| 1. |
- Ossler, Frederik, et al.
(författare)
-
Dynamics of hydrogen loss and structural changes in pyrolyzing biomass utilizing neutron imaging
- 2021
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 176, s. 511-529
-
Tidskriftsartikel (refereegranskat)abstract
- We present results from neutron-imaging studies of slow, vacuum pyrolysis of beech, poplar and conifer wood, and pelletized biomass from room temperature up to 1000 °C. A detailed and quantitative method to extract 2D (in situ neutron radiography, NR) and 3D (ex situ neutron computed tomography, NCT) information on structural transformation and elemental hydrogen content has been developed. NCT and X-ray tomography (XCT) experiments on a carbonized beech twig permitted comparison of the spatial distribution of hydrogen, better sensed by NCT, and carbon, oxygen, and heavier elements, better sensed by XCT. We have developed a methodology to directly compare structure and hydrogen-loss dynamics measured using neutron imaging with thermogravimetric analysis and differential thermogravimetry and thus can better understand the correlations between hydrogen and carbon release dynamics. While the methodology has been developed for the carbonization of biomass, we expect that it could be applied to in situ dynamic monitoring of other hydrogenous reacting systems with the appropriate spatial and temporal scales.
|
|
| 2. |
- Ossler, Frederik, et al.
(författare)
-
In situ monitoring of hydrogen loss during pyrolysis of wood by neutron imaging
- 2019
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:2, s. 1273-1280
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogen is an element of fundamental importance for energy but hard to quantify in bulk materials. Neutron radiography was used to map . in situ loss of elemental hydrogen from beech tree wood samples during pyrolysis. The samples consisted of three wood cylinders (finished dowel or cut branch) of approximately 1 cm in length. The samples were pyrolyzed under vacuum in a furnace vessel that was placed inside a cold neutron imaging beamline using a temperature ramp of 5 °C/min from ambient up to 400 °C. Neutron radiographs with exposures of 30 s were sequentially recorded with a charge-coupled device over the course of the experiment. Relative absorbance/scattering of the neutron beam by each sample was based on intensity (or brightness) values as a function of pixel position. The much larger neutron cross section for hydrogen compared to carbon and oxygen enables almost direct conversion of neutron attenuation into sample hydrogen content for each time step during the pyrolysis experiment. Target and vessel temperatures were recorded concurrently with collection of the radiographs so that changes could be directly correlated to different states of pyrolysis. The most visible change appeared at the initial phase of the 400 °C plateau as evidenced by strong hydrogen loss and primarily diametric shrinking of the samples. The loss of elemental hydrogen between initial and final states of pyrolysis was estimated to be about 70%.
|
|
| 3. |
- Makowska, Małgorzata, et al.
(författare)
-
Flexible sample environment for high resolution neutron imaging at high temperatures in controlled atmosphere.
- 2015
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:12
-
Tidskriftsartikel (refereegranskat)abstract
- High material penetration by neutrons allows for experiments using sophisticated sample environments providing complex conditions. Thus, neutron imaging holds potential for performing in situ nondestructive measurements on large samples or even full technological systems, which are not possible with any other technique. This paper presents a new sample environment for in situ high resolution neutron imaging experiments at temperatures from room temperature up to 1100 °C and/or using controllable flow of reactive atmospheres. The design also offers the possibility to directly combine imaging with diffraction measurements. Design, special features, and specification of the furnace are described. In addition, examples of experiments successfully performed at various neutron facilities with the furnace, as well as examples of possible applications are presented. This covers a broad field of research from fundamental to technological investigations of various types of materials and components.
|
|
| 4. |
- Ossler, Frederik, et al.
(författare)
-
In-situ neutron imaging of hydrogenous fuels in combustion generated porous carbons under dynamic and steady state pressure conditions
- 2017
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 116, s. 766-776
-
Tidskriftsartikel (refereegranskat)abstract
- We report results from experiments where we characterize the surface properties of soot particlesinteracting with high-pressure methane. We find considerable differences in behavior of the soot materialbetween static and dynamic pressure conditions that can be explained by multiscale correlations inthe dynamics, from the micro to macro of the porous fractal-like carbon matrix. The measurements werepossible utilizing cold neutron imaging of methane mixed with combustion generated carbon (soot)inside steel cells. The studies were performed under static and dynamic pressure conditions in the range10e90 bar, and are of interest for applications of energy storage of hydrogenous fuels. The very high crosssections for neutrons compared to hard X-ray photons, enabled us to find considerable amounts of nativehydrogen in the soot and to see and quantify the presence of hydrogen atoms in the carbon soot matrixunder different pressure conditions. This work lays the base for more detailed in-situ investigations onthe interaction of porous carbon materials with hydrogen in practical environments for hydrogen andmethane storage.
|
|
