Bone is not composed of hydroxyapatite (HAp), but of carbonate apatite (CO3Ap). Although the decomposition of CO3Ap begins at around 400°C, and thus, the fabrication of CO3Ap blocks by sintering is difficult, CO3Ap blocks have recently been fabricated via a dissolution–precipitation reaction in Na2HPO4 solution using a CaCO3 block as a precursor. Compared to sintered HAp, which is not resorbed by osteoclasts, CO3Ap is resorbed by osteoclasts. Furthermore, CO3Ap upregulates the differentiation of osteoblasts. Therefore, CO3Ap can be used as a replacement for bones with regards to the so-called bone remodeling process. Clinical trials have confirmed the safety and usefulness of CO3Ap granules, including the replacement of CO3Ap granules to new bone. In Dec 2017, CO3Ap was approved as an artificial bone substitute by the Pharmaceuticals and Medical Devices Agency. CO3Ap granules can be used for all dental and maxillofacial surgeries, including the bone reconstruction aimed for dental implantation.
The high strength and low dielectric constant of silicon nitride (Si3N4) ceramics are an irreconcilable conflict. It is a compromise to introduce a suitable reinforcing phase in Si3N4 ceramics to receive well dielectric properties without excessive loss of mechanical properties. In this paper, Si3N4 nanowires were in-situ synthesized by pyrolysis of polysilazane with Si3N4 nanopowders as catalyst without introduction of impurities in Si3N4 porous ceramics. The formed Si3N4 nanowires not only improve the mechanical property but also reduce dielectric constant of porous Si3N4 ceramic.
Chabazite was successfully synthesized from Kaolin for the first time via a calcination-hydrothermal process. The effects of Si/Al ratio, (OH)−/Si ratio, calcination time and hydrothermal time on the synthesis process were investigated one by one, and the final synthesis scheme under this condition was obtained. The adsorption isotherms of CO2 and N2 were measured at 30–90°C and 0–120 kPa to measure the gas adsorption properties of chabazite. In this paper, the adsorption capacity of chabazite to CO2 and N2 could reach 1.61 and 0.66 mmol/g respectively at 120 kPa and 30°C. In addition, chabazite showed excellent CO2/N2 selectivity over the full pressure range.
Aluminum Nitride (AlN) shows high thermal conductivity, high electrical resistivity, and chemical stability and expected as a candidate for a substrate of AlxGa1−xN based thin films for LEDs. In the present study, we demonstrate low temperature (800°C) and fast growth (9.2 µm/h) of one-directionally grown AlN film by atmospheric pressure halide CVD method, in which AlN films grow under air pressure without any requirement of vacuum systems. For obtaining uniaxial AlN films, seeding layer prepared at the initial stage of the growth plays an important role. Growth mechanisms and effects of the seeding layer is discussed based upon optical and miscrostructural analyses.
The microwave dielectric properties of La(Mg0.5−xMexSn0.5)O3 (Me = Ca, Sr) ceramics are studied, in order to develop a wireless dielectric resonator antenna temperature sensor. The microwave dielectric properties of La(Mg0.5−xMexSn0.5)O3 (Me = Ca, Sr) ceramics are determined using X-ray diffraction patterns, Rietveld refinement patterns, Raman spectra, and by observing the microstructures. La(Mg0.5−xMexSn0.5)O3 (Me = Ca, Sr) ceramics are prepared using a conventional solid state method. As the degree of substitution of Ca2+ and Sr2+ increases, the position of the A1g(O) Raman mode shifts toward a lower frequency. The La(Mg0.4Ca0.1Sn0.5)O3 ceramic exhibits a minimum full width at half maximum for the A1g(O) Raman vibration mode in the series of La(Mg0.5−xMexSn0.5)O3 (Me = Ca, Sr) ceramics. La(Mg0.49Ca0.01Sn0.5)O3 ceramics that were sintered at 1600°C for 4 h have an apparent density of 6.57 g/cm3, a dielectric constant (εr) of 19.9, a quality factor (Q×f) of 94,300 GHz, and a temperature coefficient at the resonant frequency (τf) of −87 ppm/°C. The development process and test results for a dielectric resonator antenna temperature sensor that uses La(Mg0.49Ca0.01Sn0.5)O3 ceramics are recorded. The resonant frequency is 9.35 GHz and the 3 dB bandwidth measured at room temperature is 6.4 MHz. A sensitivity of −1.03 MHz/°C is achieved.
The molecular orbital calculations based on the DV-Xα method were carried out for several vanadate phosphors of Sr2VO4Cl, Ca2VO4Cl, Ba2V2O7, Mg3(VO4)2, and Zn3(VO4)2, of which the luminescent colors range from deep-blue to yellow through green. The structural refinement with the X-ray diffraction technique preceded the DV-Xα calculations to provide a theoretical interpretation on the relationship between the crystal structures and the luminescent colors (luminescence energies) of the vanadate phosphors. The partial density of states obtained in the DV-Xα calculations reasonably explained the lowest excitation energies of the vanadate phosphors. The calculations also exhibited the difference in the bonding characters among the ligand oxygens in a VO4 tetrahedron due to the structural distortion. The relatively large contributions of the ionically coordinated oxygens were proposed on determining the luminescence energies. A linear correlation was deduced between the luminescence energies and the averaged V–O distances with the selected oxygens ionically coordinated to V.
MC3T3-E1 cell differentiation is more pronounced after 14 days incubation on charged nitrogen-doped TiO2 surfaces compared to on an untreated, neutral Ti surface. The protein fibronectin (Fn) was detected by an immunogold-labeling technique and Ca and P were detected by time-of-flight secondary ion mass spectrometry. Both techniques revealed that an adhesive protein such as Fn adsorbs equally on negatively-charged, positively-charged, and untreated Ti surfaces in culture medium. However, the adsorption of Ca and P was only detected on charged nitrogen-doped TiO2 surfaces. The enhanced adsorption of inorganic ions and Fn is probably responsible for promoting initial stage of osteoblast differentiation. The conformation of adsorbed Fn was observed by high-speed atomic force microscopy and found to be in the side-on orientation on the positively-charged surface. This finding may help elucidate the relation between Fn conformation and cell activity on surface potential-controlled nitrogen-doped TiO2 surfaces in future.
As with any concrete dam, temperature stress is a major issue and when it exceeds its maximum limits cracks may occur, the roller compacted concrete (RCC) arch dam is no exception. To overcome this issue, the specific setting of induced joints in the dam can induce cracks at these positions reducing the effect of temperature cracks. However, the study of the induced joints usually ignores the influence of concrete age on the induced joints, thus the obtained equivalent strength of the induced joints deviate from the actual situation. In this paper, the axial tensile test of the both-way interval induced joint test piece of RCC is carried out, in which quantitative analysis is performed on the variation rules of its equivalent strength under different ages and degrees of weakening. The finite element calculation software was also used to perform numerical simulation of the axial tensile test piece, and conduct comparison and analysis between the simulation and test results, thus verifying the correctness and reliability of the equivalent strength model of the both-way interval non-penetrating induced joint established by the test. According to the stress distribution cloud map of the simulated induced joint, the development process of the induced crack under the load was analyzed to propose a more reasonable type of induced joint layout, thus further optimizing the fracture test of the RCC induced joints, and providing a basis for the design of induced joints in actual engineering practice.
We report herein that porous and electrochemically active NiO thin films were prepared through the deposition and thermal decomposition of a Nickel-containing metal organic framework. First, Ni3(HCOO)6 thin film layers were deposited on an electrically conductive substrate, then the layers were thermally decomposed into NiO in a temperature range from 543 to 673 K. The electrochemical response of the resultant NiO thin films was highest when the thermal decomposition temperature was as low as 543 K. The cylcic voltammetry revealed that the current response of the present thin film with the highest performance was twice larger than a previously reported one. The deposition of a Ni3(HCOO)6 thin film by a chemical bath technique followed by thermal decomposition may be a facile and promising route to obtain binder-free, porous metal oxide layers for electrochemical applications.