Enhancing the Quality of the Characteristic Transmittance Curve in the Infrared Region of Range 2.5–7 µm of the Optical Magnesium Fluoride (MgF2) Ceramic Using the Hot-Pressing Technique in a Vacuum Environment

Nguyen Tuan Hieu,Phung Van Minh,Nguyen Dinh Thai,Tran Duc Long,Van Thom Do

doi:10.1155/2020/7258431

Abstract

This paper carries out an experimental study to enhance the quality of the characteristic transmittance curve in the infrared range of 2.5–7 µm of the optical magnesium fluoride (MgF2) ceramic. This work evaluates the effectiveness of using vacuum environment in the MgF2 ceramic hot-pressing technique by comparing the density and the quality of the transmittance characteristic curve of two types of specimens manufactured by the hot-pressing technique corresponding to open air and vacuum environment under the same technological parameters including temperature 650°C, time 30 min, and pressure 200 MPa. The results present that, in comparison with using the hot-pressing technique in the open air, when using the hot-pressing technique in a vacuum environment, the transmittance increases about 4–10%, the characteristic transmittance curve is smoother and has fewer peak points, and the wide of peak points are smaller. When hot-pressing in a vacuum environment, the temperature can be up to 750°C in order to obtain the magnesium fluoride (MgF2) ceramic with the highest quality of characteristic line in the infrared range of 2.5–7 µm. Seventeen specimens are manufactured to conduct the experimental study in order to figure out the optimal set of technological parameters (temperature T = 640.9°C, time t = 33.0 min, and pressure P=231.4 MPa) when hot-pressing in a vacuum environment by the experimental planning approach.

Highlights

Nguyen Tuan Hieu,1 Van Thom Do,2 Nguyen Dinh Thai,1 Tran Duc Long,1 and Phung Van Minh2
When investigating the characteristic transmittance curve in the infrared range of magnesium fluoride (MgF2) ceramic, we can capture the peak points corresponding to the absorption stretches. ere are some important point as follows. e peak point at 2.8 μm wavelength corresponds to the hydroxylate absorption stretching band (OH stretching), the peak point at 4.3 μm wavelength corresponds to the carbon dioxide absorption stretching band, the peak point at 5 μm wavelength corresponds to the bifluoride absorption stretching band, the peak point at 6.7 μm wavelength corresponds to the OH-banding, and other peak points at 3 μm and 6.1 μm wavelengths correspond to the bands caused by the humility [7]
We can see clearly that by using the hot-pressing technique in a vacuum environment, the density of the specimen increases. e reason can be explained that when operating in the open air, the air will diffuse into the specimen structure and the porosity of the pressed product increases

Summary

Research Article

Enhancing the Quality of the Characteristic Transmittance Curve in the Infrared Region of Range 2.5–7 μm of the Optical Magnesium Fluoride (MgF2) Ceramic Using the Hot-Pressing Technique in a Vacuum Environment. The optimal technological parameters such as temperature, time, and pressure need to be adjusted It is the main motivation for our team to carry out an experimental study to find out the optimal function of the working system with the highest quality of the characteristic transmittance curve of hot-pressed magnesium fluoride (MgF2) ceramic. From the transmittance of seventeen specimens at the 4.5 μm wavelength, we obtain the experiment planning data set by using the experimental planning method to determine the coefficients of the regression function as shown in equation (1). en, we use Maple 2016 application (Waterloo Maple Inc, Waterloo, Ontario, Canada) to find out the optimal value of the regression function and the optimal data set of the working system

Results and Discussions

Specimen type I Specimen type II

Conclusions