Increasing Soaking Time Research Articles

Effect of acid corrosion on properties of composite insulator core rod

In recent years, there have been a number of composite insulator decay-like fracture faults characterized by resin degradation and irregular fracture morphology, which seriously threaten the safety and stability of power system. At present, the research of composite insulator’s decay-like fracture is still in the initial stage at home and abroad, and there is no clear conclusion on the causes of its fracture, influencing factors and other important scientific and technical issues, and there is no unified understanding of the mechanism of decay-like fracture. In view of the above problems, this paper carries out acid corrosion test on core rod samples to explore the corrosion law of nitric acid on core rod and its influence on properties. The results show that acid corrosion is one of the factors causing the degradation of epoxy resin. With the increase of nitric acid concentration and soaking time, the degradation rate of epoxy resin accelerates, and the core rod sample gradually changes from emerald green to yellowish brown, then to light yellow, and finally to white hair like glass fibre. The effect of the sample under the long-time action of low concentration nitric acid is the same as that under the short-time action of high concentration nitric acid. Nitric acid will continuously erode into the core rod, resulting in the decrease of hardness and performance on the core rod surface.

Effect of Soaking Time and Sb2O3 Concentration on Number of Bubble and Optical Properties of Borosilicate Glasses

Borosilicate glasses were fabricated with antimony oxide (Sb2O3)-doped in the formula of SiO2-B2O3-Na2O-CaO-ZnO, by using the melt-quenching method at 1200 °C which various soaking time of 3, 4, 5, 6, and 7 h. The results show that the density, molar volume and refractive index of glasses increased with increasing of Sb2O3 concentration. However, the density of glasses decreases with increasing soaking time. The transmittance spectra present the absorption around 1050 nm and 450 nm which corresponds to Fe2+ ion and Fe3+ ion, respectively. This absorption strength decreases with increasing Sb2O3 concentration which shows the highest strength at 0.0 mol% of Sb2O3 content. Moreover, the decrease in the number of bubbles in the glass is dependent on the increase of the Sb2O3 concentration and soaking time.

Effect of Spheroidization Treatment on Friction Stir Processing of Al- 14 wt.% Si Alloy

Three different rotational speeds (800, 1000 and 1250 rpm) and traverse speeds of (0.42 mm/sec) at a constant taped pin have been employed to produce the stir zones generated from friction stir processing (FSP) of near eutectic Al- 14 wt.% Si alloy. The processed samples were thoroughly analyzed macroscopically and microscopically. The as-cast microstructure of eutectic (α Al+ Si) and primary Si were fragmented to produce spheroidization of small size of Si and deformed matrix. The stir zones showed an increase in hardness from around 45-50 Hv for as-cast to 40-65 depending on the variables applied. All the processed samples were characterized by advanced and retreated regions with large single piping defects formed mainly at the retreated region. High temperature spheroidization at 500 oC with two soaking times of 10 and 20 hrs was applied for the processed sample of 1000 rpm to investigate the effect of heat treatment on the silicon fragmentation and hardness. Growth and fragmentation of Si have taken place at soaking time of 10 hrs. At soaking time of 20 hrs noticeable microvoids and macrovoids were formed at the stir zones. Microhardness of both the advancing and the retreating regions decreased with increasing soaking time.

Molecular structure characterization of coal under the water–rock interaction in acid mine drainage (AMD)

AMD weakens the compressive strength of coal pillar and threatens the safety of coal mine production. In order to study the effect of AMD on coal, this paper uses X-ray diffraction (XRD) and Fourier transform infrared (FTIR) test techniques to detect the molecular structure of coal samples treated with different immersion acidity and immersion time. The results show that with the increase of soaking acidity and soaking time, the layer spacing (d002) from 0.349 to 0.353 and La from 55.719 to 57.420 nm, showing a positive correlation; Lc from 1.85 to 1.66 nm and N from 5.31 to 4.71, showing a negative correlation. It shows that the original microcrystalline structure in the coal sample changes due to the chemical reaction of organic matter, the spacing and average diameter of the microcrystalline layers increase, the average height and the number of carbon layers decrease, and the degree of order gradually decreases. Aromatic hydrogen(farH), aromatic carbon(farc), the relative abundance of aromatic and aliphatic functional groups(I) and A(CH2)/A(CH3) gradually decrease, degree of condensation (DOC) and oxygen-containing structural(‘C’) gradually increase. The research results show the molecular structure characteristics of coal in AMD water–rock interaction, and provide a reference for studying the macroscopic characteristics of coal under the action of AMD.

Effect of CO2 soaking time on replacement efficiency and reservoir properties of tight oil and gas reservoirs

In dry fracturing, CO2 enters a tight reservoir as the fracturing fluid and replaces the oil and gas therein by soaking. This enhances the oil and gas recovery and enables CO2 storage, thus reducing CO2 emissions and yielding the dual benefits of environmental protection and improved oil field production. The macroscopic benefits of soaking oil and gas reservoirs with CO2 are evident; however, there are few studies on the micro-erosion effect of CO2 on the pore throats of reservoirs during the replacement process. In this context, this study analyzed the influences of soaking time and permeability on the CO2 displacement efficiency in terms of the macroscopic displacement. The effects of CO2 displacement on the pore throat morphology, mineral composition, and fluid distribution of oil and gas reservoirs were qualitatively and quantitatively studied by scanning electron microcopy (SEM), mineral composition testing by X-ray diffraction, and fluid distribution scanning by computed tomography. The corrosion reaction between CO2 and rocks during the replacement process was chemically analyzed. The results showed that: (1) The CO2 replacement efficiency in the tight oil reservoirs was <20% under the same soaking time. The displacement efficiency increased by less than 3% with increasing soaking time. As the core permeability increased, the displacement efficiency increased as much as 15%–20%. In the gas reservoir, the replacement efficiency was >75%, and the weight of influence of the soaking time on the CO2 replacement efficiency was slightly greater than that of the core permeability; however, their difference was not significant. (2) The SEM, XRD, and CT scanning results showed that the pore morphology of the core is dissolved and blurred after CO2 replacement. The main eroded mineral component in the core was calcite. The porosity of the core increased after erosion, particularly near the fracture. The greater the distance from the crack, the lower the efficiency of CO2 dissolution and replacement to the pores by diffusion. (3) The analysis of the reaction mechanism between CO2 and rocks showed that CO2 dissolves and diffuses into the pore fluid in the post-pressure soaking stage, thus expanding the crude oil and acidifying the formation water. The generated carbonated fluid dissolves in the reservoir rock to some extent, which can appropriately increase the porosity and permeability of the reservoir rock. This paper provides a reference for the qualitative and quantitative study on the mechanism of macrocosm and microcosm replacement after CO2 dry fracturing.

Evolution of Unidirectional Solidification Microstructure and Hydrogenated Treatment of Nb-Ti-Co Quasiperitectic Alloys

Titanium alloys have a wide range of applications, and the internal placement of hydrogen into them can modulate the microstructure of the alloys and thus have great potential for further development. However, few studies have been reported on the application of this technique to Nb-Ti-Co ternary alloys, which needs to be urgently investigated. In this paper, four types of alloys (Nb10Ti61Co29, Nb15Ti55Co30, Nb20Ti50Co30, and Nb25Ti50Co25) are selected near the eutectic point of the phase diagram to study their placement of hydrogen by both static and dynamic processes of hydrogen’s placements, focusing on the effects of the temperature, time, and hydrogen-flow rate of such processes on the amount of hydrogen placements. The relationship between the hydrogen replacement parameters and the mechanical properties of the alloys is constructed. The results show that the placed-hydrogen amount of Nb-Ti-Co as-cast alloy grows with the increase of hydrogen-flow rate and soaking (or holding) time, with an upper limit of the placed-hydrogen amount, and the pattern of the directionally- solidified alloys is similar to that of the as-cast alloys; however, at a certain soaking time and hydrogen- flow rate, although the placed hydrogen amount of both alloys rises with the increase of temperature, the placed-hydrogen amount of Nb-Ti-Co directionally-solidified alloys is always larger than that of the as-cast alloys. However, the amount of hydrogen placement in the Nb-Ti-Co directionally-solidified alloys is always larger than that in the as-cast alloys, and the amount of hydrogen placement decreases significantly as the growth rate of the alloys increases. In addition, the microhardness decreases with increasing growth rate in the directionally-solidified specimens, and the amount of hydrogen placement and microhardness increase with growing Nb content.

External Corrosion Behavior of Steel/GFRP Composite Pipes in Harsh Conditions.

In this study, we report on the corrosion behavior of hybrid steel/glass fiber-reinforced polymer (GFRP) composite pipes under harsh corrosive conditions for prolonged durations. Specimens were immersed in highly concentrated solutions of hydrochloric acid, sodium chloride, and sulfuric acid for durations up to one year. Detailed qualitative analysis using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and energy-dispersive X-ray spectroscopy (EDX) is presented. It is shown that the hybrid pipes have excellent corrosion resistance with a corrosion rate of less than 1% of the corrosion rate for conventional steel pipes. That low corrosion rate can be attributed to the formation of pores in the GFRP layer due to increased absorption and saturation moisture in the material with increased soaking time. This can be reduced or even prevented through a more controlled process for fabricating the protective layers. These promising results call for more utilization of GFRP protective layers in novel design concepts to control corrosion.

Development of a Snake Gourd Seed Decorticating Machine

Aims: A snake gourd seeds sheller which comprises of hopper, decorticating chamber, and the cleaning chamber was designed, fabricated and evaluated in this study.&#x0D; Methodology: A 3-level factorial response surface methodology (RSM) of design expert version 6.0.8 of 2002 was used to identify the relationship between the response functions and the process variables of the device. The factors considered are shaft speed (300, 350, 400 rpm), soaking time (8, 15, and 20 minutes.), hammer diameter (115, 135 and 150 mm) and feed rate (90, 120, 150 kg/hr.) in the determination of shelling efficiency while air speed (2, 4, and 6 m/s) and angle of air injection (20, 40, 600) were used in the determination of cleaning efficiency.&#x0D; Results: The shelling efficiency was observed to increase with increase in hammer speed, hammer diameter and soaking time but decreased with increase in machine feed rate. The maximum shelling efficiency of 97.61% was recorded when the soaking time is 20 minutes, hammer speed is 400 rpm, hammer diameter is 150 mm and feeding rate is 90 kg/hr. The cleaning efficiency increases with increase in air speed and angle of air injection. The cleaning efficiency of the machine was found to be 92.5 % when the angle of injection and air speed is 600 and 5.0 m/s respectively. The effect of the speed and the angle of injection was found to be significant (p&lt;0.05).&#x0D; Conclusion: The study concluded that with the result of the performance evaluation of the machine, it is suitable for inclusion in the process line for the seed and hence its potential could be harnessed.

Study on mechanisms and influencing factors of the inter-fracture asynchronous huff-n-puff technology of horizontal well in the tight oil reservoir

Tight oil reservoirs have become an important alternative oil resource, and the geological reserve of tight oil reserves is abundant. Currently, the tight oil reservoir is mostly developed by volumetric fractured horizontal wells with the elastic drive of natural energy. However, because there is no energy supplement, the production of volumetric fractured horizontal well declines rapidly, and the final recovery ratio is low. The water huff-n-puff technology is the common method for the energy supplement of the horizontal well. In order to improve the oil recovery of the inter-fracture residual oil in the later stage of water huff-n-puff development of the volumetric fractured horizontal well, mechanisms and influencing factors of the inter-fracture asynchronous huff-n-puff technology of the horizontal well is studied in this paper. Results show that the inter-fracture displacement and the capillary imbibition are mechanisms of the inter-fracture asynchronous huff-n-puff technology of horizontal well. Moreover, The cumulative oil production of horizontal well of the inter-fracture asynchronous huff-n-puff technology decreases and tends to be stable gradually with the increase of the injection rate and increases approximately linearly with the increase of injection volume. With the increase of soaking time, the cumulative oil production of horizontal well of the inter-fracture asynchronous huff-n-puff technology increases and tends to be stable gradually. The increase of production rate leads to the decrease of the cumulative oil production of horizontal well of the inter-fracture asynchronous huff-n-puff technology. The inter-fracture asynchronous huff-n-puff technology of the horizontal well is an efficient method to improve the development effect of water huff-n-puff of horizontal wells, and the study provides a certain guidance for improving the development effect of water huff and puff.

Evaluation and optimization of various treatment methods for enhancing the properties of brick-concrete recycled coarse aggregate

Crushed brick-concrete recycled aggregate (BCRA) represents a sustainable and environmentally friendly alternative to natural aggregates (NAs) in practical engineering. However, compared with NA, the high porosity and low strength of BCRA means it struggles to meet engineering requirements, which limits its large-scale application. This paper reports upon an experimental study to enhance the quality of BCRA via soaking in different types of solutions (pozzolanic materials, sodium silicate, polyvinyl alcohol, and silicon-based additive). The physical and mechanical properties of treated and untreated BCRA were evaluated by testing the apparent density, water absorption, and crushing value. Meanwhile, the optimization schemes for different treatment techniques were recommended using the multi-objective grey target decision method. In addition, the surface morphology of BCRA was characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy, to examine the microstructure of the BCRA surface before and after different treatment processes. The results show that 80% cement, 10% fly ash, and 10% silica fume slurries had notable effects on the apparent density and mechanical strength of BCRA, in which the apparent density increased by 0.6–1.8% and the crushing value decreased by 3.5–19.7%; however, the water absorption of BCRA increased by 1.7–8.5%. The physical and mechanical properties of BCRA increased under an increase of sodium silicate concentration and soaking time, though its strengthening effects were limited. Polyvinyl alcohol and silicon-based additives were best able to improve the waterproofing of BCRA, and the water absorption of the BCRA after treatment was reduced by 5.1–17.8% and 30.5–44.9%, respectively. Clear microstructural improvements can also be observed on the treated BCRA surface. To summarize, the BCRA treated by the four treatment methods exhibited surfaces that were denser, less porous, and more homogeneous and regular. These results will provide a useful reference for the future engineering applications of treated BCRA.

Effect of water content on oxidation activity of residual coal in Goaf

In order to study the effect of water on the oxidation activity of residual coal in goaf, FTIR experiment was used to analyze the effect of water quality on the oxidation functional groups of coal under different soaking time; The experimental results show that based on the change trend of oxidation functional groups of coal in acidic and alkaline environment, the change of acidity and alkalinity of water will lead to the increase of - Oh peak area of coal sample; With the increase of soaking time of weak alkaline mine water, the content of Oh in coal sample is higher; The peak area of main oxidation functional groups of coal first increases and then decreases with the increase of soaking time.

Interface between FGH96 Superalloy and Refractory Slurry with Different Soaking Time

In this paper, the contact interface between FGH96 superalloy melts and refractory slurry with corundum powder and silica sol at 1600°C with different soaking time in 10-240 min range was investigated. The morphology and composition of the contact interface were studied by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the reaction layer formed on the contact interface between the melting superalloy and the refractory slurry, and is mainly consist of Alumina and contains a small amount of other metal elements such as Ti and Cr. The reaction layer was not smooth on the micro level, and there was a peninsula-like structure protruding into the internal part of the melting superalloy on the reaction zone, and even started to fall off at some places to form islands. With the increase of soaking time, the reaction between melt of superalloy and refractory slurry increased gradually and the reaction layer began to combine with the refractory slurry substrate and form obvious interaction layered structure, resulting in the corrosion of refractory slurry substrate. With the soaking time over 120 min, the stable contact interface was destroyed. Thermodynamic calculation shows that the substitution reaction between Al in superalloy and SiO2 in refractory slurry meets the thermodynamic conditions, and the reaction can proceed forward.

Effect of Slice Weight and Soaking Time on the Physico-Chemical Properties of Cassava Flour (Manihotesculentus) used for Bakery Products

Quality cassava(Manihotesculentus, Crantz) flour is often influenced by process variables such as slice weight and soaking time which may affect its nutritional quality. In this study, the effect of process variables (slice weight and soaking time) on quality of cassava flour was carried out. Cassava root was peeled, washed and cut into varied sizes (25.86 - 54.14 g) and soaked at varied time (7.03 - 40.97 h). The proximate composition, physical and chemical properties of the flour were carried out using standard methods. The result in our findings showed that slice weight and soaking time had significant increase (p&lt;0.05) on the proximate and physico-chemical properties of the flour.The amylose and amylopectin content of the flour increased with increasing soaking time while the hydrogen cyanide content decreased with increase in soaking time. Overall, the quality cassava flour displayed desirable properties for its incorporation into baked goods.

A new method for weakening slaking of collecting eroded aggregates by water erosion

In most of previous studies about aggregate breakdown caused by water erosion, a critical process that water inevitably fragments the eroded aggregates by water erosion again is generally ignored. This will reduce the accuracy of research results. Hence, alcohol has been added to the collecting device of eroded aggregates to weaken the slaking of eroded aggregates by the researchers, but the optimal alcohol-to-water ratio for protecting the size fraction distribution of eroded aggregates remains unclear. Aggregate with a size fraction of 2–5 mm obtained by dry sieving of black soil in Northeast China was selected as the research object to analyse the effects of five alcohol-to-water ratios on aggregate characteristics and their variation with soaking time. The results showed that the size distribution in terms of mass percentage under different soaking times was similar. For the same soaking time, the mass percentage of 2–5-mm aggregates gradually decreased with decreasing alcohol ratio, but the aggregates with the second-highest mass percentage were gradually distributed among smaller size fractions. Compared with the alcohol soaking aggregates, the mean weight diameter (MWD) of the aggregates soaked in the other ratio of alcohol-to-water decreased gradually with the increase of soaking time, and the disintegration of the aggregates was the most evident at the initial stage of soaking. A percentage of aggregate destruction (PAD) of 20% served as the dividing line to evaluate the stability of soil aggregates. In this case, eroded aggregate collection should be completed within 12 min at an alcohol-to-water ratio of 1:1. Alternatively, eroded aggregate collection should be completed within 6 min at an alcohol-to-water ratio of 2:3. The above results can provide a reference for improving the accuracy of data collection regarding eroded aggregates. Especially in the study of water erosion which needs to collect eroded aggregates, alcohol can be added to the collecting device before the experiment. The amount of alcohol should be added according to the amount of water that may be generated, so as to protect eroded aggregates and weaken the slaking of eroded aggregates.

Influence of Acidic Substances on Compression Deformation Characteristics of Loess

Current research theories on acid-contaminated soils indicate that acids can alter the physical properties of soils, which in turn can affect their engineering mechanical properties. However, compressibility, one of the most important mechanical properties of loess, may be affected by acidic substances. To investigate the influence of acid on the compression properties of loess, this study uses a uniaxial compressor to investigate the changes of compression properties of loess under different acid concentrations and different acid immersion times and attempts to predict the causes of macroscopic compressibility changes from the microscopic pore changes of acid-etched loess. The test results show that when the soaking time is the same, the hydrochloric acid concentration increases from 0 to 3.0 mol/L, the compression coefficient Cc increases by 43.20–87.5%, and the compression yield stress σpc decreases by 51.36–60.86%; when the concentration of hydrochloric acid is the same, the soaking time increases from 1 day to 12 days, the compression coefficient Cc increases by 119.05–197.46%, and compressive yield stress σpc decreases by 10.67–22.02%. The microscopic images of loess soaked for 12 days at 3.0 mol/L hydrochloric acid concentration were compared with those of the original loess. The percentages of micropore, small pore, mesopore, and macropore areas of original loess were 20.90%, 79.10%, 0%, and 0%, respectively. The percentages of micropore, small pore, mesopore, and macropore areas of acid-etched loess were 6.24%, 37.21%, 1.14%, and 55.40%, respectively. The enhancement of the compressive properties of acid-etched loess is the result of the coupling of acid concentration and soaking time, and the change of macroscopic compressive properties may be related to the increase of microscopic macropore area after acid erosion. The results of this study can be used as a reference for the study of soil mechanical properties in acid-contaminated soils.

OPTIMISATION OF CONDITIONS FOR BARNYARD MILLET GERMINATION

Development of foods that promote health and wellbeing is one of the key priorities of food industry. Barnyard millet, important minor millet is highly digestible (81.13 per cent) and contains fair amount of protein (12 per cent) coupled with low carbohydrate (58.56 per cent) of slow digestibility (25.88 per cent). The nutritive value and taste of barnyard milled can be improved by germination. The present study concentrates in the optimization of conditions for barnyard millet germination to maximise the nutritive value and overall acceptance. The barnyard millet was cleaned, soaked in water with varying time intervals followed by 24 hrs germination. The dried grains were powdered, sieved and then subjected to organoleptic evaluation. The parameters such as moisture absorption, sprout length, malt yield and germination percentage were worked out. Based on organoleptic evaluation, the germinated barnyard millet flour, 10hrs soaking and 24 hrs germination was found to be the best and utilized for the production of value added products. As the soaking time increases (4 to 18hrs) the moisture absorption increases from 35.16 and 54.12 per cent. The sprout length reaches a maximum of 0.4 cm at 18hrs of soaking. The malt yield differs from 59.62 to 71.54 per cent with respect to soaking time.

Microstructure and mechanical property evolution of post weld heat treated bainitic steel welds

Abstract The achievement of excellent combination of high tensile strength and good ductility has been the key factor that facilitates the Advanced High Strength Steels (AHSS) to be the candidate materials for automotive applications. Carbide free bainitic steels are a class of AHSS that primarily have microstructure consisting blend of fine bainitic laths and interwoven retained austenite in the interlath boundaries of bainite. Solid state welding techniques are regarded to be the most sought after fabrication processes as they result in retention of basic microstructural constituents, especially nonequilibrium phases like bainite. Keeping this fact in view, friction stir welding was carried out on 3 mm thick carbide free bainitic steel plate with varying tool rotational speeds. The temperatures of stir zones were recorded. The microstructural changes and phase analysis from base metal (BM) to Thermomechancally Affected Zone (TMAZ) and Stir Zone (SZ) were studied. The microhardness profiling was done across the weld covering the BM, TMAZ and SZ. The abrupt increase in the hardness of stir zone and microstructure stability i.e., retention of bainitic microstructure along with the retained austenite were observed. The tool rotational speed of 150 RPM has been optimized. Post weld heat treatments were undertaken at different temperatures and increased soaking time on the welded samples of optimized rotational speed to facilitate bringing down the stir zone hardness to the base metal. Basing the phase analysis and EBSD data obtained, the post weld heat treatment cycle conducted at 500OC with a soaking time of 1 h has been optimized.

Effects of forming temperature, soaking time and dwell time on the microstructure and mechanical properties of thixoformed nickel-based superalloy parts

Thixoforming has unique characteristics over the traditional casting and forging processes, but there is few research focusing on thixoforming of nickel-based superalloys. In this paper, nickel-based superalloy GH4037 parts were successfully formed by thixoforming with different parameters. The effects of forming temperature, soaking time and dwell time on the microstructure and mechanical properties of the formed parts were investigated. The results indicated that forming temperature and soaking time exerted a crucial role in microstructure evolution. With the increase of temperature and soaking time, the proportion of liquid phases in the microstructure increased. During thixoforming, liquid phases were squeezed from the middle region to the peripheral region, resulting in more liquid phases at the edge of the parts. MC-type carbides rich in Ti, V, W and Mo were observed in the liquid phases. When semi-solid billet was heated at 1380 °C for 30 min, the best mechanical properties including an ultimate tensile strength of 973 MPa, a yield strength of 634 MPa and an elongation of 45.6% were achieved. The dwell time had a slight effect on the microstructure and mechanical properties of the parts. The fracture surfaces of the tensile specimens exhibited mostly dimple surfaces and presented a transgranular ductile fracture mode.

Characterization of the Dynamic Imbibition Displacement Mechanism in Tight Sandstone Reservoirs Using the NMR Technique

An experimental technique is developed to investigate the dynamic imbibition displacement mechanism in tight sandstone formations of the Yanchang group of the Ordos basin. By combining the dynamic imbibition core flooding experiments and NMR technique, the effects of the injection volume and rate on displacement efficiency are investigated. Moreover, the displacement efficiency of dynamic imbibition is compared with that of static imbibition. This study gains insights into the micromechanisms of dynamic imbibition in tight sandstone formations. It is found that the relative displacement efficiency of dynamic imbibition increases with the increase of injection volume. But the increment amplitude decreases with the increase of injection volume. With the same injection volume, the core displacement efficiency of dynamic imbibition with high permeability is obviously improved. However, the core displacement efficiency decreases rapidly with the increase of injection volume. Optimal injection volumes are recommended for tight sandstone formations with different permeabilities. With the increase of the displacement rate, the core displacement efficiency of dynamic imbibition shows a trend of first rising and then declining. There exists an optimal displacement rate in dynamic imbibition displacement, and the optimal displacement rate almost linearly increases with the increase of core permeability. The static imbibition displacement efficiency increases with the increase of soaking time, but the increment amplitude slows down obviously. The displacement efficiency of static imbibition in small pores is higher than that of dynamic imbibition. The displacement efficiency of dynamic imbibition in large pores or microcracks is significantly higher than that of static imbibition. This study provides theoretical support for the optimization and improvement of the waterflooding recovery process in tight sandstone reservoirs.

Hydrophobic treatment of bamboo with rosin

Bamboo is an eco-friendly and sustainable material that has great potential in construction. However, the excellent hydrophilic properties of bamboo restrict its further application in building materials. Rosin is a natural resin with low molecular weight. Its main component is resin acid, which is highly hydrophobic. It is also an eco-friendly material for treating bamboo. The objective of this study was to improve the hydrophobicity of bamboo with rosin. A rosin-ethanol solution was prepared, and bamboo was subjected to vacuum pressure impregnation with this solution at room temperature. During treatment, the rosin retention rate in bamboo increased rapidly with increased soaking time and tended to become stable after 4 h. After rosin treatment, the water uptake of bamboo decreased by 24.7%, meanwhile the swelling coefficient from air-dry to water-saturated conditions in the radial and tangential directions decreased by 23.11% and 21.36%, respectively. The water vapor sorption behavior of bamboo was investigated using a dynamic vapor sorption apparatus, and the results were analyzed using the Guggenheim-Anderson-de Boer model. After rosin treatment, the sorption isotherms of bamboo were still type II, with a decrease in the equilibrium moisture content of bamboo across relative humidity values. Bamboo surface wettability also decreased after rosin treatment, with an initial contact angle of 93°. Scanning electron microscopy revealed that the rosin formed a continuous and uniform film on the surface of bamboo and covered the vessels and pits.