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In this study, we investigated the effect of calcium sources with different solubilities and the carbonic anhydrase (CA) enzyme on carbonate mineralization reaction, and analyzed the reaction rate, the morphology of the formed precipitate, and the surface. The CO2 mineralization rate was affected by the rate of CO2 hydration and the rate of Ca ionization. For all of the calcium sources tested, CA improved the overall carbonate mineralization rate, but depending on the solubility of each calcium source, the reaction rates were in the order of CaCl2 > Ca(OH)2 > CaO. From CaCl2, calcium carbonate was generated rapidly. This was due to the high concentration of calcium ions in the solution because it was easily dissolved. But because of its high surface energy, calcite and vaterite coexisted. On the other hand, Ca(OH)2 and CaO had relatively low solubility and the rate of calcium carbonate production was slow, but after the reaction, CaCO3 with a calcite structure was formed. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

N/S dual-doped carbon materials were synthesized from coffee waste and cysteine for use as porous carbon electrode materials for electric double layer capacitors. The capacitance of the carbon materials was calculated from the experimental results of cyclic voltammetry and galvanostatic charge-discharge tests. The N/S-doped carbon materials obtained from heat-treatment with cysteine exhibited a higher discharge capacitance, 71.3 F/g, than that of the carbon without the cysteine treatment, 43.8 F/g, at 1 A/g. This is because the N/S dual-doped carbons possess a higher wettability than that of the other carbon material, even though the N/S doping with cysteine destroys the porous carbon structure, which reduces the BET surface area of the carbon samples. Elemental analysis was performed to determine the portions of nitrogen and sulfur elements doped into the carbon. From the XPS results, various states of nitrogen and sulfur elements were identified, and SEM/TEM images were obtained to observe their morphologies and porous structures.

Due to the significant amount of CO2 released from the cement industry, a CO2 sequestration process suitable for cement-manufacturing plants is required to reduce greenhouse gas emission and to mitigate global warming. In the present study, a new overall process of CO2 treatment is proposed for the cement industry that includes the extraction of KCl and CaCl2 from the cement by-products, KCl membrane electrolysis for KOH formation, and CO2 capture-mineralization using the extracted KOH and CaCl2. For this three-step process, various experiments were conducted to determine how the results varied in relation to experimental conditions and to find the most suitable conditions for process operation. The KCl and CaCl2 were extracted using pure water and HCl solutions at various concentrations, respectively, from industrial cement kiln dust. KCl membrane electrolysis was carried out to measure the electrochemical performance in relation to the KCl or KOH concentration, temperature, and applied current density. The single process of CO2 capture-mineralization was tested by measurement of the CO2 removal efficiency in relation to variation of the Ca/CO2 ratio and gas retention time. In addition, the purity of the CaCO3 produced was evaluated in relation to the Ca/CO2 ratio, and the CO2 removal efficiency was examined over time on stream.

Electrocatalytic reduction of CO2 to formate has become one way to increase the value of CO2 and to overcome the climate change issue. Novel catalysts for the critical role of enhancing reaction selectivity have been continuously explored to provide the best performance. Lately, composite materials have drawn much attention because the synergistic effect between the components provides enhanced physical and chemical properties. Here, we present a highly efficient CO2 reduction reaction to formate on a tin­(IV) oxide/zinc oxide (SnO2/ZnO) composite electrocatalyst with a grainy hollow nanofiber (HNF) structure. The faradaic efficiency (FE) of formate on the SnO2/ZnO composite HNF reaches as high as 97.9% at −1.34 V vs reversible hydrogen electrode (RHE), outperforming many tin-based catalysts. At −1.54 V (vs RHE), the SnO2/ZnO HNF exhibits 2 times and 4 times higher current density for formate generation than those of SnO2 HNF and nanoparticles (NPs), respectively. This superior catalytic performance is attributed to its one-dimensional continuous structure as well as to the synergistic effects between SnO2 and ZnO, which facilitate faster electron transfer and improve the conductivity of SnO2/ZnO composite HNF.

In this study, Ag/C composite catalysts with different weight ratios (20, 50, and 75 wt% Ag) were synthesized by spray pyrolysis to improve the performance of electrochemical CO2 reduction for CO production. Among the electrocatalysts tested, the Ag75/C composite catalyst (75 wt% of Ag nanoparticles dispersed in carbon black support) showed the highest electrochemical CO2 reduction performance, along with high stability that surpassed that of pure Ag particles. Above all, this is because Ag nanoparticles were dispersed on the surface of (and inside) the carbon black support. This enlarged the Ag surface area, thereby increasing the number of electrochemical CO2 reduction sites. Additionally, the carbon black support has a hierarchically porous structure that improved the transport of the catholyte, reactant, and products, enabling enhanced electrochemical CO2 reduction to CO. Furthermore, the use of carbon black support in the Ag/C composite catalysts allows the binder to bind more carbon microspheres than Ag nanoparticles, reducing the Ag surface area covered by the binder in comparison with that for pure Ag particles. Thus, the charge transfer resistance of a Ag/C composite catalyst was much lower than that of pure Ag particles due to the improved interconnection, contact, and number of electrochemical reaction sites provided by the combination of carbon black support and Ag nanoparticles. All of these interpretations imply that carbon black is an appropriate support able to play a key role in improving CO productivity via electrochemical CO2 reduction.

Porous carbon materials are promising candidates for anode materials in rechargeable potassium-ion batteries. However, their high surface area and low crystallinity usually cause side reactions with electrolytes and slanted charge/discharge profiles. Herein, we report the synthesis of porous carbon microspheres with highly graphitized structure and enhanced potassium-ion storage properties. The prepared carbon microspheres exhibit a low working potential of ~0.2 V, high Coulombic efficiency, and a stable reversible capacity of 292.0 mAh/g after 100 cycles, which is significantly higher than that of commercial graphite (137.5 mAh/g after 100 cycles). These desirable performances are attributed to the high crystallinity of carbon and its porous structure, which provide active sites for potassium-ion storage and alleviate the stress caused by the large volume change during the insertion and extraction of potassium ions.

Low-cost rechargeable batteries are ardently required for large-scale energy storage applications. In this regard, nonaqueous potassium-ion batteries (KIBs) are ascendant candidates due to the abundance of potassium resources, yet their energy density and cycle stability are insufficient for practical use. In this study, we report the Sb-based multicomposite comprising Sb nanoparticles, amorphous carbon (C), and reduced graphene oxide (rGO) as an anode material for KIBs. By adopting the tartaric acid as a carbon source and a chelating agent simultaneously, a multicomposite electrode with uniform and fine-sized Sb particles is realized. The Sb-C-rGO multicomposite exhibits a reversible capacity of 310 mAh g-1 at 0.5 A g-1 and 79% of it is retained after 100 cycles. Electrochemical tests show that the capacity fading in the Sb-C-rGO cell is attributed to the side reactions in the K metal and electrolyte, rather than the degradation of Sb nanoparticles. Furthermore, the formation of the metastable product is elucidated by Ostwald's step rule and density functional theory calculations. The present synthesis approach and the understanding of the failure and working mechanisms provide general insight into developing the alloying-type electrode materials for rechargeable batteries.

The direct conversion of CO2 to syngas with controllable H2/CO ratio has been investigated using electrochemical reduction of CO2 in aqueous media. Despite considerable progress on electrocatalytic syngas production, it remains challenging to generate a stable H2/CO ratio over a wide range of applied potentials. In this study, we investigated Ag/TiO2 catalysts, by which we achieved a stable H2/CO ratio with high Faradaic efficiency (93–100%) and partial current densities (~164 mA·cm−2) for syngas production in a flow cell. The H2/CO ratio was controlled by changing the catalyst properties resulting from oxygen vacancies and phase difference of TiO2. The H2/CO ratio of Ag/TiO2 catalysts was increased by introducing oxygen vacancy defects in the bulk and on the surface of TiO2 anatase. Furthermore, the H2/CO ratio was also increased by changing the TiO2 phases from anatase to rutile, even if the rutile phase possessed fewer oxygen vacancies. The 40 wt% Ag/TiO2 catalysts calcined in different gases (Ag/TiO2 anatase-air, Ag/TiO2 anatase-H2/Ar, and Ag/TiO2 rutile-air) exhibited H2/CO ratios of 0.1–0.3, 0.5–1.1, and 0.5–1.5, respectively, within the range of potential from −0.35 to −0.65 V (vs. RHE).

The electrochemical properties of hollow cobalt oxide and cobalt selenide microspheres are studied for the first time as anode materials for Na-ion batteries. Hollow cobalt oxide microspheres prepared by one-pot spray pyrolysis are transformed into hollow cobalt selenide microspheres by a simple selenization process using hydrogen selenide gas. Ultrafine nanocrystals of Co3O4 microspheres are preserved in the cobalt selenide microspheres selenized at 300 °C. The initial discharge capacities for the Co3O4 and cobalt selenide microspheres selenized at 300 and 400 °C are 727, 595, and 586 mA h g(-1), respectively, at a current density of 500 mA g(-1). The discharge capacities after 40 cycles for the same samples are 348, 467, and 251 mA h g(-1), respectively, and their capacity retentions measured from the second cycle onward are 66, 91, and 50%, respectively. The hollow cobalt selenide microspheres have better rate performances than the hollow cobalt oxide microspheres.

The synthesis and electrochemical performance of a composite of Co 9 S 8 nanoparticles and amorphous carbon is studied as an anode material for sodium-ion batteries. The Co 9 S 8 –carbon composite powder was fabricated through a one-pot spray pyrolysis process using thiourea and polyvinylpyrrolidone as sulfur and carbon sources, respectively. The Co 9 S 8 nanoparticles are entirely covered by an amorphous carbon layer. The initial discharge and charge capacities of the Co 9 S 8 –carbon composite powder were 689 and 475 mA h g −1 , respectively, at a current density of 0.5 A g −1 . The Co 9 S 8 –carbon composite powders exhibited a stable cyclability with a reversible capacity of 404 mA h g −1 for the 50th cycle and a superior rate capability compared with bare Co 1− x S powder. The improvement of Na-storage performance could be attributed to the small size and entanglement of the Co 9 S 8 nanoparticles within the carbon matrix.

Nickel sulfide-reduced graphene oxide (RGO) composite powders with spherical shapes are prepared by a one-pot spray pyrolysis process. The optimum mole ratio of nickel nitrate and thiourea to obtain nickel sulfide–RGO composite powders with high initial capacities and good cycling performance is 1:8. The bare nickel sulfide and nickel sulfide–RGO composite powders prepared directly by spray pyrolysis have mixed crystal structures of hexagonal α-NiS and cubic Ni 3 S 4 phases. The bare nickel sulfide powders are prepared from the spray solution without graphene oxide sheets. The nickel sulfide–RGO composite powders have sharp mesopores approximately 3.5 nm in size. The discharge capacities of the nickel sulfide–RGO composite powders for the 1st and 200th cycles at a current density of 1000 mA g −1 are 1046 and 614 mA h g −1 , respectively, and the corresponding capacity retention measured from the second cycle is 89%. However, the discharge capacities of the bare nickel sulfide powders for the 1st and 200th cycles at a current density of 1000 mA g −1 are 832 and 16 mA h g −1 , respectively. The electrochemical impedance spectroscopy (EIS) measurements reveal the high structural stability of the nickel sulfide–RGO composite powders during cycling.

A novel anode material for sodium-ion batteries consisting of 3D graphene microspheres divided into several tens of uniform nanospheres coated with few-layered MoS2 by a one-pot spray pyrolysis process is prepared. The first discharge/charge capacities of the composite microspheres are 797 and 573 mA h g−1 at a current density of 0.2 A g−1. The 600th discharge capacity of the composite microspheres at a current density of 1.5 A g−1 is 322 mA h g−1. The Coulombic efficiency during the 600 cycles is as high as 99.98%. The outstanding Na ion storage properties of the 3D MoS2–graphene composite microspheres may be attributed to the reduced stacking of the MoS2 layers and to the 3D structure of the porous graphene microspheres. The reduced stacking of the MoS2 layers relaxes the strain and lowers the barrier for Na+ insertion. The empty nanospheres of the graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling.

We report a new process to prepare VO2(R)-carbon composite microspheres, which can be used as an anode material in lithium ion batteries. Crystalline V2O3-carbon composite microspheres prepared by a one-pot spray pyrolysis process are transformed into VO2(R)-carbon composite microspheres by heat treatment at 300 °C under air atmosphere. Polyvinylpyrrolidone (PVP), which is used as the carbon source, affects the morphologies, crystal structures, and electrochemical properties of the vanadium oxide materials. The carbon content of the VO2(R)-carbon composite powders is about 12.5 wt%. The bare vanadium oxide powders prepared from the spray solution without PVP show rod-like or spherical morphologies. The initial discharge and charge capacities of the VO2(R)-carbon composite powders are 1091 and 659 mA h g−1, respectively. The discharge capacity of the VO2(R)-carbon composite powders after 100 cycles is 637 mA h g−1 and their capacity retention after 100 cycles measured from the second cycle is 96.0%. The high structural stability encountered during lithium insertion and extraction improves the electrochemical properties of the VO2(R)-carbon composite powders.

One-pot method for metal oxide-carbon composite microsphere with three-dimensional ordered macroporous (3DOM) structure is first introduced. The 3DOM structured SnO2 -carbon microspheres prepared as the first target material show superior electrochemical properties as anode material for lithium ion batteries. The newly developed process can be applied to the preparation of 3DOM-structured metal oxide-carbon composite microspheres for wide applications.

An ultraselective and ultrasensitive trimethylamine (TMA) sensor was achieved using MoO 3 nanoplates-prepared by ultrasonic spray pyrolysis followed by a heat treatment at 450 °C. The small and thin MoO 3 nanoplates with gas-accessible structures showed an unusually high response to 5 ppm TMA (ratio of resistance to air and gas = 373.74) at 300 °C with detection limit as low as 45 ppb. Moreover, the ratios of the cross-responses to interfering gases (i.e., 5 ppm C 2 H 5 OH, CO, CH 4 , C 3 H 8 , H 2 , and NO 2 ) to the response to 5 ppm TMA were extremely low (0.008–0.016). The source of the ultraselective and highly sensitive detection of TMA with negligible interference from other gases is discussed with respect to the acid/base properties, size, and morphology of the MoO 3 sensing materials.

Yolk-shell MoO3 microspheres are prepared by a two-step process in which molybdenum oxide-carbon (MoO(x)-C) composite microspheres are first obtained by spray pyrolysis, followed by combustion at 400 °C in air. The yolk-shell microspheres exhibit excellent electrochemical properties and structural stability.

We review the effect that various structures and composites synthesized by spray pyrolysis have on the electrochemical performance of next-generation electrodes for medium and large lithium ion batteries. The morphologies of electrode particles in particular have a strong influence on the capacity, power, safety, and cycle life. Recent progress in improving the electrochemical performance of electrodes is provided with a particular focus on electrodes composed of nanoparticles, core–shell or yolk–shell structures, and carbon-based composites. Finally, we propose a direction for future research for high-performance lithium ion batteries incorporating fabrication by spray pyrolysis.

Pure LiCoO2 nanopowders and those coated with lithium boron oxide (LBO) glass are prepared directly using high-temperature flame spray pyrolysis. Prior to post-treatment, the LiCoO2 powders with nanometer-size particles have low discharge capacities and poor cycle properties, irrespective of the amount of glass material. Post-treatment at 500 °C does not improve these properties significantly; however, the LBO glass-modified LiCoO2 powders post-treated at 600 and 700 °C demonstrates good cycle performance. The discharge capacity of the 5 wt% glass-modified LiCoO2 powders post-treated at 600 °C with a mean particle size of 120 nm, decreases from 122 to 109 mAh g−1 after 50 cycles, with a capacity retention of 89%. The capacity retentions of the pure and 2, 5, and 10 wt% glass-modified LiCoO2 powders post-treated at 700 °C are 86, 96, 98, and 98% after 50 cycles, respectively.

Li2TiO3–LiCrO2 cathode powders of various compositions are prepared by spray pyrolysis. Pure Li2TiO3 powder and Li2TiO3–LiCrO2 composite cathode powder have a spherical shape, nonaggregated structure, and fine sizes even after post-treatment at 700 °C under nitrogen atmosphere. The optimum post-treatment temperature to obtain composite powders with high initial discharge capacity, high coulombic efficiency, and good cycle properties is 700 °C. The initial charge capacities increase when the LiCrO2 content of the composite increase. However, the 0.55Li2TiO3–0.45LiCrO2 composite cathode powders have the highest initial discharge capacity of 203 mAh g−1, in which the capacity retention after 30 cycles is 96%. The dQ/dV curve of the first charge curve has a distinct oxidation peak at approximately 3.9 V, which corresponds to Cr oxidation. The oxidation peak shifts to a lower voltage range at approximately 3.6 V after the first cycling because an irreversible reaction takes place in the initial charge process. The composite cathode powders with low LiCrO2 content have low initial charge/discharge capacities and good cycle properties because of the stabilizing effect of high amounts of an inactive Li2TiO3 component.

In this study, we report the first preparation of phase-pure Co9S8 yolk–shell microspheres in a facile two-step process and their improved electrochemical properties. Yolk–shell Co3O4 precursor microspheres are initially obtained by spray pyrolysis and are subsequently transformed into Co9S8 yolk–shell microspheres by simple sulfidation in the presence of thiourea as a sulfur source at 350 °C under a reducing atmosphere. For comparison, filled Co9S8 microspheres were also prepared using the same procedure but in the absence of sucrose during the spray pyrolysis. The prepared yolk–shell Co9S8 microspheres exhibited a Brunauer–Emmett–Teller (BET) specific surface area of 18 m(2) g(−1) with a mean pore size of 16 nm. The yolk–shell Co9S8 microspheres have initial discharge and charge capacities of 1008 and 767 mA h g(−1) at a current density of 1000 mA g(−1), respectively, while the filled Co9S8 microspheres have initial discharge and charge capacities of 838 and 638 mA h g(−1), respectively. After 100 cycles, the discharge capacities of the yolk–shell and filled microspheres are 634 and 434 mA h g(−1), respectively, and the corresponding capacity retentions after the first cycle are 82% and 66%.

This paper introduces a facile one-pot method for synthesizing a new structured material, named "ant-cave microball", by continuous ultrasonic spray pyrolysis. The ant-cave-structured microballs are prepared from a colloidal spray solution with polystyrene nanobeads and sucrose. Networking between the nanovoids formed by decomposition of the polystyrene nanobeads results in the formation of nanochannels. The electrochemical properties of these ant-cave-structured MoO3-C microballs, prepared as the first target material for lithium ion batteries, are investigated. The nanochannels are uniformly distributed inside the microballs with MoO3 and carbon components uniformly distributed within the microballs. Further, the microballs have initial discharge and charge capacities of 1212 and 841 mA h g(-1), respectively, at a current density of 2 A g(-1), and the initial discharge and charge capacities based on the weight of MoO3 (disregarding carbon component) are as high as 1814 and 1259 mA h g(-1). The microballs deliver a high discharge capacity of 733 mA h g(-1) even after 300 cycles. This is although microsized MoO3 powders with a filled structure have discharge capacities of 1256 and 345 mA h g(-1) for the first and 300th cycles, respectively.

The preparation of precursors of BaTiO3 nanopowders with various amounts of Ag by spray pyrolysis is reported. The precursor powders obtained with hollow and thin-wall particles are composed of uniformly dispersed Ba, Ti, and Ag components. After post-treatment and a simple milling process, the precursor powders, irrespective of the amount of Ag, are transformed into Ag–BaTiO3 composite nanoparticles. The mean particle size of the Ag (10 mol%)–BaTiO3 powders is 142 nm. BaTiO3 pellets containing Ag exhibit dense structures even at a low sintering temperature of 1000 °C. BaTiO3 pellets with 10 mol% Ag show the highest dielectric constant of 2950, as opposed to the pure BaTiO3 pellets (without Ag), whose dielectric constant is 1827.

Core–shell-structure Ag–BaTiO3 composite nanopowders are prepared directly by flame spray pyrolysis. The single-crystalline Ag was located in the core part of the composite powder, and the Ba and Ti components are uniformly distributed in the shell part. The X-ray diffraction (XRD) patterns of the Ag–BaTiO3 composite powders have the main crystal peaks of Ag and broad peaks at around 28°. The Ag–BaTiO3 pellets with low Ag contents (below 20 wt%) have a dense structure and fine grain size. Abnormal grain growth of the Ag(30 wt%)–BaTiO3 pellets occurs even at a low sintering temperature of 1000 °C. The Ag–BaTiO3 pellet had a mixed crystal structure of BaTiO3 and Ag phases. Silver is uniformly distributed in the BaTiO3 matrix without phase separation. The dielectric constants of the BaTiO3, Ag(10 wt%)–BaTiO3, and Ag(30 wt%)–BaTiO3 pellets are 830, 2130, and 4680, respectively.

Spherically shaped vanadium pentoxide (V 2 O 5 ) cathode powders with porous or dense morphologies are prepared directly via spray pyrolysis by varying the preparation temperatures between 600 and 1000 °C. The powders prepared at 600 °C consist of nanometer-sized rod-shaped crystals with porous structures. The V 2 O 5 powders prepared at 1000 °C have spherical shapes, clean surfaces, and dense structures, because of complete melting of the powders that occurs inside the hot-wall reactor. The Brunauer–Emmett–Teller (BET) surface areas of the V 2 O 5 powders decrease from 24.7 to 3.2 m 2 g −1 when the preparation temperature increases from 600 to 1000 °C. The V 2 O 5 powders prepared at 1000 °C have better cycle properties than those prepared at 600 and 800 °C. The discharge capacity of the V 2 O 5 powders prepared at 1000 °C decreases from 432 mAh g −1 to 263 mAh g −1 after 20 cycles, in which the capacity retention is 61%.

Li 2 O–2B 2 O 3 glass-modified LiMn 2 O 4 cathode powders are prepared using spray pyrolysis. The powders with 1 and 5 wt% glass material have a spherical shape, dense structure, and large grain size. The BET surface areas of LiMn 2 O 4 powders with 0 and 1 wt% glass material are 15.0 and 5.9 m 2 g −1 , and their mean crystallite sizes are 29 and 49 nm. The lithium boron oxide (LBO) glass material improves the cycle properties as well as the initial discharge capacities of the LiMn 2 O 4 powders at a constant current density of 1 C. The discharge capacity of LiMn 2 O 4 powders without any glass material decreases from 116.3 to 92.6 mAh g −1 after 100 cycles, the reduced capacity being 80% of the initial capacity. However, the discharge capacity of the LiMn 2 O 4 powders with 1 wt% glass material decreases from 131.0 to 113.2 mAh g −1 after 100 cycles; thus, the capacity retention is 86% of the initial capacity.

Nano-sized Ba 0.7 Sr 0.3 TiO 3 powders are prepared by post-treatment of the precursor powders with hollow and thin wall structure at temperatures between 900 and 1100 °C. Ethylenediaminetetraacetic acid and citric acid improve the hollowness of the precursor powders prepared by spray pyrolysis. The mean sizes of the powders post-treated at temperatures of 900, 1000 and 1100 °C are 42, 51 and 66 nm, respectively. The densities of the Ba 0.7 Sr 0.3 TiO 3 pellets obtained from the powders post-treated at 900, 1000 and 1100 °C are each 5.36, 5.55 and 5.38 g cm −3 at a sintering temperature of 1300 °C. The pellet obtained from the powders post-treated at 1000 °C has higher maximum dielectric constant than those obtained from the powders post-treated at 900 and 1100 °C.

Fe powders as the heat pellet material for thermal batteries are prepared from iron oxide powders obtained by spray pyrolysis from a spray solution of iron nitrate with ethylene glycol. The iron oxide powders with hollow and thin wall structure produce Fe powders with elongated structure and fine primary particle size at a low reducing temperature of 615 °C. The mean size of the primary Fe powders with elongated structure decreases with increasing concentration of ethylene glycol dissolved into the spray solution. The heat pellets prepared from the fine-size Fe powders with elongated structure have good ignition sensitivities below 1 watt. The heat pellets formed from the Fe powders obtained from the spray solution with 0.5 M EG have an extremely high burn rate of 26 cms−1.

Nanosized LiCrO 2 ·Li 2 MnO 3 composite powders are prepared by a new concept spray pyrolysis. The precursor and post-treated powders have a Li 2 CrO 4 impurity introduced by the partial oxidation of LiCrO 2 . The powders have a pure layered structure corresponding to the LiCrO 2 ·Li 2 MnO 3 composite after Li 2 CrO 4 is removed by washing with distilled water. The real composition of the washed cathode powders is Li 1.18 Cr 0.404 Mn 0.477 O 2 . The aggregated post-treated powders are converted into nanosized powders after washing with distilled water; milling is not required for this conversion. The mean size of the nanosized LiCrO 2 ·Li 2 MnO 3 powders is 48 nm. The LiCrO 2 ·Li 2 MnO 3 cathode sample post-treated at 750 °C has initial charge and discharge capacities of 272 and 233 mAh g −1 at a constant current density of 18 mA g −1 , respectively. The discharge capacity of the cathode sample post-treated at 750 °C decreases from 233 to 222 mAh g −1 by the 44th cycle, in which the capacity retention is 95%.

Nano-sized LiNi1/3Co1/3Mn1/3O2 powders in the range from 56 to 101 nm with hexagonal α-NaFeO2 structures are prepared directly by flame spray pyrolysis. Post-treatment of the powders at 700 °C increases their crystallinity and mean particle sizes. The intensity ratios of the powders’ (0 0 3) and (1 0 4) peaks in the XRD patterns prepared from spray solutions with lithium excesses of 10, 15 and 20% of the stoichiometric amount are 0.83, 1.25 and 1.25, respectively. The powder prepared with 15% excess lithium results in the highest initial discharge capacity of 174 mAh g−1 when post-treated at 700 °C. The discharge capacity of the powder post-treated at 800 °C decreases from 168 to 120 mAh g−1 after 30 cycles.

Pure and Ag-doped BaTiO 3 nanopowders were prepared by spray pyrolysis. Precursor powders, prepared from a spray solution with citric acid and ethylenediaminetetraacetic acid (EDTA) as chelating agents, had large, hollow particles irrespective of Ag doping. Both pure and Ag-doped powders had partially aggregated particles after post-treatment at 900 °C that could be easily milled to nanoparticles. The mean sizes of the pure and Ag-doped BaTiO 3 particles were 75 and 91 nm, respectively. The Ag-doped particles were mainly of cubic BaTiO 3 crystal structure, with small Ag phases observed. High-density BaTiO 3 pellets were formed by sintering the powders at the low temperature of 1000 °C. The silver was uniformly distributed in a tetragonal BaTiO 3 phase without phase separation in the doped pellet. The dielectric constants of the pellets formed from the pure and Ag-doped BaTiO 3 powders were 1826 and 2400, respectively.

Spherical BaTiO3-coated Ag powders with dense structures were directly prepared by spray pyrolysis. Ag powder with 1 wt % BaTiO3 has particles of 0.53 µm mean diameter. BaTiO3 had good properties for coating Ag powders: it decreased the sintering of the Ag powder at temperatures between 700 and 900°C. Complete melting of pure Ag powder, forming dense Ag thick film, occurred at 700°C. Whereas at this temperature, partial melting of the 1 wt % BaTiO3-coated Ag powder occurred, forming Ag thick film with a porous structure. The pure Ag thick film shrunk 45% at 900°C. However, the thick films formed from 1 and 5 wt % BaTiO3-coated Ag powder had respective shrinkages of 31 and 21%, respectively at 900°C. The sheet resistances of the Ag thick films formed from the 1 wt % BaTiO3-coated Ag powder were 7.54, 4.93 and 4.09 m Ω/sq at firing temperatures of 700, 800 and 900°C, respectively.

Li 3 V 2 (PO 4 ) 3 /C nanoparticles are prepared by spray pyrolysis. Particles formed from spray solutions containing citric acid and ethylenediaminetetraacetic acid (EDTA) as chelating agents are large and hollow with thin walls. The optimum concentrations of citric acid and EDTA are each 0.1 M. Powders subsequently treated at 700 °C under a reducing atmosphere have particles of single phase, monoclinic Li 3 V 2 (PO 4 ) 3 . The Li 3 V 2 (PO 4 ) 3 /C powders contains 14.9 wt% carbon. The hollow structures are easily pulverized into nanoparticles by simple milling process. However, Li 3 V 2 (PO 4 ) 3 powder formed from spray solution without chelating agent has larger, aggregated structures. Both powders’ charge curves show four plateaus at ca. 3.62, 3.70, 4.08 and 4.55 V. The initial discharge capacities of the Li 3 V 2 (PO 4 ) 3 /C powders at constant current densities of 0.1, 1 and 3 C were 147, 122 and 86 mAh g −1 , respectively. The capacity retention of the Li 3 V 2 (PO 4 ) 3 /C nanoparticles at a high current density of 1 C after 100th cycle was 78%.

Nano-sized BaNd2Ti5O14 (BNT) powders were prepared by spray pyrolysis from solutions containing ethylenediaminetetraacetic acid and citric acid. Treatment at temperatures ≥900 °C and subsequent milling resulted in nanoparticle powders with orthorhombic crystal structures. The mean particle size of the powder post-treated at 1000 °C was 160 nm. Nano-sized Bi2O3–B2O3–ZnO–SiO2 glass powder with 33 nm average particle size was prepared by flame spray pyrolysis and used as a sintering agent for the BNT. BNT pellets sintered at 1100 °C without the glass had porous structures and fine grain sizes. Those similarly sintered with the glass had denser structures and larger grains.

Nanometer AlN powders were prepared by combining spray pyrolysis with carbothermal reduction and nitridation (CRN). The aluminum oxide/carbon composite powders prepared by spray pyrolysis from a sucrose spray solution were several microns in size, with hollow and porous structures. Precursor powder with 67 wt% carbon content was transformed into phase-pure AlN powder by CRN at temperatures above 1,400 °C. The hollow-structured AlN powder was ground to 20 nm mean size by simple milling.

Li3V2(PO4)3 and Li3V2(PO4)3/C powders are prepared by ultrasonic spray pyrolysis from spray solutions with and without sucrose. The precursor powders have a spherical shape and the crystal structure of V2O3 irrespective of the concentration of sucrose in the spray solution. The powders post-treated at 700 °C have the pure crystal structure of the Li3V2(PO4)3 phase irrespective of the concentration of sucrose in the spray solution. The Li3V2(PO4)3 powders prepared from the spray solution without sucrose have a non-spherical shape and hard aggregation. However, the Li3V2(PO4)3/C powders prepared from the spray solution with sucrose have a spherical shape and non-aggregation characteristics. The Li3V2(PO4)3 powders prepared from the spray solution without sucrose have a low initial discharge capacity of 122 mAh g−1. However, the Li3V2(PO4)3/C powders prepared from the spray solutions with 0.1, 0.3, and 0.5 M sucrose have initial discharge capacities of 141, 130, and 138 mAh g−1, respectively. After 25 cycles, the discharge capacities of the powders formed from the spray solutions with and without 0.1 M sucrose are 70% and 71% of the initial discharge capacities, respectively.

ZnO–B2O3–SiO2–CaO glass frits were directly prepared by high temperature spray pyrolysis for use in Cu electrodes. The frits prepared at temperatures above 1400 °C were spherical, amorphous, of fine size and dense structure. The mean particle size and geometric standard deviation of the frits prepared at 1400 °C were 0.87 μm and 1.37, respectively. The temperatures of glass transition, crystallization and melting were 454, 534 and 800 °C, respectively. The glass layer fired at 800 °C had a dense structure due to the material's complete melting, despite some crystals being observed by SEM. A copper electrode formed from copper paste with glass frits had a dense structure when fired at 800 °C. The specific resistances of electrodes formed from copper paste with and without glass frits were 2.5 and 8.5 μΩ cm, respectively.

Nanosized BaO–B 2 O 3 –SiO 2 glass powders are directly prepared by flame spray pyrolysis. The mean size of the BaO–B 2 O 3 –SiO 2 glass powders with amorphous phase and spherical shape is 30 nm. The effects of glass powders on the sintering characteristics of the BaTiO 3 pellet formed from the nanosized BaTiO 3 powders are investigated. The mean size and BET surface area of the BaTiO 3 powders prepared by spray pyrolysis are 110 nm and 9.1 m 2 /g. The BaTiO 3 pellet with glass additive has large grain size with several microns, dense structure and pure tetragonal crystal structure at a sintering temperature of 1000 °C. The XRD pattern of the pellet has distinct split of (2 0 0) and (0 0 2) peaks at 2 θ ≈ 44.95°. The dielectric constant of the pellet without glass additive is 2180. However, the dielectric constants of the pellets with 1, 3, 5 and 7 wt% glass additive with respect to BaTiO 3 are 2496, 2514, 2700 and 2225, respectively.

Pb-free glass frits prepared by spray pyrolysis for Al electrodes were of fine size, spherical morphology and dense structure. Their mean size and geometric standard deviation when prepared at 1,200 °C were 1.0 μm and 1.4, respectively. Their glass transition temperature ( T g ) was 374 °C. An Al electrode formed from Al paste with glass frits had a dense structure and good adhesion to the Si substrate. It had a well-developed back-surface field layer of 17.5 μm thickness. Al electrodes formed from Al paste without glass frits had sheet resistances between 21 and 32 mΩ sq −1 as the firing temperature changed from 600 to 900 °C. This compared with values from electrodes formed with frits that decreased from 20 to 7 mΩ sq −1 over the same range of firing temperatures.

The characteristics of silver-glass composite powders directly prepared by spray pyrolysis from spray solutions with different precursor types of Pb, Si and Ti components were investigated. The composite powders had spherical shape and submicron size irrespective of precursor types of glass material and glass content of the powders. The silver conducting films formed from the composite powders had dense structures irrespective of precursor types of glass material and glass content of the powders. The silver conducting film formed from the composite powders obtained from the spray solution with fumed titania as the source material of the Ti component had the lowest sheet resistance of 2.8 mΩ/sq. The sheet resistances of the silver conducting films changed from 2.8 mΩ/sq to 3.7 mΩ/sq according to the glass content of the composite powders at a firing temperature of 700 °C.

LiMn2O4 powders have been directly prepared by flame spray pyrolysis from an aqueous spray solution of the metal salts. The powders prepared at a low fuel gas flow rate (3 L min−1) comprise particles with a bimodal size distribution, i.e., submicron- and nanometer-sized particles, and have crystal structures of LiMn2O4 and Mn3O4 phases. However, the powders prepared at a high fuel gas flow rate (5 L min−1) comprise nanometer-sized particles and have pure crystal structure of LiMn2O4 phase. The powders comprising nanosized particles are well crystallized, and the particles have a polyhedral structure. The mean particle size of these powders is 27 nm. The powders prepared directly by flame spray pyrolysis comprise nanosized particles and have the pure crystal structure of LiMn2O4, irrespective of the amount of excess lithium in the precursor solution. The initial discharge capacities of these powders increase from 91 to 112 mAh g−1 when the amount of excess lithium is increased from 0% to 30% of the stoichiometric amount. The optimum amount of excess lithium required to prepare LiMn2O4 powders with nanosized particles and the maximum possible initial discharge capacity is 10%.

Bi-based glass powders with particle size of 34 nm were prepared by high-temperature flame spray pyrolysis. The glass transition temperature (Tg) of the powders was 442 °C. Dielectric layers fired at temperatures of 480 and 500 °C contained voids, while those fired at temperatures above 540 °C had clean surfaces and no voids. The dielectric layers sintered at temperatures of 560 and 580 °C had transmittances of 70% in the visible range. Further, it was observed that the dielectric layers formed from the nanosized glass powders obtained from spray solutions containing excess boron had higher transmittances (80% in the visible range at a sintering temperature of 580 °C) than the layers formed from spray solutions containing stoichiometric amounts of boron.

Ag–Pd (85:15) alloy and Ag–Pd–glass composite powders comprising spherical particles with dense structures were prepared directly by spray pyrolysis at 1100 °C. The mean sizes of the Ag–Pd alloy and Ag–Pd–glass composite powders were 1.1 and 0.9 μm, respectively, and the crystal phases of the Ag–Pd and Ag–Pd–glass composite powders had alloy compositions. Ag–Pd conductive films formed from the Ag–Pd–glass composite powders had a denser structure than did those formed from the Ag–Pd alloy powders. The shrinkage of the conductive films formed from the Ag–Pd–glass composite powders was 25.9% and 58.6% at firing temperatures of 550 °C and 800 °C, respectively. The specific resistances of the conductive films formed from the Ag–Pd–glass composite powders were found to be as low as 12.7 μΩ cm and 4.9 μΩ cm at firing temperatures of 550 °C and 800 °C, respectively.

Size-controlled silver-glass composite powders with nanometer sizes were directly prepared by high-temperature flame spray pyrolysis. The mean size of the composite powders is changed from 45 to 75 nm by controlling the concentrations of the spray solution. Nanosized composite powders are prepared from the spray solution of 0.1 M at a high flow rate of carrier gas as 20 L min − 1 . However, nanosized composite powders are prepared from the spray solution of 3 M at a low flow rate of carrier gas as 5 L min − 1 . The nanosized composite powders have good firing characteristics at 450 °C. The sheet resistance of the silver conducting film formed from the pure silver powders is 30 mΩ/sq. The silver conducting films formed from the composite powders obtained from the spray solutions with concentrations above 0.5 M have lower sheet resistances than that obtained from the pure silver powders. The minimum sheet resistance formed from the composite powders obtained from the spray solution of 0.5 M is as low as 16 mΩ/sq.