P(NIPA-co-AM)超大孔水凝胶的制备及其性能

以N-异丙基丙烯酰胺(NIPA)、丙烯酰胺(AM)为单体,过硫酸铵为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,采用泡沫分散聚合法制备N-异丙基丙烯酰胺与丙烯酰胺共聚物[P(NIPA-co-AM)]超大孔水凝胶,研究了丙烯酰胺、引发剂、交联剂、盐酸、碳酸氢钠用量对水凝胶溶胀、退溶胀性能的影响,通过DSC、SEM、FTI...     

Hydroxyapatite starting from calcium carbonate and orthophosphoric acid: synthesis,characterization, and applications

Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂], Ca-HA, is the emblematic mineral phase of bones, and is known for its complexity and difficult to reproduce chemical synthesis. Among the routes developed for obtaining this calcium phosphate, the so-called double-decomposition method is well described and often utilized. However, the Ca-HA synthesized by this way forms a larger mass of ammonium nitrate by-product than the desired product itself. Pure Ca-HA for orthopedic or dental applications usually uses thermal treatment to eliminate residual nitrogen compounds by releasing them in the atmosphere. Contemporary sol–gel methods currently in fashion produce even more degradation products including solvents and precursor organics. We now report on a green synthesis procedure which makes pure Ca-HA with minimum by-product. The synthesis calls for reacting phosphoric acid with calcium carbonate in water suspension to form a Ca-HA gel of fine particles. This gel can be filtered and the solids recovered, dried, and sintered, but can also be used as-is for environmental applications such as heavy metal ions or textile dye removal from polluted waste streams. This green Ca-HA has been used to trap heavy metals in flue gases and in municipal waste water treatment plants. This low-cost and low-environmental impact material can be developed for medical use because of its absence of impurities, and in catalytic productions for remediation of many environmental problems. Recent results show Ca-HA can also serve in reforming biogas compositions into useful products, after deposition of selected metal elements. Some of these results will be communicated in this paper.     

Hydrothermal synthesis of composites of well-crystallized hydroxyapatite and poly(vinyl alcohol) hydrogel

Composites of hydroxyapatite (HAp) and poly(vinyl alcohol) (PVA) hydrogel were fabricated by the hydrothermal treatment of calcium phosphate powder. Alpha-tricalcium phosphate (α-TCP) or beta-tricalcium phosphate (β-TCP) powder was dispersed in PVA hydrogel and exposed to water vapor at 120 °C, 140 °C or 160 °C for 6 h. Low crystallinity HAp was formed in specimens prepared from α-TCP and PVA hydrogel prior to hydrothermal treatment, which was caused by hydrolysis of α-TCP. This allowed specimen shape to be retained after hydrothermal treatment. β-TCP showed less reactivity in forming HAp in the PVA hydrogel, which led to the formation of large rod-shaped crystals approximately 15 μm in length. Specimens from β-TCP and PVA were too soft to retain their shape after hydrothermal treatment. HAp with controlled morphology was prepared using different types of tricalcium phosphate precursor. The application of α-TCP allowed the in situ fabrication of HAp/PVA composites.     

Radiation synthesis of PVP/alginate hydrogel containing nanosilver as wound dressing

Hydrogels with polyvinyl pyrrolidone (PVP) and alginate were synthesized and silver nanoparticles were incorporated in hydrogel network using gamma radiation. PVP (10?and 15?%) in combination with 0.5?and 1?% alginate was gamma irradiated at different doses of 25?and 40?kGy. Maximum gel percent was obtained with 15?% PVP in combination with 0.5?% alginate. The fluid absorption capacity for the PVP/alginate hydrogels was about 1881–2361?% at 24?h. Moisture vapour transmission rate (MVTR) of hydrogels containing nanosilver at 24?h was 278.44?g/(m²h). The absorption capacity and moisture permeability of the PVP/alginate–nanosilver composite hydrogel dressings show the ability of the hydrogels to prevent fluid accumulation in exudating wound. The hydrogels containing nanosilver demonstrated strong antimicrobial effect and complete inhibition of microbial growth was observed with 70?ppm nanosilver dressings. PVP/alginate hydrogels containing nanosilver with efficient fluid handling capacity and antimicrobial activity was found suitable for use as wound dressing.     

Preparation and characterization of water-borne epoxy shape memory composites containing silica

Shape memory silica/epoxy composites were successfully prepared by hydrolysis of tetraethoxysilane (TEOS) within the epoxy matrix via latex, freeze-drying, and hot-press molding method. The silane coupling agent 3-triethoxysilylpropylamine (KH550) was introduced to improve the interfacial properties between the in-situ generated silica particle and epoxy matrix. The morphology structure and the effect of the content of the in-situ formed silica on the mechanical and shape memory properties of the silica/epoxy composites were studied. The experimental results indicated that the silica particles were homogenously dispersed and well incorporated into the epoxy matrix. Significant improvements were achieved in the mechanical property of the organic–inorganic hybrid materials. The silica/epoxy composites exhibited high shape recovery and fixity ratio approximately 100% even after 10 thermo-mechanical cycles.     

新型互穿网络超大孔水凝胶的制备、性能及表征

以丙烯酸、丙烯酰胺为基体，以乙烯基吡咯烷酮为预聚体，利用新型两步聚合法和发泡技术，制备了聚（丙烯酸．丙烯酰胺），聚乙烯基吡咯烷酮互穿网络超大孔水凝胶．采用差示扫描量热法（DSC）、红外光谱（FT-IR）和扫描电镜（SEM）等分析技术对所得水凝胶进行了表征，并研究了水凝胶的溶胀行为和凝胶强度．实验结果表明：该水凝胶具有相互连通的孔结构，溶胀行为在几分钟内即可完成；以新型两步法制备的互穿网络结构（IPN），大大提高了超大孔水凝胶的强度，新型两步法是制备IPN的有效方法之一．     

Synthesis and characterization of TiC-reinforced iron-based composites Part I On synthesis and microstructural characterization

The present investigation establishes a liquid processing route where thermit based reactions have been used to synthesize in-situ TiC-reinforced Fe-based composites in a single step. The main raw material used is siliceous sand, which is a waste product of aluminum extraction plants. A dispersion of TiC in Fe-based matrix has been obtained by aluminothermic reduction of siliceous sand, containing oxides of different elements like iron, titanium, silicon etc., in the presence of carbon. The reduction is highly exothermic in nature and leads to a self-propagating high-temperature synthesis (SHS) of the Fe-TiC composites. The matrix structure and volume fraction of TiC of the composites have been found to depend upon the amount of carbon added in the charge. It has been found that microstructures of Fe-TiC composites are not stable at high temperature due to the nonstoichiometric nature of TiC particles.     

Preparation and characterization of amphotericin B-loaded silk fibroin nanoparticles-in situ hydrogel composites for topical ophthalmic application

Journal of Materials Science - The objective of this study was to develop and characterize a novel combined systems of amphotericin B-loaded silk fibroin nanoparticles (AmB-FNPs) and in situ...     

Microwave-assisted synthesis and characterization of zinc oxide/carbon nanotube composites

A composite material of zinc oxide and carbon nanotubes were successfully synthesized via a sol process using zinc acetate dihydrate and treated multi-wall carbon nanotubes under microwave irradiation. The morphology, microstructure and chemical bonding of as-obtained composites were well characterized using X-ray diffraction, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy. Zinc oxide nanoparticles were dispersively coated on the surface of carbon nanotube when the precursor was dried under microwave irradiation without post-annealing. X-ray diffraction results obviously showed the mixture of two phases of carbon nanotube and wurzite zinc oxide whose size is approximately 15 nm. The formation of zinc oxide nanoparticles on carbon nanotube surface in the composite prepared by microwave heating is much better than the composite heated by conventional annealing. Fourier transform infrared spectroscopic results suggest that carboxylic groups and uniform heating by microwave heating could play key roles on the nucleation of zinc oxide on carbon nanotube surface.     

Photochemical synthesis and characterization of Ag/TiO2 nanotube composites

TiO₂ nanotubes were fabricated by a hydrothermal method. Silver nanoparticles with diameters around 3–5 nm were loaded onto the surface of TiO₂ nanotubes via a deposition approach followed by a photochemical reduction process under ultraviolet irradiation. Transmission electron microscopy (TEM), N₂ adsorption measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis), and fluorescence spectroscopy (FL) were applied to characterize the as-prepared Ag/TiO₂ nanotube composites. The photocatalytic activity of the as-prepared materials was investigated by photodegrading of methyl orange. The results showed that silver particles were in zero oxidation state and highly dispersed on the surface of TiO₂ nanotubes when the concentration of Ag⁺ was low. The presence of metallic silver can help the electron-hole separation by attracting photoelectrons. The Ag/TiO₂ nanotube composites with a suitable amount of silver showed a further improvement on the photocatalytic activity for degradation of methyl orange in water.     

In situ synthesis method and damping characterization of magnesium matrix composites

Magnesium matrix composites reinforced with 8 wt% TiC was in situ synthesized using remelting and dilution technique. X-ray diffraction analysis revealed the presence of TiC phase in sintered block and magnesium matrix composites. Uniform distribution of fine TiC particulates in matrix material was obtained through microstructure characterization. The results of damping characterization revealed that damping capacity of materials is independent of frequency, but dependent on strain and temperature. There were damping peak in damping–strain curve, which is due to the foul and tangle of dislocations. There were two damping peaks at damping–temperature curve under respective temperature of 130 °C and 240 °C. The former damping peak of magnesium matrix composites is due to dislocation motion, and the latter is due to interface and grain boundary sliding. Generally, damping capacity of magnesium matrix composites is higher than that of AZ91 magnesium alloy, which is due to the addition of TiC particulates.     

TiO2/聚苯胺复合材料的合成、结构表征及光催化性能

在室温下,以苯胺为单体、钛酸四丁酯为反应物,通过化学氧化原位聚合和溶胶-凝胶的方法制备了TiO2/聚苯胺复合材料。利用X-射线衍射仪、傅立叶变换红外光谱仪、紫外-可见吸收光谱仪、热失重分析仪等对复合材料表面的微观结构及热稳定性进行了表征。通过光催化降解甲基橙实验评价了TiO2/聚苯胺复合光催化剂在紫外光条件下的光催化活性,实验表明,TiO2/聚苯胺复合材料的催化效率大大提高,特别是TiO2/聚苯胺(质量比例为1/2)复合材料对甲基橙的降解效率最高达到85.7%。     

Synthesis and mechanical characterization of polymer-matrix composites containing calcium carbonate/white cement filler

With a view to develop polymer-matrix composites of high mechanical strength, composites containing 0.5% to 5.0% of each of calcium carbonate or white cement were prepared by uniformly mixing polystyrene and inorganic materials followed by casting in an aluminum mold. The values of fracture toughness, flexural strength and elastic modulus were found to increase with increasing amount of the inorganic component in the polymer. In addition, for a given percentage of inorganic components, the values of mechanical strength of white cement containing composites were found to be more than those of calcium carbonate containing composites. The optical microphotographs of the composites show that there is uniform distribution of filler in the polymers.     

A micromechanical characterization of graphite-fiber/epoxy composites containing a heterogeneous interphase region

An improved micromechanical model based on the method of cells is introduced in order to describe three-phase, continuous-fiber composite materials containing a heterogeneous interphase region. The model's capability represents a significant improvement over that of the previous version (which is applicable to a homogeneous interphase) in that additional microstress information is obtained within the interphase region. A critical assessment of the model demonstrates that the predictions are consistent with data reproduced by using other micromechanical models. The study includes a parametric simulation in which the effective properties and the mechanical stresses associated with model graphite-fiber/epoxy composites are predicted as a function of the dimensions and Young's modulus of the interphase. Three different interphases are modeled such that the Young's modulus varies between that of the fiber and the matrix according to a generalized parabolic function of the radial coordinate. The parabolic functions are specified such that two of the model composites possess an interphase whose effective Young's modulus is above that of the matrix. The third interphase is specified such that its effective Young's modulus is below that of the matrix. The data indicate that the interphase dimensions and the functional form describing the interphase Young's modulus significantly influence the composite microstresses. These data may be used to help identify optimum material combinations during composite material synthesis.     

Bioactive injectable triple acting thermosensitive hydrogel enriched with nano-hydroxyapatite for bone regeneration: in-vitro characterization,Saos-2 cell line cell viability and osteogenic markers evaluation

Hydrogels forming in-situ have gained great attention in the area of bone tissue engineering recently, they were also showed to be a good and less invasive alternative to surgically applied ones. The primal focus of this study was to prepare chitosan-glycerol phosphate thermosensitive hydrogel formed in-situ and loaded with risedronate (bone resorption inhibitor) in an easy way with no requirement of complicated processes or large number of equipment. Then we investigated its effectiveness for bone regeneration. In-situ forming hydrogels were prepared using chitosan cross-linked with glycerol phosphate and loaded with risedronate and nano-hydroxyapatite as bone cement. The prepared hydrogels were characterized by analyzing their gelation time at 37?°C, % porosity, swelling index, in-vitro degradation, rheological properties, and in-vitro drug release. Results showed that the in-situ hydrogels prepared using 2.5% (w/v) chitosan cross-linked with 50% (w/v) glycerol phosphate in the ratio (9:1, v/v) reinforced with 20?mg/mL and nano-hydroxyapatite possessed the most sustained drug release profile. This optimized formulation was further evaluated using DSC and FTIR studies, in addition to their morphological properties using scanning electron microscopy. The effect on Saos-2 cell line viability was evaluated also using MTT assay on the optimized hydrogel formulation in addition to their action on cell proliferation using fluorescence microscope. Moreover, calcium deposition on the hydrogel and alkaline phosphatase activity were evaluated. Risedronate-nano-hydroxyapatite loaded hydrogels significantly enhanced the Saos-2 cell proliferation in addition to enhanced alkaline phosphatase activity and calcium deposition. Such results suggest that risedronate-nano-hydroxyapatite loaded hydrogels present great biocompatibility for bone regeneration. Proliferation of cells, as well as deposition of mineral on the hydrogel, was an evidence of the biocompatible nature of the hydrogel. This hydrogel formed in-situ present a good less invasive alternative for bone tissue engineering.     

Development and characterization of magnesium composites containing nano-sized silicon carbide and carbon nanotubes as hybrid reinforcements

Magnesium based hybrid composites containing nano-sized silicon carbide and carbon nanotubes reinforcements with minimal porosity were successfully fabricated using powder metallurgy technique with microwave sintering and hot extrusion. It was found that the addition of nano-sized silicon carbide and carbon nanotubes reinforcements lowered the coefficient of thermal expansion of magnesium. Moreover, increasing presence of silicon carbide particles led to a progressive reduction in coefficient of thermal expansion for a constant overall amount of reinforcements indicating that carbon nanotubes lowered the coefficient of thermal expansion to a lesser extent when compared to silicon carbide. Micro-hardness, 0.2% YS and UTS (except for Mg+1%CNT) showed improvement, while failure strain decreased when nano-sized silicon carbide and carbon nanotubes were added to magnesium. The failure mode of magnesium and magnesium composites was predominantly brittle exhibiting the presence of cleavage steps.     

Hydroxyapatite spheres with controlled porosity for eye ball prosthesis: processing and characterization

Porous hydroxyapatite spheres were prepared by a modified gelcasting method producing a ceramic prosthesis with controled porosity. The spheres are approximately 2.2 cm in diameter with a relatively homogeneous pore size distribution from 10 to 40 m in diameter. The samples were characterized by X-ray powder diffractometry (XRD) and Fourier transform infra-red spectroscopy (FTIR) to identify the phases both prior to and after the gelcasting process. Surface morphology analysis and porosity evaluations were performed with scanning electron microscopy (SEM), while surface area measurements were carried out by the BET technique. © 2001 Kluwer Academic Publishers     

双氯灭痛壳聚糖水凝胶微球的制备及其性能研究

在Span80与植物油形成的反相胶束体系中,通过戊二醛交联制备出壳聚糖水凝胶微球(CHM)。采用红外光谱和透射电镜等方法对CHM结构及粒子形态进行了研究。同时对CHM的溶胀度及其对模型药物双氯灭痛的体外释放行为进行了考察。结果表明,CHM具有较好的控制药物释放的作用。交联程度对微球粒径、溶胀度及药物释放性能影响较大。     

In situ synthesis and characterization of porous polymer-ceramic composites as scaffolds for gene delivery

The use of three-dimensional scaffolds in gene delivery has emerged as a popular and necessary delivery vehicle for obtaining controlled gene delivery. In this report, techniques to synthesize composite scaffolds by combining natural polymers such as agarose and alginate with calcium phosphate (CaP) are described. The incorporation of CaP into the agarose or alginate hydrogels was performed in situ and the presence of CaP was confirmed by X-ray diffraction (XRD). The crystallite size of the CaP particles was determined to be 7.20 nm. Lyophilized, porous composites were examined under scanning electron microscopy (SEM) to estimate the size of the pores, an essential requirement for an ideal scaffold. The swelling properties of the composite samples were also investigated to study the effect of CaP incorporation on the behavior of the hydrogels. By incorporating CaP into the hydrogel, the aim is to synthesize a scaffold that is mechanically strong and chemically suitable for use as a gene delivery vehicle in tissue engineering.