Physical properties and enzymatic hydrolysis of poly(L‐lactide)–TiO2 composites

Amorphous poly(L ‐lactide) (PLLA) composite films with titanium dioxide (TiO₂) particles were prepared by solution‐casting using methylene chloride as a solvent, followed by quenching from the melt. The effects of surface treatment, volume fraction, size, and crystalline type of the TiO₂ particles on the mechanical properties and enzymatic hydrolysis of the composite films were investigated. The tensile strength of the PLLA composite films containing TiO₂ particles except for anatase‐type ones with a mean particle size of 0.3–0.5 μm was lowered and the Young's modulus became higher with increasing the content of TiO₂ particles. The tensile strength of the composite films containing anatase‐type TiO₂ with a mean particle size of 0.3–0.5 μm at contents of 20 wt % or less was almost the same as that of the pure PLLA film. The enzymatic hydrolysis of PLLA matrix was accelerated by the addition of the hydrophilic anatase‐type TiO₂ particles (nontreated or Al₂O₃ treated) with a mean particle size of 0.3–0.5 μm at relatively high contents such as 20 wt %. On the other hand, the enzymatic hydrolysis of PLLA matrix was inhibited by composite formation with the hydrophobic rutile‐type TiO₂ particles (Al₂O₃‐stearic acid treated, or ZrO₂‐Al₂O₃‐stearic acid treated). These results suggest that the mechanical properties and enzymatic hydrolyzability of the PLLA can be controlled by the kind and amount of the added TiO₂ particles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 190–199, 2005     

Corrosion studies with a new laboratory-scale system simulating large-scale diesel engines operating with residual fuels: Part II. Particle and deposit characteristics

Particle and deposit characteristics were studied with a new laboratory-scale deposition–corrosion apparatus designed to simulate the particle formation and deposition in large-scale diesel engines. Synthetic ash particles containing V, Ni, and Na are generated with an ultrasonic nebuliser. Total particle mass concentrations varied from 463 to 1739 mg/N m³ and highest concentrations were reached with SO₂(g) feed and cold dilution. Mass size distributions at the size range of 0.01–15 μm (aerodynamic size) were unimodal at 1.4 μm. Particle morphology changed dramatically from 1 to 5 μm sized solid particles without SO₂(g) feed into flat wet “pools” with SO₂(g) feed. It seemed that condensing sulphuric acid had dissolved the particles. Small 70–90 nm spherical particles were also observed with SO₂(g) feed. On the other hand, hardly any S was found in the deposits, which indicated that S as SO₂(g)/SO₃(g) was transported through the deposit pile into the base material.     

Preparation and characterization of poly(2‐chloroaniline)/SiO2 nanocomposite via oxidative polymerization: Comparative UV–vis studies into different solvents of poly(2‐chloroaniline) and poly(2‐chloroaniline)/SiO2

Poly(2‐chloroaniline)/silica (P2ClAn)/SiO₂ nanocomposites have been chemically prepared by oxidative polymerization of 2‐chloroaniline in acidic medium containing SiO₂. The prepared composites were characterized by FTIR, UV–vis, TGA, XRD, SEM, ESEM, conductivity, and magnetic susceptibility. The incorporation of P2ClAn in composites was endorsed by FTIR studies. The effect of the solution concentration of P2ClAn and P2ClAn/SiO₂ prepared in protonated, deprotonated, and reprotonated structures on the UV–vis spectra was investigated into three different solvents (DMF, NMP, and H₂SO₄). In all forms, the oxidation state of P2ClAn and P2ClAn/SiO₂ composite increased with increasing concentration of the testing solution into H₂SO₄. Thermogravimetric study exhibited that the composite has a higher thermal stability than P2ClAn. XRD measurement of the composite revealed that the crystal structure of incorporated SiO₂ undergone a distortion and converted into amorphous. Thus, the XRD pattern of P2ClAn was predominant. SEM analysis results revealed interesting morphological features for the composites converted to different forms and confirmed the formation of monodispersed composite particles. ESEM image of P2ClAn/SiO₂ has particle diameter of less than 1 μm. The conductivity of P2ClAn and P2ClAn/SiO₂ was measured by four‐probe technique. Magnetic susceptibility measurements revealed that the composite has a paramagnetic properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:935–943, 2006     

Solvent Extraction Investigations on Pu(IV) and Th(IV) Complexes with Hydrophilic SO3-Ph-BTP and SO3-Ph-BTBP Ligands

ABSTRACT

Complexation of Pu(IV) and Th(IV) cations by the title ligands – hydrophilic sulfophenyl triazinyl derivatives of bis-triazinyl-pyridine and -bipyridine – was studied in solvent extraction systems containing a TODGA extractant and one of these hydrophilic ligands. Stoichiometries and stability constants of the complexes formed in an acidic (HNO₃) aqueous phase have been determined. The Pu(IV) complexes are significantly stronger than their Th(IV) analogues. Only two complexes of each metal with SO₃-Ph-BTP (1:1 and 1:2) have been detected, and only one (1:1) with SO₃-Ph-BTBP; both numbers being less than expected based on the coordination numbers of the metal ions and on the denticities of the ligands. Possible reasons of this discrepancy are discussed.     

Effect of filler size distribution on the mechanical and physical properties of alumina‐filled silicone rubber

The properties of silicone rubber filled with three kinds of binary mixtures of alumina particles with different size distribution (i.e., 30 μm + 0.5 μm, 10 μm + 0.5 μm, and 5 μm + 0.5 μm) were investigated as a function of relative volume fraction of the 0.5 μm particles in the hybrid alumina (V_s) at a fixed total filler content of 55 vol%. The results indicate that each binary mixture of alumina‐filled silicone rubber exhibited improved thermal conductivity and tensile strength, and decreased dielectric constant, compared to a single particle size filler‐reinforced one, and the maximum improvements were obtained at the V_s ranging from 0.2 to 0.35; the coefficient of thermal expansion (CTE) of filled silicone rubber obviously reduced with increase in the V_s, whereas the elongation at break slightly decreased. At V_s = 0, the larger particles‐filled silicone rubber showed higher thermal conductivity, CTE, dielectric constant, and elongation at break, and lower tensile strength compared with the those of the smaller particles‐filled one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

The influence of oxidation on the texture and the number of oxygen-containing surface groups of carbon nanofibers

The effect of liquid-phase oxidation on the texture and surface properties of carbon nanofibers has been studied using XRD, TEM, SEM, N₂-physisorption, TGA-MS, XPS and acid-base titrations. Oxidation was performed by refluxing the nanofibers in HNO₃ and mixtures of HNO₃/H₂SO₄ for different times. The graphite-like structure of the treated fibers remained intact, however, the specific surface area and the pore volume increased with the severity of oxidation treatment. For the first time it is shown that the most predominant effect that gives rise to these textural modifications is the opening of the inner tubes of the fibers. Moreover, it is demonstrated that both the total oxygen content (O/C=0.02-0.07 at/at) as well as the number of acidic groups (1-3 nm⁻²) are a function of the type of oxidizing agent used and the treatment time. The total oxygen content of the oxidized samples turns out to be substantially higher than can be accommodated in the form of oxygen-containing groups at the exterior surface.     

SO2 removal from flue gas by activated semi-cokes: 1. The preparation of catalysts and determination of operating conditions

The objective of this work was to use waste semi-coke as the raw material to prepare catalysts of industrial-scale size for SO₂ removal from flue gas and to find the optimal preparation methods. Results showed that lignite semi-coke was a suitable raw material, and that the catalyst, prepared by pre-activating in an autoclave, oxidizing with HNO₃, loading with CuSO₄ and finally calcining at 700 °C, exhibited the best desulfurizing property with a sulfur retention of about 9.6% SO₂/100 gC at a reaction temperature of 90 °C. Also, the effects of H₂O content in the flue gas, reaction temperature and space velocity on the desulfurizing property were investigated to determine optimum operating conditions. An H₂O content of 7% was appropriate for catalysts in this work. In the temperature range 80-120 °C, the catalyst showed good performance for SO₂ removal and was gradually deactivated at temperatures above 120 °C. Space velocity exhibited an optimal value of 830 h⁻¹. The kinetic behavior varied with space velocity and the desulfurizing property was controlled by diffusion at space velocities below 830 h⁻¹, and controlled by adsorption or catalytic reaction at space velocities above 830 h⁻¹.     

Biocomposite foams from poly(lactic acid) and rubber wood sawdust: Mechanical properties,cytotoxicity, and in vitro degradation

The objectives of this work were to seek a simple method for preparation of poly(lactic acid) (PLA) foams and evaluate properties of these foams for scaffold application. Using a typical blowing agent and compression molding, biocomposite foams were successfully prepared from a PLA/rubber wood sawdust (PLA/RWS) blend. Selection of RWS for the biocomposites was based on particle size. RWS particles in two size ranges were used: 212–600 μm and ≤75 μm. Alkaline and silane treatments were applied to the RWS before blending with PLA. The tensile properties, Izod impact strength, foam morphology, and thermal degradation of the biocomposite foams were evaluated. Cytotoxicity and in vitro degradation were tested to determine the potential of the biocomposite foam for use as a scaffold in tissue engineering. Silane treatment improved mechanical properties by increasing the interfacial adhesion between PLA and RWS. The density and void fraction of the foam samples had a greater effect on mechanical properties than pore size. Proliferation of MG-63 cells increased with culture time, indicating that the foam samples were not cytotoxic. Promising samples were tested for degradation in a lysozyme/phosphate-buffered saline and showed a slow rate of in vitro degradation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48259.     

Thermal and dynamic mechanical properties of microwave and heat‐cured poly(methyl methacrylate) used as dental base material

In this study, the particle size distribution, molecular weight, thermal analysis (TGA) differential scanning calorimetry (DSC) and thermogravimetric analysis, and dynamic mechanical analysis (DMA) of poly(methyl methacrylate) used as dental base material were investigated. The commercial raw material used were prepared for microwave curing, and they were cured by microwave and conventional heat methods. The average particle size of the powder studied (103.1 μm) were much larger than that of the commercial powders (50–78 μm) for conventional curing. The particle size dietribution were almost symmetrical and narrow. The viscosity‐average molecular weight were larger for microwave curing and increased with curing time. The glass transition temperature T_g measured (about 110°C) by DSC increased with curing period in microwave oven. The values of T_g were close to each other for both curing techniques. The degradation temperature range observed by TGA were 200–377°C. The movements of molecular chains in their conformations were studied by DMA in the form of changes in different mechanical properties with temperature. It was shown that crosslinking increased with increase of curing time. The changes were more noticeable in microwave curing compared to conventional heat curing. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2971–2978, 1999     

Effect of different oxidation treatments on the chemical structure and properties of commercial coal tar pitch

Different oxidation treatment was used for the increase of the softening point of a commercial coal tar pitch. H₂SO₄, HNO₃, H₂O₂ and air are selected as treatment reagents. These preliminary investigations show that the oxidation treatment of commercial coal tar pitch with different reagents at 160 °C and heat treatment to 250 °C causes considerable changes in the chemical composition of obtained pitches. This leads to increase of TI and QI fraction, and results in considerable increase in the softening point of the pitches. The yield of modified pitches is considerable in the case of treatment with H₂SO₄, H₂O₂, and HNO₃ and lesser in the case of air blowing. The data obtained also indicate some differences in the composition and softening point of pitches obtained after modification with different reagents. These differences could influence the applicability of the obtained pitches in the various areas of carbon material production.     

PHYSICAL ANALOGS AND PERFORMANCE OF A BOX MODEL FOR COMPOSITION AND GROWTH OF H2SO4/H2O AND HNO3/H2SO4/H2O AEROSOL IN THE STRATOSPHERE

A physical box model simulating the aerosol particle evolution along air mass trajectories is developed to provide a tool for interpreting the local observations of stratospheric aerosols (i.e., polar stratospheric clouds). The model calculates the composition and the size distributions of H₂SO₄/H₂O and HNO₃/H₂SO₄/H₂O liquid droplets. The parameterization of the physical processes affecting the dynamics of HNO₃ and H₂SO₄ solid hydrates and ice particle size distributions is also included, but not used. This work is restricted to some speculations about the liquid to solid transition, according to existing theories. The evolution of liquid particles is simulated taking into account nucleation, diffusive condensation/evaporation and coagulation. This paper reports the physical and numerical details of the model, which are discussed within the framework of the current understanding of the stratospheric aerosol physics. Performance and limitations of the model are discussed on the basis of the evolution of particle size, and composition along synthetic air mass thermal histories. Size distributions and size-dependent acid weight fractions of the liquid stratospheric aerosols consisting of HNO₃/H₂SO₄/H₂O are calculated in the cases of air mass thermal histories with different cooling rates and with rapid temperature fluctuations.     

Flame retardant,mechanical, and hot air aging properties of ethylene-propylene-diene monomer/ammonium polyphosphate/nano-silic composite rubber

In this work, effect of the ratio of nonhalogenated flame retardants (ammonium polyphosphate [APP] and nano-silica [nano-SiO₂]) on the mechanical, thermal, and flame retardant properties of ethylene-propylene-diene monomer (EPDM) composite rubber were investigated. Vulcanization characteristics, high temperature compression permanent deformation, thermal oxygen aging, dynamic thermodynamic analysis, thermal stability, cone calorimetry, limiting oxygen index (LOI), horizontal vertical combustion (UL-94), and scanning electron microscopy were carried out. The experimental results showed that the mechanical properties of the composite rubber decreased with the addition of APP. However, the addition of nano-SiO₂ was found to significantly improve the mechanical properties of the composite rubber when it was incorporated. In terms of flame retardant properties of EPDM composite rubber, the combination of APP and nano-SiO₂ has a synergistic flame retardant effect in comparison to the use of single APP flame retardant. The heat release rate of EPDM composite rubber decreased by 34%, the total heat release decreased by 19%, the LOI increased by 76%, and the flame retardant grade of EPDM composite rubber reached V-0. The EPDM composite rubber fabricated in the present study showed excellent fire resistance and desirable mechanical properties, which are of practical significance for further expanding the application ranges of EPDM rubbers.     

Effect of particle size of as-milled powders on microstructural and magnetic properties of Y3MnxAl0.8-xFe4.2O12 ferrites

Yttrium iron garnet ferrite using the chosen stoichiometry of (Y₃)(Mn_xAl_0.8-xFe_4.2)O₁₂ with x = 0.1 and different milling powder sizes were prepared through ball milling for various milling times to study the effect of powder size reduction on the resulting microstructural and magnetic properties. Sintered yttrium iron garnet ferrites were characterized by X-ray diffraction analysis and scanning electron microscopy. The particle size (D₅₀) of as-milled calcined powder was decreased using ball milling (from 3.682 μm for a 0.5-hour-long milling to 1.606 μm for a 2.5-hour-long milling). Scanning electron microscopy analyses confirmed that the sintered grain exhibited a crystal size that was increased from initial values (average crystal grain sizes of 3.5 ± 0.1 μm for 0.5 hour of milling) up to 6.2 ± 0.1 μm after 2.5 hour of ball milling and the subsequent sintering process. The same sintered specimen after 2.5 hour of ball milling exhibited an obvious increase in saturation magnetization (4πM_s), remanence (B_r), and squareness ratio (namely B_r/4πM_s); it also caused a notable decline in coercivity (H_c) and ferromagnetic resonance line width (∆H), which were attributed to the introduction of a smaller size of calcined powder after milling and subsequently resulted in a larger sintered grain. Furthermore, a sufficient spin-wave line width (∆H_k) and low insertion loss (|S₂₁|) were obtained for the operation of the microwave device. The aforementioned results are all beneficial to the use of yttrium iron garnet ferrite in microwave applications. A correlation between the calcined powder size after milling, grain crystal size after sintering, and magnetic properties was evident in this study. The strict control of calcined powder size after milling is critical in tailoring suitable magnetic properties for yttrium iron garnet ferrite manufacturing processes.     

The reinforcement of red clay on natural rubber and its reinforcing mechanism

Three kinds of red clay were fractionated according to the particle size using ultrasonic and centrifugal method. The mechanical properties of the clay‐rubber composite with various clay fractions were determined. At the same time, both the content of the metal components in the clay and the affect to the aging properties were determined. The result shows that within a certain range, the clay particle size only affects some of the mechanical properties of clay‐rubber composite. The characteristic morphological structure of the clay provides a significant reinforcing action on clay‐rubber composite. We speculate that mechanism of the reinforcement of clay on rubber is that the clay forms a rigid or semi‐rigid chain aggregation structure in rubber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physical and chemical analyses of unburned carbon from oil-fired fly ash

In the hydrometallurgy process of extracting vanadium and nickel products from oil-fired fly ash, a large amount of unburned carbon remains as a by-product. Because of insufficient knowledge of the physical and chemical properties and related applications of the unburned carbon, the residue has been disposed to landfill or incinerated. In order to explore the utilization of unburned carbon, this preliminary study analyzed its morphology, particle size distribution, specific surface area, pore size distribution, density and chemical composition. The results indicate that the chemical composition is 73-91% carbon, 5-19% ash, 2.5-11.5% volatile substances, and 0.7-1.9% water, it consists of porous spherical particles and some crumbled particles with particle sizes mainly in the range 1-100 μm, the specific surface area is 16-33 m²/g, the pore size ranges between 0.02 and 10 μm, the real density is about 2.05-2.16 g/cm³, the apparent density about 0.15 g/cm³ and it can be characterized as a puffy, readily wind-blown powder.     

氢氧化铝对复合绝缘子用硅橡胶的性能影响研究

研究了氢氧化铝的粒径及填充量对复合绝缘子用热硫化硅橡胶的力学性能、电学性能、阻燃性、憎水性能的影响。实验结果表明：当氢氧化铝粒径为2.4μm时,硅橡胶的力学性能及阻燃性能达到最佳,憎水性及电学性能适中;氢氧化铝填充量为115～125份之间时,硅橡胶综合性能最佳,漏电起痕达到1A4.5,阻燃性能满足FV-0。     

Reductive roasting of nickel laterite ore with sodium sulphate for Fe-Ni production. Part II: Phase transformation and grain growth

In Part II, the correlation between Fe–Ni grain growth and characteristic fusion temperatures of the Na₂SO₄–laterite mixtures, and phase transformations of the reduced pellets were investigated. For the mechanism of sodium sulphate, Na⁺ is able to liberate the hosted nickel and iron within lizardite, while SO₄^2– is the sulphur source for the formation of Fe–FeS eutectic compound which can decrease the characteristic fusion temperatures to promote the growth of ferronickel grains. The mean particle size of ferronickel increased from 7.4 μm to 48.6 μm with the addition of 20 wt% Na₂SO₄.     

Impact of the aluminum sulfate 18-hydrate particle size on the coordination crosslinking behaviors of acrylonitrile–butadiene rubber–aluminum sulfate 18-hydrate composites

In this study, aluminum sulfate 18-hydrate [Al₂(SO₄)₃·18H₂O] particles of different sizes, which were obtained via high-energy ball-milling technology, were successfully compounded with acrylonitrile–butadiene rubber (NBR) to fabricate crosslinked rubber composites. The results suggest that high-energy ball milling had no significant change on the crystal structure of Al₂(SO₄)₃·18H₂O, but it significantly reduced the particle size. The effects of the particles size on the coordination crosslinking behaviors and mechanical properties of the NBR–Al₂(SO₄)₃·18H₂O composites were fully explored. The coordination crosslinking reaction was demonstrated to occur between the nitrile group (─CN) and Al(III). Moreover, with the decreasing particle size, the composites achieved a better interfacial adhesion and more crosslinking points, and this led to significant increases in the crosslinking density and the mechanical properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47717.     

Characterization of activated carbon, graphitized carbon fibers and synthetic diamond powder using TPD and DRIFTS

A high surface area activated carbon, graphitized carbon fibers and synthetic diamond powder were characterized by X-ray diffraction, temperature-programmed desorption and diffuse reflectance infrared (IR) spectroscopy (DRIFTS). The activated carbon was analyzed as received as well as after either a nitric acid treatment to introduce oxygen functional groups on its surface or a high temperature treatment (HTT) in H₂ at 1223 K to remove surface groups. TPD evolution profiles of CO and CO₂ were combined with DRIFTS spectra of these carbon surfaces before and after pretreatments in H₂ at 723 and 1223 K to provide complementary information regarding the nature of these surface groups. Significant amounts of both low- and high-temperature CO₂ desorption occurred from the HNO₃-treated carbon, indicating that both strongly and weakly acidic groups were introduced on this surface and, in addition, comparable amounts of CO and CO₂ were desorbed. With the graphitized carbon fibers and diamond powder, larger amounts of CO were desorbed compared to CO₂, indicating the presence of predominantly weakly acidic or non-acidic groups on these surfaces. For the HNO₃-treated carbon, IR peaks associated with surface carboxylic acid groups initially present disappeared after treatment at 723 K, while bands attributable to anhydride, quinone, ester and phenol species remained. Small amounts of ether, furan and phenol groups were detected on the graphitized fiber surface, while ketonic carbonyl groups were dominant on diamond. Significant amounts of chemisorbed hydrogen were also detected, presumably occurring on edge atoms made available by the decomposition of CO-yielding complexes at temperatures >873 K.     

Optimization of borosilicate glass/CaTiO3-TiO2 composite via altering prefiring temperature and particle size

Low-temperature co-fired ceramic (LTCC) with middle permittivity is very crucial to the miniaturization of components. Based on our previous study on the glass/CaTiO₃-TiO₂ composite, prefiring temperature and particle size of CaTiO₃-TiO₂ ceramic were optimized in this study to promote the performance of the composites. Comparing with our previous study, after being sintered with 50 wt% glass at 875°C, CaTiO₃-TiO₂ ceramic prefired at 1275°C with particle size of 3.38 μm showed excellent properties of sintering density = 3.33 g/cm³, ε_r = 30.2, tan δ = 0.0005 (7 GHz). In addition, surface roughness of green tapes was also improved after optimization. The material has a good chemical stability and shrinkage matching with silver, making it a very promising candidate material for LTCC applications.