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Excellent mechanical and electrical properties of graphene-based paper-like materials are essential for applications in flexible conductors, energy-storage devices, etc. The graphene oxide (GO) supernatant separated by centrifugation and ultrasonication has been used to prepare graphene oxide paper and reduced graphene oxide paper (rGOP) with high strength and conductivity. However, this method has cumbersome steps and low supernatant concentration, which greatly increases time and energy consumption, and is not suitable for rapid batch preparation of high-strength and high-thickness rGOP. Herein, a high-speed mechanical shearing method has been used to efficiently exfoliate graphite oxide suspension into high-concentration GO slurry with large lateral size, and rGOP has been further prepared by blade coating and HI acid chemical reduction. Compared with the product prepared by ultrasonic exfoliation method, the average area of GO sheets obtained via the mechanical shear exfoliation method can reach around 16.31 μm2. As a result, the mechanical properties and conductivity of the prepared rGOP have been increased by 30% and 23.5%, respectively, with the tensile strength and electrical conductivity of 478.2 MPa and 208.4 S/cm being obtained. The developed method is of great significance for the large-scale production and emerging applications of lightweight and high-performance rGOP.

It remains a challenge to prepare special engineering paper with excellent mechanical properties, high temperature resistance and chemical resistance. The emergence of high-performance fiber provides support for the technical progress of special engineering paper. Herein, a novel method to obtain a novel self-reinforced poly (ether ether ketone) (PEEK) composite paper (SR-DI-PEEK/paper) by vacuum filtration, impregnation and hot pressing. Specially, PEEK fibers were used as the skeleton fiber and a small amount of aramid pulp was added as the decanted fiber. By optimizing the process of SR-DI-PEEK/paper preparation, the best mechanical properties of SR-DI-PEEK/paper was presented. Compared with the composite paper prepared with Phenolic solution (PF-PEEK/paper) and Polyimide solution (PI-PEEK/paper), the mechanical properties of SR-DI-PEEK/paper was significantly improved. In particular, when the concentration of impregnation was 3 wt%, the tensile index of SR-DI-PEEK/paper reached 51.10 N m g−1 (tensile strength 47.16 kN m−1), which is 16.48 times than that of the un-impregnated PEEK/paper (2.86 kN m−1). SR-DI-PEEK/paper also exhibited excellent chemical resistance among acid, alkali, and polar solvents, while the tensile index maintained 96.3% after 40 wt% H2SO4 treatment. Besides, SR-DI-PEEK/paper showed superior thermal performance, while the temperatures corresponding to the weight loss of 5% were 574 °C.

Electromagnetic interference (EMI) shielding materials with high performance and low density are urgently needed with the rapid development of electronic communications. In this work, tuning solid–air interface of graphene paper was carried out to enhance multiple reflections of incident electromagnetic waves for high-performance EMI shielding. The large amount solid–air interface (57.8 m2 g−1) endowed the porous graphene paper with a high EMI shielding effectiveness (SE) of 31.0 dB, 50% enhancement from its counterpart of solid graphene paper. This porous graphene paper also showed an ultralow density of 0.02 g cm−3, an 18.5-fold decrease from its counterpart of solid graphene paper. Moreover, the EMI SE of obtained graphene papers exhibited proportional relationship with their specific surface area, further confirming the vital role of solid–air interface in the enhancement of EMI shielding. This work quantitatively demonstrates the significance of solid–air interface area for enhancing the EMI shielding performance and proposes an efficient guideline for the design of high-performance and low-density EMI shielding materials.

The flame resistance of kraft paper was greatly modified by an eco-friendly, phosphorus-containing and reactive flame retardant, ammonium phosphite, which was grafted on kraft paper via pad-bake method. The results showed that the limiting oxygen index of treated kraft paper could increase from 19.1 to 48.2%. The results of vertical flammability tests imply that the char length of treated sample decreased from 210 to 45 mm. Thermogravimetry analysis showed that treated kraft paper had the lower initial decomposition temperature and more residues than control sample. Thermogravimetry analysis/infrared spectrometry indicated that the flammable volatile species of treated kraft paper reduced obviously compared with that of control sample. Fourier transform infrared spectroscopy suggested that ammonium phosphite was grafted on the cellulose molecules by P–O–C covalent bonds and the flame retardant is reactive in condensed phase. Scanning electron microscopy showed that the modification had little effect on the surface of kraft paper and the residual carbonized frame of treated kraft paper retained the fiber shape after combustion. EDX results showed that the flame retardant introduced a large amount of phosphorus and nitrogen into kraft paper. X-ray diffraction indicated that the modification did not significantly affect the crystal structure of kraft paper. And the strength of kraft papers slightly declined after the modification, but it still remained well.

Starch is one of the most popular biodegradable polymers in nature, which is gaining increasing attention because of its abundant availability and low cost. However, starch film itself is very brittle and its barrier property is poor for many applications. Polyvinyl alcohol (PVA), a versatile polymer in paper industry, is used to improve the barrier property of starch film. In this study, painting paper with exceptional barrier properties against organic solvents is successfully prepared for art creation purpose by coating a thin layer of environmentally friendly starch/PVA film on its surface. The coated paper can resist the penetration of the ink from marker pens. Furthermore, the solvent resistance and mechanical flexibility of freestanding starch/PVA hybrid film were investigated in detail. It found that the excellent barrier properties of the coated painting paper against solvents are due to the superior solvent resistance and mechanical flexibility of starch/PVA hybrid film. Therefore, the biodegradable and cost-effective strategy in this study provides a promising approach to enhance the barrier property of painting paper against solvents, which can find potential applications in painting field.

We report on a corroborative study of the structural, morphological and electrical property alterations of free-standing graphene oxide (GO) papers subject to thermal reduction. Structural analysis performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman techniques prove that the onset of major structural changes, characterized by removal of oxygen functionalities, occur in the 200–300 °C temperature range. The results are corroborated with related morphological changes observed using Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) imaging. Elemental analysis shows the GO paper reduced at 600 °C to contain an 85 wt. % carbon content and a remnant oxygen level of 13.31 wt. %. At the highest reduction temperatures, we see evidence of vacancy-type defects impeding the overall effectiveness of the reduction process. Detailed electrical resistance measurements and current–voltage (I-V) profiling conducted using four-point probe method reveals a several orders of magnitude drop in the sample resistance once the reduction temperature exceeds 200 °C, in good agreement with the structural and morphological changes. The fundamental insights revealed through these studies will be important for future applications where the electrical and mechanical properties of free-standing GO and reduced graphene oxide (rGO) are exploited in practical devices. Graphical abstract

Fiber length and fiber-to-fiber bonding effects on tensile strength and fracture toughness of kraft paper have experimentally been investigated. Laboratory sheets were made from kraft pulp, each with a distinct set of fiber lengths. Additionally, the fiber–fiber bond strength was improved by carboxymethyl (CMC) grafting. The tensile strength and work of fracture toughness results were compared to predictions from a shear-lag model which considers the fiber–fiber bond shear strength, the fiber tensile strength and fiber pull-out work. The tensile strength and fracture work for papers with weak fiber–fiber bonds increased with fiber length consistent with the shear-lag model. CMC-treated fibers provided strong fiber–fiber bonds. Papers made from such fibers displayed high strength and work of fracture independent of fiber length which indicates that the failure process is governed by fiber failures rather than bond failures. The fracture toughness, expressed as the critical value of the J-integral, increased strongly with fiber length for both untreated and CMC-treated papers. The results show that long fibers and CMC addition are extremely beneficial for improving the fracture toughness.

We described a new concept, carbon paper-free membrane electrode assembly (MEA) fabricated from Nafion membrane and multi-walled carbon nanotubes-based electrocatalyst, in which platinum nanoparticles were deposited on carbon nanotubes after coating with pyridine–polybenzimidazole (PyPBI). Polymer-coated carbon nanotubes served as platinum nanoparticles support and current collector in carbon paper-free MEA. The fabricated carbon paper-free MEA was systematically studied by in situ cyclic voltammetry, SEM and fuel cell test. Pt utilization efficiency of carbon paper-free MEA improved with decreasing in Pt loading and reached 62% with 0.1 mgPt cm−2. Meanwhile, the mass power density reached 1.1 W mg Pt −1 , which was comparable to that of MEA with carbon paper. Fuel cell performance maintained 50% after 100000 startup–shutdown cycles, suggesting that carbon paper-free MEA was applicable in real fuel cell operation. To the best of our knowledge, this is the first study of carbon paper-free MEA in polymer electrolyte fuel cells.

Multiwalled carbon nanotubes (MWNT) were deposited via dropcasting and dried using vacuum filtration. Because of the slightly larger pore size (5–10 µm) of the paper substrate used as compared to the length of the nanotubes (0.5–2 µm), a variety of MWNT networks were formed both on the surface and through the thickness of the paper. Using a combination of impedance spectroscopy, equivalent circuit modeling, and microscopy techniques, it was possible to describe in detail how the electrical properties change as a function of how the MWNTs are distributed on the porous substrate by varying the number of deposited layers (1–20) as well as the dispersion concentration (0.1–5 mg/mL). In the in-plane, four different electrical responses were observed and modeled: (1) a substrate dominated spectrum representing unconnected MWNTs, (2) one that included bundle and junction responses as well as some inductances representing sparsely distributed MWNT networks, (3) followed by a parallel RL circuit for partially connected MWNT networks, and (4) finally a series RL circuit for fully connected MWNT networks. In the thru-plane, only two different electrical responses were observed and modeled. The results for the in-plane and thru-plane properties were used to generate percolation curves that show that electrical conductivity can change as much as 10 orders of magnitude for the same exact MWNTs. These results indicate that not only do the characteristics of the nanotubes themselves play a role but also the structure of the underlying substrate and the details of how the films are deposited.

Herein, an eco-friendly and straightforward method was provided for the fabrication of superhydrophobic paper from native wood cellulose fibers via in situ hydrolysis of tetraethyl titanate(IV) without any chemical pretreatment. By simply adjusting the amount of acetic acid (HAc), the surface micro/nanomorphology could be well controlled. After papermaking and hexadecyltrimethoxysilane modification, superhydrophobic paper can be easily achieved with static water contact angle of 152.3° (± 1.3°). The paper also possessed good self-cleaning property against contamination and durability toward mechanical damages of finger wiping over 50 cycles as well as excellent oil/water separation, which expands its utility in various paper-based technologies. The whole procedure possesses the advantages of friendly raw material, mild reaction conditions and with no toxic modifier, which hold potential application in cellulose-based superhydrophobic material in large scale.

Carbon fiber paper (CFP) has been widely investigated as a gas diffusion layer for high-performance fuel cells, while the paper formation, one of the most important properties of CFP, has been rarely reported before owing to the lack of accurate characterization methods. Herein, using a 2D laboratory sensor, a quantitative analysis was conducted to comprehensively analyze CFP formation, carbon fiber (CF) flocs and their influencing factors. Within the study scope of this paper, improved paper formation was always accompanied with a smaller floc area and a lower ratio of large-size flocs for CFP prepared with the same length of CF. CF was too long negatively affected paper formation, as the look-through index rose from 282 (2 mm CF) to 940 (8 mm CF). Either using polyethylene oxide as a disperser or reducing the CF concentration could reduce the look-through index of the CFP (2 mm CF) to below 200. The crowding factor of the CF suspension was suggested to be no more than 5. In addition, improvement in CFP formation led to higher tensile strength and lower air permeability in CFP. All these results are expected to prepare CFP with superior formation, thereby improving other properties of CFP.

Sulfur quantum dots are promising alternatives for traditional heavy metal-containing quantum dots due to their benign chemical properties and low cytotoxicity. Herein, cysteine-decorated sulfur dots were prepared from facile modification of pristine sulfur dots and can be acted as a chemosensor for the fluorometric and colorimetric dual-channel detection of cobalt (Co2+) with high sensitivity and selectivity. Visual colors of the as-prepared chemosensor in the presence of Co2+ changed from blue to colorless under UV light and also can transform from colorless to yellow under sunlight based on the photoinduced electron transfer effect. The detection limit of cysteine-decorated sulfur dots toward Co2+ was determined as low as 0.16 μM with a wide detection range, which is lower than the permitted guideline level by Department of Environmental Protection for drinking water (1.7 μM). Furthermore, portable paper sensor-based cysteine-decorated sulfur dots were fabricated for Co2+ detection and showed superior detection ability. Aided by a common smartphone as detector, the rapid, on-site and accurate quantification of Co2+ in real water samples can be accomplished. Our research has provided a novel chemosensor based on sulfur dots for dual-channel detection of Co2+, which would expand applications of sulfur dots in environmental monitoring, diseases diagnosis, cell imaging, light-emitting diodes, etc. Cysteine-decorated sulfur dots were acted as a chemosensor for fluorometric and colorimetric dual channel detection of Co2+ based on the photoinduced electron transfer effect.

Three types of carbon nanotubes coated on paper-like sintered stainless steel fibers (PSSF) were synthesized and applied for continuous catalytic wet hydrogen peroxide oxidation (CWPO) of phenol. The novel metal-free nitrogen-doped carbon nanotube-coated PSSF catalyst (N-CNTs/PSSF) was designed by direct chemical vapor deposition using melamine as solid precursor for the first time, and CNTs/PSSF and Fe2O3-deposited CNTs/PSSF (Fe-CNTs/PSSF) catalysts were synthesized for comparison. Characterization results showed that all the catalysts exhibited three-dimensional networks structure, with nanotubes wrapping on the stainless steel fibers successfully, and the N-CNTs showed distinct irregular corrugated morphology with nitrogen-doping level about 5.18 at.%. CWPO of phenol revealed that the N-CNTs/PSSF catalyst achieved favorable catalytic activity and highest stability during 100-h reaction (phenol and TOC conversions reached about 90% and 50%, respectively), while phenol conversions of CNTs/PSSF and Fe-CNTs/PSSF catalysts decreased over time to 72% and 58%, respectively. The N-CNTs/PSSF catalyst also showed the lowest Fe weight loss ratio (about 2.44 wt%) among the three catalysts. The favorable catalytic results of N-CNTs/PSSF can be ascribed to the synergistic effects of the strong affinity toward polar molecules of N-CNTs, as well as the enhancement in contact efficiency associated with three-dimensional networks structure of the PSSF.

Based on surface science, adsorption of mineral oil, water, gas products (typified by CO2 and CH4), and acids (typified by formic acid) on meta-aramid insulation paper has been investigated by molecular dynamics simulations. When the adsorption process finishes, the free volume fraction in the crystalline region is very small owing to the stable molecular arrangement of fiber. In addition, the number of pores on the surface of the meta-aramid fiber and the pore size are small, and the stable configuration of hydrogen bonds plays an important role, so it is difficult for the mineral oil and aging products to enter the meta-aramid crystalline region. The irregular arrangement of molecules in the amorphous region means that it is easier for the mineral oil and aging products to enter the amorphous region than the crystalline region, and the influence of these substances on the amorphous region is greater than that on the crystalline region. The order of the adsorption strengths of the four types of aging products on meta-aramid fiber is formic acid > water > CO2 > CH4. Therefore, it is necessary to monitor the acid and water contents in transformers with meta-aramid insulation paper as the solid insulation material.

As one of the most promising energy-storage devices, supercapacitors have drawn great research interests because of their outstanding electrochemical behavior. Carbon paper holds great prospect as an electrode material for supercapacitors since it is inexpensive and highly conductive. In this paper, the modified Hummer’s method is employed as an effective strategy to produce activated carbon paper with rougher surfaces and increased specific surface areas. It is further observed that hydrophilic groups such as hydroxyl (–OH), carbonyl (>C=O), and carboxyl (–COOH) have been introduced into the surface of carbon paper over treatment and they serve as strong polar sites to absorb water molecules, leading to improved hydrophilicity. Thus, the as-treated carbon papers with both increased specific surface areas and improved surface hydrophilicity exhibited excellent capacitive characteristics. Moreover, the charge/discharge test over 2000 cycles shows their excellent long-term capacitive retention.

This study clarifies the absorption behavior of micro-droplets of water on treated paper to support the design of functional microstructures, such as electronics and micro-fluid channels, on paper. The period of time between when a micro-droplet of water ejected from an ink-jet head lands on the paper’s surface and its complete disappearance by absorption was defined as the micro-sizing degree (MSD), and an MSD measurement method was established. The MSD was evaluated using microscopic high-speed video images of the side view recorded every millisecond. Several grades of commercially available ink-jet paper media and laboratory sheets having different levels of water repellency prepared from a pulp and a sizing agent were examined. The MSD of commercial ink-jet papers, which are known to absorb water very quickly, was 3–6 ms. Weakly sized laboratory sheets exhibited a lower MSD of 2–3 ms. The absorption behavior was analyzed in terms of the capillary pressure with and without the Laplace pressure; the theoretical and experimental results agreed moderately well. The results indicated that the Laplace pressure cannot be neglected in the analysis. The MSD of a wet surface where a preceding micro-droplet had already landed was higher than that on a dry or partially wet surface, presumably because water remains inside pores for an unexpectedly long time.

Flexible graphene-based paper is promising for wide applications due to its outstanding electrical and thermal conductivities. Graphene flakes with large size are usually known as the key factor for improved paper performance. However, we find that a combination of flakes with large and small sizes is more favorable for both electrical and thermal conductivities than pure large flakes. In this work, flexible paper with enhanced electrical and thermal properties was fabricated by mixing graphene flakes with various size distributions. Large-size graphene (LSG) flakes play the role of a backbone structure, whereas small-size graphene (SSG) flakes fill the voids in the paper without disturbing the high orientation. The physical properties of the as-prepared graphene papers with contents of SSG varying from 0 to 100% have been investigated. It is found that the electrical and thermal conductivities of the paper with 25 wt% SSG are both around 140% higher than that of pure LSG paper. Our results indicate that the lightweight and flexible graphene-based paper has great potential for lateral heat dissipation applications requiring heat movement in a particular direction.

The use of papers in packaging and development of novel technological applications for paper substrates largely depends on the control of the hydrophilic properties of the cellulose fibres and improvement of the water-repellent properties. This review provides an actual summary of available literature on theoretical concepts and practical methods to improve the hydrophobicity of cellulose fibres and paper webs. In the first part, the interaction of water with cellulose fibres and paper webs is described at different levels ranging from the molecular scale over the micro- to macroscale fibre properties towards the interactions with porous substrates. The concepts for hydrophobicity and superhydrophobicity applied to cellulose fibres are reviewed, considering the surface chemistry and topographical features. In the second part, current techniques for hydrophobization based on sizing or direct fibre surface functionalization are described. Besides traditional sizing procedures, novelties in nanoparticle applications as hydrophobic sizing agent are reviewed. Novel trends in physical, chemical and nanotechnological fibre surface modifications or surface coatings are reviewed to turn the wetting properties into the superhydrophobic regime. The main future concern in controlling cellulose wettability lies in the development of sustainable modification techniques based on renewable resources such as biopolymers and green chemistry.

In this study, nylon microcapsules were prepared on a paper surface using an interfacial polymerization technique for the preparation of smart paper. Filter paper impregnated with ethylenediamine solution and NaOH solution was left in a beaker containing cyclohexane or chloroform. Subsequently, the organic solvent terephthaloyl chloride was added to the beaker and interfacial polymerization occurred on the paper surface. When cyclohexane was used as the organic solvent, formation of nylon microcapsules on the paper surface was confirmed. Fixation of nylon microcapsules on the paper surface was successfully performed using interfacial polymerization. On the other hand, it was not possible to form nylon microcapsules on the paper surface when interfacial polymerization with chloroform was carried out. These results are due to differences in the spreading coefficient of the organic solvent on the ethylenediamine solution adsorbed on the paper surface.

Facile and robust immobilization of metal nanoparticles onto porous supporting matrix is an important issue in heterogeneous catalysis. This study reports a facile procedure for the synthesis and immobilization of small catalytic active silver nanoparticles (AgNPs) on cellulose paper (CP), which possesses interconnected fibrous structure and can be employed as cost-effective supports. Amino groups were first introduced to CP, through a silane coupling technique, to provide stable anchoring centers for silver ions. Small-sized AgNPs without aggregation were facilely synthesized and stably immobilized onto the fiber surface of CP followed by NaBH4 reduction. The as-prepared AgNPs incorporating composites exhibited excellent catalytic activity for the reduction of 4-nitrophenol. The rate constant of the catalytic reaction was calculated to be 1.46 × 10−2 s−1. More importantly, these amino-modified paper-based composite catalysts can be easily recovered and reused for at least six cycles due to their enhanced mechanical and catalytic stability.

Free-standing carbon nanotube film (bucky paper) is a very important material for various applications, but its commercial production is still limited due to size, cost and properties. In the present work, different methods are used to prepare five different types of bucky papers, namely normal, pure refluxed, oxidized, oxidized refluxed and functionalized by using as-produced multiwalled carbon nanotubes (MWCNTs), refluxed MWCNTs, air-oxidized MWCNTs, oxidized refluxed MWCNTs and HNO3 functionalized MWCNTs, respectively. Morphological, physical and structural changes appeared due to different methods are analysed by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectroscopy and Raman spectroscopy. Changes in the relative characteristic peak ratio (i.e. I G /I D, I G′ /I D and I G′ /I G) as a function of MWCNTs quality are determined. It is observed that oxidized refluxed MWCNTs have an average value of I G /I D, I G′ /I D and I G′ /I G ratio as 4.12, 7.15 and 1.71, respectively, which is higher as compared to other samples. The mechanical properties of different bucky papers are studied by performing tensile tests. The result showed that tensile strength, Young’s modulus and toughness of oxidized refluxed MWCNTs bucky paper are 3.9 MPa, 440 MPa and 780 Jm−3, respectively, which are higher as compared to as-produced MWCNTs bucky paper. The air oxidation and back-to-back refluxing generates nanoscale irregularities within the hexagonal C-structure of a nanotube wall. This helps in improving intermolecular bonding and packing which resulted into significant improvement in the mechanical properties. These bucky papers prepared by economical ways of air oxidation and refluxing in an alkali-soluble emulsifier assisted aqueous medium are potential candidates for field emission devices, energy storage devices and structural materials.

The ability of the bacteria Gluconacetobacter sucrofermentans to produce high-quality cellulose is well known. This bacterial cellulose has unique properties, as the result of an ultrathin crosslinked structure. It is almost chemically pure (until 98% cellulose), has a high crystallinity, mechanical strength, elasticity and durability. It is compatible with plant cellulose and could be grown on a vegetal fibrous network what makes bacterial cellulose an excellent candidate to reinforce damaged papers. The objective of this work is to promote the production of bacterial cellulose on the surface of a variety of papers by the direct application of a culture of G. sucrofermentans and to test if this procedure could be an economic and feasible possibility in reinforcing papers or cellulosic surfaces. After 7 days of cultivation, G. sucrofermentans deposits a thin layer (ca. 10 µm) of bacterial cellulose on the papers surfaces. Microscopic observations have shown a heterogeneous covering of the surfaces, while the modified papers maintain their thickness and their basic weight. The treatment has not increased the papers mechanical properties, but maintains them after artificial aging. The changes in optical properties of the reinforced papers, such as opacity and colorimetric coordinates, are minor even after further aging. Air permeance is the paper characteristic that experiences more variations because the layers of bacterial cellulose inhibit the airflow through the papers. The changes in the static and dynamic contact angles suggest that the bacterial cellulose structure is more compact and make the surface more hydrophobic than the original paper surface. © 2017, Springer Science+Business Media New York.

The effect of percentage solids content, coating film thickness and plastic pigment on mechanical properties of coated paper was studied. The results showed that the tensile strength, TEA, stretch and tensile stiffness were improved as the percentage solids content and the coating film thickness were increased. Bending stiffness slightly increased when solids content was increased and showed higher values on increasing the coating film thickness. The addition of plastic pigment to both clay based and GCC based coating mixtures improved the mechanical properties considered in this study. Although tensile strength and tensile stiffness increased with the addition of plastic pigment of smaller particle size, stretch and TEA showed a reverse trend.

Cellulose insulation paper as a part of oil–paper insulation systems plays an important role in the reliability of converter transformers. The reliability of converter transformers equipped with traditional cellulose paper is adversely affected by space charge under DC voltage. The addition of nanoparticles into other dielectrics has been demonstrated to improve electrical performance. However, studies on the space charge behavior of cellulose paper reinforced with nanoparticles are rarely reported. This paper presents the results of a study aimed at elucidating the effect of nano-aluminum nitride (AlN) concentration on the space charge behavior of cellulose paper. Samples with various nano-AlN concentrations were fabricated and pretreated first. The micro-morphologies of prepared cellulose papers were observed using a field-emission scanning electron microscope. The space charge distribution was measured using a pulsed electroacoustic instrument. The results show the dependence of the charge injection as well as charge dissipation on the concentration of nano-AlN. The isothermal decay current method is used to obtain trap information. Based on the density and distribution of traps, the underlying mechanism of the effect of various concentrations on the space charge behavior is theoretically explained.

Biogas-powered fuel cells that use low-quality biogas produced from organic waste hold a great promise for providing ultra-clean electric energy with on-site power generators. However, natural biogas contains a small amount of H2S, which causes a rapid deactivation of steam-reforming metal catalysts, such as Ni. In this work, we successfully prepared two types of paper-structured catalyst, separately containing manganese oxides (MnO x ) and nickel/magnesium oxides (Ni/MgO), for desulfurization and methane-steam reforming, respectively. In the sequential desulfurization and methane-steam reforming, paper catalyst assembly, designed by stacking MnO x papers upstream and Ni/MgO papers downstream in a dual-layered form, enabled continuous hydrogen production from simulated biogas containing ca. 2000 ppm H2S impurities, whereas single-layered Ni/MgO papers immediately lost their catalytic activity due to the H2S poisoning. This combination of flexible, stackable, and easy-to-handle paper-structured catalysts has the potential to improve the energy efficiency and to process economics of providing hydrogen to biogas-powered fuel-cell systems.

Papers coated with pigments bonded by polymer latexes have been tested by dynamic mechanical analysis. Measurements in tension and in three-point bending have been performed to determine the influence of the interaction zone between the coating and the paper on the properties of the coated paper. Comparisons have also been made with results from measurements in torsion. Experimental values of Young's modulus and the peak height of tan δ were higher than values theoretically calculated from data obtained on the separate layers, the paper and the coating. This deviation is interpreted as being due to the influence of an interaction zone between the coating and the base paper. If the thickness of the interaction zone is taken into account in the theoretical model, a better correlation with the experimental values is obtained for the peak height of tan δ. Higher values of the experimental data for the shear modulus of coated paper than from a weight-average calculation of the shear modulus of the pure components were obtained. This can be explained as being due to an increased stiffness of the coated paper as a result of the interaction zone, that was not adjusted for in the model. Further evidence for the existence of the interaction zone was provided by the pigment and latex distributions in the cross-section of coated papers determined in a scanning electron microscope using energy dispersive X-ray analysis.

Polyhydroxybutyrate (PHB) is a hydrophobic, biodegradable biopolymer, which can be a potential substitute for currently used synthesized polymers in the packaging in- dustry. However, its utility is often limited by its brittleness and poor mechanical properties, mainly because of its through- thickness fractures. In this study, we laminate and crystallize PHB on glassine paper by hot-pressing and tune the crystal- lization conditions to minimize cracking. Glassine paper is im- permeable to PHB granules and allows the formation of a distinguishable bilayer of PHB. It was found that glassine paper serves as a soft substrate, which increases the number of nu- cleation sites of the spherulites and prevents growth of the cracks in the neighboring PHB layer. Quenching the films to the crystallization temperature was found to minimize cracking enough to reduce the water vapor transmission rate to 15- 25 gm � 2 day � 1 , irrespective of the crystallization temperature; however, the mechanical properties improved only at the crys- tallization temperatures below 77 C, perhaps due to the local stress in the existing cracks at higher crystallization tem- peratures. The optimum crystallization conditions were found to be quenching the film in an ice bath and crystallization at room temperature, by which we obtained mechanical strength and Young's modulus of 80 MPa and 2:5 GPa, respectively, and a water vapor transmission rate of 20 g m � 2 day � 1 . Our results suggest a simple and cost-effective method to produce PHB films with enhanced mechanical and barrier properties.

Made available in DSpace on 2015-10-22T07:18:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-01. Added 1 bitstream(s) on 2015-10-22T09:46:00Z : No. of bitstreams: 1 WOS000347696500011.pdf: 661717 bytes, checksum: 8be94e4a0664ccdb5e47a823a7e099ca (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) INEO (Brazil) The effects of humidity on the electrical properties of thermal inkjet-printed copper tetrasulfonated phthalocyanine (CuTsPc) films onto paper substrates are reported. DC electrical measurements revealed that sample resistance decreases from 10(12) Omega in moderate vacuum to approximately 10(7) Omega at highly water-saturated atmosphere. This behavior is attributed to the creation of water pathways on the cellulose fibers that allow ionic species such as impurities, protons (H+), and dissociated Na+ ions from the CuTsPc molecules, to flow. The contribution of the CuTsPc molecules and their dissociated Na+ ions on the sample resistance was elucidated analyzing the electrical response of bare and printed paper substrates. An increase of relative humidity levels (RH) from 10 % to 40-45 % revealed an increase of current of four orders of magnitude for printed samples, whereas less than one order of magnitude was registered for bare paper substrates. Electrical measurements as a function of temperature have shown that moisture can inhibit the semiconducting properties of CuTsPc. Thermal gravimetric studies revealed that approximately 11 % of mass accounting to the presence of water is released above 70 A degrees C, the same temperature in which the sample recovers its dry-state semiconducting behavior. The semiconducting properties of CuTsPc can also be observed upon white light illumination, whereas the charge carrier extraction is governed by the RH level. These results point out the important role of humidity on the electrical properties of paper-based organic, electronic, and optoelectronic devices. Universidade Estadual Paulista (UNESP), Faculdade de Ciências e Tecnologia, BR-19060900 Presidente Prudente, SP, Brasil Instituto Federal de Educação, Ciência e Tecnologia de Santa Catarina (IFSC), BR-89245000 Araquari, SC, Brasil Universidade Estadual Paulista (UNESP), Faculdade de Ciências e Tecnologia, BR-19060900 Presidente Prudente, SP, Brasil

Mineral particles intended for the coating of paper and board were surface-treated with a copolymer based on styrene and acrylic acid. The mineral pigment used was ground CaCO3. The polymer was grafted to the mineral by first adsorbing the acrylic acid to the surface and then allowing this monomer to take part in the polymerization with the styrene. The grafting was performed in the aqueous phase, which was considered to be a prerequisite. The surface treatment of the mineral particles markedly improved the surface strength of papers coated with these pigments. This was interpreted as being a result of improved compatibility between the surface-treated pigment and the synthetic binder used in the coating layer. The surface treatment caused some decrease in the gloss of the coated papers but appeared otherwise not to impair important properties of the coated product. To some extent the surface treatment was also applied to kaolin particles. An improvement in the surface strength of papers coated with the modified particles was also observed with this pigment.