Fluxes Of Cu Research Articles

Inhibiting the formation of interfacial voids in Cu/In/Cu microbump via Zn doping into Cu substrate

To address warpage issues in 3D-IC, low temperature soldering technology such as Cu/In bonding has been developed in recent years. However, the formation of Kirkendall voids at the original Cu/In interface would lead to degradation of joint reliability. By adding Zn, the diffusional flux of Cu was inhibited, and the numbers of interfacial voids larger than 50 nm decreased substantially by 66% at top interface and 58% at bottom interface, respectively. In this study, Cu-15Zn/In/Cu system was investigated and could be regarded as a promising option for advanced electronic packaging in the future.

Modified LIX®84I-Based Polymer Inclusion Membranes for Facilitating the Transport Flux of Cu(II) and Variations of Their Physical-Chemical Characteristics.

A unique facilitation on the transport flux of Cu(II) was investigated by using modified polymer inclusion membranes (PIMs). LIX®84I-based polymer inclusion membranes (LIX®-based PIMs) using poly(vinyl chloride) (PVC) as support, 2-nitrophenyl octyl ether (NPOE) as plasticizer and Lix84I as carrier were modified by reagents with different polar groups. The modified LIX®-based PIMs showed an increasing transport flux of Cu(II) with the help of ethanol or Versatic acid 10 modifiers. The metal fluxes with the modified LIX®-based PIMs were observed varying with the amount of modifiers, and the transmission time was cut by half for the modified LIX®-based PIM cast with Versatic acid 10. The physical-chemical characteristics of the prepared blank PIMs with different Versatic acid 10 were further characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), contract angle measurements and electro-chemical impedance spectroscopy (EIS). The characterization results indicated that the modified LIX®-based PIMs cast with Versatic acid 10 appeared to be more hydrophilic with increasing membrane dielectric constant and electrical conductivity that allowed better accessibility of Cu(II) across PIMs. Hence, it was deduced that hydrophilic modification might be a potential method to improve the transport flux of the PIM system.

Thermomigration suppression in Sn3.5Ag solder joints by hot-end FeCoNiMn alloy

Temperature gradient is inevitable in solder joints in advanced electronic packaging; it induces thermomigration (TM), critically affecting the reliability of micro solder joints. Although a FeCoNiMn alloy (FCNM) can resist thermal aging in solder joints, its TM resistance has seldom been examined. Thus, this study investigated the TM in Cu/Sn3.5Ag (SA3.5)/FCNM solder joints between a cold end (50 °C) and a hot end (200 °C) at different times. A multielement intermetallic compound (MEIMC), (Cu, Mn, Fe, Co, Ni)6Sn5, is formed at the SA3.5/FCNM interface in the reflowed and aged solder joints. A (Fe, Co, Ni, Mn)Sn2 MEIMC also formed, but it was very thin. The (Cu, Mn, Fe, Co, Ni)6Sn5 was completely decomposed by TM from the hot-end FCNM. In contrast, the (Cu, Mn, Fe, Co, Ni)6Sn5 MEIMC thickened as the rapid TM flux of Cu from the hot-end Cu cap; however, the low chemical flux from FCNM hindered its formation, which was replaced by Cu6Sn5 formation near the Cu/SA3.5 interface. The findings demonstrate that FCNM providing a very low chemical flux is a remarkably promising diffusion barrier for TM in micro solder joints.

Selective recovery of Cu(II) through polymer inclusion membranes mediated with 2-aminomethylpyridine derivatives

The Cu(II) separation behaviors with polymer inclusion membranes (PIMs) are explored by modifying 2-aminomethylpyridine derivatives with hydrophobic alkyl chains, including 2-[N-(tert-butyloxycarbonylmethyl)- 2-picolyamino]acetate (AMB), N,N-dioctyl-2-aminomethylpyridine (AMD), tert-butyl 2-(N-octyl-2-picolyamino) acetate (AMC), and N,N-didecyl-2-aminomethylpyridine (AME). The transport flux and selectivity of Cu(II) are determined by optimizing composition and structure of carriers and plasticizers. The results show that the hydrophobic modification of 2-aminomethylpyridine derivatives can boost the selective transport of copper ions in PIMs and membrane stability. In the optimum composition of 30 wt.% PVC, 30 wt.% AME, and 40 wt.% NPOE, the initial flux of Cu(II) is 5.8×10−6 mol·m−2·s−1. The FT-IR and XPS spectra identify that the alkyl amine functional groups of AME involve in the transport of copper chloride species. The SAXS analysis demonstrates that the generated micro-channels in PIMs induced by the hydrophobic modification of 2-aminomethylpyridine derivatives can contribute to the enhanced Cu(II) flux.

Release flux of heavy metals from river sediments at different flow rates

Abstract This paper simulates sediment motion under different hydrodynamic conditions, aiming to investigate the release flux of heavy metals in river sediments. During the lab experiments, carried out in a circular rectangular flume device, water velocity in the flume was altered by controlling the gate switch, and the flow rate was controlled from 0 to 1 m/s. Sediment from the Le'an River and chlorine-removed tap water were used as experimental sediment and water, respectively. Through analyses of Cu, Zn, Cd, and Pb concentration in water at different flow rates, the relationship between the release flux (y) of Cu, Zn, Cd, and Pb and the flow rate (x) was established with a fitting error of less than 15%. In order to judge the reliability of the conclusions, experimental results were verified outdoors. The results showed when the sediment particle size is between 0 and 250 μm, within 1 hour, a quadratic polynomial correlation between the release flux of Cu, Cd, and Pb from river sediments and water velocity when the water pH is 5–9 and the flow rate is 0–65 cm/s; when the water pH is 5–9, the flow rate is 0–35 cm/s, the release flux of Zn from river sediments was shown to have a quadratic polynomial relationship with water velocity. The error between the calculated and measured values of heavy metals released from sediment in the Le'an River were within 5–30%. Our results can provide a theoretical reference for the control and treatment of heavy metal pollution in rivers and further improve corresponding water quality models.

Quantification of spatial and temporal variations in trace element fluxes originating from urban areas at the catchment scale

The release of trace elements (TE) associated with the development of human activities has accelerated since the nineteenth century, leading to the pollution of river systems. Despite a drastic reduction in industrial inputs in northern Europe, diffuse pollution originating from urban areas still prevents achieving the good status required by the European Water Framework Directive. The objectives of the current study, which is a part of a wider project, were to determine the impact of hydrological dynamics on the total exports of TE from an urban catchment and to develop an assessment tool to evaluate the level of contamination of a catchment based on its specific particulate TE fluxes. Accordingly, this research investigated the behavior of TE contamination in a 950 km2 catchment (Orge River, France) showing a strong urbanization gradient in downstream direction. Particulate and dissolved samples were collected in the river during a hydrological year at four stations reflecting the increasing urbanization gradient. Trace element concentrations were measured in the samples using inductively coupled plasma/mass spectrometry (ICP-MS). Daily and annual TE fluxes were calculated at the four stations to evaluate the contribution of urban areas to the total TE exports from the catchment. The quantification of TE fluxes showed that up to 70% of particulate Cu, Zn, Sb, and Pb exported by the Orge River originated from the urban areas located in the lower catchment portions, especially during average water flow periods characterized by frequent rain events. Moreover, the results show that 50% of the dissolved fluxes of Cu, Zn, and Pb are supplied by urban areas during the entire year, regardless of hydrological conditions, and that the specific contribution of floods to these fluxes (i.e., the June 2016 event) is lower than that in other catchments because of the continuous supply of dissolved metal fluxes to the river in this urbanized environment. These results underline the need to integrate all hydrological conditions for the management of TE contamination in urban areas and not to focus on storm events only. Finally, based on a literature survey, the ratios of specific fluxes were homogeneous across different highly urbanized catchments, and they could be used as a tool to compare the levels of anthropogenic pressure in these contrasted study sites. This observation demonstrates the similar impacts of societal development on urban river geochemistry worldwide, although they occurred during different time periods.

Plasticization-induced oriented micro-channels within polymer inclusion membranes for facilitating Cu(II) transport

Although polymer inclusion membranes (PIMs) have been potentially used for facilitating the ion transport, the internal structure evolution of the PIMs is still controversial. This work focused on the effect of the composition and structure of PIMs on the transport of Cu(II), which were composed of poly(vinyl chloride) (PVC) as skeleton, 2-nitrophenyloctyl ether (NPOE) as the plasticizer, and commercial LIX84I as the carrier. The results suggested that the transport flux of Cu(II) is significantly dependent on the membranous composition. While correlating the membranous composition, the microstructural information of the PVC-based PIMs was explored and evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and electrochemical impedance spectroscopy (EIS), respectively. XRD patterns and SAXS spectral features indicated that the significant structure transition occurred while increasing the NPOE content. Micro-channels of around 9 nm average diameter were clearly disclosed by SAXS for the PIM containing 40 wt% PVC, 30 wt% NOPE and 30 wt% LIX84I. And the well-organized pathway within in the PIMs was essential for efficient Cu(II) transport. The membrane's electrical parameters including dielectric constant and conductivity were also found to be depended on the membranous composition and structure. Besides, the selective transport of Cu(II) towards Ni(II) and Co(II) with PIM were further examined.

Release of copper and lead from the sediment-water interface under <i>in-situ</i> coverage of amino biochar via Diffusive Gradients in Thin-films (DGT)

湖泊沉积物的重金属污染防治一直是环境领域的热点问题.本研究采用氨基生物炭作为覆盖材料，利用梯度扩散薄膜技术（DGT），研究了上覆水不同pH及水流扰动条件下Cu（Ⅱ）、Pb（Ⅱ）在沉积物水界面间的原位释放特征，以及氨基生物炭对湖泊沉积物重金属污染的原位修复效果.研究结果表明，在0 r/min或100 r/min水动力条件下，可移动态重金属离子有不断由沉积物向其他介质扩散的趋势，1.81 kg/m²的氨基生物炭覆盖强度可降低Cu（Ⅱ）、Pb（Ⅱ）释放通量达89%以上，有效减小了水环境中重金属的潜在生态风险.在pH=5的酸性及pH=9的碱性水环境中原位修复效果较差，水体中大量的H⁺或络合物均会削弱氨基生物炭对重金属离子的吸附，当上覆水在pH=7的中性条件时原位修复效果最佳.100 r/min水流扰动下的上覆水Cu（Ⅱ）、Pb（Ⅱ）含量在释放平衡时较0 r/min条件下高出0.036~0.096 μg/mL，说明高强度的水流扰动易造成覆盖材料的扬起和浮动，导致覆盖材料与重金属发生解吸.;The prevention and control of heavy metal pollution in lake sediments has always been a hot issue in the environmental field. In this study, amino modified biochar was used as the covering material and Diffusive Gradients in Thin-films (DGT) was used to monitor the characteristics of in-situ release of Cu(Ⅱ) and Pb(Ⅱ) at the sediment-water interface with different pH and water flow disturbance conditions. The in-situ remediation effect of amino modified biochar on heavy metal pollution was also analyzed. The results show that the mobile heavy metal ions have a tendency to diffuse from the sediment to other media at 0 r/min or 100 r/min hydrodynamic conditions. The cover strength of 1.86 kg/m² for amino modified biochar can reduce the release flux of Cu (Ⅱ) and Pb (Ⅱ) over 89%, which effectively reduces the potential ecological risk of heavy metals in the water environment. A large amount of H⁺ or complex in the water will weaken the adsorption of heavy metal ions by amino biochar. When the overlying water is in neutral condition with pH=7, the in-situ remediation effect is the best. The content of Cu(Ⅱ) and Pb(Ⅱ) in the overlying water under the disturbance of 100 r/min water flow is 0.036-0.096 μg/mL higher than that at 0 r/min when the equilibrium is released. The high-intensity water flow disturbance easily caused the lifting and floating of the covering material, resulting in desorption of heavy metals escaping from the covering material.

Sources, Distribution, and Fluxes of Major and Trace Elements in the Yangtze River

Surface water samples were collected from 20 sampling sites in the main stream and its major tributaries of the Yangtze River from April to May 2017. The concentrations of dissolved trace and major elements were analyzed to determine the spatial variation, source identification, and riverine fluxes using various multivariate statistical techniques, including correlation analysis, principal component analysis (PCA), and cluster analysis (CA) with the goal of determining the influence of natural factors and human activities, including the operation of the Three Gorges Dam on the distribution and loading of major and trace elements in the Yangtze River water environment. Spatial distribution results showed that Cu, Zn, Pb, Cd, and As were the major elements affected by human activities in the Yangtze River, and their concentrations downstream were significantly higher than those in the middle and upper reaches (P<0.05). All elements had fairly high concentration values in both channels of the Yangtze River mainstream in Chongqing city and Hanjiang River in Wuhan city, which were mainly related to the enhanced human activities. However, the low concentrations of multi-elements in the reach of the Yangtze River in Yichang were largely caused by the retention effect of Three Gorges Project on element transport, which decreased the riverine loadings of multi-elements. Principal component analysis (PCA) indicated that Na, Mg, K, Ca, Fe, Mn, Co, Ni, Mo, Cr, and V were mainly associated with the weathering and erosion of various rocks and minerals in the river basin. And Cu, Zn, and Pb were mainly affected by enhanced human activities, such as industrial wastewater, metal smelting, and mineral mining, whereas Cd and As were mainly related to agricultural activities. The spatial distribution of trace and major elements showed that concentrations of some elements in the Yangtze River channels were enhanced by human activities. Generally, the heavy metal pollution in the Yangtze River Basin was lower than that in other rivers of the world. However, the annual fluxes of Cu, Zn, Pb, Cd, and As could have far-reaching ecological effects on the Yangtze River estuary and offshore ecological environment.

The Zn accumulation behavior, phase evolution and void formation in Sn-xZn/Cu systems by considering trace Zn: a combined experimental and theoretical study

The strong effects of Zn addition on the reaction in Sn/Cu systems are widely known. Nevertheless, the micro-mechanism for Zn accumulation behavior, phase evolution and void formation in Sn-xZn/Cu systems remain unclear. In this work, the effect of Zn addition on the interface behavior is investigated. Structures of Sn-xZn/Cu are prepared by the reaction between Sn-xZn solders (x = 0, 0.2, 0.5 and 0.8 wt.%) and the electroplated Cu (EP Cu) joints. During the thermal aging of Sn/EP Cu joints, many voids formed inside the Cu3Sn phase, especially close to the Cu3Sn/EP Cu interface. Whereas the voids were greatly suppressed with Zn addition. During the thermal aging, Zn gradually accumulated near the interface of IMCs/EP Cu. As thermal aging time to168 h and Zn content to 0.8 wt.%, Zn participated in the interface reaction, three layers with different contrasts, (Cu, Zn)6Sn5, Cu6(Sn, Zn)5 and (Cu,Sn)3Zn were formed. Theoretical analysis shows that Zn atom accumulated near the interface of IMCs/EP Cu due to lower diffusion energy barriers (Edf) of Zn than Cu atom. The preferential occupation of Zn atoms in Cu6(Zn,Sn)5 and (Cu,Zn)6Sn5 are Sn3 (4e) and Cu3 (4a) site because of the lowest lattice strain. The diffusion path interstice size for Cu atom via the IMCs layer gradually shrink with the increment of charge transfer in Zn-rich layers, corresponding the Edf of Cu atom gradually rise. As a result, the fluxes of Cu and Sn via the IMCs layer were balanced out, which reduced the Kirkendall voids formation.

Groundwater-surface water exchange associated metals at two intertidal transects, Dan'ao Estuary, Daya Bay, China.

In the evaluation of aquatic environments in estuarine waters, the groundwater-surface water exchanges and associated metal fluxes are difficult to quantify and often ignored. This study made such an attempt based on field data at two intertidal transects in the estuarine wetland of Dan'ao River, the largest river flowing into Daya Bay, China. The results of groundwater-surface water exchange associated six common metals (Cu, Zn, As, Cd, Pb, and Cr) indicate the following: the cumulative concentrations of the six metals are ranked as seawater > groundwater > river water. Among all estuarine groundwaters, the sum of metal concentrations in rhizospheric groundwater at the upstream transect is the highest, owing to the enriching effects of mangrove rhizospheres on metals. The net fluxes of Cu, Zn, As, Cd, and Cr at the upstream transect are 4.8-13.8, 11.9-16.7, 147.8-190.2, 4.1-4.9, and 10.0-12.6 times higher than those at the downstream one. The much higher groundwater discharge rates at the upstream mangrove transect plays a vital role in increasing metal fluxes from groundwater to surface water in this estuary.

Reconstructing the historical pollution levels and ecological risks over the past sixty years in sediments of the Beijiang River, South China

Three sediment cores were collected from the Beijiang River to investigate the effects of human activities on the geochemical fractions of trace metals (Ni, Cr, Cu, Zn, Cd, Pb and Fe) and to reconstruct the ecological risks for the period 1951–2015. Cd had the highest concentration in exchangeable and carbonate fractions and was probably contributed by smelting wastewater. High Cu, Zn and Pb contents were observed in the iron oxide fraction (mean values of 32.2%, 38.2% and 43.9%, respectively), reflecting the influence of mining activities. Flood events led to coarser sediment grain sizes and higher trace metal residual fractions at upstream sites (S1 and S2). Similar to the mining history of the basin, the excess metal fluxes of Cu, Zn, Pb, and Fe in the 210Pb-dating core (S3) increased slowly from 1951 to 1987, increased rapidly from 1988 to 1998 and decreased gradually after 1999 because of government intervention. However, the excess Cd flux decreased continuously from 1951 to 1961, increased from 1961 to 2005, and declined by approximately 78.2% from 2005 to 2014. The excess Ni and Cr fluxes increased noticeably after 1996 because of the increasing sedimentation rate after the construction of the Feilai Gorge Dam. The enrichment factor (EF) and ratio of secondary and primary phases (RSP) indicated that sediments (S3) were moderately to strongly polluted by Cu, Zn and Pb from 1961 to 2007 and extremely polluted by Cd from 1951 to 2011. Human activities increased the bioavailable metal concentrations and resulted in a high risk of toxicity to benthic organisms, especially during intense mining activity (1990s) and Cd pollution incidents (2005). Cd and Pb were primarily responsible for the sediment toxicity in the Beijiang River. The integrated pollution and risk assessment methods provided a clearer understanding of the aquatic environmental quality.

Effect of pulsed current on the microstructure evolution of Cu–Sn intermetallic compounds

ABSTRACTThe dissolution behaviour between Cu and Sn during spark plasma sintering (SPS) was investigated with emphasis on the intrinsic effect of the applied pulsed current. Metallographic analyses revealed that the phase formation of Cu–Sn intermetallics was significantly influenced by the applied pulsed current as a series of phase evolutions along the sintering temperature occurred: Cu6Sn5 + Sn → Cu6Sn5 + Cu3Sn → Cu3Sn. The evolution of Cu–Sn intermetallic compounds (IMCs) was analysed by considering the accelerated atomic diffusion and the increased flux of Cu into the IMCs with a pulsed current, which can provide new insights into the basic understanding of the SPS process and promote the development of rapid forming process of IMCs joints for applications at higher temperatures.

Kinetics of thin film intermetallic compound formation in the Cu/SnxIn100-x system characterized using color change observations

A high-throughput technique is developed to investigate intermetallic compound (IMC) growth kinetics in Cu/Sn and Cu/SnxIn100-x bilayer systems based on combinatorial deposition of solder thin films and observation of color changes. A model for IMC growth kinetics in the Cu/Sn system is developed and found to be in close agreement with experimental data. The model considers the diffusive fluxes of Cu and Sn through the IMC layer and the reaction fluxes of Cu and Sn atoms at the Cu/IMC and IMC/Sn interfaces, respectively. It is observed that IMC growth is controlled by the rate of reaction between Cu and Sn for thin IMCs at low temperatures, while Cu diffusion along IMC grain boundaries and Sn diffusion through the IMC lattice are rate-limiting for thick IMCs at high temperatures. It is also discovered that an addition of 44% In into Sn solder leads to the fastest IMC growth in Cu/SnxIn100-x bilayer films.

Influence of saline groundwater discharge on river water chemistry in the Athabasca oil sands region – A chloride stable isotope and mass balance approach

A chloride mass and stable isotope (δ37Cl) balance approach was employed to calculate the effect of saline groundwater discharge into the Athabasca and Clearwater rivers in the Athabasca Oil Sands Region (AOSR) in north-eastern Alberta, Canada. Saline groundwater affected by halite, carbonate, and anhydrite dissolution discharges Na-Cl type water with total dissolved solids (TDS) up to 51,700 mg/L from exposed Devonian and Cretaceous units in the river valleys in this area. In this study, nine springs discharging groundwater with a median Cl concentration of 9800 mg/L were sampled and chloride stable isotope ratios were determined, with δ37Cl values ranging from 0.2 to 1.0‰. In contrast, river waters had historical monthly median Cl concentrations between 5.9 and 49.5 mg/L and δ37Cl values between −2.2 and −1.4‰. The discharge rate of saline groundwater was calculated to be 100 ± 20 L/s into the Clearwater River and 134 ± 68 L/s into the Athabasca River. The chemical composition and discharge rates of saline groundwater were used to estimate its contribution to the mass fluxes of major ions, metals, and PAHs in the Athabasca and Clearwater rivers. Overall, saline groundwater contributed less than 0.2% of river discharge, but 0.04–39% of major ion concentrations in the rivers, with highest contributions under winter low-flow conditions. In the Clearwater River, saline groundwater contributed 23–39% of average monthly Cl flux and 18–32% of average monthly Na flux. For the same major ion fluxes in the Athabasca River, saline groundwater contributed 12–18% and 6–12%, respectively. The influence of saline groundwater discharge on the mass flux of trace elements in the rivers was found to be negligible, contributing less than 1% of river fluxes of Cu, Ni, Pb, and Zn. Similarly, the influence on mass flux of PAHs in the rivers was found to be negligible (<0.03%) but quantifiable. These results provide important insights on the natural contributions of saline groundwater discharge to river chemistry in the AOSR, a necessary factor to consider when monitoring for anthropogenic effects of oil sands development on river water quality.

Atmospheric deposition of trace elements at urban and forest sites in central Poland – Insight into seasonal variability and sources

This paper includes the results of chemical composition of bulk deposition samples collected simultaneously at urban (Poznań city) and forest (Jeziory) sites in central Poland, between April 2013 and October 2014. Rainwater samples were analyzed for trace elements (As, Zn, Ni, Pb, Cu, Cr, Cd) and physicochemical parameters. Overall, three metals, i.e. Zn, Pb and Cu were the most abundant anthropogenic constituents of rainwater samples from both locations. In Poznań city, the rainwater concentrations of trace elements did not differ significantly between spring and summer. However, they were elevated and more variable during the cold season (fall and winter), suggesting strong contribution from local high-temperature processes related to coal combustion (commercial and residential sector). In contrast to the urban site, relatively low variability in concentrations was found for Cu, Ni, Zn at the forest site, where direct impact of emission from vehicle traffic and coal-fired combustion (power plants) was much lower. The bulk deposition fluxes of Ni, As, Pb and Zn at this site exhibited a clear trend, with higher values during the cold season (fall and winter) than in spring and summer. At the urban site, the sums of total bulk deposition fluxes of Zn, Cu, Pb, Ni, As, Cr, Cd were as follows: 8460.4, 4209.2, 2247.4, 1882.1, 606.6, 281.6 and 31.4μgm−2. In addition, during the winter season, a significantly higher deposition fluxes of Cu and Zn were observed for rain (on average 103.8 and 129.4μgm−2, respectively) as compared to snow (19.7μgCum−2 and 54.1μgZnm−2). This suggests that different deposition pattern of trace elements for rain, mixed and snow was probably the effect of several factors: precipitation type, changes in emission and favorable meteorological situation during rain events.

Intestinal fate of dietary zinc and copper: Postprandial net fluxes of these trace elements in portal vein of pigs

In pig, the assessment of bioavailability of dietary trace minerals with classical approaches such as relative bioavailability estimates or digestive tract balances have often generated inconsistent responses. In the present study, net portal-drained-viscera fluxes were monitored after a meal to assess intestinal absorption of zinc (Zn) or copper (Cu) according to dietary sources and levels of these trace minerals. Twelve pigs were surgically equipped with portal and carotid catheters and a portal ultrasonic flow probe for 12-h postprandial measurements. In a cross-over design, pigs received boluses of inorganic (I) or organic (O) dietary Cu and Zn at adequate (A, 20 and 200mg, respectively) or high (H, 40 and 400mg, respectively) level just before a 0.8-kg meal (semi-purified diet). Whatever treatments, arterial Zn increased by 72% at 45min postprandial and gradually declined thereafter (P<0.01). Arterial Zn were greater by 11% after O than I (P=0.02) and by 19% after H than A (P<0.01) meals. Net portal-drained-viscera fluxes of Zn during the first 240min postprandial were greater by 44% after O than I (P=0.10) and by 51% after H than A (P=0.07) meals. For Cu, portal-drained-viscera fluxes of Cu up to 240min postprandial were greater (P=0.03) after A than H meals. Those results suggest that Zn is absorbed rapidly, likely in the upper digestive tract of pigs and, whatever dietary levels, more efficiently after O meals. It appears that H levels of both Zn and Cu interfered with intestinal absorption of Cu and/or stimulate post-absorption enterocyte sequestration of this mineral.

Coupling effect of thermomigration and cross-interaction on evolution of intermetallic compounds in Cu/Sn/Ni ultrafine interconnects undergoing TLP bonding

Abstract

Effect of Ni on growth kinetics, microstructural evolution and crystal structure in the Cu(Ni)–Sn system

The role of Ni addition in Cu on the growth of intermetallic compounds in the Cu–Sn system is studied based on microstructure, crystal structure and quantitative diffusion analysis. The diffraction pattern analysis of intermetallic compounds indicates that the presence of Ni does not change their crystal structure. However, it strongly affects the microstructural evolution and diffusion rates of components. The growth rate of (Cu,Ni)3Sn decreases without changing the diffusion coefficient because of the increase in growth rate of (Cu,Ni)6Sn5. For 3 at.% or higher Ni addition in Cu, only the (Cu,Ni)6Sn5 phase grows in the interdiffusion zone. The elongated grains of (Cu,Ni)6Sn5 are found when it is grown from (Cu,Ni)3Sn. This indicates that the newly formed intermetallic compound joins with the existing grains of the phase. On the other hand, smaller grains are found when this phase grows directly from Cu in the absence of (Cu,Ni)3Sn indicating the ease of repeated nucleation. Grain size of (Cu,Ni)6Sn5 decreases with further increase in Ni content, which indicates a further reduction of activation barrier for nucleation. The relations for the estimation of relevant diffusion parameters are established considering the diffusion mechanism in the Cu(Ni)–Sn system, which is otherwise impossible in the phases with narrow homogeneity range in a ternary system. The flux of Sn increases, whereas the flux of Cu decreases drastically with the addition of very small amount of Ni, such as 0.5 at.% Ni, in Cu. Analysis of the atomic mechanism of diffusion indicates the contribution from both lattice and grain boundary for the growth of (Cu,Ni)6Sn5 phase.

Combined analysis of trace elements and isotopic composition of particulate organic matter in suspended sediment to assess their origin and flux in a tropical disturbed watershed

Approximately 40% of the volume of domestic sewage generated in the São Paulo State is untreated and released into water bodies, causing serious pollution problems that affect the water quality and especially the suspended sediments transported by rivers. Thus, this paper investigates the seasonal influence on the origin and fluxes of Cu, Co, Cr, Zn, Cd, Ni, Sc and particulate organic matter (POM) in sediments transported by a disturbed watershed in the São Paulo State, i.e. the Sorocaba River basin. POM was characterized using particulate organic carbon, particulate organic nitrogen, C:N ratio and δ13C and δ15N stable isotopic composition. Eight sample collections of fine suspended sediments (FSS) were carried out at the mouth of the Sorocaba River from July 2009 to May 2010. During the study period, the discharge rate followed the seasonal variation trend of the past 25 years. Zn was the most abundant trace element in the FSS, followed by Cr, Cu, Ni, Co, Sc and Cd. There was a higher concentration of trace elements during the dry season, except for Sc and Co, which did not vary seasonally. The POM showed the same trend, with higher concentrations during the dry season. The calculated enrichment factors and geoaccumulation index indicated that most of the trace elements are of geogenic origin, except for Zn, which showed significant anthropogenic contributions (55%). The elemental and isotopic analysis of C and N and C:N ratio indicated that the anthropogenic origin of POM found in the FSS is related mainly to domestic sewage (97%), while the significant correlation found between the concentrations of Zn and POM indicates that the main anthropogenic source of Zn is related to this domestic sewage. The FSS load transported during the study period was of 373,194 t y−1, of which 87% occurred during the rainy season.