scholarly journals Formation of nanocrystalline graphite in polymer-derived SiCN by polymer infiltration and pyrolysis at a low temperature

2021 ◽  
Author(s):  
Mingxing Li ◽  
Laifei Cheng ◽  
Fang Ye ◽  
Conglin Zhang ◽  
Jie Zhou
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Volume Fraction ◽  
Free Carbon ◽  
High Yield ◽  
Carbon Yield ◽  
Graphitization Degree ◽  
Transmission Electron ◽  
Nanocrystalline Graphite ◽  
Polymer Infiltration

AbstractThe microstructure of polymer-derived ceramics (PDCs) was closely related to processing. This study demonstrated that SiCN matrix prepared by polymer infiltration and pyrolysis (PIP) at 900 °C inside a Si3N4 whisker (Si3N4w) preform with submicro-sized pores differed from its powder-consolidated analogue in both the content and structure of free carbon. Chemical analysis showed that PIP process had a higher free carbon yield. Raman spectroscopy and transmission electron microscopy (TEM) observation discovered a higher graphitization degree of free carbon and the existence of nanocrystalline graphite in SiCN matrix. Dielectric properties of Si3N4w/SiCN composites were greatly enhanced when volume fraction of SiCN matrix reached 24.5% due to dielectric percolation caused by highly-lossy free carbon. Reconsolidation of hydrocarbon released during pyrolysis by gas-state carbonization in Si3N4 whisker preform was supposed to account for the high yield and graphitization degree of free carbon in PIP process.

The influence of Pt and SrTiO3 interlayers on the microstructure of PbTiO3 thin films deposited by laser ablation on (001) MgO

1995 ◽  
Vol 10 (4) ◽  
pp. 791-794 ◽  
Author(s):  
S. Stemmer ◽  
S.K. Streiffer ◽  
W-Y. Hsu ◽  
F. Ernst ◽  
R. Raj ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Laser Ablation ◽  
Volume Fraction ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Transmission Electron ◽  
Electrical Conductivities ◽  
Different Types ◽  
Oriented Material

We have used conventional and high-resolution transmission electron microscopy to investigate the microstruture of epitaxial, ferroelectric PbTiO3 films grown by pulsed laser ablation on (001) MgO single crystals, and on MgO covered with epitaxial Pt or SrTiO3. Pronounced variations are found in the widths and lengths of a-axis-oriented domains in these films, although the volume fraction of a-axis-oriented material varies only weakly for the different types of samples. In addition, the films deposited onto Pt-coated MgO have a larger grain size than those deposited onto bare MgO or SrTiO3/MgO. Possible reasons for the variations in the distribution of a-axis-oriented material in these samples include differences in the elastic properties and electrical conductivities of the different substrate combinations.

Preparation and Property of Al87Ce3Ni8.5Mn1.5 Nanophase Amorphous Composites

2011 ◽  
Vol 412 ◽  
pp. 263-266
Author(s):  
Hong Wei Zhang ◽  
Li Li Zhang ◽  
Feng Rui Zhai ◽  
Jia Jin Tian ◽  
Can Bang Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Phase ◽  
Volume Fraction ◽  
Material Structure ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Different Temperatures

The higher mechanical strength of Al87Ce3Ni8.5Mn1.5 nanophase amorphous composites has been obtained with two methods. The first nanophase amorphous composites are directly produced by the single roller spin quenching technology. The method taken for the second nanophase amorphous composites is at first to obtain amorphous single-phase alloy, followed by annealed at different temperatures .The formative condition, the microstructure, the particle size, the volume fraction of α-Al phase and microhardness of nanophase amorphous composites etc have been investigated and compared by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The microstructure of composites produced by the second method is higher than the former, the fabricated material structure of the system is more uniform and the process is easier to control.

scholarly journals Thickening of T1 Precipitates during Aging of a High Purity Al–4Cu–1Li–0.25Mn Alloy

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 30 ◽  
Author(s):  
Ines Häusler ◽  
Reza Kamachali ◽  
Walid Hetaba ◽  
Birgit Skrotzki
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Purity ◽  
External Load ◽  
Volume Fraction ◽  
Single Layer ◽  
Age Hardening ◽  
Defect Type ◽  
Transmission Electron

The age hardening response of a high-purity Al–4Cu–1Li–0.25Mn alloy (wt. %) during isothermal aging without and with an applied external load was investigated. Plate shaped nanometer size T1 (Al2CuLi) and θ′ (Al2Cu) hardening phases were formed. The precipitates were analyzed with respect to the development of their structure, size, number density, volume fraction and associated transformation strains by conducting transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies in combination with geometrical phase analysis (GPA). Special attention was paid to the thickening of T1 phase. Two elementary types of single-layer T1 precipitate, one with a Li-rich (Type 1) and another with an Al-rich (Defect Type 1) central layer, were identified. The results show that the Defect Type 1 structure can act as a precursor for the Type 1 structure. The thickening of T1 precipitates occurs by alternative stacking of these two elementary structures. The thickening mechanism was analyzed based on the magnitude of strain associated with the precipitation transformation normal to its habit plane. Long-term aging and aging under load resulted in thicker and structurally defected T1 precipitates. Several types of defected precipitates were characterized and discussed. For θ′ precipitates, a ledge mechanism of thickening was observed. Compared to the normal aging, an external load applied to the peak aged state leads to small variations in the average sizes and volume fractions of the precipitates.

Observations of G-P Zone Reversion in Al-Zn-Mg Alloys by Small-Angle X-Ray Scattering and Transmission Electron Microscopy

1965 ◽  
Vol 9 ◽  
pp. 59-73
Author(s):  
R. W. Gould ◽  
E. A. Starke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Small Angle ◽  
Volume Fraction ◽  
Magnesium Content ◽  
Mg Alloys ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ray Scattering

AbstractA study of the reversion process in Al-Zn-Mg alloys has been made using small-angle X-ray scattering and transmission electron microscopy techniques. The rate and mode of Guinier-Preston zone dissolutions was investigated as a function of magnesium content, prior zone radius, and reversion temperature. Results indicate that in this system the reversion process is characterized by the preferential dissolution of the smallest G-P zones present after cold aging with a corresponding decrease in the volume fraction of zones. The amount of reversion at a specific temperature is dependent on magnesium content, however, the rate of reversion is independent of magnesium content.

The Influence of the ECAP Temperature on Microstructure and Mechanical Properties of a Magnesium Alloy

2006 ◽  
Vol 503-504 ◽  
pp. 609-614 ◽  
Author(s):  
Olya B. Kulyasova ◽  
Rinat K. Islamgaliev ◽  
Nikolay A. Krasilnikov
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Thermal Stability ◽  
Transmission Electron Microscopy ◽  
Magnesium Alloy ◽  
Volume Fraction ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Significant Difference ◽  
Thermal Stability Of

The influence of the equal channel angular pressing (ECAP) temperature (150-350oC) on microstructure of the AM60 magnesium alloy has been investigated using transmission electron microscopy. It was demonstrated that application of various ECAP regimes leads to significant difference in a grain size and volume fraction of precipitates in investigated material. Thermal stability of precipitates and correlation between microstructure and tensile strength are discussed.

Effect of Secondary Decomposition on Coercivity of Fe-Co-Cr Alloys with 15% Co

2015 ◽  
Vol 233-234 ◽  
pp. 623-628 ◽  
Author(s):  
Vladimir P. Menushenkov ◽  
Vladimir S. Shubakov
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Magnetic Properties ◽  
Coercive Force ◽  
Volume Fraction ◽  
Magnetic Measurements ◽  
Magnetic Treatment ◽  
Magnetic Insulation ◽  
Transmission Electron ◽  
Microstructure And Magnetic Properties

The microstructure and magnetic properties of Fe-Co-Cr alloys with 15 wt % Co were investigated using transmission electron microscopy and magnetic measurements. The secondary decomposition within both the α2-phase matrix and the α1-phase particles was observed for magnets subjected thermo-magnetic treatment and subsequent stepped aging or continuous-cooling treatments. During high-temperature treatments (630-600оC), when the α2phase is dominant (the volume fraction is more than 50%), the secondary decomposition of this phase takes place (α2→ α1'+ α2'). The deterioration of magnetic insulation of α1-phase particles results in the decrease in the coercive force of alloys. Below 600оC, when the α1phase is dominant (the volume fraction is more than 50%), the splitting of elongated α1-phase particles occurs. When the temperature of stepped-aging decreases in high steps, the secondary decomposition (α1→ α1'+ α2') leads to the splitting of initial α1-phase particles into fine slightly elongated particles and the decrease in the coercive force.

Sign in / Sign up

Export Citation Format

Share Document