Pub Date : 2024-09-04DOI: 10.1088/1361-6463/ad714e
O D Schneble, I A Leahy, J D Zimmerman, M B Tellekamp
Transition metal oxides with insulator-metal transitions (IMTs) are uniquely suited for volatile memristor devices that mimic the spiking of biological neurons. Unlike most non-volatile memristors, which often operate via ion migration into filaments, volatile devices utilize a reversible phase change that returns to a ground state in the absence of applied stimulus. In these devices, Joule heating triggers the IMT and changes the bulk resistivity rather than influencing conduction through defects, as in previous studies. This volatile resistive switching behavior has previous been leveraged in niobium and vanadium oxides, but not in rare-earth nickelates, despite their tunable transition temperatures. This study demonstrates an electrically driven IMT in the prototypical rare-earth nickelate, NdNiO3, in large area devices. While previous work examining the electrically-driven IMT in NdNiO3 suggests defect-dominated conduction, this study shows clear s-type negative differential resistance (NDR) consistent with temperature-dependent resistivity measurements. The NDR peak-to-valley voltage scales linearly with temperature as expected for conductivity pathways dominated by bulk IMT behavior. Unlike other transition metal oxides, which are modeled using the insulator-metal phase fraction as the internal state variable, a thermoelectric model with temperature as the internal state variable is found to more accurately describe the current–voltage characteristic of NdNiO3 volatile memristors. Overall, we report the synthesis, fabrication, and characterization of NdNiO3 volatile memristors with resistivity dominated by bulk-like IMT behavior which is scalable and not dependent upon oxygen vacancy migration or defect mediated conduction pathways.
{"title":"Electrically-driven IMT and volatile memristor behavior in NdNiO3 films","authors":"O D Schneble, I A Leahy, J D Zimmerman, M B Tellekamp","doi":"10.1088/1361-6463/ad714e","DOIUrl":"https://doi.org/10.1088/1361-6463/ad714e","url":null,"abstract":"Transition metal oxides with insulator-metal transitions (IMTs) are uniquely suited for volatile memristor devices that mimic the spiking of biological neurons. Unlike most non-volatile memristors, which often operate via ion migration into filaments, volatile devices utilize a reversible phase change that returns to a ground state in the absence of applied stimulus. In these devices, Joule heating triggers the IMT and changes the bulk resistivity rather than influencing conduction through defects, as in previous studies. This volatile resistive switching behavior has previous been leveraged in niobium and vanadium oxides, but not in rare-earth nickelates, despite their tunable transition temperatures. This study demonstrates an electrically driven IMT in the prototypical rare-earth nickelate, NdNiO<sub>3</sub>, in large area devices. While previous work examining the electrically-driven IMT in NdNiO<sub>3</sub> suggests defect-dominated conduction, this study shows clear s-type negative differential resistance (NDR) consistent with temperature-dependent resistivity measurements. The NDR peak-to-valley voltage scales linearly with temperature as expected for conductivity pathways dominated by bulk IMT behavior. Unlike other transition metal oxides, which are modeled using the insulator-metal phase fraction as the internal state variable, a thermoelectric model with temperature as the internal state variable is found to more accurately describe the current–voltage characteristic of NdNiO<sub>3</sub> volatile memristors. Overall, we report the synthesis, fabrication, and characterization of NdNiO<sub>3</sub> volatile memristors with resistivity dominated by bulk-like IMT behavior which is scalable and not dependent upon oxygen vacancy migration or defect mediated conduction pathways.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1088/1361-6463/ad7149
Qinqin Shao, Ruohan Shen, He Tian, Xiaodong Pi, Deren Yang, Rong Wang
4H silicon carbide (4H-SiC) is one of the most promising candidates in high-power and high-frequency devices, owing to its excellent properties such as wide bandgap, high electron mobility, high electric breakdown field and high thermal conductivity. The physical-vapor-transport (PVT) approach has been broadly adopted to grow 4H-SiC single-crystal boules. Because of the high-temperature growth of 4H-SiC single-crystal boules, the PVT system is a ‘black-box’ system, which decreases the yield and thus increases the cost of 4H-SiC single-crystals. Although advanced modern characterization tools, e.g. atomic force microscopy, x-ray topography, x-ray diffraction and Raman scattering spectroscopy, can provide deep insight into the structural and defect properties of 4H-SiC boules, it is rather limited to gain in-situ information of the growth process by these ex-situ methods. Therefore, the in-situ visualization on the evolution of structural morphologies and defects conducted by x-ray computed tomography (xCT) is of great importance for further development. In this topical review, the application of the xCT technology on the in-situ visualization of the evolution of the growth front, growth rate, defects, and the mass transport of the source material of 4H-SiC are reviewed. The ex-situ characterization of 4H-SiC single-crystal boules are also briefly introduced. This topical review provides insight into the growth process, structural morphology, and defect evolution of PVT-grown 4H-SiC single-crystal boules.
{"title":"In-situ and ex-situ characterizations of PVT-grown 4H-SiC single crystals","authors":"Qinqin Shao, Ruohan Shen, He Tian, Xiaodong Pi, Deren Yang, Rong Wang","doi":"10.1088/1361-6463/ad7149","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7149","url":null,"abstract":"4H silicon carbide (4H-SiC) is one of the most promising candidates in high-power and high-frequency devices, owing to its excellent properties such as wide bandgap, high electron mobility, high electric breakdown field and high thermal conductivity. The physical-vapor-transport (PVT) approach has been broadly adopted to grow 4H-SiC single-crystal boules. Because of the high-temperature growth of 4H-SiC single-crystal boules, the PVT system is a ‘black-box’ system, which decreases the yield and thus increases the cost of 4H-SiC single-crystals. Although advanced modern characterization tools, e.g. atomic force microscopy, <italic toggle=\"yes\">x</italic>-ray topography, x-ray diffraction and Raman scattering spectroscopy, can provide deep insight into the structural and defect properties of 4H-SiC boules, it is rather limited to gain <italic toggle=\"yes\">in-situ</italic> information of the growth process by these <italic toggle=\"yes\">ex-situ</italic> methods. Therefore, the <italic toggle=\"yes\">in-situ</italic> visualization on the evolution of structural morphologies and defects conducted by <italic toggle=\"yes\">x</italic>-ray computed tomography (<italic toggle=\"yes\">x</italic>CT) is of great importance for further development. In this topical review, the application of the <italic toggle=\"yes\">x</italic>CT technology on the <italic toggle=\"yes\">in-situ</italic> visualization of the evolution of the growth front, growth rate, defects, and the mass transport of the source material of 4H-SiC are reviewed. The <italic toggle=\"yes\">ex-situ</italic> characterization of 4H-SiC single-crystal boules are also briefly introduced. This topical review provides insight into the growth process, structural morphology, and defect evolution of PVT-grown 4H-SiC single-crystal boules.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"29 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1088/1361-6463/ad6e00
Yan Zhang, Zhaofu Zhang, Yuzheng Guo, John Robertson, Shijing Wu, Sheng Liu, Yunyun Sun
This review provides a comprehensive overview of recent advancements in molecular dynamics (MD) simulations of dry friction on rough substrates. While nanoscale roughness plays a crucial role in nanotribological investigations, the exploration of rough substrates remains insufficient based on MD simulations. This paper summarizes research on rough surfaces constructed from various descriptions, including the multi-asperity surface, groove-textured surface, fractal surface, Gaussian surface, stepped surface and randomly rough surface. In addition, the friction behavior of rough substrates coated with solid films is comprehensively elucidated. Present investigations on rough surfaces primarily focus on the effect of basic frictional variables, surface morphology characteristics and different motion types. The studies conducted on rough substrates exhibit a higher degree of resemblance to realistic interfaces, thereby offering valuable insight into the design of surface morphology to achieve enhanced frictional performance.
{"title":"Recent advances in molecular dynamics simulations for dry friction on rough substrate","authors":"Yan Zhang, Zhaofu Zhang, Yuzheng Guo, John Robertson, Shijing Wu, Sheng Liu, Yunyun Sun","doi":"10.1088/1361-6463/ad6e00","DOIUrl":"https://doi.org/10.1088/1361-6463/ad6e00","url":null,"abstract":"This review provides a comprehensive overview of recent advancements in molecular dynamics (MD) simulations of dry friction on rough substrates. While nanoscale roughness plays a crucial role in nanotribological investigations, the exploration of rough substrates remains insufficient based on MD simulations. This paper summarizes research on rough surfaces constructed from various descriptions, including the multi-asperity surface, groove-textured surface, fractal surface, Gaussian surface, stepped surface and randomly rough surface. In addition, the friction behavior of rough substrates coated with solid films is comprehensively elucidated. Present investigations on rough surfaces primarily focus on the effect of basic frictional variables, surface morphology characteristics and different motion types. The studies conducted on rough substrates exhibit a higher degree of resemblance to realistic interfaces, thereby offering valuable insight into the design of surface morphology to achieve enhanced frictional performance.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"4 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A double-pulse femtosecond laser is used to process single-crystal silicon. Modulating the delay time was discovered to increase the ablation depth and improve the morphology of the ablated surface. The hole fabricated by a dual-pulse with a 200 ps interval is 24.4% deeper than that created by a single pulse of the same energy. Moreover, utilizing a dual pulse with an interval ranging from 100 to 1000 ps produces a considerably smoother ablation area as compared to the single pulse. The effect of the sub-pulse energy ratio of the double-pulse femtosecond laser on the size and morphology of the ablated area was also investigated. As the sub-pulse energy ratio decreases from 3:1 to 1:3, the size of the ablation area initially decreases and then increases, while the size of the ablation area is minimized when the sub-pulse ratio is 1:1, enabling precise control over the machining size. As the energy of the second sub-pulse increases, the ablation area becomes smoother due to the plasma heating of the double-pulse femtosecond laser.
{"title":"Single-crystal silicon ablation with temporally delayed femtosecond laser double-pulse trains","authors":"Zhengjie Fan, Liangtian Yi, Jing Lv, Wenjun Wang, Guoji Li, Jianlei Cui","doi":"10.1088/1361-6463/ad7300","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7300","url":null,"abstract":"A double-pulse femtosecond laser is used to process single-crystal silicon. Modulating the delay time was discovered to increase the ablation depth and improve the morphology of the ablated surface. The hole fabricated by a dual-pulse with a 200 ps interval is 24.4% deeper than that created by a single pulse of the same energy. Moreover, utilizing a dual pulse with an interval ranging from 100 to 1000 ps produces a considerably smoother ablation area as compared to the single pulse. The effect of the sub-pulse energy ratio of the double-pulse femtosecond laser on the size and morphology of the ablated area was also investigated. As the sub-pulse energy ratio decreases from 3:1 to 1:3, the size of the ablation area initially decreases and then increases, while the size of the ablation area is minimized when the sub-pulse ratio is 1:1, enabling precise control over the machining size. As the energy of the second sub-pulse increases, the ablation area becomes smoother due to the plasma heating of the double-pulse femtosecond laser.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"9 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-03DOI: 10.1088/1361-6463/ad6fb2
Engin Aşlar
This study aims to investigate both light-induced fading effects on thermoluminescence (TL) and optically stimulated luminescence (OSL) signals under three different light sources (fluorescent, UV-254 and daylight) and dose reassessment with phototransferred TL (PTTL) signals in Beryllium oxide dosimeters. TL and OSL signals were deconvoluted for each light source. Accordingly, variations in the maximum peak temperature, activation energy, peak area value for the TL signal, and intensity and lifetime values for the OSL signal were monitored. Each peak, OSL component, and total area value exhibited different behaviors depending on the light source. Considering the total area condition, the TL intensity decreased by ∼90%, ∼80%, and ∼70% in UV-254, daylight, and fluorescent light exposure, respectively, at the end of the 120 min. On the other hand, the OSL total area intensity faded quickly for both UV-254 and daylight, while it decreased by ∼45% for fluorescent light. According to these results, regardless of TL and OSL measurements, the dosimeters should be kept primarily away from daylight and fluorescent light after irradiation, instead of UV-254, which is rarely encountered in daily life. The feasibility of dose reassessment using PTTL signals under UV-254 light was investigated within a wide dose range from 0.1 to 128 Gy. It is feasible to reassess doses between 0.5 and 32 Gy considering the total area intensity of PTTL signals. In conclusion, PTTL signals can be easily used in fields of the order of Gy, such as in reevaluating doses in radiotherapy applications.
{"title":"Light-induced fading effects on TL and OSL signals and feasibility of dose re-assessment with PTTL signals in BeO dosimeters","authors":"Engin Aşlar","doi":"10.1088/1361-6463/ad6fb2","DOIUrl":"https://doi.org/10.1088/1361-6463/ad6fb2","url":null,"abstract":"This study aims to investigate both light-induced fading effects on thermoluminescence (TL) and optically stimulated luminescence (OSL) signals under three different light sources (fluorescent, UV-254 and daylight) and dose reassessment with phototransferred TL (PTTL) signals in Beryllium oxide dosimeters. TL and OSL signals were deconvoluted for each light source. Accordingly, variations in the maximum peak temperature, activation energy, peak area value for the TL signal, and intensity and lifetime values for the OSL signal were monitored. Each peak, OSL component, and total area value exhibited different behaviors depending on the light source. Considering the total area condition, the TL intensity decreased by ∼90%, ∼80%, and ∼70% in UV-254, daylight, and fluorescent light exposure, respectively, at the end of the 120 min. On the other hand, the OSL total area intensity faded quickly for both UV-254 and daylight, while it decreased by ∼45% for fluorescent light. According to these results, regardless of TL and OSL measurements, the dosimeters should be kept primarily away from daylight and fluorescent light after irradiation, instead of UV-254, which is rarely encountered in daily life. The feasibility of dose reassessment using PTTL signals under UV-254 light was investigated within a wide dose range from 0.1 to 128 Gy. It is feasible to reassess doses between 0.5 and 32 Gy considering the total area intensity of PTTL signals. In conclusion, PTTL signals can be easily used in fields of the order of Gy, such as in reevaluating doses in radiotherapy applications.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"40 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-02DOI: 10.1088/1361-6463/ad726e
K N Kornev, A A Logunov, S A Dvinin
A low-current gliding discharge (current range 1–5 A) in high-speed air flows of 100–250 m s−1 was experimentally studied. A high-voltage direct current source with a maximum voltage of 4.5 kV was used to create the discharge. The average electron concentration ne ∼ 1014 cm−3 and the plasma ionization degree were determined by measuring the Stark broadening of the hydrogen Hβ line (λHβ = 486.1 nm). The estimates of the electric field (E ∼ 100 V cm −1 ÷ 600 V cm−1) in the discharge positive column were found using time-synchronized high-speed video recordings and oscillograms. The gas rotational temperature Tg = 7000–9500 K and the vibrational temperature Tv = 7000–11 000 K were estimated using optical emission spectroscopy. Time-resolved spectroscopy is used to investigate the effective plasma channel spatial regions from which the N, NH, N2+, O and OH molecules radiate. The difference of the obtained radii indicates the presence of a radial temperature gradient and inhomogeneous plasma composition in the discharge cross section. The possibility of using of gliding discharge to ignite hydrocarbon-air mixtures in the ramjet engines combustors has been experimentally demonstrated.
实验研究了 100-250 m s-1 高速气流中的低电流滑行放电（电流范围 1-5 A）。产生放电的是一个最大电压为 4.5 kV 的高压直流电源。通过测量氢 Hβ 线的斯塔克展宽（λHβ = 486.1 nm），确定了平均电子浓度 ne ∼ 1014 cm-3 和等离子体电离度。放电正柱中的电场（E ∼ 100 V cm -1 ÷ 600 V cm-1）是通过时间同步的高速视频记录和振荡图估算出来的。气体旋转温度 Tg = 7000-9500 K 和振动温度 Tv = 7000-11000 K 是通过光学发射光谱估算的。时间分辨光谱法用于研究 N、NH、N2+、O 和 OH 分子辐射的有效等离子体通道空间区域。获得的半径差异表明放电截面存在径向温度梯度和不均匀等离子体成分。实验证明了在冲压式喷气发动机燃烧器中使用滑行放电点燃碳氢化合物-空气混合物的可能性。
{"title":"Low-current gliding DC discharge in high-speed flows","authors":"K N Kornev, A A Logunov, S A Dvinin","doi":"10.1088/1361-6463/ad726e","DOIUrl":"https://doi.org/10.1088/1361-6463/ad726e","url":null,"abstract":"A low-current gliding discharge (current range 1–5 A) in high-speed air flows of 100–250 m s<sup>−1</sup> was experimentally studied. A high-voltage direct current source with a maximum voltage of 4.5 kV was used to create the discharge. The average electron concentration <italic toggle=\"yes\">n</italic><sub>e</sub> ∼ 10<sup>14</sup> cm<sup>−3</sup> and the plasma ionization degree were determined by measuring the Stark broadening of the hydrogen H<italic toggle=\"yes\"><sub>β</sub></italic> line (<italic toggle=\"yes\">λ</italic><sub>H<italic toggle=\"yes\">β</italic></sub> = 486.1 nm). The estimates of the electric field (<italic toggle=\"yes\">E</italic> ∼ 100 V cm <sup>−1</sup> ÷ 600 V cm<sup>−1</sup>) in the discharge positive column were found using time-synchronized high-speed video recordings and oscillograms. The gas rotational temperature <italic toggle=\"yes\">T</italic><sub>g</sub> = 7000–9500 K and the vibrational temperature <italic toggle=\"yes\">T</italic><sub>v</sub> = 7000–11 000 K were estimated using optical emission spectroscopy. Time-resolved spectroscopy is used to investigate the effective plasma channel spatial regions from which the N, NH, N<sub>2</sub><sup>+</sup>, O and OH molecules radiate. The difference of the obtained radii indicates the presence of a radial temperature gradient and inhomogeneous plasma composition in the discharge cross section. The possibility of using of gliding discharge to ignite hydrocarbon-air mixtures in the ramjet engines combustors has been experimentally demonstrated.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Here, we propose and develop a silicon (Si)-based perovskite plasmon-emitting diode (PED) with controlled linear polarization in this study. Such polarization originates from the efficient excitation of surface plasmons by excitons in the active layer of the device and the efficient outcoupling by a wedged boundary of a metal electrode. Furthermore, a p-type Si substrate serves as an anode of the diode, and a hole blocking layer of SiO2 is introduced in the PEDOT:PSS/Si heterojunction for carrier injection balance. Pure green emission light has been achieved from devices with varied thicknesses of the emitting layer, and the maximum degree of polarization is measured to be 0.79. The field distribution and polarization of the PED were simulated and measured. Such a low-cost Si-based plasmonic diode provides a promising way to realize simpler and more compact multiple-functional light sources, which are extensively demanded for optoelectronic integration.
{"title":"Silicon-based perovskite plasmonic diode with highly polarized emission","authors":"Xin-Rui Mao, Zihao Chu, Xiaogen Yi, Riyu Cong, Yanping Li, Wanjin Xu, Guangzhao Ran","doi":"10.1088/1361-6463/ad7037","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7037","url":null,"abstract":"Here, we propose and develop a silicon (Si)-based perovskite plasmon-emitting diode (PED) with controlled linear polarization in this study. Such polarization originates from the efficient excitation of surface plasmons by excitons in the active layer of the device and the efficient outcoupling by a wedged boundary of a metal electrode. Furthermore, a p-type Si substrate serves as an anode of the diode, and a hole blocking layer of SiO<sub>2</sub> is introduced in the PEDOT:PSS/Si heterojunction for carrier injection balance. Pure green emission light has been achieved from devices with varied thicknesses of the emitting layer, and the maximum degree of polarization is measured to be 0.79. The field distribution and polarization of the PED were simulated and measured. Such a low-cost Si-based plasmonic diode provides a promising way to realize simpler and more compact multiple-functional light sources, which are extensively demanded for optoelectronic integration.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"60 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In pursuit of diamond nanoparticles, a capacitively-coupled radio frequency flow-through plasma reactor was operated with methane-argon gas mixtures. Signatures of the final product obtained microscopically and spectroscopically indicated that the product was an amorphous form of graphite. This result was consistent irrespective of combinations of the macroscopic reactor settings. To explain the observed synthesis output, measurements of C2 and gas properties were carried out by laser-induced fluorescence and optical emission spectroscopy. Strikingly, the results indicated a strong gas temperature gradient of 100 K per mm from the center of the reactor to the wall. Based on additional plasma imaging, a model of hot constricted region (filamentation region) was then formulated. It illustrated that, while the hot constricted region was present, the bulk of the gas was not hot enough to facilitate diamond sp3 formation: characterized by much lower reaction rates, when compared to sp2, sp3 formation kinetics are expected to become exponentially slow. This result was further confirmed by experiments under identical conditions but with a H2/CH4 mixture, where no output material was detected: if graphitic sp2 formation was expected as the main output material from the methane feedstock, atomic hydrogen would then be expected to etch it away in situ, such that the net production of that sp2-hybridized solid material is nearly a zero. Finally, the crucial importance of gas heating was corroborated by replacing RF with microwave source whereby facile sp3 production was attained with H2/CH4 gas mixture.
{"title":"Importance of gas heating in capacitively coupled radiofrequency plasma-assisted synthesis of carbon nanomaterials","authors":"Tanvi Nikhar, Sankhadeep Basu, Shota Abe, Shurik Yatom, Yevgeny Raitses, Rebecca Anthony, Sergey V Baryshev","doi":"10.1088/1361-6463/ad6d78","DOIUrl":"https://doi.org/10.1088/1361-6463/ad6d78","url":null,"abstract":"In pursuit of diamond nanoparticles, a capacitively-coupled radio frequency flow-through plasma reactor was operated with methane-argon gas mixtures. Signatures of the final product obtained microscopically and spectroscopically indicated that the product was an amorphous form of graphite. This result was consistent irrespective of combinations of the macroscopic reactor settings. To explain the observed synthesis output, measurements of C<sub>2</sub> and gas properties were carried out by laser-induced fluorescence and optical emission spectroscopy. Strikingly, the results indicated a strong gas temperature gradient of 100 K per mm from the center of the reactor to the wall. Based on additional plasma imaging, a model of hot constricted region (filamentation region) was then formulated. It illustrated that, while the hot constricted region was present, the bulk of the gas was not hot enough to facilitate diamond <italic toggle=\"yes\">sp</italic><sup>3</sup> formation: characterized by much lower reaction rates, when compared to <italic toggle=\"yes\">sp</italic><sup>2</sup>, <italic toggle=\"yes\">sp</italic><sup>3</sup> formation kinetics are expected to become exponentially slow. This result was further confirmed by experiments under identical conditions but with a H<sub>2</sub>/CH<sub>4</sub> mixture, where no output material was detected: if graphitic <italic toggle=\"yes\">sp</italic><sup>2</sup> formation was expected as the main output material from the methane feedstock, atomic hydrogen would then be expected to etch it away <italic toggle=\"yes\">in situ</italic>, such that the net production of that <italic toggle=\"yes\">sp</italic><sup>2</sup>-hybridized solid material is nearly a zero. Finally, the crucial importance of gas heating was corroborated by replacing RF with microwave source whereby facile <italic toggle=\"yes\">sp</italic><sup>3</sup> production was attained with H<sub>2</sub>/CH<sub>4</sub> gas mixture.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Perfluoroisobutyronitrile (C4F7N) gas mixture is considered one of the most promising alternative gases for SF6 due to its excellent environmental protection and insulation performance. At present, the Shanghai region of China has adopted 8.5% C4F7N-86% CO2-5.5% O2 proportion gas mixture as the insulation medium for 126 kV gas insulated switchgear and has put it into practical engineering application. This paper conducted decomposition experiments on the proportion gas mixture under spark discharge, suspension discharge, and corona discharge conditions, respectively. The composition analysis of the decomposition products was carried out using a gas chromatography mass spectrometry and a gas chromatography-pulsed discharge helium ionization detector, which got decomposition products of the C4F7N/CO2/O2 gas mixture under discharge faults mainly include CO, CF4, C3F8, C4F8, C3F6, and CF3CN. According to the decomposition path of the C4F7N gas mixture, this paper selected three primary decomposition products (CO, CF4, C3F8) and one secondary decomposition product (C4F8) for the correlation characterization of discharge types, and proposed the ratios of c(CO)/c(CF4) and c(C4F8)/c(C3F8) as the characteristic quantities to characterize the different discharge types. Finally, in order to accurately identify the C4F7N/CO2/O2 gas mixture discharge type, this paper chose the decision tree algorithm to build a identification tree. The final identification result indicates that the ratio of c (CO)/c (CF4) and c (C4F8)/c (C3F8) can be used as the identification criterion for typical discharge fault types.
{"title":"Discharge fault type identification of C4F7N/CO2/O2 mixed insulating gas for engineering based on product components","authors":"Guangkai Cui, Cong Wang, Yuan Yang, Hao Wang, Youping Tu, Zhong Zheng, Hua Jin","doi":"10.1088/1361-6463/ad714c","DOIUrl":"https://doi.org/10.1088/1361-6463/ad714c","url":null,"abstract":"Perfluoroisobutyronitrile (C<sub>4</sub>F<sub>7</sub>N) gas mixture is considered one of the most promising alternative gases for SF<sub>6</sub> due to its excellent environmental protection and insulation performance. At present, the Shanghai region of China has adopted 8.5% C<sub>4</sub>F<sub>7</sub>N-86% CO<sub>2</sub>-5.5% O<sub>2</sub> proportion gas mixture as the insulation medium for 126 kV gas insulated switchgear and has put it into practical engineering application. This paper conducted decomposition experiments on the proportion gas mixture under spark discharge, suspension discharge, and corona discharge conditions, respectively. The composition analysis of the decomposition products was carried out using a gas chromatography mass spectrometry and a gas chromatography-pulsed discharge helium ionization detector, which got decomposition products of the C<sub>4</sub>F<sub>7</sub>N/CO<sub>2</sub>/O<sub>2</sub> gas mixture under discharge faults mainly include CO, CF<sub>4</sub>, C<sub>3</sub>F<sub>8</sub>, C<sub>4</sub>F<sub>8</sub>, C<sub>3</sub>F<sub>6</sub>, and CF<sub>3</sub>CN. According to the decomposition path of the C<sub>4</sub>F<sub>7</sub>N gas mixture, this paper selected three primary decomposition products (CO, CF<sub>4</sub>, C<sub>3</sub>F<sub>8</sub>) and one secondary decomposition product (C<sub>4</sub>F<sub>8</sub>) for the correlation characterization of discharge types, and proposed the ratios of c(CO)/c(CF<sub>4</sub>) and c(C<sub>4</sub>F<sub>8</sub>)/c(C<sub>3</sub>F<sub>8</sub>) as the characteristic quantities to characterize the different discharge types. Finally, in order to accurately identify the C<sub>4</sub>F<sub>7</sub>N/CO<sub>2</sub>/O<sub>2</sub> gas mixture discharge type, this paper chose the decision tree algorithm to build a identification tree. The final identification result indicates that the ratio of c (CO)/c (CF<sub>4</sub>) and c (C<sub>4</sub>F<sub>8</sub>)/c (C<sub>3</sub>F<sub>8</sub>) can be used as the identification criterion for typical discharge fault types.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"34 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-30DOI: 10.1088/1361-6463/ad6e99
Irina Oganesyan, Alina Begley, Dušan Mrđenović, Julian A Harrison, Renato Zenobi
Plasma medicine is a field that utilizes reactive species generated from atmospheric low-temperature plasmas for applications such as sterilization, blood coagulation, and cancer therapy. Commercial plasma devices are available for wound healing, but research on the chemical modifications induced by these plasmas is scarce. This study explores the chemical modifications in hemoglobin when exposed to a helium plasma dielectric barrier discharge, with the aim of explaining the potential mechanisms through which it contributes to blood coagulation and enhances wound healing. Optical microscopy of cold atmospheric plasma (CAP) treated whole capillary blood showed an increase in red blood cell (RBC) size and the formation of rouleaux structures. The treatment of whole blood leads to hemolysis of RBCs and the release of intracellular protein content. We then treated purified hemoglobin protein at physiological concentrations, which led to the formation of aggregates that could be observed using ion mobility mass spectrometry (IM–MS), size exclusion chromatography, and optical microscopy. The aggregates formed fibril-like structures as observed using atomic force microscopy. The formation of hemoglobin aggregates is hypothesized to be the result of new intermolecular interactions formed following the CAP-mediated protein oxidation. We studied the changes to hemoglobin structure after treatment with a CAP using high-resolution MS and found that the hemoglobin subunits are oxidized with the addition of at least 4 oxygen atoms each. The intact tetrameric hemoglobin structure remains unchanged; however, the monomeric and dimeric proteins adopt a more compact structure, as observed by IM–MS. We propose that CAP treatment of fresh blood leads to hemolysis, and that the extracellular protein, primarily hemoglobin, is oxidized leading to the formation of aggregates.
等离子体医学是一个利用大气低温等离子体产生的反应物进行消毒、血液凝固和癌症治疗等应用的领域。目前已有用于伤口愈合的商用等离子体设备，但有关这些等离子体诱导的化学变化的研究却很少。本研究探讨了血红蛋白暴露于氦等离子体介质阻挡放电时的化学变化，旨在解释其促进血液凝固和促进伤口愈合的潜在机制。对冷大气等离子体（CAP）处理过的全毛细血管血液进行光学显微镜观察，结果显示红细胞（RBC）体积增大，并形成了胭脂红结构。处理全血会导致红细胞溶血，并释放出细胞内的蛋白质成分。然后，我们以生理浓度处理纯化的血红蛋白，从而形成了可通过离子迁移质谱法（IM-MS）、尺寸排阻色谱法和光学显微镜观察到的聚集体。使用原子力显微镜可观察到聚集体形成纤维状结构。据推测，血红蛋白聚集体的形成是 CAP 介导的蛋白质氧化后形成的新的分子间相互作用的结果。我们利用高分辨率质谱研究了使用 CAP 处理后血红蛋白结构的变化，发现血红蛋白亚基被氧化，每个亚基至少增加了 4 个氧原子。完整的四聚体血红蛋白结构保持不变；然而，正如 IM-MS 所观察到的，单体和二聚体蛋白采用了更紧凑的结构。我们认为，CAP 处理新鲜血液会导致溶血，细胞外蛋白质（主要是血红蛋白）被氧化，从而形成聚集体。
{"title":"Oxidative aggregation of hemoglobin–a mechanism for low-temperature plasma-mediated wound healing","authors":"Irina Oganesyan, Alina Begley, Dušan Mrđenović, Julian A Harrison, Renato Zenobi","doi":"10.1088/1361-6463/ad6e99","DOIUrl":"https://doi.org/10.1088/1361-6463/ad6e99","url":null,"abstract":"Plasma medicine is a field that utilizes reactive species generated from atmospheric low-temperature plasmas for applications such as sterilization, blood coagulation, and cancer therapy. Commercial plasma devices are available for wound healing, but research on the chemical modifications induced by these plasmas is scarce. This study explores the chemical modifications in hemoglobin when exposed to a helium plasma dielectric barrier discharge, with the aim of explaining the potential mechanisms through which it contributes to blood coagulation and enhances wound healing. Optical microscopy of cold atmospheric plasma (CAP) treated whole capillary blood showed an increase in red blood cell (RBC) size and the formation of rouleaux structures. The treatment of whole blood leads to hemolysis of RBCs and the release of intracellular protein content. We then treated purified hemoglobin protein at physiological concentrations, which led to the formation of aggregates that could be observed using ion mobility mass spectrometry (IM–MS), size exclusion chromatography, and optical microscopy. The aggregates formed fibril-like structures as observed using atomic force microscopy. The formation of hemoglobin aggregates is hypothesized to be the result of new intermolecular interactions formed following the CAP-mediated protein oxidation. We studied the changes to hemoglobin structure after treatment with a CAP using high-resolution MS and found that the hemoglobin subunits are oxidized with the addition of at least 4 oxygen atoms each. The intact tetrameric hemoglobin structure remains unchanged; however, the monomeric and dimeric proteins adopt a more compact structure, as observed by IM–MS. We propose that CAP treatment of fresh blood leads to hemolysis, and that the extracellular protein, primarily hemoglobin, is oxidized leading to the formation of aggregates.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"20 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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