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Издательство СО РАН

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Новосибирск, Морской пр., 2




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Химия в интересах устойчивого развития

2007 год, номер 2

Mechanochemical Reduction of Sulphides for Nanocrystalline Metals Preparation

P. Balaz and E. Dutkova
Institute of Geotechnics, Slovak Academy of Sciences,
Watsonova 45, 043 53 Košice (Slovakia)
E-mail: balaz@saske.sk
Страницы: 127-131

Аннотация >>
The mechanochemical reduction of copper sulphide (Cu2S) and lead sulphide (PbS) with elemental Fe as well as reduction of copper sulphide (Cu2S) with silicon are studied. Metallic Cu and Pb are obtained due to the reducing power of iron and silicon, respectively. The obtained particles are characterized by XRD, VSM, SEM and TEM methods. While for Cu2S and PbS the reduction by iron is rather straightforward leading to Cu and Pb metals in 10-23 nm dimensions, the process of Cu2S reduction by silicon is more intricated. In this case the overall process proceeds via complicated mechanism with several overlapping steps. Phase transformations in copper sulphide phases, the formation of elemetal nanocopper with X-ray determined particle size of 23 nm and formation of ternary sulphide Cu8SiS6 with anomalous surface area values are the main products of the mechanochemical reaction.

Calculation of BCC phase diagram using the cluster-site approximation and first principle calculations

S. Bourki and M. Zereg
Theoretical Physics Laboratory, Department of Physics,
Faculty of Science University of Batna, Batna 05000 (Algeria)
E-mail: bourki-sabrina@univ-batna.dz
Страницы: 133-138

Аннотация >>
A combination of First Principle Calculations (FPC) and statistical thermodynamics, i.e., the Cluster-Site Approximation (CSA), is applied to describe the bcc-based Fe-Al phase diagram. The formation energies of ordered compounds are calculated using Full-Potential Linearised Augmented Plane Wave (FP-LAPW) results, and the entropy term is evaluated using the so-called modified Cluster Variation Method (CVM). The CSA model has been used to model the bcc bases in the Fe-Al system. The results obtained from this combination are compared with those obtained from the irregular tetrahedron approximation of the CVM, with the same FP-LAPW total energies.

Mechanochemical Treatment of Contaminated Marine Sediments for PAH Degradation

F. Cangialosi, G. Intini, L. Liberti, M. Notarnicola, T. Pastore and S. Sasso
Department of Environmental Engineering and Sustainable Development, Technical University of Bari, 8 v.le Turismo, 74100 Taranto (Italy)
E-mail: g.intini@poliba.it
Страницы: 139-145

Аннотация >>
Mechanochemical (MC) treatment for degrading recalcitrant harmful PAH compounds (namely, anthracene and benzo[a]pyrene) adsorbed on marine sediments was investigated in laboratory. Optimal operating conditions (i.e., mill rotation speed, milling time, milling-to-milled mass ratio), together with explanation of their physical effects on sediment particle size and specific surface area were assessed, leading to fast (30-60 min) and very effective (>98 %) degradation of both contaminants under the experimental conditions investigated. Attempts carried out through HPLC analysis and DTA checks before and after MC treatment permitted to envisage likely pathways for chemical reactions occurring during the process, yielding amorphous carbon as final product. Further research is planned to exclude the formation of noxious gaseous by-products.

Mechanochemical Treatment of Contaminated Marine Sediments for PCB Degradation

F. Cangialosi, G. Intini, L. Liberti, D. Lupo, M. Notarnicola and T. Pastore
Department Environmental Engineering and Sustainable Development, Technical University of Bari,
v.le Turismo 8, 74100 Taranto (Italy)
E-mail: f.cangialosi@poliba.it
Страницы: 147-156

Аннотация >>
Results of a laboratory investigation aimed at determining technical efficiency as well as kinetics of chemical degradation of PCBs contaminating marine sediments by mechanochemical treatment with NaBH4 are presented. Optimization of operating conditions allowed PCBs degradation to be achieved in very effective (>98 %) and fast (<30 min) manner. A kinetic approach to PCBs degradation accounting for variation of reaction rates for different PCB congeners was developed and a mathematical model useful for scaling-up MC treatment was convincingly achieved.

Mechanistic Aspects of Mechanically Induced Phase Transformations

F. Delogu1, G. Mulas2, S. Enzo2, L. Schiffini2 and G. Cocco2
1Dipartimento di Ingegneria Chimica e Materiali, University degli Studi di Cagliari,
Piazza d'Armi, I-09123 Cagliari (Italy)
E-mail: delogu@dicm.unica.it
2Dipartimento di Chimica, University degli Studi di Sassari,
Via Vienna 2, I-07100 Sassari (Italy)
Страницы: 157-162

Аннотация >>
In the field of mechanochemistry, the exact nature of the atomistic processes underlying physical and chemical transformations under mechanical processing conditions is a long-standing problem. Far from being satisfactorily solved, the lively debate associated has constantly stimulated the development of conceptual frameworks alternative to the defect-enhanced thermal diffusion scenarios initially proposed. Different approaches laying emphasis on the capability of mechanical forces to induce atomic scale mixing phenomena independent of thermal contribution were thus investigated. Along this line of inquiry, molecular dynamics simulations were here employed to gain deeper insight into the atomic-scale processes induced at the phase boundary between crystalline Ni and Zr metal lattices by the application of a shear stress. The numerical findings show that the application of shear stresses determines the deformation of the crystal and the formation of a sliding interface. Atoms with defective coordination appear at the interfacial region and gradually arrange into complex aggregates, the dynamics of which promotes the migration of atomic species and their gradual mixing near the interface. Chemical disordering processes take place at the interface, resulting in the formation of an amorphous domain.

Mechanochemical Synthesis and Li+ Ion Conductivity of Li3N-based Amorphous Solid Electrolytes

A. Hayashi, T. Ohtomo, F. Mizuno and M. Tatsumisago
Department of Applied Chemistry, Graduate School of Engineering,
Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)
E-mail: hayashi@chem.osakafu-u.ac.jp
Страницы: 163-167

Аннотация >>
Amorphous solid electrolytes were synthesized in the systems Li3N-P2S5 and Li3N-P via mechanochemical route. Amorphous materials were obtained at the compositions with x = 50 and 60 in the system
xLi3N×(100-x)P2S5 (mol. %), while crystalline Li2S was obviously formed at the compositions with x = 70 and 80. The conductivity increased with increasing Li3N content, and then decreased in the composition range x > 60. The highest conductivity of 2.2×10-5 S/cm at room temperature was achieved at the composition with x=60. The formation of insulative Li2S in the compositions with higher Li3N content is responsible for the decrease of conductivity. Li3N was reacted with P instead of P2S5 by milling in order to prevent the formation of Li2S. The obtained materials were basically amorphous, but partially included crystalline materials such as Li3P and Li7PN4. The 80Li3N×20P (mol. %) material exhibited the highest conductivity of 1.0×10-5 S/cm at room temperature in the system Li3N-P.

Influence of Activation Method of Sorbents on Their Properties

Š. Jakabsky1, M. Lovas1, S. Hredzak1 and F. MacaŠek2
1Institute of Geotechnics of the Slovak Academy of Sciences,
Watsonova 45, 043 53 Košice (Slovakia)
E-mail: jakabsky@saske.sk
2Department of Nuclear Chemistry, Faculty of Natural Sciences, Comenius University,
Mlynska dolina CH-1, Bratislava 842 15 (Slovakia)
Страницы: 169-173

Аннотация >>
The contribution describes chemical, physical and mineralogical properties of so-called Albanian (ore origin) leaching residuum from dumping ground of former Sered' Nickel Works (West Slovakia). The main mineral component of this residuum represents synthetic magnetite, which is known by its ability to sorb some substances. The changes in grain size and specific surface were studied as a function of grinding time and mill. The activation in ball mill during 25 min resulted in a two-fold increase in specific surface. Contrary to this fact, grinding in attritor led to a three-fold increase in specific surface already after 15min, i.e. from 1.31 to 3.86 m2/cm3.
For adsorption tests and following magnetic filtration the leaching residuum ground in the solution of K4Fe(CN)6 was applied. Obtained results point to the fact, that magnetic sorbent prepared in such a way and magnetic filtration enable substantial reduction of ion concentration of heavy metals such as copper, manganese and zinc.

Fabrication of Al-La-Ni-Fe Bulk Metallic Glasses by Spark-Plasma Sintering of Mechanically Alloyed Powders

J. S. Kim, O. T. H. Nguyen, P. P. Choi, J. C. Kim and Y. S. Kwon
Research Center for Machine Parts and Materials Processing, School of Materials Science
and Engineering, University of Ulsan, P. O. Box 18, Ulsan 680-749 (South Korea)
Страницы: 175-179

Аннотация >>
High-energy ball-milling in hexane medium was employed to prepare amorphous Al-La-Fe-Ni alloys of three different nominal compositions (Al82La10Ni4Fe4, Al85La9Ni3Fe3 and Al88La6Ni3Fe3). Using a planetary ball mill (AGO-2) at a rotational speed of 300 rpm, nearly complete amorphization could be achieved for the Al82La10Ni4Fe4 alloy after milling for 350 h. In contrast, the Al85La9Ni3Fe3 and Al88La6Ni3Fe3 samples remained crystalline to a certain extent even after prolonged milling and contained fcc Al crystallites. The glass forming ability was found to increase with decreasing Al and increasing La content, which can be ascribed to the enhanced atomic size mismatch of the constituents on La addition. Amorphous Al82La10Ni4Fe4 powder undergoes two-stage crystallization with onset temperatures at 640 and 700 K and glass transition at 566 K. Differences to DSC traces of previously studied melt-spun samples are believed to be mainly due to carbon impurity incorporation and compositional changes during milling. Taking into account the DSC data, consolidation of amorphous Al82La10Ni4Fe4 powder was attempted by means of spark-plasma sintering at a temperature of 613 K and applied pressures of 400 and 600 MPa. Compacts produced under these conditions were found to have relative densities of 80 and 96 %, respectively.

LiCoO2-Supported Catalysts for Hydrogen Generation from Sodium Borohydride Solution

O. V. Komova1, V. I. Simagina1, N. V. Kosova2, O. V. Netskina1, G. V. Odegova1, T. Yu. Samoilenko1, E. T. Devyatkina2 and A. V. Ishchenko1
1Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences,
Pr. Akademika Lavrentieva 5, Novosibirsk 630090 (Russia)
E-mail: komova@catalysis.nsc.ru
2Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences,
Ul. Kutateladze 18, Novosibirsk 630128 (Russia)
Страницы: 181-187

Аннотация >>
Effect of LiCoO2 support prepared by traditional ceramic and mechanochemical route on the activity of Rh and Pt catalysts in the reaction of NaBH4 hydrolysis was studied and compared with traditional supports, such as γ-Al2O3, TiO2 (anatase) and carbon (sibunit). Catalysts supported on LiCoO2 prepared using mechanical activation were found to have the highest catalytic activity. However, the endurance tests of 1 % Rh-LiCoO2 и 1 % Pt-LiCoO2 catalysts showed their gradual degradation. To understand the reason of this phenomenon, the interaction of LiCoO2 with NaBH4 solution was studied by XRD, FTIR, DRS and TEM.

Application of mechanochemistry-assisted treatment to aqueous extraction of isofraxidin from Acanthopanax senticosus

Y. Liu, Y. P. Xu and L. J. Jin
Department of Bioscience and Biotechnology, School of Environmental & Biological Science & Technology, Dalian University of Technology, Dalian 116023 (China)
E-mail: liuying6416@sina.com
Страницы: 189-195

Аннотация >>
Mechanochemistry-assisted treatment (MT) was applied for the first time to extract isofraxidin from Acanthopanax senticosus using water as solvent. Six extraction variables, i.e. solvent, Na2CO3 content, sample granularity, extraction time, liquid/solid ratio (ml/g), extraction temperature were investigated with respect to the yield of isofraxidin. The most favourable conditions were obtained by using superfine powered plant material (D95 of 47 mm) with Na2CO3 content of 0.5 mass %, extracted with water (liquid/solid ratio of 20:1, ml/g) for 3 min at 25 oC. The results obtained using the optimized conditions were compared to those with heat reflux extraction. MT extraction was found to increase the yield of isofraxidin considerably while excluding organic solvents and reducing both extraction time and temperature.

Formation of Cold and Detonation Sprayed Coatings from TiB2-Cu Nanocomposite Powders Produced by Mechanical Milling

O. I. Lomovsky1, D. V. Dudina1, V. Yu. Ulianitsky2, S. B. Zlobin2, V. F. Kosarev3, S. V. Klinkov3, M. A. Korchagin1, I. A. Rozhkov1, D.-H. Kwon4, J.-S. Kim4 and Y.-S. Kwon4
1Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences,
Ul. Kutateladze 18, Novosibirsk 630128 (Russia)
E-mail: dudina@solid.nsc.ru
2Lavrentyev Institute of Hydrodynamics, Siberian Branch of the Russian Academy of Sciences,
Pr. Akademika Lavrentieva 15, Novosibirsk 630090 (Russia)
3Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Sciences,
Ul. Institutskaya 4/1, Novosibirsk 630090 (Russia)
4Research Center for Machine Parts and Materials Processing, School of Materials Science and Engineering, University of Ulsan,
San-29 Moogu-2 Dong, Namgu, Ulsan 680-749 (South Korea)
Страницы: 197-201

Аннотация >>
Microstructure development of TiB2-Cu nanocomposite powders during cold and detonation spraying was investigated. The powders were produced by self-propagating high-temperature synthesis (SHS) followed by mechanical milling. A computer model was developed to calculate the temperatures during detonation spraying. The change in the nanostructure of the powders during spraying was studied: due to low temperatures in cold spraying the size of TiB2 particles in the coatings was well retained, in detonation sprayed coatings the growth of the particles was observed, the mode of spraying affecting the microstructure and the size of the particles.

Hydrogen in Mechanically Prepared Ti-h-BN Systems

O. S. Morozova1, T. I. Khomenko1, A. V. Leonov2, Ch. Borchers3, E. Z. Kurmaev4 and A. Moewes5
1Semenov Institute of Chemical Physics, Russian Academy of Sciences,
Ul. Kosygina 4, Moscow 119991 (Russia)
E-mail: om@polymer.chph.ras.ru
2Lomonosov Moscow State University,
Leninskiye Gory, Moscow GSP-2, 119992 (Russia)
3Institute for Material Physics, University of Goettingen,
Friedrich-Hund-Platz 1, Goettingen D-37077 (Germany)
4Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences,
Ul. S. Kovalevskoy 18, Yekaterinburg GSP-170, 620219 (Russia)
5Department of Physics and Engineering Physics, University of Saskatchewan,
Saskatoon (Canada)
Страницы: 203-211

Аннотация >>
The effect of BN addition on hydrogen uptake by Ti after and during mechanochemical activation under flow conditions was studied using kinetic, structural, microscopic and spectroscopic techniques. An addition of hexagonal BN significantly stimulated Ti-H2 interaction during and after the milling process. The hydrogen uptake temperature (Tmax) decreased from 960 to 590 K after mechanical treatment of Ti with h-BN in helium flow due to formation of porous BN matrix containing randomly distributed Ti nanofragments. No titanium surface or bulk modification by N (B) atoms was found. Contrary to this, new types of occupation sites available for hydrogen in Ti lattice were formed under the milling in H2/He flow. These centres responsible for a drastic reduction of H2 desorption temperature from 1000 to 670-610 K were attributed to the presence of interstitial N atoms. Similar effect on hydrogen distribution between the site types was observed for TiH2/h-BN as-milled system.

Methodological Aspects in the Study of Mechanochemical Processes

G. Mulas1, F. Delogu2, S. Enzo1, L. Schiffini1 and G. Cocco1
1Department of Chemistry, University of Sassari,
Via Vienna 2, I-07100 Sassari (Italy)
E-mail: mulas@uniss.it
2Department of Chemical Engineering and Materials Science, University of Cagliari,
Piazza d'Armi 1, 09123 Cagliari (Italy)
E-mail: delogu@dicm.unica.it
Страницы: 213-218

Аннотация >>
A methodological approach is presented to study gas-solid interactions under mechanochemical activation. Based on a detailed analysis of bulk microstructure, surface features control of milling energy parameters, the H2 sorption kinetics in Mg2Ni/Ni nanostructured powders was studied. Hydriding rate and specific parameters such as turnover frequency, mechanochemical gain and instantaneous yield were used to analyze the process on an absolute scale, to elucidate the reaction mechanism and highlight mechanochemical effects.

Mechanochemical Synthesis of Fast Lithium Ion Conducting Solid Electrolytes in the Li2S-P2S5-SiS2-Al2S3 System

Yu. Shibutani, F. Mizuno, A. Hayashi and M. Tatsumisago
Department of Applied Chemistry, Graduate School of Engineering,
Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)
Страницы: 219-223

Аннотация >>
Glassy solid electrolytes with higher Li2S content were mechanochemically prepared in the Li2S-P2S5 based multicomponent system, and showed high conductivity by the addition of glass formers SiS2 and Al2S3. The 78Li2S ×19.8P2S5×1.1SiS2×1.1Al2S3 (mol. %) glass exhibited the conductivity of 1.2×10-4 S/cm at room temperature, which was twice as high as the conductivity of the 78Li2S×19.8P2S5×2.2SiS2 glass without Al2S3. The glass ceramics obtained by crystallization of the glasses showed the same XRD patterns as superionic crystals called thio-LISICON II phase of Li4-xGe1-xPxS4, which is one of the best Li+ ion conducting crystals with very high conductivity over 10-3 S/cm at ambient temperature. The conductivity of the glass ceramic prepared by heating the glass at 230 oC was 1.2×10-3 S/cm, which was one order of magnitude higher than that of the corresponding glass. The precipitated thio-LISICON II analogs are responsible for the high conductivity of the glass ceramics.

Mechanochemical Synthesis of Belite Cements from Coal Fly Ash/Portlandite Mixture

N. Števulova1, M. Balintova1, J. Briancin2 and Z. Szeghyova3
1Department of Environmental Engineering, Faculty of Civil Engineering, Technical University of Košice, Vysokoškolska 4, Košice, 04120 (Slovakia)
E-mail: Nadezda.Stevulova@tuke.sk
2Institute of Geotechnics of the Slovak Academy of Sciences,
Watsonova 45, Košice, 04353 (Slovakia)
3Regional Public Health Authority,
Ipesska 1, Košice, 042 20 (Slovakia)
Страницы: 225-229

Аннотация >>
In this paper, the synthesis of the C2S cement by using reactive mixture containing fly ash (class F) from fluidized coal combustion and Ca(OH)2 (CaO/SiO2 ratio of 2) by mechanochemical treatment and subsequent heating is studied. Changes in structure and phase composition of milled and calcinated products of reactive mixture are compared with those of starting mixture. Two hours milling leads to mechanochemical decomposition of portlandite and to the structural and compositional metastability of mixture. The formation of the new compounds as C2S precursors (CSH and a-C2SH gels with low degree of ordering and a- and b-C2S nanocrystalline phases) was confirmed after 2 h milling by X-ray diffraction and infrared spectroscopy. Creation of a- and b-C2S and gehlenite in milled reactive mixture takes place at lower temperature (600oC) compared to non-milled starting mixture (1200oC). Mechanochemical synthesis in combination with thermal treatment offers opportunities for the increased utilization of coal fly ash as a basic raw material for belite production.

Preparation of Coatings by Mechanical Alloying

L. Takacs1 and ГЃ. Revesz1,2
1Department of Physics, University of Maryland,
Baltimore County, Baltimore, MD 21250 (USA)
E-mail: takacs@umbc.edu
2Department of General Physics, Eötvös University,
Budapest, H-1518, P.O.B. 32, Budapest (Hungary)
E-mail: reveszadam@ludens.elte.hu
Страницы: 231-235

Аннотация >>
Conventional mechanical alloying (MA) is used to process mixtures of powders and generates a product that is also in powder form. MA can also be adapted to the preparation of coatings. For example, if a plate is attached to the wall of the milling container, the impacts by the milling balls activate the surface of the plate, deliver particles from the powder charge and pound them onto or into the surface. The structure and properties of the coating depend on the milling conditions and the properties of the components. In this paper, some aspects essential to the preparation of coatings are discussed. In particular, the importance of the relative hardness of the components is demonstrated by comparing the deposition of aluminium on steel and nickel on aluminium. Mechanical deposition is a promising method that may be utilized to produce a variety of coatings, but its successful application requires detailed understanding and control of the process.

Mechanochemical Synthesis of Proton Conductive M3H(SO4)2 (M = Na, K, Rb) Crystals

T. Tezuka, Y. Yamashita, A. Hayashi, K. Tadanaga and M. Tatsumisago
Department of Applied Chemistry, Graduate School of Engineering,
Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)
E-mail: t-tezuka@chem.osakafu-u.ac.jp
Страницы: 237-241

Аннотация >>
M3H(SO4)2 (M = Na, K, Rb) crystals, which are known to undergo superprotonic phase transition in the case of M = K and Rb, were prepared via mechanochemical process from equimolar M2SO4 and MHSO4. The phase transitions of M3H(SO4)2 prepared by mechanical milling using a high energy ball mill apparatus were confirmed from DTA-TG and conductivity measurements, although the phase transition temperatures were slightly lower than that of M3H(SO4)2 prepared via solution process. The Rb3H(SO4)2 prepared by mechanical milling showed reproducible ionic conductivity of 1×10-3 S/cm at 230 oC under dry N2 atmosphere.

Synthesis of BiAO4 by Mechanochemical Solid State Reaction between Bi2O3 and A2O5 (A = V, P, Nb and Sb)

T. Tojo, Q.W. Zhang and F. Saito
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University,
Katahira 2-1-1, Aobaku, Sendai, 980-8577 (Japan)
E-mail: zhangqw@tagen.tohoku.ac.jp
Страницы: 243-247

Аннотация >>
Bismuth vanadate (BiVO4) can be synthesized by mechanochemical reaction between bismuth oxide (Bi2O3) and vanadium oxide (V2O5) by using a planetary ball mill at ambient temperature. The following solid state reaction takes place mechanochemically during the milling: Bi2O3 + V2O5 ® 2BiVO4. The particles of the sample look like agglomerates of fine grains with sizes less than 200 nm, and the agglomerates seem to be consisting of primary particles with several microns. The mechanochemical reaction ratio between Bi2O3 and V2O5 is saturated around 90 %. Heating treatment above 300oC leads to the formation of homogeneous BiVO4 with an increase in reaction ratio up to about 99.4 %. The mechanochemical method enables us to synthesize other bismuth complex oxides (BiAO4; A = P, Nb and Sb).

Mechanochemical Doping of a Non-Metal Element into Zinc Oxide

J. Wang, J. F. Lu, Q. W. Zhang, S. Yin, T. Sato and F. Saito
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University,
Katahira 2-1-1, Aobaku, Sendai, 980-8577 (Japan)
E-mail: zhangqw@tagen.tohoku.ac.jp
Страницы: 249-253

Аннотация >>
We developed a method for narrowing the band gap in an oxide powder such as ZnO by doping other components such as S (sulphur) and N (nitrogen). The method consists of grinding a mixture of ZnO powder and non-metal element in air, followed by heating the milled sample at 400 oC. The former enables us to cause mechanochemical reaction between the components, and the latter allows us to enhance the bonding strength, as well as to remove the unreacted starting samples away from the surface of the oxide particles. The temperature has to be chosen in the heating operation so as to avoid any decomposition of the doped sample. The detailed information on doping S and N into ZnO powder, as well as its photo-catalytic reactivity, is shown in this report.

Mechanochemical Synthesis of Cu-Al/Al2O3 Composite in CuO-Al System Under Different Conditions

K. Wieczorek-Ciurowa1, D. Oleszak2 and K. Gamrat1
1Cracow Universty of Technology, Institute of Inorganic Chemistry and Technology,
24, Warszawska, 31-155 Cracow (Poland)
E-mail: kwc@usk.pk.edu.pl
2Warsaw University of Technology, Institute of Materials Engineering,
141, Wo³oska, 02-507 Warsaw (Poland)
Страницы: 255-258

Аннотация >>
The objective of the present work was to show the beneficial effects of mechanochemical treatment of CuO-Al system for fabrication of composites consisting of Cu(Al) solid solution and Al2O3 ceramic with ultrafine grain microstructures. In particular, our research focused on explanation of the mechanism and kinetics of mechanochemically induced reactions in metal oxide-active metal system.

Study on the Formation of Nano Vacancy Ordered Phases by Mechanical Alloying

T. P. Yadav1, N. K. Mukhopadhyay2, R. S. Tiwari1 and O. N. Srivastava1
1Department of Physics, Banaras Hindu University,
Varanasi-221 005 (India)
2Department of Metallurgical Engineering, Banaras Hindu University,
Varanasi-221 005 (India)
Страницы: 259-264

Аннотация >>
In the present investigation, the powder mixture of Al (70 at. %), Ni (15 at. %) and Cu (15 at. %) was mechanically milled in an attritor ball mill for 10, 20, 40, 60, 80 and 100 h in hexane medium at 400 rpm. The isothermal annealing of 100 h mechanically milled powder was done at 700 oC for 20, 40 and 60 h. The powders were characterized using X-ray diffraction, differential thermal analysis and transmission electron microscopy techniques. It was observed that mechanical alloying led to the formation of nano vacancy ordered (t3) phase after 80 h of milling. In the case of 100 h mechanical milling (MM) and subsequent annealing at 700 oC for 20, 40 and 60 h, powder exhibited the formation of ordered and perfect t3 phase with larger grain sizes. The phase formation and transformations in the above systems were discussed.