Contemporary medical and dental adhesives often have difficulty sticking to wet surfaces or weaken with long-term exposure to water. Substantial research has been dedicated to finding a means of achieving adhesion in an aqueous environment. A study evaluates the adsorption of catechol relative to other chemical groups as means of gauging how effective they may be as adsorptive groups in adhesives. Contact angle and surface-tension measurements of solutions of catechols and other chemical groups were used to determine their works of adhesion. Adsorption isotherms were also constructed to ascertain Langmuir constants. Solutes containing catechol groups were compared to solutes containing other polar groups to see how well catechol adsorbs to hydroxyapatite, the mineral component of bones and teeth, relative to other chemical groups found in adhesives. The results of this study show that catechol and molecules containing catechol groups have higher rates and energies of adsorption to hydroxyapatite than do groups such as alcohols, amines, and carboxylic acids.

The mechanical, thermal, and fracture morphological characterization of low-density polyethylene (LDPE) composites reinforced with vapor-grown carbon nanofibers (VGCNFs) is presented in this article. VGCNF/LDPE composites with different VGCNF weight percentages were prepared by single-screw extrusion followed by injection molding. Scanning electron microscopy showed that VGCNFs were predominantly dispersed uniformly within the LDPE matrix. Differential scanning calorimetry has shown that the VGCNF/LDPE composites crystallized at higher temperatures than pure LDPE polymer. Tensile testing has shown that strength and Young's modulus of VGCNF/LDPE composites were improved by 15% and 44%, respectively, when the VGCNF loading reached 3 wt%.

Central to commercializing metal-air batteries is the development of highly efficient and stable catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, a composite catalyst with a unique interpenetrating network (denoted as NiCo2O4@MnO2-CNTs-3) was synthesized and exhibited better bifunctional activity (ΔE = 0.87 V) and durability than both Pt/C and Ir/C catalysts. The improved performance arises from three factors: (i) MnO2 promotes the ORR while NiCo2O4 facilitates the OER; (ii) carbon nanotubes improve the electronic conductivity; and (iii) the highly porous structure enables the adsorption-desorption of O2 and enhances the structural stability. As a result, the primary and rechargeable Zn-air battery affords a high power density and specific capacity (722 mA h g-1), an outstanding discharge stability (255 mW cm-2 after 1000 cycles) and a high cycling stability (over 2280 cycles). Electron microscopy and electrochemical analysis revealed that the degradation of the rechargeable Zn-air battery performance resulted from the damage of the air electrode and the hydrogen evolution reaction on the zinc electrode. A flexible Zn-air battery employing a solid-state electrolyte showed an exciting stability (540 cycles) and high power density (85.9 mW cm-2), suggesting that the anion exchange membrane effectively prevents the migration of Zn2+ ions and the deposition of carbonates.

Microalgae is envisioned by many experts to be one of the key future feedstocks for producing transportation fuels and other chemical products. The concept has many positive aspects inclusive of being fully renewable, having minimal carbon footprint, and being able to be implemented in low value agricultural lands. There has been a tremendous amount of developmental work done to commercialize the concept since the mid-1900s; however, the reality is that the cost for a gallon of microalgae oil is still too expensive to be considered a viable option to produce biobased diesels at this time. Expanding the production of more than one or two products from a microalgae biorefinery is an economic must. Products derived from the algal cake must be developed and commercialized to offset the high cost of oil production. This paper will investigate the status of the concept and provide insight into directions needed to improve economic viability.

No abstract

This study presents a comparative analysis of the crystallization behavior of low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) nanocomposites. Carbon nanotubes (CNTs) were used as a nucleating agent to generate a nanohybrid shish‐kebab architecture. Materials characterizations were performed to evaluate the crystal morphology and crystallization kinetics using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The lamellae of polyethylene were always found to grow laterally on the tube axis of CNTs. The parameters of the Avrami model for primary crystallization were determined. SEM indicated the crystal morphology changed from spherulitic to disk‐shaped with the addition of CNTs, while DSC‐based thermal examination indicated that the CNTs can provide nucleation sites to polyethylene to accelerate the crystal growth rate. HDPE was found to crystallize faster than LDPE on CNTs. The highly branched nature of LDPE's macromolecular chains are known to cause reduced chain mobility, which resulted in lower crystallinity values with smaller crystallite sizes for LDPE in this study. In comparison, the more linear HDPE chains have an increased polymer density and chain mobility, resulting in an improved nucleation ability of HDPE chain segments on CNTs.

No abstract

No abstract