Wyniki wyszukiwania - BazTech

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Sieci metalo-organiczne jako multifunkcjonalne materiały przyszłości : mechanochemiczne podejście do syntezy

Jędrzejowski D.

Wiadomości Chemiczne

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2018

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[Z] 72, 9-10

645--666

EN

Metal-organic frameworks (MOFs) are a relatively new class of advanced inorganic-organic materials. Due to their modular structures and possible incorporation of various properties, that materials find more and more applications in many fields of science and industry. MOFs are coordination polymers, i.e. compounds with coordination bonds propagating infinitely in at least one dimension. Their characteristic feature is the presence of potential free spaces, i.e. pores. The free spaces often appear after proper activation, e.g. thermal activation. Other common properties of MOFs include for instance large specific surface areas and pore volumes, modifiable size and chemical environment of the pores, and network flexibility. All these properties result in the use of MOFs in e.g. selective sorption, separation or storage of gases, heterogeneous catalysis, design and fabrication of sensors, etc. During more than twenty years of the history of MOFs, many methods of their synthesis have been developed, including the most popular in solution at elevated temperatures (e.g. solvothermal method). Nevertheless, the activity of pro-ecological environments and the requirements set by international organizations encourage scientists to create new methods of synthesis, which, according to the guidelines presented by the 12 principles of green chemistry, will be safer, less aggressive, less toxic and less energy-consuming. One of the answers to meet these requirements is the use of mechanosynthesis. Mechanochemical synthesis relies on the supply of energy to a system by mechanical force, by grinding or milling. By combining or transforming solids in this way, the presence of a solvent, which is most often the main source of contamination and waste, can be minimised or completely excluded. Mechanical force is typically used for purposes other than MOF synthesis, e. g. catalyst grinding. Nevertheless, the use of mechanical force in synthesis is becoming more and more popular. The most important advantages of this approach, apart from its environmental impact, are very high efficiency (usually close to 100%) and drastically reduced reaction time. Of course, there are examples where these advantages are not observed. In such cases, mechanosynthetic modifications are introduced, such as e.g. addition of small amount of liquid (Liquid-Assisted Grinding) and/or a small addition of simple inorganic salt (Ion- and Liquid-Assisted Grinding). Furthermore, new instrument setups are being developed to monitor reaction mixtures in situ during mechanosynthesis, e.g. by use of such techniques as powder X-ray diffraction and Raman spectroscopy. This enables valuable insights into mechanisms and allows for mechanosynthesis optimization.

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X-ray diffraction and Mössbauer spectroscopy studies of a mechanosynthesized Fe75B25 alloy

Jartych E., Kubalova L. M., Fadeeva V. I.

Nukleonika

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2015

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Vol. 60, No. 1

43 --46

EN

In this work, the process of formation of metastable phases was investigated for the Fe75B25 composition. Mechanical synthesis was performed in a MAPF-2M high-energy planetary ball mill under an argon atmosphere. X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Mössbauer spectroscopy (MS) were applied to recognize the phases. After 6 h of milling, the material consisted of two phases, that is, metastable tetragonal t-Fe2B and amorphous phases. During further thermal processing, the metastable phase was transformed into the stable Fe2B phase.

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Próba wytworzenia kompozytu na osnowie Cu[sub]xAl[sub]y zbrojonego cząsteczkami Al2O3 przy pomocy procesu mechanosyntezy

Reguła T., Darłak P., Tchórz A., Lech-Grega M.

Prace Instytutu Odlewnictwa

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2010

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T. 50, z. 1

29-35

PL

W niniejszej publikacji przedstawiono próbę wykorzystania procesu mechanochemicznej syntezy do otrzymywania kompozytów na osnowie związków międzymetalicznych Cu-Al zbrojonych homogenicznie rozmieszczoną ceramiką AI2O3. W tym celu, wykorzystano wysokoenergetyczny młyn kulowy, w którym przeprowadzono reakcję redukcji malachitu Cu2(OH)2CO3, sproszkowanym metalicznym Al[sup]0. Otrzymane w ten sposób materiały poddano badaniom przy pomocy dyfrakcji rentgenowskiej XRD oraz mikroskopii SEM. Wykazano, że możliwe jest otrzymywanie kompozytu opartego na osnowie związku międzymetalicznego Cu9AI4 zbrojonego AI2O3, w skutek szeregu reakcji chemicznych indukowanych bodźcami mechanicznymi.

EN

The study describes the attempts to use a mechanochemical synthesis in the fabrication of composites based on Cu-Al intermetallic compounds reinforced with homogeneously distributed ceramic AI2O3 phase. For this purpose, a high-energy ball mill was used to obtain the reaction of malachite reduction Cu2(OH)2CO3 with powdered aluminium Al[sup]0. The aim was to produce, besides the (AI2O3) ceramic phase, intermetallic CuxAly phases. Thus obtained materials were subjected to examinations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been proved that it is possible to fabricate a composite based on the intermetallic Cu9AI4 compound reinforced with AI2O3, as a result of numerous chemical reactions induced by various stimuli of strictly mechanical nature.