Structural changes and enhanced accessibility of natural cellulose pretreated by mechanical activation

2013 ◽  
Vol 71 (2) ◽  
pp. 453-464 ◽  
Author(s):  
Huayu Hu ◽  
Yanjuan Zhang ◽  
Xiaoping Liu ◽  
Zuqiang Huang ◽  
Yanmeng Chen ◽  
...  
Keyword(s):  
Mechanical Activation ◽  
Structural Changes ◽  
Natural Cellulose

The Influence of Mechanical Activation of Fly Ash on the Toxic Metals Immobilization by Fly Ash-Based Geopolymers

2018 ◽  
Vol 761 ◽  
pp. 3-6 ◽  
Author(s):  
Violeta Nikolić ◽  
Miroslav Komljenović ◽  
Nataša Džunuzović ◽  
Tijana Ivanovic
Keyword(s):  
Fly Ash ◽  
Mechanical Activation ◽  
Toxic Metals ◽  
Structural Changes ◽  
Gas Adsorption ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Water Soluble ◽  
Alkali Activation ◽  
Alkali Activated

This paper investigates the influence of mechanical activation of fly ash on the toxic metals immobilization by fly ash-based geopolymers. Fly ash was firstly mechanically and then alkali-activated. Mechanical activation of fly ash was conducted in a planetary ball mill. Alkali activation of fly ash was carried out at room temperature by use of sodium silicate solution as an activator. Toxic metals (Pb and Cr) were added in the form of water soluble salts during the synthesis of geopolymers. The immobilization process was assessed via investigation of the mechanical and leaching properties of geopolymers. Structural changes of geopolymers during the toxic metals immobilization were assessed by means of gas adsorption and SEM analyses. Mechanical activation of fly ash led to a significant increase in geopolymer strength and to a reduced leaching of toxic metals from geopolymers.

scholarly journals Mechanical Activation of Ti-2B System: XRD Investigation of Structural Features

2016 ◽  
Vol 18 (2) ◽  
pp. 149 ◽  
Author(s):  
N.A. Kochetov ◽  
I.D. Kovalev
Keyword(s):  
Mechanical Activation ◽  
Structural Changes ◽  
Materials Science ◽  
Profile Analysis ◽  
Structural Condition ◽  
Structural Features ◽  
Temperature Combustion ◽  
Diffraction Peaks ◽  
Spontaneous Reaction ◽  
High Temperature Combustion

XRD investigation of Ti-2B system was carried out with the purpose of determining of structural changes in this system during mechanical activation. The size of coherentscattering region (CSR size) and kind II stresses (microstresses) were calculated by diffraction peaks profile analysis. It was determined that initiation of the synthesis reaction directly in mill is taking place at achievement the value of microstresses for titanium approximately equal to its yield point. Spontaneous reaction in a mill indicates that mechanical activation gives essential structural changes in Ti-2B system. So mechanical activation has essential influence on structural condition of Ti-2B system. Titanium diboride synthesized by high-temperature   combustion and by mechanosynthesis have approximately equal crystallites size. These results could clarify the processes of materials structural condition after mechanical activation and have a matter for materials science.

Мechanochemically synthesized nickel-containing aluminosilicate modifiers for tribotechnical aluminum alloys

2021 ◽  
Vol 4 ◽  
pp. 50-57
Author(s):  
S. A. Kovaleva ◽  
◽  
T. F. Grigoreva ◽  
P. A. Vitiaz ◽  
V. I. Zhornik ◽  
...  
Keyword(s):  
Mechanical Activation ◽  
Structural Changes ◽  
Primary Silicon ◽  
High Energy ◽  
Micro Hardness ◽  
Composite Powders ◽  
Oh Groups ◽  
Silicon Crystals ◽  
Nickel Composites ◽  
Wear And Corrosion Resistance

Silumins are promising antifriction alloys for the manufacture of friction units. They have a low density, high wear and corrosion resistance. However, they own low hardness and strength, which leads to the need to develop modifying and strengthening additives. Aluminosilicates have a density close to silumin and can be used for its strengthening, but they are characterized by low wettability by metals. To improve wettability, it is necessary to modify the aluminosilicates with metals. The aim of this work is to study the mechanochemical synthesis of aluminosilicate/Nickel composites and modification of silumin using them. Structural changes in powder mixtures of natural aluminosilicates with Nickel during high-energy mechanical processing in a planetary ball mill, as well as in alloys of the composition silumin + potassium fluoroborate and silumin + potassium fluoroborate + aluminosilicate/Nickel obtained by hot pressing of mechanoactivated powders, were studied using Fourier-infrared spectroscopy and x-ray diffraction analysis. It is shown that mechanical activation of a mixture of silumin + potassium fluoroborate powders leads to a redistribution of silicon during sintering with the formation of large primary silicon crystals and a decrease in micro hardness by ~ 20 %. Mechanical activation of aluminosilicates with Nickel leads to the formation of composite powders with the removal of OH groups and the formation of SiO2 framework structures. The use of such a modifier during sintering of the silumin alloy leads to the formation of a homogeneous fine structure of the alloy with the grinding of eutectic and primary silicon grains, which increases the micro hardness of the alloy by 1.5 times.

scholarly journals SYNTHESIS OF THE NANOCOMPOSITE BASED ON IMPACT DIAMONDS AND SILICON CARBIDE UNDER CONDITIONS OF HIGH PRESSURE AND TEMPERATURE

2020 ◽  
Vol 4 (53) ◽  
pp. 43-51
Author(s):  
Petr A. VITYAZ ◽  
◽  
Vladimir T. SENYUT ◽  
Viktor I. ZHORNIK ◽  
Igor V. VALKOVICH ◽  
...  
Keyword(s):  
Mechanical Activation ◽  
Structural Changes ◽  
Structure Type ◽  
High Pressure And Temperature ◽  
Fine Grained ◽  
Physicomechanical Characteristics ◽  
Hard Rocks ◽  
Fine Grained Structure ◽  
Preliminary Mechanical Activation ◽  
Nanocomposite Matrix

The article studies the structure, phase composition and physicomechanical characteristics of the nanocomposite based on impact diamonds. It is shown that the additions of a binder based on SiC and Si lead to reduction of the defectiveness of the nanocomposite and increase in the uniformity of its structure compared to the material without additives. Moreover, increase in the binder content also leads to the inversion of the structure type of the nanocomposite from polycrystalline to matrix. It is established that the addition of amorphous carbon black and boron affects the refinement of the nanocomposite matrix structure due to the formation of secondary finedispersed nanostructured SiC and boron carbide. Preliminary mechanical activation of the reaction mixture leads to structural changes in the synthesized material in comparison with the material obtained without the use of mechanical activation. In this case, the hardness of the samples obtained under comparable synthesis modes increases, which is associated both with the formation of a fine-grained structure of the material and with the phase transformation of lonsdaleite to diamond. An analysis of the microhardness and heat resistance of the obtained samples makes it possible to conclude that the achieved level of physicomechanical parameters of the diamond nanocomposite allows it to be used in a stone-processing tool for treating medium hard rocks.

Behavior of TiO2-B System under Mechanical Activation

2015 ◽  
Vol 1084 ◽  
pp. 7-10
Author(s):  
Dmitry G. Demyanyuk ◽  
Oleg Yu. Dolmatov ◽  
Dmitry S. Isachenko ◽  
Mikhail S. Kuznetsov ◽  
Andrew O. Semenov ◽  
...  
Keyword(s):  
Mechanical Activation ◽  
Contact Area ◽  
Structural Changes ◽  
Furnace Charge ◽  
Power Intensity ◽  
Micro Particles ◽  
Surface Contact ◽  
Surface Contact Area

The mechanical activation of the base mixture of TiO2-B was researched in terms of the structural changes leading to the formation of a mixture of micro particles whose volume increases with the increase of the power intensity of the mechanical activation of the furnace charge and it also increases the surface contact area of the components of the mixture participating in the synthesis. The limit of the mechanical activation of the researched system is 120g.

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