**4. Texture and properties of carbonaceous mesophase as a liquid crystal**

The as-received liquid-crystalline AR mesophase pitch as shown in **Figure 9(a, b)** possesses a streamline "fibrous" texture with highly preferred orientation visible via orthogonal observation by rotating the object stage of the PLM. Following melting and melt-stirred treatments at 320°C as shown in **Figure 9(c, d)**, respectively, the optical texture of the melting pitch is nearly maintained, and the conformation and orientation of the macromolecules in the melt-stirred pitch are disrupted to become partially disordered or turbulent (severely deformed) depending upon the degree of stirring [19]. The purpose of this thermo-stirring treatment is to investigate the influence of liquid-crystalline texture of mesophase pitch precursors on the morphology, microstructure, and physical properties of resulting carbon fibers as shown in **Figure 10**.

It can be found that the as-prepared naphthalene-based mesophase pitch as being transmitted from the reaction autoclave to a metal plate at a molten status

**107**

**Figure 12.**

*based AR mesophase pitch.*

**Figure 11.**

**Figure 10.**

*(b) PLM micrograph of the drawn pitch fiber.*

*carbon fibers as degree of melt-stirring increases.*

*Preparation, Characterization, and Applications of Carbonaceous Mesophase: A Review*

*(a) Optical photograph of a naphthalene-based synthetic pitch with good wire-drawing performance and* 

*Typical (a) molten flow curve of distance-temperature and (b) viscosity-temperature curve of naphthalene-*

*Schematic of the microstructure evolution from mesophase pitch precursor to transverse texture-controlled* 

*DOI: http://dx.doi.org/10.5772/intechopen.88860*

*Preparation, Characterization, and Applications of Carbonaceous Mesophase: A Review DOI: http://dx.doi.org/10.5772/intechopen.88860*

#### **Figure 10.**

*Liquid Crystals and Display Technology*

and a regular planar molecular structure constructed by a number of naphthenic structure, as well as a relatively large molecular weight of ~2600 g/mol, consisting of mesogen units (a ladder-shaped molecular structure) formed by ~20 naphthalene molecules through thermally induced aromatic growth [3, 10, 11] according to the analyses of **Figures 6**–**8**. The suitable softening point (260–280°C) and appropriate H/C mol ratio (0.52–0.60), as well as high liquid-crystalline mesophase content (100 vol.%) and ideal fine flow texture as displayed in **Figures 9** and **11**, are the significant characteristics of such carbonaceous mesophase. The analysis results of other characterizations are

*Typical PLM micrographs of the (a, b) as-received, (c) melted, and (d) melt-stirred naphthalene-based AR* 

**4. Texture and properties of carbonaceous mesophase as a liquid crystal**

The as-received liquid-crystalline AR mesophase pitch as shown in **Figure 9(a, b)** possesses a streamline "fibrous" texture with highly preferred orientation visible via orthogonal observation by rotating the object stage of the PLM. Following melting and melt-stirred treatments at 320°C as shown in **Figure 9(c, d)**, respectively, the optical texture of the melting pitch is nearly maintained, and the conformation and orientation of the macromolecules in the melt-stirred pitch are disrupted to become partially disordered or turbulent (severely deformed) depending upon the degree of stirring [19]. The purpose of this thermo-stirring treatment is to investigate the influence of liquid-crystalline texture of mesophase pitch precursors on the morphology, microstructure, and physical properties of resulting carbon fibers as shown in **Figure 10**. It can be found that the as-prepared naphthalene-based mesophase pitch as being transmitted from the reaction autoclave to a metal plate at a molten status

not shown here (refer to previous work [2, 3, 10, 11, 15, 18]).

**106**

**Figure 9.**

*mesophase pitch.*

*Schematic of the microstructure evolution from mesophase pitch precursor to transverse texture-controlled carbon fibers as degree of melt-stirring increases.*

#### **Figure 11.**

*(a) Optical photograph of a naphthalene-based synthetic pitch with good wire-drawing performance and (b) PLM micrograph of the drawn pitch fiber.*

#### **Figure 12.**

*Typical (a) molten flow curve of distance-temperature and (b) viscosity-temperature curve of naphthalenebased AR mesophase pitch.*

exhibits good wire-drawing performance and ideal viscoelastic property and the unwittingly drawn wires (i.e., large-diameter pitch fibers) possess an orderly liquid-crystalline texture as shown in **Figure 11**, which is closely related to its plastic flowing behavior and low apparent viscosity upon melting as shown in **Figure 12**. This is favorable for pitch melt spinning and other rheology applications [5].
