A Comprehensive Study of Hydrolyzed Polyacrylamide as a Binder for Silicon Anodes.

Silicon anodes have a high theoretical capacity for lithium storage, but current composite electrode formulations are not sufficiently stable under long-term electrochemical cycling. The choice of polymeric binder has been shown to impact stability and capacity of silicon anodes for electrochemical energy storage. While several promising polymeric binders have been identified, there is a knowledge gap in how various physicochemical properties-including adhesion, mechanical integrity, and ion diffusion-impact electrochemical stability and performance. In this work, we comprehensively investigate the physical properties and performance of a molecular-weight series (3-20 × 106 g/mol) of partially hydrolyzed polyacrylamide (HPAM) in silicon anodes. We quantify the mechanical strength, electrolyte uptake, adhesion to silicon, copper, and carbon, as well as electrochemical performance and stability and find that HPAM satisfies many of the properties generally believed to be favorable, including good adhesion, high strength, and electrochemical stability. HPAM does not show any electrolyte uptake regardless of any molecular weight studied, and thin films of mid- and high-molecular-weight HPAM on silicon surfaces suppress lithiation of silicon. The resulting composite electrodes exhibit an electrochemical storage capacity greater than 3000 mAh/g initially and 1639 mAh/g after 100 cycles. We attribute capacity fade to failure of mechanical properties of the binder or an excess of the solid electrolyte interphase layer being formed at the Si surface. While the highest-molecular-weight sample was expected to perform the best given its stronger adhesion and bulk mechanical properties, we found that HPAM of moderate molecular weight performed the best. We attribute this to a trade-off in mechanical strength and uniformity of the resulting electrode. This work demonstrates promising performance of a low-cost polymer as a binder for Si anodes and provides insight into the physical and chemical properties that influence binder performance

Syntax for free: representing syntax with binding using parametricity

We show that, in a parametric model of polymorphism, the type ∀ α. ((α → α) → α) → (α → α → α) → α is isomorphic to closed de Bruijn terms. That is, the type of closed higher-order abstract syntax terms is isomorphic to a concrete representation. To demonstrate the proof we have constructed a model of parametric polymorphism inside the Coq proof assistant. The proof of the theorem requires parametricity over Kripke relations. We also investigate some variants of this representation

Evaluation of Poisson’s Ratio of Asphalt Concrete

Poisson´s ratio can be defined as the negative ratio of strains perpendicular to the load direction to the strains parallel to the loading direction. If elastic or viscoelastic models are used, Poisson´s ratio, together with elastic modulus, is a main input used to predict distresses in flexible pavement structures such as rutting and cracking. In asphalt concrete, Poisson’s ratio is commonly measured using two different testing configurations: indirect tension (IDT) and uniaxial. However, results from these two testing configuration can potentially have differences. Design methodologies such as the Mechanistic Empirical Design Guide (MEPDG, now PavementME) have been shown to be very sensitive to variations of Poisson’s ratio. The objective of this research is to determine whether or not there are significant differences between the values of Poisson’s ratio measured in indirect tension configuration and uniaxial configuration. This work also aims to investigate the potential variations of values of Poisson’s ratio among a number of asphalt mixture treated with different types of asphalt modifiers: poplyphosphoric acid (PPA) alone and in combination with liquid anti-stripping agent (LAA). Cylindrical shaped samples specified in AASHTO T 342 were used to measure Poisson’s ratio in uniaxial configuration, and disc shaped samples specified in AASHTO T 322 were used to measure Poisson’s ratio in an IDT configuration. Samples were tested at each combination at the following temperatures, -10 C, 4 C, 21 C, 37 C, and 54 C, and frequencies, 25 Hz, 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz. No statistical difference was found in values of Poisson’s ratio measured within each testing configuration. IDT Poisson’s ratio were significantly different to those of uniaxial configuration (3:1). This reduction of Poisson’s ratio by about 60% could lead to an increment of predicted distresses, such as longitudinal cracking, using PavementME by more than 400% of its design limit

Common Binder Head and Knotter Head Troubles

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Water‐Soluble Inorganic Binders for Lithium‐Ion and Sodium‐Ion Batteries

Inorganic materials form an emerging class of water-soluble binders for battery applications. Their favourable physicochemical properties, such as intrinsic ionic conductivity, high thermal stability (>1000 °C), and compatibility to coat a diverse range of electrode materials make them useful binders for lithium-ion and sodium-ion batteries. Li and Na containing phosphates and silicates are attractive choices as multifunctional inorganic aqueous binders (IABs). This review discusses these binders\u27 structural, thermal, and ionic properties, followed by exploiting their ionically conducting nature for all-solid-state batteries. Subsequently, the application of these compounds as binders and surface coating agents for different anodes and cathodes in lithium-ion and sodium-ion batteries is discussed. Eventually, a first evaluation of their environmental impacts and economic aspects is presented as well

State Highlights 11/7/1941

This is the student newspaper from Western State High School, the high school that was on the campus of Western Michigan University, then called State Highlights, in 1941

Chelating effect in short polymers for the design of bidentate binders of increased affinity and selectivity

The design of new strong and selective binders is a key step towards the development of new sensing devices and effective drugs. Both affinity and selectivity can be increased through chelation and here we theoretically explore the possibility of coupling two binders through a flexible linker. We prove the enhanced ability of double binders of keeping their target with a simple model where a polymer composed by hard spheres interacts with a spherical macromolecule, such as a protein, through two sticky spots. By Monte Carlo simulations and thermodynamic integration we show the chelating effect to hold for coupling polymers whose radius of gyration is comparable to size of the chelated particle. We show the binding free energy of flexible double binders to be higher than that of two single binders and to be maximized when the binding sites are at distances comparable to the mean free polymer end-to-end distance. The affinity of two coupled binders is therefore predicted to increase non linearly and in turn, by targeting two non-equivalent binding sites, this will lead to higher selectivity

Investigating cohesive healing of asphalt binders by means of a dissipated energy approach

The paper reports the results of an experimental investigation in which the cohesive healing properties of different types of asphalt binder were evaluated by means of the dissipated energy ratio approach. A specifically designed testing methodology was proposed which involves comparing the response of binders subjected to continuous oscillatory shear loading carried out without rest periods and with single rest periods introduced at predefined levels of damage A rheological parameter (Healing Ratio) was introduced to quantify the magnitude of healing occurring during rest time and to rank the consequent healing potential of binders. Obtained results indicate that the investigated binders did not completely recover their original fatigue resistance after rest time, confirming the existence of some intrinsic irreversible damage, the amount of which depends on the total damage experienced before load removal. Experimental results also indicate that healing performance of binders can be significantly enhanced by polymer modification. Keywords: Healing, Fatigue, Dissipated energy ratio, Asphalt binder, Polymer modificatio

Spartan Daily, September 30, 1935

Volume 24, Issue 3https://scholarworks.sjsu.edu/spartandaily/2331/thumbnail.jp