Romain Lucas’s research while affiliated with University of Limoges and other places

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Publications (70)


Characterisation of energy-dissipating mechanisms by Acoustic Emission technique during mechanical loading of Ti2AlC and Ti3AlC2 MAX phases: Influence of phase composition and porosity
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June 2023

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20 Reads

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2 Citations

Open Ceramics

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Romain Lucas

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Cover Image, Volume 139, Issue 38
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  • Full-text available

October 2022

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70 Reads

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Charlotte Vernisse

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This cover image by Vincent Sol and co‐authors shows the development of novel bio‐based hydrogels which are attractive materials for many biomedical purposes, such as drug delivery or wound healing. A light‐triggered antibacterial activity can be conferred to hydrogels after their conjugation to appropriate photosensitizers on xylan. The study of the morphology and rheology of the hydrogels showed that the materials obtained present interconnected porous structures and good mechanical integrities, as well as high swelling ratios. Photo‐bactericidal activity of these hydrogels have been showed under white light irradiation against Staphylococcus aureus and Pseudomonas aeruginosa. DOI: 10.1002/app.52744

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Photosensitizer-hyaluronic acid complexes for antimicrobial photodynamic therapy (aPDT)

June 2022

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88 Reads

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4 Citations

Journal of Porphyrins and Phthalocyanines

The number of drug-resistant bacteria is increasing significantly. To combat such issues, antimicrobial PDT (aPDT) provides an efficient way to eliminate these species efficiently, cost-effectively, and more importantly, without the associated mechanism of resistance. The hemisynthesis and synthesis of photosensitizers such as polyaminated chlorin-p6and 5-(4-aminophenyl)-10,15,20-tris(4-N-methylpyridinium)porphyrin triiodide and their water stable and solubleformulation with hyaluronic acid bio-polymer (PS-HA) is reported. Structures of porphyrin-HA formulations were characterized by IR, DSC, DLS, zeta potential, SEM imaging, UV-vis analysis and rheological evaluation confirming the covalent conjugation of PSs on conjugateplatform (hyaluronic acid). These conjugateformulations were tested against the Gram-negative Escherichia coli (CIP 53.126) and Gram-positive Staphylococcus aureus(CIP 76.25) bacteria for their potency for aPDT.


FT‐IR spectra of xylan (a) before and (b) after porphyrin grafting 4 (Xyl‐P6) [Color figure can be viewed at wileyonlinelibrary.com]
¹H NMR spectrum of modified xylan in DMSO‐d6 (Xyl‐P6, DS = 0.037) [Color figure can be viewed at wileyonlinelibrary.com]
FT‐IR spectra of (a) native xylan, (b) Xyl‐P5 and (c) hydrogel formed from Xyl‐P5 [Color figure can be viewed at wileyonlinelibrary.com]
SEM images of cross sections of freeze‐dried HG‐xyl‐P hydrogels: (a) HG‐xyl‐P1, (b) HG‐xyl‐P2, (c) HG‐xyl‐P3, (d) HG‐xyl‐P4, (e) HG‐xyl‐P5 and (f) HG‐xyl (control hydrogel without porphyrin)
Swelling ratios of HG‐xyl‐P1, HG‐xyl‐P2, HG‐xyl‐P3, HG‐xyl‐P4, HG‐xyl‐P5 and HG‐xyl as a function of time [Color figure can be viewed at wileyonlinelibrary.com]

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Cationic porphyrin–xylan conjugate hydrogels for photodynamic antimicrobial chemotherapy

June 2022

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64 Reads

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5 Citations

Bio‐based hydrogels are attractive materials for many biomedical purposes such as drug delivery or wound healing. A light‐triggered antibacterial activity can be conferred to hydrogels after their conjugation to appropriate photosensitizers (PS). In this study, we have synthesized and characterized hydrogels consisting of cationic porphyrin–xylan conjugates. A cationic porphyrin was covalently attached to xylan by an esterification reaction. Different porphyrin‐xylan derivatives were obtained with degrees of substitution ranging from 0.003 to 0.053. Then, the derivatives were cross‐linked after reaction with diethylenetriaminepentaacetic (DTPA) dianhydride to obtain the corresponding hydrogels. The study of the morphology and rheology of the hydrogels showed that the materials obtained present interconnected porous structures, good mechanical integrities as well as high swelling ratios. Antimicrobial activity of cationic porphyrin–xylan conjugate hydrogels was tested under white light irradiation against Staphylococcus aureus and Pseudomonas aeruginosa. All of the tested hydrogels showed photo‐bactericidal activity against the two tested strains.


Figure 9. Comparison of the PDOS of each atom at the interface and the corresponding surface slab for the Zr|OO|Zr|OO-ZrC(111) top site interface model. The upper part of the spectra of each plot are for atoms in the interface structure and those at the lower part are for the atoms in the corresponding surface slabs. Atoms labeled as near are closer to the interface plane than atoms labeled as far.
Surface mismatch parameter Υ calculated for different combinations of ZrC and c-ZrO 2 surface.
Rigid, W rigid ad and relaxed, W relaxed ad work of adhesion for different interface models using different numbers of c-ZrO 2 (111) layers at both fcc and on-top adhesion sites at the interface region.
Charge transfer analysis of the interfacial structure between ZrC(111) surface and different numbers of layers of c-ZrO 2 (111) in the Zr|OO|Zr|OO-ZrC(111) top site interface model. Values reported are net charges (electrons/atom) obtained with respect to the charges on the atom in the corresponding surface slabs that form the interface.
Characterizing the ZrC(111)/c-ZrO2(111) Hetero-Ceramic Interface: First Principles DFT and Atomistic Thermodynamic Modeling

May 2022

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94 Reads

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1 Citation

Molecules

The mechanical and physical properties of zirconium carbide (ZrC) are limited to its ability to deteriorate in oxidizing environments. Low refractory oxides are typically formed as layers on ZrC surfaces when exposed to the slightest concentrations of oxygen. However, this carbide has a wide range of applications in nuclear reactor lines and nozzle flaps in the aerospace industry, just to name a few. To develop mechanically strong and oxygen-resistant ZrC materials, the need for studying and characterizing the oxidized layers, with emphasis on the interfacial structure between ZrC and the oxidized phases, cannot be understated. In this paper, the ZrC(111)//c-ZrO2 (111) interface was studied by both finite temperature molecular dynamic simulation and DFT. The interfacial mechanical properties were characterized by the work of adhesion which revealed a Zr|OO|Zr|OO//ZrC(111) interface model as the most stable with an oxygen layer from ZrO2 being deposited on the ZrC(111) surface. Further structural analysis at the interface showed a crack in the first ZrO2 layer at the interfacial region. Investigations of the electronic structure using the density of state calculations and Bader charge analysis revealed the interfacial properties as local effects with no significant impacts in the bulk regions of the interface slab.


Structure and energetics of ZrC(100)||c-ZrO2(001) interface: A combination of experiments, finite temperature molecular dynamics, periodic DFT and atomistic thermodynamic modeling

April 2022

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48 Reads

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4 Citations

Ceramics International

The oxidation process of ZrC is very important as it affects its initial excellent mechanical and physical properties. ZrC is an ultra-high temperature ceramic, but forms low refractory oxides at lower temperatures of 500–600 °C. To develop core/shell materials by coating the ZrC surface with another material that forms protective layers on ZrC and prevents it from oxidation (such as SiC), there is the need to study and characterize the oxidized layer surrounding ZrC particles. XPS, ToF-SIMS, TEM-ED and EDX analyses were used to study the covering oxidized layer, and polycrystalline ZrO2(mainly cubic phase) was identified. Some traces of the tetragonal phase are observed to be present as shells around the ZrC particles with a thickness of about 4 nm on the average. Periodic DFT was subsequently used to characterize the interface formed between ZrC(100) and c-ZrO2(001) phases. A strong interface was noticed mainly with charge transfer from Zr (c-ZrO2 side) at the interface to O and C (ZrC side) atoms at the interface. The interfacial properties are local to only the first and second layers of ZrO2, and not on the third and fourth layers of ZrO2, as Bader charge analysis revealed substantial charge transfer at the interface region with no charge redistribution in the second ZrO2 layer and subsequent bulk layers. The main physical quantity, ideal work of adhesion (Wad), used to characterize the interface, remains quite constant for all ZrO2 layers, and converges at three layers of ZrO2. The interfacial bonds formed are observed to be stronger than the free surfaces in the corresponding ZrC and c-ZrO2 used to generate the interface.


Electric Current‐Assisted Synthesis of the Ti2AlC MAX Carbide Phase by Arc Melting and Heat Treatment Using Spark Plasma Sintering

Herein, two current‐assisted techniques, arc melting and spark plasma sintering (SPS), are investigated for the synthesis of the Ti2AlC carbide MAX phase. Synthesis parameters are adjusted to improve the composition of the samples and limit the proportion of secondary phases. A 3 min heating at low power (15% of the maximum current of 180 A) on the arc melting furnace leads to a sample containing more than 71 wt% of Ti2AlC. The impact of parameters such as time, power, and generator amperage is considered. By SPS, a two‐step cycle is used to ensure the formation of the titanium aluminide compounds before reaching higher temperatures. A first dwell at 600 °C for 15 min and a second dwell at 1200 °C for 10 min, under a load of 75 MPa, leads to a sample containing more than 85 wt% of Ti2AlC. Without pressure, a single‐phase Ti2AlC sample is obtained. It is found that the application of a load is not beneficial to the formation of Ti2AlC but shifts the composition toward the formation of Ti3AlC2. The composition of this sample is further investigated by energy‐dispersive X‐ray spectroscopy (EDXS) and wavelength‐dispersive X‐ray fluorescence (WDXRF) to check the presence of impurities.


Grafting of Organic Molecular Precursors onto ZrC(100)//t-ZrO2(001) surfaces: when Experimental and Theoretical Studies meet

October 2021

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36 Reads

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7 Citations

Applied Surface Science

To control ZrC oxidation, one method is to coat the surface with SiC. This project therefore aims at grafting polymeric precursors on functionalized ZrC surfaces en-route to synthesizing ZrC/SiC core/shell composites. The exposed surface on the zirconia side of t-ZrO2(001) (tetragonal ZrO2) on top of a ZrC(100) substrate is first modified in presence of water. Water preferentially adsorbs molecularly and a subsequent functionalization with allylchlorodimethylsilane (ACDMS) in a SN reaction, appeared quite weak. However, the subsequent grafting of a repetitive unit of the polymeric precursor, built from diphenylsilane and 1,4-diethynylbenzene monomers through a hydrosilylation reaction, is a highly favorable and exothermic reaction. As the main problem occurs during the nucleophilic substitution reaction between ACDMS and hydroxyl groups on the surface, two bifunctional organic molecules, 3-butenoic acid as well as glycolic acid, were also exploited. 3-butenoic acid adsorbed strongly to the Zr atoms of the surface, through chelating effects of the carboxylic acid group. The subsequent hydrosilylation reaction with a repetitive unit of the preceramic precursor was also a favorable exothermic reaction, indicating a promising approach for the grafting of organic macromolecules. In parallel, to associate experimental results, methyldiphenylsilane was grafted onto functionalized ZrC using 3-butenoic acid.


Polymer-Derived Ultra-High Temperature Ceramics (UHTCs) and Related Materials

October 2021

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133 Reads

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15 Citations

Ultra-high temperature ceramics (UHTCs) represent an emerging class of materials capable of providing mechanical stability and heat dissipation upon operation in extreme environments, e.g. extreme heat fluxes, chemically reactive plasma conditions. In the last decades, remarkable research efforts and progress were done concerning the physical properties of UHTCs as well as their processing. Moreover, there are vivid research activities related to developing synthetic access pathways to UHTCs and related materials with high purity, tunable composition, nano-scaled morphology or improved sinterability. Among them, synthesis methods considering preceramic polymers as suitable precursors to UHTCs have received increased attention in the last years. As these synthesis techniques allow the processing of UHTCs from the liquid phase, they are highly interesting e.g. for the fabrication of ultra-high temperature ceramic composites (UHT CMCs), additive manufacturing of UHTCs, etc. In the present Chapter, UHTCs are in particular discussed within the context of their physical properties as well as energetics. Moreover, various synthesis methods using preceramic polymers to access UHTCs and related materials (i.e., (nano)composites thereof with silica former phases) are summarized and critically evaluated.



Citations (46)


... The FTIR spectra of HA, HaMA and crosslinked HaMA are shown in Figure 4B. A new peak at 1,731 cm −1 was observed in HaMA when compared to the HA related with the methacrylation and C=C bond peak was also increased at 1,643 cm -1 [39]. Then upon crosslinking reaction the peaks decreased showing that methacrylate groups went into reaction. ...

Reference:

Fabrication and characterization of pHEMA hydrogel conduit containing GelMA-HaMA IPN for peripheral nerve regeneration
Photosensitizer-hyaluronic acid complexes for antimicrobial photodynamic therapy (aPDT)
  • Citing Article
  • June 2022

Journal of Porphyrins and Phthalocyanines

... The 1 HNMR spectral data of P 3 A conforms to the published values. 41,45,51 For P 3 Am, c-P 2 Am 2 and PAm 3 , the 1 HNMR spectral plots ( Figure S8-S10) and tabulated spectral data (Table S1) agree with the published values 42,43 and con rm the identity of the compounds. The HRMS (ESI) data of the acetamidophenyl and aminophenyl porphyrins further indicate their purity; the mass error in each case was less than 5 ppm ( Figure S20-S25). ...

Cationic porphyrin–xylan conjugate hydrogels for photodynamic antimicrobial chemotherapy

... TiC is a good electrical conductor, with a conductivity of 1.47 × 104 S/cm. This makes it a desirable choice for applications where electrical conductivity is important [10][11][12][13][14][15][16][17][18][19]. The production of ZrC-TiC composite is important for the combination of these superior properties. ...

Characterizing the ZrC(111)/c-ZrO2(111) Hetero-Ceramic Interface: First Principles DFT and Atomistic Thermodynamic Modeling

Molecules

... [1][2][3] ZrC is usually used as a high-temperature structural material to make wearresistant and corrosion-resistant crucibles and cutting tools, ablation-resistant coatings, etc. 4-7 However, ZrC will be detectable oxidized in the air above 500 • C and form ZrO 2 . 8,9 Compared with ZrC, the hardness of ZrO 2 is much lower, while the coefficient of thermal expansion (CTE) is significantly larger. 10,11 As a result, the oxidation induced loose ZrO 2 layer is prone to damage under external force, and thus exacerbates the continued oxidation of ZrC. ...

Structure and energetics of ZrC(100)||c-ZrO2(001) interface: A combination of experiments, finite temperature molecular dynamics, periodic DFT and atomistic thermodynamic modeling
  • Citing Article
  • April 2022

Ceramics International

... As already described in previous papers [23][24][25] and according to TEM-ED experiments, the presence of a different phase from ZrC bulk was noticed at the surface of the particles. An EDX analysis revealed this phase to be zirconium oxide with an estimated thickness of 5 nm. ...

Grafting of Organic Molecular Precursors onto ZrC(100)//t-ZrO2(001) surfaces: when Experimental and Theoretical Studies meet
  • Citing Article
  • October 2021

Applied Surface Science

... Extracts were analyzed by HPLC-UV-DAD (1200 HPLC-UV-DAD series; Agilent Technologies, Santa Clara, CA, USA ) using an Eclipse XDB-C8 reverse phase column (4.6 mm × 150 mm, 3.5 µm particle size; Agilent Technologies) and an XDB-C8 guard column (4.6 mm × 12.5 mm, 5 µm particle size; Agilent Technologies) following the SCOR/UNESCO reference method described by Van Heukelem and Thomas (2001) [10] with slight modifications since the version described in Serive et al. (2017) [11]. Elution gradient consisted of a 30 min gradient from 95% to 5% of solvent A (70:30 methanol, 28 mM aqueous ammonium acetate), solvent B being 100% methanol. ...

Xylan-Based Cross-Linked Hydrogel for Photodynamic Antimicrobial Chemotherapy
  • Citing Article
  • September 2021

ACS Applied Bio Materials

... In this case, the metal particles are present in elemental form within the ceramic matrix after pyrolysis. It was further shown that base metals such as Fe, Co, Ni, Ti, Hf, Mo, W, and Zr could also be incorporated [5,10,[21][22][23][24][25][26]. Different phase compositions can be obtained depending on the metal's tendency to form carbides or silicides. ...

Formation of ZrC–SiC Composites from the Molecular Scale through the Synthesis of Multielement Polymers

Materials

... Among the ceramic precursors, polycarbosilanes are commonly used for their ability to generate SiC-based ceramics with a wide range of applications in the additive manufacturing eld, [5][6][7] shaping of the membrane, 8,9 and for bulk material production. [10][11][12] Among all the silicon-based preceramic polymers, allylhydridopolycarbosilane (AHPCS), also known as SMP-10 (StarPCS SMP-10, Starre Systems, USA), has attracted growing interest from the scientic community, with nearly 300 references in publications since 2015. This polymer is of great interest because its Si/C ratio is close to one, leading to a nearly stoichiometric SiC ceramic aer pyrolysis with a low amount of residual carbon. ...

Preparation of ZrC/SiC composites by using polymer-derived ceramics and spark plasma sintering
  • Citing Article
  • May 2020

Journal of the European Ceramic Society

... However, these UHTCs have disadvantages, such as poor fracture toughness and thermal shock resistance [69]. Additionally, difficulties emerge in processing these UHTCs due to their high hardness [245]. Numerous studies are reported on synthesizing powders, nanowires, and bulk materials of transition-metal carbide ceramics [246][247][248][249][250][251], few are on transition-metal carbide ceramic fibers and their application [252]. ...

Polymer‐Derived Ultra‐High Temperature Ceramics (UHTCs) and Related Materials
  • Citing Article
  • May 2019