Hydroxyapatite coating on titanium by a low energy plasma spraying mini-gun

Plasma-sprayed hydroxyapatite (HA) coatings are used on metallic implants to improve osseointegration and bone growth. The purpose of this work was to determine the microstructure and composition of HA coatings obtained with a newly developed low energy plasma spray mini-gun employing an HA feedstock powder with smaller granulometry than that commonly used. The microstructure and the phase composition of the coatings obtained by varying the number of mini-gun runs were examined using scanning electron microscopy, X-ray diffraction and Fourier transform infrared and micro-Raman spectroscopy. In all cases, the results indicate the presence of an amorphous phase and oxyapatite in the coatings due to hydroxyl group removal. No other foreign crystalline phases were detected. The absence of foreign phases was attributed to the fast cooling rate of the small particles used in the experiments and the low amount of energy employed with the mini-gun. Decomposition in the υ1PO4 region of the Raman spectra allowed a semi-quantitative evaluation of the phase contents as a function of the number of runs. Micro-Raman spectroscopy appears to be a powerful technique providing comprehensive and localised information concerning calcium phosphate phases in coatings

Анализ и исследование условий образования и эффективности мер предотвращения солеотложений при эксплуатации скважин на Шингинском нефтяном месторождении (Томская область)

Предотвращение солеобразования оборудования эксплуатационных скважин. Объектом являются добывающие и нагнетательные скважины, пробы попутно-добываемой и нагнетаемой воды. Целью работы является увеличения межремонтного периода работы осложнённого фонда скважин и разработки рекомендаций по увеличению срока защиты подземного оборудования. В процессе исследования проводились анализ химического состава и определение типа попутно добываемой, пластовой и нагнетаемой воды, изучение внутренней структуры солеотложения, прогноз вероятности образования солеотложений в подземном оборудовании скважин, анализ экономической эффективности за счет изменения межремонтного периода работы скважин.Scale formation is a major problem in the oil industry. They may occur downhole or in surface facilities. The formations of these scales plug production lines and equipment and impair fluid flow. Their consequence could be production equipment failure, emergency shutdown, increased maintenance cost, and an overall decrease in production efficiency. The failure of production equipment and instruments could result in safety hazards

A comparative physico-chemical study of chlorapatite and hydroxyapatite: from powders to plasma sprayed thin coatings

Due to their bioactivity and osteoconductivity, hydroxyapatite (HA) plasma sprayed coatings have been widely developed for orthopedic uses. However, the thermodynamic instability of HA leads frequently to a mixture of phases which limit the functional durability of the coating. This study investigates the plasma spraying of chlorapatite (ClA) powder, known to melt without decomposition, onto pure titanium substrates using a low energy plasma spray system (LEPS). Pure ClA powder was prepared by a solid gas reaction at 950° C and thermogravimetric analysis showed the good thermal stability of ClA powder in the range 30-1400° C compared to that of the HA powder. Characterization of ClA coating showed that ClA had a very high crystalline ratio and no other crystalline phase was detected in the coating. HA and ClA coatings composition, microstructure and in vitro bioactivity potential were studied, compared and discussed. In vitro SBF test on HA and ClA coatings revealed the formation of a poorly crystalline apatite on the coating surface suggesting that we could expect a good osteoconductivity especially for the ClA coating prepared by the LEPS system

Numerical analysis of the flow behavior in the throat section of an experimental conical nozzle

The flow pattern in supersonic nozzles is defined by the aerodynamic profiles of the geometry of the internal walls, among other parameters, the throat being a critical section. In the present work, the objective is to analyze the behavior of the flow in the straight section of the throat of an experimental conical nozzle of a solid fuel probe rocket engine. The over-expanded flow was simulated with the ANSYS-Fluent code in a 2D computational domain, using the RANS model and the Menter turbulence model, and the Sutherland equation for viscosity as a function of the temperature. Five case studies were performed for the throat length in the range of 1-10 mm. Fluctuations of Mach number, pressure and temperature, oblique shock waves in the throat section were obtained for the length of 10 mm; for shorter lengths the intensity of the shock magnitude decreased. It is concluded that, for the throat length of 1 mm, the flow is transonic without the presence of oblique shocks. In the diverging section, shock waves vary in intensity and change position

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.This study was carried out under a MNT ERA-Net Project named NANOMED. The authors gratefully thank the Midi-Pyrénées region (MNT ERA Net Midi-Pyrénées Région, NANOMED2 project) and the Institute National Polytechnique de Toulouse (BQR INPT 2011, BIOREVE project) for supporting this research work, especially the financial support for research carried out in the CIRIMAT and the LGP laboratories (France), and the Basque government and Tratamientos Superficiales Iontech, S.A. for their financial and technical support under the IG-2007/0000381 grant for the development of the LEPS device and deposition of the coatings carried out in Inasmet-Tecnalia. The French industrial collaborators (TEKNIMED SA and 2PS SA) were financed by the OSEO programs

Propriedades psicométricas e invariância de medida de uma escala de autoeficácia acadêmica em estudantes universitários de cinco países da América Latina

Our objective was to analyze the measurement invariance of the Academic Situations Specific Perceived Self-Efficacy Scale (ASSPSES) among Peruvian, Mexican, Colombian, Argentinean, and Brazilian college students, and its relationship with academic emotional exhaustion (AEE). In addition to the ASSPSES, the Emotional Exhaustion Scale (EES) was used. Two thousand one hundred forty-two college students (70.26% women) between the ages of 16 and 35 (M = 21.79 years) participated. The one-dimensional structure of ASSPSES was corroborated in each sample with a confirmatory factor analysis and the measurement invariance analysis was carried out with a multi-group factor analysis (MGFA) and with the differential item functioning. The relationship with the AEE was tested with the Pearson correlation coefficient. Regard the results, in all of the samples, the one-dimensional model presented adequate psychometric indicators with respect to both dimensionality and reliability. Similarly, regarding the analysis of measurement invariance, a strong variance was attained, and DIF is weak, which together with the MGFA results provides favorable evidence of measurement invariance. We conclude that ASSPSES is an invariant measure among the analyzed groups although replicating the study is necessary for the consolidation of the findings. These findings contribute to the understanding of the internal structure of the ASSPSES, something that had been awaiting evaluation, given how the scale is used in various contexts.El objetivo fue analizar la invarianza de medición de la Escala de Autoeficacia Percibida Específica para Situaciones Académicas (EAPESA) entre estudiantes universitarios peruanos, mexicanos, colombianos, argentinos y brasileños, y su relación con el agotamiento emocional académico (AEA). Además de la EAPESA, se usó la Escala de Cansancio Emocional (ECE). Participaron 2142 estudiantes universitarios (70.26 % mujeres) entre los 16 y 35 años (M = 21.79). La estructura unidimensional de la EAPESA se corroboró en cada muestra con un análisis factorial confirmatorio, y la invarianza de medición se llevó a cabo con un análisis factorial de grupo múltiple (AFGM) y con el funcionamiento diferencial de los ítems (FDI). La relación con el AEA se evaluó con el coeficiente de correlación de Pearson. Respecto a los resultados, en todas las muestras el modelo unidimensional presentó adecuados indicadores psicométricos, tanto en lo que respecta a su dimensionalidad como en cuanto a su confiabilidad. Del mismo modo, en cuanto al análisis de invarianza de medición, se alcanza la invarianza fuerte, y el FDI es débil, lo que junto con el AFGM brinda evidencia favorable de invarianza de medición. Se concluye que la EAPESA es una medida invariante entre los grupos analizados, aunque es necesario replicar la investigación para consolidar los hallazgos. Estos resultados contribuyen a entender la estructura interna de la EAPESA, algo que estaba aguardando una valoración, ya que dicha escala es usada en varios contextos.El objetivo fue analizar la invarianza de medición de la Escala de Autoeficacia Percibida Específica para Situaciones Académicas (EAPESA) entre estudiantes universitarios peruanos, mexicanos, colombianos, argentinos y brasileños, y su relación con el agotamiento emocional académico (AEA). Además de la EAPESA, se usó la Escala de Cansancio Emocional (ECE). Participaron 2142 estudiantes universitarios (70.26% mujeres) entre los 16 y 35 años (M = 21.79). La estructura unidimensional de la EAPESA se corroboró en cada muestra con un análisis factorial confirmatorio, y la invarianza de medición se llevó a cabo con un análisis factorial de grupo múltiple (AFGM) y con el funcionamiento diferencial de los ítems (FDI). La relación con el AEA se evaluó con el coeficiente de correlación de Pearson. Respecto a los resultados, en todas las muestras el modelo unidimensional presentó adecuados indicadores psicométricos, tanto en lo que respecta a su dimensionalidad como en cuanto a su confiabilidad. Del mismo modo, en cuanto al análisis de invarianza de medición, se alcanza la invarianza fuerte, y el FDI es débil, lo que junto con el AFGM brinda evidencia favorable de invarianza de medición. Se concluye que la EAPESA es una medida invariante entre los grupos analizados, aunque es necesario replicar la investigación para consolidar los hallazgos. Estos resultados contribuyen a entender la estructura interna de la EAPESA, algo que estaba aguardando una valoración, ya que dicha escala es usada en varios contextos