Particle Charge Detector Research Articles

Synthesis and Application of a Cationic Polyacrylamide Dry Strength Agent with Anionic Content

A new net-cationic polyacrylamide dry strength agent was synthesized through free radical polymerization using acrylamide (AM), itaconic acid (IA), N,N-dimethylacrylamide (F), and sodium methallyl sulfonate (T). Ethylene diamine tetraacetic acid was used as a chelating agent; dimethylaminoethyl methacrylate methyl chloride (DMC) solution was used as a cationic monomer, and ammonium persulfate (APS) was used as an initiator. Orthogonal design and single-factor experiments were utilized to study the effect of many factors, such as reaction time, the ratio of monomers, and the dosage of APS and DMC on the cationic polyacrylamide. The synthesized products were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), particle charge detector (PCD), and zeta potential analysis. The results showed that the optimum conditions were as follows: optimal monomer proportion: m(AM):m(IA):m(T):m(F) = 23.79:2.39:0.21:0.32; w (DMC) = 28%; w (APS) = 1.0%, reaction time was 3 hours, reaction temperature was 93 °C, stirring speed was 130 rpm, and reaction pH value was 3.0. The solid content of the polymer was 21.2%. By adding the cationic polyacrylamide to old corrugated container pulp, the tensile index increased by 29.7% and the burst index increased by 66.1%, displaying the obvious enhancement of the paper.

Nanotitania-coated multi-walled carbon nanotube composite by facile colloidal processing route for photocatalytic applications

Multi-walled carbon nanotubes (MWCNTs) and titanium dioxide nanocomposites (MWCNTs/TiO2) were fabricated by a simple novel colloidal processing route and tested as a photocatalyst for degradation of methylene blue under UV irradiation. The novel idea behind this work is to make MWCNTs and TiO2 nanoparticle suspensions separately highly oppositely charged and utilize the electrostatic force of attraction between two entities to deposit nanotitania onto MWCNTs surface. Particle charge detector, scanning electron microscopy, transmission electron microscope, energy dispersive X-rays, X-rays diffraction (XRD), and Raman spectroscopy were used to characterize the composite. XRD and Raman spectroscopic analysis showed the crystalline structure of deposited TiO2 over MWCNTs surface structure as anatase phase. It was found that MWCNTs/TiO2 composite structure have much higher photocatalytic activity compared to TiO2 nanoparticles. The composite material developed may find potential applications in the degradation of organic pollutants in aqueous medium under UV irradiation.

Preparation of starch-based styrene acrylate emulsion used as surface-treatment agent for decorative base paper

Abstract A series of cationic starch (CS-8)-based styrene (St) acrylate latex preparations was prepared by the core-shell emulsion polymerization method. The latex was used in the surface-treatment of decorative base papers, for good printability and absorbability. CS-8, which has a low relative viscosity, was used as the emulsifier and dispersant. The influencing factors (dosage of CS-8 as well as the kinds and dosages of functional monomers) were studied and the optimal conditions were achieved. Then, the products were characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR), laser particle size analysis and particle charge detection. The results showed that the excellent performance and good surface-treatment effects of the St acrylate emulsion (SAE) were achieved when the reaction conditions were as follows: 10 wt% starch, 2 wt% methacryloyloxyethyltrimethyl ammonium chloride (DMC) as the cationic monomer and 20 wt% ethyl acrylate (EA) as the acrylate monomer. Under the optimal conditions, the latex particle size was around 160 nm, the latex viscosity was 10 mPa·s and the latex charge density was 0.60 mmol·l-1. The printability of the decorative base paper was significantly improved and the absorbability of the paper sheet was maintained. The surface-treatment effect of the cationic starch-based SAE was superior to that of commercial polyurethane (PU).

Surface etching of methacrylic microparticles via basic hydrolysis and introduction of functional groups for click chemistry

Controlled basic hydrolysis of poly(methyl methacrylate-co-ethylene glycol dimethacrylate) P(MMA-co-EGDMA) microparticles with a diameter d50=6μm led to high densities of carboxylic groups at the particles’ surface of up to 1.288μeqg−1 (equivalent to 1.277μmolm−2). The microparticles’ core has not been altered by this surface activation procedure as seen by fluorescent staining. The kinetics of the hydrolysis reaction was investigated via electrophoretic light scattering and particle charge detection employing polycation titration under shear condition. The activated microparticle’s surface was subsequently exploited in carbodiimide-mediated coupling reactions using a variety of molecular reactants, that is, 11-azido-3,6,9-trioxaundecan-1-amine, cysteamine, propargylamine, and fluoresceinamine, thus enabling the introduction of chemically reactive moieties such as azides, thiols, and alkynes. Fluorescent staining of the particles’ surface successfully demonstrated the versatile applications of surface functionalized microparticles via copper-catalyzed huisgen cycloaddition. Carrying on this two-step procedure in a controlled manner provides an excellent way for relatively simple but highly effective surface functionalization.

Organic cation exchanged montmorillonite and vermiculite as adsorbents for Cr(VI): Effect of layer charge on adsorption properties

The binding of anions at interlayer sites of organo-clay minerals is supposed to be stronger and more specific than on the external surfaces. In this study the Cr(VI) adsorption properties of two hydrous phyllosilicates, a montmorillonite and a vermiculite modified with Hexadecylpyridinium (HDPy), Hexadecyltrimethylammonium (HDTMA) and Benzethonium (BE) were investigated at pH 3–9. Structural features were determined by X-ray diffraction. The surface charge of the organo-clays at different pH was analyzed by polyelectrolyte titration in the cell of a particle charge detector. The effect of competing anions Cl−, NO3− and SO42− on Cr(VI) adsorption was determined.The interlayer space structures of the organo-vermiculites were paraffin-type, whereas it was pseudotrimolecular for the organo-montmorillonites. Besides organic cations also considerable amounts of inorganic cations were present in the interlayer space. As a consequence of organic cation treatment the surface charge of the clays shifted from negative to positive values up to 269mmolckg−1; it was highly affected by the specific surface area, layer charge and pH. Depending on the kind of organic cation, organo-vermiculites and -bentonites showed comparable adsorption capacity for Cr(VI), which was at pH 4.5 0.38 and 0.30molkg−1 for HDPy- and HDTMA-vermiculites, respectively and 0.37 and 0.26molkg−1 for the corresponding bentonites. For all organo-clays the adsorbed amount of Cr(VI) decreased with increasing pH. The effect of competing anions, Cl−, NO3− and SO42− on Cr(VI) adsorption appeared to be small. For organo-vermiculites a higher portion of anion adsorption sites was located in the interlayer space. In context with the high share of adsorption sites in the interlayer space it is suggested that both organo-vermiculites and organo-bentonites are promising adsorbents of Cr(VI) in water purification methods.

Influence of lysozyme complexation with purified Aldrich humic acid on lysozyme activity

Humic acid is an important component of dissolved organic matter and in two previous papers it has been shown that purified Aldrich humic acid (PAHA) forms strong complexes with the oppositely charged protein lysozyme (LSZ). The complexation and aggregation of enzymes with humic acids may lead to changes in their activity. Therefore, the enzyme activity of LSZ in the PAHA – LSZ complex as a function of mass ratio PAHA:LSZ was investigated at two pH values (pH 5 and pH 8 where PAHA and LSZ are oppositely charged) and two ionic strengths (5 mmol l−1; 50 mmol l−1). The newly prepared complex was characterized and the mass ratios PAHA:LSZ at the isoelectric point (IEP) of the complex at the assayed conditions were obtained with the Mütek particle charge detector. The LSZ activity was measured with an assay specific for LSZ. The activity of LSZ decreased upon complex formation with PAHA and the PAHA effect on the enzyme activity was increased by the subsequent aggregation. A critical PAHA:LSZ mass ratio for the behaviour of the enzyme activity was that at the IEP of the complex. Before this mass ratio was reached the LSZ activity strongly decreased under all conditions. Beyond this mass ratio both pH and ionic strength affected the activity of LSZ in the complex. The results can be explained by the effects that pH and ionic strength have on (i) the electrostatic attraction between LSZ and PAHA in the complex and (ii) the electrostatic repulsion between the complexes. These two factors plus the hydrophobic attraction determine the structure of the complexes and the size of the aggregates and hence the screening of the active site of the protein.

The role of poly(methacrylic acid) conformation on dispersion behavior of nano TiO2 powder

To exploit the advantages of nanoparticles for various applications, controlling the dispersion and agglomeration is of paramount importance. Agglomeration and dispersion behavior of titanium dioxide (TiO2) nanoparticles was investigated using electrokinetic and surface chemical properties. Nanoparticles are generally stabilized by the adsorption of a dispersant (polyelectrolyte) layer around the particle surface and in this connection ammonium salt of polymethacrylic acid (Darvan C) was used as dispersant to stabilize the suspension. The dosages of polyelectrolyte were optimized to get best dispersion stability by techniques namely particle charge detector (13.75mg/g) and adsorption (14.57mg/g). The surface charge of TiO2 particles changed significantly in presence of dispersant Darvan C and isoelectric point (iep) shifted significantly towards lower pH from 5.99 to 3.37. The shift in iep has been quantified in terms of free energy of interaction between the surface sites of TiO2 and the adsorbing dispersant Darvan C. Free energies of adsorption were calculated by electrokinetic data (−9.8 RT unit) and adsorption isotherms (−10.56 RT unit), which corroborated well. The adsorption isotherms are of typical Langmuir type and employed for calculation of free energy. The results indicated that adsorption occurs mainly through electrostatic interactions between the dispersant molecule and the TiO2 surface apart from hydrophobic interactions.

Preparation and characterization of styrene acrylate emulsion surface sizing agent modified with rosin

AbstractA series of core‐shell type cationic soap‐free latex were prepared by using styrene(St), butyl acrylate(BA), and methyl methacrylate(MMA) as main materials and introducing rosin as the functional monomer. Cationic starch (CS‐8), which has low relative viscosity, was used as the emulsifier and dispersant. The influencing factors of the reaction were studied and the optimal conditions were achieved. Then the products were characterized by scanning electron microscope (SEM), FT‐IR, laser particle sizer, and particle charge detector (PCD). The results showed that the excellent performance and good sizing effects of SAE were achieved when the reaction conditions were as follows: the starch amount was 8 wt %, the charge of the initiator (APS) was 0.5%, and the amount of rosin was 2 wt %. Under these conditions, the particle size of the latex was around 100 nm and had a narrow distribution, and the charge density of latex was 0.61 mmol L−1. The water‐resistant performance of paper was improved significantly when SAE was modified with rosin, and the Cobb value decreased by 46.8% compared to that of the paper sized by SAE without rosin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Humic substance charge determination by titration with a flexible cationic polyelectrolyte

The anionic charge of humic substances (HS) plays a major role in the interaction of HS with other components. Therefore, the potential of the polyelectrolyte titration technique to obtain the charge density of HS in simple 1–1 electrolyte solutions has been investigated. Titrations are carried out with an automatic titrator combined with the “Mütek particle charge detector” which allows determination of the Mütek potential and the pH as a function of the added amount of titrant which is a solution of poly-diallyldimethylammonium chloride (polyDADMAC), a cationic strong polyelectrolyte. When the Mütek potential reverses its sign the iso-electric point (IEP) of the polyDADMAC–HS complex is reached. The polyDADMAC/HS mass ratio at the IEP gives information on the HS charge density and from the pH changes in solution an estimate of the charge regulation in the HS–polyDADMAC complex can be obtained. In general, for polyDADMAC–HS complexes an increase in the dissociation of the acid groups of HS is found (charge regulation). The charge regulation decreases with increasing concentration of 1–1 background electrolyte. Cation incorporation can be neglected at 1–1 electrolyte concentrations ⩽ 1 mmol L −1 and a 1–1 stoichiometry exists between the polyDADMAC and HS charge. However, at these low salt concentrations the charge regulation is substantial. A detailed analysis of purified Aldrich humic acid (PAHA) at pH 5 and a range of KCl concentrations reveals that the anionic charge of PAHA in the complex increases at 5 mmol L −1 KCl by 30% and at 150 mmol L −1 KCl by 12%. On the other hand, increasing amounts of K + become incorporated in the complex: at 5 mmol L −1 KCl 5% and at 150 mmol L −1 KCl 24% of the PAHA charge is balanced by K +. By comparing at pH 5 the mass ratios polyDADMAC/PAHA in the complex at the IEP with the theoretical mass ratios of polyDADMAC/PAHA required to neutralize PAHA in the absence of charge regulation and K + incorporation, it is found that at 50 mmol L −1 KCl the extra negative charge due to the interaction between polyDADMAC and PAHA is just compensated by K + incorporation in the complex. Therefore, a pseudo 1–1 stoichiometry exists at about 50 mmol L −1 1–1 electrolyte concentration and only at this salt concentration polyDADMAC titrations and conventional proton titrations give identical results. Most likely this is also true for other HA samples and other pH values. For FA further study is required to reveal the conditions for which polyDADMAC and proton titrations give identical results.

Preparation and Characterization of Styrene Acrylate Emulsion(SAE) Surface Sizing Agent with Rosin as Functional Monomer

A series of core-shell type cationic soap-free latex were prepared by using styrene(St), butyl acrylate(BA) and methyl methacrylate(MMA) as main materials and introducing rosin as the functional monomer. In this reaction, starch(CS-8), which has low relative viscosity , was used as the emulsifier and dispersant. The influencing factors of the reaction were especially studied and the optimum conditions were got. Then the products were characterized by using scanning electron microscope (SEM), FT-IR, laser particle sizer, particle charge detector(PCD). The results show that the excellent performance and good sizing effects of SAE are achieved when the reaction conditions are as follows: the starch amount is 8%(wt), the charge for the initiator(APS) is 0.5%, and the amount of rosin is 2%(wt). And the water-resistant performance of paper is improved significantly when the rosin is chosen as the functional monomer.

Single polyelectrolyte multilayers deposited onto silica microparticles and silicon wafers

Single polyelectrolyte component multilayers, exemplified by poly(vinyl amine) (PVAm), have been prepared using a method of 3,3′,4,4′-benzophenonetetracarboxylic-dianhydride (BTCDA)-mediated electrostatics and hydrogen bonds LbL assembly. The PVAm with low (15,000 g/mol) and high (340,000 g/mol) molar mass was adsorbed at pH 9.5 onto silica microparticles with particle diameter of 0.015–0.040 mm. The BTCDA cross-linking of the PVAm adsorbed onto silica microparticles results in a surface covered with carboxylic groups. The silica/PVAm–BTCDA, negatively charged over a wide range of pH, can adsorb a new positively charged PVAm layer. A regular increase in the single (PVAm/BTCDA) n polyelectrolyte multilayer onto silica microparticles was observed by streaming potential measurements using a particle charge detector. X-ray photoelectron spectroscopy, the elemental and thermogravimetric analysis, were employed to monitor the (PVAm–BTCDA) n multilayer construction. The topography and thickness of the films deposited on silicon wafers, as a function of the number of PVAm layers, was investigated by atomic force microscopy. Both molar masses (15,000 and 340,000 g/mol) of PVAm were suitable for building (BTCDA)-mediated LbL assembly onto silica microparticles, even the behavior of PVAm on the multilayer formation strongly depends on the molar mass.

Reaction of soil water repellency to artificially induced changes in soil pH

Soil water repellency (SWR) is widely thought to be influenced by soil pH, however, few studies have systematically investigated the relationship between these variables. Specifically the hypothesis that the pH may control repellency via changes in the variable surface charge of soil material has not yet been tested. In previous work, methods for changing soil pH have also involved changes in soil moisture, but it has been argued that the potential influence of soil moisture changes needs to be eliminated before the actual relationship between pH and SWR can be isolated. The paper addresses this research gap using a new method, which enables adjustment of the pH of soils with low moisture content via the gas phase and thus involves minimal change in moisture content, allowing the response of SWR to pH changes to be evaluated. The method was applied to 14 soil samples from Germany, The Netherlands, the UK, and Australia, using the water drop penetration time ( WDPT) as the indicator of SWR. Additionally, sessile drop contact angles (Θ sess ) were measured on the four samples from Germany and the titratable surface charge of these four soils was measured at selected pH values using a particle charge detector (PCD). Changes in SWR with soil pH were found to be influenced by the density and type of sites able to interact with protons at the available surfaces of organic and mineral materials in soil. The maximum SWR occurred for soil at natural pH and where the charge density was minimal. As pH increased, negative surface charge increased due to deprotonation of sites and WDPT decreased. Two types of behaviour were observed: i) a decrease in repellency with decreasing pH, probably because of a sufficient number of proton accepting surface sites with a significant amount of positive surface charge, ii) no decrease in repellency with decreasing pH in soils with insufficient proton accepting surface sites to develop significant positive surface charge. The data suggest that the availability and relative abundance of proton active sites at mineral surfaces, and those at organic functional groups influence the response of the soil samples to changes in pH. The variety of geographic origins and histories of the soils examined provides a distinction between site specific and more widely applicable soil characteristics of pH dependent SWR.

Determination of the mass‐specific distribution of the substituents in cationic starch derivatives

AbstractThe mass‐specific charge distribution in molar mass fractions of cationic starch derivatives was investigated. The molar mass fractions were produced by semi‐preparative SEC (SP‐SEC). The derivatives were cut into an amylopectin‐rich fraction F1, an intermediate fraction F2, containing low molar mass amylopectin and high molar mass amylose, and an amylose‐rich fraction F3. The weight‐average molar mass (Mw) and molar mass distribution (MMD) of the fractions were determined by SEC with multi‐angle laser light scattering (SEC‐MALLS). The mass‐specific charge of each fraction was calculated from the consumption of anionic titrant solution using polyelectrolyte titration (PET) in combination with particle charge detection (PCD). The difference in substituent distribution between the fractions was tested by the Student's t‐test. The weight‐average molar mass of the starch derivatives was not dependent on the degree of substitution (DS) or the derivatization process. Depending on the DS value or derivatization process, different substituent distributions were observed. The results for the mass‐specific charge distribution in different molar mass fractions of cationic starch derivatives with graded DS between 0.015 and 0.130 from the slurry process were discussed. The heterogeneity of substituent distribution decreased with increasing DS of the starch derivative. This was the case for samples from both the slurry and semi‐dry processes. The heterogeneity of derivatization was highest for low DS samples up to DS 0.03, with the amylopectin‐rich fraction incorporating more charges than the amylose‐rich fraction. This was more pronounced for the sample from the slurry process than from the semi‐dry process.

Application Relevant Characterization of Aqueous Silica Nanodispersions

This work describes the application relevant characterization of eight commercially available silica powders dependent on dispersing procedure using different instruments: photon correlation spectroscopy, nitrogen adsorption, and particle charge detector. The particle size of silica was found to be different in dispersion from that of all types of fumed silica, where, after proper dispersion, the measured average particle size is similar and much higher than the primary particle size. The different properties of these two silica types will be discussed.

Preparation and application of cationic cellulose fibers modified by in situ grafting of cationic PVA

Rendering the cellulose fiber cationic via in situ graft copolymerization has been regarded as one of the effective approaches to improve the filler retention and distribution. In this work, cationic cellulose fibers were prepared by in situ copolymerization of vinyl acetate (VAc) and diallyldimethyl ammonium chloride (DADMAC) onto softwood sulphite pulp fibers using ceric ammonium nitrate (CAN) as a free radical initiator, followed by alkaline hydrolysis. Effects of various process parameters were systematically investigated, such as temperature, reaction time, initiator concentration, etc. Fourier transform infrared spectroscopy (FT-IR) was performed to confirm the existence of the grafted copolymers on the surface of sulphite pulps. The charge density of modified fibers was determined via back titration using a Particle Charge Detector MÜtek PCD 03. The difference between grafted fibers and virgin fibers was also revealed by the SEM observation. The resulting cationic pulps led to significant improvement of filler retention and distribution. Further improvement in filler retention was achieved by the synergy between cationic pulps and a conventional cationic polymer. In addition, the improved distribution of filler along fiber surfaces achieved by the addition of cationic pulp was demonstrated by both optical microscope and SEM observation.

Study on the interaction between anionic and cationic latex particles and Portland cement

The interaction between organic latex polymers and the surface of hydrating cement was investigated by measuring the zeta potential and adsorbed amount of polymer on cement. First, differently charged model latex particles were synthesized in aqueous media by well-known emulsion polymerization technique. The latex polymers were characterized by differential scanning calorimetry (DSC), dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM). Electrokinetic latex surface properties were investigated by means of streaming potential measurements using a particle charge detector (PCD). It is shown that the anionic latexes adsorb a considerable amount of Ca 2+ from the cement pore solution. Next, adsorption of the latex polymers on the surface of hydrating cement was confirmed by zeta potential measurements using the electroacoustic method. A water to cement ratio in the cement paste as low as 0.5 was studied, representing actual conditions in mortar and concrete. Additionally, adsorption isotherms were determined in a sedimentation test using the depletion method. For all latex polymers, Langmuir type adsorption isotherms were found. The latex dosages required to achieve saturated adsorption on the cement surface obtained from zeta potential measurements correspond well with those determined in the sedimentation test. Electron microscopy photographs confirm that the charged latex polymers adsorb selectively on surface areas of hydrating cement showing opposite charge. This way, domains of organic latex polymers exist on the cement surface. They provide adhesion between the inorganic cement matrix and the organic polymer film formed later on by particle coalescence as a result of cement hydration and drying.

Non-destructive characterization and alignment of aerodynamically focused particle beams using single particle charge detection

We describe the first experimental measurements of aerodynamically focused particle beams using single particle image-charge detection. An aerodynamic lens produces particle beams, which at times is not aligned with the bore of the lens, thus complicating the process of aligning a particle beam with the focus of a laser beam. A key result of this work is the development of a non-optical technique for aiming a beam of particles in vacuum into the focus of a laser beam. In the present application, the laser beam is fixed in space by the geometry of a large stationary vacuum system and it is necessary to blindly aim a narrowly focused particle beam across the laser beam. Our aiming device is based on the non-destructive detection of electrically charged particles as they pass through a small metal tube that picks up the image charge of the transiting particle. Individual electrosprayed particles larger than 70 nm produce an electrical pulse that can be thresholded and counted. The duration of the detector signal provides a way to measure particle velocity and the amplitude of the signal is proportional to particle charge. The rate of particle injection into vacuum, single particle velocity and charge and particle beam shape and position can be measured with the charge detector. We show data for aiming and focusing electrosprayed polystyrene latex spheres ranging in size from 70 to 190 nm. Particle injection rates as high as 3000 per second and particle beam diameters as small as 250 μ m were achieved by using the charge detector to optimize the performance of the aerodynamic lens to focus the particles before they entered. We also describe how this detector and injector system will be implemented for real-time particle analysis for aerosol mass spectrometry and single particle X-ray diffractive imaging.

Humic acid protein complexation

Interactions of purified Aldrich humic acid (PAHA) with lysozyme (LSZ) are investigated. In solution LSZ is moderately positively and PAHA negatively charged at the investigated pH values. The proton binding of PAHA and of LSZ is determined by potentiometric proton titrations at various KCl concentrations. It is also measured for two mixtures of PAHA–LSZ and compared with theoretically calculated proton binding assuming no mutual interaction. The charge adaptation due to PAHA–LSZ interaction is relatively small and only significant at low and high pH. Next to the proton binding, the mass ratio PAHA/LSZ at the iso-electric point (IEP) of the complex at given solution conditions is measured together with the pH using the Mütek particle charge detector. From the pH changes the charge adaptation due to the interaction can be found. Also these measurements show that the net charge adaptation is weak for PAHA–LSZ complexes at their IEP. PAHA/LSZ mass ratios in the complexes at the IEP are measured at pH 5 and 7. At pH 5 and 50 mmol/L KCl the charge of the complex is compensated for 30–40% by K +; at pH 7, where LSZ has a rather low positive charge, this is 45–55%. At pH 5 and 5 mmol/L KCl the PAHA/LSZ mass ratio at the IEP of the complex depends on the order of addition. When LSZ is added to PAHA about 25% K + is included in the complex, but no K + is incorporated when PAHA is added to LSZ. The flocculation behavior of the complexes is also different. After LSZ addition to PAHA slow precipitation occurs (6–24 h) in the IEP, but after addition of PAHA to LSZ no precipitation can be seen after 12 h. Clearly, PAHA/LSZ complexation and the colloidal stability of PAHA–LSZ aggregates depend on the order of addition. Some implications of the observed behavior are discussed.

Selection and Optimization of Dispersant in Ceramic Slurry Processing by Different Techniques: Comparison, Correlation, and Standardization

This article describes the selection and optimization of dispersant dosage in colloidal processing of ceramic slurry by techniques such as particle charge detector (PCD), capillary suction time (CST), rheological measurement, and wet point and flow point techniques. In general, experimental results are found to be in good agreement with each other with some degree of variation. PCD, CST, and rheological techniques are related by a simple linear function. The experimental and calculated values are well matching within an error limit of 10%. Attempt has been made to develop formula for correlating results of optimization from one technique to those obtained from another technique. The region where the suspension is well dispersed, CST is linearly correlated with PCD. The advantages and limitations of each technique have been described and discussed.

Anchoring of Silver Nanoparticles on Graphite and Isomorphous Lattices

Recently, multiwalled N-doped carbon nanotubes were decorated with Ag nanoparticles (NPs) by a simple procedure. Now, as a continuation of our earlier work, Ag NP−graphite and Ag NP−molybdenite composites were prepared with this easy, fast, and inexpensive method. Graphite or molybdenite (MoS2) powder was suspended in N,N‘-dimethylformamide (DMF) in the presence of different silver salts. As DMF is a good reducing agent of silver cations, in situ formation of Ag NPs took place in the suspension. We supposed that the Ag NP formation is possible on the surface of the supports due to the interaction between the unoccupied silver orbitals and the π-electrons of graphite or the 3p sulfur orbitals of MoS2. This is the first report about the Ag NP−MoS2 nanocomposites synthesis. A complete spectral and structural characterization of these composites was accomplished by UV−vis and Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, and particle charge detector. According to these measurements, nanocomposites were formed depending on the original silver salt, support, surface charge, and stabilizing agent.