OBJECTIVES:Postherpetic neuralgia (PHN) is a severe and distressing complication in elderly patients with herpes zoster and is associated with increased sympathetic nervous system activity. Spinal cord stimulation (SCS) implantation has been shown to effectively relieve PHN. In recent years, heart rate variability (HRV) analysis, as a reliable and objective indicator of autonomic nervous system (ANS) activity, has been widely used in the assessment of chronic pain. This study aims to investigate the clinical effects of SCS implantation on HRV in patients with PHN and its correlation with pain outcomes. METHODS:A total of 28 patients who met the inclusion criteria and were treated in the Department of Pain Medicine, the Third Xiangya Hospital of Central South University between November 2023 and March 2024 were retrospectively included. All patients underwent SCS implantation. HRV parameters before and after SCS implantation were collected, including the standard deviation of all normal-to-normal intervals over 24 hours (SDNN), root mean square of successive differences (RMSSD), standard deviation of successive differences (SDSD), percentage of adjacent normal-to-normal intervals differing by more than 50 milliseconds (PNN50), low-frequency power (LF), high-frequency power (HF), the LF/HF ratio, and total power (TP) within 5 minutes across all frequency bands. Univariate linear regression analysis was performed to explore the correlations among HRV parameters before and after SCS treatment. RESULTS:After SCS implantation, the HRV time-domain indices SDNN, RMSSD, SDSD, and PNN50, as well as the frequency-domain indices LF, HF, and TP, were significantly increased (all P<0.05), while the change in LF/HF ratio was not statistically significant (P>0.05). SCS treatment also had positive effects on pain relief, improvement of negative emotions, and reduction of psychological stress (all P<0.05). Differences were observed among implantation segments. In patients receiving SCS implantation below the T8 thoracic segment, SDNN, LF, and HF decreased significantly (all P<0.05). Correlation analysis revealed that pain scores were significantly correlated with SDNN. Significant correlations were also observed among the HRV time-domain indices SDSD, RMSSD, and PNN50 (all P<0.05), whereas correlations among frequency-domain indices were relatively weak. The changes in time-domain and frequency-domain HRV indices showed a synergistic trend. CONCLUSIONS:Pain outcomes in patients with PHN are accompanied by synchronous changes in autonomic nervous system activity. SCS implantation can improve HRV stability in patients with PHN and contribute to better cardiac rhythm regulation. HRV measurement may serve as evidence reflecting ANS activity in patients with PHN.

The irradiation stability of carbon-fiber-reinforced carbon matrix (C/C) composites is crucial for their potential use in the safe operation of reactors. This study used positron annihilation spectroscopy and conventional characterization techniques to investigate the behavior of C/C composites under He ion irradiation at various temperatures and dosages. The material's vacancy defects rapidly increased as the irradiation dose increased, increasing the fiber and matrix's disorder and ultimately causing amorphization. Additionally, there is a differential in shrinkage between the matrix and fiber. The material's vacancy defects gradually disappear as the irradiation temperature rises, the fiber and matrix's ordered structure gradually returns, and the interface between them becomes difficult to distinguish. The results of slow positron beam Doppler broadening spectroscopy and thermal desorption spectroscopy show that the evolution of vacancies is closely linked to helium retention and release and that the most likely form of helium atoms in C/C composites is helium–vacancy complexes. These results provide insight on how to restore the material structure in C/C composites and comprehend the damage mechanism caused by radiation.

High-speed aircraft thermal protection systems demand high-thermal-conductivity carbon/carbon (C/C) composites, yet their thermophysical properties and ablation resistance remain constrained by microstructural evolution during graphitization. To address this limitation, this study fabricated the CMP/C composites using mesophase pitch-based carbon fibers (MPCFs) as reinforcement through a hybrid manufacturing approach combining chemical vapor infiltration with hot isostatic pressing. The synergistic effects of ultra-hightemperature graphitization on microcrystalline development, texture evolution, and pore distribution were systematically investigated with respect to thermal conductivity, thermal expansion, and ablation resistance. The results show that graphitization at 3000 degrees C significantly improves the ordering and size of graphite microcrystals, yielding a maximum thermal conductivity of 290.43 W & sdot;m- 1 & sdot;K- 1 along the X-direction. This efficient heat dissipation mechanism reduces the highest temperature at the ablation end to only 1774 degrees C and leads to a decrease in its linear and mass ablation rates by 26.3 % and 21.1 %, respectively. The results demonstrate that ultra-high temperature graphitization serves as a critical processing strategy for enhancing thermal conductivity in CMP/C composites, while achieving an optimal balance among high thermal conductivity, low thermal expansion, and superior ablation resistance. These findings provide valuable design principles for engineering CMP/C composites toward next-generation thermal protection systems capable of operating under extreme thermal conditions.

OBJECTIVE:To determine the impact of neuropathic lesion on cortical synchronization in processing spontaneous pain-like behavior. BACKGROUND:In vivo optical monitoring of neuronal activity may provide insightful mechanisms underlying the complexity of spontaneous pain-like behavior in freely moving animals. METHODS:We examined the synchronized pattern of the pyramidical neurons in anterior cingulate cortex during spontaneous grooming behavior using optical monitoring of Ca2+ activity. A chronic constriction injury of infraorbital nerve model was performed to induce trigeminal neuropathic pain. We then analyzed the synchronized patterns of cortical population and computed Shannon entropy values to assess the uncertainty of neural coding during spontaneous pain-like behavior. RESULTS:Following nerve injury, mice exhibited significantly prolonged isolated grooming behavior compared to the control group. Our data indicate that, while neuropathic pain enhanced synchronized activity of cortical network during spontaneous grooming behavior, craniofacial nociception reduced the uncertainty of neural firing. Interestingly, this transition to a synchronized state of cortical ensembles in neuropathic pain conditions was significantly disrupted by spontaneous grooming behavior. CONCLUSION:Our findings provided a method of monitoring the synchronized activity of cortical ensemble in freely moving animals. Synchronization index may be used to decode spontaneous neuropathic pain-like behavior.

Mechanical allodynia refers to a hypersensitive status in response to innoxious stimuli caused by neuropathic pain. A therapeutic strategy to reverse the sensory impairment is neuromodulation treatment selectively targeting the dorsal root ganglion. However, the supra-spinal mechanism of neuromodulation therapy remains elusive. By combination of the multiple-channel neurophysiology recording and cellular manipulation in freely moving rats, we investigated the gate function of nucleus accumbens in control of nociceptive inputs, and its role in pulsed-radiofrequency neuromodulation therapy for neuropathic pain, using a clinically relevant neuromodulation parameter. We initially identified a gaining representation of the nucleus accumbens in response to nociceptive (pinprick), but not innoxious inputs (4 g Von Frey filament) in naïve rats. In neuropathic pain condition, the gate function was disrupted to drive an enhancement of accumbal activity during mechanical allodynia behavior. Pulsed radiofrequency neuromodulation of dorsal root ganglion was utilized to reverse pain hypersensitivity and accumbal homeostasis. Furthermore, we found that the accumbal gaining was not only a dynamic integration of painful signals, but also to serve as a gate of nociceptive perception required for neuromodulation therapy. In addition, the supra-spinal modulation effect on allodynic phenotype was imitated through optogenetic activation of the accumbal terminals of the spinal cord projections. Our data indicates that the accumbal gate is essential for integration and control of sensory inputs, potentially acting as one neuromodulatory target to reverse pain sensitization.

Mesophase transformation of pitch occurs prior to carbonization and critically influences the microstructure and properties of the resulting carbon. However, most studies focus on open systems, and the behavior and mechanism of mesophase transformation under confinement remain poorly understood. In this study, the mesophase transformation of petroleum pitch was investigated using different graphite microcolumns to simulate confined spaces of fiber preforms with controlled surface and geometric characteristics. The results indicate that active sites on confined space surfaces capture pitch molecules and promote their ordered stacking, thereby accelerating mesophase transformation. Meanwhile, increasing surface defect density further enhances this confinement-induced promotion. The geometric factor (S/V) of the confined space critically influences the transformation efficiency. When the S/V ratio increases from 0.015mm-1 to 0.064mm-1, the mesophase transformation rate of isotropic pitch sharply rises from 19% to 100% within 2h. These findings offer both theoretical insight and practical guidance for controlling mesophase transformation to improve the performance of high-thermal-conductivity carbon/carbon composites.

BACKGROUND:Neuropathic pain is characterized by disrupted large-scale brain dynamics. While paresthesia-based spinal cord stimulation (SCS) offers superior efficacy compared to pharmacological interventions, its clinical potential is constrained by poorly understood central mechanisms. EEG microstate analysis provides a powerful framework for capturing rapid spatiotemporal brain dynamics, offering further insights to elucidate how SCS potentially reconfigures the organization of neural activity. METHODS:We recruited patients with acute and chronic herpes zoster-associated neuralgia (HZAN) to investigate the modulatory effects of SCS. Using a Group (acute vs. chronic) × Condition (SCS-on vs. SCS-off) interaction design, we evaluated topographies, temporal metrics, and microstate-based functional connectivity to comprehensively characterize condition-dependent brain dynamics. RESULTS:SCS significantly attenuated the temporal predominance (duration, coverage, and occurrence) of Microstate A (auditory/visual and arousal), accompanied by a reciprocal expansion of Microstate B (visual network). Transition dynamics were markedly reconfigured, specifically through increased transition probability from A to B and a decrease from C (salience) to A. Intriguingly, exploratory analysis indicated that the transition probability from A to B (SCS-off) was positively correlated with post-treatment VAS scores. Furthermore, microstate-based connectivity analysis captured four functional modulation trends: functional inflexibility, reversal, alignment, and shared modulation. Finally, frequency-specific Microstate-A subnetwork strength emerged as a robust predictor of SCS therapeutic efficacy, particularly in acute HZAN. CONCLUSIONS:Paresthesia-based SCS potentially functions as a systemic reconfigurator of large-scale brain dynamics. By modulating and reconfiguring the aberrant spatiotemporal architecture and connectivity, SCS holds the potential to nudge the brain away from pathological entrapment toward a more adaptive and flexible functional mode. These results underscore the potential of microstate-based metrics as non-invasive biomarkers for optimizing individualized neuromodulation in HZAN.

Polymer-derived SiCN ceramics (PDCs-SiCN) have emerged as promising high-temperature microwave-absorbing materials due to their excellent high-temperature resistance and tunable dielectric properties. A fundamental understanding of the correlations among pyrolysis processes, compositional/structural evolution, and dielectric properties is essential for precise regulation of their microwave absorption performance. This study investigates the pyrolysis behavior of polysilazane and employs controlled annealing treatments to modulate the crystallization state and compositional structure of PDCs-SiCN. The results indicate that the formation of the Si-C-N network during pyrolysis stems from the generation and cross-linking of Si4C and SiN4 macromolecules, whereas the polymerization and growth of carbon-containing side chains form the free carbon phase. The separation and crystallization of these two phases at high temperatures significantly affect the dielectric properties. The abundant heterogeneous interfaces in SiCN1500-1400 notably enhance interfacial polarization, yielding remarkable microwave absorption with a minimum reflection loss (RLmin) of -54.25 dB in the mid-frequency range, and maintaining good absorption properties after 30 min of high-temperature oxidation at 1000 degrees C. In contrast, SiCN1500-1500, characterized by substantial SiC content, enhances dipole polarization, exhibiting excellent high-frequency microwave absorption with an RLmin of -20.27 dB. This work broadens the technical foundation for developing lightweight, high-temperature, wideband microwave absorbing components in highspeed aerospace vehicles.

Mesophase pitch-based carbon fibers (MPCFs) possess exceptional thermal conductivity and modulus, but their high-tech applications are severely constrained by low compressive strength. To address this limitation, it is crucial to comprehensively understand the microstructure-dependent compression behavior of MPCFs. This study systematically investigates the compression response of MPCFs with varying graphite microstructures by innovatively combining in-situ micropillar compression experiments with molecular dynamics simulations. Results elucidate the critical roles of grain size, orientation, amorphous carbon content, and pore structure in governing compression behavior. Specifically, as graphitic microcrystals develop, increased grain size and enhanced orientation induce collective buckling of graphitic sheets. Meanwhile, reduced amorphous regions and highly oriented pores weaken lateral support, promoting extensive sheet reorientation and leading to shear or kinking failure at lower stress levels. Consequently, the compressive strength of MPCFs decreases from 1273 MPa to 454 MPa, with fracture morphology transitioning from uniform microcracks to axial cracks along (002) planes. Correspondingly, the compressive strength of their polymer composites declines by 57.9 %, with the failure mode shifting from matrix-dominated shear delamination to penetration damage caused by brittle fracture of fibers. This study provides integrated micro-macro insights into the compressive failure mechanisms of MPCFs, guiding the design of compression-resistant MPCFs and their composites.

Carbon-bonded carbon fiber (CBCF) composites are widely used in thermal protection systems due to their low density and high thermal stability. Nevertheless, conventional CBCFs are primarily designed to suppress throughthickness heat conduction, while the potential of in-plane heat spreading as an effective thermal management strategy remains largely underexplored. This work constructs an anisotropic CBCF architecture via a shearinduced pressure filtration strategy to preferentially align highly thermal conductive mesophase pitch-based carbon fibers (MPCFs) in the in-plane direction. By shear-induced pressure alignment and regulating the fiber volume fraction, the evolution from a random fibrous network to a highly oriented topology is quantitatively correlated with anisotropic heat-transfer behavior. At an optimal fiber content of 10.06 vol%, the CBCF achieves an in-plane thermal conductivity of 23.81 W m- 1 K- 1 and a through-thickness thermal conductivity of 0.83 W m- 1 K-1, yielding an anisotropy ratio of 28.69 while maintaining a low density of 0.26 g cm- 3. Under hightemperature ablation, the optimized CBCF exhibits an 80% reduction in linear ablation rate and a 14.6% decrease in backside temperature relatively. Furthermore, the oriented fibrous network delivers excellent compressive resilience at 25% strain. These results demonstrate that decoupling in-plane heat spreading from through-thickness thermal blocking through anisotropic fiber architecture offers an effective structural strategy for lightweight thermal protection materials operating in extreme aerothermal environments.

Secondary headaches and orofacial pains, caused by underlying diseases or dysfunctions, are more prevalent than primary headaches and orofacial pains. To date, no clinical guidelines have been established for the diagnosis and treatment of the 11 categories of chronic secondary headaches and orofacial pains on the “International Classification of Diseases, 11th Revision (ICD-11)”. To improve the recognition and management of these painful diseases and to standardize diagnostic and therapeutic practices among clinicians in China, the Expert Panel for the Development of Chinese Clinical Guidelines for Chronic Secondary Headache and Orofacial Pain (hereinafter referred to as Expert Panel) compiled the present guideline. This guideline focuses on 8 common chronic secondary headache and orofacial pain disorders that are frequently underdiagnosed or misdiagnosed, but have well-defined diagnostic and therapeutic protocols within the painology department currently. These disorders include: cervicogenic headache, trigeminal neuralgia, glossopharyngeal neuralgia, sphenopalatine neuralgia, temporomandibular joint disorders, head and facial herpes zoster-related neuralgia, post-stroke persistent headache, and cancer-related head and facial pain. The Expert Panel systematically retrieved and evaluated the available evidence on the definition, epidemiology, pathogenesis clinical manifestations, diagnostic criteria, differential diagnosis, treatment, and recent advances for each of the 8 disorders. The guideline provides recommendations for both pharmacological therapy and minimally invasive treatments based on the evidence, to serve as a practical reference for painologists, neurologists, general practitioners, and other healthcare professionals involved in the management of these chronic secondary headache and orofacial pain.

Porous thermal insulators are vital for aerospace and energy systems, yet achieving a balance between lightweight architecture, mechanical robustness, and stability under oxidizing high-temperature conditions remains a significant challenge. Here, a biomimetic strategy was developed to construct hollow silicon carbide fibers (SiC-HF) using carbon fiber felt as a template. Continuous SiC coatings were formed in situ and the carbon core was selectively removed, yielding an ultralight porous network with a density of 0.033 mg & sdot;cm-3 and a porosity of 97.6 %. The hierarchical hollow-fiber architecture imparted exceptional elasticity to the SiC-HF, enabling recovery after compressions of up to 40 % strain and preserving structural integrity across both cryogenic and high-temperature conditions. In addition, the multiscale pore system suppressed gas-phase and solid-phase conduction while attenuating radiative transfer, resulting in a low thermal conductivity of 0.0692 W & sdot;m-1 & sdot;K-1 at room temperature and stable insulation at elevated temperatures. Moreover, the SiC-HF exhibits strong oxidation resistance, showing only 24.65 % mass change at 1300 degrees C for 2 h. This work offers a robust pathway to oxidation-resistant porous ceramics and delivers valuable design insights for developing next-generation thermal protection materials suited to extreme environments.

Battered Sensory Never Syndrome (BSNS) is a condition characterized by persistent, long-term mechanical compression of the sensory roots, dorsal root ganglia (DRG), and sensory fibers of the spinal nerve roots. This leads to symptoms such as hyperalgesia or allodynia, paresthesia, and radicular pain-like syndromes where pain worsens with weight-bearing or physical activity. High-voltage DRG pulsed radiofrequency (PRF) is effective for BSNS, but optimal treatment parameters for the best clinical efficacy remain undefined. This study aims to compare the clinical outcomes of various PRF temperatures and durations in patients with BSNS. Patients with BSNS were randomized to one of four high-voltage (80 V) PRF parameter groups: 42℃/3min, 42℃/12min, 55℃/3min, and 55℃/12min. The primary outcome measures included the Numerical Rating Scale (NRS) and the Oswestry Disability Index (ODI). The secondary outcome measures included the Hamilton Anxiety Scale (HAMA), the Hamilton Depression Scale (HAMD), the Pittsburgh Sleep Quality Index (PSQI) scores, the effective rate of pain relief, the proportion of patients with a ≥ 50% reduction in ODI score, and medication usage. These were evaluated before PRF and within 12 months after surgery. All patients included in our study had a mean age over 60, with the majority being female. Four patient groups showed significant reductions in NRS, ODI, HAMA, HAMD scores (P < 0.05) and decreased medication use within 12 months post-PRF, with no statistically significant differences between the groups (P > 0.05). The PSQI scores decreased significantly only in the 42 °C/3min group at 1 month,3 and 6 months (P < 0.05), also without intergroup significance (P > 0.05). The subgroup analysis by time and temperature revealed that NRS scores (P = 0.009), the number of patients with effective pain relief (P = 0.039) and ODI reduction ≥ 50% (P = 0.045) 1 month after PRF in the 55℃ group were significantly better than those in the 42℃ group, while no statistically significant difference was found between 3-min and 12-min durations (P > 0.05). High-voltage DRG PRF effectively treats BSNS patients within a treatment duration range of 3 to 12 min. Treatment at 55 °C offers superior pain relief and physical function improvement without neuropathic complications.

Direct pyrolysis of cost-effective asphalt typically generates highly ordered structures that are not conducive to sodium-ion storage. Conventional pre-oxidation strategies can inhibit structural ordering, yet they introduce tedious steps and yield hard carbons with inadequate closed porosity, thereby restricting their reversible capacity. In this study, a renewable, oxygen-rich bio-asphalt (HOBA) is employed to eliminate the need for pre-oxidation. The numerous oxygen-containing functional groups (e.g., CO, CO) in HOBA drive spontaneous self-crosslinking, effectively suppressing carbon ordering during subsequent carbonization. Furthermore, a one-step co-pyrolysis of HOBA with ZnCl2 is employed to achieve efficient dual-ion (Zn2+/Cl-) refinement of the HOBA microstructure. On one hand, ZnCl2 promotes HOBA dehydrogenation/deoxygenation, while concomitantly enhancing HOBA crosslinking through Cl- capturing H+ to form HCl. On the other hand, the oxygen-rich nature of HOBA promotes Zn2+ to form ZnO, which etches the carbon skeleton to generate open pores. During subsequent carbonization (>900 degrees C), the synergistic development of graphitic domains and pore contraction transforms these open pores into closed pores. Impressively, the modified HOBAHC-30 % exhibits a significant improvement in reversible capacity (351.57 vs. 263.15 mAh g(-1)) while maintaining a high ICE (87.16 % vs. 85.52 % for HOBAHC-0 %). Moreover, a series of in situ and ex situ characterizations confirm the "absorption-insertion-pore filling" sodium storage mechanism of HOBAHC-30 %. Notably, the Na3V2(PO4)(3)//HOBAHC-30 % full cell exhibits outstanding cyclability (81.32 % capacity retention after 120 cycles at 200 mA g(-1)) and high energy density (217.20 Wh kg(-1) at 34.65 W kg(-1)), which remains robust even at 502.92 W kg(-1) (116.37 Wh kg(-1)). This study proposes a dual-ion interfering strategy to achieve rational precursor-reagent pairing, offering new insights into the synthesis of high-performance asphalt-based hard carbon anodes.

Background: Low back pain (LBP) is the leading cause of disability worldwide, severely impairing patients' quality of life, consuming substantial healthcare resources, and increasing medical costs while reducing productivity. Low back pain has become the leading cause of disability worldwide and a major global public health issue. Objective: To enhance the ability of diagnosis and treatment for LBP to meet the needs of clinical diagnosis and treatment. Main ideas: Based on high quality evidence based medical research on the diagnosis and treatment of LBP published domestically and internationally between January 2010 and December 2023, the expert group of the Pain Disease Diagnosis and Treatment Special Capacity Enhancement Project of the National Health Commission of China's Capacity Building and Continuing Education Centerhas formed recommendations for common treatment methods through rigorous argumentation and expert voting, to provide references for standardized diagnosis and treatment of LBP. This guideline adopts GRADE methodology to evaluate the level of evidence and strength of recommendation for the treatments of common chronic specific low back pain (cSLBP) and chronic non-specific low back pain (cNSLBP). Conclusion: LBP is characterized by high prevalence, significant disability rates, and frequent recurrence, imposing substantial burdens on individuals, families, and society. For patients, improving understanding of cLBP, practicing effective self-management, and actively cooperating with treatment are crucial for disease prognosis. Healthcare providers must enhance patient education and clinical competencies while strictly adhering to diagnostic and therapeutic guidelines for comprehensive cLBP management. Policymakers and academic organizations should focus on developing evidence-based clinical guidelines, strengthening healthcare system oversight, and promoting widespread implementation of standardized cLBP care protocols.

[This corrects the article DOI: 10.1016/j.heliyon.2023.e13830.].

Carbon/carbon (C/C) composites are critical structural materials for advanced reactors, including molten salt reactors. However, the irradiation mechanisms, particularly the differences in irradiation-induced damage between fibers and matrices, remain inadequately understood. In this study, the irradiation behavior of mesophasepitch-based carbon-fiber-reinforced carbon matrix composites was investigated under 1.8-MeV Ar-ion irradiation at a dose of 3 x 1016 ions/cm2 at room temperature. Following irradiation, both the carbon fiber and matrix underwent amorphization and exhibited significant changes in surface morphology, the matrix exhibiting pronounced volumetric shrinkage compared to the fiber. Additionally, irradiation resulted in the degradation of the ordered graphite layers and closure of the initial cracks within the fiber and matrix. Notably, the matrix contained a greater number of initial cracks and crack closure was more pronounced during irradiation compared to the fiber. The differential shrinkage observed between the fiber and matrix is primarily attributed to the differences in the irradiation-induced closure behavior of the initial cracks in each component. These findings provide insights into enhancing the irradiation performance of C/C composites by adjusting the microstructural composition of the fiber and matrix.

High-thermal-conductivity mesophase pitch-based carbon fiber reinforced carbon (HTC-CMP/C) composites encounter severe challenges with intrinsic oxidation and thermal ablation at ultra-high temperature, thus enhancing their thermal protection performance is crucial for stable operation. In this study, a dual-skeleton reinforced CMP/C-HfC composites were fabricated via reactive melt infiltration, and the ZrC/SiC@CMP/C-HfC composites were simultaneously prepared based on a coating-matrix integration strategy. The results show that the prepared CMP/C-HfC composites exhibit flexural strengths of sigma 0.5 = 169.03 MPa and sigma 1.0 = 247.15 MPa, representing 52.8 % and 63.04 % improvements over CMP/C composites, respectively. The mass ablation rate and linear ablation rate are 0.367 mg s-1 and -1.167 mu m s-1, showing 86.1 % and 107.5 % reductions compared to CMP/C composites. Moreover, the ZrC/SiC coating further effectively mitigates ablation-induced powdering and spalling in CMP/C-HfC composites while enhancing both thermal conductivity and flexural mechanical properties. This balanced enhancement of mechanical-thermal-ablative protection performances relies on the synergistic effects of the dual-skeleton structure combining continuous HfC framework and HTC-CMP/C skeleton, and effective thermal protection of the coating system. This work provides novel insights and valuable references for thermal protection design in CMP/C composites.

Mesophase pitch has become a superior precursor of high thermal conductivity pitch-based carbon fibers due to its high aromaticity, high carbon content and ability to be graphitized. However, mesophase pitch is prone to pyrolysis during melt spinning, which leads to structural defects such as pores in the carbon fiber, thus inhibiting the continuous improvement of carbon fiber properties. In this paper, a kinetic model was built by revealing the pyrolysis of petroleum-based mesophase pitch, establishing an association between pyrolysis weight loss and spinning process and spinning state. The results indicate that the pyrolysis products of petroleum-based mesophase pitch mainly consist of high-temperature volatile components and small molecules produced by continuous decomposition of macromolecules. When the pyrolysis weight loss of mesophase pitch is less than 2.2 wt%, it has good spinnability, and the surface and cross section of spun fiber are smooth and defect-free. Ultimately, the carbon fibers show a tensile strength of 3.09 GPa, a tensile modulus of 855 GPa, and a thermal conductivity of 727 W center dot m(-1)center dot K-1. It is demonstrated that the pyrolysis kinetics model of petroleum-based mesophase pitch is reliable for guiding the optimization of melt spinning processes and enhancing the physical properties of carbon fibers.

Large-diameter mesophase pitch-based graphite fibers exhibit superior thermal conductivity but suffer from weaker elongation at break, posing adverse challenges for their continuous production and weaving processability, and consequently hindering large-scale commercialization. To address this issue, this study employs a complete set of engineered production lines to spin 1K-bundle pitch fibers with a diameter of 30 mu m, followed by continuous oxidation and 1600 degrees C heat treatment to prepare continuous large-diameter mesophase pitch-based carbon fibers. The fibers exhibit a tensile strength/modulus of 1.56 GPa/267 GPa, and an elongation at break of 0.58 %, demonstrating good yarn spreading and weaving processability. Ultimately, the process of 3000 degrees C graphitization indirectly actives their latent thermal conductivity, yielding a mesophase pitch-based graphite fibers with a thermal conductivity of up to 1294 W & sdot;m- 1 & sdot;K- 1, which surpasses that of commercial carbon fiber K1100 by 17.7 %. This is because a smaller draw-down ratio leads to smaller shrinkage ratio and the flow rate gradient, causing a smaller flow direction change behavior of the MP liquid-crystal molecules, thereby maintaining high molecular orientation. The "two-step" process used in this study effectively resolves the contradiction between high thermal conductivity and poor weavability of large-diameter fibers, providing a feasible technical route for the development and commercialization of ultra-high thermal conductivity mesophase pitchbased carbon fibers.