Increasing Soaking Time Research Articles

High temperature long-lasting corrosion inhibition mechanism of sodium dodecyldiphenyl ether disulfonate on ADC12 aluminum alloy in oxalic acid solution

The high temperature corrosion inhibition mechanism of sodium dodecyl diphenyl ether disulfonate (MADS) on ADC12 aluminum alloy in oxalic acid solution at 80 °C was investigated using electrochemical measurements, surface characterization and theoretical computations. The results manifested that MADS still had excellent performance in high-temperature oxalic acid solution, and was a highly efficient and long-lasting corrosion inhibitor with an optimal corrosion inhibition efficiency (ƞ) of 90.90 %. With increasing soaking time, the ƞ increased to 98.70 %. MADS molecule adsorbed on the aluminum alloy surface in an L-shaped walking scooter configuration through physicochemical adsorption to form a dense, thin and stable hydrophobic film, inhibiting the formation of aluminum oxalate and Al2O3, and protecting it from corrosion.

Effect of ultrasonication and temperature on hydration process and hardness of two cowpea types

AbstractUltrasonication deployment provides a green and non‐thermal option to traditional hydrothermal treatment. This study presents the impact of ultrasonication and soaking temperatures (30 and 50°C) on the water uptake and hardness of two cowpea types under increasing soaking times (15–240 min). Moisture content and hardness of the studied samples were measured using standard test methods and instruments. An increase in soaking temperature and the use of ultrasonication enhanced water uptake and reduced hardness. Ultrasonication improved mass transfer, which enhanced the diffusion of water uptake. The samples' water uptake and softening characteristics were significantly modeled with high accuracy (R2 = 0.99) using sigmoidal and first‐order kinetics equations, respectively. The impact of sonication was found to be more significant at 30°C soaking of the studied cowpeas as the soaking time increased. This work justified using ultrasonication as a green technique to enhance the softening of cowpeas.

Experimental study on influencing factors of CO2 huff and puff effect in the tight water-bearing reservoir

The presence of a water phase in tight oil reservoirs is inevitable. To investigate the effect and influencing factors of the CO2 huff and puff technique on enhancing oil recovery in water-bearing tight oil reservoirs, CO2–water–crude oil phase experiments were conducted. The results reveal that the solubility of CO2 and the expansion coefficient of crude oil decrease with increasing water content in the system. Furthermore, CO2 huff and puff experiments were performed to analyze the effects of the number of huff and puff cycles, soaking time, soaking pressure, water saturation, and permeability on the performance of CO2 huff and puff under saturated/unsaturated water conditions. The experimental findings indicate that the oil recovery increases logarithmically with the number of huff and puff cycles. Increasing soaking time and soaking pressure gradually enhances recovery until reaching optimal soaking time and pressure. However, further increasing soaking time and pressure beyond the optimal values has minimal effect on recovery. Compared to the cases under unsaturated water conditions, the optimal number of huff and puff cycles, soaking time, and pressure are higher under saturated water conditions. Additionally, the CO2 huff and puff effect deteriorates with increasing water saturation in low permeability reservoirs.

Investigation on electrochemical corrosion behavior of Cu-14Fe -(0, 0.05)Ce alloys

This work thoroughly investigated the electrochemical corrosion behaviors of Cu-14Fe-(0, 0.05) Ce alloys. Experimental findings revealed that the addition of Ce did not change the phase constituent, but refined α-Fe phase particle from 0.30 ± 0.04 to 0.22 ± 0.03 μm and increased its content from 1.24% to 2.17%. With the increase of corrosion time, adding Ce could increase the linear polarization resistance by up to 3 times, and correspondingly the corrosion rate was reduced to half. Moreover, Ce addition contributed to the densification of corrosion products. The α-Fe phase preferentially underwent anodic dissolution reaction, generating corrosion product Fe2O3. The increase of soaking time resulted in the occurrence of anodic dissolution of Cu-matrix phase, along with the formation of Cu2O and Cu2Cl(OH)3.

Investigation on effects of water-shale interaction on acoustic characteristics of organic-rich shale in Ordos Basin, China

The water-shale interaction affect the shale structure, leading to wellbore instability and increasing drilling costs. The extent of structural changes within the shale can be determined non-destructively by analyzing its acoustic characteristics. Experiments were conducted to investigate the acoustic properties of shale from the Yanchang Formation in the Ordos Basin before and after exposure to brines of varying types, soaking times, and salinities. The study investigated the effects of brine type, soaking time, and salinity on shale’s acoustic properties, including changes in acoustic wave propagation speed, P/S wave velocity ratio, and both time-domain and frequency-domain amplitudes. The results indicate that although the type of brine has a limited impact on the water-shale interaction, KCl exhibits a significant inhibitory effect. However, the soaking time and the brine salinity have a significant impact on the acoustic properties of shale. As the soaking time increases, the decrease in wave velocity increases, the P/S wave velocity ratio increases, and the decrease in time-domain amplitude increases. The amplitude of the main frequency in the frequency domain signal also decreases with the increase of reaction time, which is consistent with the analysis results of the time domain signal. As the salinity of brine increases, the decrease in wave velocity decreases, the P/S wave velocity ratio decreases, and the decrease in time-domain amplitude decreases. The amplitude of the main frequency in the frequency domain signal also decreases with the increase of brine salinity, which is consistent with the analysis results of the time domain signal. This work establishes the relationship between water-shale interaction and acoustic characteristics, which can quantitatively evaluate the degree of interaction between water and shale without damaging shale. Furthermore, this research provides new insights and guidance for predicting drilling collapse cycles and optimizing drilling fluid compositions.

Geomechanical properties of laminated shale and bedding shale after water absorption: A case study of the Chang 7 shale in Ordos basin, China

There are abundant oil and gas resources in China's continental shale formations, and these formations often contain sandy lamina, tuffaceous lamina and carbonate lamina parallel to the bedding planes, resulting in complex geomechanical properties. During the drilling process, the mechanical weak surface structure inside the shale and the hydration effect of drilling fluid may easily cause wellbore instability, which reduces the safety and benefit of drilling. To explore the geomechanical properties of laminated shale and bedding shale after water absorption, a series of tests were conducted on the Chang 7 laminated shale and bedding shale in the Ordos Basin. The result indicates that the compressive strength and elastic modulus of laminated shale and bedding shale show a trend of decreasing first and then starting to drop as β (the angle between bedding/lamina and the direction of stress) keeps increasing, and laminated shale has stronger anisotropy, lower compressive strength and elastic modulus. The moisture content of laminated shale and bedding shale increases as the soaking time increases, which leads to a decrease in the compressive strength. Compared to bedding shale, laminated shale reaches water saturation faster and has a higher moisture content. Based on the macroscopic and microscopic images before and after shale hydration, it can be concluded that natural microfractures are easily formed at the interface between the lamina and shale matrix, and brittle minerals at the edges of natural microfractures are prone to detachment, thereby increase the hydration area and intensify the hydration process. Compared to bedding shale formations, laminated shale formations have a higher hole-size elongation ratio and are more prone to collapse according to on-site data. This study reveals the geomechanical properties of laminated shale under the dual influence of anisotropy and hydration, provides support for drilling design in such formations.

Influences of bedding angle and soaking time on the mechanical behaviour of silty mudstone: laboratory testing and theoretical modelling

Silty mudstone is highly susceptible to the influence of hot and humid environments, leading to the deterioration of its mechanical properties presenting a geohazard and even resulting in geological disasters. Accurately characterizing the effects of bedding and water–rock interaction on the mechanical behaviour of silty mudstone is a crucial prerequisite for the protection and reinforcement of silty mudstone slopes. To this end, uniaxial compression tests and Brazilian splitting tests were conducted to examine the mechanical properties of bedded silty mudstone. Based on the test results, the effects of bedding angle and soaking time on mechanical properties such as tensile strength, uniaxial compressive strength and elastic modulus of bedded silty mudstone were revealed. The test results showed that the tensile strength increased exponentially with increasing bedding angle. The observed split failure patterns of bedded silty mudstone encompassed splitting–pulling damage, shear damage and splitting damage. The uniaxial compressive strength of silty mudstone exhibited a U-shaped variation with an increase in bedding angle. The specimen with a bedding angle of 45° had the lowest uniaxial compressive strength at 7.64 MPa. Furthermore, the elastic modulus of silty mudstone was positively correlated with the bedding angle. The failure patterns of bedded silty mudstone under uniaxial compression included splitting-tension damage, shear-slip damage and splitting-shear damage. The saturated tensile strength, uniaxial compressive strength and elastic modulus of bedded silty mudstone exhibited an exponential decrease with increasing soaking time. The test data confirmed the applicability of the Jaeger equation to the uniaxial compressive strength of bedded silty mudstone. Subsequently, a modified Hoek–Brown failure criterion was derived by combining fracture mechanics theory and test results and introducing a softening factor. The parameters A , D and m in the above failure criterion decreased exponentially with increasing soaking time and an empirical Hoek–Brown failure criterion considering the soaking time was established. Compared with previous theoretical models, this model is more adaptable to the actual engineering situation, which results in more accurate calculations.

Effect of humidification on antimony-based flexible phase change memory

Ambient humidity has an important impact on the performance of flexible electronic devices, and wearable electronic devices will inevitably involve a high humidity environment. To investigate the impact of humidification on flexible phase-change memory, we prepared Sb phase-change film and memory device unit with polyether ether ketone as substrate, and studied the effect of humidification on the properties of the film and device. The results show that the effective transition from an amorphous to a crystalline state can still be achieved by the film after soaking in water for 55 min, and the phase transition temperature increases with the increase of soaking time. Water molecules refine the film grains, resulting in increased crystalline resistance. Sb is a hydrophilic material, and its hydrophilicity decreases after crystallization. The reversible conversion of SET-RESET can be realized under different pulse widths even after the phase change memory device is soaked in water and bent many times. This study shows that antimony-based flexible phase change memory has certain deformation self-healing ability and moisture resistance, which provides a way to expand its application environment.

Improving Strength by Increased Compaction of Gypsum—Enriched Soil under Long-Term Soaking Conditions

This study investigated the effect of compaction effort and soaking time on the shear strength properties of fine-grained gypsum-containing soils. The objective was to demonstrate that increasing compaction effort increases soil strength, specifically cohesion and the angle of shear strength, when subjected to soaking in freshwater. Unconsolidated undrained triaxial tests were carried out on CBR soil samples with different soaking times. The results showed a transition from brittle to ductile failure behaviour as the soaking time increased. Mohr–Coulomb failure envelopes showed reduced cohesion and angle of shear strength with increasing soak time. Regression models were developed to establish correlations between soaked and unsoaked strength parameters. Strong relationships were found between soil strength properties, compaction effort and soaking time. Empirical equations were proposed to estimate the cohesion and angle of shear strength from compaction effort and soaking time. This study highlighted the importance of considering gypsum-rich soils in civil engineering design. Gypsum dissolution during wetting significantly affected soil strength parameters. The regression models and empirical equations provide engineers with tools to assess the influence of compaction effort and soaking time on soil strength, thus aiding decision making when designing structures on gypsum-rich soils.

Effects of soaking glutinous sorghum grains on physicochemical properties of starch

Glutinous sorghum grains were soaked (60–80 °C, 2–8 h) to explore the effects of soaking, an essential step in industrial processing of brewing, on starch. As the soaking temperature increased, the peak viscosity and crystallinity of starch gradually decreased, while the enzymatic hydrolysis rate and storage modulus first increased and then decreased. At 70 °C, the content of amylose, the enzymatic hydrolysis rate of starch, and the final viscosity first increase and then decrease with the increase of soaking time, reaching their maximum at 6 h, increased by 53.1 %, 11.0 %, and 10.4 %, respectively, as compared with the non-soaked sample. At 80 °C (4 h), the laser confocal microscopy images showed a network structure formed between the denatured protein chains and the leached-out amylose chains. The molecular weights of starch before and after soaking were all in the range of 3.82–8.98 × 107 g/mol. Since 70 °C is lower than that of starch gelatinization and protein denaturation, when soaking for 6 h, the enzymatic hydrolysis rate of starch is the highest, and the growth of miscellaneous bacteria is inhibited, which is beneficial for subsequent processing technology. The result provides a theoretical basis for the intelligent control of glutinous sorghum brewing.

The Influence of Immertion on Marshall Parameters and Residual Strength Index of Rubber Asphalt Mixture

The bad drainage system in the road pavement area also causes the road body to be submerged in water for quite a long time, causing the bond between the asphalt and aggregate to loosen, resulting in decreased service life. Developments in the field of road construction have now implemented many innovative ideas, one of which is namely the use of rubber asphalt with asphalt containing natural rubber which has 1.5 to 2 times the strength compared to conventional asphalt. In evaluating the performance of an asphalt mixture, especially the AC-WC Wear layer mixture, it can be analyzed using the Marshall test method by taking into account the conditions being tested, namely the test object being immersion in water or continuously flooded with water. The method used in this research is an experiment with treatment conditions for AC-WC rubber asphalt mixture specimens which are continuously immersion in water for 1 day, 2 days and 3 days. The research results showed that there was an increase in the VMA, VIM, and flow parameters, while the VFB, stability, and Residual Strength Index parameters decreased with increasing soaking time. Based on the research results, it can be concluded that although there is an influence on the performance of the asphalt mixture with the use of rubber asphalt, the decrease that occurs is not too large and is still within the required specifications.

Study on the process of mass transfer and deterioration of limestone under dynamic dissolution of CO2 solution

The long-term erosion of rock by solution can induce a series of karst problems. Therefore, this study focused on limestone and conducted dynamic dissolution experiments under deionized water and CO2 solution conditions to study the deterioration mechanism of limestone under nonequilibrium conditions. The results showed that the degree of degradation of the mechanical properties of the samples in a CO2 solution was obviously greater. In a deionized water environment, the degradation of the mechanical properties of the sample is mainly controlled by the physical softening action of the solution. In the CO2 solution environment, the degradation process can be divided into two stages. In the early stage of the experiment (10 days to 20 days), the degradation of mechanical properties of the sample is also controlled by the physical softening action of the solution. With increasing soaking time, the main rock-forming minerals of limestone gradually react with the CO2 solution, the degradation of the sample is controlled mainly by the chemical corrosion of the CO2 solution, and its degradation rate is much greater than that of physical softening. The results can be used as a reference for assessing the long-term stability of underground engineering in limestone karst development areas.

Study on the Gelation Process and Mechanical Properties of Organic Polymer Grouting Materials Applied to Fissure Sealing in Underground Mines.

In this study, organic polymer polyurethane grouting materials were prepared using isocyanate and polyether polyol as the main agents and various additives, the slurry coagulation process was investigated, and the mechanical properties of the polymer samples were tested to explore the influence of the density and soaking time of the polymer on the strength of the samples. The microstructure of the polymer was observed via electron microscopy, and relying on image analysis software, the structural parameters of the polymer cell were analyzed and calculated; the model equation between density and yield strength was established based on the strength model of porous materials developed by Gibson and Ashby. The results show that the initial viscosity and gel time of the polyurethane slurry decrease with the increase of the initial temperature, and the viscosity changes abruptly when the slurry reaches the gel point. The mechanical properties of the polymer increased with increasing density and decreased with increasing soaking time. The interior of the polymer is a porous structure and the pores are approximately spherical; the higher the density of the polymer material, the more uniform the stress distribution of the material, and the higher the percentage of the matrix, which in turn leads to better mechanical properties of the material. The diameter of the polymer cell is negatively correlated with the density, and the model established based on the microscopic parameters of the cell can better predict the yield strength of the polymer. This study helps to deepen the understanding of the microstructure and mechanical properties of polyurethane and provides a certain reference for the application of polyurethane in underground mine reinforcement engineering.

Investigation of Phosphorus Spin on Dopant on SOI Wafer

Silicon on insulator (SOI) wafer has allowed the integrated circuit (IC) industry to create superior, high-performance solutions. In addition, doping techniques are vital in the silicon sector due to the need to regulate the material electrical properties. The spin on dopant (SOD) approach is an alternative method that involves spinning a solution containing dopant onto SOI wafers. This research aims to determine the impact of thermal diffusion temperature and soaking time on sheet resistance of doped SOI wafer using SOD approach. Additionally, the homogeneity of doping was studied by utilizing mapping techniques. Three inches boron-doped SOI wafers were cut and cleaned according to Radio Corporation of America (RCA) standards. N-type dopants of Filmtronics SOD P509 were deposited on SOI wafer by using a spin coater, for 40 seconds at 4,000 revolutions per minute (rpm). The thermal diffusion temperature and soaking time were set between 700°C to 1000°C for 30 to 120 minutes. After thermal diffusion, hydrofluoric acids (HF) were diluted and used to etch samples. All materials were evaluated using a four-point probe, Hall Effect and Atomic Force Microscope (AFM). The results show that when the thermal diffusion soaking time increases, sheet resistance decreases until activated dopants are saturated. When sheet resistance decreases, dopant concentration rises. Temperature and soaking time increase carrier density and surface roughness, while decreasing Hall mobility. From mapping techniques, it shows low non-uniformity value which less than 10% suggests good thermal diffusion control.

Carbonitriding Effect on Fatigue Behaviour and Mechanical Properties of Steel Beam

This work deals with the influence of carbonitriding on the fatigue behavior of notched beam (v-notch) with a depth of 1mm and an angle of 45° is studded. The experimental work include mechanical tests, heat treatments and fatigue test. The heat treatment is done by using carbonitriding at a constant temperature of 800 °C, and soaking time variation 30, 60, and 90 minutes, then followed after treatment by quenching of water and tempering process. The experimental fatigue test results of this work affected by soaking time. The fatigue test has been performed on a cantilever rotating-bending samples. The result shows that the fatigue strength and lifetime increased with increasing soaking time. It is found that The Fatigue Life Improvement Factor (FLIF) at time 30, 60 and 90 minutes for notched beam (v-notch) was increasing by 11.3%, 18.6% and 20.2% respectively with respect to un-treat specimens.

Multiphase Multicomponent Transport Modeling of Cyclic Solvent Injection in Shale Reservoirs

Summary A thorough understanding of fluid transport in ultratight shale reservoirs is crucial for designing and optimizing cyclic solvent injection processes, known as huff ’n’ puff (HnP). We develop a two-phase multicomponent numerical model to investigate hydrocarbon and solvent transport and species mixing during HnP. Unlike the conventional modeling approaches that rely on bulk fluid (advective) transport frameworks, the proposed model considers species transport within nanopores. The chemical potential gradient is considered the driving force for the movement of nonideal fluid mixtures. A binary friction concept is adopted that considers friction between different fluid molecules and between fluid molecules and pore walls. After validating the developed model against analytical solutions and experimental data, the model examines solvent HnP enhanced oil recovery (EOR) mechanisms by considering four-component oil and Eagle Ford crude oil systems. The impacts of injection pressure, primary production duration, soaking time, and solvent type on the oil recovery are examined. The results reveal that the formation of a solvent-oil mixing zone during the huff period and oil swelling and vaporization of oil components during the puff period are key mechanisms for enhancing oil recovery. Furthermore, the incremental recovery factor (RF) increases with injection pressure, even when the injection pressure exceeds the minimum miscibility pressure (MMP), implying that MMP may not play a critical role in the design of HnP in ultratight reservoirs. The results suggest that injecting solvents after a sufficient primary production period is more effective, allowing reservoir pressure depletion. Injecting the solvent without enough primary production may result in significant production of the injected solvent. The results show that the solvent-oil mixing zone expands, and the solvent recycling ratio decreases as soaking time increases. However, short soaking periods with higher HnP cycles are recommended for improving oil recovery at a given time frame. Finally, CO2 HnP outperforms CH4 or N2 HnP due to the higher ability of CO2 to extract a larger amount of intermediate and heavy components into the vapor phase, which has higher transmissibilities as compared with the liquid phase.

Evaluation of slake durability for carbonaceous rocks exposed to water soaking using electrical resistivity

The present study investigated the electrical conduction and slake durability behaviors of carbonaceous rocks subjected to water soaking. Several series of electrical resistivity and slake durability tests were conducted on carbonaceous rocks with different mineralogical characteristics to explore the intrinsic connection between these two property indexes. Based on the experimental data, a new empirical model was developed to estimate slake durability index of carbonaceous rocks at varied soaking times. The results showed that the clay minerals content of investigated carbonaceous rocks ranged from approximately 20 % to 50 %. The clay minerals are beneficial in enhancing the electrical conduction of carbonaceous rocks, but impose a negative impact on the slake durability, attributing to their superior performance of hydrophilicity and swelling. Electrical resistivity decreased sharply with increasing soaking time within the first 8 days and then it achieved a stable state as soaking time further increased, which was mainly due to the completion of pore saturation and salts/minerals dissolution. The slake durability index exhibited similar evolution characteristics to those of electrical resistivity, which deteriorated sharply to a low or very low level after soaking for 16 days. The clay minerals experienced water absorption and mineral expansion during the first 8 days soaking, leading to the development of micro-cracks that facilitates water intrusion and accelerates the slake durability deterioration. These two processes were essentially complete as the soaking time further increased, and the clay minerals played an insignificant role at this stage. Liner increasing trends were observed in the plot of electrical resistivity decrease versus slake durability index decrease, and the slope values presented a power function relation with the clay minerals content of carbonaceous rocks. The proposed empirical model well captured the trends in the experimental data, with an absolute difference in percentage δ below30 % and a root mean square error RMSE value of 5.613 %. The outcomes of this study provided a viable answer to assess slake durability of carbonaceous rocks exposed to adverse external environments using non-destructive testing techniques.

Pengaruh Lamanya Perendaman Terhadap Absorpsi, Ketahanan Aus, dan Kuat Tekan Paving Block

Paving blocks are considered advantageous over other road surfaces, and it is undeniable that paving blocks are an alternative road surface whose quality is still affected by water flooding. The objective of this study was to determine the effects of soaking time and age of paving blocks in terms of absorption, wear resistance, and compressive strength. The paving blocks used were manual (Holland) brick models obtained from Banyubiru and mechanical ones obtained from PT Pohon Cemara Semarang. The variations soaking times were 0, 12, 24, 36, 48 (hours) for 7, 14, 21, 28 (days) old pavers. The tests conducted were absorption, wear resistance, and compressive strength tests of paving blocks, carried out in the UNISSULA civil engineering laboratory. The results of absorption tests manual and machine paving block showed that value of the absorption test increased with increasing soaking time. The results of wear resistance of manual and machine pavers show that the untreated samples had a lower wear value and all test results met the requirements of SNI 03-0361-1996 Quality A. The maximum compressive strength of manual paving blocks at 28 days of age without treatment is 13.334 MPa. The maximum compressive strength of machine-made pavers is 25.297 MPa for paving blocks without immersion.

Effect of different preservation treatments on the formation of semicarbazide in Litopenaeus vannamei and the potential molecular mechanisms

This research was conducted to explore the influence of different preservation treatments, namely sodium hypochlorite (NW), acidic electrolyzed water (AEW), acidic electrolyzed water ice (AEWI) and ozone water (OW) on the production of semicarbazide in Litopenaeus vannamei. Results showed that the level of semicarbazide increased along with the increase of sodium hypochlorite concentration and immersion time. For AEW group, with the increase of soaking time, the content of semicarbazide reached its maximum value after 24 h and then decreased. The semicarbazide content with the AEWI and OW treatments showed a downward trend with time. A strong negative correlation (r = –0.79) was observed between arginine content and semicarbazide in the NW group. For the former three treatment solutions, it was speculated that semicarbazide formation was related to amino acids decomposition with chlorine, while the semicarbazide produced during ozone treatment was presumed to originate from the biological metabolism of Litopenaeus vannamei.

The effects of TiO2 addition on the anticorrosion performance of ECTFE coating under lighting

In this study, TiO2 particles were dispersed into ethylene-chlorotrifluoroethylene copolymers (ECTFE), and TiO2/ECTFE composite coating was prepared with the TiO2/ECTFE mixture via electrostatic spraying and low temperature thermal processing. The prepared coating was soaked in 3.5 wt% NaCl solution under lighting or dark for anticorrosion performance study. The microstructure of the treated coating was characterized with XRD, Raman, FT-IR and SEM. The results indicate that the low frequency impedance (|Z| 0.01 Hz) of the TiO2/ECTFE coating maintained above the 109 orders of magnitude after 90-day soaking. It is evident that the addition of TiO2 enhances the protective performance of the coating on steel, while simultaneously compromising its own integrity. With increasing soaking time, C-H groups in ECTFE coating would be exposed gradually and lighting would speed this process, making the surface roughness of coating reduced. This is because halogens in the polymer chain of ECTFE would be stretched gradually. TiO2 would also change the bond length of C-H groups and make the C-H groups oxidized under lighting. The strengthening effect of TiO2 can be ascribed to the filler and barrier effects of TiO2 particles together with the prior consumption of dissolved oxygen by photo-generated electrons. However, the fast degradation of TiO2/ECTFE coating under lighting is the result of local agglomeration of TiO2 particles, and oxidation of the C-H groups by photo-generated holes.