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Orthodontic appliances usually require the joining of different stainless-steel parts in order to achieve adequate control over tooth movement during the active treatment. The aim of this study was to assess the tensile and shear breaking force of the joints between forty orthodontic bands and forty attachments (buccal tubes), joined by laser and TIG welding, without filler material. For the laser welding technique, we used an XXS Laser (OROTIG) welding unit and for the TIG welding technique, a PUK D2 (LAMPERT) welding unit. The tensile and shear breaking force of the welded joints was determined using the Z010 Zwick/Roell testing machine. The independent-samples t-test showed statistically significant differences between the laser and TIG groups for both the tensile and the shear breaking force tests, the laser welded samples having better mechanical strength than the TIG welded samples. For practical use, under normal loading forces, both techniques are suitable for this particular application in orthodontics. In patients with parafunctional habits, that could develop higher bite forces, the failure of the welded joints might occur if the welding surface is not increased, especially for the TIG welding technique.

Bulk metallic glasses (BMGs) represent a viable alternative for replacing classic materials used in medical devices. This paper presents the research conducted in order to obtain copper based BMGs using two different chemical compositions: Cu48Zr47Al5 and Cu45Zr45Al5Ag5. The samples were obtained by copper mold casting and their structure and properties were investigated using X-Ray diffraction (XRD), differential scanning calorimetry (DSC) and optical microscopy.

The analysis of reinforced polymers is one of the most important sources of information for materials properties designers. In this regard, due to their intrinsic properties, the fabrics play an essential role when they are used as reinforcement elements. The composites properties can be designed by alternating various types of fabrics, by modifying the orientation of every reinforcement layer, by modifying the matrix properties or by choosing the matrix. This study regards the tensile behavior of four fabric reinforced composites with four different epoxy resins as matrix. All the materials have the same reinforcement structure but the matrix is, in each case, another epoxy resin and more two classes of materials had been studied one is containing the natural polymerized matrix materials and the other one the materials that had been thermally treated according to technical sheet of each polymer. The tests were done one year after the materials formation.

Either considering chemical munitions or chemical improvised explosive devices, the armies should be able to counter their effects from two different perspectives: the agent used and the way to disperse it. While the agent to be delivered can be more or less lethal, the real factor that gives efficiency to the attack is the manner the agent is delivered. The state-of-the-art tested garment indicate that current knowledge regarding protective equipment for chemical warfare agents remains very limited. In this context, the present study aimed at the possibility of using the MWCNT-OH-based polyurea-composite material, obtained by our group in a previous study, in the field of protection against hazardous chemicals.

The increased demand for energy sources is the driving force to convert organic compounds into alternative fuels. Plastic waste disposal affects the environment, since they are not easily recycled and, during the recycling process, they can produce waste ash, heavy metals, or potentially harmful gas emissions. In the plant design for plastic converting into fuel, the chemical reactor is one of the advanced equipment in the field of chemical and process engineering. This study emphasizes the feasibility of pyrolysis process for valorisation plastics by producing energy-efficient products. In this respect, samples of polypropylene, polyethylene and polystyrene were used as models and subjected to pyrolysis processes at 450 °C, in the presence of two types of mesoporous silica materials, MCM-41 and SBA-15, using a modern developed reactor. The use of mesoporous materials increased the calorific value of the obtained oil and gas, thus improving the economic potential of the process end products. This study dealt with the extraction of oil from plastics termed as plastic pyrolysis oil (PPO) and plastics pyrolysis gas (PPG), with a composition rich in different types of hydrocarbons and they can be marketed at much cheaper rates compared to that present in the market.

For more than half a century, the use of plastic in agriculture has given farmers opportunities for growing fruits and vegetables regardless of the season, and at the same time achieving better quality compared to open-field cultivation. The use of plastics, through various specific techniques, helps reduce the consumption of various resources such as water, energy, fertilizers or pesticides.We could say that without these plastics a significant amount of cultivated fruits and vegetables could not be harvested in early conditions and could not be preserved and conditioned in controlled parameters.Plastic is a very important material for economy but also in everyday life. The use of plastic in agriculture has increased from year to year, thus contributing to both the increase of agricultural production and the improvement of the quality of food.Plastics are a wide range of synthetic or semi-synthetic materials that are used for various purposes. In the plastic industry, are used raw materials, such as cellulose, coal, natural gas, salt and, of course, crude oil. Plastics are extremely versatile materials and are ideal for a wide range of applications for industry as well as for consumers.

Single walled carbon nanotubes (SWCNT) and multi walled carbon nanotubes (MWCNT)/ vinyl ester nanocomposites with three different contents of carbon nanotubes (CNTs) have been prepared by the simple melt-compounding method. A fine and homogeneous dispersion of CNTs throughout vinyl ester resin has been noticed by SEM images. Two mechanical tests (compression and three point bending test) show that, compared to neat vinyl ester resin, compression modulus and compression strength of the nanocomposites have been significantly improved by about 9% and 14%, respectively, when incorporating only 0.15 wt.% MWCNTs. Furthermore, thermal behavior of SWCNT and MWCNT/ vinyl ester nanocomposites has been investigated and discussed based on differential scanning calorimetry (DSC) and thermo- mechanical analysis (TMA). Glass transition temperature (Tg) and coefficient of thermal expansion (CTE) have been increased and decreased, respectively, with increasing of CNTs content.

The bulk metallic glasses composites are a new class of bulk metallic glasses (BMGs), containing an amorphous metal matrix and reinforcing materials of metallic or ceramic nature in order to obtaining the desired combination of mechanical properties including strength, hardness, ductility and toughness. Composite materials of cylindrical form with the diameter of 10 mm and 5 mm in height were successfully prepared by hot-pressing of Zr – based glassy alloy powder and Fe – based nanocrystalline alloy powder in different volume fraction. The samples obtained were structural investigated by scanning electron microscopy and X-Ray diffraction and mechanically characterized by hardness and compression tests. It was found that increasing the volume ratio of the Fe-based nanocrystalline alloy up to a certain value leads to an increase in hardness and mechanical compressive strength.

Flame straightening is a technology process used to eliminate deformations. This method relies on local heating of the material to correct geometry or damaged parts. In the local automobile services its main use is for repairs of less critical deformed components. The maximum temperature and thermal gradient, heating time, cooling rate and number of heating cycles affect the mechanical properties since local heating can alter material microstructure. The aim of this research was to determine the mechanical characteristics of thin steel plates repaired by local heating associated with plastic deformation (similar to hot working) and cold straightening (similar to local cold working) for automotive side and door panels made of structural steel. Thin sheet plates, 0.9mm thickness, were deformed by impact and repaired by local heating using the flame and induction heating then plastically deformed while hot as well as straightened without heating. The heat repaired samples were studied by light microscopy to determine microstructure change and samples were tensile tested to determine their mechanical characteristics. Local excessive grain growth generates anisotropy, the assembly behaves as a composite material with regions that show significant plastic deformations while others little or no deformations at al. Without procedures adjusted to each material repairs involving heating are to be avoided, cold working should be employed when replacement is not possible.

This study comprises the studies performed on six in vivo failed centromedullary fixation devices, three made of stainless steel 316L and three of titanium alloy Ti-6Al-4V. Fractographic studies were performed using stereomicroscopy and scanning electron microscopy while metallographic studies were performed by light microscopy. Loading mode which caused failure was inferred based upon surface fracture topography and light microscopy studies were performed to observe if abnormal microstructures or inclusions could be the cause of the failure. In all cases the chemical composition was according to standard specifications and the microstructures appeared normal with low inclusionary content. The mode of failure was found to be fatigue and the crack initiation site was on the implant surface on roughness features and surface induced defects.