Flammability and mechanical properties of Al(OH)3 and BaSO4 filled polypropylene

The flammability and mechanical properties of Al(OH)₃/BaSO₄/polypropylene (PP) composites were investigated. The flow, morphological, and thermal properties were also analyzed by melt flow index (MFI), Scanning electron microscopy (SEM), and Differential scanning calorimeter (DSC) studies, respectively. Total filler amount was fixed at 30 wt % to optimize physical characteristics of the composites. In addition to the flame retardant filler Al(OH)₃, BaSO₄ was used to balance the reduction in impact strength at high filler loadings. Substantial improvement in mechanical properties was achieved for 20 wt % Al(OH)₃ (i.e., 10 wt % BaSO₄) composition while maximum flammability resistance was obtained for 30 wt % Al(OH)₃ composite. SEM studies showed that the presence of aggregated Al(OH)₃ particles led to low interfacial adhesion between them and PP matrix ending up with decreased mechanical strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of CaO granules using the granulation method

ABSTRACT

Improving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)₂ particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min^?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%.     

Preparation of high surface area CaCO3 by reacting CO2 with aqueous suspensions of Ca(OH)2: Effect of the addition of sodium polyacrylate

High surface area CaCO₃ was produced through the reaction between CO₂ and an aqueous suspension of Ca(OH)₂ with the addition of an additive, sodium polyacrylate. The surface area of CaCO₃ prepared was affected markedly by the amount of additive and the solution pH when adding the additive. The CaCO₃ with the highest surface area (87.7 ± 1.3 m²/g) was obtained under the conditions that the initial Ca(OH)₂ concentration was 2.4 wt.%, the amount of sodium polyacrylate added was 0.2 wt.%, and the solution pH at which the additive was added was in the range of 11.4-11.1. The high surface area CaCO₃ also had a high pore volume. The CaCO₃ was highly reactive toward SO₂, and a conversion of 0.95 was achieved when it was sulfated at 950 °C and 4000 ppm SO₂ in air for 1 min. Prior calcination reduced the reactivity of this high surface area CaCO₃.     

Preparation and characterization of CaO nanoparticles from Ca(OH)2 by direct thermal decomposition method

CaO is an important material because of its application as catalyst and effective chemisorbents for toxic gases. In this research CaO nanoparticles were prepared via direct thermal decomposition method using Ca(OH)₂ as a wet chemically synthesized precursor. Nanocrystalline particles of Ca(OH)₂ have been obtained by adding 1 and 2 M NaOH aqueous solutions to 0.5 M CaCl₂·2H₂O aqueous solutions at 80 °C. The precursor [Ca(OH)₂] was calcined in N₂ atmosphere at 650 °C for 1 h. Samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectrum (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunaure–Emett–Teller (BET). SEM images showed that CaO nano-particles were nearly spherical in morphology. TEM images illustrated that produced CaO nano-particles had the mean particle size of 91 and 94 nm for 1 and 2 M NaOH concentration, respectively. As a result, this method could be used for production of CaO nano-particles on large-scale as a cheap and convenient way, without using any surfactant, organic medium or complicated equipment.     

Detrital Mg(OH)2 and Al(OH)3 in Microwaved Hydrotalcites

Microwave irradiation power (90, 180, 270 or 360 W) determines the composition and the structure of the compounds obtained when pH is increased, decreased or maintained constant during preparation. Although in all cases the X-ray diffraction patterns show that the obtained compounds are hydrotalcite-like, the surface areas (40 up to 240 m²/g) as well as other microcrystalline compounds have to be inferred, such as Al(OH)₃ or Mg(OH)₂.     

CaO‐containing LaCO3OH nanogears and their luminescence and de‐NOx properties

Large‐scale, uniform, monodisperse LaCO₃OH cherry‐blossom‐like nanogears and/or nanocubes have been synthesized under hydrothermal reaction conditions. Upon the addition of only 5 mol% Ca²⁺ ions into a La nitrate salts solution with pH 8.5, LaCO₃OH crystals with novel cubic or nanogear structures are formed in the hexagonal phase. The hydrothermal reactions were carried out without the addition of a template or catalysts. Both 24 hour and 48 hour hydrothermal reactions yield 100% pure LaCO₃OH with no irregular particles. We examined the photoluminescence properties of the as‐synthesized powders of the pure LaCO₃OH nanogears and found one broad emission band centered at 394 nm after excitation at λ  =  280 nm. The NO reduction activity was also examined over highly dispersed CaO‐containing La₂O₃ obtained after calcination the LaCO₃OH at 800^○C for 2 hours. The CaO‐containing La₂O₃ catalysts showed good stability for NO reduction with CH₄ in the presence of O₂ and H₂O vapor.     

Influences of solid content of slurry on the microstructure of CaO crucible prepared by slip casting

CaO crucible was prepared from Ca(OH)₂ slurry via a slip-casting method in order to avoid hydration problem caused by free CaO during preparation process. The effect of solid content of Ca(OH)₂ slurry on microstructure of CaO crucible was investigated. It was found that the rheological property of the slurry was significantly improved when the solid content of the slurry within a certain range. The change of solid content of slurry affects the microstructure of the final products. When the solid content of the slurry was 71 wt%, the manufactured CaO crucible was of smallest mean pore size (2.58 μm) after 1600°C heating treatment. The heated CaO sample was of lower apparent porosity (4.1%) and higher bulk density (2.93 g/cm³). And the size distributions of most CaO grains are between 10 and 40 μm.     

Microstructures and strength of microporous MgO-Mg(Al,Fe)2O4 refractory aggregates

Microporous MgO-Mg(Al, Fe)₂O₄ refractory aggregates were prepared using magnesite, Al(OH)₃ and Fe₂O₃ applying an in-situ decomposition synthesis method. At 1400–1600 °C, there was a Mg(Al, Fe)₂O₄ with Fe³⁺, which had two structures. One was a ring structure formed from Al(OH)₃ pseudomorph particle as a template and a low content of Fe³⁺. The other was the dot and strip structures precipitated in magnesite pseudomorph particles with a high content of Fe³⁺. Besides, at 1550–1600 °C, microporous MgO-Mg(Al, Fe)₂O₄ refractory aggregates had an excellent compressive strength (75.8–81.5 MPa) and apparent porosity (26.8%?28.2%).     

Effect of titanium chelating compound on hydration resistance of CaO material

The hydration resistance of CaO materials prepared by Ca(OH)₂ calcination with titanium chelating compounds is investigated in this paper. The crystalline phases and microstructure characteristics of sintered specimens were studied by X-ray diffraction (XRD), define FTIR spectroscopy, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The results showed that the hydration resistance of CaO samples was improved significantly, especially for samples with 9 wt% Ti chelating compound. The specimens with Ti chelating compound showed an increase in bulk density and a decrease in apparent porosity after heating when compared to the specimens without additive. The grain surface of CaO grain and the gaps between the CaO grain boundaries were covered with calcium phosphate glass phase, calcium phosphate showed two different shapes: irregular shape and rod shape. The formation and distribution of these two forms were the key factors that affecting the hydration resistance of CaO samples.     

Construction of carbon quantum dots embed α-Co/Ni(OH)2 hollow nanocages with enhanced supercapacitor performance

The etching strategy of metal-organic frameworks is an effective process to prepare hollow electrode materials for enhanced electrochemical performance. But the relatively low conductivity of these electrode materials limits their further application. In this work, a series of carbon quantum dots (CQDs) embedded ZIF-67 precursors (ZIF-67@CQDs-X, X = 1.25, 2.50, 5.00, 7.50) are synthesized firstly. Then, by a facile and controllable chemical etching process, the CQDs doped α-Co/Ni(OH)₂ hollow nanocages (α-Co/Ni(OH)₂@CQDs-X, X = 1.25, 2.50, 5.00, 7.50) are successfully constructed. The optimized α-Co/Ni(OH)₂@CQDs-2.50 electrode delivers a high specific surface area (277.99 m² g⁻¹) and dramatically enhanced conductivity. Therefore, α-Co/Ni(OH)₂@CQDs-2.50 electrode presents a high specific capacitance (700 C g⁻¹, 1 A g⁻¹), superior rate performance (550 C g⁻¹, 10 A g⁻¹) and excellent cycling lifespan (retaining 79.93% of initial capacitance after 10 000 cycles). Coupled with the high-performance PPD/rGO as a negative electrode, the fabricated Co/Ni(OH)₂@CQDs-2.50//PPD/rGO device exhibits an outstanding energy density of 57.29 Wh kg⁻¹ at the power density of 0.375 kW kg⁻¹. It is proved that the CQDs embedding and chemical etching strategy are an effective way for constructing hollow materials with enhanced energy storage performance.     

Influence of amorphous Al(OH)3 on the hydration of tricalcium aluminate

The influence of amorphous Al(OH)₃ on the hydration of tricalcium aluminate was investigated in pastes and in suspensions. In suspensions it was found that amorphous Al(OH)₃ started to dissolve almost immediately, and a stage was passed in which most of the anions present in the aqueous phase were polymeric aluminate units. Paste hydration results could be understood by assuming that highly soluble amorphous Al(OH)₃ dissolved and, by so doing, adjusted the concentrations in the aqueous phase so as to cause precipitation of some less soluble form of Al(OH)₃, thereby retarding hydration.     

Preparation of CaCO3 using mega-crystalline calcite in electrical furnace and batch type microwave kiln

Mega-crystalline calcite (m-CC) breaks apart easily during calcination, and cannot be easily converted to CaO due to its characteristic that requires massive heat consumption. To solve this problem, the calcination characteristics were compared using electrical furnace (EF) and batch type microwave kiln (BM). After hydrating the manufactured CaO, Ca(OH)₂ was produced, and through the carbonation process, CaCO₃ was synthesized.The results of the XRD pattern of CaO that was formed through calcinations indicated that decarbonation reaction occurred as 98.2 wt.% by EF for 240 min, and 97.8 wt.% by BM for 30 min at the same temperature of 950 °C. Hydration results revealed that CaO by EF was high-reactive whereas CaO by BM was medium-reactive. CaCO₃ was synthesized through the carbonation process. At 25 °C, in both cases, colloidal-shaped CaCO₃ was found, and the more spindle-shaped CaCO₃ by cubic-shaped self assembly was synthesized at higher temperatures. However, in case of EF, Ca(OH)₂ existed in products.     

Hydrothermal Formation of the Head-to-Head Coalesced Szaibelyite MgBO2(OH) Nanowires

The significant effect of the feeding mode on the morphology and size distribution of the hydrothermal synthesized MgBO₂(OH) is investigated, which indicates that, slow dropping rate (0.5 drop s⁻¹) and small droplet size (0.02 mL d⁻¹) of the dropwise added NaOH solution are favorable for promoting the one-dimensional (1D) preferential growth and thus enlarging the aspect ratio of the 1D MgBO₂(OH) nanostructures. The joint effect of the low concentration of the reactants and feeding mode on the hydrothermal product results in the head-to-head coalesced MgBO₂(OH) nanowires with a length of 0.5–9.0 μm, a diameter of 20–70 nm, and an aspect ratio of 20–300 in absence of any capping reagents/surfactants or seeds.     

Layered double hydroxide/NaSb(OH)6–poly(vinyl chloride) nanocomposites: Preparation,characterization, and thermal stability

A novel layered double hydroxide/NaSb(OH)₆‐based nanocomposite (Sb‐LDH) has been prepared via intercalation of thio‐antimonite (SbS₃^3?) and reconstruction of LDH using Mg‐Al LDH as precursors. It is composed of LDH nanolayers with thickness of 25 nm and NaSb(OH)₆ nanoparticles with diameter of 3–25 nm. The presence of NaSb(OH)₆ will decrease the decomposition intensity and hinder the decomposition of Mg‐Al LDH because of the potential synergetic effect. When applied to poly(vinyl chloride) (PVC) composites, both Mg‐Al LDH and Sb‐LDH can enhance the thermal stability and increase the decomposition temperature of PVC. Compared with Mg‐Al LDH, Sb‐LDH results in higher decomposition temperatures and whiteness and higher initial and long‐term stabilities due to the presence of NaSb(OH)₆, which can react with HCl and coordinate with Cl in the PVC chains. Because Mg‐Al LDH will accelerate the dehydrochlorination of PVC driving by the Lewis acid such as AlCl₃, the thermal stability of PVC decreases with increasing nanofiller loading. When 1 wt % Sb‐LDH was added, the color change time and Congo red time of PVC composites are 140 min and 154 min, respectively. With enhanced thermal stabilization, this novel LDH nanocomposite could gain promising application in thermal stabilizer for PVC resins. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effects of (di-,tri-valent)-cation partitioning and intercalant anion-type on the solubility of hydrotalcites

Synthetic hydrotalcites were produced by a co-precipitation method. The hydrotalcites are represented by the general formula [M^II_(1-x)M^III_(x)(OH)₂][Aⁿ⁻]_x/n·zH₂O, where M^II is a divalent cation (eg, Mg²⁺or Ca²⁺), M^III is a trivalent cation (eg, Al³⁺) and Aⁿ⁻ is the interlayer anion. Herein, M^II = Mg, and M^III = Al such that [Mg/Al] = [2, 3] (atomic units) and Aⁿ⁻, represents intercalant species including: OH⁻, SO₄²⁻ and CO₃²⁻ anions. The thermochemical data of each compound including their solubility constants (K_so), density and molar volume were quantified at T = 25 ± 0.5°C, and P = 1 bar. The solubilities of the synthetic hydrotalcites, irrespective of their divalent-trivalent cation partitioning ratio, scaled as CO₃²⁻ < SO₄²⁻ < OH⁻; in order of decreasing solubility. The type of anion, very slightly, affected the solubility with less than ±1 log unit of variation for [Mg/Al] = 2, and ±2 log units of variation for [Mg/Al] = 3. The solubilities of these phases were strongly correlated with that of gibbsite (Al(OH)₃); such that activity of the [AlO₂⁻] species was solubility determining with increasing pH. The tabulated thermodynamic data were used to construct solid-solution models for phases encompassing both cation distribution ratios and to calculate stable phase equilibria relevant to alkali-activated slag (AAS) systems for diverse activator compositions.     

3D supramolecular open-framework constructed by inorganic [B5O6(OH)4]− and organic [CH3COO]− anions

A borate compound [Ni(en)₃][B₅O₆(OH)₄][CH₃COO] (1) has been synthesized under mild hydrothermal conditions. The newly synthesized compound was characterized by single-crystal X-ray diffraction, elemental analysis and thermogravimetry. The three-dimensional (3D) supramolecular open-framework of compound 1 is constructed by inorganic [B₅O₆(OH)₄]⁻ building units and organic [CH₃COO]⁻ anions through hydrogen bonds, and the charge-balancing [Ni(en)₃]^2 + cations are located in 3D channels. It is very interesting that there exist two helical chains formed by [B₅O₆(OH)₄]⁻ building units and organic [CH₃COO]⁻ anions through hydrogen bonds in compound 1 along different axes. Magnetic measurement indicates that compound 1 exhibits paramagnetic behavior down to 4 K.     

Improvement of sensitive Ni(OH)2 nonenzymatic glucose sensor based on carbon nanotube/polyimide membrane

An improved nonenzymatic glucose sensor was fabricated of Ni(OH)₂ on carbon nanotube/polyimide (PI/CNT) membrane by a simple electrochemical method. Three different morphologies of Ni(OH)₂ have been formed by changing the conditions used in synthesis process. The formation mechanism for Ni(OH)₂ nanospheres was studied to provide a deep understanding of crystal growth. The electrochemical behaviors of different Ni(OH)₂ nanostructures were investigated by cyclic voltammetry and chronoamperometry in alkaline solution. At an applied potential of +0.60 V, the sensor based on PI/CNT–Ni(OH)₂ nanospheres shows a high sensitivity of 2071.5 μA mM⁻¹ cm⁻² and a detection limit of 0.36 μM (signal/noise = 3). The proposed sensor exhibits high sensitivity, long-term stability and good reproducibility, and performs well for detection of glucose in human blood serums. Therefore, this novel fabrication method for glucose sensor is promising for the future development of nonenzymatic glucose sensors.     

Evaluation of commercial Mg(OH)2, Al(OH)3 and TiO2 as antimicrobial additives in thermoplastic elastomers

Health concerns have driven the production of antimicrobial materials aimed at controlling the spread of diseases. Styrene-ethylene/butylene-styrene (SEBS)-based thermoplastic elastomers (TPE) incorporated with titanium dioxide (TiO₂), magnesium hydroxide (Mg(OH)₂) and aluminium hydroxide (Al(OH)₃) are one way to produce antimicrobial polymers. The purpose of this study is to characterise SEBS-based TPE compounds incorporated with TiO₂, Mg(OH)₂ and Al(OH)₃. The mechanical, optical and antimicrobial characteristics of TPE samples were investigated. The differences between the means in the mechanical properties of all loaded materials were not significant. The optical results show a reduction in polymer transparency, with total opacity after the incorporation of TiO₂. Among the additives tested, TiO₂ offered the best antimicrobial action. There was no fungal growth on the loaded TPE surface. The incorporation of TiO₂ in SEBS-based TPE materials may be used in the industry to develop antimicrobial products, which, when complemented with additional disinfection treatments, can contribute to public health.     

Corrosion behavior of ytterbium hafnate exposed to water-vapor with Al(OH)3 impurities

In this work, Yb₄Hf₃O₁₂ ceramic, a typical rare-earth hafnate, was exposed to water vapor with Al(OH)₃ impurities at 1400 ℃, and microstructural evolution and corrosion mechanisms were investigated. The long-term corrosion can be divided into initial hydration and gasification of Hf⁴⁺ and steady-state corrosion after the formation of Al₅Yb₃O₁₂. In the initial stage, Hf⁴⁺ and the surrounding O^2- tend to be hydrated and then volatilized in the form of Hf(OH)₄, causing a metastable state of Yb₄Hf₃O₁₂ on the surface. Besides, the preferential corrosion of small grains, grain boundary, and specific crystal plane on the surface and sintered and densified grains result in varied corrosion behavior from the early linear law to the later parabolic law. In the steady-state corrosion stage, due to the consumption of Hf⁴⁺, more vacancies promote bonding and diffusion of Al³⁺ to form corrosion product (Al₅Yb₃O₁₂), and during this stage, regrowth and shedding of the corrosion layer reach a dynamic balance.     

Microstructures and properties of microporous mullite-corundum aggregates for lightweight refractories

Five microporous mullite-corundum refractory aggregates were prepared from Al(OH)₃ and kaolinite gangue through in situ decomposition synthesis technique. The effects of the sintering temperature (1400–1600°C) and the particle sizes of raw materials (20.6–94.5 μm) on the microstructures and strengths of the aggregates were investigated through X-ray diffractometer, scanning electron microscopy, and energy-dispersive spectrometer etc., to find out the technological conditions to be controlled in industrial production. The higher sintering temperature promoted the reaction between Al(OH)₃ and kaolinite gangue, leading to the development of primary-mullite as well as the generation of secondary-mullite, which promoted the formation of the neck and improved the strength. Meanwhile, the dense mullite layers were formed continuously on the surface of Al(OH)₃ pseudomorphs, making the micropores inside the pseudomorphs become closed pores, which increased the closed porosity of the aggregates. The reduction of the particle sizes of raw materials changed the particle packing behavior, accelerated the rearrangement of the Al(OH)₃ pseudomorph particles during the process of reactive sintering, and then reduced the closed porosity. To realize the industrial production of microporous mullite-corundum refractory aggregate with high strength (103 MPa) and high closed porosity (16.1%), the sintering temperature should be at about 1600°C, and the median diameter of raw materials should be at 94.5 μm.