The behaviour of selected yttrium containing bioactive glass microspheres in simulated body environments

The study aims at the manufacture and investigation of biodegradable glass microspheres incorporated with yttrium potentially useful for radionuclide therapy of cancer. The glass microspheres in the SiO₂–Na₂O–P₂O₅–CaO–K₂O–MgO system containing yttrium were prepared by conventional melting and flame spheroidization. The behaviour of the yttrium silicate glass microspheres was investigated under in vitro conditions using simulated body fluid (SBF) and Tris buffer solution (TBS), for different periods of time, according to half-life time of the Y-90. The local structure of the glasses and the effect of yttrium on the biodegradability process were evaluated by Fourier Transform Infrared (FT-IR) spectroscopy and Back Scattered Electron Imaging of Scanning Electron Microscopy (BEI-SEM) equipped with Energy Dispersive X-ray (EDX) analysis. UV–VIS spectrometry and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used for analyzing the release behaviour of silica and yttrium in the two used solutions. The results indicate that the addition of yttrium to a bioactive glass increases its structural stability which therefore, induced a different behaviour of the glasses in simulated body environments.     

Synthesis, structural and magnetic characterization of iron-zinc-borate glass ceramics containing nanocrystalline zinc ferrite

Two different glass ceramics with the composition of the (Fe₂O₃)_x·(B₂O₃)_(60−x)·(ZnO)₄₀, where x = 12.5 and 15 mol%, have been synthesized using the melt-quench method. The X-ray diffraction (XRD) patterns show the presence of nanometric zinc ferrite (ZnFe₂O₄) crystals, with spinel structure, in a glassy matrix after cooling from melting temperature. The estimated amount of crystallized zinc ferrite varies between 16 and 35%, as a function of the chemical composition. Glass transition (T_g), crystallization (T_p) and melting (T_m) temperatures were determined by differential thermal analysis (DTA) investigations. Fourier transform infrared (FTIR) data revealed that the BO₃ and BO₄ are the main structural units of these glass ceramics network. FTIR spectra of these samples show features at characteristic vibration frequencies of ZnFe₂O₄. Electron paramagnetic resonance (EPR) measurements show the presence of isolated Fe³⁺ ions predominantly situated in rhombic vicinities and as well as the Fe³⁺ species interacting by dipole–dipole interaction or to their superexchange coupled pairs in clustered formations. The magnetic properties of the studied glass ceramics were investigated by vibrating sample magnetometer (VSM). From the magnetization curves for glass ceramic containing 15 mol% Fe₂O₃ it was found that the nanoparticles exhibit ferromagnetic interactions combined with superparamagnetism with a blocking temperature, T_B. For studied samples the hysteresis is present. The coercive field is dependent on composition and magnetic field being around 0.05 μ_B/f.u for measurements performed in maximum 0.4 T.     

Preparation,characterization and dielectric behaviour of some yttrium doped strontium stannates

Samples of Sr_{(1− 3x/2)}YxSnO₃ are prepared by usual solid state reaction route. X- ray diffraction studies confirm the formation of single cubic perovskite single phase. The dielectric constant and dielectric loss at 1 kHz were measured in the temperature range from room temperature up to -150†C. The dielectric constant decreases and losses increase with increased yttrium content in the samples. The percentage porosity and unit cell parameters are also calculated for the samples.     

Synthesis and characterization of manganese containing mesoporous bioactive glass nanoparticles for biomedical applications

Mesoporous bioactive glass (BG) nanoparticles based in the system: SiO₂–P₂O₅–CaO–MnO were synthesized via a modified Stöber process at various concentrations of Mn (0–7 mol %). The synthesized manganese-doped BG nanoparticles were characterized in terms of morphology, composition, in vitro bioactivity and antibacterial activity. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis confirmed that the particles had spherical morphology (mean particle size: 110?nm) with disordered mesoporous structure. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn, Ca, Si and P in the synthesized Mn-doped BG particles. Moreover, X-ray diffraction (XRD) analysis showed that Mn has been incorporated in the amorphous silica network (bioactive glass). Moreover, it was found that manganese-doped BG particles form apatite crystals upon immersion in simulated body fluid (SBF). Inductively coupled plasma atomic emission spectroscopy (ICP-OES) measurements confirmed that Mn is released in a sustained manner, which provided antibacterial effect against Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. The results indicate that the incorporation of Mn in the bioactive glass network is an effective strategy to develop novel multifunctional BG nanoparticles for bone tissue engineering.     

Synthesis and characterization of photoluminescent cerium-doped yttrium aluminum garnet

Powder phosphor yttrium aluminum garnet (YAG), doped with trivalent cerium (Ce³⁺) is synthesized by sol-gel method. The formation of YAG and YAG:Ce (cerium-doped yttrium aluminum garnet) was investigated by means of X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were also used. The purified crystalline phases of YAG and YAG:Ce were obtained at 1000 °C. The maximum average grain size is about 20-23 nm for undoped samples and 28-34 nm for doped samples. The crystalline YAG:Ce emission shows one peak in the range 480-535 nm with the maximum near 520 nm. Photoluminescence (PL) intensity of 5d → 4f transition of Ce³⁺ increased with increasing annealing temperature. With increasing the concentration of Ce³⁺, the photoluminescence peak shifts towards the red region.     

Study of yttrium containing bioactive glasses behaviour in simulated body fluid

The influence of yttrium oxide on the bioactivity of glasses in the system SiO₂-Na₂O-P₂O₅-CaO-B₂O₃-K₂O-MgO was studied in a simulated body fluid (SBF). Two series of glasses with different bioactivity were investigated. The reaction layers formed on the surface of the exposed glasses were evaluated by means of back scattered electron imaging of scanning electron microscopy equipped with energy dispersive X-ray analysis (BEI-SEM/EDXA). The concentration of Y, Ca and P released from the glasses into SBF, during 21 days was determined using inductively coupled plasma-emission spectroscopy ICP-AES and inductively coupled plasma-mass spectroscopy ICP-MS. Introducing yttrium in the selected bioactive glass tended to diminish the bioactivity of the glasses. The thickness of the calcium phosphate layer decreased with increasing yttrium oxide content. The same effect was also observed when yttrium oxide partially replaced only calcium, magnesium and phosphorous oxide in the precursor glass. The data show that we can produce bioactive glasses with yttrium oxide as a component. By suitable tailoring of the rest of the glasses the yttrium effect on the glass behavior in SBF should be possible to control and thus produce yttrium containing glasses with desired bioactivity.     

Isothermal devitrification of an oxynitride LAS glass composition monitored by X-ray powder diffraction

The crystallisation of a Li_0.6Al_0.1Si_0.6O_1.575N_0.05 glass matrix has been studied by means of X-ray powder diffraction at 730°C. Data diffraction and EDS analysis have shown the simultaneous formation of two crystalline phases Li₂SiO₃ and Li_0.6Al_0.6Si_2.4O₆ (so-called virgilite) with no evidence for the presence of nitrogen in these phases. The Avrami exponent has been determined for each phase from several time-dependent X-ray diffraction studies. The values of the Avrami exponent, close to 2.25, suggest that crystallisation is tri-dimensional and controlled by a diffusion process with a decreasing nucleation rate at 730°C. With respect to the aluminium-containing phase, a long time heat treatment at this temperature has not revealed a phase transition from the metastable hexagonal symmetry to the stable tetragonal one. The XRD correlation length values, from the Scherrer equation, are close to 450 Å. Furthermore, SEM micrographs have confirmed the volume crystallization of this glass composition and the approximate linear dimension of the regions of diffracting materials.     

含钇多金属氧酸盐的合成及稀土多元扩渗与电性能

用降解法或直接法合成了未见报道的四种含钇多元杂多配合物.通过化学分析、ICP和TG曲线确定了其化学式为K18-2nH3[Y(Xn+W11O39)2]·mH2O(X=B3+,Si4+,P5+)和K10H3[Y(SiW9Mo2O39)2];利用IR、XRD、183W-NMR、循环伏安等手段对其结构进行了表征,结果表明杂多阴离子为α-型或β2-型Keggin结构.采用稀土多元渗的方法对配合物进行了气相热扩渗,经ICP和XPS测试表明微量的稀土元素La、Sm和Dy可以渗入到配合物的体相,并与组份元素存在键合作用;导电性的测试结果表明室温时,扩渗后试样的电导率提高了约104～106倍,且与中心原子有关.     

Abrasive wear behaviour of bio-active glass ceramics containing apatite

In this study, abrasive wear behaviour of bio-active glass ceramic materials produced with two different processes is studied. Hot pressing process and conventional casting and controlled crystallization process were used to produce bio-active ceramics. Fracture toughness of studied material was calculated by fracture toughness equations using experimental hardness results of the bio-active glass ceramic material. Two fracture toughness equations in the literature were used to identify the wear behaviour of studied ceramics. Wear resistance results that identified with both of the equations were similar. The results showed that the abrasive wear resistance of the bio-active glass ceramics produced with hot pressing process was found to be higher than that of the ceramics produced by conventional casting and controlled crystallization process.     

含咔唑PPV类超支化聚合物的合成及性能

以CpCo（CO）2为催化剂在紫外光照射的条件下，以3，6-二[（4-乙炔基）苯乙烯基]-N-辛基-咔唑双炔和1-辛炔作为单体，通过[2＋2＋2]环三聚反应合成了含咔唑PPV类超支化聚合物。采用红外光谱、核磁共振谱、热失重分析、紫外吸收光谱、荧光光谱、循环伏安法等方法对聚合物进行结构表征与性能测试，所得到的聚合物都溶于普通的有机溶剂（比如四氢呋喃、二氯甲烷、氯仿、甲苯等）。这类聚合物都表现出优异的热稳定性，它们的起始分解温度在378℃以上，在800℃时，聚合物的残余碳化率高达63％；荧光光谱显示，在光激发的条件下，聚合物在二氯甲烷溶液中发射蓝光，其荧光量子效率高达80％，电化学分析表明聚合物具有较好的空穴传输能力。     

Gallium containing glass polyalkenoate anti-cancerous bone cements: glass characterization and physical properties

A gallium (Ga) glass series (0.48SiO(2)-0.40ZnO-0.12CaO, with 0.08 mol% substitution for ZnO) was developed to formulate a Ga-containing Glass Polyalkenoate Cement (GPC) series. Network connectivity (NC) and X-ray Photoelectron Spectroscopy (XPS) was employed to investigate the role of Ga(3+) in the glass, where it is assumed to act as a network modifier. Ga-GPC series was formulated with E9 and E11 polyacrylic acid (PAA) at 50, 55 and 60 wt% additions. E11 working times (T(w)) ranged from 68 to 96 s (Lcon.) and 106 s for the Ga-GPCs (LGa-1 and LGa-2). Setting times (T(s)) ranged from 104 to 226 s (Lcon.) and 211 s for LGa-1 and LGa-2. Compression (σc) and biaxial flexural (σf) testing were conducted where Lcon. increased from 62 to 68 MPa, LGa-1 from 14 to 42 MPa and LGa-2 from 20 to 47 MPa in σc over 1-30 days. σf testing revealed that Lcon. increased from 29 to 42 MPa, LGa-1 from 7 to 32 MPa and LGa-2 from 12 to 36 MPa over 1-30 days.     

Synthesis and characterization of yttrium aluminum garnet nanostructures by cathodic electrodeposition method

Pure nanostructures of yttrium aluminum garnet (YAG) was prepared based on the cathodic electrodeposition method from the mixture of YCl₃ and AlCl₃ dissolved in water/ethanol solution. At first, hydroxide precursors cathodically were grown on the steel substrates then, the hydroxide powders heat treated at 850 °C for 4 h in dry air atmosphere. The formation of crystalline YAG nanopowder was confirmed by X-ray diffraction (XRD), thermogravimetric analysis (DSC-TGA), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FT-IR). The results of the SEM showed that applied current density and bath temperature have the prominent effect on the morphology and particle size of the products. The results revealed that cathodic electrodeposition followed by heat-treatment can be used as a facile method for preparation of YAG nanostructures with different morphology.     

Synthesis of europium-doped yttrium hydroxide and yttrium oxide nanosheets

A new approach has been developed for the preparation of Y(OH)₃:Eu and Y₂O₃:Eu nanosheets using the sol–gel method and hydrothermal reactions. XRD patterns showed that the product was purely hexagonal-phase Y(OH)₃. TEM images revealed that the nanosheets are square shaped (1 × 1 μm²) with a thickness of several tens of nanometers. In addition, it was found that cubic-phase Y₂O₃ nanosheets can be obtained by calcination of Y(OH)₃ at 900 °C for 1 h. More importantly, the thus-prepared Y(OH)₃:Eu and Y₂O₃:Eu nanosheet phosphors were found to exhibit a relatively high photoluminescence (PL) intensity.     

含二氮杂萘酮联苯结构聚芳酯的合成和性能

以新二酸4-[4-(4-羧基苯氧基)苯基]-2-(4-羧基苯基)二氮杂萘-1-酮(1)和4种商品二酚进行溶液缩聚反应,制备出一系列古杂萘联苯结构新型聚芳酯,其特性粘度在0．50-0．58 dL·g-1之间．以FT-IR．1H-NMR证明了聚合物的结构．该类聚芳醇的玻璃化转变温度在209-272℃之间,在N2气氛下10％的热失重温度在468-481℃之间．聚芳本具有无定型结构,可溶解于N-甲基吡咯烷酮(NMP),N,N-二甲基乙酰胺(DMAc),间甲酚,吡啶和氯仿(CHCls)中．扭曲和非共平面的结构存在使该系列聚芳酯既耐高温又具有良好的溶解性能．     

含咔唑结构二胺的合成及其表征

通过亲核取代反应由3,3'-联咔唑和对氯硝基苯合成含咔唑结构的二硝基化合物,并对其还原,得到一种含咔唑结构的二胺,该二胺具有空穴传输基团.用红外光谱、飞行质谱、核磁氢谱及紫外光谱等对该化合物进行了表征.     

Synthesis and characterization of three-dimensional ordered mesoporous-macroporous bioactive glass

Three-dimensional ordered mesoporous-macroporous bioactive glass (MMBG) was synthesized by a combination of surfactant and polystyrene bead templates, the sol-gel method, and the evaporation-induced self-assembly process. The incorporation of regular spherical macropores only slightly perturbed the mesoporous network. The bioactivity of the MMBG was assessed by its immersion in simulated body fluid for different lengths of time and the subsequent determination of hydroxycarbonate apatite formation. The synthesized MMBG displayed good in vitro bioactivity and may have potential applications in bone tissue engineering.     

Positron lifetime study of the devitrification process in a cordierite glass

The devitrification of the 13.3% MgO-32.0% Al₂O₃-52.7% SiO₂-2.0% BaO ceramic-glass via isochronal heating up to a stable crystalline structure has been studied by the positron annihilation technique. The lifetime spectra showed two components. This devitrification results as a two-stage process. The long-lifetime ₂, attributed to the pick-off annihilation ofortho-Ps states, decreased on crystallization, but it was insensitive to the hexagonal-orthorhombic transformation of the crystalline cordierite. On the contrary, the effective lifetime of positrons annihilating in states that are not Ps, increased. This increase has been attributed to the Al/Si order process inherent to the hexagonal-orthorhombic transformation. Moreover, the Ps fraction in the crystalline phases was higher than in the glassy phase. However the free volume model might qualitatively explain the relationship observed betweenI ₂ and ₂.