North Carolina State University

About: North Carolina State University is a education organization based out in Raleigh, North Carolina, United States. It is known for research contribution in the topics: Population & Thin film. The organization has 44161 authors who have published 101744 publications receiving 3456774 citations. The organization is also known as: NCSU & North Carolina State University at Raleigh.

Nanocellulose properties and applications in colloids and interfaces

Abstract: In this review we introduce recent advances in the development of cellulose nanomaterials and the construction of high order structures by applying some principles of colloid and interface science. These efforts take advantage of natural assemblies in the form of fibers that nature constructs by a biogenetic bottom-up process that results in hierarchical systems encompassing a wide range of characteristic sizes. Following the reverse process, a top-down deconstruction, cellulose materials can be cleaved from fiber cell walls. The resulting nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. This originates from the appealing intrinsic properties of nanocelluloses: nanoscale dimensions, high surface area, morphology, low density, chirality and thermo-mechanical performance. Directing their assembly into multiphase structures is a quest that can yield useful outcomes in many revolutionary applications. As such, we discuss the use of non-specific forces to create thin films of nanocellulose at the air–solid interface for applications in nano-coatings, sensors, etc. Assemblies at the liquid–liquid and air–liquid interfaces will be highlighted as means to produce Pickering emulsions, foams and aerogels. Finally, the prospects of a wide range of hybrid materials and other systems that can be manufactured via self and directed assembly will be introduced in light of the unique properties of nanocelluloses.

Controlled, Rapid Deposition of Structured Coatings from Micro- and Nanoparticle Suspensions

Abstract: The objective of the study was to develop the operational basis for rapid and controlled deposition of crystal coatings from particles of a wide size range. We deposited such structured coatings by dragging with constant velocity a small volume of liquid confined in a meniscus between two plates. Two types of structured coatings were characterized: latex colloidal crystals and thin layers from metallic nanoparticles. The crystal deposition was sped up by use of preconcentrated suspensions. Crystal coatings larger than a few square centimeters were deposited in minutes from aqueous suspension volumes of approximately 10 μL. The governing mechanism of crystal deposition is convective assembly at high volume fractions. The two major process parameters that allow control over the coating thickness and structure were the deposition speed and particle volume fraction. The evaporation rate was not found to affect the process to a large extent. A volumetric flux balance was used to relate the deposition paramete...

Trends in power semiconductor devices

Abstract: This paper reviews recent trends in power semiconductor device technology that are leading to improvements in power losses for power electronic systems. In the case of low voltage ( 100 V) power rectifiers, the silicon P-i-N rectifier continues to dominate but significant improvements are expected by the introduction of the silicon MPS rectifier followed by the GaAs and SiC based Schottky rectifiers. Equally important developments are occurring in power switch technology. The silicon bipolar power transistor has been displaced by silicon power MOSFETs in low voltage ( 100 V) systems. The process technology for these MOS-gated devices has shifted from V-MOS in the early 1970s to DMOS in the 1980s, with more recent introduction of the UMOS technology in the 1990s. For the very high power systems, the thyristor and GTO continue to dominate, but significant effort is underway to develop MOS-gated thyristors (MCTs, ESTs, DG-BRTs) to replace them before the turn of the century. Beyond that time frame, it is projected that silicon carbide based switches will begin to displace these silicon devices.