Synthesis and Sintering

High-temperature spark plasma sintering of h-BN composites reinforced with carbon nanotubes, carbon fibers, and graphene nanoplates

Hossein Eslami-Shahed, Khanali Nekouee, Farhad Moravvej-Farshi, Fatemeh Dabir — Mon, 16 Dec 2024 02:55:36 -0400

In this study, two h-BN-based composites reinforced with carbon fibers (CF) and carbon fibers/carbon nanotubes (CNTs)/graphene nanoplates (GNPs) have been produced successfully through a high-temperature spark plasma sintering. 1 Wt.% short carbon fibers (length of 5 mm) with 0.1 Wt.% of CNTs and also 0.1 Wt.% of GNPs as hybrid composite were mixed through a simple mixing method including a high energy sonicating and stirring on the hot plate in ethanol media until drying. Moreover, h-BN/1 Wt. % CF composite was mixed with a similar method to compare impacts of CNTs and GNPs addition on the mechanical properties and microstructure of h-BN/CF composite. The high-temperature spark plasma sintering processes were performed at vacuum conditions of almost 20-25 MPa with a starting pressure of 10 and a final applied pressure of 50 MPa at a maximum temperature of 1900˚C. Both prepared samples showed near full densification of higher than 98.1 % of the theoretical density determined by Archimedes’ principle. Investigation of the crystalline phases by XRD represented only related peaks to h-BN. The FESEM images indicated an almost uniform distribution of reinforcement in the h-BN matrix. Furthermore, the polished surface of the provided samples showed only the pulled-out carbon fibers effects while the fracture surfaces confirmed the presence of CF and it’s tunneling effects. The obtained mechanical properties revealed 273±12 MPa of bending strength, 1.32±0.1 GPa of Vickers hardness, and 4.79±0.2 MPa.m^0.5 fracture toughness for the prepared hybrid composite.

Silver nanowires: recent advances in synthesis, transparent conductive coatings, and EMI shielding applications

Ali Borchloo, Reza Shoja-Razavi, Hamed Naderi-Samani — Thu, 12 Dec 2024 12:47:44 -0400

Indium tin oxide (ITO) is a broadly utilized transparent conductor, although it possesses several limitations such as high cost and brittleness. This paper investigates silver nanowires (AgNWs) as suitable material due to their improved electrical conductivity, flexibility, and transparency. We investigated several techniques for creating AgNWs, including template, chemical, polyol, and electrochemical approaches. The polyol method is highlighted as very cost-effective and efficient; however, it produces nanoparticle byproducts. We explore changes to the polyol technique that aim to improve yield and purity. The review examines how AgNWs are made, talking about nucleation, phase transitions of silver atoms, and the formation of pentagonal grains. These characteristics show how effectively the polyol approach works for generating high-quality AgNWs on a large scale. We investigated the relationship between AgNW concentration of, the additive's characteristics, and the surface tension and viscosity of the resultant ink, with a focus on how these variables influence different coating processes. The study reviews the process of converting AgNWs into conductive inks for use in transparent conductive films (TCFs), with applications including transparent heaters, touch panels, sensors, solar cell electrodes, and electromagnetic interference (EMI) shielding devices. The research overview concludes with a discussion of potential future directions and the promising role of AgNWs in advancing TCF technologies.

Synthesis and characterization of ZnS and Ag-ZnS nanoparticles for photocatalytic degradation of aqueous pollutants

Fri, 06 Dec 2024 03:09:30 -0400

Photocatalytic degradation has drawn much interest recently as a substitute technique for eliminating environmental contaminants from the aqueous phase. In this study, pure and Ag-doped zinc sulfide (ZnS) nanoparticles were synthesized for the photocatalytic degradation of methylene blue (MB) under UVA light irradiation using a simple chemical co-precipitation method. The nanopowders' structural, optical, morphological, and chemical properties were characterized using XRD, FTIR, UV-Vis, and FESEM techniques. XRD analysis confirmed the hexagonal crystal structure of the nanoparticles, while FTIR identified stretching vibrations corresponding to O–H, C–H, C=O, C–N, and Zn–S bonds. The UV-Vis analysis revealed an optical band gap in the range of 5.2–5.4 eV. Photocatalytic performance tests under UVA light demonstrated that Ag doping significantly enhanced the photocatalytic efficiency of ZnS nanoparticles in degrading MB. Upon exposure to UVA light, the synthesized Ag-ZnS nanoparticles achieved impressive decolorization efficiency within 25 minutes, compared to 35 minutes for pure ZnS. The findings indicate that Ag-ZnS is a highly promising photocatalyst for the efficient removal of aqueous pollutants, including methylene blue dye.

Neutron shielding performance of polyethylene-7% B and Al-30 wt% B4C composites fabricated via hot-press sintering

Fri, 15 Nov 2024 00:00:00 -0400

The current research aims to investigate the neutron shielding features of polyethylene-7% B and Al-30 wt% B₄C composites that are fabricated via the hot-press sintering. The practical analysis was conducted via Neutron radiography and simulation through MCNP code. The results illustrated the Al-30 wt% B₄C with 5 mm thickness has equivalent neutron absorption properties with 14 mm thickness of PE-%7 B. Composites with higher density and homogenous distribution of B₄C have a better neutron shield property. Al-30 wt% B₄C Composite fabricated at 650 °C has a higher neutron absorption property. Experimental and simulation findings confirmed each other at the lower thicknesses and Al-30 wt% B₄C has better neutron shielding than PE-7% B. At thicknesses over 1 cm, the amount of cross-sectional area of polyethylene-7% B and Al-30 wt% B₄C composites are near to each other. By increasing the thicknesses of composites, the relative total dose reduction and the shield properties of composites are enhanced.