Thin Ceramic Layers Research Articles

Fine grained textured BaTiO3-based piezoelectric ceramics with outstanding strain properties for the lead-free multilayer actuator

Textured BaTiO3-based piezoelectric ceramics show the excellent application potential as their piezoelectric characteristics almost approach the commercial lead-based ceramics. Piezoelectric multilayer actuators (MLAs) with low driving voltages and compact structures are great in line with the equipment trend of miniaturization and functional integration. However, the coarse textured grains result in few grain layers in each thin ceramic layer of MLAs, hardly guaranteeing the electromechanical dependability. In this work, we combined the composition regulation with a modified template grain growth (TGG) to prepare fine-grained textured ceramics. The Zr4+ and Sn4+ co-substituted (Ba0.95Ca0.05)(Ti0.94Zr0.05Sn0.01)O3 (BCZTS) was chosen as the matrix composition. Unreacted BaCO3 (BC, 7.3 % in content) was artificially introduced into matrix to realize the partial reaction template grain growth (RTGG), reducing textured grains from 9.7 μm to 6.9 μm. Textured BCTZS-BC MLAs achieved high texture degree of 92 % and further smaller grain size of 3.4 μm at 1300 °C, due to inhibition on mass transfer and improvement on thermal conductivity of Pt electrodes. The high strain of 0.12 % in textured MLAs is almost 2.3 times enhancement compared to non-textured counterparts, and the ultralow strain hysteresis Hs of 5.6 % at 30 kV/cm is equivalent to that in PZT MLAs. The microscopic coercive voltage is 3.1 V with a maximum displacement of 210 p.m., which is mainly ascribed to the smaller domain sizes and the favorable “4O” domain configuration in textured MLAs.

Resistance of ceramic / metal Functionally Graded Materials in the flame of a combustion chamber under harsh thermal and environmental conditions

Ceramic/metal Functionally Graded Materials (FGM) are efficient systems to increase the performance of materials used in thrusters, which operate under harsh thermal and environmental conditions. In this context, an experimental study has been carried out to firstly develop the FGM using atmospheric plasma spraying process and secondly investigate the resistance of the materials in the flame of a combustion chamber under oxidising atmosphere. Several configurations of FGM have been tested, in order to analyse the influence of the different layer thickness and composition, on their resistance. The link between the different FGM configurations and their endurance in the combustion flame has been established. The best performance was demonstrated with a thin ceramic layer of rich yttria stabilised hafnia deposited on the top surface. All the configurations showed an excellent resistance with limited degradation signs.

Encapsulation of Nanoparticle Organic Hybrid Materials within Electrospun Hydrophobic Polymer/Ceramic Fibers for Enhanced CO2 Capture

AbstractLiquid‐like nanoparticle organic hybrid materials (NOHMs) consisting of a silica core with ionically grafted branched polyethyleneimine chains (referred to as NIPEI) are encapsulated within submicron‐scale polyacrylonitrile (PAN)/polymer‐derived‐ceramic electrospun fibers. The addition of a room‐temperature curable, liquid‐phase organopolysilazane (OPSZ) ceramic precursor to the PAN/NOHM solution enhances the internal dispersion of NOHMs and forms a thin ceramic sheath layer on the fiber exterior, shielding the hydrophilic NIPEI to produce near‐superhydrophobic non‐woven fiber mats with contact angles exceeding 140°. 60:40 loadings of NOHMs to PAN/OPSZ can be reliably achieved with low OPSZ percentages required, and up to 4:1 NOHM:polymer loadings are possible before losing hydrophobicity. These fibers demonstrate up to ≈2 mmol CO2 g−1 fiber capture capacities in a pure CO2 atmosphere through the nonwoven fibrous networks and the permeability of the OPSZ shell. The hybrid fibers additionally show enhanced capture kinetics under pure CO2 and 400 ppm CO2 conditions, indicating their promising application as a direct air capture platform.

Resonance, Rayleigh flows, and thermal choking: Compressible coolant states in porous electromagnetic heat exchangers

Electromagnetic (EM) heat exchangers (HX) are systems that convert EM energy into heat or mechanical work. One potential design consists of a porous lossy ceramic material heated by EM waves with a compressible gas coolant. EM heating of ceramics is nonlinear, since the loss factor is temperature dependent. Designing such EM HXs requires an understanding of coupling between temperature, the electric field, and gas dynamics at the pore scale. To mimic this microscale phenomenon, a single channel with a high-speed gas coolant in perfect thermal contact with a thin solid ceramic layer is considered, with an applied plane-wave electric field propagating normal to the channel walls. From a thin-domain asymptotic analysis, the conservation laws reduce to a Rayleigh flow in the gas coupled with averaged thermal energy conservation equations at leading order. The model predicts that the kinetic energy of the gas increases up to 12.5 times the inlet value when thermal runaway occurs in the ceramic region for the cases considered, and thermal choking is possible when the coolant reaches the sonic state. Local maxima of efficiency occur on a discrete set of ceramic thicknesses that correspond to Fabry–Bragg resonances of the electric field.

Direct utilization of gaseous fuels in metal supported solid oxide fuel cells

Direct utilization and internal reforming of gaseous fuels is investigated on symmetric-architecture metal supported solid oxide fuel cells (MS-SOFCs) with thin ceramic electrolyte and scaffold backbone layers, and low cost ferritic stainless steel supports on both sides. Infiltrated Pr-oxide and Ni/samarium-doped ceria catalysts are added to the cathode and anode electrodes, respectively. Initial performance and durability is evaluated for MS-SOFCs operating with natural gas, propane, ammonia, and dimethyl ether at 700 °C. Cells for natural gas and propane utilize a novel high entropy alloy (HEA) catalyst for internal reforming with performance and degradation rates similar to H2 (0.5 W cm−2 and ∼12%/100 h). Initial testing with sulfur shows reversible degradation for levels found in natural gas and irreversible degradation for higher levels found in commercial propane. Overall, MS-SOFCs show successful fuel flexibility.

Analysis of water jet cutting of metal-ceramic elements made through atmospheric plasma spraying technique

Ceramic layers like alumina or zirconia present many industrial applications in many different domains. Ceramic thin layers were obtained through atmospheric plasma spraying (APS) using a robotized arm. Combinations of 25-–75, 50–50 and 75–25 % between Al2O3 and ZrO2 ceramic powders were made in order to obtain the ceramic layers. Structural (optical - OM, scanning electron – SEM and atomic force microscopy - AFM) characterizations of the thin ceramic layers were made before and after the operation of water jet cutting (Waterjet Cutting Machine (TK-TRUMP50-G3020)). By water jet cutting we follow to determine the behavior of the ceramic layer – metallic substrate system at these materials under pressure and water. The process was performed with a high cutting speed and a clean cut however taking in the account the porous nature of the ceramic layers made through APS the water jet and water bed affect the substrate and corrosion occur on the experimental samples.

Improvements of Arboblend V2 Nature Characteristics through Depositing Thin Ceramic Layers.

The paper aims to investigate the behavior of Arboblend V2 Nature biopolymer samples covered with three ceramic powders, Amdry 6420 (Cr2O3), Metco 143 (ZrO2 18TiO2 10Y2O3) and Metco 136F (Cr2O3-xSiO2-yTiO2). The coated samples were obtained by injection molding, and the micropowder deposition was achieved by using the Atmospheric Plasma Spray (APS) method, with varied thickness layers. The present study will only describe the results for nine-layer deposition because, as the number of layers’ increases, the surface quality and mechanical/thermal characteristics such as wear, hardness and thermal resistance are also increased. The followed determinations were conducted: the adhesion strength, hardness on a microscopic scale by micro-indentation, thermal analysis and structural and morphological analysis. The structural analysis has highlighted a uniform deposition for the ZrO2 18TiO2 10Y2O3 layer, but for the layers that contained Cr2O3 ceramic microparticles, the deposition was not completely uniform. The thermal analysis revealed structural stability up to a temperature of 230 °C, the major degradation of the biopolymer matrix taking place at a temperature around 344 °C. The samples’ crystalline structure as well as the presence of the Cr2O3 compound significantly influenced the micro-indentation and scratch analysis responses. The novelty of this study is given by itself the coating of the Arboblend V2 Nature biopolymer (as base material), with ceramic microparticles as the micropowder coating material. Following the undertaken study, the increase in the mechanical, tribological and thermal characteristics of the samples recommend all three coated biopolymer samples as suitable for operating in harsh conditions, such as the automotive industry, in order to replace plastic materials.

Five‐layer reverse tape casting of IT‐SOFC

AbstractTape casting is a well‐established method for manufacturing thin ceramic layers with controllable thickness and porosity. This study investigates the potential of 10Sc1CeSZ material for the electrolyte and anode layers for intermediate‐temperature solid oxide fuel cells (IT‐SOFC) in an anode‐supported cell (ASC) geometry. In order to use La0.6Sr0.4Co0.2Fe0.8 Oxide (LSCF) cathode material, a Gd0.2Ce0.8 Oxide (GDC) barrier layer is needed; however, thermal expansion coefficient mismatch results in delamination of the GDC from the electrolyte during high temperature sintering when fabricated by conventional tape casting procedures. For the first time, ASCs have been manufactured by a five‐layer tape casting technique; barrier layer, novel composite layer, electrolyte, anode functional layer, and anode substrate. Ni‐ScCeSZ composite cells were tested between 650 and 800°C in H2:N2 fuel (85% H2) on the anode and air on the cathode to yield a maximum power density of .46 W/cm2. These results demonstrate the feasibility of this new five‐layer tape casting technique to produce IT‐SOFC.

Ammonia-fed reversible protonic ceramic fuel cells with Ru-based catalyst

The intermediate operating temperatures (~400–600 °C) of reversible protonic ceramic fuel cells (RePCFC) permit the potential use of ammonia as a carbon-neutral high energy density fuel and energy storage medium. Here we show fabrication of anode-supported RePCFC with an ultra-dense (~100%) and thin (4 μm) protonic ceramic electrolyte layer. When coupled to a novel Ru-(BaO)2(CaO)(Al2O3) (Ru-B2CA) reversible ammonia catalyst, maximum fuel-cell power generation reaches 877 mW cm−2 at 650 °C under ammonia fuel. We report relatively stable operation at 600 °C for up to 1250 h under ammonia fuel. In fuel production mode, ammonia rates exceed 1.2 × 10−8 NH3 mol cm−2 s−1at ambient pressure with H2 from electrolysis only, and 2.1 × 10−6 mol NH3 cm−2 s−1 at 12.5 bar with H2 from both electrolysis and simulated recycling gas.

Binder-Free, Thin-Film Ceramic-Coated Separators for Improved Safety of Lithium-Ion Batteries.

Separators play a crucial role in ensuring the safety of lithium-ion batteries (LIBs). Commercial polyolefin-based separators such as polyethylene (PE) still possess serious safety risks under abuse conditions because of their poor thermal stability. In this work, a novel type of binder-free, thin ceramic-coated separators with superior safety characteristics is demonstrated. A thin layer of alumina (Al2O3) is coated on commercial PE separators using the electron-beam physical vapor deposition (EB-PVD) technique. Scanning electron microscopy (SEM), contact angle, impedance spectroscopy, and adhesion test techniques were employed to evaluate structure–property correlations. When compared to commercial slurry-coated separators, the EB-PVD-coated separators display (i) higher thermal stability, (ii) stronger ceramic–polymer adhesion, and (iii) competitive electrochemical performance of full LIB cells. Thermal stability, in terms of improved shutdown and breakdown characteristics of the separator, was studied using the in situ impedance technique up to 190 °C. In addition, the improved adhesion of the ceramic layer deposited on the PE separator was studied following the tape adhesion strength test. We prove that the thin (binder-free) ceramic layer coated by EB-PVD is far more effective in improving separator safety than those made using the conventional thick slurry coating.

BaTiO3 films for multilayer devices by tape casting

The diversity of the applicational scope of modern printed electronics relentlessly requires the improvement of operational properties simultaneously with reducing the overall dimensions of devices. One of the most effective ways to overcome this major obstacle is the reduction of functional layers thickness in respect to the size of the device. In the present article, we are discussing a simple way of practical implementation of miniaturization concept through the application of a well-known high-productive industrial method of tape casting for obtaining thin nanostructured ceramic layers based on BaTiO3 nanopowders for MLCC. Using of nanosized powders per se imply a new approach of developing suspensions with suitable rheology for tape casting. We demonstrate, that a length of polymer molecule defines the size of floccules and therefore influences the thickness and surface quality of tape casted films. A certain nanopowder/polymer ratio contributes to the formation of the tapes with the surface roughness comparable with the size of one nanoparticle (20-25 nm). Moreover, it was established that developed suspensions are extremely sensitive to temperature changes. Lowering the temperature significantly affects the flow character of suspension and thus the thickness of casted tapes. Considering this fact, we propose an effective self-developed pre-cooling method of nanopowder suspension casting, which allows obtaining extremely thin and smooth tapes with a thickness of less than 1 µm and surface roughness of 20–25 nm by tape casting method.

Optimization of Lithium Content and Sintering Additives in Tape Cast Lithium Garnet Electrolyte Sheets

The lithium garnet (LLZO) remains one of the most promising electrolyte materials for producing solid state batteries. Tape casting is one method for producing the thin ceramic electrolyte layer required for a high-performance solid state battery. Processing of LLZO is complicated by several factors including lithium volatilization, abnormal grain growth and phase instability. Many of these issues are exacerbated in tape cast sheets by the sheets’ higher surface area to volume ratio, when compared to pellet processing methods. We report on an environmentally friendly aqueous tape casting process for LLZO using methylcellulose as a binder and compare final sheet properties to other, solvent-based, options. Solids loading, binder content, dispersant composition, and wetting agent type are varied to improve ease of casting and enhance properties of the as-cast tape. Lithium content in sintered LLZO sheets is controlled by the inclusion of excess Li2CO3 as lithium source in the ceramic tape itself and by a novel method of producing a lithium-saturated furnace atmosphere. Sintering time and temperature are optimized, and rapid thermal processing is investigated as a method of reducing lithium loss. Al2O3 and MgO are examined for use as sintering additives. Characterization of LLZO sheets is performed with XRD, EIS and SEM. Li2CO3 and sintering additive levels are optimized for ionic conductivity and density. The optimization effort improved the conductivity and density of 100µm thick sintered sheets to greater than 3x10-4 S/cm conductivity and 90% density. Figure 1

Oxidized Zirconium Components Maintain a Smooth Articular Surface Except Following Hip Dislocation

BackgroundOxidized zirconium (OxZr) offers theoretical advantages in total hip and knee arthroplasty (THA and TKA, respectively) relative to other biomaterials by combining the tribological benefits of ceramics with the fracture toughness of metals. Yet, some studies have found that OxZr does not improve outcomes or wear rates relative to traditional bearing materials such as cobalt-chromium (CoCr). Separately, effacement of the thin ceramic surface layer has been reported for OxZr components, though the prevalence and sequelae are unclear. MethodsTo elucidate the in vivo behavior of OxZr implants, the articular surfaces of 94 retrieved THA and TKA femoral components (43 OxZr TKA, 21 OxZr THA, 30 CoCr THA) were analyzed using optical microscopy, non-contact profilometry, and scanning electron microscopy. ResultsWe found that OxZr components maintain a smooth articular surface except following hip dislocation. Three of four OxZr femoral heads revised following dislocation exhibited severe damage to the articular surface, including macroscopic regions of ceramic-layer effacement and exposure of the underlying metal substrate; these components were 23-32 times rougher than pristine OxZr controls. When revised for dislocation, OxZr femoral heads were substantially rougher than CoCr femoral heads (median Sa = 0.431 v. 0.020 μm, P = .03). In contrast, CoCr femoral heads exhibited low overall roughness values regardless of whether they dislocated (median Sa = 0.020 v. 0.008 μm, P = .09, CoCr dislocators v. non-dislocators). ConclusionsEffacement of the ceramic surface layer and substantial articular surface roughening is not atypical following dislocation of OxZr femoral heads, making OxZr much less tolerant than CoCr to hip dislocation.

Influence of Ceramic Coating on Mechanical Properties of Stainless Steel

Crystal structure and phase composition of stainless steel substrates (AISI 304 type) was studied and it was found that they adopted the cubic symmetry. The calculated elementary cell parameter for the mayor Fe-Ni phase (weight fraction 99%) was a = 3.593 A, whereas the mean grain size was = 2932 A. Morphology of the stainless steel substrate surface was studied with profilometry. Mechanical properties of the stainless steel substrates and stainless steel substrates coated with ceramic layer of barium strontium titanate were studied with microhardness tester. For measurements performed according to the Vickers method the average microhardness was found HV = 189 or HV = 186 for the “in-line” and “mapping” measurement pattern, respectively. The sol-gel method was used to coat the surface of the stainless steel substrate with a thin ceramic layer of the chemical composition Ba0.6Sr0.4TiO3. It was found that the stainless steel substrate covered with sol-gel deposited ceramic coating exhibited the average hardness within the range HV = 217 up to HV = 235 for loading force F = 98 mN and F = 0.98 N, respectively. The Knopp method was also used and it was found that the stainless steel substrate with Ba0.6Sr0.4TiO3 coating exhibited hardness HK = 386.

Utilization of Waste Materials for the Manufacturing of Better-Quality Wear and Corrosion-Resistant Steels

Decarburization of steels during heat treatment is a major problem for wear applications and for thin structural components as it often results in poorer surface hardness, strength, and fatigue performance. Additionally, corrosion is a major problem in many engineering applications. To address these issues, this study introduces a novel low-cost surface treatment that utilizes raw materials obtained from automotive waste. This technique was applied on a high-carbon low-alloy martensitic steel that is commonly used in industrial applications for its hardness, strength, and low production cost. The reduction in decarburization led to improved abrasion performance, while the steel’s corrosion resistance was significantly improved through the formation of a thin ceramic layer across the steel’s surface. This treatment, therefore, not only offers a cost-effective solution to decarburization and corrosion, but it also promotes a more sustainable future.

Polymerizable Ceramic Ink System for Thin Inkjet-Printed Dielectric Layers.

An innovative ceramic ink system for thin inkjet-printed dielectric layers is presented, with which it is possible to avoid undesired drying effects. This system contains surface-modified Ba0.6Sr0.4TiO3 (BST) particles, a cross-linking agent, and a thermal radical initiator. The polymerization starts immediately after the ink drop contacts the heated substrate and therefore leads to very homogeneous topographies. Since an organic/inorganic composite ink is used, no sintering is needed after printing and thus printing on flexible substrates is possible. A comparison of the printing and drying behavior between modified and nonmodified BST with the described ink system is performed. The successful surface modification is confirmed via X-ray photoelectron spectroscopy (XPS). Topographies of different printed structures are compared by white light interferometry, the occurring polymerization is confirmed by measurements with an oscillatory rheometer, layer thicknesses are determined by scanning electron microscopy (SEM) images, and the capacitance of a printed capacitor is measured via impedance spectroscopy. It is successfully shown that the developed ink system enables the production of thin ceramic layers (<1 μm) with very homogeneous topographies since undesired drying effects can be avoided. The printed dielectric layers on flexible substrates have a high ceramic content and a high permittivity of 40.

Ultra-thin ion exchange film on the ceramic supporter for output power improvement of reverse electrodialysis

In this study, ultra-thin ion exchange film on the ceramic supporter (UTFCS) composed of thin polymer layer and nanoporous ceramic layer with low electrical resistance was developed. The electrical properties and permselectivity of UTFCSs were evaluated and the properties of UTFCSs were compared with other ion exchange membranes. Fabricated UTFCSs were applied to a reverse electrodialysis (RED) system to evaluate the output characteristics and compared with other ion exchange membranes. The power density of RED using UTFCS was 36.6 mW/m2, which was 8% higher than that of a commercial anion exchange membrane. In addition, possibility as power source was experimentally verified by driving LEDs. The proposed UTFCS can be applied not only to RED but also to energy development such as fuel cells and microbial cells.

Independent driving method for significant hysteresis reduction of piezoelectric stack actuators.

Piezoelectric actuators are used extensively in precision positioning platforms. However, the positioning accuracy is severely affected by the hysteresis characteristics of piezoelectric ceramics. Piezoelectric stack actuators (PSAs) are usually composed of hundreds of thin piezoelectric ceramic layers connected in parallel, and their hysteresis quantity is the accumulation of that in each layer, which results in large nonlinear deformation. A new driving method is proposed for PSAs to drive each layer independently, and all the layers are driven in sequence. The independent driving logic is analyzed, and the scheme of the driving circuit is presented to replace the traditional voltage amplifier, which guarantees that there is no need to change the original driving signal. Experimental results show that the hysteresis of a homemade seven-layer PSA is reduced from approximately 12.5% to 2.7% compared with the traditional parallel driving method in various frequencies. The proposed independent driving method can reduce hysteresis significantly and achieve good linearity in an open-loop control, which does not need high-performance sensors or hysteresis models.

Strength of transparent ceramic composites with spinel

Protective windows have to be very hard and possess a certain thickness to provide a good wear resistance, as well as low weight and cost to be used economically. But, common transparent systems like bulletproof glass are quite heavy because they need a minimum thickness to provide protection. Therefore, laminate systems consisting of a thin transparent ceramic layer with a very high hardness and a low-cost as well as a lower-weight transparent substrate are considered in the current work as an alternative solution to thick monolithic ceramics. Since reliability is a main aspect for the application, mechanical characterization is carried out using ring-on-ring bending tests for different laminate structures. Apart from various commercially available hardened and unhardened glasses, also a polymer material is taken into account as thicker substrate material for a thin spinel ceramic. In particular, polycarbonate as well as float glass, B270 and Borofloat® by Schott or Gorilla glass® 3 by Corning are used as substrate materials. Tests are carried out with either ceramic or substrate material under tension. Properties derived using laminate theory are compared and discussed with respect to the properties of the individual materials. The Young’s moduli of the monolithic materials are measured via an impulse excitation technique. In an outlook, implications for the application of the laminates are discussed.

Electro-chemical Corrosion of a Cast Iron Protected with a Al2O3 Ceramic Layer

Thin layers of Al2O3 were used to protect a standard FC250 cast iron at electro-corrosion in acid rain electrolyte solution. In comparison with a cast-iron material we present the results obtained on the metallic covered sample using linear and cyclic potentiometry. The material surface was investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The results present a generalized corrosion with a higher resistance for covered samples (more than 30 times) in comparison with the simple cast iron. The main causes of the corrosion of the covered samples are based on the thin ceramic layer imperfections like pores or micro-cracks that facilitate the contact of the electrolyte solution with the metallic substrate.