This study focused on a detailed examination of the thermal behavior of Brushite-based calcium phosphate (CaHPO 4 .2H 2 O, DCPD) to identify and characterize the intermediate phases which have been the subject of previous several controversies. For that, in situ high-temperature X-ray diffraction supported by infrared spectroscopy, thermal analysis, and scanning electron microscopy analysis were used and the results showed that the progressive thermal stress of DCPD in air resulted in a heterogeneous formulation consisting of dibasic calcium phosphate anhydrous (CaHPO 4 , DCPA) and an amorphous phase, which appears at low temperatures (~160 °C) and persists up to 375 °C. The deep examination of the amorphous phase by infrared spectroscopy revealed that its chemical composition is similar to that of disordered calcium pyrophosphate (Ca 2 P 2 O 7 , CPP) with the appearance of a characteristic band δ(P-O-P), located at 740 cm-1. This IR band is shifted to low frequencies (725 cm-1) as the temperature is increased, indicating the crystallization of the amorphous phase into γ-CPP. The high temperature treatment (≥ 375 °C) leads to b-CPP polymorph. According to the present characterization results, obtaining pure DCPA from the thermal dehydration of DCPD is not effective and leads to biphasic materials including an amorphous phase.
доктор економічних наук, професор, професор кафедри економіки та міжнародних економічних відносин Полтавської державної аграрної академії Гончаренко В.В. доктор економічних наук, професор, професор кафедри міжнародних економічних відносин Харківського національного університету імені В.Н. Каразіна Рижик І.О. кандидат економічних наук, завідувач кафедри економіки та менеджменту Полтавського інституту бізнесу ПВНЗ «МНТУ»
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