Acid Corrosion Resistance Research Articles

Two-Step Fabrication of BPO4 Ceramics with Acid Corrosion Resistance and Neutron Shielding Performance

There has been an urgent demand for novel neutron shielding materials (NSMs) with high mechanical strength and low acid corrosion rate to be used in compact shielding design. In this contribution, BPO4 ceramics (BPCs), one of the candidates for such materials, was successfully fabricated by a two-step method using H3BO3 and H3PO4 as raw materials. The evolution of the microstructures was then investigated, followed by testing of mechanical/thermal properties, acid corrosion resistance, and neutron shielding performance. The experimental results indicated that the calcination temperature as well as H3BO3 content in raw materials intuitively affected the densification process of the BPCs. The as-pared BPCs showed reliable mechanical properties with maximum CMOR, compressive strength and elastic modulus of 26.99 MPa, 86.89 MPa and 28.42 GPa, respectively, which also showed a high neutron shielding rate and low acid corrosion rate of 65.11% and 0.016%. The obtained results imply that the BPCs was a promising NSM for use in compact shielding design.

Magnetically-separable acid-resistant CoFe2O4@Polymer@MIL-100 core-shell catalysts for the acetalization of benzaldehyde and methanol

Novel reusable acid-resistant magnetic polymer nanospheres-immobilized MIL-100 (CoFe2O4@Polymer@MIL-100) catalyst was prepared by a layer-by-layer method to achieve a controllable structure. The obtained core-shell catalyst consisted of modified magnetic nanoparticles as the core, a carboxylic-functionalized polymer as the protective layer, and an MIL-100 shell as the active catalytic layer by chemical bonds on the polymer. The catalysts showed good stability, good magnetic saturation, and acid corrosion resistance. The thickness of the MIL-100 shell could be adjusted by controlling the metal salt concentration and the number of layer-by-layer cycles. Nano-sized MIL-100 showed better mass transfer efficiency and catalytic activity. A conversion of 97.7% after 10 min was observed during acetalization when using CoFe2O4@Polymer@MIL-100 as the catalyst. CoFe2O4@Polymer@MIL-100 could be reused at least five times. The use of a polymer layer on CoFe2O4@Polymer@MIL-100 prevented acidic ligands from corroding the magnetic core. Chemical bonds between MIL-100 and functional magnetic polymer cores improved the catalyst’s stability. CoFe2O4@Polymer@MIL-100 exhibited high activity, excellent stability, and easy magnetic separation.

Construction of flexible fiber-shaped boron-doped diamond film and its supercapacitor application

Flexible fiber-shaped supercapacitors (FSSCs) are promising candidates as electrode materials for the development of deformable electronic devices. Although tremendous efforts have been focused on the preparation of flexible electrode materials, traditional FSSCs materials face problems of inferior stability and complicated processes. Boron-doped diamond (BDD) holds promise as a FSSC electrode, owing to its well-established preparation process, strong acid and alkali corrosion resistance, environmentally and skin-friendly characteristics. Here, we reported a novel strategy for the construction of BDD-based FSSCs by growing a BDD film on a flexible tantalum (Ta) fiber substrate through hot filament chemical vapor deposition technique. Results showed that the BDD fiber film featured 10 folds improvement in specific capacitance than a planar BDD electrode. A symmetric supercapacitor device was assembled using the BDD fiber electrode and achieved an energy density of 25.6 mJ cm−2 at a power density of 0.6 mW cm−2, and a desirable stability with higher capacitance retention of 93.5% after 20,000 cycles. Furthermore, the symmetric BDD fiber device exhibited satisfactory bendability with high specific capacitance retention under various bending deformations. The findings in this research work hold promise for the fabrication of high performance flexible FSSCs.

Fabrication of transparent wear-resistant superhydrophobic SiO2 film via phase separation and chemical vapor deposition methods

Glass with superhydrophobic, transparent, and wear-resistant properties are quite desirable for the applications in high building glass curtain, wind shield glass, and solar cell cover glass. How to fabricate a superhydrophobic surface with both high transparency and good wear resistance is still a great challenge because roughness and transparency are mutually exclusive. Here, transparent, wear-resistant, superhydrophobic inorganic coating on glass substrate has been successfully achieved by a two-step process combining phase separation and chemical vapor deposition (CVD). Firstly, a wear-resistant inorganic porous film with honeycomb-shaped pores is prepared on the glass surface by applying the phase separation method based on the epoxy resin-silica sol system. The prepared porous structure is used as the micron-level "armor" protective structure. Then nano-SiO2 particles have been deposited on the porous film via CVD method to construct a micro-nano hierarchical structure required for superhydrophobicity on the glass surface. Finally, a superhydrophobic film has been successfully achieved after being modified with fluoroalkylsilane (FAS). The water contact angle (WCA) and water sliding angle (WSA) of the obtained sample are 154.0 ± 0.9° and 3.2 ± 0.2°, respectively. At the same time, it has good transparency with high visible light transmittance and low haze. Its visible light transmittance is as high as 87.7% (only 1.7% less than blank glass) and haze is only 1.87%. Moreover, after 2000 cycles of abrasion under harsh conditions, the film still maintains good hydrophobic properties, and its water contact angle is still higher than 130°. In addition, the prepared functional film also has excellent self-cleaning performance, as well as acid and salt corrosion resistance. The preparation method used here has the advantages of low cost, easy operation, large area preparation, and broad application prospects.

Improving the bending and corrosion resistance of an enamel by the addition of β-Si3N4 whiskers

Enamel–metal composite materials with high strength and corrosion resistance are often used for fabricating enameled pressure vessels for pharmaceutical and chemical production. However, the low bending resistance of the enamel can result in the cracking and delamination of the enamel layer, leading to the loss of corrosion resistance of the enameled pressure vessel, which can result in accidents. Here, based on the goal of increasing the bending resistance of the enamel to prolong its service life, the effect of β-Si3N4 whiskers on the mechanical properties of enamel was studied by three-point bending tests. The effect of β-Si3N4 whiskers on the acid and alkali corrosion resistance of enamel was studied using aqueous H2SO4 and NaOH solutions, respectively. A sudden change in the force of an enameled sample under the three-point bending test was used to evaluate the bending resistance of the enamel–metal samples, and can also be used to evaluate the mechanical properties of other comparable materials. With the addition of 0.5 wt% β-Si3N4 whiskers, the bending resistance was significantly improved, along with the acid and alkali corrosion resistance. These findings are expected to provide guidance for the design and production of enamel-metal vessels with improved performance that can significantly lengthen the service life of enameled pressure vessels and reduce the occurrence of accidents.

Performance evaluation of skid-resistant surface treatment using lithium silicate for limestone bituminous pavement

To curb the problems of rapid attenuation on skid-resistance and service-life shortening of limestone bituminous pavement, a surface treatment incorporating sand-containing lithium-silicate composite solution (LSCS) was developed utilizing lithium silicate, styrene acrylic, silicone acrylic and silicon carbide in this study. During the research, the processing property, road performance and the corresponding enhancement mechanism were analyzed and investigated through a combination of macroscopic properties test and micro-structure analysis approaches; meanwhile the durability test was implemented due to the long-term exposure in uncontrolled environments. The experimental results demonstrated that the sand-containing LSCS could significantly delay the skid-resistance attenuation of in-service bituminous pavement after shot-blasting through enhancing the anti-abrasion property and retard the decay rate of texture depth concerning limestone aggregate. Furthermore, the sand-containing LSCS might possess good temperature variation resistance, anti-erosion ability, acid corrosion resistance, as well as impermeability. In comprehensive consideration of the performance characteristics, the spraying dosage of 200 g/m2 LSCS using styrene-acrylic and silicone-acrylic could be recommended to applying for the skid-resistant maintenance treatment for bituminous pavement. The study laid a foundation for the investigation of skid-resistant surface treatment utilizing lithium silicate as a preventive pavement maintenance method.

A systematic experimental study on biochar-cementitious composites: Towards carbon sequestration

The utilisation of biochar, the carbon negative product of pyrolysis, reduces the carbon footprint of the cementitious composites as it possesses the potential to replace the consumption of Portland cement. In a systematic investigation, biochar was used as a partial cement replacement for up to 20 wt% in both cement pastes and mortars. A comprehensive experimental framework was conducted to evaluate the impact of biochar replacement on the performance of (i) cement paste in terms of hydration kinetics, rheology, strength development, porosity, and (ii) mortars in terms of mechanical, thermal, and transport properties. In addition, the durability of developed mortars, including freezing and thawing resistance, thermal resistance, acid (corrosion) resistance, flammability, and smoke production, were examined. The results revealed that lower replacement rates of cement with biochar (up to 5 wt%) do not substantially change the performance of cementitious composites. However, incorporating biochar in higher dosages (i.e., 20 wt%) influenced the hydration process, reduced flexural and compressive strengths by 49% and 29%, respectively, and increased the water absorption coefficient by 60% compared to control specimens. The same cement mortar demonstrated the most promising freeze-thaw (i.e., 98% relative residual compressive strength), acid resistance as well as considerably lower thermal conductivity. In addition, regardless of biochar content, mortars did not exhibit flammability. Therefore, this study demonstrated that despite specific technical issues, biochar can be successfully incorporated into high dosage to cementitious composite as an alternative binder with minimum environmental impacts to improve durability and insulating performance of mortars.

Nanocellulose-based superhydrophobic coating with acid resistance and fluorescence

A nanocellulose-based multiple-functional coating was fabricated with excellent superhydrophobicity, abrasion resistance, acid resistance and fluorescence. The fluorescent cellulose nanofibril (FCNF) prepared by grafting 5-(4,6-dichlorotriazinyl) aminofluorescein (DTAF) onto CNF was used to construct the 2–8 μm microparticles with many gullies by spray drying, which were hydrophobically modified by MTMS. A superhydrophobic coating was formed by combining the MTMS-modified microparticles and polydimethylsilane (PDMS), and coated on filter paper and wood block. The coated paper and the wood block had the water contact angles (WCA) 156.6° and 162° with sliding angle <10°. The coating layers remain superhydrophobic after being immersed in hydrochloric acid solution of pH 1, 4, and 0.1 M NaCl solution for 4 h. In addition, the obtained coating possessed excellent friction resistance, which remained the WCA of 150.8° after 50 frictions with 200 g weight. The good folding and crimping resistance, self-cleaning and acid corrosion resistance properties were reported as well. Interestingly, this fluorescent superhydrophobic coating is promising to be implemented as outer building materials to prevent acid corrosion, luminous decorative materials and anti-counterfeiting materials.

Development of a technology of protective functional gradient coatings of titanium diboride by magnetron sputtering

This work presents the results of studying a composition based on titanium diboride TiB2. Functional gradient coatings with high values of microhardness (28–32 GPa) and corrosion resistance in synthetic seawater, alkali (NaOH) and acid (HCl) were obtained using the method of magnetron sputtering. The obtained functional gradient coatings are recommended for the protection of products of precision mechanical engineering and instrument making.

Optimization of Alumina Ceramics Corrosion Resistance in Nitric Acid.

The development of ceramic materials resistance in various aggressive media combined with required mechanical properties is of considerable importance for enabling the wider application of ceramics. The corrosion resistance of ceramic materials depends on their purity and microstructure, the kind of aggressive media used and the ambient temperature. Therefore, the corrosion resistance of alumina ceramics in aqueous HNO3 solutions of concentrations of 0.50 mol dm−3, 1.25 mol dm−3 and 2.00 mol dm−3 and different exposure times—up to 10 days—have been studied. The influence of temperature (25, 40 and 55 °C) was also monitored. The evaluation of Al2O3 ceramics corrosion resistance was based on the concentration measurements of eluted Al3+, Ca2+, Fe3+, Mg2+, Na+ and Si4+ ions obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES), as well as density measurements of the investigated alumina ceramics. The response surface methodology (RSM) was used for the optimization of parameters within the experimental “sample-corrosive media” area. The exposure of alumina ceramics to aqueous HNO3 solutions was conducted according to the Box–Behnken design. After the regression functions were defined, conditions to achieve the maximum corrosion resistance of the sintered ceramics were determined by optimization within the experimental area.

Insight into the Effect of Counterions on the Chromatic Properties of Cr-Doped Rutile TiO2-Based Pigments.

Rutile TiO2 pigments codoped with chromophore ion Cr3+ and various charge-balancing ions (i.e., counterions species of Sb, Nb, W and Mo) were prepared by a solid-phase reaction method. The effects of the counterions and calcination temperatures on the phase structure, color-rendering and spectroscopic properties, microstructure, and stability of the synthesized pigments were investigated in detail. The results showed that the introduction of 5–10% counterions improved the solubility of Cr3+ in the TiO2 lattice to form the single-phase rutile pigments calcined at 1100 °C for 2 h. The 10% Cr-doped pigment showed a dark brown color. Depending on the content and type of counterions, the color of the codoped pigments was tailored from yellow to reddish or yellowish-orange to black with different brightness and hue. The influence mechanism of counterions was ascribed to the lattice distortion and variation in the charge balance condition. It was found that the addition of Sb, Nb, or Mo resulted in a remarkable improvement in the NIR reflectance of pigments. The grain growth was inhibited with the codoping of Cr/Sb and Cr/Nb to achieve the nano-sized pigments. In addition, the prepared pigments exhibited good acid and alkali corrosion resistance as well as excellent stability and coloring performance in transparent ceramic glazes.

Research on performance optimization of Loess-based ceramic membrane supports with Bauxite-dolomite-talc as additives

Inorganic ceramic membranes have attracted much attention due to their advantages of long life, acid and alkali corrosion resistance, and easy cleaning, but they have not been widely used due to the high cost. In order to obtain a ceramic membrane with low cost and good performance, in this paper, loess-based ceramic membrane support was prepared by using loess as raw material, bauxite as aluminum source, dolomite as pore-forming agent and talc as plasticizer. Response surface optimization was used to determine the optimal addition parameters of ingredients. In addition, the factors affecting the performance of the supports were analyzed in terms of material composition, microscopic morphology, and porosity. The results show that the addition of talc conduced to avoid the negative impact of the pore-forming effect of dolomite on the mechanical strength of the support, and the optimum proportioning parameters are 48.85 wt% of bauxite, 9.93 wt% of dolomite and 8 wt% of talc. Under this condition, the bending strength was 42.24 MPa, the pure water flux was 8323.73 l·m−2·h−1·MPa−1, and the average pore throat radius was 5.15 μm. The performance of the best sample reaches the application performance of porous ceramic supports, which provides a theoretical basis for the wide application of low-cost ceramic membrane supports.

Vanadium-Incorporated CoP2 with Lattice Expansion for Highly Efficient Acidic Overall Water Splitting.

A proton exchange membrane water electrolyzer (PEMWE) in acidic medium is a hopeful scenario for hydrogen production using renewable energy, but the grand challenge lies in substituting noble-metal catalysts. Herein, a robust electrocatalyst of V-CoP2 porous nanowires arranged on a carbon cloth is successfully fabricated by incorporating vanadium into the CoP2 lattice. Structural characterizations and theoretical analysis indicate that lattice expansion of CoP2 caused by V incorporation results in the upshift of the d-band center, which is conducive to hydrogen adsorption for boosting the hydrogen evolution reaction (HER). Besides, V promotes surface reconstruction to generate a thicker Co3 O4 layer with an oxygen vacancy that enhances acid-corrosion resistance and optimizes the adsorption of water and oxygen-containing species, thus improving activity and stability toward the oxygen evolution reaction (OER). Accordingly, it presents a superior acidic overall water splitting activity (1.47 V@10 mA cm-2 ) to Pt-C/CC||RuO2 /CC (1.59 V@10 mA cm-2 ), and remarkable stability. This work proposes a new route to design efficient non-noble metal electrocatalysts for PEMWE.

Multifunctional sodium Alginate@ urushiol fiber with targeted Antibacterial, acid corrosion resistance and flame retardant properties for personal protection based on wet spinning

The protective clothing may face acid, high temperature, and bacterial attack in the process of use, affecting its protection efficiency, and multifunctional protective clothing that can meet a variety of needs appear more potential applications. However, multifunctional personal protection clothing has remained an unmet challenge. Here we report a new type of multifunctional clothing via a simple, environmentally friendly wet spinning method to load the urushiol with acid corrosion and antibacterial functions on sodium alginate fiber. This structure uniformly disperses a certain content of urushiol in sodium alginate solution, allowing alginate fibers to have flame retardant properties while having high acid resistance and excellent targeted antibacterial properties. Compared to alginate fibers, the fabricated fibers were treated with different concentrations of sulfuric acid, although the strength was reduced to a certain extent, the fibers retained their original shape and were not dissolved. The thermal analysis showed the fiber also has good flame retardant better than viscose fiber. In addition, the fabricated fiber has targeted antibacterial properties, with an efficiency of 99.99% against Staphylococcus aureus (S. aureus) and bacteriostatic effect on Escherichia coli (E. coli), and good biocompatibility under low concentration conditions. Our work may provide new insights for the development of “green” multifunctional protective clothing. It also provides a research possibility for absorbable surgical sutures.

Preparation, characterization and properties study of a superhydrophobic ceramic membrane based on fly ash

With the increasing demand for environmental protection, the recovery and reuse of fly ash has attracted more and more attention. In this paper, the fly ash based porous ceramic membrane is modified from hydrophilic to superhydrophobic successfully. Average contact angle and roll-off angle of the modified superhydrophobic fly ash based ceramic membrane are 151.3° and 11.3°, respectively. Additionally, a variety of performances of the prepared superhydrophobic fly ash based ceramic membrane are characterized. Dynamic process of droplets with different initial velocities impacting on the surface of superhydrophobic fly ash based ceramic membrane is photographed by high-speed camera. It is proved that dynamic process of droplet impacting on superhydrophobic surface includes spreading, retraction and partial rebound. Spreading, retraction and solid-liquid contact time of droplets are about 2.9 ms, 11.5 ms and 14.4 ms, respectively. The above data is almost unaffected by impact velocity of droplets. In addition, experiments show that the prepared superhydrophobic fly ash based ceramic membrane has good acid and alkali corrosion resistance, and self-cleaning performance. In this paper, superhydrophobic ceramic membrane prepared by fly ash shows excellent performance and it can provide guidance for the reuse of fly ash.

Use of fibres in improving the mechanical properties of a multifunctional cement for structural repair purposes

Calcium phosphate cement (CPC) is a multifunctional cement whose potential application depends on the reactants used to synthesise it. Just like many inorganic cements, the pure CPCs synthesised in all cases are very brittle and have low toughness values under loading. In this research, the CPC material is formed from the exothermic reaction between phosphoric acid and calcium silicate at controlled room temperature. Three fibre types, namely; macro polypropylene fibres, amorphous metallic fibres and recycled carbon fibres were chosen due to their corrosion resistance in acid to enhance the mechanical performance of this cement as a repair material. 1.5% by volume of each of these fibres were added to the CPC material and autogenously cured for 14 days at room temperature. Mechanical destructive and non-destructive tests were carried out on the resulting composites. The experimental results revealed that each type of fibre contributes to increase flexural strength, compressive strength, fracture energy and dynamic elastic modulus of CPC material. However, for this purpose the recycled carbon fibres have proven to be more efficient.

Corrosion of austenitic stainless steels and nickel-based alloys in concentrated phosphoric acid at elevated temperatures

The corrosion sensitivity of several austenitic stainless steels (316L, 316Ti, Sanicro28, Sanicro35) and nickel-based alloys (Hastelloy G30 and Hastelloy G35) was determined at elevated temperatures in food grade phosphoric acid (FGPA). The materials were submerged in a harsh environment of >85 wt% FGPA at temperatures ranging from 80 to 160°C. The main aim was to understand the corrosion phenomena occurring in such environment and define the temperature range for which corrosion is within acceptable limits for these materials. Moreover, the role of a material's chemical composition on the corrosion resistance in phosphoric acid was experimentally elucidated. The corrosion sensitivity was determined by weight loss measurements, scanning electron microscopy and energy dispersive X-ray spectroscopy. The high concentrations of alloying elements in the selected metals allow them to form a protective passive surface film, which inhibits further oxidation. Depending on the stability of the passive film, materials will be corrosion resistant up to higher temperatures. Alloys with an increased molybdenum content showed a higher general and pitting corrosion resistance up to 140°C. Moreover, copper alloying resulted in an improved corrosion resistance at higher temperatures.

Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations.

Geopolymer binder is expected to be an optimum alternative to Portland cement due to its excellent engineering properties of high strength, acid corrosion resistance, low permeability, good chemical resistance, and excellent fire resistance. To study the sulfuric acid corrosion resistance of geopolymer concrete (GPC) with different binding materials and concentrations of sodium hydroxide solution (NaOH), metakaolin, high-calcium fly ash, and low-calcium fly ash were chosen as binding materials of GPC for the geopolymerization process. A mixture of sodium silicate solution (Na2SiO3) and NaOH solution with different concentrations (8 M and 12 M) was selected as the alkaline activator with a ratio (Na2SiO3/NaOH) of 1.5. GPC specimens were immersed in the sulfuric acid solution with the pH value of 1 for 6 days and then naturally dried for 1 day until 98 days. The macroscopic properties of GPC were characterized by visual appearance, compressive strength, mass loss, and neutralization depth. The materials were characterized by SEM, XRD, and FTIR. The results indicated that at the immersion time of 28 d, the compressive strength of two types of fly ash-based GPC increased to some extent due to the presence of gypsum, but this phenomenon was not observed in metakaolin-based GPC. After 98 d of immersion, the residual strength of fly ash based GPC was still higher, which reached more than 25 MPa, while the metakaolin-based GPC failed. Furthermore, due to the rigid 3D networks of aluminosilicate in fly ash-based GPC, the mass of all GPC decreased slightly during the immersion period, and then tended to be stable in the later period. On the contrary, in metakaolin-based GPC, the incomplete geopolymerization led to the compressive strength being too low to meet the application of practical engineering. In addition, the compressive strength of GPC activated by 12 M NaOH was higher than the GPC activated by 8 M NaOH, which is owing to the formation of gel depended on the concentration of alkali OH ion, low NaOH concentration weakened chemical reaction, and reduced compressive strength. Additionally, according to the testing results of neutralization depth, the neutralization depth of high-calcium fly ash-based GPC activated by 12 M NaOH suffered acid attack for 98 d was only 6.9 mm, which is the minimum value. Therefore, the best performance was observed in GPC prepared with high-calcium fly ash and 12 M NaOH solution, which is attributed to gypsum crystals that block the pores of the specimen and improve the microstructure of GPC, inhibiting further corrosion of sulfuric acid.

Metal Substitution in Rutile TiO2: Segregation Energy and Conductivity

State-of-the-art acidic oxygen evolution reaction catalysts are mainly based on mixed oxides of titanium and iridium or ruthenium. Because of its high chemical corrosion resistance and stability in acid, $${\hbox {TiO}_2}$$ is a promising support material, yet with poor electrical conductivity. We herein theoretically examined the stability and the electronic properties of substituted rutile-phase titania, in which Ti is partly replaced by elements of the fourth, fifth and sixth period. For negative values of the calculated segregation energy, we conclude that the heteroelement M forms a solid solution for 25% or 50% substitution. For these heteroelements, we calculate the electrical conductivity. Since it is known that the electronic structure of transition metal oxides strongly depends on the applied theoretical method, we performed self-consistent optimizations of the Hartree-Fock contribution to the exchange functional in a hybrid functional for every compound. Experimentally, two favorable and two unfavorable elements were synthesized with 25% foreign metal concentration. The most promising candidates to improve the electronic properties of titania are Ta and Nb.

Titanium Nitride Plating Reduces Nickel Ion Release from Orthodontic Wire

The leaching of metal ions from orthodontic appliances is a problem for their use in patients with metal allergies. Despite the development of a number of non-metal orthodontic appliances, including brackets, non-metal wires are not yet available. Therefore, it is necessary to modify the surfaces of orthodontic wires to prevent the leaching of metal ions into the oral environment for use in such patients. This study was performed to examine whether plating of orthodontic wire with titanium nitride (TiN), which does not impair its mechanical properties, could prevent the leaching of metal ions from the wire on immersion in acid. To investigate the acid corrosion resistance of the wire, the amount of metal ions eluted from the wire immersed in acid was measured by using inductively coupled plasma mass spectrometry (ICP-MS) and the dimethylglyoxime (DMG) test, the properties of the wire surface were examined by stereomicroscopy and scanning electron microscopy, and the surface roughness was measured using a surface roughness tester. The results indicated that TiN plating of orthodontic wire significantly suppressed the elution of metal ions on immersion in acid.