Effects of CaB2O4 Content on the Sintering Behavior of Hexagonal Boron Nitride

2011 ◽  
Vol 675-677 ◽  
pp. 131-134
Author(s):  
Yu Xia Cao ◽  
Ling Zhong Du ◽  
Wei Gang Zhang
Keyword(s):  
Boron Nitride ◽  
Diffraction Analysis ◽  
Apparent Density ◽  
Cross Sections ◽  
Hexagonal Boron Nitride ◽  
Sintering Behavior ◽  
Rockwell Hardness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes

CaB2O4 was added into hexagonal boron nitride (hBN) to improve the sintering behaviors of hBN. CaB2O4 and hBN were mixed and then pressed into plates. The plates were sintered at 2000°C for 5h under a N2 ambience. The phase compositions with different CaB2O4 contents were examined with X-ray diffraction analysis. The fracture cross-sections of the hBN plates were investigated by SEM. The apparent density and Rockwell hardness were also measured. The results show that the hBN particles had a plate-like shape and the grain sizes of hBN increased with increasing CaB2O4 contents. The apparent density and Rockwell hardness decreased with increasing CaB2O4 contents. When the CaB2O4 content was 15(wt) %, the hBN has the average grain sizes of 3μm in diameter and 200nm in thickness, the apparent density of 1.06 g/cm3 and the Rockwell hardness of 3, respectively.

Powder characteristics and sintering behavior of Ag-doped YBa2Cu3O7−x produced by aerosol decomposition

1992 ◽  
Vol 7 (4) ◽  
pp. 827-836 ◽  
Author(s):  
Timothy L. Ward ◽  
Toivo T. Kodas ◽  
Altaf H. Carim ◽  
Donald M. Kroeger ◽  
Huey Hsu
Keyword(s):  
Submicron Particles ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Powder Synthesis ◽  
X Ray ◽  
Grain Sizes ◽  
Powder Characteristics ◽  
Scanning Electron ◽  
Nitrate Solutions ◽  
Reaction Routes

YBa2Cu3O7−x (1-2-3) powders and 1-2-3 powders doped with 14 wt. % Ag (AgYBa2Cu3O7−x) were produced using aerosol decomposition of nitrate solutions. Powder produced at T > 900 °C consisted of submicron particles and had Tc ≍ 92 K in magnetic susceptibility measurements. As-produced Ag-doped powder was a composite of nearly phase-pure 1-2-3 and crystalline Ag (by x-ray diffraction) for reactor temperatures between 900 °C and 950 °C, whereas powder produced at T≥ 970 °C contained significant amounts of Y2BaCuO5 which were not found in 1-2-3 synthesis in the absence of Ag. This implied that the melting of Ag (∼960 °C) or the Ag-O eutectic (∼940 °C) promoted decomposition of 1-2-3 during powder synthesis. Dilatometry showed that 1-2-3 and Ag/1-2-3 powders densified rapidly between 800 °C and 875 °C, achieving nearly 90% of theoretical density after heating to 875 °C at 5 °C/min in air. Pellets of the Ag-doped powder were also sintered for 2-60 h at 895 °C in air. Scanning electron and optical microscopy revealed that Ag grains remained fine and uniformly distributed, varying in size from ∼1 μm after 2 h to 3–7 μm after 60 h, while 1-2-3 grains became plate-shaped with thicknesses of 1–5 μm and lengths of 10–30 μm after 60 h. Thus, the use of aerosol Ag /1-2-3 powders allows the use of lower processing temperatures and shorter times to produce dense ceramics with smaller Ag and 1-2-3 grain sizes than can be obtained using solid-state reaction routes.

scholarly journals AB-stacked nanosheet-based hexagonal boron nitride

2021 ◽  
Vol 77 (2) ◽  
Author(s):  
Jae-Kap Lee ◽  
Jin-Gyu Kim ◽  
K. P. S. S. Hembram ◽  
Seunggun Yu ◽  
Sang-Gil Lee
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Metastable Phase ◽  
Stacking Sequence ◽  
Lateral Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure High Temperature ◽  
Crystalline Growth

Hexagonal boron nitride (h-BN) has been generally interpreted as having an AA stacking sequence. Evidence is presented in this article indicating that typical commercial h-BN platelets (∼10–500 nm in thickness) exhibit stacks of parallel nanosheets (∼10 nm in thickness) predominantly in the AB sequence. The AB-stacked nanosheet occurs as a metastable phase of h-BN resulting from the preferred texture and lateral growth of armchair (110) planes. It appears as an independent nanosheet or unit for h-BN platelets. The analysis is supported by simulation of thin AB films (2–20 layers), which explains the unique X-ray diffraction pattern of h-BN. With this analysis and the role of pressure in commercial high-pressure high-temperature sintering (driving nucleation and parallelizing the in-plane crystalline growth of the nuclei), a growth mechanism is proposed for 2D h-BN (on a substrate) as `substrate-induced 2D growth', where the substrate plays the role of pressure.

scholarly journals Catalyst-Free Bottom-Up Synthesis of Few-Layer Hexagonal Boron Nitride Nanosheets

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Shena M. Stanley ◽  
Amartya Chakrabarti ◽  
Joshua J. DeMuth ◽  
Vanessa E. Tempel ◽  
Narayan S. Hosmane
Keyword(s):  
Electron Microscopy ◽  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
X Ray Diffraction ◽  
Bottom Up ◽  
X Ray ◽  
Boron Nitride Nanosheets ◽  
Catalyst Free ◽  
Transmission Electron ◽  
Novel Catalyst

A novel catalyst-free methodology has been developed to prepare few-layer hexagonal boron nitride nanosheets using a bottom-up process. Scanning electron microscopy and transmission electron microscopy (both high and low resolution) exhibit evidence of less than ten layers of nanosheets with uniform dimension. X-ray diffraction pattern and other additional characterization techniques prove crystallinity and purity of the product.

X-ray diffraction analysis of aluminum nitride sintered with cubic boron nitride

1997 ◽  
Vol 6 (8) ◽  
pp. 927-930 ◽  
Author(s):  
N.P. Bezhenar ◽  
S.A. Bozhko ◽  
N.N. Belyavina ◽  
V.Ya. Markiv
Keyword(s):  
Boron Nitride ◽  
Aluminum Nitride ◽  
Diffraction Analysis ◽  
Cubic Boron Nitride ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Exfoliation of Hexagonal Boron Nitride (h-BN) in Liquide Phase by Ion Intercalation

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 716 ◽  
Author(s):  
Danae Gonzalez Ortiz ◽  
Celine Pochat-Bohatier ◽  
Julien Cambedouzou ◽  
Mikhael Bechelany ◽  
Philippe Miele
Keyword(s):  
Aqueous Solution ◽  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
X Ray Diffraction ◽  
Electronic Microscopy ◽  
X Ray ◽  
Boron Nitride Nanosheets ◽  
Green Approach ◽  
Step Procedure ◽  
Ion Intercalation

A green approach to prepare exfoliated hexagonal boron nitride nanosheets (h-BNNS) from commercially pristine h-BN involving a two-step procedure was investigated. The first step involves the dispersion of pristine h-BN within an aqueous solution containing gelatin and potassium or zinc chloride using a sonication method. The second involves the removal of larger exfoliated h-BNNS through a centrifugation procedure. The exfoliation was caused not only by the sonication effect but also by intercalation of K+ and Zn2+ ions. Transmission electronic microscopy, X-ray diffraction and Raman spectroscopy techniques show that the obtained h-BNNS generally display a thickness of about a few (2–3) layers with an exfoliation efficiency as high as 16.3 ± 0.4%.

Sintering of Frustum Shaped Polycrystalline Diamond Compact at Non-Hydrostatic Pressure

2014 ◽  
Vol 665 ◽  
pp. 11-16
Author(s):  
Jian Lai Zou ◽  
Zi Li Kou ◽  
Chao Xu ◽  
Pei Wang ◽  
Shuai Yin ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Hexagonal Boron Nitride ◽  
Polycrystalline Diamond ◽  
Sem Analysis ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Micro Structure ◽  
X Ray ◽  
Diamond Layer ◽  
Polycrystalline Diamond Compact

This work present the study of the sintering of polycrystalline diamond compact with hyperbolic truncated cone profile using hexagonal boron nitride assembly, rather than salt mold, which is different from conventional assembly and this kind of polycrystalline diamond compact is widely used in percussion rock bits and roller cone rock bits. The well-sintered polycrystalline diamond compact without transition layer is prepared on a WC-10wt% Co substrate at temperature 1450°C for 3 min at non-hydrostatic high pressure of 5.5Gpa.Different analyzing techniques, such as X- ray diffraction, micro-Raman spectroscopy, scanning electron microscopy were applied to characterize the micro-structure, residual stress and sintering behavior. The SEM analysis indicates that diamond-diamond (D-D) direct bonding had formed in the polycrystalline diamond layer. The Raman spectroscopy shows compressive stress in the polycrystalline diamond layer is much higher than that sintered using traditional assembly.

scholarly journals Получение гетерогенных наночастиц Al/BN в микроволновой плазме

2020 ◽  
Vol 46 (10) ◽  
pp. 25
Author(s):  
Ш. Корте ◽  
М.К. Кутжанов ◽  
А.М. Ковальский ◽  
А.С. Конопацкий ◽  
Д.Г. Квашнин ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Boron Nitride ◽  
Microwave Plasma ◽  
Hexagonal Boron Nitride ◽  
Shear Stresses ◽  
X Ray Diffraction ◽  
Short Term ◽  
X Ray ◽  
Transmission Electron

In this work, the interaction of a mixture of Al and BN nanopowder with hydrogen microwave plasma was studied. Using X-ray diffraction analysis, scanning and transmission electron microscopy, the formation of AlN and AlB2 nanocrystals as a result of short-term (~ 30 ms) interaction of Al vapor with h-BN was established. Obtained results also indicate the formation of hydrogenated hexagonal boron nitride h-BN-H. The critical shear stresses were calculated for the interfaces between BN and Al, AlB2, and AlN. Approaches for increasing the strength of the composite materials based on hexagonal boron nitride and aluminum are discussed.

Preparation of n-type polyaniline/hexagonal boron nitride composites with a large thermoelectric power factor

2021 ◽  
pp. 096739112110425
Author(s):  
Volkan Ugraskan ◽  
Ebubekir Ceran ◽  
Ozlem Yazici
Keyword(s):  
Boron Nitride ◽  
Power Factor ◽  
Hexagonal Boron Nitride ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
X Ray Diffraction ◽  
Thermoelectric Power Factor ◽  
X Ray ◽  
Seebeck Coefficients ◽  
Vis Spectroscopy

In the present study, it was aimed to investigate the thermoelectric (TE) properties of polyaniline/hexagonal boron nitride (PANI/h-BN) composites. First, h-BN was synthesized from boric acid and urea. Then, PANI-HCl was synthesized by oxidative chemical polymerization. Finally, the composites were prepared using different weight ratios of h-BN. The composites were characterized using attenuated total reflection accessory attached Fourier-transform infrared spectroscopy, UV-vis spectroscopy, X-ray diffraction, and scanning electron microscopy/energy dispersive X-ray analyzer. TE investigation of the composites showed that the addition of h-BN significantly contributes to the TE properties of PANI-HCl. The addition of h-BN increased the power factor of PANI-HCl from 0.07 μWm−1K−2 to 143.05 μWm−1K−2. Furthermore, all the composites showed negative Seebeck coefficients which are the characteristics of n-type semiconductors.

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