多孔碳酸钙微球的快速制备

在室温下采用复分解法不添加控制剂,通过快速混合溶液制备出多孔碳酸钙微球,考察不同碳源、钙源和浓度体系对产物的影响。样品通过X-射线衍射、场发射扫描电子显微镜和比表面与孔隙分析仪进行表征。结果表明,在0.25 mol/L浓度条件下,采用Ca(CH_3COO)_2与(NH_4)_2CO_3溶液快速反应制备得多孔碳酸钙微球分散性好、粒度均匀,晶型为单一球霰石相,纯度较高;孔径主要分布在45 nm左右,比表面积达7.19 m~2/g。     

碳酸钙中空微球的仿生合成及机理分析

以氯化钙、碳酸钠为原料,以聚丙烯酰胺(PAM)和十二烷基硫酸钠(SDS)形成的PAM/SDS核壳状复合物为软模板,仿生合成了中空微球碳酸钙。以透射电子显微镜、选区电子衍射、扫描电子显微镜、X射线衍射仪进行了表征,结果表明,制备得到的中空碳酸钙直径3⁶μm,分散性良好,中空球的球壁完整,壁厚约500 nm,由506μm,分散性良好,中空球的球壁完整,壁厚约500 nm,由50⁷0 nm的纳米粒子聚集而成。实验考察了PAM、SDS浓度的变化对产品的影响,并探讨了中空碳酸钙微球的形成机理。结果表明,PAM、SDS对中空碳酸钙微球的形成起着重要的作用。     

碳酸钙中空微球的仿生合成及机理分析

以氯化钙、碳酸钠为原料,以聚丙烯酰胺(PAM)和十二烷基硫酸钠(SDS)形成的PAM/SDS核壳状复合物为软模板,仿生合成了中空微球碳酸钙。以透射电子显微镜、选区电子衍射、扫描电子显微镜、X射线衍射仪进行了表征,结果表明,制备得到的中空碳酸钙直径3~6μm,分散性良好,中空球的球壁完整,壁厚约500 nm,由50~70 nm的纳米粒子聚集而成。实验考察了PAM、SDS浓度的变化对产品的影响,并探讨了中空碳酸钙微球的形成机理。结果表明,PAM、SDS对中空碳酸钙微球的形成起着重要的作用。     

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.     

Fabrication of dense and porous biphasic calcium phosphates: Effect of dispersion on sinterability and microstructural development

The particle size distribution of a commercial Mg-doped hydroxyapatite powder was tailored through two different milling procedures, carried out under wet or dry conditions. Wet milling gave rise to finer particles, with a narrower size distribution. Tailoring the particles size was the key to produce homogeneous gelcast green bodies, as well as fully dense and fine microstructures. In fact, wet-milled samples achieved full densification and compressive strength of about 300 MPa, five times higher than the values achieved by the dry milled samples. During the calcination treatments, HA progressively decomposed into β- and α-TCP phases, promoted by the progressive Mg²⁺ substitution inside the HA and β-TCP lattices. As a result, a biphasic (HA/β-TCP) calcium phosphate ceramic was successfully obtained. Gelcast macroporous materials were prepared by direct foaming, starting from both milled powders. Highly porous samples (73%-77% porosity) with a high degree of interconnectivity within pores were successfully produced. However, dry milled-foamed materials were characterized by a significant residual porosity within the struts, whereas in wet-milled foams struts and pore windows were highly compact, the key to provide sufficient mechanical strength to such highly porous open-cell foams, thus suggesting a possible use as implantable scaffolds.     

自结合多孔六铝酸钙合成方法研究

以活性α-氧化铝和自制的活性石灰(煅烧温度为750℃)为主要原料,按照原料特点及六铝酸钙的理论组成进行配料,试验采取共磨粉外加55%(质量分数)蒸馏水制成泥料,振动成型,常温养护12 h及110℃干燥24 h后,于1 450℃经6 h烧成。并利用XRD和SEM分析烧后试样的相组成和显微结构。试验结果表明,以活性α-氧化铝和活性石灰为原料经1 450℃焙烧6 h可以形成六铝酸钙。活性石灰的水化膨胀所形成的多孔结构使氧化铝与氧化钙反应生成的六铝酸钙晶体自由生长,形成珊瑚状结构。片状结构六铝酸钙晶体在三维空间交叉生长加强了结构的稳定性,在整个结构中出现大量分布均匀的微小间隙。     

Preparation of porous carbon microspheres

Porous carbon microspheres with good morphology, high yield, and controllable particle size were prepared from phenolic resin. The particle size and pore structure of the carbon microspheres were mainly inherited from their precursors, resol microspheres, which were made through curing emulsified resol in water at 120°C under saturated pressure. The average particle size and specific surface area of the porous carbon microspheres was related to the concentration of resol and polyvinyl alcohol along with the heating program. The carbonization yield to 700°C was 55 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 798–803, 2006     

Controlled synthesis of nanoplate,nanoprism and nanopyramid-shaped CdSe decorated on porous TiO2 photocatalysts for visible-light-driven hydrogen evolution

Herein, we report a successful synthesis of porous TiO₂ monoliths decorated with unique nanoplate, nanoprism, and nanopyramid-shaped CdSe particles through a mild selenylation of CdO embedded inside porous TiO₂ monoliths via a hydrothermal method in a very controlled manner. Compared with pure TiO₂, as-synthesized CdSe/TiO₂ photocatalyst not only enhances light absorption but also leads to a highly efficient charge-carrier separation. Particularly, the nanoplate-shaped 7% CdSe/TiO₂ photocatalyst (molar percentages of CdSe to TiO₂ is 7:100) exhibits an exceptional hydrogen evolution rate up to 3650?μmol?h^?1 g^?1 without resorting to any noble-metal co-catalysts under visible-light irradiation owing to synergistic effects envisaged by a rational material design. Our results may provide a useful strategy to develop a highly-efficient visible-light-driven hydrogen production system via water splitting.     

Preparation and characterization of porous calcium-phosphate microspheres

Porous calcium-phosphate bioceramics are very important materials in bone tissue engineering. Recently, microsphere systems have been widely utilized in the treatment of defective tissues, including bone, cartilage and muscle. In this study, porous calcium-phosphate microspheres were prepared from calcium-deficient hydroxyapatite (d-HA) powders through a water-in-oil emulsion technique using camphene as the porogen and subsequently sintered at 700, 1100, 1200, or 1400 °C for 6 h. The microspheres produced in this study were characterized according to their morphology, properties, and biodegradation. The results indicated an interconnected porous structure with pore sizes ranging between several microns to as large as 250 μm. Approximately 35–50% of the pores were larger than 100 μm. In the microspheres sintered at 700 °C (Sample H), only the hydroxyapatite (HA) phase was present; when heated to 1100 °C (Sample BH), β-TCP was observed with HA; at 1200 °C (Sample ABH), the phase compositions included β-TCP and α-TCP, as well as a small quantity of HA; and at 1400 °C (Sample AH), the phases of samples included mainly α-TCP and HA. The degradation of the scaffolds was evaluated after immersion in distilled water for up to 28 days. Obvious dissolution and precipitation behavior was seen in the samples ABH and AH. The precipitates formed on the surface of ABH and AH could be carbonate-containing calcium-deficient HA (carbonated-CDHA) after immersion in distilled water for 28 days.     

Production of calcium hexaluminate porous planar membranes with high morphological stability and low thermal conductivity

High-quality Al₂O₃ porous ceramic planar membranes suffer from severe deformation and cracking, which occur during sintering process. This study reports on solving this problem, by introducing calcium hydroxide powder in the alumina slurry. Phase-inversion tape-casting technology, applied during molding, and sintering at 1550 °C, favored an in-situ expansion reaction, which effectively suppressed deformation, and well-formed and crack-free calcium hexaluminate porous planar membranes were obtained. The produced membranes had a low thermal conductivity (0.69 W·m⁻¹ K⁻¹ at 85 °C), ascribed to the in-situ formed plate-like structure of calcium hexaluminate (CA₆) and to the high porosity. After hydrophobic modification, the membranes were applied in membrane distillation processing. High rejection rate (>99.9%) and water flux (19.8 L·m^-2 h⁻¹) were achieved at 85 °C, using a 4 wt% NaCl solution as a feed solution.     

Facile synthesis,in vitro biocompatibility,and antibacterial activity of porous hollow hydroxyapatite microspheres

In this study, porous hollow hydroxyapatite (HAp) microspheres are prepared using chitosan microspheres as novel sacrificial templates and their microstructure, biocompatibility, and drug delivery properties are evaluated. Scanning electron microscope (SEM) observations show that HAp microspheres are spherical in morphology with a diameter of 100–300 μm and have a porous and core–shell structure. X-ray diffractometer patterns show that HAp microspheres consist of apatite phase. MTT assay indicates that HAp microspheres are biocompatible and have no significant cytotoxicity. SEM observations show that HAp microspheres support attachment and proliferation of osteoblast MC3T3-E1 cells. After being soaked in the solution of tetracycline hydrochloride (TH, model drug), HAp microspheres adsorb TH with an adsorption capacity of 47% to derive TH-loaded HAp microspheres. When exposed to two types of representative bacteria: Escherichia coli and Staphylococcus aureus, TH-loaded HAp microspheres maintain the biological activity of TH to inhibit the growth of bacteria.     

Polycaprolactone-blended gelatin microspheres and their morphological study

Polycaprolactone (PCL)-blended gelatin microspheres were prepared in the size ranges of 5–20 μm as well as 70–340 μm and modified through different compositions of PCL to gelatin in the oil-in-water emulsion solvent evaporation method. The formation of the polymer particles and particle morphology, stability, crystallinity, and thermal behavior of the polymer blends were studied. The changes in physiochemical properties of the blends were also studied with the addition of very less amount of polyvinylpyrrolidone (PVP), as it enhances the particle size distribution of microspheres as well as the surface morphology. Differential scanning calorimetry analysis shows the shifting of exothermic peak in the PCL/gelatin blend, and the PCL/gelatin blend stabilized by PVP results in the decrease in crystallinity. PCL-blended gelatin microspheres were smooth with definite shape and fine dispersibility with the increased concentration of gelatin to the polymer while lower concentration of the gelatin caused agglomeration. Optimization of the gelatin and PVP ratio to the polymer matrix results in large-size spherical stable microparticles. The stabilizing ability of microsphere decreases with the increased concentration of PCL during the solvent evaporation method. The addition of PVP to the PCL/gelatin blend enhanced the particle size distribution of microspheres as well as the surface morphology.     

Solution combustion synthesis of bioceramic calcium phosphates by single and mixed fuels—A comparative study

Calcium phosphate based bioceramics have been synthesized by a modified combustion synthetic route using both citric acid and succinic acid separately and in mixture as fuels and nitrate and nitric acid as oxidants. Calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphate sources. The effects of citric acid to succinic acid ratio on the phase formation have been investigated. The precursors and the calcined products have been characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. Succinic acid has been used as a fuel for the first time to synthesize hydroxyapatite.     

An EDTA-assisted hydrothermal synthesis of BiVO4 hollow microspheres and their evolution into nanocages

BiVO₄ hollow microspheres have been synthesized in the presence of ethylenediaminetetraacetic acid (EDTA) by a microwave hydrothermal method. The as-prepared hollow microspheres were composed of hundreds of nanorods. Increasing the amount of EDTA produced a new nanocage structure. The evolution process of BiVO₄ with different microstructures indicated that the amount of EDTA added played a crucial role in determining the shape of the samples. Additionally, it was found that the existence of EDTA was vital to mediate the crystal growth, and the hydrothermal time and temperature were key parameters in determining the BiVO₄ morphologies. A possible formation mechanism is proposed.     

Commercial synthesis of monoalkyl phosphates

Historically, phosphate esters have been prepared by the reaction of alcohols with phosphoric anhydride or polyphosphoric acid. Recently, hybrid reagents have been developed. A review of the commercial production of long-chain monoalkyl phosphate esters is presented. The titled esters are the subject of increased interest, especially in low-irritation surfactant formulations.     

可降解聚乳酸多孔微球的制备探究

以聚乳酸为壁材,碳酸氢铵为致孔剂,采用双乳液溶剂挥发法,制备出具有孔状的聚乳酸微球,探讨制备条件对聚乳酸微球的影响.结果表明,在内外水相体积比1∶7.5,初乳化搅拌速度1 000 r/min下制得的PLA多孔微球的球形和孔结构较好.     

Synthesis of nanosized powders and coatings of calcium phosphates

Hydroxyapatite powders with a particle size of nearly 100 nm, i.e., rather close to bone crystals shaped as 60 × 20 × 5-nm flattened prisms, were synthesized by the pyrolysis of a solution of calcium oleate in tributylphosphate. The possibility of synthesizing hydroxyapatite coatings on different ceramic materials was demonstrated. The pyrolysis of a solution of strontium oleate in tributylphosphate was established to produce the Sr10(PO₄)₆(OH)₂ compound isotypical to hydroxyapatite, which in turn creates prospects for synthesizing materials based on hydroxyapatite with some calcium atoms substituted by strontium.     

Single-source-precursor synthesis of porous W-containing SiC-based nanocomposites as hydrogen evolution reaction electrocatalysts

In this paper, W-containing SiC-based ceramic nanocomposites were successfully prepared by a polymer-derived ceramic approach using allylhydridopolycarbosilane ...     

Uniform and porous Mn-doped Co3O4 microspheres: Solvothermal synthesis and their superior supercapacitor performances

Uniform and porous Mn-doped Co₃O₄ microspheres (Mn@Co₃O₄ MSs) assembled with many nanoparticles (NPs) were prepared through an initially solvothermal reaction and subsequent annealing treatment at 550 ^oC in air. These Mn@Co₃O₄ MSs had an average diameter of about 9?μm and possessed a BET specific surface area of 70.4?m²/g. The pore diameter was mainly centered at 12.3?nm and the mean pore size was measured to be 15?nm. When the Mn@Co₃O₄ MSs were used as electrode material for supercapacitors, the electrochemical performances were assessed in 2?M KOH aqueous solution using a typical three-electrode configuration. Such Mn@Co₃O₄-MSs-modified electrode exhibited a highly specific capacitance of 773?F/g at 1 A/g, 62.7% rate capability at 16 A/g, and 73.9% capacitance retention of its original value after 5000 cycles at 5 A/g. The excellently electrochemical behaviors indicate that such Mn-doped Co₃O₄ MSs can be used as a superior electrode material for advanced supercapacitors in the future. The current synthesis strategy is facile and can be further employed to prepare other electrode materials with outstanding electrochemical performances.     

Immobilization of lipase on magnetic porous microspheres

开发了以磁性多孔微粒作为载体固定化脂肪酶的方法,进行了载体的FTIR、XRD、SEM、TEM、BET、TGA和VSM等测定与分析,考察了固定化时间、酶载量和缓冲液pH值等因素对固定化酶在有机相中催化烯丙醇酮转酯化反应性能的影响。结果表明,制备的磁性微粒是以Fe₃O₄为磁核,呈现多孔,比表面积12.16 m²/g,平均孔径为171.7 nm,磁铁含量38%并为超顺磁性;在酶与载体质量比为1∶1、pH值8.0及固定化时间6 h制得固定化酶的效果最佳,固定化酶的活力回收率可达240%。以其作为载体制备获得固定化酶操作稳定性得到显著提高,重复利用30批次后残余活力为74.5%,而游离酶7批次后仅为37.1%。