Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： HR3C steel is a new type of austenitic heat-resistant steel which has been widely used for superheater and re-heater tubes in the ultra-supercritical (USC) boiler. The mechanical properties of HR3C steel were dependent on the stability of the microstructure, particularly the large amount of precipitates formed during service. The precipitation of s phase in HR3C steel during long-term aging for 2000 h at temperature of 700 and 750 ℃ was investigated by OM, SEM and TEM. The phase calculation method was applied to understand the factors influencing the precipitation. After 1000 h of the aging duration, irregular mass second phase was found to precipitate at the grain boundary, followed by the subsequent increasing and coarsening with time. The constituent elements of the phases were determined as Fe and Cr through SEM equipped with EDS. Further SAED analysis results led to the confirmation that these phases were basically s- FeCr compound. Combined with the prediction made through New PHACOMP method, the microstructure or phase structure in initial state may affect the subsequent precipitation behavior.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Bulk Nb-doped lead telluride Pb1.1Te was prepared by using a combined process of mechanical alloying (MA) and spark plasma sintering (SPS). Then its transport properties such as electrical resistivity, Seebeck coefficient and thermal diffusion coefficient were measured in a temperature range from 323 K to 673 K. As a result, the doped Nb can effectively enhance the phonon scattering ability of the lead telluride Pb1.1Te, and optimize its electrical performance as well. Large power factors of over 20 mW/(cm� K2) were obtained in a wide temperature range (523-623 K). In addition, the thermal conductivity decreased with the increasing Nb content, which may also be resulted from the increase of the phonon scattering ability, thereby an optimal ZT value may be found. A maximum ZT value of 1.27 was obtained for Pb1.03Nb0.07Te at 673 K, which was twice as high as that for the un-doped Pb1.1Te.
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区研究》
Abstract：为了探讨近30 a来我国干旱区荒漠植被的净初级生产力 (NPP)及其与水热因子相关性随时间的变化，运用CASA(Carnegie Ames Stanford approach)模型估算我国荒漠植被1982—2015年生长季的NPP，并运用线性回归和GIS空间分析方法分析了NPP的时空变化特征，利用滑动相关系数分析了荒漠植被NPP与水热因子的关系。结果表明：① 单位面积NPP均值为42 g·m-2·a-1，NPP整体水平较低。空间上呈西北部、东部边缘较高，中部、南部和中东部较低的分布特征。② 荒漠植被NPP年均总量为5.783×1013 g·a-1。从荒漠植被NPP的年际变化来看，1982—2015年中国荒漠植被NPP总量以1.64×1012 g·(10a)-1的线性速率（P=0.054）上升，荒漠植被生长状况总体上不断改善，但总量趋势呈现阶段性变化，1982—1993年荒漠植被NPP总量呈极显著增长态势（1.25×1012g·a-1，P0.05）。从空间变化来看，47.65%的荒漠植被NPP呈增加态势，主要分布在阿拉善高原、天山北麓、塔里木盆地西部边缘、柴达木盆地的东南边缘、阿尔金山南麓和昆仑山脉。③ 从荒漠植被NPP与各气候因子之间的相关关系随时间的变化来看，NPP与气温的滑动相关系数随时间的变化保持为负相关，与降水、干燥度的滑动相关系数保持为正相关，与太阳总辐射的滑动相关系数随时间变化并未表现出显著的变化趋势。总体上，荒漠植被与水热因子的相关关系在研究时段均有进一步减弱的态势，即荒漠植被NPP对气候因子的变化愈来愈不敏感。
Subjects: Biology >> Ecology submitted time 2018-06-09 Cooperative journals: 《生态学报》
Abstract：基于1982-2015年气象数据，采用线性趋势分析和GIS空间分析方法对我国近34年季节性昼夜增温的时空格局进行分析；并结合GIMMS-NDVI 3g遥感数据和植被区划数据，采用偏相关分析方法探讨不同植被分区植被对季节性不对称性增温的响应。结果表明：（1）近34年来中国昼夜气温普遍存在极为显著的上升趋势；昼夜增温在各季节均表现出不对称特征，且该不对称特征存在明显的季节性差异，春季、夏季、秋冬和冬季白天增温速率分别为夜间增温速率的1.49倍、0.98倍、0.73倍和1.69倍；（2）不同分区植被对季节性昼夜不对称增温的响应各异：相对于夜间增温，白天增温对植被活动影响程度更大，影响区域更为广泛；春季和冬季昼夜增温对植被活动的影响范围更广，且春、秋季昼夜增温对植被NDVI的上升普遍起到促进作用；（3）季节非对称性昼夜增温对不同分区的植被活动有不同的影响，这种影响程度随季节的变化存在明显差异。通过分析中国昼夜增温的季节性变化趋势及其对不同类型植被的影响，有助于加深我们对全球气候变化背景下季节性昼夜不对称增温对中国陆地植被动态影响的认识。
Subjects: Materials Science >> Materials Science (General) submitted time 2017-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract：由于油气输送管道腐蚀因素复杂，腐蚀破坏形式多，腐蚀相关理论还不够完善，因而没有一种适用于各种情况的防腐技术，管道防腐在未来的发展中是将各种技术综合起来，以减缓管道的腐蚀。更高钢级的管线钢的使用不仅可以减少成本，还能够提高效率，本文简要介绍了现在使用的防腐技术，并阐述了环境因素（微生物、CO2浓度）、管道运行参数（流速、压力）和焊缝区对油气输送管道腐蚀的影响。建议对X100/X120在各种环境下的腐蚀规律及机理、各种因素对腐蚀影响的关联性等进行研究，以确定更加经济合理的腐蚀防护措施。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-10 Cooperative journals: 《中国腐蚀与防护学报》
Abstract：摘要：研究了Cr13马氏体不锈钢在盐酸喷射条件下的腐蚀形貌，发现射流中心与样品表面接触区域产生圆状点蚀坑、四周形成放射性分布的彗星状腐蚀沟槽；随腐蚀时间延长，蚀坑和沟槽密度增加；扫描电镜观察发现，彗星状腐蚀沟槽由点蚀坑和尾部的沟槽组成；点蚀坑起源于MnS夹杂处，彗星尾部沟槽主要发生在马氏体区，而?铁素体区没有明显腐蚀。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract：采用应力松弛方法研究了2种HR3C耐热钢的初始态试样和时效态试样的高温蠕变变形行为，并分析了其微观组织特点。结果表明，尽管2种HR3C耐热钢的化学成分相近，但其蠕变行为有明显差异。相同条件下，晶粒较粗的HR3C耐热钢初始态与时效态的蠕变速率均低于晶粒较细的HR3C耐热钢，具有较高的蠕变抗力。2种HR3C耐热钢经过高温时效处理后，蠕变抗力均明显降低。晶粒较细小的HR3C钢在高温时效后其应力指数(n)与蠕变表观激活能(Q)的降低幅度更加显著，表明晶粒较细的HR3C耐热钢的蠕变抗力的稳定性低于晶粒较粗的HR3C耐热钢。
Hits
Hits
Downloads
Comment