Solid-state Mixing Research Articles

Thresholds for igniting exothermic reactions in Al/Ni multilayers using pulses of electrical, mechanical, and thermal energy

We use pulses of electrical, mechanical, and thermal energy to determine the ignition thresholds of self-propagating reactions in Al/(Ni-7 V) and Al/Inconel multilayers. The energy density and power density required to initiate reactions in a Al/(Ni-7 V) foil with a 50 nm bilayer is compared for all three techniques to demonstrate the importance of heat loss on ignition thresholds and its dependence on the test volume and the surrounding thermal resistance. In addition, ignition is shown to occur at temperatures as low as 232 °C when heat losses are very small suggesting that ignition can be controlled by atomic mixing in the solid state. The experiments demonstrate that the ignition threshold drops with increasing ignition volume, and it rises with increasing bilayer spacing and with increasing intermixed thickness. These trends are also supported by an analytical model we derive to predict the effects of ignition volume, multilayer microstructure, and physical properties on the ignition threshold. We calculate an activation energy of 77.3 ± 1.3 kJ/mol for solid state mixing based on measured ignition temperatures.

Properties of Nanocomposites Based on Polyethylene (UHMWPE) and Carbon Nanotubes Mixed by High-Energy Ball Milling and UV-Source Irradiated

Nanocomposites, based on ultra high molecular weight polyethylene (UHMWPE) and multiwall carbon nanotubes (CNTs, 0.5 wt.%) were incorporated by solid-state dry mixing and then UV light irradiated. During these treatments, functional chemical groups were induced in both the components. Physical and mechanical tests were performed on the pristine UHMWPE as well as on the nanocomposite to evaluate their features. Experimental results highlighted that the nanocomposite exhibits higher viscosity, wear resistance, and conductivity than the pristine UHMWPE and the non-UV-irradiated nanocomposite. This suggested that the two functionalized components (CNTs and UHMWPE) interact.

SINTERING AND ELECTRICAL PROPERTIES IN AIR FOR A-SITE DEFICIENT (Sr0.7La0.3)1-yTiO3 PEROVSKITE SAMPLES WITH AND WITHOUT TiO2 PHASE

The sintering and electrical properties of A-site-deficient perovskites, namely, ( Sr 0.7 La 0.3)0.85 TiO 3 with TiO 2 and ( Sr 0.7 La 0.3)0.88 TiO 3 with a single perovskite phase, were investigated in air using powders synthesized by solid-state mixing. ( Sr 0.7 La 0.3)0.85 TiO 3 showed much higher sintering characteristics than ( Sr 0.7 La 0.3)0.88 TiO 3. The relative density of ( Sr 0.7 La 0.3)0.85 TiO 3 reached 96% at 1500 °C with zero holding time, but decreased with increasing holding time, owing to pore formation inside the sample. The resistivity of ( Sr 0.7 La 0.3)0.85 TiO 3 was lower than that of ( Sr 0.7 La 0.3)0.88 TiO 3 at measurement temperatures ≤600 °C, although the reverse was observed at temperatures ≥700 °C. Because the total resistivity of ( Sr , La ) TiO 3 perovskites should be governed primarily by grain boundary resistivity at low temperatures, ( Sr 0.7 La 0.3)0.88 TiO 3 with many grain boundaries showed higher resistivity, compared to that of ( Sr 0.7 La 0.3)0.85 TiO 3.

Improved Electrical Properties of BaTiO3 – coated CaCu3Ti4O12 Dielectrics

ABSTRACTWe report a significant improvement in the electrical properties of CaCu3Ti4O12 (CCTO) dielectrics by the BaTiO3 (BTO) additive. The addition of BTO to CCTO was performed using two different methods of a solid-state mixing and a sol-gel coating. Compared with pure CCTO ceramics (εr ∼ 52,000 and tanδ ∼ 0.38 at 100 kHz), BTO-added CCTO samples commonly showed a large improvement in the dielectric loss property although their dielectric constants were depressed around one order of magnitude; εr ∼ 5900 and tanδ ∼0.05 for 5 mol% BTO-coated CCTO sample and εr ∼ 4,075 and tanδ ∼ 0.02 for 5 mol% BTO-mixed CCTO sample. In addition, BTO-coated CCTO samples showed relatively lower leakage current than those of BTO-mixed CCTO samples, implying that the sol-gel coating is more effective for improving the electrical properties of CCTO.

Development of mixed conducting dense nickel/Ca-doped lanthanum zirconate cermet for gas separation application

La1.95Ca0.05Zr2O7-δ (LCZ) and Ni–LCZ cermet have been prepared by combustion synthesis and conventional solid state mixing methods respectively. Both the materials are sintered in air and controlled atmosphere (5% H2 in Ar). The density obtained for the material sintered at 1400°C in controlled atmosphere is found to be more than 99.5%. This sintering temperature (1400°C) is considered to be much lower compared to the conventional sintering temperature. The corresponding total conductivity for such Ni–LCZ cermet materials is ∼400S/cm measured at 750°C having 40vol% of Ni and 60vol% LCZ.

Amélioration de l’ostéointégration d’implants en titane recouverts d’hydroxyapatite et de nanotubes de carbone : étude in vivo

Ultra High Temperature Ceramic (UHTC) materials have attracted great interest for aerospace applications of hypersonic vehicles. They are subject to high aerodynamic forces and extreme heat fluxes where the surface temperature exceeds 2400 °C. The present work is first part of an experimental and numerical study of a new nanocomposite based on a ceramic matrix TiO2/MgO reinforced by Graphene Nano Platelets (GNP) or Carbone nanotubes (CNT). In the experimental part, the nanocomposite TiO2/MgO was elaborated by solid state mixing solutions, and the graphene oxides GO prepared by Hummers’s modified method, the obtained GO was reduced by Acid Ascorbic AA to achieved reduced graphene oxide rGO. On the other hand, the numerical part had been modelling two microstructures; the first is a ceramic composite reinforced by GNP, and the second is the same ceramic reinforced by CNT. Mori-Tanaka model is used as homogenization tool, with the multiscale representative volume element RVE approach. The goal of this work is to improve the stiffness and fracture toughness mechanisms by using nano particles. Wherein, the micromechanics models predict the mechanical performance of nanocomposites reinforced by aligned nano inclusion. The finite element model of composite is based on a Python code.

An investigation of X-ray luminosity versus crystalline powder granularity

At the High-throughput Discovery of Scintillator Materials Facility at Lawrence Berkeley National Laboratory, scintillators are synthesized by solid-state reaction or melt mixing, forming crystalline powders. These powders are formed in various granularity and the crystal grain size affects the apparent luminosity of the scintillator. To accurately predict a ?full-size? scintillator?s crystal luminosity, the crystal luminosity as a function of crystal granularity size has to be known. In this study, we examine Bi4Ge3O12 (BGO), Lu2SiO5:Ce (LSO), YAlO3:Ce (YAP:Ce), and CsBa2I5:Eu2+ (CBI) luminosities as a function of crystalline grain size. The highest luminosities were measured for 600- to 1000-?m crystal grain sizes for BGO and LSO, for 310- to 600-?m crystal grain sizes for CBI, and for crystal grains larger than 165?m for YAP:Ce. Crystal grains that were larger than 1 mm had a lower packing fraction, and smaller grains were affected by internal scattering. We measured a 34percent decrease in luminosity for BGO when decreasing from the 600- to 1000- ?m crystal grain size range down to the 20- to 36-?m range. The corresponding luminosity decrease for LSO was 44percent for the same grain size decrease. YAP:Ce exhibited a luminosity decrease of 47percent when the grain size decreased from the 165- to 310-?m crystal grains to the 20- to 36-?m range, and CBI exhibited a luminosity decrease of 98percent when the grain size decreased from the 310- to 600-?m crystal grain range to the 36- to 50-?m range. We were able to very accurately estimate full-size crystal luminosities from crystalline grains that are larger than 90 ?m.

ChemInform Abstract: Crystal to Crystal Transformations and Polymorphism in Anionic Hydrogen Bonding Networks Stabilized by Crown Ether Metal Complexes

AbstractReview: 79 refs.

A-Site and B-Site Non-stoichiometry and Sintering Characteristics of (Sr1−xLax)1−yTi1−zO3 Perovskites

The A-Site and B-Site non-stoichiometry and sintering characteristics of (Sr1−xLax)1−yTi1−zO3 perovskites were studied using samples prepared by solid-state mixing. A-Site or B-Site deficiency was observed for La-doped SrTiO3 perovskites, and this increased with increasing La content. For A-Site deficient (Sr1−xLax)1−yTiO3 perovskites, the cell volumes decreased although the reverse was observed for B-Site deficient (Sr1−xLax)Ti1−zO3 perovskites. This may be related to number of B-Site vacancies in the perovskites through charge compensation. It was found that A-Site and B-Site deficiencies increase the density of (Sr1−xLax)1−yTi1−zO3 perovskites. These characteristics may prove useful in the development of solid oxide fuel cell interconnect materials.

Fabrication of polypropylene/carbon nanotubes composites via a sequential process of (rotating solid-state mixing)- plus-(melt extrusion)

In this study, a simple but effective method to realize excellent comprehensive performances in polypropylene (PP)/multi-walled carbon nanotubes (MWNTs) was developed. Before melt extrusion, solid-state iPP powders and MWNTs were pre-mixed upon high-speed rotating. By this way, the dispersion extent of nanotubes was significantly improved as comparing to the common one-step melt extrusion strategy. As validated by scanning electron microscopy, most of MWNTs exist as a form of filament bundles with size of hundreds nanometers; no obvious agglomerate was found even at high MWNTs content, 5%. The improvements of the major mechanical properties and electric conductivity were much efficient for the composites obtained via the two-step process of rotating solid-state mixing (RSSM)- plus-melt extrusion. The tensile strength, Young’s modulus and impact strength at 5% MWNTs content were enhanced for 35%, 42% and 45%, respectively, indicating an excellent strength–rigidity–toughness balance, which was hardly achieved in polyolefin/carbon nanotubes composite. It is believed that the method developed in this study is so far the most effective and convenient for efficiently dispersing nanotubes into the nonpolar, intractable thermoplastics and resulting in good properties, among a variety of fabrication method suggested in the previous researches. Importantly, the used RSSM equipment is a kind of frequently used dispersion machine, thus it has tremendous potential to be applied in industrial producing immediately.

Fabrication and characterisation of Cr and Co doped Bi 1.5Zn 0.92Nb 1.5O 6.92 pyrochlores

Cr and Co doped Bi 1.5Zn 0.92Nb 1.5O 6.92 pyrochlore ceramics were produced by solid state mixing of oxides. Cr and Co were doped into the Nb and Nb–Zn sites considering the compositions of Bi 1.5Zn 0.92Nb 1.5− x Cr x O 6.92− x , (Bi 1.5Zn 0.46)(Zn 0.46−3 x/6 Nb 1.5−3 x/5 Cr x )O 6.92− x/2 for Cr doping and Bi 1.5Zn 0.92Nb 1.5−3 x/5 Co x O 6.92, (Bi 1.5Zn 0.46)(Zn 0.46−3 x/6 Nb 1.5−3 x/5 Co x )O 6.92− x/2 for Co doping. The solubility limit of Cr in BZN was higher than that of Co and the solubility limit increased when doping was made both into Nb and Zn sites. The second phases appeared when x > 0.2 for Cr and x > 0.15 for Co doping into the Nb–Zn sites. Simultaneous Cr doping into the Nb- and Zn-sites of BZN pyrochlore gave higher dielectric constant than doping into the Nb-site of pyrochlore. However, Co doping into the Nb- and Zn-sites and only into the Nb-site of BZN gave identical dielectric results in the range of 202–218. The temperature coefficient of dielectric constant decreased with Cr doping and increased with Co doping.

Spontaneous crystal growth of co-crystals: the contribution of particle size reduction and convection mixing of the co-formers

Previously reported methods for co-crystal synthesis have employed a variety of strategies and these include co-grinding, co-precipitation, growth from the solution, melt and slurry (M. Zaworotko, Polymorphism in Co-crystals and Pharmaceutical Co-crystals, XX Congress of the International Union of Crystallography, Florence, 2005) and spontaneous co-crystal formation without pre-milling activation (C. Maheshwari, J. Jayasankar, N. A. Khan, G. E. Amidon and N. Rodriguez-Hornedo, CrystEngComm, 2009, 11, 493–500). In this contribution the impact of particle size and pre-milling of the components on spontaneous co-crystal formation is described. This report builds on concepts outlined in a perspective by the authors on future developments in co-crystal formation (N. Blagden, D. J. Berry, A. Parkin, H. Javed, A. Ibrahim, P. T. Gavan, L. L. Dematos and C. C. Seaton, New. J. Chem., 2008, 32, 1659–1672) in this area. In particular, the opportunity for spontaneous co-crystal formation utilizing a solid component mixing process with a separate pre-milling step to activate the process is presented. Previously reported systems known to form co-crystals were examined, namely caffeine and urea as the model drug, and malonic acid and 2-methoxybenzamide (2-MB) as well-documented molecular complex formers. The synthesis approach adopted for this study involves pre-milling of the solid components to a particular particle size range and subsequent tracking of any co-crystal formation in a physical mixture during a solid-state convection mixing of the components. For both systems, three different size fractions (20–45 µm), (75–125 µm), and (180–250 µm) were examined. An assessment of transformation from component phase to molecular complex indicated that, typically, the co-crystals started to form after 30 min, as reflected in the evolution of co-crystal powder X-ray diffraction peaks with time. Notably, the rate of co-crystal formation rapidly increased for the smallest size fraction (20–45 µm). No buried eutectic or extensive amorphous intermediate phase was identified and this outcome suggests that the propensity for crystallization was associated with inter-particle contact and that this is linked to an increase in contact areas with decreasing particle size.

Crystal to crystal transformations and polymorphism in anionic hydrogen bonding networks stabilized by crown ether metal complexes

15-crown[5] or 18-crown[6] complexes of alkali, transition metal and ammonium cations together with polyprotic inorganic and organic anions have been used to construct crystalline molecular salts based on hydrogen bonded anionic networks. This new class of organic-inorganic complexes displays a variety of crystal-to-crystal transformations, mainly associated to the loss/uptake of water molecules and/or to the ionic reorganization accompanying phase transitions on varying the temperature. The dehydration and phase transition processes have been investigated by DSC, TGA and variable temperature X-ray powder diffraction. Most of the complexes described herein have been prepared by solid state mixing of the solid reactants.

Effect of 80-MeV nitrogen ion irradiation on ZnO nanoparticles: Mechanism of selective defect related radiative emission features

We report on the 80-MeV nitrogen ion irradiation on spherical ZnO nanoparticles fabricated by way of solid state mixing. The structural and compositional analyses of the as-synthesized ZnO nanoparticles were done by X-ray diffraction, electron microscopy and energy dispersive spectroscopy studies. As evident from the optical absorption spectra, the energetic ion irradiation, on the nanoparticle system, is governed by evolution of new characteristic absorption features owing to modification in the electronic states. Again, in the luminescence spectra, though the near band-edge emission was not observable for pristine ZnO, it was recovered (at ∼385 nm) upon irradiation. As far as the defect related emission is concerned, a competition between the formation and annihilation of different defects (especially, zinc vacancies and interstitials) at different ion fluences was realized. Correlating the luminescence spectra and the theoretical investigation, it can be understood that during irradiation the formation of zinc related defects are energetically favorable than the oxygen related counterparts. Exploration of defect related radiative features corresponding to definite structural organization/modification would help in making next generation light emitting and display devices, where a select emission response is desired.

Dielectric properties of Sm, Nd and Fe doped Bi 1.5Zn 0.92Nb 1.5O 6.92 pyrochlores

New pyrochlore ceramics have been produced by doping Sm and Nd into the Bi site and Fe into the Nb site in the Bi 1.5Zn 0.92Nb 1.5O 6.92 (BZN) pyrochlore. Doped pyrochlore ceramics were produced by conventional solid state mixing of oxides at different doping levels using the compositions of Bi 1.5− x Sm x Zn 0.92Nb 1.5O 6.92, Bi 1.5− x Nd x Zn 0.92Nb 1.5O 6.92 and Bi 1.5Zn 0.92Nb 1.5− x Fe x O 6.92− x . The solubility limit of cations was determined as x = 0.13, 0.18 and 0.15 for Sm, Nd and Fe, respectively. While Sm and Nd increased the dielectric constant ( ɛ), Fe doping led a decrease in ɛ. Dielectric constant of Sm and Nd doped BZN increased to 199 at x = 0.13 (Sm) and to 219 at x = 0.18 (Nd). At low Fe dopings ( x = 0.05), the dielectric constant of BZN increased to 242 but decreased to 211 at x = 0.15. The dielectric losses were lower for Sm and Nd dopings than Fe but in all cases it was lower than 0.006. The dielectric constant of Sm, Nd and Fe doped BZN ceramics was nearly independent of frequency within the frequency range between 1 kHz and 2 MHz, but decreased considerably with temperature between 20 and 200 °C. Temperature coefficient of Sm doped BZN (−354 ppm/°C) was lower than Nd and Fe doped BZN ceramics at solubility limits (−538 ppm/°C for Nd and −565 ppm/°C for Fe).

Partial oxidation of liquid hydrocarbons in the presence of oxygen-conducting supports: Effect of catalyst layer deposition

Ni-substituted barium hexaaluminate (BNHA) catalysts supported onto gadolinium-doped ceria (GDC), an oxygen-conductor, were prepared using two different methods: (1) conventional incipient wetness impregnation (IWI), in which a non-porous GDC support was impregnated in the conventional manner with aqueous precursors, then dried and calcined to form a supported hexaaluminate, and (2) solid-state mixing (SSM), in which solid hexaaluminate and GDC particles were mechanically ground together and thermally treated to produce a final catalyst. These catalysts were compared to bulk, unsupported BNHA; 3 wt% Ni/alumina; and 3 wt% Ni/GDC (the latter two prepared by conventional impregnation) for the partial oxidation (POX) of n-tetradecane. The reaction studies included examining the effect of 50 ppm S as dibenzothiophene (DBT) and 5 wt% 1-methylnaphthalene (MN) on the product yield under POX conditions. Temperature programmed oxidation (TPO) was used to characterize carbon formation in the reactor. The materials were characterized by BET, ICP-OES, XRD, and SEM/EDS prior to the reaction tests. Characterization of the two GDC-supported BNHA catalysts prior to the reaction studies indicated no significant differences in the bulk composition, surface area, and crystal structure. However, SEM images showed a larger amount of exposed GDC support surface area for the material prepared by IWI. Both of the GDC-supported BNHA materials demonstrated greatly reduced deactivation, with significantly reduced carbon formation compared to bulk BNHA. This was attributed to the oxygen-conducting property of the GDC, which reduced the rate of deactivation of the reaction sites by DBT and MN. The material prepared by IWI demonstrated more stable hydrogen and carbon monoxide yield than the material prepared by SSM. Although both catalysts deactivated in the presence of DBT and MN, the activity of the catalyst prepared by IWI recovered activity more quickly after the contaminants were removed. This material also maintained >50% of its initial hydrogen yield for more than 4 h after exposure to DBT and MN, while the hydrogen for the material prepared by SSM dropped to this same level within 2 h. Incipient wetness impregnation appears to provide a higher degree of interaction between the oxygen-conducting GDC support and the hexaaluminate, resulting in less rapid deactivation, which appears to be due primarily to carbon deposition.

Time resolved spectroscopic studies on some nanophosphors

Time resolved spectroscopy is an important tool for studying photophysical processes in phosphors. Present work investigates the steady state and time resolved photoluminescence (PL) spectroscopic characteristics of ZnS, ZnO and (Zn, Mg)O nanophosphors both in powder as well as thin film form. Photoluminescence (PL) of ZnS nanophosphors typically exhibit a purple/blue emission peak termed as self activated (SA) luminescence and emission at different wavelengths arising due to dopant impurities e.g. green emission for ZnS: Cu, orange emission for ZnS: Mn and red emission for ZnS: Eu. The lifetimes obtained from decay curves range from ns to ms level and suggest the radiative recombination path involving donor-acceptor pair recombination or internal electronic transitions of the impurity atom. A series of ZnMgO nanophosphor thin films with varied Zn: Mg ratios were prepared by chemical bath deposition. Photoluminescence (PL) excitation and emission spectra exhibit variations with changing Mg ratio. Luminescence lifetime as short as 10−10 s was observed for ZnO and ZnMgO (100: 10) nanophosphors. With increasing Mg ratio, PL decay shifts into microsecond range. ZnO and ZnMgO alloys up to 50% Mg were prepared as powder by solid state mixing and sintering at high temperature in reducing atmosphere. Time resolved decay of PL indicated lifetime in the microsecond time scale. The novelty of the work lies in clear experimental evidence of dopants (Cu, Mn, Eu and Mg) in the decay process and luminescence life times in II–VI semiconductor nanocrystals of ZnS and ZnO. For ZnS, blue self activated luminescence decays faster than Cu and Mn related emission. For undoped ZnO nanocrystals, PL decay is in the nanosecond range whereas with Mg doping the decay becomes much slower in the microsecond range.

Ferroelectric properties of Bi4−xCexTi3O12 (<x<4) thin film array fabricated from Bi2O3∕CeO2∕TiO2 multilayers using multitarget sputtering

We fabricated a ferroelectric Bi4−xCexTi3O12 thin film library by solid-state mixing of Bi2O3∕CeO2∕TiO2 multilayers using a multitarget rf magnetron sputtering equipped with an automated shutter. Polarization-electrical field and the structure are mapped as a function of Ce content (x) from 0 to 4. The remnant polarization decreases as Ce content increases, and at x⩾0.8, Bi4−xCexTi3O12 samples exhibit a paraelectric property due to the formation of impurity phases such as Bi2Ti2O7 and CeO2. Among the thin film samples of the library, Bi3.85Ce0.15Ti3O12 exhibited the largest remnant polarization of 13.0μC∕cm2.

Refertilization of Jurassic oceanic peridotites from the Tethys Ocean — Implications for the Re–Os systematics of the upper mantle

The influence of melt migration and solid state mixing of pyroxenites on Re–Os isotopic and major element systematics of oceanic mantle rocks have been studied in serpentinized spinel lherzolites and associated spinel and spinel–garnet pyroxenite layers from the Totalp ultramafic massif near Davos (eastern Swiss Alps). The ultramafic body originally was emplaced and serpentinized on the Jurassic Liguria–Piedmont ocean floor and was little modified during the Alpine orogeny. Field and petrographic observations indicate that refertilization of the peridotites occurred by migration of melt between abundant websterite layers and the peridotites, as well as by mechanical stretching and thinning of websterite layers down to the subcentimeter scale, thus producing fertile lherzolite compositions.Osmium concentrations in the peridotites are in the range observed for normal upper mantle peridotites, whereas Re concentrations in some peridotites are substantially higher than typical mantle values (up to 0.76 ppb). Initial Os isotopic compositions and Re/Os ratios in the peridotites range from subchondritic to suprachondritic (γOs (160 Ma) between −5.5 and +7.2). Re/Os, γOs (160 Ma) and Re concentrations correlate with fertility indicators such as Al2O3 and Na2O, suggesting limited influence of serpentinization on Re–Os systematics of the peridotites. These correlations extend beyond estimates for primitive upper mantle (PUM) compositions suggesting that depletion by partial melting cannot have been the only process producing the variations.The pyroxenites generally have higher Re (up to 3.2 ppb Re), but lower Os concentrations than lherzolites, and suprachondritic initial γOs (+9.0 to +497). Websterites with suprachondritic γOs (160 Ma) alternate with peridotites with chondritic or even subchondritic 187Os/188Os, indicating substantial small-scale Os isotopic heterogeneity. The combined petrographic observations and contrasting compositions of peridotites and pyroxenites indicate that the correlations of γOs (160 Ma) with fertility indicators reflect mixing of peridotites with a long-term depletion history and Re-enriched melts. The pyroxenites may represent residues of eclogites that melted during asthenospheric upwelling or could be cumulates which precipitated from asthenospheric melts.These data provide new evidence that the lower section of the suboceanic lithospheric mantle contains fertile components that are enriched in Re and radiogenic Os. Melt migration evidently does not completely homogenize small-scale Os isotopic heterogeneities in the lower lithosphere, thus accounting for the presence of old depleted peridotites in young oceanic lithospheric mantle.

Synthesis of Co–50Ni nanocrystals obtained by a modified polyol method

Solid solution Co–50Ni nanometric crystals were obtained by a modified polyol method, which mainly consists of a solid state mixing of PVP (polyvinylpirrolidone) with stoichiometric amounts of Ni(NO3)2·6H2O and Co(NO3)2·6H2O, followed by dissolution in ethylene glycol. Co–50Ni nanocrystals were characterized by X-ray diffraction and transmission electron microscopy (TEM). It was found that the lattice parameter of the solid solution nanomaterial was intermediate between pure Ni and pure Co. In addition, that spherical morphology of the nanocrystals shifted to elongated shapes when they were grown under the action of an electromagnetic field.