• MATERIALS

    Obtaining abrasives on the base of composite Ni-P coatings for surface treatment of rock materials

    Machines. Technologies. Materials., Vol. 16 (2022), Issue 3, pg(s) 105-107

    The electroless deposition of Ni-P coatings is well known classic method for production of metal coatings on polymers. The addition of dispersed particles of different types and sizes to the base solution for electroless deposition significantly improves the properties of the coating by increasing its wear resistance and micro-hardness. Thereby, the metallized polymers find new and different applications. By using a device, designed and developed in IPC-BAS, tribological tests of composite Ni-P coatings deposited on substrate of polyethylene terephthalate (PET) are performed. Three types of dispersed particles (diamond (D), BN and SiC) are co-deposited in the Ni-P coatings. Their application as abrasive material for surface treatment of rock materials is evaluated. The structure, morphology and elemental composition of Ni-P coatings are characterized by SEM and EDS.

  • MATERIALS

    Analysis of mechanical properties and microstructure of Ti-Al-C composites after spark plasma sintering

    Machines. Technologies. Materials., Vol. 16 (2022), Issue 2, pg(s) 70-73

    Titanium rich alloys of Ti-Al-C and Ti-Al-B system was synthesised by Spark Plasma Sintering (SPS) and Field Activated Pressure Assisted Sintering (FAPAS) methods with altering sintering temperatures in the range of 950°C-1020°C with different current for the duration of 5 minutes. The initial powders of the composite 85%Ti and 15%Al was processed by High Velocity Energy Distribution (HVED) in a solution of kerosene at the specific energy of 25MJ/kg to reduce the size of the particles to nano-scale. This method of using different parameters of production technology have helped to analyse the most efficient, energy saving, and less waste generation technological process with improved mechanical properties. The metal-based samples were examined by optical and electron microscopy. Mechanical properties of composites were determined by measuring microhardness.
    The aim of the investigation was to determine the dependence between parameters of production technology and properties of Ti-AlC composites.

  • MATERIALS

    Investigation on the efficiency of internal crystallization chemical admixtures for cement concrete – structural characteristics

    Machines. Technologies. Materials., Vol. 14 (2020), Issue 3, pg(s) 124-128

    In recent years, the use of internal crystallization chemical admixtures for concrete and mortar to increase their water-tightness and other physical and mechanical characteristics has been of increasing importance in modern construction. These types of chemical modifiers allow for the effective replacement of conventionally performed waterproofing works (membranes, rolls, brushed or sprayed coatings, etc.) by purposefully improving the physical-mechanical characteristics of structural concretes, rendering them, to one degree or another, impermeable to water or/and aggressive agents from different origins. In the specialized world market for such products there are several leading competing companies – producers of internal-crystallization chemical admixtures, which have different activity in Bulgaria. Based on results of purposeful set of structural investigations (DTA, SEM, BET) conducted the purpose of the report is to assist participants  in the construction investment process in understanding the nature, specific characteristics and differences in the performance (effectiveness) of different products in terms of their ability to limit the ingress of water into concrete and reinforced concrete sections, as well as their ability to increase the durability of concrete as the main structural material.

  • MATERIALS

    SURFACE MORPHOLOGY AND WETTABILITY OF GRADIENT (Ti,Al,V)N/TiO2 COATING

    Machines. Technologies. Materials., Vol. 11 (2017), Issue 12, pg(s) 599-603

    Physical surface properties including surface roughness, topography, morphology, and wettability could influence the implant material behavior, bio-response, bacterial contamination and contact with other bio-active surfaces or fluids. This work investigates microand nanoscale roughness parameters and surface morphology of PVD deposited (Ti,Al,V)N/TiO2 coating using optical microscopy, white light interferometry (WLI), contact profilometer and scanning electron (SEM) microscopy. Results indicated that vacuum oxidized surface possessed medium roughness values, anisotropy in surface texture and irregular morphology. The vacuum oxidation of the nitride maintained the oxide with nano-crystal size and showed pores at the interface between the layers. The effect of prolonged exposure to Ringer-Braun solution droplet on the modified crystalline structure of the oxide was also explained.