Towards the Industrial Application of Spark Ablation for Nanostructured Functional Materials

Nanostructuring of functional materials is an essential part in the design of energy related devices – but the industrial tools we have to make these materials are lacking. This dissertation explores the green, flexible, and scalable spark discharge process for the fabrication of complex nanostructured materials, and the application of said materials in energy devices. A novel spark generator concept with a 60-fold increased mass production rate was developed, where spark energy and spark repetition rate have been decoupled from gas and material properties. The application of spark discharge materials in two types of energy storage and conversion devices was studied: amorphous-Si photovoltaic cells, MgH2-based hydrogen storage. The possibility of using spark discharge to functionalize nanoparticles with metal coatings was investigated using two spark generators in series. The new spark generator provides true scaling: it produces materials identical to that of the old designs, and the mass production rate – about a gram per day – scales linearly with the spark repetition rate. Arrays of ?100 nm high-purity silver nanospheres were deposited as scattering agents in solar cells, improving their external quantum efficiency by 30 %. A method for synthesizing MgH2 nanoparticles was developed, which show promising hydrogen storage properties. Nanocomposites of Mg with NbOx catalyst nanoparticles were synthesized using two sparks in series, increasing the H2 desorption rate of MgH2. Using a hollow electrode spark, 40 nm gold nanoparticles were coated with silver, and vice versa. The possibility to make useful quantities of high-quality nanomaterials – e.g. high-purity metals or light metal hydrides – from nearly any element makes spark discharge a powerful tool in materials design. The new spark generator provides sufficient quantities to make it economical to develop an industrial nanoparticle facility using multiple sparks in parallel.ChemEApplied Science

Spark ablation device

A spark ablation device for generating nanoparticles comprising a spark generator; the spark generator comprising first and second electrodes, wherein the spark generator further comprises at least one power source which is arranged to be operative at a first energy level for maintaining a discharge between the first and second electrodes, which power source is arranged for repetitively increasing the energy of the discharge to a predetermined secondary level that is higher than the first energy level for ablating a portion of the electrodes.ChemE/Chemical EngineeringApplied Science

Precursor-Less Coating of Nanoparticles in the Gas Phase

This article introduces a continuous, gas-phase method for depositing thin metallic coatings onto (nano)particles using a type of physical vapor deposition (PVD) at ambient pressure and temperature. An aerosol of core particles is mixed with a metal vapor cloud formed by spark ablation by passing the aerosol through the spark zone using a hollow electrode configuration. The mixing process rapidly quenches the vapor, which condenses onto the core particles at a timescale of several tens of milliseconds in a manner that can be modeled as bimodal coagulation. Gold was deposited onto core nanoparticles consisting of silver or polystyrene latex, and silver was deposited onto gold nanoparticles. The coating morphology depends on the relative surface energies of the core and coating materials, similar to the growth mechanisms known for thin films: a coating made of a substance having a high surface energy typically results in a patchy coverage, while a coating material with a low surface energy will normally “wet” the surface of a core particle. The coated particles remain gas-borne, allowing further processing.ChemE/Chemical EngineeringApplied Science

Basis of Design for a process to refine green plants

DelftChemTechApplied Science

Refining Green Plants to Protein Cakes and other useful products in the African country Zambia

DelftChemTechApplied Science

3D-impaction printing of porous layers

Porous layers composed of nanoparticles (NPs) have a wide range of (potential) applications including catalysts, (chemical) sensors, thermoelectric materials and electronics. These application domains will profit strongly from our NP printing process which is flexible with respect to i) the composition of the NPs and ii) the possibility of composing arbitrary mixtures of different NPs (external mixtures). Our printer is a combination of a spark ablation NP generator supplying unagglomerated 5 nm particles with a hypersonic impactor equipped with an xyz stage. The profiles of printed lines are measured, and the impact velocity is described by theory. Printed gold lines on a polymer contact lens are sufficiently sintered by the impact energy to show the plasmon mode of gold (“golden“ color).Electronic Components, Technology and MaterialsChemE/Materials for Energy Conversion & Storag

Plasmonic nanoparticle films for solar cell applications fabricated by size-selective aerosol deposition

A soft deposition method for incorporating surface plasmon resonant metal nanoparticles within photovoltaic devices was studied. This self-assembly method provides excellent control over both nanoparticle size and surface coverage. Films of spherical Ag nanoparticles with diameter of ?100 nm were fabricated by depositing size-selected aerosols on various substrates using electrophoresis. This novel deposition method opens the route to embed plasmonic nanoparticles in the intermediate reflector of a micromorph silicon tandem PV cell. We have for the first time fabricated working tandem cells of this type. Compared to a flat reference device the Ag particles enhanced the short-circuit current density due to improved light trapping. The enhancement is, however, limited by the sulfidation on the surface of Ag nanoparticles and a further optimization of the cell fabrication method is required to prevent a reduction of open-circuit voltage and fill factor.ChemE/Chemical EngineeringApplied Science

Green manufacturing of metallic nanoparticles: A facile and universal approach to scaling up

High-yield and continuous synthesis of ultrapure inorganic nanoparticles (NPs) of well-defined size and composition has invariably been one of the major challenges in nanotechnology. Employing green techniques that avoid the use of poisonous and expensive chemicals has been realized as a necessity for manufacturing NPs on an industrial scale. In this communication, we show that a newly developed high-frequency spark (HFS) quenched by a high-purity gas yields a series of monometallic and bimetallic NPs in large quantities, with well-defined (primary) particle size (sub-10 nm) and chemical composition. The mass production rate is linearly dependent on the operating frequency, and can reach up to 1 g h−1, providing a universal and facile technology for producing multicomponent hybrid NPs. Considering also that the methodology requires neither any specialized machinery, nor any chemical reagents, product purification, or any further waste processing, it provides a green, sustainable and versatile platform for manufacturing key building blocks toward industrial scale production.ChemE/Materials for Energy Conversion & StorageQN/Zandbergen LabAtmospheric Remote Sensin