Crystalline Additives Research Articles

Improving redox reactions of Spiro-OMeTAD via p-type molecular scaffold to reduce energy loss at Ag-electrode in perovskite solar cells

2,2’,7,7’-Tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9’-spirobifluorene (Spiro) is an essential hole-transport material used in perovskite solar cells (PSCs). However, the redox reaction of Spiro and its impact at the interface with the metal electrode are not yet fully understood. In this study, we introduced a crystalline additive (CA) to regulate the redox process of Spiro and its interface with an Ag electrode. Our findings indicate that CA functions as a molecular scaffold, improving the crystallinity and stability of radicals in Spiro throughout the entire redox reaction. This enhancement increases the hole mobility of Spiro and strengthens the internal electric field, thereby improving hole extraction and transport efficiency at both interfaces. Moreover, the optimized redox reaction of Spiro reduces energy loss at the Ag electrode, significantly boosting the power conversion efficiency to 25.21%. Furthermore, CA mitigates the aggregation of lithium salt and enhances the stability of the device. Our findings contribute to a deeper understanding of hole-transport mechanisms of Spiro and emphasize the importance of reducing energy loss at the Spiro/Ag electrode interface in PSCs.

The effect of crystalline technology on concrete as coating to improve its durability

This research delves into the effects of incorporating Crystalline Additives (CAs) in concrete, specifically exploring alterations in compressive strength, water penetration resistance, and chemical durability when subjected to corrosive solutions, including H2SO4 and HCl. The investigation encompasses four concrete compositions: Standard Concrete, Concrete with Single Layer Crystalline Coating, Concrete with Double Layer Crystalline Coating, and Concrete featuring Type V Cement. Results indicate that the application of Crystalline coating contributes to notable enhancements in the average compressive strength, albeit falling short of the peak strength achieved with Type V cement. Notably, exposure to a 5% H2SO4 solution triggers more pronounced deterioration compared to exposure to 5% HCl, leading to discernible reductions in both weight and compressive strength. Despite Crystalline coating’s beneficial impact on compressive strength, it remains outperformed by the application of Type V Cement, as evidenced by superior average compressive strength values. Conversely, the efficacy of Crystalline coating in countering water penetration remains inconclusive, as evidenced by the water penetration test outcomes. This ambiguity underscores the necessity for further research to ascertain the true extent of Crystalline coating’s influence on water resistance.

Effect of self-healing behavior and self-healing technologies on the structural characteristics of cracked RC/ECC composite beams

The improving potential of self-healing behavior and self-healing technology to degradation of structural characteristics of cracked reinforced concrete structures was explored at the member level. Reinforced concrete/engineered cementitious composite (RC/ECC) composite beams were prepared by three self-healing technologies, including crystalline additives (CA), two types of superabsorbent polymers (SAP), and beam without self-healing technology was used as reference specimens. The self-healing properties of structural characteristics of beams were studied by four-point bending tests, including bear capacity, stiffness, ductility index, energy absorption capacity (EAC), and failure mode. The self-healing behavior of damage was evaluated by ultrasonic wave test and damage identification test based on natural frequency. Self-healing behavior of four types of RC/ECC composite beams improved the structural characteristics after cracking to varying degrees. The stiffness of CB-0, CB-S, CB-C, and CB-SH after self-healing increased by 10.80%, 22.88%, 36.71%, and 28.80% compared to that without self-healing, respectively. Recovery ability of structural characteristics of RC/ECC composite beam is enhanced by self-healing technologies. Moreover, CA exhibits a superior improvement in the recovery ability of the structural characteristics compared with two types of SAP. Moreover, the natural frequency and ultrasonic velocity of pre-cracked beams after self-healing were higher than those without self-healing, especially when self-healing technologies were applied. There is a positive correlation between the recovery ability of ultrasonic velocity and self-healing behavior of the structural characteristics of RC/ECC composite beams. This also explains why the structural characteristics of pre-cracked beams have been improved to varying degrees due to different self-healing techniques.

The Usage of Crystalline Additive on Concrete Performance

Indonesia as a maritime country has a number of structures in coastal areas that are made from concrete. Sulfate attack is one of the common deteriorations that could occur due to the exposure of saltwater to the concrete. Unfortunately, the Type II and Type V cements, which are the special cements that are resistant to sulfate, are rarely used due to their high prices. The objectives of this research are to compare the performance of concrete mixture that was prepared by using the standard cement mixed with crystalline material and the concrete mixture that was prepared by using two different brands of Type V cement. There were five concrete mixture variations tested for their compressive strength and permeability. To assess the permeability of the concrete, the specimens were placed under pressured water for 72 hours and the water penetration depth was measured. From the research results, it was found that the usage of crystalline additive (CA) made the compressive strength increased at a faster rate and the concrete mixture that contained Type I cement and 0.7% of crystalline material had the highest compressive strength value. In terms of the permeability of the concrete, it can be seen that the specimens that were mixed with CA were more effective in stopping the water to penetrate the specimens than the specimens prepared with either of Type V cement.

Self-Healing Products of Cement Pastes with Supplementary Cementitious Materials, Calcium Sulfoaluminate and Crystalline Admixtures

The phase composition of self-healing products generated in cracks affects self-healing performance. This study investigated the self-healing products of cementitious materials using supplementary cementitious materials (SCMs), a calcium sulfoaluminate (CSA) expansion agent, and crystalline additives (CAs). Ground-granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF) were used as SCMs, and anhydrite, Na2SO4, Na2CO3, and MgCO3 were used as crystalline additives (CAs). An artificial crack method was used to collect the self-healing products in the crack of the paste. The phase composition of the self-healing products was analyzed through X-ray diffraction (XRD)/Rietveld refinements and thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and their morphology and ion concentration were examined through scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS). From the results, the main compound of self-healing products was found to be calcite. GGBFS and FA decreased the content of portlandite, and the use of CAs led to the formation of alkali sulfate and alkali carbonate. The SEM–EDS analysis results showed that when GGBFS and FA were used, a large proportion of the self-healing products contained C-S-H and C-A-H, and the use of CSA led to the formation of monosulfate and ettringite.

Self-healing in fiber-reinforced alkali-activated slag composites incorporating different additives

Despite that considerable research has explored self-healing of portland cement-based materials, potential self-healing in alkali-activated binders remains largely unexplored. Therefore, this paper deploys a wide array of experimental techniques to investigate the self-healing properties of PVA fibre-reinforced alkali-activated slag-based composites incorporating crystalline additives (CA) and bentonite minerals (BN). X-ray microcomputed tomography (μCT) with three-dimensional image segmentation and analysis, scanning electron microscopy with energy dispersive X-ray (SEM-EDS) analysis, inductively coupled plasma optical emission spectroscopy (ICP-OES), optical microscopy, and water sorptivity measurements were used to visualize, quantify, and identify the nature of healing compounds. While specimens incorporating CA exhibited significant self-healing, less self-healing was observed in specimens incorporating bentonite. X-ray μCT results indicated that the healing mechanism mainly occurred at surface cracks and calcium carbonate was the prevalent self-healing product formed. It was found that rising the pH and concentration of calcium ions of the curing medium and using polyvinyl alcohol (PVA) fibers in the mixture acted synergistically to accelerate crack self-healing in alkali-activated slag composites.

Improving the Resistance of Cement-Based Composites to Sulphur Dioxide

The paper describes an investigation into the influence of a crystalline additive on the sulphur dioxide resistance of cement-based composites. Cement mortars made with the assistance of secondary crystallization were exposed to an aggressive environment and tested for ways how the crystalline additive (CA) influences their degradation. The results indicate that the crystalline additive improved the resistance of the cement-based composites to sulphur dioxide attack.

Effect of exposure conditions on self healing behavior of strain hardening cementitious composites incorporating various cementitious materials

This project studies the self-healing potential of strain hardening cementitious composites (SHCC) incorporating calcium-sulfoaluminate based expansive additive (CSA) and crystalline additive (CA). Four mixes, control mix (M1), 10%CSA mix (M2), 1.5%CA mix (M3) and 10%CSA+1.5%CA mix (M4), were used in the investigation. Pre-cracked specimens were subjected to different exposure conditions; namely, tap water (EC1), regularly refreshed tap water (EC2), wet/dry cycles (EC3) and air exposure (EC4). The recovery of mechanical properties can be obtained, particularly for M2 and M4 mixes. The concentration of carbonate ions in exposed water plays an important role on self-healing process. Calcium carbonate formation on crack mouth is preferable in terms of water tightness; however, this formation decreases the recovery of mechanical properties. The results from chemical analysis showed that the healing products are composed of CaCO3, C–S–H and ettringite. The proportion of healing minerals depends on exposure condition and the type of cementitious materials used.

Self-healing of surface cracks in mortars with expansive additive and crystalline additive

Abstract This research studies the self-healing potential of cement-based materials incorporating calcium sulfoaluminate based expansive additive (CSA) and crystalline additive (CA). Mortar specimens were used throughout the study. At the age of 28 days, specimens were pre-cracked to introduce a surface crack width of between 100 and 400 μm. Thereafter, the specimens were submerged in water to create a self-healing process. The experimental results indicated that the mixtures with CSA and CA showed favorable surface crack closing ability. The optimal mix design was found to be a ternary blend of Portland cement, 10 wt.% CSA and 1.5 wt.% CA, by which a surface crack width up to about 400 μm was completely closed, and the rate of water passing was dropped to zero within 28 days. It was hypothesized that the amount of leached Ca 2+ from the matrix plays an important role on the precipitation of calcium carbonate which is the major healing product. The analyses showed that those specimens with CSA/CA additions released more Ca 2+ than that control specimen. Moreover, those specimens with additives had higher pH value which would favor calcium carbonate precipitation.