Layer Forces Research Articles

Ce2Ir3Ga5 : A new locally noncentrosymmetric heavy fermion system

Recently, a new type of unconventional superconductivity with a field-induced transition between two different superconducting (SC) states was discovered in the heavy fermion system CeRh2As2. This unusual SC state was proposed to be based on specific symmetries of the underlying structure, i.e., a globally centrosymmetric layered structure, but where the Ce layers themselves lack inversion symmetry. This new type of SC state has attracted strong interest, prompting the search for further heavy fermion systems crystallizing in structures with appropriate symmetries. We report the discovery and the study of a new Ce-based heavy fermion system with a globally centrosymmetric structure but without inversion symmetry on the Ce-site, Ce2Ir3Ga5. A single crystal x-ray diffraction study revealed an orthorhombic U2Co3Si5 type structure. Resistivity, specific heat, and magnetization measurements indicate a moderate-heavy fermion behavior with a Kondo energy scale of the order of 40 K. Most experimental results suggest the absence of magnetic order, but a tiny anomaly in the specific heat opens the possibility for a very weak, itinerant type of ordering. Published by the American Physical Society 2024

Chromatic Acclimating Synechococcus Dominate in Mesoscale Eddies

AbstractMesoscale eddies are found almost everywhere in global ocean. They can last for weeks to months with scales up to over 100 km and play important roles in global biogeochemical cycles. In this study, we analyzed the phylogenetic and pigment type composition of Synechococcus in a cyclonic eddy (CE, cold eddy) and an anticyclonic eddy (ACE, warm eddy) located in western South China Sea in summer, 2018. Nutrients pumping enhanced Synechococcus abundance markedly in the upper euphotic layers of CE. High diversity of both phylogenetic clades and pigment types of Synechococcus were discovered in the sampling area, with clear composition difference between CE and ACE. The chromatic acclimating pigment type (PT) 3dA dominated in CE while PT 3dB dominated in ACE. The potential weak chromatic acclimator PT 3eA contributed a significant proportion in both CE and ACE. To better understand the difference of PT composition in CE and ACE, we further investigated the phylogenetic composition of Synechococcus in CE and ACE. Clade CRD 1, which were the main strains in upwelling regions, were dominant in CE, where cooler and nutrient rich subsurface water was pumped to the upper layers. Warm water adapted clade II and clade III dominated in ACE. Our study, for the first time, indicated that chromatic acclimation was important in shaping the vertical profile of Synechococcus community in mesoscale eddies of the subtropical oceans.

Ni/CeZr deposition on metallic mesh supports for CO2 methanation. Adherence and morphology

Structured supports suitable for highly demanding reactions in heat and mass transfer such as the Sabatier reaction were synthesised. The use of a metallic mesh as the support is promising. In this work, a treatment strategy for the metallic substrate and deposition of the support and the catalytic phase was proposed to obtain a thin, homogeneous, and crack-free layer that avoid the attack of the metallic substrate under the reaction conditions. The metallic surface of the meshes was thermally pre-treated under different conditions to generate roughness. A layer of Ce and Zr oxides was deposited from Nyacol® to generate the catalyst support that act, at the same time, as a barrier between the reaction atmosphere and the surface of the meshes. Subsequently, nickel was deposited as an active phase by impregnation. The elimination of the excess was studied by air blowing and centrifugation. The morphology, phase structure and adhesion of the layer were investigated by SEM, EDX and adherence test. The results showed that the load and the adhesion of the layer were affected by the mesh size and the conditions of the excess removal as well as the concentration of the slurry. The adhesion of the active phase was excellent under severe conditions.

Anomalies in the Dirac bands in the proximity of correlated electrons.

Dirac fermions, particles with zero rest mass, are observed in topological materials and are believed to play a key role in the exotic phenomena in fundamental science and the advancement of quantum technology. Most of the topological systems studied so far are weakly correlated systems and the study of their properties in the presence of electron correlation is an interesting emerging area of research, where the electron correlation is expected to enhance the effective mass of the particles. Here, we studied the properties of Dirac bands in a non-symmorphic layered Kondo lattice system, CeAgSb2, employing high-resolution angle-resolved photoemission spectroscopy and first-principles calculations. In addition to the Dirac cones due to non-symmorphic symmetry, this material hosts Dirac fermions in the squarenet layer in the proximity of a strongly correlated Ce layer exhibiting Kondo behavior. Experimental results reveal crossings of the highly dispersive linear bands at the Brillouin zone boundary due to non-symmorphic symmetry. In addition, there are anisotropic Dirac cones constituted by the squarenet Sb 5p states forming a diamond-shaped nodal line. These Dirac bands are linear in a wide energy range with an unusually high slope. Interestingly, near the local Ce 4f bands, these bands exhibit a change in the slope akin to the formation of a 'kink' observed in other materials due to electron-phonon coupling. The emergence of such exotic properties in proximity to strongly correlated electronic states has significant implications in the study of complex quantum materials including unconventional superconductors.

(Invited) Nanomembrane Coating for Advanced Electrocatalysis

Advanced electrocatalysis that possesses higher selectivity and durability is more and more important for the electrification of chemical processes, which is expected in the renewable energy society in the future. Electrochemical reactions are often determined by the competition between the thermodynamic redox potential and the applied potential. Because the redox potential is characteristic for determining the product, it is often difficult to adjust the selectivity just by surface chemistry. Against this background, surface modification of electrodes is a well-studied field. Surface modification improves membrane functionality and selectivity, resulting in electrocatalysts with higher productivity and selectivity. Surface protective layers are also associated with material durability, as they prevent toxic and harmful substances from approaching the surface and prevent dissolution of the electrode material into the electrolyte. We are investigating the use of "nanomembrane" coatings on electrodes to achieve better selectivity and durability.Electrochemical reduction deposition of ultrathin layers of Cr and Mo on Pt cathodes has been shown to yield O2-tolerant hydrogen-evolving electrodes in the appropriate pH range. Electrochemical measurements indicate that these surface layers act as a membrane film. Many bulky ions and O2 molecules cannot pass through these surface layers, but H2 molecules can, consistent with electrochemical and spectroscopic measurements. First, the electrochemical properties of Pt modified with other elements such as Cr and Mo were investigated and monitored for catalytic activity under different atmospheres. Next, in-operando X-ray absorption spectroscopy (XAS) was used to investigate the working state of the material: electrochemical measurements in H2 and O2 confirmed that the oxygen reduction reaction (ORR) was severely suppressed and the hydrogen evolution reaction (HER) was maintained. XAS results also showed that the oxidation state of Pt can be freely changed by a potential sweep with or without a coating layer. We extended this work to nanofilm coating on oxygen-evolving anodes for water splitting, and succeeded in anodic deposition of a thin Ce layer on Ni-Fe electrodes; the Ce layer not only prevents unwanted ions from reaching the electrode surfaces, but also prevents Fe ions from leaching from the electrodes, thus improving the durability of the electrodes. In this presentation, key findings of these nanomembrane coatings and future prospects for selective and durable electrodes will be discussed.

The Coating Effect on Interconnect Materials After >10 Years of Furnace Exposures

One of the key components in the SOFC stack is the interconnect which requires versatile material properties for a proper functioning, e.g., high temperature corrosion stability, low ASR degradation and low chromium evaporation. At the same time, a high production capacity needs to be reached in order to fulfil the supply demand required for GW levels. The high production capacity is realized through Alleima AB’s production line with coil-coil physical vapor deposition of coated interconnects for SOFC and SOEC applications [1].More specifically, Sanergy HT 441 is the standard material intended to be used as an SOC interconnect. The substrate is a ferritic stainless steel (ASTM 441) which is coated with thin layers of Ce and Co (<1 µm). The material can be coated on both sides using the same coating or with a different coating. At elevated temperatures the Co coating forms a protective (CoMn)3O4 spinel layer which drastically reduces Cr evaporation while the Ce layer improves the corrosion resistance by reducing the chromia scale growth at the coating/substrate interface and thereby maintaining a low and stable ASR over time.Since long-term stability is a critical property for interconnects, Alleima has over the years gathered data from furnace samples and can thus present results where some samples have been exposed at elevated temperatures during >10 years. The main results include the effect of Ce thickness or choice of substrate on mass gain and subsequent chromia growth. Selected samples with coating elements different than Co have also been investigated. Samples have been further investigated using scanning electron microscopy for cross-sections, x-ray diffraction for characterization of phases and residual stresses as well as glow discharge optical emission spectroscopy for elemental analysis.

Boosting oxygen activation in ceria-oxide via gallium addition

CeO2 is a well-suited support due to its higher oxygen storage capacity and reversible redox ability, which is associated with the oxygen activation. Herein we report the effective oxygen activation in CeO2 by gallium incorporation, varying the Ga/Ce molar ratios from 0.25 to 0.75. Structural results and operando spectroscopies under reaction conditions revealed that gallium incorporation improves the oxygen activation in CeO2, being more effective at low gallium content (Ga/Ce of 0.25). Atomic-scale computations demonstrated that the 0.25 Ga/Ce molar ratio generates Ga atomic-size channels that allow an easy way for oxygen diffusion from bulk to the surface. Ga incorporates into the subsurface Ce layer causing a collective effect: weakening the surface Ce-O bonds, boosting the surface oxygen activation, then enhancing the CO oxidation ability. Once this happens, it leaves behind O-vacancies, which may occupy either bulk oxygen from the CeO2 or further renovation of oxygen atoms from the environment.

Layer-resolved electronic behavior in a Kondo lattice system, CeAgAs2

We investigate the electronic structure of an antiferromagnetic Kondo lattice system CeAgAs2 employing hard x-ray photoemission spectroscopy. CeAgAs2, an orthorhombic variant of HfCuSi2 structure, exhibits antiferromagnetic ground state, Kondo like resistivity upturn and compensation of magnetic moments at low temperatures. The photoemission spectra obtained at different photon energies suggest termination of the cleaved surface at cis-trans-As layers. The depth-resolved data show significant surface-bulk differences in the As and Ce core level spectra. The As 2p bulk spectrum shows distinct two peaks corresponding to two different As layers. The peak at higher binding energy correspond to cis-trans-As layers and is weakly hybridized with the adjacent Ce layers. The As layers between Ce and Ag-layers possess close to trivalent configuration due to strong hybridization with the neighboring atoms and the corresponding feature appear at lower binding energy. Ce 3d core level spectra show multiple features reflecting strong Ce-As hybridization and strong correlation. Intense f 0 peak is observed in the surface spectrum while it is insignificant in the bulk. In addition, we observe a features at binding energy lower than the well-screened feature indicating the presence of additional interactions. This feature becomes more intense in the bulk spectra suggesting it to be a bulk property. Increase in temperature leads to a spectral weight transfer to higher binding energies in the core level spectra and a depletion of spectral intensity at the Fermi level as expected in a Kondo material. These results reveal interesting surface-bulk differences, complex interplay of intra- and inter-layer covalency, and electron correlation in the electronic structure of this novel Kondo lattice system.

Design and characteristics of a novel single-plane Compton gamma camera based on GAGG scintillators readout by SiPMs

We designed a novel, compact, single-plane Compton gamma camera based on GAGG:Ce scintillators read out by silicon photomultipliers. The Compton gamma camera comprises the scatterer and the absorber layers consisting of 8x8 arrays of 3 mm x 3 mm x 3 mm GAGG:Ce pixels. The individual pixels in the scatterer layer are optically coupled to the corresponding pixels in the absorber by the matching 3 mm x 3 mm x 20 mm plexiglass lightguides, and hence both the scatterer and the absorber pixel in one column are readout by the same SiPM. We present the first results of the measured characteristics of the detector. The average energy resolution at 662 keV of the front and the back GAGG:Ce layer is found to be 8.9% ± 1.9% and 10.8% ± 1.6%, respectively. The Compton events are reconstructed based on kinematic conditions and detector geometry and the first image of a 662 keV gamma source is reconstructed using a simple back projection algorithm.

A super-high brightness and excellent colour quality laser-driven white light source enables miniaturized endoscopy.

A laser-driven white light source promises intrinsic advantages for miniaturized endoscopic illumination. However, it remains a great challenge to simultaneously achieve high brightness and excellent colour rendition due to the shortage of highly efficient and thermally robust red-emitting laser phosphor converters. Here, we designed CaAlSiN3:Eu@Al (CASN@Al) converters with neglectable efficiency loss by tightly bonding all-inorganic phosphor films on an aluminium substrate. A layer-by-layer phosphor converter (LuAG/CASN@Al), i.e., stacking a green-emitting Lu3Al5O12:Ce (LuAG) layer on CASN@Al, was constructed to enhance light conversion efficiency and reduce reabsorption loss under blue laser excitation, which thus produces an excellent white light source with a luminous efficacy of 258 lm W-1 and a colour rendering index of 91. A miniaturized endoscopy with a coupling efficiency twice that of the commercial white LEDs was demonstrated by using the laser-driven white light and showed a central illuminance as high as 52 730 lx, more vivid images and long-term reliability.

Layered array Al2O3-LuAG: Ce composite ceramic phosphors for high-brightness display

Thermally robust and efficient composite ceramic phosphors (CCPs) combined both the merits of matrix and phosphor have received growing interests. However, high matrix content (e.g., Al2O3 >40 wt%) brings diluted activated ion concentration and dropped photoluminescence (PL) quantum yield (QY). Here, a novel layered array Al2O3-LuAG: Ce CCP, where Al2O3 and LuAG: Ce thin layers (10–250 µm) are alternately arranged, was presented. Owing to the special structure, thermal phonons and photons are respectively routed into Al2O3 layers and LuAG: Ce layers, which weakens the influence of Al2O3 and heat accumulation on PL properties. Consequently, it exhibits high PLQY (84.1%) and good thermal conductivity (17.1 W·m−1·K−1). When it is irradiated under high-power density (27.2 W·mm−2) blue laser, the luminous efficiency and lumen-density are promoted to 220 lm·W−1 and 5994 lm·mm−2, respectively. This work provides a promising new microstructure in developing novel phosphor converters for high-brightness laser phosphor display.

Spin-density-wave order controlled by uniaxial stress in CeAuSb2

The tetragonal heavy fermion compound CeAuSb$_2$ (space group $P4/nmm$) exhibits incommensurate spin density wave (SDW) order below $T_{N}\approx6.5~K$ with the propagation vector $\mathbf{q}_A = (\delta_A,\delta_A,1/2)$. The application uniaxial stress along the [010] direction induces a sudden change in the resistivity ratio $\rho_a/\rho_b$ at a compressive strain of $\epsilon \approx -0.5$\%. Here we use neutron scattering to show that the uniaxial stress induces a first-order transition to a SDW state with a different propagation vector $(0,\delta_B,1/2)$ with $\delta_B=0.25$. The magnetic structure of the new (B) phase consists of Ce layers with ordered moments alternating with layers with zero moment stacked along the $c$-axis. The ordered layers have an up-up-down-down configuration along the $b$-axis. This is an unusual situation in which the loss of spatial inversion is driven by itinerant magnetic order. We argue that the change in SDW wavevector leads to a concomitant Fermi surface reconstruction, similar to other materials where a SDW can be controlled by uniaxial stress or magnetic field such as Sr$_3$Ru$_2$O$_7$.

Magnetic properties of the layered heavy-fermion antiferromagnet CePdGa6

We report the magnetic properties of the layered heavy fermion antiferromagnet CePdGa$_{6}$, and their evolution upon tuning with the application of magnetic field and pressure. CePdGa$_{6}$ orders antiferromagnetically below $T\rm_{N}$ = 5.2 K, where there is evidence for heavy fermion behavior from an enhanced Sommerfeld coefficient. Our results are best explained by a magnetic ground state of ferromagnetically coupled layers of Ce $4f$-moments orientated along the $c$-axis, with antiferromagnetic coupling between layers. At low temperatures we observe two metamagnetic transitions for fields applied along the $c$-axis corresponding to spin-flip transitions, where the lower transition is to a different magnetic phase with a magnetization one-third of the saturated value. From our analysis of the magnetic susceptibility, we propose a CEF level scheme which accounts for the Ising anisotropy at low temperatures, and we find that the evolution of the magnetic ground state can be explained considering both antiferromagnetic exchange between nearest neighbor and next nearest neighbor layers, indicating the influence of long-range interactions. Meanwhile we find little change of $T\rm_{N}$ upon applying hydrostatic pressures up to 2.2 GPa, suggesting that significantly higher pressures are required to examine for possible quantum critical behaviors.

The Time for Industrialization Has Come: A Pre-Coated Solution for the GW Scale

Green Hydrogen has become present in all mass media thanks to their ubiquitous role to overcome the issues related to climate change. It is estimated that green hydrogen and their associated technologies (i.e. fuel cells and electrolysers) will represent 25 % of the total energy mix by 2050 if a 100 % renewable system is achieved. Among these technologies are Solid Oxide Cells (SOC). This technology has the capability to be the more efficient technologies among fuel cell and electrolyser’s technologies as well as the technology made from cheaper and more abundant materials. In addition to this, it has also the capability to function much more easily in reversible mode that their fuel cell and electrolyser siblings (AEM, PEM or even AEM) which give them a great versatile capacity.In order to make Green Hydrogen a reality and to succeed, an immense work in terms of industrialization needs to be done. In the following years, the industry needs to prove that is ready to deliver the systems in the large volumes that it is going to be demanded if we want to give response to our climate goals (i.e. GW per year). For instance, by 2030 it is estimated that 500 000 micro-CHP (combined heat and power) units will be installed only in the European Union which would require the production of at least as many fuel cell systems for such application. This large number, make a very rapid fuel cell industrialization necessary and a suitable value chain must thus be created.Sandvik Materials Technology (SMT) is a material provider for the more demanding industries and applications. During our more than 160 years of history, the company has delivered large volumes of materials in forms of tubes and strips, for instance. Solid Oxide Cell systems are constituted by many tubes and strips made of special stainless steel alloys in which SMT is specialized of. More recently, SMT has developed a coil-to-coil process to produce pre-coated strip for the fabrication of bipolar plates and interconnects in both PEM fuel cells and electrolysers but as well for SOC. The pre-coated concept allows the industry to have a cost-effective process ready for the rapid ramp-up of both fuel cell and electrolysis technologies.Regarding SOC, Sanergy HT 441 is designed to be used as interconnect material. The product is made at industrial scale by Physical Vapor Deposition in the above-mentioned roll-to-roll coating method. It is based on an ASTM 441 steel grade double coated with thin layers of Ce and Co (< 1 µm). The material can be double side coated with the same coating or with a different coating in the other side. This material has shown to form a protective (Co,Mn)3O4 spinel layer that improves corrosion resistance and heavily reduces Cr evaporation. Recent studies has shown that Cr evaporation is reduces up to 10 times thanks to the Ce and Co coating. On the other hand, very recently it has been put on the table challenges with use of Co due to both societal and economical conflicts. At Surface Research in SMT, different Co-free coated materials has been developed in order to offer a different solution to this. Therefore, this work will show the solutions that SMT put in the market to industrialize fuel cells and electrolysis, and concretely SOCs.

Large and Versatile Plasmonic Enhancement of Photoluminescence Using Colloidal Metallic Nanocubes

Improving phosphor photoluminescence efficiency is a key parameter to boost the performances of many optical devices. In this work, colloidal silver nanocubes, homogeneously spread on a luminescent surface, have proved to help both injecting and extracting light in and out of the photoluminescent layer and hence contributed significantly to the enhancement of the fluorescence. This approach has been applied to two materials: the well-known Y$_3$Al$_5$O$_{12}$:Ce yellow phosphor and an optical quartz. The emission efficiency, for sol-gel derived YAG:Ce layers, has increased of 80\% in the presence of an optimal nanoparticle density -- whereas for quartz, a weakly fluorescent material, the photoluminescence signal can be enhanced by a 200-fold factor. A physical analysis based on simulations shows that the disorder is an important factor and that the surface density of Ag nanoparticles is a crucial parameter.

EFFICIENCY OF GETTERING STRUCTURAL DEFECTS BY A BLACK SILICON LAYER

The possibility of gettering structural defects of silicon substrates with a near-surfa¬ce layer of black silicon (b-Si) is considered. The gettering efficiency was estimated according to the results of studying the resistivity, defect density, and effective minority carrier lifetime on test and control substrates. It is shown that in the thermal oxidation process, the b-Si layer serves as an effective drain for excess interstitial atoms and metallic impurities, thereby significantly reducing the density of nuclei of structural defects in silicon. As a result, the resistivity of the substrates decreases, and the carrier lifetime increases. It is advisable to form a b-Si layer as a getter on the rear non-working side of the substrates.

Cu, Sm co-doping effect on the CO oxidation activity of CeO2. A combined experimental and density functional study

The co-doping effect of a rare earth (RE) metal and a transition metal (TM) on ceria oxidation catalysis through the evaluation of samarium-copper co-doped catalysts with Ce-Sm-xCu-O (x: 0–20 at.%, Ce/Sm = 1) nominal compositions, is discussed. The CO oxidation reaction was used as a prototype reaction due to its pivotal role in the fuel cell technology. Ce-Sm-20Cu-O catalyst presented a 64% increase in the CO oxidation activity compared to that of pristine ceria. Diffraction and Raman studies proved that the Cu, Sm co-doping induces many defects related to the dopants (Sm, Cu) and the oxygen vacant sites, while the presence of hybrid CuO/Ce-Sm(Cu)-O fluorite/SmO8 (cubic metastable) phases is the most representative scenario of this oxide microstructure. A size polydispersity of CuO phases was achieved by introducing air cooling during the microwave heating. Cu, Sm atoms were uniformly doped in CeO2 structure according to the HAADF-STEM studies. These results are in agreement with EDS analysis, where Cu, Sm and Ce are located in all the analyzed areas without any preferential distribution. The XPS studies demonstrated the co-presence of Cu2+/Cu1+ and Ce4+/Ce3+ redox couples in agreement with the Bader charge analysis from the ab initio calculations, the latter influencing greatly the oxidation activity of the catalysts. Density functional theory (DFT) calculations shed light on the oxide surface and the underlying mechanism governing the oxidation catalysis taking place. In particular, Cu2+ and Sm3+ dopants were found to be located in the nearest neighbor (NN) sites of oxygen vacancies. Different oxygen vacancies configurations were studied (single vs. double, surface vs. subsurface), where the single vacancies are more stable on the surface, whereas the double vacancies configurations are more stable on the subsurface. Regarding the Ce3+ location, in the presence of single and double oxygen vacancy, the Ce3+ ions prefer to be located in the 1st NN/2nd NN and 2nd NN of the first Ce layer, relative to the oxygen vacancy, respectively. The total Density of States (DOS) analysis of the co-doped systems revealed that the dopants induced new surface states inside the ceria band gap, which can accommodate the unpaired electrons of the vacant oxygen sites. These electronic modifications justify the much lower energy of oxygen vacancy formation (Evf) in both cases, the Sm-doped, and Cu, Sm -doped CeO2 (1 1 1) geometries. Specifically, the Evf lowering upon doping was found to be almost two times larger for the Cu adjacent oxygen vacancies (Cu2+-□) compared to the Sm ones (Sm3+-□), consistent with the CO adsorption trend as the Cu-Sm-CeO2 (1 1 1) system is energetically more favorable than the Sm-CeO2 (1 1 1) and pure CeO2 (1 1 1) surfaces.

Inspection the corrosion prevention performance and dry/wet interfacial adhesion qualities of the melamine-cured polyester coating applied on the treated mild steel surface with a nanostructured composite cerium-neodymium film

The aim of this study is to investigate the influence of a cerium-neodymium (Ce-Nd) conversion coating on the corrosion protection performance and surface characteristics of a polyester/melamine coating (PMC) applied on the mild steel (MS) surface. The energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM) methods were exploited to examine the surface morphology and roughness of the deposited layers. Also, an X-ray photoelectron spectroscopy (XPS) analysis was carried out for the characterization of the deposited Ce-Nd film chemical composition. The influence of MS surface chemical treatment via Ce-Nd film on the PMC corrosion protection activity was surveyed through accelerated salt spray (SS) and electrochemical impedance spectroscopy (EIS) tests. The impact of Ce, Nd, and Ce-Nd conversion coatings on the adhesion properties of PMC was studied by the pull-off (PO) test in dry and wet conditions. Through the steel surface decoration with Ce-Nd oxide film the highest improvement in the work of adhesion (about 47.5 %) and surface free energy (about 42.7 %), compared to the untreated sample, were obtained. The results of the cathodic delamination (CD) test revealed a 69 % improvement of the PMC resistance against disbondment by employing the Ce-Nd conversion coating. Pull-off test results evidenced that the steel substrate modified by Ce-Nd film resulted in the maximum improvement (about 57 %) in dry adhesion strength and the lowest adhesion loss of about 20 % compared to the bare (untreated) sample. FE-SEM and AFM observations showed the uniform growth of the Ce and Nd layers and Ce-Nd complexes (with particle sizes almost less than 100 nm) on the substrate, coincidentally. EIS results evidenced 67 %, 43 %, and 77 % improvement in total resistance (Rt) of the epoxy coating with artificial defect on the steel surface with Ce, Nd and Ce-Nd treatments, respectively, confirming that the redox reactions have been limited in the Ce-Nd/PMC interface more than each of Ce and Nd treatments.It should be noted that the Ce-Nd is a novel non-toxic and environmentally friendly chemical treatment method for replacement of the conventional metals' surface pretreatment methods like phosphating and chromating with numerous advantages like excellent corrosion resistance as well as good adhesion to the metal surface and subsequent organic film. One major practical application of the developed coating can be in the automotive and gas/oil industries for the car body and pipe surface chemical treatment prior to the application of the organic coating.

Single and double bed stacked wire mesh cartridges for the catalytic treatment of diesel exhausts

Stacked stainless steel wire mesh monoliths were developed as supports for Pt/Co,Ce catalysts for diesel exhaust treatment. After the calcination of the metal structures at 900 °C, a Co,Ce layer was deposited over the meshes by means of an equimolar suspension of Co3O4 and CeO2 nanoparticles, followed by the incorporation of 1 wt.% Pt. Also, a double bed catalyst configuration was studied: a Pt,CeO2 pre-filter diesel catalyst oxidation (DOC) was developed to efficiently oxidize NO to NO2 which helps in regenerating the accumulated soot within the Co,Ce catalyzed diesel particulate filter (DPF). The catalytic monoliths, both as single and double bed configurations, were evaluated for the simultaneous combustion of volatile organic compounds (ethyl acetate, n-hexane or toluene) and soot. Co,Ce and Pt/Co,Ce structures presented similar catalytic activities, with a maximum soot combustion rate at 420 °C, whereas this value decreased to 400 °C for the double bed catalyst. Catalytic experiments with or without gaseous O2 or NO in the feed were carried out to ascertain the role of the catalytic components. The structured and powder catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), energy dispersive X-ray spectroscopy (EDX) and Laser Raman spectroscopy. The catalyst coating adherence was confirmed by ultrasound tests and the pressure drop of the catalytic structures was measured.

Influence of cerium content and heat treatment on Ce:YAG@glass wool nanostructures

The paper reports the influence of cerium content and heat treatment on composition, structural features and optical properties of nanostructures constituted by a layer of Ce:YAG nanoparticles on glass wool (Ce:YAG@GW). The Ce:YAG@GW nanostructures were obtained embedding the glass wool (GW) in a gel-like precursor and calcining at 800 and 900 °C. Gel-like precursor of urea glass route (UGR) method has been used to prepare both nanostructures and Ce:YAG nanoparticles prepared as references. Structural properties were investigated by using X-ray diffraction (XRD) and infrared spectroscopy (IR). Results showed that the composition of the final products strongly depends both on the cerium content and temperature. Optical properties of best materials have been investigated in order to verify their suitability for lighting applications. Obtained results show relatively high quantum efficiency for Ce:YAG@GW treated at 800 °C comparing with the Ce:YAG nanoparticles obtained at the same temperature confirming the improved luminescence properties of the nanoparticles when they are applied on GW surface.