火花塞陶瓷绝缘体高温分流电阻的研究

火花塞陶瓷绝缘体的高温分流电阻会影响火花塞的使用性能和寿命,笔者研究了氧化铝中Na2O含量、配方组成和烧结温度对火花塞陶瓷绝缘体高温分流电阻的影响。结果表明:随着氧化铝原材料中Na2O含量的增加,试样的高温分流电阻逐渐降低;在配方组成中,当CaO的含量由33%增加至40%,氧化铝原材料中Na2O含量为0.1%时,试样在500℃时的分流电阻由517MΩ提升至1 192MΩ;烧结温度低于1 580℃时,试样的高温分流电阻较低。     

Low temperature synthesis and spark plasma sintering of a boron carbide with a low residual carbon content

Using spark plasma sintering (SPS), >98.5 % dense boron carbide (B₄C) samples were made from commercially available and lab-synthesised powders made via a low temperature synthesis (LTS) process. The work showed that the LTS powder can be produced in batches of tens to hundreds of grams whilst maintaining a high purity material with lower levels of residual free carbon (20.6–21.3 wt.% C) than commercially available samples (22.4 wt.% C). The LTS material was seen to exhibit higher hardness values (37.8 GPa) than the commercial grade material (32.5 GPa) despite featuring a coarser average grain size (10.8 μm and 2.4 μm respectively). This is largely thought to be due to the influence of ZrO₂ and AlB₂ impurities introduced to the material during micronising milling of the powder after synthesis, as opposed to the influence of the materials lower carbon content.     

Effect of low content sintering aids addition on β-SiC sintered by spark plasma sintering

The influence of low content of sintering aids addition on the properties of β-SiC sintered by spark plasma sintering was studied based on X-ray diffraction and SEM observations. Three dopants, respectively Al₂O₃, Al₂O₃-Y₂O₃ and Al₂O₃-AlN were chosen, and the investigation was undertaken in the [0.5–5 wt%] content range. The analyses revealed the possibility to increase the density of sintered pellets close to 100% of theoretical density (T.D.), even with the addition of very low sintering aids contents, as low as 0.5 wt%, for each dopant. The combination with high sintering pressure allowed keeping a fine microstructure and a pristine cubic crystalline structure while avoiding the formation of secondary phases.     

Magnesium fluoride (MgF2) – A novel sintering additive for the preparation of transparent YAG ceramics via SPS

The effect of MgF₂ as a sintering additive for the preparation of YAG ceramics via spark plasma sintering (SPS) is investigated with promising results, as nearly complete densification (0.58% porosity) is achieved at relatively low temperature and moderate pressure. Higher temperature and dwell time resulted in a translucent/transparent body. On the other side, significant grain growth was observed with MgF₂ addition.     

Ce3+ doped Lu3Al5O12 ceramics prepared by spark plasma sintering technology using micrometre powders: Microstructure,luminescence, and scintillation properties

Ce³⁺ doped Lu₃Al₅O₁₂ (Ce:LuAG) ceramics were fabricated by the solid-state reaction method through spark plasma sintering (SPS) from 1350 °C to 1700 °C for 5 min at a pressure of 50 MPa using micro powders. The average grain size of the SPSed ceramics gradually grew from 0.42 µm (1400 °C) to 1.55 µm (1700 °C), which is nearly one order of magnitude lower than that of vacuum sintered (VSed) Ce:LuAG ceramics (~24.6 µm). Characteristic Ce³⁺ emission peaking at around 510 nm appeared and 92% photoluminescence intensity of room temperature can be reserved at 200 °C revealing excellent thermal stability. The maximum radioluminescence intensity reached around 3 times of VSed Ce:LuAG ceramics and 7.8 times of BGO crystals. The maximum scintillation light yield under γ-ray (¹³⁷Cs) excitation reached 9634 pho/MeV @ 2 μs. It is concluded that SPS technology is a feasible way to develop Ce:LuAG ceramics and further optical enhancement can be expected.     

Yb doped MgO transparent ceramics generated through the SPS method

Yb doped (0, 0.02, 0.1 and 0.5 at%) MgO transparent ceramics were synthesized through spark plasma sintering (SPS) at the relatively low temperature of 1100 °C for 5–60 min under a pressure of 105 MPa. The effects of dopant concentration and sintering holding time on the densification and microstructure evolution of MgO ceramics were investigated. All ceramics reached a relative density greater than 99.20%. The 0.02% Yb-doped MgO ceramic sintered at 1100 °C for 60 min showed the highest in-line transmittance, of 80% at 1030 nm, a value close to that of MgO single crystals. Yb dopant improved the transmittance, degree of densification and control of grain growth. Herein, the influence of Yb doping on the crystalline phase and microstructure was explored, and the photoluminescence properties of Yb in transparent MgO ceramics were investigated.     

计及信息不确定性的风电机组健康状态实时评估方法

运行工况识别作为风电机组状态监测与健康管理领域的重要环节,往往受到不确定信息以及高速实时数据流的影响,造成健康状态评估难以有效实施。在此背景下,文中提出一种基于Spark流式处理的健康状态实时评估方法。首先,采用大数据分析技术实现风电机组运行工况的空间划分;然后,在充分考虑风电机组监测信息不确定性的情况下,结合数据采集与监控(SCADA)历史运行数据,对基于高斯云模型和高斯云变换的健康状态评估模型进行训练,并以健康指数作为风电机组健康状态评估的指标。最后,将该评估方法应用在中国北方某风电场1.5 MW风电机组故障前的健康状态评估中。算例分析结果表明,该方法可监测到风电机组健康状态的变化趋势,初步实现了故障的早期预警。     

旋压变形量对B4C增强铝基复合管微观组织及力学性能的影响

本文采用等离子放电烧结+异步错距旋压方法制备了不同旋压变形量的B₄C颗粒含量为10wt.%的铝基复合材料管材,研究了变形量对复合管材微观组织和力学性能的影响。 研究结果表明:随着旋压变形量的增加,B₄C铝基复合管材内部B₄C颗粒分布由类似网状结构变为均匀分布,B₄C颗粒与基体铝合金之间界面形成了冶金结合;等离子放电烧结过程中的颗粒之间的“尖端放电”效应使得颗粒之间的界面处产生局部高温,促进了界面之间的结合,在界面处产生了AlB₂和Al₃BC金属间化合物;旋压变形量的增加,细化了铝合金的晶粒尺寸,减小了B₄C的颗粒尺寸,但旋压过程中导致的大尺寸B₄C颗粒的断裂弱化了细晶强化和颗粒强化对抗拉强度的作用。     

主流大数据处理开源架构的分析及对比评测

结合电信增值业务领域中对大数据处理的实际需求,对现有主流的分布式大数据处理架构(Hive、Impala、Spark)的核心进行分析与实测,比较它们在大数据处理过程中的优劣及适用的场景,从而为大数据分析所面临的架构适用性选型提供参考.     

放电等离子技术连接铬酸镧陶瓷

铬酸镧陶瓷脆性高、难以变形,使其在加工上存在难度。利用陶瓷连接技术可以将小部件连接为大部件,实现低成本制造形状复杂的大型陶瓷构件。以铬酸镧的前驱体料浆作为中间层材料,利用放电等离子技术进行了铬酸镧陶瓷的连接,测定了连接件的连接强度,并借助SEM、EDS等手段分析了连接温度及保温时间对连接件强度的影响。结果表明,连接温度为1400℃时,连接件可以获得最高的连接强度,连接过程中母材中出现第二相Cr4O5。