Quantitative Analysis of the Degradation Behavior of Silicon Solar Cell Irradiated by 1 MeV Electron Beams Using Photocarrier Radiometry Combined with Lock-in Carrierography

Silicon solar cells with cover glass irradiated by 1 MeV electron beams at various fluences were investigated using photocarrier radiometry (PCR) combined with lock-in carrierography (LIC, spectrally gated dynamic photoluminescence). The minority carrier transport properties (i.e., minority carrier lifetime τ, diffusion coefficient D, surface recombination velocities S) and the degradation of these properties were studied using PCR. The relative damage coefficient obtained by LIC was consistent with the PCR measurement. The local series resistance of the solar cell before and after irradiation was characterized by LIC. The results showed that the series resistance increased with electron fluences.     

Nondestructive Microstructural Analysis of Porous Bioceramics by Microfocus X-ray Computed Tomography (μCT): A Proposed Protocol for Standardized Evaluation of Porosity and Interconnectivity Between Macro-pores

Microfocus X-ray computed tomography (μCT) has now become widely available for the nondestructive evaluation of porous bioceramics suitable for use as a bone substitute in orthopedic surgery. As part of an official Japanese working committee, we recently participated in the preparation of a proposed standard protocol for the quantitative μCT analysis of porous bioceramics sent to the International Organization for Standardization (ISO). In this protocol, the recommended basic conditions for analysis were [field of view (XY plane): 3.0 mm, spatial resolution: 6 μm/pixel (or the closest minimal values available for both parameters on a particular μCT system), matrix size: 512 pixels], and we have now further determined the optimal values for more detailed parameters (e.g., threshold determination). To validate the utility of the complete protocol, three different types of ceramic sample [a ceramic of β-tricalcium phosphate (β-TCP) and two types of hydroxyapatite (HAp) with different porosities] were evaluated with three different types of cone-beam μCT scanner (the Shimadzu SMX-100CT, Shimadzu inspeXio-90CT, and Skyscan-1174 scanners). Acquired images were quantified using 3D-reconstruction software, VGStudio MAX (version 1.2). After comparing data obtained from these three μCT scanners, we have found that determinations of both porosity and pore-interconnectivity were very similar from one system to the other although the total number of measured pores did vary between scanners. The present data indicate that our protocol for μCT analysis is reliable enough to quantify the porosity and interconnectivity of porous bioceramics and would therefore facilitate both large-scale screening and quality control of porous bioceramic samples.     

Measurement of the (p, \rho,T) Properties for Pure Hydrocarbons at Temperatures up to 600 K and Pressures up to 200 MPa

The data available for the thermodynamic properties of propane, \(n\) -butane, and isobutane at temperatures above 440 K are outdated and show significant discrepancies with each other. The ambiguity associated with these data could be limiting to the development of any understanding related to the effects of mixing of these substances with other materials such as \(\text{ CO}_{2}\) , ammonia, and non-flammable or lower-flammable HFC refrigerants. In this study, the (p, \(\rho \) , T) properties of propane, \(n\) -butane, and isobutane were measured at temperatures ranging from (360 to 600) K and pressures ranging from (50 to 200) MPa. Precise measurements were carried out using a metal-bellows variable volumometer with a thermostatted air bath. The expanded uncertainties \((k = 2)\) in the temperature, pressure, and density measurements were estimated to be \(<\) 5 mK, 0.02 MPa, and 0.88 kg  \(\cdot \)  m \(^{-3}\) ( \(T\le 423\)  K, \(p<100\)  MPa), 0.76 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T\le 423\)  K, \(p\ge 100\)  MPa), 0.76 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T>423\)  K, \(p < 100\)  MPa), and 2.94 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T>423\)  K, \(p \ge 100\)  MPa), respectively. The data obtained throughout this study were systematically compared with the calculated values derived from the available equations of state. These models agree well with the measured data at higher temperatures up to 600 K, demonstrating their suitability for an effective and precise examination of the mixing effects of potential alternative mixtures.     

Measurements of Vapor Pressures from 280 to 369 K and (p, ρ, T) Properties from 340 to 400 K at Pressures to 200 MPa for Propane

Measurements of (p, ρ, T) properties for compressed liquid propane have been obtained by means of a metal-bellows variable volumometer at temperatures from 340 to 400 K at pressures up to 200 MPa. The volume- fraction purity of the propane sample was 0.9999. The expanded uncertainties (k = 2) of temperature, pressure, and density measurements have been estimated to be less than 3 mK; 1.5 kPa ( MPa), 0.06% (7 MPa MPa), 0.1% (50 MPa MPa) , and 0.2% (p>150 MPa); and 0.11%, respectively. Four (p, ρ, T) measurements at the same temperatures and pressures as literature values have been conducted for comparisons. In addition, vapor pressures were measured at temperatures from 280 to 369 K. Furthermore, comparisons of available equations of state with the present measurements are reported.Paper presented at the 17th European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

In vitro degradation of poly-<Emphasis Type="SmallCaps">l</Emphasis>-<Emphasis Type="SmallCaps">d</Emphasis>-lactic acid (PLDLA) pellets and powder used as synthetic alloplasts for bone grafting

The objective of this study was to evaluate the in vitro degradation of pellet and powder forms of a poly-L: -D: -lactic acid material used to produce plates and screws for orthopedic, oral, and maxillofacial applications. Materials and methods In order to produce the powder form the as-received pellets were milled in a cryogenic chamber. Particles size distribution (PSD) histograms were developed for both forms. The materials were then characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA) before and after immersion in simulated body fluid for 30, 60, and 90 days. Results SEM showed that for both forms material degradation started after 30 days of immersion in SBF and evolved until 90 days. Degradation started at the amorphous zones of the polymer and exposed of deeper crystalline layers. The pellet and powder samples PSD showed polydispersed patterns with mean diameters of 673.98 mum and 259.55 mum. Thermal onset degradation temperatures were 365.64 degrees C and 360.30 degrees C, and of 363.49 degrees C and 359.83 degrees C before immersion and after 90 days in SBF for the pellet and powder forms, respectively. The Tg's of the pellets and the powder were approximately 61.5 degrees C and 66 degrees C, and their respective endothermic peaks were observed at approximately 125 degrees C and 120 degrees C. The specific heat (c) was approximately 8.5 J/g and 6.2 J/g for the pellet and powder material, respectively. Conclusion According to the results obtained, cryogenic milling resulted in particle plastic deformation, and alterations in glass transition temperature, melting temperature, and specific heat of the material.