Search Results (365)

This research explores microcrystalline diamond particles in poly(L-lactic acid) matrices to create structured porous composites for advanced biodegradable materials. While nanodiamond–polymer composites are well-documented, microcrystalline diamond particles remain unexplored for controlling hierarchical porosity in systems required by tissue engineering, thermal management, and filtration industries. We investigate diamond–polymer composites with concentrations from 5 to 75 wt% using freeze-drying methodology, employing two particle sizes: 0.125 μm and 1.00 μm diameter particles. Systematic porosity control ranges from 11.4% to 32.8%, with smaller particles demonstrating reduction from 27.3% at 5 wt% to 11.4% at 75 wt% loading. Characterization through infrared spectroscopy, X-ray computed microtomography, and Raman analysis confirms purely physical diamond–polymer interactions without chemical bonding, validated by characteristic diamond lattice vibrations at 1332 cm⁻¹. Thermal analysis reveals modified crystallization behavior with decreased melting temperatures from 180 to 181 °C to 172 °C. The investigation demonstrates a controllable transition from large-volume interconnected pores to numerous small-volume closed pores with increasing diamond content. These composites provide a quantitative framework for designing hierarchical structures applicable to tissue engineering scaffolds, thermal management systems, and specialized filtration technologies requiring biodegradable materials with engineered porosity and enhanced thermal conductivity. Full article

Chemical mechanical polishing (CMP) is a critical technique for fabricating ultra-smooth and high-quality surfaces of single crystal diamond (SCD), where processing parameters profoundly influence polishing performance. To achieve superior diamond surface finishes, this study first investigates the effects of key process parameters, including oxidant concentration, catalyst type, and abrasive particle size, on surface quality through single-factor experiments. Subsequently, an Archimedes optimization algorithm (AOA)-based prediction model for diamond CMP surface roughness (Sa) is developed and validated experimentally. Results reveal that high-concentration oxidants, fine-particle abrasives, and dual-catalyst polishing systems synergistically enhance surface quality. The AOA-based prediction model demonstrates a root-mean-square error (RMSE) of 0.006 and a correlation coefficient (R) of 0.98 between the predicted and experimental Sa values. Under the conditions of a dual-catalyst type, 35% oxidant concentration, and 500 nm abrasive particle size, the model predicts a surface roughness of 0.128 nm, with an experimental value of 0.125 nm and a relative error of less than 3%. These findings highlight the capability of the model to accurately forecast surface roughness across diverse process parameters, offering a novel predictive framework for precision CMP of SCD. Full article

Kimberlite has attracted considerable interest among geologists as the primary source of natural gem-quality diamonds. The term “transitional kimberlite” was previously introduced to categorize rocks that exhibit bulk geochemical and Sr–Nd isotopic characteristics intermediate between those of archetypal kimberlite (formerly Group-I) and orangeite (formerly Group-II). Nevertheless, the petrogenesis of transitional diamond-bearing kimberlites remains poorly understood due to limited research. The diamondiferous transitional Wafangdian kimberlite in the North China Craton (NCC) thus provides a valuable opportunity for a detailed case study. We investigated fresh hypabyssal transitional Wafangdian kimberlites using bulk-rock major and trace element geochemistry to constrain near-primary parental magma compositions and decipher their petrogenesis. Geochemical compositions identify samples affected by crustal contamination based on elevated SiO₂, Pb, heavy rare earth element (HREE) concentrations, and Sr isotopic ratios. Compositional variations among macrocrystic samples (MgO: 29.7–31.5 wt.%; SiO₂: 30.6–34.7 wt.%; CaO: 3.9–7.5 wt.%; Mg^# [atomic Mg/(Mg + Fe²⁺) × 100]: 85–88) result from substantial entrainment and partial assimilation of peridotite xenoliths (up to 35%). In contrast, variations within aphanitic samples (MgO: 24.0–29.7 wt.%; SiO₂: 27.7–30.9 wt.%; CaO: 6.0–11.8 wt.%; Mg^#: 81–85) are attributed to fractional crystallization of olivine and phlogopite (~1–32%). Based on these constraints, the near-primary parental magma composition for the Wafangdian kimberlite is estimated as ~29.7 wt.% SiO₂, ~29.7 wt.% MgO, and Mg^# 85. Trace element concentrations in the transitional Wafangdian kimberlites resemble those of archetypal kimberlites globally (e.g., Nb/U > 26, La/Nb < 1.4, Ba/Nb < 16, Th/Nb < 0.25), indicating a shared convective mantle source. However, the Wafangdian kimberlites exhibit distinct characteristics: ε_Nd(t) values ranging from −3.44 to −1.77, higher Al₂O₃ and K₂O contents, and lower Ce/Pb ratios (10–20) compared to archetypal kimberlites. These features suggest the mantle source region was profoundly influenced by deeply subducted oceanic material. Full article

The scalable synthesis of high-quality single-crystal diamond films remains pivotal for next-generation extreme-performance devices. Iridium substrates offer exceptional promise for heteroepitaxy, yet early-stage growth mechanisms limiting crystal quality are poorly understood. An integrated multiscale investigation combining first-principles DFT calculations, molecular dynamics simulations, and experimental validation is presented to resolve the oriented attachment process governing diamond growth on Ir(100). Robust interfacial bonding at the interface and optimal carbon coverage are revealed to provide thermodynamic driving forces for primary nucleation. A critical angular tolerance enabling defect-free coalescence through crystallographic realignment is identified by molecular dynamics. Concurrent nucleation growth pathways are experimentally confirmed through SEM, AFM, and Raman spectroscopy, where nascent crystallites undergo spontaneous orientational registry to form continuous epitaxial domains. Grain boundary annihilation is observed upon lattice rotation aligning adjacent grains below the critical angle. Crucially, intrinsic atomic steps are generated on the resultant coalesced layer, eliminating conventional etching requirements for homoepitaxial thickening. This work advances fundamental understanding of single-crystal diamond growth mechanisms, facilitating enhanced quality control for semiconductor device manufacturing and quantum applications. Full article

Aluminum nitride (AlN) ceramic materials have relatively low thermal conductivity and poor heat dissipation performance, and are increasingly unsuitable for high-power LED packaging. In this study, diamond films were deposited on AlN ceramic substrates by microwave plasma chemical vapor deposition (MPCVD). The effects of different process parameters on the crystal quality, surface morphology and crystal orientation of diamond films were studied, and the high thermal conductivity of diamond was used to enhance the heat dissipation ability of AlN ceramic substrates. Finally, the junction temperature and thermal resistance of LED devices packaged on AlN ceramic–diamond composite substrate, AlN ceramic substrate and aluminum substrate were tested. The experimental results show that compared with the traditional aluminum and AlN ceramic substrates, AlN ceramic–diamond composite substrates show excellent heat dissipation performance, especially under high-power conditions. Full article

This study systematically investigates the effects of aging treatment (AT) on the microstructure and properties of Cr/DLC coatings deposited via cathodic arc ion plating onto the surface of ECAP-7075 aluminum alloy. Utilizing a comprehensive approach combining performance tests (nanoindentation, nanoscratch testing, dynamic polarization analysis) with characterization tests (scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy), the synergistic effects of equal channel angular pressing (ECAP) and aging treatment(AT) were elucidated. The results demonstrate that the combined ECAP and AT significantly enhance the coating’s performance. Specifically, AT promotes the precipitation of η’ phase within the 7075 aluminum alloy substrate, increases the size of Cr₇C₃ crystallites in the Cr-based interlayer, improves the crystallinity of the Cr₇C₃ phase on the (060) or (242) crystal planes, and elevates the sp³-C/sp²-C ratio in the diamond-like carbon(DLC) top layer, leading to partial healing of defects and a denser overall coating structure. These microstructural transformations, induced by AT, result in substantial improvements in the mechanical properties (hardness reaching 5.2 GPa, bond strength achieving 15.1 N) and corrosion resistance (corrosion potential increasing to -0.698 V) of the Cr/DLC-coated ECAP-7075 aluminum alloy. This enhanced combination of properties makes these coatings particularly well-suited for high-performance aerospace components requiring both wear resistance and corrosion protection in demanding environments. Full article

Syngenetic fluid inclusions in natural diamonds are indicators of the composition of fluids responsible for growth and crystallization conditions. The chloride concentration in saline fluid inclusions of natural diamonds reaches 50 wt%. We study the dissolution of diamonds in the H₂O-KCl-NaCl system at temperatures of 1200 °C and 1400 °C and a pressure of 5.5 GPa using a BARS high-pressure multi-anvil apparatus. Two scenarios of diamond dissolution were experimentally investigated: (i) metasomatism by saline brines at high oxygen fugacity of the magnetite–hematite buffer; (ii) interaction with reduced carbon-unsaturated water–chloride fluid at low fO₂ imposed by the iron–wüstite buffer. It is found that the presence of alkaline chlorides in the aqueous fluid significantly accelerates diamond dissolution at high oxygen fugacity but inhibits the process under reduced conditions. The morphology of diamond dissolution features is controlled by the presence of water in the fluid over the entire range of the studied P-T-fO₂ conditions. Experimental results indicate that the interaction with oxidizing highly saline fluids during metasomatic events could negatively affect diamond preservation in mantle rocks and eventually lead to the formation of uneconomic kimberlites. Under reducing conditions, water–chloride fluids favor diamond preservation. Full article

Beyond its renowned gemological value, diamond serves as a vital economic mineral and a unique messenger from Earth’s deep interior, preserving invaluable geological information. Since the Mengyin region is the source of China’s greatest diamond deposits, research on the diamonds there not only adds to our understanding of their origins but also offers an essential glimpse into the development of the North China Craton’s mantle lithosphere. In this article, 50 diamond samples from Mengyin were investigated using gemological microscopy, Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, DiamondView™, and X-ray micro-computed tomography (CT) scanning technologies. The types of Mengyin diamonds are mainly Type IaAB, Type IaB, and Type IIa, and the impurity elements are N and H. Inclusions in diamonds serve as direct indicators of mantle-derived components, providing crucial constraints on the pressure–temperature (P–T) conditions during their crystallization. Mengyin diamonds have both eclogite-type and peridotite-type inclusions. It formed at depths ranging from 147 to 176 km, which corresponds to source pressures of approximately 4.45–5.35 GPa, as determined by the Raman shifts of olivine inclusions. The discovery of coesite provides key mineralogical evidence for subduction of an ancient oceanic plate in the source region. The surface morphology of diamonds varies when they are reabsorbed by melts from the mantle, reflecting distinctive features that record subsequent geological events. Distinctive surface features observed on Mengyin diamonds include fusion pits, tile-like etch patterns, and growth steps. Specifically, regular flat-bottomed negative trigons are mainly formed during diamond resorption in kimberlite melts with a low CO₂ (X_CO2 < ~0.5) and high H₂O content. The samples exhibit varying fluorescence under DiamondView™, displaying blue, green, and a combination of blue and green colors. This diversity indicates that the diamonds have undergone a complex process of non-uniform growth. The nitrogen content of the melt composition also varies significantly throughout the different growth stages. The N3 center is responsible for the blue fluorescence, suggesting that it originated in a long-term, hot, high-nitrogen craton, and the varied ring band structure reveals localized, episodic environmental variations. Radiation and medium-temperature annealing produce H3 centers, which depict stagnation throughout the ascent of kimberlite magma and are responsible for the green fluorescence. Full article

Single-crystal 4H silicon carbide (4H-SiC) is a key substrate material for third-generation semiconductor devices, where surface and subsurface integrity critically affect performance and reliability. This study systematically examined the evolution of surface morphology and subsurface damage (SSD) during nanoscratching of 4H-SiC under varying normal loads (0–100 mN) using a nanoindenter equipped with a diamond Berkovich tip. Scratch characteristics were assessed using scanning electron microscopy (SEM), while cross-sectional SSD was characterised via focused ion beam (FIB) slicing and transmission electron microscopy (TEM). The results revealed three distinct material removal regimes: ductile removal below 14.5 mN, a brittle-to-ductile transition between 14.5–59.3 mN, and brittle removal above 59.3 mN. Notably, substantial subsurface damage—including median cracks exceeding 4 μm and dislocation clusters—was observed even within the transition zone where the surface appeared smooth. A thin amorphous layer at the indenter-substrate interface suppressed immediate surface defects but promoted subsurface damage nucleation. Crack propagation followed slip lines or their intersections, demonstrating sensitivity to local stress states. These findings offer important insights into nanoscale damage mechanisms, which are essential for optimizing precision machining processes to minimise SSD in SiC substrates. Full article

We have tested the performance of spectroscopic single-crystal Chemical Vapor-Deposited (sCVD) diamond detectors with radioactive sources and with a pulsed deuterium-tritium neutron generator. The tests demonstrate that the detectors could provide good timing and spectroscopic information at high neutron fluxes. The spectroscopic information can be obtained at a 14 MeV neutron rate as high as 10¹⁰ n/cm²/s, despite some limitations associated with pulse character of the used neutron generator. Monte-Carlo simulations were performed in order to achieve better understanding of neutron interaction with the detector material. Possible applications for the use of the detectors at Soreq Applied Research Accelerator Facility (SARAF) are considered. The detectors could be used as reliable neutron rate monitors in the vicinity of a strong accelerator-based source of energetic neutrons. The detectors could also be utilized as time-of-flight tagging counters in nuclear physics experiments under condition of high neutron fluxes during short beam pulses. In particular, measurement of the ¹²C(n,n′)3α cross-section is discussed. Full article

The single-crystal diamond (SCD), owing to its extreme physical and chemical properties, serves as an ideal substrate for quantum sensing and high-frequency devices. However, crystal anisotropy imposes significant challenges on fabricating high-quality micro-nano structures, directly impacting device performance. This work investigates the effects of femtosecond laser processing on the SCD under two distinct crystallographic orientations via single-pulse ablation. The results reveal that ablation craters along the <100> orientation exhibit an elliptical shape with the major axis parallel to the laser polarization, whereas those along the <110> orientation form near-circular craters with the major axis at a 45° angle to the polarization. The single-pulse ablation threshold of the SCD along <110> is 9.56 J/cm², representing a 7.8% decrease compared to 10.32 J/cm² for <100>. The graphitization threshold shows a more pronounced reduction, dropping from 4.79 J/cm² to 3.31 J/cm² (31% decrease), accompanied by enhanced sp² carbon order evidenced by the significantly intensified G-band in the Raman spectra. In addition, a phase transition layer of amorphous carbon at the nanoscale in the surface layer (thickness of ~40 nm) and a narrow lattice spacing of 0.36 nm are observed under TEM, corresponding to the interlayer (002) plane of graphite. These observations are attributed to the orientation-dependent energy deposition efficiency. Based on these findings, an optimized crystallographic orientation selection strategy for femtosecond laser processing is proposed to improve the quality of functional micro-nano structures in the SCD. Full article

We provide an approach to detect a nitrogen-vacancy (NV) center, which might be a defect in a diamond nanomembrane, using a dual-coupling optomechanical system. The NV center modifies the energy-level structure of a dual-coupling optomechanical system through dressed states arising from its interaction with the mechanical membrane. Thus, we study the photon blockade in the cavity of a dual-coupling optomechanical system in which an NV center is embedded in a single-crystal diamond nanomembrane. The NV center significantly influences the statistical properties of the cavity field. We systematically investigate how three key NV center parameters affect photon blockade: (i) its coupling strength to the mechanical membrane, (ii) transition frequency, and (iii) decay rate. We find that the NV center can shift, give rise to a new dip, and even suppress the original dip in a bare quadratic optomechanical system. In addition, we can amplify the effect of the NV center on photon statistics by adding a gravitational potential when the NV center has little effect on photon blockade. Therefore, our study provides a method to detect diamond nanomembrane defects in a dual-coupling optomechanical system. Full article

This study systematically investigates the impact of hydrolytic degradation on the crystallization kinetics and morphology of poly(butylene succinate-co-adipate) (PBSA). Gel Permeation Chromatography (GPC) confirmed extensive chain scission, significantly reducing the polymer’s weight-average molecular weight (M_w from ~103,000 to ~16,000 g/mol) and broadening its polydispersity index (PDI from ~2 to 7 after 64 days). Differential scanning calorimetry (DSC) analysis revealed that hydrolytic degradation dramatically accelerated crystallization rates, reducing crystallization time roughly 10-fold (e.g., from ~3000 s to ~300 s), and crystallinity increased from 34% to 63%. Multiple melting peaks suggested the presence of lamellae with varying thicknesses, consistent with the Gibbs–Thomson equation. Isothermal crystallization kinetics were evaluated using the Avrami equation (with n ≈ 3), reciprocal half-time of crystallization, and a novel inflection point slope method, all confirming accelerated crystallization; for instance, the slope increased from 0.00517 to 0.05203. Polarized optical microscopy (POM) revealed evolving spherulite morphologies, including hexagonal and flower-like dendritic spherulites with diamond-shape ends, while wide-angle X-ray diffraction (WAXD) showed a crystallization range shift to higher temperatures (e.g., from 72–61 °C to 82–71 °C) and a 14% increase in crystallite diameter, aligning with increased melting point and lamellar thickness and overall increased crystallinity. Full article

Diamond, a crucial carbon phase in the deep Earth, forms under ultrahigh-pressure (UHP, P > 4 GPa) conditions and serves as an important indicator mineral for the UHP environment. Based on their host rocks, diamonds are classified into mantle-derived diamonds, UHP metamorphic diamonds, impact diamonds, etc. While carbon constitutes the primary component of diamonds, nitrogen represents one of the most significant impurity elements. The study of the occurrence mode of nitrogen and the C-N isotope composition is essential for exploring the formation mechanism of diamond. Nitrogen primarily exists in diamonds as either isolated atoms (N) or aggregated forms (N2 or N4), with the dominant mode being controlled by temperature and residence time in the mantle. As temperature and residence time increase, isolated nitrogen progressively transforms into aggregated forms. As a result, mantle-derived diamonds typically contain nitrogen predominantly as N2 or N4, whereas metamorphic diamonds and impact diamonds mainly retain isolated N. Global C-N isotopic composition of over 4400 diamonds reveals a wide compositional range, with δ¹³C ranging from −38.5‰ to +5.0‰, and δ¹⁵N from −39.4‰ to +15.0‰. These values significantly exceed the typical mantle δ¹³C and δ¹⁵N values of −5‰ ± 3‰, indicating that the diamond formation may be influenced by subducted crustal materials. During crystallization, diamonds can encapsulate surrounding materials as inclusions, which are divided into three types based on their formation sequence relative to the host diamond: preformed, syngenetic, and epigenetic. Syngenetic inclusions are particularly valuable for constraining crystallization conditions and the genesis of diamonds. Furthermore, geochronology studies of radioactive isotope-bearing syngenetic inclusions are helpful to clarify the age of diamond formation. Usually, mantle-derived diamonds exhibit Archean age, whereas metamorphic diamonds are associated with subduction, showing younger ages that could be associated with metamorphic events. Therefore, the formation conditions and genesis of diamonds can be clearly constrained through integrating investigations of inclusions, nitrogen occurrence modes, and C-N isotopic compositions. The characteristics of occurrence modes, inclusions, and C-N isotope compositions of different types of diamonds are systematically reviewed in this paper, providing critical insights into their genesis and contributing to a deeper understanding of diamond formation processes in Earth’s interior. Full article

The precise control of thermal–kinetic parameters governs epitaxial perfection in functional oxide heterostructures. Herein, using Iridium/MgO(100) as a model system, the traditional “low-speed/high-temperature” paradigm is revolutionized through the combination of ab initio calculations, multiscale simulations, and subsequent deposition experiments. First-principles modeling reveals the mechanisms of Volmer–Weber (VW, island growth mode) nucleation at low coverage and Stranski–Krastanov (SK, layer-plus-island growth) transitions driven by interface metallization, stress release, and energy reduction, which facilitates coherent monolayer formation by lowering the energy barrier by ~34%. Molecular dynamics simulations demonstrate that the strategic co-optimization of substrate temperature (T_sub) and deposition rate (V_dep) induces an abrupt cliff-like drop in mosaic spread. Experimental validations confirm that this T-V synergy achieves unprecedented interfacial coherence, whereby AFM roughness reaches 0.34 nm (RMS) and the XRC-FWHM of 0.13° approaches single-crystal benchmarks. Notably, our novel “accelerated heteroepitaxy” protocol reduces growth time without compromising quality, addressing the efficiency–quality paradox in industrial-scale diamond substrate fabrication. These findings establish universal thermal–kinetic design principles applicable to refractory metal/oxide heterostructures for next-generation quantum sensors and high-power electronic devices. Full article