Varnish microlaminations: new insights from focused ion beam preparation     

David Krinsley  Jeffrey Ditto  Kurt Langworthy  Tyler Thompson 《自然地理学》2013,34(3):159-173

The cross-sectional texture of rock varnish varies considerably with the scale of analysis and technique used to image a sample. Each jump in resolution results in new insight, with the current state-of-the-art resting at the nanoscale. One key to nanoscale analysis involves focused ion beam (FIB) techniques used most frequently in material science and semiconductor failure analysis. FIB preparation remains challenging, however, for samples like rock coatings with heterogeneous density and abundant porosity. A new technique involving multiangle ion thinning and in situ plan-view lift-out facilitated a scanning transmission electron microscopy study of rock varnish from Death Valley. The results reveal variability in lateral continuity of nanometer microlaminae that can be interrupted by post-depositional diagenesis involving leaching of Mn and Fe, and this variability could explain why some of the visual varnish microlaminations (VML) used in paleoclimatic research can sometimes appear discontinuous. Because these breaks result from post-depositional processes, they do not undermine the paleoclimatic interpretations of VML.  相似文献   

新型有机-无机杂化涂层-气相色谱/质谱联用测定正构烷烃性能研究     

邓海冬  帅琴  丁晓晓  顾涛  朱丹 《岩矿测试》2012,31(6):1015-1020

水体中正构烷烃的含量反映了研究区域有机物污染水平.痕量正构烷烃的测定常常需要结合分离富集方法才能保证灵敏度和选择性,液液萃取等常规分离富集方法存在耗时长、有机溶剂使用量大等缺点,而新型固相微萃取(SPME)分离富集技术相比而言具有高效简便、富集效率高的特点.本文采用溶胶-凝胶法自制稳定性和耐基质性能更优的有机-无机杂化SPME涂层,结合气相色谱-质谱(GC - MS)检测技术,对水样中26种正构烷烃进行同时测定.在优化的SPME - GC/MS条件下,采用浸入式萃取方式,萃取温度为25℃,萃取时间为30 min,26种正构烷烃的分析信号与浓度之间有良好的线性关系(线性相关系数为0.9935 ～0.9999),方法检出限为0.011 ～0.085μg/L(k=3),相对标准偏差(RSD,n=5)为3.9％ ～10.0％.新型有机-无机杂化涂层与传统的分离富集技术相比,减少了有机溶剂的使用,提高了工作效率;与商用PDMS涂层相比,增加了正构烷烃同时检测的种类,提高了灵敏度,检出限低2～10倍.自制的有机-无机杂化SPME涂层体现出优异的分析性能和应用潜力.  相似文献   

铬的迁移形式、成矿机理新探          下载免费PDF全文

郑大中  郑若锋 《地质找矿论丛》2012,27(1):1-8

通过对地球深部富氢流体、若干金属氢化物及合金氢化物的形成条件与性质、铬矿物的化学成分及其共生伴生矿物的研讨,结合铬铁矿成矿的地质背景,认为铬氢化物、铬合金氢化物是铬成矿的主要迁移形式。它们从地球深部富氢强还原环境随岩浆迁移至地壳浅部,由于H2,CO,CH4等逃逸、氧化,氧逸度大增,温度、压力下降,铬氢化物和铬合金氢化物分解、氧化、固化富集成铬矿床。  相似文献   

津巴布韦舒鲁圭透镜状铬铁矿成因          下载免费PDF全文

王铁军  刘晓阳  林锐华  杨秀峰 《地质找矿论丛》2012,27(4):485-490

通过对津巴布韦舒鲁圭透镜状铬铁矿地质背景、构造控矿特征、矿体赋存空间特征、蚀变岩组合、矿石结构构造特征的总结分析,提出舒鲁圭铬铁矿流体成矿假说,认为太古宙超基性杂岩侵入的同时,富含铬合金氢化物的H2-CH4超临界流体沿构造带侵入到地壳浅部,并与构造带内水混合,水与铬合金氢化物发生化学反应,产生的铬尖晶石沉淀在构造带内,形成透镜状铬铁矿体。  相似文献   

海拉尔盆地贝尔凹陷储层物性特征及控制因素   总被引：8，自引：2，他引：6  

曹瑞成  曲希玉  文全  鲍春艳  刘剑营  刘娜  刘立 《吉林大学学报(地球科学版)》2009,39(1):23

贝尔凹陷铜钵庙组-南屯组的储层类型为中-低孔低渗型,存在两个异常高孔隙发育带：第一异常高孔隙带为1 300~1 800 m,第二异常高孔隙带为2 400~2 700 m。异常高孔隙发育带的控制因素为：①火山碎屑物质对孔隙的保存及其溶解形成的次生孔隙;②碎屑颗粒包壳对原生孔隙的保存;③大气水淋滤形成的次生孔隙;④有机酸溶蚀形成的次生孔隙。其中大气水淋滤形成的次生孔隙对异常高孔隙的贡献较小。由于贝尔凹陷内有机质热解产生的有机酸主要溶蚀对象是火山碎屑岩,且火山碎屑岩溶蚀产生的各种阳离子是绿泥石和伊利石的主要组成元素,所以贝尔凹陷异常高孔隙发育的根本控制因素是储层岩石类型的特殊性。  相似文献   

Shaking table tests of steel frame with superelastic Cu–Al–Mn SMA tension braces          下载免费PDF全文

Yoshikazu Araki  Kshitij C. Shrestha  Nao Maekawa  Yuji Koetaka  Toshihiro Omori  Ryosuke Kainuma 《地震工程与结构动力学》2016,45(2):297-314

Shaking table tests are performed on a one‐bay one‐story steel frame with superelastic Cu–Al–Mn shape memory alloy (SMA) tension braces. The frame is subjected to a series of scaled ground motions recorded during the 1995 Kobe earthquake, Japan. The test results demonstrate that the SMA braces are effective to prevent residual deformations and pinching. It is also shown that the time history responses observed from the shaking table tests agree well with the numerical predictions using a rate‐independent piecewise‐linear constitutive model calibrated to the quasi‐static component tests of the SMA braces. This suggests that the loading rate dependence of Cu–Al–Mn SMAs as well as the modeling error due to the piecewise linear approximation can be neglected in capturing the global response of the steel frame. Numerical simulations under a suite of near‐fault ground motion records are further performed using the calibrated analytical models to demonstrate the effectiveness of the SMA braces when the variability of near‐fault ground motions is taken into account. A stopper, or a deformation restraining device, is also proposed to prevent premature fracture of SMA bars in unexpectedly large ground motions while keeping the self‐centering capability in moderate to large ground motions. The effectiveness of the stopper is also demonstrated in the quasi‐static component and shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

确定厚型防火涂料高温导热系数的实用方法     

万夫雄  郑文忠 《地震学刊》2014,(2):211-215

目前,厚型防火涂料高温导热系数的取值尚不清楚,因而无法准确地对厚型防火涂料保护的结构进行抗火理论分析和设计。针对这一问题,本研究将厚型防火涂料视为主要由粘结基料和隔热骨料所组成的复合物,利用并联和串联2种计算模型,分别建立了厚型防火涂料的高温导热系数计算公式;采用得到的高温导热系数值进行温度场分析,并将计算值与实测值进行对比。结果表明,利用并联模型公式得到的厚型防火涂料高温导热系数取值最为合理。据此,给出了确定厚型防火涂料高温导热系数的实用方法,为解决厚型防火涂料高温导热系数的取值问题提供了一条有效途径。  相似文献   

形状记忆合金橡胶对高架桥梁碰撞减震效果的试验研究   总被引：2，自引：0，他引：2  

李素超  郭安薪  崔丽丽  李惠 《地震学刊》2014,(5):559-565

地震作用下,高架桥梁相邻主梁间的碰撞会引起结构位移和加速度响应增大、应力提高,导致混凝土开裂、脱落和伸缩缝被挤压破坏,甚至引发桥梁落梁和倒塌等,因此采取减轻或者避免桥梁结构在地震作用下碰撞的措施显得尤为必要。设计制备了具有变形自恢复能力的形状记忆合金橡胶碰撞缓冲器,通过桥梁地震碰撞的振动台试验,研究了形状记忆合金橡胶缓冲器对桥梁碰撞的控制效果,提出了碰撞缓冲器吸能效率和结构自身耗能控制率指标。研究表明,形状记忆合金橡胶碰撞缓冲器具有稳定的吸能效率,能够大幅度降低桥梁结构碰撞加速度和碰撞力,这对于提高城市交通网络的地震安全性能具有重要意义。  相似文献   

Penetration of molten iron alloy into the lower mantle phase     

Takashi Yoshino 《Comptes Rendus Geoscience》2019,351(2-3):171-181

The core–mantle boundary is the only interface where the metallic core and the silicate mantle interact physically and chemically. Many geophysical anomalies such as low shear velocity and high electrical conductivity have been observed at the bottom of the mantle. Perturbations in the Earth's rotation rate at decadal time periods require the existence of a thin conductive layer with a conductance of 10⁸ S. Substantial additions of molten iron from the outer core into the mantle may produce these geophysical anomalies. Although iron enrichment by penetration has only been observed in (Mg,Fe)O, the second dominant mineral in the lower mantle, the penetration process leading to iron enrichment in the silicate mantle has not been experimentally confirmed. In this study, high-pressure and high-temperature experiments were conducted to investigate the penetration of molten iron alloy into lower mantle phases; postspinel, polycrystalline bridgmanite and polycrystalline (Mg,Fe)O. At the interface between (Mg,Fe)O aggregate and molten iron alloy, liquid metal penetrated the (Mg,Fe)O aggregate along grain boundaries and formed a thin layer containing metal-rich blobs. In contrast, no penetration of molten iron alloy was observed at the interface between molten iron alloy and silicate phases. Penetration of liquid iron alloy into the (Mg,Fe)O aggregate is caused by the capillarity phenomenon or Mullins–Sekerka instability. Neither mechanism occurs at the boundary of pure polycrystalline MgO, indicating that the FeO in (Mg,Fe)O plays an essential role in this phenomenon. Infiltration of molten iron alloy along grain boundaries (capillarity phenomenon) is the dominant process and precedes penetration due to the Mullins–Sekerka instability. The capillarity phenomenon is governed by the balance of forces between surface tension and gravity. In the case where the ultralow velocity zone (ULVZ) with a low shear velocity is composed of Fe-rich (Mg,Fe)O, the maximum penetration distance of molten iron alloy by capillary rise is limited to 20 m. The addition of iron-rich melt to the base of the mantle is therefore unlikely to be the main cause of the high conductance of the CMB region predicted from decadal variation of the length of day. Furthermore, the absence of molten iron alloy penetration into silicate phases does not allow an extensive modification of the chemical composition of the mantle by core–mantle interaction.  相似文献   

高层钢结构地震反应形状记忆合金拉索控制研究   总被引：3，自引：0，他引：3  

丁阳  张笈玮 《地震工程与工程振动》2005,25(3):152-157

本文通过形状记忆合金(SMA)材料的超弹性性能试验确定了SMA材料的各项参数和常温状态下的本构模型。对采用SMA拉索实施振动控制的20层钢结构的Benchmark模型的地震响应进行了时程分析。计算结果表明,实施SMA拉索控制后,层间相对位移可降低70％左右,且SMA材料很好的耗能作用有效地减少了地震能量向上部楼层的传递,对上部结构具有一定的隔振作用;顶层相对位移的控制效果达到51％;顶层加速度可降低43％;地震波强度和拉索初应变对拉索的被动控制效果影响较大。最后给出了拉索的安装位置与拉索的应变之间的关系曲线,建议了合理的布置方案。  相似文献