Morphological and chemical characterisation of biomimetic bone like apatite formation on alkali treated Ti6Al4V titanium alloy

The present study is an attempt to enhance the apatite-forming ability of titanium metal induced by the alkaline (NaOH) treatment. A cell free culture medium, acellular DMEM solution was utilised to develop bone-like apatite on alkali-treated titanium alloy surface. The main advantage of this process is the development of bone like apatite with essential trace elements on the metallic substrate by using the DMEM culture medium as a soaking medium. The formed apatite deposits were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS). The obtained results suggest that the method utilized in this work can be successfully applied to obtain deposition of uniform coatings of crystalline hydroxyapatite on alkali treated titanium substrates.     

骨磷灰石与人工合成磷灰石的比较

用红外吸收光谱(FTIR)和电子探针(EPMA)技术对比研究了人体骨磷灰石与3种工艺合成的磷灰石的官能团和成分的差异.结果表明,用Ca(NO3)2和(NH4)2HPO4制备的磷灰石容易残存NO3-离子,钙磷摩尔比是1.69.用Ca(OH)2和H3PO4制备的磷灰石容易含过多的CO32-和HPO42-,钙磷摩尔比为1.73.溶胶-凝胶法制备的磷灰石粉体成分和结构与人体骨骼中的磷灰石最接近,钙磷摩尔比为1.66.这种相似性使其具有与人体骨骼相近的良好的生物相容性和生物活性.     

Structural characterisation of apatite coatings

The current, most frequently employed, commercial route to produce hydroxyapatite prosthetic coatings is plasma spraying. However, this has several important limitations especially for textured surfaces. Low temperature methods of coating fabrication such as cathodic electrodeposition are attractive alternatives. However, quantitative characterisation of the phase composition of thin electrodeposited coatings can be problematic. An X-ray diffraction method, which provides quantitative compositional information without reference to external or internal standards, is introduced and validated. The method can also be applied when Bragg peaks from the supporting substrate are apparent within the data and preferred orientation can be tolerated. This method has been used to examine in detail the microstructure of electrodeposited coatings which are compared directly with those formed by a commercial plasma spraying process.We show that, unlike the plasma sprayed coatings, the electrodeposited material consists of a single crystalline phase (hydroxyapatite) and a significantly reduced amorphous phase. The electrodeposited coatings also possess significantly more microstrain and a smaller crystallite size than the corresponding plasma sprayed material.     

Multi-layered graphenic structures as the effect of chemical modification of thermally treated anthracite

Graphenic materials have been produced from thermally treated highly metamorphosed carbon material – anthracite using two different methods: (1) the improved Hummers method followed by thermal reduction and (2) cycloaddition of azomethine ylide. Distinct differences were found between both anthracite-derived graphenic materials. The oxidation Hummers process resulted in a wide variety of oxygen functional groups incorporated into the carbon layers, while subsequent thermal reduction caused separation of graphene sheets but reduced the oxygen moieties. The cycloaddition of azometine ylide led to the formation of functionalized graphene sheets containing mostly 3,4-bonded N-methyl-2-(3,4-dihydroxyphenyl)pyrrolidine groups. The first attempts of application of anthracite-derived fillers to epoxy composites showed the improvement of their mechanical and viscoelastic properties, comparable to composites with graphene nanofillers.     

Physico-chemical characterization of thermally treated bentonite

Samples of original and thermally treated bentonite at 650 °C 4 h were characterized with chemical analysis, X-ray diffraction, thermal analysis, mercury porosimetry, differential scanning calorimetry, physisorption measurement and scanning electron microscopy. These consequence of the heating have been found. The chemical analysis shows high silica and alumina contents and small quantities of Fe⁺³, Ca⁺² and Mg⁺². XRD analysis shown the presence the main minerals are montmorillonite and opal CT, in the subordinate quantity illite. The result of the heating was the decomposition of clay minerals. Further, the increase in silica and alumina contents. A significant changes in the original pore structure have been found. The changes were characterized by the expressed increase in the content of total porosity caused by the achieved occurence of the pores covering pore radius area over 2000 nm. This effect represents the increased openness of the pore structure which may have the significant role in the intensity of alkali-activation process as a factor contributing to the increase of the contact of alkali activator solution with the activated solid. As a possible consequence of the increased openness could be the acceleration of alkali-activation process resulting, for example, in the acceleration of the strength development of binding system based on the thermally treated bentonite.     

Structural and phase changes in iron-on-silicon treated by compression plasma flows

Studies of structural and phase composition changes in pre-surface layers of iron-on-silicon treated by compression plasma flows (CPFs) (power density absorbed by the target varied from 0.6 to 1.4 GWt/m², pulse duration - 100 μs) are carried out by X-ray diffraction and scanning electron microscopy. The formation of tetragonal iron disilicide α-FeSi₂, silicon dendrite formation (average tip radius ∼0.2 μm, primary spacing increases with power density of the flow from 0.6 to 2 μm) are revealed. Radiation heat losses are established to be dominant at high power densities.     

Infrared spectroscopic study of thermally treated lignin

Precipitated lignin from black liquor produced from rice straw pulping was thermally treated at different temperatures (25 to 260 ° C) for 1h. Lignin was also thermally treated at 230 ° C for various time intervals (0.5 to 2h). The infrared spectra from 200 to 4000 cm^–1 were studied. It was found that the absorbance of OH as well as OCH₃ bands decreased with increasing temperature and heating time. On the contrary, C=0 increased with increasing temperature and time. The OH and OCH₃ vibrational bands began to disappear when the temperature rose above 230 ° C. A correlation between the absorbance of OH, OCH₃ and C=O is made to give more information concerning the effect of thermal treatment on the molecular structure changes of lignin.     

Physical,chemical and electric characterization of thermally treated rice husk ash and its potential application as ceramic raw material

Rice husk ash (RHA) is composed essentially by carbon and high levels of silica that justify the economically viable use of RHA in production of ceramic materials. Therefore, this study presents the physical, chemical, and electric characterization of two RHAs submitted to thermal treatment at different temperatures. Grain size, specific weight, specific surface area, total carbon analysis as well as X-ray fluorescence spectrometry, scanning electron microscopy, X-ray diffraction, and complex impedance spectroscopy were carried out. The results indicate that the thermal treatments afforded to produce high-silica RHA with cristobalite and tridymite crystalline phases that indicate the potential of RHA to be used as raw material to obtain advanced silica-based ceramic products. RHA particle size increased with treatment temperature, followed by a slight increase in specific weight and a drastic drop in surface area. Electrical characterization showed that silica particles are closely packed to a carbon film.     

Structural and spectroscopic studies of mechanochemically activated nanosized apatite from Syria

Phosphorite sample from Syria is subjected to mechanochemical treatment in planetary mill equipped with 20 mm steel milling bodies. A complex of chemical and physical methods was applied, namely chemical analysis, powder XRD, IR spectroscopy, and SEM in order to prove changes in the structure of the minerals in the modified samples. These changes are manifested mainly in transformations of a considerable part of apatite into a nanosized phase, breakage of the coordination complex CaO₆F, and localization of OH⁻ groups in the position of F⁻ and CO₃²⁻ in the position of PO₄³⁻ of the apatite structure. As a result of these transformations the assimilable content of in the activated samples is increased and this gives opportunity to suppose that the activated phosphorite could be used as a phosphorous fertilizer.     

Structural design optimization on thermally induced vibration

The numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in the software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal‐induced vibration coupled with both linear and non‐linear transient heat conduction is firstly proposed. Based on the finite element method, the linear structural dynamics is treated simultaneously with linear and non‐linear transient heat conduction. In the heat conduction, the non‐linear factors include the radiation and temperature‐dependent materials. The sensitivity analysis of transient linear and non‐linear heat conduction is performed with the precise time integration method; and then, the sensitivity analysis of structural transient responses is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration. In the adjoint method, two adjoint vectors of structure and of heat conduction are used to derive the adjoint equations. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With the coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. Numerical examples are given to validate the proposed methods and to demonstrate the importance of the coupled design optimization. Copyright © 2003 John Wiley & Sons, Ltd.     

Encapsulation of apatite particles for improvement in bone regeneration

The layering of fluorapatite on hydroxyapatite bodies provides a means of decreasing the solubility of hydroxyapatite, providing fluoride for possible stimulation of bone formation and delaying the release of calcium and phosphate from the more soluble hydroxyapatite. The purpose of this work was to encapsulate hydroxyapatite particles with fluorapatite spanning a thickness more than several crystallites deep. A three-step procedure was employed. Hydroxyapatite powder was immersed in an electrolyte solution until an equilibrium was established between the solid and the dissolved calcium at pH 4.67 and 37 °C. Equilibrium was determined by measurement of dissolved calcium with a calcium-specific ion-specific electrode. A 5×10^–2 M ammonium fluoride added to the suspension resulted in a rapid decrease of both calcium and fluoride in the solution. Analysis with X-ray diffraction indicated that a fluoride rich layer containing calcium fluoride deposited onto the particle surface. Scanning electron microscopy revealed submicron spherical precipitate clusters on the hydroxyapatite particles. These clusters transformed to fluorapatite by soaking in a 0.1 M K₂HPO₄ solution at pH 8 and 70 °C. A total time of 10 h was necessary for complete transformation of CaF_{_2} into fluorapatite.     

A mineralogical perspective on the apatite in bone

A crystalline solid that is a special form of the mineral apatite dominates the composite material bone. A mineral represents the intimate linkage of a three-dimensional atomic structure with a chemical composition, each of which can vary slightly, but not independently. The specific compositional–structural linkage of a mineral influences its chemical and physical properties, such as solubility, density, hardness, and growth morphology. In this paper, we show how a mineralogic approach to bone can provide insights into the resorption–precipitation processes of bone development, the exceedingly small size of bone crystallites, and the body's ability to (bio)chemically control the properties of bone. We also discuss why the apatite phase in bone should not be called hydroxylapatite, as well as the limitations to the use of the stoichiometric mineral hydroxylapatite as a mineral model for the inorganic phase in bone. This mineralogic approach can aid in the development of functionally specific biomaterials.     

Structural analyses of carbonate-containing apatite samples related to mineralized tissues

Crystallographic and structural aspects of two carbonate-containing (one with and another without Zn ions) and a pure hydroxyapatite sample were investigated by high resolution electron microscopy. For five different zone axes and for the three samples a good correspondence was always found between simulated lattice images and observed micrographies. Numerous structural defects were detected in the carbonate-containing apatites, whereas none were found in the similarly prepared pure hydroxyapatite. The incorporation of Zn ions in the crystal lattice of the carbonate-containing apatite reduces the number of defects.     

催化化学气相沉积过程中硫元素引发的炭形貌衍变

以甲苯为碳源,二茂铁为催化剂,噻吩为生长促进剂,通过化学气相沉积方法得到了多分叉结构的炭.借助SEM、XRD和EDX考察了硫元素对产物的形貌和微观结构的影响.结果表明,当甲苯中的噻吩体积分数在0.01%～1%变化时,产物形貌由树状逐渐衍变为分支状.树状炭南较长而笔直的多分叉炭纤维构成,而分支状炭则由较短且弯曲的炭纤维构成.XRD结果表明硫元素对产物的微观结构没有明显的影响.     

Bonelike apatite formation on niobium metal treated in aqueous NaOH

The essential condition for a biomaterial to bond to the living bone is the formation of a biologically active bonelike apatite on its surface. In the present work, it has been demonstrated that chemical treatment can be used to create a calcium phosphate (CaP) surface layer, which might provide the alkali treated Nb metal with bone-bonding capability. Soaking Nb samples in 0.5 M NaOH, at 25 degrees C for 24 h produced a nano-porous approximately 40 nm thick amorphous sodium niobate hydrogel layer on their surface. Immersion in a simulated body fluid (SBF) lead to the deposition of an amorphous calcium phosphate layer on the alkali treated Nb. The formation of calcium phosphate is assumed to be a result of the local pH increase caused by the cathodic reaction of oxygen reduction on the finely porous surface of the alkali-treated metal. The local rise in pH increased the ionic activity product of hydroxyapatite and lead to the precipitation of CaP from SBF that was already supersaturated with respect to the apatite. The formation of a similar CaP layer upon implantation of alkali treated Nb into the human body should promote the bonding of the implant to the surrounding bone. This bone bonding capability could make Nb metal an attractive material for hard tissue replacements.     

Structural and optical properties of thermally evaporated 1,4,8,11,15,18,22,25-octahexylphthalocyanine thin films

Metal-free 1,4,8,11,15,18,22,25-octahexylphthalocyanine was prepared directly by the cyclotetramerization of 3,6-dihexylphthalonitrile using lithium butoxide in butanol. Thin films of the material were deposited on glass substrates by the thermal evaporation technique. The structure of the films was found to be in the form, and showed a strong peak indicating preferential orientation. The surface morphology of the thin films was investigated by atomic force microscopy and showed that the molecules of 1,4,8,11,15,18,22,25-octahexylphthalocyanine grow in stacks of parallel rows. The spectrophotometric measurements of transmittance and reflectance were carried out in the wavelength range 190–3000 nm. The refractive index, n, and absorption index, k, were found to be independent of annealing at 373 K. The B band absorption occurred at 356 nm, and the Q band showed a doublet at 667 and 739 nm. Other optical parameters, such as absorption coefficient and optical dielectric constant ε, were determined.     

Structural and optical properties of thermally evaporated zinc phthalocyanine thin films

Thermally evaporated zinc phthalocyanine (ZnPc) films in the as deposited condition were identified to be as-amorphous. It undergoes structural transformation upon annealing up to 613 K. The optical properties and spectral behavior of as deposited and annealed thin films of ZnPc were studied using spectrophotometric measurements of the transmissivity and reflectivity at normal incidence of light in the wavelength range 200–2500 nm. The refractive index, n, and absorption index, k, were calculated and it was found that they are independent of film thickness in the thickness range 205–530 nm. Annealing at 613 K increases absorbance of films by 5–6 times in comparison with absorbance of as deposited ones and shifts peak positions of all bands towards low energy side of spectra except the peak position of N-band is shifted towards high energy side of spectra. The absorption spectra in the UV–VIS. region has been analyzed in terms of both molecular orbital and band theories. Indirect allowed transitions near the onset and fundamental absorption edges were observed. The energy at the onset was obtained and equals to 1.45 and 1.51 eV for as deposited and annealed films, respectively. The fundamental energy gap was obtained and equals to 2.94 and 2.88 eV for as deposited and annealed films, respectively. The absorption spectra shows four absorption bands. The oscillator strength, f, the electric dipole strength, q², the molar extinction coefficient, ζ_molar, were calculated for as deposited and annealed ZnPc thin films.     

Structural and electrical studies of thermally evaporated nanostructured CdTe thin films

CdTe thin films were deposited on KCl and glass substrates using thermal evaporation technique under high vacuum conditions. CdTe bulk compound grown by vertical directional solidification (VDS) technique was used as the source material to deposit thin films. Powder X-ray diffraction technique was employed to identify the phase of the as grown bulk CdTe compound as well as its thin films. Surface morphology and the stoichiometry of the bulk compound and thin films was carried out by using scanning electron microscope (SEM) with an attachment of energy dispersive spectrometer(EDS). Microstructural features associated with the as deposited CdTe thin films were studied by using transmission electron microscope (TEM). The films deposited on to glass substrates at different temperatures have been used to study the I-V characteristics of the films. These parameters have been studied in detail in order to prepare good quality nanostructured thin films of CdTe compound. CdTe bulk compound grown by VDS method and its thin films prepared by thermal evaporation method found to have single phase with cubic structure. Size of the particles in the as deposited films vary between 5 and 40 nm In the present study efforts have been made to correlate the electrical and optical properties of the CdTe thin films with the corresponding microstructural features associated with them.     

Evolution of the pozzolanic activity of a thermally treated zeolite

Zeolites generally show pozzolanic activity due to their structural characteristics. The utilisation of pozzolans as additions to cements results in added technical advantages of the construction materials. In this study, the pozzolanic activity of a thermally treated natural mordenite-type zeolite from the Palmarito open-air deposit (Cuba) was evaluated with respect to a non-treated zeolite. Initially, a thermal treatment of the zeolite was performed at different temperatures within the range 300–1000 °C for 5 h in order to evaluate the better temperature of treatment. Afterwards, the pozzolanic activity was determined for each temperature after 7 days of reaction with a saturated Ca(OH)₂ solution that simulates the release of lime from ordinary Portland cement during the hydration reaction. The higher pozzolanic activity was achieved with the thermal treatment performed at 300 °C. Therefore, a further study studied the evolution of the mineralogical phases produced during pozzolanic reaction up to 90 days, carried out with the zeolite treated at that temperature. Consumption of Ca²⁺ in solution and formation of C–S–H-like phases with low Ca/Si ratio were experimentally observed as the main pozzolanic products. The thermodynamic study confirms high reactivity of the zeolite at short-term and chemical stability of the reaction products after 28 days. The zeolite thermally treated at 300 °C confirmed an increase in the pozzolanic activity with respect to the non-treated zeolite.