Papers by Author: Ling Chen

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Authors: Xiao Xi Li, Ling Chen, Jian Dong Ye, Lin Li, Yan Ran Huang
Abstract: A new consolidation in-situ forming process for high-performance alumina ceramic using acetate starch was investigated. The pasting behavior and thermogelling properties of acetate starch and the effects of different amount of acetate starch and solid loading on the rheologic behavior of the ceramic slip, as well as the linear shrinkage, density, strength and microstructure of the green body were discussed. The results indicate that acetate starch paste has good thermal stability and gelling ability. When the content of acetate starch is about 0.5%~1.5% (mass fraction), the apparent viscosity of alumina slurry, which is always less than 1Pa·s even for 58% (volume fraction) dense suspension, increased with increasing the acetate starch content and solid loading. That results in easier to cast. Moreover, with the increasing of solid loading the linear shrinkage and dry strength of green bodies decreased and the relative density increased. With the increasing starch content, the linear shrinkage rate and the density of the dried body decreased, while the strength of the dried body almost linearly increased. The green body with homogeneously-distributed density and pore size was also obtained in this work. It is concluded that Al2O3 ceramics can be consolidation in-situ formed based on the gelling network of thermally swelled and gelatinized acetate starch.
980
Authors: Ling Chen, Xian Liang Song, Jian Dong Ye, Bing Li
Abstract: The forming of Al2O3 ceramics was carried out by the colloidal in-situ consolidation using modified starch in this work. The effects of the modified starch content in the alumina suspensions on their rheological behavior, consolidation, microstructure and properties of the green bodies were investigated. The different shape and high relative density of ceramic green bodies were achieved by this method. The results indicated that the alumina suspensions with modified starch were easier to cast due to their low viscosity and high fluidity. After drying, the linear shrinkage of the green bodies was low, ranging between about 1.5% and 2.2% and their bulk density was higher than 57% of the theoretical density. The maximum bending strength of the dried green bodies reached to 8.2 MPa and the microstructure of the green bodies was uniform with a narrow unimodal distribution of pore size. It is concluded that the colloidal in-situ consolidation casting using modified starch can perform near-net shaping of ceramic components with high-performance and it is a potential forming technique for ceramics.
1027
Authors: Ling Chen, Xu Peng, Yun Huang, Lin Li, Xiao Xi Li
Abstract: Porous ceramic materials usually require an optimal porosity and pore-size distribution to maximize the yield of the required function. In the starch consolidation forming for porous ceramic materials, the porosity and pore size distribution are corresponding closely to the particle size and swelling property of starch. In order to control the porosity and pore size distribution of the porous alumina ceramics, different modified starches with different amounts were added to the alumina slurry with a 58 vol% alumina solid volume loading. The effects of different modified starches and their content on the rheological behavior of the alumina slurry and the porosity, pore size distribution, compressive strength and microstructure of the sintered body were investigated. The results indicated that alumina/starch composite slurry still maintain stable and plastic in suitable condition of slurry preparation. After drying and sintering, materials with ultimate porosities between 22.7 and 68.7% were obtained. The pore of the resulting materials distributed uniformly and the average size was varied from 10 to 40μm. It concluded that the average size was controlled by the modified starch type, amount and the degree of modification. When the amount of the modified starches was reached to 60 vol% the porosities of the sintered samples were varied from 63.5 to 68.7% with different modified starch type and their bending strength varied within the range of 24-32 MPa.
697
Authors: Ling Chen, Hong Xiang, Xiao Xi Li, Jian Dong Ye, Xiu Peng Wang, Lin Li, Xi Mei Zhang
Abstract: In this study modified starch were used as anti-washout promoters of injectable calcium phosphate cement (CPC) and the effects of the modified starch on the injectability, anti-washout performance, setting time, compressive strength, phase evolution and microstructure of this cement were investigated. The injectability of the cement was improved by adding the modified starch (0.5-2.0%). After mixing with modified starch (0.5-2.0%), the cement showed better anti-washout performance than that without modified starch after immersed and shaken in SBF. Especially, when the content of the modified starch was 1.0%, the remaining percentage of the cement was reached to 92.6%, but only 5.9% of the CPC paste remained and set for the sample without modified starch after shaken for 2 hrs. The compressive strength of cements significantly increased from 44 MPa to 54 MPa when 0.5% of modified starch was added. And a slight increase on the mechanical strength can be observed for other concentrations. Powder X-ray diffraction analysis revealed no significant difference for the conversion of the cement to hydroxyapatite for any concentrations of modified starches. The influence of the modified starch on the microstructure of the set cement was also studied. The results showed the modified starch would reduce the acicular crystal size of hydroxyapatite accompanied with little flaky crystals generation and made a compact structure. It is concluded that modified starch, a suitable anti-washout promoter, improved the performance of CPC.
843
Authors: Jian Dong Ye, Xiu Peng Wang, Ling Chen
Abstract: A novel calcium phosphate cement (CPC) was prepared by mixing partially crystallized calcium phosphate (PCCP) containing carbonate and dicalcium phosphate anhydrous (DCPA) in this work. The effects of the carbonate content on the phase composition, strength, prosity, and degradation of the set bodies were studied. The results showed that the cement formed into hydroxyapatite (HAp) after setting, in which carbonate doped into the HAp crystal lattice. With the increase of the carbonate to phosphate ratio in PCCP, the compressive strength of the cement declined and the setting of the cement accelerated. Furthermore, the calcium phosphate cement formed a more porous structure with the increase of the carbonate to phosphate ratio in PCCP. The results also indicated that the degradation of CPC may be speeded up by introducing carbonate to the cement.
1227
Authors: Xia Zhang, Lin Li, Jian Rong Huang, Ling Chen, Xiao Xi Li, Guo Qin Liu, Bing Li
Abstract: Naringin esters are paid more attention in medical and functional food industry than naringin due to their higher stability and solubility in lipidic environments. Naringin palmitic acid esters were enzymatically synthesized with naringin and palmitic acid. The effects of solvent type, temperature, concentration and types of enzymes and the molar ratio of substrates on the conversion of naringin were investigated. Novozym 435 performed higher catalytic ability in tert-amyl alcohol in the esterification of naringin with palmitic acid. The conversion yield of naringin increased with the increase of temperature (30-70°C) and of the concentration of enzyme. The structure of the naringin palmitate was characterized by FT-IR, 1H-NMR and HPLC-MS. 1H-NMR spectroscopic analysis indicated the presence of an ester bond on the C-6 of the glucose moiety of naringin molecule.
1350
Authors: Ling Chen, Xiao Xi Li, Lin Li, Bing Li
Abstract: Colon-targeting drug delivery systems (CDDSs) are employed to improve the bioavailability of protein and peptide drugs through the oral route. So it is important to prepare the drug carriers for oral CDDS. In this study, the Enzyme-Resistant starch (RS) was studied for use as a vehicle in oral colon-targeting drug delivery. The characteristics of RS powders were investigated by X-ray diffraction, polarizing microscopy, DSC and SEM, and their film were examined by enzymatic digestion test. The results showed that RS could be a promising film-former for pharmaceutical coatings, having good stability to enzymatic digestion. Furthermore, a novel peroral formulation using RS coating and bovine serum albumin as a model drug was studied for colon-specific drug delivery in vitro. Drug release studies have shown that RS coating could delivery the drug to the colon and the release rate in simulated colonic fluids was dependent on the biodegradation of RS and its coatings. It is indicated that the RS coated tablet is a potential system for oral CDDS.
129
Authors: Ling Chen, Hong Xiang, Xiao Xi Li, Jian Dong Ye, Xiu Peng Wang, Lin Li
Abstract: Calcium phosphate cements (CPCs) are well-known orthopedic materials for filling bone. However, CPC pastes tend to disintegrate immediately when contacting with blood or other aqueous (body) fluids, which is a main limitation of its clinical applications in bone repairing, reconstruction and augmentation. To improve the anti-washout performance of CPC, modified starches such as pre-gelatinized starch, etherified starch, and esterified starch were added to the liquid phase of CPC in this work. CPC with good anti-washout performance was prepared and the effects of the modified starches on the properties of CPC were investigated. The results showed that the CPC with the modified starches were more stable in simulated body fluid than that without modified starch, especially the CPC with the etherified starch (II). X-ray diffraction analysis revealed that the modified starches did not inhibit CPC components from converting to hydroxyapatite. Furthermore, the anti-washout mechanism of the modified starches in CPC was discussed. It is concluded that the addition of the modified starches such as pre-gelatinized starch, etherified starch, and esterified starch to CPC can improve its anti-washout performance and should be of value in clinical surgery where the cement is exposed to blood.
1628
Authors: Xiu Peng Wang, Jian Dong Ye, Ling Chen, Ying Jun Wang
Abstract: In this study, an ACP-DCPD based Calcium phosphate cement (CPC) scaffold with a porosity of 88% was prepared by using Na3PO4 as a poregen and then modified by collagen and chitosan. The results showed that collagen and chitosan obviously increased the compressive strength. Cell culture showed that the cell can migrate, attach, proliferate and differentiate on the surface of the materials and the pores walls. This CPC scaffold modified with collagen or chitosan was a promising material to be used in bone tissue engineering.
983
Authors: Bing Li, Hui Ling Zhong, Hong Jie Li, Ling Chen, Lin Li, Xiao Xi Li
Abstract: Artificial neural networks have been successfully used in classification, formulation optimization, defect diagnosis and performance prediction in ceramic industry. However, an artificial neural network based on the traditional backpropagation (BP) algorithm showed some disadvantages in mapping the nonlinear relationship between the composition and contents of the ceramic materials and their properties. In this paper, a new PSO-Grain (Particle Swarm Optimization Gain) BP algorithm was introduced, and an improved artificial neural network model was employed to predict the properties of an alumina green body. The training performance of the neural network using the PSO-Gain BP algorithm was analyzed and it was indicated the POS-Gain BP based neural network could reduce convergence to local minima and was more efficient than the traditional BP based network. The prediction accuracy of the properties such as linear shrinkage and bending strength using the PSO-Gain BP based neural network was higher than that of the BP based neural network.
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