Material stability investigation of polyamide material before and after laser sintering

Abstract

Polymers are the long chain organic materials that are held together by directional covalent bonds. These kind of organic materials are either synthesized or naturally obtained and they have wide range of application in the medical field due to its physical properties, chemical properties and multifarious processing technique. For the past two decade, these polymers were used to produce variety of medical devices and implants by laser sintering. Since laser based additive manufacturing technique was a thermal process, there may be a change in the material property after sintering and which may affect the usage of the polymer in medical field. This work presented here aims to investigate the material property of biocompatible eos PA12 polymer powder and a laser sintered part. The Scanning Electron Microscope (SEM) with Energy Dispersive Spectroscopy (EDAX), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Differential Scanning Calorimeter (DSC) analysis were carried out to investigate the properties. The experimental investigation carried out in order to get insight into laser-material interaction and the corresponding results indicated that the laser energy influences the material properties of polyamide powder.     

A New Signal‐On Photoelectrochemical Biosensor Based on a Graphene/Quantum‐Dot Nanocomposite Amplified by the Dual‐Quenched Effect of Bipyridinium Relay and AuNPs

A new photoelectrochemical (PEC) biosensor was developed by using carboxyl‐functionalized graphene and CdSe nanoparticles. This sensitive interface was then successfully applied to detection of thrombin based on the dual‐quenched effect of PEC nanoparticle, which relied on the electron transfer of a bipyridinium relay and energy transfer of AuNPs. After recognition with an aptamer, the PEC nanoparticle was removed and a signal‐on PEC biosensor was obtained. Moreover, the bio‐barcode technique used in the preparation of PEC nanoparticle could avoid cross‐reaction and enhances the sensitivity. Taking advantages of the various methods mentioned above, the sensitivity could be easily enhanced. In addition, in this work we also investigated graphene that was modified with different functional groups and AuNPs of different particle sizes. Under optimal conditions, a detection limit of 5.9×10^?15 M was achieved. With its simplicity, selectivity, and sensitivity, this strategy shows great promise for the fabrication of highly efficient PEC biosensors.     

Self‐Immolative Poly(4,5‐dichlorophthalaldehyde) and its Applications in Multi‐Stimuli‐Responsive Macroscopic Plastics

End‐capped poly(4,5‐dichlorophthalaldehyde) (PCl₂PA), which is a new self‐immolative CD_r polymer with the unique capability of depolymerizing continuously and completely in the solid state when an end cap is cleaved from the polymer by reaction with a specific molecular signal, is described. End‐capped poly(4,5‐dichlorophthalaldehyde) is sufficiently stable to enable patterning of three‐dimensional macroscopic polymeric materials by selective laser sintering. These unique materials are capable of 1) autonomously amplifying macroscopic changes in the material in response to specific molecular inputs, and 2) altering their responses depending on the identity of the applied signal. Thus, not only does end‐capped PCl₂PA provide new and unique capabilities compared to the small subset of existing CD_r polymers, but it also provides access to a new class of stimuli‐responsive materials.     

Interaction of Inorganic Nanoparticles with Graphene

The changes in the electronic and magnetic properties of graphene induced by interaction with semiconducting oxide nanoparticles such as ZnO and TiO₂ and with magnetic nanoparticles such as Fe₃O₄, CoFe₂O₄, and Ni are investigated by using Raman spectroscopy, magnetic measurements, and first‐principles calculations. Significant electronic and magnetic interactions between the nanoparticles and graphene are found. The findings suggest that changes in magnetization as well as the Raman shifts are directly linked to charge transfer between the deposited nanoparticles and graphene. The study thus demonstrates significant effects in tailoring the electronic structure of graphene for applications in futuristic electronic devices.     

还原态氧化石墨烯载Pd纳米催化剂对甲酸氧化的电催化性能

采用改进的Hummers法氧化石墨后,对其超声剥离成氧化石墨烯水溶液,继之通过乙二醇还原Pd金属离子和氧化石墨烯,得到了还原态氧化石墨烯（RGO）负载Pd纳米催化剂,并用于甲酸的电催化氧化.透射电子显微镜和X射线衍射结果显示：负载于RGO上的Pd粒子平均粒径为3.8nm,其优先在RGO的褶皱和边缘处生长.电化学测试表明：RGO上残存的含氧基团降低了Pd催化剂受CO毒化的程度,Pd/RGO催化剂表现出了较商业化Pd/C更高的电催化活性和更好的稳定性.     

Determination of the Heat Transfer Coefficient of Metal Oxide Based Water Nanofluids in a Laminar Flow Regime Using an Adaptive Neuro-Fuzzy Inference System

In order to enhance the thermal properties of turbine oil (TO), three different nanoparticles (CuO, Al₂O₃, and TiO₂) are loaded into the TO. To measure the thermal performance of nanoparticle-based TO nanofluids at laminar flow and under constant heat flux boundary conditions, an experimental setup was applied. The obtained data clearly demonstrate the positive effect of all nanoparticles on the heat transfer rate of TO. As the most important factor, the heat transfer coefficient of the abovementioned two-phase systems is increased upon increasing both the volume concentration and the flow rate. An adaptive neuro-fuzzy inference system (ANFIS) is applied for modeling the effect of critical parameters on the heat transfer coefficient of nanoparticle-TO based nanofluids numerically. The results are compared with experimental ones for training and test data. The results suggest that the developed model is valid enough and promising for predicting the extant of the heat transfer coefficient. R² and MSE values for all data were 0.990208751 and 108.1150734, respectively. Based on the results, it is obvious that our proposed modeling by ANFIS is efficient and valid, which can be expanded for more general states.     

Preparation of FePd‐RGO Bimetallic Composites with High Catalytic Activity for Formic Acid Electro‐Oxidation

FePd‐RGO composites through the growth of uniformly dispersed iron‐palladium bimetallic nanoparticles (NPs) on reduced graphene oxide (RGO) nanosheets were prepared by a two‐step method. The firstly formed Fe is used as the seed for the subsequent Pd growth. The formation of Fe NPs on RGO in the first step is performed by an in‐situ reduction reaction with the reducer ethylene glycol under oil bath at 180°C. NPs in the as‐prepared FePd‐RGO have an average particle size of 6.5 nm, and Pd is added to one side of Fe which leads to the formation of Fe‐Pd bimetallic interfaces. As compared with the commercial Pd black at the same loading, the composites have higher electro‐catalytic activity, better electrochemical stability and higher resistance to CO poisoning for formic acid electro‐oxidation.     

Gold nanoparticles supported on three‐dimensional nitrogen‐doped graphene: an efficient catalyst for selective aerobic oxidation of hydrocarbons under mild conditions

The development of efficient and selective aerobic oxidation of alkylarenes to form more functional compounds by heterogeneously catalysed routes still presents a great challenge in the fine chemical industry and is a major research topic. In this work, gold nanoparticles supported on three‐dimensional nitrogen‐doped graphene‐based frameworks (Au NPs@3D‐(N)GFs) were successfully synthesized and found to have an impressive performance as bifunctional catalysts (nitrogen dopant as base and gold nanoparticles as active site) in the controlled oxidation of alkylarenes. The catalyst was found to be a simple bench top, stable, recyclable and selective catalytic system for the aerobic oxidation of various types of alkylarenes into their corresponding ketones at room temperature under environmentally friendly conditions with good yields and high selectivity. Copyright © 2015 John Wiley & Sons, Ltd.     

3D Printing of Poly(3-hydroxybutyrate) Porous Structures Using Selective Laser Sintering

Summary: Poly(3-hydroxybutyrate) (PHB) 3D porous cubes were successfully built with Selective Laser Sintering (SLS), one of the many existing 3D printing technologies. The resulting cubes presented shape and dimensions very close to the corresponding virtual model. Moreover, they were resistant to handling without presenting any visible damage. The PHB powder did not present variation in thermal properties and chemical composition after 32.15 hours of SLS process as observed by proton nuclear resonance (¹H NMR) and differential scanning calorimetry (DSC) analysis, indicating that it can be re-utilized to print additional structures without affecting the reproducibility of the process.