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The study compares the microstructure of three commercial dental cobalt matrix alloys with related chemical composition declared by the manufacturer. Casts were produced with lost wax method, then melted and casted with centrifugal induction casting machine. The Co-Cr-Mo alloys were casted according to the manufacturers procedure. The samples' chemical composition and phase composition, respectively, using WD-XRF (Wavelength Dispersive X-Ray Fluorescence) and XRD (X-ray Diffarction) methods were analysed. Casts microstructure by mean of LOM (Light Optical Microscopy), SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) were investigated. Vickers hardness HV10 was measured. Quantitative microstructure evaluation was performed by means of computer image processing. The results of the chemical composition indicate the high stability of the chemical composition for alloy A. In case of alloys B and C, there was a significant difference in carbon content. Quantitative differences in image of microstructure between of castings A and B, C were noticed. The greater amount of precipitates was recorded for castings with higher carbon content. In all investigated castings, the presence of β matrix solution and M23C6 carbide precipitations was found.

ReseaRch on Resistance to coRRosive weaR of dental cocrMo alloy containing post-pRoduction scRap Badanie odpoRności na zużycie koRozyjne stoMatologicznego stopu cocrMo zawieRającego złoM popRodukcyjny*

The aim of the study was to investigate the influence of kaolinite (KA) and beeswax (BW) addition on the structural and physical properties of thermoplastic starch (TPS) films. The casting method was applied and glycerol was used as a plasticizer. Microstructure analyzes were made by a stereoscopic and a scanning electron microscope. Tensile tests were carried out under static load conditions at three different deformation velocities of V = 0.0001, 0.001, and 0.01 m/s. The studies of surfaces characteristic were performed using water contact angle and water vapor isotherm measurements. The most homogeneous structure of the surface with higher mean values of failure stress and elasticity modulus was observed for thermoplastic starch films with kaolinite addition. The significant reduction in dynamics changes of water contact angle (10 %) of BW films in the time 0-20 s as well as tensile strength decrease was noted (compared to pure TPS films). The research results suggest the validity of using BW and KA to improve the barrier and mechanical properties of TPS films. Further research should focus on to improve the starch-beeswax-kaolinite combination and increase the homogeneity of the structure of films in order to upswing their simultaneous impact on barrier and mechanical properties.

The research subject was the analysis of the microstructure, barrier properties, and mechanical resistance of the psyllium husk (PH)-modified thermoplastic starch films. The tensile tests under various static loading conditions were not performed by researchers for this type of material before and are essential for a more precise assessment of the material’s behavior under the conditions of its subsequent use. The film samples were manufactured by the casting method. PH addition improved starch gelatinization and caused a decrease in failure strain by 86% and an increase in failure stress by 48% compared to pure films. Fourier transform infrared spectroscopy results showed the formation of additional hydrogen bonds between polysaccharides in starch and PH. An increase in the number of hydrophilic groups in the modified films resulted in a faster contact angle decrease (27.4% compared to 12.8% for pure ones within the first 5 s); however, it increased the energy of water binding and surface complexity. The modified films showed the opacity at 600 nm, 43% higher than in the pure starch film, and lower transmittance, suggesting effectively improving barrier properties to UV light, a potent lipid-oxidizing agent in food systems.

The investigations on the response of bone tissue under different loading conditions are important from clinical and engineering points of view. In this paper, the influence of nesfatin-1 administration on rat humerus mechanical properties was analyzed. The classical three-point bending and impact tests were carried out for three rat bone groups: control (SHO), the humerus of animals under the conditions of established osteopenia (OVX), and bones of rats receiving nesfatin-1 after ovariectomy (NES). The experiments proved that the bone strength parameters measured under various mechanical loading conditions increased after the nesfatin-1 administration. The OVX bones were most susceptible to deformation and had the smallest fracture toughness. The SEM images of humerus fracture surface in this group showed that ovariectomized rats had a much looser bone structure compared to the SHO and NES females. Loosening of the bone structure was also confirmed by the densitometric and qualitative EDS analysis, showing a decrease in the OVX bones’ mineral content. The samples of the NES group were characterized by the largest values of maximum force obtained under both quasi-static and impact conditions. The energies absorbed during the impact and the critical energy for fracture (from the three-point bending test) were similar for the SHO and NES groups. Statistically significant differences were observed between the mean Fi max values of all analyzed sample groups. The obtained results suggest that the impact test was more sensitive than the classical quasi-static three-point bending one. Hence, Fi max could be used as a parameter to predict bone fracture toughness.

Using the recasted alloys in dental prosthetics could affect the quality of the metal-ceramic bond. However, scientists, alloys producers, and prosthetists are still of different opinions. e purpose of this study was to estimate the influence of recasting of the NiCrMo alloy on the metal-ceramic bond quality. e research was carried out on macro-, micro-and nanoscales using the threepoint bending test procedure and hardness tests as well as atomic force microscopy and SEM analyses. e SEM analyses showed good integrity of the metal-ceramic bond. e τ b index of all test samples was greater than 45 MPa. e highest values were recorded for the samples made of 50% and 100% of a brand new material. SEM analysis made after the bending test confirmed good metal-ceramic bond and exhibited adhesive-cohesive fracture. e largest hardness of metal plates was found for the samples containing 50% of the recycled material. Atomic force microscopy studies showed that the alloy containing 50% of the recycled material was characterized by the highest values of surface roughness parameters.

Highlights Cleaning cereal grain after harvest is very important for the quality of the product. Technological progress enables the design of new equipment for cleaning cereal grain. Grain segregation allows selecting the best grain to increase yields. The quality of segregation depends on the technological parameters of the device. Abstract. This article presents the results of laboratory tests of a new rotary cleaning device used for the separation and cleaning of barley grain. This device has the characteristics of a multi-stage screen assisted by an air stream (i.e., pneumo-separation). The prototype was constructed at the University of Life Sciences in Lublin, Poland. The tests were conducted on a test stand, which allowed changes in the operating parameters of the cleaning device and their measurement. The tests included determining the influence of the sieve drum inclination angle (a) on the effectiveness and efficiency of barley grain cleaning. The tests were carried out using two drum rotational speeds: 5 rpm and 75 rpm. The quality of the separation and cleaning of barley grain was evaluated using six cleaning process parameters: plump grain separation coefficient (Spg), fine grain separation coefficient (Sfg), fine impurities separation coefficient (Sfi), chaff separation coefficient (Sch), total coefficient of cleaning effectiveness (E), and plump grain cleaning efficiency (qpg). The results showed significant effects of the sieve drum inclination angle on the efficiency and effectiveness of barley grain cleaning. Keywords: Barley grain, Conical sieve, Grain separation, Rotary cleaning device.