国际电工委员会防爆电气设备分委员会休斯敦会议报道

国际电工委员会（IEC）第62届会议于1998年10月11日～23日在美国休斯敦（Houston）市召开。在此期间,第31技术委员会（TC31）──爆炸性环境用防爆电气设备以及下属的3个分技术委员会,即SC31A──隔爆外壳、SC31G一本质安全型电气设备和SC31H──可燃性粉尘环境用电气设...     

防爆电气设备及防爆电气配线的选型

８．１选型时的注意事项对防爆电气设备及防爆电气配线进行选型时，必须考虑设备使用环境中的可燃性气体或蒸气的危险特性、防爆结构的特征、环境条件、影响温升的其他诸条件等。（１）可燃性气体或蒸气的危险特性（ａ）对隔爆型防爆结构或本质安全型防爆结构的电气设备，...     

S800系列齐纳式安全栅

一、概述Ｓ８００系列齐纳安全栅是多用途通用型齐纳安全栅。能与自动化仪表、自动控制装置、通讯设备、报警器等各种仪器、设备组成本质安全防爆系统,做为本安关联设备,被广泛用于化工、石油、冶金等各行业中,以限制危险能量进入具有爆炸性危险气体环境。Ｓ８００系列齐纳安全栅符合ＧＢ３８３６１—８３《爆炸性环境用防爆电气设备　通用要求》和ＧＢ３８３６４－８３《爆炸性环境用防爆电气设备　本质安全型电路和电气设备“ｉ”》标准的有关规定,并经国家指定的检验单位检验合格,取得防爆合格证书。　　二、基本工作原理齐纳式…     

本质安全型设备外部电路连接装置的防爆要求

通过对本质安全型设备外部连接装置的介绍,了解符合本质安全性能的设备不仅要注重对电路参数的评价、计算,还要重视设备硬件上的一些要求。特别是通过设备外部电路连接装置的要求对设备的本质安全性能所起到至关重要的作用,来确保本质安全型设备的防爆性能。     

防爆“n”型电气设备中nL-限制能量设备

主要阐述了防爆"n"型电气设备中nL-限制能量型设备的原理、设计理念、检验方法及与防爆本质安全型设备的差异。详细介绍了国家标准中对防爆"n"型电气设备型中nL-限制能量设备的具体要求和规定。     

防爆正压通风型电气设备

欧洲标准除了规定比较常用的危险场所用设备防爆型式,如增安型、隔爆型或流程控制技术用本质安全型外,还规定称之为正压通风型“p”的防爆型式。正压通风型是一种能使非防爆电气设备在危险场所中安全使用的特殊方法。DIN VDE0170/0171—3 EN50016叙述了这种防爆型式的概念和特殊技术要求。     

四项国标起草工作会议在温州召开

1993年5月21～25日,全国防爆电气设备标准化技术委员会秘书处在温州召开国家标准起草工作会议,对《爆炸性气体环境用防爆电气设备 通用要求》、《爆炸性气体环境用防爆电气设备 隔爆型电气设备“d”》、《爆炸性气体环境用防爆电气设备 增安型电气设备“e”》、《爆炸性气体环境用防爆电气设备本质安全型电路和电气设备“i”》四项国家标准(征求意见稿)进行修改。来自全国防爆标委会有关成员单位的18名代表参加了会议。     

粉尘防爆电机的选择

介绍粉尘防爆电机采用的标准及相关规定和有关技术知识,粉尘防爆的原理,着重介绍用外壳和限制表面温度保护的电气设备,同时提供易燃、易爆粉尘和可燃纤维特性仅供参考。     

海洋平台本安防爆设备参数选择及配接要求

对海洋平台外供电本质安全型防爆电气产品的基本配置、系统组成、及本安系统中的本质安全装置、关联装置、连接电缆参数选择及配接要求进行了详细论述,有助于正确选型、安装、使用和维护本质安全型防爆电气设备,保证现场生产运营安全。     

塑本质安全型员工,创本质安全型企业

人员、设备、环境的和谐统一是本质安全型企业的重要标志,这三者之中人是决定性的因素,因此要打造本质安全型电力企业就必须要有本质安全型的员工。详细介绍了塑造本质安全型员工的途径和方法,进而实现本质安全型的电力企业。     

Dielectric and Piezoelectric Properties of Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>-K<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>-NaNbO<Subscript>3</Subscript>Lead-Free Ceramics

The ternary lead-free piezoelectric ceramics system of (1 – x) [0.88Na_0.5Bi_0.5TiO₃-0.12K_0.5Bi_0.5TiO₃] – xNaNbO₃(x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) were synthesized by conventional solid state reaction method. The crystal structure, dielectric, piezoelectric properties and P-E hysteresis loops were investigated. The crystalline structure of all compositions is mono-perovskite phase ascertained by XRD, and the lattice constant was calculated from the XRD data. Temperature dependence of dielectric constant _r and dissipation factor tan measurement revealed that all compositions experienced two phase transitions: from ferroelectric to anti-ferroelectric and from anti-ferroelectric to paraelectric, and these two phase transitions have relaxor characteristics. Both transition temperatures T_d and T_m are lowered due to introduction of NaNbO₃. P-E hysteresis loops show that 0.88Na_0.5Bi_0.5TiO₃-0.12K_0.5Bi_0.5TiO₃ ceramics has the maximum P_r and E_c corresponding to the maximum values of electromechanical coupling factor K_p and piezoelectric constant d_33. The piezoelectric constant d₃₃ and electromechanical coupling factor K_p decrease a little, while the dielectric constant ₃₃^T/₀ improves much more when the concentration of NaNbO₃ is 8 mol%.     

The Similar Defect Chemistry of Highly-Doped SrBi<Subscript>2</Subscript>Ta<Subscript>2</Subscript>O<Subscript>9</Subscript> and SrBi<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>9</Subscript>

The equilibrium electrical conductivities of undoped SrBi₂Ta₂O₉ (SBT) and SrBi₂Nb₂O₉ (SBN) have been shown to behave quite differently. SBT has the behavior expected for a 1% acceptor-doped oxide, while SBN behaves like a 1% donor-doped oxide. This difference has been related to the substantial cation place exchange that occurs between the Bi^{+ 3} and Sr^{+ 2} ions in the alternating layers of the structure. It was proposed that this place exchange is not entirely self-compensating, as would be expected for a simple, isotropic oxide, but that there is some local compensation within each layer by lattice and/or electronic defects. It is now shown that the equilibrium conductivity of 3% donor-doped SBT is similar to that of undoped SBN, while the equilibrium conductivity of 3% acceptor-doped SBN resembles that of undoped SBT. Thus the defect chemistrys of the two compounds are quite similar, but the equilibrium conductivities are displaced along a doping axis.     

Mechanical and electrical properties of Bi<Subscript>1.5-x</Subscript>La<Subscript>x</Subscript>Zn<Subscript>0.92</Subscript>Nb<Subscript>1.5</Subscript>O<Subscript>6.92</Subscript> pyrochlore ceramics

BiFeO₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (BF-PMN-PT) ternary ceramics with pure perovskite phase were prepared through a two-step solid reaction method. Based on structural analysis, the ternary phase diagram of BF-PMN-PT solid solution at room temperature has been established. The Curie temperature T_C, remnant polarization P_r and piezoelectric constant d₃₃ vary in the range of 138 to 225 °C, 15.12 to 23.65 μC/cm² and 129 to 276 pC/N, respectively. The coercive field Ec increases gradually from 5.77 to 29.56 kV/cm upon PT content increasing. The magnetic study suggests that the magnetism turns from diamagnetism for PMN-PT to paramagnetism for BF-PMN-PT by adding BiFeO₃ into PMN-PT and adding more content of BF does not change the paramagnetism further.     

Raman and infrared spectroscopy of Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript> - BaTiO<Subscript>3</Subscript> ceramics

Lead-free Na_0.5Bi_0.5TiO₃ -BaTiO₃ ceramics have been prepared in the whole range of concentrations and studied at room-temperature by means of X-ray, Raman scattering and infrared techniques. X-ray measurements revealed rhombohedral, rhombohedral-tetragonal boundaries and tetragonal modifacations depending on the contents of BaTiO₃. The distinct changes of the Raman and infrared spectra with increasing of BaTiO₃ content, which were correlated with X-ray results, were observed. The broad phonon spectra indicated the disorder in the A site of Na_0.5Bi_0.5TiO₃ -BaTiO₃ system.     

Improvement of Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>Co<Subscript>2</Subscript>O<Subscript>y</Subscript> thermoelectric performances by Na doping

Bi₂Sr_2-xNa_xCo₂O_y thermoelectric materials with x = 0, 0.025, 0.05, 0.075, 0.10, 0.125, and 0.15 have been prepared by the classical solid state reaction. Microstructure has shown an important grain growth when Na is added, leading to very high bulk densities confirmed through density measurements. These modifications have produced a drastic decrease of electrical resistivity without significant modification of Seebeck coefficient. As a consequence, Power Factor has been increased in all Na-doped samples, reaching the maximum value (0.21 mW/K².m at 650 °C) for 0.075 Na samples, which is fairly close to the reported for single crystals.     

Microwave Dielectric Properties of CuO-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-Doped ZnNb<Subscript>2</Subscript>O<Subscript>6</Subscript> Ceramics with Low Sintering Temperature

Microwave dielectric properties of low temperature sintering ZnNb₂O₆ ceramics doped with CuO-V₂O₅-Bi₂O₃ additions were investigated systematically. The co-doping of CuO, V₂O₅ and Bi₂O₃ can significantly lower the sintering temperature of ZnNb₂O₆ ceramics from 1150 to 870C. The secondary phase containing Cu, V, Bi and Zn was observed at grain boundary junctions, and the amount of secondary phase increased with increasing CuO-V₂O₅-Bi₂O₃ content. The dielectric properties at microwave frequencies (7–9 GHz) in this system exhibited a significant dependence on the relative density, content of additives and microstructure of the ceramics. The dielectric constant ( _r) of ZnNb₂O₆ ceramics increased from 21.95 to 24.18 with increasing CuO-V₂O₅-Bi₂O₃ additions from 1.5 to 4.0 wt%. The quality factors (Q× f) of this system decreased with increasing CuO-V₂O₅-Bi₂O₃ content and ranged from 36118 to 67100 GHz for sintered ceramics, furthermore, all Q× f values of samples with CuO-V₂O₅-Bi₂O₃ additions are lower than that of un-doped ZnNb₂O₆ ceramics sintered at 1150C for 2 h. The temperature coefficient of resonant frequency ( _f) changed from –33.16 to –25.96 ppm/C with increasing CuO-V₂O₅-Bi₂O₃ from 1.5 to 4.0 wt%     

Coke-tolerant La<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript>-Ni-Gd<Subscript>0.1</Subscript>Ce<Subscript>0.9</Subscript>O<Subscript>1.95</Subscript> composite anode for direct methane-fueled solid oxide fuel cells

Direct CH₄-fueled solid oxide fuel cells (SOFCs) have been studied for a few decades, but carbon depositions on the Ni-based anodes are still remained as a major problem. In order to enhance coke tolerances and durability of SOFCs, La₂Sn₂O₇ nano-powders are prepared by co-precipitation. The SOFCs with the different amounts of the La₂Sn₂O₇ nano-powders in the Ni-GDC anodes are tested under dry CH₄, and the 0.3 wt.% La₂Sn₂O₇-Ni-GDC (0.3LNG) anodes show the highest cell performances of all anodes. The maximum power density of the cell is approximately 0.55 W cm^?2 at 650 °C. The durability of the 0.3LNG cell is significantly enhanced without any carbon formations, showing approximately 0.69 V over 600 h at 0.3 A cm^?2, whereas the conventional Ni-GDC cell is stopped only after 90 h. It suggests that the 0.3LNG is a promising anode material to enhance coke-tolerances and durability of direct-methane fuel cells.     

Lead-free (K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)<Subscript>0.95</Subscript>(LiSb)<Subscript>0.05</Subscript>Nb<Subscript>0.95</Subscript>O<Subscript>3</Subscript>-BaTiO<Subscript>3</Subscript> piezoceramics

Lead-free (1-x)(K_0.5Na_0.5)_0.95(LiSb)_0.05Nb_0.95O₃-xBaTiO₃ (abbreviated as (1-x)KNNLS-xBT) piezoceramics were synthesized by conventional solid state sintering and the effect of BaTiO₃ on the microstructure, dielectric and piezoelectric properties was investigated. It was found that both orthorhombic-tetragonal (T _O-T) and tetragonal-cubic (T _C) phase transition temperatures decreased obviously with increasing BaTiO₃ content. Although proper amount of BaTiO₃ facilitated the sintering of (1-x)KNNLS-xBT ceramics, the addition of BaTiO₃ affected the relaxor behavior slightly and it was not beneficial to improve piezoelectric strain coefficient d ₃₃, remnant polarization P _r and piezoelectric coupling constant k _p.     

Analysis of domain structure in the Ce<Subscript>0.8</Subscript>Sm<Subscript>0.15</Subscript>Ca<Subscript>0.05</Subscript>O<Subscript>1.875</Subscript> sample

A Ce_0.8Sm_0.15Ca_0.05O_1.875 (S15C05DC) sample is synthesized by a solid-state reaction serving as a potential electrolyte material for intermediate-temperature solid oxide fuel cells. The sintered sample was found to be dense with a cubic fluorite structure. The addition of Ca²⁺ can act as a CeO₂ sintering aid for accelerating the process. The microstructures and properties of the sample were analyzed by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy, thermomechanical analysis, and transmission electron microscopy. Existing oxygen vacancies in the sample are indicated by a Raman peak at 558 cm^?1. The thermal expansion coefficient of the S15C05DC sample at 200–800 °C is approximately 12–14 × 10^?6 °C^?1. The control of domain size is an important factor for improving the conductivity of S15C05DC. Local clustered nano-domains, with higher Sm₂O₃ concentrations, were found to regularly arrange to induce the formation of a nanoscale C-type superlattice structure. While Ca doping decreased the formation of the C-type Sm₂O₃ structure.     

Nano-sized Pr<Subscript>0.8</Subscript>Sr<Subscript>0.2</Subscript>Co<Subscript>1-x</Subscript>Fe<Subscript>x</Subscript>O<Subscript>3</Subscript> powders prepared by single-step combustion synthesis for solid oxide fuel cell cathodes

Different sets of perovskite-type oxides of general formula Pr_0.8Sr_0.2Co_1-xFe_xO_3-δ (x = 0.0, 0.2, 0.5, 0.8 and 1.0) were successfully prepared by low-cost single-step combustion synthesis at low temperatures based on the auto-ignition reaction of a nitrate solution in the presence of citric acid. Thermogravimetric and differential thermal analysis was carried out on nitrate-citrate precursors to determine the perovskite-phase formation process. The results revealed that the nitrate-citrate precursor exhibited self-propagating combustion behavior. Pr_0.8Sr_0.2Co_1-xFe_xO_3-δ powders showed an orthorhombic single-phase, with their unit cell volume increasing as a function of the Fe content (x). Scanning electron microscopy observations showed that the prepared powders were nanocrystalline. The Pr_0.8Sr_0.2Co_1-xFe_xO_3-δ powders were characterized as fuel cell electrodes on Ce_0.8Sm_0.2O_2-δ pellets in symmetrical cells, and the electrochemical properties of the electrode/electrolyte interfaces were investigated using electrochemical impedance spectroscopy (EIS) as a function of the temperature, Fe content (x) and oxygen partial pressure.