RESUMO
We developed and analyzed a novel non-sparking material based on CuAlBe for applications in potentially explosive environments. Using a master alloy of CuBe, an established material for anti-sparking tools used in oil fields, mines, or areas with potentially explosive gas accumulations, and pure Al, we used an Ar atmosphere induction furnace to obtain an alloy with ~10 wt% Al and ~2 wt% Be percentages and good chemical and structural homogeneity. The new material was tested in an explosive gaseous mixture (10% H2 or 6.5% CH4) under extremely strong wear for 16,000 cycles, and no hot sparks capable of igniting the environment were produced. The material was used in the form of hot-rolled plates obtained from melted ingots. The experimental results reflect the use of a suitable material for non-sparking tools. This material has good deformability during hot rolling, abnormal grain growth during deformation under heat treatment and special thermo-mechanical processing, and no high chemical composition variation. Additionally, there are slightly different corrosion resistance and mechanical properties between the melt and hot-rolled state of CuAlBe material. Through hot rolling, the material's corrosion resistance increased, reducing the chances of generating sparks capable of causing explosions.
RESUMO
Orthodontic mini-implants are devices used for anchorage in various orthodontic treatments. We conducted a pilot study which aimed to observe preliminary trends regarding the impact of heat treatment on the elastic modulus of Ti6Al4V alloy and stainless steel 316L mini-implants. The initial phase involved testing the impact of heat treatment on the mechanical properties of Ti6Al4V alloy and stainless steel 316L mini-implants. MATERIAL AND METHODS: Ten self-drilling mini-implants sourced from two distinct manufacturers (Jeil Medical Corporation® and Leone®) with dimensions of 2.0 mm diameter and 10 mm length were tested. They were separated into two material groups: Ti6Al4V and 316L. Using the CETRUMT-2 microtribometer equipment, indentation testing was conducted employing a diamond-tipped Rockwell penetrator at a constant force of 4.5 N. RESULTS: Slight differences were observed in the elastic modulus of the Ti6Al4V alloy (103.99 GPa) and stainless steel 316L (203.20 GPa) compared to natural bone. The higher elastic moduli of these materials indicate that they are stiffer, which could potentially lead to stress-shielding phenomena and bone resorption. Heat treatment resulted in significant changes in mechanical properties, including elastic modulus reductions of approximately 26.14% for Ti6Al4V and 24.82% for 316L, impacting their performance in orthodontic applications. CONCLUSION: Understanding the effects of heat treatment on these alloys is crucial for optimizing their biomechanical compatibility and longevity in orthodontic treatment. To fully evaluate the effects of heat treatment on mini-implants and to refine their design and efficacy in clinical practice, further research is needed.
RESUMO
BACKGROUND: The aim of the study was to assess the protective effect of applying potassium iodide (KI) over silver diamine fluoride (SDF) on demineralized root dentin in the case of a sustained acidogenic attack. METHODS: Forty caries-free third molars were used in the study. A diamond disc was used to separate the roots and the tooth crowns from the roots. Each root fragment was randomly distributed in one of the four study groups: C-samples were not demineralized; DD-demineralized samples; RS1-demineralized samples covered with SDF+KI (RS-Riva Star product, SDI limited, Bayswater, Australia); RS2-demineralized samples covered with SDF+KI and submersed to another acidic challenge for 3 days. SEM and EDX were used for the morphological and elemental analysis. Vickers hardness assessment was performed using a tribometer CETR UMT-2 (Bruker Corporation, Berlin, Germany). One-way ANOVA and post hoc Bonferroni tests were used for the statistical analysis with a significance level of p < 0.05. RESULTS: Morphological and elemental changes were observed on the surface of the study samples. Significant differences were observed between the recorded hardness values of groups C and DD (p = 0.005), C and RS2 (p = 0.002), DD and RS1 (p = 0.011); RS1 and RS2 (p = 0.004). CONCLUSIONS: The application of SDF and KI (Riva Star product) on root dentin caries resulted in the formation of a heterogeneous outer layer that sealed the dentin and increased the microhardness of the treated surface. In the conditions of the present study, this layer did not provide enough protection for root dentin exposed to continuous attacks.
RESUMO
The paper aims to investigate the behavior of Arboblend V2 Nature biopolymer samples covered with three ceramic powders, Amdry 6420 (Cr2O3), Metco 143 (ZrO2 18TiO2 10Y2O3) and Metco 136F (Cr2O3-xSiO2-yTiO2). The coated samples were obtained by injection molding, and the micropowder deposition was achieved by using the Atmospheric Plasma Spray (APS) method, with varied thickness layers. The present study will only describe the results for nine-layer deposition because, as the number of layers' increases, the surface quality and mechanical/thermal characteristics such as wear, hardness and thermal resistance are also increased. The followed determinations were conducted: the adhesion strength, hardness on a microscopic scale by micro-indentation, thermal analysis and structural and morphological analysis. The structural analysis has highlighted a uniform deposition for the ZrO2 18TiO2 10Y2O3 layer, but for the layers that contained Cr2O3 ceramic microparticles, the deposition was not completely uniform. The thermal analysis revealed structural stability up to a temperature of 230 °C, the major degradation of the biopolymer matrix taking place at a temperature around 344 °C. The samples' crystalline structure as well as the presence of the Cr2O3 compound significantly influenced the micro-indentation and scratch analysis responses. The novelty of this study is given by itself the coating of the Arboblend V2 Nature biopolymer (as base material), with ceramic microparticles as the micropowder coating material. Following the undertaken study, the increase in the mechanical, tribological and thermal characteristics of the samples recommend all three coated biopolymer samples as suitable for operating in harsh conditions, such as the automotive industry, in order to replace plastic materials.
