Rensselaer Polytechnic Institute

About: Rensselaer Polytechnic Institute is a education organization based out in Troy, New York, United States. It is known for research contribution in the topics: Terahertz radiation & Finite element method. The organization has 19024 authors who have published 39922 publications receiving 1414699 citations. The organization is also known as: RPI & Rensselaer Institute.

Nanometre-size tubes of carbon

Abstract: We review the present state of understanding of the structure, growth and properties of nanometre-size tubes of carbon. Two different types of carbon nanotubes, namely single-shell nanotubes made of single layers of graphene cylinders and multishell nanotubes made of concentric cylinders of graphene layers have now become available. The subtle structure parameters such as helicity in the carbon network and the nanometre diameters give the nanotubes a rich variety in physical properties. Recent experimental progress on the measurements of properties using electron-energy loss spectroscopy, Raman spectroscopy, electron-spin resonance, electrical conductance, mechanical stiffness and theoretical predictions on electronic and mechanical properties of nanotubes will be discussed. In addition to synthesis techniques, methods to purify and make aligned arrays of nanotubes will be described. Different approaches for fabricating composite structures using nanotubes as moulds and templates and their future implications in materials science will be evaluated. Finally, promising areas of future applications, for example as tiny field-emitting devices, micro-electrodes, nanoprobes and hydrogen storage material will be outlined.

Inkjet Printing of Electrically Conductive Patterns of Carbon Nanotubes

Abstract: The advantageous physical properties of carbon nanotubes (CNTs), such as excellent thermal conductivity, good mechanical strength, optional semiconducting/metallic nature, and advanced field-emission behavior, have been utilized in a number of different devices for several years. The area-selective synthesis of well-organized CNTs on prepatterned growth templates using either catalytic or plasma-enhanced chemical vapor deposition methods (CCVD and PECVD, respectively) opens up further novel fields for advanced future applications. However, these promising techniques require complex lithography processes and sophisticated deposition facilities (PECVD) or are limited to thermally durable growth substrates (CCVD). Recent advances in nanotube chemistry enable both the dissolution and dispersion of CNTs in various solvents. These results suggest new alternatives for fabricating CNT patterns by simply dispensing/printing the dissolved/dispersed particles on substrates. Alternatively, controlled flocculation of CNT suspensions in flow channels or on prepatterned stamps can be accomplished to produce patterns of nanotubes on various surfaces. Herein, a cost-effective and scaleable deposition method for generating conductive multi-walled carbon nanotube (MWCNT) patterns on paper and polymer surfaces is presented. MWCNTs grown by CCVD were chemically modified to make the nanotubes dispersible in water, and in turn the aqueous dispersion was dispensed on various substrates using a commercial desktop inkjet printer. The electrical behavior of the printed patterns is investigated and the limitations of the process are discussed. For functionalization (Figure 1a), the MWCNTs were first refluxed in nitric acid to produce carboxyl, hydroxyl, and carbonyl groups at the defect sites of the outer graphene layer of the nanotubes. In a subsequent step, these hydroxyl and carbonyl groups were oxidized further with potassium permanganate solution (in perchloric acid) to achieve additional carboxyl groups on the surfaces of the nanotubes. Modifications of the as-grown CNT structure may be identified by comparison of the Raman spectra ACHTUNGTRENNUNGof the as-produced nanotubes (Figure 1b) and the fully ACHTUNGTRENNUNGfunctionalized nanotubes (Figure 1c) in the vicinity of the

Graphene–aluminum nanocomposites

Abstract: Composites of graphene platelets and powdered aluminum were made using ball milling, hot isostatic pressing and extrusion. The mechanical properties and microstructure were studied using hardness and tensile tests, as well as electron microscopy, X-ray diffraction and differential scanning calorimetry. Compared to the pure aluminum and multi-walled carbon nanotube composites, the graphene–aluminum composite showed decreased strength and hardness. This is explained in the context of enhanced aluminum carbide formation with the graphene filler.

Steric mass-action ion exchange: Displacement profiles and induced salt gradients

Abstract: The study of nonlinear competitive equilibrium is of fundamental importance in understanding the behavior of proteins in preparative ion-exchange chromatographic separations. In this work we present a steric mass-action (SMA) ion-exchange equilibrium formalism, which explicitly accounts for the steric hindrance of salt counterions upon protein binding in multicomponent equilibria. An analytical solution has been derived for the calculation of isotachic effluent profiles of displaced proteins and induced salt gradients under ideal chromatographic conditions. A stability analysis has been employed to establish the order of the feed components in the displacement train. Theoretical predictions are compared to experimental results for the separation of proteins by cation-exchange displacement chromatography. These results demonstrate the efficacy of the SMA formalism in predicting complex behavior present in ion-exchange displacement systems. Furthermore, the analytical solution of ideal isotachic displacement profiles with the SMA formalism enables rapid methods development and optimization of ion-exchange displacement separations.