Testing Self Healing Properties in Polymers

Mussels and barnacles have the ability to stick to underwater surfaces with the help of a cross-linked protein structure. Reduction in the plastic consumption can be achieved by using toughened polymers. Synthesized cross-linking polymers can be used for underwater adhesion by mimicking the protein structure used by mussels and barnacles. One such polymer is poly(3,4-dihydroxystyrene-co-styrene) having enhanced toughness. Traditionally, blister tests measure the adhesion between a substrate to a surface but this was modified to serve as the driving force to drive crack propagation in controlled flaws. The modified blister tests were carried out on polystyrene (PS) samples. Once the method of controlled crack propagation was perfected, the testing was extended to samples of the copolymer of styrene and 3,4-dihydroxystyrene. Samples were made in aluminium pans by solution casting PS in toluene and drying them in an inert oven. Melting PS pellets in the pans directly on a hot plate at 350°F is another way of making samples. The samples were indented with a Vickers micro-hardness tester. Samples were pressurized and changes in crack size and geometry were monitored via optical microscope. The parameters for successful control of crack growth such as sample thickness, air pressure and exposure time were optimized. These parameters will be used to consistently test and study samples for controlled crack growth. This is a part of the ongoing research about toughened polymers

Intermetalic Growth Rate in Transient Liquid Phase Sintering of Pb-Free Solder Interconnects

Following the electron devices are widely used in daily life, Pb-free solder alloy, as the replacement of Pb solder joint material, needs extensive researches to observe the properties for using and simulation purpose. Solder are used as the joint to connect two work pieces in printed wiring board of electronics. Most lead-free solders comprise tin (Sn) as the majority component, and nominally pure b-Sn is the majority phase in the microstructure of these solders. The most important thing for solder joint that researchers care about is its life cycle. Due to the incomplete of the mechanical profile of Pb-free solder joint for now, this research worked on obtain data of life cycles. At the boundary of the Sn phase and Ag phase, the intermetallic would grow during the heating process, which affects the life cycle of the solder. This study incorporates mechanical testing and measurement of the intermetallic in scanning electron microscope (SEM) images in image J, to get enough data of life cycle to form a profile and the effects of the intermetallic. The measurement on images shows that the intermetalic layer grows in scallop-shape and the thickness increases with the temperature and sintering time. The growth rate can be modeled as a linear equation of the power of one half of the sintering time. This measurement will contribute to the ongoing research about the transit liquid phase sintering and the ball-grid array (BGA) reliability

Characterization of Lead-Free Piezo-Ceramics

Lead zirconate titanate (PZT) has been the most commonly used piezoelectric material due to its high piezoelectric performance under varied operating conditions. However, it has been noticed that the lead component is toxic, causing some environmental issues and a lead free substitute material was introduced. The substituted environmental friendly piezoelectric material, Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) system that can fulfill the need of high piezoelectricity has been developed. The research was conducted to characterize the BZT-xBCT system with five different compositions (x=0.06, 0.08, 0.1, 0.12 and 0.14).. XRD was applied to examine the crystal structure of the samples before and after poling and polarization measurement was conducted. The results from the experiments allow us to find out the piezoelectricity performance of BZT-xBCT system of different compositions that have distinct crystal structures on microscopic scale. It is found that after poling, the intensity peaks do not shift, compared with that before poling, but the ratio between two peaks at the same 2theta degree increases, which means the domain structure changes. Polarization curves for 0.08, 0.1, 0.12 and 0.14 are as expected but the 0.06 one is not. This research will contribute to ongoing research on BZT-XBCT system, and better understanding of piezoelectric materials

Tool for Correlating EBSD and AFM Data Arrays

Ceramic and semiconductor research is limited in its ability to create holistic representations of data in concise, easily-accessible file formats or visual data representations. These materials are used in everyday electronics, and optimizing their electrical and physical properties is important for developing more advanced computational technologies. There is a desire to understand how changing the composition of the ceramic alters the shape and structure of the grown crystals. However, few accessible tools exist to generate a dataset with the proper organization to understand correlations between grain orientation and crystallographic orientation. This paper outlines an approach to analyzing the crystal structure using data collected from atomic force microscopy (AFM) and electron backscattered diffraction (EBSD) scans to build an accurate image of the crystal structure and orientation in the ceramic. The following tool takes data from AFM and EBSD scans of the same surface to create an accessible and easily-manipulatable data organization that stores several parameters relating to the crystallographic information of the surface. While this code was tested using on barium strontium titanate, but can of other materials with crystalline surfaces can take advantage of this analysis tool

Grain Boundary Migration of NiO-MgO Alloys

Grain boundary engineering offers enhanced control of microstructure development during processing, leading to improved final material properties. However, using the effects of the interfacial energy anisotropy on grain boundary mobility to control microstructure development is not well understood. The NiO-MgO system is studied as it has complete solid solubility and a transition in the faceting behavior with composition due to changes in the interfacial energy anisotropy. NiO-MgO powders were produced through the amorphous citrate process and modifications to the process were made to reduce particle and agglomerate size. The powders were pressed and sintered in various conditions to produce fine grained high purity dense samples. Wet milling demonstrated a reduction in the overall particle and agglomerate size of the powders. Pressureless sintering showed an increase in the densification of the NiO-MgO compacts with increased heating rate. Wet milling and high heating rates produced near fully dense samples with relative apparent densities of \u3e95% and open porositie

Note: Thermal analog to atomic force microscopy force-displacement measurements for nanoscale interfacial contact resistance

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate

Evaluation of the factors that promote improved experience and better outcomes of older adults in intermediate care setting

The aim of this article was to identify the main contributing factors to optimising improved experience and better outcomes for older adults participating in intermediate care setting. Background: Intermediate care is an integrated team intervention for patients experiencing an acute change in their function and well-being. Crisis intervention is one of several intermediate care pathways and provides a timely, person-centred, goal setting assessment to determine appropriate care and support for patients in the community. Method: This systematic review was conducted using key search terms and Boolean operators. A Critical Appraisal Skills Programme (CASP) tool was used to evaluate the studies and the data was extracted and synthesised systematically to develop themes relating to the research question. Results: Seven qualitative primary research studies and one mixed methods study were identified. The main themes were ‘communicating with patients’ and ‘patient participation’. Results showed neither themes are parallel entities but co-dependent. Patient-centred approaches to communication by professionals encouraged active patient participation, in turn optimising patient outcomes. Conclusion: This review showed that patient participation in intermediate care requires professionals using advanced communication skills and taking time to actively listen to what is important to the patients. In addition, poor professional communication resulted in passive patient participation. Implications for future practice are discussed

Analysis of noise temperature sensitivity for the design of a broadband thermal noise primary standard

A broadband primary standard for thermal noise measurements is presented and its thermal and electromagnetic behaviour is analysed by means of a novel hybrid analytical?numerical simulation methodology. The standard consists of a broadband termination connected to a 3.5mm coaxial airline partially immersed in liquid nitrogen and is designed in order to obtain a low reflectivity and a low uncertainty in the noise temperature. A detailed sensitivity analysis is made in order to highlight the critical characteristics that mostly affect the uncertainty in the noise temperature, and also to determine the manufacturing and operation tolerances for a proper performance in the range 10MHz to 26.5 GHz. Aspects such as the thermal bead design, the level of liquid nitrogen or the uncertainties associated with the temperatures, the physical properties of the materials in the standard and the simulation techniques are discussed