Evaluation of CaO-SiO2-P2O5-Na2O-Fe2O3 bioglass-ceramics for hyperthermia application

Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO x (52-x)SiO2 x 4P2O5 x xFe2O3 x 3Na2O (2 < or = x < or = 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050 degrees C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x > or = 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them.     

Relation between cement composition and compressive strength of pure pastes

In Europe, cement paste compressive strength models are frequently described by a power law similar to that of Féret. The French LCPC has also adopted this mathematical approach in its recent concrete mixture proportioning model. However the coefficient k and exponent b of the adopted power law were calibrated with only one Portland cement clinker, starting from pure pastes with various concentrations. These parameters do not take into account the chemical properties of the clinker. The purpose of this work was to check if the clinker chemical nature had an influence on the mechanical performances of the pastes (at 28 days). Complementary tests with eight cements coming from six different cement plants were then carried out. The mathematical treatment of the results made it possible to connect coefficient k to the silica content of the clinkers and more particularly to their C₃S rates. It is linked to the strength of hydrated cement paste. Thus, the suggested approach significantly improves the accuracy of paste strength calculation. These results can be used to calculate concrete strength.     

Structural studies of some V2O5-P2O5-B2O3-Fe2O3 glass systems

X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0–7.5 mol % and heat treated at 300 °C for various times. The structure and phase separation could be determined for each glass composition. V₂O₅ was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe₂O₃ content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V⁴⁺ and V⁵⁺. The symmetry of V₂O ₇ ⁴⁻ and VO ₄ ³⁻ groups was found to increase with increasing Fe₂O₃ content. It was also found that some PO₄ changed to BO₃, forming a non-bridging oxygen.     

Non-isothermal kinetic studies for binary TeO2-P2O5 glass system

A study of TeO₂–P₂O₅ glass system has been carried out by Differential Thermal Analysis (DTA) to elucidate the kinetics of crystallization for these glassy samples. The results of DTA performed at different heating rates are discussed. The values of the glass transition temperature, T _g , as well as the glass crystallization temperature, T _c , are found to be dependent upon the heating rate. From this dependence, the values of activation energy for both the glass transition and crystallization are evaluated and discussed     

Formation of a high-strength bioactive glass-ceramic in the system MgO-CaO-SiO2-P2O5

Formation of a high-strength bioactive glass-ceramic in the system MgO-CaO-SiO₂-P₂O₅ was investigated by observing the microstructure of the crystallized products. Crystallization of the parent glass in a bulk form led to the occurrence of large cracks in the crystallized product. This was attributed to the precipitation of fibrous-wollastonite crystals growing perpendicular to the outer surfaces of the glass after uniform precipitation of fine oxyapatite/fluoroapatite crystals. On the other hand, crystallization of the same glass in a powder compact led to the formation of a crack-free dense crystallized product due to uniform precipitation of both apatite and wollastonite fine crystals throughout the glass article. The uniform precipitation of the wollastonite crystals was attributed to the simultaneous formation of fine crystals in the individual glass particles.     

Fe2O3掺杂对ZnO-B2O3-P2O5-RnOm玻璃热学性能的影响

在ZnO-B<,2>O<,3>-P<,2>O<,5>-R<,n>O<,m>玻璃中掺杂0～5%(摩尔含量)的Fe<,2>O<,3>,分析了Fe<,2>O<,3>对热膨胀系数(α)、密度(ρ)、电阻率(RV)的影响,通过差热分析(DTA)、红外光谱和X射线衍射(XRD)分析了玻璃的结构.研究表明:Fe<,2>O<,3>的摩...     

Optical absorption studies for TeO2-P2O5 and Bi2O3-TeO2-P2O5 glasses

A range of TeO₂-P₂O₅ and Bi₂O₃-TeO₂-P₂O₅ glass systems were prepared. The optical absorption spectra were measured in the spectral range 300–800 nm and it was found that the fundamental absorption of these glasses is dependent on the glass composition. The optical energy gap of binary glasses increases with increasing TeO₂ content while the addition of Bi₂O₃ to TeO₂-P₂O₅ decreases the optical energy gap. The absorption edges of these glasses arise from direct forbidden transitions and occur at photon energies in the range of 2.17 to 2.97 eV for TeO₂-P₂O₅ glasses and 2.63 to 2.32 eV for Bi₂O₃-TeO₂-P₂O₅ glasses depending on their composition.     

A.c. conductivity for amorphous TeO2-P2O5 glass system

The a.c. conductivity for the TeO₂-P₂O₅ glassy system was measured in the temperature range 300–573 K and in the frequency range 100 Hz to 10 kHz. The a.c. conductivity () increased with frequency according to the relation ()^s. The frequency exponent s was found to decrease with increasing temperature. The composition dependence of the conductivity was also investigated. The density of states was also calculated using the Elliott model. The a.c. conductivity increased over the studied temperature range. The obtained experimental data have been analysed with reference to various theoretical models. The analysis shows that the correlated barrier hopping (CBH) model is the most appropriate mechanism for conduction in the TeO₂-P₂O₅ glass system.     

Conduction mechanism at high electric field and switching phenomena in V2O5-P2O5 and V2O5-P2O5-TeO2 glasses

A previous investigation [1] suggests that the conduction in some vanadate glasses is ohmic up to a field of the order of 10⁵ V cm^–1 with an activation energy range from 0.31 to 0.48 eV depending on composition, but independent of temperature above room temperature. In this work the electrical conductivity of these glasses at high electric field is reported. The results suggest that above a field of 4×10⁵ V cm^–1 conduction becomes non-ohmic, and this is found to be due to lowering the potential barrier to the carrier at high electric field. Memory switching is observed in thin blown film samples of both binary and ternary glass systems, and is associated with field-induced crystallization of a localized region and the formation of a conduction channel in the switched area due to a self-heating effect.     

Effect of the addition of Fe2O3 and heat treatment duration on the magnetic susceptibility of V2O5-P2O5-B2O3 glass system

The effect of the addition of Fe₂O₃ and heat treatment duration on the magnetic susceptibility of vanadium borophosphate glass were studied. The magnetic susceptibility of glass samples was found to increase with increasing Fe₂O₃ content, which may be explained by the formation of the FeO₆ group and the change of Fe²⁺ to Fe³⁺ which has higher paramagnetic properties. No detectable changes in the magnetic susceptibility with heat treatment for the samples containing 0.0, 0.5 and 1.0 mol% Fe₂O₃ was observed. The magnetic susceptibility for the heat treated samples containing 2.5, 5.0 and 7.5 mol% Fe₂O₃ decreases sharply with increasing duration of heat treatment up to 6 h and then remains almost constant. The sharp decrease in magnetic susceptibility of 2.5 mol% Fe₂O₃ is attributed to the increase in the number of ferrous ions. The sharp decrease for samples containing 5.0 and 7.5 mol% Fe₂O₃ is attributed to the increase in the number of Fe³⁺ in tetrahedral co-ordination. The rate of crystallization owing to the heat treatment was calculated and was found to increase with increasing iron oxide content. The geometry of crystallization was found to be in three-, two-and one-dimension(s) for samples containing 2.5, 5.0 and 7.5 mol% Fe₂O₃, respectively.     

氧化物掺杂对钒磷铋系玻璃性能的影响

本研究制备了以V2O5、P2O5、B2O3为基体,掺杂Na2O、Li2O、CuO、Sb2O3、B2O3为辅助原料的低熔点钒磷铋系玻璃。研究了氧化物的添加对钒磷铋系玻璃的骨架网络结构、特征温度、热膨胀系数和化学稳定性的影响。实验结果表明:CuO的添加使钒磷铋系玻璃特征温度明显下降,而Na2O、Li2O、Sb2O3和B2O3的添加使钒磷铋系玻璃特征温度均有不同程度的上升。添加B2O3能够大幅度降低钒磷铋系玻璃的热膨胀系数。氧化物对钒磷铋系玻璃的耐水性影响程度为:CuO>B2O3>Sb2O3>Na2O>Li2O;耐酸性影响程度为:B2O3>CuO>Sb2O3>Na2O>Li2O;耐碱性的影响程度为:Sb2O3>Na2O>CuO>B2O3≈Li2O。配比为5%Na2O,5%Li2O,3.5%CuO,10%Sb2O3和5%B2O3制得的钒磷铋系玻璃,热膨胀系数更接近于氧化铝陶瓷基板,拥有较高的耐腐蚀性,能够用于电子浆料中。     

EPR and magnetic susceptibility studies on V2 O5-P2O5-PbO glasses

EPR and magnetic susceptibility investigations on the glass system with 04+ ion content are explained using a simulation program on the assumption of the superposition of two signals, one with hyperfine structure (hfs) typical for isolated ions and another one consisting of a broad line without hfs characteristic for clustered ions. The hfs is not shown for x<3mol%V₂O₅. The EPR data show the presence of V₄₊ ions in a square-pyramidal co-ordination (C_4V) for 3x20mol%V₂O₅. The progressive disappearance of hfs for high V²O⁵ content (>20 mol %) suggests the increase of the associated ion number coupled by superexchange interactions. This result is consistent with magnetic susceptibility data for >3 mol % where the temperature dependence of magnetic susceptibility is described by the Curie–Weiss type law with a negative paramagnetic Curie temperature. The magnetic susceptibility results allowed the estimation of the V⁴⁺/V⁴⁺ + V⁵⁺ ratio in the sample studied.     

Structural and microstructural transitions during phase separation and crystallization of Al2O3-SiO2-P2O5-Y2O3 glass

A highly refractory glass in the system Al₂O₃-SiO₂-P₂O₅-Y₂O₃ has been designed and produced such that, upon heating, an essentially fully crystalline glass—ceramic evolves containing mullite (nominally 3Al₂O₃·2SiO₂) and xenotime (YPO₄) as the final principal phases. Phase separation in this glass occurred during cooling from the melt and continued during annealing. XPS of the Al 2p, P 2p and the Y 3d electrons revealed that the average chemical environment of each of these elements is measurably different in the annealed glass and in the completely crystallized material. This indicates that the compositions of the separated glass phases are very different from those of the crystal phases which form from them. Additional rearrangement of the glass structure was observed at 1173 K. Extensive formation of mullite was initially detected at 1223 K and was followed by the crystallization of xenotime and the transient compounds of Y₄Al₂O₉, Y₂Si₂O₇, AlPO₄ and YP₅O₁₄. The optimum crystal nucleation and crystallization temperatures of 1173 and 1473 K, respectively, were determined from DTA, XRD, SEM and TEM studies.     

Mechanochemical synthesis of hydroxyapatite from Ca(OH)2-P2O5 and CaO-Ca(OH)2-P2O5 mixtures

Dry grinding of Ca(OH)₂-P₂O₅ and CaO-Ca(OH)₂-P₂O₅ mixtures was conducted by a planetary ball mill to investigate the mechanochemical solid-phase reaction for the synthesis of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp). HAp was synthesized by grinding of the two sets of mixtures. The formation of HAp from the Ca(OH)₂-P₂O₅ mixture was more advantageous than that from the CaO-Ca(OH)₂-P₂O₅ one. This synthesis reaction from the former mixture was almost completed within 30 min of grinding. The presence and amount of H₂O contained in the starting mixtures played a key role to promote the formation of HAp. Especially, in the former mixture, the prolonged grinding assisted the solid-phase reaction of the intermediate DCPD and Ca(OH)₂ to produce HAp more effectively.     

水泥胶砂抗压强度不确定度的分析与计算

在建筑材料的检测中,检测标准只对检测的变异系数有要求,单个检测单位的变异系数只能表征偶然因素对检测结果准确度的影响,而不能使检测人员和用户确切获知检测结果和被检对象的真值之间可能的最大误差,检测结果不确定度的引入,可以解决对检测结果的准确度不能直接定量表示的难题。本文对水泥胶砂抗压强度不确定度的来源、计算和合成等进行了阐述,可以作为建材检测单位确定其他检测项目不确定度的借鉴。     

Fe2O3掺杂对ZnO-B2O3-P2O5-RnOm玻璃耐水性的影响

在ZnO-BO-P2O5-RnOm系统玻璃中分别掺杂1％～5％(摩尔分数)的Fe2O3,系统的分析了掺杂Fe2O3对玻璃的耐水性、流散性产生的影响,通过X射线衍射(XRD)谱分析了晶相的变化.研究表明:掺杂Fe2O3能显著的提高磷酸盐玻璃的耐水性,由于极易于分解的非桥氧P-O键与铁离子链接,生成具有良好耐水性的P-O-...