The Effect of Power, Pulse Rate and Treatment Time of Sonication on the Nucleation and Growth of α-Lactose Monohydrate (α-LM) Single Crystals from Aqueous Solution

Colourless triclinic single crystals of Na6[TeMo6O24] · 22 H2O were grown from aqueous solution (space group P 1, a = 1030.89(9), b = 1056.7(1), c = 1106.32(9) pm, α = 90.120(7), β = 115.220(6), γ = 105.195(7), Ζ = 1, 295 Κ, 336 parameters, 3181 reflections, Rg = 0.0186). There are three crystallographically independent Na+ cations. Two of them are coordinated octahedrally by water molecules only. The third Na+ cation is bound to five H2O and one oxygen atom (O(4)) belonging to the Anderson-Evans type anion [TeMo6O24]6-. The sodium-centered coordination octahedra are linked by common edges exclusively formed by water molecules to yield chain-like polycations {Na3(H2O)11}n,3n+ which are bound by the Na(1)-O(4) contact to the anions situated on crystallographic centers of inversion forming a layer-like arrangement. Further connections between the polycations and the [TeMo6O24]6- anions are established by hydrogen bonds involving all the oxygen atoms of the anion except O(4) as almost equivalent proton acceptors regardless of their bonding mode to Te or Mo.

Download Full-text

Effect of Al Content in the Mg-Based Alloys on the Composition and Corrosion Resistance of Composite Hydroxide Films Formed by Steam Coating

Materials ◽

10.3390/ma12071188 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1188 ◽

Cited By ~ 1

Author(s):

Takahiro Ishizaki ◽

Tomohiro Miyashita ◽

Momo Inamura ◽

Yuma Nagashima ◽

Ai Serizawa

Keyword(s):

Aqueous Solution ◽

Corrosion Resistance ◽

Treatment Time ◽

Mg Alloys ◽

Mg Alloy ◽

Potential Range ◽

Protective Film ◽

Al Content ◽

Passive Behavior ◽

Superior Corrosion Resistance

Mg alloys are expected to be used in fields of the transportation industry because of their lightweight property, however, they show low corrosion resistance. To improve the corrosion resistance, preparation of the protective film on Mg alloys is essential. In this study, composite hydroxide films were prepared on three types of Mg alloys with different aluminum contents—that is, AZ31, AZ61, and AZ91D—by steam coating to investigate the relationship between the Mg-Al layered double hydroxide (LDH) content in the film and the Al content in the Mg alloys. Scanning electron microscopy (SEM) observation demonstrated that films were formed densely on all Mg alloy surfaces. X-ray diffraction (XRD) analyses revealed that all films prepared on AZ61 and AZ91D were composed of Mg(OH)2, AlOOH, and Mg-Al LDH, while the film containing Mg(OH)2 and Mg-Al LDH were formed only on AZ31. The Mg-Al LDH content in the film prepared on AZ61 was relatively higher than those prepared on AZ31 and AZ91D. The content of AlOOH in the film increased with an increase in the Al content in the Mg alloys. The film thickness changed depending on the treatment time and type of Mg alloy. Polarization curve measurements in 5 mass% NaCl solution demonstrated that the film prepared on the AZ61 showed complete passive behavior within the potential range of −1.0 to −0.64 V. In addition, immersion tests in 5 mass% NaCl aqueous solution for 480 h demonstrated that the film on the AZ61 had superior durability against 5 mass% NaCl aqueous solution. These results indicated that the film on the AZ61 had the most superior corrosion resistance among all samples. The results obtained in this study suggest that the LDH content in the film could be related to the corrosion resistance of the film.

Download Full-text