Showing papers in "Journal of The Korean Ceramic Society in 2020"
TL;DR: In this article, the authors present an overview of recent development in the use of ABO3 perovskites as resistive-type gas sensors, clearly elucidating current experimental strategies, and sensing mechanisms involved in realization of enhanced sensing performance.
Abstract: Perovskite-type oxides with general stoichiometry ABO3 (A is a lanthanide or alkali earth metal, and B is transition metal) constitute a rich material playground for application as resistive-type gas-sensing layers. Immense interest is triggered by, among other factors, stability of abundant elements (≈ 90% in the periodic table) in this stoichiometry, relatively easy tunability of structure and chemical composition, and their off-stoichiometry stability upon doping. Moreover, their capability to host cationic and abundant oxygen vacancies renders them with excellent electrical and redox properties, and synergistic functions that influence their performance. Herein, we present an overview of recent development in the use of ABO3 perovskites as resistive-type gas sensors, clearly elucidating current experimental strategies, and sensing mechanisms involved in realization of enhanced sensing performance. Finally, we provide a brief overview of limitations that hamper their potential utilization in gas sensors and suggest new pathways for novel applications of ABO3 materials.
48 citations
TL;DR: In this article, the current status of lead-free, all-inorganic halide perovskite quantum dots (LFAIHP QDs) is discussed, and the limitations of these materials, possible methods to overcome them and prospects for these materials in the future are provided.
Abstract: Halide perovskite is attracting significant attention in optoelectronic because of its unique properties. Lead-free halide perovskites, in particular, have been studied intensively for their nontoxicity. In addition to the attention given to lead-free halide perovskites, the manufacture of these materials on a quantum scale has also received considerable attention due to the quantum confinement effect. This review discusses the current status of lead-free, all-inorganic halide perovskite quantum dots (LFAIHP QDs). First, synthetic methods for producing quantum dots are introduced; then materials are discussed with a focus on tin, bismuth, antimony, copper-based and double perovskite quantum dots. The properties of these materials-such as their physical structure, optical properties, electrical properties, and stability-are discussed. The application of these materials for solar cells, light-emitting diodes, photodetectors, photocatalysts, and memory devices are also examined. Finally, the limitations of LFAIHP QDs, possible methods to overcome them and prospects for these materials in the future are provided.
35 citations
TL;DR: A review on the joining of SiC is given in this article in response to the interest surge on this material for a number of applications, such as high-temperature applications.
Abstract: A review on the joining of SiC is given in response to the interest surge on this material for a number of applications. Because the engineering design for the majority of applications requires complicated shapes, there has been a strong demand for the development of reliable joining techniques for SiC, especially for high-temperature applications. However, the joining of SiC-based materials is inherently difficult because of the high degree of covalent bonding in SiC and the low self-diffusivity. This review discusses basic mechanisms and properties of the SiC joining techniques developed to date; they are divided into eight different categories. In addition, critical assessment is given for each technique in the context of high-temperature application (≥ 1000 °C). Finally, comments are provided for the use of these techniques in advanced nuclear reactors where stringent irradiation stability under neutron irradiation as well as hermeticity and joint strength are required.
33 citations
TL;DR: In this paper, a review on the approaches for mechanical reinforcing methods for silica aerogels and recent achievements toward improving the strength and stiffness of native silica aerosol is presented.
Abstract: Aerogels are considered as outstanding future materials owing to their wide surface area and three-dimensional network of silica particles, low density, low-thermal conductivity, high porosity, and low dielectric property. Their outstanding characteristics represent excellent potential applications in thermal insulation systems, aeronautical domains, environmental clean-up and protection, as heat storage devices, transparent windows, thickening agents in paints, etc. Among these applications, thermal insulating materials can play a vital role in living systems and for saving energy in various domestic and industrial processes. However, native silica aerogels are fragile and sensitive to relatively low pressures, which limit their application. More robust aerogels with higher strength and stiffness can be obtained by compounding silica networks with organoalkoxysilanes, polymers or using porous scaffolds as supports. This paper presents a review on the approaches for mechanical reinforcing methods for silica aerogels and recent achievements toward improving the strength of native silica aerogels. In addition, various characteristics derived from composite aerogels are analyzed synthetically.
30 citations
TL;DR: In this paper, the sustainable use of red mud (RM) as a supplementary cementitious material in concrete was investigated, and the results indicated that the RM-based concrete had superior properties.
Abstract: The current work investigates the sustainable use of red mud (RM) as a supplementary cementitious material in concrete. The large amount of RM produced by the alumina industry creates disposal problems, as RM pollutes the surrounding environment and leads to ecological imbalance. To develop suitable uses for RM, concrete in which some of the cement was replaced with RM was experimentally investigated. The RM content, strength, and curing age of the concrete were considered as the parameters in this work, and the mechanical properties and durability of the RM-based concrete were tested to investigate its performance. The results indicated that the RM-based concrete had superior properties. Concrete in which 10% of the cement was replaced with RM exhibited high strength and durability compared to a 100% cement-based concrete control. To examine the micro-level behavior of the RM concrete, the microstructure was studied using X-ray diffraction and scanning electron microscopy.
29 citations
TL;DR: In this paper, the authors investigated the characteristics of metakaolin-based geopolymers and methods for fast setting and made hypotheses about the reaction mechanism between Ca2+ and geopolymer.
Abstract: The setting of metakaolin-based geopolymer depends on the raw materials and mix proportions Setting, when material is cured at room temperature, takes about 1 day and is longer than setting time of Portland cement For the fast setting of geopolymers, some studies increased the curing temperature or used raw materials with high CaO content Also, Ca2+ and Mg2+ compounds were used as additives Setting can be easily controlled and accelerated by adding Ca2+ compounds However, it has been reported that knowledge of the reaction mechanism and final products between Ca2+ and geopolymers is still limited In this study, we investigated the characteristics of metakaolin-based geopolymers and methods for fast setting of geopolymers, and made hypotheses about the reaction mechanism between Ca2+ and geopolymers
28 citations
TL;DR: Protonic ceramic electrolysis cells (PCECs) have attracted great attention for efficient energy conversion as discussed by the authors, and their extended applications have been investigated for electrochemical ammonia synthesis.
Abstract: Proton-conducting oxides exhibit significant hydrogen ion (proton) conductivity at intermediate temperatures around 300–600 °C Owing to their distinguished features compared to high-temperature oxygen ion-conducting oxide electrolytes and low-temperature proton-conducting polymer electrolytes, diverse electrochemical applications based on the proton-conducting oxides have attracted great attention for efficient energy conversions This review particularly aims to introduce protonic ceramic electrolysis cells (PCECs) and their extended applications The constituent materials, recent developments, remaining issues in PCECs as well as the application integrated with PCEC for electrochemical ammonia synthesis will be presented In addition, for each section, the relevant prospects and recommendations for future research directions will be discussed
27 citations
TL;DR: In this article, the authors present research on the development of nanostructures for use in commercial solid oxide fuel cells (SOFCs) and highlight various aspects of research and applications across the globe.
Abstract: Solid oxide fuel cells (SOFCs) are considered to be the focus of investigation for energy systems owing to their efficiency in converting chemical energy into electrical energy, low carbon footprint, and fuel flexibility. Despite their high performance and durability, SOFCs suffer from critical problems such as carbon coking, agglomeration, and poor redox stability. This review presents research on the development of nanostructures for use in commercial SOFC systems and highlights various aspects of research and applications across the globe. The materials utilized for anodes, electrolytes, and cathodes are discussed and compared, detailing how their respective properties can attain high catalytic activity, conductivity, and stability at low temperatures with the aim of direct application using diverse fuels such as hydrogen, hydrocarbons, and carbon fuels. This review also discusses and compares the various processes used for the synthesis of the electrodes and electrolytes used in SOFCs, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), infiltration, and in situ exsolution, that have gained much attention with a view to increase the active areas, decrease the Ohmic resistance, and reduce the manufacturing price.
25 citations
TL;DR: In this paper, the authors investigated the recent progress of the 2D materials and metal-organic framework (MOF) in the taste sensing applications from the review, they concluded that these materials would be promising candidates for taste sensing application, thereby leading to the development of food industry.
Abstract: In food industries, the detection of different tastes in low level is required to enhance the quality of products Recently, 2-D materials and metal–organic framework (MOF) have attracted extensive attention owing to their unique properties, and they can be used in various applications, especially chemical and biochemical sensing In this review, we investigate the recent progress of the 2-D materials and MOF in the taste sensing applications From the review, we could conclude that these materials would be promising candidates for taste sensing applications, thereby leading to the development of food industry
23 citations
TL;DR: In this article, various concentrations of strontium ions loaded titanium dioxide nanorods and common TiO2 nanorod (control) were synthesized by electrochemical anodization technique to get the implant with superior bioactivity.
Abstract: In the present work, various concentrations of strontium ions loaded titanium dioxide nanorods and common titanium dioxide nanorods (control) were synthesized by electrochemical anodization technique to get the implant with superior bioactivity. Cell viability and antibacterial efficacy studies were estimated using MTT assay and solid agar medium. The characterisation results confirmed that Sr2+ was successfully incorporated into TiO2 nanorods. Compared with common TiO2 nanorods (control), Sr2+ loaded TiO2 nanorods showed higher surface roughness, adhesion strength, and water wetting angle. MTT assay showed better cell response on Sr-TiO2 nanorod surface as compared to control and the antibacterial test showed that Sr2+ loaded TiO2 nanorods have superior antibacterial activity against pathogenic bacterial strain E. coli and S. aureus. Sr2+ incorporated TiO2 nanorod arrays can be used as a potential candidate for hard tissue implant applications.
23 citations
TL;DR: In this article, a piezoelectric composite film is fabricated by mixing lead-free 0.942[Na 0.535 K0.480 NbO3]-0.058LiNbO 3 (KNNLN) nanocube powder with polydimethylsiloxane (PDMS) matrix.
Abstract: The research on harvesting the wasted mechanical energy and using it as a useful energy source has been in the spotlight. Conventional ceramic-based devices have disadvantages such as mechanical brittleness and high-temperature processing. To overcome these weaknesses, the piezoceramic materials mixed with polymer matrix have been studied to produce flexible piezoelectric devices. Herein, a piezoelectric composite film is fabricated by mixing lead-free 0.942[Na0.535 K0.480NbO3]-0.058LiNbO3 (KNNLN) nanocube powder with polydimethylsiloxane (PDMS) matrix. KNNLN nanocube powder is synthesized by a solid-state reaction method, which can typically present outstanding stoichiometric composition and perovskite crystalline structure. The cube-shaped particles are thought to show higher stress concentration at corners and edges of the nanocube than spherical particles when external mechanical input is applied. The flexible KNNLN nanocube–PDMS nanocomposite device generates the piezoelectric signals of ~ 28 V and ~ 220 nA during bending motion, which is a high-performance energy harvesting efficiency compared to previous KNN-based flexible piezoelectric composites generators. KNNLN nanocube-based composite can replace toxic lead-based nanocomposites for future flexible devices such as eco-friendly self-powered energy harvester and biocompatible sensor.
TL;DR: In this article, the strength performance of geopolymer concrete (GC) with different proportions of fly ash and ground granulated blast furnace slag is presented. And the potential of GC against acid resistance, porosity, water absorption and sorptivity is presented in this paper.
Abstract: A geopolymer binder is measured as an alternative and elective material to customary Portland binders. Utilization of Fly ash (FA) as a primary binding material limits the waste creation of thermal power stations and reduces environmental impacts. This paper presents the strength performance of geopolymer concrete (GC) with different proportions of FA and ground granulated blast furnace slag. The potential of GC against acid resistance, porosity, water absorption, and sorptivity is presented in this paper. Apart from this, rapid chloride penetration test was performed to assess the chloride resistance of GC. XRD and SEM analysis was done on selected samples of GC to categorize microstructural performance. The results depicted that mixes M5 and M10 have attained higher compressive strengths, i.e., 49.0 and 57.6 MPa, while the acid durability loss factor values are less by 28% and 19%, respectively compared to other mixes of GC.
TL;DR: In this article, the authors optimized the strontium hydroxyapatite (Sr-HA) and β tricalcium phosphate (β-TCP) ratio in the fabricated scaffolds to enhance their mechanical strength and bioactivity with controlled biodegradability.
Abstract: Strontium ion-substituted calcium phosphate-based ceramic scaffolds enhance osteogenesis. The objective of the present study was to optimize the strontium hydroxyapatite (Sr-HA) and beta tricalcium phosphate (β-TCP) ratio in the fabricated scaffolds to enhance their mechanical strength and bioactivity with controlled biodegradability. Porous polyurethane sponge scaffolds containing Sr-HA and β-TCP in varying concentration were developed by dipping 3D sponge pieces into a slurry containing 10% gelatin, proper concentration of biphasic calcium phosphate (BCP) and 3% poly vinyl alcohol. Four different samples [Sr-BCP, Sr-BCP (20/80), Sr-BCP (30/70), Sr-BCP (40/60)] were prepared and were characterized for biodegradability, water uptake capability and cytotoxicity using various techniques. Pure, crystalline, cytocompatible Sr-BCP Scaffolds possessing both micropores and macropores with porosity greater than 80% and water uptake capability above 100% were obtained. Thus, the effective substitution of Sr-HA and β-TCP in varying proportion makes the composite scaffold a distinctive material of bone tissue engineering.
TL;DR: Polarized hydroxyapatite–barium titanate composite surfaces showed comparatively less macrophage activity than unpolarized surfaces, indicating immunocompatibility for which these materials can be used a preferred material in tissue engineering applications.
Abstract: For fabricating the filler materials for tissue re-growth, the primary concern should be focused on the immunocompatibility of the material. Lymphocyte T-cells and macrophages activate each other and induce immune suppressive effects. Polarized hydroxyapatite–barium titanate composite surfaces showed comparatively less macrophage activity than unpolarized surfaces. Lymphocytes isolated from human umbilical cord blood were cultured separately on both polarized and unpolarized samples. The macrophage with nitric oxide and myeloperoxidase showed less activity on polarized composite surfaces as compared to lipopolysaccharide of stimulated cells from which it can be inferred that the polarized composites showed immunocompatibility for which these materials can be used a preferred material in tissue engineering applications.
Abstract: Recent trends in the construction industry involve the use of industrial by-products as building materials to improve waste management and reduce excessive CO2 emissions from the cement industry. Red mud (RM) is a by-product of alumina refinery plants. When improperly disposed, red mud harms the surrounding area, owing to its highly alkaline nature. In the current work, up to 15% of the cement in concrete was replaced with red mud, in increments of 2.5%. In addition, to enhance the pozzolanic reaction, metakaolin was used as a ternary mineral; it replaces 10% of the cement. A slump cone test was conducted to evaluate the workability. Compressive, flexural, and split tensile strength tests were conducted to observe the mechanical properties. A rapid chloride penetration test and water absorption tests were conducted to determine the durability properties of the concrete. X-ray fluorescence analysis was conducted to determine the chemical composition of both the red mud and the metakaolin. A scanning electron microscope analysis was conducted to characterize the microstructure of the RM concrete. The 12.5% red-mud replacement mix showed the greatest improvement in mechanical properties among all the mixes. As the red-mud replacement increased, the chloride-ion passage was reduced. Moreover, a denser microstructure formation was observed with the red-mud replacement, as compared to standard concrete.
TL;DR: In this article, the reactivity among cement particles, a microstructural approach towards analyzing the material, and its performance, was presented to evaluate the strength and few durability properties.
Abstract: Agricultural wastes like sugarcane bagasse ash and rice husk ash can be reused as supplementary cement materials to produce eco-friendly buildings as plants of grass family contain more silica, which enhances the pozzolanic reactivity of the plant ashes. Researches so far were limited to evaluate the strength and few durability properties. This paper focuses on the reactivity among cement particles, a microstructural approach towards analyzing the material, and its performance. Compressive, splitting tensile strength tests, durability tests like water absorption and RCPT have been performed for 5%, 10%, 15%, and 20% replacement of sugarcane bagasse ash in cement. An increase in strength, less absorption, and low permeability were observed from 0 to 15% replacement. 15% replacement of SCBA in concrete cured for 56 days has shown maximum durable compared to other samples that are cured for 28 and 56 days. The enhanced performance of PPC owes to thick lattice formed due to compounds formed, which lead to the densification of concrete.
TL;DR: In this paper, the Ca/P molar ratio, pH, and reaction temperature were varied to investigate their influence on the Ca-deficient hydroxyapatite formation.
Abstract: Hydroxyapatite (HA) was synthesized through the precipitation method and different processing parameters (Ca/P molar ratio, pH, and reaction temperature) were varied to investigate their influence on the HA formation. No HA powder was obtained at pH 10 and 25 °C, even when using a Ca/P ratio as high as 2.2. However, HA powders were successfully produced at pH above 11, 25 °C, and Ca/P ratio of 2.2. At pH 10 and 25 °C, the concentration of the H+ ions in the reaction solution increased and so did the Ca loss, resulting Ca-deficient hydroxyapatite (CdHA) formation. While HA was formed instead due to a lower Ca loss when the pH was increased to 11 and 11.3. As the reaction temperature was increased to 70 and 90 °C, the HA formation occurred regardless of the pH because of the decreased solubility of HA in the solution.
TL;DR: In this paper, a soft-hard composite fiber has been fabricated by electrospinning method using iron oxide as soft magnetic material and cobalt ferrite as hard magnetic material, and the change in the oxidation state of iron oxide can be controlled with sintering atmosphere and influences on the magnetic properties.
Abstract: Soft-hard magnetic composites have attracted much attention as magnetic materials for permanent magnets due to high coercivity and saturation magnetization in various fields such as motor, storage device and magnetic actuators Hard magnetic materials with low saturation magnetization improve magnetic properties through exchange coupling effect with soft magnetic materials Rare earth metals, which are used as magnetic materials in permanent magnetic, have issued such as high cost due to resource scarcity Transition metals have been used for fabricating magnetic material with high magnetic properties due to low cost and abundant in the resource Spinel magnetic materials with transition metals have excellent chemical, thermal stability, large magnetocrystalline anisotropy and magnetic properties Composite magnetic materials in one dimensional (1D) morphology are effective in improving coercivity In this work, soft-hard composite fiber has been fabricated by electrospinning method using iron oxide as soft magnetic material and cobalt ferrite as hard magnetic material The change in the oxidation state of iron oxide can be controlled with sintering atmosphere and influences on the magnetic properties In comparing with simple CoFe2O4, the fabricated Fe3O4–CoFe2O4 exhibits excellent saturation magnetization of 13363 emu g−1 and enhanced coercivity of 27469 Oe
TL;DR: In this paper, a review on the application of 2D inorganic nanosheets as supercapacitor electrodes and versatile building blocks for synthesizing novel hybrid electrode materials is presented.
Abstract: Exfoliated two-dimensional (2D) nanosheets of inorganic solids exhibit various unique characteristics such as unusually high morphological and structural anisotropy, great diversity in composition and structure, and tunable physicochemical properties. The large 2D surface area and high electrochemical activity of inorganic nanosheets render them as potential materials for supercapacitor electrodes. The electrode performance of these nanosheets can be further improved by their hybridization with highly conductive and/or electrochemically active species. This review focuses on the application of 2D inorganic nanosheets as supercapacitor electrodes and versatile building blocks for synthesizing novel hybrid electrode materials. The crucial roles of 2D inorganic nanosheets in high-performance electrode materials for supercapacitors are discussed and several intriguing examples of 2D inorganic nanosheet-based electrode materials have also been provided. The perspective for future research in this field is discussed along with various strategies to optimize the electrode performance of 2D inorganic nanosheet-based hybrid materials.
TL;DR: In this paper, 0.35BaTiO3 (BF-35BT) lead-free piezoelectric ceramics were prepared using a conventional solid-state method to determine the effects of sintering temperature on their microstructures and electrical properties.
Abstract: In this study, 0.65Bi1.05FeO3–0.35BaTiO3 (BF-35BT) lead-free piezoelectric ceramics were prepared using a conventional solid-state method to determine the effects of sintering temperature on their microstructures and electrical properties. The average grain size increased with sintering temperature, but not significantly, and the relative density of the ceramics increased and then decreased at high sintering temperatures due to the volatilization of Bi2O3. At the optimal sintering temperature (1030 °C), BF-35BT ceramics showed minimum coercive field (Ec) with enhanced remanent polarization (Pr) and consequently resulted in a high converse piezoelectric coefficient (d*33) value of 305 pm/V. The results indicate that the optimum sintering temperature, maximum relative density, and appropriate grain size, which are significantly related to the domain size and configuration, as well as the minimum concentration of associated charged defects, are critical factors that influence the piezoelectric performance of BF-35BT ceramics.
TL;DR: In this article, a review deals with the latest advances in the fabrication of Fe3O4 nanocomposite particles with a core-shell structure as well as their critical characteristics and advantages to be used in magnetically responsive particle suspensions.
Abstract: Magnetorheological (MR) fluids are a type of smart material of which rheological properties can be controlled through mesostructural transformations. They are generally magnetically responsive particle suspensions, which consist of magnetizable particles dispersed in a non-magnetic liquid medium. Ferromagnetic or ferrimagnetic particles with a micrometer size are suitable for MR fluid suspensions, since they can be polarized by the external magnetic field to form chain-like aggregates (mesostructures) that have a strong yield strength and can induce a high shear viscosity. Fe3O4 particles are good candidates for high-performance MR materials due to their low density and high magnetic properties as well as their excellent surface activities. To improve the stability of the MR suspension, many studies on the synthesis of Fe3O4-containing nanocomposites have been carried out recently. This review deals with the latest advances in the fabrication of Fe3O4 nanocomposite particles with a core–shell structure as well as their critical characteristics and advantages to be used in MR suspensions. We focused on the synthesis strategy of various Fe3O4 nanoparticles with a core–shell structure as well as their performance in the magnetic fields.
TL;DR: In this article, a Sb-reduced graphene oxide (rGO) composite material by reduction of Sb2O3 nanoparticles was synthesized, which showed higher capacity and better cycling performance compared to bare Sb nanoplatelets.
Abstract: Metallic antimony (Sb) is considered as a promising anode material for sodium-ion batteries (SIBs) owing to its high theoretical capacity (660 mAh/g) based on alloying/dealloying reactions with sodium ions. The main issues of Sb, however, are its large volume expansion upon cycling. In this study, we synthesized Sb-reduced graphene oxide (rGO) composite material by reduction of Sb2O3 nanoparticles. We confirmed that ~ 5 nm sized Sb nanoparticles are well distributed onto the rGO sheets, and Sb–rGO composite electrodes showed higher capacity and better cycling performance compared to bare Sb nanoplatelets. This improvement is attributed to increased electrical conductivity owing to incorporation of rGO, which also acts as a buffer against volume expansion of Sb particles during electrochemical reactions. The moderate rate performance of Sb–rGO composite materials was further improved by electrode formulation modification using a carboxymethylcellulose (CMC) binder. An electrode architecture containing Sb–rGO composite material with CMC binder achieved a high capacity (~ 400 mAh g−1) at a high rate (~ 30 C).
TL;DR: The recent progresses in ceramic nanohybrids based on LDH materials and their related curative application systems for gene therapy, chemotherapy, phototherapy, and combination therapy are reviewed and highlighted.
Abstract: Layered double hydroxides (LDHs) have attracted considerable interest in bio-related applications owing to their good biocompatibility, biodegradability, facile preparation, and versatile functionality such as tailored drug loading, efficient cellular delivery, targeted delivery, and the controlled release of gene, drug, or other bioactive molecules. In particular, LDHs can accommodate various therapeutic agents and have been extensively explored to achieve novel multifunctional ceramic nanohybrids for therapeutic applications. Here, we review and highlight the recent progresses in ceramic nanohybrids based on LDH materials and their related curative application systems for gene therapy, chemotherapy, phototherapy, and combination therapy. Concretely, the synthetic strategies, structural features, and functions of LDHs as nonviral vectors and their versatile hybrid systems are discussed.
TL;DR: In this article, a cantilever-type piezoelectric energy harvester based on a single crystal macro-fiber composite (SFC) was proposed for improving durability.
Abstract: In the energy harvester, the fatigue caused by cyclic vibration is an important challenge affecting the lifetime of the device. The aim of this study is to evaluate the fatigue behavior of the cantilever-type piezoelectric energy harvester (PEH) based on a single crystal macro-fiber composite (SFC), and propose a method for improving durability. The initial output of the fabricated PEH shows 6 mW root mean square power at 0.5 gravitational acceleration at resonance frequency (23 Hz). In fatigue test under cyclic vibration, the dramatic power decrease and waveform distortion caused by the mechanical crack at the top electrode line were identified after 5
$$\times$$
106 cycles. To improve the issue, the stress distribution on the top electrode line was analyzed by finite element analysis and the reinforced structure was proposed by attaching a 50 µm-thick polyimide film. The reinforced PEH shows the durable output power until 107 fatigue cycles without a significant output power loss. These study potentially can be applied to the development of reliable SFC-based PEH with long-term lifetime.
TL;DR: In this paper, surface-modified magnetite nanoparticles were modified with various types of the precursor to include anionic terminal functional groups, and the surface modified particles exhibited improved dispersion behaviour in the aqueous solution owing to a change in the electrostatic force due to the surface charge on each particle.
Abstract: The dispersibility in an aqueous solution of magnetite nanoparticles was enhanced by appropriate anionic surface treatment. The Fe3O4 nanoparticles were modified with various types of the precursor to include anionic terminal functional groups. The nanoparticles modified by polyacrylic acid, tri-sodium citrate dihydrate or ammonia exhibited an increased zeta potential owing to the large amount of terminal hydroxyl and carboxyl groups. As a result, the surface-modified particles exhibited improved dispersion behaviour in the aqueous solution owing to a change in the electrostatic force due to the surface charge on each particle. In addition, the physical properties of the surface-modified magnetite nanoparticles were discussed.
TL;DR: In this paper, the effect of Si/Al ratio and aging time on the microstructure and mechanical properties of kaolin-based geopolymers was investigated, where SEM, XRD, and piston on three ball test were applied at the different Si/al ratio and the aging time.
Abstract: Geopolymers are a class of aluminosilicate-based ceramics that contain 3D network synthesized by condensation of tetrahedral aluminosilicate units, produced by the aluminosilicate raw materials and alkaline activators. The Si/Al ratio and aging time are the crucial parameters which influence the reaction degree of geopolymerization process and the reaction time, affecting the final properties, respectively. Here, we investigated the effect of Si/Al ratio and aging time on the microstructure and mechanical properties of kaolin-based geopolymers, where SEM, XRD, and piston on three ball test were applied at the different Si/Al ratio and the aging time. Given the higher ratio of Si/Al and longer aging time, geopolymer-based matrix was densified and high crystalline phases were evolved. Furthermore, the highest flexural strength of specimen, with the Si/Al ratio of 2.49 and aging time of 1 day, was 19.5 MPa.
TL;DR: In this article, N-doped copper nitride (Cu3N) has been successfully fabricated using reactive RF sputtering, which exhibits significantly reduced optical bandgap and improved photocurrent density compared with that of pristine Cu3N.
Abstract: Copper nitride (Cu3N) has attracted wide attention for solar energy conversion applications owing to suitable Eg of 1.6–1.9 eV, non-toxicity, and possibility to fabricate homojunction solar cells. The Cu3N has a body-centered site of anti-ReO3 structure, which can be easily occupied by transition metals. Hence, many studies on the band gap tuning of Cu3N have been conducted with doping of various elements. However, N-doped Cu3N film has not been reported experimentally yet although it was theoretically predicted to have very stable doping and new partially filled narrow band gap. Herein, via systematically controlling the nitrogen partial pressure (R = N2/N2 + Ar), we successfully fabricated N-doped Cu3N film using reactive RF sputtering. The N-doped Cu3N film (only specific R = 0.5) exhibits significantly reduced optical bandgap (1.1 eV) and improved photocurrent density (1.66 mA/cm2 at 10 V) compared with that of pristine Cu3N film.
TL;DR: In this paper, a thin SiC coating layer was deposited on the graphite mold using the chemical vapor deposition (CVD) method to utilize the lubrication properties of graphite and the anti-oxidation properties of SiC.
Abstract: Compression glass molding is a promising technique for mass production of near net-shaped, high-precision, and low-cost optical glass elements. However, the glass molding process causes the damage of glass and the mold during demolding because of the chemical or physical adhesion of the glass to the mold. To overcome this limitation, graphite molds are used owing to their good lubrication and easy machining. However, graphite materials show rapid oxidation at high temperatures in the presence of oxygen. Therefore, in this study, a thin SiC coating layer was deposited on the graphite mold using the chemical vapor deposition (CVD) method to utilize the lubrication properties of graphite and the anti-oxidation properties of SiC. The specimen obtained using the low-temperature CVD method showed high carbon content and good lubrication properties than that obtained using the high-temperature CVD method.
TL;DR: In this paper, the authors present manifold possibilities of using saccharides and their derivatives in colloidal processing of ceramics, including sugar acids (galacturonic and lactobionic acid) as highly effective deflocculants for nanopowders, acryloyl derivatives of monosaccharides, sugar alcohols as organic monomers in gelcasting; polysaccharides as binders; and lascorbic acid as an activator of radical polymerization in gel casting.
Abstract: Herein, we present manifold possibilities of using saccharides and their derivatives in colloidal processing of ceramics. Sugar-based compounds are attractive alternatives for commonly used organic additives, because they are renewable materials, are non-toxic to human skin, and have a positive influence on the rheological behavior and stability of ceramic suspensions which is reflected in the properties of green and sintered bodies. The examined substances include sugar acids (galacturonic and lactobionic acid) as highly effective deflocculants for nanopowders; acryloyl derivatives of monosaccharides and sugar alcohols as organic monomers in gelcasting; polysaccharides as binders; and l-ascorbic acid as an activator of radical polymerization in gelcasting. The multifunctionality of the selected compounds as well as their thermal decomposition during sintering of ceramics is discussed. The study also reviews the related literature focusing on sugar-based compounds in ceramic processing.
TL;DR: In this paper, the amount of interstitial oxygen (δ) in Sr-doped lanthanum nickel oxide (La2−SrxNiO4+δ), as a function of Sr content has been investigated by the thermogravimetry analysis (TGA) and X-ray photoelectron spectroscopy (XPS).
Abstract: The amount of interstitial oxygen (δ) in Sr-doped lanthanum nickel oxide (La2–xSrxNiO4+δ) as a function of Sr content has been investigated by the thermogravimetry analysis (TGA) and X-ray photoelectron spectroscopy (XPS). La2–xSrxNiO4+δ (0 ≤ x ≤ 0.5) ceramics were prepared by the general solid-state reaction process and sintered in different ambient of argon, air or oxygen, respectively. An increase in the amount of Sr decreased δ in La2–xSrxNiO4+δ, while the Ni2+/Ni3+ ratio analyzed by Ni3p XPS decreased indicating that the oxidation state of Ni increased. Particularly when the sample was sintered in a low oxygen partial pressure condition such as in Ar ambient, the hole concentration strongly depended on the Sr content, suggesting that the hole generation seems mostly originated from Sr2+ substitution into the La3+ site.