivity of the activated precursors cause a reduction of the maximum shrinkage rate temperature of 500°C with respect to the solid state reacted precursors. Despite these facts, it is found that the ceramics sintered from classically obtained precursors have similar densities at the optimum conditions as the ones obtained by mechanosynthesis, but with lower purity. Mechanical activation is shown as a good alternative to synthesize LaGaO3 based ceramics with Sr and Mg doping, which are candidates for electrolytes in solid oxide fuel cells (SOFC), but care with the sintering strategies must be taken into account to assure a high density of the ceramics. [Copyright &y& Elsevier]

Abstract: 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 5.4ks 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. [Copyright &y& Elsevier]

Abstract: The formation of perovskite nanopowders of the common proton-conducting, electrolyte material Ba(Zr1− x Y x )O3− δ is demonstrated by room temperature mechanosynthesis for the compositional range x=0, 0.058 and 0.148. This is achieved with a planetary ball mill at 650rpm in zirconia vials, starting from BaO2 with ZrO2, (ZrO2)0.97(Y2O3)0.03 or (ZrO2)0.92(Y2O3)0.08 precursors, respectively. Powder X-ray diffraction (XRD) reveals the formation of the perovskite phase in the early stages of milling with phase purity being achieved after milling times of 240min for composition x=0.058 whereas 420min is necessary for composition x=0.148. In contrast, traces of ZrO2 are apparent in composition x=0 even after milling times of 420min. The use of BaCO3 as precursor does not allow the formation of the perovskite phase for any composition. The perovskite crystallites are spherical in shape with an average size determined from XRD of ca. 30nm in agreement with transmission electron microscopy observations. FTIR spectra demonstrate that contamination levels of BaCO3 in the mechanosynthesized powders are very low. The spherical shape and nanoscale of the crystallites allow densification levels that are highly competitive when compared to BaZrO3-based materials formed by alternative synthesis techniques documented in the literature. [Copyright &y& Elsevier]

Abstract: The Fe x (Cr2O3)1−x system, with 0.10≤ X ≤0.80, was mechanically processed for 24h in a high-energy ball-mill. In order to examine the possible formation of iron–chromium oxides and alloys, the milled samples were, later, thermally annealed in inert (argon) and reducing (hydrogen) atmospheres. The as-milled and annealed products were characterized by X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy and magnetization. The as-milled samples showed the formation of an Fe1+Y Cr2−Y O4−δ nanostructured and disordered spinel phase, the α1-Fe(Cr) and α2-Cr(Fe) solid solutions and the presence of non-exhausted precursors. For the samples annealed in inert atmosphere, the chromite (FeCr2O4) formation and the recrystallization of the precursors were verified. The hydrogen treated samples revealed the reduction of the spinel phase, with the phase separation of the chromia phase and retention of the Fe–Cr solid solutions. All the samples, either as-milled or annealed, presented the magnetization versus applied field curves typical for superparamagnetic systems. [Copyright &y& Elsevier]

Abstract: xLiH+M composites, where M=Mg or Ti, are suggested as new candidates for negative electrode for Li-ion batteries. For this purpose, the xLiH+M electrode is prepared using the mechanochemical reaction: MH x + xLi→ xLiH+M or by simply grinding a xLiH+M mixture. The most promising electrochemical behaviour is obtained with the (2LiH+Mg) composite prepared via a mechanochemical reaction between MgH2 and metallic Li leading to a very divided composite in which Mg crystallites of 20nm size are embedded in a LiH matrix. Reversible capacities of 1064mAhg−1 (three times as much as the one of graphite) and 600mAhg−1 are reached for these phase mixtures after 1 and 28h of grinding in vertical and planetary mill, respectively. The (2LiH+Ti) mixture prepared via the mechanochemical reaction between TiH2 and Li exhibits a reversible capacity of 428mAhg−1. From X-ray diffraction measurements, the performances of the electrodes are attributed to the electrochemical conversion reaction: M+ xLiH↔MH x + xLi+ + xe− (M=Mg, Ti) followed for M=Mg by an alloying process where M reacts with lithium ions to form Mg1−x Li x alloys. [Copyright &y& Elsevier]

Abstract: Al2O3–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 28nm and 60nm, respectively. After annealing at 800°C for 60min, Mo crystallite size remained constant. However, α-alumina crystallite size increased to 120nm. After annealing a partial transformation of α-Al2O3 into different polymorphic, γ-Al2O3 with a crystallite size of 50nm was observed. [Copyright &y& Elsevier]

The technologies that are needed for the atomically precise fabrication of diamondoid nanorobots in macroscale quantities at low cost require the development of a new nanoscale manufacturing technology called positional diamondoid molecular manufacturing, enabling diamondoid nanofactories that can build nanorobots. Achieving this new technology will require the significant further development of four closely related technical capabilities: (1) diamond mechanosynthesis; (2) programmable positional assembly; (3) massively parallel positional assembly; and (4) nanomechanical design. The Nanofactory Collaboration is coordinating a combined experimental and theoretical effort involving direct collaboration among dozens of researchers at multiple institutions in four countries to explore the feasibility of positionally controlled mechanosynthesis of diamondoid structures using simple molecular feedstocks, which is the first step along a direct pathway to developing working nanofactories that can fabricate diamondoid medical nanorobots. [ABSTRACT FROM AUTHOR]

Abstract: Dense ceramics with La0.80Sr0.20Ga0.85Mg0.15O2.825 and La0.80Sr0.15Ga0.85Mg0.20O2.825 compositions have been prepared by sintering of mechanosynthesized precursors. The perovskite is synthesized after 85h of milling in a planetary mill. Single phases have been obtained at conditions that are not possible if traditional solid-state reaction (SSR) method is used. The influence of milling time and composition in the reactivity of the precursors is studied. Highest purity is obtained in Sr=0.15 and Mg=0.20 composition, with relative density higher than 97%. The total elimination of typical secondary phases for these compositions, as SrLaGaO4 and SrLaGa3O7, allows the total conductivity of the ceramics to be improved. The influence of the grain size and the nature of the grain boundaries on the electrical characteristic of the ceramics are also discussed. [Copyright &y& Elsevier]

Abstract: The feasibility of a novel homogeneous templated grain growth approach for the processing of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 ceramics is studied. Novelty rests on the use of a nanocrystalline powder synthesized by mechanochemical activation for the matrix, and also for obtaining the templates via conventional sintering. Templates are (100) faceted cube-shaped microcrystals with an average size of 12μm. The role of processing parameters such as the presence of PbO excess, and a hot-pressing step previous to the final thermal treatment is studied. Extensive growth of the templates and nearly full densification are demonstrated. The approach used here involves only conventional ceramic technology from a single source powder, and can be used as a means of obtaining larger crystals. [Copyright &y& Elsevier]

Abstract: The room temperature mechanosynthesis of La1− x Sr x Ga1− y Mg y O3− δ was demonstrated for a broad compositional range (x =0.05, y =0.10; x =0.20, y =0.20). This was achieved in atmospheric air with a planetary ball mill at 650 rpm in nylon containers rotating at 1300 rpm in the opposite direction. The maximum milling time was 360 min so that Zr contamination was kept below 0.25 mass%, as detected by ICP-AES. Powder X-ray diffraction revealed the formation of a perovskite phase since the early milling stages that becomes dominant in the patterns collected after milling for 360 min. The average crystallite diameter determined from XRD was ca. 30 nm, in good agreement with transmission electron microscopy observations. Ceramics with 93% of the theoretical density were obtained after sintering at 1300 °C. [Copyright &y& Elsevier]