External Additives Research Articles

Effects of additives on properties of Zr50Al15Ni10Cu25amorphous powders in low-pressure sintering

Amorphous Zr50 Al15 Ni10 Cu25 powders were prepared by mechanical alloying technique from low-purity raw materials. The beneficial effects of a certain amount of external additives such as C, Si3 N4 and SiC powders added to the amorphous powders on the thermal stability, densification and mechanical properties of the Zr50 Al15 Ni10 Cu25 amorphous powders after low-pressure sintering were investigated. The blended powers were hand-pressed into bars in the air under 35 MPa pressure. The preformed bars were sintered in an argon atmosphere under low pressure. The samples were characterized by XRD, SEM, TEM, DSC and tensile testing. The results suggest that the crystallization process of Zr50 Al15 Ni10 Cu25 during sintering could be inhibited for the increase in activation energy when the proper amount of external particles was added to the matrix. Furthermore, suitable additives could help to densify the matrix and improve its mechanical properties in the low-pressure sintering process.

Catalyst-Free Approach to Construct C-C Bond Initiated by N-O Bond Cleavage under Thermal Conditions.

An unexpected and novel approach to construct the sp(2) C-sp(3) C bond has been developed via N-O bond cleavage without any external catalysts or additives. It is a very simple, efficient, and environmentally friendly method and will be a very attractive radical process toward new C-C bond formation.

Metal-organic chemical vapor-deposited cobalt oxide films as negative electrodes for thin film Li-ion battery

In this study, thin films of cobalt oxide (Co3O4) have been grown by the metal-organic chemical vapor deposition (MOCVD) technique on stainless steel substrate at two preferred temperatures (450 °C and 500 °C), using cobalt acetylacetonate dihydrate as precursor. Spherical as well as columnar microstructures of Co3O4 have been observed under controlled growth conditions. Further investigations reveal these films are phase-pure, well crystallized and carbon-free. High-resolution TEM analysis confirms that each columnar structure is a continuous stack of minute crystals. Comparative study between these Co3O4 films grown at 450 °C and 500 °C has been carried out for their application as negative electrodes in Li-ion batteries. Our method of electrode fabrication leads to a coating of active material directly on current collector without any use of external additives. A high specific capacity of 1168 micro Ah cm−2 μm−1 has been measured reproducibly for the film deposited at 500°C with columnar morphology. Further, high rate capability is observed when cycled at different current densities. The Co3O4 electrode with columnar structure has a specific capacity 38% higher than the electrode with spherical microstructure (grown at 450°C). Impedance measurements on the Co3O4 electrode grown at 500 °C also carried out to study the kinetics of the electrode process.

Evidences of plasmonic effect in an organic–inorganic hybrid photovoltaic device using flower-like ZnO@Au nanoparticles

Using flower-like ZnO@Au nanoparticles as external additives in an organic–inorganic hybrid solar cell device, we investigate the surface plasmon resonance (SPR) effect of gold nanoparticles. The active layer of the device consists of a usual polymeric blend of poly(3-hexylthiophene) and surface functionalized ZnO nanorods, which is conventionally known for its poor power conversion efficiency. We present the experimental evidences of improvement over UV–visible absorption properties and photocurrent generation due to the SPR effect. As a result, improvement is reported for short circuit current density and efficiency of the device on addition of flower-like ZnO@Au nanostructures.

Gold-catalyzed direct hydrogenative coupling of nitroarenes to synthesize aromatic azo compounds.

The azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable heterogeneous-gold-catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of N=N bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface-mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.

Gold‐Catalyzed Direct Hydrogenative Coupling of Nitroarenes To Synthesize Aromatic Azo Compounds

AbstractThe azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable heterogeneous‐gold‐catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of NN bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface‐mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.

Role of additives; sodium dodecyl sulphate and manganese chloride on morphology of Zn1−xMnxO nanoparticles and their photoluminescence properties

In the present study Zn1−xMnxO (x = 0, 0.05 and 0.1) nanoparticles (NPs) have been synthesised in aqueous solution phase at mild reaction temperature 100 °C in moderate alkaline medium (pH = 9.5), and the role of external additives; like sodium dodecyl sulphate and manganese chloride on the morphology and size of the products has been explored on the basis of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectral analyses data. ZnO hexagonal nano-plates, core–shell like spherical/ellipsoidal Zn0.95Mn0.05O structures and thin sheets, thorn/needle mixed shaped Zn0.9Mn0.1O structures have been observed in TEM and SEM images. Zn(OH)2 formed in moderate alkaline medium, converted to Zn(II) hydroxo complex ions on dissolution, which further recrystallizes to produce wurtzite ZnO at 100 °C. From XRD and EDX analysis, successful doping of Mn2+ ions at the Zn2+ sites in ZnO host has been proved. In the photoluminescence spectra, the observed blue shifts in NBE peaks and decrease of emissions intensity on Mn doping have thoroughly been discussed in the present investigation.

The charge properties and durability of new submicron silica

Submicron silicas produced by hybrid process and their corresponding surface-modified counterparts are compared with respect to their applicability as external additives for electrophotographic toners. The principal metric for comparison is triboelectrostatic charge (T-ESC) stability under extended activation periods. Experimental samples are surface-modified submicron silicas produced by a hybrid process. The hybrid materials have sufficient hydrophobicity and can work as spacer particles to prevent the embedding of small particle size external additives. Further characteristics and advantages for this new external additive type will be presented. The surface modification improves charge stability and the spacer effect, especially under extreme environmental conditions, that can impact toner performance.

Study of the Effect of External Additives on Toner Admix Performance

The charge-admix-exchange process happening in the xerographic developer between aged and fresh toner, as well as carrier particles carrying different electrostatic charges, is a complex and not well-understood process from a theoretical point of view. Fast electrostatic charging of fresh toner particles to a desired steady state in a developer is very important to achieve high quality prints, especially in the case of high speed printing devices. One common way that formulators try to improve toner admix is by adjusting the external additive package [1-3].The goal of this study was to gain a better understanding of how different additive morphology and surface treatment influence admix. More specifically, we investigated what happens with the electrostatic charge of toner when aged and fresh developers are mixed in equal proportions and the mixture exercised over a short time period.Results of the study of a simple model developer containing a positively charging toner, a single fumed silica surface treated with a silane containing an amino group, and a silicone coated ferrite carrier, will be presented. The collected data indicate that the carrier's ability to gain electrostatic charge quickly decreases as a result of the transfer of silica particles or molecules of the silica treating agent to the carrier's surface. This leads to an unfavorable performance in the admix test.In the second part of the work, the effect of different types of spacer additives on carrier poisoning and admix was studied. The obtained results show that the formulations containing spacer particles have more stable charge vs. exercise time and better admix characteristics than the formulation containing only one silica additive.

Catalyst-Free Synthesis of Hollow-Sphere-Like ZnO and Its Photoluminescence Property

Hollow-sphere-like ZnO was successfully prepared by a facile combustion route at 950°C, and no external catalysts or additives were introduced. The morphology and structure of the hollow-sphere-like ZnO were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and energy dispersive spectrometer (EDS). The possible growth mechanism was discussed in detail. In addition, the as-obtained hollow-sphere-like ZnO exhibited a strong green emission at 518 nm and a weak UV emission at 385 nm. We believe that the hollow-sphere-like ZnO material may be a good candidate for application in optical devices and catalyst systems.

Crystallization of silibinin from organic solutions using supercritical and aqueous antisolvents

Silibinin, an anticancer drug, was crystallized from organic solutions using supercritical and aqueous antisolvents. Silibinin was dissolved in acetone and ethanol at concentration range of 0.01–0.04g/mL, and the drug solutions were placed in contact with two different antisolvents, carbon dioxide and water. The mixing of the drug solutions and antisolvents led to the prompt precipitation of silibinin in a solid crystal form. The experimental variables, such as temperature, solution concentration, mixing rate and solution/antisolvent volume ratio were manipulated. When the experiments were conducted with a supercritical antisolvent, the effects of external additives on the crystal habit were examined. α-d-Glucose penta acetate, triton X-100 and urea were added to the solution at concentration range of 0.001–0.003g/mL as external additives. The temperature increase of 20°C induced 25% increase in particle size. As the solution concentration was increased from 0.01 to 0.04g/mL, the average particle size decreased from 35.5 to 22.0μm in supercritical antisolvent experiments, while the particle size increased from 8.9 to 30.4μm in aqueous antisolvent experiments. The use of different kinds of external additives resulted in different modifications of the particle shape and structures.

Hierarchical Zeolites by Desilication: Occurrence and Catalytic Impact of Recrystallization and Restructuring

The manifestation of zeolite recrystallization and the formation of amorphous aluminosilicate species during desilication are examined to better understand the properties of alkaline-treated hierarchical zeolites and their catalytic performance. This is achieved using a systematic experimental strategy, starting from treating the filtrate of alkaline-treated silicalite-1 in the presence of various external additives. No recrystallization is evidenced upon addition of tetrapropylammonium (TPA+) and/or aluminum hydroxide ions [Al(OH)4–], confirming the low probability of zeolite nucleation and/or growth during desilication. Conversely, ordered mesoporous materials (OMMs) form upon addition of cetyltrimethylammonium (CTA+) to the filtrate. By using other silicon sources, i.e., tetramethyl orthosilicate or the organosilane dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium, we verify the facile formation of amorphous materials during alkaline treatment of USY zeolites in the presence of hydrophobic micelle-forming alkyl moieties. A systematic characterization by X-ray diffraction, transmission electron microscopy, N2 and Ar adsorption, inductively coupled plasma optical emission spectroscopy, and Fourier transform infrared spectroscopy of pyridine adsorbed, demonstrates that zeolites exposed to base solutions containing CTA+ display weaker zeolitic properties, compared to those prepared using TPA+, and should be considered as hierarchical zeolite/OMM composites. Catalytic tests in the alkylation of toluene with isopropyl alcohol or benzyl alcohol evidence that CTA+-derived composites do not outperform the conventional USY zeolite. Only the hierarchical USY zeolite prepared by alkaline treatment in the presence of TPA+ yielded a superior catalytic performance.

Pulmonary toxicity of printer toner following inhalation and intratracheal instillation

The pulmonary effects of a finished toner were evaluated in intratracheal instillation and inhalation studies, using toners with external additives (titanium dioxide nanoparticles and amorphous silica nanoparticles). Rats received an intratracheal dose of 1 mg or 2 mg of toner and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months. The toner induced pulmonary inflammation, as evidenced by a transient neutrophil response in the low-dose groups and persistent neutrophil infiltration in the high-dose groups. There were increased concentrations of heme oxygenase-1 (HO-1) as a marker of oxidative stress in the bronchoalveolar lavage fluid (BALF) and the lung. In a 90-day inhalation study, rats were exposed to well-dispersed toner (mean of MMAD: 3.76 µm). The three mass concentrations of toner were 1, 4 and 16 mg/m3 for 13 weeks, and the rats were sacrificed at 6 days and 91 days after the end of the exposure period. The low and medium concentrations did not induce neutrophil infiltration in the lung of statistical significance, but the high concentration did, and, in addition, upon histopathological examination not only showed findings of inflammation but also of fibrosis in the lung. Taken together, the results of our studies suggest that toners with external additives lead to pulmonary inflammation and fibrosis at lung burdens suggest beyond the overload. The changes observed in the pulmonary responses in this inhalation study indicate that the high concentration (16 mg/m3) is an LOAEL and that the medium concentration (4 mg/m3) is an NOAEL.

Humidity switching properties of sensors based on multiwalled carbon nanotubes/polyvinyl alcohol composite films

ABSTRACTMultiwalled carbon nanotubes (CNTs) were used as the conductive filler of composites for switching type humidity sensor. The CNTs were oxidized by mixed acids (H2SO4 : HNO3) at a mild temperature to modify carboxylic acid (COOH) groups on the surface of the nanotubes. The dispersibility of acid treated CNTs (CNTs‐COOH) in water is much improved, which is beneficial for dispersing CNTs in the polyvinyl alcohol (PVA) matrix without external additives. The obtained CNTs‐COOH/PVA sensors show nonlinear response to relative humidity (RH), that is, switching properties. The resistances of the sensors remain constant before 80% relative humidity (RH) and then increase sharply with RH, indicating excellent switching characteristic of the sensors. The 10 wt % CNTs‐COOH/PVA sensor shows a sensitivity (ΔR/Ro) of 32.3 at 100% RH. The humidity switching properties of CNTs‐COOH/PVA are much better than that of pristine CNTs/PVA. The improvements are attributed to the improved balance between the dispersibility of CNTs‐COOH and electrical conductivity of the composite films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39726.

Rhodium‐Catalyzed Synthesis of Amides from Aldehydes and Azides by Chelation‐Assisted CH Bond Activation

CH activation: A RhIII-catalyzed direct aldehyde CH amidation has been achieved with sulfonyl, aryl, and alkyl azides as the amine sources, and release of N2 as the only byproduct (see scheme). More importantly, this catalytic reaction proceeds in the absence of external oxidants or additives, under mild conditions, at neutral pH under air. This reaction represents a new avenue for practical intermolecular CN bond formation by aldehyde CH bond activation. Cp*=1,2,3,4,5-Pentamethylcyclopentadiene

New Submicron Silica Produced by Hybrid Production Process

New surface modified submicron silicas produced by a hybrid production process are compared to commercially prepared surface-modified colloidal silica with respect to their applicability as external additives for electrophotographic toners. The principal metric for comparison is tribo-electrostatic charge (T-ESC) stability under an extended activation period, but relative dispersibility on toner and the influence of environmental extremes on tribo-charge properties are also examined. The hybrid materials have sufficient hydrophobicity and can work as spacer particles to prevent the embedding of small particle size external additives. Further characteristics and advantages for this new external additive type will be presented.

Silica-Polymer Composite Particles for Toners: Synthesis, Characterization and Performance

Evolution of toner technology together with a demand for faster printing puts new requirements on external additives used in toner formulations. Spacer particles, which are added to protect the toner surface from mechanical stress resulting from collisions with the particles of carrier or the doctor blade, have become a progressively more important part of the additives packages.Polymeric particles, colloidal silica, and low surface area fumed silica are usually used as spacers. However, each of these materials has significant drawbacks. For instance, triboelectric charging properties of polymeric particles are not always optimal, large colloidal silica often drops off from toner surface, and low surface area fumed silica typically has broader than desired aggregate size distribution.At the NIP28 conference we introduced the organic/inorganic composite spacer additives which combine benefits of polymeric and colloidal silica spacer additives [1]. We demonstrated that the new particles have lower drop off from the toner surface than colloidal silica additives.In this paper we demonstrate how the new material particle size and shape could be controlled and present results of a print test where a model toner was formulated with the silica-polymer composite spacer additives.

Preparation of conducting halloysite/polyaniline coaxial tubular nanocomposites in the presence of decorating halloysite as in situ dopant

Halloysite nanotubes decorated with self-assembled protonic acids monolayer (SPAM-HNTs) was successfully prepared by anchoring the organic sulfonic acid onto the surface of tubular halloysite, and performed as in situ dopant to obtain the conducting SPAM-HNTs/PANI nanocomposites via in situ chemical oxidative polymerization of aniline. The surface functionalization of HNTs with protonic acids monolayer was found to play an important role in the formation of the well-defined coaxial tubular structure as well as the high doping degree of PANI. Moreover, the thermal stability of the SPAM-HNTs/PANI nanocomposite was clearly enhanced, and the SPAM-HNTs/PANI nanocomposite was possessed of good conductivity in magnitude up to 10−1S/cm at room temperature without any other external additives. The effect of the SPAM-HNTs feeding ratio on the electrical conductivity of the products was also emphasized.

New Submicron Silica Produced by the Fumed Process

Submicron silicas produced by fumed processes and their corresponding surface-modified counterparts are compared with respect to their applicability as external additives for electrophotographic toners. The principal metric for comparison is tribo-electrostatic charge (T-ESC) stability under extended activation periods. Experimental samples are surface-modified submicron silicas produced by a fumed process. These materials have sufficient hydrophobicity and can work as spacer particles to prevent the embedding of small particle size external additives. This spacer-attribute thereby eliminates problems with charge stability and flowability, especially under extreme environmental conditions, that can impact toner performance.

External Additives for Toners: Characteristics of Fumed Silica, Colloidal Silica, and Next Generation Materials

Demand for higher print resolution and reduced energy consumption is driving development of smaller and softer toners. Embedding of external additives into soft toners during the development and deterioration of properties such as cohesion and tribocharge is one of the major problems that toner formulators face. In order to protect small particles on the toner surface from being embedded, large particle silica is often used as a spacer particle. Over the last ten years, spacer additives have become a crucial component of modern formulations. Cabot has recently significantly extended its portfolio of external additives for toners with an emphasis on large particle silica. In particular, several new grades based on 60 m2/g fumed silica, and colloidal silicas with particle sizes between 40 and 200 nm have been introduced. In this paper, we present performance data for a set of fumed and colloidal silicas that illustrates the effect of different surface treatments. In addition, Cabot has developed novel silica-polymer composite particles that show promise as spacer additives. These materials show reduced drop off from the toner surface compared to colloidal silica of similar size, potentially allowing formulators to use larger size spacer particles.