This paper presents the results of the combined study of experiments and modeling of the pitting corrosion behavior of low carbon steel. The effects of pH are elucidated via experiments on low carbon steel exposed to various corrosive media. The corrosion rates for the steel samples immersed in various corrosive media were determined by polarization experiments via a gamry potentiostat. The microscopic observations of the surfaces reveal clear evidence of corrosion pits that increase in size with increasing exposure duration. The observed pit size distribution and the evolution of pit size are modeled using statistical models. The implications of the results are used for the application of low carbon steels in corrosive environment.

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A B S T R A C T Characterization of synthesized cassava leaf nanoparticles (CLNPs 4.96 + 0.25, 3.51 + 0.18 µm, 86.90 + 4.35, 74.50 + 3.73

Synthesis and characterization of cassava bark nanoparticles (CBNPs) was carried out using ball milling at 36, 48, 60 and 72 hours. The morphology study was done using SEM and the Gwyddion software was used to determine the particle sizes from the SEM images. The particle distribution for the un-milled cassava bark (CB) was between 1.25 + 0.06 to 19.92 + 1.00 µm, while after milling for 36, 48, 60 and 72 hours the average particle size were 4.07 + 0.20, 4.00 + 0.20 µm, 80.90 + 4.05, 74.50 + 3.73 nm respectively. 13.68 + 0.68 nm was obtained by XRD using Scherrer equation after milling for 72 hours and the XRD results revealed the presence of compounds such as SiO2, CaCO3 and KAlSi3O8. TEM was used to determine nanoparticle size distribution after milling for 72 hours and the particle size ranged from 9.73 + 0.49 to 114.60 + 5.73 nm for cassava bark nanoparticles (CBNPs), EDX results showed trace element of Si, Ca, K, Fe, Al, O in the CB milled for 72hours.

In an attempt to improve the production of clay bricks for housing and general construction purposes, a 215 X 102.5 X 65 mm manual brick moulding machine was designed and fabricated. The machine parts were made of mild steel, because of its availability and versatile machinability. The efficiency of the machine was examined using local clay, sourced within the University of Ilorin, Ilorin, Nigeria. Water was added to the clay after sieving to form a paste, and then packed into a mould box, before manually rammed and compacted with the machine mould cover. This process allowed for the formation of required shape, which was sent to kiln for baking to obtain stronger bricks. The machine is capable of producing a total of four bricks at a time using the available four mould boxes. The production time of the four bricks was found to be relatively equal to the time used by an automated one to produce equal number of bricks, indicating favourable efficiency. Thus, the fabricated manual machine can be used for mass production of clay bricks for improved and effective housing delivery.

Diamond-like carbon (DLC) coatings have become very attractive for various industrial applications, such as cutting tools, automotive engines, biomedical implants, micro-electromechanical devices (MEMS). Due to their surface energies and ability to interact with lubricants to form surface protective films, good adhesion with substrate, increased wear resistance, improved electrical conductivity, decreased internal compressive stresses during deposition and thermal stability there are used in automobile components. In the automobile industry, DLC coatings are usually applied on combustion engine components such as piston, tappet, camshaft, piston rings and gudgeon pin, valve stem and head and rocker arm. DLC coatings helps in reducing friction and wear of the moving parts. However, there are challenges facing the use of DLC coated components during service, which are; internal compressive stresses, low adhesion and low thermal stability leading to failures such as rolling contact fatigue, micro-pitting, delamination, oxidation and scuffing. Hardness and internal compressive stress increase with increasing sp 3 content (sp 3 /sp 2 ) ratio in DLCs. Internal compressive stress for DLC coatings > 1GPa in tribological applications is not good, due to the elastic strain energy that drives fractures along the coating/substrate interface, leading to delamination through blistering. The addition of non-metals (Si, N, F or O) or metals (W, Cr, Ta, Ti, Mo or Cu) can improve thermal stability of DLC up to about 500 o C. Above, 500 o C transformation of sp3 to sp2 begins to occur leading to graphitization. The addition of metals increases the interfacial fracture toughness and moderates the internal stress by creating two (2) interface; substrate/adhesion layer interface and adhesion layer/functional coating interface. This present paper will discuss the various failures that occur on DLC coatings such as internal compressive stresses, low adhesion and low thermal stability of non-metal and metal doped DLC coatings, regarding their applications in automobile engines. The effect of annealing conditions, tribological properties of non-metal and metal doped DLC, effect of sp3/sp2 ratio, and possible ways of reducing these failures on DLC coatings be discussed also.

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Diamond-like carbon (DLC) coatings are amorphous carbon material which exhibits typical properties of diamond such as hardness and low coefficient of friction, characterized based on the sp3 bonded carbon and structure. The proportion of sp2 (graphetically) and sp3 (diamond-like) determines the properties of the DLC. This coating can be applied to automobile engine component in an attempt to provide energy efficiency by reducing friction and wear. However, DLC coatings are faced with issues of thermal instability caused by increasing temperature in the combustion engine of a vehicle. Therefore, it became necessary to seek ways of improving this coating to meetup with all tribological requirements that will be able to resist transformational change of the coating as the temperature increases. This chapter discusses the need for diamond-like carbon coatings for automobile engine applications, due to their ultra-low friction coefficient (<0.1) and excellent wear resistance (wear rate ~ 7 x 10−17 m3/N.m). The importance of DLC coatings deposited using PECVD technique, their mechanical and tribological properties at conditions similar to automobile engines would also be discussed. Non-metallic (hydrogen, boron, nitrogen, phosphorus, fluorine and sulfur) or metals (copper, nickel, tungsten, titanium, molybdenum, silicon, chromium and niobium) has been used to improve the thermal stability of DLC coatings. Recently, incorporation of Ag nanoparticles, TiO2 nanoparticles, WO3 nanoparticles and MoO3 nanoparticles into DLC has been used. The novel fabrication of diamond-like carbon coatings incorporated nanoparticles (WO3/MoO3) using PECVD for automobile applications has shown an improvement in the adhesion properties of the DLC coatings. DLC coatings had a critical load of 25 N, while after incorporating with WO3/MoO3 nanoparticles had critical load at 32 N and 39 N respectively.