Synthesis and investigation of alkaline earth metal molybdates

In the last several decades, many different preparation techniques have been used for the preparation of AMoO4 (A = Mg, Ca, Sr and Ba) ceramics. Nowadays, the results of obtained compounds, depending on the preparation route, are important and have significant influence to the science and technologies. Therefore, the choice of synthesis technique usually depends on variety factors that can shorten, facilitates and reduce the preparation way. From this point of view, the solution-based synthetic methods play a crucial role in the design and production of fine ceramics and they have been successful in overcoming many of the limitation of the traditional solid-state, high-temperature methods. Thus, the development of the aqueous sol-gel synthesis technique for the preparation of M’–Mo–O tartrate (M’=Mg, Ca, Sr and Ba) gel precursors and Powellite type CaMoO4:xEu3+ compounds in the sol-gel processing using tartaric acid as a complexing agent is the main object of these investigations. Thus, in this case, for the first time in our knowledge the aqueous tartaric acid-assisted sol-gel synthesis technique was successfully proposed for the preparation of M–Mo–O tartrate gel precursors and MMoO4 ceramic materials (M=Mg, Ca, Sr and Ba) as well as europium oxide doped CaMoO4 double oxide. TG and DSC analysis of Mg–Mo–O, Ca–Mo–O, Sr–Mo–O and Ba–Mo–O tartrate gels clearly showed that the crystallization of final double oxides starts below 500 oC. Besides, the combustion of volatile components and the burning of carbon residue occurs up to 600 ° C. Using X-ray diffraction (XRD), it has been observed that the characteristic peaks of MgMoO4, CaMoO4, SrMoO4 and BaMoO4 compounds are observed at temperatures between 500 oC and 1000 oC. According to the scanning electron microscopy, the morphology of the surface of ceramic compounds depends really much from the nature of alkaline earth metal in M–Mo–O tartaric precursor. The FT–IR spectra of Eu2O3 doped calcium molybdate samples annealed at 650 °C did not show any bands attributable to carbonates or residual organic species. Finnaly, according to the UV–Vis spectra is clear that all synthesized CaMoO4:xEu3+ samples were optically active compounds at shorter wavelengths (200–310 nm) that arises from MoO42–functional groups. Reflection peaks in 360–470 nm wavelength region are attributed to the Eu3+ characteristic excitations, which are significantly influenced by both annealing temperature and dopant concentration in CaMoO4 lattice. The peak intensity of the CaMoO4:x%Eu3+ samples annealed at 750 °C reached the maximum only with doping of 5 mol% of Eu3+ ions and further increasing of dopant concentration leads to the quenching of reflectance of obtained optical materials

Šarminių žemių metalų molibdatų sintezė ir tyrimas

In the last several decades, many different preparation techniques have been used for the preparation of AMoO4 (A = Mg, Ca, Sr and Ba) ceramics. Nowadays, the results of obtained compounds, depending on the preparation route, are important and have significant influence to the science and technologies. Therefore, the choice of synthesis technique usually depends on variety factors that can shorten, facilitates and reduce the preparation way. From this point of view, the solution-based synthetic methods play a crucial role in the design and production of fine ceramics and they have been successful in overcoming many of the limitation of the traditional solid-state, high-temperature methods. Thus, the development of the aqueous sol-gel synthesis technique for the preparation of M’–Mo–O tartrate (M’=Mg, Ca, Sr and Ba) gel precursors and Powellite type CaMoO4:xEu3+ compounds in the sol-gel processing using tartaric acid as a complexing agent is the main object of these investigations. Thus, in this case, for the first time in our knowledge the aqueous tartaric acid-assisted sol-gel synthesis technique was successfully proposed for the preparation of M–Mo–O tartrate gel precursors and MMoO4 ceramic materials (M=Mg, Ca, Sr and Ba) as well as europium oxide doped CaMoO4 double oxide. TG and DSC analysis of Mg–Mo–O, Ca–Mo–O, Sr–Mo–O and Ba–Mo–O tartrate gels clearly showed that the crystallization of final double oxides starts below 500 oC. Besides, the combustion of volatile components and the burning of carbon residue occurs up to 600 ° C. Using X-ray diffraction (XRD), it has been observed that the characteristic peaks of MgMoO4, CaMoO4, SrMoO4 and BaMoO4 compounds are observed at temperatures between 500 oC and 1000 oC. According to the scanning electron microscopy, the morphology of the surface of ceramic compounds depends really much from the nature of alkaline earth metal in M–Mo–O tartaric precursor. The FT–IR spectra of Eu2O3 doped calcium molybdate samples annealed at 650 °C did not show any bands attributable to carbonates or residual organic species. Finnaly, according to the UV–Vis spectra is clear that all synthesized CaMoO4:xEu3+ samples were optically active compounds at shorter wavelengths (200–310 nm) that arises from MoO42–functional groups. Reflection peaks in 360–470 nm wavelength region are attributed to the Eu3+ characteristic excitations, which are significantly influenced by both annealing temperature and dopant concentration in CaMoO4 lattice. The peak intensity of the CaMoO4:x%Eu3+ samples annealed at 750 °C reached the maximum only with doping of 5 mol% of Eu3+ ions and further increasing of dopant concentration leads to the quenching of reflectance of obtained optical materials

Sol-gel Derived Europium Doped CaMoO4:Eu3+ with Complex Microstructural and Optical Properties

The crystalline compounds CaMoO4 doped with Eu3+ ions were prepared from nitrate-tartrate precursor gels at 650, 700, 750 and 800 °C temperatures. The obtained samples were characterized by thermal analysis (TG/DSC), Furier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and reflection measurements (UV-vis). TG/DSC analysis revealed the possible decomposition mechanism of synthesized Ca-Mo-O nitrate-tartrate gel. XRD data exhibited that even at 650 °C temperature the crystalline powelite (CaMoO4) structure has formed. To understand the crystal growth process of the CaMoO4:xEu3+ compounds (x = 1, 2, 3, 4, 5 and 6 mol%), the influence of temperature on the surface morphology of the end products by SEM analysis was investigated. No evidence of organic residual in the final materials was found, confirmed by FT-IR analysis. UV-vis reflectance spectra revealed that by increasing of Eu3+ ions concentrations in the host material the reflection peaks of Eu2O3 also increased. DOI: http://dx.doi.org/10.5755/j01.ms.20.1.4797</p

Dupuytren’s contracture: incidence of injury-induced cases and specific clinical expression

Background and objectives: Dupuytren’s contracture is a chronic fibroproliferative hand disorder with a varying pattern of genetic predisposition across different regions and populations. Traumatic events have been found to have influence on the development of this illness and are likely to trigger different clinical forms of this disease. The aim of this study was to evaluate the phenomenon of development of Dupuytren’s contracture (DC) following an acute injury to the hand, and to observe the incidence and clinical diversity of such cases in daily clinical practice. Materials and Methods: We collected data of patients presenting with primary Dupuytren’s contracture in the Lithuanian population and evaluated the occurrence and clinical manifestation of this specific type of DC, arising following acute hand trauma. The diagnosis of DC was based on clinical signs and physical examination. Digit contractures were measured by goniometry, and the staging was done according to Tubiana classification. Injury-induced (injury-related) cases were identified using the “Criteria for recognition of Dupuytren’s contracture after acute injury” (established by Elliot and Ragoowansi). Results: 29 (22%) of a total of 132 cases were injury-induced DCs. Twenty-six of 29 patients in this group presented with stage I–II contractures. Duration of symptoms was 6 (SD 2.2) and 3.8 (SD 2.2) years in the injury-related and injury-unrelated DC groups, respectively. Mean age on the onset of symptoms in the injury-induced and non-injuryinduced groups was 52 (SD 10.7) and 56 (SD 10.9), respectively. Patients from both groups expressed strong predisposition towards development of DC. Conclusions: Around one-fifth of patients seeking treatment for primary Dupuytren’s contracture seemed to suffer from injury-induced Dupuytren’s contracture. [...]

Synchronization of Separate Sensors’ Data Transferred through a Local Wi-Fi Network: A Use Case of Human-Gait Monitoring

This paper addresses the challenge of synchronizing data acquisition from independent sensor systems in a local network. The network comprises microcontroller-based systems that collect data from physical sensors used for monitoring human gait. The synchronized data are transmitted to a PC or cloud storage through a central controller. The performed research proposes a solution for effectively synchronizing the data acquisition using two alternative data-synchronization approaches. Additionally, it explores techniques to handle varying amounts of data from different sensor types. The experimental research validates the proposed solution by providing trial results and stability evaluations and comparing them to the human-gait-monitoring system requirements. The alternative data-transmission method was used to compare the data-transmission quality and data-loss rate. The developed algorithm allows data acquisition from six pressure sensors and two accelerometer/gyroscope modules, ensuring a 24.6 Hz sampling rate and 1 ms synchronization accuracy. The obtained results prove the algorithm’s suitability for human-gait monitoring under its regular activity. The paper concludes with discussions and key insights derived from the obtained results