Monoatomic tantalum induces ordinary-pressure phase transition from graphite to n-type diamond

Chen, Chengke; Fan, Dong; Xu, Hui; Jiang, Meiyan; Li, Xiao; Lu, Shaohua; Ke, Changcheng; Hu, Xiaojun

doi:10.1016/j.carbon.2022.05.013

Cited by 11 publications

(4 citation statements)

References 55 publications

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“…This is in good agreement with the results that the monodispersed Ta atoms were distributed in our sample prepared by HFCVD. [ 20,21 ] In addition, we recently find that these monodispersed Ta atoms let graphite transit to diamond in the low‐pressure CVD process [ 20 ] or annealing process without pressure. [ 21 ] It is noticed that there are graphite in as‐deposited HF‐UNCD films, while the content of graphite is small and diamond grains become much larger after PPT process.…”

Section: Resultsmentioning

confidence: 99%

“…[ 20,21 ] In addition, we recently find that these monodispersed Ta atoms let graphite transit to diamond in the low‐pressure CVD process [ 20 ] or annealing process without pressure. [ 21 ] It is noticed that there are graphite in as‐deposited HF‐UNCD films, while the content of graphite is small and diamond grains become much larger after PPT process. This suggests that graphite in grain boundaries transits to diamond via the help of monodispersed Ta atoms during the CH 4 /N 2 PPT process, which connects the surrounded smaller nanosized diamond grains to aggregate larger diamond grains.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, we reported that for the UNCD films deposited by hot filament chemical vapor deposition (HF‐CVD), namely HF‐UNCD films, monodispersed Ta atoms from hot filament wires were found in the samples, which played an important role in the diamond formation in CVD [ 20 ] and let graphite transit to diamond during high‐temperature annealing under normal pressure. [ 21 ] This suggests that the microstructure evolution of HF‐UNCD films will be different from that of MP‐UNCD films due to the existence of monodispersed Ta atoms during the PPT process, giving diverse influences in the EFE properties of the films. Also, HF‐CVD process can synthesize larger‐area diamond films than MP‐CVD process, implying stronger potential in the fabrication of EFE devices.…”

Section: Introductionmentioning

confidence: 99%

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Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

Chen

et al. 2022

Physica Status Solidi (a)

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Diamond films possess distinctive and superior properties such as high hardness, chemical inertness, high electron fieldemission (EFE) capacity, and semiconductivities (via doping), which have gained interest among researchers in recent years. [1][2][3] However, the characteristics of diamond films change markedly with their microstructure. The ultrananocrystalline diamond (UNCD) films consist of ultrasmall diamond grains with the size about 5 nm and sp 2 -bonded carbon in grain boundaries. Therefore, the UNCD films show better conductivity and superior EFE properties compared with the microcrystalline diamond films which contain large and faceted diamond grains. [4][5][6][7] However, the sp 2 -bonded carbon contained in the grain boundaries of the UNCD films is still inadequately conductive, which limits the EFE properties of these films. Fortunately, UNCD films possess a versatile granular structure, which can be altered easily to form nanographitic phase that leads to better conductivity and hence superior EFE properties. [8,9] It was reported that through the addition of N 2 in CH 4 /Ar plasma, a noticeable increase in the width of the grain boundaries resulted, which enhanced the n-type conductivity of UNCD films to a high level as σ ¼ 143 S cm À1 . [10][11][12] Arenal et al., [13] grew the films in a plasma containing a large proportion of N 2 species, that is, CH 4 /[80%Ar-20%N 2 ], at high substrate temperature (>700 °C), which resulted in the formation of needle-like diamond grains, exhibiting a high conductivity of σ ¼ 200 S cm À1 for UNCD films. Sankaran et al., [14] investigated the effects of substrate temperature on the granular structure of UNCD films grown in CH 4 /(100%N 2 ) plasma and observed that needle-like diamond grains were obtained only at a substrate with high temperature (700 °C). Moreover, the high conductivity in diamond films grown in CH 4 /(100%N 2 ) plasma (at 700 °C) was concluded due to the existence of nanographitic phase encapsulating the needle-like diamond grains. Furthermore, they observed that the C 2 and CN species (one carbon atom connected to one nitrogen atom) in the plasma were the main constituents, which resulted in the

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

Chen

et al. 2022

Physica Status Solidi (a)

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“…Fortunately, it was reported that graphite could direct transform into diamond without additional pressure and only by annealing at temperatures lower than or equal to 1000 °C; , the mechanism was recently discovered, and atomically dispersed Ta atoms from hot filaments were found to play a key role in this unusual phase transition. , These insights inspired us to explore whether there are other metals that can play a more advantageous role than Ta and to discover the universal rules that will help predict the role of certain elements in the phase transition. This will stimulate the development of a universal synthesis method for diamond based on graphite under ordinary pressure, which is significant for the applications of diamond.…”

Section: Introductionmentioning

confidence: 99%

Monodispersed Transition Metals Induced Ordinary-Pressure Phase Transformation from Graphite to Diamond: A First-Principles Calculation

Chen

Guo

et al. 2023

ACS Appl. Mater. Interfaces

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High pressure and high temperature are normally required for the transformation of graphite to diamond; thus, finding a method that allows the transformation to occur under ordinary pressure will be extremely promising for diamond synthesis. Here, it is found that graphite spontaneously transforms into diamond without any pressure by adding monodispersed transition metals, and the universal rules that will help predict the role of certain elements in the phase transition were studied. The results show that the favorable transition metals possess an atomic radius of 0.136–0.160 nm and an unfilled d-orbital of d2s2–d7s2, which allow more charge transfer and accumulation at the proper position between the metal and dangling C atoms, leading to stronger metal–C bonds and a lower energy barrier for the transition. This provides a universal method to prepare diamond from graphite under ordinary pressure and also provides a way for the synthesis from sp2 to sp3 bonded materials.

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Nanodiamond Coating in Energy and Engineering Fields: Synthesis Methods, Characteristics, and Applications

Zhao,

Song,

Zhang

et al. 2024

Small

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Nanodiamonds are metastable allotropes of carbon. Based on their high hardness, chemical inertness, high thermal conductivity, and wide bandgap, nanodiamonds are widely used in energy and engineering applications in the form of coatings, such as mechanical processing, nuclear engineering, semiconductors, etc., particularly focusing on the reinforcement in mechanical performance, corrosion resistance, heat transfer, and electrical behavior. In mechanical performance, nanodiamond coatings can elevate hardness and wear resistance, improve the efficiency of mechanical components, and concomitantly reduce friction, diminish maintenance costs, particularly under high‐load conditions. Concerning chemical inertness and corrosion resistance, nanodiamond coatings are gradually becoming the preferred manufacturing material or surface modification material for equipment in harsh environments. As for heat transfer, the extremely high coefficient of thermal conductivity of nanodiamond coatings makes them one of the main surface modification materials for heat exchange equipment. The increase of nucleation sites results in excellent performance of nanodiamond coatings during the boiling heat transfer stage. Additionally, concerning electrical properties, nanodiamond coatings elevate the efficiency of solar cells and fuel cells, and great performance in electrochemical and electrocatalytic is found. This article will briefly describe the application and mechanism analysis of nanodiamonds in the above‐mentioned fields.

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Monoatomic tantalum induces ordinary-pressure phase transition from graphite to n-type diamond

Cited by 11 publications

References 55 publications

Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

Monodispersed Transition Metals Induced Ordinary-Pressure Phase Transformation from Graphite to Diamond: A First-Principles Calculation

Nanodiamond Coating in Energy and Engineering Fields: Synthesis Methods, Characteristics, and Applications

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