Nanocrystalline Composite Layer Realized by Simple Sintering Without Surface Treatment, Reducing Hydrophilicity and Increasing Thermal Conductivity.

The surface treatment for a polymer-ceramic composite is additionally performed in advanced material industries. To prepare the composite without a surface treatment, the simplest way to manufacture an advanced ceramic-particle is devised. The method is the formation of a nanocrystalline composite layer through the simple liquid-phase sintering. Using magnesia (MgO) which shows hydrophilicity, a nanocrystalline surface layer is realized by liquid-phase sintering. The amorphous matrix of nanocrystalline composite layer makes MgO hydrophobic and ensures miscibility with polymers, and the nanocrystalline MgO ensures high thermal conductivity. In addition, the liquid phase removes the open pores and makes the surface morphology smooth MgO with smooth surface (MgO-SM). Thermal interface materials (TIM) prepared with MgO-SM and epoxy show a high thermal conductivity of ≈7.5 W m-1 K-1 , which is significantly higher than 4.5 W m-1 K-1 of pure MgO TIM. Consequently, the formation process of a nanocrystalline surface layer utilizing simple liquid-phase sintering is proposed as a fabrication method for a next-generation ceramic-filler. In addition, it is fundamentally identified that the thermal conductivity of MgO depends on the Mg deficiency, and therefore a poly-crystal MgO-SM (produced at a low temperature) has a higher thermal conductivity than a single-crystal MgO (produced at a high temperature).

Molten-Salt Processed Potassium Sodium Niobate Single-Crystal Microcuboids with Dislocation-Induced Nanodomain Structures and Relaxor Ferroelectric Behavior.

We herein report a facile molten-salt synthetic strategy to prepare transparent and uniform Li, Ba-doped (K,Na)NbO3 (KNN) single-crystal microcuboids (∼80 µm). By controlling the degree of supersaturation, different growth modes were found and the single-crystal microcuboids were synthesized via island-like oriented attachment of KNN particles onto the growing surface. The distinct relaxor ferroelectric (RFE) properties were achieved in the single-crystal microcuboids, which were different from the normal ferroelectric (FE) properties found in their KNN ceramic counterparts prepared through a solid-state reaction using the same initial precursors. The RFE properties were realized by dislocation-induced nanodomain formation during oriented attachment growth of single-crystal microcuboids, which is different from the current strategies to derive the nanodomains by the local compositional inhomogeneity or the application of an electric field. The dislocations served as nucleation sites for ferroelectric domain walls and block the growth of domains. The KNN single-crystal microcuboids exhibited a higher effective piezoelectric coefficient (∼459 pm/V) compared to that of the bulk KNN ceramic counterpart (∼90 pm/V) and showed the broad diffuse maxima in the temperature dependence dielectric permittivity. The high maximum polarization (69.6 µC/cm2) at a relatively low electric field (30 kV/cm) was beneficial for energy storage applications. Furthermore, the KNN-based transparent, flexible pressure sensor directly monitored the mechanical motion of human activity without any external electric power. This study provides insights and synthetic strategies of single-crystal RFE microcuboids for other different perovskites, in which nanodomain structures are primarily imposed by their chemical composition.

Effect of Cathode Microstructure on Electrochemical Properties of Sodium Nickel-Iron Chloride Batteries.

Sodium metal chloride batteries have become a substantial focus area in the research on prospective alternatives for battery energy storage systems (BESSs) since they are more stable than lithium ion batteries. This study demonstrates the effects of the cathode microstructure on the electrochemical properties of sodium metal chloride cells. The cathode powder is manufactured in the form of granules composed of a metal active material and NaCl, and the ionic conductivity is attained by filling the interiors of the granules with a second electrolyte (NaAlCl4). Thus, the microstructure of the cathode powder had to be optimized to ensure that the second electrolyte effectively penetrated the cathode granules. The microstructure was modified by selecting the NaCl size and density of the cathode granules, and the resulting Na/(Ni,Fe)Cl2 cell showed a high capacity of 224 mAh g-1 at the 100th cycle owing to microstructural improvements. These findings demonstrate that control of the cathode microstructure is essential when cathode powders are used to manufacture sodium metal chloride batteries.

Supraparticle Engineering for Highly Dense Microspheres: Yttria-Stabilized Zirconia with Adjustable Micromechanical Properties.

Various supraparticles have been extensively studied owing to their excellent catalytic properties that are attributed to their inherent porous structure; however, their mechanical properties have not garnered attention owing to their less dense structure. We demonstrate a rational approach for fabricating assembled supraparticles and, subsequently, highly dense microspheres. In addition, 3 mol % yttria-stabilized zirconia (3YSZ) and alumina particles were selected as building blocks and assembled into higher-order architectures using a droplet-based template method (spray drying) for validation with proof-of-concept. Moreover, structural features such as density, size, sphericity, and morphology of supraparticles were controlled by adjusting the competing kinetics occurring between the assembly of building blocks and evaporation of the solvent in the droplets. The preparatory aqueous suspension and process parameters were optimized as well. A detailed understanding of the formation mechanism facilitated the yield of tailor-made supraparticles and, thereafter, highly dense microspheres (approximate relative density = 99%) with excellent sphericity (>98%) via heat treatment. The microspheres displayed highest hardness (26.77 GPa) and superior elastic modulus (210.19 GPa) compared with the mechanical properties of the 3YSZ samples reported to date. Ultimately, the proposed supraparticle engineering provided insight for controlling the structural features and resultant micromechanical properties, which widely extends the applicability of supraparticle-based functional materials for practical purposes that require materials with high density and excellent mechanical properties.

High Magnetic Field Sensitivity in Ferromagnetic-Ferroelectric Composite with High Mechanical Quality Factor.

In this study, composite devices were fabricated using ferromagnetic FeSiB-based alloys (Metglas) and ferroelectric ceramics, and their magnetic field sensitivity was evaluated. Sintered 0.95Pb(Zr0.52Ti0.48)O3-0.05Pb(Mn1/3Sb2/3)O3 (PZT-PMS) ceramic exhibited a very dense microstructure with a large piezoelectric voltage coefficient (g31 = -16.8 × 10-3 VmN-1) and mechanical quality factor (Qm > 1600). Owing to these excellent electromechanical properties of the PZT-PMS, the laminate composite with a Metglas/PZT-PMS/Metglas sandwich structure exhibited large magnetoelectric voltage coefficients (αME) in both off-resonance and resonance modes. When the length-to-width aspect ratio (l/w) of the composite was controlled, αME slightly varied in the off-resonance mode, resulting in similar sensitivity values ranging from 129.9 to 146.81 VT-1. Whereas in the resonance mode, the composite with small l/w exhibited a large reduction of αME and sensitivity values. When controlling the thickness of the PZT-PMS (t), the αME of the composite showed the largest value when t was the smallest in the off-resonance mode, while αME was the largest when t is the largest in the resonance mode. The control of t slightly affected the sensitivity in the off-resonance mode, however, higher sensitivity was obtained as t increased in the resonance mode. The results demonstrate that the sensitivity, varying with the dimensional control of the composite, is related to the mechanical loss of the sensor. The composite sensor with the PZT-PMS layer exhibited excellent magnetic field sensitivity of 1.49 × 105 VT-1 with a sub-nT sensing limit, indicating its potential for application in high-performance magnetoelectric sensor devices.

Selective Phase Control of Dopant-Free Potassium Sodium Niobate Perovskites in Solution.

As one of the perovskite families, potassium sodium niobates (K1-xNax)NbO3 (KNN) have been gaining tremendous attention due to their various functional properties which can be largely determined by their crystallographic phase and composition. However, a selective evolution of different phases for KNN with controlled composition can be difficult to achieve, especially in solution chemical synthesis because of its strong tendency to stabilize into orthorhombic phase at conventional synthetic temperature. We herein developed a facile solution approach to control the phase and composition of dopant-free KNN particles selectively through the modification of reaction parameters. A conventional hydrothermal synthesis method yielded orthorhombic KNN particles, while the monoclinic phase, which has never been observed in a bulk counterpart, was kinetically generated by the compositional modification of an intermediate phase under a high-intensity ultrasound irradiation. Cubic KNN particles were stabilized when ethylene glycol was used as a co-solvent together with deionized water through bonding between ethylene glycol molecules and the surface of the KNN. Composite-structured piezoelectric harvesters were fabricated using each phase of KNN particles and the ß-phase poly(vinylidene fluoride-co-trifluoroethylene) polymer. Maximum output power was found for the harvester containing orthorhombic KNN particles. This facile synthetic methodology could pave a new pathway for fabricating numerous phase-controlled materials.

A Comparison Study of Fatigue Behavior of Hard and Soft Piezoelectric Single Crystal Macro-Fiber Composites for Vibration Energy Harvesting.

Designing a piezoelectric energy harvester (PEH) with high power density and high fatigue resistance is essential for the successful replacement of the currently using batteries in structural health monitoring (SHM) systems. Among the various designs, the PEH comprising of a cantilever structure as a passive layer and piezoelectric single crystal-based fiber composites (SFC) as an active layer showed excellent performance due to its high electromechanical properties and dynamic flexibilities that are suitable for low frequency vibrations. In the present study, an effort was made to investigate the reliable performance of hard and soft SFC based PEHs. The base acceleration of both PEHs is held at 7 m/s2 and the frequency of excitation is tuned to their resonant frequency (fr) and then the output power (Prms) is monitored for 107 fatigue cycles. The effect of fatigue cycles on the output voltage, vibration displacement, dielectric, and ferroelectric properties of PEHs was analyzed. It was noticed that fatigue-induced performance degradation is more prominent in soft SFC-based PEH (SS-PEH) than in hard SFC-based PEH (HS-PEH). The HS-PEH showed a slight degradation in the output power due to a shift in fr, however, no degradation in the maximum power was noticed, in fact, dielectric and ferroelectric properties were improved even after 107 vibration cycles. In this context, the present study provides a pathway to consider the fatigue life of piezoelectric material for the designing of PEH to be used at resonant conditions for long-term operation.

Enhancement of Magnetoelectric Conversion Achieved by Optimization of Interfacial Adhesion Layer in Laminate Composites.

We report the effect of epoxy adhesion layers with different mechanical or physical property on a magnetoelectric (ME) composite laminate composed of FeBSi alloy (Metglas)/single-crystal Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3/Metglas to achieve an improved ME conversion performance. Through theoretical simulation, it was revealed that the Young's modulus and the thickness of interfacial adhesives were major parameters that influence the conversion efficiency in ME composites. In the experimental evaluation, we utilized three epoxy materials with a distinct Young's modulus and adjusted the average thickness of the adhesion layers to optimize the ME conversion. The experimental results show that a thin epoxy layer with a high Young's modulus provided the best performance in the inorganic-based ME conversion process. By tailoring the interfacial adhesion property, the ME laminate generated a high conversion coefficient of 328.8 V/(cm Oe), with a mechanical quality factor of 132.0 at the resonance mode. Moreover, we demonstrated a highly sensitive alternating current magnetic field sensor that had a detection resolution below 10 pT. The optimization of the epoxy layers in the ME laminate composite provided significant enhancement of the ME response in a simple manner.

Dimensional and compositional change of 1D chalcogen nanostructures leading to tunable localized surface plasmon resonances.

As part of the oxygen family, chalcogen (Se, Te) nanostructures have been considered important elements for various practical fields and further exploited to constitute metal chalcogenides for each targeted application. Here, we report a controlled synthesis of well-defined one-dimensional chalcogen nanostructures such as nanowries, nanorods, and nanotubes by controlling reduction reaction rate to fine-tune the dimension and composition of the products. Tunable optical properties (localized surface plasmon resonances) of these chalcogen nanostructures are observed depending on their morphological, dimensional, and compositional variation.

Laser Irradiation of Metal Oxide Films and Nanostructures: Applications and Advances.

Recent technological advances in developing a diverse range of lasers have opened new avenues in material processing. Laser processing of materials involves their exposure to rapid and localized energy, which creates conditions of electronic and thermodynamic nonequilibrium. The laser-induced heat can be localized in space and time, enabling excellent control over the manipulation of materials. Metal oxides are of significant interest for applications ranging from microelectronics to medicine. Numerous studies have investigated the synthesis, manipulation, and patterning of metal oxide films and nanostructures. Besides providing a brief overview on the principles governing the laser-material interactions, here, the ongoing efforts in laser irradiation of metal oxide films and nanostructures for a variety of applications are reviewed. Latest advances in laser-assisted processing of metal oxides are summarized.

Next Generation Ceramic Substrate Fabricated at Room Temperature.

A ceramic substrate must not only have an excellent thermal performance but also be thin, since the electronic devices have to become thin and small in the electronics industry of the next generation. In this manuscript, a thin ceramic substrate (thickness: 30-70 µm) is reported for the next generation ceramic substrate. It is fabricated by a new process [granule spray in vacuum (GSV)] which is a room temperature process. For the thin ceramic substrates, AlN GSV films are deposited on Al substrates and their electric/thermal properties are compared to those of the commercial ceramic substrates. The thermal resistance is significantly reduced by using AlN GSV films instead of AlN bulk-ceramics in thermal management systems. It is due to the removal of a thermal interface material which has low thermal conductivity. In particular, the dielectric strengths of AlN GSV films are much higher than those of AlN bulk-ceramics which are commercialized, approximately 5 times. Therefore, it can be expected that this GSV film is a next generation substrate in thermal management systems for the high power application.

Self-Growth of Centimeter-Scale Single Crystals by Normal Sintering Process in Modified Potassium Sodium Niobate Ceramics.

In this manuscript, an interesting phenomenon is reported. That is the self-growth of single crystals in Pb-free piezoelectric ceramics. These crystals are several centimeters in size. They are grown without any seed addition through a normal sintering process in modified potassium sodium niobate ceramics. It has been achieved by the composition designed to compensate the Na(+) loss which occurs during the liquid phase sintering. The composition of the crystals is (K0.4925Na(0.4925-x)Ba(0.015+x/2))Nb(0.995+x)O3 [x is determined by the Na(+) loss, due to Na2O volatilization]. These crystals have high piezoelectric voltage coefficients (g33, 131 10(-3)Vm/N), indicating that they are good candidates for piezoelectric sensors and energy harvesting devices. We hope that this report can offer the opportunity for many researchers to have an interest in these crystals.

Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water.

Hydroxyapatite and silk combination-coated dental implants result in superior bone formation in the peri-implant area compared with hydroxyapatite and collagen combination-coated implants.

PURPOSE: The objective of this study was to compare bone formation after installation of uncoated (UC), hydroxyapatite-coated (HA), collagen plus HA-coated (CH), and silk plus HA-coated (SH) implants. MATERIALS AND METHODS: Implants in the UC group had acid-etched surfaces. Surface coating was applied using the aerosol deposition method. Cellular responses on the coated surfaces were examined with scanning electron microscopy. Cellular responses to the surfaces were studied with the corresponding coated discs and MG63 cells. Subsequently, 3-(4, 5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphatase (ALP) assays were performed. Peri-implant bone formation was evaluated with the rabbit tibia model. Twenty-four implants from each group were installed. The animals were sacrificed 6 weeks after implant installation. Peri-implant bone formation and implant-to-bone contact were measured in histologic sections. Significance of differences across groups was evaluated using analysis of variance. RESULTS: Scanning electron microscopic images showed that the CH and SH groups exhibited cells that appeared more spread out than those in the other groups. The SH group exhibited the highest value in the MTT assay. The CH group exhibited the highest level of ALP activity. Comparisons of these modifications with the acid-etched surfaces showed that the CH and SH groups displayed significantly greater peri-implant bone formation (P < .001). CONCLUSION: The SH group displayed significantly greater new bone formation and bone-to-implant contact than did the other groups.

Hydroxyapatite and collagen combination-coated dental implants display better bone formation in the peri-implant area than the same combination plus bone morphogenetic protein-2-coated implants, hydroxyapatite only coated implants, and uncoated implants.

PURPOSE: The objective of this study was to compare peri-implant bone formation among uncoated (UC), hydroxyapatite (HA), collagen plus HA (CH), and collagen, HA, plus bone morphogenetic protein-2 (BMP-2) implant groups. MATERIALS AND METHODS: Implants in the UC group had acid-etched surfaces. The surface coating was applied using the aerosol deposition method. The coated surfaces were examined by scanning electron microscopy, x-ray diffraction (XRD), and Fourier-transformed infrared absorption analysis. Subsequently, 6 implants from each group (total, 24 implants) were installed in the tibias of rabbits. The animals were sacrificed at 6 weeks after implant installation. Peri-implant bone formation and bone-to-implant contact (BIC) were measured in histologic sections. Significant differences among groups were evaluated using analysis of variance. RESULTS: Based on the measured XRD patterns, there was a characteristic HA phase (International Centre for Diffraction Data [ICDD], 086-0740) coated on the titanium (ICDD, 089-3725). Subsequent coating processes for collagen and BMP-2 did not display additional diffraction peaks, but maintained the diffraction patterns of the HA-coated titanium. The presence of collagen was verified by infrared absorption analysis. When comparing these modifications with UC surfaces, only the CH coating displayed significantly greater peri-implant bone formation and BIC (P = .003 and P < .001, respectively). Adding BMP-2 to the implant surface did not produce any advantage compared with the CH coating. CONCLUSIONS: In this study, the CH group displayed significantly greater new bone formation and BIC than the other groups. There was no significant difference among the other groups.

New bone formation between bare titanium surface and hydroxyapatite coating by the aerosol deposition technique in the nasal mucosal penetration model.

OBJECTIVE: The aim of this study was to compare new bone formation with titanium (Ti) surface and hydroxyapatite (HA)-coated titanium surface in mucosal perforation model. MATERIALS AND METHODS: HA coating to the Ti disc and implant were done by aerosol deposition technique. Alkaline phosphatase assay and cell migration assay were done in Ti and HA surface disc with MG63 cells. For the in vivo test, 5 New Zealand white rabbits were used. Two penetration defects were prepared in the nasal bone. Subsequently, 2 types of implants were installed into the defect (diameter: 3.0 mm, length: 6.0 mm). Approximately 5.0 mm of the fixture's surface penetrated into the nasal cavity. In the experimental group, HA-coated implants were used. The same design of implants without coating was used in the control group. The animals were sacrificed 8 weeks postoperatively. Subsequently, a histomorphometric analysis was done. RESULTS: Alkaline phosphatase activity was significantly higher in HA-coated surface than in titanium surface (P < 0.05). In addition, more cells were migrated into the HA-coated surface when compared to Ti surface. In the animal experiments, mean new bone formation was 30.68 ± 14.16% in the experimental group and 6.92 ± 5.12% in the control group (P = 0.001). Mean bone-to-implant contact was 31.71 ± 8.41% in the experimental group and 7.98 ± 5.58% in the control group (P < 0.001). Mean height of the bone regeneration was 3.70 ± 0.76 mm in the experimental group and 1.04 ± 0.67 mm in the control group. The difference between the 2 groups was statistically significant (P < 0.001). CONCLUSIONS: HA-coated implants exhibited more bone regeneration in the mucosal penetration model than the uncoated implants.

Effect of fluorine addition on the biological performance of hydroxyapatite coatings on Ti by aerosol deposition.

Dense and well-adherent fluoridated hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2-x )F( x ), FHA] coatings with various amounts of fluorine contents (x = 0, 0.5, 1.0, 1.5, and 2.0) were deposited on commercially available pure titanium by aerosol deposition using FHA powders in order to investigate the effect of fluorine content on the properties of the coatings. FHA powders with different compositions were synthesized by solid-state reactions of hydroxyapatite (HA) and fluorapatite (FA) powders at various ratios. X-ray diffraction and Fourier transform infrared spectroscopy results showed that fluoride ions were successfully incorporated into the HA lattice for both the FHA powders and the FHA coatings. Scanning electron microscopy analysis revealed dense microstructures and good substrate adhesion of the coatings with high adhesion strengths of more than 33.1 MPa. The dissolution behavior in a tris-buffered saline solution indicated that the dissolution rate of the FHA coatings decreased as a result of increasing the fluorine content in the coatings. In addition, in vitro cellular tests, including cell attachment, proliferation, and alkaline phosphatase activity of MC3T3-E1 preosteoblast cells grown on the coatings, demonstrated that an FHA coating with a moderate degree of F(-) substitution, x = 1.0, had a stronger stimulating effect on cell proliferation and differentiation. These results suggested that there exists an optimum fluorine content level in the FHA coatings for the best long-term stability and cellular responses.

Effect of NiZnFeO4 content on PZT-pZN + NiZnFeO4 magnetoelectric composite.

We fabricated and characterized the magnetoelectric (ME) properties of 3-0 ME composite materials comprised of the high piezoelectric voltage coefficient material, 0.9Pb(Zr0.52Ti0.48)O3-0.1 Pb(Zn1/3Nb2/3)O3 + 0.005Mn (PZT-PZN), and the magnetostrictive material, Ni0.8Zn0.2Fe2O4 (NZF). As the ME effect is generated by the product coupling between the piezoelectric properties and the magnetostrictive properties, the NZF content should be optimized for a higher ME coefficient. The dielectric constant and spontaneous polarization (P) were decreased with increasing NZF content before the percolation of the NZF particulates. However, as the NZF content exceeded the percolation content, the dielectric loss was dramatically increased due to the low resistivity of NZF. While the piezoelectric constant was decreased with increasing NZF content, the maximum magnetization was linearly increased. When we combined the piezoelectric and magnetostrictive effects, the ME composite sintered at 1200 degrees C with 20% NZF showed a maximum dE/dH of 27 mV/cm x Oe at a magnetic bias of 1240 Oe.

Hydroxyapatite coating on magnesium with MgF2 interlayer for enhanced corrosion resistance and biocompatibility.

Hydroxyapatite (HA) was coated onto pure magnesium (Mg) with an MgF(2) interlayer in order to reduce the surface corrosion rate and enhance the biocompatibility. Both MgF(2) and HA were successfully coated in sequence with good adhesion properties using the fluoride conversion coating and aerosol deposition techniques, respectively. In a simulated body fluid (SBF), the double layer coating remarkably enhanced the corrosion resistance of the coated Mg specimen. The in vitro cellular responses of the MC3T3-E1 pre-osteoblasts were examined using a cell proliferation assay and an alkaline phosphatase (ALP) assay, and these results demonstrated that the double coating layer also enhanced cell proliferation and differentiation levels. In the in vivo study, the HA/MgF(2) coated Mg corroded less than the bare Mg and had a higher bone-to-implant contact (BIC) ratio in the cortical bone area of the rabbit femora 4 weeks after implantation. These in vitro and in vivo results suggested that the HA coated Mg with the MgF(2) interlayer could be used as a potential candidate for biodegradable implant materials.

Aerosol deposition of hydroxyapatite and 4-hexylresorcinol coatings on titanium alloys for dental implants.

PURPOSE: Aerosol deposition is a newly developed technique, and it can deliver the drug from a hydroxyapatite (HA)-coated surface. 4-Hexylresorcinol (4-HR) is a well-known antiseptic. The influence of the 4-HR component of HA coatings on titanium surfaces was studied in vitro and in vivo. MATERIALS AND METHODS: X-ray diffraction and Fourier transform infrared techniques were used for the evaluation of the coating. The cellular response of the coating was evaluated by scanning electron microscopic study, MTT assay, alkaline phosphatase assay, and osteocalcin assay. In addition, the dental implant was coated with HA or HA + 4-HR. The implant was installed into the tibia of a rabbit after contamination by Aggregatibacter actinomycetemcomitans. The torque test and histologic analysis were then performed at 8 weeks after the operation. RESULTS: By use of an aerosol deposition technique, the combination of HA and 4-HR was successfully coated onto a titanium surface, which was confirmed by x-ray diffraction and Fourier transform infrared techniques. MG63 cells attached more rapidly to the HA + 4-HR coating than to the HA-only coating. The HA + 4-HR coating had significantly increased osteocalcin expression and alkaline phosphatase activity compared with the HA-only coating (P < .05). The dental implant coated with HA + 4-HR had a significantly higher removal torque value than that coated with HA alone at 8 weeks after surgery (P < .05). On histologic analysis, both the bone formation value and the bone-to-implant contact value were significantly higher in the HA + 4-HR group than in the HA-only group at 8 weeks after surgery (P < .05). CONCLUSIONS: Collectively, the HA + 4-HR-coated dental implant had clear advantages over the HA-coated dental implant. Therefore HA + 4-HR coatings can be considered for patients who need immediate implant installation after tooth extraction or who have poor-quality bone.