多孔羟基磷灰石的制备与表征

羟基磷灰石(HA)以其良好的生物相容性和生物活性成为重要的骨修复材料。实验以α-Ca3(PO4)2为原料采用水热合成法制备了多孔羟基磷灰石板材。借助XRD、SEM和FTIR研究了产物的物相组成、微观结构和化学组成。结果表明:随着水热时间的延长,HA析晶更完整且呈针状分布。经1200℃处理后进行的水热反应,形成的孔较均匀且细小。反应过程吸收了部分CO2,但未进入结构。该材料从结构和尺寸方面考虑能够用于生物医用材料。     

义眼台用羟基磷灰石的制备和性能

采用均相共沉淀法直接合成了高纯度羟基磷灰石粉体,通过改变反应物加入方式和反应时间调控粉体形貌和组成,分析了体系pH值对产物纯度的影响;以硅溶胶为粘结剂、尿素为造孔剂,室温下压制成型,高温烧结制备了孔隙度高、力学性能良好的多孔羟基磷灰石块体,考察了粉体粒径、造孔剂含量对孔隙度和抗压强度等性能的影响。结果表明,纳米粉有利于块体成型,随造孔剂含量增加,块体密度减小、孔隙度增加,当羟基磷灰石与尿素质量比为1.5:1时,孔隙度达69%,抗压强度达8 MPa,满足义眼台应用需求。     

含硅羟基磷灰石的湿法合成及骨水泥的性能研究

以Ca（OH）2、H3PO4和（C2H5）4SiO4为原料，在反应液40℃。pH值为9～11，热处理温度为1000℃的条件下。用共沉淀法合成Si-HAP粉体，利用XRD、SEM测试分析表明。Si进入了HAP晶格中，导致Si-HAC晶粒尺寸减小。用液相调和粉体制得Si-HAC。通过对其凝结时间、抗压强度和孔隙率的测试，结果表明，Si含量在1％时Si-HAC的凝结时间小、抗压强度高。     

Rapid microwave synthesis of hydroxyapatite phosphate microspheres with hierarchical porous structure

Hierarchical Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA) microspheres can be applied as microcarriers in cell carriers and drug delivery. However, it is difficult to prepare monodispersed and hierarchical microspheres in short time with conventional method. Here, we report the preparation of hierarchical HA microspheres through a novel microwave-assisted method in several minutes, where similar structured calcium carbonate (CaCO₃) microspheres acts as sacrificial hard-templates. The SEM images indicated that surface microstructure and microspheres size were effectively controlled by changing starting parameters such as microwave react time and stirring speed. XRD patterns and BET results further proved that the pure HA microspheres with great specific surface area can be prepared in a short time. The Ca ions release of samples showed that the degradation of HA microspheres decreased with microwave processing time of samples. Drug release of samples showed that on one hand vancomycin release concentration decreased with microwave processing time of samples, on the other hand increased obviously with the lower pH value of buffer solution. Human osteoblasts-like cells were cultured with different concentration of microspheres extracts to investigate in vitro biocompatibility. The results of the CCK-8 assay and Live/Dead staining proved that the cells grew well in all sample extracts, suggesting that cells responded well to the microspheres. Our work provides a novel and rapid way to produce hierarchical HA microspheres for bone repair or drug delivery.     

Effective diffusion distance for isothermal sintering of hydroxyapatite

Abstract

The microstructural evolution of hydroxyapatite (HAp) was quantified for isothermal sintering at 1100°C. The aggregated state of the powder particles is thought to be responsible for the relatively high value of the average pore separation throughout isothermal sintering. The measured grain size exponent of 6·7 is not compatible with the values expected for volume diffusion or grain boundary diffusion under the assumptions of the Combined Stage Sintering Model and hence the Master Sintering Curve. The measured exponent for a previously defined flux weighted effective diffusion distance gave a more reasonable value of 3·4. The theoretical exponent in the Combined Stage Sintering Model was then corrected to accommodate a non-linear relationship between the effective diffusion length and pore size. The results demonstrate how the effective lengthscale in the Combined Stage Sintering Model can be corrected to accommodate aggregation in the microstructure.     

Comparative hydrothermal synthesis of hydroxyapatite by using cetyltrimethylammonium bromide and hexamethylenetetramine as additives

Comparative synthesis ways for preparing HA (Ca₁₀(PO₄)₆(OH)₂) nanoparticles in presence of hexamethylenetetramine (HMTA) and cetyltrimethylammonium bromide (CTAB) were carried out. The reactions were performed in a Teflon-lined stainless-steel reactor at 120 °C during 12 h. The effects of the additive concentration and the cooling mode (fast and slow) were analyzed. The obtained powders were characterized by X-ray Diffraction (XRD), Raman Spectroscopy, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). The two hydrothermal ways carried out for preparing HA nano powders produced a pure crystalline phase of HA. When the fast cooling mode was used, the obtained particles exhibited smaller mean particle sizes. The highest concentrations of used additives (HTMA or CTAB) resulted in opposite effect on the obtained mean particle size of HA particles. These observations were associated to the different behavior of these additives in the HA formation processes.     

超增溶胶团原位合成法制备纳米AlPO4-5分子筛

应用自制模板剂,采用超增溶胶团原位合成法,制备纳米AIPO4-5分子筛微粒.利用XRD、TEM和BET吸附等分析测试手段对所得AIPO4-5微粒的组成、半径大小和形貌进行了表征.表明超增溶胶团原位合成法制得的纳米AIPO4-5分子筛粒子呈现非常均匀的单分散状态,晶型发育也较完善,纳米尺寸小.     

Tailoring the morphology of hydroxyapatite particles using a simple solvothermal route

Nanometric and sub-micrometric monodispersed hydroxyapatite (HAp) particles with different morphologies (spheres and rods) were synthesized via a simple solvothermal method using Ca(NO₃)₂·4H₂O and P₂O₅ as starting materials without any requirement to use organic templates. The growth, evolution and purity of the nanoparticles were investigated by controlling the synthesis conditions, including the alkalinity and the temperature of the solvothermal treatment. The increasing of the alkaline ratio results in a great change of the elaborated particles’ morphology that evolved from anisotropic forms (nanorods, sub-micrometric rod) at pH 9, short rod particles at pH 9.5 to spherical ones at higher pH (pH≥10).Powder X-Ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Nitrogen adsorption and desorption studies (BET) were used to characterize the structure and composition of the as-prepared samples.The thermal analysis of the synthesized particles conducted by differential scanning calorimetry (DSC) shows a good stability for all morphologies with a degradation temperature reaching 1300 °C.     

Green synthesis of templated porous carbons

Porous carbon materials such as activated carbons are widely used industrially for the purposes of purification, decolourization, deodorization, and gas storage, among others. Routes for the synthesis of these materials employing templates have increasingly attracted attention due to the ease of manipulating the characteristics of the final product. In the present work, a simple synthesis method was applied for the production of highly porous carbon materials using commercial sugar as the carbon source, Aerosil silica as a template, and deionized water. The synthesis procedure was as follows: (I) Gel formation; (II) carbonization of the gels; (III) removal of the silica template; (IV) activation. The materials were characterized by N₂ and CO₂ physisorption, Raman spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy, and thermogravimetric analysis. The aging time had an important influence on the specific area and porosity of the material, with physisorption analysis revealing a high specific area and pore volume. The activation procedures further contributed to significantly increasing the specific area (up to 1158 m² g⁻¹) and pore volume (up to 1.65 cm³ g⁻¹). The X-ray diffractograms and Raman spectra identified the formation of semi-crystalline structures in the material, with the presence of a random distribution of graphite and graphene oxide, in addition to amorphous carbon. FTIR analysis showed the presence of bands corresponding to aromatic groups. The results demonstrated that it was possible to obtain materials with excellent potential for use in different industrial sectors using simple raw materials and a technique that is easy to reproduce.     

Ibuprofen release from porous hydroxyapatite tablets

The present study investigated drug release profiles from porous hydroxyapatite [Ca₅(PO₄)₃OH, HAP] tablets. HAP tablets prepared synthetically and porous structure was generated via microemulsion after sintering at 700 °C. The influence of tablet's microemulsion concentration on drug release profiles from sintered porous tablets was investigated by using ibuprofen (C₁₃H₁₈O₂) as model drug.A numerical approach based on Fick's second diffusion law was used to investigate drug release kinetics from porous HAP tablets. Via this equation, diffusion coefficients were calculated for each tablet and compared. Drug release from the tablets was influenced by the porosity and tortuosity of the porous network. The drug release from porous HAP tablets was increased by microemulsion concentration. It is possible to obtain HAP based drug delivery system which has different drug release behavior by controlling microemulsion concentration in tablets before sintering.     

Synthesis of hydroxyapatite nanoparticles using surface carboxyl-functionalized carbon dots as template

Carbon dots (CDs), which are discrete, nearly spherical nanoparticles with sizes below 10?nm and large amounts of carboxylic acid moieties on the surface, have been proposed as an ideal template candidate for heterogeneous nucleators to regulate hydroxyapatite (HAp) nucleation and growth. In this paper, small HAp nanoparticles formed on carboxyl-functionalized CDs in situ were fabricated via the hydrothermal method. Investigation for the corresponding morphologies and detailed formation mechanisms of samples were conducted by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and Rietveld refinement. The optimum size and crystallinity of HAp particle had been obtained in the preparation when the additive content of CDs was 1.11?g/L. Moreover, results also suggested that CDs were served as nucleators in the HAp particles. Therefore, a novel synthetic strategy is presented for small HAp nanoparticles using CDs as template.     

In-situ grown hydroxyapatite whiskers reinforced porous HA bioceramic

To improve the mechanical properties of a porous bioceramic without reducing its porosity, a new kind of porous hydroxyapatite (HA) bioceramic with in-situ grown HA whiskers was fabricated using a simple sintering method. CaSO₄·2H₂O was used as a pore-forming medium and also as a catalyst for the growth of in-situ HA whiskers. The bioceramic was analyzed by XRD, SEM and mechanical tests. In-situ grown HA whiskers were stratified on the cliffs of pores in the bioceramic. The compressive strength is as high as 21.7 MPa with the porosity of about 26%. The results show that porous HA bioceramic can be improved in both compressive strength and porosity by the addition of CaSO₄·2H₂O. This novel HA bioceramic has a higher compressive strength without reducing its porosity in a certain weight ratio of CaSO₄·2H₂O, which depends on its two-step fracture pattern. This novel structure provides a new and promising reinforced pattern for porous materials.     

Microwave assisted synthesis of biomorphic hydroxyapatite

Hydroxyapatite has been synthesized using eggshell membrane as bio-template along with the assistance of microwave heating. Eggshell membrane is infiltrated with calcium and phosphorous precursors before heating it in a domestic microwave oven. Hydroxyapatite formed retained the interwoven hierarchical structure of the eggshell membrane. Structural analysis was performed using X-ray diffraction, and the microstructural features are characterized by scanning electron microscopy. Distinct morphological features were present in microwave processed hydroxyapatite when compared to the conventionally processed one. Transmission electron microscopic investigations and BET surface area analysis were also carried out.     

Mechanochemical synthesis and cold sintering of mussel shell-derived hydroxyapatite nano-powders for bone tissue regeneration

According to the circular economy principles, processing routes aiming at reducing the natural resources consumption and the energy demand can be addressed as ‘green’. In this framework, mussel shells, a natural feedstock of calcium carbonate, were successfully transformed into nano-crystalline hydroxyapatite by mechanochemical synthesis at room temperature after mixing with a phosphoric acid solution. The as-synthesized powder was then consolidated up to 82 % relative density by cold sintering (600 MPa, 200 °C). The materials were fully investigated by physical, chemical and thermal characterization techniques. Cold-sintered samples were also subjected to biaxial flexural strength test, showing a flexural resistance of 23 MPa. Cell viability assessment revealed that cold sintered hydroxyapatite derived from mussel shells promotes faster adhesion and spreading of human bone marrow-derived mesenchymal stem cells, in comparison to a commercial hydroxyapatite sintered at 1050 °C. Therefore, cold-sintered mussel shells-derived hydroxyapatite can be a promising future candidate scaffold for bone tissue regeneration.     

In situ synthesis and characterization of nano-size hydroxyapatite in poly(vinyl alcohol) matrix

Hydroxyapatite (HAp) crystals were prepared via an in situ biomimetic process in the presence of poly(vinyl alcohol) (PVA). The effect of polymer amount and its molecular weight on the physical properties of the HAp crystals were investigated. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) analysis, confirmed the formation of the crystalline HAp at room temperature. Microstructural features such as size and morphology of the resulting HAp samples were characterized using BET, scanning and transmission electron microscopy. The results indicate that the development (size and shape) of the HAp nanocrystals precipitated in an aqueous solution of PVA was influenced by the molecular weight of the polymer in such a way that smallest crystallite size was observed in the case of PVA with the highest molecular weight. It is believed that the HAp formation was initiated through the interaction of Ca²⁺ ions with the negative side groups on the polymer surface. The larger number of reaction sites in the PVA polymer with higher molecular weight led to a higher number of HAp nuclei and therefore smaller crystallite size.     

The effect of vitamins to hydroxyapatite growth on porous polyurethane substrate

This work presents a study on the possibility of obtaining hydroxyapatite thin layers on porous polyurethane support using a modified coating method, which is based on a biomimetic technique. To investigate bone-like apatite coatings formation on polyurethane surface, two types of solutions such as supersaturated calcification solution (SCS) and modified SCS (M-SCS) were used. The modified supersaturated calcification solution was prepared with added at original SCS appropriate quantities of vitamin A and vitamin D₂. The hydroxyapatite deposits are investigated by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX) and ATR-IR spectroscopy. The presence of vitamins (A and D₂) in M-SCS solution favours the formation of hydroxyapatite layer on polymeric substrate. The results obtained from SEM images have showed that porous polyurethane/hydroxyapatite scaffolds with estimated porosity of over 60% in an interconnected network, were produced under vitamins influence.     

Effects of gelatin addition on the microstructure of freeze-cast porous hydroxyapatite ceramics

Porous hydroxyapatite (HAP) ceramics was prepared by freeze casting and gelatin was used to adjust the pore morphology and microstructure of the porous HAP ceramics. With the gelatin concentration increase, the viscosity of HAP slurry was increased, and the linear shrinkage ratio of the specimen sintered at 1300 °C was also increased. The gelatin addition had great effects on the pore size and pore morphology of the porous HAP ceramics. The experimental results showed that the pore morphology of HAP ceramics was changed from a two-dimensional flat pore to a three-dimensional reticulated pore after gelatin addition.     

Modeling and optimization of combustion synthesis for hydroxyapatite production

In this study, the combustion synthesis of hydroxyapatite was studied and optimized under controlled experimental conditions. The hydroxyapatite content, crystallinity and crystallite size were monitored under changes in type of fuel, pH or red/ox ratio, muffle temperature, and reaction time. The products were characterized by X-ray diffraction, refinement of crystalline phases by the Rietveld method, scanning electron microscopy, and infrared spectroscopy with the Fourier transform. The decomposition of hydroxyapatite, which was the major phase, produced beta tricalcium phosphate in all samples, as indicated by their diffractograms. Infrared spectroscopy analysis revealed the presence of b-type carbonate groups in the structure; thus, the synthesized compound has the following chemical formula: Ca_10-x (PO₄)_6-x (CO₃)_x (OH)_2-x, where 0 < x < 2, which corresponds to carbonated hydroxyapatite (CHAp). The combustion process was modeled using a first-degree polynomial, and we found that the interaction between time and temperature to be the most influential parameter. Optimization indicated that processing conditions at 650 °C for 30 min, using urea at pH = 2 and ϕ_e = 1.134, produced the best result in terms of HAp composition, yielding 89.25% wt.     

Direct synthesis of phenol from benzene over hydroxyapatite catalysts

The direct synthesis of phenol from benzene in the gas phase was studied over hydroxyapatite catalysts. The reaction was carried out in a fixed-bed reactor at atmospheric pressure and reaction temperature of 450°C in the presence of ammonia. A high selectivity (about 97%) of phenol formation at about 3.5% conversion of benzene was achieved over catalysts containing Ca and Cu ions in the cation part of hydroxyapatite. Besides phenol as the main reaction product, aniline is also formed. The reaction mechanism involves formation of N₂O from NH₃ in the first step of reaction. Benzene is oxidized by active oxygen species which are formed on the catalyst by decomposition of N₂O.     

Electrochemical synthesis of nickel hexacyanoferrate nanoarrays with dots, rods and nanotubes morphology using a porous alumina template

Transition metal hexacyanoferrate (MeHCF) have attracted extensive attention because of their outstanding properties including, electrocatalysis, molecular magnetism, biosensing and ion-exchange. This paper describes an approach for fabrication of ordered nanoarrays of Ni hexacyanoferrate (NiHCF) structures with different morphologies such as dots, rods and tubes in order to advance their properties and applications. The method is based on the conversion of Ni into NiHCF nanostructures by electrochemical oxidation in the presence of hexacyanoferrate ions, using nanoporous anodic alumina oxide (AAO) as a template. The structure and morphology of formed Ni and NiHCF nanoarrays were confirmed by scanning electron microscopy (SEM), showing agreement with the pore structures of the AAO template. The electrocatalytic activity of NiHCF nanorod array electrodes showed high catalytic properties for the detection of hydrogen peroxide and the potential to be used as a platform for direct biosensing applications. The ion-exchange ability of fabricated NiHCF nanostructures (nanorods and nanotubes) toward alkali cations such as Na⁺ has been successfully confirmed.