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Semiconductor Fabrication
Published in Nassir H. Sabah, Electronics, 2017
In chemical vapor deposition (CVD), chemical reactions involving gases and vapors at the surface of the wafer lead to deposition of material on this surface. A variety of materials can be deposited in this manner, including silicon, polysilicon, dielectrics such as SiO2 or silicon nitride, metals such as tungsten and copper, and barrier metals such as titanium nitride and tungsten nitride. Depending on the material to be deposited, CVD can take place at atmospheric pressure (APCVD), at a low pressure of 0.25–10 mm of mercury (LPCVD), or can be plasma enhanced (PECVD). An important advantage of CVD is its good step coverage, meaning a good coverage of both the vertical and horizontal surfaces of a steplike geometry on the surface of the wafer. Such geometries become more prominent with continuing reduction in minimum feature size.
Carbon Nanomaterials in Electrolysis and Hydrogen
Published in Shuhui Sun, Xueliang Sun, Zhongwei Chen, Yuyu Liu, David P. Wilkinson, Jiujun Zhang, Carbon Nanomaterials for Electrochemical Energy Technologies, 2017
Yuyu Liu, Hongbing Zhao, Rongzhi Chen, Jinli Qiao, David P. Wilkinson, Jiujun Zhang
Finally, it should be mentioned that a few more catalysts, including MoS2 [19,72,73], tungsten nitride [74], NiP2 [75], WS2 [73], cobalt phosphide [5], MoSe2 [76,77], CoSe2 [78], and iron phosphide [79] were studied by being supported on carbon cloth (CC) for high HER performance. Zhang et al. [19] realized the active-edges control of MoS2 nanosheets on CC (MoS2⊥CC) by growth control during the synthesis procedure. MoS2 nanosheets vertically grown on CC were confirmed to be the best morphology with maximum active edges. This three-dimensional cathode, MoS2⊥CC, can reach a great current density of 200 mA cm−2 at a small overpotential of 205 mV. The preeminent HER performance can rival the best MoS2-based catalyst ever reported.
Proton Exchange Membrane Water Electrolysis
Published in Lei Zhang, Hongbin Zhao, David P. Wilkinson, Xueliang Sun, Jiujun Zhang, Electrochemical Water Electrolysis, 2020
Zhao Jin, Shuai Hou, Zhaoyan Luo, Rongpeng Ma, Yang Li, Yibo Wang, Junjie Ge, Changpeng Liu, Wei Xing
Tungsten nitride has high stability and strong corrosion resistance in an acidic electrolyte, but its catalytic activity against the HER is poor [111]. We can increase its activity by introducing carbon or other metal heteroatoms. Zhu et al. [112] rationally designed tungsten nitride-carbon composites to optimize the activity of tungsten nitride, and prepared nitrogen-rich porous graphene-based carbon-bonded tungsten nitride (WNx) by an ion exchange method. This catalyst has a highly porous structure and is highly rich in nitrogen, and exhibits excellent HER catalytic performance and good stability due to their synergistic effects. This work provides practical methods and ideas for the future research of tungsten nitride-carbon composites.
Dissipative induced magnetic field on axisymmetric stagnation point flow of Propylene Glycol (PG) infused with multiple shape Tin (Sn), and Tungsten W (nanometer) particles
Published in Waves in Random and Complex Media, 2022
Shakil Shaiq, Azeem Shahzad, Jawad Ahmed, Muhammad Nadeem, Muhammad Ayub
In today's world, nanofluids play an important role in pharmaceutical procedures, microelectronics, and nanotechnology, etc. Nanofluids have a wide range of well-known applications, including heat exchange, ceramic layers for solar cells, targeted drug delivery, and hybrid power engines [1]. Choi et al. [2] anticipated that these nonmaterials are submerged in base fluids like water, engine oil, propylene glycol, and ethylene glycol, etc. Their preliminary research revealed that nanoparticles of metal such as (Tin, aluminum, zinc), nitrides (Tungsten nitride), carbides, carbon nanotubes CNTs, and oxides (silicon dioxide, copper oxide, etc.) improve the thermal conductivity of natural base fluids. The nanofluid boundary layer flow over a rotating disk was investigated by Ahmed et al. [3] and came to the conclusion that Brownian motion and thermophoresis have a significant impact on fluid flow and heat transfer. Some new considerable contributions are cited in Refs. [4–7] and many more therein.
Bismuth (III) oxide decorated graphene oxide filled epoxy nanocomposites: thermo-mechanical and photon attenuation properties
Published in Advanced Composite Materials, 2023
Srilakshmi Prabhu, S. G. Bubbly, S. B. Gudennavar
Inorganic fillers, formed by combination of carbon-based nanomaterials with metal oxides, into a polymer matrix introduces synergistic properties in composites, whilst mitigating the disadvantages of traditional shielding materials such as heavy metals (lead and lead based materials), glass matrix composites, concrete and ceramics. In scientific sense, this presents a novel strategy to design and develop high-performance radioprotective materials for several reasons. Firstly, the surface decoration of GO with metal oxides and their molecular attachment would transform GO as a carrier of these metal oxides, thereby resulting in their uniform distribution in the matrix [19]. This would result in the formation of continuous network across the reinforced phase enhancing the radiation-matter interaction, leading to faster radiation attenuation. Secondly, surface decoration most likely influences the size and micro-structure of the modified structures, thus affecting the overall physico-mechanical properties of the reinforced phase [7, 20, 21]. For instance, Hashemi et al. demonstrated that the decoration of GO onto highly interconnected and dense structure of iron tungsten nitride (ITN) would yield hybrid composites (GO-ITN) of high density (24.21 g cm−3), which not only offers good shielding properties but also displays high electrical conductivity [21]. Polyaniline composites (1.2 mm thick) containing 50 wt% GO-ITN showed 78.073%/57.128%/44.995% greater X-ray attenuation at 30/40/60 kV tube voltage compared to neat polymer. Further, the combination of low-Z elements (especially carbon and oxygen) and heavy metals (cerium, gadolinium, bismuth, etc.) influence the attenuation behaviour by increasing the probability of Compton scattering, thus enhancing overall shielding properties [19, 22]. The nanocomposites fabricated using blend of PMMA and PVA containing 0.3 wt% GO showed transmission of < 50% for γ-rays from 60Co source [23]. Similarly, the fabric used in commercial scrubs and gowns by clinical staff was modified using 1 wt% GO nanoparticles using layer-by-layer technique to develop efficient X-ray shields [24].
Metal nitride-based nanostructures for electrochemical and photocatalytic hydrogen production
Published in Science and Technology of Advanced Materials, 2022
Harpreet Singh Gujral, Gurwinder Singh, Arun V. Baskar, Xinwei Guan, Xun Geng, Abhay V. Kotkondawar, Sadhana Rayalu, Prashant Kumar, Ajay Karakoti, Ajayan Vinu
Chemical vapor deposition (CVD) is a popular method for the synthesis of a range of materials of various shapes, sizes, and morphologies including single or bimetallic compositions of MN. In the CVD approach, a chemical reaction is induced in the vapor phase at various temperatures and low-pressure accompanied by the deposition of the final material on the substrate. The process is versatile and can be applied to form multiple types of compounds including but not limited to the involvement of the substrate. For example, Ji et al. [105] prepared an integrated strategy to synthesize large monolayer hexagonal boron nitride (h-BN) on the surface of polycrystalline copper foil by the low-pressure CVD technique. The author also demonstrated the fabrication of monolayer, bi-, and tri-layer hexagonal BN structures using this technique. The boron and nitrogen were brought in the vapor phase by heating ammonia borane at ~70°C and fed in the CVD reactor to initiate the growth of hBN at 1050°C under H2 flow over an electropolished Cu foil. The Cu substrate orientation and the conditions for electropolishing influenced the morphology of the monolayers. It was also observed that the bilayers of different morphologies including triangle, trapezoid, and hexagon, could be achieved over monolayers. Similarly, Chang et al. [106] synthesized an h-BN using ammonia borane precursor on the surface of Cu foil with a thin passivating oxide layer as substrate. Similar to the report of Ji et al. [105], the epitaxial relationship between the Cu foil and the h-BN leads to the formation of large-sized crystalline domains of approximately 1–20 μm within the ∼100 μm film. Other materials such as tungsten nitride (WN) have also been grown using CVD technique. For example, Wang et al. [107] synthesized ultrathin single-crystal WN using the salt-assisted chemical vaporization deposition technique on a silica substrate as shown in Figure 5. WN was synthesized by evaporation of WO3 premixed with NaCl from an alumina boat within the tube furnace followed by the introduction of ammonia (NH3) for the formation of WN. The resulting h-WN films were triangular in orientation and around 3 nm in thickness. It was found that films do not grow in the absence of salt, suggesting the role of salt in the formation of intermediate compounds that are more volatile and facilitate the deposition of WN films. The structure could also be tuned by varying the concentration of ammonia introduced in the systems and an increase in the ammonia concentration leads to the transition of 2D ultrathin WN to 3D nanostructures, suggesting the versatility of this approach. Similarly, syntheses of many other transition MNs with different structures including 0D, 1D, and 2D using the CVD technique and the strategies of manipulating the electronic properties through doping, defect engineering and hybridization have been previously reviewed by Wang et al. [49].