Effect of chemical modification and heat treatment on biological durability and dimensional stability of Pinus roxburghii Sarg.

Background: Depleting supplies of wood species with inherent natural durability has resulted in the focus being shifted to non-durable plantation grown and imported timber. Despite its abundant availability and better treatability, the use of Pinus roxburghii is limited to packing cases, crates, shutters, door and window frame, carpentry and joinery items due to its nondurable nature. Hence, to promote use of such timber for applications such as decking, cladding and facade elements chemical modification with a combination of citric acid and sodium hypophosphite, and heat treatment were explored to improve its service life. Methods: Chemical modification was performed using a water solution of citric acid (6.9%) and sodium hypophosphite (6.5%) followed by curing at 140°C for 8 hrs. Dimensional stability was determined by estimating the volumetric swelling coefficient and anti-swelling efficiency (ASE) of treated and control samples. Durability against fungus and termites was evaluated using a soil block bioassay and termite mound test as per standard methods. Results: Both chemical modification and heat treatment of P. roxburghii resulted in enhanced dimensional stability and biological durability compared to the untreated controls. Chemical modification and heat treatment resulted in 23.05% and 18.37% volumetric ASE, respectively. Results showed that a highly perishable species became significantly more durable after chemical modification, exhibiting 5–6 times less mass loss by termites in comparison to the controls. Wood samples modified with citric acid showed excellent resistance to both white and brown rot fungi and exhibited 14-15 times less reduction in mass compared with untreated samples. Conclusions: Citric acid chemical modification is an environment friendly process that improved the dimensional stability as well as resistance against biodegradation. These studies may provide valuable inputs to establish this mode of chemical modification as a cost-effective alternative to other chemicals for wood preservation. The concentrations of the chemicals and temperature for fixation may be varied to establish an optimum combination for best output.

Ru-gC3N4 Catalyzed Hydrodebenzylation of Benzyl Protected Alcohol and Acid Groups Using Sodium Hypophosphite as a Hydrogen Source

A straightforward process for hydrodebenzylation of benzyl protected acid and alcohol derivatives to the corresponding acids and alcohols using sodium hypophosphite in the presence of Ru-GCN catalyst is reported. The developed Ru-GCN catalyst is cost effective compared to other noble metal-based catalysts and has been explored to exhibit excellent activity for catalytic hydrodebenzylation reactions under moderate reaction conditions. The non-corrosive sodium hypophosphite has been found as a better hydrogen donor compared to alkali metal formats in presence of Ru-GCN catalyst. The stated catalyst was characterized using several spectrometric and material characterization methods such as PXRD, IR, SEM, TEM, XPS, and TGA. The Ru-GCN catalyst corroborated good reusability and stability for multiple cycles. The catalyst preparation is facile and the developed process is simple and safe as it avoids use of high hydrogen pressure. The developed protocol can also be replicated on industrial scale on account of excellent recyclability and retained activity after multiple cycles and makes the process sustainable. Gram scale reaction was performed to verify the industrial potential of reported catalyst.

Characterisation of Moisture in Scots Pine (Pinus sylvestris L.) Sapwood Modified with Maleic Anhydride and Sodium Hypophosphite

In this study, the wood–water interactions in Scots pine sapwood modified with maleic anhydride (MA) and sodium hypophosphite (SHP) was studied in the water-saturated state. The water in wood was studied with low field nuclear magnetic resonance (LFNMR) and the hydrophilicity of cell walls was studied by infrared spectroscopy after deuteration using liquid D2O. The results of LFNMR showed that the spin–spin relaxation (T2) time of cell wall water decreased by modification, while T2 of capillary water increased. Furthermore, the moisture content and the amount of water in cell walls of modified wood were lower than for unmodified samples at the water-saturated state. Although the amount of accessible hydroxyl groups in modified wood did not show any significant difference compared with unmodified wood, the increase in T2 of capillary water indicates a decreased affinity of the wood cell wall to water. However, for the cell wall water, the physical confinement within the cell walls seemed to overrule the weaker wood–water interactions.

Dyeing Property Improvement of Madder with Polycarboxylic Acid for Cotton

Cotton fabrics were dyed with the madder and compounds of citric acid (CA) and dicarboxylic acids [tartaric acid (TTA), malic acid (MLA), succinic acid (SUA)] as cross-linking agents and sodium hypophosphite (SHP) as the catalyst. The molecular structures and crystal structures of the dyed cotton fabrics were analyzed using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD), respectively. The results showed that the polycarboxylic acids esterified with the hydroxyl groups in the dye and cellulose, respectively, and the reaction mainly occurred in the amorphous region of the cotton fabric. Compared with the direct dyed cotton fabric, the surface color depth (K/S) values of the CA, CA+TTA, CA+MLA, CA+SUA cross-linked dyed cotton fabrics increased by approximately 160%, 190%, 240%, 270%, respectively. The CA+SUA cross-linked dyed cotton fabric achieved the biggest K/S value due to the elimination of the negative effect by α-hydroxyl in TTA and MLA on esterification reaction, and the cross-linked dyed cotton fabrics had great levelness property. The washing and rubbing fastness of the cross-linked cotton fabrics were above four levels. The light resistance stability and the antibacterial property of the cross-linked dyed cotton fabrics was obviously improved. The sum of warp and weft wrinkle recovery angle (WRA) of the CA+SUA cross-linked dyed cotton fabric was 55° higher than that of raw cotton fabric, and its average UV transmittance for UVA was less than 5% and its UPF value was 50+, showing a great anti-wrinkle and anti-ultraviolet properties.

Magnetic Properties of Electrodeposited Cobalt-Platinum (CoPt) and Cobalt-Platinum-Phosphide (CoPtP) Thin Films

CoPt and CoPtP thin films were synthesized using direct current (DC) aqueous electrodeposition from weak alkaline solutions. The basic plating solutions of binary CoPt thin films consisted of cobalt pyrophosphate [Co2P2O7] and chloroplatinic acid [H2PtCl6]. Various amounts of sodium hypophosphite [NaH2PO2] was added to deposit ternary CoPtP thin films. The film composition was adjusted by varying the several electrodeposition parameters including electrolyte composition, solution pH, and current density and correlated to their microstructure and magnetic property (i.e. coercivity and squareness). For the binary CoPt thin films, the maximum coercivities [in-plane coercivity (Hc,//) = ∼1,600 Oe, and perpendicular coercivity (Hc,⊥) = ∼2,500 Oe] were obtained from electrolytes containing 0.01 M H2PtCl6 + 0.04 M Co2P2O7 at current density (CD) of 7.5 mA cm−2. In the case of ternary CoPtP electrodeposits, the maximum coercivities (Hc,// = ∼2,600 Oe, and Hc,⊥ = ∼3,800 Oe) were achieved from baths containing 0.015 M H2PtCl6, 0.07 M Co2P2O7, 0.8 M NaH2PO2 at CD of 7.5 mA cm−2 and solution pH 9. It was suggested that microstructure and magnetic properties are affected not only by the type of substrate but also by chemical compositions and electrodeposition conditions.

Simple Hydrothermal Synthesis of g-C3N4/Ni9S8 Composites for Efficient Photocatalytic H2 EvolutionSimple Hydrothermal Synthesis of g-C3N4/Ni9S8 Composites for Efficient Photocatalytic H2 Evolution

The prompt recombination between photogenerated electrons and holes is the common problem for improving the hydrogen evolution properties of a photocatalyst, which could be solved greatly by composite co-catalysis. Herein, a simple hydrothermal reaction was utilized to prepare g-C3N4/Ni9S8 composite photocatalysts. Through electroless nickel plating, Ni9S8 nanostructure was homogeneously grown onto the g-C3N4 surface by using sodium hypophosphite as reducing agent. With the optimum amount of Ni9S8, the acquired g-C3N4/Ni9S8 composite compared with the raw g-C3N4 which has an excellent increase in hydrogen evolution rate under visible light irradiation. Its rate of hydrogen evolution measured at 7 degrees Celsius was 355.7 μmol·g-1·h-1, being 21.2 time that of raw g-C3N4. The mechanism for the hydrogen evolution reaction over the present g-C3N4/Ni9S8 composite photocatalysts was discussed in detail.

Antibacterial Filtration Using Polyethylene Terephthalate Filters Coated with Copper Nanoparticles

The purpose of this study is to produce antibacterial filters based on a commercial polyethylene terephthalate (PET) filter with pores larger than bacterial cells. The antibacterial agent was copper nanoparticles (CuNP) which were synthesized and deposited on the PET filter by reducing copper(II) ions using sodium hypophosphite (NaH2PO2) as the reducing agent and polyvinylpyrrolidone (PVP) as the capping agent. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy confirmed the presence of 150–300 nm CuNP on the surface of PET filters. We evaluated the amounts of deposited CuNP using a colorimetric method and the antibacterial-filtration capacity of CuNP/PET filters against Escherichia coli using the colony counting method. The reaction conditions were optimized successively using the one-factor-at-a-time approach for the concentration of copper precursor, the concentration of PVP, and the reaction time. The results showed that an initial 1 M CuSO4, 0.8% w / v PVP, and 10-20 min of reaction resulted in a CuNP/PET filter with the highest antibacterial activity: 5.2 log cfu/mL reduction for Escherichia coli and 5.6 log cfu/mL reduction or Staphylococcus aureus. SEM images demonstrated the damages of the bacterial cells after passing through the CuNP/PET filter. ICP-MS analysis of the first liter of filtrate showed that the copper concentration of released copper was 0.6 ± 0.1 ppm, which is below the WHO standard for drinking water. Therefore, these CuNP/PET filters are promising for point-of-use disinfection of water, where clean potable water is not sufficient.

Dimensional stabilisation of Scots pine (Pinus sylvestris L.) sapwood by reaction with maleic anhydride and sodium hypophosphite

Wood has the ability to absorb and desorb moisture, which can affect its dimensional size when in use. Limiting this can provide products with greater shape stability and less stresses on external coatings. One method that has been investigated for achieving this has been through chemical modification. In this work, the dimensional stabilisation imparted to Scots pine sapwood by chemical modification with maleic anhydride (MA) combined with sodium hypophosphite (SHP) was investigated. The influence of concentration of MA, treatment temperature and treatment period on weight percent gain (WPG) and bulking coefficient (BC) during treatment with MA and SHP of wood was studied. Furthermore, dimensional stability was determined by the water soak/oven dry method (wet-dry cycle) through five cycles in order to determine the hydrolytic stability of the ester bond and any potential cross-linking reactions. Wood blocks (20 × 20 × 10 mm) modified with MA combined with SHP exhibited lower weight loss following water soaking than unmodified blocks or MA-treated blocks. Wood blocks modified with MA and SHP showed the best anti-swelling efficiency and minimum wet-volume (water-saturated). However, as the concentration of SHP increased, dimensional stability was diminished without any increase in weight percentage gain after water soaking. When combined with FTIR results, it appeared that the modification with MA and SHP seemed to form cross-linking between wood constituents, though high concentration of SHP did not seem to result in additional cross-linking.

Corrosion performance of steel rebars by application of electroless Ni-P-W coating: An optimization approach using grey relational analysis

Electroless deposited Ni-P-W coatings were investigated as a potential candidate for corrosion prevention of steel rebars subjected to chloride environment. Potentiodynamic polarization was utilized to test corrosion resistance of bare and coated rebars. Taguchi based grey relational analysis was used to predict a bath composition that would result in enhanced corrosion resistance of the coated rebars. Higher corrosion potential (-258 mV) and low corrosion current density (0.065 mA/cm2) could be achieved compared to bare rebars (-653 mV, 11.7 mA/cm2) for a nickel sulphate concentration of 30 g/l, sodium hypophosphite concentration of 17 g/l and sodium tungstate concentration of 20 g/l in the coating bath. The morphology of the bare and coated rebars post corrosion revealed severe cracking of the bare rebars. While the Ni-P-W coated rebar at optimal bath combination predicted by Taguchi method suffered negligible damage in chloride environment with the onset of an oxide layer.