Two-step sinter-crystallization of K2O–CaO–P2O5–SiO2 (45S5-K) bioactive glass

Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K₂O-26.9CaO-46.1SiO₂-2.6P₂O₅ mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration.     

Streamflow Simulation by SWAT Using Different Precipitation Sources in Large Arid Basins with Scarce Raingauges

Streamflow from the mountains is the main source of water for the lower plain in arid regions. Accurate simulation of streamflow is of great importance to the arid ecosystem. However, many large arid drainage basins in northwestern China have low density of precipitation stations, which makes the streamflow modeling and prediction very difficult. Based on raingauge data and Tropical Rainfall Measuring Mission (TRMM) data combined with raingauge data, different approaches were explored for spatializing precipitation in large area with scarce raingauges. Spatialized precipitation was then input into Soil and Water Assessment Tool (SWAT), a semi-distributed hydrological model, to simulate streamflow. Results from a case study in the Manas river basin showed that simulated hydrographs using both the approaches are able to reproduce the watershed hydrological behavior. Moreover, statistical assessment indicated that hydrological model driven by the spatialized precipitation based on radar combined with raingauge data performed better than that based on gauge data. Radar precipitation estimator can provide a practical data source for hydrological modeling at a basin scale where the raingauge network is sparse.     

Plant algae method for arsenic removal from arsenic contaminated groundwater

Field studies were carried out in Urumqi River Basin in Northwest China. The study focused on experimentation on a plant algae method that was tested by taking various water chemistries into consideration. The results from a greenhouse experiment evaluated for four doses of P (0, 100, 200, and 300 μmol/L) using two ferns (30 and 60 day old) on 15 L of contaminated groundwater per plant revealed that the biomass of 30-day old ferns gained was higher than 60-day fern. As solution-P increased from 0 to 450 μmol/L, Phosphorus concentration in the fronds increased from 1.9 to 3.9 mg/kg and 1.95 to 4.0 mg/kg for 30-d and 60-d ferns respectively. This study showed that the plant algae method may be a good solution to maximize arsenic uptake in the short term under normal climatic conditions.     

Influence of Particle Size on Nonisothermal Crystallization in a Lithium Disilicate Glass

In this study, lithium disilicate (LS₂) glass samples with different particle sizes ranging from less than 105 to 850 μm were prepared. These specimens were inserted in a Pt‐Rh DSC crucible and heated to 850°C at different rates (? = 0.5–30 K/min) to identify their crystallization peaks. The activation energies for the overall crystallization (E) and the Avrami coefficient (n) were evaluated using different nonisothermal models. Specifically, n was evaluated using the Augis–Benett model and the Ozawa method, and E was evaluated using the Kissinger and Ligero methods. As expected, the coarse particles mainly crystallized in the volume, while surface crystallization was predominant in the samples with particle sizes of less than 350 μm. This result was confirmed through SEM analysis of the double stage heat‐treated samples. In contrast with previous studies, our results demonstrated that the activation energy decreased as the particle size increased. In addition, no clear correlation between the peak intensity (δT_p) and the particle size was observed.     

Babassu Biodiesel Doped with Antioxidants: Assessment of Thermo-Oxidative Stability by Borchardt and Daniels Method

In this study, three antioxidants namely N,N′-di-sec-butyl-p-phenylenediamine (PDA), 2,4,6-Tri-tert-butylphenol/2,6-Di-tert-butylphenol (IONOL), and unsaturated cardanol (U-CDN) were added to babassu biodiesel (BB) at a concentration of 100 mg kg⁻¹ to improve its oxidative stability. Differential Scanning Calorimetry (DSC) was used to evaluate the oxidative stability of the samples using synthetic air atmosphere and two temperatures (25 and 110 °C) instead of the conventional Rancimat method. The kinetic parameters were calculated according to Borchardt and Daniels method (ASTM E2041). All doped samples showed higher thermo-oxidative stability when compared to pure babassu biodiesel with increasing activation energies of 66.5% for PDA, 19.4% for IONOL, and 3.9% for U-CDN. At 25 °C, the babassu biodiesel showed a high oxidation reaction rate of 1.76 × 10⁻¹⁵ min⁻¹. For the doped samples at the same temperature, that rate was reduced by a factor of 2, 200, and 3 × 10⁸ times for U-CDN, IONOL, and PDA, respectively. At 110 °C, the BB and the BB + U-CDN samples showed high reaction rates, whereas the formulations with IONOL and PDA had rates reduced by 10 and 7.4 × 10³ times, respectively. The thermal data showed R² values higher than 0.99. All results confirmed the action of the antioxidants in retarding oxidation reactions in biodiesel. DSC is a promising alternative method for the determination of oxidative stability of biodiesel and its formulations with antioxidants.     

Permeability of Refractory Castables at High Temperatures

Temperature is an important factor affectng the permeation of fluids in refractory castables. Because of experimental difficulties, however, permeability parameters are usually obtained at room temperature and then extrapolated to the temperature of interest, with no concern regarding porous structure modification (thermal expansion, etc.). In this work, an apparatus has been developed to evaluate the air-flow permeability of refractory castables at temperatures up to 800°C. The objective is to investigate modifications in the permeability constants obtained by Forchheimer's equation to provide a more realistic relationship with castable processing and molten-metal corrosion parameters.     

In situ activated 3,5-dinitrobenzoic acid covalent attached to nanostructured platform for NADH electrooxidation

The activation of 3,5-dinitrobenzoic acid (3,5-DNBA) in situ is proposed for electrocatalytic detection of NADH at low overpotentials. Thus, 3,5-DNBA was strategically connected to a nanostructured surface based on MWCNTs and PEI (an amine rich polymer). Then, R–NO/R–NHOH was electrogenerated in situ by cycling the potential between 0.15 and −0.55 V versus SCE. The formation of an intermediate charge transfer complex is proposed for the reaction between NADH and redox mediator. The apparent Michaelis–Menten constant (K_M) obtained by RDE voltammetry and amperometry was in good agreement, around 10⁻⁵ mol L⁻¹. The k_obs for the catalytic reaction evaluated by chronoamperometry and RDE voltammetry, was in good agreement and was found to be around 10⁴ L mol⁻¹ s⁻¹. The sensor provides a linear response range for NADH from 4.0 up to 42.0 μmol L⁻¹ with a sensitivity of 71 nA L μmol⁻¹, detection and quantification limits of 1.2 and 4.0 μmol L⁻¹ respectively, with a response time of 0.16 s.     

Assessment of Forchheimer's Equation to Predict the Permeability of Ceramic Foams

Correct estimation of the pressure drop in filtration processes that involve fluid velocity variations is of major importance, because it allows the filtration rate and/or the energy consumed on fluid flow to be more accurately controlled. Permeability of porous filters has been often described by Forchheimer's equation, which establishes a nonlinear dependence between pressure drop and fluid velocity. Two constants, k ₁ and k ₂, dependent only on the medium, quantify the viscous and inertial effects on the pressure drop curve. In this work, experimental data of airflow through 10 pores per linear inch ceramic foam filters are used to show that a single sample may have completely distinct permeability constants depending on the data range chosen for analysis. The Darcian permeability constant k ₁ displays higher variation than the non-Darcian permeability constant k ₂. The conclusion is that special attention must be taken to represent permeability of highly porous structures in a large velocity range. The predictability of Forchheimer's equation generally worsens when less data are included in the curve fitting, particularly at low velocities. Careful consideration should be made if constants k ₁ and k ₂ are intended to be used for permeability estimation beyond the fitting range.     

A practical procedure to assess critical defects in pressure vessels subjected to fatigue loads

PSA pressure vessels are equipments used in refining industries for cleaning the hydrogen upcoming from the reforming or hydrogen generation unities. In one regular inspection, some embedded cracks were found in the entrance nozzle-head weld. Then, instead of advance its decommissioning and waste much time until the refinery purchase a new vessel, a structural stress analysis using the finite element method was performed in order to obtain the stress field at the site of the crack, considering the real loading cycle. Despite the acting load is only the internal pressure, the nozzle-head weld is a region where a complex stress state is present (bending and axial stresses). ASME VIII Division 2, Appendix 5 addresses this issue by applying a rule for multiaxial fatigue life estimation for non-proportional loading. With ASME estimated fatigue life results, it was applied the British Standard 7910 procedure to decide if the equipment can operate safely. The calculation also assesses the crack growing by using a modified bi-linear Paris law. Finally, it was computed how long the cracks would take to get to their critical size and then retire definitively the equipment.     

A rapid method for evaluation of the oxidation stability of castor oil FAME: influence of antioxidant type and concentration

The oxidation stability of castor oil fatty methyl ester (FAME), doped with four different phenolic antioxidants, was evaluated using a rapid method of thermal and air-contact degradation. The methodology is based on the induction times observed when the samples are contacted with pure oxygen at elevated pressures and temperatures. The results indicate different performances of the antioxidants as well as synergisms between antioxidants and biodiesel. In general, the addition of antioxidants increased from 6-15 times the stability of castor oil FAME., with BHA (butylated hydroxyanisol) showing the best results for improving antioxidation in castor oil biodiesel.