羟基磷灰石/聚乳酸复合材料制备的研究进展

聚乳酸是一类重要的生物降解聚合物,羟基磷灰石是人体骨骼的基本成分。以羟基磷灰石为增强材料、聚乳酸为基体制备的羟基磷灰石/聚乳酸复合材料,是无机/有机生物复合材料的典型代表,具有良好的力学性能与生物相容性,在很多领域有重要的应用。本文主要综述了羟基磷灰石/聚乳酸复合材料的制备方法。     

超声化学法合成羟基磷灰石-明胶复合材料

以Ca（NO3）2,（NH4）2HPO4,明胶和戊二醛为原料,用超声化学法合成了尺寸约为30nm×100nm,平均长径比在2-3,分散性良好的羟基磷灰石-明胶复合材料。对比研究了超声化学法与传统化学沉淀法对复合材料结晶性能和力学性能的影响。结果表明,与传统化学沉淀法相比,超声化学法可以在较短时间内显著提高羟基磷灰石的结晶度、改善结晶状态,使复合材料的抗拉强度和抗压强度分别达到52．4MPa和56．8MPa。     

Thermal Conductivity of Platelet-Filled Polymer Composites

Platelet-shaped particles of similar size and shape were investigated as fillers for improving the thermal conductivity of polymer–ceramic composite materials. The conductivities of composites filled with hard, stiff ceramic particles exceeded 3.5 W·(m·K)⁻¹, or >20 times the conductivity of the polymer matrix, and were shown to be almost independent of the intrinsic filler conductivity range of 33–300 W·(m·K)⁻¹. In contrast, the thermal conductivity of composites filled with soft, platelet-shaped BN fillers reached over 13 W·(m·K)⁻¹. A mechanism is proposed whereby deformation of the soft filler particles provides improved particle-to-particle connectivity and allows greater packing density, resulting in the ability to achieve much higher conductivity than is possible for hard and stiff particles of similar initial morphology. Experimental results are discussed in light of various thermal conductivity prediction models in the literature.     

氮化硅/羟基磷灰石复合材料的制备研究

主要用超声分散结合滴定工艺制备了氮化硅／羟基磷灰石(Si3N4/HAp)复合粉体，并经冷压成型、冷等静压成型及无压烧结制备了氮化硅／羟基磷灰石复合材料。X射线衍射(XRD)及扫描电镜(SEM)研究发现，氮化硅的加入促进了羟基磷灰石的分解，细化了晶粒，可降低羟基磷灰石的烧结温度。     

A Process for Cf/SiC Composites Using Liquid Polymer Infiltration

A continuous carbon fiber/silicon carbide matrix composite material has been produced by a low-cost process. In this process the space in a two-dimensional carbon fiber preform is filled with a SiC powder by a pressure infiltration method. High particle packing densities are achieved within the fiber preform in this way. The compact body is heat-treated at 400°C to form a porous framework, which is then infiltrated with a liquid preceramic polymer, Ceraset^TM SN. Subsequently the infiltrated polymer is pyrolyzed in argon at 1300°C. The microstructure of the final composite is characterized, and mechanical properties of these composites are discussed.     

PA1010/羟基磷灰石复合材料的制备与性能

利用熔融共混法制备了聚酰胺1010(PA1010)/羟基磷灰石(HA)复合材料,采用傅立叶变换红外光谱、热重分析仪和差示扫描量热仪测试了PA1010/HA复合材料的结构特征和热稳定性,利用电子万能试验机测试了PA1010/HA复合材料的力学性能。结果表明:复合材料中PA1010与HA之间通过氢键作用结合,而氢键作用的主要发生位置在PA1010酰胺键的氨基与HA的羟基之间;PA1010/HA复合材料具有良好的热稳定性,HA的加入对PA1010/HA复合材料的熔点基本没有影响,随着HA含量的增加,其熔融焓和结晶焓都降低。HA的加入,增强了PA1010/HA复合材料的拉伸性能和弯曲性能,与纯PA1010相比,分别提高了33.4%,98.3%。     

Preparation of Hydroxyapatite Lathlike Particles Using High-Speed Dispersing Equipment

Hydroxyapatite lathlike monocrystalline particles were prepared using high-energy dispersing equipment in combination with a pH shock-wave method. The Ca/P atomic ratios were very close to theoretical, and the acidic group content was very small. The particles were nonporous, with anisotropic crystal growth and average grain size ∼140–1300 nm in length, ∼20–100 nm in width, and ∼10–40 nm in thickness. The high-speed dispersing equipment created the proper hydrodynamic conditions for lathlike particle growth in the [001] direction. The hydroxyapatite particles formed aggregates of 1–5 μm average diameter.     

羟基磷灰石涂层的制备

本文以五氧化二磷、无水乙醇、硝酸钙为原料,通过溶胶-凝胶法制备羟基磷石灰涂层。选用2mm/s的速度浸渍提拉载玻片,在载玻片上进行涂膜,经60℃干燥后在650℃烧结保温3h,可在载玻片上得到羟基磷灰石涂层。研究结果表明:制备溶胶合适的配比为Ca(NO3)22·4H2O:P2O5(摩尔比)=10:3,即Ca/P原子比=5:3(约等于1.67)。     

Properties of 0–3 Lead Zirconate Titanate–Polymer Composites Prepared in a Centrifuge

The purpose of this work was to present the electrical and piezoelectric properties of the 0-3 piezoceramic–polymer composites prepared by spinning the lead zirconate titanate (PZT) powders with polyester resin in a centrifuge. PZT powders with average sizes of 55 and 160 μm were used and mixed in the resin with different volumetric percentages. The dielectric and piezoelectric properties such as permittivity, loss angle, electromechanical coupling factor, and piezoelectric coefficient were measured. The mechanical quality factor was calculated. The acoustic impedance was accessed by the echo-shift method. The results were analyzed and fit to mechanical models. Distribution of the ceramic particles in the polyester-resin phase was examined by scanning electron microscopy. Smaller-ceramic-particle composites seemed to form denser samples. Most of the properties showed linearly varying as the volumetric percentage of the ceramic phase. The fabrication using the centrifuging techniques resulted in more homogeneity of the ceramic and polymer phases, and the fabricated samples could be loaded up to 65% or more with the ceramic powders.     

Functionally Graded Polyurethane/Cellulose Nanocrystal Composites

The preparation and investigation of functionally graded polymer nanocomposites, which have a concentration gradient of cellulose nanocrystals (CNCs) along one direction, is reported here. As a test bed, a series of nanocomposites consisting of a thermoplastic polyurethane (PU) and 0–15% w/w CNCs is prepared via solvent casting and the mechanical properties of films of these materials are characterized by dynamic mechanical analyses and tensile tests. The formation of graded materials is accomplished by lamination of films with varying CNC content. The processing conditions are optimized to achieve intimate fusion of the individual layers. The elimination of internal interfaces is evidenced by an elongation at break of up to 500%. In order to explore potential applications of graded PU/CNC nanocomposites, structure‐dependent actuation in response to water is demonstrated in a bioinspired architecture. In addition, the damping behavior of cylindrical shaped composites is investigated by way of compression tests. The results show that functionally graded PU/CNC composites show good damping behavior over a much larger range of forces than the neat PU or the homogeneous nanocomposites.     

Dense Layered Molybdenum Disilicide–Silicon Carbide Functionally Graded Composites Formed by Field-Activated Synthesis

Dense, layered, single- and graded-composition composites of MoSi₂ and SiC were formed from elemental powders in one step, using the field-activated pressure-assisted combustion method. Compositions ranging from 100% MoSi₂ to 100% SiC were synthesized, with relative densities ranging from 99% to 76%, respectively. X-ray diffractometry results indicated the formation of pure phases when the concentration of MoSi₂ was high and the appearance of a ternary phase, Mo_4.8Si₃C_0.6, when the concentration of SiC was high. Electron microprobe analysis results showed the formation of stoichiometric and uniformly distributed phases. A layer-to-layer variation in composition of 10 mol% was sufficient to prevent thermal cracking during formation of the layered functionally graded materials.     

Increasing the Crystallinity of Hydroxyapatite Nanoparticles in Composites Containing Bioaffinitive Organic Polymers by Mechanical Stressing

Crystallinity of hydroxyapatite (HAp) in bioaffinitive disperse systems was increased by a wet mechanochemical treatment at room temperature. Silk fibroin (SF) and/or hyaluronic acid (HYA) were used as bioorganics. With the mechanochemical treatment, the crystallite size and the aspect ratio of HAp decreased and became closer to that of swine trabecular bone. Mechanochemical effects on the HAp nanocrystals were discussed in terms of coherent chemical interaction between HAp and bioorganics.     

Recent Developments of New Components for Dental Adhesives and Composites

The currently used commercial self‐etching enamel‐dentin adhesives and restoratives composites are mainly based on a mixture of various monofunctional and cross‐linking dimethacrylates. New developments of enamel‐dentin adhesives concern the improvement of technique insensitivity and storage stability. Improvements of restorative composites are focused on the reduction of the polymerisation shrinkage, as well as the improvement of wear resistance, biocompatibility, and processing properties. In the past five years, many research efforts have been carried out to develop new monomers and tailor‐made components for filling materials, such as fillers or initiators. New phosphonic acid ether acrylates and cross‐linking bis(acrylamide)s enable the preparation of self‐etching enamel‐dentin adhesives with improved storage stability. With free‐radically polymerisable cyclic monomers, such as bicyclic cyclopropyl acrylates or cyclic allyl sulfides, low‐shrinkage storage‐stable restorative composites could be prepared. In case of the cationic polymerisable cyclic monomers, like siloxane‐based cycloaliphatic epoxides, the lower curing rate, stronger exothermic effect and lower curing depth compared to dimethacrylate‐based composites presently prevent their dental application. Designed methacrylates with tailor‐made properties and sol‐gel polycondensates can also contribute to the improvement of the currently used restorative composites. Radical polymerisable dental materials are initiated by light curing and by redox initiator systems. Under acidic conditions amine containing initiator systems are deactivated by acid‐base reaction. Non amine‐based initiators have to be developed for acidic monomer containing dental materials. The use of discrete nano‐filler particles mainly concerns the reinforcement and, in some cases, the increase of X‐ray opacity of composite filling materials.

     

C/C复合材料表面羟基磷灰石/聚丙烯酰胺梯度复合涂层的制备与表征(英文)

以丙烯酰胺单体和声化学法制备的纳米羟基磷灰石(hydroxyapatite,HAp)粉为原料、异丙醇为分散介质,采用水热电泳聚合沉积法在C/C复合材料表面制备HAp/聚丙烯酰胺(polyacrylamide,PAM)梯度复合涂层。用电导率仪、X射线衍射仪、扫描电子显微镜、能谱仪、Fourier变换红外分析仪和万能材料试验机等对悬浮液的电导率以及涂层的物相组成、结构、断面微观形貌和结合强度进行了研究,结果表明:异丙醇中碘的浓度为8g/L时,所制备的涂层由HAp和PAM两相组成;HAP被包裹在黏度较大的PAM中,涂层表面均匀,涂层与基体之间结合紧密,未发现明显的裂纹;涂层中元素沿基体–界面方向呈梯度分布;涂层与基体结合强度最大值达到19.10MPa。     

贝壳粉制备球形羟基磷灰石

贝壳粉和磷酸二氢铵以及磷酸氢二铵反应制备球形羟基磷灰石,用常规方法制备出贝壳基球形碳酸钙,然后按Ca/P=1.67(摩尔量之比)把原料投入水热釜中,在140℃下反应24 h,得到收率几乎定量的球形羟基磷灰石,并用SEM、XRD和IR表征产物的外观形貌和结构。     

Preparation of Hydroxyapatite Fibers by Electrospinning Technique

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA) fibers were prepared by electrospinning a precursor mixture of Ca(NO₃)₂·4H₂O and (C₂H₅O)₃PO with a polymer additive, followed by a thermal treatment. The X-ray diffraction (XRD) analysis of the annealed composite fibers revealed that pure HA phase could be obtained by annealing at 600°C for 1 h. The scanning electron microscopy (SEM) analysis showed the surface of as-electrospun composite fibers with an average diameter of 50 μm was smooth due to the amorphous nature of the polymer. However, the surface of the calcined HA fibers was rough because of the complete removal of the polymer. The pure HA fibers obtained by electrospinning in this work were up to 10 mm in length and 10–30 μm in diameter and the hydroxyapatite grain size was ∼1 μm in the HA fibers.     

Estimation of Concentration of Particles in Polymerizing Fluid during Centrifugal Casting of Functionally Graded Polymer Composites

The concentration of uniformly distributed particles in a fluid changes with time in the direction of gravitational or centrifugal force to form a concentration gradient. The change in the concentration is an outcome of velocity variation of particles in a fluid. A modified equation for terminal velocity, v _m of particles in polymerizing-fluid under centrifugal force is proposed to estimate the changes in the volume fraction of particles in the graded composites. The proposed equation introduces the effect of cure kinetics of polymer and its effect on particle movement in the model that was based on the modified Stoke’s law, considering the parameters related to particle hindrance, centrifugal force, particle dimensions, viscosity variation etc. The model predictions of concentration changes at the different locations of samples were compared with calcium carbonate filled polysulphide-modified-epoxy graded composites prepared by centrifugal casting.. The effect of particle size, delayed curing rate of matrix were explored. The simulated results are in good agreement with those of experiments.     

Preparation and Characterization of Organic/Inorganic Polymer Composites Based on Mg‐Silicates

Summary: An organic‐inorganic hybrid material consisting of a 3‐(methacryloxy)propyl functionalized SiO₂/MgO framework was synthesized. This hybrid was successfully reacted with styrene, butyl acrylate and butyl methacrylate via a free radical emulsion polymerization to form polymer composites. The polymer composites were investigated by means of FT‐IR spectroscopy, TGA, DSC and rheometry. It is shown that the polymer is linked covalently to the organic/inorganic hybrid. Although the polymer content is rather low, the composites exhibit a polymer‐like character and enhanced mechanical properties compared to the corresponding homopolymers.

     

羟基磷灰石生物陶瓷涂层制备方法评述

根据医用生物陶瓷羟基为磷灰石及医用金属材料的生物，力学特性，本文认为在金属基体表面涂覆羟基磷灰石是综合金属材料及生物陶瓷材料各自优越性阳有希望的途径这一。评述了羟基磷灰石涂层的制备方法，论证了较为优化的涂层结构。     

多孔羟基磷灰石陶瓷的制备与性能研究

将羟基磷灰石粉末与过氧化氢、聚乙烯醇等物质混合成型、干燥、烧结,制得孔径理想、互通性能良好的多孔羟基磷灰石陶瓷.通过对制备方法、组分、工艺条件等不同因素的研究,探讨这些因素对羟基磷灰石性能的影响.由压汞仪测得制品的气孔率随粘结剂含量的增大而降低.用SEM对其表面微观形貌进行观察.