What is the value of water contact angle on silicon?

Silicon is a widely applied material and the wetting of silicon surface is an important phenomenon. However, contradictions in the literature appear considering the value of the water contact angle (WCA). The purpose of this study is to present a holistic experimental and theoretical approach to the WCA determination. To do this, we checked the chemical composition of the silicon (1,0,0) surface by using the X-ray photoelectron spectroscopy (XPS) method, and next this surface was purified using different cleaning methods. As it was proved that airborne hydrocarbons change a solid wetting properties the WCA values were measured in hydrocarbons atmosphere. Next, molecular dynamics (MD) simulations were performed to determine the mechanism of wetting in this atmosphere and to propose the force field parameters for silica wetting simulation. It is concluded that the best method of surface cleaning is the solvent-reinforced de Gennes method, and the WCA value of silicon covered by SiO2 layer is equal to 20.7° (at room temperature). MD simulation results show that the mechanism of pure silicon wetting is similar to that reported for graphene, and the mechanism of silicon covered by SiO2 layer wetting is similar to this observed recently for a MOF

Whey protein aerated gels as a new product obtained using ambient temperature magnesium and iron(II) induced gelation

The objective of the research was to obtain aerated gels by magnesium and iron(II) ion induced gelation of preheated whey protein isolate dispersions. Preliminary research allowed finding conditions of the pH, protein, and ion concentrations to produce aerated gels capable of holding air bubbles. A novel method applying gelation and aeration process simultaneously was used. Aeration using a laboratory mixer at 2000 r.p.m. produced stronger aerated gels than using a homogenizer at 8000 r.p.m. The gelation process was monitored using an ultrasound viscometer and a constant increase of dynamic viscosity was noted. A different aerated gel microstructure was observed for magnesium and iron(II) induced gels, which probably resulted in differences in the texture and viscosity, as well. The aeration process decreased hardness. In some cases texture parameters correlated with the viscosity measured using an ultrasound viscometer. Aerated whey protein gels could be applied as matrices for food applications or to controlled release of active ingredients

Influence of Solution pH on Stability of Fumed Silica–Polyacrylic Acid Systems

The influence of polyacrlic acid (PAA) adsorption on fumed silica (SiO2) surface on suspension stability has been studied. Сhanges in the suspension stability were monitored using a Turbiscan LabExpert with a TLAb Cooler cooling module at 25oC. PAA is an anionic polymer containing carboxyl groups; therefore all the measurements were carried out at different pH 3, 6 and 9. Analysis of obtained transmission and backscattering curves and Turbiscan Stability Indexes (TSI) allowed determination of the most probable mechanism of the system stability.Вивчено вплив адсорбції поліакрилової кислоти (ПAК) на поверхні високодисперсного кремнезему (SiO2) на стабільність суспензії. Зміни стабільності суспензії спостерігались за допомогою приладу Turbiscan LabExpert із охолоджуючим модулем TLAb Cooler при 25oC. ПAК є аніонним полімером, що містить карбоксильні групи, тому всі вимірювання проводились при різних рН (3, 6 та 9). Аналіз одержаних кривих перенесення та зворотнього розсіяння, а також індексів стабільності (Turbiscan Stability Indexes (TSI)) дозволив визначити найбільш вірогідний механізм стабілізації вивчених систем.Изучено влияние адсорбции полиакриловой кислоты (ПAA) на поверхности высокодисперсного кремнезема (SiO2) на стабильность суспензии. Изменения стабильности суспензии наблюдались с помощью прибора Turbiscan LabExpert с охлаждающим модулем TLAb Cooler при 25oC. PAA является анионным полимером, содержащим карбоксильные группы, поэтому все измерения проводились при различных рН (3, 6 и 9). Анализ полученных кривых переноса и обратного рассеяния, а также индексов стабильности (Turbiscan Stability Indexes (TSI)) позволил определить наиболее вероятный механизм стабилизации изученных систем

Influence of polyvinylpyrrolidone adsorption on stability of silica aqueous suspension - effects of polymer concentration and solid content

The influence of polyvinylpyrrolidone (PVP) adsorption on the silica suspension stability was studied. The effects of silica content, polymer addition and suspension dilution with water were examined. The turbidimetry method was applied to examine stability of the investigated systems as a function of time. It was shown that the suspension without polymer was characterized by the smallest stability, whereas the systems containing PVP (before and after dilution) are successively stable. The specific conformation of PVP chains on the solid surface is responsible for the stabilization–flocculation properties of PVP in the colloidal suspension

Analysis of waste mud stability

Drilling fluids play a number of functions, e.g. they remove cuttings, lubricate the drill bits, maintain stability of the hole and prevent the inflow-outflow of fluids between well and the shales. For this reason, they are made of complex polymeric-mineral microcomposites of differentiated chemical and mineralogical-phase content with varying share of colloidal phase in dispersed solid phase in water, i.e. water-based muds (WBM) or oil environment, i.e oil-based muds (OBM). The major factor providing stability of the presented systems is the high participation of clayey minerals (smectite group), long-chain polymers and chemicals stabilizing dispersions. The results of analyses of concentrated dispersions of waste muds from a few regions in Poland are presented inthe paper. These are plastic-viscous dispersions of rheological parameters described most frequently by the Herschel-Bulkley model, the flow of which is connected with deformations of internal structures in the analyzed systems taking place in a function of temperature. There are also presented measurement results of light transmission and backscattering in the analyzed range of temperatures, i.e. 20 to 60°C with the use of Turbiscan Lab., Formulaction. The stability indicator is the turbiscan stability index (TSI)

Development and physicochemical properties of reformulated, high-protein, untempered sugar-free dark chocolates with addition of whey protein isolate and erythritol

The aim of this study was to determine the effect of whey protein isolate (WPI) and erythritol on physicochemical properties of untempered high-protein (16%, 20% and 24% of protein), sugar-free dark chocolates intended for athletes and diabetics. Surface properties were determined from contact angles, roughness and colour analysis. Melting characteristics were evaluated by Turbiscan. Water activity and viscosity were also tested. Higher WPI concentrations produced more hydrophobic surfaces of the samples and slightly increased their surface roughness. Increased whey protein addition improved shelf life, mechanical properties of chocolates and their resistance to melting; however, it had a minor effect on colour coordinates. Confocal microscopy proved the differences in the microstructure, samples with the highest WPI addition demonstrated more packed and denser structure. Application of WPI and erythritol induced an anti-blooming effect, which enabled skipping of tempering operation, and thus contributing to lower chocolate production costs and their improved nutritional profile