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This study examined how piranha solution affects denture base acrylic resin color stability. Twenty acrylic resin specimens (disc shape, 20 mm diameter, 2 mm thick) were made for color stability. The specimens were randomly divided into Group W (no treatment) and Group P (piranha solution treatment). Color stability is measured with Photoshop. The data was analyzed using a T-test. There was significant variance in group P values (P ≤ 0.05). Compared to Group W, the Piranha solution treatment group (Group P) affected color value (L), hue (a), and chroma (b). This study found that the piranha solution can modify the color of heat cure acrylic surface qualities. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive comparison of two different chemical pretreatments of wheat straw (WS) and rice straw (RS) was made. The pretreatment was performed using piranha solution and p-toluenesulfonic acid (PTSA) to dissolve the biomass's complex lignin and hemicellulose matrix to enhance its methane production. Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopes (SEM), and X-ray diffraction (XRD) analysis, were used to analyze the characteristics of untreated and pretreated feedstock. WS and RS treated with piranha solution showed maximum methane yield (1234 mL and 1196 mL, respectively). The piranha pretreatment increased the methane yield of wheat straw by 2.37 folds and rice straws by 2.31 folds. The maximum VFA concentration was observed in WS on the 14th day in the piranha-treated sample, 1553.33 ± 2.8 mg.L-1, while in RS on the 21st day in the untreated sample, 676 ± 5.77 mg.L-1. SEM analysis of piranha-treated WS indicated a reduction in recalcitrant structure. Deformation of C-O, C=C, C-C-O, and C-H bonds in cellulose, hemicellulosic, and lignin as a result of chemical pretreatment in WS and RS was also indicated by FTIR analysis. The modified Gompertz model (MGM) and logistic function model (LFM) appropriately defined the degradation process and explained cumulative biogas' kinetic. Pretreatment with piranha solution reduces the complexity of WS and RS, thus increasing methane production by reducing the retention time. [ABSTRACT FROM AUTHOR]

Silicon anodes with a high theoretical capacity possess great potential applications in power batteries for electric vehicles, while their volume expansion always leads to crystal pulverization and electrode polarization. An ideal solution to alleviate such pulverization and polarization of silicon crystals is to simultaneously use nano-sized silicon crystals and introduce high viscosity and elasticity polymer binders. This work has achieved the adjustable introduction of hydroxyl groups to silicon nanocrystals under the optimal reaction temperature (e.g., 80 °C) and appropriate piranha solution composition (e.g., H2SO4/H2O2 = 3:1 v/v), ultimately forming an amorphous coating layer of ~1.3 nm on the silicon surface. The optimized silicon anode exhibits superior electrochemical performance (with an initial Coulombic efficiency of 85.5%; 1121.4 mA h g−1 at 1 A g−1 after 200 cycles) and improved hydrophilicity. The introduced hydroxyl groups significantly enhance the hydrophilicity of silicon in the electrolyte and the electrochemical activity of the silicon anodes. The hydroxyl groups achieve stronger bonding between silicon and polymer binders, ultimately improving the mechanical strength and stability of the electrode. The introduction of hydrophily functional groups on the surface of silicon crystals can be explored as an active strategy to solve the above issues. This surface engineering method could be extended to more fields of infiltrating silicon-based functional materials. [ABSTRACT FROM AUTHOR]

Herein, surface modification of halloysite nanotubes (HNTs) was conducted to enhance hydrophobicity via piranha etching and treatment with trimethylchlorosilane (TMCS) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS). The surface-modified HNTs (m-HNTs) were added to the epoxy coating, and the corrosion protection performance was evaluated in terms of the mixing ratio. The m-HNTs were characterized by Fourier transform IR spectroscopy, X-ray photoelectron spectroscopy, and field emission transmission electron spectroscopy. The addition of m-HNTs to the epoxy coating led to an improvement in its barrier and adhesion properties. In addition, electrochemical impedance spectroscopy was conducted to evaluate the corrosion protection performance of the epoxy coating with different mixing ratios. Corrosion protection performance was successfully improved by an increase in m-HNTs. The results were in accordance with those of the barrier and adhesion properties. [ABSTRACT FROM AUTHOR]

Stable F-T-based catalyst development in direct CO hydrogenation to higher alcohols is still a challenge at present. In this study, CuFe/SiO2 catalysts with a SiO2 support treated with a piranha solution were prepared and evaluated in a long-term reaction. The treated catalyst showed higher total alcohols' selectivity and great stability during a reaction of more than 90 h. It was found that the treatment with the piranha solution enriched the surface hydroxyl groups on SiO2, so that the Cu–Fe active components could be firmly anchored and highly dispersed on the support, resulting in stable catalytic performance. Furthermore, the in situ DRIFTS revealed that the adsorption strength of CO on Cu+ on the treated catalyst surface was weakened, which made the C-O bond less likely to be cleaved and thus significantly inhibited the formation of hydrocarbon products. Meanwhile, the non-dissociated CO species were obviously enriched on the Cu0 surface, promoting the formation of alcohol products, and thus the selectivity of total alcohols was increased. This strategy will shed light on the design of supported catalysts with stabilized structures for a wide range of catalytic reactions. [ABSTRACT FROM AUTHOR]

This study aimed to achieve bioactivity on the PEEK surface using piranha solution through a lower functionalization time. For this purpose, the functionalization occurred with piranha solution and 98% sulfuric acid in the proportions of 1:2, 1:1, and 2:1 at periods of 30, 60, and 90 s. The samples treated for longer times at higher concentrations registered the characteristic spectroscopy band associated with sulfonation. Additionally, both chemical treatments allowed the opening of the aromatic ring, increasing the number of functional groups available and making the surface more hydrophilic. The piranha solution treatments with higher concentrations and longer times promoted greater heterogeneity in the surface pores, which affected the roughness of untreated PEEK. Furthermore, the treatments induced calcium deposition on the surface during immersion in SBF fluid. In conclusion, the proposed chemical modifications using sulfuric acid SPEEK 90 and, especially, the piranha solution PEEK-PS 2:1-90, were demonstrated to be promising in promoting the rapid bioactivation of PEEK-based implants. [ABSTRACT FROM AUTHOR]

The main aim of this research was the preparation of a polymer–ceramic composite with PA-12 as the polymer matrix and modified aluminosilicate cenospheres (CSs) as the ceramic filler. The CSs were subjected to an early purification and cleaning process, which was also taken as a second objective. The CSs were surface modified by a two-step process: (1) etching in Piranha solution and (2) silanization in 3-aminopropyltriethoxysilane. The composite was made for 3D printing by FDM. Raw and modified CSs and a composite with PA-12 were subjected to the following tests: surface development including pores (BET), real density (HP), chemical composition and morphology (SEM/EDS, FTIR), grain analysis (PSD), phase composition (XRD), hardness (HV), and static tensile tests. The composites were subjected to soaking under simulated body fluid (SBF) conditions in artificial saliva for 14, 21, and 29 days. Compared to pure PA-12, PA-12_CS had generally better mechanical properties and was more resistant to SBF at elevated temperatures and soaking times. These results showed this material has potential for use in biomedical applications. These results also showed the necessity of developing a kinetic aging model for aging in different liquids to verify the true value of this material. [ABSTRACT FROM AUTHOR]

Purpose: To test the impact of mechanical and chemical treatments of PEEK on surface roughness (SR), surface free energy (SFE), and tensile bond strength (TBS) to veneering resin composites. Materials and Methods: PEEK specimens (N = 680) were fabricated and divided into treatment groups (n = 170/group): 1. air abrasion (AIA); 2. etching with piranha solution (PIS); 3. air abrasion + piranha acid etching (AIP); and 4. no treatment (NO). Ten specimens of each treatment group were assessed with a contact angle measuring device and profilometer to determine SFE and SR, respectively. The remaining 160 specimens of each group were divided into subgroups according to coupling method (n = 32/subgroup): 1. Monobond Plus/ Heliobond (MH); 2. Visio.link (VL); 3. Clearfil Ceramic Primer (CCP); 4. Signum PEEK Bond (SPB); and 5. control, no coupling (CG). Specimens were veneered using Signum Composite/SiCo or Signum Ceramis/SiCe (both: n = 16), incubated in water (60 days at 37°C) and thermocycled (5000 cycles of 5°C/55°C). TBS was measured and data analyzed by three- and one-way ANOVA, Kruskal-Wallis and Mann-Whitney tests (p < 0.05). Results: A significant effect of surface treatment (p < 0.001) and coupling agent application (p < 0.001) on TBS was observed. AIA specimens with/without PIS showed the highest SFE, SR, and TBS. No differences were measured between PIS and NO, and between AIA and AIP. When no coupling agent was used, no adhesion was obtained. CCP resulted in low adhesion values, whereas MH, SPB, and VL exhibited increased TBS. No significant impact of the veneering resin composite on TBS was found (p = 0.424). Conclusion: AIA and AIP combined with VL, SPB, and MH can be recommended for clinical use. [ABSTRACT FROM AUTHOR]

Abstract: Here, we report a non-aggressive method to obtain nanocellulose (NC) from the parenchyma of Agave salmiana leaves. This is accomplished by using a low concentration of a "piranha solution" to achieve solubilization and remove non-cellulosic components, isolating the NC in a single hydrolysis step. X-ray diffraction analysis has shown an increase in the crystallinity index of cellulose from 35 to 60 a result of the hydrolysis, and analysis by Fourier-transform infrared spectroscopy and Raman spectroscopy demonstrated that the cellulose had been purified. To test the thermal, mechanical, and optical properties of the NC, it was used to produce a paper. Analysis by scanning electron microscopy showed that the paper was formed from cellulose nanoplatelets (CNPs) stacked on top of each other.Graphical abstract: [ABSTRACT FROM AUTHOR]

The aim of this work was to improve mechanical properties such as flexural strength and interlaminar shear strength (ILSS) of polyetheretherketone (PEEK) thermoplastic polymer which has very high processing temperature due to its high melting temperature. Carbon fiber (CF) surface was modified by two different methods: oxidative and non-oxidative. Piranha solution and chromate solution were used for chemical treatment (oxidative treatment), and silicone based polymers were used for polymer coating (non-oxidative). The changes on the surface structure and surface chemistry were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR), respectively. FTIR results indicate that coating fibers decreases carbon element content, whereas increases the oxygen and silicone content as well as their functional groups on the surface. Flexural strength and ILSS properties of CF/PEEK composites were measured according to ASTM D-790 and ASTM D2344, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost yet effective method of irreversible bonding between two elastomeric polydimethylsiloxane (PDMS) interfaces using Piranha solution is investigated. Piranha solutions at a weight ratio of 3:1 using different acids and hydrogen peroxide were attempted. The average tensile strengths of the device bonded with concentrated sulfuric acid-based piranha solution and nitric acid-based piranha solution were found to be 200 ± 20 kPa and 100 ± 15 kPa respectively. A PDMS surface treated with Piranha Solution demonstrated an increase in hydrophilicity. In addition, relatively straightforward swelling studies of PDMS using a weight loss method with common organic solvents were also investigated. Experimental results show that hexane, toluene, ethyl acetate, n-propyl alcohol and acetone swell PDMS significantly over a duration of up to 1 h and above; PDMS samples reached a steady state of swelling only after 5 min of immersion in other solvents. This will enable researchers to develop devices for the future according to the interaction between the material and the solvents in contact. [ABSTRACT FROM AUTHOR]

Emission of nitrogen oxides (NOx) from chemical processing of materials is a serious environmental concern, frustrating the development of many innovative technologies. For example, sulfonitric oxidation is the most widely used method for processing carbon nanotubes (CNTs), producing a large amount of NOx. As a result, large scale applications of CNTs for downstream purposes remain challenging. Herein, a NOx‐free oxidation method is proposed for CNTs processing. It starts with mechanically grinding, and then oxidizing the CNTs by hydroxyl radicals in sealed reactors. Such processed CNTs are shorter, possess balanced surface oxygen containing groups without compromising the original CNT integrity, and can disperse readily in water. These are desirable for making various CNT composites, including those with conducting polymers for supercapacitors. The reactors in the process are industrially adoptable, promising a great technological and commercial future. [ABSTRACT FROM AUTHOR]