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Practically hafnium forms with carbon the only one chemical compound ( see also section C–Hf in Table I-2.13) – hafnium monocarbide HfC 1−x with extremely broad …
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Nanocrystalline hafnium nitrides and hafnium carbides are synthesized, from powder mixtures based on partially hydrated hafnium tetrachloride, ph-HfCl 4, and on magnesium, by a three-step process, namely a short mechanical activation step followed by a brief annealing step and a leaching step. Grinding of ph-HfCl 4 + Mg leads to the …
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Hafnium carbide prepared in this way gave the following analysis: Hf* = 92.2 wt%; C = (Total: 7.97%, Free: 0.78%); 0 = 910 ppm. Reaction between hafnium carbide and tantalum oxide It has been reported [7] earlier that the rate of CO evolution in the carbide-oxide reactions is much faster when the reaction is carried out in the solid state.
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The isothermal oxidation of HfC single crystals with (100) orientation was carried out using an electromicrobalance at temperatures of 600 to 900 C at an oxygen pressure of 2 to 8 kPa. Nonisothermal oxidation was performed by a simultaneous thermogravimetry-differential thermal analysis-mass spectrometry analysis. A polished …
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Type of activity: Medium Study (4 months, 25 KEUR) . Background and Motivation . Hafnium Carbide (HfC) is one example of advanced ceramic fiber matrices. It is a …
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Achieving Dislocation Strengthening in Hafnium Carbide through High Pressure and High Temperature | The Journal of Physical Chemistry C. ACS Publications. C&EN. Website …
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Aldrich - 594636; Hafnium(IV) carbide <1.25 μm particle size; CAS No. 1; catalyst | Find related products, papers, technical documents, MSDS & more at Sigma-Aldrich
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To this end, hafnium carbide (HfC) has attracted scientists' and engineers' attention in the field of TPS [10]. Compared to traditional ZrB2, HfC exhibits comparable mechanical and thermal properties (expansion, conductivity, specific heat et al.), but its oxide, HfO2, has a higher melting point (≈2800 °C) and lower saturated vapor pressure [11].
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The TPS is an isolator material which have range temperature −121 °C until 1.649 °C. This paper analyzes Tantalum Carbide (TaC) and Hafnium Carbide (HfC) for spacecraft material. We show that Tantalum Carbide (TaC) and Hafnium Carbide (HfC) would rise above the TPS materials temperature. The comparison among RCC, HRSI, …
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Wednesday, June 13, 2018. George Bedinger, a mineral commodity specialist for the U.S. Geological Survey, compiled this information on hafnium, a metal used in superalloys and the nuclear industry. Hafnium is a ductile metal with a brilliant silver luster. It does not exist as a free element in nature; it is always associated with zirconium.
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Abstract. Hafnium diboride (HfB 2) nanoparticles have been prepared by a solid-state reaction of hafnium dioxide (HfO 2), metallic magnesium (Mg) and sodium borohydride (NaBH 4) at 700°C in an autoclave.The structure and morphology of the obtained product are investigated by X-ray powder diffraction (XRD), transmission …
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This paper reviews the crystal chemistry, synthesis, densification, microstructure, mechanical properties, and oxidation behavior of zirconium diboride (ZrB 2) and hafnium diboride (HfB 2) ceramics.The refractory diborides exhibit partial or complete solid solution with other transition metal diborides, which allows compositional tailoring of …
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Four different absorber materials are inserted in the same capsule: hafnium carbide, hafnium carbide with a molybdenum silicide additive, samarium hafnate, and europium hafnate. The two capsules are planned for irradiation in the flux trap of the High Flux Isotope Reactor at two different neutron fluence levels and with a target specimen ...
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An in situ polymerizable complex method to produce zirconium carbide, hafnium carbide and their ternary carbides at a relatively low temperature (1300 °C) using simple and mainly nontoxic starting reagents is presented. In this aqueous process, citric acid (CA) was used to chelate the metal ion and ethylene glycol (EG) to form a …
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The chemical formula for Hafnium Carbide is HfC. It is the most refractory binary compound known to man. Similarly, hafnium nitride (HfN) is the most refractory nitride known with a melting point of approximately 3305 °C. Key Properties. Property Value; Density ( g.cm-3 ) 12.2: Melting Point ( °C )
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Abstract. Hafnium carbide HfC (at%: 42%C; 49%Hf; 7%O) was investigated under rapid heating by a current pulse, in a time of 5–8 μs. The …
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Hafnium carbide-based solid solution ceramics with yttria additions were consolidated via hot pressing utilizing chromium carbide as a transient liquid sintering agent. Selected samples were oxidized at temperatures exceeding 2200 °C under high velocity airflow to determine their potential for service in ultra-high temperature …
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The present paper reports on the comparative high-temperature emissivity characterization of hafnium and tantalum carbide ultra-high temperature ceramics to evaluate their potential as novel absorbing materials for concentrating solar power plants. ... Financial support by the Access to Research Infrastructures activity in the 7th …
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The results suggest a transition in the oxidation activity of Cf/HfC at 1650–1700 °C in reduced pressure (<10 kPa), from reaction-control to diffusion-control, due to the accumulation of porous ...
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72 Hf 178.480000000 Hafnium. See more Hafnium products. Hafnium (atomic symbol: Hf, atomic number: 72) is a Block D, Group 4, Period 6 element with an atomic weight of 178.49. The number of electrons in each of Hafnium's shells is 2, 8, 18, 32, 10, 2 and its electron configuration is [Xe] 4f 14 5d 2 6s 2.
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Hafnium carbide nanoparticles for noninflammatory photothermal cancer therapy. Journal of Colloid and Interface Science 2023-12 ... Thermosensitive Hydrogel Loaded with Nickel–Copper Bimetallic Hollow Nanospheres with SOD and Enzymatic-Like Activity Promotes Acute Wound Healing. ACS Applied Materials & Interfaces
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Synthesis and Electrochemical Properties of Two-Dimensional Hafnium Carbide. . 2017 Apr 25;11 (4):3841-3850. doi: 10.1021/acsnano.7b00030. Epub 2017 Apr 6.
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work, plasmonic group IV transition metal carbide (TiC, ZrC, and HfC) nanostructures were ... and catalytic activity.19,32,33 While reports on plasmonic nitride nanoparticles (NPs) have soared over the past few years, there has yet to be detailed investigation ... hafnium dioxide (HfO 2, 99.95%, 61-80 nm) were purchased from U.S. Research ...
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Abstract. We demonstrate fabrication of a two-dimensional Hf-containing MXene, Hf 3 C 2Tz, by selective etching of a layered parent Hf 3 [Al (Si)] 4 C 6 compound. A substitutional solution of Si on Al sites effectively …
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To this end, hafnium carbide (HfC) has attracted scientists' and engineers' attention in the field of TPS [10]. ... Despite of those achievements, there is still scarce work focusing on the oxidation activity of the HfC based composite in on-ground simulated aerodynamic heating environment [15,16]. Therefore, in this work, an inductively ...
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where T is temperature, K, and x is the value of index in HfC 1−x formula (Eqs. ()–() were recommended for the range of temperatures from 1200 to 2500 K).The thermodynamic functions of stoichiometric hafnium carbide are tabulated by Turchanin et al. [58, 59] in the range of 0–3000 K, by Schick [] in the range of 0–3900 K and by Barin [] …
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Unlike the porous ablated structure of hafnium carbide with plenty of holes, a dense oxide scale formed on the surface for ablated HfC 0.76 N 0.24 specimen. ... Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction. Science, 323 (2009), pp. 760-764. CrossRef View in Scopus Google Scholar [29]
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To this end, hafnium carbide (HfC) has attracted scientists' and engineers' attention in the field of TPS [10]. ... The oxidation activities lead to the formation of a continuous HfO 2 oxide scale on the C f /HfC to further resistant inner diffusions of oxygen species (O 2 and O). The thermal balance is interrupted when the surface ...
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For example, hafnium carbide begins to oxidize at about 800 °C [7] with the formation of a HfO 2 layer on the sample surface, which cracks and breaks its integrity as a diffusion barrier, thereby facilitating the penetration of oxygen and accelerating oxidation. However, with the temperature rise to 1600–1800 °C, the formed oxide layers are ...
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Hafnium carbide (HfC) is a potential candidate of ultrahigh-temperature ceramics (UHTCs) and has attracted significantly widespread interest in recent years. Here, we have synthesized high-purity HfC samples with NaCl-type structure by using a high …
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