Investigations On Silver-Copper Nanopaste As Die-Attach Material For High Temperature Applications

Satu nano-pes argentum-kuprum (Ag-Cu) yang dirumuskan dengan mencampurkan nanopartikel Ag dan Cu dengan penambah organik (pelekat resin, terpineol dan ethylene glycol) telah dihasilkan bagi diaplikasikan sebagai bahan lampir-dai suhu tinggi. Pelbagai peratus berat nanopartikel Cu (20-80 wt%) telah ditambahkan ke dalam nano-pes Ag-Cu, diikuti oleh pensinteran di udara terbuka pada suhu 380°C selama 30 min tanpa bantuan tekanan luar, untuk mengkaji kesan terhadap sifat-sifat fizikal, elektrikal, terma dan mekanikal. A silver-copper (Ag-Cu) nanopaste formulated by mixing Ag and Cu nanoparticles with organic additives (i.e., resin binder, terpineol and ethylene glycol) which is meant for high-temperature die-attach applications has been developed. Various weight percent of Cu nanoparticles (20-80 wt%) has been loaded into the Ag-Cu nanopaste, followed by sintering in open air at temperature of 380°C for 30 min without the need of applied external pressure

Direct Transfer Patterning of Electrically Small Antennas onto Three‐Dimensionally Contoured Substrates

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90030/1/1166_ftp.pd

Growth mechanisms of GaN microrods for 3D core-shell LEDs: The influence of silane flow

The three dimensional growth of GaN structures as a basis for the fabrication of 3D GaN core-shell LEDs has attracted substantial attention in the past years. GaN nanorods or microrods with high aspect ratios can be grown by selective area epitaxy on a GaN buffer through a SiOx mask. It has been found earlier that silane substantially initiates vertical growth, with the exact underlying mechanisms being still unclear. Here, the influence of silane on the 3D GaN column growth was investigated by performing detailed growth experiments in combination with a thorough surface analysis in order to get insight into these mechanisms. The vertical growth rate is significantly enhanced by high silane fluxes, whereas the saturation of growth rate with the time is reduced. Thus, homogenous GaN columns with an aspect ratio of more than 35 could be achieved. A thin Si-rich layer on the non-polar m-plane facets of the columns has been detected using a combination of transmission electron microscopy, energy dispersive X-ray spectroscopy and Auger electron spectroscopy. This layer is suggested to be the reason for the increase in growth rate, modifying the effective collection range of the species along the sidewalls, and preventing the lateral growth

Salt-induced changes of colloidal interactions in critical mixtures

We report on salt-dependent interaction potentials of a single charged particle suspended in a binary liquid mixture above a charged wall. For symmetric boundary conditions (BC) we observe attractive particle-wall interaction forces which are similar to critical Casimir forces previously observed in salt-free mixtures. However, in case of antisymmetric BC we find a temperature-dependent crossover from attractive to repulsive forces which is in strong contrast to salt-free conditions. Additionally performed small-angle x-ray scattering experiments demonstrate that the bulk critical fluctuations are not affected by the addition of salt. This suggests that the observed crossover can not be attributed alone to critical Casimir forces. Instead our experiments point towards a possible coupling between the ionic distributions and the concentration profiles in the binary mixture which then affects the interaction potentials in such systems.Comment: 5 pages, 4 Figure

Antimony-doped graphene nanoplatelets

Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb3+ and Sb5+) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalystsclose0

Tunable Ag@SiO2 core-shell nanocomposites for broad spectrum antibacterial applications

Silica encapsulated silver nanoparticle core-shell nanocomposites of tunable dimensions were synthesised via a one-pot reverse microemulsion route to achieve controlled release of Ag+ ions for broad spectrum antibacterial application. Silver release rates and bactericidal efficacy against Gram-positive and Gram-negative bacteria, S. aureus and P. aeruginosa respectively, were inversely proportional to nanoparticle core diameter (3-8 nm) and silica shell (7-14 nm) thickness, and readily tuned through a facile hydrothermal etching protocol employing a PVP stabiliser to introduce mesoporosity

Improvement in NO2 Sensing Properties of Semiconductor-Type Gas Sensors by Loading of Au Into Porous In2O3 Powders

Porous (pr-) In2O3 powders loaded with and without noble metals (Au, Pd, or Pt) were prepared by ultrasonic spray pyrolysis employing the PMMA microspheres as a template (typical particle size (ps): 28 or 70 nm with a diameter), and their NO2 sensing properties were examined. The Au loading on the pr-In2O3 was effective to increase the NO2 response at lower operating temperature (?200°C), while the metal loading of Pd or Pt were hardly effective. In addition, a decrease in the PMMA microspheres (from 70 to 28 nm in ps) largely increased the NO2 response,and an optimized amount of Au loaded on the pr-In2O3 sensor was 1.0 wt%. The decrease in the thickness of the sensing layer improved the NO2 response and response speed. It was suggested that the Au loading enhanced the amount of the negatively adsorbed NO2 on the bottom part of the sensing layer, leading to the increase in the NO2 response. Furthermore, the introduction of additional macropores (ps: 150 nm) to the 1.0 wt% Au loaded pr-In2O3 sensor increased the response to a low concentration of NO2 (0.025 ppm) at 30°C. Therefore, it was found that easy gas diffusion from the surface to the bottom part of the sensing layer increased the effective concentration of NO2, and thus the NO2 response was increased

Nationwide improvement in outcomes of emergency admission for ulcerative colitis in England, 2005‐2013

Background The UK IBD Audit Programme reported improved inpatient care processes for ulcerative colitis (UC) between 2005 and 2013. There are no independent data describing national or institutional trends in patient outcomes over this period. Aim To assess the association between the outcome of emergency admission for UC and year of treatment. Methods Retrospective analysis of hospital administrative data, focused on all emergency admissions to English public hospitals with a discharge diagnosis of UC. We extracted case mix factors (age, sex, co‐morbidity, emergency bed days in last year, deprivation status), outcomes of index admission (death and first surgery), 30‐day emergency readmissions (all‐cause, and selected causes) and outcome of readmission. Results There were 765 deaths and 3837 unplanned first operations in 44 882 emergency admissions, with 5311 emergency readmissions (with a further 171 deaths and 517 first operations). Case mix adjusted odds of death for any given year were 9% lower (OR 0.91, 95% CI: 0.89‐0.94), and that for emergency surgery 3% lower (OR 0.97, 95% CI: 0.95‐0.98) than the preceding year. Results were robust to sensitivity analysis (admissions lasting ≥4 days). There was no reduction in odds for all‐cause readmission, but rates for venous thromboembolism declined significantly. Analysis of institutional‐level metrics across 136 providers showed a stepwise reduction in outliers for mortality and unplanned surgery. Conclusions Risk of death and unplanned surgery for UC patients admitted as emergencies declined consistently, as did unexplained variation between hospitals. Risk of readmission was unchanged (over 1 in 10). Multiple factors are likely to explain these nationwide trends