Composite Suspensions Research Articles

In Vitro Biocompatibility and Antibacterial Activity of Electrospun Ag Doped HAp/PHBV Composite Nanofibers

The authors report herein in vitro antibacterial property and osteoblast biocompatibility of electrospun Ag doped HAp/PHBV (Ag-HAp/PHBV) composite nanofibers as an osteoconductive and antibacterial material for bone tissue engineering applications. Ag-HAp powders were synthesized and stable composite suspensions of Ag-HAp/PHBV were prepared with the aid of a cationic surfactant DTAB for the electrospinning process. Continuous and uniform composite nanofibers were generated within a diameter range of 400–900 nm. Obtained nanocomposite scaffolds provide a favorable environment for bone mineralization, SaOS-2 osteoblastic cell attachment and growth as well as they present antibacterial activity against E. coli and S. aureus bacteria without any noticeable cytotoxic effect.

Controlled hydrothermal synthesis of BiOxCly/BiOmIn composites exhibiting visible-light photocatalytic degradation of crystal violet

A series of BiOxCly/BiOmIn composites were prepared using autoclave hydrothermal methods. The composition and morphologies of the BiOxCly/BiOmIn composites were controlled by adjusting the experimental conditions: the reaction pH value, temperature, and KCl/KI molar ratio. The products were characterized using X-ray diffraction, scanning electron microscopy-electron dispersive X-ray spectroscopy, UV–vis diffuse reflectance spectroscopy, Brunauer–Emmett–Teller specific surface areas, cathodoluminescence, high-resolution transmission electron microscopy, and high-resolution X-ray photoelectron spectroscopy. The photocatalytic efficiencies of composite powder suspensions were evaluated by monitoring the crystal violet (CV) concentrations. In addition, the quenching effects of various scavengers indicated that the reactive O2− played a major role, and OH or h+ played a minor role in CV degradation. The intermediates formed during the decomposition process were isolated, identified, and characterized using high performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry to elucidate the CV decomposition mechanism.

Electrorheological properties of polyaniline-vanadium oxide nanostructures suspended in silicone oil

In the present work, organic/inorganic hybrid nanostructures comprised of polyaniline and vanadium oxide were synthesized via a simple hydrothermal technique. The polyaniline/vanadium oxide hybrid morphology was tailored from rods to spheres by controlling the relative concentration of the reactants. The synthesized composites were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) for structural and morphological analyses. Electrorheological (ER) properties of the as-prepared nanocomposites suspended in silicone oil were investigated by a rotational viscometer under both steady and dynamic shear. The ER activity of the composite material suspensions showed higher ER effects for the product with the rod-like structures than for the product with the sphere-like structures. The typical ER behaviour showed by the polyaniline-vanadium oxide nanocomposites demonstrated their potential application as an ER smart material.

Surface Treatment of Cellulosic Paper with Starch-Based Composites Reinforced with Nanocrystalline Cellulose

Starch-based composites have become promising materials for eco-friendly packaging applications because of their biodegradability and cost-effectiveness. However, the inherently poor mechanical and barrier properties of starch-based composite films hinder their market potential. Here, nanocrystalline cellulose (NCC) was isolated from cotton cellulose powders using sulfuric acid hydrolysis. Starch-based composite suspensions/films reinforced with 0.1–0.5 wt % of NCC were prepared and characterized. Surface sizing application of the reinforced composite suspensions on cellulosic paper was subsequently studied for improving the mechanical properties and the resistance to air permeability of cellulosic paper. Results revealed that NCC reinforced composite suspensions showed the characteristics of non-Newtonian fluids. The rheological behavior of these suspensions showed strong NCC concentration dependence. NCC addition improved the thermal stability of starch-based composite films. In addition, both the mecha...

Effects of micro and nano β‐TCP fillers in freeze‐gelled chitosan scaffolds for bone tissue engineering

ABSTRACTTissue engineering holds an exciting promise in providing a long‐term cure to bone‐related defects and diseases. However, one of the most important prerequisites for bone tissue engineering is an ideal platform that can aid tissue genesis by having biomimetic, mechanostable, and cytocompatible characteristics. Chitosan (CS) was chosen as the base polymer to incorporate filler, namely beta‐tri calcium phosphate (β‐TCP). This research deals with a comparative study on the properties of CS scaffolds prepared using micro‐ and nano‐sized β‐TCP as filler by freeze gelation method. The scaffolds were characterized for their morphology, porosity, swelling, structural, chemical, biodegradation, and bioresorption properties. Rheological behavior of polymer and polymer‐ceramic composite suspensions were analyzed and all the suspensions with varying ratios of β‐TCP showed non‐Newtonian behavior with shear thinning property. Pore size, porosity of micro‐ and nano‐sized composite scaffolds are measured as 48–158 μm and 77% and 43–155 μm and 81%, respectively. The scaffolds containing nano β‐TCP possess higher compressive strength (∼2.67 MPa) and slower degradation rate as compared to composites prepared with micro‐sized β‐TCP (∼1.52 MPa). Bioresorbability, in vitro cell viability by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, proliferation by Alamar blue assay, cell interaction by scanning electron microscope, and florescence microscopy further validates the potentiality of freeze‐gelled CS/β‐TCP composite scaffolds for bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41025.

Hybrid Comopsites Shaped by Casting Methods

In the presented work two methods of casting: gravity casting and centrifugal casting have been described. The main aim of the study was development procedures for producing the AlSi / SiC+C hybrid composite. Composite suspensions with the same phase composition were cast into molds with different coefficients of thermal conductivity. This allowed to determine the influence of thermal conditions on the formation of the structure and distribution of particles in the matrix. In the paper the conditions of casting, macro-and microstructure and selected properties of the casts have been presented. The structure of components and cast composites was examined by light and electron microscope, applying properly made preparations.

Influence of particle size and tunable interactions on isotropic–nematic transition of block copolymer single crystal platelet suspensions

We have studied the influence of the particle size and the tunable lateral interactions on the isotropic–nematic (I–N) phase transition of a plate-like colloidal system. The particles are single crystals of a block copolymer PS-b-PLLA (BCSC) prepared using a self-seeding procedure. These lozenge shape crystals have a uniform thickness and a narrowly distributed lateral size. The equilibrium phase behavior and I–N phase transition have been characterized using crossed polarizers at the room temperature. A nematic phase exists for all systems with size ranging from 700 to 4000nm. For smaller crystals (<1200nm), the I–N phase transition follows a process of slow sedimentation and subsequent macroscopic phase separation, resulting in a highly oriented nematic phase with a sharp I–N interface. For larger crystals (⩾1200nm), the I–N phase transition follows a process of nucleation and subsequent sedimentation, resulting in a random orientation of crystals in the nematic phase and a rough I–N interface. The I–N transition occurs at a very low volume fraction (<0.2%) for all systems, which is at least one order of magnitude lower than the theoretical prediction (2–7%). However, addition of a small amount of ethanol into the solution, the I–N transition can be significantly suppressed. These results demonstrate the existence of a lateral attraction between crystals, which is due to the polar attraction between the uncovered PLLA crystalline domains. Polar ethanol molecules can adsorb to the PLLA crystalline surface and screen the attraction. The attraction exhibits highly orientation-dependent. To further demonstrate this highly directional attraction, we have prepared two composite single crystal suspensions with PLLA homopolymer, which have a much wider open angle for the polar attraction. Indeed, the resulting liquid crystalline phases show much less horizontal ordering.

Rheological and zeta potential behaviour of kaolin and bentonite composite slurries

The results of the yield stress–pH and zeta potential–pH behaviour of pure kaolin and bentonite slurries, and mixed bentonite–kaolin slurries were evaluated. A high and low Ca(II) content kaolin clays were used. The location of the pH of maximum yield stress of the two pure kaolin slurries is very different, pH 9 for the high Ca(II) kaolin and 2.5 for the low. The trend of the variation of the yield stress with pH for the bentonite–kaolin composite slurries was similar to that of pure high Ca(II) kaolin irrespective of bentonite content. For the low Ca(II) kaolin, the maximum yield stress of the composite suspensions is located at the same low pH as that of pure low Ca(II) kaolin and bentonite suspensions, at pH∼2.5. Bentonite content was found to determine the magnitude of the yield stress. The sequence of KOH addition, whether during or after the preparation stage, did have a significant effect on the yield stress but only for the composite slurries with a high bentonite content. A higher degree of swelling and delamination of the bentonite particles in one of the preparation methods was attributed as the cause. Zeta potential results showed that both the pure and mixed clays are negatively charged at all pH. However the magnitude is reduced by Ca (II). Low Ca(II) kaolin suspension was found to obey the yield stress–DLVO model. This study has provided an excellent approach of controlling and tailoring rheological properties of kaolin suspension with bentonite or vice versa for specific applications.

Rheological Properties of SiC-ZrB&lt;SUB&gt;2&lt;/SUB&gt; Composite Suspensions

为制备高性能SiC-ZrB 2 网眼多孔陶瓷, 对SiC-ZrB 2 复合浆料的流动性质进行了初步研究。分析SiC和ZrB 2 粉体在水溶液中的流动性质, 并对分散剂硅溶胶和粘结剂羧甲基纤维素(CMC)的添加量进行了优化。基于以上优化结果, 重点探索了固含量和ZrB 2 添加量对浆料流动性质的影响。固含量为65wt%的浆料可作为有机泡沫浸渍过程的最佳条件, 而ZrB 2 添加量不可超过25wt%。

Salmonella and Escherichia coli O157:H7 Survival in Soil and Translocation into Leeks (Allium porrum) as Influenced by an Arbuscular Mycorrhizal Fungus (Glomus intraradices)

A study was conducted to determine the influence of arbuscular mycorrhizal (AM) fungi on Salmonella and enterohemorrhagic Escherichia coli O157:H7 (EHEC) in autoclaved soil and translocation into leek plants. Six-week-old leek plants (with [Myc+] or without [Myc-] AM fungi) were inoculated with composite suspensions of Salmonella or EHEC at ca. 8.2 log CFU/plant into soil. Soil, root, and shoot samples were analyzed for pathogens on days 1, 8, 15, and 22 postinoculation. Initial populations (day 1) were ca. 3.1 and 2.1 log CFU/root, ca. 2.0 and 1.5 log CFU/shoot, and ca. 5.5 and 5.1 CFU/g of soil for Salmonella and EHEC, respectively. Enrichments indicated that at days 8 and 22, only 31% of root samples were positive for EHEC, versus 73% positive for Salmonella. The mean Salmonella level in soil was 3.4 log CFU/g at day 22, while EHEC populations dropped to ≤ 0.75 log CFU/g by day 15. Overall, Salmonella survived in a greater number of shoot, root, and soil samples, compared with the survival of EHEC. EHEC was not present in Myc- shoots after day 8 (0/16 samples positive); however, EHEC persisted in higher numbers (P = 0.05) in Myc+ shoots (4/16 positive) at days 15 and 22. Salmonella, likewise, survived in statistically higher numbers of Myc+ shoot samples (8/8) at day 8, compared with survival in Myc- shoots (i.e., only 4/8). These results suggest that AM fungi may potentially enhance the survival of E. coli O157:H7 and Salmonella in the stems of growing leek plants.

Preparation and enhanced electro-responsive characteristic of reduced graphene oxide/polypyrrole composite sheet suspensions

We used reduced graphene oxide (RGO) as a core to prepare core–shell-structured RGO-supported polypyrrole composite dielectric sheets and demonstrated that the composite sheets possessed significantly enhanced electro-responsive electrorheological (ER) characteristic compared to conventional granular polypyrrole. The morphology and structure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier-transform infrared spectra. The ER characteristic of the sheets when dispersed in silicone oil was investigated by rheological tests under external electric fields. It showed that the shear yield stress of the sheet suspension was significantly higher than that of a suspension containing conventional granular polypyrrole at the same electric field strengths. A complex flow behavior was observed in the sheet suspension, which was different from the Bingham flow behavior in the granular polypyrrole suspension. The sheet suspension also showed higher field-shear moduli and two viscoelastic plateaus as a function of applied stress amplitude. The enhanced ER response was analyzed by the dielectric data and optical microscopy image of the ER structure.

Effects of HA/ZrO2 composite powder on mesenchymal stem cells proliferation and osteogenic differentiation

To evaluate the effects of hydroxyapatite/Zirconiumoxide (HA/ZrO2) composite powder on proliferation and osteogenic differentiation of rabbit mesenchymal stem cells (MSCs) by using molecular biology methods in vitro. HA/ZrO2 composite powder prepared by using powder of HA and ZrO2 with different proportions sintered at 1600°C were compared with pure HA powder and pure ZrO2 powder. The effects of the composite powder suspensions on the proliferation of the rabbit MSCs were measured by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT assay), alkaline phosphatase (ALP) activities were measured by the ALP colorimetric assay, and the cellular expression levels of Collagen I, osteocalcin and osteopontin mRNAs were determined by Reverse Transcription Polymerase Chain Reaction (RT-PCR). The HA phase was transformed into the β-Ca3(PO4)2(β-TCP), α-Ca3(PO4)2 and CaZrO3 phases in the composite powder after sintering at 1600°C, with a positive correlation between the contents of the HA phase and the new phases. The MTT assay showed that both pure HA powder and HA containing composite powder were able to promote cellular proliferation, but pure ZrO2 powder had no effect in stimulating cell proliferation (P<0.05). Vonkossa staining revealed that the composites and pure HA powder were capable of reducing the percentages of positively stained cells. The ALP colorimetric assay demonstrated that the ALP activities of cells maintained in culture media with HA and HA containing composite powder were significantly higher than that of cells cultured in regular media or media containing pure ZrO2 (P<0.05). RT-PCR results showed that the composite powder were able to stimulate the expression of Collagen I and osteocalcin. The HA/ZrO2 composite powder can also facilitate osteogenic differentiation.

Aspects of fabrication aluminium matrix heterophase composites by suspension method

Composites with an aluminium alloy matrix (AlMMC) exhibit several advantageous properties such as good strength, stiffness, low density, resistance and dimensional stability to elevated temperatures, good thermal expansion coefficient and particularly high resistance to friction wear. Therefore such composites are more and more used in modern engineering constructions. Composites reinforced with hard ceramic particles (Al2O3, SiC) are gradually being implemented into production in automotive or aircraft industries. Another application of AlMMC is in the electronics industry, where the dimensional stability and capacity to absorb and remove heat is used in radiators. However the main problems are still: a reduction of production costs, developing methods of composite material tests and final product quality assessment, standardisation, development of recycling and mechanical processing methods. AlMMC production technologies, based on liquid-phase methods, and the shaping of products by casting methods, belong to the cheapest production methods. Application of a suspension method for the production of composites with heterophase reinforcement may turn out to be a new material and technological solution. The article presents the material and technological aspects of the transfer procedures for the production of composite suspensions from laboratory scale to a semi-industrial scale.

Dielectric analysis of chitosan–iron composite microspheres suspensions: Access to internal and interface electrokinetic information of microspheres

Iron doped chitosan microspheres (IDM) with different concentrations of iron (wt.%) were prepared and dielectric behavior of the IDM suspensions was investigated in the frequency range from 40Hz to 110MHz. Dielectric spectra of these suspensions showed distinct relaxations at MHz frequency range which are attributed to the interfacial polarization between IDM particle and medium solution. The relaxation varied with the concentration of iron (wt.%) in IDM and the changing trends of relaxation parameters showed that: an appropriate iron doping concentration can increase adsorption capacity of chitosan, however, when the doping concentration exceeds a certain value, the capacity will be reduced. Furthermore, the phase parameters of the suspensions were calculated by using Hanai method. The obtained permittivity ɛp of IDM demonstrates a significant change with the iron concentration (wt.%). In addition, the interfacial electrokinetic parameters, surface conductivity λ, charge density σ and zeta potential ζ, were also estimated from the phase parameters and these parameters indicate that: the interfacial properties between the IDM and continuous medium were little affected by iron concentration in IDM.

Graphene as a Nanocarrier for Tamoxifen Induces Apoptosis in Transformed Cancer Cell Lines of Different Origins

A cationic amphiphile, cholest-5en-3β-oxyethyl pyridinium bromide (PY(+) -Chol), is able to efficiently disperse exfoliated graphene (GR) in water by the physical adsorption of PY(+) -Chol on the surface of GR to form stable, dark aqueous suspensions at room temperature. The GR-PY(+) -Chol suspension can then be used to solubilize Tamoxifen Citrate (TmC), a breast cancer drug, in water. The resulting TmC-GR-PY(+) -Chol is stable for a long time without any precipitation. Fluorescence emission and UV absorption spectra indicate the existence of noncovalent interactions between TmC, GR, and PY(+) -Chol in these suspensions. Electron microscopy shows the existence of segregated GR sheets and TmC 'ribbons' in the composite suspensions. Atomic force microscopy indicates the presence of 'extended' structures of GR-PY(+) -Chol, which grows wider in the presence of TmC. The slow time-dependent release of TmC is noticed in a reconstituted cell culture medium, a property useful as a drug carrier. TmC-GR-PY(+) -Chol selectively enhanced the cell death (apoptosis) of the transformed cancer cells compared to normal cells. This potency is found to be true for a wide range of transformed cancer cells viz. HeLa, A549, ras oncogene-transformed NIH3T3, HepG2, MDA-MB231, MCF-7, and HEK293T compared to the normal cell HEK293 in vitro. Confocal microscopy confirmed the high efficiency of TmC-GR-PY(+) -Chol in delivering the drug to the cells, compared to the suspensions devoid of GR.

New grades of submicron and nanosized powders of cubic boron nitride

A technique for producing new grades of submicron and nanosized powders of cubic boron nitride (cBN) is developed. It includes preliminary treatment of powders and their surface modification to control the hydrophilic–hydrophobic balance. Processes are developed for producing submicron and nanosized powders of cubic boron nitride that change their hydrophilic–hydrophobic balance. Thermal treatment in inert environments makes the surface of cBN powders hydrophobic and electrochemical treatment makes it hydrophilic. New grades of submicron and nanosized powders of cubic boron nitride are created. Hydrophobic KSM-F and KN-F powders are recommended for the production of polycrystalline materials and tools on their basis and hydrophilic KSM-E and KN-E powders for composite coatings, suspensions, and pastes.

Progressive Sorption and Oxidation/Hydrolysis of Fe(II) Affects Cadmium Immobilization by Bacteria-Iron Oxide Composites

Iron-bacteria composite suspensions were prepared by exposure of Anoxybacillus flavithermus cells to increasing concentrations of Fe2+ cations under different degrees of oxidation. Cd2+ immobilization was investigated during and after the synthesis of the iron-bacteria composites via scanning electron microscopy and isotherm sorption experiments conducted at varied ratios of total iron to bacteria (expressed by the variable ρ, mg Fe per g dry bacteria). At ρ less than about 20, precipitation of Fe(III) oxide was hindered, and for ρ up to about 50 Cd immobilization was decreased relative to iron-free control experiments, even for conditions where Fe(III) oxide was forming. For ρ above 50 to the maximum investigated value of 124, the Cd immobilization capacity of the iron-bacteria composite suspensions was partly recovered. Surface complexation models developed to describe the data indicate that 1) Fe2+ and Cd2+ cations compete with comparable affinities for the reactive sites on the bacterial cell walls, and 2) sorption of the progressively oxidizing iron can reduce the total concentration of bacterial surface sites available for metal adsorption by more than 40%, inferred to be due to masking or blocking of the binding sites by Fe(II) or Fe(III) monomers or oligomers or precipitated Fe(III) oxides. This study demonstrates that the immobilization of metal cations in bacteria-bearing settings cannot be examined independently of redox processes such as the oxidation, hydrolysis and precipitation of iron.

Effect of aliphatic spacer length on the electrorheological properties of side-chain liquid crystalline polymer-silica composite suspensions

Side-chain liquid crystal polymer (SCLCP)-silica composites were synthesized to enhance the electrorheological (ER) response by forming polar liquid crystal polymer-inorganic composites. Three types of SCLCP-silica composites were prepared to examine the effect of the aliphatic spacer length on the ER response of the composite suspensions. The SCLCPs consisted of a polymethacrylate backbone carrying cyanobiphenyl mesogenic groups as the side chains with various lengths of aliphatic spacer. The ER response increased with increasing electric field strength and decreasing aliphatic spacer length. The increasing ER response with decreasing spacer length was consistent with the behavior of the composite suspension dielectric properties. With the same spacer length, the ER response increased with increasing SCLCP/silica ratio.

Preparation of Highly Water-repellent Surface by Spontaneous Formation of Double Scale Roughness Pattern

Hydrophobic organic-inorganic hybrid composite suspensions were prepared by mixing hydrophobic octylsilyl titanium dioxide particles having average diameter of 35 nm with drying oil or moisture cure room temperature vulcanization silicone gum in volatile silicone. They were spread on a glass plate by using a linear motor coater and an applicator. Spatially periodic stripe patterns parallel to the direction of dragging the applicator were usually generated. The phenomenon is called directional viscous fingering, i.e. spontaneous pattern formation by the growth of fluctuation in morphology of mobile interface during the dragging coat. The pattern spontaneously formed on the surface became double scale when stored samples were coated. In this case, the large scale spatially periodic pattern was formed by the directional viscous fingering and the small ragged random pattern may be due to the giant molecules formed by cross-linking of silicone gum. Double scale roughness patterns were also generated by double dragging coat. The large and small scale pattern was formed by the first and second dragging coat, respectively. The formation of double scale roughness enhanced the water-repellent property of the hydrophobic surface. In some cases, water contact angle increased by 20 degrees to realize super water-repellent surface with a value exceeding 150 degrees.

Cement-Polymer Composites for Oilwell Cementing

The selection of an optimal cementitious material is critical to maintain zonal isolation for the lifetime of oil & gas or gas storage wells not only for primary cementing but also after well abandonment. Polymer powder/cement composites present good mechanical and durability properties since polymer latex promotes improved adhesion and flexibility to the hardened cement paste. So, for well constructions in aggressive environment, polymer powder/cement composites would be good candidates. During the well construction, the cement slurry placement strongly depends on its rheological behaviour. In this paper, we studied rheological properties of polymer powder/cement composite suspensions: they present a transition from a gel to a liquid behaviour in oscillatory shear. The replacement of cement particles by polymer particles induces a decrease of the storage modulus in the gel state. The good quality of the polymer particle dispersion and their high affinity for cement particles were observed by Scanning Electron Microscopy (SEM). Solid state NMR (29 Si and 27 Al) and calorimetry allowed to highlight the influence of the polymer addition on both the hydration and hardening of the cement matrix. All these results helped us to understand the relations between the slurry composition, its rheological behaviour and the properties of the hardened materials which allowed us to design new cementing materials.