ABSTRACT
This paper focuses on the microstructure and tribological properties of novel hardfacing alloy based on Fe-C-Mn-B doped with Ni, Cr, and Si. The 4 mm-thick coating was deposited on the AISI 1045 carbon steel by the MIG-welding method using flux-cored wires in three passes. The transition zone thickness between the weld layers was ~80 µm, and the width of the substrate-coating interface was 5-10 µm. The following coating constituents were detected: coarser elongated M2B borides, finer particles of Cr7C3 carbides, and an Fe-based matrix consisting of ferrite and austenite. The nanohardness of the matrix was ~5-6 GPa, carbides ~16-19 GPa, and borides 22-23 GPa. A high cooling rate during coating fabrication leads to the formation of a fine mesh of M7C3 carbides; borides grow in the direction of heat removal, from the substrate to the friction surface, while in the transition zone, carbides become coarser. The dry sliding friction tests using a tribometer in PoD configuration were carried out at contact pressure 4, 7, 10, and 15 MPa against the AISI 1045 carbon steel (water-quenched and low-tempered, 50-52 HRC). The leading wear phenomenon at 4 and 7 MPa is fatigue, and at 10 and 15 MPa it is oxidation and delamination.
ABSTRACT
Complex composite materials are used in many areas of dentistry. Initially, chemically hardened materials were also used, and in this group nanohybrid composites are highly valued. They are often used today, mainly for the direct reconstruction of damaged hard tooth tissue materials for rebuilding damaged tissues using indirect adhesive techniques. The research was conducted to determine the mechanical properties of materials with nanofillers. The article focuses on methods of important test methods for dental prosthetics: resilience, abrasion, wear test, impact strength, hardness, SEM, and chemical analysis. As part of this work, five different series of hybrid composites with nano-fillers were tested. The mechanical properties of composites, such as compressive strength, microhardness, flexural strength, and modulus of elasticity, depend mainly on the type, particle size, and amount of filler introduced. The obtained test results showed that the type and amount of nanofiller have a significant influence on the mechanical and tribological properties. The introduction of nanofillers allowed us to obtain higher mechanical properties compared to classic materials discussed by other researchers. The study observed a change in vibrations in the IR spectrum, which allowed a comparison of the organic structures of the studied preparations.
ABSTRACT
INTRODUCTION AND OBJECTIVES: In the United States, breast cancer (BC) is the most common non-skin cancer. In Poland, it is estimated that the number of new breast cancer cases affects about 13,500 women each year. There are many methods for nutritional status assessment. One of them is bioimpedance analysis (BIA). Direct bioimpedance measures (resistance, reactance, phase angle (PA)) determined by bioelectrical impedance analysis (BIA) detectf changes in tissue electrical properties. The study was conducted to investigate whether there are any tissue electrical differences in patients with breast cancer. MATERIALS AND METHODS: The direct bioimpedance measures determined by bioelectrical impedance analysis (BIA) were performed on 34 patients with BC and 34 healthy volunteers. The measurements were made with ImpediMed bioimpedance analysis SFB7 BioImp v1.55 (Pinkenba Qld 4008, Australia). RESULTS: Reactance and resistance at 50 kHz was found to be significantly greater in patients with BC than in the control group (53.59° ± 1.53 vs. 47.26° ± 1.25, respectively, p=0.0031; 603.24° ± 15.38 ohm vs. 515.87° ± 11.48 ohm, respectively, p=0.00004). CONCLUSION: Pre-surgical patients diagnosed with BC have altered tissue electrical properties. Further observations of a larger patient group would be valuable to calculate survival, validate the prognostic significance of PA, and monitor nutritional and therapeutic interventions in this patient population.
