Arnaud Nanfak, Abdelmoumene Hechifa, Samuel Eke, Abdelaziz Lakehal, Charles Hubert Kom, Sherif S. M. Ghoneim
This contribution presents a two-step hybrid diagnostic approach, combining k-means clustering for subset formation, followed by subset analysis conducted by human experts. As the feature input vector has a significant influence on the performance of unsupervised machine learning algorithms, seven feature input vectors derived from traditional methods, including Duval pentagon method, Rogers ratio method, three ratios technique, Denkyoken method, ensemble gas characteristics method, Duval triangle method, and Gouda triangle method were explored for the subset formation stage. The seven proposed individual methods, corresponding to the seven feature input vectors, were implemented using a dataset of 595 DGA samples and tested on an additional 254 DGA samples. Furthermore, a combined technique based on a support vector machine was introduced, utilising the diagnostic results of the individual methods as input features. From training and testing, with diagnostic outcomes of 91.09% and 90.94%, the combined technique demonstrated the highest overall diagnostic accuracies. Using the IEC TC10 database, the diagnosis accuracies of the proposed diagnostic methods were compared to existing methods of literature. From the results obtained, the combined technique outperformed the proposed individual methods and existing methods used for comparison.
{"title":"A combined technique for power transformer fault diagnosis based on k-means clustering and support vector machine","authors":"Arnaud Nanfak, Abdelmoumene Hechifa, Samuel Eke, Abdelaziz Lakehal, Charles Hubert Kom, Sherif S. M. Ghoneim","doi":"10.1049/nde2.12088","DOIUrl":"10.1049/nde2.12088","url":null,"abstract":"<p>This contribution presents a two-step hybrid diagnostic approach, combining <i>k</i>-means clustering for subset formation, followed by subset analysis conducted by human experts. As the feature input vector has a significant influence on the performance of unsupervised machine learning algorithms, seven feature input vectors derived from traditional methods, including Duval pentagon method, Rogers ratio method, three ratios technique, Denkyoken method, ensemble gas characteristics method, Duval triangle method, and Gouda triangle method were explored for the subset formation stage. The seven proposed individual methods, corresponding to the seven feature input vectors, were implemented using a dataset of 595 DGA samples and tested on an additional 254 DGA samples. Furthermore, a combined technique based on a support vector machine was introduced, utilising the diagnostic results of the individual methods as input features. From training and testing, with diagnostic outcomes of 91.09% and 90.94%, the combined technique demonstrated the highest overall diagnostic accuracies. Using the IEC TC10 database, the diagnosis accuracies of the proposed diagnostic methods were compared to existing methods of literature. From the results obtained, the combined technique outperformed the proposed individual methods and existing methods used for comparison.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 3","pages":"175-187"},"PeriodicalIF":3.8,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12088","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141684788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Silicone rubber (SiR) is commonly used in reinforced insulation parts for high-voltage direct current (HVDC) cable accessories due to its excellent insulation, elasticity, and high-temperature resistance. HVDC cable accessories always suffer from the local electric field concentration due to the electrical conductivity mismatch between reinforced insulation and main insulation, which can ultimately lead to electric breakdown. The non-linear conductive composites based on SiR have the ability to adaptively adjust the distribution of the electric field in cable accessories. This is expected to solve the problem of localised electric field concentration. The zinc oxide (ZnO) and glycidyl methacrylate (GMA) are used as fillers and grafted modifier respectively to improve the non-linear electrical conductivity of ZnO/SiR-GMA composites. The results indicate that grafting GMA can increase electrical conductivity of SiR, while doping ZnO filler enables SiR to have non-linear conductivity characteristics. The combination of doping and grafting modification of the composites achieves excellent non-linear conductive properties at lower ZnO filler content. Additionally, the mechanical properties of the modified composites are enhanced. The simulation results indicate that ZnO/SiR-GMA is the most effective material for homogenising the electric field when used as reinforced insulation for cable intermediate joints.
硅橡胶(SiR)具有优异的绝缘性、弹性和耐高温性,因此常用于高压直流(HVDC)电缆附件的增强绝缘部件。由于增强绝缘和主绝缘之间的导电性能不匹配,高压直流电缆附件总是存在局部电场集中的问题,最终可能导致电气击穿。基于 SiR 的非线性导电复合材料能够自适应地调整电缆附件中的电场分布。这有望解决局部电场集中的问题。氧化锌(ZnO)和甲基丙烯酸缩水甘油酯(GMA)分别用作填料和接枝改性剂,以提高 ZnO/SiR-GMA 复合材料的非线性导电性。结果表明,接枝 GMA 可提高 SiR 的导电性,而掺杂 ZnO 填料可使 SiR 具有非线性导电特性。复合材料的掺杂和接枝改性相结合,可在较低的氧化锌填料含量下实现优异的非线性导电特性。此外,改性复合材料的机械性能也得到了提高。模拟结果表明,在用作电缆中间接头的增强绝缘材料时,ZnO/SiR-GMA 是均匀电场的最有效材料。
{"title":"Improvement in non-linear electrical conductivity of silicone rubber by incorporating zinc oxide fillers and grafting small polar molecules","authors":"Qingguo Chi, Huiyang Zhang, Zhaotong Meng, Changhai Zhang, Yongquan Zhang, Yue Zhang, Chao Yin, Tiandong Zhang","doi":"10.1049/nde2.12080","DOIUrl":"10.1049/nde2.12080","url":null,"abstract":"<p>Silicone rubber (SiR) is commonly used in reinforced insulation parts for high-voltage direct current (HVDC) cable accessories due to its excellent insulation, elasticity, and high-temperature resistance. HVDC cable accessories always suffer from the local electric field concentration due to the electrical conductivity mismatch between reinforced insulation and main insulation, which can ultimately lead to electric breakdown. The non-linear conductive composites based on SiR have the ability to adaptively adjust the distribution of the electric field in cable accessories. This is expected to solve the problem of localised electric field concentration. The zinc oxide (ZnO) and glycidyl methacrylate (GMA) are used as fillers and grafted modifier respectively to improve the non-linear electrical conductivity of ZnO/SiR-GMA composites. The results indicate that grafting GMA can increase electrical conductivity of SiR, while doping ZnO filler enables SiR to have non-linear conductivity characteristics. The combination of doping and grafting modification of the composites achieves excellent non-linear conductive properties at lower ZnO filler content. Additionally, the mechanical properties of the modified composites are enhanced. The simulation results indicate that ZnO/SiR-GMA is the most effective material for homogenising the electric field when used as reinforced insulation for cable intermediate joints.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 3","pages":"162-174"},"PeriodicalIF":3.8,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12080","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141120301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Arnaud Nanfak, Eke Samuel, Issouf Fofana, Fethi Meghnefi, Martial Gildas Ngaleu, Charles Hubert Kom
A key factor in ensuring the efficient and safe operation of power transformers is the early and accurate diagnosis of incipient faults. Among the tools available to achieve this goal, dissolved gas analysis (DGA) is widely used by power transformers' maintenance professionals. It is a preventive maintenance tool, used for condition monitoring, fault diagnosis and unplanned outage prevention. With the development of artificial intelligence (AI), many intelligent-based methods using AI tools have been proposed in the literature for DGA data interpretation. Although these methods achieve high diagnostic accuracies and improve DGA efficiency, they are generally complicated and the research documented in these publications is difficult to replicate. Traditional DGA-based methods are simple, easy to understand and implement, and widely used by power transformers' maintenance professionals. Many methods proposed in recent years overcome the limitations of the pioneer methods and are increasingly effective. The authors present a detailed and comprehensive literature review of the traditional DGA-based methods for mineral oil-immersed power transformer faults diagnosis. This review also addresses ways to improve the efficiency of the available traditional methods. Some pitfalls that need to be taken into account to improve the efficiency of the DGA-based diagnostic methods are also presented.
{"title":"Traditional fault diagnosis methods for mineral oil-immersed power transformer based on dissolved gas analysis: Past, present and future","authors":"Arnaud Nanfak, Eke Samuel, Issouf Fofana, Fethi Meghnefi, Martial Gildas Ngaleu, Charles Hubert Kom","doi":"10.1049/nde2.12082","DOIUrl":"10.1049/nde2.12082","url":null,"abstract":"<p>A key factor in ensuring the efficient and safe operation of power transformers is the early and accurate diagnosis of incipient faults. Among the tools available to achieve this goal, dissolved gas analysis (DGA) is widely used by power transformers' maintenance professionals. It is a preventive maintenance tool, used for condition monitoring, fault diagnosis and unplanned outage prevention. With the development of artificial intelligence (AI), many intelligent-based methods using AI tools have been proposed in the literature for DGA data interpretation. Although these methods achieve high diagnostic accuracies and improve DGA efficiency, they are generally complicated and the research documented in these publications is difficult to replicate. Traditional DGA-based methods are simple, easy to understand and implement, and widely used by power transformers' maintenance professionals. Many methods proposed in recent years overcome the limitations of the pioneer methods and are increasingly effective. The authors present a detailed and comprehensive literature review of the traditional DGA-based methods for mineral oil-immersed power transformer faults diagnosis. This review also addresses ways to improve the efficiency of the available traditional methods. Some pitfalls that need to be taken into account to improve the efficiency of the DGA-based diagnostic methods are also presented.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 3","pages":"97-130"},"PeriodicalIF":3.8,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12082","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140675766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Self-healing polyurethane diacrylate (PUDA) composites with outstanding thermal conductivity were prepared with variable boron nitride (BN) and a small number of graphene nanoplatelets (GNPs) (1 wt%). The thermal conductivity of PUDA composites containing 1 wt% GNPs and 29 wt% BN reached 1.73 W/(m·K), showing 27.2% increment compared to PUDA composites only with 30 wt% BN. BN and GNPs mutually promoted the dispersion in the PUDA matrix, and the small number of GNPs was enough to bridge the gaps between BN, so that GNPs and BN exerted a synergistic enhancement effect on the thermal conductivity of PUDA composites with a synergistic efficiency of 1.343. The PUDA composites maintained the tensile strength of 8.21 MPa with good electrical insulation (4.55 × 109 Ω cm). The high degrees of recovery of mechanical strength (>90%) and thermal conductivities (>84%) were also realised by the healing effect of the reversible DA reaction. The PUDA composites with excellent comprehensive properties show broad application potential in the thermal management of electronic devices.
{"title":"Enhanced thermal conductivity and self-healing property of PUDA/boron nitride micro-sheets composites with a small number of graphene nano-platelets","authors":"Shiyu Zhang, Zhihui Shang, Dongliang Ding, Xu Wang, Ya Wu, Shifeng Nian, Zhenguo Liu, Qiuyu Zhang, Yanhui Chen","doi":"10.1049/nde2.12073","DOIUrl":"10.1049/nde2.12073","url":null,"abstract":"<p>Self-healing polyurethane diacrylate (PUDA) composites with outstanding thermal conductivity were prepared with variable boron nitride (BN) and a small number of graphene nanoplatelets (GNPs) (1 wt%). The thermal conductivity of PUDA composites containing 1 wt% GNPs and 29 wt% BN reached 1.73 W/(m·K), showing 27.2% increment compared to PUDA composites only with 30 wt% BN. BN and GNPs mutually promoted the dispersion in the PUDA matrix, and the small number of GNPs was enough to bridge the gaps between BN, so that GNPs and BN exerted a synergistic enhancement effect on the thermal conductivity of PUDA composites with a synergistic efficiency of 1.343. The PUDA composites maintained the tensile strength of 8.21 MPa with good electrical insulation (4.55 × 10<sup>9</sup> Ω cm). The high degrees of recovery of mechanical strength (>90%) and thermal conductivities (>84%) were also realised by the healing effect of the reversible DA reaction. The PUDA composites with excellent comprehensive properties show broad application potential in the thermal management of electronic devices.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 3","pages":"150-161"},"PeriodicalIF":3.8,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12073","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140221894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High conductivity loss and low breakdown strength of traditional polypropylene (PP) film in the high-temperature environment are the key factors limiting the application of metallised film capacitors (MFCs). The effect of cyclic olefin copolymers (COCs) with different glass transition temperatures (Tgs) on the dielectric performance of PP/COC composites at high temperature are studied. The results showed that the addition of COC enhanced the intermolecular interaction force, which led to the reduction of defects in the films. In addition, COC with high Tg inhibits the movement of molecular chains and enhances the thermal stability of the film, which limits the transport of carriers at high temperatures. The conductivity and breakdown strength of the modified films (with a Tg of 134°C for COC) at 125°C are 91.6% lower and 45.7% higher, respectively, than that of pure PP. This method shows great potential in improving the dielectric properties of PP at high temperatures.
{"title":"Improving the dielectric properties of polypropylene for metallised film capacitors based on cyclic olefin copolymer blending","authors":"Meng Xiao, Mengdie Zhang, Boxue Du, Kailun Fan","doi":"10.1049/nde2.12072","DOIUrl":"10.1049/nde2.12072","url":null,"abstract":"<p>High conductivity loss and low breakdown strength of traditional polypropylene (PP) film in the high-temperature environment are the key factors limiting the application of metallised film capacitors (MFCs). The effect of cyclic olefin copolymers (COCs) with different glass transition temperatures (Tgs) on the dielectric performance of PP/COC composites at high temperature are studied. The results showed that the addition of COC enhanced the intermolecular interaction force, which led to the reduction of defects in the films. In addition, COC with high Tg inhibits the movement of molecular chains and enhances the thermal stability of the film, which limits the transport of carriers at high temperatures. The conductivity and breakdown strength of the modified films (with a Tg of 134°C for COC) at 125°C are 91.6% lower and 45.7% higher, respectively, than that of pure PP. This method shows great potential in improving the dielectric properties of PP at high temperatures.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 3","pages":"140-149"},"PeriodicalIF":3.8,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12072","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140252647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Film capacitors are playing an increasingly important role in power-related fields, driven by the continuous development of dielectric materials and practical needs. Long-term accumulation has also led to an increasing wealth of data related to film capacitors. Sonification opens up a new way for people to make good use of data from film capacitors. A framework for sonifying film capacitors data based on TwoTone is presented. Based on the analysis and discussion, it is clear that the sonification results can easily represent the monotonic variation pattern of film capacitors data. What's more, the sonification results increase the possibility that people pay attention to the changing trend of film capacitors data when there is no significant difference in the visual perception of the data. In addition to providing a new way of music generation of electrical equipment, the method proposed is expected to contribute to theory reference in typical scenarios, such as factory calibration of film capacitors, monitoring of film capacitor operation status, and presentation of statistical data of film capacitors' dielectric materials, which will help us to better understand the distribution characteristics of polymer films.
{"title":"Data sonification of film capacitors","authors":"Yong-Xin Zhang, Di-Fan Liu, Xin-Yi Wei, Xin-Jie Wang, Fang-Yi Chen, Qi-Kun Feng, Wen-Yuan Cao, Wen-Zhuo Dong, Faisal Mehmood Shah, Yu-Xiao Liu, Zhi-Yuan Wu, Jian-Tao Wang, Shao-Long Zhong, Zhi-Min Dang","doi":"10.1049/nde2.12078","DOIUrl":"10.1049/nde2.12078","url":null,"abstract":"<p>Film capacitors are playing an increasingly important role in power-related fields, driven by the continuous development of dielectric materials and practical needs. Long-term accumulation has also led to an increasing wealth of data related to film capacitors. Sonification opens up a new way for people to make good use of data from film capacitors. A framework for sonifying film capacitors data based on TwoTone is presented. Based on the analysis and discussion, it is clear that the sonification results can easily represent the monotonic variation pattern of film capacitors data. What's more, the sonification results increase the possibility that people pay attention to the changing trend of film capacitors data when there is no significant difference in the visual perception of the data. In addition to providing a new way of music generation of electrical equipment, the method proposed is expected to contribute to theory reference in typical scenarios, such as factory calibration of film capacitors, monitoring of film capacitor operation status, and presentation of statistical data of film capacitors' dielectric materials, which will help us to better understand the distribution characteristics of polymer films.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 2","pages":"88-95"},"PeriodicalIF":2.7,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12078","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140077412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Song Gao, Liwei Wang, Jingtong Lu, Shuai Zhang, Hongyu Sun, Kai Huang, Jianchun Xu, Yanan Hao
Mechanical antennas have garnered considerable attention due to their ability to address the challenges posed by the significant size and high energy consumption associated with traditional electric antennas when operating at low frequencies. Here, a compact and structurally stable mechanical antenna design is presented. The proposed antenna is constructed using cylindrical piezoelectric ceramics, which have dimensions smaller than 1/1000 of the wavelength. The scrutiny of the influence exerted by the antenna feed area and material thickness on the radiation performance was undertaken, followed by an exhaustive discourse on these effects. Experimental measurements demonstrate the practical functionalities of signal coding, transmission, and reception in the low-frequency communication system. Notably, at a frequency of 288 kHz, a single proposed antenna achieves an effective information transmission distance of 60 m using binary information coding. This remarkable outcome underscores the potential of this design in facilitating the development of portable and cost-effective wireless communication equipment for low-frequency applications.
{"title":"Electromagnetic optimization of piezoelectric ceramic and its application in mechanical antenna","authors":"Song Gao, Liwei Wang, Jingtong Lu, Shuai Zhang, Hongyu Sun, Kai Huang, Jianchun Xu, Yanan Hao","doi":"10.1049/nde2.12077","DOIUrl":"10.1049/nde2.12077","url":null,"abstract":"<p>Mechanical antennas have garnered considerable attention due to their ability to address the challenges posed by the significant size and high energy consumption associated with traditional electric antennas when operating at low frequencies. Here, a compact and structurally stable mechanical antenna design is presented. The proposed antenna is constructed using cylindrical piezoelectric ceramics, which have dimensions smaller than 1/1000 of the wavelength. The scrutiny of the influence exerted by the antenna feed area and material thickness on the radiation performance was undertaken, followed by an exhaustive discourse on these effects. Experimental measurements demonstrate the practical functionalities of signal coding, transmission, and reception in the low-frequency communication system. Notably, at a frequency of 288 kHz, a single proposed antenna achieves an effective information transmission distance of 60 m using binary information coding. This remarkable outcome underscores the potential of this design in facilitating the development of portable and cost-effective wireless communication equipment for low-frequency applications.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 1","pages":"1-6"},"PeriodicalIF":2.7,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12077","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139615665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sandeep Sanjeeva, Jyothilakshmi Rudresh, K. B. Vinayakumar, K. K. Nagaraja
Growing and controlling the c-axis orientation of the aluminium nitride (AlN) thin film on unheated Si (111) substrates using reactive magnetron sputtering are challenging. Sputtering parameters such as nitrogen concentration and sputtering power were effectively tuned to grow the c-axis oriented AlN thin film. The results show that a low concentration of (25%) N2 is enough for forming AlN at a reduced flow rate, whereas a higher flow rate requires a higher concentration of N2. Low concentration with a low flow rate is preferred to grow AlN at low temperature and power. The poor crystallinity of AlN with (100) orientation was improved by varying the power from 75 to 175 W. The X-ray diffraction results confirmed the improvisation of crystallinity of grown AlN films and indicated the strong dependence of preferred c-axis orientation on sputtering power. Also, the dependence of sputtering power on microstrain and stress was analysed. The surface morphology study by field emission scanning electron microscopy and topography measured by an atomic force microscope shows a dependence on sputtering power. The high c-axis orientation was observed at 175 W with low surface roughness, low leakage current density (2 × 10−9 A/cm2) and low dielectric constant (6.8).
利用反应磁控溅射技术在未加热的硅(111)基板上生长和控制氮化铝(AlN)薄膜的 c 轴取向是一项挑战。我们对氮浓度和溅射功率等溅射参数进行了有效调整,以生长出 c 轴取向的氮化铝薄膜。结果表明,低浓度(25%)的氮气足以在较低的流速下形成氮化铝,而较高的流速则需要较高浓度的氮气。要在低温和低功率条件下生长氮化铝,最好采用低浓度和低流速。X 射线衍射结果证实了生长的 AlN 薄膜结晶度的提高,并表明优先 c 轴取向与溅射功率密切相关。此外,还分析了溅射功率对微应变和应力的影响。通过场发射扫描电子显微镜进行的表面形貌研究和原子力显微镜测量的形貌显示了对溅射功率的依赖性。在表面粗糙度低、漏电流密度低(2 × 10-9 A/cm2)和介电常数低(6.8)的情况下,175 W 时观察到高 c 轴取向。
{"title":"A strong dependence of sputtering power on c-axis oriented aluminium nitride on Si (111): A structural and electrical study","authors":"Sandeep Sanjeeva, Jyothilakshmi Rudresh, K. B. Vinayakumar, K. K. Nagaraja","doi":"10.1049/nde2.12076","DOIUrl":"10.1049/nde2.12076","url":null,"abstract":"<p>Growing and controlling the c-axis orientation of the aluminium nitride (AlN) thin film on unheated Si (111) substrates using reactive magnetron sputtering are challenging. Sputtering parameters such as nitrogen concentration and sputtering power were effectively tuned to grow the <i>c</i>-axis oriented AlN thin film. The results show that a low concentration of (25%) N<sub>2</sub> is enough for forming AlN at a reduced flow rate, whereas a higher flow rate requires a higher concentration of N<sub>2</sub>. Low concentration with a low flow rate is preferred to grow AlN at low temperature and power. The poor crystallinity of AlN with (100) orientation was improved by varying the power from 75 to 175 W. The X-ray diffraction results confirmed the improvisation of crystallinity of grown AlN films and indicated the strong dependence of preferred <i>c</i>-axis orientation on sputtering power. Also, the dependence of sputtering power on microstrain and stress was analysed. The surface morphology study by field emission scanning electron microscopy and topography measured by an atomic force microscope shows a dependence on sputtering power. The high <i>c</i>-axis orientation was observed at 175 W with low surface roughness, low leakage current density (2 × 10<sup>−9</sup> A/cm<sup>2</sup>) and low dielectric constant (6.8).</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 1","pages":"7-17"},"PeriodicalIF":2.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12076","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polyvinylidene fluoride-based ferroelectric polymers are favoured in the field of advanced high-energy-storage dielectric capacitors due to their strong spontaneous polarisation and high dielectric constant (εr). It has been confirmed that the ferroelectric behaviour and energy storage performance can be regulated by copolymerising polyvinylidene fluoride with bulky monomers such as chlorotrifluoroethylene, and hexafluoropropylene. Past research based on these copolymers mostly focused on the preparation of composites, yet with limited discussion on the effect of copolymer composition. In this work, a series of P(VDF-CTFE) films with different chlorotrifluoroethylene contents were fabricated through a solution-casting method. The introduction of bulky chlorotrifluoroethylene units can tune the polymer crystal structure and crystallinity, alter the state of polymer chains and the response of dipoles to electric fields, and lead to dramatic changes in dielectric properties, breakdown strength (Eb), and energy storage density (Ue). As a result, the copolymer with a chlorotrifluoroethylene content of 15 wt% obtained the best overall performance, and the Ue reached 16.73 J/cm3 at 650 kV/mm. This work provides a basis for the optimisation of the properties of polyvinylidene fluoride-based ferroelectric polymers and the development of high Ue dielectric.
{"title":"The effects of chlorotrifluoroethylene (CTFE) units on the dielectric and energy storage properties of P(VDF-CTFE)","authors":"Haoran Xie, Xi Yuan, Hang Luo, Dou Zhang","doi":"10.1049/nde2.12075","DOIUrl":"10.1049/nde2.12075","url":null,"abstract":"<p>Polyvinylidene fluoride-based ferroelectric polymers are favoured in the field of advanced high-energy-storage dielectric capacitors due to their strong spontaneous polarisation and high dielectric constant (<i>ε</i><sub>r</sub>). It has been confirmed that the ferroelectric behaviour and energy storage performance can be regulated by copolymerising polyvinylidene fluoride with bulky monomers such as chlorotrifluoroethylene, and hexafluoropropylene. Past research based on these copolymers mostly focused on the preparation of composites, yet with limited discussion on the effect of copolymer composition. In this work, a series of P(VDF-CTFE) films with different chlorotrifluoroethylene contents were fabricated through a solution-casting method. The introduction of bulky chlorotrifluoroethylene units can tune the polymer crystal structure and crystallinity, alter the state of polymer chains and the response of dipoles to electric fields, and lead to dramatic changes in dielectric properties, breakdown strength (<i>E</i><sub>b</sub>), and energy storage density (<i>U</i><sub>e</sub>). As a result, the copolymer with a chlorotrifluoroethylene content of 15 wt% obtained the best overall performance, and the <i>U</i><sub>e</sub> reached 16.73 J/cm<sup>3</sup> at 650 kV/mm. This work provides a basis for the optimisation of the properties of polyvinylidene fluoride-based ferroelectric polymers and the development of high <i>U</i><sub>e</sub> dielectric.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 1","pages":"18-25"},"PeriodicalIF":2.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12075","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu-Huai Wang, Zhuo Chen, Jin Li, Zhi-Xiang Liu, Rong Chen, Hein Htet Aung, Hu-Cheng Liang, Bo-Xue Du
A flexible smart coating with electroluminescence effect was designed and fabricated on the surface of gas insulated switch gear (GIS)/gas insulated transmission line (GIL) epoxy insulators based on two-step curing process. As the AC voltage increases, the luminous area on the insulator surface expands from the centre to the periphery, and the light intensity shows a linear relationship with the applied voltage. Besides, the flexible smart coating can effectively identify the location of metal particle defects and the degree of electric field distortion. The flexible smart coating enhances the surface flashover voltage due to its higher dielectric constant. Simultaneously, metal particle contamination can substantially reduce the insulation performance of epoxy insulators, particularly when they are located near the high-voltage side. It is hoped that this study can provide a reference for the smart detection of surface defects GIS/GIL basin insulators.
{"title":"Flexible smart surface coating for GIS/GIL epoxy insulators","authors":"Yu-Huai Wang, Zhuo Chen, Jin Li, Zhi-Xiang Liu, Rong Chen, Hein Htet Aung, Hu-Cheng Liang, Bo-Xue Du","doi":"10.1049/nde2.12074","DOIUrl":"10.1049/nde2.12074","url":null,"abstract":"<p>A flexible smart coating with electroluminescence effect was designed and fabricated on the surface of gas insulated switch gear (GIS)/gas insulated transmission line (GIL) epoxy insulators based on two-step curing process. As the AC voltage increases, the luminous area on the insulator surface expands from the centre to the periphery, and the light intensity shows a linear relationship with the applied voltage. Besides, the flexible smart coating can effectively identify the location of metal particle defects and the degree of electric field distortion. The flexible smart coating enhances the surface flashover voltage due to its higher dielectric constant. Simultaneously, metal particle contamination can substantially reduce the insulation performance of epoxy insulators, particularly when they are located near the high-voltage side. It is hoped that this study can provide a reference for the smart detection of surface defects GIS/GIL basin insulators.</p>","PeriodicalId":36855,"journal":{"name":"IET Nanodielectrics","volume":"7 1","pages":"26-32"},"PeriodicalIF":2.7,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1049/nde2.12074","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139391328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}