Growth of single-crystal W whiskers during humid H2/N2 reduction of Ni, Fe–Ni, and Co–Ni doped tungsten oxide

Wang, Shiliang; He, Yuehui; Zou, Jin; Wang, Yong; Huang, Han

doi:10.1016/j.jallcom.2009.02.126

Cited by 9 publications

(5 citation statements)

References 21 publications

(22 reference statements)

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“…Different structures and morphologies have been reported. For example, different WO x reported morphologies include nanoparticles, 10,11 nanoplates, 12 whiskers, 13 nanotubes, 14 and nanorods, 6,15 etc. excluding conventional thin and thick films.…”

mentioning

confidence: 99%

Synthesis of Three-Dimensional Tungsten Oxide Cactus-Shaped Nanostructures Supported on Carbon Nanotubes Template

Choo

Niu

et al. 2011

Electrochem. Solid-State Lett.

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We report that three-dimensional cactus-shaped tungsten oxide WO x (x ¼ 2-3) nanostructures have been synthesized over a large area using a simple one-step metal-organic chemical vapor deposition (MOCVD) technique at unusually lower temperatures than previously reported, making use of vertically aligned carbon nanotubes (CNTs) as the base template in a core-shell configuration. Each WO 3 crystallite forms independently perpendicular to the CNT spine resulting in the cactus-like structures. The presence of these structures has been shown to lead to improved electron emission properties, where the turn-on field was lowered from pristine CNTs at 3.47-2.31 V lm À1 with an increase in the field enhancement factor from $1225 to $3985. The growth mechanism of the nanostructures is discussed.Among all the transition metal oxides, tungsten oxides WO x (x ¼ 2-3) have been extensively studied due to their wide range of unique material properties, which includes electrochromic, optochromic and gasochromic properties. 1-9 These unique properties make WO x highly flexible for applications such as electrochromic windows, 1,2 solar cells, 3 gas sensors, 4,5,9 and photocatalyst materials. 6 One way to control and enhance its unique materials properties is to modify its morphology and physical structure. Different structures and morphologies have been reported. For example, different WO x reported morphologies include nanoparticles, 10,11 nanoplates, 12 whiskers, 13 nanotubes, 14 and nanorods, 6,15 etc. excluding conventional thin and thick films.There are many advantages in obtaining these unique nanosized structures. For example, there is a significant increase in the surface area of the nanostructured WO x as compared with thin films, leading to an increase in the efficiency of WO x based sensors. In the recent few years, nanostructured WO x , especially WO x nanowires, has also found potential applications in field emission applications due to their unique high-aspect ratio structures, 16-18 with good robustness and longevity. 19,20 One of the most attractive features lies with the morphology of WO x , where it has the capability to form tree-like structures when physical growth methods, such as conventional thermal deposition, 11,21,22 are used. This was reported by Zhu et al. as early as 1999, 21 where unique structures could be obtained through heating a W foil partly covered by a SiO 2 plate in an Ar atmosphere at 1600 C. There were also reports of three-dimensional regular (3D) network of WO x nanowires obtained through thermal evaporation of W powders in the presence of oxygen at 1400-1500 C. 22 In this letter, we report a simple approach to obtain 3D WO x nanostructures at a much lower temperature process of 600 C (as compared to >1000 C for standard furnace process). The uniqueness lies in using highly conductive multiwalled carbon nanotubes (CNTs) as the base template for the WO x nanowires to first encapsulate around forming a core-shell structure. Subsequently, unique 3D cactus-shaped nanostructures can be obtained ...

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mentioning

confidence: 99%

Synthesis of Three-Dimensional Tungsten Oxide Cactus-Shaped Nanostructures Supported on Carbon Nanotubes Template

Choo

Niu

et al. 2011

Electrochem. Solid-State Lett.

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“…For example, a vacuum pyrolysis/carbothermal treatment (VPC) as reported by Li et al . Various physical vapor deposition methods, like an electron‐beam‐induced deposition , direct chemical vapor deposition methods (CVD) , a nickel‐catalyzed CVD leading to single crystalline wires , and also an electron and ion beam induced chemical vapor deposition method producing amorphous tungsten wires have been reported . During the last years a new and sophisticated method for the production of nanowires was established.…”

Section: Introductionmentioning

confidence: 99%

Downsizing of single crystalline high aspect ratio tungsten nanowires

Milenković

Drensler

Hassel

2015

Physica Status Solidi (a)

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Directional solidification of eutectic NiAl–W alloys offers an intuitive method to produce tungsten nanowires. Through the use of two different methods, the well‐established Bridgman method and a newer type floating zone method, the direct influence of process parameters, like the withdrawal rate and the temperature gradient, onto the sample microstructure were studied. The sharp temperature gradient, built up using a four mirror system focusing the light emitted by halogen lamps inside the optical floating zone furnace allows producing nanowires with a diameter as small as 75 nm. Differences in the solid/liquid interface morphology depending on the solidification method used are discussed.

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“…Very recently, W nanowires and the oxide nanowires, with well-defined singlecrystalline structure and unique geometry, have attracted intensive attention due to their great potential applications as field emitters and strength agents [2][3][4][5][6][7][8][9][10][11][12][13]. So far, various methods have been developed to fabricate W nanowires, such as direct CVD [2][3][4][5], metal-catalyzed CVD [14][15][16][17][18], electron beam induced deposition [19][20][21] and self-organization methods [22,23]. In terms of feasibility, metal-catalyzed CVD method has been developed to be one of the most successful methods for controlling synthesis of semiconductor nanowires [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

“…Here, we further reported the successful growth of tetragonal W nanowire arrays on W substrates by Ni-catalyzed CVD method. It was quite interesting to note that the growth of the W nanowires on W substrate, which was unlike the growth of columned W nanowires induced by the Ni, Ni-Fe or Ni-Co catalysts located at the wire tips [14][15][16][17], was induced by the Ni catalysts at the root of nanowires. The synthesized W nanowire with a high aspect ratio and a sharp tip, would be an ideal configuration for the field emission applications.…”

Section: Introductionmentioning

confidence: 99%

Growth of single-crystal W whiskers during humid H2/N2 reduction of Ni, Fe–Ni, and Co–Ni doped tungsten oxide

Cited by 9 publications

References 21 publications

Synthesis of Three-Dimensional Tungsten Oxide Cactus-Shaped Nanostructures Supported on Carbon Nanotubes Template

Synthesis of Three-Dimensional Tungsten Oxide Cactus-Shaped Nanostructures Supported on Carbon Nanotubes Template

Downsizing of single crystalline high aspect ratio tungsten nanowires

Low-temperature growth of tetragonal tungsten nanowire arrays on tungsten substrate using Ni solid catalysts

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