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High efficiency of hybrid implants based on calcium-magnesium silicate ceramic, diopside, as a carrier of recombinant BMP-2 and xenogenic demineralized bone matrix (DBM) as a scaffold for bone tissue regeneration was demonstrated previously using the model of critical size cranial defects in mice. In order to investigate the possibility of using these implants for growing autologous bone tissue using in vivo bioreactor principle in the patient’s own body, effectiveness of ectopic osteogenesis induced by them in intramuscular implantation in mice was studied. At the dose of 7 μg of BMP-2 per implant, dense agglomeration of cells, probably skeletal muscle satellite precursor cells, was observed one week after implantation with areas of intense chondrogenesis, initial stage of indirect osteogenesis, around the implants. After 12 weeks, a dense bone capsule of trabecular structure was formed covered with periosteum and mature bone marrow located in the spaces between the trabeculae. The capsule volume was about 8-10 times the volume of the original implant. There were practically no signs of inflammation and foreign body reaction. Microcomputed tomography data showed significant increase of the relative bone volume, number of trabeculae, and bone tissue density in the group of mice with BMP-2-containing implant in comparison with the group without BMP-2. Considering that DBM can be obtained in practically unlimited quantities with required size and shape, and that BMP-2 is obtained by synthesis in E. coli cells and is relatively inexpensive, further development of the in vivo bioreactor model based on the hybrid implants constructed from BMP-2, diopside, and xenogenic DBM seems promising.

Calcium-magnesium silicate ceramics, diopside, is a promising material for use in bone plastics, but until now the possibility of its use as a carrier of recombinant bone morphogenetic protein-2 (BMP-2) has not been studied, as well as the features of reparative osteogenesis mediated by the materials based on diopside with BMP-2. Powder of calcium-magnesium silicate ceramics was obtained by solid-state synthesis using biowaste – rice husks and egg shells – as source components. Main phase of the obtained ceramics was diopside. The obtained particles were irregularly shaped with an average size of about 2.3 μm and ~20% porosity; average pore size was about 24 nm, which allowed the material to be classified as mesoporous. Diopside powder adsorbs more than 150 μg of recombinant BMP-2 per milligram, which exceeds binding capacity of hydroxyapatite, a calcium-phosphate ceramic often used in hybrid implants, by more than 3 times. In vitro release kinetics of BMP-2 was characterized by a burst release in the first 2 days and a sustained release of approximately 0.4 to 0.5% of the loaded protein over the following 7 days. In vivo experiments were performed with a mouse model of cranial defects of critical size with implantation of a suspension of diopside powder with/without BMP-2 in hyaluronic acid incorporated into the disks of demineralized bone matrix with 73-90% volume porosity and macropore size from 50 to 650 μm. Dynamics of neoosteogenesis and bone tissue remodeling was investigated histologically at the time points of 12, 21, 48, and 63 days. Diopside particles were evenly spread in the matrix and caused minimal foreign body reaction. In the presence of BMP-2 by the day 63 significant foci of newly formed bone tissue were formed in the implant pores with bone marrow areas, moreover, large areas of demineralized bone matrix in the implant center and maternal bone at the edges were involved in the remodeling. Diopside could be considered as a promising material for introduction into hybrid implants as an effective carrier of BMP-2.

Calcium-magnesium-alumino-silicate (CMAS) corrosion is a critical factor which causes the failure of thermal barrier coating (TBC). CMAS attack significantly alters the temperature and stress fields in TBC, resulting in their delamination or spallation. In this work, the evolution process of TBC prepared by suspension plasma spraying (SPS) under CMAS attack is investigated. The CMAS corrosion leads to the formation of the reaction layer and subsequent bending of TBC. Based on the observations, a corrosion model is proposed to describe the generation and evolution of the reaction layer and bending of TBC. Then, numerical simulations are performed to investigate the corrosion process of free-standing TBC and the complete TBC system under CMAS attack. The corrosion model constructs a bridge for connecting two numerical models. The results show that the CMAS corrosion has a significant influence on the stress field, such as the peak stress, whereas it has little influence on the steady-state temperature field. The peak of stress increases with holding time, which increases the risk of the rupture of TBC. The Mises stress increases nonlinearly along the thick direction of the reaction layer. Furthermore, in the traditional failure zone, such as the interface of the top coat and bond coat, the stress obviously changes during CMAS corrosion.

During flight, many silicates (sand, dust, debris, fly ash, etc.) are ingested by an engine. They melt at high operating temperatures on the surface of thermal barrier coatings (TBCs) to form calcium-magnesium-aluminum-silicate (CMAS) amorphous settling. CMAS corrodes TBCs and causes many problems, such as composition segregation, degradation, cracking, and disbanding. As a new generation of TBC candidate materials, rare-earth zirconates (such as Sm 2 Zr 2 O 7 ) have good CMAS resistance properties. The reaction products of Sm 2 Zr 2 O 7 and CMAS and their subsequent changes were studied by the reaction of Sm 2 Zr 2 O 7 and excess CMAS at 1350 °C. After 1 h of reaction, Sm 2 Zr 2 O 7 powders were not completely corroded. The reaction products were Sm-apatite and c-ZrO 2 solid solution. After 4 h of reaction, all Sm 2 Zr 2 O 7 powders were completely corroded. After 24 h of reaction, Sm-apatite disappeared, and the c-ZrO 2 solid solution remained.

Calcium-magnesium-alumina-silicate (CMAS) corrosion is an important cause for thermal barrier coating (TBC) failure, which has attracted increased attentions. In this study, some thermal barrier coating (TBC) materials including YSZ (yttria partially stabilized zirconia), GdPO 4 , and LaPO 4 were prepared into bulks, and the effects of their surface roughness on wettability and spreading characteristics of molten CMAS were investigated. As-fabricated and polished bulks with different surface roughness were exposed to CMAS corrosion at 1250 °C for 1 and 4 h, following by macro and micro observations. Results revealed that compared with the as-fabricated bulks, molten CMAS on the polished samples had lower wettability and a smaller spreading area, mainly attributable to the reduced capillary force to drive the melt spreading. Meanwhile, GdPO 4 and LaPO 4 bulks exhibited lower CMAS wettability than YSZ bulk. It is thus considered that reducing the surface roughness is beneficial to CMAS corrosion resistance of TBCs.

In the present study, mesoporous calcium–magnesium–silicate was prepared via cetyltrimethylammonium bromide (CTAB)-assisted sol–gel method in both acidic and alkaline mediums. The effects of synthesis medium on structural properties, and drug delivery behavior of mesoporous calcium–magnesium–silicate by using ibuprofen as model drug are investigated. The X-ray diffraction results of the samples calcined at 600 °C showed that the sample synthesized at alkaline environment is composed of CaSiO 3 and CaMgSiO 4 phases, whereas in acidic condition the sample consists of akermanite, CaMgSiO 4 , CaSiO 3 , and MgO. The specific surface area of the mesoporous calcium–magnesium–silicate samples prepared in acidic and alkaline conditions were 220 and 140 m 2 /g, respectively. The mesoporous calcium–magnesium–silicate sample synthesized in the acidic condition resulted in smaller particles with a size ranging between 50 and 100 nm. Encapsulation of ibuprofen into mesoporous calcium–magnesium–silicate was studied as a function of time. Graphical Abstract

The primary research interests in this area of materials science are focused on discovering a potential biomaterial. The need for biomaterial in biomedical applications has been massive in hard tissue engineering due to the significant spike in human bone diseases and bone injuries. In the last 30 years, scientists have achieved great progress in the development of materials in orthopaedic application as a result of the innovation of ceramic materials The aim of the work is to synthesis diopside (CaMgSi 2 O 6 ) and wollastonite (CaSiO 3 ) through sol–gel combustion method by using tartaric acid as a fuel and prepare a diopside/wollastonite composite out of it. The synthesized precursors were thermally treated to eliminate the secondary phase and pure phase of diopside and wollastonite were achieved at 850 ºC and 800 ºC respectively. The product was characterized by powder X-ray diffractometer (PXRD) for phase identification and functional group analysis was carried out using Fourier—Transform Infrared spectroscopy. The electron microscopy imaging and elemental analysis (SEM/EDAX) was used to study the surface morphology of the material. Later the diopside-wollastonite composite was prepared in three different ratios and sintered at 600 ºC for 3 h. In in vitro bioactivity test reveals the initiation of apatite deposition the surface of the ceramic composite scaffold after 3 days of immersion in simulated body fluid (SBF) medium. The obtained results show tremendous improvisation of apatite deposition and the mechanical stability (113Mpa) which is three times greater than the pure diopside.

Calcium-magnesium-alumina-silicate (CMAS) corrosion is a serious threat to thermal barrier coatings (TBCs). Ti 2 AlC has been proven to be a potential protection layer material for TBCs to resist CMAS corrosion. In this study, the effects of the pellet surface roughness and temperature on the microstructure of the pre-oxidation layer and CMAS corrosion behavior of Ti 2 AlC were investigated. The results revealed that pre-oxidation produced inner Al 2 O 3 layer and outer TiO 2 clusters on the pellet surfaces. The content of TiO 2 decreased with decreasing pellet surface roughness and increased along with the pre-oxidation temperature. The thickness of Al 2 O 3 layer is also positively related to the pre-oxidation temperature. The Ti 2 AlC pellets pre-oxidized at 1050 °C could effectively resist CMAS corrosion by promoting the crystallization of anorthite (CaAl 2 Si 2 O 8 ) from the CMAS melt rapidly, and the resistance effectiveness increased with the pellet surface roughness. Additionally, the CMAS layer mainly spalled off at the interface of CaAl 2 Si 2 O 8 /Al 2 O 3 layer after thermal cycling tests coupled with CMAS corrosion. The Al 2 O 3 layer grown on the rough interface could combine with the pellets tightly during thermal cycling tests, which was attributed to obstruction of the rough interface to crack propagation.

Thermal barrier coatings (TBCs) have been seriously threatened by calcium-magnesium-alumina-silicate (CMAS) corrosion. The search for novel ceramic coatings for TBCs with excellent resistance to CMAS corrosion is ongoing. Herein, CMAS corrosion resistance behavior and the mechanism of a promising Hf6Ta2O17 ceramic coating for TBCs are investigated. The results show that temperature is the most important factor affecting the CMAS behavior and mechanism. At 1250 °C, the corrosion products are composed of dense reaction products (HfSiO4, CaXHf6−xTa2O17−x) and CMAS self-crystallization products. At 1300 and 1400 °C, the corrosion products are mainly dense CaTa2O6 and HfO2, which prevent further CMAS infiltration.

To obtain high gas turbine efficiency, a film cooling hole is introduced to prevent the destruction of thermal barrier coating systems (TBCs) due to hot gases. Furthermore, environmental calcium-magnesium-aluminum-silicate (CMAS) particulates plug the film cooling hole and infiltrate the TBCs to form a CMAS-rich layer, which results in phase transformations and significant modifications in the thermomechanical properties that impact the TBCs during cooling. This study aimed to establish a three-dimensional thermo-fluid-solid coupling TBCs model with film cooling holes and CMAS infiltration to analyze the temperature and residual stress distribution via simulations. For the interfacial stress around the cooling hole at the TC/BC interface, the film cooling holes alleviated the interfacial residual stress by 60% due to the reduction in temperature by 40%. In addition, CMAS infiltration intensified the interfacial residual stress via phase transformation. As a result of the influence of larger penetration depths and expansion rates of phase transformation, a significant increase in residual stress was observed. At the beginning of CMAS infiltration, the interfacial stress would be more dominated by the effect of infiltration depth. In addition, the failure due to interfacial normal and tangential stresses was more likely to be found at the infiltration zone near the cooling hole.