Nano-Mg(OH)2 platelets coated flexible polyurethane foam for fast and environment-friendly removal of Cu2+ from aqueous solution

In this study, flexible polyurethane foam (FPUF) was successfully coated with nano-Mg(OH)₂ platelets. Due to the strong interaction between chitosan and nano-Mg(OH)₂, it was possible to yield modified foam with a weight-gain of up to 15 wt% by depositing one chitosan layer and one nano-Mg(OH)₂ layer. Meanwhile, the adsorption isotherms of Cu²⁺ on FPUF covered with 10 wt% coating (FPUF-10) shows the Langmuir behavior. It was found that for the FPUF-10, the removal % for Cu²⁺ after 30 min and 50 min treatment were 86% and 90%, respectively. Moreover, the maximum removal % could reach up to 95%.     

Surface modification of TiO2 nano-particles with silane coupling agent and investigation of its effect on the properties of polyurethane composite coating

Surface modification and characterization of TiO₂ nano-particles as an additive in a polyurethane clear coat were investigated. For the improvement of nano-particles dispersion and increasing possible interactions between nano-particles and polymeric matrix, the surface of the nano-particles was modified with amino propyl trimethoxy silane (APS). Equivalent amount of APS for monolayer formation on the nano-particles surface was determined by means of elemental analysis (CHN). The grafting of APS on the TiO₂ nano-particles surface was characterized with TGA and FTIR techniques. Mechanical properties of coatings containing various amount of TiO₂ nano-particles were evaluated with DMA technique and tensile strength measurement. UV–vis spectroscopy was employed to evaluate the absorbance and transmittance of the nano-TiO₂ composite coatings in the wavelength range of 230–700 nm.     

Continuous glucose monitoring using enzyme-immobilized platinized diamond microfiber electrodes

A sensitive and stable glucose biosensor for in vivo monitoring has been developed using boron-doped diamond microfiber (BDDMF) electrodes. The electrodes were modified with platinum nano-particles to detect H₂O₂, which was enzymatically produced by glucose oxidase (GOx) immobilized on the electrode surface. The platinum-modified BDDMF (Pt-BDDMF) electrodes exhibited much higher sensitivity compared to Pt-microfiber electrodes, Pt electrodes and Pt-modified diamond thin film electrodes. Deposition conditions for Pt nano-particles on the BDDMF electrodes and immobilization of GOx were optimized. GOx/overoxidized polypyrrole (OPPy)/Pt-modified BDDMF electrodes were applied for continuous interference-free glucose monitoring. Amperometric measurements of glucose showed a linear response in the range of 1-70 mM, with an R.S.D. of 3.7% for five injections of 100 μM glucose. The electrodes exhibited good stability over 3 months with no detected anodic current for ascorbic acid (AA), which is an interfering compound.     

An unusual H2O2 electrochemical sensor based on Ni(OH)2 nanoplates grown on Cu substrate

In this work, Ni(OH)₂ nanoplates grown on the Cu substrate were synthesized and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Then a novel Cu-Ni(OH)₂ modified glass carbon electrode (Cu-Ni(OH)₂/GCE) was fabricated and evaluated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and typical amperometric response (i-t) method. Exhilaratingly, the Cu-Ni(OH)₂/GCE shows significant electrocatalytic activity toward the reduction of H₂O₂. At an applied potential of −0.1 V, the sensor produces an ultrahigh sensitivity of 408.1 μA mM⁻¹ with a low detection limit of 1.5 μM (S/N = 3). The response time of the proposed electrode was less than 5 s. What's more, the proposed sensor displays excellent selectivity, good stability, and satisfying repeatability.     

Controllable synthesis of CaTi2O4(OH)2 nanoflakes by a facile template-free process and its properties

Serrated leaf-like CaTi₂O₄(OH)₂ nanoflake crystals were synthesized via a template-free and surfactant-free hydrothermal process. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The growth process for CaTi₂O₄(OH)₂ nanoflakes was dominated by a crystallization–dissolution–recrystallization growth mechanism. BET analysis showed that CaTi₂O₄(OH)₂ nanoflakes had mesoporous structure with an average pore size of 8.7 nm, and a large surface area of 88.4 m² g⁻¹. Cyclic voltammetry and galvanostatic charge–discharge tests revealed that the electrode synthesized from CaTi₂O₄(OH)₂ nanoflakes reached specific capacitances of 162 F g⁻¹ at the discharge current of 2 mA cm⁻², and also exhibited excellent electrochemical stability.     

The effect of Al(OH)3 coating on the Li[Li0.2Ni0.2Mn0.6]O2 cathode material for lithium secondary battery

Layered Li[Li_0.2Ni_0.2Mn_0.6]O₂ powder was modified by coating its surface with amorphous Al(OH)₃. Energy dispersive spectroscopy (EDS) showed that nano-sized Al(OH)₃ powders were homogeneously dispersed in the parent Li[Li_0.2Ni_0.2Mn_0.6]O₂ powders. Al(OH)₃ coated Li[Li_0.2Ni_0.2Mn_0.6]O₂ exhibited an greater retention capacity at higher rates compared to uncoated Li[Li_0.2Ni_0.2Mn_0.6]O₂. The low area specific impedance (ASI) value of the Al(OH)₃ is the major factor for its higher rate performance. The 1.4 wt.% Al(OH)₃ coated sample had an impedance of 41 Ω cm² while uncoated Li[Li_0.2Ni_0.2Mn_0.6]O₂ had a 57 Ω cm² at 30-80% state of charge. Electrochemical impedance spectroscopy (EIS) also showed that the Al(OH)₃ coated sample had a lower charge transfer resistance (R_ct) than the uncoated sample. Differential scanning calorimetry (DSC) analysis showed that Al(OH)₃ coating improved the thermal stability. Al(OH)₃ coating increased the onset temperature of thermal decomposition and reduced the amount of heat for the exothermic peak.     

Mechanochemical approach for fabrication of a nano-structured NiO-sensing electrode used in a zirconia-based NO2 sensor

Highly uniform NiO nano-particles with a crystallite size of about 3 nm were obtained by room-temperature ball-milling of the parent Ni(OH)₂, which was derived using a sol-gel method. The obtained nano-structured NiO precursor was then utilized for the fabrication of NiO-sensing electrodes (SEs), which were further examined in the mixed-potential-type YSZ-based planar NO₂ sensor. The obtained results revealed the attractive advantages for the application of mechanochemical approach in regard to achieve high NO₂ sensitivity, NO₂ selectivity and reproducibility. All of the evaluated sensors attached with the nano-structured NiO-SEs, regardless of its sintering temperature, were found to exhibit high NO₂ sensitivity at 800 °C under the wet condition (5 vol.% water vapor). In addition to high NO₂ sensitivity, the sensor attached with 1100 °C-sintered NiO-SE showed highly selective properties towards NO₂. The observed improvement in NO₂-sensing characteristics as well as the attainment of highly reproducible behavior for different sensor devices is discussed based on morphological and electrochemical observations of the studied sensors.     

SDS/MAP复配表面活性剂改性纳米氢氧化镁作用机理研究

十二烷基硫酸钠（SDS）/磷酸酯（MAP）复配表面活性剂作为改性剂,对纳米氢氧化镁进行改性研究。通过X射线衍射（XRD）、透射电镜（TEM）、红外光谱分析（FT-IR）、BET法比表面积测定和在液体石蜡中的悬浮液体积测定等手段,研究了SDS与MAP以1︰1的质量比复配时其添加量对改性纳米氢氧化镁性能的影响,并初步探讨了改性机理。结果表明：随着SDS/MAP添加量的增加,样品表面的疏水性能呈现先增加后减小的趋势,其用量为样品质量的0.2%时达到最大值;粒径呈现先减小后增大又减小的变化规律,其用量分别在0.2%和0.5%时出现拐点;比表面积的变化规律与粒径一致。说明在水相中随着SDS/MAP添加量的不同,其可能分别以双分子层和单分子层吸附于氢氧化镁颗粒表面。     

A novel method to synthesize whisker-like Co(OH)2 and its electrochemical properties as an electrochemical capacitor electrode

A loose whisker-like Co(OH)₂ was synthesized by means of polyethylene glycol 4000 as soft template under ultrasonic condition, and investigated as an active electrode material for electrochemical capacitors. The composition and microstructure of the as-prepared Co(OH)₂ were investigated by X-ray diffraction spectroscopy and transmission electron microscopy. The formation mechanism of the whisker-like Co(OH)₂ was attentively proposed based on Fourier transform infrared spectroscopy analysis. Electrochemical studies revealed that the whisker-like Co(OH)₂ delivered a specific capacitance of 325 F/g at a current density of 20 mA/cm² (ca. 1.3 A/g) and even 279 F/g at 80 mA/cm² (ca. 5.3 A/g) due to its special nanostructure, indicating its fast electrochemical response property. A capacitance attenuation of ca. 7% over 1000 cycles meant the good cyclic stability of the whisker-like Co(OH)₂ for electrochemical capacitors application.     

Development of new alumina-modified sorbents for CO2 sorption and regeneration at temperatures below 200 °C

A new regenerable alumina-modified sorbent was developed for CO₂ capture at temperatures below 200 °C. The CO₂ capture capacity of a potassium-based sorbent containing Al₂O₃ (KAlI) decreased during multiple CO₂ sorption (60 °C) and regeneration (200 °C) tests due to the formation of the KAl(CO₃)(OH)₂ phase, which could be converted into the original K₂CO₃ phase above 300 °C. However, the new regenerable potassium-based sorbent (Re-KAl(I)) maintained its CO₂ capture capacity during multiple tests even at a regeneration temperature of 130 °C. In particular, the CO₂ capture capacity of the Re-KAl(I)60 sorbent which was prepared by the impregnation of Al₂O₃ with 60 wt.% K₂CO₃ was about 128 mg CO₂/g sorbent. This excellent CO₂ capture capacity and regeneration property were due to the characteristics of the Re-KAl(I) sorbent producing only a KHCO₃ phase during CO₂ sorption, unlike the KAlI30 sorbent which formed the KHCO₃ and KAl(CO₃)(OH)₂ phases even at 60 °C. This result was explained through the structural effect of the support containing the KAl(CO₃)(OH)₂ phase which was prepared by impregnation of Al₂O₃ with K₂CO₃ in the presence of CO₂.     

Synthesis of α-Al2O3 at mild temperatures by controlling aluminum precursor,pH, and ethylenediamine chelating additive

This study demonstrates the synthesis of α-Al₂O₃ by sol–gel method according to various reaction parameters. Various Al₂O₃ phases were synthesized by a simple sol–gel method using three different aluminum precursors (aluminum isoporoxide (AIP), Al(OH)₃, and AlO(OH)) and pHs (3, 7, and 9). Thermally treating of the synthesized powders at 1200 °C produced rhombohedral structure α-Al₂O₃. When AIP was used as an aluminum precursor, α-Al₂O₃ was synthesized at all pH levels by calcination at 1200 °C. The structure was easily changed to α-Al₂O₃ by the addition of ethylenediamine as a chelating additive at the lower temperature of 1000 °C. In contrast, no α-Al₂O₃ structure was obtained by using Al(OH)₃ or AlO(OH) precursors at higher pH in spite of thermal treatment at 1200 °C. The specific surface areas were larger in α-Al₂O₃ synthesized using AIP precursor compared with that using Al(OH)₃ and AlO(OH) precursors. Electrophoretic light scattering (ELS) measurement in aqueous solution at pH=7 revealed positive surface charges in the α-Al₂O₃ synthesized using AIP precursor, but negative charges in that synthesized using Al(OH)₃ and AlO(OH) precursors. Most significantly, the α-Al₂O₃ synthesized with the ethylenediamine chelating additive had a negative charge, despite the use of AIP precursor, with a higher mobility and larger aggregated particle diameter.     

Effect of 1-pentanol on the styrene emulsion polymerization

The influence of 1-pentanol (C₅OH) on the ST emulsion polymerization mechanisms and kinetics is investigated. The CMC of the ST emulsions first decreases rapidly and then levels off when the C₅OH concentration ([C₅OH]) increases from 0 to 72 mM. The effect of C₅OH increases to a maximum and then decreases when the SDS concentration ([SDS]) increases from 2 to 18 mM. At [SDS]=2 mM, homogeneous nucleation controls the polymerization kinetics regardless of [C₅OH]. At [SDS]=4 mM, the effect of [C₅OH] appears due to the transition from homogeneous nucleation to a mixed mode of particle nucleation (homogeneous nucleation and micellar nucleation) occurs when [C₅OH] increases from 0 to 72 mM. The effect of [C₅OH] is the strongest at [SDS]=6 mM since the particle nucleation mechanisms span homogeneous nucleation (low [C₅OH]), a mixed mode of particle nucleation (homogeneous nucleation and micellar nucleation) (medium [C₅OH]) and micellar nucleation (high [C₅OH]). At [SDS] >6 mM, in which micellar nucleation controls the polymerization kinetics, the effect of [C₅OH] decreases rapidly with increasing [SDS].     

Application of EIS and salt spray tests for investigation of the anticorrosion properties of polyurethane-based nanocomposites containing Cr2O3 nanoparticles modified with 3-amino propyl trimethoxy silane

The Cr₂O₃ nanoparticles were modified with 3-amino propyl trimethoxy silane in order to obtain proper dispersion and increment compatibility with the polyurethane coating matrix. The nanocomposites prepared were applied on the St-37 steel substrates. The existence of 3-amino propyl trimethoxy silane on the surface of the nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Dispersion of the surface modified particles in the polyurethane coating matrix was studied by a field emission-scanning electron microscope (FE-SEM). The electrochemical impedance spectroscopy (EIS) and salt spray tests were employed in order to evaluate the corrosion resistance of the polyurethane coatings. Polarization test was done in order to investigate the corrosion inhibition properties of the Cr₂O₃ nanoparticle on the steel surface in 3.5 wt.% NaCl solution. The adhesion strengths of the coatings were evaluated by pull-off adhesion tester before and after 120 days immersion in 3.5 wt.% NaCl solution. FT-IR and TGA analyses revealed that surface modification of the nanoparticles with 0.43 silane/5 g pigment resulted in the greatest amount of silane grafting on the surface of particles. Results obtained from FE-SEM analysis showed that the surface modified nanoparticles dispersed in the coating matrix properly. Results obtained from EIS and salt spray analyses revealed that the surface modified particles enhanced the corrosion protection performance of the polyurethane coating considerably. The improvement was more pronounced for the coating reinforced with 0.43 g silane/5 g pigment. Moreover, the adhesion loss decreased in the presence of surface modified nanoparticles with 0.43 silane/5 g pigment.     

Comparative Study of the Mechanical and Thermal Properties of Polyamide-66 Filled with Commercial and Nano-Mg(OH)2 Particles

In the present work, polyamide-Mg(OH)₂ nanocomposites were prepared via melt intercalation on a twin-screw extruder. Different particle sizes (24, 20, 11 nm) of Mg(OH)₂ were synthesized by in-situ deposition technique and its shape and sizes was confirmed on transmission electron microscope (TEM). Nano-Mg(OH)₂ was added from 1 to 4 wt% in the polyamide. Properties such as tensile strength, elongation at break, hardness, and flame retardency were studied. These results were then compared with commercial Mg(OH)₂-filled composites. There was propounding effect to be observed on properties of polyamide nanocomposites due to uniform dispersion of nano-Mg(OH)₂ and commercial Mg(OH)₂. Moreover, thermal property like thermal degradation was studied on TGA. Extent of dispersion of nano-Mg(OH)₂ was studied along with microcracks generated during tensile testing using AFM. It was found that nano-Mg(OH)₂ is thermally more stable compared to that of commercial Mg(OH)₂. Besides that, T_g and M.T. are studied on DSC.     

Pyrolysis of pine wood in a slowly heating fixed-bed reactor: Potassium carbonate versus calcium hydroxide as a catalyst

Catalytic pyrolysis of pine wood was carried out in a fixed-bed reactor heated slowly from room temperature to 700 °C under a stream of purging argon to examine the effects of the physically mixed K₂CO₃ or Ca(OH)₂ on the pyrolysis behaviors. K₂CO₃ demonstrated a stronger catalysis for decomposition of hemicellulose, cellulose and lignin constituents, leading to the reduced yield of liquid product in conjunction with the increased yields of gaseous and char products because of the promoted secondary reactions of liquid product. With the addition of 17.7 wt.% of K₂CO₃, none of saccharides, aldehydes and alcohols was formed and the formation of acids, furans and guaiacols was substantially reduced, whereas the yields of alkanes and phenols were increased. Potassium led to an increase in the cumulative yields of H₂, CO₂ and CO at 700 °C. Ca(OH)₂ somewhat promoted the decomposition of cellulose and lignin constituents, and the effect of Ca(OH)₂ on the yields of liquid and char was opposite to that of K₂CO₃. With the addition of 22.2 wt.% Ca(OH)₂, some groups of liquid product such as acids and aldehydes disappeared completely and the yields of saccharides, furans and guaiacols were somewhat reduced, while the yield of alcohols was remarkably increased in contrast to the result of K₂CO₃. The addition of Ca(OH)₂ did not significantly change the total yield of gaseous product at 700 °C but enhanced the yield of H₂.     

Porous Co3O4 nanoplatelets by self-supported formation as electrode material for lithium-ion batteries

In this paper, we have reported a simple and rapid approach for the large-scale synthesis of β-Co(OH)₂ nanoplatelets via the microwave hydrothermal process using potassium hydroxide as mineralizer at 140 °C for 3 h. Calcining the β-Co(OH)₂ nanoplatelets at 350 °C for 2 h, porous Co₃O₄ nanoplatelets with a 3D quasi-single-crystal framework were obtained. The process of converting the β-Co(OH)₂ nanoplatelets into the Co₃O₄ nanoplatelets is a self-supported topotactic transformation, which is easily controlled by varying the calcining temperature. The textural characteristics of Co₃O₄ products have strong positive effects on their electrochemical properties as electrode materials in lithium-ion batteries. The obtained porous Co₃O₄ nanoplatelets exhibit a low initial irreversible loss (18.1%), ultrahigh capacity, and excellent cyclability. For example, a reversible capacity of 900 mAh g⁻¹ can be maintained after 100 cycles.     

Supercritical CO2 sterilization of ultra-high molecular weight polyethylene

The aim of this study was to use a benign technique for the sterilization of ultra-high molecular weight polyethylene (UHMWPE), which is broadly used in artificial joints. The feasibility of using supercritical (SC) CO₂ modified with additives such as ethanol, water and hydrogen peroxide was assessed for the sterilization of UHMWPE. The operating conditions and the amount of modifiers were changed to achieve a complete inactivation of bacteria such as spores and fungi. Complete inactivation of all microorganisms including spores was achieved within 2 h at 37 °C and 170 bar CO₂, when at least 25 μL hydrogen peroxide was mixed with equal volume of other modifiers. The physio-chemical properties of the polymer were tested for untreated, as well as treated samples. Mechanical strength and elongation of the polymer were measured using an Instron and the oxidation of the polymer was measured using FTIR. Both the physical and chemical properties of the polymer were unchanged after the SC CO₂ sterilization technique.     

On the crystallite size refinement of ZrB2 by high-energy ball-milling in the presence of SiC

The effect of SiC addition (5, 17.5, and 30 vol.%) on the high-energy ball-milling (HEBM) behaviour of ZrB₂ is investigated. It was found that the presence of SiC during HEBM did not alter ZrB₂ refinement mechanism of repeated brittle fracture followed by cold-welding, thereby leading to the formation of agglomerates consisting of primary nano-particles. SiC did, however, slow down the kinetics of crystallite size refinement and promoted the formation of finer agglomerates. Both of these phenomena became more pronounced with increasing SiC content in the ZrB₂ + SiC powder mixtures, and they were attributed to the energy dissipation effect of the nanocrystalline SiC particles during HEBM of the ZrB₂ + SiC powder mixture. This study offers the first evidence that the addition of harder materials to softer materials can slow down the refinement of crystallite sizes, and thus provides a new mechanism to control crystallite sizes during HEBM. The simultaneous attainment of nano-particles of ZrB₂ and SiC, reduced agglomerate sizes, and homogeneous SiC dispersion at the nanometre scale may have important implications for the ultra-high-temperature ceramic community, as it simplifies the processing route and is likely to facilitate the sintering of ZrB₂-SiC composites.     

Study of the effects of nanometer β-Ni(OH)2 in nickel hydroxide electrodes

Nanometer β-Ni(OH)₂, showed by XRD, was prepared by our supersonic coordination-precipitation method, with an average grain size of about 50 nm by TEM. Proton diffusion coefficient of nanometer Ni(OH)₂ and spherical Ni(OH)₂ were 1.93 × 10⁻¹¹, and 5.50 × 10⁻¹³ cm²/s, respectively, with combination of chronocoulometry and cyclic voltammetry. Charge-discharge test of simulated batteries at 0.2 °C showed that addition of 8 mass% of our prepared nanometer Ni(OH)₂ in nickel hydroxide electrodes led to increases in cathode discharge specific capacity (CDSC) by nearly 10% and the chargeability of the electrode by about 50 mAh/g, and a decrease in polarization. Cycle life test of AA-type MH-Ni batteries discovered that effect of nanometer Ni(OH)₂ in increasing CDSC was more apparent for the first 100 cycles and not much difference was found after 350 cycles. XAS demonstrated a higher oxidation state of Ni in fully charged nanometer Ni(OH)₂ composite electrode (Nano-E) and a lower one in discharged Nano-E, compared with micrometer Ni(OH)₂ spherical electrodes (Micro-E). A larger structure distortion was found in Nano-E, offering more vacancies for proton diffusion. Thus conversion between Ni²⁺ and Ni³⁺ was promoted during the charge-discharge process, which was assumed to be one explanation of increasing CDSC with the addition of nanometer Ni(OH)₂.