In the past decade, a wide variety of ZnO crystals were prepared through wet chemical processing. However, the fundamentals of the nanoscale morphological variation of ZnO crystals on the crystal growth in aqueous solution systems have not been sufficiently studied. This paper is a review of the various morphologies of ZnO crystals in relation to the preparation conditions, including the source chemicals, the role of seeds or substrates, and the presence of organic molecules as a shape modifier. Versatile guidelines for controlling the nanoscaled morphologies of ZnO crystals in the forms of individual particles and films as assembly of nanocrystals are proposed on the basis of the classification of typical phenomena. The essential parameters, such as the growth rate, growth site, and growth direction of ZnO crystals, are successfully tuned by varying the degree of supersaturation, the presence of seeds or substrates, and the addition of specific organic molecules, respectively.

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The relation of applied pressure–height of piston during pressure filtration was measured for aqueous 7 vol % suspensions of positively charged 150 nm alumina particles at 0.2 mm/min of crosshead speed of piston. Application of alternating current field in the frequency range from 0.01 to 1000 Hz at 10 V accelerated the colloidal phase transition from dispersed to flocculated suspension, and decreased the consolidation pressure. The characteristics of the flocculated suspension with decreasing suspension height was analyzed based on the viscoelastic models (Maxwell and Voigt models). The flocculated suspension behaved as a liquid like at a low particle concentration in both the models. The applied pressure was related to the product of viscosity of liquid element and crosshead speed of Voigt model. The influence of solid element of Voigt model became stronger with decreasing suspension height (increasing solid content of the flocculated suspension). The applied pressure was proportional to the Young’s modulus of solid element in the final region of filtration.

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High purity, multi-walled carbon nanotubes (MWNTs) were synthesized by catalytic chemical vapor deposition (CCVD) using acetylene as the carbon source based on a zeolite NaX template loaded with different iron contents. Well shaped zeolite NaX nanocrystals (FAU) of 50 nm were synthesized by a hydrothermal method according to a well designed composition of 3.5Na₂O:Al₂O₃:2.1SiO₂:1000H₂O. The ion-exchange method was used for supporting different Fe²⁺ contents in the zeolite NaX nanocrystals to provide effective catalysts for carbon nanotube (CNT) formation. Thermal treatment of Fe²⁺-exchanged zeolite NaX nanocrystals resulted in the formation of α-Fe₂O₃ phase at 450°C in air. Transmission electron microscopy (TEM) images showed that the inner and outer tube diameters of the MWNTs were in the range of 3.8–5.0 nm and 6.3–8.8 nm, respectively, which were smaller than those of conventional thick MWNTs. The yield of the MWNTs was increased up to 47.1% with increasing iron content in pores of the zeolite crystals, which allowed the pores to be defined as containers for catalysts and as a guide template for MWNT growth.

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Chitosan–γ-glycidoxypropyltrimethoxysilane (GPTMS)–tetraethoxysilane (TEOS) hybrid membranes were prepared by the sol–gel method. The effects of Si(IV) released from them on cell proliferation and differentiation were examined in terms of cell metabolic activity and the alkaline phosphatase (ALP) activity of MG63 osteoblastic cells. The amount of Si(IV) released from the hybrid membranes increased with the TEOS content. The released Si(IV) inhibited cell proliferation but promoted cell differentiation. Thus, the osteocompatibility of the chitosan hybrid membranes in the chitosan–GPTMS–TEOS system can be controlled by the amount of Si(IV) released from them when they are applied to cell culture.

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The effect of doping a wide range of transition metals (TMs) including V, Cr, Mn, Fe, Co, and Ni into rutile TiO₂ films grown on Nb-doped TiO₂(110) single-crystal substrates was investigated by photoemission spectroscopy and X-ray absorption spectroscopy. For all TM-doped TiO₂ films, the Ti 2p and O 1s core levels were similarly shifted to lower binding energies with increasing film thickness and the shifts were similarly saturated at a film thickness of about 15 nm. These peak shifts could be interpreted in terms of the Fermi level shift, indicating that dopants trap excess electrons from the Ti 3d band like acceptors. The present systematic data revealed that the magnitude of the saturated Fermi level shift correlates well with the effective charge transfer energy.

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Dense ZrB₂–SiC and HfB₂–SiC composites were fabricated at 1800°C by spark plasma sintering (SPS) using TaSi₂ as sintering aid. The volume content of SiC was 5–30% and that of TaSi₂ was 5% in the initial compositions. The additive of TaSi₂ contributed to the densification of composites by the decomposition and simultaneous solid solution of Ta atoms into boride grains which was probably associated with the decrease of activation energy of boride grain boundaries. With increasing SiC content, the electrical conductivity of ZrB₂–SiC and HfB₂–SiC composites decreased from 19.89 to 11.99 and 22.29 to 13.42 × 10⁵ Ω⁻¹·m⁻¹ respectively. Generally, the thermal conductivity of composites showed an increasing tendency with increasing SiC content, indicating the maximum values of 49.93 and 118.39 W/m·K respectively for ZrB₂–SiC and HfB₂–SiC composites produced with 30 vol % SiC content in the initial compositions. Additionally, the Vickers hardness of composites increased with the increment of SiC content from 16.9 to 20.2 and 24.0 to 28.5 GPa for ZrB₂–SiC and HfB₂–SiC composites respectively. The fracture toughness of ZrB₂–SiC composites showed an increasing tendency from 3.70 to 4.44 MPa·m^1/2 with increasing SiC content while those of HfB₂–SiC composites did not show a changing tendency and was in a range of 3.28–3.54 MPa·m^1/2. The elastic moduli of composites declined from 464.8 to 453.2 and 494.4 to 481.9 GPa for ZrB₂–SiC and HfB₂–SiC composites respectively with increasing SiC content.

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Facile synthesis and size control of Ag nanoparticles by a photochemical reduction was demonstrated. UV–visible spectra and photographs of the synthesized solutions with and without sodium citrate at different UV exposure times showed that sodium citrate played a crucial role for the growth of Ag nanoparticles. According to UV exposure of the Ag colloidal solutions with 0.250 mM sodium citrate for 0, 7, 15, 30, and 60 min, the average particle sizes were 0, 2.45, 5.58, 7.03, and 11.08 nm, respectively. Ag nanoparticles exhibited great increase in sizes, from 5.71 to 36.43 nm after UV exposure for 60 min, as the sodium citrate concentration increased from 0.125 to 0.500 mM. The photochemical reduction is hypothesized to decompose of citrate ions and result from photoelectron transfer from the neutral Ag atoms to the Ag⁺ ions to form Ag nanoparticles. These results suggest that the photochemical reduction method can provide Ag nanoparticles in the presence of sodium citrate at room temperature without using a reducing agent.

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Diamond:fullerene nanocomposite thin films were fabricated, and the photovoltaic properties were investigated. C₆₀ and diamond were used as n-type and p-type semiconductors, respectively, and the nanostructures of the thin films were investigated by transmission electron microscopy and X-ray diffraction. Energy levels of the clusters were calculated by molecular orbital calculations, and the nanostructure and electronic property were discussed.

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Ag nanoparticles and multi-wall carbon nanotubes (MWNTs) were incorporated into a SnO₂ photosensitive precursor solution, and a direct-patternable film was prepared by photochemical metal-organic deposition. SnO₂ film transmittance and crystallinity were slightly reduced by light absorption of Ag nanoparticles and light scattering by MWNTs. In the case of mixed incorporation of Ag nanoparticles and MWNTs, the sheet resistance of SnO₂ hybrid films was decreased relative to incorporation of either single material. Direct-patterning of SnO₂ hybrid films was performed without photoresist or dry etching. These results suggest that a micro-patterned system can be simply fabricated at a low cost, and the electrical properties of SnO₂ films can be improved by incorporating Ag nanoparticles with MWNTs.

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In this study, we fabricated the n-channel metal-ferroelectric-insulator-semiconductor field effect transistors (MFIS-FETs) using an Au/polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE)/ZrO₂/Si(100) structures. The ZrO₂ thin film had the equivalent oxide thickness (EOT) value of around 9 nm. And the P(VDF-TrFE) film on a ZrO₂/Si structure showed good ferroelectric property with memory window width of 2.5 V for a bias voltage sweeping of ±7 V. The leakage current density of this MFIS structure showed very excellent insulation property with about 9 × 10⁻⁸ A/cm² at 5 V. Based on these results, we fabricated and investigated MFIS-FETs with ferroelectric polymer P(VDF-TrFE) film and ZrO₂ buffer layer. The memory window width and on/off ratio of the MFIS-FET was about 4.5 V and 10³, respectively. These results predicted that the P(VDF-TrFE) thin film would be useful for the realization of 1-transistor type ferroelectric memory.

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Ferroelectric materials are of interest due to their applications, such as in ferroelectric field effect transistor memory (FeFET). For this application, reducing retention time according to the leakage current is an important matter. Ferroelectric materials are able to be improved through multilayer fabrication of ferroelectric films. This study investigated multilayer ferroelectric thin films using strong candidate ferroelectric materials such as Bi_3.25La_0.75Ti₃O₁₂ (BLT) and Nd₂Ti₂O₇ (NT). The ferroelectric materials were prepared with a stable interface using broad stoichiometry, without occurrence of a secondary phase or a disruption in stoichiometry. For the characterization of BLT, NT, and BLT/NT multilayer ferroelectric films, various analyses and measurements were carried out, including X-ray diffraction, X-ray photoelectron spectroscopy, current–voltage and polarization–voltage. The multilayer ferroelectric films showed improved ferroelectric properties using multilayer fabrication with a highly insulating ferroelectric film.

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Cupric oxide (CuO) thin films were prepared and their microstructures and photovoltaic properties were investigated. Thin film devices based on the CuO/C₆₀ heterojunction structure were fabricated on F-doped SnO₂ by spin-coating, and displayed photovoltaic activity under AM1.5 simulated sunlight conditions. The CuO thin film microstructure was examined using X-ray diffraction and transmission electron microscopy, which indicated the presence of CuO nanoparticles of size 10–30 nm. The energy levels for the solar cell and its constituent components were also discussed.

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The formation of BiFeO₃ without impurity phases, such as excess bismuth and iron, has been possible in only a narrow pressure-temperature-stoichiometric window. A direct-patterned BiFeO₃ film using photochemical metal-organic deposition (PMOD) was fabricated without a conventional etching. BiFeO₃ film was formed on a SrTiO₃ buffer layer with a perovskite structure and a lattice constant of 3.905 Å in order to study the substrate effect during phase formation. This study showed the phase formation and electrical properties of the direct-patternable PMOD BiFeO₃ thin films. The SrTiO₃ buffer layer was found to somewhat prevent the formation of a Fe excess phase in BiFeO₃ after anneal at 550°C for 20 min under O₂ and N₂ atmospheres. The measured remnant polarization (P_r) and coercive field (E_c) values of the Pt/BiFeO₃(200 nm)/SrTiO₃(40 nm)/Pt/Si structure were 10 µC/cm² and 300 kV/cm, respectively. Leakage current of perovskite BiFeO₃ film was found to be dominated by Poole–Frenkel emission as other perovskite ferroelectrics. To obtain an image, a spin-coated BiFeO₃ film was exposed to UV for 15 min and then rinsed in hexane. From this work, it was revealed that the direct-patterning of BiFeO₃ films could be applicable for the fabrication of micro-patterned systems using a SrTiO₃ buffer layer with controlled reactant stoichiometry.

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Influence of SiC composition with different particle size on mechanical properties and microstructure of reaction-bonded SiC have been investigated using infiltration process of liquid Si. SiC specimens were prepared by reaction-bonding sintering at 1620°C in vacuum using different SiC–C composition. Reaction-bonded SiC specimens show dense with 3.0–3.05 gr/cm³ of density. SiC specimens with bi-modal SiC composition show a fine microstructure than those of uni-modal SiC composition. In addition, in the specimens with bi-modal SiC composition, the microstructure of the sample with use of fine SiC starting powders is finer rather than those of use of relatively coarse SiC starting powders. The flexural strength and fracture toughness of specimens with bi-modal SiC composition are higher than those of uni-modal SiC composition. The main fracture mode of specimens with a high strength is intergranular fracture.

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A textured alumina was fabricated from anisotropic α-alumina particles (platelets) by heating at 1650°C for 15 min under applied pressure of 60 MPa using a PECS (Pulse Electric Current Sintering) technique. Subsequently, the thermal conductivity, mechanical properties and dielectric breakdown of the textured alumina were evaluated, are compared to those of conventional polycrystalline alumina and single crystal alumina. The results showed that the thermal conductivity of the textured alumina could be to exhibit almost the same dielectric breakdown as the conventional alumina, that is, the dielectric breakdown was 15 kV/mm and thermal conductivity was 36 W/mK, when the alumina was cut on the vertical plane in the load direction while sintering.

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10 mol % Sc₂O₃-stabilized ZrO₂ (10ScSZ) was sintered by several processes including spark plasma sintering, milliwave sintering and conventional sintering. The electrical conductivity of the sintered 10ScSZ samples was obtained by AC impedance spectra, and compared with grain size and the crystal phase. As average grain size decreased, the electrical conductivities decreased and increased at temperatures higher and lower than the phase transition point, respectively. These trends suggested that the fraction of a low conductivity rhombohedral phase increases with increasing grain size at a temperature lower than the phase transition point, and that the total thickness of the grain boundary affects the electrical conductivity at a temperature higher than the phase transition point.

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Zeolite A whose surface was evenly covered with tiny scaly calcium deficient hydroxyapatite (Ca-def HA) nanocrystals was prepared through the ion exchange reaction of ammonium and calcium ions as a novel encapsulation material for the long-term immobilization of radioactive Sr-90. The maximum capacity for Sr ion uptake in the zeolite A/Ca-def HA nanocomposite was determined to be 0.40 mmol g⁻¹, which was comparable to the value for zeolite A alone; this was because of the loose arrangement of Ca-def HA nanocrystals on the surfaces. The nanocomposite obtained was heated at 800 to 1200°C to improve the solution stability of adsorbed Sr ions. The low crystalline Ca-def HA became tricalcium phosphate (TCP) after heating at over 850°C. A phase change from zeolite A to an amorphous phase was observed at 850°C and to feldspar at 1000°C. The elution of Sr ions from the nanocomposites heated was compared to those from the heated zeolite A, under alkaline conditions (pH 10.2) similar to those found in geological layers deeper than 300 m. The elution amounts of Sr ions from the nanocomposites decreased with heating temperatures over 950°C compared with those of zeolite A, due to the complete coverage of TCP crystals. These results indicate that calcium phosphate nano-layers on the zeolite A surfaces play an important role for the long-term encapsulation of Sr ions in the nanocomposites.

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Aluminum nitride nanopowder was fabricated from transition alumina nanopowder by gas reduction–nitridation method. It was sintered by spark plasma sintering with 1 wt % Ca₃Al₂O₆ as a sintering additive in nitrogen. The nanopowder with Ca₃Al₂O₆ was densified up to 3.16 Mg/m³ of density at 1450°C, restraining grain growth. The nanopowder without additive was densified at 1550°C. The sintering temperature for dense aluminum nitride ceramic could be reduced by 1 wt % Ca₃Al₂O₆ as a sintering additive.

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Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics have been utilized as a restorative dental material. Pre-sintered Y-TZP ceramics are machined using the Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) techniques. In this study, pre-sintered 3 mol % yttria-stabilized zirconia (3Y-TZP) bioceramics reinforced with Al₂O₃ particles were prepared by sintering at relatively low temperature. The machining characteristics of the developed 3Y-TZP composites were investigated using an end-milling process. A series of experiments were performed on a high speed spindle with several sensors: a tool dynamometer, an acceleration sensor, and an acoustic emission sensor. The tool dynamometer was installed below the work-piece, a three-axis acceleration sensor was installed on the spindle head, and the acoustic emission sensor was installed on the fixture. The machining characteristics of the composites material were evaluated in a high speed machining process under various cutting conditions by changing the cutting speed, depth-of-cut, and feedrate. The machined surface was investigated using SEM photographs.

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The internal structure of a fine particle of barium titanate is studied by the variational principle method on the basis of the self-consistent anharmonic theory. An anharmonic oscillator is used as a trial Hamiltonian, and Morse potential is assumed as the interatomic potential in the particle. It is concluded that the structure of the vertical section of a ferroelectric particle has a gradient distribution from the ferro phase at the center to the para phase at the surface.

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Various zeolites have been synthesized from coal fly ash (FA) by hydrothermal treatment with NaOH solution. Phillipsite-type zeolite was synthesized selectively from FA (FA-phillipsite), and succeeded in in situ combining the FA-phillipsite with sepiolite to form FA-phillipsite/sepiolite composite. The adsorption behaviour of two harmful heavy metal ions (Pb²⁺ and Cd²⁺) were investigated for the FA-phillipsite and FA-phillipsite/sepiolite composite (30 mass % sepiolite). It was found that the NaOH hydrothermal treatment produced not only phillipsite but also Na⁺-substituted sepiolite. Both the FA-phillipsite and the FA-phillipsite/sepiolite composite showed high adsorbing-ability for Pb²⁺ (2.90 and 2.68 meq g⁻¹) and Cd²⁺ (1.62 and 1.74 meq g⁻¹) ions. The adsorption efficiency of the composite was much higher in the measured value than in the calculated one estimated from the maximum adsorbing-ability of the untreated sepiolite. This indicates that the Na⁺-substituted sepiolite in the composite has excellent adsorbing-ability for Pb²⁺ and Cd²⁺ ions. Since sepiolite has superior forming performance, the FA-derived phillipsite/sepiolite composite powder was able to be molded into various shapes e.g. pellet and tube. The FA-phillipsite/sepiolite composite is expected to be a new adsorbent for practical use.

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Ca₃Sc₂Si₃O₁₂:Ce³⁺ phosphor was synthesized by what we have named Emulsion–Evaporation (EE) method, where W/O emulsions of metallic ions and precipitants were mixed and condensed in a rotary evaporator. The EE-derived precursor was amorphous below 600°C and directly crystallized to CSS above 800°C without passing any impurity phases. SEM/EDS and ²⁹Si-NMR analyses revealed that the EE process is superior in achieving homogeneity. Ca₃Sc₂Si₃O₁₂:Ce³⁺ phosphor fired at 1350°C showed higher fluorescent emission than those prepared by a normal precipitation (PP) without EE route and by a solid state (SS) synthesis.

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The adhesion between silver paste film and ceramic substrate was improved by an incorporation of SnO₂ conducting oxide. The SnO₂ incorporated silver paste composite film was prepared by SnO₂ solution pouring into commercial silver paste. The SnO₂ in silver paste film was crystallized through high temperature anneal and the electrical property of the SnO₂–silver paste composite film was improved. A densification of the composite paste was enhanced with crystallized SnO₂ phase after high temperature anneal. The SnO₂ crystalline phase was contributed to electrical conductivity of composite paste due to its semiconducting behavior. After densification, void formation was effectively prevented by SnO₂ phase formation. By the incorporation of conducting oxide solution into commercial silver paste, we could use commercial resin-type silver paste on ceramic substrate.

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The formation of crack patterns during the pyrolysis step, which converts the carbon fiber-reinforced plastic composite (CFRP) to a C_f/C composite as one step in the liquid silicon infiltration (LSI) process, was investigated. Generally, cracks occur as a result of variances in thermal shrinkage between the matrix and the fiber during pyrolysis. The addition of carbon black powder as a filler resulted in a reduction in the shrinkage, but more cracks were formed. The transversal crack increased, and the partial delamination was newly occurred as the filler was increased. The properties of the matrices also changed; the fracture toughness decreased, and the void area increased. Consequently, the crack formation occurs not only by the thermal shrinkage difference between fiber and matrix but also the effect of matrix fracture toughness or void content. The flexural strength of LSI-processed samples was also measured, and the filler improved the mechanical strength but reduced its reliability.

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Dependence of thermal conductivity on the crystallization behavior of CaMgSi₂O₆ glass-ceramics was investigated as a function of TiO₂, V₂O₅ and MoO₃ content. With the co-addition of TiO₂, V₂O₅ and MoO₃, the glass transition temperature (T_g) was decreased, while the peak temperature of crystallization (T_p) was increased. The onset temperature of crystallization (T_c) was dependent on the types and amount of additives. Due to the differences of T_c with additives, the crystallization behaviors such as the degree of crystallization and crystallite size of the specimens were changed. The thermal diffusivity of the specimens sintered at 900°C for 1 h was increased with the crystallite size. With increasing of the degree of crystallization, the thermal conductivity of the specimens was increased, while the temperature coefficient of thermal conductivity was decreased.

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Silicon carbide (SiC) whiskers were produced at different positions in the chemical vapor deposition (CVD) furnace. The effect of shifts in specimen position on vapor–solid (VS) whisker growth was studied. First, we confirmed the major factors influencing CVD whisker growth by controlling the specimen position. The source reactant depletion effect and temperature gradient acted to reduce the whisker diameter by 33.3 and 61.7%, but the gas residence time only accounted for 4.2% of whisker diameter reduction. The specimen upon which all three factors acted showed a 74.2% decrease in diameter. Transmission electron microscopy (TEM) observation showed that all whiskers had highly crystalline FCC structures. The front perpendicular specimen showed higher stacking fault densities, whereas the back horizontal specimen possessed no stacking faults. These results suggest that position variation led to a growth rate difference, which affected the stability of whisker growth. Based on this idea, we confirmed the possibility of synthesizing whiskers of two different diameters on the same substrate. This can propose a new network structure consisting of combined whiskers. This report focuses on varying the whisker deposition size by controlling the deposition position instead of changing the deposition conditions as is common.

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The effect of post-annealing on ZnO thin films implanted with Eu at 1 × 10¹⁷ ions/cm² was studied to characterize the structural and luminescent properties, and the distribution of Eu in thin films. After post-annealing at 600°C, the broadening of the ZnO(002) diffraction peak was the same as that of the as-implanted sample. The sample showed orange luminescence due to Eu³⁺. After post-annealing at 900°C, a sharp diffraction peak of ZnO(002) was observed. The orange luminescence due to Eu³⁺ had disappeared, and instead, the intense luminescence of the band-edge of ZnO was observed in the sample. Ion images of Zn and Eu indicated that the Eu separated from the ZnO during the post-annealing. It is thought that the difference in luminescence is due to the separation of Eu from ZnO.

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Alumina based closed pore dominated substrates have been fabricated by using superplastically foaming method developed by our group. Co-dispersing of magnesium aluminate spinel (Spinel) and zirconia without dopant (0YZ) provided adequate superplastisity to alumina matrix, while individual dispersion of spinel or zirconia resulted in only small deformation. The dielectric constant of superplastically foamed alumina decreased monotonically with porosity. Introduced pores were all closed nature at least up to 30% of porosity, at that porosity the permittivity became half as that of full dense one. Effect of the sweating water or ambient humidity has been proved to be identical to those of full dense one, which is favorable for semiconductor substrate.

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In this study, we fabricated Organic Field Effect Transistors (OFETs) using an Au/P3HT/SiO₂/n⁺⁺-Si structure. The organic poly(3-hexylthiophene) (P3HT) films with various thickness, which were controlled by changing weight concentration of P3HT in chloroform (CHCl₃) solvent, have been fabricated using a sol–gel method. The correlations of mobility and on/off current ratio depend on various thickness of P3HT films are revealed. The mobility of the P3HT films were about 1.1, 2.2, and 2.8 × 10⁻³ [cm² V⁻¹ s⁻¹] for 0.4, 0.7, and 1.0 wt %, respectively. We also observed the trade off relation on mobility and on/off ratio with increasing anneal temperature from 100 to 140°C. The surface morphology with various thicknesses was scanned by using atomic force microscopy (AFM) in order to verify the relations between the thickness of film and device performance. We observed the increase of on current with thickness of active layer. These results indicate that the accumulated carriers between semiconductor and insulator are strongly affected by the degree of molecular packing and size of molecular bonding.

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Nb-doped SrTiO₃ thermoelectric ceramic composites with potassium titanate (KTO) nanowires addition were fabricated by the pressure-less sintering method in an Ar atmosphere. KTO addition significantly reduced the thermal conductivity and enhanced the electrical conductivity. Meanwhile, the Seebeck coefficient was almost independent of KTO addition, thus, enhancing the dimensionless thermoelectric figure of merit, ZT. The sample with 3 wt % KTO addition gave the maximum ZT of 0.34 at 900 K. The reason for the enhanced thermoelectric properties by KTO addition was also investigated.

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Nanocrystalline cobalt boride (Co₂B) has been successfully synthesized by the reaction of CoCl₂ with NaBH₄ in the temperature range of 500–600°C in an autoclave. Characterized by X-ray powder diffraction (XRD), transmission electron micrographs (TEM), and Raman spectra, the composition and morphology of the products were confirmed. The mechanism for the formation of crystalline Co₂B was proposed. This work contributes one facile method for preparing metallic borides.

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