Synthesis of zinc borate by inverse emulsion technique for lubrication

Abstract

Lubricating oil additives based on boron compounds are promising materials for lubrication due to their tribological advantages such as antiwear efficiency, good film strength, and high temperature resistance. This article deals with the preparation of zinc borate particles that are well dispersed and colloidally stabilized in mineral oil. This method starts with preparing two inverse emulsions (water-in-oil) with sorbitan monostearate (Span 60) as a surfactant, light neutral oil as a continuous phase, and the aqueous solutions of borax decahydrate (Na 2 B 4 O 7 Á10H 2 O) and zinc nitrate (Zn(NO 3 ) 2 Á6H 2 O) as the dispersed phases. The produced particles were zinc borate crystals having both rod-like and spherical morphologies, and the diameters of spherical particles were changing between 20 and 30 nm. FTIR spectra of the obtained particles showed the characteristic peaks of trihedral borate (B(3)-O) and tetrahedral borate (B(4)-O) groups as well as the specific peaks of the sorbitan monostearate. TG showed 30.42% and 22.08% mass loss at 600°C for the samples prepared by inverse emulsion and precipitation techniques, respectively. The endothermic peak at 50°C is observed due to the melting of sorbitan monostearate and the heat of melting is evaluated as -3.50 J/g. Tribological studies revealed that sorbitan monostearate not only outperformed as a dispersing agent of inorganic particles, but also it proved to be an anti-wear agent. Zinc borate produced by precipitation decreased the wear scar diameter from 1.402 to 0.639 mm and the friction coefficient from 0.099 to 0.064. The inverse emulsion was effective in decreasing wear scar diameter and the friction coefficient by lowering them to 0.596 and 0.089 mm, respectively.

Preparation and Characterization of Copper Borates as Lubricant Additives

“…10. The friction coefficients of the oil without any additive and the oil with 1% Span 60 were reported as 0.99 and 0.066 respectively in a previous study [18]. However, in the present study they were determined as 2.02 and 0.035.…”

“…The wear scar diameter of the fixed ball was 806 µm and 494 µm for mineral oil and mineral oil with Span 60 as seen in Table 6. They were reported to be 1,402 µm, 639 µm in a previous study [18]. Both studies indicated the decrease of the wear scar diameter with Span 60 additive.…”

Dehydration, Water Vapor Adsorption and Desorption Behavior of Zn[B3O3(OH)5] · H2O and Zn[B3O4(OH)3]

“…[1][2][3] Hydrated borates are compounds of boron, oxygen, metals, and hydrogen atoms. The basic elements forming the crystalline structure of the borates are trigonal BO 3 and tetrahedral BO 4 groups that form the fundamental building blocks.…”

“…[1][2][3] Hydrated borates are compounds of boron, oxygen, metals, and hydrogen atoms. The basic elements forming the crystalline structure of the borates are trigonal BO 3 and tetrahedral BO 4 groups that form the fundamental building blocks. [4] The composition of borates can be represented by aM x O Á bB 2 O 3 Á cH 2 O, where a=c ratio is related to the BO 3 :BO 4 [5,6] Zinc borate hydrates are formed in water and the type of zinc borate formed changes with temperature, reactant concentration, and pH.…”

“…[8] The structural formula differentiates the interstitial water and the water present as B-OH in hydrated metal borates. [5,6] For example, industrially important flame retardant zinc borates 3ZnO Á 2B 2 3 ], respectively. [5,6] Zn[B 3 O 3 (OH) 5 ] Á H 2 O has monomeric triborate dianions in its structure.…”