Vacuum最新文献

{"title":"Enhancement of the quality of mc-Si ingot grown by vacuum directional solidification furnace with growth rate increase reducing the cost of the wafer for PV application: Carbon and oxygen analysis","authors":"Sugunraj Sekar ,&nbsp;Srinivasan Manickam ,&nbsp;Ramasamy Perumalsamy","doi":"10.1016/j.vacuum.2024.113816","DOIUrl":"10.1016/j.vacuum.2024.113816","url":null,"abstract":"<div><div>In this paper, we propose a numerical model to investigate the dissolution of oxygen atoms from the porous silica crucible, SiO gas formation, back diffusion of CO gas and segregation of carbon and oxygen during the growth of multi-crystalline silicon (mc-Si) by vacuum directional solidification (VDS) at different growth rates (3, 6 and 9 mm/h) by silt valve opening rate. The dissolution of oxygen decreases during the rapid growth of ingot because the reaction between the molten silicon and the porous silica crucible is constrained. This limitation on oxygen dissolution from the porous silica crucible further diminishes chemical reaction inside the VDS furnace. Consequently, the segregation pattern of the carbon and oxygen is affected at higher growth rate. During the VDS mc-Si growth, a growth rate of 9mm/h yields better quality of the VDS grown mc-Si ingots compared to other growth rates, this rate reduces SiC precipitation and SiO₂ cluster formation due to lower concentration of carbon and oxygen. The obtained carbon concentration minimizes the wire saw defects. Based on these numerical results (9 mm/h), we have implemented experimental work. Prepared samples are analyzed using FTIR spectra and minority carrier lifetime measurements. The effect of oxygen concentration in the samples is analyzed in the minority carrier lifetime measurements. The oxygen and carbon concentrations are calculated by FTIR spectra and their results are compared with the numerical simulation.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113816"},"PeriodicalIF":3.8,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decay of secondary electron yield of MgO–Au composite film at different incident electron energies","authors":"Zhangcong Xia ,&nbsp;Yunrong Wang ,&nbsp;Guofeng Liu ,&nbsp;Tao Deng ,&nbsp;Haodong Wang ,&nbsp;Jie Li ,&nbsp;Wenbo Hu ,&nbsp;Shengli Wu ,&nbsp;Xin Zhong","doi":"10.1016/j.vacuum.2024.113789","DOIUrl":"10.1016/j.vacuum.2024.113789","url":null,"abstract":"<div><div>The relationship between the incident electron energy and secondary electron yield (SEY) decay of MgO–Au composite film was investigated by the designed comparison experiments. Besides the incident current and the properties of the film, the SEY value and the incident electron energy were found to be the other two key factors affecting the SEY decay rate. The value of SEY and the incident electron energy have opposite influences on the SEY decay rate, which makes it necessary to analyze the curve of incident electron energy versus SEY decay rate by dividing it into three parts. In addition, the empirical formulas for SEY decay were derived from experimental data, enabling the estimation of the SEY and decay rate of the MgO–Au composite film at any moment during SEY decay. Furthermore, the cause of SEY decay was also analyzed based on the relationship between incident electron energy and the SEY decay rate. The thermal dissipation, surface roughness, and deposition of contaminants were proven not to be the determinants of SEY decay. The experiment results in this paper supported the inference that the charging effect was the primary cause of SEY decay.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113789"},"PeriodicalIF":3.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Changes in electronic structure within NiSx (0.60 < x < 1.53) compound series","authors":"Saroj Dahal,&nbsp;Dhan Rana,&nbsp;Boris Sinkovic","doi":"10.1016/j.vacuum.2024.113806","DOIUrl":"10.1016/j.vacuum.2024.113806","url":null,"abstract":"<div><div>In this article, changes in electronic properties of NiS_<em>x</em> series of films with different sulfur content (<em>x</em> = <em>S/Ni</em>) are studied using X-ray (XPS) and ultra-violet (UPS) photoelectron spectroscopy techniques. NiS_<em>x</em> (0.60 <em>&lt; x &lt;</em> 1.53) films are synthesized on native oxide of Si(111) substrates via reactive deposition of Ni and S in an ultra-high vacuum chamber by varying the sulfur pressures and substrate temperatures. The binding energy (BE) of Ni2<em>p</em>_3<em>/</em>2 core level, the separation between the Ni2<em>p</em>_3<em>/</em>2 main peaks and satellite peaks, and the Ni3<em>d</em> valence band binding energies are all found to vary nearly linearly with the sulfur content in NiS_x series of compounds, suggesting a direct dependence of Ni electronic charge on the sulfur content. The shift of the Ni3d and S3p states (to higher and lower BE, respectively) with an increase in the S content provides experimental confirmation of the theoretical prediction previously reported (Wen et al., 2020) [1]. All NiS_<em>x</em> films showed density of states (DOS) at the Fermi level, indicating their metallic nature. The Ni2<em>p</em>_3<em>/</em>2 binding energy shift of NiS_<em>x</em> films are much smaller than that of oxide-based compounds, confirming the significantly more covalent nature of the sulfides. NiS_x film grown on Si (111) substrate showed nickel silicide interface formation. This study provides information on the growth and trends in the electronic properties of NiS_<em>x</em> relevant for their applications in catalysis, energy storage, and electronic devices.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113806"},"PeriodicalIF":3.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Baric exothermic fragmentation of crystals","authors":"Mahach N. Magomedov","doi":"10.1016/j.vacuum.2024.113814","DOIUrl":"10.1016/j.vacuum.2024.113814","url":null,"abstract":"<div><div>Currently, an extensive study of the properties of matter at high pressures is underway. However, little attention is paid to the baric fragmentation of the crystal. Our work is devoted to the study of the nature of this effect. Based on the analytical method (i.e. without computer simulation), the change in the specific (per unit area) surface energy (σ) of the crystal from the normalized volume (<em>v</em>/<em>v</em>_o) along various isotherms was studied. It is shown that there is a maximum on the isotherm σ(<em>v</em>/<em>v</em>_o), with (<em>v</em>/<em>v</em>_o)_max &lt; 1. With an isothermal deviation (at decreasing or increasing) of the <em>v</em>/<em>v</em>_o value from the (<em>v</em>/<em>v</em>_o)_max, the σ(<em>v</em>/<em>v</em>_o) function decreases, passing at certain values, (<em>v</em>/<em>v</em>_o)_<em>frS</em> &lt; (<em>v</em>/<em>v</em>_o)_max &lt; 1 or (<em>v</em>/<em>v</em>_o)_<em>frL</em> &gt; 1, to the negative values. This behavior of the σ(<em>v</em>/<em>v</em>_o) function at <em>v</em>/<em>v</em>_o &lt; (<em>v</em>/<em>v</em>_o)_<em>frS</em> or <em>v</em>/<em>v</em>_o &gt; (<em>v</em>/<em>v</em>_o)_<em>frL</em> should cause spontaneous fragmentation of the crystal, in which the crystal will strive in any way to increase its specific (per atom) surface: either free (when stretched), or intercrystalline (when compressed). It is indicated that the crystal under all-round stretching passes into the liquid or gas phase without reaching the (<em>v</em>/<em>v</em>_o)_<em>frL</em> value. However, a negative value of the surface energy can be achieved with all-round compression of the crystal. It is shown that the negative value of the σ(<em>v</em>/<em>v</em>_o) function should stimulate both fragmentation of the crystal structure and heating of the fragmenting medium (exothermic effect) and the appearance of additional pressure in this medium due to the appearance of the inner surface. Calculations of (<em>v</em>/<em>v</em>_o)_max and (<em>v</em>/<em>v</em>_o)_<em>frS</em> values for Ne, Li and Au crystals at different temperatures have been performed. Based on the experimental data, the pressures are indicated, which correspond to the calculated (<em>v</em>/<em>v</em>_o)_<em>frS</em> values. It was shown that these static pressures are quite achievable in modern experiments.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113814"},"PeriodicalIF":3.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of B/N dual doping on mechanical and tribological properties of Mo-S-B-N sputtered films","authors":"Ningxin Wei ,&nbsp;Hang Li ,&nbsp;Jianliang Li ,&nbsp;Jiewen Huang ,&nbsp;Jian Kong ,&nbsp;Qiujie Wu ,&nbsp;Huaping Tan ,&nbsp;Yan Shi ,&nbsp;Dangsheng Xiong","doi":"10.1016/j.vacuum.2024.113803","DOIUrl":"10.1016/j.vacuum.2024.113803","url":null,"abstract":"<div><div>Doping with non-metal element is effective to improve the porous morphology and enhance the mechanical and tribological properties of transition metal dichalcogenides (TMDs) based film. However, the mechanical properties of TMDs based film with single additive should be enhanced further for better wear resistance. In this work, B/N dual-doping was used to further enhance the deformation resistance and toughness of MoS₂ based films deposited by magnetron sputtering, while the effect of B/N dopants on the structure, mechanical and tribological properties has been investigated. Mo-S-B-N film with B content of 20.91 at. % and N content of 18.13 at. % consists of MoS₂ and amorphous nitride/boride, in which B/N dual doping film forms a higher ordered MoS₂ lamellar structure compared to B doping film. With a hardness of 11.6 ± 0.9 GPa and improved toughness, the film achieves a low wear rate and average friction coefficient is achieved. Comparing B/N dual doping film to B doping film, the stable formation of tribolayer with more strengthened deformation resistance results in the steady friction and the improved wear resistance, while the limited TMDs reorientation leads to the slight increase of friction coefficient.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113803"},"PeriodicalIF":3.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ordered mesoporous CrCeOx catalyst prepared by hard template for toluene and formaldehyde combustion","authors":"Minghui Guo,&nbsp;Bao Tian,&nbsp;Limin Si,&nbsp;Xinying Zhang,&nbsp;Yunsheng Xia","doi":"10.1016/j.vacuum.2024.113811","DOIUrl":"10.1016/j.vacuum.2024.113811","url":null,"abstract":"<div><div>The <em>meso</em>-Cr-Ce catalysts with different proportions of chromium and cerium were prepared using three-dimensional ordered mesoporous silica (KIT-6) as hard template by vacuum assisted impregnation method. The physicochemical properties of the catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen adsorption-desorption (BET), transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and temperature programmed reduction (TPR) techniques. The oxidation removal performance of toluene and formaldehyde was evaluated. The results show that all catalysts have better catalytic oxidation activity than the bulk counterpart. The <em>meso</em>-Cr-Ce-1 catalyst of same Cr/Ce molar ratio was larger in surface area (up to 186 m²/g) and could be reduced at lower temperatures, and exhibited the highest catalytic oxidation performance. At 30,000 h⁻¹ of space velocity and 1000 ppm of VOC, toluene and formaldehyde conversions reached 90 % at 240 and 160 °C, respectively, and the apparent activation energies were 64.1 and 37.2 kJ/mol. The excellent performance of the catalyst is associated with its well-developed mesoporous structure, high specific surface area, good low temperature reducibility and dispersion and synergistic effect of active components.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113811"},"PeriodicalIF":3.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MoS2 stabilize Ti3C2 MXene for excellent catalytic effect of thermal decomposition of ammonium perchlorate","authors":"Zhehong Lu ,&nbsp;Jingyi Li ,&nbsp;Binxin Li ,&nbsp;Ruixuan Yuan ,&nbsp;Guolin Cao ,&nbsp;Shaoliang Guan ,&nbsp;Wei Jiang ,&nbsp;Jie Zhu","doi":"10.1016/j.vacuum.2024.113812","DOIUrl":"10.1016/j.vacuum.2024.113812","url":null,"abstract":"<div><div>Ammonium perchlorate (AP), the most widely used oxidizer in energetic materials, is crucial for studying catalytic thermal decomposition. Newly discovered Ti₃C₂ MXene and MoS₂ demonstrating promising prospects in the field of the pyrolysis catalyst in AP. In this study, we employed a hydrothermal method to anchor nano-sized MoS₂ in situ on the surface of Ti₃C₂ MXene, leading to the fabrication of MoS₂-Ti₃C₂ nanocomposites. Various characterizations indicated that MoS₂ was attached to the surface and edges of Ti₃C₂, thereby enhancing the stability and conductivity. Results revealed that upon the addition of 4 wt% MoS₂-Ti₃C₂, the low-temperature decomposition peak of AP reduced from 331.2 °C to 296.6 °C, while the high-temperature decomposition peak advanced from 427.5 °C to 387.1 °C, showing a superior catalytic effect compared to the individual MoS₂ or Ti₃C₂. Additionally, the catalytic mechanism of MoS₂-Ti₃C₂ on the thermal decomposition of AP may involve enhanced electrical conductivity, facilitating rapid proton transfer (H⁺), accelerated redox reactions, prompt release of gas products, and thereby expediting the progression of the decomposition reaction. Consequently, it can be anticipated that anchoring MoS₂ on the surface of Ti₃C₂ represents an effective strategy for enhancing the catalytic activity of Ti₃C₂ MXene towards the thermal decomposition of AP.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113812"},"PeriodicalIF":3.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomic layer deposition of tin monosulfide thin film using Sn(acac)2 and H2S","authors":"Dowwook Lee ,&nbsp;Hyeongtag Jeon","doi":"10.1016/j.vacuum.2024.113808","DOIUrl":"10.1016/j.vacuum.2024.113808","url":null,"abstract":"<div><div>In this study, we deposited tin monosulfide (SnS) thin film using Tin(II) 2,4-pentanedionate [Sn(acac)2] precursor and hydrogen sulfide (H2S) reactant. And we performed post annealing to improve the crystallinity of SnS thin films. The process window was 130 °C–150 °C, and the growth rate was 0.34 Å/cycle. To investigate crystallinity and the phase of SnS thin films, grazing incidence x-ray diffraction (GI-XRD) and Raman spectroscopy were performed. SnS thin films showed a single orthorhombic phase after annealing. In addition, transmission electron microscopy (TEM) was utilized to confirm the two-dimensional (2D) layered structure of SnS thin films. Post-annealed SnS thin film clearly showed a 2D layered structure. X-ray photoelectron spectroscopy (XPS) was performed to confirm the bonding state of the thin film. The results indicated that the SnS thin film only shows binding energies corresponding to the oxidation states of Sn²⁺ in the Sn 3d spectra and S^2- in the S 2p spectra. Ultraviolet–visible (UV–vis) spectroscopy and ultraviolet photoelectron spectroscopy (UPS) were performed to confirm the optical properties and to calculate the band structure of the thin film. All of SnS thin film showed a p-type characteristic. The post-annealed SnS thin films exhibited better electric properties, confirmed by Hall measurement.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113808"},"PeriodicalIF":3.8,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fracture behavior, mechanical properties, and microstructural analysis of vacuum automated GMAW welded dissimilar A353 and A516 steels for pressure vessels","authors":"Song Zhao ,&nbsp;Zhe Wu ,&nbsp;Zhongbin Wei ,&nbsp;Shoufa Liu ,&nbsp;Guangfan Hu","doi":"10.1016/j.vacuum.2024.113773","DOIUrl":"10.1016/j.vacuum.2024.113773","url":null,"abstract":"<div><div>In this study, the performance of the automatic gas metal arc welding (GMAW) process in vacuum for similar and dissimilar joints of A353 and A516 steel plates with different thicknesses was intensively evaluated. Fracture of all vacuum-welded samples occurred in the heat-affected zone (HAZ) of A516 steel, highlighting the significant influence of HAZ microstructure and width on the cryogenic impact energy and strength of these joints. According to microscopic observations and impact tests, the fractures were fully ductile for notches in the weld and A353 HAZ, where dimples were observed on the fracture surfaces and the impact energy exceeded 50 J. This ductile behavior is particularly significant for notches in the weld due to the presence of a vacuum during welding prevents the formation of gas voids and oxide and hydride compounds that are normally the origin of cracks. However, for notches in the A516 HAZ, where the cleavage faces were observed on the fracture surfaces and the impact energy was less than 30 J, the fractures were quite brittle. For dissimilar vacuum-welded samples, the impact energy and fracture type for notches in the weld and A353 HAZ were nearly the same as those in similar A353 joints. However, for notches in the A516 HAZ, the impact energy and fracture type were close to those observed in the A516 joints. Yield strength and ultimate tensile strength (UTS) of A353-A353 non-vacuum-welded samples compared to vacuum-welded samples decreased by more than 78 % and 40 %, respectively. As well as, yield strengths and UTSs of A516-A516 non-vacuum samples compared to vacuum samples decreased by more than 34 % and 4 %, respectively. On the other side, the impact samples with a notch position in the weld suffered brittle fracture instead of ductile fracture because their impact energy decreased by about 40 %.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"232 ","pages":"Article 113773"},"PeriodicalIF":3.8,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and zero-dimensional simulation study of an embedded bismuth LaB6 hollow cathode","authors":"Dongsheng Cai ,&nbsp;Pingyang Wang ,&nbsp;Zhiwei Hua","doi":"10.1016/j.vacuum.2024.113807","DOIUrl":"10.1016/j.vacuum.2024.113807","url":null,"abstract":"<div><div>Experiments and zero-dimensional simulation were conducted to evaluate the discharge performance of an embedded bismuth LaB₆ hollow cathode. The experimental results demonstrate that the embedded bismuth hollow cathode can operate in diode mode without any external heating, with a mass flow rate of approximately 0.21 mg/s. In Keeper-cathode mode, the discharge voltage for bismuth was slightly lower than that of xenon and exhibited strong stability, with a maximum discharge variation of less than 0.5 V at a discharge current of 2 A. The simulation results showed that at the same mass flow rate, the electron and ion densities in the insert region of the bismuth hollow cathode were higher than those of xenon, whereas the opposite was true for the orifice region. Notably, at discharge currents below 4 A, the power deposition of bismuth in both the insert and orifice regions was lower than that of xenon, indicating reduced erosion.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"231 ","pages":"Article 113807"},"PeriodicalIF":3.8,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}