Diamond nanothreads are one-dimensional crystalline nanomaterials formed by the polymerization of organic molecules under high pressure. Their sp³-hybridized carbon framework endows them with exceptional mechanical, thermal, and electrical properties. This paper systematically reviews the progress in structural prediction, synthesis strategies, and property studies of this material. Theoretical investigations have demonstrated that diamond nanothreads possess wide band gaps, high carrier mobility, and excellent mechanical performance, and that their electronic structure can be effectively tuned through heteroatom doping, defect introduction, and lattice strain. Regarding the synthesis, a variety of ordered crystalline nanothreads have been successfully prepared via high-pressure solid-state reactions using precursors such as benzene, fluorobenzene, pyridazine, s-triazine, and cubane. Through rational precursor molecular design, cocrystal engineering, and regulation of reaction conditions, functionalization and heteroatom doping synthesis have been realized. In recent years, the successful preparation of polymer single crystals with sizes up to hundreds of micrometers using 1-naphthoic acid as the precursor has enabled, for the first time, the direct measurement of anisotropic thermal conductivity. This paper also provides an outlook on future research directions concerning precise structural control, multifunctionalization, and reduced-pressure synthesis.

Two-dimensional (2D) diamond, an atomically thin carbon-based material, not only inherits the exceptional properties of bulk diamond but is also expected to exhibit unique physical characteristics arising from nanoscale effects. Currently, research on 2D diamond remains in its infancy, being primarily driven by theoretical investigations, while experimental efforts have mainly focused on its controllable synthesis and structural characterization. Owing to pronounced interfacial effects, the direct application of conventional high-pressure synthesis methods to nanoscale systems is considerably limited, making it challenging to achieve a stable transition from sp² to sp³ hybridization, thereby posing numerous critical scientific challenges for the study of 2D diamond. This review systematically summarizes recent theoretical and experimental advances in the structural features, synthesis strategies, and physicochemical properties of 2D diamond, and provides perspectives on future research directions and scientific opportunities in the field of 2D diamond.

Fullerenes, represented by C₆₀ and C₇₀, are typical molecular-crystal carbon allotropes. Under high-temperature and high-pressure (HTHP) conditions, they can undergo a continuous sequence of structural evolution, including orientational ordering, initial intermolecular bonding, low-dimensional polymerization, multidimensional cross-linking, cage collapse, and amorphization. Therefore, fullerenes serve as an important bridge between molecular-crystal carbon and high-density covalent carbon networks. This review focuses on the phase transitions and polymerization behavior of fullerenes under combined pressure-temperature control. The structural features and formation mechanisms of the fcc to sc orientational transition, dimerization, typically through [2+2] cycloaddition, one-dimensional chain polymerization, two-dimensional layered polymerization, including tetragonal and rhombohedral phases, and possible three-dimensional structures are systematically summarized. The effects of different loading paths and kinetic factors on phase boundaries and product ordering are also discussed. In addition, the multi-pathway competition and disordering tendency of C₇₀ driven by molecular anisotropy are comparatively reviewed. The regulatory roles of guest species in metallofullerenes and solvated fullerenes on the polymerization pathways and physical properties of fullerenes under HTHP conditions are further discussed. Finally, based on recent progress in fullerene-derived sp³-rich superhard amorphous carbon and related novel carbon structures, potential research directions for the controllable synthesis of high-pressure carbon materials through precursor engineering and multidimensional regulation strategies are proposed.

Glassy carbon is a nearly fully sp²-bonded amorphous carbon allotrope. Its highly disordered atomic structure and isotropic nature make it an ideal model system for studying pressure-induced transitions in amorphous materials and a versatile precursor for the synthesis of novel amorphous carbon materials. This review summarizes recent advances in understanding the structural transformations, property evolution, and transition mechanisms of glassy carbon under high-pressure and high-pressure-high-temperature (HPHT) conditions, as well as its emerging applications in high-pressure science. Experimental and theoretical studies have shown that glassy carbon undergoes a pressure-induced sp² to sp³ bonding transition, forming a tetrahedral amorphous carbon phase with high transparency, electrical resistivity, strength, and bulk modulus. Although this high-pressure phase is not recoverable at ambient conditions, HPHT treatment can produce new amorphous carbon materials, including compressed glassy carbon and nearly fully sp³-bonded amorphous diamond. In addition, the unique nano-pore structure of glassy carbon and its pressure-induced permeability have enabled the development of nanostructured diamond capsules capable of preserving high-pressure phases at ambient conditions. This capability opens new opportunities for high-pressure research and for the practical utilization of high-pressure materials beyond the confines of high-pressure apparatus.

Since the successful synthesis of bulk sp³ amorphous carbon in 2021, this material has attracted considerable attention owing to its ultrahigh hardness, mechanical isotropy, potential for shaping and machining, and distinctive electronic structure. These features make it a promising candidate for applications in ultra-precision machining and optoelectronic detection. Recent studies have mainly focused on the formation mechanism, thermodynamic stability, structural and property regulation, and synthesis process optimization of sp³ amorphous carbon materials derived from fullerenes under high-pressure and high-temperature conditions. These studies have not only deepened the understanding of the formation mechanism of sp³ amorphous carbon, but also promoted the further development of its functional applications. This review systematically summarizes the relevant research progress and discusses future key directions, including the large-size and high-quality synthesis, precision shaping, and functional application expansion of sp³ amorphous carbon.

Diamond has emerged as a quintessential representative of next-generation semiconductor materials, owing to its ultra-wide bandgap, exceptional thermal conductivity, high breakdown field strength, and outstanding carrier mobility. It has thus attracted extensive attention from fields such as power electronics, radio-frequency communications, and quantum information technologies. Intrinsic single-crystal diamond serves as the foundational substrate for diamond semiconductor development, requiring impurity concentrations at the parts per billion (ppb) level and extremely low dislocation densities. While the high-pressure high-temperature (HPHT) method yields material of higher purity and superior crystal quality, its utility is limited by small crystal dimensions. Consequently, HPHT-grown diamond is frequently employed as a substrate for chemical vapour deposition (CVD) homoepitaxy, enabling the preparation of large-area, high-quality single crystals. Regarding doping, the boron (B) atom, with a size difference of merely 6.5% compared to carbon (C), readily incorporates into the diamond lattice, facilitating the production of high-performance p-type diamond. Related devices, such as Schottky barrier diodes, have been successfully demonstrated. In contrast, n-type doping presents a fundamental challenge: potential dopants like phosphorus (P) and sulphur (S) possess atomic radii 35%–57% larger than carbon, making their incorporation and activation within the lattice exceedingly difficult. The ultra-high pressure and high-temperature diffusion method, which modulates this atomic size disparity under extreme pressures (e.g., about 15 GPa), emerges as a promising new pathway towards achieving shallow-level n-type doping. Concerning surface terminations, hydrogen termination induces a high-mobility two-dimensional hole gas (2DHG), whilst oxygen termination enhances interface stability and provides chemical passivation. However, their thermal stability windows (approximately 400 and 600 ℃, respectively) remain inferior to those of substitutionally doped diamond, limiting their application in high-temperature and high-frequency devices. Therefore, breakthroughs in n-type doping, enhanced thermal stability of surface terminations, and the development of large-area, cost-effective fabrication processes are critical to advancing diamond semiconductor technology towards commercialisation in power electronics, quantum technologies, and high-performance sensing. This review aims to analyse and discuss these pivotal issues, exploring both the prospects and the persistent challenges facing diamond semiconductor development.

Carbon exhibits complex structural transformations, melting behavior, and electronic-property evolution under extreme compression. This behavior is relevant to carbon-rich planetary interiors, the dynamic response of high-density carbon ablators in inertial confinement fusion, and the formation of post-diamond phases. This review focuses on the dynamic phase diagram of carbon. We summarize the equilibrium reference states of graphite, diamond, liquid carbon, and BC8 carbon, and discuss typical dynamic loading paths under shock, ramp, and multiple-shock compression together with their corresponding in situ diagnostics. We focus on the graphite-to-diamond/lonsdaleite-like transformation, diamond melting and liquid-carbon structure, and the kinetic accessibility of BC8 carbon. Existing studies show that the phases observed under dynamic compression are governed not only by pressure and temperature, but also by loading time, stress state, initial structure, and diagnostic window. Therefore, a dynamic phase diagram of carbon should extend the conventional pressure-temperature (p-T) description by incorporating loading path, leading to a p-T-path representation. This perspective may provide guidance for experimental design, in situ structural diagnostics, and equation-of-state model constraints for carbon under extreme conditions.

Addressing the urgent demand for high-performance polycrystalline diamond compact (PDC) cutters in deep/ultra-deep oil and gas exploration, this work optimized the PDC synthesis formulation through orthogonal experimental design. Under high pressure conditions (8.5 GPa and 1 750 ℃), we successfully fabricated both conventional homogeneous mixed PDC cutter (H-PDC) and gradient-structured PDC cutter (G-PDC) featuring a “fine-grained work layer/coarse-grained transition layer” structure. Microstructural characterization reveals that the gradient structure facilitates uniform distribution of cobalt binder, suppresses cobalt aggregation, enhances interlayer interfacial bonding, and generates higher residual compressive stress. The cobalt mass fraction in the G-PDC work layer is 9.16%. After acid leaching for cobalt removal, the cobalt mass fraction decreased to 2.49%. Performance evaluations demonstrate that G-PDC achieves a wear resistance lifespan of 920 passes, superior to H-PDC (800 passes). The average impact toughness of G-PDC reaches 740.0 J, representing approximately 107% improvement over H-PDC. Furthermore, the gradient structure alleviates thermal expansion mismatch, increasing the thermal stability temperature by about 30 ℃. This research confirms that combining high pressure synthesis technology with gradient structural design can synergistically enhance the wear resistance, impact toughness, and thermal stability of PDC cutters, providing a viable pathway for developing next-generation superhard composites for extreme conditions.

Formation of nitrogen-vacancy (NV) centers and their apparent charge-state response in high-pressure high-temperature (HPHT) type-Ⅰb diamond were investigated. Effects of the initial substitutional nitrogen content (C-center nitrogen), electron irradiation, vacuum annealing, and HPHT pretreatment on the photoluminescence (PL) behavior of NV centers were compared. Two groups of HPHT diamond single crystals with different C-center nitrogen contents were subjected to electron irradiation, vacuum annealing (600−1000 ℃), and HPHT pretreatment (5 GPa, 1100−1900 ℃). Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and photoluminescence spectroscopy were employed to analyze nitrogen aggregation, lattice state, and NV-related photoluminescence responses. The results show that high-nitrogen samples exhibit more pronounced NV-related emission, whereas irradiation-induced vacancies in the low-nitrogen samples tend to remain as GR1 centers. As the vacuum annealing temperature increases, the overall emission intensities of NV⁰ and NV⁻ increase, while the apparent photoluminescence response of NV⁻ relative to NV⁰ generally decreases. HPHT pretreatment does not directly generate a large number of NV centers but promotes nitrogen aggregation and modifies the apparent NV⁻/NV⁰ charge-state ratio during subsequent irradiation and annealing. These results indicate that HPHT pretreatment can serve as a preceding processing parameter for regulating the initial defect state before irradiation and the subsequent apparent charge-state ratio of NV centers.

Aluminum nitride (AlN) ceramics are important heat-dissipation materials for high-power electronic devices. However, the high sintering temperature required by conventional processing routes limits practical application of AlN ceramics and increases fabrication costs. Therefore, it is necessary to develop preparation method that is capable of achieving densification at relatively low temperature. To address the difficulty of simultaneously obtaining high densification and high thermal conductivity in polycrystalline AlN ceramics under reduced-temperature sintering conditions, this work adopts a stepwise research strategy. First, the densification behavior and thermal conductivity of pure AlN under high-pressure assistance were investigated to identify the optimal sintering conditions. Under additive-free conditions, pure-phase AlN ceramics with clean grain boundaries and high densification were prepared at 5.0 GPa and 1400 ℃, achieving a thermal conductivity of 101.6 W/(m·K). Based on these optimized conditions, the AlN/diamond composite system was further studied, and the effects of diamond volume fraction on the structure and properties of the composites were systematically examined. The results show that the thermal conductivity of the composites first decreases and then increases with increasing diamond volume fraction, reaching 112.4 W/(m·K) at 33.3%. Mechanistic analysis indicates that interfacial thermal resistance dominates at low diamond contents, whereas at high diamond contents the enhancement of heat transport by thermally conductive diamond pathways becomes more significant. By taking full advantage of the processing benefits of high-temperature and high-pressure technology, this work achieves substantial improvement of AlN-based materials at temperatures lower than those required in conventional sintering, thereby providing a new route for the low-temperature fabrication of high-performance thermally conductive ceramics.

Rhombohedral C₆₀ polymer holds significant potential for applications in two-dimensional materials and catalysis, yet the synthesis of high-purity, high-quality rhombohedral C₆₀ remains challenging. In this study, rhombohedral C₆₀ polymer was successfully synthesized under conditions of 6 GPa and 650 ℃. The obtained sample was confirmed to be a high-purity two-dimensional rhombohedral phase through characterization techniques including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and aberration-corrected transmission electron microscopy. The effects of pressure and temperature (6–10 GPa, 650–800 ℃) on the polymerization of C₆₀ were investigated, clarifying the phase boundary between the rhombohedral phase and disordered amorphous carbon clusters. Variable-temperature Raman spectroscopy revealed that the rhombohedral C₆₀ polymer remains stable up to about 350 ℃, beyond which it depolymerizes and reverts to the original face-centered cubic C₆₀ molecules. This work provides a clear processing window for the synthesis of high-quality rhombohedral C₆₀ polymer, laying an experimental foundation for its further application in functional materials.

To investigate the effects of phosphorus doping on diamond crystal growth, diamond single crystals doped with phosphorus were synthesized along the (111) plane using the temperature gradient method. The experiments were conducted under conditions of 5.5 GPa and 1 300 ℃, with Fe₃P added into the FeNiCo-C system. The synthesized diamond samples were characterized by Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy (XPS). With increasing Fe₃P addition, the diamond color gradually lightens, and the crystal morphology changes from octahedral to hexoctahedral. Moreover, the addition of Fe₃P alters the catalyst properties, leading to the increases of nitrogen solubility of the catalyst. Thus, fewer nitrogen atoms enter the diamond lattice, resulting in a decrease of nitrogen impurity content in the diamonds. Phosphorus doping increases internal stress and induces lattice distortion in the diamond crystal, resulting in degrading of the diamond quality. This conclusion is supported by the shift and broadening of the Raman peak. The incorporation of phosphorus atoms inhibits the formation of NV⁻ centers in diamond crystals. XPS results confirm the successful incorporation of phosphorus into the diamond lattice. This study provides useful insights for understanding the synthesis mechanism of phosphorus-doped diamond crystals, and supports potential applications of phosphorus-doped diamond crystals.

The traditional domestic hinge-type cubic presses are typically operated using limit switch for positioning, fully-open rapid hydraulic oil filling, and fixed-rate pressurization/depressurization modes. Such configurations are limited by poor six-cylinders positioning accuracy and hydraulic filling synchronization, and the pressurization and depressurization rates fail to meet the stringent requirements of ultra-high two-stage pressurization for eccentric load control and mechanical stability. In this study, systematic modification and upgrade were implemented on a domestic cubic press with 650 mm cylinders. To suppress or eliminate the floating and deformation of the frame under overpressure conditions, self-locking pin shaft was designed and assembled, and pre-compensation for frame deformation under high pressure was performed. In addition, aim at improving alignment accuracy and hydraulic filling synchronization, a dual-pump multi-mode hydraulic circuit and an equal-volume cylinder oil-filling process were built. Furthermore, a three-stage feeding method combined with an independent displacement action mode was innovatively proposed. A closed-loop control program was developed to operate in parallel with the original press control system, enabling the real-time acquisition, synchronous monitoring, and closed-loop adjustment of data sets including press operational status, oil pressure, and heating temperature. Additionally, a strategy combining proportional-integral-derivative (PID) control with precision pressure-control module components was proposed to achieve ultra-slow pressurization and depressurization. The correlation between synthesis chamber pressure and oil pressure, and the correlation between heating temperature and power were experimentally calibrated. Furthermore, the high-temperature and high-pressure (HTHP) synthesis of centimeter-sized nano-polycrystalline diamond bulk specimen was conducted. The results indicate that the optimized and upgraded domestic 650 mm cubic press is capable of synthesis large-volume samples at 15 GPa and over 2000 ℃, which significantly expands the application area of domestic cubic presses.