An electron microscopy study of high-thermal-conductivity ribbon-shape carbon fibers

1993 ◽  
Vol 51 ◽  
pp. 618-619
Author(s):  
Kerry E. Robinson
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Liquid Crystalline ◽  
Structural Information ◽  
Low Cost ◽  
Microscopy Study ◽  
High Thermal Conductivity ◽  
Mesophase Pitch ◽  
Thermal Conductivities ◽  
Shaped Fibers

In an effort to develop a low-cost high thermal conductivity carbon fiber, ribbon-shaped fibers were meltspun from a liquid crystalline, mesophase pitch precursor. Initial tests indicated that the ribbon-shaped fibers could be processed more easily and exhibited improved thermal conductivities when compared to commercial round fibers. Evidently, it is the more linear, polycrystalline structure within these fibers that accounts for their improved thermal conductivities. Thus, studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to fully analyze the transverse and longitudinal structure of these high thermal conductivity fibers.Ribbon-shaped fibers, melt-spun from a synthetic mesophase pitch and then heat treated, were tested to determine their tensile strengths, tensile moduli and thermal conductivities. A Jeol JSM-I C848 SEM at an accelerating voltage of 20 kV was used to obtain general structural information, such as extent and texture of lamellar organization of the graphitic layers within the fibers, and the microstructure of the fibers was studied by TEM.

Electron microscopy and diffraction of crystalline dendrimers and macrocycles

1993 ◽  
Vol 51 ◽  
pp. 1218-1219
Author(s):  
C. J. Buchko ◽  
P. M. Wilson ◽  
Z. Xu ◽  
J. Zhang ◽  
S. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Scanning Calorimetry ◽  
Tertiary Butyl ◽  
Phenyl Acetylene ◽  
Selected Area Electron Diffraction ◽  
Liquid Crystalline Phases ◽  
Resolution Electron

The synthesis of well-defined organic molecules with unique geometries opens new opportunities for understanding and controlling the organization of condensed matter. Here, we study dendrimers and macrocycles which are synthesized from rigid phenyl-acetylene spacer units, Both units are solubilized by the presence of tertiary butyl groups located at the periphery of the molecule. These hydrocarbon materials form crystalline and liquid crystalline phases which have been studied by differential scanning calorimetry, hot stage optical microscopy, and wide-angle x-ray scattering (WAXS).The precisely defined architecture of these molecules makes it possible to investigate systematic variations in chemical architecture on the nature of microstructural organization. Here we report on the transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution electron microscopy (HREM) studies of crystalline thin films formed by deposition of these materials onto carbon substrates from dilute solution. Electron microscopy is very attractive for gaining structural information on new molecules due to the scarcity of material to grow single crystals suitable for conventional crystallography.

Highly thermal conductive resins formed from wide-temperature-range eutectic mixtures of liquid crystalline epoxies bearing diglycidyl moieties at the side positions

2017 ◽  
Vol 8 (18) ◽  
pp. 2806-2814 ◽  
Author(s):  
Youngsu Kim ◽  
Hyeonuk Yeo ◽  
Nam-Ho You ◽  
Se Gyu Jang ◽  
Seokhoon Ahn ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Wide Temperature Range ◽  
Epoxy Resins ◽  
Liquid Crystalline ◽  
High Thermal Conductivity ◽  
Temperature Range ◽  
Eutectic Mixtures ◽  
Liquid Crystalline Epoxy ◽  
Conductive Resins

Liquid crystalline epoxy resins with a wide temperature range exhibit a high thermal conductivity of 0.4 W m−1 K−1.

Preparation and Properties of Rigid Carbon Felt Thermal Insulation

2015 ◽  
Vol 833 ◽  
pp. 48-51 ◽  
Author(s):  
Wei Shi ◽  
Jia Yan Li ◽  
Qi Fan You ◽  
Tong Lu ◽  
Yi Tan
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Insulation ◽  
Bending Strength ◽  
High Thermal Conductivity ◽  
Carbon Felt ◽  
Matrix Concentration ◽  
Thermal Conductivities

Matrix derived from resin after carbonization in rigid carbon felt thermal insulation has many advantages. The microstructures and properties of these materials were investigated in this paper. Results showed that matrix tend to accumulate at the intersections of fibers. This can improve mechanical properties and have a little influence on thermal conductivities of the composites. The excellent bending strength of 2.66MPa, compressive strength of 0.91MPa and a high thermal conductivity of 0.81W/(m·K) (at 1500°C) with a matrix concentration of 32.7% is achieved. However, high thermal conductivity is harmful for those materials which are used as thermal insulators.

Thermal-Wave Probing at Various Spatial Scales

MRS Bulletin ◽  
2001 ◽  
Vol 26 (6) ◽  
pp. 465-470 ◽  
Author(s):  
Danièle Fournier
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Thermal Wave ◽  
Spatial Scales ◽  
High Thermal Conductivity ◽  
Heterogeneous Microstructures ◽  
Thermal Conductivities

In recent years, high thermal conductivity has been found in materials with heterogeneous microstructures, that is, ceramics and films with granular microstructures having different phases. Understanding the thermal conductivities and microstructures of these materials is more difficult, however, than in the case of single-crystal materials because they consist of grains and grain boundaries.

scholarly journals Graphene oxide-loaded shortening as an environmentally friendly heat transfer fluid with high thermal conductivity

2017 ◽  
Vol 21 (5) ◽  
pp. 2247-2254
Author(s):  
Thammasit Vongsetskul ◽  
Peeranut Prakulpawong ◽  
Panmanas Sirisomboon ◽  
Jonggol Tantirungrotechai ◽  
Chanasuk Surasit ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Environmentally Friendly ◽  
High Thermal Conductivity ◽  
Chemical Degradation ◽  
Heat Transfer Fluid ◽  
Increasing Temperature ◽  
Scanning Electron

Graphene oxide-loaded shortening (GOS), an environmentally friendly heat transfer fluid with high thermal conductivity, was successfully prepared by mixing graphene oxide (GO) with a shortening. Scanning electron microscopy revealed that GO particles, prepared by the modified Hummer?s method, dispersed well in the shortening. In addition, the latent heat of GOS decreased while their viscosity and thermal conductivity increased with increasing the amount of loaded GO. The thermal conductivity of the GOS with 4% GO was higher than that of pure shortening of ca. three times, from 0.1751 to 0.6022 W/mK, and increased with increasing temperature. The GOS started to be degraded at ca. 360?C. After being heated and cooled at 100?C for 100 cycles, its viscosity slightly decreased and no chemical degradation was observed. Therefore, the prepared GOS is potentially used as environmentally friendly heat transfer fluid at high temperature.

scholarly journals Mesophase Pitch-Based Carbon Fibers: Accelerated Stabilization of Pitch Fibers under Effective Plasma Irradiation-Assisted Modification

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6382
Author(s):  
Yuanshuo Peng ◽  
Ruixuan Tan ◽  
Yue Liu ◽  
Jianxiao Yang ◽  
Yanfeng Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Heating Rate ◽  
Carbon Fibers ◽  
High Performance ◽  
Low Cost ◽  
Tensile Modulus ◽  
Mesophase Pitch ◽  
Stabilization Time ◽  
Plasma Irradiation

Stabilization is the most complicated and time-consuming step in the manufacture of carbon fibers (CFs), which is important to prepare CFs with high performance. Accelerated stabilization was successfully demonstrated under effective plasma irradiation-assisted modification (PIM) of mesophase pitch fibers (PFs). The results showed that the PIM treatment could obviously introduce more oxygen-containing groups into PFs, which was remarkably efficient in shortening the stabilization time of PFs with a faster stabilization heating rate, as well as in preparing the corresponding CFs with higher performance. The obtained graphitized fiber (GF-5) from the PF-5 under PIM treatment of 5 min presented a higher tensile strength of 2.21 GPa, a higher tensile modulus of 502 GPa, and a higher thermal conductivity of 920 W/m·K compared to other GFs. Therefore, the accelerated stabilization of PFs by PIM treatment is an efficient strategy for developing low-cost pitch-based CFs with high performance.

Microstructure of high thermal conductivity mesophase pitch-based carbon fibers

2021 ◽  
Vol 36 (5) ◽  
pp. 980-985
Author(s):  
Chong Ye ◽  
Huang Wu ◽  
Shi-peng Zhu ◽  
Zhen Fan ◽  
Dong Huang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Fibers ◽  
High Thermal Conductivity ◽  
Mesophase Pitch

NUMERICAL STUDY ON THE THERMAL PERFORMANCE OF A PHASE CHANGE HEAT EXCHANGER (PCHE) WITH INNOVATIVE FRACTAL TREE-SHAPED FINS

Fractals ◽  
2020 ◽  
Vol 28 (05) ◽  
pp. 2050083
Author(s):  
XIANGDONG LIU ◽  
FEIFAN LIU ◽  
QIAOBO DAI ◽  
FENG YAO ◽  
TIANJUN ZENG ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Phase Change ◽  
Solidification Front ◽  
Numerical Study ◽  
Low Cost ◽  
Pure Copper ◽  
Evaluation Criteria ◽  
Temperature Response ◽  
High Thermal Conductivity

For alleviating energy shortage and environmental problems, it is of great importance to improve the energy charging and discharging efficiency of thermal energy storage systems. In this context, an innovative phase change heat exchanger (PCHE) with fractal tree-shaped fins is presented in this paper. A numerical investigation of the solidification behaviors in the PCHE with fractal tree-shaped fins is conducted. The dynamic temperature response and the solidification front evolution in the PCHE are analyzed and discussed. Furthermore, two evaluation criteria, including total solidification time and energy charging efficiency, are introduced to quantitatively study the effect of fin material on the solidification heat transfer characteristics. The results indicate that the fractal tree-shaped fin leads to a uniform temperature distribution of phase change material (PCM). The temperature response of fin is faster than that of PCM due to its high thermal conductivity. Moreover, the fractal tree-shaped fin breaks the restriction of gradually forward fashion of solidification front in the traditional PCHE and dramatically improves the energy discharging performance. The material of fractal tree-shaped fins is an essential factor affecting the solidification performance of the PCHE. The energy discharging performance of PCHE with pure copper fins is the best, whereas that with cupronickel fins is the worst. However, from the perspective of practical application, aluminum is the best potential alternative because of its relatively high thermal conductivity, lighter weight, and low cost.

Transmission electron microscopy study of an oriented thermotropic liquid crystalline polymer

1984 ◽  
Vol 42 ◽  
pp. 380-381
Author(s):  
B.A. Wood
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Fiber Spinning ◽  
Casting Technique ◽  
Flexible Spacer ◽  
Transmission Electron ◽  
Diffraction Patterns

Electron microscopy studies of fibers spun from lyotropic polymer mesophases are far more common in the literature than reports of TEM of thermotropic polymers, but recently publications have appeared reporting oriented electron diffraction patterns and “banding” in TEM images of thermotropic polyesters. Considering the advantages of fiber spinning from the melt, an understanding of the detailed morphology of thermotropic polymers, their ordering in flow fields, and the influence of quenched-in mesomorphic orientation on 3-D crystalline order is desirable. The experimental study described herein utilizes a solution casting technique to produce oriented thin films of a block polyester containing alternating rigid mesogenic and flexible spacer groups (Fig. 1a).

Sign in / Sign up

Export Citation Format

Share Document