Optical waveguiding and morphology of chitosan thin films

An investigation was made of the optical and waveguiding properties of thin films fabricated from solutions of chitosan-acetic acid (chitosan/HAc) and chitosan/HAc doped with rare-earth metal ions (Er⁺⁺⁺ or Nd⁺⁺⁺). For all three films, the refractive indices were approximately 1.5 and there was nearly no absorption in the range of 300 to 2700 nm. The optical loss in a waveguides was less than 0.5 dB/cm. Morphological observations disclosed that all the films possessed a dense and homogeneous amorphous structure with smooth surfaces. Extrinsic scattering, especially the scattering caused by surface impurities, was the dominating factor affecting the optical loss value. It is also interesting to note that for all the films, doped with rare-earth metal ions or not, the morphological characteristics were alike and the optical properties were similar. Doping rare-earth metal ions into chitosan thin films did not seriously influence optical waveguiding. This paper reports, we believe, the first study of chitosan films for optical applications. The experimental results demonstrate that chitosan and its derivatives are potential candidates for optical materials. © 1996 John Wiley & Sons, Inc.     

Physicochemical,setting, rheological,and mechanical properties of a novel bio-composite based on apatite cement,bioactive glass,and alginate hydrogel

Calcium phosphate cements (CPC) have been widely investigated as bone substitutes, owing to their attractive features in terms of physicochemical and biocompatibility properties. However, the clinical applicability of this group of biomaterials is still critically limited by its poor strength and rheological properties in terms of injectability and cohesion. The present work aims to develop novel composite cement based on calcium phosphate cement (CPC) and bioactive glass (BG), associated with sodium alginate hydrogel (Alg). The composition, microstructure, setting, rheological, and mechanical properties of this composite cement were further investigated. Evaluation of setting properties showed that BG participates crucially in the setting reaction as a calcium and phosphate provider and serves as a setting accelerator. Thus, the setting time appears lower in these cements than in the reference CPC cement: it decreases from 75 to 42 min as the BG content increases from 10 to 25 wt% and is delayed from 42 to 73 min while the Alg amount augmented from 1 to 5 wt%. The rheological evaluation revealed that injectability was slightly improved with increasing BG content compared to the injectability of CPC, reaching a value close to 100% when combined with Alg hydrogel. The anti-washout property appeared to be weak for the CPC with or without BG, which are disintegrated in solution. The cohesiveness was significantly improved by introducing Alg hydrogel; furthermore, the addition of 5 wt% of alginate hydrogel induced an increase in the compressive strength about twice (7.2 MPa) higher than that of the reference CPC (4.0 MPa). According to the above findings, the addition of BG acts as a setting accelerator leading to a fast apatite formation, while the introduction of Alg hydrogel as a rheological promoting agent improves the injectability and cohesion. The combination of BG and Alg as additives increased the compressive strength compared to the reference cement.     

Calcium monosilicates as components of composite materials

The structure and physicochemical properties of calcium monosilicates are studied using X-ray diffraction, atomic-force microscopy, scanning electron microscopy, thermogravimetric analysis, and optical spectrometry. It was shown that replacing titanium dioxide with calcium monosilicates for the production of composite materials on the basis of PVC (polyvinylchloride) allows for the obtainment of composites more tolerant to ultraviolet irradiation.     

硫酸钙晶须在室温硫化硅橡胶中的应用

研究硫酸钙晶须制备方法和用量对室温硫化硫酸钙晶须/硅橡胶复合材料性能的影响。结果表明,当硫酸钙晶须用量为10份时,复合材料的物理性能总体提高显著。扫描电子显微镜分析结果显示,烟气脱硫法硫酸钙晶须杂质较多,在硅橡胶中分散不均匀;电石渣法硫酸钙晶须内部结构完整,在硅橡胶中分散均匀。随着硫酸钙晶须用量增大,硅橡胶的粘度增大。热重分析结果显示,与烟气脱硫法硫酸钙晶须相比,电石渣法硫酸钙晶须对复合材料热稳定性能的改善较明显。     

TiO_2/壳聚糖/明胶复合棉织物的制备及功能特性

采用了溶胶-凝胶法制备了TiO_2溶胶,使纳米TiO_2在棉织物的表面和内部原位生成,从而实现无机纳米TiO_2粒子与棉织物的牢固结合;再与壳聚糖明胶混合液进行浸轧,制备TiO_2/壳聚糖/明胶复合棉织物材料。用扫描电镜和X射线衍射仪对样品的形貌和结构进行表征,并测试了样品的力学性能、耐洗牢度和光催化性能。结果表明:原位生成的TiO_2与棉织物结合牢固,粒径均匀,分散性较好;纳米TiO_2主要是锐钛矿晶型;所制得试样对活性红染液具有良好的光催化降解作用。     

钛白副产硫酸亚铁制备铁系超细材料的研究进展

介绍了利用钛白副产硫酸亚铁制备草酸亚铁、磷酸铁、磷酸铁锂、纳米磁性材料、氧化铁颜料等铁系超细材料的技术研究。指出加强超细铁系材料的工业化研究,对于钛白副产硫酸亚铁综合利用并增加其附加值具有十分重要的现实意义。     

Crystallization of calcium phosphates from a model solution of synovial liquid in the presence of titanium compounds

The crystallization of calcium phosphates from a model solution of human synovial liquid with the participation of titanyl ions has been studied in this work. The possibility of precipitating calcium phosphates on titanium samples is checked. The energies of adhesion and cohesion of these substances on titanium are calculated.     

The technology of sphene concentrate treatment to obtain titanium salts

The rate of titanium (IV) extraction from sphene concentrate by its treatment with sulfuric acid solutions was determined. The sulfatization conditions to form stable titanium (IV) sulfate solutions suitable for preparing crystal substances—titanyl sulfate and ammonium titanyl sulfate—were found. The kinetics of the crystallization was studied. The phase composition of the titanium salts was established, and the content of impurities was determined by using X-ray analysis. It was shown that the technology for producing titanium salts is simple, which makes it possible to prepare in a few operations the precursors for the synthesis of hard-to-get expensive titanium-containing materials.     

Synthesis,characterization and in-vitro biocompatibility of electrophoretic deposited europium-doped calcium silicate on titanium substrate

Europium (Eu) has attracted attention to be incorporated as biologically active ions to achieve different biological and functional properties of biomaterials. In this study, calcium silicate (CS) coatings doped with different amount of Eu (up to 10 mol%) were successfully formed on titanium substrates via electrophoretic deposition. A low amount of Eu (2.5 mol%) gave a relatively denser coating and improved coating adhesion strength (～3.3 N). All Eu–CS coatings provided good apatite forming ability, yet lower degradation rate, as compared to CS coating. Moreover, it was observed that the human fetal osteoblast (hFOB) cells could attach and proliferate on all Eu–CS coatings, suggesting their biocompatible nature. Eu2.5CS not only showed comparable cell proliferation with CS, but also enhanced the osteogenic activity of the CS coating. All results suggested that Eu2.5CS coatings are promising coating materials for biomedical implants, particularly bone tissue engineering applications.     

Development of Injectable Calcium Sulfate and Self-Setting Calcium Phosphate Composite Bone Graft Materials for Minimally Invasive Surgery

The demand of bone grafting is increasing as the population ages worldwide. Although bone graft materials have been extensively developed over the decades, only a few injectable bone grafts are clinically available and none of them can be extruded from 18G needles. To overcome the existing treatment limitations, the aim of this study is to develop ideal injectable implants from biomaterials for minimally invasive surgery. An injectable composite bone graft containing calcium sulfate hemihydrate, tetracalcium phosphate, and anhydrous calcium hydrogen phosphate (CSH/CaP paste) was prepared with different CSH/CaP ratios and different concentrations of additives. The setting time, injectability, mechanical properties, and biocompatibility were evaluated. The developed injectable CSH/CaP paste (CSH/CaP 1:1 supplemented with 6% citric acid and 2% HPMC) presented good handling properties, great biocompatibility, and adequate mechanical strength. Furthermore, the paste was demonstrated to be extruded from a syringe equipped with 18G needles and exerted a great potential for minimally invasive surgery. The developed injectable implants with tissue repairing potentials will provide an ideal therapeutic strategy for minimally invasive surgery to apply in the treatment of maxillofacial defects, certain indications in the spine, inferior turbinate for empty nose syndrome (ENS), or reconstructive rhinoplasty.     

Preparation and Physicochemical Characterization of New Nanocomposites Based on β-Type Chitosan and Nano-Hydroxyapatite as Potential Bone Substitute Materials

In the present study, β-type chitosan [ß (1–4) N-acetyl D-glucosamine] was obtained through a modified procedure from squid pens (Loligo Vulgaris) and characterized to determine its average molecular weight and degree of N-deacetylation. Then, the β-chitosan was used for the first time, in a combination with different proportions of nano-hydroxyapatite (n-HA), to develop new series of nanocomposites as potential bone substitute materials that are able to overcome the poor physicochemical and mechanical properties of pure artificial hydroxyapatite. The β-chitosan/n-HA nanocomposites were prepared through in situ coprecipitation technique and characterized with the aid of FTIR, XRD, and EDS. Surface morphology of the nanocomposites was examined using SEM and TEM. The mechanical properties were also studied through measuring the compressive strength of the developed composites.     

Optimizing preparation of NaCS–chitosan complex to form a potential material for the colon‐specific drug delivery system

A novel polyelectrolyte complex (PEC) formed by sodium cellulose sulfate (NaCS) and chitosan was prepared as a candidate material for colon‐specific drug delivery system. It was found in experiments that the properties of two raw materials and the process parameters, such as the degree of substitution (DS) and concentration of NaCS, the viscosity and concentration of chitosan, were very important factors on the properties of the final product—NaCS–chitosan‐PEC. The preparation of NaCS–chitosan complex was optimized by using response surface methodology to evaluate the effects of these parameters on the degradation properties of NaCS–chitosan in the simulated colonic fluid (SCF). The DS of NaCS was in the range from 0.2 to 0.6, the concentration of NaCS from 2 to 4% (w/v), the viscosity of chitosan from 50 to 550 mPa s, and the concentration of chitosan from 0.5 to 1.5% (w/v). A mathematical model was developed to describe the effect of these parameters and their interactions on the degradation of NaCS–chitosan complex. The optimum operation conditions for preparing NaCS–chitosan complex were determined to DS of NaCS of 0.2, the concentration of NaCS of 4.0% (w/v), chitosan viscosity of 327 mPa s, and the concentration of chitosan 0.5% (w/v), respectively. Validation of experiments with 5 confirmatory runs indicated the high degree of prognostic ability of response surface methodology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

稀土氧化钇改性磷酸钙骨水泥的研究

磷酸钙骨水泥是一种新型的自固化的非陶瓷羟基磷灰石人造骨材料,具有良好的生物相容性、自固化能力、易于塑形、与成骨活性相协调的溶解性能可作为药物、生物活性因子缓释载体等优越的性能。稀土掺杂羟基磷灰石,对羟基磷灰石的合成有促进作用,并且使其具有更稳定的性质。钇的加入有助于羟基磷灰石生物活性的提高。笔者利用钇掺改善羟基磷灰石生物活性作为探讨。其采用氧化钇对磷酸钙骨水泥进行改性研究,考察磷酸钙骨水泥凝结时间、可注射性和孔隙率等基本性能。采用X射线衍射分析骨水泥粉末在水化过程中的变化及其最终产物。采用电镜观察产物的微结构和表面形貌。研究结果表明:钇加入没有影响磷酸钙骨水泥的水化,并且随着钇含量的增加磷酸钙骨水泥的固化体凝结时间逐渐延长,其中氧化钇含量在5%时凝结时间最短;骨水泥浆体的可注射性变大,其中氧化钇含量在1.5%时可注射性最大(壳聚糖溶液)。磷酸钙骨水泥水化最终产物为片状或棒状的羟基磷灰石,其结构呈紧密联系,但表面有较多的孔隙,且随着钇含量的增加孔隙率有增加的趋势。     

La_2O_3掺杂(Bi_(0.5)Na_(0.5))_(0.94)Ba_(0.06)TiO_3陶瓷的介电和压电性能的研究

用固相反应法制备La2O3掺杂的铁电陶瓷(Bi0.5Na0.5)0.94Ba0.06TiO3(BNBT6)。X射线衍射曲线表明掺杂0-0.6wt%La2O3的BNBT6为钙钛结构。研究了La2O3掺杂对BNBT6陶瓷介电性能和压电性能的影响。结果表明La2O3掺杂量为0.3wt%的BNBT6陶瓷综合性能最佳,其中介电常数为1981.4,介电损耗为0.0625和压电常数为145pc/N。SEM图象表明La2O3掺杂提高了陶瓷的致密度。     

Properties of a ternary calcium sulfoaluminate–calcium sulfate–fly ash cement

In this paper, cement combinations based on calcium sulfoaluminate cement (CSAC) were developed and the effect of fly ash and the hemihydrate form of calcium sulfate on the properties of the systems was studied. Fly ash (FA), anhydrite (ANH), flue-gas desulfurization gypsum (FGDG) and plaster gypsum (PL) were used to develop appropriate CSAC/calcium sulfate and CSAC/calcium sulfate/addition systems, the hydration of which was studied. Tested properties of cements were the compressive strength and the setting times. The results suggest that the use of fly ash in the presence of anhydrite accelerates the formation of a strong ettringite-rich matrix that firmly accommodated unreacted fly ash particles, both synergistically contributing to a dense microstructure. At a given sulfate content, the use of anhydrite was shown to be favourable in terms of the setting times, heat patterns and strength development compared to the hemihydrate-based formulations.     

Relationship between particle scale capillary forces and bulk unconfined yield strength

One of the main problems in industrial applications is the handling of fine cohesive materials. This cohesion can cause hang-ups in process equipment and stop or slow down processing. Conversely, just a small quantity of cohesion in a bulk powder can prevent particle size segregation. It is obvious that understanding cohesion from a fundamental point of view is useful in describing process flow behavior. Capillary force between particles is one source of cohesion between particles. This paper presents a theory that can be used to model the cohesive behavior of bulk materials based on capillary forces between particles.     

纳米硫酸钙制备及应用研究进展

纳米硫酸钙因其特有的物理化学性质和力学性能在医疗、建材、橡胶材料、阻燃材料、复合材料等领域有着较为广泛的应用前景。本文介绍了近些年来国内纳米硫酸钙材料的制备方法,主要介绍了微乳液法制备硫酸钙纳米材料（纳米管／纳米粒／纳米棒）,并对纳米硫酸钙的研究现状和发展趋势进行了概述。     

Preparation of calcium sulfate dihydrate and calcium sulfate hemihydrate with controllable crystal morphology by using ethanol additive

Calcium sulfate hemihydrate (CSH) with controlled crystal morphology has attracted broad interests due to its superior physical and chemical properties, as well as excellent biological performance. In this study, calcium sulfate dehydrate (CSD) was firstly synthesized via the reaction of H₂SO₄ and Ca(OH)₂ using ethanol as morphology modifier. The prepared CSD was then converted to CSH through a hydrothermal method. It was found that the precipitation time of CSD powders was dramatically shortened and the morphology of CSD crystals was changed from thick tabular to short-rod with the increment in ethanol addition. The finally-obtained CSH crystals were found to have hexagonal prisms shape with smaller aspect ratios. The CSH powder with the desired crystal morphology would provide improved setting behavior and biological performance of the CSH bone cement.     

Crosslinked chitosan doped with Y2(CO3)3 and surface energy and electrorheological properties

Novel electrorheological materials based on crosslinked chitosan doped with Y₂(CO₃)₃ were synthesized with biocompatible chitosan as the substrate of the materials. The electrorheological performance, surface energy, and thermal decomposition behavior of the materials were investigated as functions of the composition change. The results show that doping Y₂(CO₃)₃ can improve effectively the electrorheological performance of crosslinked chitosan with the formation of a metal–polymer complex when the doping degree is suitable. The surface energy plays an important role in influencing the electrorheological properties of the material. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Sr,Mg co-doping of calcium hydroxyapatite: Hydrothermal synthesis,processing, characterization and possible application as dentin substitutes

The aim of this study was to investigate the influence of binary Sr, Mg ion-doping compared to the single-ion doping effects on the phase composition and morphology of hydrothermally obtained calcium hydroxyapatite (HAP) powders and on the phase composition, microstructure, and mechanical properties of the sintered materials. Additionally, the focus of this study was to investigate the possible utilization of the binary doped Sr,Mg-HAP compacts as dentin substitutes in restorative dentistry by evaluating their bonding ability with commercially available restorative materials using the shear bond strength test (SBS). The hydrothermally obtained mono-doped Mg5 and Sr5 showed the monophasic apatite structure, while in all co-doped samples β-TCP phase was formed, resulting in biphasic calcium phosphate (BCP) powders. It was confirmed that co-doping with Sr and Mg ions led to the thermal stabilization of the β-TCP phase by suppressing the phase transition into α-TCP when sintered at 1200 °C. Moreover, the co-presence of Mg ions significantly improved the hardness of Sr-doped HAP from 3.74 to 5.02 GPa. Sr,Mg-HAP dental inserts were found to achieve sufficient bonding (13.53 MPa) through the micromechanical interlocking with Z250 dental composite and Single Bond Universal dental adhesive applied with a total etch approach. The SBS values obtained for the SrMg-HAP insert were similar to the literature data on bonding ability with human dentin, indicating that binary doped Sr,Mg-HAP ceramics present a promising material for application in restorative dentistry as dentin substitutes.