In this paper,we report on the influence of annealing treatment on as-grown Ib-type diamond crystal under high pressure and high temperature in a china-type cubic anvil high-pressure apparatus.Experiments are carried ...In this paper,we report on the influence of annealing treatment on as-grown Ib-type diamond crystal under high pressure and high temperature in a china-type cubic anvil high-pressure apparatus.Experiments are carried out at a pressure of 7.0 GPa and temperatures ranging from 1700 C to 1900 C for 1 h.Annealing treatment of the diamond crystal shows that the aggregation rate constant of nitrogen atoms in the as-grown Ib-type diamond crystal strongly depends on diamond morphology and annealing temperature.The aggregation rate constant of nitrogen remarkably increases with the increase of annealing temperature and its value in octahedral diamond is much higher than that in cubic diamond annealed at the same temperature.The colour of octahedral diamond crystal is obviously reduced from yellow to nearly colorless after annealing treatment for 1 h at 1900 C,which is induced by nitrogen aggregation in a diamond lattice.The extent of nitrogen aggregation in an annealed diamond could approach approximately 98% indicated from the infrared absorption spectra.The micro-Raman spectrum reveals that the annealing treatment can improve the crystalline quality of Ib-type diamond characterized by a half width at full maximum at first order Raman peak,and therefore the annealed diamond crystals exhibit nearly the same properties as the natural IaA-type diamond stones of high quality in the Raman measurements.展开更多
Ag-Cu-In-Ti low-temperature filler was used to braze the diamond and copper,and the effects of brazing temperature and soaking time on the microstructure and mechanical properties of the joints were investigated.In ad...Ag-Cu-In-Ti low-temperature filler was used to braze the diamond and copper,and the effects of brazing temperature and soaking time on the microstructure and mechanical properties of the joints were investigated.In addition,the joint formation mechanism was discussed,and the correlation between joint microstructure and mechanical performance was established.Results show that adding appropriate amount of In into the filler can significantly reduce the filler melting point and enhance the wettability of filler on diamond.When the brazing temperature is 750°C and the soaking time is 10 min,a uniformly dense braze seam with excellent metallurgical bonding can be obtained,and its average joint shear strength reaches 322 MPa.The lower brazing temperature can mitigate the risk of diamond graphitization and also reduce the residual stresses during joining.展开更多
Atomic surfaces are strictly required by high-performance devices of diamond.Nevertheless,diamond is the hardest material in nature,leading to the low material removal rate(MRR)and high surface roughness during machin...Atomic surfaces are strictly required by high-performance devices of diamond.Nevertheless,diamond is the hardest material in nature,leading to the low material removal rate(MRR)and high surface roughness during machining.Noxious slurries are widely used in conventional chemical mechanical polishing(CMP),resulting in the possible pollution to the environment.Moreover,the traditional slurries normally contain more than four ingredients,causing difficulties to control the process and quality of CMP.To solve these challenges,a novel green CMP for single crystal diamond was developed,consisting of only hydrogen peroxide,diamond abrasive and Prussian blue(PB)/titania catalyst.After CMP,atomic surface is achieved with surface roughness Sa of 0.079 nm,and the MRR is 1168 nm·h^(-1).Thickness of damaged layer is merely 0.66 nm confirmed by transmission electron microscopy(TEM).X-ray photoelectron spectroscopy,electron paramagnetic resonance and TEM reveal that·OH radicals form under ultraviolet irradiation on PB/titania catalyst.The·OH radicals oxidize diamond,transforming it from monocrystalline to amorphous atomic structure,generating a soft amorphous layer.This contributes the high MRR and formation of atomic surface on diamond.The developed novel green CMP offers new insights to achieve atomic surface of diamond for potential use in their high-performance devices.展开更多
Diamond coatings possess numerous excellent properties,making them desirable materials for high-performance surface applications.However,without a revolutionary surface modification method,the surface roughness and fr...Diamond coatings possess numerous excellent properties,making them desirable materials for high-performance surface applications.However,without a revolutionary surface modification method,the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces.This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage,without causing damage to the metal substrate.Through experiments and simulations,the influence mechanism of surface graphitization and interfacial thermal stress was elucidated,ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness.Compared to the original diamond coatings,the obtained surfaces exhibited a 63%-72%reduction in friction coefficients,all of which were below 0.1,with a minimum of 0.06,and a 59%-67%decrease in specific wear rates.Moreover,adhesive wear in the friction counterpart was significantly inhibited,resulting in a reduction in wear by 49%-83%.This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties.This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces,with the potential to significantly enhance the performance and expand the application range of diamond-coated components.展开更多
Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.W...Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.We investigated the formation of nitrogen-induced diaph-ite structures(hybrid diamond-graphite phases)and their role in changing the conductivity.Nitrogen doping in a hy-drogen-rich plasma environment promotes the emergence of unique sp^(3)-sp^(2)bonding interfaces,where diamond grains are covalently integrated with graphitic domains,facilitating a structure-driven electronic transition.High-resolution transmis-sion electron microscopy and selected area electron diffraction reveal five-fold,six-fold and twelve-fold symmetries,along with an atypical{200}crystallographic reflection,confirming diaphite formation in 5%and 10%N-doped UNCD films,while high-er doping levels(15%and 20%)result in extensive graphitization.Raman spectroscopy tracks the evolution of sp^(2)bonding with increasing nitrogen content,while atomic force microscopy and X-ray diffraction indicate a consistent diamond grain size of~8 nm.Cryogenic electronic transport measurements reveal a conductivity increase from 8.72 to 708 S/cm as the nitrogen dop-ing level increases from 5%to 20%,which is attributed to defect-mediated carrier transport and 3D weak localization.The res-ulting conductivity is three orders of magnitude higher than previously reported.These findings establish a direct correlation between diaphite structural polymorphism and tunable electronic properties in nitrogen-doped UNCD films,offering new ways for defect-engineering diamond-based electronic materials.展开更多
Lonsdaleite,also known as hexagonal diamond,is an allotrope of carbon with a hexagonal crystal structure,which was discovered in the nanostructure of the Canyon Diablo meteorite.Theoretical calculations have shown tha...Lonsdaleite,also known as hexagonal diamond,is an allotrope of carbon with a hexagonal crystal structure,which was discovered in the nanostructure of the Canyon Diablo meteorite.Theoretical calculations have shown that this structure gives it exceptional physical properties that exceed those of cubic diamond,making it highly promising for groundbreaking applications in superhard cutting tools,wide-bandgap semiconductor devices,and materials for extreme environments.As a result,the controllable synthesis of hexagonal diamond has emerged as a cutting-edge research focus in materials science.This review briefly outlines the progress in this area,with a focus on the mechanisms governing its key synthesis conditions,its intrinsic physical properties,and its potential applications in various fields.展开更多
Diamond combines many unique properties,including high stability,strong optical dispersion,excellent mechanical strength,and outstanding thermal conductivity.Its structure,surface groups,and electrical conductivity ar...Diamond combines many unique properties,including high stability,strong optical dispersion,excellent mechanical strength,and outstanding thermal conductivity.Its structure,surface groups,and electrical conductivity are also tunable,increasing its functional versatility.These make diamond and its related materials,such as its composites,highly promising for various applications in energy fields.This review summarizes recent advances and key achievements in energy storage and conversion,covering electrochemical energy storage(e.g.,batteries and supercapacitors),electrocatalytic energy conversion(e.g.,CO_(2)and nitrogen reduction reactions),and solar energy conversion(e.g.,photo-(electro)chemical CO_(2)and nitrogen reduction reactions,and solar cells).Current challenges and prospects related to the synthesis of diamond materials and the technologies for their energy applications are outlined and discussed.展开更多
The features of optical defects in a chemical vapor deposition (CVD) synthetic type Ⅱ a diamond were characterized using photoluminescence (PL) spectroscopy, before and after electron irradiation. The sample was cut ...The features of optical defects in a chemical vapor deposition (CVD) synthetic type Ⅱ a diamond were characterized using photoluminescence (PL) spectroscopy, before and after electron irradiation. The sample was cut within a {100} growth layer, and irradiated with 2 MeV electrons along the <100> axis. PL spectra of sample were collected under 532 nm and 355 nm laser excitation, at room temperature and 77 K, and linear scanning analysis along incident depth was applied to determine the distribution of defects. The pre-irradiation characterization results revealed uniformly distributed PL centers at 389 nm, 469 nm, 533 nm, 575 nm (ZPL of NV 0), 637 nm (ZPL of NV -), and 736.7/737.1 nm (ZPL doublet of SiV -). After irradiation, the differential responses of these as-grown defects were observed, alongside the emergence of irradiation-induced defects, namely 489 nm center, H3 center (ZPL at 504 nm) and GR1 center (ZPL at 741 nm). The maximum penetration depth of 2 MeV electron-irradiation induced defects was determined to be 2.1 mm. This work primarily presents the depth profiles of both as-grown and irradiation-induced defects in 2 MeV electrons irradiated diamond. The result provides experimental data for better understanding of the radiation effect in diamonds. Serving as a reference for diamond enhancement by electron irradiation.展开更多
It is a key challenge to prepare two-dimensional diamond(2D-diamond).Herein,we develop a method for synthesizing 2D-diamond by depositing monodisperse tantalum(Ta)atoms onto graphene substrates using a hot-filament ch...It is a key challenge to prepare two-dimensional diamond(2D-diamond).Herein,we develop a method for synthesizing 2D-diamond by depositing monodisperse tantalum(Ta)atoms onto graphene substrates using a hot-filament chemical vapor deposition setup,followed by annealing treatment under different temperatures at ambient pressure.The results indicate that when the annealing temperature increases from 700℃ to 1000℃,the size of the 2D-diamond found in the samples gradually increases from close to 20 nm to around 30 nm.Meanwhile,the size and number of amorphous carbon spheres and Ta-containing compounds between the graphene layers gradually increase.As the annealing temperature continues to rise to 1100℃,a significant aggregation of Ta-containing compounds is observed in the samples,with no diamond structure detected.This further confirms that monodisperse Ta atoms play a key role in graphene phase transition into 2D-diamond.This study provides a novel method for the ambient-pressure phase transition of graphene into 2D-diamond.展开更多
Diamond with silicon vacancies has an important role as a promising single-photon source applicable in the quantum information field.However,in a microwave plasma chemical vapor deposition(MPCVD)system,due to the pres...Diamond with silicon vacancies has an important role as a promising single-photon source applicable in the quantum information field.However,in a microwave plasma chemical vapor deposition(MPCVD)system,due to the presence of unintentional silicon doping sources such as quartz windows,the behavior of silicon vacancy formation in silicon-doped diamond is complex.In this work,the underlying mechanism of formation of silicon vacancies by unintentional silicon doping in diamond is investigated from the perspective of growing surface kinetics in a two-gas-flow MPCVD system.This system is equipped with a novel susceptor geometry designed to deliver an additional gas flow directly onto the substrate surface.Increasing the concentration of growth doping substances on the substrate surface thereby enhances the efficiency of silicon vacancy formation in diamond.At the same time,by changing the substrate deposition angle the distribution of gas and plasma on the substrate surface is changed,thereby regulating the concentration and distribution of silicon vacancies formed by unintentional silicon doping.Experimental and computational results demonstrate that the difference in silicon vacancies formed by unintentional silicon doping in diamond depends on the substances present on the substrate surface and the distribution of plasma.展开更多
Diamond is a promising semiconductor material for future space exploration,owing to its unique atomic and electronic structures.However,diamond materials and related devices still suffer from irradiation damage under ...Diamond is a promising semiconductor material for future space exploration,owing to its unique atomic and electronic structures.However,diamond materials and related devices still suffer from irradiation damage under space irradiation involving high-energy irradiating particles.The study of the generation and evolution of point defects can help understand the irradiation damage mechanisms in diamond.This study systematically investigated the defect dynamics of diamond in 162 crystallographic directions uniformly selected on a spherical surface using molecular dynamics simulations,with primary knock-on atom(PKA)energies up to 20 keV,and temperatures ranging from 300 K to 1800 K.The results reveal that the displacement threshold energy of diamond changes periodically with crystallographic directions,which is related to the shape of potential energy surface along that direction.Additionally,the number of residual defects correlates positively with PKA energy.However,temperature has dual competing effects:while it enhances the probability of atomic displacement,it simultaneously suppresses the probability of defect formation by accelerating defect recombination.The calculation of sparse radial distribution function indicates that the defect distribution shows a certain degree of similarity in the short-range region across different PKA energies.As the PKA energy increases,defect clusters tend to become larger in size and more numerous in quantity.This study systematically investigates the anisotropy of displacement threshold energy and elucidates the relationship between various irradiation conditions and the final states of irradiation-induced defects.展开更多
The interfacial strength has a significant impact on mechanical properties of diamond composites.In this work,polycrystalline diamonds(PCDs)with medium-entropy alloy(MEA)binders and traditional Co binder were prepared...The interfacial strength has a significant impact on mechanical properties of diamond composites.In this work,polycrystalline diamonds(PCDs)with medium-entropy alloy(MEA)binders and traditional Co binder were prepared at high-pressure and high-temperature.Microstructures and interfacial strengths are carefully characterized using TEM.The results show that diamond particles are well bonded to form skeletons in all PCDs.The interfaces between MEA binders and diamond can be fully coherent.Due to the effect of Cr element and Cr-carbide,the PCD with Co_(50) Ni_(40) Fe_(10)-Cr_(3)C_(2) binder exhibits the highest interfacial bonding strength(1176.6 MPa)and highest fracture toughness(9.97 MPa m^(1/2)).The mechanical analyses indicate that both the interface and diamond skeleton have important effects on the fracture toughness of PCD.The interface with a higher bonding strength,a higher engineering strain and a higher elastic modulus can endure more stress,thereby improving the fracture toughness.展开更多
Sapphire hemispherical domes are machined through milling and shaping using brazed diamond tools.A mathematical model describing roughness for this processing method is established,and the relationship between roughne...Sapphire hemispherical domes are machined through milling and shaping using brazed diamond tools.A mathematical model describing roughness for this processing method is established,and the relationship between roughness and its influencing factors is analyzed.Experiments on the hemispherical dome shaping process are conducted to validate the model,analyzing the variation in roughness under different tool and workpiece rotational speeds.The results are consistent with the predictions of the established roughness model,suggesting that the model can be used to guide subsequent process experiments.Milling and shaping efficiency using brazed diamond tools typically can reach 14 g/min.The machined sapphire surfaces exhibit relatively few microcracks and minimal damage,with almost all exclusively visible grooves resulting from brittle fracture removal.The surface roughness after machining is below 2.5μm.Milling sapphire domes with brazed diamond tools represents a novel shaping technique characterized by high efficiency and high quality.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50572032 and 50731006)
文摘In this paper,we report on the influence of annealing treatment on as-grown Ib-type diamond crystal under high pressure and high temperature in a china-type cubic anvil high-pressure apparatus.Experiments are carried out at a pressure of 7.0 GPa and temperatures ranging from 1700 C to 1900 C for 1 h.Annealing treatment of the diamond crystal shows that the aggregation rate constant of nitrogen atoms in the as-grown Ib-type diamond crystal strongly depends on diamond morphology and annealing temperature.The aggregation rate constant of nitrogen remarkably increases with the increase of annealing temperature and its value in octahedral diamond is much higher than that in cubic diamond annealed at the same temperature.The colour of octahedral diamond crystal is obviously reduced from yellow to nearly colorless after annealing treatment for 1 h at 1900 C,which is induced by nitrogen aggregation in a diamond lattice.The extent of nitrogen aggregation in an annealed diamond could approach approximately 98% indicated from the infrared absorption spectra.The micro-Raman spectrum reveals that the annealing treatment can improve the crystalline quality of Ib-type diamond characterized by a half width at full maximum at first order Raman peak,and therefore the annealed diamond crystals exhibit nearly the same properties as the natural IaA-type diamond stones of high quality in the Raman measurements.
基金National MCF Energy R&D Program(2019YFE03100400)。
文摘Ag-Cu-In-Ti low-temperature filler was used to braze the diamond and copper,and the effects of brazing temperature and soaking time on the microstructure and mechanical properties of the joints were investigated.In addition,the joint formation mechanism was discussed,and the correlation between joint microstructure and mechanical performance was established.Results show that adding appropriate amount of In into the filler can significantly reduce the filler melting point and enhance the wettability of filler on diamond.When the brazing temperature is 750°C and the soaking time is 10 min,a uniformly dense braze seam with excellent metallurgical bonding can be obtained,and its average joint shear strength reaches 322 MPa.The lower brazing temperature can mitigate the risk of diamond graphitization and also reduce the residual stresses during joining.
基金financial support from the National Key Research and Development Program of China(2018YFA0703400)the Fundamental Research Funds for the Provincial Universities of Zhejiang(GK239909299001021)+1 种基金the Ninth China Association for Science and Technology Youth Talent Lift Project Support Plan(KYZ015324002)the Changjiang Scholars Program of Chinese Ministry of Education。
文摘Atomic surfaces are strictly required by high-performance devices of diamond.Nevertheless,diamond is the hardest material in nature,leading to the low material removal rate(MRR)and high surface roughness during machining.Noxious slurries are widely used in conventional chemical mechanical polishing(CMP),resulting in the possible pollution to the environment.Moreover,the traditional slurries normally contain more than four ingredients,causing difficulties to control the process and quality of CMP.To solve these challenges,a novel green CMP for single crystal diamond was developed,consisting of only hydrogen peroxide,diamond abrasive and Prussian blue(PB)/titania catalyst.After CMP,atomic surface is achieved with surface roughness Sa of 0.079 nm,and the MRR is 1168 nm·h^(-1).Thickness of damaged layer is merely 0.66 nm confirmed by transmission electron microscopy(TEM).X-ray photoelectron spectroscopy,electron paramagnetic resonance and TEM reveal that·OH radicals form under ultraviolet irradiation on PB/titania catalyst.The·OH radicals oxidize diamond,transforming it from monocrystalline to amorphous atomic structure,generating a soft amorphous layer.This contributes the high MRR and formation of atomic surface on diamond.The developed novel green CMP offers new insights to achieve atomic surface of diamond for potential use in their high-performance devices.
基金support from the National Natural Science Foundation of China(NSFC)[No.52475464,52475463]National Natural Science Foundation of Jiangsu Province(No.BK20231442)+4 种基金the Fundamental Research Funds for the Central Universities(No.NS2024032)the International Joint Laboratory of Sustainable Manufacturing,Ministry of Education and the Fundamental Research Funds for the Central Universities(No.NG2024007)China Scholarship Council(No.202206830048)the Foundation of the Graduate Innovation Center,Nanjing University of Aeronautics and Astronautics(No.kfjj20200510)Funding for Outstanding Doctoral Dissertation in NUAA(No.BCXJ23-09)。
文摘Diamond coatings possess numerous excellent properties,making them desirable materials for high-performance surface applications.However,without a revolutionary surface modification method,the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces.This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage,without causing damage to the metal substrate.Through experiments and simulations,the influence mechanism of surface graphitization and interfacial thermal stress was elucidated,ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness.Compared to the original diamond coatings,the obtained surfaces exhibited a 63%-72%reduction in friction coefficients,all of which were below 0.1,with a minimum of 0.06,and a 59%-67%decrease in specific wear rates.Moreover,adhesive wear in the friction counterpart was significantly inhibited,resulting in a reduction in wear by 49%-83%.This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties.This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces,with the potential to significantly enhance the performance and expand the application range of diamond-coated components.
文摘Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.We investigated the formation of nitrogen-induced diaph-ite structures(hybrid diamond-graphite phases)and their role in changing the conductivity.Nitrogen doping in a hy-drogen-rich plasma environment promotes the emergence of unique sp^(3)-sp^(2)bonding interfaces,where diamond grains are covalently integrated with graphitic domains,facilitating a structure-driven electronic transition.High-resolution transmis-sion electron microscopy and selected area electron diffraction reveal five-fold,six-fold and twelve-fold symmetries,along with an atypical{200}crystallographic reflection,confirming diaphite formation in 5%and 10%N-doped UNCD films,while high-er doping levels(15%and 20%)result in extensive graphitization.Raman spectroscopy tracks the evolution of sp^(2)bonding with increasing nitrogen content,while atomic force microscopy and X-ray diffraction indicate a consistent diamond grain size of~8 nm.Cryogenic electronic transport measurements reveal a conductivity increase from 8.72 to 708 S/cm as the nitrogen dop-ing level increases from 5%to 20%,which is attributed to defect-mediated carrier transport and 3D weak localization.The res-ulting conductivity is three orders of magnitude higher than previously reported.These findings establish a direct correlation between diaphite structural polymorphism and tunable electronic properties in nitrogen-doped UNCD films,offering new ways for defect-engineering diamond-based electronic materials.
基金the National Natural Science Foundation of China(12274170 and 52225203)。
文摘Lonsdaleite,also known as hexagonal diamond,is an allotrope of carbon with a hexagonal crystal structure,which was discovered in the nanostructure of the Canyon Diablo meteorite.Theoretical calculations have shown that this structure gives it exceptional physical properties that exceed those of cubic diamond,making it highly promising for groundbreaking applications in superhard cutting tools,wide-bandgap semiconductor devices,and materials for extreme environments.As a result,the controllable synthesis of hexagonal diamond has emerged as a cutting-edge research focus in materials science.This review briefly outlines the progress in this area,with a focus on the mechanisms governing its key synthesis conditions,its intrinsic physical properties,and its potential applications in various fields.
基金西南大学中央高校基本科研业务费项目(SWU-KT22030)重庆市教育委员会科学技术研究项目(KJQN202300205)Deutsche Forschungsgemeinschaft(DFG,German Research Foundation,457444676).
文摘Diamond combines many unique properties,including high stability,strong optical dispersion,excellent mechanical strength,and outstanding thermal conductivity.Its structure,surface groups,and electrical conductivity are also tunable,increasing its functional versatility.These make diamond and its related materials,such as its composites,highly promising for various applications in energy fields.This review summarizes recent advances and key achievements in energy storage and conversion,covering electrochemical energy storage(e.g.,batteries and supercapacitors),electrocatalytic energy conversion(e.g.,CO_(2)and nitrogen reduction reactions),and solar energy conversion(e.g.,photo-(electro)chemical CO_(2)and nitrogen reduction reactions,and solar cells).Current challenges and prospects related to the synthesis of diamond materials and the technologies for their energy applications are outlined and discussed.
基金This work is supported by National Natural Science Foundation of China(No.42372054)。
文摘The features of optical defects in a chemical vapor deposition (CVD) synthetic type Ⅱ a diamond were characterized using photoluminescence (PL) spectroscopy, before and after electron irradiation. The sample was cut within a {100} growth layer, and irradiated with 2 MeV electrons along the <100> axis. PL spectra of sample were collected under 532 nm and 355 nm laser excitation, at room temperature and 77 K, and linear scanning analysis along incident depth was applied to determine the distribution of defects. The pre-irradiation characterization results revealed uniformly distributed PL centers at 389 nm, 469 nm, 533 nm, 575 nm (ZPL of NV 0), 637 nm (ZPL of NV -), and 736.7/737.1 nm (ZPL doublet of SiV -). After irradiation, the differential responses of these as-grown defects were observed, alongside the emergence of irradiation-induced defects, namely 489 nm center, H3 center (ZPL at 504 nm) and GR1 center (ZPL at 741 nm). The maximum penetration depth of 2 MeV electron-irradiation induced defects was determined to be 2.1 mm. This work primarily presents the depth profiles of both as-grown and irradiation-induced defects in 2 MeV electrons irradiated diamond. The result provides experimental data for better understanding of the radiation effect in diamonds. Serving as a reference for diamond enhancement by electron irradiation.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.U1809210)the International Science Technology Cooperation Program of China(Grant No.2014DFR51160)+3 种基金the One Belt and One Road International Cooperation Project from the Key Research and Development Program of Zhejiang Province,China(Grant No.2018C04021)the National Natural Science Foundation of China(Grant Nos.50972129,50602039,and 52102052)the Fund from Institute of Wenzhou,Zhejiang University(Grant Nos.XMGL-CX-202305 and XMGLKJZX-202307)the Project from Tanghe Scientific&Technology Company(Grant No.KYY-HX-20230024).
文摘It is a key challenge to prepare two-dimensional diamond(2D-diamond).Herein,we develop a method for synthesizing 2D-diamond by depositing monodisperse tantalum(Ta)atoms onto graphene substrates using a hot-filament chemical vapor deposition setup,followed by annealing treatment under different temperatures at ambient pressure.The results indicate that when the annealing temperature increases from 700℃ to 1000℃,the size of the 2D-diamond found in the samples gradually increases from close to 20 nm to around 30 nm.Meanwhile,the size and number of amorphous carbon spheres and Ta-containing compounds between the graphene layers gradually increase.As the annealing temperature continues to rise to 1100℃,a significant aggregation of Ta-containing compounds is observed in the samples,with no diamond structure detected.This further confirms that monodisperse Ta atoms play a key role in graphene phase transition into 2D-diamond.This study provides a novel method for the ambient-pressure phase transition of graphene into 2D-diamond.
基金supported by the National Natural Science Foundation of China(Grant No.62274084)the Fundamental Research Funds for the Central Universities(Grant No.0210-14380193).
文摘Diamond with silicon vacancies has an important role as a promising single-photon source applicable in the quantum information field.However,in a microwave plasma chemical vapor deposition(MPCVD)system,due to the presence of unintentional silicon doping sources such as quartz windows,the behavior of silicon vacancy formation in silicon-doped diamond is complex.In this work,the underlying mechanism of formation of silicon vacancies by unintentional silicon doping in diamond is investigated from the perspective of growing surface kinetics in a two-gas-flow MPCVD system.This system is equipped with a novel susceptor geometry designed to deliver an additional gas flow directly onto the substrate surface.Increasing the concentration of growth doping substances on the substrate surface thereby enhances the efficiency of silicon vacancy formation in diamond.At the same time,by changing the substrate deposition angle the distribution of gas and plasma on the substrate surface is changed,thereby regulating the concentration and distribution of silicon vacancies formed by unintentional silicon doping.Experimental and computational results demonstrate that the difference in silicon vacancies formed by unintentional silicon doping in diamond depends on the substances present on the substrate surface and the distribution of plasma.
基金supported by the Science and Technology Innovation Program of Hunan Province,China(Grant No.2021RC4026)the National Natural Science Foundation of China(Grant Nos.12204538,12104507,and 92365203)Hunan Provincial Science Fund for Distinguished Young Scholars(Grant No.2022JJ10060).
文摘Diamond is a promising semiconductor material for future space exploration,owing to its unique atomic and electronic structures.However,diamond materials and related devices still suffer from irradiation damage under space irradiation involving high-energy irradiating particles.The study of the generation and evolution of point defects can help understand the irradiation damage mechanisms in diamond.This study systematically investigated the defect dynamics of diamond in 162 crystallographic directions uniformly selected on a spherical surface using molecular dynamics simulations,with primary knock-on atom(PKA)energies up to 20 keV,and temperatures ranging from 300 K to 1800 K.The results reveal that the displacement threshold energy of diamond changes periodically with crystallographic directions,which is related to the shape of potential energy surface along that direction.Additionally,the number of residual defects correlates positively with PKA energy.However,temperature has dual competing effects:while it enhances the probability of atomic displacement,it simultaneously suppresses the probability of defect formation by accelerating defect recombination.The calculation of sparse radial distribution function indicates that the defect distribution shows a certain degree of similarity in the short-range region across different PKA energies.As the PKA energy increases,defect clusters tend to become larger in size and more numerous in quantity.This study systematically investigates the anisotropy of displacement threshold energy and elucidates the relationship between various irradiation conditions and the final states of irradiation-induced defects.
基金financially supported by the Regional Innova-tion and Development Joint Funds of the National Natural Science Foundation of China(No.U20A20236)the Central South Univer-sity Innovation-Driven Research Programme(No.2023CXQD030)the Huaqiao University Engineering Research Center of Brittle Materials Machining(MOE,No.2023IME-002).
文摘The interfacial strength has a significant impact on mechanical properties of diamond composites.In this work,polycrystalline diamonds(PCDs)with medium-entropy alloy(MEA)binders and traditional Co binder were prepared at high-pressure and high-temperature.Microstructures and interfacial strengths are carefully characterized using TEM.The results show that diamond particles are well bonded to form skeletons in all PCDs.The interfaces between MEA binders and diamond can be fully coherent.Due to the effect of Cr element and Cr-carbide,the PCD with Co_(50) Ni_(40) Fe_(10)-Cr_(3)C_(2) binder exhibits the highest interfacial bonding strength(1176.6 MPa)and highest fracture toughness(9.97 MPa m^(1/2)).The mechanical analyses indicate that both the interface and diamond skeleton have important effects on the fracture toughness of PCD.The interface with a higher bonding strength,a higher engineering strain and a higher elastic modulus can endure more stress,thereby improving the fracture toughness.
基金supported by the Na-tional Natural Science Foundation of China(No.51675457)the Jiangsu Key Laboratory of Precision and Micro-man-ufacturing Technology.
文摘Sapphire hemispherical domes are machined through milling and shaping using brazed diamond tools.A mathematical model describing roughness for this processing method is established,and the relationship between roughness and its influencing factors is analyzed.Experiments on the hemispherical dome shaping process are conducted to validate the model,analyzing the variation in roughness under different tool and workpiece rotational speeds.The results are consistent with the predictions of the established roughness model,suggesting that the model can be used to guide subsequent process experiments.Milling and shaping efficiency using brazed diamond tools typically can reach 14 g/min.The machined sapphire surfaces exhibit relatively few microcracks and minimal damage,with almost all exclusively visible grooves resulting from brittle fracture removal.The surface roughness after machining is below 2.5μm.Milling sapphire domes with brazed diamond tools represents a novel shaping technique characterized by high efficiency and high quality.
