scholarly journals Characterization and Microstructural Evolution of Continuous BN Ceramic Fibers Containing Amorphous Silicon Nitride

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6194
Author(s):  
Yang Li ◽  
Min Ge ◽  
Shouquan Yu ◽  
Huifeng Zhang ◽  
Chuanbing Huang ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Silicon Nitride ◽  
Melt Spinning ◽  
Composite Ceramic ◽  
Mass Content ◽  
Composite Fibers ◽  
Composite Ceramics ◽  
Ceramic Fibers ◽  
Amorphous Silicon Nitride ◽  
The Mean

Boron nitride (BN) ceramic fibers containing amounts of silicon nitride (Si3N4) were prepared using hybrid precursors of poly(tri(methylamino)borazine) (PBN) and polycarbosilane (PCS) via melt-spinning, curing, decarburization under NH3 to 1000 °C and pyrolysis up to 1600 °C under N2. The effect of Si3N4 contents on the microstructure of the BN/Si3N4 composite ceramics was investigated. Series of the BN/Si3N4 composite fibers containing various amounts of Si3N4 from 5 wt% to 25 wt% were fabricated. It was found that the crystallization of Si3N4 could be totally restrained when its content was below 25 wt% in the BN/Si3N4 composite ceramics at 1600 °C, and the amorphous BN/Si3N4 composite ceramic could be obtained with a certain ratio. The mean tensile strength and Young’s modulus of the composite fibers correlated positively with the Si3N4 mass content, while an obvious BN (shell)/Si3N4 (core) was formed only when the Si3N4 content reached 25 wt%.

scholarly journals Microstructures and Properties of Ceramic Fibers of h-BN Containing Amorphous Si3N4

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3812
Author(s):  
Jing Tan ◽  
Min Ge ◽  
Shouquan Yu ◽  
Zhenxi Lu ◽  
Weigang Zhang
Keyword(s):  
Dielectric Constant ◽  
Tensile Strength ◽  
Electron Beam ◽  
Melt Spinning ◽  
Composite Ceramic ◽  
Composite Fibers ◽  
Ceramic Fibers ◽  
The Mean ◽  
Electron Beam Curing ◽  
Amorphous Si3n4

Composite ceramic fibers comprising about 80 wt% boron nitride (h-BN) and 20 wt% Si3N4 were fabricated through melt-spinning, electron-beam curing, and pyrolysis up to 1600 °C in atmospheres of NH3 and N2, using a mixture of poly[tri(methylamino)borazine] (PBN) and polysilazane (PSZ). By analyzing the microstructure and composition of the pyrolyzed ceramic fibers, we found the formation of binary phases including crystalline h-BN and amorphous Si3N4. Further investigations confirmed that this heterogeneous microstructure can only be formed when the introduced ratio of Si3N4 is below 30% in mass. The mean modulus and tensile strength of the fabricated composite fibers were about 90 GPa and 1040 MPa, twice the average of the pure h-BN fiber. The dielectric constant and dielectric loss tangent of the composite fibers is 3.06 and 2.94 × 10−3.

Kinetics of silicon nitride crystallization in N+-implanted silicon

1989 ◽  
Vol 4 (2) ◽  
pp. 394-398 ◽  
Author(s):  
V. S. Kaushik ◽  
A. K. Datye ◽  
D. L. Kendall ◽  
B. Martinez-Tovar ◽  
D. S. Simons ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Crystalline Silicon ◽  
Wafer Surface ◽  
Amorphous Silicon Nitride ◽  
Silicon Lattice ◽  
Nitrogen Ions ◽  
The Mean ◽  
Nitride Layers ◽  
Kinetics Of

Implantation of nitrogen at 150 KeV and a dose of 1 ⊠ 1018/cm2 into (110) silicon results in the formation of an amorphized layer at the mean ion range, and a deeper tail of nitrogen ions. Annealing studies show that the amorphized layer recrystallizes into a continuous polycrystalline Si3N4 layer after annealing for 1 h at 1200 °C. In contrast, the deeper nitrogen fraction forms discrete precipitates (located 1μm below the wafer surface) in less than 1 min at this temperature. The arcal density of these precipitates is 5 ⊠ 107/cm2 compared with a nuclei density of 1.6 ⊠ 105/cm2 in the amorphized layer at comparable annealing times. These data suggest that the nucleation step limits the recrystallization rate of amorphous silicon nitride to form continuous buried nitride layers. The nitrogen located within the damaged crystalline silicon lattice precipitates very rapidly, yielding semicoherent crystallites of β–Si3N4.

Preparation and Dielectric Properties of Si3N4/BN(CB) Composite Ceramic

2016 ◽  
Vol 35 (5) ◽  
pp. 523-529
Author(s):  
Xiao Weiling ◽  
Xiao Peng ◽  
Luo Heng ◽  
Zhou Wei ◽  
Li Yang
Keyword(s):  
Electron Microscopy ◽  
Electromagnetic Wave ◽  
Composite Ceramic ◽  
Mass Content ◽  
Composite Ceramics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nano Carbon ◽  
Pass Through ◽  
Scanning Electron

AbstractSi3N4/nano-carbon black (CB) composite ceramics with boron nitride (BN) as interphase were fabricated by gelcasting. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that the structures of BN interphase and BN coated CB were formed and were uniform distributed in the Si3N4 ceramic. The permittivity (ε′ε″) of BN-coated CB was obviously lower than that of the pure CB, and the impedance of the BN-coated CB particles was close to the Z0 (Z0 = 1, Z0 is impedance under vacuum) compared with that of the CB particles; therefore, electromagnetic wave can enter into the BN-coated CB particles and be dissipated due to the high conductivity of CB particles. When incorporating the BN(CB) into Si3N4 substrate, the electromagnetic wave can pass through Si3N4/nano-CB composite ceramics easily and be absorbed by CB, so the tgδ of the composite ceramic increased as the mass content of BN(CB) increased. The tgδ of the composite ceramic was about 0.43 when the content of BN(CB) increased to 15 wt%.

A TEM investigation of silicon nitride whiskers

1987 ◽  
Vol 45 ◽  
pp. 160-161
Author(s):  
Tapan Roy
Keyword(s):  
Silicon Nitride ◽  
High Resolution ◽  
Ceramic Matrix Composites ◽  
High Resolution Electron Microscopy ◽  
Molten Silicon ◽  
Matrix Composites ◽  
Ceramic Fibers ◽  
Resolution Electron ◽  
Point To Point ◽  
Technological University

Ceramic fibers are being used to improve the mechanical properties of metal matrix and ceramic matrix composites. This paper reports a study of the structural and other microstructural characteristics of silicon nitride whiskers using both conventional TEM and high resolution electron microscopy.The whiskers were grown by T. E. Scott of Michigan Technological University, by passing nitrogen over molten silicon in the presence of a catalyst. The whiskers were ultrasonically dispersed in chloroform and picked up on holey carbon grids. The diameter of some whiskers (<70nm) was small enough to allow direct observation without thinning. Conventional TEM was performed on a Philips EM400T while high resolution imaging was done on a JEOL 200CX microscope with a point to point resolution of 0.23nm.

scholarly journals Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 722
Author(s):  
Enrico Wölfel ◽  
Harald Brünig ◽  
Iurie Curosu ◽  
Viktor Mechtcherine ◽  
Christina Scheffler
Keyword(s):  
Tensile Strength ◽  
Dynamic Loading ◽  
Melt Spinning ◽  
Structural Changes ◽  
High Surface ◽  
Single Fiber ◽  
Scanning Calorimetry ◽  
Matrix Interaction ◽  
Pull Out ◽  
Fiber Matrix

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.

scholarly journals Hydrogen effects on the thermal conductivity of delocalized vibrational modes in amorphous silicon nitride (a−SiNx:H)

2021 ◽  
Vol 5 (3) ◽  
Author(s):  
Jeffrey L. Braun ◽  
Sean W. King ◽  
Eric R. Hoglund ◽  
Mehrdad Abbasi Gharacheh ◽  
Ethan A. Scott ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Vibrational Modes ◽  
Amorphous Silicon Nitride

scholarly journals Effect of Thermal Annealing on the Photoluminescence of Dense Si Nanodots Embedded in Amorphous Silicon Nitride Films

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 354
Author(s):  
Qianqian Liu ◽  
Xiaoxuan Chen ◽  
Hongliang Li ◽  
Yanqing Guo ◽  
Jie Song ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Thermal Annealing ◽  
Chemical Vapor ◽  
Peak Position ◽  
Excitation Wavelength ◽  
Very High Frequency ◽  
Amorphous Silicon Nitride ◽  
Silicon Nitride Films ◽  
High Frequency Plasma

Luminescent amorphous silicon nitride-containing dense Si nanodots were prepared by using very-high-frequency plasma-enhanced chemical vapor deposition at 250 °C. The influence of thermal annealing on photoluminescence (PL) was studied. Compared with the pristine film, thermal annealing at 1000 °C gave rise to a significant enhancement by more than twofold in terms of PL intensity. The PL featured a nanosecond recombination dynamic. The PL peak position was independent of the excitation wavelength and measured temperatures. By combining the Raman spectra and infrared absorption spectra analyses, the enhanced PL was suggested to be from the increased density of radiative centers related to the Si dangling bonds (K0) and N4+ or N20 as a result of bonding configuration reconstruction.

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