Recent progress in two-dimensional metallenes and their potential application as electrocatalyst

In this article,we looked at metallenes,a novel class of two-dimensional(2D)metals that are attracting interest in the energy and catalysis sectors.Catalysis is one area where their exceptional physicochemical and electrical characteristics might be useful.Metallenes are unique because they include several metal atoms that are not in a coordinated bond.This makes them more active and improves their atomic uti-lization,which in turn increases their catalytic potential.This article delves into the potential of two-dimensional metals as electrocatalysts for carbon dioxide reduction,fuel oxidation,oxygen evolution,and oxygen reduction reactions in the context of sustainable energy conversion.Owing to the exception-ally high surface-to-volume ratio,large surface area as well as their optimized atomic use efficiency,2D materials defined by atomic layers are crucial for surface-related sustainable energy applications.Due to its exceptional properties,such as high conductivity and the ability to enhance the exposure of active metal sites,2D metallenes have recently attracted a lot of interest for use in catalysis,electronics,and energy-related applications.With their highly mobility,adjustable surface states,and electrical struc-tures that can be fine-tuned,2D metallenes are promising nanostructure materials for use in energy con-version with the sustainable applications.

Competitive effect, but not competitive response, varies along a climatic gradient depending on tree species identity

Background: Understanding the role of species identity in interactions among individuals is crucial for assessing the productivity and stability of mixed forests over time. However, there is limited knowledge concerning the variation in competitive effect and response of different species along climatic gradients. In this study, we investigated the importance of climate, tree size, and competition on the growth of three tree species: spruce(Picea abies), fir(Abies alba), and beech(Fagus sylvatica), and examined their competitive response and effect along a climatic gradient.Methods: We selected 39 plots distributed across the European mountains with records of the position and growth of 5,759 individuals. For each target species, models relating tree growth to tree size, climate and competition were proposed. Competition was modelled using a neighbourhood competition index that considered the effects of inter-and intraspecific competition on target trees. Competitive responses and effects were related to climate.Likelihood methods and information theory were used to select the best model.Results: Our findings revealed that competition had a greater impact on target species growth than tree size or climate. Climate did influence the competitive effects of neighbouring species, but it did not affect the target species? response to competition. The strength of competitive effects varied along the gradient, contingent on the identity of the interacting species. When the target species exhibited an intermediate competitive effect relative to neighbouring species, both higher inter-than intraspecific competitive effects and competition reduction occurred along the gradient. Notably, species competitive effects were most pronounced when the target species' growth was at its peak and weakest when growing conditions were far from their maximum.Conclusions: Climate modulates the effects of competition from neighbouring trees on the target tree and not the susceptibility of the target tree to competition. The modelling approach should be useful in future research to expand our knowledge of how competition modulates forest communities across environmental gradients.

致密砂岩碳酸盐矿物SEM-CL和EPMA矿物学表征及其成岩意义——以川西坳陷须家河组为例

扫描电镜—阴极发光(SEM-CL)可通过同时分析矿物的微观结构和阴极发光特性来反映成岩机制及流体来源,但碳酸盐矿物在SEM-CL下的发光特性及其影响因素尚不明确。应用光学显微镜阴极发光(OM-CL)、电子探针(EPMA)和SEM-CL等技术手段,以川西坳陷须家河组致密砂岩中碳酸盐矿物为研究对象,分析碳酸盐矿物在OM-CL和SEM-CL下发光特性的差异,评估影响碳酸盐矿物SEM-CL发光特性的因素,探讨砂岩中方解石胶结物的成岩意义。结果表明,相比OM-CL,SEM-CL在区分碳酸盐岩屑和碳酸盐胶结物方面具有更高的灵敏度。当Mn/Fe值低于0.1或Mn/Fe值介于0.1~0.5且Fe含量低于0.1%时,碳酸盐矿物具有中低强度的SEM-CL发光强度;当Mn/Fe值高于0.5且Fe含量高于0.1%时,碳酸盐矿物在SEM-CL照射下几乎不发光。Mn/Fe值和Fe含量是影响SEM-CL照射下碳酸盐矿物发光强度的主要因素。阴极发光分析和EPMA元素组成面扫描分析表明,方解石胶结物的元素分布是均质的,形成于同一成岩世代,晚于长石等矿物的溶解。岩屑砂岩和岩屑石英砂岩的方解石胶结物具有相同的来源,表现为高Mn/Fe特征;钙屑砂岩的方解石胶结物具低Mn高Fe特征,成分组成与白云石岩屑相似,推测流体可能受到白云石岩屑溶解的影响。

Late Eocene–early Miocene provenance evolution of the Crocker Fan in the southern South China Sea

There are many large-scale Cenozoic sedimentary basins with plentiful river deltas,deep-water fans and carbonate platforms in the southern South China Sea.The Crocker Fan was deposited as a typical submarine fan during the late Eocene–early Miocene,and stretches extensively across the entire Sarawak–Sabah of the northern Borneo area.However,systematic analyses are still lacking regarding its sediment composition and potential source suppliers.No consensus has been reached yet on the provenance evolution and sedimentary infilling processes,which seriously impeded the oil-and-gas exploration undertakings.By combining with sedimentaryfacies identification,heavy mineral assemblages,elemental geochemistry and detrital zircon U-Pb dating,this paper aims to generalize an integrated analysis on the potential provenance terranes and restore source-to-sink pathways of the Crocker Fan.In general,the Crocker Fan was initially formed over the Cretaceous–lower/middle Eocene Rajang Group by an angular Rajang unconformity.The continual southward subduction of the protoSouth China Sea resulted in magmatic activities and subsequent regional deformation and thrusting along the Lupar Line in the northern Borneo.The lowermost Crocker sequence is featured by a thick conglomerate layer sourced from in-situ or adjacent paleo-uplifts.From the late Eocene to the early Miocene,the Crocker Fan was constantly delivered with voluminous detritus from the Malay Peninsula of the western Sundaland.The Zengmu Basin was widely deposited with delta plain and neritic facies sediments,while the Brunei-Sabah Basin,to the farther east,was ubiquitously characterized by turbiditic sequences.The Crocker Fan successions are overall thick layers of modest-grained sandstones,which formed high-quality reservoirs in the southern South China Sea region.

New interpretation on the provenance changes of the upper Pinghu–lower Huagang Formation within Xihu Depression,East China Sea Shelf Basin

Both Pinghu and Huagang formations are important hydrocarbon reservoirs of the Xihu Depression in the East China Sea Shelf Basin.Clarifying the source suppliers and restoring source-to-sink transport routes are of great significance to the future petroleum and gas undertakings.Previous researchers were largely confined by either limitation of geological records,highly dependence on a singular method or low-precision dating techniques.Our study integrated heavy mineral assemblages,geochemical analyses and detrital zircon U-Pb dating to reconstruct multiple source-to-sink pathways,and to provide a better understanding on the provenance evolution for the upper Pinghu–lower Huagang depositions of the Xihu Depression.At least three major provenances have been confirmed and systematically investigated for their separate compositional features.The Hupijiao Uplift(or even farther northern area)was dominated by a major Paleoproterozoic population peaked at ca.1830 Ma along with minor Mesozoic clusters.The Haijiao Uplift to the west and the Yushan Low Uplift to the southwest,on the other hand,generate opposite U-Pb age spectra with apparently larger peaks of Indosinian and Yanshanian-aged zircons.To be noted,both Indosinian and Paleoproterozoic peaks are almost identical in proportion for the Haijiao Uplift.The overall sedimentary pattern of late Eocene-early Oligocene was featured by both spatial and temporal distinction.The Hupijiao Uplift was likely to cast limited impact during the late Eocene,whereas the broad southern Xihu Depression was transported by a large abundance of materials from the nearby Haijiao and Yushan Low Uplifts.The northern source substantially extended its influence to the farther south during the early Oligocene by delivering plentiful sediments of higher-degree metamorphic parent rocks.Combined with the proximal western and southwestern suppliers,the overall Xihu Depression was under control from both distant and local provenances.

Low-frequency laboratory measurements of the elastic properties of solids using a distributed acoustic sensing system

In recent decades,low-frequency(LF)experiments based on the forced-oscillation(FO)method have become common practice in many rock physics laboratories for measuring the elastic and anelastic properties of rocks.However,the use of the electronic displacement sensors in traditional acquisition systems of FO devices such as conventional capacitive transducers or strain gauges seriously limits both the efficiency and productivity of LF measurements,and,due to the limited contact area of the displacement sensors with a sample under test,increases the requirements for sample homogeneity.In this paper,we present the first results obtained in the development of a new laboratory method elaborated to measure the elastic properties of solids.The method is a further development of the FO method where traditional data acquisition is replaced by acquisition based on fiber-optic distributed acoustic sensing(DAS)technology.The new method was tested in a laboratory study using two FO setups designed for measurements under uniaxial and confining pressures.The study was carried out on a sample made from polymethyl methacrylate(PMMA)and an aluminium standard,first under uniaxial pressure at FO frequencies of 1,10,30,60 and 100 Hz,and then under confining pressure at an FO frequency of 1 Hz.Both uniaxial and confining pressures were equal to 10 MPa,and the strain in the PMMA sample in all measurements did not exceed 4×10^(-8).The performance of DAS acquisition was compared with the measurements conducted at a strain of 1×10^(-6) using the traditional FO method based on the use of semiconductor strain gauges and the ultrasonic method.The results of the DAS measurements are in good agreement with the FO measurements carried out using semiconductor strain gauges and with the literature data.

Geochronology and origin of Paleoproterozoic charnockites with old crustal signature in the Haisyn block of the Ukrainian shield

Results of a geochemical and geochronological study of the Paleoproterozoic rock assemblage in the Haisyn block of the Ros-Tikych Domain of the Ukrainian Shield are reported.Within the block,the Haisyn Complex comprises granitoids,including pyroxene-bearing diorites,quartz diorites,granodiorites,amphibole-biotite and biotite granites,and aplite and pegmatite granites.Monazite U-Pb isotope age of charnockitic syenite belonging to the Haisyn Complex was defined at 2027±6 Ma.This age coeval with the time of granulite facies metamorphism and emplacement of numerous granitic intrusions in the area.The Sm–Nd apatite isochron yielded an age of 2100±150 Ma.TheεNd isochron value of-5 indicates a long crustal residence time of the crustal protolith.Geochemical data do not indicate any enrichment of the studied rocks in relation to the Eoarchean and Neoarchean charnockites developed in the same area.So,if the model of partial melting of the older crustal protolith is involved then the degree of melting must be quite high.However,deep negative anomalies of Sr,Eu,Zr,and Ti indicate that plagioclase,zircon,and Fe–Ti oxides probably remained unmelted in the source.The Haisyn block was buried in the lower crust at high temperature and pressure conditions in the Paleoproterozoic time.Such a situation resulted in partial melting of the existing crust and formation of melts,containing undigested zircon and bearing ancient Nd isotope signature.

Efficient Improvement of Nutritional Content in Rice Grains by Precise Base Editing of OsROS1

Aleurone forms the outermost layer of the rice endosperm and plays a critical role in apoplastic nutrient uptake during endosperm development.Thickening the aleurone layer has been proposed to significantly increase the nutrient content of rice grains.In this study,we used a CRISPR/Cas9-mediated precise base editing method to target OsROS1,a gene associated with aleurone thickness,in the background of the japonica glutinous rice cultivar Zhennuo 19。

Biodegradation of occluded hydrocarbons and kerogen macromolecules of the Permian Lucaogou shales,Junggar Basin,NW China

Three kerogen samples(JJZG-1,JJZG-2 and JJZG-3)isolated from the Permian Lucaogou shales of varying biodegradation levels(BLs≈0,3 and 7,respectively)were subjected to sequential stepwise pyrolysis combined with on-line detection of gas chromatography-mass spectrometry(GC-MS).Occluded fractions(bitumenⅡ)released at low-temperature steps(≥410℃)show consistent biodegradative signatures with that reported for solvent-extracted fractions(bitumenⅠ)of the original shales,e.g.,broad range of abundant n-alkanes,isoprenoids and regular hopanes for the non-biodegraded JJZG-1;trace n-alkanes and abundant hopanes for the moderately biodegraded JJZG-2;and no n-alkanes but still prominent hopanes including the microbially produced 25-nohopanes for the severely biodegraded JJZG-3.This consistency between bitumenⅡand bitumenⅠfractions indicates the biodegradability of the kerogenoccluded bitumenⅡwith limited protection from host kerogen.A minor level of protection was suggested by the trace distribution of n-alkanes in the bitumenⅡof JJZG-2,whereas the bitumenⅠhad no nalkanes.The kerogen itself was more resistant to biodegradation as reflected by the persistence of high abundances of both n-alkanes and hopanes in the high temperature(≥460℃)products of all three kerogen samples.However,the relative abundances of these product groups did show some evidence of biodegradation alteration,e.g.,ratios of n-C_(15)alkene/C_(27)hop-17(21)-ene at 510℃pyrolysis decreased by order of magnitude from the non-biodegraded(JJZG-1=27.4)to highly biodegraded(0.3 for JJZG-3)samples.The reduced biodegradation impact on the kerogen fraction(Cf.bitumen fractions)was also evident by the absence of 25-norhopanes in the high-temperature analysis of the JJZG-3 kerogen.

黄河河口镇至龙门区间来水来沙变化及其对水利水保措施的响应

采用现代统计学中的变点分析法、历时曲线法和双累积曲线法对黄河中游河口镇到龙门区间1952-2000年降水、径流和泥沙量进行了综合分析。结果表明:黄河河龙区间多年平均降水量为434.5mm,径流量53.3×108m3,输沙量7.2×108t。上世纪50年代以来,区间面平均降雨量并未发生显著的趋势性变化,而径流和输沙量均发生了显著性趋势性减少,但在这种趋势性减少过程中,上世纪90年代则表现出微弱增加。与前期相比,在消除降雨量影响后,区间径流量降低幅度一般在20%-30%,而输沙量在低频率部分(相当于汛期)减小幅度达40%,高频部分(相当于非汛期)有所增加。根据建立的区间面平均降雨量与径流量及输沙量关系分析,黄河河龙区间因人类活动的直接作用使区间径流量年均减少18.8×108m3,输沙量年均减少3.7×108t。与前期相比,区域水土保持措施是区间径流和泥沙减少的主要驱动力。

三种VOCs物性对其在活性炭上吸附行为的影响

为了探讨VOC物性对活性炭吸附行为的影响,对活性炭表面物化性质进行了表征。并以甲苯、丙酮、二甲苯为吸附质,在同等实验条件下进行了固定床吸附实验。实验结果显示活性炭对3种VOCs的吸附量为二甲苯>甲苯>丙酮。将实验结果与VOC物性进行关联分析,结果表明:活性炭对有机气体的吸附量随着吸附质的分子量、分子动力学直径、沸点、密度的增大而增大,且呈现良好的正线性关系;而吸附质的极性指数和蒸气压则与活性炭吸附量呈现出相反的关系;3种活性炭对吸附质吸附能的排序均为二甲苯>甲苯>丙酮。

基于APSIM模型的灌溉降低冬小麦产量风险研究

华北平原是我国冬小麦主产区,干旱是影响该地区冬小麦产量稳定的最主要的灾害之一。进行产量风险评估以及如何通过灌溉降低干旱产量风险对于该地区冬小麦稳产高产具有重要的现实意义。该文利用澳大利亚的APSIM农业生产系统模拟模型,以华北平原北京和山东禹城为例,分析了不同降水年型条件下冬小麦的产量风险;通过不同灌溉方案的设计和模拟,分析了不同的灌溉方案在各种年型条件下对降低冬小麦产量风险的作用。结果表明:北京和禹城地区冬小麦生育期内绝大部分年份降水不能满足作物的需水,严重缺水年型出现的频率均在30%左右,两地该年型的平均产量仅为2445和2466kg/hm2,产量风险较高。灌溉对于降低产量风险具有明显的作用,但需根据不同的缺水年型选择适宜的灌溉方案。在兼顾冬小麦稳产高产和提高水分利用效率的前提下,严重和中度缺水年型进行3次补充灌溉,分别为底墒水、拔节水和开花水,而在轻度缺水年型条件下,底墒水和拔节水两次灌溉即可大大降低干旱带来的产量风险,灌水定额为50～70mm,且随缺水程度的降低和灌溉次数的增加,可以适当减小灌水定额。

内蒙古苏尼特左旗南两类花岗岩同位素年代学及其构造意义

内蒙古北部索伦缝合带(索伦-苏尼特左旗-锡林浩特)被多数中外学者认为是西伯利亚板块南缘和华北板块北缘的最终缝合带。本文选择该缝合带上苏尼特左旗南两类花岗岩——与俯冲有关和与碰撞有关的岩浆岩(分别叫弧岩浆岩和碰撞花岗岩)进行同位素年代学研究。结果表明:①弧岩浆活动有两期,分别约为490Ma和310Ma(锆石U-Pb,SHRIMP);碰撞花岗岩的侵位年代在230～250Ma(Rb-Sr全岩和锆石U-Pb);②根据本文新的年代学数据,索伦缝合带的最终缝合时间可能是在230～310Ma,这显然不同于国内多数学者坚持的“晚泥盆世碰撞”模式;而Sengor等推测的“晚二叠世碰撞”模式与本文数据一致。

华北地区冬小麦产量潜力分布特征及其影响因素

利用华北地区农业气象观测站作物资料,验证APSIM-Wheat作物模拟模型区域尺度有效性,结合1961—2007年47年逐日气候资料,分析冬小麦潜在产量、水分限制产量和水氮限制产量时空分布特征,明确了气候因素对冬小麦不同等级产量潜力分布特征的影响程度。对APSIM-Wheat模型在华北地区区域尺度上进行验证,结果显示区域化模型在华北地区有较好的适用性。华北地区冬小麦各层次产量在时间上总体呈下降趋势,空间上呈带状分布,不同层次产量空间分布特征有所差别:冬小麦潜在产量从东北向西南减少,水分限制产量从东南向西北递减,水氮限制产量从东向西先增加后降低在山东济宁地区达到最大;河北省为冬小麦潜在产量和水氮限制产量的高值区,同时为水分限制产量的低值区,增加灌溉是提高其产量的主要途径;山东省为冬小麦潜在产量和水分限制产量的高值区,水氮限制产量的低值区,增施氮肥是提高其产量的主要途径;河南省为冬小麦潜在产量的低值区,辐射是其主要限制因素。决定冬小麦潜在产量时空分布特征的最主要气候要素为生长季内总辐射,总辐射与潜在产量呈极显著正相关关系;决定冬小麦水分限制产量分布特征的最主要气候要素为冬小麦生长季内降水量,呈极显著正相关关系;气候要素对于冬小麦水氮限制产量空间分布特征的解释方差较小,仅为0.48,故土壤等其他因素对其空间分布影响较大。气候变化背景下,如不改变作物品种,冬小麦各级产量潜力呈下降趋势,造成其下降的主要原因为总辐射下降以及随积温增加冬小麦生长季缩短,决定冬小麦产量潜力空间分布的主要因素为总辐射和降水量。

黄河中游河口—龙门区间多年平均流域水平衡特征——区域蒸散量估算模型验证与下垫面参数校核

采用黄河中游河口镇至龙门区间1980-2000年间径流及气象数据,通过对Zhang等2001建立的区域(流域)多年平均蒸散量估算模型进行验证和下垫面参数校核工作,探索了干旱半干旱地区水循环要素相应于不同土地覆被类型的结构变化及水平衡特征和规律。结果表明,由于研究区处于干旱半干旱气候区,采用原模型及参数对蒸散量的预测能力好于对径流的预测能力。使用优化后的下垫面参数使原模型对河龙区间蒸散量和径流预测能力得以改进,一致性指标分别从0.89和0.21提高到0.94和0.63。对实际蒸散量进行预测的相对误差和均方误从3.6%和17.2mm减小到1.5%和7.9mm,对径流进行预测的相对误差从42.7%减小到18.0%。聚类分析和下垫面参数优化结果表明,河龙区间流域水循环要素变化特征受不同土地覆被影响可以分为3个明显不同的区域。由于大面积林地截流蒸发的作用,南部林地覆被区具有较高蒸发系数,适用下垫面参数值为1.61。西北部风沙地貌区受粉沙覆盖层和地下径流补给影响,使该区蒸发系数较小,适用值为0.1。中部典型黄土丘陵覆盖区适用值为0.45。

海南5年生木麻黄优良无性系的选择与评价

在海南岛东林场和文昌林科所两个试验点通过观测树高、胸径、保存率、干形和抗风性,开展了24个木麻黄无性系的选择研究。结果表明:两个试验点24个无性系在树高和胸径生长都有极显著差异,5年生的平均树高、胸径和单株材积分别为13.2 m、10.6 cm和0.048 m3,最优无性系平均树高和胸径分别达到15.2 m和13.0 cm,平均材积为106.67 m3/hm2,年均材积生长量为21.33m3/hm2,最优无性系年均材积生长量29.89 m3/hm2;通过6个性状的综合评价,在岛东试验点选出适合该地区的6个无性系分别为A1、F41、NS-8、A13、F40和ZaJiao;在文昌试验点选出适合低洼地的6个无性系分别为F71、701、A13、A8、F20、ZJ-001;根据无性系的树高和胸径生长曲线,发现造林后第2年无性系的生长速度最快,5年生木麻黄的无性系仍处于高速生长期。

13X微孔沸石和MCM-41介孔材料的合成及用于处理含Cd^(2+)废水

以天津蓟县钾长石矿粉为主要原料,经选矿、煅烧、水热处理等工艺成功合成了13X微孔沸石．以气相氧化硅、氢氧化钠、十六烷基三甲基溴化铵等为主要原料,在水热条件下合成了MCM-41有序介孔材料．采用XRD和N_2吸附-脱附等手段对合成的13X沸石和MCM-41介孔材料的物相、比表面积、孔径、孔体积等进行了分析对比．在此基础上,对13X沸石和MCM-41介孔材料处理含Cd^(2+)废水的效果和机理进行了对比研究,确定了不同分子筛用量、不同初始pH值、不同混合时间下13X沸石和MCM-41介孔分子筛对水中Cd^(2+)的吸附率和吸附量．研究发现,尽管MCM-41的比表面积和孔径远大于13X沸石,但其对水中Cd^(2+)的处理效果却低于13X沸石,这与13X沸石和MCM-41的孔道结构类型、化学组成、表面荷电性质等有关．

乌克兰地盾超大型碱交代型铀矿床特征及热点深源成矿模式

碱交代型铀矿床是乌克兰最主要的铀矿床类型,文章分析了乌克兰地盾地质构造作用,认为研究区是一个元古宙时期长期多期次岩浆热液活动中心,并与深部壳幔热物质隆升有关,是一个较典型的元古宙热点作用区,总结了热点作用早期、中期和晚期特点;较系统地介绍了米丘林、谢维林、新康士坦丁诺夫、瓦图津、黄水和五一(超)大型钠交代型铀矿床的地质特征,从铀矿化含矿主岩具多样性和相对独立性、交代作用的统一性、成矿物质的深源性和成矿时代的相近性等多方面阐明了矿床的成矿机理,建立了乌克兰地盾中部铀成矿省元古宙热点深源钠交代型铀成矿模式,乌克兰地盾中部铀矿省不同类型矿床形成于统一的热点作用区,较好地解释了其产出空间相对集中性、时间相对一致性和成因上相似性的特点,对实际找矿预测具有重要意义。

核壳结构p-n异质结复合光催化剂BiFeO_3@TiO_2的制备及其在可见光催化降解中的应用（英文）

化石燃料的迅速消耗导致环境污染与能源危机日益加剧.太阳能高效利用与转换是解决该难题的有效途径之一.在众多光催化剂中,TiO_2因其高催化活性、高稳定性、低毒性以及低成本等优势而普遍受到关注,但TiO_2存在着带隙过宽而无法利用可见光的缺陷,严重制约了其在光催化方向的实际应用.核壳型复合纳米材料具有较大的比表面积、较高的光吸收能力以及所吸附的污染物分子易于从吸附面扩散到光致降解面等特点,而表现出较强的有机污染物吸附性能以及良好的光催化活性.以磁体材料为核将TiO_2包覆于磁体表面,可以制备具有磁分离特性的磁载光催化剂.而铁酸铋作为一种在室温下同时具有铁电性和铁磁性的钙钛矿型材料,由于其较窄的带宽(2.1 e V)在可见光催化氧化方面也受到了极大的关注.本文首先通过柠檬酸自燃烧法制备了可磁性分离的BiFeO_3粉体,再以水解沉淀法将TiO_2包裹在BiFeO_3前驱体上形成了不同质量比(1:1,1:2,2:1)的核壳结构的BiFeO_3@TiO_2复合粉体,并以甲基紫为例,对其在紫外光和可见光照射下的光催化性能分别展开了研究.结果表明,BiFeO_3@TiO_2复合粉体的光催化性能较单独的BiFeO_3或TiO_2均有所提升.其中质量比为1:1的BiFeO_3@TiO_2复合粉体(TiO_2壳层厚度为50–100 nm)展现出最强的光催化氧化活性,且在可见光下有更高的光催化效率.经表征分析,该复合粉体光催化性能高的原因可能归结于BiFeO_3与TiO_2两者之间形成了p-n异质结界面,有效地提高了电荷载流子的传输分离效率,同时BiFeO_3较窄的禁带宽度拓展了纳米TiO_2的光谱吸收范围,增强其光吸收能力.光电化学Mott-Schottky测试结果进一步证实:BiFeO_3粉体在与TiO_2复合之后,其电荷载流子传输与供体密度均有显著提升.自由基猝灭实验表明,在甲基紫光催化降解中起主要作用的为羟基自由基与光生电子,并结合能带理论与自建电场理论对降解机理进行了阐述.进一步研究表明,甲基紫降解效果最优条件为:复合粉体的投加量为1 g/L,甲基紫初始浓度为10 mg/L,初始pH为5.另外,质量比1:1的BiFeO_3@TiO_2对甲基橙和刚果红染料废水也具有较好的降解效果,表现出良好的工业应用前景.

胶莱盆地晚白垩世玄武岩的年代学和地球化学特征及其对华北岩石圈减薄-增生的制约

已有研究认为华北岩石圈减薄的时空不均一是显著的,主要表现在软流圈来源的岩浆最早出现的时间呈现南北差异。本文通过40Ar-39Ar法获得胶莱盆地西官庄拉斑玄武岩的年龄为96±3Ma,属于青山群火山岩的一部分,早于王氏群大西庄碱性玄武岩(73Ma)。两套岩石均缺乏Nb、Ta负异常,分别具有与E-MORB和OIB类似的微量元素配分特征。西官庄拉斑玄武岩((87Sr/86Sr)t=0.7058,εNd(t)=0.37～0.57)和大西庄碱性玄武岩((87Sr/86Sr)t=0.7040,εNd(t)=5.5～5.7)的同位素组成特征均显示软流圈的印记。前者为软流圈熔体与古老富集岩石圈地幔相互反应的产物,而后者是软流圈部分熔融的产物。研究区岩浆的εNd(t)值随年龄的降低而逐渐增大,暗示古老岩石圈减薄过程中软流圈的上涌,说明研究区晚白垩世-早新生代岩石圈仍在经历减薄作用。类似的岩浆演化趋势在辽西和辽东地区也有发现,不过演化的时间分别为120～100Ma和80～60Ma,再次证明华北岩石圈减薄作用的时空不均一性。