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Povzetek: The impact of the microstructural properties of a Ti6Al4V alloy on its electrochemical properties, as well as the effect of the α- and β-phases present within it, is still unclear. With the introduction of new, emerging technologies, such as selective laser melting and post heat treatments, the effect of the microstructure on an alloy's corrosion properties has become increasingly interesting from a scientific perspective. When these alloys are produced through different methods, despite an identical chemical composition they have diverse microstructures, and consequently display varying resistance to corrosion. In the present research study, Ti–6Al–4V alloy specimens produced by three different processes, leading to the formation of three different microstructures were investigated: heat treated specimen fabricated by selective laser melting, wrought and cast specimens. The impact of the microstructure of these alloys when immersed in artificial saliva was studied through the use of various electrochemical techniques, by microscopical examinations, and time-of-flight secondary ion mass spectrometry. Corrosion properties were investigated by the measurement of open circuit potential, linear polarization, and potentiodynamic curve measurements followed by microscopical examinations, and time-of-flight secondary ion mass spectrometry examination was conducted to reveal spatial distribution of alloying species on oxide film. It was found that the difference between specimens containing an α+β microstructure was small and not dependent on the aspect ratio of the β-phase, alloy grain size, and vanadium partitioning coefficient, but rather on the size, shape, and content of this phase.
Ključne besede: Ti6Al4V, dental alloy, microstructure, corrosion resistance, heat treatment, ToF-SIMS
Objavljeno v DiRROS: 26.10.2023; Ogledov: 437; Prenosov: 220
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Povzetek: The aim of the study was to evaluate the corrosion properties of three different grades of high-speed steel following a heat treatment procedure involving deep cryogenic treatment after quenching and to investigate how these properties are connected to the microstructure and hard- ness of the material. The hardness of steels was measured, and microstructural properties were determined through observation of the metallographically prepared steels using scanning electron microscopy. These studies were complemented corrosion evaluation by the use of corrosion potential measurement and linear polarization measurement of steels in a sodium tetraborate buffer at pH 10. The results showed that the deep cryogenic procedure of high-speed steel changed the microstructure and consequently affected the hardness of the investigated steels to different extents, depending on their chemical composition. Corrosion studies have confirmed that some high-speed steels have improved corrosion properties after deep cryogenic treatment. The most important improvement in corrosion resistance was observed for deep cryogenically treated high-speed steel EN 1.3395 (M3:2) by 31% when hardened to high hardness values and by 116% under lower hardness conditions. The test procedure for differentiating corrosion properties of differently heat-treated tool steels was established alongside the investigation.
Ključne besede: deep cryogenic treatment, corrosion, microstructure, hardness
Objavljeno v DiRROS: 01.08.2023; Ogledov: 272; Prenosov: 137
Celotno besedilo (5,82 MB)
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Povzetek: An efficient approach for tailoring surface properties of polymers is presented, which enables rapid modification leading to superhydrophilic properties. The approach is based on vacuum-ultraviolet radiation (VUV) pretreatment of the surface to create reactive dangling bonds. This step is followed by a second treatment using neutral oxygen atoms that react with the dangling bonds and form functional groups. The beneficial effect of VUV pretreatment for enhanced functionalization was clearly demonstrated by comparing VUV pretreatment in plasmas created in different gases, i.e., hydrogen, nitrogen, and oxygen, which differ in the intensity of VUV/UV radiation. The emission intensity of VUV radiation for all gases was measured by vacuum ultraviolet spectroscopy. It was shown that VUV has a strong influence on the treatment time and final surface wettability. A superhydrophilic surface was obtained only if using VUV pretreatment. Furthermore, the treatment time was significantly reduced to only a second of treatment. These findings show that such an approach may be used to enhance the surface reaction efficiency for further grafting of chemical groups.
Ključne besede: plasma treatment, vacuum-ultraviolet radiation treatment, surface functionalization, polymer polyvinyl chloride, vacuum-ultraviolet spectroscopy, vacuum-ultraviolet photons
Objavljeno v DiRROS: 06.06.2023; Ogledov: 369; Prenosov: 185
Celotno besedilo (4,42 MB)
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Povzetek: The effect of deep cryogenic treatment (DCT) on corrosion resistance of steels AISI 52100 and AISI D3 is investigated and compared with conventional heat-treated counterparts. DCTʼs influence on microstructural changes is subsequently correlated to the corrosion resistance. DCT is confirmed to reduce the formation of corrosion products on steelsʼ surface, retard the corrosion products development and propagation. DCT reduces surface cracking, which is considered to be related to modified residual stress state of the material. DCTʼs influence on each steel results from the altered microstructure and alloying element concentration that depends on steel matrix and type. This study presents DCT as an effective method for corrosion resistance alteration of steels.
Ključne besede: steel, deep cryogenic treatment, corrosion, Raman, open access
Objavljeno v DiRROS: 19.05.2023; Ogledov: 286; Prenosov: 212
Celotno besedilo (3,13 MB)
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Povzetek: Background: Gastric cancer (GC) is the fourth most common cancer and the third leading cancer-related cause of death worldwide since most patients are diagnosed at an advanced stage. The majority of GCs are adenocarcinomas (ACs), and the poorly characterized clear cell AC represents a unique subgroup of GCs and is an independent marker of poor prognosis. Even though the prognosis for patients with advanced GC is poor we present a report of a patient with long-term survival despite having liver metastases from clear cell gastric AC. Case presentation: A 45-year-old male with clear cell gastric AC underwent subtotal gastrectomy and postoperative chemoradiation. Only a year and a half after his initial treatment the disease spread to his liver. He received two lines of chemotherapy treatment within the next two years before a right hepatectomy was suggested. Due to an initially insufficient future liver remnant (FLR), transarterial chemoembolization (TACE) and portal vein embolization (PVE) were performed, which made the surgical procedure possible. Shortly after a disease progression in the remaining liver was detected. In the following three years the patient was treated with a carefully planned combination of systemic therapy and different interventional oncology techniques including selective internal radiation therapy (SIRT) and TACE. And as illustrated, an attentive, patient-tailored, multimodality treatment approach can sometimes greatly benefit our patients as he had an overall survival of 88 months despite the poor prognosis of his disease. Conclusion: To the best of our knowledge, this report is the first to describe a patient with liver metastases from clear cell gastric AC treated with interventional oncology techniques (PVE, TACE, and SIRT) in combination with other locoregional and systemic therapies thereby presenting that these interventional oncology techniques can be successfully integrated into long-term management of non-conventional liver tumors.
Ključne besede: gastric adenocarcinoma, survival, multimodality treatment
Objavljeno v DiRROS: 15.09.2022; Ogledov: 396; Prenosov: 238
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