Zeitschriftenartikel zum Thema „PRISTINE LFP“

The LiFePO4 (LFP) cathode has a theoretical specific capacity of 170 mAh/g. This material is stable, safe, and environmentally benign. Li-ion batteries with LFP cathodes have a long cycle life with excellent charging/discharging performance. In our contribution, we show that the surface modification of the LFP cathode using ultrathin alumina films grown by atomic layer deposition (ALD) can improve Li-ions charge transfer and rate performance of the Li-ion in half-cell configuration with the LFP cathode. We used two types of LFP cathodes in our study with Li-metal as an anode in a half cell configuration. The first LFP electrode had a thickness of 25 μm and consisted of particles of 0.5 - 1 μm in size [1], while the second one (commercial NANOMYTE BE-60E (NEI Corp.)) had a thickness of 70 μm and the average LFP particle size was 2 μm. Ultrathin Al2O3 films were grown on LFP cathodes by ALD at 100 °C using trimethylaluminum (TMA) and water vapors. Due to the self-saturation surface-limited nature of the ALD reaction, even substrates of highly complex morphology can be uniformly coated, where the limitation is the reach of the precursor vapor molecules. The thickness of the ALD layers depends linearly on the number of ALD cycles and ranges from 0.5 to 2 nm for 5 to 20 cycles. Galvanostatic charging/discharging experiments were performed to evaluate the rate capability of the electrodes. Pristine and Al2O3 coated LFP electrodes were laser cut to 18 mm diameter circular electrodes, inserted in the electrochemical test cells PAT-Cell (EL-CELL), and tested using PAT-Tester-x-8 analyzer. LFP with Al2O3 protecting layers was compared to the pristine LFP electrode. For the LFP cathode with the thickness of 25 μm the pristine sample saturates at the specific capacity of 32 mAh/g at 1.8 c-rate, while for the electrode treated with 5 and 20 cycles of Al2O3 the specific capacity dropped to 80 and 60 mAh/g, respectively. The electrodes protected by Al2O3 film always exhibited better rate capability than the pristine sample. A more detailed analysis of the performance was accomplished for the NANOMYTE electrodes. A specific discharge capacity of 160 mAh/g at a c-rate of 0.2 was achieved for both pristine and Al2O3-protected electrodes. Two supercycles with the c-rate 0.2, 0.5, and 1 were applied to the samples. The specific capacity of the pristine LFP electrode dropped from 160 mAh/g for the c-rate 0.2 to about 90 mAh/g at the c-rate 1, while the electrode which was protected by 5 cycles of Al2O3 exhibited a capacity of 120 mAh/g. Investigation of the rate capability fading using electrochemical impedance spectroscopy revealed a gradual increase of the Nyquist plot semicircle diameter as a function of cycles. According to the equivalent circuit model, the semicircle diameter corresponds to the charge transfer at the solid/electrolyte interface. The charge transfer resistance at the solid/electrolyte interface increases with charge/discharge cycling. The charge transfer resistance of the pristine electrode increased more steeply than that of the electrode with 5 cycles of Al2O3. Improvement of the charge transfer resistance of the LFP electrode covered by thin Al2O3 film can be explained by the formation of the Li3.4Al2O3 phase upon lithiation. The diffusivity of the Li ions in the Li3.4Al2O3 phase is several orders of magnitude higher than that of in the Al2O3 film [2]. The results obtained by electrochemical characterization are compared to the X-ray photoelectron spectroscopy performed on samples before and after galvanostatic charging/discharging measurements. [1] A. Fedorkova et al., J. Power Sources 195 (2010) 3907. [2] S. C. Jung et al., J. Phys. Chem. Lett. 4 (2013) 2681.

In our recent papers, it was shown that the thermal nanocrystallization of glassy analogs of selected cathode materials led to a substantial increase in electrical conductivity. The advantage of this technique is the lack of carbon additive during synthesis. In this paper, the electrochemical performance of nanocrystalline LiFePO4 (LFP) and LiFe0.88V0.08PO4 (LFVP) cathode materials was studied and compared with commercially purchased high-performance LiFePO4 (C-LFP). The structure of the nanocrystalline materials was confirmed using X-ray diffractometry. The laboratory cells were tested at a wide variety of loads ranging from 0.1 to 3 C-rate. Their performance is discussed with reference to their microstructure and electrical conductivity. LFP exhibited a modest electrochemical performance, while the gravimetric capacity of LFVP reached ca. 100 mAh/g. This value is lower than the theoretical capacity, probably due to the residual glassy matrix in which the nanocrystallites are embedded, and thus does not play a significant role in the electrochemistry of the material. The relative capacity fade at high loads was, however, comparable to that of the commercially purchased high-performance LFP. Further optimization of the crystallites-to-matrix ratio could possibly result in further improvement of the electrochemical performance of nanocrystallized LFVP glasses.

In this work, we investigated three types of graphene (i.e., home-made G, G V4, and G V20) with different size and morphology, as additives to a lithium iron phosphate (LFP) cathode for the lithium-ion battery. Both the LFP and the two types of graphene (G V4 and G V20) were sourced from industrial, large-volume manufacturers, enabling cathode production at low cost. The use of wrinkled and/or large pieces of a graphene matrix shows promising electrochemical performance when used as an additive to the LFP, which indicates that the features of large and curved graphene pieces enable construction of a more effective conducting network to realize the full potential of the active materials. Specifically, compared to pristine LFP, the LFP/G, LFP/G V20, and LFP/G V4 show up to a 9.2%, 6.9%, and 4.6% increase, respectively, in a capacity at 1 C. Furthermore, the LFP combined with graphene exhibits a better rate performance than tested with two different charge/discharge modes. Moreover, from the economic and electrochemical performance view point, we also demonstrated that 1% of graphene content is optimized no matter the capacity calculated, based on the LFP/graphene composite or pure LFP.

Surface modification using thin layers grown by atomic layer deposition (ALD) is an effective strategy for performance improvement of Li-ion batteries. Ultrathin Al2O3 layers are the most studied coating material. In our contribution we compare properties of Al2O3 and ZnO ultrathin layers prepared by ALD on lithium-iron-phosphate (LFP) cathodes and Si-graphite anodes. Ultrathin Al2O3 and ZnO films were grown at 100 °C using trimethylaluminum (TMA) and diethylzinc (DEZ) precursors, respectively, with water vapors as reactant. The growth rates of the Al2O3 and ZnO films were about 0.1 nm/cycle on control flat Si substrates. ALD layers thickness in this study ranged from 5 to 20 cycles. A modified deposition recipe utilizing a prolonged precursor dwell time in the reactor chamber for coverage of the highly porous battery electrodes has been utilized. As TMA, DEZ and H2O all have rather high vapor pressures, we assume that significant part of the electrodes were coated. Porous LFP cathodes (NANOMYTE BE-60E, NEI Corp.) with the thickness of 70 μm were used as a substrate. The average particle size of the LFP substrate was ~ 2 μm with the specific surface area of 15 m2/g and active material loading of 7.3 mg/cm2. Experimental capacity C of the LFP electrode is 170 mAh/g in the voltage range 2.5 - 4.1 V using 0.1 charging/discharging c-rate. As an anode material porous silicon-graphite composite electrode sheets NANOMYTE BE-150E (NEI Corp) with the thickness of 65 μm and composition of active material 20% Si and 65 % graphite were used. The nominal capacity C of the silicon-graphite anode is 750mAh/g in the voltage range 0.05 - 1V using 0.05 charging/discharging c-rate. In our contribution we present specific discharge capacity of the electrodes as a function of charging/discharging cycles. For both pristine and Al2O3 protected LFP cathode sheets specific discharge capacity of 160 mAh/g was achieved at the c-rate of 0.2. The specific capacity of the pristine LFP electrode dropped from 160 mAh/g at the c-rate 0.2 to about 90 mAh/g for the c-rate 1, while the electrode protected by 0.5 nm of Al2O3 saturated at 120 mAh/g. Properties of ZnO- protected LFP cathodes are compared to that covered by Al2O3. Electrochemical properties of the silicon-graphite anode were studied using low c-rate of 0.05. During the first cycles the specific capacity is relatively low due to the formation of the solid-electrolyte interface layer at the surface. After several cycles the capacity increased to the nominal value of 750 mAh/g. In our study we compare the charging/discharging capability of the pristine silicon-graphite anode and that of the electrodes covered by 5 -20 ALD cycles of Al2O3 and ZnO films during the first charging/discharging cycles. We discuss the effect of ALD protecting layers on the rate capability of the silicon-graphite anode. Finally, the results of the electrochemical measurements are compared to those obtained by X-ray photoelectron spectroscopy.

Resolving chemical species at the nanoscale is of paramount importance to many scientific and technological developments across a broad spectrum of disciplines. Hard x-rays with excellent penetration power and high chemical sensitivity are suitable for speciation of heterogeneous (thick) materials. Here, we report nanoscale chemical speciation by combining scanning nanoprobe and fluorescence-yield x-ray absorption near-edge structure (nano-XANES). First, the resolving power of nano-XANES was demonstrated by mapping Fe(0) and Fe(III) states of a reference sample composed of stainless steel and hematite nanoparticles with 50-nm scanning steps. Nano-XANES was then used to study the trace secondary phases in lithium iron phosphate (LFP) particles. We observed individual Fe-phosphide nanoparticles in pristine LFP, whereas partially (de)lithiated particles showed Fe-phosphide nanonetworks. These findings shed light on the contradictory reports on Fe-phosphide morphology in the literature. Nano-XANES bridges the capability gap of spectromicroscopy methods and provides exciting research opportunities across multiple disciplines.

Lithium metal is one of the most attractive anode materials for rechargeable batteries. However, its high reactivity with electrolytes, huge volume change, and dendrite growth upon charge or discharge lead to a low CE and the cycle instability of batteries. Due to the low surface diffusion resistance, LiF is conducive to guiding Li+ deposition rapidly and is an ideal component for the surface coating of lithium metal. In the current study, a fluorinated layer was prepared on a lithium metal anode surface by means of chemical vapor deposition (CVD). In the carbonate-based electrolyte, smooth Li deposits were observed for these LiF-coated lithium anodes after cycling, providing excellent electrochemical stability for the lithium metal anode in the liquid organic electrolyte. The CE of Li|Cu batteries increases from 83% for pristine Li to 92% for LiF-coated ones. Moreover, LiF-Li|LFP exhibits a decent rate and cycling performance. After 120 cycles, the capacity retention of 99% at 1C is obtained, and the specific capacity is maintained above 149 mAh/g. Our investigation provides a simple and low-cost method to improve the performance of rechargeable Li-metal batteries.

As the battery market grows, developing a battery waste management economy becomes imperative. After primary use, the main options for discarded batteries are recycling, refurbishment, reuse, or disposal. Recycling involves extracting valuables materials from ground-up battery cells, while reuse and refurbishment involve direct use of packs or their components, with or without maintenance adjustments. Recycling and disposal are the most common battery waste pathways, while reuse and refurbishment practices require further understanding of battery degradation before being implemented on a large scale. Furthermore, relatively high recycling costs are motivation to pursue more cost-efficient recycling methods like direct recycling. This work expands on previous studies on the statistical distribution of the state-of-health (SOH) of used LiFePO4 (LFP) cells extracted from a hybrid-bus battery pack.1 We characterize samples from used and pristine A123 M1-A and M1-B 26650 cells using XRD and SEM. We will compare the cell materials’ morphologies and structure to their electrochemical performance in two diagnostic tests: a constant-current cycling test and an electrochemical impedance spectroscopy test. Preliminary data have been collected from used M1-A cells that demonstrated starkly different states-of-health during electrochemical testing—ranging in residual capacities from 2.2 Ah to 0.30 Ah. The low-SOH M1-A cell had severe anode delamination and morphological cracks in the center of the cylinder cross-section. Cathode delamination in the cell also increased towards the center of the cylinder. The high-SOH M1-A cell’s electrodes had a consistent morphology throughout the cell, but delamination was worst at the center of the cylinder’s cross-section. In this presentation, we will summarize our x-ray diffraction and scanning electron microscopy data for the cells described in Table 1. We will also discuss technical pathways for direct recycling of active materials from LFP battery waste. Ramirez-Meyers and J. Whitacre. “(Invited) Statistical Distribution and Feasibility for Re-Use of A123 LiFePO4 Cells from a Hybrid-Bus Battery Pack.” ECS Meeting Abstracts, no. 6, p. 1052. IOP Publishing, 2020. Figure 1

A new hydrocarbon-based (HC) composite membrane was developed using liquid crystal polymer (LCP)-nonwoven fabrics for application in proton exchange membrane water electrolysis (PEMWE). A copolymer of sulfonated poly(arylene ether sulfone) with a sulfonation degree of 50 mol% (SPAES50) was utilized as an ionomer for the HC membranes and impregnated into the LCP-nonwoven fabrics without any surface treatment of the LCP. The physical interlocking structure between the SPAES50 and LCP-nonwoven fabrics was investigated, validating the outstanding mechanical properties and dimensional stability of the composite membrane in comparison to the pristine membrane. In addition, the through-plane proton conductivity of the composite membrane at 80 °C was only 15% lower than that of the pristine membrane because of the defect-free impregnation state, minimizing the decrease in the proton conductivity caused by the non-proton conductive LCP. During the electrochemical evaluation, the superior cell performance of the composite membrane was evident, with a current density of 5.41 A/cm2 at 1.9 V, compared to 4.65 A/cm2 for the pristine membrane, which can be attributed to the smaller membrane resistance of the composite membrane. From the results of the degradation rates, the prepared composite membrane also showed enhanced cell efficiency and durability during the PEMWE operations.

LAPONITE® (LAP) nanoplatelets were incorporated within a regenerated silk fibroin (RSF) microfibrous mat via electrospinning, which exhibited better cell adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) than the pristine RSF ones.

Abstract The combination of cellulosic materials and clays, such as Laponite, can provide composites with superior optical and mechanical properties compared to pristine cellulose. Synthetic clays can also be used as a host matrix for the immobilization of luminescent complexes, as the incorporated complexes may present enhanced emission quantum efficiency, photo and thermostability compared to the non-immobilized ones. In this way, we, herein, report the preparation of luminescent composites through the incorporation of a Eu(III) complex [Eu3+(tta)n] containing Laponite (Lap) into cellulose nanofibers (CNF). The thermogravimetry results show that the obtained CNF/Lap@[Eu3+(tta)n] films present higher thermal resistance than the CNF film. The Eu3+(tta)n species were found in the composite structure with preserved luminescence characteristics, and no leaching or degradation of the organic ligand was observed with the preparation of the composites.

The impulse heat-sealing properties of wheat gluten films were investigated. Films containing 30 wt% glycerol were compression molded at 100–130 °C and then sealed in a lap-shear or peel-test geometry at 120–175 °C. The tensile properties of the pristine films and the lap-shear and peel strength of the sealed films were evaluated and the seals were examined by scanning electron microscopy. Glycerol was added to the film surfaces prior to sealing in an attempt to enhance the seal strength. It was observed that the wheat gluten films were readily sealable. At a 120 °C sealing temperature and without glycerol as adhesive, the lap-shear strength was greater than or similar to that of polyethylene film, although the peel strength was poorer. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed, especially in the absence of glycerol adhesive, from a cohesive (material failure) to an adhesive type. From previous results, it is known that the high-temperature (130 °C) compression-molded film was highly cross-linked and aggregated, and this prevents molecular interdiffusion and entanglement and thus leads to incomplete seal fusion and, in general, adhesive failure. The presence of glycerol adhesive had a beneficial affect on the peel strength but no, or only a minor, effect on the lap-shear strength.

AbstractWeight reduction and improved strength are two common engineering goals in the joining sector to benefit transport, aerospace, and nuclear industries amongst others. Here, in this paper, we show that the suitable addition of carbon nanomaterials to a tin-based solder material matrix (C-Solder® supplied by Cametics Ltd.) results in two-fold strength of soldered composite joints. Single-lap shear joint experiments were conducted on soldered aluminium alloy (6082 T6) substrates. The soldering material was reinforced in different mix ratios by carbon black, graphene, and single-walled carbon nanotubes (SWCNT) and benchmarked against the pristine C-solder®. The material characterisation was performed using Vickers micro-indentation, differential scanning calorimetry and nano-indentation, whereas functional testing involved mechanical shear tests using single-lap aluminium soldered joints and creep tests. The hardness was observed to improve in all cases except for the 0.01 wt.% graphene reinforced solders, with 5% and 4% improvements in 0.05 carbon black and SWCNT reinforced solders, respectively. The maximum creep indentation was noted to improve for all solder categories with maximum 11% and 8% improvements in 0.05 wt.% carbon black and SWCNT reinforced ones. In general, the 0.05 wt.% nanomaterial reinforced solders promoted progressive cohesion failure in the joints as opposed to instantaneous fully de-bonded failure observed in pristine soldered joints, which suggests potential application in high-performance structures where no service load induced adhesion failure is permissible (e.g. aerospace assemblies). The novel innovation developed here will pave the way to achieving high-performance solder joining without carrying out extensive surface preparations.

Abstract We previously showed that all-trans-retinoic acid (tRA) exacerbated pre-existing autoimmunity in lupus; however, its effects before disease onset are unknown. Here, using a pristane-induced model, we show that tRA exerts tissue-specific effects when given at the initiation vs. continuation phase of lupus. Pre-pristane treatment with tRA aggravated glomerulonephritis through increasing renal expression of pro-fibrotic protein laminin β1, activating bone marrow CD11b- conventional dendritic cells, increasing the splenic CD4:CD8 ratio, and upregulating the interaction of ICAM-1 and LFA-1 that led to the infiltration of inflammatory cells to the spleen. Transcriptomic analysis revealed that prior to lupus induction, tRA significantly upregulated genes associated with cell differentiation, activation, and migration. Moreover, compared to pristane alone, tRA pre-treatment potentiated, whereas tRA post-treatment significantly suppressed, the renal expression of proinflammatory TNF-α, IL-1β, CCL2, and CCL3. While it may benefit the kidney, post-pristane treatment with tRA worsened the onset and severity of pristane-induced arthritis through promoting neutrophil and mononuclear cell infiltration into the joints. Together, these findings suggest that tRA supplementation regardless of the time of administration promotes chemokine-driven migration and tissue-specific infiltration of inflammatory cells, thereby exacerbating lupus-associated kidney or joint inflammation. Interestingly, both pre- and post-treatments with tRA modulated the gut microbiota in a similar fashion, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus.

In this investigation, the electrospraying of CNTs on an electrospun PVDF-Co-HFP membrane was carried out to fabricate robust membranes for the membrane distillation (MD) process. A CNT-modified PVDF-Co-HFP membrane was heat pressed and characterized for water contact angle, liquid entry pressure (LEP), pore size distribution, tensile strength, and surface morphology. A higher water contact angle, higher liquid entry pressure (LEP), and higher tensile strength were observed in the electrosprayed CNT-coated PVDF-Co-HFP membrane than in the pristine membrane. The MD process test was conducted at varying feed temperatures using a 3.5 wt. % simulated seawater feed solution. The CNT-modified membrane showed an enhancement in the temperature polarization coefficient (TPC) and water permeation flux up to 16% and 24.6%, respectively. Field-effect scanning electron microscopy (FESEM) images of the PVDF-Co-HFP and CNT-modified membranes were observed before and after the MD process. Energy dispersive spectroscopy (EDS) confirmed the presence of inorganic salt ions deposited on the membrane surface after the DCMD process. Permeate water quality and rejection of inorganic salt ions were quantitatively analyzed using ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS). The water permeation flux during the 24-h continuous DCMD operation remained constant with a >99.8% inorganic salt rejection.

A hot melt adhesive – mainly used for bonding plastic component in automotive field – was modified with different iron-based particles to give it a reversible behaviour. Mechanical and physical properties of these reversible adhesives were experimentally assessed in the work. The modified adhesives, coupled with electromagnetic induction, are able to guarantee separation of the joints without any damage to the substrates for recycling, reuse or repairing of components. Single lap joint specimens were prepared using epoxy/glass fibres substrates and tests were carried out on neat and modified adhesive with 5% weight of iron and iron oxide. Three different Fe particles size were tested: 450 µm, 60 µm and 1–6 µm. The particles size of iron oxide was 50 nm. Separation was studied using single lap joint specimens under electro-magnetic induction. Experimental results showed that the maximum peak load decreases when the average particles sizes increase. The peak loads of the smallest particles were equal to the ones of the pristine adhesive. The elongation of the adhesives increases when the adhesive is modified with both iron and iron oxide particles. Finally, experimental tests on single lap joints coupled with electro-magnetic induction showed that separation of the substrates is possible using iron oxide particles. Electro-magnetic tests conducted on particles alone, helped to understand that bigger particles are able to overcome the melting temperature of the adhesive but hot-melt adhesives modified with these particles are not able to reach the melting. These tests showed that the number of particles into the adhesive matrix is very important for this kind of tests.

This paper presents a numerical investigation into the effects of missing fasteners on the mechanical characteristics of double-lap, multi-row composite bolted joints. A highly efficient explicit finite element model, which was validated effective and accurate by experiments, was developed and employed to conduct the virtual tests. Single-column and multi-column joints with various positions of missing fastener were considered. It is shown that the removal of fasteners can reduce the joint stiffness significantly, especially in joints with fewer columns or missing fasteners in the outside rows. The removal of fasteners can also cause considerable reductions in both the initial significant failure loads and ultimate loads of multi-column joints, while in single-column joints only the initial significant failure loads are influenced. Considering the load distribution, it is suggested that bolts in the same column as or in the adjacent column to the missing fastener experience a notable growth in load. Meanwhile, if a bolt bears more loads in the pristine joint, the larger changes in stiffness, ultimate strength, and load distribution may be obtained when it is lost.

Poly(hexamethylene adipamide), nylon 66, is a popular plastic that requires high surface wettability and strong adhesive bonds for many applications. However, pristine nylon is difficult to bond due to its hydrophobic nature and poor surface wettability. The objective of this work was to modify the physio-chemical surface properties of nylon 66 via a novel atmospheric plasma surface treatment approach using oxygen (O2) or water vapor (H2O) plasma glow. The surface hydrophilicity of the plasma-treated nylon surface was substantially enhanced immediately after either helium (He)/H2O or He/O2 plasma surface treatment. The average water contact angle was reduced from 65 degrees to ~30 degrees after He/H2O plasma and ~40 degrees after He/O2 plasma treatments. The improved hydrophilicity was also evidenced by the increased intensities of the surface oxygen and hydroxyl bonds in the X-ray photoelectron spectra. The interfacial adhesion strength of nylon surfaces before and after plasma treatment was further evaluated by uniaxial tensile tests of nylon single-joint lap shears bonded with three adhesives, i.e., thermoset epoxy resins EPON 825/ JEFFAMINE D-230 and EPON825/JEFFAMINE D-2000, and the thermoelastic polyurethane adhesive Sikaflex 252. The most significant improvements in bond strengths due to plasma treatment were found for lap shears bonded with the EPON 825/JEFFAMINE D-230 epoxy resin; their shear strengths with maximum loads were more than doubled—from 299–451 to 693–1594 N—after plasma treatment and were further enhanced by a factor of four to 895–1857 N after a subsequent silane treatment. In contrast, the bond strength of lap shears bonded with EPON 825/JEFFAMINE D-2000 and Sikaflex was not significantly improved because of the different a, re-affirming the importance of adhesive bulk properties This work presents the preliminary success of effective surface functionalization leading to enhanced interfacial adhesive bonds for nylon 66 via the development of scalable atmospheric plasma surface treatments.

Automatic assessing the quality of an image is a critical problem for a wide range of applications in the fields of computer vision and image processing. For example, many computer vision applications, such as biometric identification, content retrieval, and object recognition, rely on input images with a specific range of quality. Therefore, an effort has been made to develop image quality assessment (IQA) methods that are able to automatically estimate quality. Among the possible IQA approaches, No-Reference IQA (NR-IQA) methods are of fundamental interest, since they can be used in most real-time multimedia applications. NR-IQA are capable of assessing the quality of an image without using the reference (or pristine) image. In this paper, we investigate the use of texture descriptors in the design of NR-IQA methods. The premise is that visible impairments alter the statistics of texture descriptors, making it possible to estimate quality. To investigate if this premise is valid, we analyze the use of a set of state-of-the-art Local Binary Patterns (LBP) texture descriptors in IQA methods. Particularly, we present a comprehensive review with a detailed description of the considered methods. Additionally, we propose a framework for using texture descriptors in NR-IQA methods. Our experimental results indicate that, although not all texture descriptors are suitable for NR-IQA, many can be used with this purpose achieving a good accuracy performance with the advantage of a low computational complexity.

Poly(lactide) (PLA) films obtained by thermoforming or solution-casting were modified by diffuse coplanar surface barrier discharge plasma (300 W and 60 s). PLA films were used as hot-melt adhesive in joints in oak wood. It was demonstrated that lap shear strength increased from 3.4 to 8.2 MPa, respectively, for the untreated and plasma-treated series. Pull-off tests performed on particleboard for the untreated and treated PLA films showed 100% cohesive failure. Pull-off strength tests on solid oak demonstrated adhesion enhancement from 3.3 MPa with the adhesion failure mode to 6.6 MPa with the cohesion failure mode for untreated and treated PLA. XPS revealed that carbonyl oxygen content increased by two-to-three-fold, which was confirmed in the Fourier-transform infrared spectroscopy experiments of the treated PLA. The water contact angle decreased from 66.4° for the pristine PLA to 49.8° after treatment. Subsequently, the surface free energy increased from 47.9 to 61.05 mJ/m2. Thus, it was clearly proven that discharge air plasma can be an efficient tool to change surface properties and to strengthen adhesive interactions between PLA and woody substrates.

The need to recycle carbon-fibre-reinforced composite polymers (CFRP) has grown significantly to reduce the environmental impact generated by their production. To meet this need, thermoreversible epoxy matrices have been developed in recent years. This study investigates the performance of an epoxy vitrimer made by introducing a metal catalyst (Zn2+) and its carbon fibre composites, focusing on the healing capability of the system. The dynamic crosslinking networks endow vitrimers with interesting rheological behaviour; the capability of the formulated resin (AV-5) has been assessed by creep tests. The analysis showed increased molecular mobility above a topology freezing temperature (Tv). However, the reinforcement phase inhibits the flow capability, reducing the flow. The fracture behaviour of CFRP made with the vitrimeric resin has been investigated by Mode I and Mode II tests and compared with the conventional system. The repairability of the vitrimeric CFRP has been investigated by attempting to recover the delaminated samples, which yielded unsatisfactory results. Moreover, the healing efficiency of the modified epoxy composites has been assessed using the vitrimer as an adhesive layer. The joints were able to recover about 84% of the lap shear strength of the pristine system.

Epoxy structural adhesives have strong adhesion, minimal shrinkage and high thermal and chemical resistance. However, despite these excellent properties, their high-energy impact resistance should be improved to satisfy the increasing demands of the automotive industry. For this reason, we used four types of silica nanoparticles with different surface groups, such as polydimethylsiloxane (PDMS), hydroxyl, epoxy and amine groups, as toughening agents and examined their effect on the glass transition temperature (Tg), crosslinking density and phase separation of epoxy structural adhesives. High-energy impact resistance, mode I fracture toughness and lap shear strength were also measured to explain the effect of surface functional groups. Silica nanoparticles with reactive functional groups increased the mode I fracture toughness of epoxy structural adhesives without sacrificing the crosslinking density. Although the mode I fracture toughness of epoxy structural adhesives could not clearly show the effect of surface functional groups, the dynamic resistance to cleavage obtained by impact wedge-peel tests showed quite different values. At a 0.3 vol% content, epoxy-functionalized silica nanoparticles induced the highest value (40.2 N/mm) compared to PDMS (34.1 N/m), hydroxyl (34.9 N/mm), and amine (36.1 N/m). All of these values were significantly higher than those of pristine epoxy structural adhesive (27.7 N/mm).

Smooth (< 0.5 nm rms) and subsurface damage-free (010) β-Ga2O3 was achieved with low-pressure chemical mechanical polishing. An applied pressure of 1 kPa along with colloidal silica and poromeric polyurethane polishing pads rotating at 30 rpm was found to be the optimal polishing parameters for (010) β-Ga2O3. Using higher pressures typically employed in the current literature induced subsurface damage in the substrates. Diffuse scatter intensity of triple-axis x-ray rocking curves was used to determine the presence of subsurface lattice damage, which was quantified by measuring peak widths below the half maximum (i.e., FWXM where X < 0.5). The initially rough surfaces of (010) β-Ga2O3 substrates due to wafer slicing and grinding were lapped and polished. A 5 μm Al2O3 slurry followed by a 0.3 μm Al2O3 slurry was used as the primary lap material removal step. The material removal rates were ∼20 and ∼9 μm/h, respectively. Then, chemical mechanical polishing was performed using colloidal alumina followed by colloidal silica. The removal rates were ∼1.3 and ∼0.4 μm/h, respectively. Only colloidal silica showed the complete removal of subsurface damage. The final (020) β-Ga2O3 rocking curve FWHM was ∼13″ and FW(0.001)M was ∼120″, which matches the widths of commercially available pristine (010) β-Ga2O3. A final cleaning step using dilute bleach and dilute citric acid to remove residual silica slurry particles from the surface was demonstrated.

My title comes from anthropologist Mary Douglas’ assertion that dirt, when understood as “matter out of place” simultaneously implies both the existence and the contravention of an established order or system and that this in turn establishes dirt as symbolic (35). Further, Phyllis Palmer has written that dirt is “a principal means to arrange culture” (139). This paper suggests both that dirt has a function in cultural constructions of gender and that action films featuring a female protagonist provide a fertile site for investigation. Normative white femininity traditionally eschews direct contact with dirt thus bringing into play interactions between work and gender. This article begins to question what it is that the appearance and disappearance of dirt signifies for the understanding of femininities in the particular cultural practice commonly recognised as action films. One need only observe advertisements for cleaning products or compare shelf space taken up by personal hygiene items for men to that taken by similar items for women to understand the continuation of the gendered nature of cleanliness. Women are expected to keep not only the environment but themselves clean as a measure of their femininity. Indeed, obsessive cleanliness formed a part of Friedan’s feminine mystique. Not only must transgressive women such as the eponymous protagonists of Thelma and Louise die, but also they must die unwashed, driving a dirty car into a hole in the ground, being pursued by a dust cloud. Having trespassed on the masculine territory of self-defence and free movement this can be their only end. Linda Williams points out that all they are guilty of is of behaving “in the time-honoured tradition of most American heroes, violently and without reflection” (27). Further, the women who suicide into the Grand Canyon at the end of the film are distanced from the two in the bright, iconic, self portrait from the beginning and it is this shiny vision of femininity that was central to the film’s promotion. They have driven west, away from civilised society, ultimately facing e what “the western still tells us and what we still continue to buy…that reality is blood and dust and death and a cold wind blowing” (Tompkins 99). The signs of the exhausting exertion of sustained non-capitulation and the adherent grime of the road they have travelled are plain on their faces. Like Ripley, once they are truly fighting alone they begin to accumulate layers of dirt on their skin. Unlike Ripley they can neither return from their nightmare nor separate themselves from their actions. Relentlessly pursued, they cannot stop to wash off the dirt just as they cannot eschew responsibility for what they have done. They have become dressed in the dust of road, no longer on it but of it. Another discourse is in operation in conjunction with the gender skewing discourse of dirt. Whenever one addresses a change in the colour of skin one engages with the discourse of race. Audiences are conditioned by Hollywood cinema to view non-Anglos in film as a potential threat. The darkening of the hero’s skin by dirt renders him or her as a perpetrator of violent acts. When the necessity for violence is over the hero cleans up (whitens up) to return to society. I am thinking here of the heroes of Stallone’s Rambo and Willis’s Die Hard series who followed Ripley. As their actions became increasingly violent they become progressively filthier. Rambo in particular, it is suggested, becomes more ‘primal’. I am not suggesting that filth is an issue involving gender, race or class in a simple way. Rather, these three issues are, as in most cases, intricately intertwined here too. By the time Sigourney Weaver’s Ripley traversed her first revenge narrative, Alien (1979) through the frontier of space, I would suggest that dirt had become a marker of the gendered action hero. The character of Ellen Ripley was originally written as a man, writer and director Ridley Scott asserting in the DVD commentary that the script was left unchanged when Weaver was cast. In Alien, Ripley plays the part of film theorist Carol Clover’s Final Girl. Clover writes that in slasher/horror films the survivor begins as the pursued, feminised victim of a male oppressor but in her ultimate triumph occupies the position of the traditional masculine avenger (35-37, 158-59). That is, she saves herself. It was new, too, that this ground breaking female hero battled against the monstrous femininities of the alien and ‘Mother’, the ship’s computer, to survive. Marking Ripley’s transgression into the strictly gendered territory of the solitarily courageous, increasingly frequent close-ups of her grimy hands and sweat-drenched face fill the screen. Alien begins in the pristine white of the sleep chamber reflecting the mainstream science fiction convention that contrasts the absence of dirt in the artificial space environment of the space ship with planet-based presence of dirt. It is Ripley who refuses to let the scouting party back onto the ship citing contamination procedure, underlining cleanliness and purity as a cultural ideal with women as its gatekeepers. The film ends in the white escape pod where Ripley immediately strips to her underwear, discarding the soiled outer layer of clothing. After one last ‘unexpected’ confrontation Ripley is shown clean and further feminised by the silk robe she is wearing and the soothing motion of stroking the cat (the only other survivor) on her lap. As she records her report she reverts to the role of Chorus, setting her apart from the action. Finally she is seen once more inside a sleep chamber as she was in the beginning. Returning to the gendered confines of ‘civilisation’ she must wash off the (masculine) signs of her struggle and return to sleep as if it were all a nightmare. Through Rambo, Die Hard’s McClane and other male action heroes the begrimed body has arguably become a signifier not only of survival but also of persistence and courage in the face of tremendous odds. Persistence and courage are gendered values. Thus, I would argue, its signifier, the dirty body, is similarly gendered. In Alien, Ellen Ripley, having triumphed through survival, reinstates her femininity (signified by cleanliness) and returns home. Ripley’s actions have been unobserved, her battlefield contained and her enemy (she thinks) proven tangible and finite. Isolated in space and relieved of being the object of the male gaze within her narrative by the deaths of her colleagues Ripley is free to begin a new discourse (and to found a new, female action tradition). Instead she takes a shower. References Alien. Dir. Ridley Scott. Perf. Sigourney Weaver. 20th Century Fox, 1979. DVD. 20th Century Fox Home Video, 1999. Clover, Carol J. Men, Women, and Chain Saws: Gender in the Modern Horror Film. Princeton, N.J.: Princeton UP, 1992. Douglas, Mary. Purity and Danger: An Analysis of the Concepts of Pollution and Taboo. London: Ark Paperbacks, 1966. Palmer, Phyllis. Domesticity and Dirt: Housewives and Domestic Servants in the United States, 1920-1945. Philadelphia: Temple UP, 1989. Tompkins, Jane. “Language and Landscape: An Ontology for the Western.” Artforum 28.6 (1990): 94-9. Williams, Linda. “What Makes a Woman Wander.” Film Quarterly 45.2 (1991-2): 27-28. Citation reference for this article MLA Style Wical, Carol. "Matter Out of Place: Reading Dirty Women." M/C Journal 9.5 (2006). echo date('d M. Y'); ?> <http://journal.media-culture.org.au/0610/10-wical.php>. APA Style Wical, C. (Nov. 2006) "Matter Out of Place: Reading Dirty Women," M/C Journal, 9(5). Retrieved echo date('d M. Y'); ?> from <http://journal.media-culture.org.au/0610/10-wical.php>.