Enhancing ductility in bulk metallic glasses by straining during cooling

Most of the known bulk metallic glasses lack sufficient ductility or toughness when fabricated under conditions resulting in bulk glass formation. To address this major shortcoming, processing techniques to improve ductility that mechanically affect the glass have been developed, however it remains unclear for which metallic glass formers they work and by how much. Instead of manipulating the glass state, we show here that an applied strain rate can excite the liquid, and simultaneous cooling results in freezing of the excited liquid into a glass with a higher fictive temperature. Microscopically, straining causes the structure to dilate, hence “pulls” the structure energetically up the potential energy landscape. Upon further cooling, the resulting excited liquid freezes into an excited glass that exhibits enhanced ductility. We use Zr44Ti11Cu10Ni10Be25 as an example alloy to pull bulk metallic glasses through this excited liquid cooling method, which can lead to tripling of the bending ductility.

Pulling Metallic Glasses Ductile

A major shortcoming of most known bulk metallic glasses (BMGs) is that they lack sufficient ductility, or toughness, when fabricated under conditions resulting in bulk glass formation. To address this, processing techniques to improve ductility that mechanically affect the glass have been developed, however it remains unclear for which BMG formers they work, and by how much. We show here that, instead of manipulating the glass state, an applied strain rate can excite the liquid, and simultaneous cooling results in freezing of the excited liquid into a glass with a higher fictive temperature. Microscopically, straining causes the structure to dilate, hence “pulling” the structure energetically up the potential energy landscape. Upon further cooling, the resulting excited liquid freezes into an excited glass that exhibits enhanced ductility. We use Zr44Ti11Cu10Ni10Be25 to demonstrate how pulling BMGs through this excited liquid cooling methods can lead to a tripling of the bending ductility.

Cost-Effective Bulk Glass Reinforced Composite Columns

The cost of construction has been increasing, stemming mostly from increased material costs. One potential method to address this issue is the introduction of novel composites for use in structural applications. Bulk glass may prove to be a superior compositing material due to its low cost and high strength. The introduction of bulk soda-lime glass to structural applications is nontrivial; due to glass’ unique properties, such as its relatively low Young’s modulus (when compared to steel) and brittleness, compositing glass has proven difficult. A novel concept of a glass-reinforced composite column (GRCC) is introduced that works to benefit from glass’ unique properties for structural applications. The results indicate that GRCCs can be designed that have costs that are estimated to be 11% less than typical timber construction members. Additionally, GRCCs are estimated to provide a 50% cost advantage over similarly strong structural steel sections. By interpreting the results of finite element modeling, which was conducted iteratively to form buckling load to cost curves, three regions were identified that occur as the glass percentage is increased. These regions also exist with columns made of other materials (such as steel). Additionally, the finite element modeling (FEM)-determined shear stresses have smaller values than the shear strengths of typical sizing agents. In conclusion, GRCCs provide significant cost advantages (up to 50% cost reduction) over steel, and slight cost advantages when compared to structural timbers, although GRCCs have the added benefit of consisting of non-degrading materials.

Chemical alteration of 238Pu-loaded borosilicate glass under saturated leaching conditions

Highly radioactive 238Pu-doped and non-radioactive samples of borosilicate glass with chemical compositions and synthesis routine similar to SON68 glass were studied under static saturated leaching conditions in distilled water at 90 °C. Dramatic differences in behavior of the radioactive and model glasses were observed. On time scale of 4 months the radioactive glass is fully covered by mechanically unstable alteration layer, possibly consisting of aluminum hydroxides with small fraction of a separate secondary Pu bearing phase. The model glass remains virtually pristine. Addition of Eu3+ into the glass allowed examination of the glass radio- and photoluminescence and to assess changes or REE3+ impurity local environment during self-irradiation and leaching. Photoluminescence spectra suggest more ordered local environment of europium ions in the alteration “gel” than in the bulk glass. Peculiar behavior of the photoluminescence spectra excited at different laser power is observed for the alteration layer and is ascribed to optical bleaching of color centers.

Comparison of AFM Nanoindentation and Gold Nanoparticle Embedding Techniques for Measuring the Properties of Polymer Thin Films

The surfaces of polymer and interfaces between polymer and inorganic particles are of particular importance for the properties of polymers and composites. However, the determination of the properties of surfaces and interfaces poses many challenges due to their extremely small dimensions. Herein, polystyrene and polymethyl methacrylate thin film on silicon wafer was used as a model system for the measurement of the properties of the polymer near free surface and at the polymer-solid interface. Two different methods, i.e., nanoindentation using atomic force microscopy (AFM) and the gold nanoparticle embedding technique, were used for these measurements. The results showed the elastic modulus of PS near the free surface determined by nanoindentation was lower than the bulk value. Based on contact mechanics analysis, nanoparticle embedding also revealed the existence of a lower-modulus, non-glassy layer near the free surface at temperatures below the bulk glass transition temperature (Tg). However, near the polymer-solid interface, the AFM nanoindentation method is not applicable due to the geometry confinement effect. On the other hand, the nanoparticle embedding technique can still correctly reflect the interactions between the polymer and the substrate when compared to the ellipsometry results.