Impact of copper mine tailings (stamp sand) on survival and development of aquatic organisms near Gay, Michigan

Heavy metal-rich copper mine tailings, called stamp sands, were dumped by mining companies directly into streams and along the Lake Superior shoreline, degrading Keweenaw Peninsula waterways. One of the largest disposal sites is near Gay, Michigan, where tailings have been moved along the shoreline by currents since mining ceased. As a result, the smallest sand particles have been washed into deeper water and are filling the interstitial spaces of Buffalo Reef, a critical lake trout spawning site. This research is the first to investigate if stamp sand is detrimental to survival and early development of eggs and larvae of lake sturgeon, lake trout, and Northern leopard frogs, and also examines if the presence of stamp sands influences substrate selection of earthworms. This study found that stamp sand had significantly larger mean particle sizes and irregular shapes compared to natural sand, and earthworms show a strong preference for natural substrate over any combination that included stamp sand. Additionally, copper analysis (Cu2+) of surface water over stamp sand and natural sand showed concentrations were significantly higher in stamp sand surface water (100 μg/L) compared to natural sand surface water (10 μg/L). Frog embryos had similar hatch success over both types of sand, but tadpoles reared over natural sand grew faster and had higher survival rates. Eggs of lake sturgeon showed similar hatch success and development over natural vs. stamp sand over 17 days, while lake trout eggs hatched earlier and developed faster when incubated over stamp sand, yet showed similar development over a 163 day period. Copper from stamp sand appears to impact amphibians more than fish species in this study. These results will help determine what impact stamp sand has on organisms found throughout the Keweenaw Peninsula which encounter the material at some point in their life history.

High temperature, low cycle fatigue of a hybrid particulate/fiber aluminum metal-matrix composite

The effect of shot particles on the high temperature, low cycle fatigue of a hybrid fiber/particulate metal-matrix composite (MMC) was studied. Two hybrid composites with the general composition A356/35%SiC particle/5%Fiber (one without shot) were tested. It was found that shot particles acting as stress concentrators had little effect on the fatigue performance. It appears that fibers with a high silica content were more likely to debond from the matrix. Final failure of the composite was found to occur preferentially in the matrix. SiC particles fracture progressively during fatigue testing, leading to higher stress in the matrix, and final failure by matrix overload. A continuum mechanics based model was developed to predict failure in fatigue based on the tensile properties of the matrix and particles. By accounting for matrix yielding and recovery, composite creep and particle strength distribution, failure of the composite was predicted.

Effects of silicon content and cooling rate on mechanical properties of heavy section ductile cast iron

The effects of Si and cooling rate are investigated for their effect on the mechanical properties and microstructure. Three alloys were chosen with varying C and Si contents and an attempt to keep the remainder of the elements present constant. Within each heat, three test blocks were poured. Two blocks had chills – one with a fluid flowing through it to cool it (active chill) and one without the fluid (passive) – and the third block did not have a chill. Cooling curves were gathered and analyzed. The mechanical properties of the castings were correlated to the microstructure, cooling rate and Si content of each block. It was found that an increase in Si content increased the yield stress, tensile strength and hardness but decreased the impact toughness, elongation and Young’s modulus. The fast cooling rates produced by the chills caused a high nodule count in the castings along with a fine ferrite grain size and a high degree of nodularity. The fine microstructures, in turn, increased the strength and ductile to brittle transition temperature (DBTT) of the castings. The fast cooling rate was not adequate to overcome the dramatic increase in DBTT that is caused by the addition of Si.

Preparation of silicon-metal nanocomposites based on electrophoretic deposition

Silicon has long been considered as one of the most promising anode material for lithium-ion batteries. However, the poor cycle life due to stress during charge/discharge cycling has been a major concern for its practical applications. In this report, novel Si-metal nanocomposites have been explored to accommodate the stress generated in the intercalation process. Several approaches have been studied with the aim of getting uniform mixing, good mechanical stability and high Si content. Among the three approaches being investigated, Si- Galinstan nanocomposite based on electrophoretic deposition showed the best promise by achieving at least 32.3% Si theoretical weight percentage, and our in current experiments we’ve already get 13% Silicon weight percentage, which gave us an anode material 46% more capacity than the current commercial product.