Wt Ag Research Articles

Synergistic Effect of Chitosan and Metal Oxide Additives on Improving the Organic and Biofouling Resistance of Polyethersulfone Ultrafiltration Membranes.

The combination of chitosan and metal oxides was utilized as an addition to improve the fouling resistance of polyethersulfone (PES) ultrafiltration membranes. Pure water flux, membrane hydrophilicity by the contact angle, scanning electron micrographs, and Fourier-transform infrared spectra were used to characterize the membranes. With the addition of metal oxides, the modified membrane's water flux increased. The PES membrane with 0.25% wt chitosan and 2.0% wt AgNO3 had the highest flux and antibacterial activity among the membranes tested. Because of its potential to improve membrane hydrophilicity, the water flux increased with the addition of chitosan and AgNO3. Because of the improved hydrophilicity, the contact angle reduced as chitosan and Ag loading was increased. The PES-chitosan-Ag2O (from AgNO3 2.0% wt) membrane had high antibacterial activity against Escherichia coli and Staphylococcus aureus, whereas the PES-2.0% wt Ag membrane did not show the same result. Finally, the addition of chitosan in the PES-Ag membrane increased the membrane's antibacterial activity substantially.

Hybrid nanoparticles embedded polyvinyl butyral nanocomposites for improved mechanical, thermal and microwave absorption performance

Polymer-based nanocomposites have been broadly investigated to improve its specific properties such as thermal and mechanical properties to use in different application areas. In this study, we aimed to ameliorate the desired physical properties of polyvinyl butyral (PVB) by introducing various amounts of silver (Ag) and cobalt (Co) nanoparticles (NPs) in the polymer matrix. The arc-discharge method submerged in liquid nitrogen was performed to synthesize the metal NPs. To produce hybrid nanocomposites, we demonstrated embedding Ag:Co nanoparticles in the PVB matrix via easy/low-cost solution casting process without any additional materials. In the results of analysis for nanocomposites, it was observed that there were improvements in thermal, mechanical and microwave absorption characteristics of the PVB polymer with interaction of NPs with the polymer. As a result of these interactions, the hybridization of PVB with the metal NPs resulted in the improved thermal stability since the glass transition temperature was increased from 45.6 to 55.1 °C. Besides, while the tensile strength (σ) of the bare PVB film was calculated as 20.52 MPa, the strength of the corresponding tensile strength (σ) of 1.0 wt.% Ag:Co nanocomposite film was improved to 43.41 MPa. Moreover, in order to determine the effect of these changes on the radar absorption feature of nanocomposites, one-dimensional A-Scan measurements were performed on 2–18 GHz frequency band. In the results, it was observed that 1.0%.wt Ag:Co nanocomposite film absorbed approximately 90% of the incoming energy. The characterization results revealed that a positive synergetic effect raised in the case of the modification of the PVB matrix with both Ag and Co NPs. In the light of these data, it was understood that the characteristics of PVB were improved with the NPs combining, and the usage area of that will also increase thanks to this improvement. These regenerated properties made the hybrid nanocomposite a promising substrate material with considerable potential applications for various transparent, flexible, and portable surface coatings.

Pressureless sintering behavior and properties of Ag–SnO2

In this study, the results of measurements on pressureless sintering behavior of Ag–SnO2 (88%wt Ag, 12%wt SnO2) pellets were reported. Dilatometric measurements, relative densities, hardness values, rupture transverse strength and electrical conductivities function of sintering temperatures were presented. A constant thermal expansion coefficient was determined, and a threshold temperature of densification (Td) was exhibited. Sintering kinetics were reported for different temperatures. Hardness values were measured, and no increase in hardness is found under Td. Three-points bending tests were used to determine the transverse rupture strength whose evolution appears importantly well under Td. In the same manner, the increase in initial electrical conductivities begins well under Td. Under the threshold temperature, the relative increase in electrical conductivity is found to be independent of initial density of green compact pellets. This work highlights different evolutions in function of sintering temperature for the electrical conductivity and transverse rupture strength on the one hand, and for the densification and hardness on the other hand.

The Effect of Silver-Zinc Zeolite Incorporation on Some Properties of Condensation Silicone Impression Material

Background: elastomeric impression materials are indicated when a high degree of accuracy is required, due to their excellent properties like details reproduction, dimensional stability and tear strength but with main two disadvantages those are their hydrophilicity as well as the absence of antibacterial activity. This study aimed to evaluate the effect of incorporation of 0.5% wt Ag-Zn zeolite into condensation silicone through the following tests; setting time, dimensional stability, reproduction of details, wettability, and hardness . Materials and methods: one hundred specimens were constructed of condensation silicone, divided into two groups for the first 50 specimens one0.5% by wt Ag -Zn zeolite was added, keeping the other fifty specimens without addition. Then each group further subdivided into five subgroups according to the conducted test. The tests performed were; setting time, dimensional stability, reproduction of details, hardness and wettability. Results: A statistically non-significant effect on the setting time and reproduction of details tests was observed, combined with a highly significant increase of wettability of condensation silicone after incorporation of 0.5% wt Ag-Zn zeolite with non-significant increase of dimensional change of condensation silicone following incorporation of 0.5% wt Ag-Zn zeolite. Hardness test results shoed statistically significant increase following the addition of Ag-Zn zeolite. Conclusion: Ag-Zn zeolite incorporated into condensation silicone, improved wettability which determine the extent to which an impression material replicates the structures of the oral cavity and production of bubble-free gypsum die. It also showed a statistically significant increase in the hardness of condensation silicone impression material, and had no effect on setting time, reproduction of details and dimensional stability.

Agarose Gel as Biomaterial or Scaffold for Implantation Surgery: Characterization, Histological and Histomorphometric Study on Soft Tissue Response

Maxillofacial, orthopedic, oral, and plastic surgery require materials for tissue augmentation, guided regeneration, and tissue engineering approaches. In this study, the aim was to develop and characterize a new extrudable hydrogel, based on agarose gel (AG; 1.5% wt) and to evaluate the local effects after subcutaneous implantation in comparison with collagen and hyaluronic acid. AG chemical–physical properties were ascertained through Fourier transform infrared (FT-IR) spectroscopy and rheological analysis. In vivo subcutaneous implants were performed, and histological and histomorphometric evaluations were done at 1, 4, 12, and 16 weeks. FT-IR confirmed that spectroscopic properties were the same for the baseline agarose and rheological characterization established that AG is a weak hydrogel. Subcutaneous AG implants induced new vessels and fibrous tissue formation rich in neutrophils; the capsule thickness around AG increased until the 12th week but remained thinner than those around hyaluronic acid and collagen. At 16 weeks, the thickness of the capsule significantly decreased around all materials. This study confirmed that 1.5% wt AG possesses some of the most important features of the ideal biocompatible material: safety, effectiveness, costless, and easily obtained with specific chemical and geometrical characters; the AG can represent a finely controllable and biodegradable polymeric system for cells and drug delivery applications.

An NiCr Alloy Piezoresistive Atmosphere Pressure Sensor based on Eutectic

Abstract In this paper, an nickel-chromium (NiCr) alloy piezoresistive atmosphere pressure sensor, based on eutectic bonding is presented. Compared with conventionally silicon piezoresistive pressure sensor, it has the advantages with low cost and easy fabrication processes. First, NiCr alloy (80:20 wt%) is used as the strain detecting material, with a smaller but acceptable sensitivity and simpler processes. Second, eutectic bonding technology based on silver-tin (Ag-Sn) alloy, which is 3.5%wt Ag and 20um thickness, is used as an alternative and easy bonding choice to complete the vacuum package. Bonding quality of eutectic bonding is evaluated by inspection through the deflection of diaphragm of silicon with more than 95% of the area successfully bonded. The Pressure-Voltage characteristic test results suggest a precision within 0.3% in square fitting. The temperature characteristics is also tested and theoretically analyzed. The temperature coefficient offset (TCO) is 620 ppm/(°C FSO).

Rate-dependent properties of Sn–Ag–Cu based lead-free solder joints for WLCSP

The increasing demand for portable electronics has led to the shrinking in size of electronic components and solder joint dimensions. The industry also made a transition towards the adoption of lead-free solder alloys, commonly based around the Sn–Ag–Cu alloys. As knowledge of the processes and operational reliability of these lead-free solder joints (used especially in advanced packages) is limited, it has become a major concern to characterise the mechanical performance of these interconnects amid the greater push for greener electronics by the European Union. In this study, bulk solder tensile tests were performed to characterise the mechanical properties of SAC 105 (Sn–1%wt Ag–0.5%wt Cu) and SAC 405 (Sn–4%wt Ag–0.5%wt Cu) at strain rates ranging from 0.0088 s −1 to 57.0 s −1. Solder joint array shear and tensile tests were also conducted on wafer-level chip scale package (WLCSP) specimens of different solder alloy materials under two test rates of 0.5 mm/s (2.27 s −1) and 5 mm/s (22.73 s −1). These WLCSP packages have an array of 12 × 12 solder bumps (300 μm in diameter); and double redistribution layers with a Ti/Cu/Ni/Au under-bump metallurgy (UBM) as their silicon-based interface structure. The bulk solder tensile tests show that Sn–Ag–Cu alloys exhibit higher mechanical strength (yield stress and ultimate tensile strength) with increasing strain rate. A rate-dependent model of yield stress and ultimate tensile strength (UTS) was developed based on the test results. Good mechanical performance of package pull-tests at high strain rates is often correlated to a higher percentage of bulk solder failures than interface failures in solder joints. The solder joint array tests show that for higher test rates and Ag content, there are less bulk solder failures and more interface failures. Correspondingly, the average solder joint strength, peak load and ductility also decrease under higher test rate and Ag content. The solder joint results relate closely to the higher rate sensitivity of SAC 405 in gaining material strength which might prove detrimental to solder joint interfaces that are less rate sensitive. In addition, specimens under shear yielded more bulk solder failures, higher average solder joint strength and ductility than specimens under tension.

Atomization of austenitic iron alloy: A.Ozols et al. (Facultad de Ingenieria, Argentina.)

In this paper, an nickel-chromium (NiCr) alloy piezoresistive atmosphere pressure sensor, based on eutectic bonding is presented. Compared with conventionally silicon piezoresistive pressure sensor, it has the advantages with low cost and easy fabrication processes. First, NiCr alloy (80:20 wt%) is used as the strain detecting material, with a smaller but acceptable sensitivity and simpler processes. Second, eutectic bonding technology based on silver-tin (Ag-Sn) alloy, which is 3.5%wt Ag and 20um thickness, is used as an alternative and easy bonding choice to complete the vacuum package. Bonding quality of eutectic bonding is evaluated by inspection through the deflection of diaphragm of silicon with more than 95% of the area successfully bonded. The Pressure-Voltage characteristic test results suggest a precision within 0.3% in square fitting. The temperature characteristics is also tested and theoretically analyzed. The temperature coefficient offset (TCO) is 620 ppm/(°C FSO).

Co-reaction of textured superconducting, conducting and insulating multilayer composites

Many applications of superconductors are limited by low values of the engineering critical current density (J/sub cc/). Significant improvements are possible through the merger of green tape and composite reaction texturing technologies. Tape casting and elastomer processing techniques have produced insulating (MgO and Al/sub 2/O/sub 3/), conducting (Ag) and superconducting (Bi-2212+MgO-fibre) tapes with uniform thickness ranging from 0.1-2 mm. Green tapes of the desired thickness can be laminated into multilayer structures and co-reacted; the superconducting layer occupying over 50% of the cross section allows the engineering of an artefact for optimal I/sub c/, and maximum J/sub c/c. The texture observed in the Bi-2212 layer is induced by specifically aligned MgO-fibres. As a necessary step in developing this technology, results are presented on (1) additions of 0-10 %wt Ag to Bi-2212 in order to modify its partial melt behaviour, (2) control of the shrinkage and densification of individual layers which is critical to uniformity and (3) chemical buffering of the Bi-2212 layer from insulating layers of doped MgO and Al/sub 2/O/sub 3/ during co-reaction.

Ag-123 composite peritectic reaction and the 123* phase formation

Typical 123 ceramic treated with a slow cooling from the peritectic reaction (peritectic tuning) results in a pseudograin morphology. It consists of an arrange of 123 flakes derived from a sympathetic nucleation. BaCuO2 and CuO accompanying phases are observed as the end of a deficient re-absorption process. XRD/SEM-EDAX/experiments were carried out on Ag-123 (∼10% wt Ag) composites obtained from peritectic tuning. The existence of Ag−Ba−Cu compounds at post-peritectic temperatures could be the cause for a better re-absorption of the accompanying phases, with typical Ag particles arrays in a modified 123 (123*) flakes matrix. Resulting 123* phase was characterized by XRD and in a previous work by RT, showing an increase in the c axis and a higher Tc (94K). It could be inferred that there is a higher crystalline coherence for this 123* flakes matrix.

Multilayer Ceramic Capacitors Based on Pb(Mg1/3Nb2/3)O3

AbstractMultilayer capacitors were made from Pb(Mg1/3Nb2/3)O3 compositon by an usual technique: ceramic green sheets formed by slip casting method, printed with an 70% wt Ag- 30% wt Pd internal electrode and sintered at temperature ranging from 950 to 11OO°C. Chip capacitors exhibit large capacitance and temperature characteristics meet Z5U specification. Electrical properties of MLC based on PMN depend on specific parameters such as the average concentration of pyrochlore phase and perovskite phase, and the homogeneity degree of dielectric layers. Load humidity life tests show a degradation of some chips which can be connected with the formation of a surface layer rich in pyrochlore phase.