Structural and thermodynamic properties of nanocrystalline fcc metals prepared by mechanical attrition

Nanocrystalline fcc metals have been synthesized by mechanical attrition. The crystal refinement and the development of the microstructure have been investigated in detail by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The deformation process causes a decrease of the grain size of the fcc metals to 6–22 nm for the different elements. The final grain size scales with the melting point and the bulk modulus of the respective metal: the higher the melting point and the bulk modulus, the smaller the final grain size of the powder. Thus, the ultimate grain size achievable by this technique is determined by the competition between the heavy mechanical deformation introduced during milling and the recovery behavior of the metal. X-ray diffraction and thermal analysis of the nanocrystalline powders reveal that the crystal size refinement is accompanied by an increase in atomic-level strain and in the mechanically stored enthalpy in comparison to the undeformed state. The excess stored enthalpies of 10–40% of the heat of fusion exceed by far the values known for conventional deformation processes. The contributions of the atomic-level strain and the excess enthalpy of the grain boundaries to the stored enthalpies are critically assessed. The kinetics of grain growth in the nanocrystalline fcc metals are investigated by thermal analysis. The activation energy for grain boundary migration is derived from a modified Kissinger analysis, and estimates of the grain boundary enthalpy are given.

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The Usefulness of X-ray Diffraction and Thermal Analysis to Study Dietary Supplements Containing Iron

Molecules ◽

10.3390/molecules27010197 ◽

2021 ◽

Vol 27 (1) ◽

pp. 197

Author(s):

Izabela Jendrzejewska ◽

Robert Musioł ◽

Tomasz Goryczka ◽

Ewa Pietrasik ◽

Joanna Klimontko ◽

...

Keyword(s):

Thermal Analysis ◽

Melting Point ◽

Dietary Supplements ◽

Polymorphic Form ◽

Food Supplements ◽

X Ray Diffraction ◽

Iron Compounds ◽

Scanning Calorimetry ◽

X Ray ◽

Amorphous Compounds

X-ray powder diffraction (XRPD) and thermal analysis (differential scanning calorimetry/derivative of thermogravimetry (DSC/DTG)) are solid-state techniques that can be successfully used to identify and quantify various chemical compounds in polycrystalline mixtures, such as dietary supplements or drugs. In this work, 31 dietary supplements available on the Polish market that contain iron compounds, namely iron gluconate, fumarate, bisglycinate, citrate and pyrophosphate, were evaluated. The aim of the work was to identify iron compounds declared by the manufacturer as food supplements and to try to verify compliance with the manufacturer’s claims. Studies performed by X-ray and thermal analysis confirmed that crystalline iron compounds (iron (II) gluconate, iron (II) fumarate), declared by the manufacturers, were present in the investigated dietary supplements. Iron (II) bisglycinate proved to be semi-crystalline. However, depending on the composition of the formulation, it was possible to identify this compound in the tested supplements. For amorphous iron compounds (iron (III) citrate and iron (III) pyrophosphate), the diffraction pattern does not have characteristic diffraction lines. Food supplements containing crystalline iron compounds have a melting point close to the melting point of pure iron compounds. The presence of excipients was found to affect the shapes and positions of the endothermic peaks significantly. Widening of endothermic peaks and changes in their position were observed, as well as exothermic peaks indicating crystallization of amorphous compounds. Weight loss was determined for all dietary supplements tested. Analysis of the DTG curves showed that the thermal decomposition of most food supplements takes place in several steps. The results obtained by a combination of both simple, relatively fast and reliable XRPD and DSC/DTG methods are helpful in determining phase composition, pharmaceutical abnormalities or by detecting the presence of the correct polymorphic form.

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Synthesis And Characterization Of Ball-Milled Nanocrystalline Fcc Metals

MRS Proceedings ◽

10.1557/proc-238-745 ◽

1991 ◽

Vol 238 ◽

Cited By ~ 4

Author(s):

J. Eckert ◽

J. C. Holzer ◽

C. E. Krill ◽

W. L. Johnson

Keyword(s):

Grain Size ◽

Melting Point ◽

Grain Boundary ◽

Bulk Modulus ◽

Ball Milling ◽

Lattice Strain ◽

Boundary Migration ◽

General Relation ◽

Heat Of Fusion ◽

Scanning Calorimetry

ABSTRACTNanocrystalline fee metals (Al, Cu, Ni, Pd, Rh, Ir) have been prepared by ball milling. The development of the microstructure is investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The final grain sizes range from 6 to 22 nm and scale with the melting point and the bulk modulus of the elements: metals with higher melting point and bulk modulus have a smaller final grain size. From this a general relation between the deformation mechanism during ball milling and the ultimate grain size achievable by this technique is inferred. With decreasing grain size the lattice strain is enhanced and deformation enthalpies of up to 40 % of the heat of fusion are stored in the material. The contributions of the lattice strain and of die excess enthalpy of the grain boundaries to the stored enthalpies are critically assessed. The kinetics of grain growth are investigated by mermal analysis. The activation energy for grain boundary migration is derived from a modified Kissinger analysis and estimates of the grain boundary enthalpy are given.

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Properties of Nanocrystalline Aluminium Fabricated by Warm-Vacuum-Compaction Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.299-300.82 ◽

2011 ◽

Vol 299-300 ◽

pp. 82-85

Author(s):

Wei Liu ◽

Qiong Hua Zhou

Keyword(s):

Grain Size ◽

Melting Point ◽

Thermogravimetric Analysis ◽

Bulk Material ◽

Coarse Grained ◽

X Ray Diffraction ◽

X Ray ◽

Microhardness Test ◽

Average Grain Size ◽

Compaction Method

Nanocrystalline aluminium bulk material with average grain size of 25.2 nm was prepared by warm-vacuum-compaction method. The as-prepared nanocrystalline aluminium was characterized by X-ray diffraction (XRD), differential scanning calarmeutry analysis (DSC), thermogravimetric analysis (TG), and Microhardness test, respectively. The experimental results show that the average grain size and microstrain of the nanocrystalline aluminium are 25.2 nm and 0.018%, respectively. The melting point of as-prepared nanocrystalline aluminium is 918.9 K, which is lower than that of coarse-grained aluminium by 14 K. The endothermic value of nanocrystalline aluminium is 196.3J/g. The average microhardness of the as-prepared nanocrystalline aluminium is 1.65 GPa, which is 11 times higher than that of coarse-grained aluminium.

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Formation of Nanocrystalline SiC Powder from Chlorine-Containing Polycarbosilane Precursors

MRS Proceedings ◽

10.1557/proc-581-205 ◽

1999 ◽

Vol 581 ◽

Cited By ~ 1

Author(s):

Brian S. Mitchell ◽

Haoyue Zhang ◽

Martin Ade ◽

Dirk Kurtenbach ◽

Eberhard Müller

Keyword(s):

Mass Spectrometry ◽

Thermal Analysis ◽

Grain Size ◽

Differential Thermal Analysis ◽

Size Range ◽

Random Network ◽

X Ray Diffraction ◽

X Ray ◽

Sic Particulates ◽

20 Nm

ABSTRACTNanocrystalline β-SiC particulates with a grain size range of 5-20 nm were prepared by heating a pre-pyrolyzed, chlorine-containing polysilane/polycarbosilane (PS/PCS) to 1600°C. The transformation from the pre-pyrolyzed PS/PCS to nanocrystalline SiC was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), mass-spectrometry and infrared spectroscopy. The results indicated that the nanocrystalline P-SiC was formed by the crystallization of the PS/PCS random network, and crosslinking of Si-Si, Si-Cl, and Si-CH2-Si bonds. The TEM observation showed that SiC particulates consist of equiaxed, randomly oriented, ultrafine grains.

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PENINGKATAN LAJU DISOLUSI ACYCLOVIR DENGAN METODE SISTEM DISPERSI PADAT MENGGUNAKAN POLOXAMER 188

SCIENTIA : Jurnal Farmasi dan Kesehatan ◽

10.36434/scientia.v5i1.61 ◽

2016 ◽

Vol 5 (1) ◽

pp. 6

Author(s):

Budi Setiawan ◽

Erizal Zaini ◽

Salman Umar

Keyword(s):

Electron Microscopy ◽

Thermal Analysis ◽

Scanning Electron Microscopy ◽

Fourier Transform ◽

Differential Thermal Analysis ◽

Fourier Transform Infrared ◽

X Ray Diffraction ◽

Poloxamer 188 ◽

X Ray ◽

Scanning Electron

Sebuah penelitian tentang sistem dispersi padat dari asiklovir dengan poloxamer 188 telah dilakukan formulasi dengan pencampuran secara fisika dengan rasio 1 : 1, 1 : 3, 1 : 5 dan dispersi padat 1 : 1, 1 : 3, 1 : 5 dan penggilingan 1:1 sebagai pembanding. Dispersi padat dibuat menggunakan metode pencairan (fusi), yang digabung dengan poloxamer 188 pada hotplate kemudian asiklovir dimasukkan ke dalam hasil poloxamer 188 lalu di kocok hingga membentuk masa homogen. Semua formula yang terbentuk termasuk asiklovir poloxamer 188 murni dianalisis karakterisasinya dengan Differential Thermal Analysis (DTA), X-ray Diffraction, Scanning Electron Microscopy (SEM), dan Fourier Transform Infrared (FTIR), kemudian pengambilan dilakukan (penentuan kadar) mengunakan spektrofotometer UV pada panjang gelombang 257,08 nm dan uji laju disolusi dengan aquadest bebas CO2 menggunakan metode dayung. Hasil pengambilan (penentuan kadar) menunjukkan bahwa semua formula memenuhi persyaratan farmakope Amerika edisi 30 dan farmakope Indonesia edisi 4 yaitu 95-110%. Sedangkan hasil uji laju disolusi untuk campuran fisik 1: 1, dan dispersi padat 1: 1, dan penggilingan 1: 1 menunjukkan peningkatan yang nyata dibandingkan asiklovir murni. Hal ini juga dapat dilihat dari hasil perhitungan statistik menggunakan analisis varian satu arah SPSS 17.

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Struvite Grown in Gel, Its Crystal Structure at 90 K and Thermoanalytical Study

Crystals ◽

10.3390/cryst9020089 ◽

2019 ◽

Vol 9 (2) ◽

pp. 89 ◽

Cited By ~ 3

Author(s):

Jolanta Prywer ◽

Lesław Sieroń ◽

Agnieszka Czylkowska

Keyword(s):

Thermal Analysis ◽

Sodium Metasilicate ◽

X Ray Diffraction ◽

Gel Growth ◽

Growth Technique ◽

Thermoanalytical Study ◽

X Ray ◽

Cell Parameters ◽

Thermal Analysis Techniques ◽

Derivative Thermogravimetry

In this article, we report the crystallization of struvite in sodium metasilicate gel by single diffusion gel growth technique. The obtained crystals have a very rich morphology displaying 18 faces. In this study, the habit and morphology of the obtained struvite crystals are analyzed. The crystals were examined and identified as pure struvite by single X-ray diffraction (XRD). The orthorhombic polar noncentrosymmetric space group Pmn21 was identified. The structure of the crystal was determined at a temperature of 90 K. Our research indicates a lack of polymorphism, resulting from the temperature lowering to 90 K, which has not been previously reported. The determined unit cell parameters are as follows a = 6.9650(2) Å, b = 6.1165(2) Å, c = 11.2056(3) Å. The structure of struvite is presented here with a residual factor R1 = 1.2% at 0.80 Å resolution. We also present thermoanalytical study of struvite using thermal analysis techniques such as thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA).

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Synthesis, crystal structure, luminescence, and photocatalytic properties of a 2D Cu(II) metal-organic frameworks based on 3,5-di(1H-benzimidazol-1-yl)pyridine and 4,4′-oxybis(benzoate) ligands

Zeitschrift für Naturforschung B ◽

10.1515/znb-2020-0041 ◽

2020 ◽

Vol 75 (8) ◽

pp. 727-732

Author(s):

Chen Zhang ◽

Jian-Qing Tao

Keyword(s):

Crystal Structure ◽

Thermal Analysis ◽

Uv Light ◽

Metal Organic Framework ◽

Metal Organic Frameworks ◽

X Ray Diffraction ◽

X Ray ◽

Uv Light Irradiation ◽

Photocatalytic Activities ◽

Metal Organic

AbstractA new Cu(II) metal-organic framework, [Cu(L)(OBA)·H2O]n (1) [H2OBA = 4,4′-oxybis(benzoic acid), L = 3,5-di(1H-benzimidazol-1-yl)pyridine] was hydrothermally synthesized and characterized through IR spectroscopy, elemental and thermal analysis and single-crystal X-ray diffraction. Complex 1 is a four-connected uni-nodal 2D net with a (44·62) topology which shows an emission centered at λ ∼393 nm upon excitation at λ = 245 nm. Moreover, complex 1 possesses high photocatalytic activities for the decomposition of Rhodamine B (RhB) under UV light irradiation.

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Preparation of high-entropy carbides by different sintering techniques

Journal of Materials Science ◽

10.1007/s10853-021-06004-y ◽

2021 ◽

Vol 56 (19) ◽

pp. 11237-11247 ◽

Cited By ~ 1

Author(s):

Johannes Pötschke ◽

Manisha Dahal ◽

Mathias Herrmann ◽

Anne Vornberger ◽

Björn Matthey ◽

...

Keyword(s):

Grain Size ◽

Single Phase ◽

X Ray Diffraction ◽

Vacuum Sintering ◽

X Ray ◽

High Entropy ◽

Mean Grain Size ◽

The Mean ◽

Gas Pressure Sintering ◽

Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

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The Potential for Natural Stones from Northeastern Brazil to Be Used in Civil Construction

Minerals ◽

10.3390/min11050440 ◽

2021 ◽

Vol 11 (5) ◽

pp. 440

Author(s):

Fabiana Pereira da Costa ◽

Jucielle Veras Fernandes ◽

Luiz Ronaldo Lisboa de Melo ◽

Alisson Mendes Rodrigues ◽

Romualdo Rodrigues Menezes ◽

...

Keyword(s):

Mechanical Properties ◽

Thermal Analysis ◽

Differential Thermal Analysis ◽

Chemical Resistance ◽

Mechanical Analysis ◽

Northeastern Brazil ◽

X Ray Diffraction ◽

X Ray ◽

Chemical Agents ◽

Natural Stones

Natural stones (limestones, granites, and marble) from mines located in northeastern Brazil were investigated to discover their potential for use in civil construction. The natural stones were characterized by chemical analysis, X-ray diffraction, differential thermal analysis, and optical microscopy. The physical-mechanical properties (apparent density, porosity, water absorption, compressive and flexural strength, impact, and abrasion) and chemical resistance properties were also evaluated. The results of the physical-mechanical analysis indicated that the natural stones investigated have the potential to be used in different environments (interior, exterior), taking into account factors such as people’s circulation and exposure to chemical agents.

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