REXP2 RESEARCH LLC

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I am an inter-organizational collaboration builder who creates teams of diverse researchers to solve complex multi-scale problems. I excel at ideation, looking for new applications of science and technology to broaden the business. Scientifically, I am interested in the relationship of micro/nano structure to the properties of materials and to the performance of products. Some images illustrating this relationship from both my professional collaborative research and personal research are shown here. Professionally, I am a materials scientist working on carbon-carbon composites, ceramics, and metals for advanced aerospace applications. Personally, I am a microscopist focusing on structure property relationships in biological and manmade materials. As you can see here, these diverse interests and expertise intersect. Please review the pages on this site and contact me for further discussion.

Carbon-carbon composite shows fiber and matrix oxidation after 4 hours of air exposure at 700 °C. Note the matrix structure with tangential basal plane symmetry. (C. Zhang, M. Chen, S.C. Paulson, R.G. Rateick Jr, V.I. Birss, "New insights into the early stages of thermal oxidation of carbon/carbon composites using electrochemical methods” Carbon [108] 178-189 (2016).)
Carbon-carbon composite shows fiber and matrix oxidation after 4 hours of air exposure at 700 °C. Note the matrix structure with tangential basal plane symmetry. (C. Zhang, M. Chen, S.C. Paulson, R.G. Rateick Jr, V.I. Birss, "New insights into the early stages of thermal oxidation of carbon/carbon composites using electrochemical methods” Carbon [108] 178-189 (2016).)
Single crystal formation in the ovary wall of Podophyllum peltatum or Mayapple. Polarized light microscopy with partially crossed polarisers reveals the structure. Polycrystalline potassium oxalate is common in botanical structures, but not single crystals.
Single crystal formation in the ovary wall of Podophyllum peltatum or Mayapple. Polarized light microscopy with partially crossed polarisers reveals the structure. Polycrystalline potassium oxalate is common in botanical structures, but not single crystals.
Phosphate + potassium glass coating on carbon-carbon composite. EDX imaging shows location of potassium. Potassium is a glass network modifier, but if free it catalyses oxidation. (“Evolution of Potassium Aluminum Phosphate Anti-Oxidant Coatings during Thermal Oxidation of Carbon-Carbon Composites”, High Temperature Corrosion Gordon Conference, July 2017, S. Paulson, V. Kharanagh, K. Xia, L. Tong, R. Rateick, V.I. Birss).
Phosphate + potassium glass coating on carbon-carbon composite. EDX imaging shows location of potassium. Potassium is a glass network modifier, but if free it catalyses oxidation. (“Evolution of Potassium Aluminum Phosphate Anti-Oxidant Coatings during Thermal Oxidation of Carbon-Carbon Composites”, High Temperature Corrosion Gordon Conference, July 2017, S. Paulson, V. Kharanagh, K. Xia, L. Tong, R. Rateick, V.I. Birss).
Birefringence from crystalline silica in the cell wals of the strobilus of Equistetum sp. (Horse Hair). Silica forms in aerial parts of some plants to provide increased strength and stiffness. Given the height and small diameter of Equistetum sp., this is a morphological and structural need. Lignified xylem walls near the base of the micrograph also show birefringence. Polarized light image under fully crossed polarizers.
Birefringence from crystalline silica in the cell wals of the strobilus of Equistetum sp. (Horse Hair). Silica forms in aerial parts of some plants to provide increased strength and stiffness. Given the height and small diameter of Equistetum sp., this is a morphological and structural need. Lignified xylem walls near the base of the micrograph also show birefringence. Polarized light image under fully crossed polarizers.
TEM micrographs of nano crystalline electroformed Ni-Co show annealing twins. Nano twinning was shown to be an effective strengthening mechanism in this alloy. A: as supplied; B: following fatigue crack growth. (M.D. Sangid, G.J. Pataky, H. Sehitoglu, R.G. Rateick, T. Niendorf, H.J. Maier, "Superior fatigue crack growth resistance, irreversibility, and fatigue crack growth–microstructure relationship of nanocrystalline alloys” Acta Materialia [59] (19) 7340-7355 (2011).)
TEM micrographs of nano crystalline electroformed Ni-Co show annealing twins. Nano twinning was shown to be an effective strengthening mechanism in this alloy. A: as supplied; B: following fatigue crack growth. (M.D. Sangid, G.J. Pataky, H. Sehitoglu, R.G. Rateick, T. Niendorf, H.J. Maier, "Superior fatigue crack growth resistance, irreversibility, and fatigue crack growth–microstructure relationship of nanocrystalline alloys” Acta Materialia [59] (19) 7340-7355 (2011).)
The spiralling lignified walls of the xylem vascular bundles, here in Asarum canadense (wild ginger), show birefringence under crossed polarisers. The xylem is birefringent on account of its ordered lignin structure. The lignin along with the spiral structure (not shown here) strengthens the walls of the vascular bundle. Lignin could be a natural carbon fibre precursor. It is a waste product of paper making.
The spiralling lignified walls of the xylem vascular bundles, here in Asarum canadense (wild ginger), show birefringence under crossed polarisers. The xylem is birefringent on account of its ordered lignin structure. The lignin along with the spiral structure (not shown here) strengthens the walls of the vascular bundle. Lignin could be a natural carbon fibre precursor. It is a waste product of paper making.
Fatigue crack growth in 3-D non-woven carbon-carbon composites follows the fibers causing crack bridging and fiber pullout. These are primary toughening mechanisms in composite materials. (“Damage tolerance of carbon-carbon composites in aerospace application” Carbon [126] 382-393 (2018) P. Chowdhury, H. Sehitoglu, R. Rateick).
Fatigue crack growth in 3-D non-woven carbon-carbon composites follows the fibers causing crack bridging and fiber pullout. These are primary toughening mechanisms in composite materials. (“Damage tolerance of carbon-carbon composites in aerospace application” Carbon [126] 382-393 (2018) P. Chowdhury, H. Sehitoglu, R. Rateick).
The food vacuoles in this paramecium are stained red after consuming Congo Red stained yeast cells. Congo red is an acid base indicator transitioning from red to blue around a pH of 3-5.2. The digestion process results in the acidification of the vacuoles.
The food vacuoles in this paramecium are stained red after consuming Congo Red stained yeast cells. Congo red is an acid base indicator transitioning from red to blue around a pH of 3-5.2. The digestion process results in the acidification of the vacuoles.
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