Papers by Keyword: pH Value

Abstract: The influence of temperature, flow rate, PH value, and oxygen content on the corrosion law in the carbon dioxide salt solution of J55 oil casing was investigated by the corrosion weight loss method. The results showed that with the increase of temperature, the corrosion rate of J55 steel first increased and then decreased and the corrosion rate reached the maximum at 100°C. The corrosion rate was closely related to the formation of corrosion products. The increase of the flow rate speeded up the transfer rate of the corrosive medium to the metal surface and hindered the formation of FeCO₃ on the metal surface. The corrosion rate was significantly higher than the corrosion rate under static conditions, and as the flow rate increased, the corrosion rate of J55 steel increased accordingly. The increase of the pH value gradually reduced the concentration of hydrogen ions, and cathodic reaction of hydrogen ion depolarization during metal corrosion process was inhibited, and the tendency to form an oxidizing protective film on the surface of carbon steel increased, thereby reducing the corrosion rate of metals. With the increase of oxygen content, there were both hydrogen evolution reaction of CO₂ and oxygen absorption reaction caused by O₂ in the cathode process. The corrosion rate of J55 steel gradually increased, and at the same oxygen content, the higher the carbon dioxide content, the greater the corrosion rate is.

Abstract: This research investigates the effect of surface roughness, water temperature, and pH value on the wettability behaviour of copper surfaces. An electron beam physical vapour deposition technique was used to fabricate 25, 50, and 75 nm thin films of copper on the surface of copper substrates. Surface topographical analysis, of the uncoated and coated samples, was performed using an atomic force microscopy device to observe the changes in surface microstructure. A goniometer device was then employed to examine the surface wettability of the samples by obtaining the static contact angle between the liquid and the attached surface using the sessile drops technique. Waters of pH 4, 7, and 9 were employed as the contact angle testing fluids at a set of fixed temperatures that ranged from 20°C to 60°C. It was found that increasing the deposited film thickness reduces the surface roughness of the as-prepared copper surfaces and thus causing the surface wettability to diverge from its initial hydrophobic nature towards the hydrophilic behaviour region. A similar divergence behaviour was seen with the rise in temperature of water of pH 4, and 9. In contrast, the water of pH 7, when tested on the uncoated surface, ceased to reach a contact angle below 90^o. It is believed that the observed changes in surface wettability behaviour is directly linked to the liquid temperature, pH value, surface roughness, along with the Hofmeister effect between the water and the surface in contact.

Abstract: The effects of the ratio of magnesium to phosphorus (Mg/P) on the compressive strength, bond strength, drying shrinkage and pH value of magnesium phosphate cement (MPC) were investigated. The results show that the consistent effect of the ratio of Mg/P on compressive strength and bond strength, as the ratio increases, the strengths are both first increased and then decreased, and the best ratio is 3:1. For setting time and drying shrinkage, the effects of the ratio of Mg/P are both obvious. Mainly manifested as the increase of the ratio, all of them show a decreasing trend. And the setting time can be shortened by 78%, furthermore, 28d the maximum drying shrinkage rate can be reduced by 29%. The effect of the ratio of Mg/P on pH value is mainly that when the ratio increases, the time of the inflection point of pH value is obviously advanced, and their final pH value is close.

Abstract: Bismuth vanadate (BiVO₄ ) powders were synthesized using Bi (NO₃)₃.5H₂O and NH₄VO₃ as raw materials, NaOH and HNO₃ for pH adjustment. The samples were characterized by X-ray diffraction ( XRD ), scanning electron microscopy (SEM ) and UV-vis diffuse reflectance spectra techniques. The results show that the pH of precursor solution has great effect on the composition and morphology of products. Synthetic product was BiVO₄ with two kinds of crystal shape ( monoclinic and tetragonal ) with pH of 3; synthetic product was pure monoclinic phase BiVO₄ when the pH is between 5-9. Whereas, V₂O₅ and Bi₂O₃ appeared when the pH was 11; synthetic product was a mixture of V₂O₅ and Bi₂O₃ with pH of 13, and BiVO₄ don’t exist. The photocatalytic activity was evaluated by the degradation of methylene blue solution. It is shown that the synthetic sample has the best photocatalytic ability with pH of 5. The degradation of methylene blue reaches 84.7% when irradiated for 240 min by high pressure mercury lamp, and the sample synthesized at 13 for pH has strong adsorption capacity and poor photocatalytic ability.

Abstract: TiO₂ nanocrystalline powders were prepared by sol-gel method with different process parameters. The phase, morphology and the luminescent property of TiO₂ nanocrystalline powders were characterized by XRD, SEM and PL, respectively. The results indicated that the synthesized TiO₂ nanocrystalline powders were transformed from anatase into rutile with the increasing of heat treatment temperature, which begin at the temperature of 500 oC and was almost completed at the temperature of 700 oC. And with the increasing of pH value the rutile proportion become larger, the nanograins become fine and powders agglomeration was decreased. The good performance TiO₂ nanocrystalline powders were obtained when prepared temperature was 500°Cand pH value was 4. PL results show broad and strong luminescence band appeared near 470nm when TiO₂ nanocrystalline powders were excited at 325nm at room temperature.

Abstract: The effects of borax on the setting time, compressive strength, bond strength, drying shrinkage and pH value were investigated for potassium magnesium phosphate cement (MKPC). The results show that with the increase of borax dosage, the setting time is gradually extended, both compressive strength and bond strength are greatly decreased, the drying shrinkage rate is increased. Especially high dosage of borax, the extension of setting time is more obvious. Compared with that without borax, when the dosage of borax is 12.5%, setting time can be prolonged by 214.8%.The influence of borax dosage on the time-dependent effect of compressive strength shows that when the dosage of borax is 2.5%~5.0%, compressive strength increases rapidly from 4h to 1d, and increases relatively slowly from 1d to 3d. When borax dosage is less than 2.5% or higher than 5%, the law of time-dependent effect of compressive strength is the opposite. Compared to borax prior to magnesia addition, the pH value of the system is larger and the time of inflection point is advanced when borax and magnesia are mixed together at the same time. The increase of borax dosage can reduce the pH value of the system, and decrease the rising rate of pH value, at the same time the required time when the final pH value is relatively stable is longer.

Abstract: Light, primarily its more energy-rich component - near ultraviolet radiation, causes gradual degradation (ageing) of paper and other organic based materials. The objective was to determine selected characteristics of the changes of white office paper, which occur under intensive ultraviolet treatment, and to calculate their light fastness, as this is an important functional feature for the number of papers. The most visible sign of paper ageing is the change of its optical characteristics. The value of specific lightness decreased by 2.2%, red / green coordinate a* moved from the red region (1.5) colour space to green (-0.8), b* coordinate moved from the blue region (-8.4) to yellow (4.7) and colour difference ΔE* reached 13.4 during 120 minutes' exposure. The pH values of paper surface gradually decreased with time of UV exposure from 8.86 to 7.91. Effects of light also deteriorated the selected mechanical characteristics of paper, such as breaking length and tear index. Out of the monitored properties, the specific lightness of paper surface showed the greatest stability (97.8%). UV radiation most affected breaking length of paper whose stability was only 79.4%.

Abstract: The development of the city traffic and its increasing traffic flux are the signs of the development of the society, but causing a serious pollution on the city's ecological environment. Cement hydration reactions are needed to generate Ca (OH)₂, C-S-H gel, and AFt, as well as other hydrated products. Meanwhile, heavy metal ions are contained and fixed in a cement paste under physical encapsulation, absorption, isomorphous replacement, and double decomposition. This paper mainly discusses the impact of hydration environment on the adsorption law of materials adsorbing heavy metal ions and the adsorption mechanism under different pH values and temperatures, analyzing specific reasons from the perspective of micro-structure. Through the analysis it can be seen that, in addition to zinc ions, the cement-based materials’ capacity of adsorbing heavy metal ions increases as the pH value and the temperature increase. Micro-structure analysis shows that cement-based materials’ main adsorption methods are different when pH values are different.

Abstract: Abstract: This paper use zeta potential test and dynamic viscosity test to research the influence of different factors such as pH value, mass fraction of solid phase and dispersant content on the liquidity of Al2O3 slurry. The test results show that, when the solid-phase mass fraction and particle size are given, the absolute value of zeta potential increases with the rise of pH value, raise at first then descrease with the adding of (NaPO3)6. This article analyzes the phenomena from a legal point of electric double layer effect. The results of liquidity test are consistent with zeta potential test. The optimum value of pH value, mass fraction of solid-phase and dispersant content are determined by formulation design. The study develop a Al2O3 slurry with high fluidity which has an important significant in slip casting process of Al2O3 ceramics.

Abstract: The ultra-thin 304 stainless steel sheet will be used in flexible displays for substrate material. In chemical mechanical polishing of ultra-thin stainless steel, the pH value of polishing slurry has an important influence on the material removal rate (MRR). In this paper, the influences of pH regulator in slurry on MRR had been studied in CMP of ultra-thin 304 stainless steel based on alumina (Al₂O₃) abrasive in acidic polishing slurry. The research results show that, in the same conditions, different pH value had a different chemical action mechanism and a different MRR. And also, different oxidant with pH regulator had a different chemical action mechanism and a different MRR. The research results can provide the reference for studying the slurry in CMP of ultra-thin stainless steel.