Structural Evolution Characteristics Research Articles

Energy evolution characteristics of ballasted track with elastic layers

Elastic layers (ELs), including under sleeper pad (USP) and under ballast mat (UBM) have been used to enhance the elasticity and mechanical performance of ballasted track. Previous studies mostly focus on macro settlement and ballast crushing of ballasted track with ELs, with little consideration of energy evolution characteristics. Investigating the energy evolution is crucial for understanding the role of ELs in energy consumption, absorption, and transformation, thereby optimizing their design and improving performance. Here, the discrete element method (DEM) simulation models of ballasted track without and with ELs under cyclic loading were established to study the influences of USP and UBM on energy evolution characteristics of track structure from a mesoscopic perspective. The results showed that the ELs reduce friction dissipation energy and damping dissipation energy inside ballasts, which helps to slow down the particle breakage and wear. Compared with damping energy dissipation, friction energy dissipation is the main form of energy dissipation of ballasted track. In the stable loading stage, elastic strain energy is the main energy form. The employment of ELs increases the proportion of elastic strain energy due to enhanced track elasticity. The stiffness of ELs significantly affects viscous strain energy and elastic strain energy in ballasted track structures.

Evolution and Factors Influencing the Spatial Patterns of Fisheries and Aquaculture Products Trade within RCEP Countries: A Complex Network Analysis

This study aims to make visible and investigate changes in the patterns of trade in fisheries and aquaculture products, which are heavily traded and of high importance for food security in many Regional Comprehensive Economic Partnership (RCEP) member countries. The study uses fisheries and aquaculture products trade data from 2002 to 2022 and applies a complex network analysis to unveil the trade network of fisheries and aquaculture products within the RCEP region. It analyzes the topological structure and spatiotemporal evolution characteristics of the trade network, and utilizes QAP model to further examine the main factors influencing the characteristics of the fisheries and aquaculture products trade network. The study finds: (1) The density of the fisheries and aquaculture products trade network in the RCEP region has significantly increased, exhibiting “small-world” characteristics. With the increasing degree of trade integration, there is still much room for improvement in the cooperation and development of fisheries and aquaculture products trade; (2) The network displays a pronounced core-periphery structure, with China and Japan consistently occupying a central position in the RCEP region’s fisheries and aquaculture products trade network; (3) Economic size, comparative advantage, foreign dependence degree, per capita arable land area, contiguity, and institutional quality are significant factors affecting the relationships and trade volume among countries in the fisheries and aquaculture products trade network.

A study on the internal vortex structure within a single-blade pump via numerical methods and particle image velocimetry experiments

This study investigates the performance and internal flow characteristics of a single-blade centrifugal pump through a comprehensive analysis integrating performance tests, Particle Image Velocimetry (PIV) tests, and numerical simulations. Across the operational speed range of 1470–2940 rpm, the predicted pump (head-flow rate curve)performance error between the numerical simulation results and the test results of the pump underrated flow conditions is found to be only 3.4%, demonstrating the high accuracy of the selected numerical method in predicting both performance metrics and internal flow structures. Key findings highlight the presence of significant circumferential and axial secondary flows in the region where the blade wraps back, resulting in the formation of high-intensity vortex structures and subsequent energy dissipation. The interaction of the blade's trailing jet with the volute casing's tongue induces periodic changes in the intensity and spatial size of these vortex structures. Furthermore, pronounced reverse vortex pairs are identified within the volute casing, attributed to axial non-uniformity in impeller outflow. These vortex pairs are associated with the preferential accumulation of solid particles, potentially contributing to wear in the volute casing of single-blade centrifugal pumps. The revelation of the evolution characteristics of vortex structure in single-blade centrifugal pumps provides theoretical support for reducing pressure pulsation and radial force of single-blade centrifugal and provides a potential solution to the technical difficulties of low efficiency and poor stability of single-blade centrifugal pumps. Overall, this study provides valuable insights into optimizing the design and operational efficiency of single-blade centrifugal pumps by elucidating their complex flow dynamics and performance characteristics under varying operational conditions.

Phase evolution and surface analysis of electron beam evaporated calcium and yttria-stabilized zirconia thin films

The manuscript investigates the structural and morphological characteristics of thin films of calcium stabilized zirconia (CSZ, 16 mol % CaO), synthesized through electron beam deposition on silicon wafers, with a focus on the phase evolution during annealing at 800 °C. The study compares these properties with yttria stabilized zirconia (YSZ, 8 mol % Y2O3) thin films. Rutherford backscattering spectrometry validates film composition, with thicknesses of ∼315 nm for CSZ and ∼285 nm for YSZ. X-ray diffraction initially identifies an amorphous structure, transitioning to a cubic phase post-annealing, with average crystallite sizes of 18.07 nm for CSZ and 16.22 nm for YSZ, corroborated by Raman spectroscopy. The lattice parameters are determined using Rietveld refinement. Surface morphology is investigated through field emission scanning electron microscope and atomic force microscopy shows a reduction in surface roughness from 6.05 nm to 1.34 nm for CSZ and from 4.54 nm to 1.64 nm for YSZ post-annealing, indicating enhanced homogeneity. Elemental distribution analysis using energy dispersive X-ray spectroscopy confirms film uniformity. The study provides insights into the structural evolution and morphological characteristics of calcium stabilized zirconia thin films, particularly at the nanoscale level, offering valuable contributions to its industrial applicability.

Pore formation and evolution mechanisms during hydrocarbon generation in organic-rich marl

Marine organic-rich marl is not only a high-quality hydrocarbon source of conventional oil and gas, but also a new type and field of unconventional oil and gas exploration. An understanding of its pore structure evolution characteristics during a hydrocarbon generation process is theoretically significant and has application prospects for the exploration and development of this special type of natural gas reservoirs. This study conducted thermal simulation of hydrocarbon generation under near-geological conditions during a whole process for cylinder samples of low mature marine organic-rich marl in the Middle Devonian of Luquan, Yunnan Province, China. During this process, hydrocarbon products at different evolution stages were quantified and corresponding geochemical properties were analyzed. Simultaneously, field emission scanning electron microscopy (FE-SEM) and low-pressure gas adsorption (CO2, N2) tests were applied to the corresponding cylinder residue samples to reveal the mechanisms of different types of pore formation and evolution, and clarify the dynamic evolution processes of their pore systems. The results show that with an increase in temperature and pressure, the total oil yield peaks at an equivalent vitrinite reflectance (VRo) of 1.03% and is at the maximum retention stage of liquid hydrocarbons, which are 367.51 mg/g TOC and 211.67 mg/g TOC, respectively. The hydrocarbon gas yield increases continuously with an increase in maturity. The high retained oil rate at the peak of oil generation provides an abundant material basis for gas formation at high maturity and over-maturity stage. The lower limit of VRo for organic matter (OM) pore mass development is about 1.6%, and bitumen pores, organic-clay complex pores together with intergranular pores, grain edge seams and dissolution pores constitute a complicated pore-seam-network system, which is the main reservoir space for unconventional carbonate gas. Pore formation and evolution are controlled synergistically by hydrocarbon generation, diagenesis and organic-inorganic interactions, and the pattern of pore structure evolution can be divided into four stages. A pore volume (PV) and a specific surface area (SSA) are at their highest values within the maturity range of 1.9% to 2.5%, which is conducive to exploring unconventional natural gas.

Mixing enhancement assisted by dual plate cavity in supersonic flow

Fast and efficient mixing of high-speed shear flow formed by fuel and oxidizer is of great importance for the improvement of rocket-based combined cycle engine performance. Nevertheless, the existence of compressibility effects of high-speed flow significantly inhibits the growth process of a mixing layer. Moreover, a finite-length combustor of the engine calls for more effective enhanced-mixing strategies to complete mixing in a shorter streamwise distance. To this end, in present paper, the strategy called dual plate cavity (DPC) is proposed to promote mixing. Three cases including the benchmark, front-DPC and back-DPC cases are selected to perform the comparative study. By means of high-order direct numerical simulations, the structure evolution characteristics and turbulence intensity distributions are researched. The index of velocity thickness is utilized to assess the mixing layer growth. The results indicate that with the introduction of DPC, the mixing process is dramatically promoted. The penetration behavior of newly found T-shaped structures into the upper main stream can engulf more fluid into the mixing region. Specifically, in the back-DPC case, the coexistence of both large-scale and small-scale structures in the far flow field can improve the turbulence intensity. The spatial correlation analysis results show that with the influence of DPC, the structure sizes are much larger than that of the benchmark case in the same streamwise position. Meanwhile, the contour line equal to 0.5 possesses property of distortion for the back-DPC case. The drastic pulsation of a mixing layer edge can obviously promote the mixing process. Through exploration of the enhanced-mixing mechanisms, this work indicates that the proposed DPC strategy is a good candidate for efficient mixing, and in the future, more detailed work including three-dimensional simulations concerning the strategy optimization is suggested to be performed.

Microstructure, Texture Evolution and Mechanical Characteristics of Ultrafine-Grained Structure in Friction Stir Processed Aluminum Alloys

Microstructure, Texture Evolution and Mechanical Characteristics of Ultrafine-Grained Structure in Friction Stir Processed Aluminum Alloys

Chemical bond dissociation insights into organic macerals pyrolysis of Qinghua bituminous coal: Vitrinite vs inertinite

Coal pyrolysis essentially involves the decomposition chemical reaction of organic matters in coal under the drive of thermal fields. This heavily depends on the directed dissociation of different types of chemical bonds in coal macrostructures. The mechanism of temperature field regulation of various chemical bond dissociation during coal pyrolysis has not been obtained. The quantitative and intuitive depiction of the chemical bond dissociation of macerals is lacking at the microscopic perspective. This work provides chemical bond dissociation insights into macerals pyrolysis based on a comprehensive study. The relationship between temperature range and various chemical bonds dissociation have been established. The pyrolysis kinetics characteristics of macerals are quantitatively described. The molecular structure evolution characteristics and different chemical bonds dissociation of macerals are directly visual depicted by molecular dynamics calculations. The work could guide the intensification of the orderly conversion regulation and the chemical energy cascade release in coal utilization.

Response Characteristics of the Community Structure and Metabolic Genes of Oil-Recovery Bacteria after Targeted Activation of Petroleum Hydrocarbon-Degrading Bacteria in Low-Permeability Oil Reservoirs.

The microbial enhanced oil recovery (MEOR) process has been identified as a promising alternative to conventional enhanced oil recovery methods because it is eco-friendly and economically advantageous. However, the knowledge about the composition and diversity of microbial communities in artificially regulated reservoirs, especially after activating petroleum hydrocarbon-degrading bacteria (PHDB) by injecting exogenous nutrients, is still insufficient. This study utilized a combination of high-throughput sequencing and metagenomics technology to reveal the structural evolution characteristics of the indigenous microbial community in the reservoir during the PHDB activated for enhanced oil recovery, as well as the response relationship between the expression of its oil production functional genes and crude oil biodegradation. Results showed that Pseudomonas (>75%) gradually evolves into a stable dominant microbial community in the reservoir during the activation of PHDB. Besides, the gene expression and KEGG pathways after crude oil undergoes biodegradation by PHDB show that the number of genes related to petroleum hydrocarbon metabolism dominates the metabolism (21.98%). Meanwhile, a preliminary schematic diagram was drawn to illustrate the evolution mechanism of the EOR metabolic pathway after the targeted activation of PHDB. Additionally, it was found that the abundance of hydrocarbon-degrading enzymes increased significantly, and the activity of alcohol dehydrogenase was higher than that of aldehyde dehydrogenase and monooxygenase after PHDB activation. These research results not only filled in and expanded the theoretical knowledge of MEOR based on artificial interference or regulation of reservoir oil-recovery functional microbial community structure but also provided guidance for the future application of MEOR technology in oil field operations.

Quantitative Research on Roof Deformation and Temporary Support Stiffness in Deep-Mine Gob-Side Entry Retaining by Roof Cutting

The important technical process to ensure the success of gob-side entry retaining by roof cutting (GERRC) was the advanced pre-splitting blasting to cut off the mechanical connection between the roadway and working face roof. The whole-cycle roof structure evolution and stress characteristics of GERRC were analyzed. The factors affecting the roof deformation of GERRC were analyzed, and the quantitative relationship between the roof deformation of GERRC and the support stiffness was determined. The results showed that the temporary support stiffness was higher, the support position to the side of the roof cutting was closer, and the roof subsidence deformation of GERRC was smaller. It is proposed to use a single support mass with a high stiffness to control the deformation of the roof, but it also made the support mass and roof elastic potential energy aggregate. To fully utilize the matching of the support stiffness and roof subsidence, improve the stability, and control the subsidence deformation of the roof in GERRC, double-row stacking supports were adopted in the inclination of GERRC, which were used to increase the stiffness of the support system.

Study on the micromorphologies and structural evolution in cold-mixed epoxy asphalt

Cold-mixed epoxy asphalt (CMEA) is a high performance paving material that can be constructed and cured at room temperature. It forms thermal and mechanical performances during curing process. In this study, the phase state and structural evolution characteristics of CMEA during curing were evaluated by curing rheological behavior, mechanical properties, and micromorphology. Viscosity tests and dynamic mechanical analyses (DMA) were applied to study the curing rheological behavior, and tensile tests were used to determine the mechanical properties. Moreover, fluorescence microscopy (FM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were implemented to investigate the micromorphological and molecular structure evolution. The results showed that the curing reaction behavior of CMEA was closely related to temperature. The viscosity–time curves of CMEA satisfied the Arrhenius equation above 45 ℃ and followed a linear trend at low temperature. During the curing of CMEA, the toughness increased in three stages: the toughness growth stage, toughness stability stage and toughness decay stage. Furthermore, the presence of asphalt and its solvent weakened the curing reaction of epoxy asphalt. However, increasing the reaction temperature could increase the epoxy group conversion rate. When the curing reaction was complete, a considerable amount of asphalt solvent mixed with the asphalt and was uniformly distributed within the three-dimensional network structure of the epoxy resin. This mixture adversely affected the toughness of the cured CMEA.

Microscopic Mechanism and Road Performance Analysis of MgO Carbonation–Solidification of Dredged Sediment

MgO carbonization is a green and low-carbon soil improvement technology. The use of MgO carbonization to solidify dredged sediment and transform it into road-building materials has significant environmental sustainability advantages. A series of microscopic characterization tests, including X-ray Diffraction (XRD), Scanning Electron Microscope–Energy Dispersive Spectrometer (SEM-EDS), and Mercury-in-Pressure (MIP) tests, were conducted to elucidate the evolution characteristics of mineral composition, microscopic morphology, and pore structure of sediment under carbonation. Based on the results, the mechanism of MgO carbonation–solidification of dredged sediment was explored. In order to verify the improvement of carbonation on the road performance of sediment, comparative tests were carried out on sediment, non-carbonated sediment, and carbonated sediment. The results indicate a significant improvement in the solidification of MgO-treated sediment through carbonation, with enhanced macroscopic strength and densified microscopic structure. This can be attributed to the encapsulation, cementation, and pore-filling effects of the hydration products and carbonation products of MgO on soil particles. The rebound modulus and splitting strength of carbonated sediment were 3.53 times and 2.16 times that of non-carbonated sediment, respectively. Additionally, the carbonated sediment showed improved saturated stability, resistance to salt solution wet–dry cycles, and resistance to freeze–thaw cycles.

Study on the effect of rubber content on the frost resistance of steel fiber reinforced rubber concrete

In cold areas, the steel fiber reinforced rubber concrete (SFRRC) pavement is exposed to natural environment and experiences varying degrees of damage from freezing and thawing. This can have a serious impact on the normal usage and safe operation of the pavement structure. This research examines the impact of varying rubber concentrations on multiple variables, such as the rate of mass reduction, relative dynamic modulus of elasticity, compressive strength, and thickness of the damage layer (Hf) during freeze–thaw (F-T) durability testing conducted on SFRRC. Furthermore, an analysis is conducted to determine the degradation pattern exhibited by SFRRC. The internal structure evolution and pore structure characteristics of SFRRC were examined using scanning electron microscopy and mercury intrusion porosimetry techniques, which revealed the underlying damage mechanism in SFRRC during F-T cycles. The results suggest that the addition of an appropriate amount of rubber can effectively enhance the frost resistance of SFRRC in water. A gradual improvement in the frost resistance of SFRRC is observed when increasing the rubber content from 0 to 10%. The optimal frost resistance is observed in SFRRC with 10% rubber content. However, when the rubber content reaches 15%, SFRRC exhibits significant degradation and lower level of resistance to freezing compared to SFRRC without rubber. Microcracks form within SFRRC due to the freezing–thawing forces experienced during the experiment, resulting in the development of a damage layer that extends from the surface to the interior. The compressive strength of the damaged layer significantly decreases as Hf increases. The addition of appropriate rubber in SFRRC improves its pore structure, leading to an increased proportion of harmless or less harmful pores and a reduction in average pore size, thereby significantly enhancing its frost resistance.

Experimental Study on Differential Thermal Response and Pore-Fracture Structure Evolution Characteristics of Coals under Microwave Irradiation: A Case Study of Five Different Rank Coals

Experimental Study on Differential Thermal Response and Pore-Fracture Structure Evolution Characteristics of Coals under Microwave Irradiation: A Case Study of Five Different Rank Coals

Evolution characteristics and influencing factors of information network in Guangdong-Hong Kong-Macao Greater Bay Area.

In the context of the digital information era, the impact of "The Internet Plus," "Big Data," and other technologies on urban social development has been far beyond any preceding era, under the influence of information technology, urban agglomeration space exhibits a new layout. Based on the search engine data of eleven cities in the Guangdong-Hong Kong-Macao Greater Bay Area from 2012 to 2021, this research constructs the inter-city information network strength linkage matrix to examine the evolution characteristics of city network structure and its driving causes. The results reveal that (1) the overall information linkage strength exhibits a pattern of steadily growing the radiating effect from the leading cities of Guangdong, Shenzhen, and Hong Kong to the surrounding cities, and a closer and more balanced information linkage network is gradually built. (2) Guangzhou-Shenzhen-Hong Kong-Guangdong-Hong Kong-Macao Greater Bay Area information linkage absolute control advantage, four cities Foshan, Dongguan, Zhuhai, Macao regional hub position steadily highlighted. The entire information connection network of the urban agglomerations tends to be flat and polycentric at the same time. (3) The regional core-edge hierarchy is well established, with the four cities of Guangzhou, Dongguan, Shenzhen, and Hong Kong creating a northwest-southeast orientation. The core metropolis regions of Guangdong, Hong Kong, and Macao in the Greater Bay Area increasingly exert a radiation spreading effect to the northeast and southwest. (4) The urban economy, transportation distance, and information infrastructure have substantial effects on the information connection intensity network of urban clusters.

Characterization of pore structures after ASP flooding for post-EOR

With the global assistance of oil fields entering the stage of improving oil recovery, diversified composite flooding technology has become one of the key research targets. This article takes composite flooding to improve oil recovery as the research object, explores the differential mechanism of crude oil displacement efficiency under water flooding and composite flooding conditions, and elucidates the dynamic evolution characteristics of pore structure before and after composite flooding. Results show that: (a) The permeability and porosity of Daqing oilfield cores have a good correlation. The porosity of cores after water driving and ternary composite driving mainly ranged from 23.6 % to 27.4 % and 22.8 %–26.8 %. The water-driving permeability mainly ranged from 168 × 10−3 μm2 to 2162 × 10−3 μm2. Ternary composite driving permeability mainly ranges from 302 × 10−3 μm2 to 2307 × 10−3 μm2. (b) Compared with water driving, quartz and clay minerals are corroded by alkali during ternary composite driving. (c) Under the condition of similar permeability, the average pore size of the core after ternary composite driving is smaller than the average pore size after water driving.

Investigation of pore structure evolution and damage characteristics of high temperature rocks subjected to liquid nitrogen cooling shock

Liquid nitrogen (LN2) can be utilized in the development of enhanced geothermal systems, as well as for deep/ultra-deep hydrocarbon reservoir stimulation, fire suppression, and other high-temperature geological projects. It is a crucial issue in the utilization of LN2 to investigate the pore structure evolution, permeability, and damage characteristics of high-temperature rocks under the influence of LN2 cooling shock. These rocks were first slowly heated to 150∼600°C and held for 2 h, followed by LN2 or natural cooling. The evolution of pore volume in high-temperature rocks affected by liquid nitrogen cooling was quantified. T2 cutoff values were determined through centrifugal tests, while the contents of irreducible and mobile fluids were estimated. Based on the aforementioned analysis as well as changes in irreducible fluid saturation, pore throat, tortuosity, and permeability, this study examines the closure and development of pores along with permeability behavior. The findings suggest that, despite a more pronounced decrease in porosity at lower heating temperatures, LN2 cooling specimens exhibit superior pore connectivity and permeability compared to those cooled naturally. LN2 stimulation not only induces crack initiation and propagation but also results in further cooling induced densification based on heating densification. 225°C is considered to be the optimal temperature for cooling contraction induced densification in this study. At higher heating temperatures, the damage to rock cooled with LN2 is more severe than that of naturally cooled. This results in a greater increase in porosity, movable fluid content and proportion, and permeability of LN2 cooled specimens compared to naturally cooled specimens. The damage mechanism can be better understood by the constructed damage model that coordinates the pore increase/decrease and mutual pore transformation from the perspective of pore evolution.

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal.

The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.

Size-dependent amorphization of cementite lamellae in a tribolayer

The deformation and structural evolution characteristics of cementite in tribolayers significantly impact the friction and wear properties of pearlitic steels. However, the mechanism and size dependency of cementite amorphization remain unclear. Herein, the focused ion beam (FIB) lift-out technique was used to prepare transmission electron microscopy (TEM) samples of tribolayers formed during dry sliding of pearlitic steel. The microstructure of and elemental distributions in the tribolayers were characterized. Furthermore, molecular dynamics (MD) simulations were employed to analyze the behavior of dislocation slip systems in ferrite that extended toward cementite and induced amorphization. The results indicated that cementite amorphization occurred prior to dissolution within the tribolayer. Dislocation slips at the phase interface resulted in C diffusion and cementite amorphization. The transformation of cementite was size dependent. Thin lamellae transformed into amorphous lamellae, while local deformation and shear bands formed in thick lamellae. These research findings could contribute to rational design of cementite and to control of its structural evolution behavior within a tribolayer, thereby enhancing the wear resistance of a material.

Product distribution and carbon structure evolution characteristics of semicoke from isothermal pyrolysis of Naomaohu coal

Isothermal pyrolysis of Naomaohu coal was carried out at a temperature ranging from 500 to 750 0C using a fixed-bed reactor. The product distributions of gas and tar were measured using gas chromatography and gas chromatography-mass spectrometry, respectively. In addition, the effect of temperature on carbon structure evolution characteristics of semicokes were also investigated. The results showed that the gas yield increased dramatically from 61.50 to 168.43 mL g−1 when the temperature increased from 500 to 750 0C. CO2 and C2-C3 gases were mainly produced during the primary pyrolysis of lower energy chemical bonds at a lower temperature. The tar content ranges from 18.6 to 20.5 wt%, with the highest at 550 0C. At higher temperature, the branched hydrocarbon and phenols can react with each other to produce more polycyclic aromatic hydrocarbon. The infrared absorption peak area associated with the functional groups of O-H, C-H, CO and C-O initially increased with temperature from 500 to 550 0C before sharply decreasing as the temperature increased from 550 to 750 0C. At a higher pyrolysis temperature, the carbon content of the semicoke and the degree of graphite crystalline structure increased. Semicoke produced at higher pyrolysis temperatures exhibited better crystalline behavior and more pores and cracks.