Preparation and Characterization of Isotactic Polypropylene Reinforced with Hydroxyapatite Nanorods

Isotactic polypropylene (PP) composites filled with hydroxyapatite nanorods (nHAs) were fabricated using a melt compounding process. The effects of nHA additions on the structure, thermal, and mechanical properties as well as bioactivity of PP were investigated. Wide-angle X-ray diffraction and differential scanning calorimetry results showed that PP crystallized exclusively in the α-form when adding nHAs. Dynamic mechanical analysis showed that nHAs enhanced the storage modulus of PP. Mechanical measurements showed that nHAs stiffened and reinforced PP but reduced its tensile ductility and impact strength considerably. Furthermore, the PP/nHA nanocomposites were found to exhibit excellent bioactivity upon immersion in a simulated body fluid solution. This was attributed to the formation of apatite mineral crystals on the nanocomposite surfaces as revealed by scanning electron microscopy and energy dispersive X-ray analysis.     

Facile Fabrication of Nanorod‐Assembled Fluorine‐Substituted Hydroxyapatite (FHA) Microspheres

Nanorod‐assembled FHA microspheres with different F contents were for the first time prepared through a facile one‐step hydrothermal method. The effect of the reaction time and pH value of reaction solutions on the FHA morphology was investigated to elucidate the self‐assembly process of FHA microspheres. The results showed pH values had significant effect on the morphology of the formed FHA crystals, which were self‐assembled into sphere‐like sturctures at high pH conditions and rod‐like structures at low pH values. The results suggested that formation of FHA crystals with varied morphology may be directly related to Ca²⁺ release kinetics from EDTA‐Ca‐Na₂ at different pH conditions. Furthermore, it was found that the chemical stability of FHA microspheres was dependent on the F content in the materials, and high F contents in FHA microspheres lead to improved chemical stability. These results suggest that the prepared self‐assembled FHA microspheres may be used for teeth substitution materials due to their unique hierarchical structures and controllable chemical stability.     

Simple model for blistering mechanism

A simple model for blistering mechanism is proposed for energies higher than 20 keV. The model assumes that through the nucleation of smaller bubbles, a critical bubble radius is reached. The planar stress results of Jeffery for a semi-infinite plate with a circular hole subject to a uniform inner normal pressure are roughly taken as valid for the three-dimensional case. Under this assumption, the thickness of the blister's cover and critical ion dose for blister formation are calculated from the knowledge of the mean projected range of ions and blister diameter taken from experimental results. The resulting values are in agreement with the experimental values reported. The model can qualitatively explain breakage at the top of the dome-shaped blisters observed in molybdenum at 1100 K.     

Ultralong Hydroxyapatite Nanowire/Collagen Biopaper with High Flexibility,Improved Mechanical Properties and Excellent Cellular Attachment

Highly flexible hydroxyapatite/collagen (HAP/Col) composite membranes are regarded to be significant for guided bone regeneration application owing to their similar chemical composition to that of natural bone, excellent bioactivity and good osteoconductivity. However, the mechanical strength of the HAP/Col composite membranes is usually weak, which leads to difficult surgical operations and low mechanical stability during the bone healing process. Herein, highly flexible ultralong hydroxyapatite nanowires/collagen (UHANWs/Col) composite biopaper sheets with weight fractions of UHANWs ranging from 0 to 100 % are facilely synthesized. The UHANWs are able to weave with each other to construct a three‐dimensional fabric structure in the collagen matrix, providing a strong interaction between UHANWs and an intermolecular force between UHANWs and the collagen matrix. The as‐prepared UHANWs/Col composite biopaper exhibits improved mechanical properties and high flexibility. More importantly, the as‐prepared highly flexible 70 wt % UHANWs/Col composite biopaper exhibits an excellent cytocompatibility and outstanding cellular attachment performance as compared with the pure collagen and 70 wt % HAP nanorods/Col membranes. In consideration of its superior mechanical properties and outstanding cellular attachment performance, the as‐prepared UHANWs/Col composite biopaper is promising for applications in various biomedical fields such as guided bone regeneration.     

CO2-3掺杂纳米羟基磷灰石晶体的合成与表征

CO2-3掺杂是提高纳米羟基磷灰石（n-HA）生物活性的有效方法之一。以 Ca（NO3）2·4H2O 和Na3PO4·12H2O为主要原料，Na2CO3作为CO2-3来源，合成纳米碳羟基磷灰石（n-CHA）晶体。采用TEM ， XRD ，FTIR ，RS对合成晶体形貌和结构进行表征。结果表明：合成的n-HA晶体长度约为60～80 nm ，宽度在20～30 nm之间，形状为针状，具有良好的结晶度，与自然骨磷灰石形貌相似；n-CHA晶体随CO2-3掺入量的增加，结晶度降低；合成的 n-CHA晶体的晶胞参数 a值随着CO2-3加入量的增大不断收缩，但 c值增大，参数比c/a值增大，符合B型取代（取代PO3-4）的晶胞参数变化规律。红外谱图中，872 cm -1附近出现AB混合型取代（同时取代O H -，PO3-4）的CO2-3面外弯曲振动特征红外峰，同时CO2-3的不对称伸缩振动红外峰在1454和1420 cm -1附近出现分裂峰，1540 cm -1附近出现弱CO2-3峰；1122 cm -1附近出现CO2-3对称伸缩振动拉曼峰，1071 cm -1附近出现CO2-3的B型替代特征拉曼峰，通过计算PO3-4，CO2-3，O H -拉曼峰的积分面积比PO3-4/CO2-3，O H -/CO23，PO3-4/O H -，表明CO2-3在替换时，先以B型为主，随着CO2-3掺入量的增加，发生A型替代（取代O H -）。实验结果表明，合成的磷灰石晶体为B型取代（取代PO3-4）为主的AB混合型取代的 n-CHA。与人骨磷灰石晶体在形态、尺寸、晶体结构和生长方式上具有相似性，可称为类骨磷灰石。     

Nickel‐Catalyzed CO2 Rearrangement of Enol Metal Carbonates for the Efficient Synthesis of β‐Ketocarboxylic Acids

4‐Methylene‐1,3‐dioxolan‐2‐ones underwent oxidative addition of a Ni⁰ catalyst in the presence of Me₂Al(OMe), followed by a coupling reaction with alkynes, to form δ,ϵ‐unsaturated β‐ketocarboxylic acids with high regio‐ and stereoselectivity. The reaction proceeds by [1,3] rearrangement of an enol metal carbonate intermediate and the formal reinsertion of CO₂.     

Viscoelastic properties of poly(ε‐caprolactone) – hydroxyapatite micro‐ and nano‐composites

Various composites have been proposed in the literature for the fabrication of bioscaffolds for bone tissue engineering. These materials include poly(ε‐caprolactone) (PCL) with hydroxyapatite (HA). Since the biomaterial acts as the medium that transfers mechanical signals from the body to the cells, the fundamental properties of the biomaterials should be characterized. Furthermore, in order to control the processing of these materials into scaffolds, the characterization of the fundamental properties is also necessary. In this study, the physical, thermal, mechanical, and viscoelastic properties of the PCL‐HA micro‐ and nano‐composites were characterized. Although the addition of filler particles increased the compressive modulus by up to 450%, the thermal and viscoelastic properties were unaffected. Furthermore, although the presence of water plasticized the polymer, the viscoelastic behavior was only minimally affected. Testing the composites under various conditions showed that the addition of HA can strengthen PCL without changing its viscoelastic response. The results found in this study can be used to further understand and approximate the time‐dependent behavior of scaffolds for bone tissue engineering. Copyright © 2012 John Wiley & Sons, Ltd.     

Nanofluid in Hydrophilic State for EOR Implication Through Carbonate Reservoir

More than 50% of oil is trapped in petroleum reservoirs after applying primary and secondary recovery methods for removal. Thus, to produce more crude oils from these reservoirs, different enhanced oil recovery (EOR) approaches should be performed. In this research, the effect of hydrophilic nanoparticles of SiO₂ at 12 nm size, in (EOR) from carbonate reservoir is systematically investigated. Using this nanoparticle, we can increase viscosity of the injection fluid and then lower the mobility ratio between oil and nanofluid in carbonate reservoirs. To this end, a core flooding apparatus was used to determine the effectiveness and robustness of nanosilica for EOR from carbonate reservoirs. These experiments are applied on the reservoir carbonate core samples, which are saturated with brine and oil that was injected with nanoparticles of SiO₂ at various concentrations. The output results depict that, with increasing nanoparticle concentration, the viscosity of the injection fluid increases and results in decreased mobility ratio between oil and nanofluid. The results confirm that using the nanoparticle increases the recovery. Also, increasing the nanoparticle concentration up to 0.6% increases the ultimate recovery (%OOIP), but a further increase to 1.0 does not have a significant effect.     

羟基磷灰石负载Ni催化剂中Ni含量对催化甲烷二氧化碳重整制合成气性能的影响

以低温沉淀方法制备的羟基磷灰石(HAp)为载体,采用浸渍法制备了一系列不同Ni含量的Ni/HAp催化剂,并采用BET、H2-TPR、XRD、SEM、FT-IR、TEM和TG-DTA技术对催化剂进行了表征。结果表明,NiO含量为13%的催化剂表现出最好的催化甲烷二氧化碳重整制合成气活性,在850℃、空速3.6×104mL/(h·gcat)的反应条件下,甲烷和二氧化碳的转化率在10 h内分别稳定在72%和83%。这主要归因于催化剂中金属和载体之间的强相互作用。虽然反应后的催化剂表面有少量的积炭,但这些积炭多以丝状炭存在,并不会影响催化剂的活性和稳定性。