Properties Of Pitch Research Articles

Electrochemical Characteristics of Pitch Coated Silicon/Graphite Anode Composites Using Surface Modification Process

The electrochemical characteristics of pitch coated graphite / silicon composites were investigated as anode material in lithium ion batteries. The anode materials were prepared with etched graphite using nickel chloride hexahydrate to create spherical pores on the graphite surface. The pore size was controlled depending on the calcination retention time and optimized for the insertion of silicon nanoparticles. Scanning electron microscopy, x-ray diffraction and thermogravimetric analysis were used to analyze the physical properties of pitch coated graphite / silicon composites. The electrochemical characteristics of the batteries were investigated by charge-discharge cycle, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy tests in the eletrolyte of 1.0 M LiPF6 ( EC : DMC : DEC = 1 : 1 : 1 vol % ). Graphite/silicon/pitch electrode showed better electrochemical properties than the graphite electrode, and even nickel etched graphite was superior to graphite. Also, it was confirmed that both capacity and rate performance were significantly improved when the ratio of graphite, silicon, and pitch is 8 : 1 : 1 ( G8 Si1 P1 ). It is found that G8 Si1 P1 have the initial discharge capacity of 680 mAh / g, the capacity retention ratio of 90 % during 100 cycles and the retention rate capability of 91 % in 2 C / 0.1 C, 87 % in 5 C / 0.1 C.

Controlling the oligomeric composition and char yield of pyrene pitches via continuous supercritical extraction

Continuous supercritical extraction (SCE) was investigated for its ability to control the oligomeric composition of a pyrene pitch generated by the catalytic polymerization of pyrene in the presence of AlCl3. Key objectives of this work were the nearly complete removal of the starting monomer, generation of a well-defined pitch with a high char yield, and isolation of a fraction consisting exclusively of intermediate-sized oligomers. Following the design and construction of an SCE unit for processing up to 500 g/h of feed pyrene pitch with supercritical toluene (Tc = 319 °C, Pc = 41.1 bar), a 2-column setup was used to isolate ∼350 g of a fraction consisting of greater than 90 % isotropic dimer plus mesogenic trimer combined. Although the char yield of this oligomeric mixture was only moderate (i.e., 47.1 %), it still significantly exceeded the weighted average char yield (i.e., 30 %) of the individual monomers present, suggesting a synergistic interplay between the different species during charring. With the above results indicating that pyrene oligomers larger than trimer (i.e., X-mers) are needed to attain higher char yields, the focus of our next continuous SCE run was simply on removing as much unreacted monomer as possible, to the exclusion of all other oligomers. Using a one-column SCE setup, a ∼350 g fraction containing almost 90 % dimer and higher oligomers was isolated, and a respectable char yield of 65.2 % was obtained with this “monomer-depleted” pitch. Furthermore, the softening point was a relatively low 185 °C, quite respectable in terms of processability. In summary, these initial results indicate the potential of continuous SCE as a tool for controlling the properties of oligomeric pyrene pitches for selected applications.

Statistical analysis for the pitch of mask-wearing Arabic speech

The study is a comparison between the statistical properties of pitch (F0) for mask-wearing speech and unmasked. The speakers are Arab, of different ages and genders. A robust algorithm for pitch tracking (RAPT) is used for estimating F0. The subjective tests denote that masked speech is attenuated, and noisy-background speech has fewer F0 candidates. Using objective tests, 60% of female and male F0s do not change when wearing masks. The remaining 40% of speech F0s change (the percentage gross error), by an approximately 20% increase and 20% decrease. The percentage classification error is about 10%. The F0 changes in females younger than 12 years old are fewer compared with similarly-aged males. The F0 changes of females older than 12 years old were approximately equal compared with similarly-aged males. An average of F0 (M) is used for each speech to divide its F0 band (50-500) Hz into two bands, lower-band (LB) (50-M) Hz and upper-band (UB) (M-500) Hz. The attributes of the two bands have been statistically analyzed. The F0 classification error (CE) for females is higher than for males, but the gross error (GE) for males is higher than for females. The F0 change values are directly proportional to the probability of F0 change.

A Sociophonetic Investigation of Chinese Gay Couples' Variability of Pitch Properties in Vlogs

Despite the accumulating body of research in sociophonetics exploring gay men’s pitch characteristics (i.e., mean vocal pitch and pitch range), previous studies usually investigate a uniform concept of ‘gay men’s speech’ by comparing heterosexual and gay men’s pitch properties. However, results were contesting and inconsistent across various studies regarding the pitch properties (pitch ranges or mean voice pitch) of gay men. Instead of treating gay men’s speech as a unified speaking style, this paper investigates the multiplicity of gay speaking styles by exploring the intra-group pitch variations among 20 pairs of Chinese gay couples in their self-shot videos. Specifically, the present study compares the pitch properties, including the mean vocal pitch, pitch range, and pitch variability, between those Chinese gay men who selfposition as ‘lao gong’ (husband) and those who self-identify as ‘lao po’ (wife) in their love vlogs (video blogs). These videos normally last from 5 to 10 minutes on a Chinese online video sharing platform - ‘Bilibili.’ After dividing these gay couples’ utterances into intonational phrases, I used the speech analysis software named Praat to measure the average pitch, pitch range (the maximum pitch value minus minimum pitch value), and pitch variability (the standard deviation of pitch values) on each intonational phrase. Compared with those ‘gay husbands,’ results showed that those ‘gay wives’ would speak with higherpitched voices (p < 0.05), wider pitch ranges (p < 0.0001), and more variable pitch values (p < 0.0001). When locating the discourse functions of these pitch characteristics in their vlogs, I argue that those ‘gay wives’ frequently utilize the so-called ‘pitch dynamism’ to construct an expressive and cute ‘wife’ persona in intimate discourse.

Hearing chimeras

I argue that chimericity is a property that we typically experience when listening to multi-instrumental music. It is the property of hearing as a unified whole a melody or a harmony that does not belong to any single sound source but instead consists of the assembling of melodic or harmonic fragments coming from different sources. Chimericity is not reducible to the low-level audible properties of pitch and loudness; it is cognized at the perceptual level thanks to the auditory mechanism of primitive grouping. My aim is to show that chimericity is a perceptual property, one that we can genuinely hear. In developing this view, I engage with the debate within the philosophy of sense perception between rich vs thin views of the content of perceptual experience.

Microstructure and mechanical properties of pitch based mixture modified by additions of graphene oxide precursor and TiB2 particles

Pitch based mixture as binder material is crucial component for structure stability and mechanical properties of carbon/graphite electrodes. In this work, coal tar pitch (CTP) mixture was modified by additions of graphene oxide (GO) precursor and fine TiB2 particles. It is found that 1 wt.%GO addition increases the crystallite size, La value and reduce the defects density of (002) planes in CTP mesophase and carbonization products with increased elastic modulus. The additions of 3 or 5 wt.%TiB2 increase the stacking height of (002) planes (Lc) of CTP pyrolysis and carbonization products with increased edge dislocation density and ultimate strain. The combined additions of TiB2 and GO generate a synergistic effect on further improving the mechanical properties of CTP carbonization products with increasing the stacking order of (002) plane, crystallite size (La and Lc) and edge dislocation density. CTP-1GO-5TiB2 shows a compressive strength 194.7 MPa higher than the pure CTP (155.4 MPa). Further findings suggest that a combined mechanism of GO and TiB2 additions can be established through stabilizing C–C bonds while reducing C-O bonds along with chemical component transformations after pyrolysis and carbonization. TiB2 particles play a key role in making the synergistic effect on improving the mechanical strength and reducing the oxidation of C–C bonds with additional increase in La value.

Evaluation of engineering properties of Fiber-reinforced Usual-temperature Synthetic Pitch (USP) modified cold mix patching asphalt

As a common-used pothole repairing material, cold mix patching asphalt (CMA) has been widely used in practice. This article aims to develop a novel CMA with good overall performance and better environmental-friendliness. A few environmental-friendly ingredients, including a modifier named Usual-temperature Synthetic Pitch (USP), polyester-basalt composite fibers, a commercial anti-stripping agent, a commercial tackifier and biodiesel, were utilized for preparing Fiber-reinforced USP modified CMAs (FUAs). Laboratory tests, including workability assessment tests, Marshall stability tests, boiling water tests, rolling sieve cohesion tests, freeze-thaw splitting tests, wheel tracking tests and three-point bending tests, etc. were conducted to evaluate the workability, Marshall stability, adhesion, moisture susceptibility, rutting resistance, bending resistance and storage stability. Two mix designs of the cutback (termed as Scheme 1 and 2) with weight ratios of 100:6:18:0.3:0.6 and 100:6:20:0.4:0.8 for binder: USP: biodiesel: anti-stripping agent: tackifier were considered. Effect of fiber content (0.2%, 0.3%, 0.4% and 0.5% by aggregate weight) was also investigated considering an optimal polyester to basalt fiber weight ratio of 3:2. The results show that the optimal fiber content is 0.4%. The engineering properties of FUAs meet the construction requirements, and they also present good storage stability. Scheme 2-based cutback shows better workability, smaller penetration and better binder-aggregate adhesion than the Scheme 1-based cutback; consequently, the Scheme 2-based FUA presents advantages over Marshall stability, rutting resistance and bending resistance. Compared with Styrene-Butadiene-Styrene (SBS) modified CMAs, FUAs possess better overall performance and advantages over environmental conservation. The FUAs, therefore, have good application prospects in pavement repair.

Correlation between molecular stacking and anisotropic texture in spinnable mesophase pitch

The correlation of the anisotropic texture and (002) the molecular stacking property of spinnable mesophase pitch (SMP) was closely examined. SMP was found to be a specific solution consisting of mesogenic and solvent components, and the mesogenic component was composed of a cluster unit of (002) stacked molecular sheets. The anisotropic texture of SMP was strongly correlated with the height of (002) molecular stacking. When the concentration ratio of the mesogenic component to the solvent component was higher than the threshold concentration, the SMP always had 100 vol% anisotropic texture and a similar or larger number of stacked (002) sheets compared with its mesogenic component in both the solid and molten states. The solvent component, in both lamellar and hexagonal phases, assisted orientation of mesogenic molecules and rearrangement of mesogenic cluster units, thereby inducing a higher degree of graphitization than that of the solvent-free mesophase pitch. A schematic phase model of SMP was proposed based on a lyotropic liquid crystalline system and a hierarchical domain model.

Generation and characterization of coal-based needle coke produced by the co-carbonization of coal liquefaction pitch and anthracene oil.

In this study, we studied the feasibility of preparing high-quality needle coke from coal liquefaction pitch. Nine types of blending pitch (coal liquefaction pitch and anthracene oil mixed with different ratios) were used as raw materials to generate needle coke via the co-carbonization method. Optical microscopy, X-ray diffraction, Raman spectroscopy and scanning electron microscopy were employed to determine the properties (microstructure, distribution of carbon microcrystals, true density and micro-strength) of the needle coke derived by the co-carbonization method. Actually, the co-carbonization of coal liquefaction pitch and anthracene oil was an essential method to control the micro-structure and property of the derived needle coke. Briefly, the needle coke derived by the co-carbonization of coal liquefaction pitch and anthracene oil had a lower content of mosaic structure of 14.17%, ideal carbon crystal content of 82.67%, and true density of 2.296 g cm−3. Briefly, the addition of anthracene oil is a suitable method to adjust the property of coal liquefaction pitch, which is also a good method to produce high-quality needle coke via the co-carbonization of coal liquefaction pitch and anthracene oil. Thus, the use of coal liquefaction pitch and anthracene oil as raw materials to generate high-quality needle coke is a considerable method to realize the clean and high value-added utilization of coal liquefaction pitch.

A machine learning approach for gender identification using statistical features of pitch in speeches

Speech processing and recognition are some of the imperative research areas, remarkably in user authentication and entertainment. There are assorted well-known approaches in the domain, and the properties of pitch are broadly used in most of the works. The objective of this work is to explore the capabilities of statistical features of the pitch in the gender identification problem. We proposed an effective combination of features, PFG-Pitch Feature for Gender, for gender identification with machine learning algorithms. The feature sets from three datasets – TIMIT, CHAINS and SLR-63- were used in the experiments. We could attain the maximum output in some ideal situations with the classical learning methods- CNN, MLP, SVM and LR. It is renowned that the outstanding performance from most of the machine learning classifiers embassies the magnitude of statistical features in speech processing.

Improvement of the thermal properties of pitch by waste plastic (polyvinyl chloride) addition

To modify the thermal properties of pitch by adding polyvinyl chloride (PVC), co-pyrolysis of PVC and coal tar pitch was performed. PVC decomposes into HCl and de-HCl PVC (polyene) above 200 °C, and these substances affect the synthesis behavior of coal tar pitch. It was confirmed that HCl induces cracking, promotes the radical reaction and lowers the polycondensation initiation temperature of coal tar pitch. Furthermore, aromatic components produced by the cyclization reaction of polyene participate in the polycondensation reaction, which increases the molecular weight of the pitch. This leads to an increase in softening point and coking value of pitch. The related mechanisms were assessed using thermal analysis (TGA, DTG, DSC) and molecular weight distribution analysis (MALDI-TOF).

Study on structures and properties of isotropic pitches and carbon fibers from co-carbonization of aromatic-rich distillate oil and polyethylene glycol

Obtaining cost-competitive carbon fibers with excellent mechanical properties remains a great challenge. Here we report the co-carbonization of polyethylene glycol (PEG) and an aromatic-rich distillate oil (HCT0-RF) to prepare isotropic pitches that have superior spinnability for the production of carbon fibers. Among all of the carbon fiber productions, H-P10-CFs exhibited the best tensile strength of 1050 MPa and elongation of 2.5 %, respectively, at the breaking point. We reason that the addition of PEG into HCTO-RF can effectively increase the yield of isotropic pitches, accompanied by restricting the appearance of the mesophase spheres. The amount of aliphatic carbon in spinnable pitches were observed to increase with the amount of PEG. Thus, the changes in molecular structure can improve the rheological properties of spinnable pitch and enhance the spinnability. In addition, the increase of aliphatic components can accelerate the oxidative reaction and promote the stabilization efficiency. Unfortunately, excessive aliphatic components would inevitably cause higher oxygen uptake content, which deteriorate the uniformity of the fiber structures during carbonization process. With the increase of PEG content, the tensile strength of these carbon fibers increased first and then decreased. The optimized PEG content should be in the range of 5–10 wt%. The PEG acted as the co-carbonization agent provides new perspective in the field of carbon fiber production.

Effect of nitric acid treatment on the pitch properties and preparation of activated carbon

Effect of nitric acid treatment on the pitch properties and preparation of activated carbon

Manufacturing Pitch and Polyethylene Blends-Based Fibres as Potential Carbon Fibre Precursors.

The advantage of mesophase pitch-based carbon fibres is their high modulus, but pitch-based carbon fibres and precursors are very brittle. This paper reports the development of a unique manufacturing method using a blend of pitch and linear low-density polyethylene (LLDPE) from which it is possible to obtain precursors that are less brittle than neat pitch fibres. This study reports on the structure and properties of pitch and LLDPE blend precursors with LLDPE content ranging from 5 wt% to 20 wt%. Fibre microstructure was determined using scanning electron microscopy (SEM), which showed a two-phase region having distinct pitch fibre and LLDPE regions. Tensile testing of neat pitch fibres showed low strain to failure (brittle), but as the percentage of LLDPE was increased, the strain to failure and tensile strength both increased by a factor of more than 7. DSC characterisation of the melting/crystallization behaviour of LLDPE showed melting occurred around 120 °C to 124 °C, with crystallization between 99 °C and 103 °C. TGA measurements showed that for 5 wt%, 10 wt% LLDPE thermal stability was excellent to 800 °C. Blend pitch/LLDPE carbon fibres showed reduced brittleness combined with excellent thermal stability, and thus are a candidate as a potential precursor for pitch-based carbon fibre manufacturing.

Research on the Rheological Properties of the Plant Oil Pitch

In the analysis of the rheological properties of the plant oil pitch, the original analysis method has a narrow range of analysis indicators, which affects the reliability of the analysis results. In this study, a new analytical method for the rheological properties of the plant oil pitch was designed. The microstructure characteristics of the plant oil pitch were obtained using a high-power microscope, the viscosity of the plant oil pitch was measured, and the ductility of the plant oil pitch was analyzed by setting the analysis index. The above parts are integrated, and the dynamic shear tester is used to complete the analysis of pitch rheological properties. So far, the analysis method for the rheological properties of the plant oil pitch has been designed. It can be seen from the comparison of the experimental links that this analysis method is better than the original analysis method in terms of the scope of analysis indicators. In conclusion, the analytical method of the rheological properties of the plant oil pitch is more reliable.

The effect of pyrolysis on the chemical, thermal and rheological properties of pitch

Pitch-based carbon fibers are of considerable interest as high-performance materials. There are reports over the last several decades detailing (i) methods of improving pitch-based carbon fiber performance, and (ii) reducing the cost of production via novel processing techniques. However, there remain considerable challenges in producing high-performance pitch-based carbon fibers consistently on an industrial scale. This is arguably due to the difficulty of scaling the melt-spinning process to compensate for variability in pitch feedstock quality and a lack of understanding of processing-structure-performance relationships. This work focuses on the early stages of heat treatment (pyrolysis) of isotropic pitch and its effect on the chemical, thermal, and rheological properties of the pitch, which help determine its processability. More specifically, we quantify significant changes in chemical structure, Mw, Tg, Ts, and shear and extensional rheology as a function of pyrolysis time at 400 °C. The extensional rheology, in particular, shows that the 'stretchability' of the pitch samples strongly depends on pyrolysis severity, and is important for characterizing 'drawability'. Using a novel analysis of the uniaxial stretching kinematics, we show an isothermal 'drawability window' that allows for the largest axial and radial Hencky strains at constant rate. We hypothesize that this extensional drawability window could facilitate the successful processing of pitch into high quality fiber, minimizing the trial-and-error approach currently used in the field.

Correlation between Molecular Stacking and Anisotropic Texture in Spinnable Mesophase Pitch

The correlation of the anisotropic texture and (002) molecular stacking property of spinnable mesophase pitch was closely examined. Spinnable mesophase pitch was found to be a specific solution which consisted of mesogenic and solvent components. Here, the mesogenic component composed of the cluster unit of the (002) stacked molecular sheets. In addition, the anisotropic texture of spinnable mesophase pitch showed a strong correlation with the height of (002) molecular stacking. When the concentration of mesogenic component to the solvent one is higher than the threshold concentration, spinnable mesophase pitch always showed 100 vol% anisotropic texture and the similar or larger number of stacked (002) sheets than that of its mesogenic component in both the solid and melt states. The solvent component in the lamellar and hexagonal phases may help the orientation of mesogenic molecules and rearrangement of mesogenic cluster units, inducing a higher graphitization degree than that of the mesophase pitch with solvent-free. The schematic phase model of spinnable mesophase pitch was proposed by the authors based on a lyotropic liquid crystalline system and the hierarchical domain model.

Accelerating the oxidative stabilization of pitch fibers and improving the physical performance of carbon fibers by modifying naphthalene-based mesophase pitch with C9 resin

A spinnable mesophase pitch with 95 vol.% optical anisotropy and 267 °C softening point was prepared through co-polymerization of 95 wt.% naphthalene pitch and 5 wt.% C9 resin. The effects of introducing C9 resin on the formation, structure and properties of naphthalene-derived mesophase pitch and the oxidative stabilization of resulting pitch fibers as well as the final physical properties of carbon fibers were systematically investigated. The results suggest that C9 resin could effectively facilitate the generation and development of liquid crystals in synthetic naphthalene pitch during the heat soaking process and introduce a certain amount of methyl side chains linking in polycyclic aromatic hydrocarbon molecules, so as to reduce the melt viscosity of modified mesophase pitch and improve its flow-spinnability and oxidative reaction capability. The pre-oxidation process of the modified pitch-spun fibers could be completed ahead of 4 h at 240 °C in an air atmosphere, compared with unmodified pitch fibers. This shows a possibility to decrease the production cost of mesophase pitch-based carbon fibers. Although the tensile strength of 1000 °C carbonized fibers prepared from the modified mesophase pitch (1.23 GPa) is slightly higher than that of original carbon fibers (1.18 GPa), the axial electrical resistivity and the thermal conductivity of corresponding graphite fibers after 3000 °C graphitization are 2.0 μΩ m and 677 W/(m K), respectively, which are significantly enhanced in comparison with those of original graphite fibers (3.2 μΩ m and 473 W/(m K).

Action of Ozone in the Low-Temperature Ozonization of Coal Tar

The action of ozone in the low-temperature ozonization of coal tar from the semicoking of Shubarkol coal (Kazakhstan) is analyzed. Two mechanisms are possible: the electrophilic addition of ozone by π bonds to the molecules of unsaturated compounds; or radical-chain reactions with the formation of a broad spectrum of oxygen-bearing products (carboxylic acids, alcohols, aldehydes, etc.). The presence of each mechanism in tar ozonization is approximately the same. Ozone plays a positive role, by doubling the content of β fraction in the tar; and decreasing the content of the unreactive α1 fraction. The β fraction determines the binding and clinkering properties of pitch, while the α1 fraction prevents the appearance of anisometric needle-coke structures in pitch coking.

Modified effect on properties of mesophase pitch prepared from various two-stage thermotreatments of FCC decant oil

The comparative study of different two-stage heat treatments was conducted to illustrate the modified effects on improving yield and spinnability of mesophase pitch. In such two-stage thermotreatments, a pressured condensation is employed to involve low-molecular-weight species into the formation of mesogens, thereby increasing pitch yields. Subsequently, vacuum polymerization could contribute to rapid development of mesophase and then reduce the residence time. The results indicate that the short duration could decrease occurrence of the intramolecular aromatization and intermolecular polymerization reactions that are readily induced by elimination of α-methyl and dehyroaromatization of naphthenic rings during the later stage of heat treatment. Consequently, the formed semi-rigid molecules in QS sub-fraction (i.e., fusible component) are seldom transformed into rigid ones mainly constituting QI sub-fraction (i.e., infusible component). Ultimately, sufficient QS sub-fraction, with a higher average Mw and a large amount of short alkyl and naphthenic substituents, is more likely to completely dissolve QI sub-fraction. Thus, the resultant mesophase exhibits an excellent fusible deformability. Besides, the structural feature of semi-rigid oligomer could somewhat loosen molecular association of layered stacking and contribute to the slippage between stacked mesogens due to its steric effects, thereby decreasing the softening points of mesophase pitch. Above modified effects are easily implementable during a suitable process of two-stage thermotreatment, such as the processes of preparing MP-4-0.01-1.0, MP-4-0.005-1.0 and MP-3-0.01-2.0 in this study. It is worthwhile to mention that the vacuum treatment is required to be conducted prior to large-scale coalescence of mesophase spheres in order to obtain spinnable mesophase pitch.