scholarly journals New Aspects of MgH2 Morphological and Structural Changes during High-Energy Ball Milling

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4550
Author(s):  
Tomasz Czujko ◽  
Ewelina E. Oleszek ◽  
Mariusz Szot
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Powder Particle ◽  
Structural Changes ◽  
High Energy ◽  
Decomposition Temperature ◽  
Milling Process ◽  
Size Analysis ◽  
Crystallographic Structure ◽  
Particle Size Reduction

Magnesium hydride, despite the decomposition temperature being incompatible with the operating temperature of a typical PEM cell, is still considered a prospective material for hydrogen storage. Hence, this paper presents new aspects of the influence of milling time on the structural changes and temperature of MgH2 decomposition, with particular emphasis on the changes taking place in the first few seconds of the milling process. This paper presents qualitative and quantitative changes in the powder particle morphology determined using scanning electron microscopy (SEM) and infrared particle size analysis (IPS) systems. The crystallographic structure of the powders in the initial state and after mechanical milling was characterized by X-ray diffraction. The decomposition temperature and activation energy were determined by the differential scanning calorimetry (DSC). Changes in the activation energy and decomposition temperature were observed after only 1–2 min of the milling process. Two basic stages of the milling process were distinguished that impacted the MgH2 decomposition temperature, i.e., mechanical activation and a nanostructuring process. The activation was associated with the initial stage of particle size reduction and an increase in the fraction of fresh chemically active powder particle surfaces. On the other hand, the nanostructuring process was related to an additional decrease in the MgH2 decomposition temperature.

scholarly journals Structure and Magnetic Properties Of Fe/Si Nanoparticles Prepared by High Energy Milling Process

2021 ◽  
Vol 11 (2) ◽  
pp. 239
Author(s):  
Muhammad Rifai ◽  
Yunasfi Yunasfi ◽  
Engkir Sukirman ◽  
Yosef Sarwanto ◽  
Mujamilah Mujamilah
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
Magnetic Properties ◽  
Iron Oxides ◽  
High Energy ◽  
Milling Process ◽  
Particle Size Reduction ◽  
High Energy Milling ◽  
Si Nanoparticle ◽  
Si Nanoparticles

The structure and magnetic properties of Fe/Si nanoparticle prepared by high energy milling process have been examined, focusing on the phase transition. Fe/Si nanoparticles were processed by high energy milling (HEM) for 10 hours to 50 hours with a weight per cent ratio of 9:1. Based on the X-ray diffraction (XRD) pattern, transmission electron microscope (TEM) observations, and vibrating sample magnetometer (VSM) analysis, the phase transition induced by HEM, were evidenced. The effect of structural state and the particle size on the magnetic properties such as magnetization was also studied. It was found that iron and iron oxides (-Fe2O3/ Fe3O4) phase were exhibited on all milled samples. The magnetization value of Fe/Si nanoparticles increased up to 20 hours with 142 emu/gr saturated magnetization and then decreased linearly with increasing milling time. Referring to the XRD result, this decline was initially caused by the iron oxide formation and magnetic interaction between iron and iron oxides nanoparticles. The phase and magnetic properties value changes related to the interaction mechanism between Fe atoms caused by interstitial occupied of Si atoms, particle size reduction, and oxidation process.

scholarly journals Green Preparation, Spheroidal, and Superior Property of Nano-1,3,5,7-Tetranittro-1,3,5,7-Tetrazocane

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Xinlei Jia ◽  
Jingyu Wang ◽  
Conghua Hou ◽  
Yingxin Tan
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Fractal Dimension ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fractal Theory ◽  
Crystal Form ◽  
Decomposition Temperature ◽  
Scanning Calorimetry ◽  
The Impact

Herein, a green process for preparing nano-HMX, mechanical demulsification shearing (MDS) technology, was developed. Nano-HMX was successfully fabricated via MDS technology without using any chemical reagents, and the fabrication mechanism was proposed. Based on the “fractal theory,” the optimal shearing time for mechanical emulsification was deduced by calculating the fractal dimension of the particle size distribution. The as-prepared nano-HMX was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). And the impact sensitivities of HMX particles were contrastively investigated. The raw HMX had a lower fractal dimension of 1.9273. The ideal shearing time was 7 h. The resultant nano-HMX possessed a particle size distribution ranging from 203.3 nm to 509.1 nm as compared to raw HMX. Nano-HMX particles were dense spherical, maintaining β-HMX crystal form. In addition, they had much lower impact sensitivity. However, the apparent activation energy as well as thermal decomposition temperature of nano-HMX particles was decreased, attributing to the reduced probability for hotspot generation. Especially when the shearing time was 7 h, the activation energy was markedly decreased.

Structure, Magnetic and Microwave Properties of Granular Fex(SiO2)1-x Alloys Obtained by Mechanochemical Synthesis

2012 ◽  
Vol 190 ◽  
pp. 585-588
Author(s):  
S.F. Lomayeva ◽  
A.N. Maratkanova ◽  
Konstantin N. Rozanov ◽  
D. A. Petrov ◽  
Eugene P. Yelsukov
Keyword(s):  
Particle Size ◽  
Phase Composition ◽  
Domain Walls ◽  
Magnetic Loss ◽  
Structural Phase ◽  
High Energy ◽  
Microwave Properties ◽  
Particle Size Reduction ◽  
Milling Medium ◽  
Energy Ball

The structural-phase composition, magnetic and microwave properties of Fex(SiO2)1-x (x=30, 70, 90, 95) nanocomposites have been studied. The composites are produced by high-energy ball milling with either Ar or acetone as a milling medium and milling time of 1 to 64 h. The microwave magnetic properties of the composite in the frequency range of 0.1 to 6 GHz are shown to depend slightly on the phase composition and be governed mainly by the particle size. Reduction of the particle size to about 1 μm results in elimination of magnetic loss at frequencies below 1 GHz, which is attributed to the domain walls motion.

scholarly journals PEMANFAATAN TEKNIK HEM UNTUK PENUMBUHAN CNT DARI GRAFIT MENGGUNAKAN Ni SEBAGAI KATALIS = UTILIZATION OF HEM TECHNIQUE FOR GROWTH OF CNT FROM GRAPHITE POWDERS BY USING Ni AS CATALYST

2016 ◽  
Vol 10 (1) ◽  
pp. 35-40
Author(s):  
Yunasfi . ◽  
P. Purwanto ◽  
Mashadi .
Keyword(s):  
Particle Size ◽  
Raman Spectroscopy ◽  
Electron Microscope ◽  
Carbon Nanotube ◽  
Surface Area ◽  
Transmission Electron Microscope ◽  
Milling Time ◽  
High Energy ◽  
Milling Process ◽  
Transmission Electron

Utilization of HEM (high energy milling) technique for growth of CNT (carbon nanotube) from graphite powders by using Ni as catalyst was carried out. Milling process performed on a mixture of graphite powder and nickel powder (Ni-C powders) with the ratio of weight percent of 98%: 2%, with a variation of milling time between 25 up to 75 hours. Characterization using PSA (Powder Size Analyzer), SAA (Surface Area Analyzer), TEM (Transmission Electron Microscope) and Raman Spectroscopy performed to obtain information about particle size, surface area, morphology and the structure bonding of the milled powder respectively. The analysis results of Ni-C powders using PSA and SAA showed the smallest particle size and biggest surface area obtained after milling process for 50 hours, i.e. 80 nm and 705 m2/g, respectively. TEM observations revealed formation of flat fibers which quantity increased with increasing milling time. This flattened fiber behave as an initiator for the growth of CNTs. Ni-C powder milling for 50 hours results more clearly show the growth of CNTs. Analysis by Raman Spectroscopy showed two bands at 1582 cm−1 as a peak of G band and at 1350 cm-1 as a peak of D band. These spectra are typical for sp2 structure. The position of G band peak is close to 1600 cm-1 as the evidence of a change to nano-crystalline graphite. The highest intensity of D band shown in the milling process for 50 hours, which indicates that this milling time produces more graphite-like structure compared to other conditions, and is predicted good for growing CNTs. AbstrakPemanfaatan teknik HEM (High Energy Milling) untuk penumbuhan CNT (carbon nanotube) dari serbuk grafit dengan menggunakan Ni sebagai katalis. Proses milling dilakukan terhadap campuran serbuk grafit dan serbuk nikel (serbuk Ni-C) dengan perbandingan berat 98% : 2%, dengan variasi waktu milling antara 25-75 jam. Karakterisasi menggunakan fasilitas PSA (Particle Size Analyzer), SAA (Surface Area Analyzer), dan TEM (Transmission Electron Microscope) serta Raman Spektroscopy yang masing-masingnya untuk mendapatkan informasi tentang ukuran partikel, luas permukaan dan morfologi serta struktur ikatan serbuk hasil milling. Hasil analisis serbuk Ni-C dengan PSA dan SAA menunjukkan ukuran partikel paling kecil dan luas permukaan paling besar diperoleh setelah proses milling selama 50 jam, masing-masing 80 nm dan 705 m2/g. Pengamatan TEM menunjukkan serbuk-serbuk berbentuk serat pipih dengan kuantitas yang meningkat dengan bertambahnya waktu milling. Serat pipih ini perupakan cikal bakal penumbuhan CNT. Serbuk Ni-C hasil milling menunjukkan penumbuhan CNT terlihat lebih jelas setelah milling selama 50 jam. Hasil analisis dengan Raman Spectroscopy memperlihatkan puncak G band pada bilangan gelombang 1582 cm−1 yang merupakan spektrum untuk struktur sp2 dari grafit dan puncak D band pada bilangan gelombang 1350 cm-1 yang mungkin merupakan deformasi struktur grafit. Posisi puncak G band mendekati 1600 cm-1 menjadi bukti perubahan ke grafit nano kristal. Intensitas D band tertinggi ditunjukkan oleh sistem komposit Ni-C hasil proses milling selama 50 jam dan hal ini sebagai indikasi bahwa proses milling selama 50 jam terhadap sistem komposit Ni-C lebih berstruktur mirip grafit (graphitic-like material) dibanding kondisi lainnya dan diprediksi bagus untuk menumbuhkan CNT. Dengan demikian, waktu milling yang optimal untuk penumbuhan CNT dari serbuk grafit dengan menggunakan Ni sebagai katalis adalah adalah 50 jam.  

scholarly journals PHYSICOCHEMICAL PROPERTIES AND POZZOLANIC PERFORMANCE OF ULTRAFINE TREATED RICE HUSK ASH (UFTRHA) AS ADDITIVE IN CONCRETE

2018 ◽  
Vol 16 ◽  
Author(s):  
Siti Asmahani Saad ◽  
Nasir Shafiq ◽  
Maisarah Ali
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Rice Husk ◽  
Amorphous Silica ◽  
Rice Husk Ash ◽  
High Energy ◽  
Size Analysis ◽  
Pre Treatment

Rice husk ash (RHA) contains high amount of amorphous silica that is ubiquitous in the pozzolanic reaction of SCM in concrete. However, usage of conventional RHA is currently unfavourable in concrete industry due to its properties inconsistency. In this regard, improvement on the RHA properties by introduction of thermochemical pre-treatment prior to burning procedure is seen as an excellent way to reach the goal. In this paper, raw rice husk was pre-treated using 0.1N hydrochloric acid (HCl) and heated at 80oC. It was then mechanically activated by high energy planetary ball mill for 15 minutes at speed of 300rpmand ball-to-powder ratio (BPR) of 15:1. The chemical composition, mineralogical properties, particle size analysis, specific surface area as well as microstructure properties of ultrafine treated rice husk ash (UFTRHA) were determined accordingly. As for amorphous silica content of the optimum sample was recorded as 98.60% incinerated at 600oC with four hours of pre-treatment soaking duration. In terms of particle size and specific surface, it was also observed that, burning temperature of 600oC, pre-treated at four hours were recorded to produce finest size of UFTRHA where d(0.1), d(0.5) and d(0.9) were obtained as 1.416?m, 4.364 ?m and 14.043 ?m respectively. Largest specific surface area value was obtained at 219.58 m2/g with the similar pre-treatment conditions. Meanwhile, the strength activity of UFTRHA from the optimum pre-treatment process was measured by testing the compressive strength of mortars. The highest compression value obtained was 50.17MPa with 3% UFTRHA replacement at 28 days.

scholarly journals Recycling Chips of Stainless Steel Using a Full Factorial Design

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 842
Author(s):  
Claudiney Mendonça ◽  
Patricia Capellato ◽  
Emin Bayraktar ◽  
Fábio Gatamorta ◽  
José Gomes ◽  
...  
Keyword(s):  
Particle Size ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Vanadium Carbide ◽  
Milling Time ◽  
Rotation Speed ◽  
Weight Ratio ◽  
High Energy ◽  
Milling Process ◽  
Full Factorial

The aim of this study was to provide an experimental investigation on the novel method for recycling chips of duplex stainless steel, with the addition of vanadium carbide, in order to produce metal/carbide composites from a high-energy mechanical milling process. Powders of duplex stainless steel with the addition of vanadium carbide were prepared by high-energy mechanical ball milling utilizing a planetary ball mill. For this proposal, experiments following a full factorial design with two replicates were planned, performed, and then analyzed. The four factors investigated in this study were rotation speed, milling time, powder to ball weight ratio and carbide percentage. For each factor, the experiments were conducted into two levels so that the internal behavior among them could be statistically estimated: 250 to 350 rpm for rotation speed, 10 to 50 h for milling time, 10:1 to 22:1 for powder to ball weight ratio, and 0 to 3% carbide percentage. In order to measure and characterize particle size, we utilized the analysis of particle size and a scanning electron microscopy. The results showed with the addition of carbide in the milling process cause an average of reduction in particle size when compared with the material without carbide added. All the four factors investigated in this study presented significant influence on the milling process of duplex stainless steel chips and the reduction of particle size. The statistical analysis showed that the addition of carbide in the process is the most influential factor, followed by the milling time, rotation speed and powder to ball weight ratio. Significant interaction effects among these factors were also identified.

scholarly journals Effect Of Different Mechanical Milling Processes On Morphology And Microstructural Changes Of Nano And Micron Al-Powders

2015 ◽  
Vol 60 (2) ◽  
pp. 1235-1239 ◽  
Author(s):  
H.-S. Kim ◽  
B. Madavali ◽  
T.-J. Eom ◽  
C.-M. Kim ◽  
J.-M. Koo ◽  
...  
Keyword(s):  
Ball Milling ◽  
Mechanical Milling ◽  
Structural Changes ◽  
Structural Evolution ◽  
High Energy ◽  
Milling Process ◽  
High Energy Ball Milling ◽  
Microstructural Changes ◽  
Al Nanoparticles ◽  
Energy Ball

Abstract In this research, effect of the various mechanical milling process on morphology and microstructural changes of nano and micron Al-powders was studied. The milling of Al-powders was performed by both high energy and low energy ball milling process. The influence of milling (pulverizing) energy on the structural changes of Al-powders was studied. Al-nanoparticles were agglomerated during the MA and its size was increased with increasing milling while micron Al-powder gets flattened shape during high energy ball milling due to severe plastic deformation. Meanwhile, structural evolution during high energy ball milling of the nano powder occurred faster than that of the micron powder. A slight shift in the position of X-ray diffraction peaks was observed in nano Al-powders but it was un-altered in macro Al-powders. The variation in lattice parameters was observed only for nano Al powders during the high energy ball milling due to lattice distortion.

Effect of Powder Particle Size and Substrate Hardening on the Formation of Nanostructured TiC Coating on AISI-D2 Steel by Mechanical Milling

2013 ◽  
Vol 829 ◽  
pp. 471-475
Author(s):  
Farhad Saba ◽  
Shahram Raygan ◽  
Hossein Abdizadeh
Keyword(s):  
Particle Size ◽  
Powder Particle ◽  
Mechanical Milling ◽  
Milling Time ◽  
Structural Characteristics ◽  
High Energy ◽  
Powder Particle Size ◽  
Aisi D2 Steel ◽  
Aisi D2 ◽  
D2 Steel

In this study TiC coating was formed on AISI-D2 steel by mechanical milling. In this regard, steel sample, balls and the powder were placed within a milling vial. Ball milling were carried out with annealed and quench-tempered samples using TiC powder having particle sizes of 44 and 200 μm for 5, 10, 15, 20, 50 and 100 h. During milling treatment, sample surface was exposed to high energy collisions and powder particles trapped between balls and sample adhered to the surface through cold welding. It was shown that the thickness and the structure of the coating depended on powder particle size; hardness and milling time. The thickness of the coating increased at first and decreased thereafter with milling time. The results showed that the substrate hardening decreased the thickness of the coating. Scanning Electron Microscopy (SEM) was employed to investigate the structural characteristics of the coatings. X-ray Diffraction (XRD) analysis was also conducted to determine the kind of phases in the coating. SEM investigations showed that the greatest thickness of the coating was reached after 20 h of milling. Furthermore, no new phases were detected in the XRD results after 100 h. It was shown that the thickness and hardness of coatings with coarse particle size were lower than that of the other. It was revealed that lattice parameter of TiC coating increased with milling time.

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