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Spark Highlights


Technical         Materials        Output         Applications         Patterning


 

Technical

First Prototype - 1988

  • Spark under Natmosphere
  • Ambient pressure
  • Measurement of charged gold particles

Temperature and quenching rate of the plasma-2017

  • Flow rate of 1.68 slpm
  • Plasma temperature around 12000 K
  • Quenching rate is around 6x108 K/s
  • After 25 μs the plasma is at room temperature

Materials

Input

  • Metals
  • Alloys
  • Metal oxides
  • Semiconductors

Influence of carrier gas and various metals-2008

  • Gases have various breakdown voltages changing the energy delivered to the spark
  • Materials have different ablation rates depending on:
    • Thermal conductivity
    • Evaporation enthalpy
    • Boiling point

Semiconducting nanoparticles-2011

  • Doping decreases electrical resistivity (0.17 Ω cm) 1015 boron atoms/cm3

Production of highly oxidizing metals-2011

  • Production of Mg nanoparticles
  • Purification of 5N Ar: 5 ppm H2O, O2
  • Bake-out of the system
  • Preloading of the system with Mg NPs

Deposition of alloy NPs-2016

  • Using alloys as starting materials gives alloyed NPs
  • The composition is not affected
  • The yield can be predicted

Core-shell particles-2018

  • Carbon encapsulation depends on condensation temperature of C:
    • Tm < Tc: core-shell particle
    • Tm ~ Tc: partially filled particle
    • Tm > Tc: composite

Making alloyed NPs using elemental electrodes-2018

  • Ablation produces ions and electrons
  • Ions have a stronger albation compared to electrons
  • Discharge is oscillatory and can be manipulated

Output

Monodisperse output- 1991

  • Deposition of charged silver particles
  • Size selection based on electrical mobility
  • 8 nm deposited on carbon film

Clusters-1991

  • Atomic clusters 1 – 40 Pd, Al atoms
  • Setup in vacuum

Narrow size distribution for large particles-1991

  • Particle size distribution has a fixed width (1.27 < σ < 1.34)
  • For large particles, the absolute spread is larger
  • By continuously adding small NPs to the aerosol, the absolute width can remain constant (1 nm)

Influence of nanoparticle material of size distributions-2008

  • Precious metals in N2 gas
  • High production rates give higher concentrations and larger particles (Au > Pt > Pd > Ag)

Deposition of uniform layers-2011

  • Deposition of Ag nanoparticles by diffusion
  • Annealing at 300 C for 30 min
  • Layer height of 104 nm
  • Surface roughness of 8.7 nm

Production of large spherical particles-2012

  • Particles > 10 nm tend to agglomerate
  • Higher temperature increases mobility and produces spherical particles

Growth of superstructures-2013

  • Nanosecond spark duration
  • Mo in air
  • Deposition of MoO3 on Cu foil 3 mm from spark

Particle size distributions from TEM data-2015

  • Direct observation of Au particle size distributions by TEM
  • Comparison of initial size and reference downstream

Cluster production at atmospheric pressure-2015

  • Measurement of Ag clusters in He gas
  • Using generic and purified helium gas
  • Selection by DMA
  • Detection by uCPC

Application

Aerosol catalysis- 1999

Methanation

4 H2 + CO2 - > CH4 + 2 H2O using Ni

Radiolabeling of carbon aerosol-2000

  • Application of radioactive Tc in liquid applied to spark electrodes