Influence of Plasma Treatment on Carbon Fabric for Enhancing Abrasive Wear Properties of Polyetherimide Composites

Interfacial adhesion between matrix and fiber plays a crucial role in controlling performance properties of composites. Carbon fibers have major constraint of chemical inertness and hence limited adhesion with the matrix. Surface treatment of fibers is the best solution of the problem. In this work, cold remote nitrogen oxygen plasma (CRNOP) was used for surface treatment. Twill weave carbon fabric (CF) (55–58 vol%) was used with and without plasma treatment with varying content of oxygen (0–1%) in nitrogen plasma to develop composites with Polyetherimide (PEI) matrix. The composites were developed by compression molding and assessed for mechanical and tribological (abrasive wear mode) properties. Improvement in tensile strength, flexural strength, and interlaminar shear strength (ILSS) was observed in composites due to treatment. Similarly, improvement in wear resistance (W _R) and reduction in friction coefficient (μ) were observed in treated fabric composites when slid against silicon carbide (SiC) abrasive paper under varying loads. A correlation between wear resistance and tensile strength was slightly better than that in Lancaster–Ratner plot indicating that ultimate tensile strength (S) and elongation to break (e) were contributing to control the W _R of the composites. It was concluded that enhanced adhesion of fibers with matrix was responsible for improvement in performance properties of composites, as evident from SEM, Fourier Transform Infrared spectroscopy-Attenuated Total Reflectance (FTIR-ATR) technique.     

Self-financed efficiency incentives: case study of Mexico

Numerous countries use public funds to subsidize residential electricity for a variety of socioeconomic objectives. These subsidies lower the value of energy efficiency to the consumer while raising it for the government. Further, while it would be especially helpful to have stringent Minimum Energy Performance Standards (MEPS) for end uses in this environment, they are hard to strengthen without imposing a cost on ratepayers. In this second-best world, where the presence of subsidies limits the government’s ability to strengthen standards, we find that efficiency-induced savings in subsidy payments can be a significant source of financing for energy efficiency incentive programs. Here, we introduce the Lawrence Berkeley National Laboratory (LBNL) Energy Efficiency Revenue Analysis (LEERA) model to estimate the greatest appliance efficiency improvements that can be achieved in Mexico by the revenue neutral financing of incentive programs from savings in subsidy payments yielded by the same efficiency improvements. We analyze Mexico’s tariff structures and the long-run marginal cost of supply to calculate the marginal savings for the government from appliance efficiency. We find that these avoided subsidy payments alone can provide enough revenue to cover the full incremental manufacturing cost of refrigerators that are 29 % more efficient and televisions that are 36 % more efficient than baseline models. For room air conditioners (ACs), the same source of financing can contribute up to one third of the incremental manufacturing cost of a model that is 10 % more efficient than baseline. We analyze the sensitivity of our results to the most important parameters and find our main conclusion that efficiency-induced avoided subsidy payments will contribute significantly to financing efficiency incentive programs in Mexico to be significant and robust.     

Mechanical and barrier properties of nanocrystalline cellulose reinforced poly(caprolactone) composites: Effect of gamma radiation

Nanocrystalline cellulose (NCC) reinforced poly(caprolactone) (PCL) composites were prepared by compression molding. The NCC content varied from 2 to 10% by weight. NCC played a significant role in improving the mechanical properties of PCL. The addition of 5 wt % NCC caused a 62% improvement of the tensile strength (TS) value of PCL films. Similarly, tensile modulus (TM) values were also improved by NCC reinforcement but elongation at break (Eb) values decreased montonically with NCC content. The water vapor permeability (WVP) of PCL was 1.51 g·mm/m²·day·kPa, whereas PCL films containing 5 wt % NCC showed a WVP of 1.22 g·mm/m²·day·kPa. The oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO₂TR) of PCL decreased by 19 and 17%, respectively, with 5 wt % NCC incorporation. It was found that the mechanical and barrier properties of both PCL and PCL‐NCC composites further improved with 10 kGy gamma irradiation treatment. The combination of NCC and radiation significantly increased the TS, TM, and Eb (by 156, 123, and 80%, respectively, compared to untreated PCL). The WVP, OTR, and CO₂TR decreased by 25–35% with respect to untreated PCL. The surface and interface morphologies of the PCL‐NCC composites were studied by scanning electron microscopy and suggested homogeneous distribution of NCC within the PCL matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Origin of voltage offset and built-in polarization in in-situ sputter deposited pzt thin films

Abstract

Voltage offset and built-in polarization were investigated in in-situ reactively sputter deposited PZT thin films on Pt, as a function of composition, doping and cooling conditions. The voltage offset increases with increasing Ti content. Hot-poling treatments show that the voltage offset originates from non-mobile defects. Cooling the samples at various O₂ partial pressures leads to a change in lattice parameters and orientation, showing a ‘bulk’ effect rather than a simple ‘surface’ effect. While doping with Nb does not change the status of the films, doping with Fe increases coercive fields but removes the asymmetrical behavior of the voltage offset after hot-poling at positive and negative voltages. Annealing/cooling cycles are reversible in the suppression/creation of voltage offset and built-in polarization, respectively, excluding the idea of oxygen and lead vacancy dipolar defects. Experimental data suggest that oxygen is lost and the vacancies diffuse during cooling without being compensated to equilibrate with surface or electrode band bending, resulting in the creation of an internal bias field.     

Which PZT thin films for piezoelectric microactuator applications?

Abstract

The effective piezoelectric coefficient e₃₁ has been measured on sol-gel processed Pb(Zr_xTi_1?x)O₃ thin films with Zr concentrations ranging from 45 to 60%. The largest value was observed at 45% Zr, although dielectric constant and effective d₃₃ peak at 53% Zr. The findings suggest that the optimal composition for microactuators and sensors is less than 45% Zr, i.e., in the tetragonal part of the phase diagram.     

蕾切尔住宅

项目地点:加拿大,蒙特利尔建筑师:Sid Lee建筑事务所摄影:Stephane Brugger Location:Montreal,Canada Architects:Sid Lee Architecture Photos:Stéphane Brügger     

Combined FPPE–PTR Calorimetry Involving TWRC Technique. Theory and Mathematical Simulations

Photopyroelectric calorimetry in the front detection configuration (FPPE) was combined with photothermal radiometry (PTR), in order to investigate dynamic thermal parameters of different layers of a detection cell. The layout of the detection cell consists of three layers: directly irradiated pyroelectric sensor, liquid layer, and solid backing material; and the scanning parameter is the thickness of the liquid layer (thermal-wave resonator cavity method). The theory developed for the two techniques indicates that both FPPE and PTR signals can lead, in the thermally thin regime for the sensor and liquid layer, to the direct measurement of the thermal diffusivity or effusivity of the sensor and/or liquid layer, or the thermal effusivity of the backing material. The two methods offer complementary results and/or reciprocally support each other.     

Modification of DNA radiolysis by DNA-binding proteins: structural aspects

Formation of specific complexes between proteins and their cognate DNA modulates the yields and the location of radiation damage on both partners of the complex. The radiolysis of DNA-protein complexes is studied for: (1) the Escherichia coli lactose operator-repressor complex, (2) the complex between DNA bearing an analogue of an abasic site and the repair protein Fpg of Lactococcus lactis. Experimental patterns of DNA damages are presented and compared to predicted damage distribution obtained using an improved version of the stochastic model RADACK. The same method is used for predicting the location of damages on the proteins. At doses lower than a threshold that depends on the system, proteins protect their specific binding site on DNA while at high doses, the studied complexes are disrupted mainly through protein damage. The loss of binding ability is the functional consequence of the amino-acids modification by OH* radicals. Many of the most probably damaged amino acids are essential for the DNA-protein interaction and within a complex are protected by DNA.     

Changes in the ethnic composition of neighbourhoods: Analysis of household's response and asymmetric preference structures

Theoretical models of ethnic residential segregation indicate asymmetries in preferences as the key driver of ethnic segregation dynamics. This study uses a pivoted choice experiment to empirically analyse the asymmetric preference structures for ethnic composition of neighbourhoods. We assume that the utilities of various alternative residential locations are dependent on the experienced levels of co‐ethnics or ethnic minorities in the current neighbourhood of residence, where the increases in current ethnic concentrations could be evaluated differently than decreases. Results from a discrete choice model estimated on data from Swiss city of Lugano confirm the existence of asymmetries, showing that individuals tend to be averse to decreases in the share of their co‐nationals, while being indifferent to any increases.