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1

Effect of ball milling on hexagonal boron nitride (hBN) and development of Al-hBN nanocomposites by powder metallurgy route

Ghosh Arka, Shukla Uddeshya, Sahoo Nityananda, Ganguly Sourav, Shrivastava Pankaj, Kumar Lailesh, Alam Syed Nasimul

Materials Science Poland

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2023

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Vol. 41, No. 1

68--93

EN

This study reports on the exfoliation of bulk hexagonal boron nitride (hBN) by high-energy ball milling and the development of Al-hBN (alumninum-hexagonal boron nitride) nanocomposites by the powder metallurgy (PM) route via the incorporation of the exfoliated hBN in the Al matrix as a nanoreinforcement. The effect of ball milling on the morphology, crystallite size, lattice strain, and thermal stability of hBN powder have also been reported in this paper. Commercially available bulk hBN was ball milled for up to 30 hours in a high-energy planetary ball mill in order to exfoliate the hBN. Although no new phases were formed during milling, which was confirmed by the XRD (x-ray powder diffraction) spectra, ball milling resulted in the attachment of functional groups like hydroxyl (OH) and amino (NH2) groups on the surface of the hBN, which was confirmed by FTIR (Fourier Transform Infrared Spectroscopy) analysis. HRTEM (high resolution transmission electron microscopy) analysis confirmed the synthesis of hBN having few atomic layers of hBN stacked together after 20 hours of milling. After 20 hours of milling, the hBN particle size was reduced from ~1 μm to ~400 nm, while the crystallite size of the 20-hourmilled hBN powder was found to be ~18 nm. Milling resulted in a flake-like structure in the hBN. Although milling involved both exfoliation as well as reagglomeration of the hBN particles, a significant decrease in the diameter of the hBN particles and their thickness was observed after a long period of milling. The average thickness of the 20-hour-milled hBN flakes was found to be ~32.61 nm. HRTEM analysis showed that the hexagonal structure of the milled hBN powder was maintained. Al-based nanocomposites reinforced with 1%, 2%, 3%, and 5% by weight hBN were fabricated by PM route. The Al-hBN powder mixtures were cold-compacted and sintered at 550◦C for 2 hours in argon (Ar) atmosphere. The maximum relative density of ~94.11% was observed in the case of Al-3 wt.% hBN nanocomposite. Al-3 wt.% hBN nanocomposite also showed a significant improvement in hardness and wear resistance compared to the pure Al sample that was developed in a similar fashion. The maximum compressive strength of ~999 MPa was observed in the case of Al-3 wt.% hBN nanocomposite and was approximately twice that of the pure Al sample developed in a similar fashion.

2

Optimization of Palm Oil Boiler Ash Biomass Waste as a Source of Silica with Various Preparation Methods

Bukit Bunga Fisikanta, Frida Erna, Humaidi Syahrul, Sinuhaji Perdinan, Bukit Nurdin

Journal of Ecological Engineering

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2022

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Vol. 23, nr 8

193--199

EN

Several studies have synthesized silica from waste. The silica synthesis method from agricultural waste aims to produce high purity silica with low contaminants at an affordable cost. This study synthesized silica from oil palm boiler ash (OPBA) by means of various methods, such as ball milling, coprecipitation, and modification with methyl trichlorosilane (MTCS). XRD characterization results showed that the OPBA synthesized with ballmill and coprecipitation method has the smallest particle size of 14.90 nm. Morphology showed the OPBA obtained by using the ballmill method, the OPBA synthesized with ballmill and coprecipitation method, as well as the OPBA synthesized with ballmill, coprecipitation, and modified with methyl trichlorosilane as spherical particles. At the same time, the FTIR results show an absorption peak which is a characteristic of silica confirmed by the XRF results, where silica content is dominant.

3

Synergistic effect of ball milling time and nano‑sized Y2O3 addition on hardening of Cu‑based nanocomposites

Salur Emin

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e103, 1--18

EN

A fruitful combination of powder metallurgy and the mechanical alloying route is one of the most promising process for producing advanced Cu-based nanocomposites. In this study, three different material systems, namely, pure copper (Cu), 5 wt% Cr reinforced Cu matrix composites, and 1 wt% Y2O3 reinforced Cu-Cr matrix nan-composites were synthesized by ball milling method at different milling times. The influence of different ball milling times (0.5, 2, and 4 h) and different types of reinforcements (Cr and Y2O3) on the powder and sintered parts properties were thoroughly analyzed with a holistic approach. The milled powders were then consolidated using a cold press followed by a liquid phase sintering process. Results revealed that the Cr and Y2O3 particles were fractionally dispersed and imbedded in the ductile Cu matrix with respect to increasing milling time. Milling for 4 h of Cu-Cr-2O3 powders produced the lowest level of particle size (28 μm) with reduced and flattened and uniformly distributed reinforcement phases due to intense plastic deformation induced shearing effect and dominant powder-ball-jar collisions. Besides, the ball milling process of the same powders concluded a decrement of crystallite size to 35 nm in concomitant with an increase of lattice strain and dislocation density ⁓ % 0.3 and 0.8×1015 line/m2 , respectively. Brinell hardness of the sample produced by these powders increased from 39 to 95 HB. A ⁓%145 striking increase of hardness could be attributed to the strong hindrance of high-dense dislocations triggered by several concurrent strengthening mechanisms. Nevertheless, relative density results of sintered samples revealed that the addition of Cr and Y2O3 along with increasing milling time deteriorated the density due to the higher hardness and brittleness of milled powders and accompanying worsened compressibility and sinterability. The source of noticed differences between hardness and density results were discussed within the process-structure-performance framework.

4

Dispersion mechanism-induced variations in microstructural and mechanical behavior of CNT-reinforced aluminum nanocomposites

Doğan Kemal, Özgün Muhammed Ihsan, Sübütay Halit, Salur Emin, Eker Yasin, Kuntoğlu Mustafa, Aslan Abdullah, Gupta Munish Kumar, Acarer Mustafa

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e55, 2022

EN

The combination of powder metallurgy and ball milling method has been widely regarded as the most beneficial route for producing multi-walled carbon nanotubes (MWCNTs)-reinforced aluminum matrix composites. In this study, the effects of different milling times (1, 2, 4, and 8 h) on the structural, morphological, and crystallographic properties of MWCNTs-reinforced Al7075 composite powders were characterized by particle size analyzer, Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). After the morphological and structural characterization of the milled powders, the microstructural and mechanical properties of the hot-pressed composites were evaluated using an optical microscope, SEM, density, and Brinell hardness measurements. Considering milled powder characterization, the MWCNTs were gradually distributed and embedded within the matrix as the milling time increased. Milling for 8 h resulted in a minimum level of particle size (11 µm) with shortened and uniformly dispersed CNTs. Brinell hardness of the composite increased from 91 to 237 HB -a ⁓%160 after 8 h of milling. Such a remarkable increment in hardness could be attributed to several concurrent strengthening effects related to dispersion, solution, grain refinement, and Orowan looping mechanisms. However, relative density results revealed that the composite produced by 2 h milled powders exhibited the highest density (%99.96). The observed differences between hardness and density results were ascribed to powders’ deteriorated packing and sintering behavior due to an increment in the hardness of particles and variation in particle size range and morphology, which resulted from following different milling protocols.

5

The influence of ball milling processing variables on the microstructure and compaction behavior of Fe–Mn–Cu alloys

Ammar Hany R., Sivasankaran Subbarayan, Alaboodi Abdulaziz S.

Materials Science Poland

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2021

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Vol. 39, No. 3

410--429

EN

In the present study, twenty seven [(Fe–35wt%Mn)100−x–Cux] alloy samples were processed using high-energy ball milling, followed by uniaxial compaction under different processing conditions. The compressibility behavior in terms of relative density (RD) was examined with milling time (MT: 1 h, 5.5 h, and 10 h), ball-to-powder mass ratio (BPMR: 5:1, 10:1, and 15:1), milling speed (MS: 100 rev/min, 200 rev/min, and 300 rev/min), compaction pressure (CP: 25–1,100 MPa), and alloy composition (Cu content [CC]: 0 wt%, 5 wt%, 10 wt%). Particle size analysis using X-ray diffraction (XRD) and high-resolution scanning electron microscopy (HRSEM) combined with energy-dispersive X-ray spectroscopy (EDS) were applied for microstructural characterization. The experiments were conducted based on the central composite design of response surface methodology (RSM), and the results for the compaction behavior were examined with the input parameters. Analysis of variance (ANOVA) test was applied to determine the most significant input parameters. The attained results revealed that increasing ball milling parameters (MT, MS, and BPMR) resulted in significant enhancements in the microstructural features, such as improved elemental dispersion and occurrence of refined particles with substantial decrease in the crystallite size. On the other hand, increasing the input parameters exhibited a detrimental influence on the compactibility and RD of the alloys. In addition, increasing the CC resulted in a substantial improvement in the compressibility and RD of the developed alloys. The recommended combination of the studied variables includes MT for 5 h, MS for 150 rev/min, BPMR of 10:1, and 10 wt%Cu to attain an acceptable compromise of enhanced microstructure features, improved compaction response, and RD.

6

Green Fabrication of Nanoscale Energetic Molecular Perovskite (H2dabco)[Na(ClO4)3] with Reduced Mechanical Sensitivity

Hu Li-shuang, Du Zelin, Liu Yang, Gong Shida, Guang Chunyu, Li Xin, Yang Zhi, Jia Qi, Liang Kaili

Central European Journal of Energetic Materials

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2021

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Vol. 18, no. 3

369--384

EN

High-energy-density molecular perovskite energetic materials with high detonation performance have attracted much attention, but poor safety performance has limited their potential applications. In this paper, nano sodium perchlorate-based molecular perovskite (H2dabco)[Na(ClO4)3] (nano DAP-1) was fabricated by green ball-milling technology. The structure and morphology of the samples were characterized and the results showed that nano DAP-1 with nearly spherical morphology has a narrow particle size distribution, < 1 μm. The thermal decomposition properties were investigated by differential scanning calorimetry (DSC). The exothermic peak of nano DAP-1 thermal decomposition was 330.0 °C, a decrease of 51.7 °C compared with that of raw DAP (381.7 °C). The apparent activation energy (Ea) of nano DAP-1 was calculated to be 160.9 kJ·mol–1, which is lower than that of raw DAP-1 (168.6 kJ·mol–1). Mechanical sensitivity studies showed that nano DAP-1 (H50: 64 cm) exhibited a lower impact sensitivity than that of the raw DAP-1 (H50: 51 cm). This work provides a simple and effective way for improving the thermal decomposition properties and safety performance of molecular perovskite energetic materials.

7

Brazeability and Microstructure of Ag-28Cu Microjoining Filler Produced by High Energy Ball Milling

Sharma Ashutosh, Chae Myoung Jin, Ahn Byungmin

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1323--1327

EN

In this paper, we have studied the evolution of morphology and brazing behavior of Ag-28Cu alloy filler processed by high energy ball milling. The milling of the powder mixture was carried out for 40 h. The structural and morphological analyses were performed by the X-ray diffraction and scanning electron microscopy. The melting temperature of the braze filler was determined by differential thermal analysis. The filler wetting properties were assessed from the spread area ratio measurements on various Ti substrates. The results indicate that the ball milling can effectively depress the filler melting point and enhance the brazeability. The milled powder mixture showed Ag(Cu) solid solution with a crystallite size of 174-68 nm after 40 h. It was shown that the high energy ball milling can be a potential method to develop low temperature brazing fillers for advanced microjoining applications.

8

A Facile Method for the Production of Sn-Ag Alloy by High Energy Ball Milling

Sharma Ashutosh, Ahn Byungmin

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1329--1333

EN

In this study, we have developed Sn-Ag alloy by a simple high energy ball milling technique. We have ball-milled the eutectic mixture of Sn and Ag powders for a period of 45 h. The milled powder for 45 h was characterized for particle size and morphology. Microstructural investigations were carried out by scanning electron microscopy and X-ray diffraction studies. The melting behavior of 45 h milled powder was studied by differential scanning calorimetry. The resultant crystallite size ofthe Sn(Ag) solid solution was found to be 85 nm. The melting point of the powder was 213.6°C after 45 h of milling showing depression of ≈6°C in melting point as compared to the existing Sn-3.5Ag alloys. It was also reported that the wettability of the Sn-3.5Ag powder was significantly improved with an increase in milling time up to 45 h due to the nanocrystalline structure of the milled powder.

9

Solid-State Mechanochemical Synthesis of Kaolinite-Urea Complexes for Application as Slow Release Fertilizer

AlShamaileh Ehab M., Al-Rawajfeh Aiman E., Alrbaihat Mohammad R.

Journal of Ecological Engineering

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2019

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Vol. 20, nr 9

267--276

EN

This study investigated a mechanochemical (MC) process for synthesizing a slow-release urea fertilizer by cogrinding the starting materials of (NH2)2CO and amorphous kaolinite in a planetary ball mill. The tests with kaolinite contents ranging from 25 to 75 wt. %, milling time ranging from 1 (h) to 3 (h) and mill rotational speeds from 200 to 700 rpm were performed to evaluate the incorporation of (NH2)2CO and release of nitrogen into the solution. The analyses conducted using XRD, TGA, FT-IR and KNDU (Kjeldahl Nitrogen Determination Unit) indicated that the MC process was successfully applied to incorporate (NH2)2CO into the amorphous kaolinite structure. The release of nitrogen from the system (kaolinite-(NH2)2CO) when dispersed in water for 24 h reached up to 20% at 25% wt of kaolinite. Moreover, under the milling speed conditions for the system (kaolinite–(NH2)2CO), release of nitrogen reached between 25 and 40%. These results indicated that the MC process can be developed to allow amorphous kaolinite to act as a carrier of nitrogen nutrients to be released slowly for use as fertilizer.

10

Reduction of Thermal Conductivity through the Dispersion of TiC Nanoparticles into a p-Type Bi0.5Sb1.5Te3 Alloy by Ball Milling and Spark Plasma Sintering

Nagarjuna Cheenepalli, Madavali Babu, Lee Myeong-Won, Yoon Suk-Min, Hong Soon-Jik

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

551--557

EN

The dispersion of nanoparticles in the host matrix is a novel approach to enhance the thermoelectric performance. In this work, we incorporate the TiC (x = 0, 1 and 2 wt.%) nanoparticles into a p-type Bi0.5Sb1.5Te3 matrix, and their effects on microstructure and thermoelectric properties were systematically investigated. The existence of TiC contents in a base matrix was confirmed by energy dispersive X-ray spectroscopy analysis. The grain size decreases with increasing the addition of TiC content due to grain boundary hardening where the dispersed nanoparticles acted as pinning points in the entire matrix. The electrical conductivity significantly decreased and the Seebeck coefficient was slightly enhanced, which attributes to the decrease in carrier concentration by the addition of TiC content. Meanwhile, the lowest thermal conductivity of 0.97 W/mK for the 2 wt.% TiC nanocomposite sample, which is ~16% lower than 0 wt.% TiC sample. The maximum figure of merit of 0.90 was obtained at 350 K for the 0 wt.% TiC sample due to high electrical conductivity. Moreover, the Vickers hardness was improved with increase the addition of TiC contents.

11

Effect of Milling Time Parameter on the Microstructure and the Thermoelectric Properties of n-Type Bi2Te2.7Se0.3 Alloys

Sharief P., Madavali B., Koo J. M., Kim H. J., Hong S., Hong S.-J.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

585-590

EN

Nanostructured thermoelectric materials receiving great attention for its high thermoelectric performance. In this research, nanostructured n-type Bi2 Te2.7 Se0.3 alloys have prepared using high energy ball milling and followed by spark plasma sintering. Also, we have varied ball milling time to investigate milling time parameter on the thermoelectric properties of n-type Bi2 Te2.7 Se0.3 powder. The powders were discrete at 10 min milling and later particles tend to agglomerate at higher milling time due to cold welding. The bulk fracture surface display multi-scale grains where small grains intersperse in between large grains. The maximum Seebeck coefficient value was obtained at 20-min milling time due to their lower carrier density. The κ values were decreased with increasing milling time due to the decreasing trend observed in their κL values. The highest ZT of 0.7 at 350 K was observed for 30-min milling time which was ascribed to its lower thermal conductivity. The Vickers hardness values also greatly improved due to their fine microstructure.

12

Wpływ warunków procesu mielenia mieszaniny proszków Fe, Cu, Ni na właściwości spieków otrzymanych techniką prasowania na gorąco

Borowiecka-Jamrozek J.

Przegląd Spawalnictwa

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2018

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R. 90, nr 3

17--20

PL

W pracy przedstawiono wyniki badań własności mechanicznych spieków otrzymanych z mieszanki elementarnych proszków żelaza, miedzi i niklu poddanych mieleniu w młynie kulowym przez okres 60 godzin. Spieki wykonano techniką prasowania na gorąco w grafitowej matrycy. Zastosowano następujące parametry wytwarzania: ciśnienie 35 MPa, temperatura 900 °C, czas 3 minuty. Badania otrzymanych spieków obejmowały: pomiar gęstości, porowatości, twardości i statyczną próbę rozciągania. Dokonano również obserwacji mikrostruktury i przełomów zerwanych próbek przy użyciu elektronowego mikroskopu skaningowego (SEM). Badania prowadzono w celu określenia przydatności wytworzonych kompozytów do produkcji narzędzi metaliczno-diamentowych. Zbadano wpływ składu chemicznego, warunków procesu wytwarzania na mikrostrukturę i własności mechaniczne wytworzonych spieków.

EN

The paper presents the results of investigations of mechanical properties of sinter obtained from a mixture of elementary iron, copper and nickel powders milled in a ball mill for a period of 60 hours. Sintering was done by hot-pressing technique in graphite matrix. The following manufacturing parameters were used: pressure 35 MPa, temperature 900 °C, time 3 minutes. Investigations of the obtained sinterings included: density, porosity, hardness and static tensile test. Observations were also made of microstructure and fracture surface of broken samples using an electronic scanning electron microscope (SEM). The study was conducted to determine the suitability of manufactured composites for the manufacture of metal-diamond tools. The influence of chemical composition, microstructure and mechanical properties of the produced sinters was investigated.

13

Effect of milling time on morphology and size of copper/CNT composite powder

Grzegorek J., Maj Ł., Maziarz W.

Composites Theory and Practice

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2018

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R. 18, nr 4

227--233

EN

The development of a sintered copper matrix composite with a small addition of carbon nanotubes (CNTs), which improves its mechanical strength without a decrease in electrical conductivity is of practical importance. Therefore, in the present paper the parameters of ball milling of a Cu+CNT powder mixture were optimized in order to obtain the highest refinement of particles of such a composite material. Investigations carried out with the help of scanning electron microscopy and sieve analysis revealed that the average particle size of the powder decreases with an increase in the volume content of the carbon nanotubes. The presence of carbon material should limit grain growth during the hot pressing of composite material, allowing much smaller grain sizes and accompanying high hardness to be obtained of the resulting compacts, as compared with similarly processed copper powder.

PL

Opracowanie spiekanych kompozytów na osnowie miedzi z niewielkim dodatkiem nanorurek węglowych, poprawiających ich własności wytrzymałościowe bez wyraźnego spadku przewodności elektrycznej, ma duże znaczenie praktyczne. Dlatego w ramach niniejszej pracy została przeprowadzona optymalizacja parametrów mielenia w młynku kulowym mieszanki proszkowej miedź + nanorurki węglowe w celu uzyskania możliwie największego stopnia rozdrobnienia cząstek takiego materiału kompozytowego. Badania przeprowadzone metodą skaningowej mikroskopii elektronowej oraz analiza sitowa wskazały, że średnia wielkość cząstek proszku generalnie spada wraz ze wzrostem zawartości nanorurek węglowych. Obecność nanorurek węglowych powinna zapobiegać rozrostowi ziarna podczas prasowania na gorąco takiego materiału kompozytowego, co pozwoli na uzyskanie znacznie mniejszego ziarna, a w konsekwencji wyższej twardości w porównaniu do wytwarzanego w ten sam sposób proszku miedzi.

14

Effect of Y2O3 Nanoparticles on Corrosion Study of Spark Plasma Sintered Duplex and Ferritic Stainless Steel Samples by Linear Sweep Voltammetric Method

Shashanka R., Chaira D., Kumara Swamy B. E.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

749--763

EN

The microstructure and corrosion properties of spark plasma sintered yttria dispersed and yttria free duplex and ferritic stainless samples were studied. Spark plasma sintering (SPS) was carried out at 1000°C by applying 50 MPa pressure with holding time of 5 minutes. Linear sweep voltammetry (LSV) tests were employed to evaluate pitting corrosion resistance of the samples. Corrosion studies were carried out in 0.5, 1 and 2 M concentration of NaCl and H2SO4solutions at different quiet time of 2, 4, 6, 8 and 10 seconds. Yttria dispersed stainless steel samples show more resistance to corrosion than yttria free stainless steel samples. Pitting potential decreases with increase in reaction time from 2 to 10 seconds. Similarly, as concentration of NaCl and H2SO4 increases from 0.5 M to 2 M the corrosion resistance decrements due to the availability of more Cl¯ and SO42¯ ions at higher concentration.

15

Preparation and Characterization of Ultrafine HMX/TATB Explosive Co-crystals

An C., Li H., Zhang Y., Ye B., Xu C., Wang J.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 4

876--887

EN

An explosive co-crystal of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) was prepared by the ball milling method. The raw materials and co-crystals were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Raman spectroscopy. Impact and friction sensitivity of the co-crystals were tested and analyzed. The results showed that the HMX/TATB co-crystals are spherical in shape and 100-300 nm in size. The co-crystals are different from anintimate mixture of HMX/TATB and they exhibit a new co-crystal structure. HMX/TATB co-crystals are formed by N-O···H hydrogen bonding between −NO2 (HMX) and −NH2 (TATB). The drop height of ultrafine HMX/TATB explosive co-crystals is 12.7 cm higher than that of ultrafine HMX, whilst the explosion probability of friction is 20% lower than that of ultrafine HMX. Ultrafine HMX/TATB explosive co-crystals are difficult to initiate under impact and friction conditions.

16

Effect of Heat Treatment on the Microstructure and Tensile Deformation Behavior of Oxide Dispersion Strengthened Alloys Manufactured by Complex Milling Process

Kim Y.-K., Kim J.-H., Gwon J.-H., Lee K.-A.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2B

1335--1340

EN

This study attempted to manufacture an ODS alloy by combining multiple milling processes in mechanical alloying stage to achieve high strength and fracture elongation. The complex milling process of this study conducted planetary ball milling, cryogenic ball milling and drum ball milling in sequential order, and then the microstructure and tensile deformation behavior were investigated after additional heat treatment. The oxide particles distributed within the microstructure were fine oxide particles of 5~20 nm and coarse oxide particles of 100~200 nm, and the oxide particles were confirmed to be composed of Cr, Ti, Y and O. Results of tensile tests at room temperature measured yield strength, tensile strength and elongation as 1320 MPa, 2245 MPa and 4.2%, respectively, before heat treatment, and 1161 MPa, 2020 MPa and 5.5% after heat treatment. This results indicate that the ODS alloy of this study gained very high strengths compared to other known ODS alloys, allowing greater plastic zones.

17

Silver matrix composites consolidated and hot extruded from ball milled powders strengthened with different types of graphene platelets

Dutkiewicz J., Ozga P., Pstruś J., Maziarz W., Grzegorek J.

Composites Theory and Practice

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2016

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R. 16, nr 4

207--211

EN

Silver matrix composites containing 1÷2% graphene platelets of various thicknesses were uniaxially hot pressed at 480°C in vacuum from powders ball milled for 5 hours. Two kinds of graphene nanoplatelets were added: (i) - nanoflakes (FLRGO) of a thickness 2÷4 nm, which led to a higher hardness (35÷49 HV) and slightly lower electrical resistivity of the composites, than that of pure hot pressed Ag and (ii) - nanographite platelets (N006) 10÷20 nm thick as confirmed by electron microscopy, which caused a similar increase in hardness up to 34÷45 HV and about a 40% higher electrical resistivity than that of pure hot pressed Ag. SEM studies showed a more homogeneous microstructure of the composites with the FLRGO graphene additions. TEM studies confirmed refinement of the thickness and lateral size of the graphene particles after milling and hot compaction down to a few nm manifested by diffused electron diffraction. The hot extrusion of hot pressed composites with FLRGO platelets caused the growth of graphene platelets and coagulation of the platelets, which contributed to a higher hardness and electrical resistivity.

PL

Kompozyty na osnowie srebra z dodatkiem płytek grafenowych o różnej grubości zostały wykonane poprzez jednoosiowe prasowanie w temperaturze 480°C z proszków mielonych 5 godzin w młynkach kulowych. Zastosowano dwa rodzaje płytek grafenowych: (i) nanopłatki FLRGO z firmy Nanomaterials o grubości 2÷4 nm, które powodowały wzrost twardości kompozytów na osnowie srebra, do wielkości 35÷49 HV i nieznaczny spadek oporności w stosunku do czystego prasowanego z proszku srebra oraz (ii) płytki nanografitu N006, których dodatek w ilości 2% wag. potwierdzono za pomocą dyfrakcji rentgenowskiej i elektronowej z firmy Angstron Materials o grubości płytek 10÷20 nm, powodował wzrost twardości do 34÷45 HV i oporności elektrycznej o około 40% w stosunku do czystego prasowanego z proszku srebra. Badania mikrostruktury metodami SEM wykazały występowanie bardziej jednorodnej mikrostruktury w kompozytach zawierających płytki grafenowe FLRGO. Badania TEM wykazały rozdrobnienie płytek N006 po mieleniu i prasowaniu, co powodowało silne rozmycie refleksów 002 grafenu w związku ze zmniejszeniem wielkości cząstek w płytkach do kilku nm. Prasowanie na gorąco spowodowało z kolei wzrost wielkości cząstek w płytkach i koagulację płytek, co wpłynęło na wzrost twardości i oporności elektrycznej.

18

Properties Of MgB2/Ga Composites Prepared By Mechanical Alloying

Yoon K., Ahn J.-H.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1271--1274

EN

In this study, we examined the effect of Ga-doping and mechanical alloying in MgB2 on microstructural and phase evolution. A comparison was made between in-situ and ex-situ processed Mg-B-Ga samples. Densification was markedly improved by ex-situ sintering of ball-milled MgB2+Ga. The Ga-doping and ball-milling prior to sintering resulted in the formation of impurity phases such as MgO, Ga5Mg2 and Ga2O3. Lattice parameter of MgB2 increased with increasing ball-milling duration as well as by Ga-doping.

19

New Wear Resistant Iron-Base Matrix Materials For The Fabrication Of Sintered Diamond Tools

Konstanty J., Romański A., Baczek E., Tyrala D.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2A

633--637

EN

The possibility of the use of inexpensive iron-base powders in the production of sintered diamond tools is again explored. Ball-milled Fe-Ni-Cu-Sn-C and Fe-Mn-Cu-Sn-C powders were consolidated to a virtually pore-free condition by hot pressing at 900°C. The resultant materials are characterised by a combination of high Knoop hardness, 260-440 and yield strength, 780-1350 MPa, and resistance to abrasion. These properties can be significantly modified by changing the milling time.

PL

W artykule zamieszczono wyniki badań nad możliwością zastosowania tanich proszków na bazie żelaza do produkcji spiekanych narzędzi metaliczno-diamentowych. Mielone proszki Fe-Ni-Cu-Sn-C i Fe-Mn-Cu-Sn-C poddano prasowaniu na gorąco w temperaturze 900°C. Otrzymane spieki posiadają gęstość zbliżoną do teoretycznej, wysoką twardość (260-400 HK0.5), granicę plastyczności (780-1350 MPa) oraz dużą odporność na zużycie ścierne. Wymienione własności są w dużym stopniu uzależnione od czasu mielenia proszków wyjściowych.

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Comparison of thermoelectric properties of polycrystalline and sintered PbTe doped with chromium and iodine

Królicka A., Hruban A., Materna A., Piersa M., Strzelecka S., Dalecki W., Romaniec M., Orliński K.

Materiały Elektroniczne

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2014

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T. 42, nr 1

5--12

EN

In this paper we compare the electrical and thermoelectric properties of polycrystalline PbTe doped with chromium and iodine, obtained by the Bridgman method and the sintered material obtained following the powder processing procedure. The highest values of the Seebeck coefficient for the polycrystalline and sintered material are as follows: - 160 μV/K (T = 675 K) and - 311 μV/K (T = 573 K), respectively, thus indicating a significant improvement in the thermoelectric properties of the sintered material. The studies of the influence of the powder particle size on the properties of the sintered material were carried out.

PL

W artykule przedstawiono porównanie własności elektrycznych i termoelektrycznych polikrystalicznego tellurku ołowiu domieszkowanego chromem i jodem, otrzymanego za pomocą metody Bridgmana z własnościami materiału spiekanego otrzymanego z proszków. Najwyższe wartości współczynnika Seebecka polikrystalicznego materiału i materiału po spiekaniu wynoszą odpowiednio: - 160 μV/K (T = 675 K) oraz - 310 μV/K (T = 573 K) i wskazują na znaczną poprawę parametrów termoelektrycznych materiału otrzymanego w wyniku spiekania. Przeprowadzono badania wpływu wielkości ziaren proszku na własności materiału spiekanego.