mohammad velashjerdi

In this research, the effect of adding different percentages of graphene oxide to polyamide and the effect of different printing directions on the mechanical properties of 3D printed samples were investigated. At first, 0.3% and 0.7% of graphene oxide nanoparticles were mixed in the matrix. Pure and composite polymer samples with different percentages of graphene oxide were printed by stereolithography in three directions. The mechanical properties of the samples were evaluated using tensile, impact and hardness tests. A scanning electron microscope was used to check the fracture surfaces of the samples. The results of the mechanical properties tests indicate a decrease in strength with the addition of go nanoparticles. With the increase of graphene oxide nanoparticles, the strength of the parts decreased by 30%. On the other hand, there was a 12% difference in tensile strength in pure polymer samples, which reached 17% with the addition of nanoparticles. Microscopic investigations showed the formation of clusters of graphene oxide nanoparticles in the composite samples, which led to stress concentration and cracking. Based on this, the printing direction has a significant effect on the mechanical properties of the printed samples. Among the pure polymer samples, the sample printed in the flat direction and among the composite samples, the nanocomposites printed in the vertical direction showed the best mechanical properties. Adding graphene oxide nanoparticles to the resin and increasing the percentage of nanoparticles in the direction of printing on the edge led to a decrease in hardness compared to the pure polymer sample.

Composite electrodeposition or Electroplating is a process primarily applied in the industry through which metal substrates are coated with an additional phase, such as low-thickness films of a range of metals. Lately, the ad-vent of coating based on metal matrix through deposition has been vital because the superior hardness has more improved wear and corrosion resistance than alloy-based or pure coatings of metal. Nickel is an engineering material, which has been broadly utilized for metal matrix applications. This paper summarizes recent research on the electrodeposition of nickel matrix composite coatings with borides ceramic particles. Some of these particles are ZrB2, BN, TiB2, Ni3B, CrB2, etc. in the nickel matrix. In addition, the most important results achieved in the field of these composite coatings were collected in this review.

Zirconium Diboride (ZrB2) powder was synthesized at low temperature via a Direct Molten Salt Reaction (DMSR) method. The influence of different salt compositions including eutectic mixture of (KF-NaF), (KF-KCl) and (KCl-NaCl) on the morphology and purity of the reaction products was studied. The obtained samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Furthermore, the formation mechanism of ZrB2 was investigated by DTA/TG. The results show that alongside eutectic mixture of chloride salt, ZrB2 powder can be obtained with eutectic mixture of fluoride salt. In addition, obtained ZrB2 powder without additional salt has hexagonal prism morphology, whereas ZrB2 particles prepared with eutectic mixture of fluoride salt have higher purity and particle size and hexagonal morphology as well. Synthesized ZrB2 Powder in chlorofluoride salt has lower particle size and purity and non-uniform morphology. Synthesized ZrB2 powder is different from starting material in term of morphology and particle size therefore the dissolution–precipitation mechanism may play a dominant role on the synthesis of ZrB2 during DMSR process.