Production of Hydroxyapatite/Bioactive Glass Biomedical Composites by the Hot-Pressing Technique

Biomedical composites of hydroxyapatite (HA) and bioactive glass (BG) have been difficult to obtain as a dense body without the undesirable occurrence of thermal reactions and phase degradation. Herein, HA–BG dense composites were produced by the hot-pressing technique. A range of HA–BG powder mixtures (30–50 wt% BG) was fully densified by hot pressing at temperatures as low as ∼700°–800°C. On the other hand, the HA–BG composites could not be densified by pressureless sintering because their composition was degraded due to a severe thermal reaction. The hot-pressed composites had significantly improved flexural strengths (∼60 MPa) as compared with those subjected to pressureless sintering (∼30 MPa) or the pure HA control (∼40 MPa). The hot-pressed HA–BG composites showed significantly enhanced bioactivity in a simulated body fluid, as well as osteoblast cell activity with respect to the pure HA, confirming their excellent in vitro biocompatibility.     

Conversion of Bioactive Borosilicate Glass to Multilayered Hydroxyapatite in Dilute Phosphate Solution

The conversion of a bioactive borosilicate glass in aqueous phosphate solution was observed to produce vastly different reaction kinetics and hydroxyapatite (HA) microstructures, depending on whether the glass was reacted continuously or intermittently in the solution. Particles (150–300 μm) of a borosilicate glass (designated H12) were reacted continuously or intermittently in 0.25 M K₂HPO₄ solution with a starting pH value of 7.0 at 37°C. The conversion kinetics of the glass particles to HA were determined from weight loss measurements. Structural and compositional changes resulting from the conversion reaction were characterized using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, and Fourier transform infrared spectroscopy. For conversion experiments carried out intermittently (12–24 h intervals, followed by drying), faster reaction kinetics and a unique multilayered microstructure, consisting of alternating layers of HA and an amorphous SiO₂-rich material with nearly uniform thickness (2–3 μm), were observed. On the other hand, particles reacted continuously in the phosphate solution for the same total time converted more slowly and produced a single HA layer. The kinetics and mechanism of forming HA under the intermittent and continuous reaction conditions are described and compared with those for bioactive silicate and borate glasses studied in previous work.     

Preparation and Characterization of Organically Modified Montmorillonite-Filled High Density Polyethylene/Hydroxyapatite Nanocomposites for Biomedical Applications

The study investigated the introduction of organically modified montmorillonite (MMT) in high density polyethylene/hydroxyapatite (HDPE/HA) composites for biomedical applications. The addition of HA and MMT increased the strength and stiffness of HDPE/HA composites with deterioration in impact strength and elongation at break values. XRD and TEM analysis provided evidence of exfoliated MMT layers in HDPE/HA composites and the MMT layers remained exfoliated even with further addition of HA. Simulated body fluid (SBF) analysis revealed that the size of apatite layer increased with increasing immersion time and the formation of apatite layers on the surface of composites indicates excellent biocompatibility properties.     

Fabrication,Characterization and Dielectric Studies of NBR/Hydroxyapatite Nanocomposites

Nitrile rubber (NBR) based nanocomposite consists of different concentrations of hydroxyapatite nanoparticles (HA) were prepared and characterized by FTIR, UV and X-ray diffraction studies. The surface morphology of the nanocomposites were analyzed using SEM and optical microscopy. The glass transition temperature and thermal stability of NBR and its nanocomposites were done by DSC and TGA respectively. The electrical properties such as AC conductivity, dielectric constant and dielectric loss tangent were investigated in the frequency range of 10²–10⁶ Hz at room temperature. The FTIR spectra confirmed the interfacial interaction between NBR and the HA nanoparticles. The shift in the UV peak with broadness of composite indicates the formation of nanoparticles within the macromolecular chain of NBR. XRD pattern ascertained the ordered arrangement of nanoparticles with a decrease in the amorphous nature of parent polymer. Both the glass transition temperature and the thermal stability of the nanocomposites were higher than pure NBR and the glass transition temperature improved with the increase in concentration of nanoparticles in NBR composite indicating the strong interfacial adhesion between the polymer and nanoparticles. From DSC studies, thermodynamic parameters such as enthalpy and entropy change of the composites were also evaluated. AC conductivity of the nanocomposite was much greater than NBR and the magnitude of conductivity enhanced with the addition of nanoparticles. The observed enhancement in dielectric constant and dielectric loss tangent of composite with the increase in concentration of nanoparticle was attributed to the increase in number of interfacial interaction between the polymer and the nanoparticles.     

壳聚糖诱导合成羟基磷灰石及其结构表征

本文运用仿生矿化的原理,以四水硝酸钙和磷酸氢二铵为反应物,在0.6%CS为诱导剂的6%双氧水溶液中合成了六方晶系与单斜晶系的HAP,并且研究了CS溶液对HAP合成的影响。通过X射线衍射分析、结构精修分析、扫描电镜观察、粒度分布分析以及热重分析,对制备的HAP进行了结构表征。结果表明,以CS为诱导剂是制备HAP的良好工艺,生成的HAP呈现针状或者片状,长在80 nm至100 nm之间,宽在15 nm至20 nm之间,并且CS能够提高单斜HAP的合成率,而且沉淀时间和反应系统的pH值对HAP的微观形貌有一定影响。     

利用热膨胀仪研究硼硅酸盐玻璃的结构弛豫行为

针对目前差示扫描量热仪、红外光谱和Raman光谱等在分析不同玻璃性质弛豫行为上的局限性,提出了建立在玻璃热膨胀性能测试基础上的分析方法。在Rekhson提出的方案基础上,结合Moynihan法,采用Tool-Narayanaswamy-Moynihan唯象模型对玻璃容积在转变区内的弛豫行为进行了研究。测试了两种具有不同热历史的硼硅酸盐玻璃的热膨胀曲线,得到了相同结构弛豫参数,验证了这种方法的可靠性。结果表明:采用改进Rekhson法得到的硼硅酸盐玻璃弛豫函数在参考温度为830K时的比例系数x为0.89,活化能H为200kJ/mol,弛豫时间τr为200s,扩展指数β为0.55;对比Moynihan热容法,该方法虽在精确性上稍差,但在工业领域应用中具有非常大的潜力。     

羟基磷灰石对硼酸盐生物活性玻璃降解性能的调控

将熔融法制备的硼酸盐生物玻璃按不同比率与羟基磷灰石混合烧结,制备出双相材料支架样品.将各组样品浸泡在生理模拟液中(5 g样品/100 mL浸泡液),置于37℃恒温条件下,进行体外生物矿化反应,考察了支架的降解性能随羟基磷灰石含量的变化情况.实验中,通过ICP测试,研究了硼元素在支架降解过程中的释放情况.通过XRD和FTIR分析了产生变化的原因,结果表明硼酸盐生物活性玻璃与羟基磷灰石在600℃混合烧结后会产生新的晶相,使得结构更加稳定,降解速度放缓,尤其克服了B元素在降解初期的过量释放.     

无机-无机纳米复合材料的构筑与性能

无机-无机纳米复合材料以其独特的光学、电学、催化性能和广泛的应用受到人们的关注，成为纳米材料领域的研究热点，本论文主要研究了核壳结构的二氧化硅／银复合材料的制备和性能。     

尼龙66／蒙脱土纳米复合材料的制备与表征

利用熔体插层法制备了尼龙66／蒙脱土纳米材料复合材料,测试了力学性能、热性能。通过XRD、TEM等手段,研究了蒙脱土在基体中的分散情况。结果表明,蒙脱土以10－100nm的尺寸均匀分散于尼龙66中,所得到的复合物的性能较尼龙66有较大提高。     

酚醛树脂/蒙脱土纳米复合材料的制备和表征

在醋酸锌催化剂作用下,采用边缩聚边插层的一步法制备了酚醛树脂／蒙脱土杂化树脂,并采用对甲苯磺酸为室温固化剂制得酚醛树脂／蒙脱土复合材料。傅立叶红外光谱和X-射线衍射分析表明：苯酚和甲醛可以进入蒙脱土硅酸盐片层间并进行缩聚反应,一方面,在缩聚过程中蒙脱土层间距d00。进一步扩大;另一方面,经缩聚反应得到的含羟甲基的酚醛树脂预聚物可与蒙脱土硅酸盐片层间羟基发生化学反应。热失重分析数据说明,随着蒙脱土含量的增加,酚醛树脂／蒙脱土固化物的耐热性提高。     

Synthesis, Processing, Mechanical, and Biological Property Characterization of Hydroxyapatite Whisker-Reinforced Hydroxyapatite Composites

Effects of hydroxyapatite (HA) whiskers addition on densification, mechanical, and biological properties of HA compacts were studied for their use as an implant material for orthopedic and dental applications. HA nanopowder was synthesized using reverse micelle as template system, and urea hydrolysis synthesis route was used to prepare micrometer-sized HA whiskers. Poly (oxyethylene)₁₂ nonylphenol ether (NP12) and cyclohexane were used as surfactant and organic solvent, respectively, for the reverse micelle microemulsion system. Desired microstructure in sintered HA composite was obtained by mixing Mg²⁺ as a dopant in HA nanopowders, and Al³⁺ as a dopant in HA whiskers. Compacts were processed using pressureless sintering. With an increase in whisker content from 0 to 10 wt%, the average compressive strength of HA compacts decreased from 120 to 90 MPa. HA composite processed with 10 wt% HA whisker showed a microhardness of 3.6 GPa and an average indentation fracture toughness of 1.5 MPa·m^1/2. Mineralization study in simulated body fluid showed deposition of octacalcium phosphate on sintered HA compacts. In vitro cytotoxicity tests with human osteoprecursor cell line confirmed excellent osteoblast cell attachment and growth on the sintered HA compacts with 0, 10, and 20 wt% HA whiskers.     

Early Stages of Calcium Phosphate Formation on Bioactive Borosilicate Glass in Aqueous Phosphate Solution

The conversion of bioactive glass to a calcium phosphate material, typically hydroxyapatite (HA), by solution–precipitation reactions in aqueous phosphate solution, has been commonly reported. This paper describes the structural and compositional characteristics of the calcium phosphate material formed during the early-stage conversion (<5 h) of a borosilicate glass (designated H12) in aqueous phosphate solution. Disks of H12 glass were reacted with 0.25 M K₂HPO₄ solution with a starting pH=7.0 at 37°C. The structure and composition of the product layer were characterized using thin film X-ray diffraction, scanning electron microscopy, and Fourier transform infrared reflectance spectroscopy. For reaction times <5 h, the results indicated the formation of brushite (CaHPO₄·2H₂O) with coarse, plate-like crystals. In comparison, the formation of HA with small needle-like crystals was found at later times. This early-stage formation of brushite has not been reported in previous studies of converting bioactive silicate and borate glasses in aqueous phosphate solution.     

PLA/MMT-HTCC纳米复合材料的绿色合成、表征及热降解动力学分析

以乳酸锌为绿色催化剂,采用丙交酯开环聚合法制备了聚乳酸/壳聚糖季铵盐改性蒙脱土(PLA/MMT-HTCC)纳米复合材料。通过红外光谱、X射线衍射(XRD)、热重分析、扫描电子显微镜和透射电子显微镜进行了表征,采用Kissinger法和Ozawa法进行热降解动力学分析,得到材料的表观活化能。结果表明,PLA/MMT-HTCC为插层型纳米复合材料,PLA/MMT-HTCC的热分解峰值温度(Tp)比PLA最多高35.18℃,通过MMT-HTCC插层的实现,材料的热分解活化能得到了提高,从而提高了其热稳定性。     

Microstructure Characterization of Simulated Tri-Isotropic Particles Embedded in Alkaline Borosilicate Glass

A preliminary study of the encapsulation of tri-isotropic (TRISO) coated particles in alkaline borosilicate glass (ABG) using melting and casting methods is presented. ABG has been developed to encapsulate simulated TRISO fuel particles that are used as nuclear fuel elements in Very High Temperature Reactors. Encapsulation is an alternative to vitrification and it is a process in which radioactive waste is encapsulated within a composite as a first barrier and a glass matrix as a second barrier. This provides two barriers against leaching and diffusion of the radioactive waste once buried in the geological repository. The study investigates the possibility of achieving high densification of glass–graphite composite by sealing the pores of TRISO particles surrogate (28 wt% CeO₂, 70 wt% graphite, and 2 wt% poly-ethylene glycol) with molten ABG at 600°C. This article follows the carbon phases during the encapsulation and highlights the interaction area between the carbon and glass phases before and after melting, using a polarized laser source (Ar, 514 nm). The laser analysis revealed that the graphite no longer was retained in graphene hexagonal structure and that it was linked with the glass network as disordered carbon atoms.     

Sol–Gel Synthesis of PZT–Glass Nanocomposites Using a Simple System and Characterization

A simple inorganic system has been developed for the sol–gel synthesis of piezoelectric PZT–glass nanocomposites. Nanocrystalline PZT are nucleated from the amorphous xerogel through controlled heat treatment at 600°C. The formation of the crystalline phase, particle size, morphology, kinetics, and mechanism of crystallization of PZT in the glass matrix have been studied using X-ray diffraction, scanning electron microscopy, and differential thermal analysis. The piezoelectric characteristics of the PZT–glass compositions have been determined, and are correlated with the microstructure and the crystalline phase of PZT.     

砷羟基磷灰石的水热合成与结构表征

以四水硝酸钙[Ca(NO3)2·4H2O]、磷酸氢二铵[(NH4)2HPO4]、十二水合砷酸钠[Na3AsO4·12H2O]为原料,在200℃下水热反应8h制得掺砷羟基磷灰石[Ca10(PO4)6-x(AsO4)x(OH)2].考察了反应液中不同砷含量对合成砷羟基磷灰石结构的影响.采用X射线衍射分析(XRD)、扫描电镜结合电子能谱分析(SEM/EDS)、傅立叶变换红外光谱分析(FTIR)等测试手段对产物的晶相、化学组成和形貌进行分析.结果表明:As取代部分磷(P)进入羟基磷灰石的晶格中,没有改变其晶体结构,但羟基磷灰石的晶胞参数发生了变化,随着As含量的增加,砷羟基磷灰石的晶体尺寸呈增大的趋势,晶体形状为短棒状.     

海藻酸钠/纳米氧化锌/生物活性玻璃多孔支架的制备及表征

以海藻酸钠(Sodium Alginate,SA)、纳米氧化锌(Zinc Oxide,ZnO)和生物活性玻璃(Bioactive Glass,BG)为原材料,采用3D打印挤出沉积成型技术制备SA/BG支架和SA/ZnO/BG支架.通过1000℃烧结,制备纯BG及ZnO/BG生物玻璃支架,通过便携式USB数字显微镜观察了支架形貌,测定各组支架的孔隙率和抗压强度,考察不同浓度的ZnO支架对大肠杆菌(Escherichia coil,E.coil)的体外抑菌效果.结果 表明,ZnO的加入使支架的抗压强度有所提高,而其支架孔隙率变化微小.ZnO的质量分数为0％ ～ 20％时,ZnO/BG支架抗压强度由1.1 MPa增加到2.0 MPa;对支架粉末进行X射线检测证实Zn以Ca2 ZnSi2O7形式存在;对支架粉末进行扫描电子显微镜和能谱(Energy Dispersive X-ray Spectroscopy,EDXS)检测,结果表明支架中有Zn元素存在;对支架进行体外抗菌试验发现掺杂了ZnO的支架,具有良好的抑菌效果.因此,通过3D打印挤出沉积成型技术制备SA/ZnO/BG支架,经过高温烧结得到的ZnO/BG支架具有三维互通的孔结构,拥有更高的力学性能,以及良好的体外抑菌效果.     

Synthesis of Antibacterial Hybrid Hydroxyapatite/Collagen/Polysaccharide Bioactive Membranes and Their Effect on Osteoblast Culture

Inspired by the composition and confined environment provided by collagen fibrils during bone formation, this study aimed to compare two different strategies to synthesize bioactive hybrid membranes and to assess the role the organic matrix plays as physical confinement during mineral phase deposition. The hybrid membranes were prepared by (1) incorporating calcium phosphate in a biopolymeric membrane for in situ hydroxyapatite (HAp) precipitation in the interstices of the biopolymeric membrane as a confined environment (Methodology 1) or (2) adding synthetic HAp nanoparticles (SHAp) to the freshly prepared biopolymeric membrane (Methodology 2). The biopolymeric membranes were based on hydrolyzed collagen (HC) and chitosan (Cht) or κ-carrageenan (κ-carr). The hybrid membranes presented homogeneous and continuous dispersion of the mineral particles embedded in the biopolymeric membrane interstices and enhanced mechanical properties. The importance of the confined spaces in biomineralization was confirmed by controlled biomimetic HAp precipitation via Methodology 1. HAp precipitation after immersion in simulated body fluid attested that the hybrid membranes were bioactive. Hybrid membranes containing Cht were not toxic to the osteoblasts. Hybrid membranes added with silver nanoparticles (AgNPs) displayed antibacterial action against different clinically important pathogenic microorganisms. Overall, these results open simple and promising pathways to develop a new generation of bioactive hybrid membranes with controllable degradation rates and antimicrobial properties.     

硼硅玻璃管道的应用

介绍硼硅玻璃管道的性能、特点和应用情况;阐述其安装方法及其注意事项。     

PLA/HTCC-MMT插层复合材料的绿色合成、表征及热降解动力学分析

以乳酸锌为绿色催化剂,采用丙交酯开环聚合法制备了聚乳酸/壳聚糖季铵盐改性蒙脱土(PLA/MMT HTCC)纳米复合材料。通过红外光谱、X射线衍射(XRD)、热重分析、扫描电子显微镜和透射电子显微镜进行了表征,采用Kissinger法和Ozawa法进行热降解动力学分析,得到材料的表观活化能。结果表明,PLA/MMT HTCC为插层型纳米复合材料, PLA/MMT HTCC的热分解峰值温度(Tp)比PLA最多高35.18 ℃,通过MMT HTCC插层的实现,材料的热分解活化能得到了提高,从而提高了其热稳定性。