BN

BN
  • 文章类型: Journal Article
    尽管已经做出了巨大的努力来通过异质外延来改善六方氮化硼(hBN)的生长,非天然基质仍然是限制质量的基本因素。这个问题可以通过同质外延来解决,即hBN在hBN基底上的生长。在这份报告中,我们证明了通过金属-有机气相外延在剥离的hBN薄片上的三角形BN晶粒的同质外延生长,并通过原子力显微镜和光致发光表明,这些三角形岛的堆叠可以偏离hBN的AA\'堆叠。我们表明,堆叠顺序是由剥离的hBN薄片边缘的晶体学方向强制执行的,扶手椅边缘允许中心对称堆叠,而锯齿形边缘导致非中心对称BN多型的生长。我们的结果表明生长具有可调层堆叠的同质外延BN的途径,这需要引起压电性或铁电性。
    Although large efforts have been made to improve the growth of hexagonal boron nitride (hBN) by heteroepitaxy, the non-native substrates remain a fundamental factor that limits the quality. This problem can be solved by homoepitaxy, which is the growth of hBN on hBN substrates. In this report, we demonstrate the homoepitaxial growth of triangular BN grains on exfoliated hBN flakes by Metal-Organic Vapor Phase Epitaxy and show by atomic force microscopy and photoluminescence that the stacking of these triangular islands can deviate from the AA\' stacking of hBN. We show that the stacking order is enforced by the crystallographic direction of the edge of the exfoliated hBN flakes, with armchair edges allowing for centrosymmetric stacking, whereas zigzag edges lead to the growth of noncentrosymmetric BN polytypes. Our results indicate pathways to grow homoepitaxial BN with tunable layer stacking, which is required to induce piezoelectricity or ferroelectricity.
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  • 文章类型: Journal Article
    目的:建立贝叶斯网络(BN)模型,探讨影响因素与2型糖尿病(T2DM)之间的具体关系,冠心病(CAD),和他们的合并症。目的是使用这些模型预测疾病发生和诊断病因,从而为制定有效的T2DM预防和控制策略提供信息,CAD,和他们的合并症。
    方法:采用案例控制设计,该研究比较了患有T2DM的个体,CAD,和他们的合并症(病例组)与健康同行(对照组)。进行单因素和多因素Logistic回归分析以确定疾病的影响因素。BN结构是使用禁忌搜索算法学习的,通过最大似然估计实现参数估计。使用混淆矩阵评估了BN模型的预测性能,并利用Netica软件进行视觉预测和诊断。
    结果:该研究涉及3,824名参与者,包括1,175个控件,1,163例T2DM,982例CAD病例,和504例合并症病例。BN模型揭示了直接和间接影响T2DM的因素,比如年龄,区域,教育水平,家族史(FH)。像运动这样的变量,LDL-C,TC,水果,和甜食摄入表现出直接的影响,吸烟时,酒精消费,职业,心率,HDL-C,肉,和主食摄入有间接影响。同样,对于CAD,具有直接和间接影响的因素包括年龄,吸烟,SBP,锻炼,肉,和水果摄入量,而睡眠时间和心率则有直接影响。关于T2DM和CAD合并症,年龄,FBG,SBP,水果,甜食摄入表现出直接和间接的影响,而运动和HDL-C表现出直接效应,和区域,教育水平,DBP,TC表现出间接影响。
    结论:使用禁忌搜索算法构建的BN模型展示了强大的预测性能,可靠性,以及在预测T2DM疾病概率中的适用性,CAD,和他们的合并症。这些发现为加强预防和控制策略以及探索BN在预测和诊断慢性疾病中的应用提供了有价值的见解。
    OBJECTIVE: Bayesian network (BN) models were developed to explore the specific relationships between influencing factors and type 2 diabetes mellitus (T2DM), coronary heart disease (CAD), and their comorbidities. The aim was to predict disease occurrence and diagnose etiology using these models, thereby informing the development of effective prevention and control strategies for T2DM, CAD, and their comorbidities.
    METHODS: Employing a case-control design, the study compared individuals with T2DM, CAD, and their comorbidities (case group) with healthy counterparts (control group). Univariate and multivariate Logistic regression analyses were conducted to identify disease-influencing factors. The BN structure was learned using the Tabu search algorithm, with parameter estimation achieved through maximum likelihood estimation. The predictive performance of the BN model was assessed using the confusion matrix, and Netica software was utilized for visual prediction and diagnosis.
    RESULTS: The study involved 3,824 participants, including 1,175 controls, 1,163 T2DM cases, 982 CAD cases, and 504 comorbidity cases. The BN model unveiled factors directly and indirectly impacting T2DM, such as age, region, education level, and family history (FH). Variables like exercise, LDL-C, TC, fruit, and sweet food intake exhibited direct effects, while smoking, alcohol consumption, occupation, heart rate, HDL-C, meat, and staple food intake had indirect effects. Similarly, for CAD, factors with direct and indirect effects included age, smoking, SBP, exercise, meat, and fruit intake, while sleeping time and heart rate showed direct effects. Regarding T2DM and CAD comorbidities, age, FBG, SBP, fruit, and sweet intake demonstrated both direct and indirect effects, whereas exercise and HDL-C exhibited direct effects, and region, education level, DBP, and TC showed indirect effects.
    CONCLUSIONS: The BN model constructed using the Tabu search algorithm showcased robust predictive performance, reliability, and applicability in forecasting disease probabilities for T2DM, CAD, and their comorbidities. These findings offer valuable insights for enhancing prevention and control strategies and exploring the application of BN in predicting and diagnosing chronic diseases.
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  • 文章类型: Journal Article
    电化学氮还原反应(eNRR)是Haber-Bosch(H-B)工艺的极有希望的替代方法,但其商业发展受到N2分子的高键能和竞争性析氢反应(HER)的存在的限制。这里,通过h-BNN和CNT的界面杂化,探索了氮化硼(h-BNN)和碳纳米管(CNT)的无金属复合电催化剂,显示出大大提高的eNRR法拉第效率(FE)为63.9%,NH3产率为36.5μgh-1mgcat。-0.691V时为-1(与RHE相比)。观察到新的C-B和C-N化学键,表明碳纳米管和h-BNN之间存在强烈的相互作用。根据拉曼光谱和优化的h-BNN/CNT模型,h-BNN和CNT之间明显的应变效应被认为在高度改进的FE中起着重要作用,与单独的h-BNN的FE(4.7%)相比。密度泛函理论(DFT)计算进一步表明,h-BNN/CNT在eNRR中具有较低的能量势垒,给他们更高的N2对NH3的选择性,而h-BNN在她体内具有较低的能量壁垒。这项工作显示了菌株效应在增强eNRR过程中的选择性方面的重要作用。
    The electrochemical nitrogen reduction reaction (eNRR) is a highly promising alternative to the Haber-Bosch (H-B) process, but its commercial development is limited by the high bond energy of N2 molecules and the presence of the competitive hydrogen evolution reaction (HER). Here, a metal-free composite electrocatalyst of boron nitride (h-BNNs) and carbon nanotubes (CNTs) was explored through the interfacial hybridization of h-BNNs and CNTs, which showed a highly improved eNRR Faraday efficiency (FE) of 63.9% and an NH3 yield rate of 36.5 μg h-1 mgcat.-1 at -0.691 V (vs RHE). New chemical bonds of C-B and C-N were observed, indicating a strong interaction between CNTs and h-BNNs. According to the Raman spectra and the optimized model of h-BNNs/CNTs, an obvious strain effect between h-BNNs and CNTs was supposed to play a significant role in the highly improved FE, compared with the FE of h-BNNs alone (4.7%). Density functional theory (DFT) calculations further showed that h-BNNs/CNTs had lower energy barriers in eNRR, giving them higher N2 to NH3 selectivity, while h-BNNs have lower energy barriers in the HER. This work shows the important role of the strain effect in boosting the selectivity in the eNRR process.
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  • 文章类型: Journal Article
    X-ray detectors based on conventional semiconductors with large atomic numbers are suffering from the poor stability under a high dose rate of ionizing irradiation. In this work, we demonstrate that a wide band gap ceramic-boron nitride with small atomic numbers could be used for sensitive X-ray detection. Boron nitride samples showed excellent resistance to ionizing radiation, which have been systematically studied with the neutron- and electron-aging experiments. Then, we fully analyzed the influence of these aging effects on the fundamental properties of boron nitride. Interestingly, we found that the boron nitride samples could maintain relatively good charge transport properties even after large dose of neutron irradiation. The fabricated X-ray detectors showed decent performance metrics, and the neutron-aged boron nitride even showed improved operational stability under continuous X-ray irradiation, suggesting the great potential for real applications.
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  • 文章类型: Journal Article
    为了克服SabatierCO2甲烷化反应的热力学和动力学障碍,该过程必须在非常高的温度和压力条件下操作,为了获得工业上可行的转化,rate,和选择性。在这里,我们报告说,这些技术相关的性能指标已经在更温和的条件下使用太阳能而不是热能,其中甲烷化反应由新型镍-氮化硼催化剂实现。在这方面,原位生成的HOB····B表面受挫的刘易斯对被认为是高Sabatier转换87.68%的原因,反应速率2.03molgNi-1h-1,选择性接近100%,在环境压力条件下实现。这一发现预示着旨在开发和实施可持续的“SolarSabatier”甲烷化过程的光化学工程策略。
    To overcome the thermodynamic and kinetic impediments of the Sabatier CO2 methanation reaction, the process must be operated under very high temperature and pressure conditions, to obtain an industrially viable conversion, rate, and selectivity. Herein, we report that these technologically relevant performance metrics have been achieved under much milder conditions using solar rather than thermal energy, where the methanation reaction is enabled by a novel nickel-boron nitride catalyst. In this regard, an in situ generated HOB⋅⋅⋅B surface frustrated Lewis\'s pair is considered responsible for the high Sabatier conversion 87.68 %, reaction rate 2.03 mol gNi -1 h-1 , and near 100 % selectivity, realized under ambient pressure conditions. This discovery bodes well for an opto-chemical engineering strategy aimed at the development and implementation of a sustainable \'Solar Sabatier\' methanation process.
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  • 文章类型: Journal Article
    氧化剂的热分解性能直接决定了固体推进剂的推力和比冲性能。六方氮化硼(h-BN)具有催化活性高、稳定性好等特点,可以提高氧化剂的放热和分解温度,然后提高推进剂的能量性能。在这项研究中,通过原位生长成功制备了一种新型的TiO2NPs/h-BN杂化材料,发现当5wt.添加%TiO2NP/h-BN,高氯酸铵(AP)的初始分解温度降低了67.6℃。由于TiO2的添加,h-BN层之间的间隙以及比表面增加,优化了它的热催化性能,并提出了AP热分解过程的催化机理。
    The thermal decomposition performance of an oxidizer directly determines the thrust and specific impulse properties of the solid propellant. Hexagonal boron nitride (h-BN) has the characteristics of high catalytic activity and good stability, which can improve the heat release and decomposition temperature of the oxidant, and then improve the energy performance of the propellant. In this study, a novel hybrid material TiO2 NPs/h-BN was successfully prepared by in situ growth, and it was found that when 5 wt.% TiO2 NPs/h-BN was added, the initial decomposition temperature of ammonium perchlorate (AP) decreased by 67.6°C. Due to the addition of TiO2, the gap between the h-BN layers as well as the specific surface increased, which optimized its thermocatalytic performance, and it also proposed a catalytic mechanism for the thermal decomposition process of AP.
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  • 文章类型: Journal Article
    研究结果强烈表明,饮食失调的认知行为疗法(CBT-ED)比其他治疗神经性贪食症(BN)和暴饮暴食症(BED)更有效。虽然人际心理治疗似乎对BED同样有效。目前,CBT-ED对持续性(成人)形式的神经性厌食症(AN)的有效性的证据不足,除了一些来自非受控试验的证据外,青少年的AN基本上没有证据。本文首先概述了CBT-ED发展的早期研究,这些研究显示出与其他以症状为中心的心理治疗具有相似的有效性,这一发现在当时被忽略。然后考虑以后的发展,包括CBT-ED与其他心理治疗的比较,努力发展基于互联网的培训和治疗,和电子应用治疗。最后,我们考虑了研究结果对未来短期和长期研究以及临床实践的影响.
    Research findings strongly suggest that cognitive behavioral therapy for the eating disorders (CBT-ED) is more effective than other treatments for bulimia nervosa (BN) and for binge eating disorder (BED), although interpersonal psychotherapy appears to be equally effective for BED. Evidence for the effectiveness of CBT-ED for the persistent (adult) form of anorexia nervosa (AN) is insufficient at present and is essentially absent for AN in adolescents except for some evidence from uncontrolled trials. This article begins with an overview of the early studies in the development of CBT-ED that showed a similar effectiveness of other symptom-focused psychotherapies-a finding that was neglected at the time. Later developments are then considered, including comparisons of CBT-ED with other psychotherapies, efforts to develop Internet-based training and treatment, and electronic applications for treatment. Finally, implications of the findings for future short- and long-term research and for clinical practice are considered.
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  • 文章类型: Journal Article
    在这项工作中,通过三维混杂氮化硼@银纳米线(BN@AgNWs)填料热网络制备了具有高热导率的聚二甲基硅氧烷(PDMS)基复合材料,并研究了它们的热导率。采用原位生长法制备了一种新型导热BN@AgNWs杂化填料。不同浓度的银离子被还原,和AgNW在BN片的表面上结晶和生长。通过添加BN@AgNWs杂化填料制备PDMS基复合材料。SEM,XPS,利用XRD和XRD对BN@AgNWs杂化填料的结构和形貌进行了表征。研究了PDMS基复合材料与不同银精矿的导热性能。结果表明,用20vol%BN@15AgNWs杂化填料填充的PDMS基复合材料的热导率为0.914W/(m·K),是纯PDMS的5.05倍,比填充BN的20vol%PDMS基复合材料的热导率高23%。基于混合填料结构提供了增强的导热机理。这项工作为设计和制造用于热管理材料的高导热混合填料提供了一种新的方法。
    In this work, polydimethylsiloxane (PDMS)-based composites with high thermal conductivity were fabricated via a three-dimensional hybrid boron nitride@silver nanowires (BN@AgNWs) filler thermal network, and their thermal conductivity was investigated. A new thermal conductive BN@AgNWs hybrid filler was prepared by an in situ growth method. Silver ions with the different concentrations were reduced, and AgNWs crystallized and grew on the surface of BN sheets. PDMS-based composites were fabricated by the BN@AgNWs hybrid filler added. SEM, XPS, and XRD were used to characterize the structure and morphology of BN@AgNWs hybrid fillers. The thermal conductivity performances of PDMS-based composites with different silver concentrates were investigated. The results showed that the thermal conductivity of PDMS-based composite filled with 20 vol% BN@15AgNWs hybrid filler is 0.914 W/(m·K), which is 5.05 times that of pure PDMS and 23% higher than the thermal conductivity of 20 vol% PDMS-based composite with BN filled. The enhanced thermal conductivity mechanism was provided based on the hybrid filler structure. This work offers a new way to design and fabricate the high thermal conductive hybrid filler for thermal management materials.
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  • 文章类型: Journal Article
    采用液体有机氢载体(LOHC)将氢运输到可以利用它的地方依赖于有效的化学脱氢的方法来获得这种燃料。因此,开发有效的策略来优化廉价的过渡金属基催化剂在LOHC脱氢的活性和稳定性方面的催化性能是一个关键的挑战。这里,我们报告了超小镍纳米团簇的设计和合成(〜1.5nm)沉积在富含缺陷的氮化硼(BN)纳米片(Ni/BN)催化剂具有更高的甲醇脱氢活性和选择性,和更高的稳定性比一些其他过渡金属基催化剂。二维(2D)BN与金属纳米颗粒的界面在引导催化活性超小Ni纳米团簇的成核和生长方面都起着很强的作用,并进一步稳定这些纳米级Ni催化剂,使其免受与BN基材相互作用的中毒。我们提供详细的光谱学表征和密度泛函理论(DFT)计算,以揭示高生产率的起源,高选择性,Ni/BN纳米催化剂表现出的高耐久性,并阐明了其与纳米簇尺寸和载体-纳米簇相互作用的相关性。这项研究提供了对支持材料在纳米团簇形成过程中以及在活性催化过程中通过固定对纳米团簇的尺寸控制的作用的见解;这双重见解对于推进对高性能自下而上设计的理解具有重要意义。耐用的催化系统的各种催化需要。
    Employing liquid organic hydrogen carriers (LOHCs) to transport hydrogen to where it can be utilized relies on methods of efficient chemical dehydrogenation to access this fuel. Therefore, developing effective strategies to optimize the catalytic performance of cheap transition metal-based catalysts in terms of activity and stability for dehydrogenation of LOHCs is a critical challenge. Here, we report the design and synthesis of ultrasmall nickel nanoclusters (∼1.5 nm) deposited on defect-rich boron nitride (BN) nanosheet (Ni/BN) catalysts with higher methanol dehydrogenation activity and selectivity, and greater stability than that of some other transition-metal based catalysts. The interface of the two-dimensional (2D) BN with the metal nanoparticles plays a strong role both in guiding the nucleation and growth of the catalytically active ultrasmall Ni nanoclusters, and further in stabilizing these nanoscale Ni catalysts against poisoning by interactions with the BN substrate. We provide detailed spectroscopy characterizations and density functional theory (DFT) calculations to reveal the origin of the high productivity, high selectivity, and high durability exhibited with the Ni/BN nanocatalyst and elucidate its correlation with nanocluster size and support-nanocluster interactions. This study provides insight into the role that the support material can have both regarding the size control of nanoclusters through immobilization during the nanocluster formation and also during the active catalytic process; this twofold set of insights is significant in advancing the understanding the bottom-up design of high-performance, durable catalytic systems for various catalysis needs.
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  • 文章类型: Journal Article
    在这项研究中,我们设计了一种三维结构的导电胶(ECAs),通过添加三种不同的纳米填料,包括BN,TiO2和Al2O3颗粒,形成几层石墨烯(FLG)/聚合物复合材料以避免FLG聚集。通过绿色从石墨(G3,G8和G20)获得三种不同横向尺寸的FLG(FLG3,FLG8和FLG20),轻而易举,低成本,和可扩展的射流空化过程。相应的特征,如拉曼光谱,扫描电子显微镜(SEM),原子力显微镜(AFM),和透射电子显微镜(TEM),验证了石墨烯薄片制备的成功。根据四点探针测量的结果,FLG20表现出最低的薄层电阻值~0.021Ω/■。优化的ECAs组成为FLG20的60%固体含量,添加2wt。%的Al2O3。薄层电阻值低至51.8Ω/■,与原始FLG/聚合物相比减少了73%。这些结果表明,这种方法不仅为更便宜、更安全地生产石墨烯铺平了道路,但在能源相关技术中也具有巨大的应用潜力。
    In this study, we designed a three-dimensional structure of electrically conductive adhesives (ECAs) by adding three different kinds of nano filler, including BN, TiO2, and Al2O3 particles, into a few-layered graphene (FLG)/polymer composite to avoid FLG aggregation. Three different lateral sizes of FLG (FLG3, FLG8, and FLG20) were obtained from graphite (G3, G8, and G20) by a green, facile, low-cost, and scalable jet cavitation process. The corresponding characterizations, such as Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM), verified the successful preparation of graphene flakes. Based on the results of four-point probe measurements, FLG20 demonstrated the lowest sheet resistance value of ~0.021 Ω/■. The optimized ECAs\' composition was a 60% solid content of FLG20 with the addition 2 wt.% of Al2O3. The sheet resistance value was as low as 51.8 Ω/■, which was a reduction of 73% compared to that of pristine FLG/polymer. These results indicate that this method not only paves the way for the cheaper and safer production of graphene, but also holds great potential for applications in energy-related technologies.
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