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Nojehdehyan H., Moztar Zadeh F., Mir Zadeh Hamid, Hesaraki S., Keyanpour-Rad M.,
Volume 2, Issue 2 (Jan 2005)

The effect of addition of NaHF2 on the cement setting and the set mass has been studied as an initial step to determine how fluoride influences the characteristics of a calcium phosphate cement, consisting of tetracalcium phosphate [TTCP:Ca4 (PO4)2O] and dicalcium phosphate dihydrate [DCPD:CaHPO4.2H2O].NaHF2 [0-10% wt% of powder phase] has been dissolved in double distilled water and used as the liquid phase of the apatite cement (AC). Powder X-ray diffraction analysis and FTIR measurements revealed that fluoride was necessary in promoting the formation of the apatite phase. The setting time was decreased significantly by the addition of NaHF2from 0% to 6%, but increased resulted in the AC (8-10%). The set AC (2%) has the highest compressive strength and the lowest porosity.The dissolution rate of set AC in weak acid, pH 5.5, was decreased with the amount of added NaHF2 from 0% to 6% but increased in the set AC 8-10%.The formation of fluoroapatite in AC (6%) was provided the low solubility and good acid resistance which is necessary for dental application.SEM observation showed needle-like apatite crystal growth over particulate matrix surface, however the amount of non-reactive TTCP or DCPD particles decreased by the addition of NaHF2. The Ca/P ratio, which was determined by EDAX, increased significantly with the addition of NaHF2.
A. Ait Yala, N. Demouche, S. Beddek, K. Hamid,
Volume 15, Issue 4 (December 2018)

Repairing a crack in a structure consists in reducing crack’s tips stresses by transferring loads trough a bridge made of the composite patch and the adhesive. This operation is impacted by four factors: shear modulus of the adhesive, the composite patch’s Young module and the thicknesses of these two materials. The design of experiments method allowed us to determine, the weight of each of the four factors and their interactions as well their best combination to obtain an efficient and lasting repair. The constraints relative to the stiffness ratio and the shear strain were taken into consideration in order to determine the best configuration that allowed the minimization of K.

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