Selective adsorption of acidic protein of bovine serum albumin onto sheet-like calcium hydroxyapatite particles produced by microreactor

The protein adsorption behavior onto sheet-like calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ (Hap) particles produced by microreactor was examined by using typical acidic bovine serum albumin (BSA) and basic lysozyme (LSZ). Since the sheet-like Hap particles were highly growth through b- (or a-) and c-axes, the particles had larger fraction of bc (or ac) crystal face. The saturated amounts of adsorbed BSA ($n_s^{\text{BSA}}$) for the sheet-like Hap nanoparticles were increased with increase in the particle size; i.e., $n_s^{\text{BSA}}$ showed a good linear relationship with the total surface area of bc and ac faces of each particle. This result strongly suggested that the sheet-like Hap particles progressed in b- and c-axes with large fraction of C sites on bc and ac particle faces and exhibit a high selective adsorption of BSA. On the contrary, very few LSZ molecules adsorbed onto sheet-like Hap particles. Hence the present study developed that the amounts of adsorbed protein, especially for BSA, can be controlled optimally by altering the size of sheet-like Hap particles. It was also found that the sheet-like Hap particles can be applied to separate completely BSA molecules from BSA–LSZ mixed solution.     

Fracture toughness determination of adhesive and co-cured joints in natural fibre composites

Adhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. On the other hand, natural fibre composites have recently gained interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the tensile fracture toughness ($G_{\text{n}}^{\text{c}}$) of adhesive joints between natural fibre composites is studied, by bonding with a ductile adhesive and co-curing. Conventional methods to obtain $G_{\text{n}}^{\text{c}}$ are used for the co-cured specimens, while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation, an optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain $G_{\text{n}}^{\text{c}}$ than the available methods is proposed (by the J-integral technique), and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively-bonded joints, the tensile cohesive law of the adhesive is derived by the direct method.     

Diffusion behavior and reactions between Al and Ca in Mg alloys by diffusion couples

The diffusion behavior and reactions between Al and Ca in Mg alloys by diffusion couple method were investigated. Results demonstrate that Al_2Ca is the only phase existing in the diffusion reaction layers.The volume fraction of Al_2Ca in diffusion reaction layers increases linearly with temperature. The standard enthalpy of formation for intermetallic compounds was rationalized on the basis of the Miedema model. Al-Ca intermetallic compounds were preferable to form in the Mg-Al-Ca ternary system under the same conditions. Over the range of 350–400?C, the structure of Al_2Ca is more stable than that of Al_4Ca, Al_(14)Ca_(13) and Al_3Ca_8. The growth constants of the layer Ⅰ, layer Ⅱ and entire diffusion reaction layers were determined. The activation energies for the growth of the layer Ⅰ, layer Ⅱ and entire diffusion reaction layers were(80.74 ± 3.01) k J/mol,(93.45 ± 2.12) k J/mol and(83.52 ± 1.50) k J/mol, respectively.In layer Ⅰ and Ⅱ, Al has higher integrated interdiffusion coefficients D~(Int, layer)ithan Ca. The average effective interdiffusion coefficients D_(Al)~(eff) values are higher than D_(Ca)~(eff) in the layer Ⅰ and Ⅱ.     

Variation in fatigue properties of cast A359-SiC composites under total strain controlled conditions: Effects of porosity and inclusions

The effects of casting defects, such as inclusions and porosity on fatigue properties of permanent mold cast bars of A359-20 vol% SiC particle composites cast and heat treated under identical conditions, were studied under total strain control conditions. The fatigue fracture surfaces and the near fracture regions were observed using optical stereo-microscope and scanning electron microscope (SEM) to identify the effects of microstructure and casting defects on fatigue properties of pairs of specimens tested under the same total strain that showed large scatter in fatigue life. It was found that the largest porosity size on the fracture surfaces of the fatigue specimens measured was around 700 μm, whereas the average dendrite arm spacing was 60–100 μm and the size of SiC particle clusters in the near fracture region was around 100 μm. Fracture surfaces of the composite bars showed that fatigue cracks frequently initiated from porosity present near the surface of the samples. Test specimens containing larger porosity size were observed to have lower fatigue life. However, some specimens with larger amounts of inclusions had a lower fatigue life than those with larger porosity size within the range observed in this study. The size and amount of inclusions, and the size and shape of the porosity near the surface seems to have the greatest influence in decreasing fatigue life. Fatigue strength, and fatigue ductility constants for permanent mold cast A359-20 vol% SiC composite were determined from the strain controlled fatigue data. They were as follows: fatigue strength exponent (b) is −0.1145, fatigue strength coefficient $({\sigma }_{\text{f}}^{\prime })$ is 558 MPa, fatigue ductility exponent (c) is −0.6066 and fatigue ductility coefficient (${\epsilon }_{\text{f}}^{\prime })$ is 0.0108.