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Promising applicable heterometallic Al2O3/PbO2 nanoparticles in shielding properties

Publication date: November–December 2020

Source: Journal of Materials Research and Technology, Volume 9, Issue 6

Author(s): Atif Mossad Ali, Shams A.M. Issa, Mohamed Rashad Ahmed, Yasser B. Saddeek, Mohd Hafiz Mohd Zaid, Mahmoud Sayed, Hamoud H. Somaily, Huseyin Ozan Tekin, Hj Ab Aziz Sidek, Khamirul Amin Matori, Hesham M.H. Zakaly

Republished by Plato

Published

on

open access

Abstract

Hetrometal oxides of (1 − x)Al2O3/xPbO2 (NPs) nanoparticles with different PbO2 content (x = 0, 0.3, 0.4, 0.5, 0.6 and 0.7) have been prepared by irradiation method. The NPs powder has been checked by X-ray diffraction (XRD). XRD measurements affirmed the presence of both pure NPs and nanocomposites of (1 − x)Al2O3/xPbO2 NPs with different PbO2 contents. The calculated structural parameters which using the experimental result of XRD charts to give a complete image of these measurements. Moreover, the results using FLUKA code showed that the values attenuation coefficient (μm), high effective atomic number (Zeff) and neutron shielding parameters increase as the lead dioxide increase in the Al2O3/PbO2 samples. While the values of half-value layer (HVL) and mean free path (MFP) decrease with increasing PbO2 content. The investigated shielding features of the chosen Al2O3/PbO2 would be advantageous for exposure control.

Keywords

XRD

Al2O3

PbO2

Hetrometal oxides

FLUKA

© 2020 The Authors. Published by Elsevier B.V.

Source: https://www.sciencedirect.com/science/article/pii/S2238785420318512?dgcid=rss_sd_all

Material

Study of the photocatalytic activity of CdS-ZnS nano-composite in the photodegradation of rifampin in aqueous solution

Publication date: Available online 2 December 2020

Source: Journal of Materials Research and Technology

Author(s): Fariba Soleimani, Alireza Nezamzadeh-Ejhieh

Republished by Plato

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The elimination of rifampin (RN) as a pollutant from an aqueous solution was performed via the photodegradation process by the coupled CdS-ZnS system under visible light irradiation. The catalyst was briefly characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and transmission electron microscope (TEM) techniques. The cubic ZnS structure and the hexagonal CdS structure with the crystallite size of 10 nm were detected from the XRD patterns. From the DRS results, the bandgap energies of 2.3, 3.9, and 2.4 eV were obtained for CdS, ZnS, and CdS-ZnS, respectively. The pH-values of 5.2 (5.25), 5.8 (5.8), and 5.9 (5.88) were obtained for the pHpzc of CdS, ZnS, and CdS-ZnS by two methods, respectively. Increased photocatalytic activity of the coupled ZnS-CdS system was achieved compared to the single systems and when the moles of CdS is 6 times higher than the ZnS component, the best activity was obtained. The optimal degradation conditions were the catalyst dose: 0.5 g/L, CRN: 8 mg/L, pH: 2, and irradiation time: 120 min. The rate constants of RN photodegradation and mineralization (from the chemical oxygen demand (COD) results) were 0.028 and 0.019 min-1, respectively. The mechanism pathway was similar to the type (II)-heterojunction system in which the accumulated holes in VB-ZnS, the accumulated electrons in CB-CdS, and hydroxyl radicals are more important reactive species in the photodegradation of RN molecules. Further, this mechanism is useful for hydrogen production by both the photogenerated electrons in CB-CdS and CB-ZnS positions. Another mechanism that can illustrate the photodegradation process is similar to the direct Z-scheme mechanism pathway in which the accumulated electrons in the CB-ZnS, the accumulated holes in the VB-CdS, and the superoxide radicals are more important active centers for the degradation of RN molecules. Also, the accumulated holes in the CB-CdS position are another active center to oxidize RN molecules. Besides, the accumulated holes in the CB-ZnS position are more suitable for hydrogen production. The photogenerated holes in the CB-CdS position are also capable to oxidize water molecules for oxygen evolution.

Source: https://www.sciencedirect.com/science/article/pii/S2238785420320573?dgcid=rss_sd_all

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A Control Volume Method Based Interface Movement Equation for One-Dimensional Stefan Problem Achieving Mass Conservation

Publication date: Available online 2 December 2020

Source: Journal of Materials Research and Technology

Author(s): Haitao Zhao, Jianjun Qi, Hongwei Chen, Zhiqiang Tian, Jian Sun, Zhonghua Sun

Republished by Plato

Published

on


Elsevier

Available online 2 December 2020

Journal of Materials Research and Technology

open access

Abstract

For heat-transfer-controlled or diffusion-controlled phase transformation simulations, the movement of the interface between different phases needs to be determined, which is commonly called the Stefan problem. Various numerical methods have been developed for this and the movement of the interface is conventionally calculated by a flux balance equation, which is usually called the Stefan condition equation. However, mass conservation errors have been reported in the literature for some of the numerical methods. In this research, a control volume method based interface movement equation was proposed to achieve mass conservation during calculation. The obtained maximum relative mass conservation error for the new interface movement equation is less than 10-13 and the total mass is constant to the machine precision. This is much smaller than that of the Stefan condition discrete equation, which is in the order of 10-2. It was also found that the mass conservation accuracy of the numerical methods partly depends on the choice of the interface movement equation. The mass change term in the Stefan condition discrete equation is only a part of the whole mass change during interface movement, leading to the mass non-conservation found in the literature. In contrast, the piecewise integration treatment in the proposed interface movement equation in this research gives a more accurate mass change description during the interface movement. The correctness of the proposed interface movement equation was also proved by a comparison with the analytical solutions.

Keywords

Stefan problem

control volume method

interface movement

mass conservation

© 2020 The Author(s). Published by Elsevier B.V.

Source: https://www.sciencedirect.com/science/article/pii/S2238785420320548?dgcid=rss_sd_all

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Material

Fe-bearing intermetallics transformation and its influence on the corrosion resistance of Al-Mg-Si alloy weld joints

Publication date: Available online 2 December 2020

Source: Journal of Materials Research and Technology

Author(s): Xia-Ming Chen, Qi-Peng Dong, Zhen-Guang Liu, Xiao-Nan Wang, Qing-Yu Zhang, Zeng-Rong Hu, Hiromi Nagaumi

Republished by Plato

Published

on


Elsevier

Available online 2 December 2020

Journal of Materials Research and Technology

open access

Abstract

This work investigated the transformation of Fe-bearing intermetallics and its influence on the corrosion behavior of Al-Mg-Si alloy weld joints. The results showed that the size and type of Fe-bearing intermetallics determined the pitting corrosion resistance of weldment regions. The partially melted zone (PMZ) suffered most serious corrosion attack, because of the formation of coarse needle-like β-AlFeSi. The heat-affected zone (HAZ) immediately behind the PMZ (HAZ-Ⅰ) experienced a complete transformation of β-AlFeSi into α-AlFeSi, but in the rest of the HAZ (HAZ-Ⅱ) was not sufficient for this transformation. Therefore, the HAZ-Ⅰ was more resistant to pitting corrosion than HAZ-Ⅱ.

Keywords

Corrosion behavior

Fe-bearing intermetallics

partially melted zone

fusion welding

Al-Mg-Si alloy

© 2020 The Author(s). Published by Elsevier B.V.

Source: https://www.sciencedirect.com/science/article/pii/S2238785420320445?dgcid=rss_sd_all

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