纳米羟基磷灰石-胶原蛋白-壳聚糖复合生物材料

采用共沉淀法制备了纳米羟基磷灰石．胶原蛋白．壳聚糖复合生物材料，用IR、XRD、TEM及万能材料实验机等方法对材料性能进行了分析表征。结果表明：羟基磷灰石．胶原蛋白．壳聚糖复合生物材料在晶相组成、化学成分、羟基磷灰石尺寸上具有类骨结构，并具有良好的力学性能．其抗压强度达到128MPa，可满足骨组织修复与替代的要求。有望成为治疗骨缺损的承力替代物。     

聚乳酸-羟基乙酸/改性纳米羟基磷灰石复合多孔支架材料的研制

聚乳酸-羟基乙酸(PLGA)/改性纳米羟基磷灰石(MHA)复合多孔组织工程支架材料的制备主要包含以下步骤:首先通过室温化学共沉淀法制备纳米羟基磷灰石,然后通过L-丙交酯在二甲苯溶液中聚合接枝纳米羟基磷灰石得到改性的纳米羟基磷灰石;最后通过改进的热致相分离两步初化法制备PLGA/MHA复合多孔支架.X射线衍射仪(XRD)显示纳米羟基磷灰石合成成功,透射电子显微镜(TEM)结果显示其为半径为30～50nm的球形,红外光谱显示聚乳酸成功的接枝到纳米羟基磷灰石表面;扫描电子显微镜(SEM)结果表明改进的热致相分离两步初化法制备的PLGA/MHA复合多孔支架的孔径在100～450μm.     

原位沉析羟基磷灰石-壳聚糖骨组织工程支架材料的研制

仿生构建羟基磷灰石-壳聚糖复合材料是制备骨组织修复材料的重要途径之一.本研究利用有机官能团对无机物矿化的调控作用,在壳聚糖多孔支架表面原位沉析羟基磷灰石(HAp).在仿生溶液中,采用简单的化学处理,使HAp晶体在壳聚糖多孔支架表面原位沉析.研究结果表明壳聚糖分子结构中的氨基作为成核位点,在碱性条件下首先与吸附Ca2 ,再通过静电作用力吸附仿生溶液中的PO43-、OH-等其它离子促使HAp晶体在壳聚糖支架材料表面的成核、长大.此类材料有望成为一种生物活性的骨组织工程材料.     

羧甲基壳聚糖/纳米羟基磷灰石复合支架材料的制备及生物安全性

为了探讨羧甲基壳聚糖/纳米羟基磷灰石(CMCTS/n-HA)复合支架材料的制备及其生物安全性,采用化学沉淀法合成了纳米羟基磷灰石粉体（n-HA）; 以无水乙醇为沥滤剂,以16.7% (质量分数)的柠檬酸水溶液作粘接剂, 通过粒子沥滤法制备CMCTS/n-HA多孔复合材料。对其孔隙率及抗压强度进行测试,并将其植入大白兔骨缺损处观察组织学变化并进行肝肾功能检测。CMCTS/n-HA复合多孔材料的孔隙率接近75％,孔隙尺寸分布约从几微米到600 μm,并且孔隙之间相互贯通,其抗压强度可达21 MPa以上,植入大白兔骨缺损处未见引起骨组织明显的炎症反应及骨坏死, 肝肾功能检测未发现有肝肾毒性。CMCTS/n-HA可以满足骨组织工程支架的基本要求。      

纳米羟基磷灰石/壳聚糖/羧甲基纤维素三元复合骨修复材料的制备和性能研究

用溶液共混法在常温常压下制备了不同比例的纳米羟基磷灰石/壳聚糖/羧甲基纤维素三元复合骨修复材料.用燃烧实验、IR、XRD、SEM及TEM对复合材料的组成结构及形貌进行了分析和观察,并初步研究了其力学性能.结果表明该复合材料中纳米羟基磷灰石均匀分散在壳聚糖和羧甲基纤维素网络结构中,三组分间还产生了一定的相互作用,其形态、尺寸及结构与自然骨类似,且其抗压强度比纳米羟基磷灰石/壳聚糖二元复合材料更高;同时,通过调节各组分比例,可制得不同抗压强度的复合材料.因此,该三元复合材料可望作为一种新型可降解的非承重部位骨修复材料,在生物医学材料的研究中具有重要意义.     

载微球纳米羟基磷灰石/壳聚糖复合多孔支架的制备与表征

首先通过乳化法合成海藻酸钠/壳聚糖(ALG/CS)复合微球,然后将其与纳米羟基磷灰石/壳聚糖H(n-HA/CS)复合材料混合均匀,用气体发泡法制备了载微球复合组织工程支架.并用扫描电子显微镜(SEM)、傅立叶变换红外光谱仪(IR)以及转靶X射线仪(XRD)等方法对该载微球多孔支架进行分析和表征.结果表明:n-HA/CS复合材料中无机相均匀分散在连续有机基质中,复合前后两组分均未发生明显变化;制备的载微球多孔支架中孔隙分布均匀,孔间贯通性良好,孔隙率较高;而其中的微球均呈球状,直径分布在150～350μm之间;微球表面粗糙且有大量微孔,载药后将利于药物的释放;微球在整个支架中分布均匀,而且与n-HA/CS基体材料间亲和性较高.本研究将为骨或软骨缺损提供一种性能优良且具有药物缓释功能的组织工程支架.     

纳米羟基磷灰石/壳聚糖-羧甲基纤维素复合支架材料的研究

用冷冻干燥法制备了不同比例的纳米羟基磷灰石/壳聚糖-羧甲基纤维素(n-HA/CS-CMC)无机/有机复合多孔支架材料, 并探讨了其复合机理及无机组分n-HA对复合支架的结构形貌、力学性能、体外降解性能的影响. 结果表明, 其复合支架主要是通过无机组分n-HA均匀分散充填在CS-CMC聚电解质有机网络结构中形成的, 且三组分间有较强的化学键合. 无机组分n-HA的加入使孔结构变得不规则, 孔隙率略有减小, 使复合支架的抗压缩强度提高, 并且可使其体外降解速度减慢. 无机组分n-HA含量为40\%复合支架材料的性能最佳, 有望用作骨组织工程支架材料.     

纳米羟基磷灰石/聚合物多孔复合支架材料

为提高骨组织工程支架材料的力学性能,改善其生物活性,综合天然与合成高分子的优点,采用溶液共混相分离法制备出聚己内酯(PCL)-壳聚糖(CS)多孔支架材料, 并进一步采用离心注浆法填充具有生物活性的纳米羟基磷灰石(HA)-聚乙烯醇(PVA)复合浆料, 制备了n-HA-PVA/PCL-CS复合多孔支架材料, 改善了PCL-CS支架材料力学性能。采用扫描电子显微镜、红外光谱、元素分析、孔隙率和抗压强度试验对材料进行了表征。结果表明, PCL-CS支架材料的内部具有蜂窝状的相互贯通的孔隙结构,孔隙率可以达到60%～80%。CS含量越大,孔隙率越大,而抗压强度越小。填充后的n-HA-PVA/PCL-CS复合多孔支架材料,孔隙率有所下降,但仍大于60%,而其弹性模量可提高至25.71 MPa。      

纳米羟基磷灰石/壳聚糖复合生物材料研究

骨的特殊性能决定了其在人体中起重要的功能作用,人工骨材料对骨缺损的治疗有重要意义。羟基磷灰石是人和动物骨骼的主要无机成分;壳聚糖是天然可降解多糖,降解产物为对人体组织无毒、无害的氨基葡萄糖。纳米羟基磷灰石/壳聚糖复合生物材料可以实现羟基磷灰石和壳聚糖两者的优势互补,具有优良的生物活性、生物相容性和力学性能。介绍了近年来纳米羟基磷灰石/壳聚糖复合生物材料的主要合成方法(如共混法、共沉淀法、原位沉析法、交替沉积法和模拟体液法等),并在此基础上介绍了基于纳米羟基磷灰石/壳聚糖的三元复合材料的研究及发展情况;最后,展望了纳米羟基磷灰石/壳聚糖复合生物材料未来的发展方向。     

丝素蛋白/纳米生物玻璃复合多孔支架的结构与性能

采用冷冻干燥法制备了丝素蛋白(SF)/纳米生物玻璃(NBG)复合多孔支架材料。并用XRD、FT-IR、SEM等对SF/NBG复合支架进行了结构与性能表征。结果表明,SF/NBG复合多孔支架孔连通性较好,孔径为150～300μm,孔隙率为80.6%～90.3%;同时NBG的加入促进了复合多孔支架中SF的构象部分由无规卷曲向β-折叠转变。复合多孔支架抗压强度和抗压模量相比于纯SF多孔支架有较大提高。采用模拟体液浸泡实验研究了复合支架的体外生物活性,并用XRD、FT-IR和FESEM对试样表面进行了表征。结果显示,复合多孔支架经模拟体液浸泡7d后,表面沉积出类骨羟基磷灰石(HA)层,NBG的加入能加快复合多孔支架表面沉积类骨HA的速度。研究结果显示SF/NBG复合多孔支架材料有望作为生物活性良好的骨组织修复材料。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

n-PbTep+−Pb1−xSnxTe heterojunctions prepared by a modified hot wall technique

$\text{n-PbTe}\text{p}{}^{\mathrm{+}}\text{?}\text{Pb}{}_{\mathrm{1?x}}\text{Sn}{}_{\mathrm{x}}\text{Te}$ heterojunctions with a long wavelength spectral cutoff (λ_c ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with R_oA equal to 170 Ω cm² and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given.     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Reactive plasma deposited SixCyHz films

Si_xC_yH_z films have been prepared at 200°C by reactive plasma deposition from SiH₄ and CH₄ diluted in helium in a tubular reactor. These films have a ratio s (equal to $\text{Si}\text{(}\text{Si+C}\text{))}$ ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH₄-CH₄-He plasma have been performed and the results are related to the composition of the deposited layers.     

Core-current-enhanced domain-wall pinning in nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon

We have studied the influence of surface fields H/sub p/ (generated by either direct or alternating core current) on soft magnetic properties of amorphous and nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon. While in an amorphous ribbon the coercive field H/sub c/ decreases with H/sub p/, in the same optimally annealed ribbon (H/sub c/=1.3 A/m, M/sub m//spl ap/M/sub s/) H/sub c/ increases with H/sub p/ for all the explored types of H/sub p/ (static and dynamic with different phases with respect to that of the magnetizing field H). The unexpected increase of H/sub c/ in nanocrystalline ribbon is associated with the influence of H/sub p/ on the surface and main (inner) domain structure. Here, we develop a model that takes into account this influence and explains the experimental results.