Synthesis of hydroxyapatite nanorods from abalone shells via hydrothermal solid-state conversion

Hydroxyapatite (HAP) has been widely applied as a biomaterial for repairing or substituting human hard tissues. In this paper, HAP nanorods were successfully produced from abalone shell powders via hydrothermal solid-state conversion without surfactants or complex agents. The field emission scanning electron microscopy (FESEM) showed that the produced HAP exhibited the typical rod-like structure. Based on the X-ray diffraction (XRD) and thermal analysis (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)), these samples contain a small amount of aragonite and calcite crystals, and their content gradually decreases by prolonging the hydrothermal time. However, this decrease only slightly changes for the longer times. The Fourier transform infrared spectroscopy (FTIR) revealed that organic matter was detected in the samples without adding surfactants or complex agents. This study provides a solution to the resource waste and environmental pollution caused by abandoned abalone shells, and we also synthesized HAP for potential bone repair materials.     

Synthesis of hydroxyapatite nanorods assisted by Pluronics

Pluronics F127, P123, and F87 were employed to synthesize hydroxyapatite nanorods for biomedical applications. The calcium phosphate precipitates were characterized by XRD, TEM/EDS, FTIR, and TGA. Pluronics affected the phase evolution of the calcium phosphate precursors in the mother solution at room temperature. The hydroxyapatite nanorods with a diameter of 20 nm, a length of 100 nm, and a Ca/P ratio of 1.70 were obtained after the precursors were heated at 140 °C for 3 h in a Teflon-lined autoclave. There is about 2 wt% Pluronic on the surface of hydroxyapatite. The hydroxyapatite with a small amount of organics on the surface can be potentially used as fillers in biomedical composites with excellent biological and mechanical properties.     

Growth and characterization of hydroxyapatite crystals by hydrothermal method

Hydroxyapatite crystals were grown by hydrothermal method using dicalcium phosphate dihydrate crystals as a starting material. The grown crystals were found to be free from carbonate inclusion. Two distinct morphologies were obtained by following two different growth methods. Controlled slow growth process and rapid growth process results in hexagonal and whisker like morphologies.     

Synthesis and in-depth analysis of highly ordered yttrium doped hydroxyapatite nanorods prepared by hydrothermal method and its mechanical analysis

In this study, undoped and yttrium (Y) doped nanocrystalline hydroxyapatite crystals were synthesized by the hydrothermal method at 180 °C for 24 h. Highly ordered and oriented hydroxyapatite (HAp) nanorods were prepared by yttrium doping and their nanostructure and physical properties were compared with those of undoped HAp rods. FESEM images showed that the doping with Y ions reduced the diameter (from 25 nm to 15 nm) and increased the length (from 95 nm to 115 nm) of the synthesized rods. The aspect ratio of the undoped and Y-doped nanorods were calculated to be 4.303 (SD = 0.0959) and 7.61 (SD = 0.0355), respectively. Specific surface area (SSA) analysis showed that SSA also increased from 66.74 m²/g to 68.57 m²/g with the addition of yttrium. Y-doped HAp nanorod reinforced HMWPE composites displayed the better mechanical performance than those reinforced with pure HAp nanorods. The possible strengthening of nanorods and the increase of SSA due to the reduction in the size of nanorods in the presence of yttrium may have contributed to the strengthening of Y-doped HAp/HMWPE composites.     

Synthesis and characterization of single crystalline PbO nanorods via a facile hydrothermal method

Single crystalline β-PbO nanorods with diameter range from 40 to 120 nm and length up to 500 nm have been synthesized via a facile hydrothermal method in the presence of citrate. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electro-microscope (HRTEM) and SAED were used to characterize the as-obtained samples. An interesting intermediate state of self-assembled β-PbO rod-like nanoparticles was found and the possible formation mechanism of single crystalline β-PbO nanorods was also discussed.     

Structural characterization of zinc-substituted hydroxyapatite prepared by hydrothermal method

Zinc-substituted hydroxyapatite (Zn-HA) powders were prepared by hydrothermal method using Ca(NO₃)₂, (NH₄)₃PO₄ and Zn(NO₃)₂ as reagents. X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) were used to characterize the crystalline phase, microstructure, chemical composition, morphology and thermal stability of Zn-HA. The results show that the substitution content of zinc (Zn) in Zn-HA powders prepared in NaOH solution is higher than that prepared in NH₃ solution, and is lower than that of the corresponding amount of starting materials. The substitution of the Zn ion for calcium ion causes a lower crystallinity of Zn-HA and changes the lattice parameters of Zn-HA, since the ionic radius is smaller in Zn²⁺ (0.074 nm) than in Ca²⁺ (0.099 nm). Furthermore, the substitution of the Zn ions restrains the growth of Zn-HA crystal and decreases the thermal stability of Zn-HA. Zn-HA powder prepared in NH₃ solution starts to decompose at 800 °C when the Zn fraction increases to 15 mol%, while that prepared in NaOH solution start to decompose at 5 mol% Zn. The substitution content of Zn significantly influences the thermal stability, microstructure and morphology of Zn-HA.     

简单水热法制备棒状纳米氧化锌及其表征

以Zn(NO3)2和NaOH为原料,在不使用任何添加剂的条件下,采用水热合成法在不同的合成时间和合成温度下制备棒状纳米ZnO颗粒。通过X射线衍射(XRD)、透射电镜(TEM)、光致发光谱(PL)、电导率测试对样品进行表征。结果表明,所制备的纳米ZnO粉末具有六方红锌矿结构并沿(101)面择优生长;随着合成时间和温度的增加,样品的纯度逐渐增加;合成时间为25h,温度为200℃时,样品的结晶最好,样品基本成棒状,平均直径约为30～40nm,长度约为300～400nm、电阻率最大,且在376nm和500～600nm处有明显发射现象。深入分析了上述结果的形成原因。     

Structural characterization of silicon-substituted hydroxyapatite synthesized by a hydrothermal method

Silicon-substituted hydroxyapatite (Si-HA) was prepared successfully by hydrothermal method. The crystalline phase, microstructure, chemical composition, morphology and thermal stability of Si-HA were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that the substitution of the silicate groups for the phosphate groups causes some OH^- loss to maintain the charge balance and changes the lattice parameters of HA. Furthermore, the substitution of the silicate groups restrains the growth of Si-HA crystal. DSC analysis shows that the small amount of silicon incorporates into HA lattice does not influence the thermal stability of HA.     

Surfactant-assisted hydrothermal synthesis and characterization of WS2 nanorods

WS₂ nanorods with diameters of about 20–100 nm and lengths of about 0.1–2 μm were successfully synthesized by a simple hydrothermal method with the help of the surfactant Cetyltrimethylammonium Bromide (CTAB). As-prepared WS₂ samples are characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, the influence of surfactant CTAB on the formation of WS₂ nanorods was investigated. A possible three-step growth mechanism of WS₂ nanorods, in which initial nucleation, self-assembly (oriented aggregation), and subsequent crystal growth (Ostwald ripening) is involved, is proposed to explain the formation of WS₂ nanorods on the basis of observations of a time-dependent morphology evolution process.     

Synthesis and characterization of morphologically different high purity gallium oxide nanopowders

High purity gallium oxide nanopowders have been synthesized by using a simple precipitation technique with calcination at elevated temperature. From the X-ray pattern, the phase purity of the synthesized powders was confirmed as β-Ga₂O_3. Elemental quantification (stoichiometry) of Ga₂O₃ was also examined from the X-ray energy dispersive analysis (EDAX). Based on the recorded Fourier Transform Infrared (FTIR) spectrum of Ga₂O_3, the IR bands due to Ga–O bond and crystal lattice vibrations have been identified in the wavenumber range 400–4,000 cm⁻¹. From the measured SEM images, it is obvious to notice that the pH value has been playing a dominant role in obtaining morphologically different gallium oxide nanopowders. Thermogravimetric analysis reveals 8.3% of weight loss when the sample was heated to the temperature of 1,100 °C from the room temperature, which also shows a crystalline phase transformation. It is very interesting to report that a broad blue emission at 455 nm has been measured from the synthesized gallium oxide nanopowders.     

Synthesis and crystallographic study of Pb-Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

The solid solutions in the system of Pb and Sr hydroxyapatite, Sr_10−xPb_xHAp (x = 0-10), were successfully synthesized by high-temperature mixing method (HTMM) at 160 °C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr-Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb₃O₂(OH)₂ in the Pb(NO₃)₂·4H₂O solution before mixing with (NH₄)₂HPO₄ solution at 160 °C, HTMM causes the decrease of crystallization of the samples with high Pb content.     

Synthesis of ultrafine lanthanum hydroxide nanorods by a simple hydrothermal process

Lanthanum hydroxide (La(OH)₃) nanorods with 6–15 nm in width and 200–400 nm in length have been prepared by a simple hydrothermal process. X-ray diffraction (XRD) shows that the nanorods are of hexagonal structure, and furthermore, high-resolution transmission electron microscopy (HRTEM) identifies that the lanthanum hydroxide nanorods are highly crystalline. Moreover, the mechanism for the hydrothermal synthesis of lanthanum hydroxide nanorods has been preliminarily presented.     

GaN纳米棒的合成与表征

利用化学气相沉淀法（CVD）以Ga2O3和NH3为原料在沉积有乙酸镍的硅衬底上合成出了GaN纳米棒,纳米棒直径在50-200nm，长度在2-10μm，表面比较光滑,利用场发射扫描电镜（FESEM），X射线衍射仪（XRD），能量散射谱（EDS）对样品进行了成分和结构分析，表明GaN纳米棒是单晶的纤锌矿结构，同时对其生长机理进行了探讨。     

ITO纳米棒的制备及其表征

利用化学共沉淀法,在InCl3和SnCl4混和溶液中添加PEG-1000,并滴加浓度为25%氨水,制备了ITO前驱体,在温度700℃煅烧3h后得到ITO纳米棒.利用SEM、XRD、TEM-EDS和傅立叶-红外光谱仪分别对ITO纳米棒的形貌和尺寸、结构和物相、EDS能谱和FT-IR光谱分析,并对ITO纳米棒形貌形成机理进行了探讨分析.研究结果表明,ITO纳米棒具有立方铁锰矿结构,且具有纯度高和分散性好等特点,平均直径约为φ300nm,长度可迭3000nm,长径比约达10.随着煅烧时间的延长,ITO纳米棒形貌不变,对尺寸影响不大.     

Synthesis of hydroxyapatite nanopowders by sol-gel emulsion technique

Hydroxyapatite nanopowders were synthesized by a sol-gel emulsion technique by varying the concentration of a non-ionic surfactant in the organic phases (oil phase) of water-in-oil (w/o) emulsion. Calcium acetate dissolved in distilled water and phosphorous pentoxide dissolved in 2-butanol were used as starting precursors. The prepared sol was emulsified in a support solvent (cyclohexane) containing 2, 4 and 5 volume% of surfactant (Span 80), followed by the addition of triethylamine, for gelation. The gel powders thus obtained were calcined at different temperatures up to 750??C. Characterization was done using XRD, SEM and TEM. Pellets were made from the developed HAP powders and tested for its biocompatibility after their immersion in the simulated body fluid.     

Synthesis and properties of bio-waste-based hydroxyapatite via hydrothermal process

In this study, a facile hydrothermal method is applied to produce hydroxyapatite (HA) particles using egg shells as calcium precursors and fruit waste extracts (banana peel) as biomolecular templates at 150 °C for a reaction time period of 12 hours (h) and 24 hours. The sintering of the green samples of hydroxyapatite were conducted at 1250 °C in air for 2 h. The results showed that pectin extracted from banana peel extracts assisted in regulating crystal growth to obtain homogeneous hydroxyapatite powder, with higher purity observed for 24 h hydrothermal reaction time. Fourier-transform infrared spectroscopy (FTIR) spectra revealed the presences of phosphate (PO₄³⁻) and hydroxyl (OH⁻) groups in the powders. A relative density of 89.6 % was achieved for sintered hydroxyapatite compacts produced via hydrothermal method for 24 h. The sintered body was characterized by having high Vickers hardness of 5.35 GPa and good fracture toughness of 1.23 MPa√m, suitable for biomedical application.     

New technique for bonding hydroxyapatite ceramics and magnesium alloy by hydrothermal hot-pressing method

The solidification of hydroxyapatite (HA:Ca₁₀(PO₄)₆(OH)₂) and its bonding with Magnesium (Mg) alloys (AZ31; Mg–3Al–1Zn) were achieved simultaneously by using a hydrothermal hot-pressing method at a low temperature as low as 150 °C with no special surface treatment of Mg alloy. A mixture of calcium hydrogen phosphate dihydrate and calcium hydroxide was used as a starting powder material for solidifying HA. 3-point bending tests were conducted to obtain an estimate of the fracture toughness for the HA/Mg interface as well as for the HA ceramics only. The fracture toughness tests showed that the induced crack from the pre-crack tip deviated from the HA/Mg interface and propagated into the HA. The fracture toughness determined on the bonded HA/Mg specimen was close to that of the HA ceramics only (0.30 MPam^1/2).     

Synthesis and characterization of carbonate hydroxyapatite

Substituted apatite ceramics are of clinical interest as they offer the potential to improve the bioactive properties of implants. Carbonate hydroxyapatite (CHA) has been synthesized by an aqueous precipitation method and precipitates with two different levels of carbonate, processed as powders. Sintering experiments were performed to establish the influence of carbonate in significantly reducing the temperature required to prepare high-density ceramics when compared with stoichiometric hydroxyapatite (HA). High-temperature X-ray diffraction was used to characterize the phase stability of the apatites on sintering. Increasing carbonate content was shown to reduce the temperature at which decomposition occurred, to phases of CaO and -TCP. Mechanical testing, performed using biaxial flexure, showed that the CHA specimens had strengths similar to stoichiometric HA. © 1998 Kluwer Academic Publishers     

Synthesis and characterization of nanocrystallined zirconia by hydrothermal method

Nano-size zirconia was prepared by hydrothermal method using commercial zirconia powder. XRD study showed that the nano-size zirconia has an appreciable amount of monoclinic phase. The nano-size zirconia obtained has average particle size in the range of 24-36 nm. The SEM of nano-sized zirconia showed diminutively different morphology than the commercial one. TEM micrographs shows well-dispersed monoclinic ZrO₂ nanoparticles. The UV-DRS absorption spectrum of alkali treated zirconia showed an absorption peak at 235 nm (5.3 eV). The FTIR spectrum showed the purity of treated zirconia.