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The Ohio State University

College of Engineering


Henk Verweij

Orton Chair in Ceramic Engineering

Ph. D., Eindhoven Technical University, 1980

Tel. (614) 247-6987 / 292-7427

Office: 291 Watts Hall

E-mail

  • Member: The American Ceramic Society, Materials Research Society
  • Dutch National Priority Program on Materials Research Board, 1995-2000
  • University of Twente Research Stimulation fund grant, 1996
  • Graduated "cum laude" from Delft Technical University

 

Prof. Verweij's primary research interests include:

  • Thermodynamics and transport properties of dense, porous and two-phase nanoscale composite ceramics
  • Preparation of those ceramics with a large extent of definition and preferably through colloidal processing with well-defined particles

Research Project Highlights

Preparation and Properties of Supported Ceramic Membranes

Ceramic membranes find widespread use in liquid filtration, gas separation and catalysis. An advantage of these membranes over organic membranes is that they can sustain much higher temperatures. Macroporous membrane supports with pore Ø › 50 nm are prepared from stable suspensions of sub-micron alpha-Al2O3 particles. Flat plates are then made by means of colloidal filtration while tubes are made by means of centrifugal deposition. Mesoporous membranes, with 2 < pore Ø < 50 nm are made by casting nanoparticle dispersions on porous supports. They can be used as a carrier for microporous membranes but also for selective blocking of large molecules and ions in liquid media. This can be applied in water treatment and sensors for measuring water potential in soil.

TEM micrograph of supported membrane cross section consisting of an active amorphous silica top-layer and 2 intermediate gamma-alumina layers. The support is not visible.

 

Supported micro-porous silica membranes with pore Ø pore < 2 nm exhibit very high selectivity for small molecules such as H2. They can be applied in pervaporation or steam-reforming reactors in which they remove H2O or H2 rapidly from the reaction medium. This makes that thermodynamically limited conversions are significantly enhanced. It was recently shown that sorption in 30 nm microporous silica membranes can be monitored with ellipsometry. The results are converted into sorption expressions and diffusion mobilities that can be used in predicting multi-component transport of the gasses.

Calculated transport of a 50/50 feed of slow A/fast B molecules with sweep gas C in a membrane with:

  • 2 mm thick alpha-Al2O3 macroporous support
  • 1.5 mm gamma-Al2O3 mesoporous intermediate
  • 100 nm microporous SiO2 top layer

 

Densifying Ceramics at Room Temperature?

The excellent surface properties of dense nanoscale ceramics can be exploited for large scale (consumer) production if this material can be applied as a coating on top of metal and plastic parts. For this reason a method was developed to pack thin layers of nanoscale particles to the highest possible density. Sintering of zirconia layers can then be well below 600°C, with chemical activation close to room temperature. Rapid surface heating can be used to densify the layers without degrading the substrate.

TEM cross-section of ZrO2 coating densified near room temperature and crystallized at 600°C.
HRTEM energy filtering map of a cross-section of a true nanocomposite of ZrO2 and Fe2O3 on SiO2/Si substrate prepared through the modified emulsion precipitation method.