Papers by Author: Xiao Ying Lu

Abstract: This paper reports that carbon nanotubes (CNTs) can be successfully grown from calcium phosphate matrix without additional catalysis of transition metal by chemical vapor deposition (CVD) using acetylene as carbon source. There is a great difference in the CNT growth from the matrix prepared with the different initial Ca/P molar ratio. The matrix prepared with lower initial Ca/P molar ratio is favorable for the growth of CNTs. A number of multi-walled CNTs with the diameter of 25~40 nm and 15~25 nm can be produced from the matrix with initial Ca/P molar ratio of 1.5 and 1.625, respectively, while no CNTs can be grown from the matrix with initial Ca/P molar ratio of 1.67. Tricalcium phosphate and hydroxyapatite crystallites with crystal size smaller than 50 nm besides carbon crystals are found in the as-obtained powders prepared with initial Ca/P molar ratio of 1.5 and 1.625. Compared with the growth of CNTs produced from all the matrixes, it is found that the CNTs grown from this matrix with Ca/P molar ratio of 1.5 have the longest tube length, cleanest and smoothest wall surface, and the content of CNTs is highest.

Abstract: This paper reports the fabrication of carbon nanotubes (CNTs) /hydroxyapatite (HA) composites via in-situ process in a chemical vapor deposition (CVD) system and the effect of HA matrix on the growth of CNTs. When the HA matrix is fabricated by a chemical coprecipitation method, deficient HA (D-HA) crystals in nano size have been observed in these composites. There are about 20% weight percent of multi-walled CNTs with a mean diameter of 40~60 nm. When the matrix used as catalyst for CNTs growth without HA in the same way, no CNTs but solid carbon fibers in submicrometer scale have been produced in these composites. Only Fe and MgO crystals can be observed in these composites. When the HA matrix is fabricated by a physical mixing with the presence of D-HA crystals, hollow CNTs with the diameter of 180~210 nm are also produced in these composites. Fe and MgO besides P₂O₅, D-HA and C crystals can be observed in the composites.

Abstract: The morphological differences of chitosan (CS) in the hydroxyapatite (HA)/CS nanocomposites were investigated in detailed, which were prepared via in situ hydrothermal precipitation. The results show that the obtained nanocomposites have excellent crystallinity and the crystal has excellent ordered structure, which is important to the composites performances in the biomedical application. Moreover, the CS arrangement and crystallinity in the composites greatly depend on the hydrothermal temperature and the pH value of precipitating agent. The temperature ranging from 373 to 413K and pH value of precipitating agent ranging from 12 to 14 were favorable to the crystallization and oriented growth of CS molecules in the composites. The CS crystals with better arrangement are assembled in the order of layer-by-layer in these composites.

Abstract: Carbon nanotubes (CNTs)/hydroxyapatite (HA) nanocomposites have been successfully fabricated by a novel method for the biomedical applications, which is in situ growing CNTs in HA matrix in a chemical vapor deposition (CVD) system. The results show that it is feasible to in situ grow CNTs in HA matrix by CVD for the fabrication of CNTs/HA nanocomposites. Multi-walled CNTs with 50-80 nm in diameter have been grown in situ from HA matrix with the pretreatment of sintering at 1473K in air. The nanocomposites are composed with carbon crystals in CNTs form, HA crystallites and calcium phosphate crystallites, one of most important CaP bioceramics. And the CNTs content is about 1% proportion by weight among the composites in our experiments, which can enhance the HA mechanical properties and the CNTs content does not affect the HA performances. These CNTs/HA nanocomposites have the potential application in the biomedical fields.

Abstract: The cylindrical chitosan (CS)/hydroxyapatite (HA) nanocomposites were hydrothermally prepared via in situ precipitation and characterized by x-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), thermogravimetry (TG) and scanning electronic microscope (SEM). The results show that the as-prepared products are composed of CS and low-crystalline HA phases, and some extent of interaction between CS and HA phases exists in the composites, which is greatly influenced by the temperature and pH value in the hydrothermal process. The crystal size of HA uniform-distributed in CS matrix is calculated to be no larger than 100nm while the crystallinity of CA is greatly increased in the hydrothermal process, which is beneficial to the mechanical properties of the composites. It is proposed that the nano-structure of HA/CS composite will have the better biomedical properties in the biomaterials applications.

Abstract: In the present study, hydroxyapatite (HA) /silk fibroin (SF) nanocomposite containing 40 wt % of SF, was synthesized in an aqueous solution of CaCl2/(NH4)2HPO4 system containing SF to mimic bone structure of nano HA crystallites in organic matrix. The experimental results show that SF promotes the preferential growth of nano HA crystallites along the plane (002) which indicates the interaction between nano HA crystallites and SF. The nanocomposite with nano HA crystallites dispersed homogeneously in SF matrix possesses a compression strength of 97.6 MPa higher than that of woven bone. The methodology has a great potential for designing and engineering of biomaterials with improved biological properties. The novel nanocomposite may be used as bone substitutes and tissue engineering scaffolds.

Abstract: Hydroxyapatite (HA) spherulites had been fabricated successfully through a novel approach including chitin emulsion and geletion processes. The freeze-dried nano-HA powder was firstly dispersed in the chitin solvent before chitin dissolves in its solvent completely. The chitin sol containing nano-HA particles was dropped into oil and emulsified making use of liquids immiscibility effect between oil and chitin sol by stirring. The n-HA/Chitin sol spherulites gelled in situ with the existence of water molecules. Subsequently, the spherular gel granules were rinsed in distilled water to leach the solvent and dried in room circumstance. Finally, special sintering routines were carried to harvest spherular HA granules. The size and porosity of HA spherulites were controlled by the rate of nano-HA to chitin, the chitin concentration in the starting slurry, the stirring rate and the temperature of oil etc. In addition porosifier such as sugar was used in order to adjust the macro- and micro-porous structures in the HA spherulites. The morphological observation showed that the HA spherulites had good sphericity and characteristic microporous structure which were favorable for medical application.