Engineering Conferences International

Please click Additional Files below to see the full abstract

Naamne, Iman l

Marder, Rachel

Kaplan, Wayne D.

CALCIUM AND THE ELONGATED GRAIN SHAPE OF ALUMINA 
 
Iman Naamne, Technion-Israel Institute of Technology, Haifa, Israel 
emannaamneh@campus.technion.ac.il 
Rachel Marder, Technion-Israel Institute of Technology, Haifa, Israel 
Wayne D. Kaplan, Technion-Israel Institute of Technology, Haifa, Israel 
 
 
Grain growth is an important process which occurs together with densification during sintering of polycrystalline 
ceramic materials.  The shape of grains can influence the properties of a sintered material, and thus it is 
important to understand the reasons behind morphological changes during thermal processing of ceramics. 
 
α-alumina is one of the most studied ceramics, in part due to its optical and mechanical properties, and thus it is 
often used as a model system for fundamental studies.  Previous studies have clearly demonstrated that doping 
alumina with Ca below the solubility limit results in accelerated and anisotropic grain growth, and as a result 
changes the crystal shape, where elongated plate-like alumina grains form. It is not clear if the elongated shape 
is due to the system approaching equilibrium, i.e. the equilibrium crystal shape of alumina due to adsorbed Ca 
to some crystallographic surfaces, or if this is a kinetic shape where Ca results in anisotropic grain boundary 
mobility. 
 
In this study, undoped and Ca-doped alumina was sintered to obtain a dense microstructure. Combined electron 
microscopy techniques were used to correlate the crystallographic shape of elongated grains in Ca-doped 
alumina, compared to the shape of equilibrated pores occluded in the alumina grains.  The possible mechanism 
by which Ca increases grain boundary mobility will be discussed.   
 
 


English

Calcium and the elongated grain shape of alumina

Kreshover, Anat Karlin

Grader, Gideon

FABRICATION AND CHARACTERIZATION OF CERAMIC DIELECTRIC HIGH GRADIENT INSULATOR  
 
Anat Karlin Kreshover, Chemical Engineering Department, Technion, Israel 
anatkarlin@campus.technion.ac.il 
Gideon Grader, Chemical Engineering Department, Technion, Israel 
 
 
 Key Words: Spark plasma sintering, layered ceramic composites, alumina, grain growth, surface breakdown.  
 
The breakdown voltage of high-voltage insulators in vacuum is lower than in air due to surface breakdown 
failure. In this failure mode, electrons originating at the cathode-dielectric-vacuum triple junction strike the 
insulator surface causing secondary electrons emission. The positive charge formed on the surface amplifies 
the number of secondary electrons emission giving rise to an electron avalanche resulting with a catastrophic 
failure of the device. One approach to overcome this failure is substitution of the dielectric insulator by a periodic 
metal-dielectric structure known as High Gradient Insulator (HGI). This periodic structure changes the sign of 
the electric field component perpendicular to the insulator surface. As a result, the incident electrons are shifted 
from the insulator surface, thus inhibiting the emission of secondary electrons and preventing the electron 
avalanche. However, the HGI structures suffer from local breakdown damages and metal evaporation from 
metallic layers onto the dielectric layers, creating short circuit pathways. In addition, the manufacturing of 
metallic-ceramic HGI has technological challenges. 
 
In this work, we suggest an alternative concept to the HGI structure, where we replace the metallic layers with 
ceramic layers that have a high dielectric constant. The proposed structure is denoted DHGI (Dielectric HGI). 
Simulations showed that this structure can alter the electric field around the insulator similarly to the HGI. The 
alumina insulator and the DHGI layer used herein must be fully dense to maintain high vacuum (P ≤ 10-6 Torr). 
We used spark plasma sintering (SPS) to produce high-quality, dense, multilayered composites with controlled 
layer configuration and thickness. To reduce the stresses between the layers and increase their compatibility, 
the DHGI layers consisted of alumina with 8wt.% addition of a colossal dielectric coefficient material TiO2 co-
doped Al and Nb (TANO, ε~104). We demonstrate the fabrication of a prototype sample composed of two layers. 
This poster focuses on the microstructural and phase analysis of this prototype sample. It is shown that during 
sintering, unique intermediate layers formed at the interface between the two original layers. We found that the 
grain size decreases gradually across the interface. Moreover, the DHGI prototype was found to have superior 
breakdown performance compared to a conventional reference pure alumina insulator.   
 
 
Figure 1 – Images of the bi-layer DHGI sintered by SPS; A) Top view, B) Side view and C) schematic 
illustration. 
 
 
 
 
 
 
Figure 2 – SEM images of the gradually decreasing alumina grains in the L2-L3 layers between 
the Al2O3@TANO and pure Al2O3 layers. 


Fabrication and characterization of ceramic dielectric high gradient insulator

Please click Additional Files below to see the full abstrac

Jones, Gareth

Harrison, Robert

Goddard, Dave

Green, Christopher

Barron, Nicholas

Pearmain, David

Morgan, Jonathan

Grimley, Carolyn

FLASH SINTERING, A NOVEL TECHNIQUE, FOR MANUFACTURING SURROGATE AND ACTIVE 
NUCLEAR MATERIALS 
 
Samira Bostanchi, Lucideon Limited 
samira.bostanchi@uk.lucideon.com 
Robert Harrison, University of Manchester 
Dave Goddard, National Nuclear Laboratory 
Nicholas Barron, National Nuclear Laboratory 
Christopher Green, National Nuclear Laboratory 
David Pearmain, Lucideon Limited 
Jonathan Morgan, University of Manchester 
Carolyn Grimley, Lucideon Limited 
 
 
Key Words: Flash Sintering, Nuclear Fuel, Cerium Oxide, Uranium Dioxide, Scale Up 
 
This project, conducted through a collaboration between National Nuclear Laboratory (NNL), Lucideon, 
University of Manchester and Orano, demonstrated a novel flash sintering technology to fabricate dense 
uranium dioxide (UO2) pellets, of a size that would be consistent with the requirements of the Nuclear 
Decommissioning Authority’s (NDA) disposal Mixed Oxide (MOX) concept. In flash sintering an electric field is 
applied during the densification of green bodies which enables lower temperatures and shorter sintering cycles 
to be used, which could lead to cost savings in the disposition of the UK’s separated civil plutonium. 
 
The use of an alternating current and bespoke non-linear control software, developed by Lucideon, have been 
shown to be important in controlling the flash process and ensuring homogeneous and consistent 
microstructures. The development started using surrogate fuel Cerium Oxide (CeO2) under the Advanced Fuel 
Cycle Programme (AFCP), whereby the process and flash sintering parameters where optimised to reliably 
produce homogeneously 96% dense 12.5mm diameter pellets. Transitioning to active materials, the process 
was then applied to UO2. Theoretical densities of 94 - 96% were achieved on green bodies ranging from 6.7 to 
14.1 mm diameter. The addition of a neutron poison, as may be required for disposal MOX, was also 
demonstrated by fabricating UO2 pellets containing 1 wt.% gadolinia (Gd2O3). 
 
A preliminary assessment was also carried out for the industrial scale-up of the technology, based on modifying 
existing continuous sintering furnaces currently used by Orano for the manufacture of MOX fuel pellets. This 
concluded that for large disposal MOX pellets, the throughput could be increased by over 70% through flash 
sintering technology with conservative estimates. The remaining challenges concern the need to keep pellets 
isolated from one another and to make electrode contacts with each pellet. The next stage in development of 
this technology would be to demonstrate the scale-up to a multi-pellet system to confirm the predicted 
throughput improvements and to demonstrate that during flash sintering plutonium dioxide readily forms a solid 
solution with UO2, as is the case with conventional sintering of MOX fuel. 
 
 
Figure 1 - The evolution of cerium oxide pellets representing the progressive optimization of flash sintering 
parameters. 
 


Flash Sintering, a Novel Technique, for Manufacturing Surrogate and Active Nuclear Materials

Tsur, Yoed

Halabi, Rawan

Baltianski, Sioma

ROLE OF NATIVE DEFECTS IN FIELD-ASSISTED SINTERING 
 
Yoed Tsur, Chemical Engineering and Grand Technion Energy Program, Technion, Israel Institute of 
Technology, Haifa, Israel 
tsur@technion.ac.il 
Rawan Halabi, Chemical Engineering, Technion 
Sioma Baltianski, Chemical Engineering, Technion  
 
 
Key Words: Flash sintering, Doping, Magnesium oxide, Oxygen vacancies, Metal vacancies. 
 
MgO has been chosen as a model material in order to elucidate the role of native defects in the flash event. This 
is due to its known and simple structure and defect chemistry, which allows to keep most things similar while 
creating vacancies of both types. Foreign cations are not candidates for mass transfer, since they must have a 
neighbor vacancy of the same site to jump into. Vacancies are created by self-compensation and have much 
more sites to jump into, namely, all next-nearest-neighbors in the lattice. Cation with similar radii and different 
charge where chosen, to minimize strain effects in substitutional doping. These are Li1+ (acceptor, 76 pm in six-
fold coordination number), Sc3+ (donor, 75 pm), and Zn2+ for isovalent doping (74 pm). Those are all quite 
comparable to the host’s cation, Mg2+, ionic radius, which is 72 pm in six-fold coordination. Acceptors enhance 
the oxygen vacancies concentration and reduce the magnesium vacancies concentration, while donors do the 
opposite. See figure 1 for illustration of size comparison.  
 
In my talk I will discuss the differences in the flash as well as influences on conventional sintering of MgO, due 
to the various doping types and resulting native defects. Preliminary results suggest that oxygen vacancies are 
the most effective agents for both conventional and flash sintering. See also R. Halabi’s poster on the subject.   
 
 
 
  
 
Figure 1 – illustration of size comparison of the different dopants.  


Role of Native Defects in Field-Assisted Sintering

Raj, Rishi

MEMRISTORS: THE ROLE OF ANODE INTERFACE RESISTANCE 
 
Rishi Raj, University of Colorado-Boulder, 
rishi.raj@colorado.edu 
 


Memristors: The Role of Anode Interface Resistance

Benthem, Klaus van

STUDIES OF GRAIN BOUNDARIES BY HIGH RESOLUTION TEM 
 
 Klaus van Benthem, University of California Davis 
benthem@ucdaviss.edu 


Studies of Grain Boundaries by High Resolution TEM

Grasso, Salvatore

FROM PIT FIRE TO ULTRAFAST HIGH-TEMPERATURE SINTERING (UHS): SHARED FEATURES OF 
ULTRA-FAST SINTERING TECHNIQUES 
 
Salvatore Grasso, School of Engineering and Material Science, Queen Mary University of London (QMUL), UK 
s.grasso@qmul.ac.uk 
 
 
Extreme heating and cooling rates, approaching 104 °C min−1 represent a paradigm shift in materials 
manufacturing. In the past two decades, new techniques like Ultrafast High-temperature Sintering (UHS)[1], and 
Flash sintering (FS) have emerged. Compared to conventional sintering, consolidation times are shortened by at 
least a thousand folds. Densification and chemical reactions proceed in a far from equilibrium condition[2]. 
Readily recognized advantages of rapid sintering are suppressed grain growth, reduced loss of volatile elements 
(Li, Na, K), and limited interdiffusion in multi-layered devices. The accelerated kinetics opens up new 
opportunities to prepare ceramics with properties not attainable using slow heating rates [3]. In the context of the 
current global environmental 
crisis, rapid sintering also 
holds the promise to 
decarbonize the sector while 
reducing the emissions of 
toxic gases associated with 
the firing step. The talk 
summarizes advances in rapid 
sintering over the past 
century. It examines the 
impact of extreme heating 
rates on the sintering 
mechanisms[4], and 
microstructural evolution 
throughout the three sintering 
stages.  
 
 
 
 
 
 
 
 
 
 
 
References: 
 
[1] M. Kermani, C. Hu, and S. Grasso, “From pit fire to Ultrafast High-temperature Sintering (UHS): A 
review on ultrarapid consolidation,” Ceram. Int., vol. 49, no. 3, pp. 4017–4029, Feb. 2023, doi: 
10.1016/J.CERAMINT.2022.11.091. 
 
[2] J. Wu et al., “Carbon free ultra-fast high temperature sintering of translucent zirconia,” Scr. Mater., vol. 
210, p. 114476, 2022, doi: 10.1016/j.scriptamat.2021.114476. 
 
[3] M. Biesuz, S. Grasso, and V. M. Sglavo, “What’s new in ceramics sintering? A short report on the latest 
trends and future prospects,” Curr. Opin. Solid State Mater. Sci., vol. 24, no. 5, p. 100868, Oct. 2020, doi: 
10.1016/j.cossms.2020.100868. 
 
[4] J. Dong et al., “Thermally-insulated ultra-fast high temperature sintering (UHS) of zirconia: A master 
sintering curve analysis,” Scr. Mater., vol. 203, p. 114076, 2021, doi: 10.1016/j.scriptamat.2021.114076. 


From Pit Fire to Ultrafast High-Temperature Sintering (UHS): Shared Features of Ultra-Fast Sintering Techniques

Lima, Isabel M.

Hass, Amir

 
UNDERSTANDING BIOCHAR FUNCTIONALITIES BASED ON FEEDSTOCK CHARACTERISTICS AND 
PROCESSING CONDITIONS 
 
Isabel M. Lima, USDA-ARS Southern Regional Research Center, 1100 Allen Toussaint Blvd, USA 
 Isabel.lima@usda.gov 
Amir Hass, Agricultural & Environmental Research Station, West Virginia State University, USA 
 
 
Key Words: biochar, switchgrass, miscanthus, thermogravimetric analysis 
 
Marginal agricultural sites require soil amendments to improve productivity. Biochar can increase soil carbon, 
improve water and nutrient retention, metal adsorption, which can lead to higher nutrient and water use 
efficiency, lower maintenance costs, improved water quality, as well as improved crop performance. A series of 
biochars were produced via slow pyrolysis, from three different biomass crops sourced from woody and 
herbaceous bioenergy crops, specifically switchgrass, miscanthus, and willow, at pyrolysis peak temperatures of 
350°C, 500°C, and 650°C. Biochars are developed with the objective to maximize their efficacy as soil 
amendment, specifically to enhance marginal soils nutrient and water holding capacity; and to improve efficiency 
of runoff mitigation practices in retaining and removal of contaminants. Biochars were characterized for select 
physical and chemical properties, such as thermogravimetric analysis, ultimate analysis, surface area, pore size 
distribution, elemental analysis, etc. This is the first of a few reports describing biochar properties as a function 
of both the feedstock and the pyrolysis temperature. These biochars will be subsequently used as soil 
amendments on reclaimed mine lands as well as marginal agricultural sites. 
 
 
 
 
 
 
 
 


Understanding biochar functionalities based on feedstock characteristics and processing conditions

Williams, Jasmine M.

Thomas, Sean C.

HIGH CARBON WOOD ASH BIOCHAR FOR MINE TAILINGS REMEDIATION: A FIELD ASSESSMENT OF 
PLANTED TREE PERFORMANCE AND METALS UPTAKE 
 
Jasmine M. Williams, University of Toronto 
jasmine.williams@mail.utoronto.ca 
Sean C. Thomas, University of Toronto 
 
Key Words: tailings, contaminants, phytoabsorption, mine restoration, tree survival 
 
Unique properties of biochar render it appealing for revegetating and decontaminating historic, barren, and 
chemically complex mine tailings; however, the scale and remote location of many mining sites make 
widespread implementation unrealistic. Bottom ash from bioenergy facilities can contain high levels of charcoal 
residue, and thus qualify as a type of biochar; the availability of this material at low cost makes it of particular 
interest in the context of tailings remediation. Nevertheless, bottom ash is variable and often contains residual 
toxic metals/metalloids that could potentially be phytoabsorbed into plant tissues. Very few field trials exist 
testing in situ applications of high carbon wood ash biochar (HCWAB), whether trace metals in ash are 
absorbed and stored within plant tissues, and if so, how this may affect plant growth and survival or possibly the 
wider food chain. A large-scale, multi-year replicated field trial was implemented on historic contaminated metal 
mine tailings in Northern Ontario (Canada) over a range of wood ash amendment dosages (0-30 t/ha); 
responses examined included substrate properties, success of planted Pinus banksiana Lamb. saplings, and 
tree tissue element concentrations. Sapling survivorship and biomass growth were inventoried annually, while 
substrate chemical parameters were measured in part using acid-digestion and ICP-MS, as well as innovative 
field tools such as Plant Root Simulator (PRS) probes. To assess elemental composition in sapling tissue, we 
propose and test a novel application of electron probe x-ray microanalysis combined with Laser-ablation 
inductively coupled mass spectrometry (LA-ICP-MS) to intact needle and branch samples across the range of 
dosages applied. Results were interpreted through analysis of variance and fitted to both linear and higher order 
log-logistic dose response models. Peak survival and growth of saplings were observed at mid-range biochar 
dosages of 3-6 t/ha. Similarly, substrate ion availability of P, K, Fe, Zn, and Pb were stable at these lower 
dosages, but increased above 6 t/ha, while substrate supply of NO-3 was significantly reduced at the high 
dosages. The trace amounts of toxic metals/metalloids of concern measured in wood ash (namely As, Cd, Cu, 
and Pb) did not lead to significantly increased sapling tissue concentrations at low to moderate dosages, but in 
some cases tissue contaminant levels increased at the highest dosage considered (30 t/ha). In the case of 
select important plant elements such as Molybdenum, concentration in HCWAB amended tailings was 
significantly linked to ultimate tree tissue storage. Our findings highlight the potential for high carbon wood ash 
biochar to be used for metal mine restoration at low to moderate dosages. 
 
 


High carbon wood ash biochar for mine tailings remediation: a field assessment of planted tree performance and metals uptake

Pallarés, Javier

Gil, Antonia

Arauzo, Inmaculada

Cortés, Cristóbal

PORE FORMATION AND POROUS STRUCTURE EVOLUTION ON CO2 ACTIVATION PROCESSES 
 
Javier Pallarés, University of Zaragoza\CIRCE (María de Luna 5, 50018 Zaragoza, Spain) 
jpallare@unizar.es,  
Antonia Gil, University of Zaragoza\CIRCE (María de Luna 5, 50018 Zaragoza, Spain) 
Inmaculada Arauzo, University of Zaragoza\CIRCE (María de Luna 5, 50018 Zaragoza, Spain) 
Cristóbal Cortés, University of Zaragoza\CIRCE (María de Luna 5, 50018 Zaragoza, Spain) 
 
Key Words: Activated carbon, random pore model, porous evolution model 
 
It has been experimentally proved that activated carbon, obtained from biomass waste precursors, presents 
adsorption properties comparable to those obtained from traditional precursors [1].  However, there are hardly 
any models that focus on the development of porosity during the process, so it is not possible to predict the final 
properties that characterize the adsorption capacity of activated carbon from the properties of the precursor 
material and the conditions of the activation process.  Within the so-called pore models, the random pore model 
(RPM) is the most popular and predicts with great precision the evolution of the porous structure due to the 
growth and coalescence of the pores [2,3].  However, in activation processes with a low degree of conversion, in 
which pore formation is the dominant mechanism, the RPM does not correctly predict the evolution of the 
specific surface area since it does not consider the appearance and creation of new porosity.  In this work, the 
relative influence of pore formation, growth and coalescence mechanisms are analyzed using a new model 
(Porous Evolution Model) that allows predicting the specific surface area created due to all these contributions.  
Experimental results on activated carbon samples obtained at different conversions times in a heated quartz 
tubular reactor that shows the feasibility of the Porous Evolution Model predicting the specific surface area and 
pore distribution evolution throughout the activation process are also provided. 
 
 
 
The work presented in this paper has been funded by the Spanish Ministry of Science, Innovation, and 
Universities RETOS-INVESTIGACIÓN program (Project RTI2018‐095349‐A‐I00) co-financed by the European 
Union with ERDF and by the PROYECTOS ORIENTADOS A LA TRANSICIÓN ECOLÓGICA Y A LA 
TRANSICIÓN DIGITAL program (Project TED2021-131397B-I00) co-financed by the European Union 
NextGeneration recovery plan.  
  
References 
[1] J. Pallarés, A. González-Cencerrado, I. Arauzo, Production and characterization of activated carbon from 
barley straw by physical activation with carbon dioxide and steam, Biomass & Bioenergy 115 (2018) 64-73. 
[2] S.K. Bhatia, D.D. Perlmutter, A random pore model for fluid-solid reactions: I.  Isothermal, kinetic control, 
AIChE Journal 26 (1980) 379-386. 
[3] J.L. Su, D.D. Perlmutter, Evolution of pore volume distribution during gasification, AIChE Journal 30 (1984) 
967-973. 
Figure 1 – (left) Porous evolution model validation and (right) relative influence of pore formation and 
growth/coalescence mechanisms 


Not a member yet