Melting Point Of Silver Research Articles

Investigating the Synergistic Effect of Decoration and Doping in Silver/Strontium Titanate for Air Remediation.

Strontium titanate (STO) and its variants have emerged as leading materials in photocatalysis, particularly for degrading nitrogen oxides (NOx), due to their non-toxic nature, structural adaptability, and exceptional thermal stability. Although the one-pot sol-gel method leads to high-quality photocatalysts, areas remain for improvement. This study examines the impact of ethanol as a cosolvent in STO synthesis, focusing on optimizing the water-to-ethanol volume ratio. The findings reveal that a 1:3 ratio significantly enhances macropore formation and photocatalytic efficiency, achieving 42% NOx degradation under LED within three hours. Furthermore, incorporating 8.0 wt.% Ag into STO substantially improves visible light absorption and enables complete NOx elimination, thanks to enhanced charge separation and localized surface plasmon resonance. Even at high temperatures (1100 °C), the Ag-STO photocatalyst maintains partial activity, despite exceeding silver's melting point. These results highlight the potential of STO-based materials for industrial applications, positioning them as a promising solution for effective NOx mitigation.

Preparation of high-performance Bi-YG ferrite based on LTCC technology and theoretical analysis of its sintering mechanism

In the preparation process of Microwave Multi-Chip Module (MMCM), it is necessary to simultaneously sinter both microwave medium (ferrite) and silver electrodes. Hence, this necessitates keeping the sintering temperature below the melting point of silver (961 °C). An excessively low sintering temperature would significantly impair the electromagnetic properties of the ferrite material. To address this concern, this study synthesizes Bi-YIG (Y3-xBixFe5O12, x = 0–1.0) ferrites with optimized characteristics, including low ferromagnetic resonance line-width (ΔH) and high saturation magnetization (Ms), at 945 °C using Low Temperature Co-fired Ceramic (LTCC) technology. The mechanism of low-temperature liquid phase sintering, facilitated by a fluxing agent, was investigated using a theoretical model. The addition of Bi2O3 fluxing agent was found to reduce the reaction activation energy, disrupt the chemical reaction equilibrium, and promote low-temperature liquid phase sintering, thus lowering the critical sintering temperature below the melting point of silver. Furthermore, optimal bismuth content was identified to regulate the dynamic balance between grain growth and boundary diffusion, suppressing abnormal grain growth and enhancing the electromagnetic properties of the ferrite. This exploration, leveraging LTCC technology, may offer valuable insights for enhancing the overall performance of MMCMs.

Effects of V<sub>2</sub>O<sub>5</sub>-Al<sub>2</sub>O<sub>3</sub> sintering aid on properties of low temperature sintered Li-Zn microwave ferrites

With the progress of modern wireless communication technology, microwave communication devices are developing toward miniaturization and integration, and low-temperature co-firing ceramic/ferrite technology is the key to meet the above demands. In this paper, V<sub>2</sub>O<sub>5</sub>-Al<sub>2</sub>O<sub>3</sub> (VA) sintering aid is used to realize low-temperature sintering (below melting point of silver that is 950 ℃) of Li-Zn microwave ferrite, which is suitable for radar phase shifter. In this work, firstly, Li-Zn ferrite pre-firing material is prepared by mechanochemical ball-milling method, and then VA composite is selected as sintering aid to prepare Li<sub>0.42</sub>Zn<sub>0.27</sub>Ti<sub>0.11</sub>Mn<sub>0.1</sub>Fe<sub>2.1</sub>O<sub>4</sub> ferrite at low temperatures. The effects of adding amount of VA sintering aid and sintering temperature on crystal structure, microstructure and magnetic properties (saturation induction, coercivity, linewidth of ferromagnetic resonance, etc.) of the materials are also studied. The VA sintering aid can reduce the sintering temperature and maintain the spinel crystal structure of Li-Zn microwave ferrite, the diffraction peaks of V<sub>2</sub>O<sub>5</sub> and Al<sub>2</sub>O<sub>3</sub> involved in the sintering process are observed from none of the samples sintered at different temperatures, because the additive amount of VA sintering aid is very low compared with that of Li-Zn ferrite, so no corresponding impurity peaks are detected. The introduction of VA sintering aid can promote the grain growth, with the average grain size increasing from 0.92 μm to 9.74 μm. In the sintering process of Li-Zn ferrite, V<sub>2</sub>O<sub>5</sub> in VA sintering aid will melt first to form liquid phase due to its low melting point, which promotes the growth of grains. At the same time, Al<sub>2</sub>O<sub>3</sub> with higher melting point can inhibit the grain growth and make the grain uniform. It is worth noting that when excessive VA sintering aid is added, the grain size of ferrite will decrease instead, because too much VA sintering aid will form a large number of liquid phases around the grains, thus splitting the grains and hindering the further growth of the Li-Zn grains. Under the condition of optimal VA sintering aid addition (0.18%, weight percentage), the saturation induction of the sample increases from 144 mT to 281 mT; the rectangular ratio increases from 0.57 to 0.78; the coercivity decreases from 705 A/m to 208 A/m; the linewidth of ferromagnetic resonance decreases from 648 Oe to 247 Oe. In summary, VA sintering aid can effectively improve the properties of Li-Zn microwave ferrite, which has a positive significance in developing low- temperature co-firing ceramic/ferrite technology.

Solid-State-Activated Sintering of ZnAl2O4 Ceramics Containing Cu3Nb2O8 with Superior Dielectric and Thermal Properties

Low-temperature co-fired ceramics (LTCCs) are dielectric materials that can be co-fired with Ag or Cu; however, conventional LTCC materials are mostly poorly thermally conductive, which is problematic and requires improvement. We focused on ZnAl2O4 (gahnite) as a base material. With its high thermal conductivity (~59 W·m−1·K−1 reported for 0.83ZnAl2O4–0.17TiO2), ZnAl2O4 is potentially more thermally conductive than Al2O3 (alumina); however, it sinters densely at a moderate temperature (~1500 °C). The addition of only 4 wt.% of Cu3Nb2O8 significantly lowered the sintering temperature of ZnAl2O4 to 910 °C, which is lower than the melting point of silver (961 °C). The sample fired at 960 °C for 384 h exhibited a relative permittivity (εr) of 9.2, a quality factor by resonant frequency (Q × f) value of 105,000 GHz, and a temperature coefficient of the resonant frequency (τf) of −56 ppm·K−1. The sample exhibited a thermal conductivity of 10.1 W·m−1·K−1, which exceeds that of conventional LTCCs (~2–7 W·m−1·K−1); hence, it is a superior LTCC candidate. In addition, a mixed powder of the Cu3Nb2O8 additive and ZnAl2O4 has a melting temperature that is not significantly different from that (~970 °C) of the pristine Cu3Nb2O8 additive. The sample appears to densify in the solid state through a solid-state-activated sintering mechanism.

Effects of V<sub>2</sub>O<sub>5</sub>-Al<sub>2</sub>O<sub>3</sub> sintering aid on properties of low temperature sintered Li-Zn microwave ferrites

With the progress of modern wireless communication technology, microwave communication devices are developing toward miniaturization and integration, and low temperature co-firing ceramic/ferrite technology is the key to meet the above demands. In this paper, V<sub>2</sub>O<sub>5</sub>-Al<sub>2</sub>O<sub>3</sub> (VA) sintering aid is used to realize low temperature sintering (below melting point of silver that is 950 ℃) of Li-Zn microwave ferrite, which is suitable for radar phase shifter. In this paper, firstly, Li-Zn ferrite pre-firing material is prepared by mechanochemical ball milling method, and then VA composite is selected as sintering aid to prepare Li<sub>0.42</sub>Zn<sub>0.27</sub>Ti<sub>0.11</sub>Mn<sub>0.1</sub>Fe<sub>2.1</sub>O<sub>4</sub> ferrite at low temperatures. The effects of adding amount of VA sintering aid and sintering temperature on crystal structure, microstructure and magnetic properties (saturation induction, coercivity, linewidth of ferromagnetic resonance, et al.) of the materials are also studied. The VA sintering aid can reduce the sintering temperature and maintain the spinel crystal structure of Li-Zn microwave ferrite, the diffraction peaks of V<sub>2</sub>O<sub>5</sub> and Al<sub>2</sub>O<sub>3</sub> involved in the sintering process are not observed for all the samples sintered at different temperatures, because the mass ratio of V<sub>2</sub>O<sub>5</sub> and Al<sub>2</sub>O<sub>3</sub> in VA sintering aid is very low compared with Li-Zn ferrite, so there are no corresponding impurity peaks. The introduction of VA sintering aid can promote the grain growth, with the average grain size increasing from 0.92 mm to 9.74 mm. In the sintering process of Li-Zn ferrite, V<sub>2</sub>O<sub>5</sub> in VA sintering aid will melt first to form liquid phase due to its low melting point, which promotes the growth of grains. At the same time, Al<sub>2</sub>O<sub>3</sub> with higher melting point can inhibit the grain growth and make the grain uniform. It is worth noting that when excessive VA sintering aid is added, the grain size of ferrite will decrease instead, because too much VA sintering aid will form a large number of liquid phases around the grains, thus splitting the grains and hindering the further growth of the Li-Zn grains. Under the condition of optimal VA sintering aid addition (0.18 <em>wt. </em>%), the saturation induction of the sample increased from 144 mT to 281 mT; The rectangular ratio increased from 0.57 to 0.78; The coercivity decreased from 705 A/m to 208 A/m; The linewidth of ferromagnetic resonance decreased from 648 Oe to 247 Oe. In summary, VA sintering aid can effectively improve the properties of Li-Zn microwave ferrite, which has a positive significance for the development of low temperature co-firing ceramic/ferrite technology.

Examination of non‐shrinkage firing using low‐temperature co‐fired alumina containing a small quantity of Cu–Ti–Nb–Ag–O additive

AbstractIn this study, we examined non‐shrinkage firing in the planar direction using low‐temperature co‐fired alumina (LTCA) containing a small quantity of Cu–Ti–Nb–Ag–O additive. A good restraint effect was obtained using AL‐43‐L alumina as a constraint layer whose particle diameter was several times larger (1 to 2 μm) than that of alumina in the LTCA material TM‐5D (0.2 μm). The x‐y shrinkage ratio of the non‐shrinkage fired sample using AL‐43‐L as the constraint layer was within 2 %. However, the density of the non‐shrinkage fired sample was much lower than that of the normal shrinkage fired sample. By producing a powder using a freeze‐dry method, we obtained a well‐sintered alumina with a relative density of approximately 95 % at 950°C, which is lower than the melting point of silver. That is, we achieved both suppression of the shrinkage rate in the x‐y direction and ensured sinterability below the melting point of silver. The thermal conductivity of the sample was 16.2 W/mK, which is extremely high for low‐temperature co‐fired ceramics materials.

Peculiarities of synthesis of Ag-doped hydroxyapatite ceramics

The study is devoted to the preparation of antimicrobial Ag-containing bioactive calcium phosphate ceramics based on carbonated hydroxyapatite and to the determination of the dependence of its phase composition and microstructure on the synthesis temperature. Composite ceramics was obtained by sintering powders of carbonated hydroxyapatite (CHA), synthesized as a result of a reaction between calcium carbonate and phosphoric acid, with the addition of silver nitrate. Ceramics were sintered at 900 and 1000 °C temperatures, i.e., temperatures below and above the melting point of silver. X-ray analysis, electron microscopy, and infrared spectroscopy showed that synthesis at a 900 °C temperature (below the melting point of metallic silver) produces a two-phase composite based on CHA with inclusions of silver nanoparticles smaller than 50 nm in size. From X-ray analysis, with an increase in silver concentration, the lattice constant a remains practically unchanged, while the constant c ‒ increases. This behavior, due to the significant difference in the ionic radii of calcium and silver (Ca2+ ‒ 0.99 Å, Ag+ ‒ 1.28 Å), usually leads to the preferential substitution of Ca(1) sites in the CHA and a linear increasing in the lattice parameters of the CHA with the Ag concentration. That is, even at relatively low temperatures, as a result of the solid-phase reaction in CHA, partial replacement of calcium ions by silver ions occurs and Ag-substituted ceramics are formed. At temperatures above 1000 °C, a single-phase silver-substituted product is synthesized where part of the Ca2+ ions is replaced by Ag+ ions. At the same time, the lattice constant c continues to increase, and in the electron microscopic images only the apatite grain structure is visible without any inclusions. Sintering of composite ceramics at a temperature when silver is in the liquid phase and more easily dissociates into ions compared to the solid phase, results in a single-phase silver-substituted ceramic.

Microstructure and dielectric properties of Ag-BaTiO3 composite ceramics

Di-phase composite ceramics based on BaTiO3 with 5 vol% of Ag filler have been prepared by sintering the mixture of powders at temperatures above the silver melting point (1000 °C–1300 °C/2 h). As predicted by finite element calculations, the addition of metallic particles should produce a field concentration in some regions of the BaTiO3 matrix and therefore, an enhanced dielectric response with respect to pure BaTiO3. The role of oxygen vacancies on the dielectric relaxation mechanisms of Ag-BaTiO3 composites has been investigated. The sintering temperature of 1200 °C provided optimized ceramics with excellent dielectric properties, i.e. with low losses (tanδ < 3%) and room temperature permittivity measured at 50 kHz exceeding 6500 (and above 13,000 at the Curie temperature), as result of a good densification (94% relative density) and a synergy effect of the metallic particles inclusions and ceramic grain size in the range of ≈1 μm, where BaTiO3 has a well-known maximum of its permittivity.

HOT EXPLOSIVE CONSOLIDATION OF NANOSTRUCTURED TUNGSTEN–SILVER PRECURSORS

Different precursors of refractory nanostructural tungsten-silver (W-Ag) composites were consolidated into cylindrical billets by hot explosive consolidation (HEC) method. Different types of compositions with a nanoscale W phase (100 nm) and coarse matrix phase of Ag were consolidated to near theoretical density under and above of melting point of silver (940 – 1050 °C). The intensity of loading in all experiments was around 10 GPa. The combination of high temperatures and two stage explosive densification processes was found to be beneficial to the consolidation of the nanostructural W based composites, resulting in high densities, good integrity, and good electronic properties. The structure and property of the samples depends on the value of consolidation temperature and dimension of consolidated particle. It was observed that for the W-Ag based composites, application of high temperature and consolidation of precursors near melting point of silver 940 °C gives samples without cracking with high value of density and uniform distribution of two phases. The features of structure/property relationship depending on phase content and consolidation conditions have been discussed.

The effect of sintering temperature on the electromagnetic properties of nanocrystalline MgCuZn ferrite prepared by sol–gel auto combustion method

In this work, the nanocrystalline MgCuZn ferrite powder was prepared through the nitrate–citrate auto-combustion route. The as-burnt powder after calcination at 600°C, sintered at different temperatures below silver melting point in the range of 850–950°C for 4h. The structural and magnetic properties were investigated as a function of sintering temperatures. The X-ray diffraction patterns exhibited the formation of a single phase cubic spinel structure. The microstructural evaluations showed homogeneous grains and also revealed that the variation of sintering temperature significantly affected the densification and grain growth of the samples. The density, grain size, initial permeability (µi) and saturation magnetization (Ms) of all the samples increased with sintering temperature. The relative quality factor (RQF) also showed highest value for the sample sintered at 950°C.

Effect of glass fillers in Cu2ZnNb2O8 ceramics for advanced microwave applications

The effect of glass addition on sintering temperature and microwave dielectric properties of Cu2ZnNb2O8 (CZN) is investigated for possible low temperature co-fired ceramic (LTCC) application. The CZN ceramic was prepared by the solid-state ceramic route. The phase formation, microstructure and elemental composition of the ceramics were studied using X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and Energy Dispersive Analysis. The CZN sintered at 975 °C/4 h has ɛr = 15.2, tan δ = 0.0007 (at 5.1 GHz) and τf of −98 ppm °C−1 and CTE = 1.9 ppm °C−1. The addition of LBS and LMZBS glasses lowered the sintering temperature of CZN to below the melting point of silver. The 1 wt% LBS added CZN sintered at 935 °C/4 h had ɛr = 14.7, tan δ = 0.001 (at 5.1 GHz), τf = −19 ppm °C−1 and CTE = −0.6 ppm °C−1. The addition of 0.7 wt% LMZBS to CZN and sintered at 935 °C/4 h had ɛr = 14.8, tan δ = 0.002 (at 5.1 GHz), τf = −39 ppm °C−1 and CTE = −0.9 ppm °C−1.

Structure, dynamic and energetic of mixed transition metal clusters

Classical molecular dynamics simulation (MD) with Sutton-Chen potential has been used to generate the minimum energy and to study the thermodynamic and dynamic properties of mixed transition metal cluster motifs of AgnNi(13−n) for n ≤ 13. Literature results of thirteen particle clusters of neat silver and nickel atoms were first reproduced before the successive replacement of the silver atom by nickel. Calculation was repeated for both silver-centred and nickel-centred clusters. It was found that the nickel-centred clusters were more stable than the silver-centred clusters. Heat capacities and hence the melting points of silver and nickel-centred clusters were determined by using the Histogram method. Species-centric order parameters developed by Hewage and Amar were used to understand the dynamic behaviour in the transition of silver-centred clusters to more stable nickel-centred clusters. This species-centric order parameter calculation further confirmed the stability of nickel-centred clusters over those of silver-centred species.

Plastic flow in shock-loaded silver at strain rates from 104 s−1 to 107 s−1 and temperatures from 296 K to 1233 K

The evolution of elastic-plastic shock waves in 99.9% purity silver samples of 0.127 to 2.0 mm thickness has been studied in a series of VISAR-instrumented planar impact experiments with initial sample temperature varied from 296 to 1233 K. The decay of elastic precursor wave at 933, 1173, and 1233 K temperatures is approximately inversely proportional to the square root of the propagation distance. The latter corresponds to the cubic dependence of initial plastic strain rate, ranged from 104 s−1 to 106 s−1, on the shear stress. At fixed strain rates, the flow stress grows linearly with the temperature but the dependence becomes stronger near the silver melting point, 1234 K. An analysis of the rise times of the plastic shock waves shows that for the same level of shear stress the plastic strain rate at the shock front is significantly higher than that at the top of the elastic precursor wave.

Improved Electrical Conducting Wires for SOFCs

Solid Oxide Fuel Cells (SOFCs) have attracted a number of researchers due to their efficiency as alternative energy devices. Studies have been conducted to investigate different components of the SOFCs to improve the performances. Current collecting wires are the components which have affected the overall performance. Since SOFCs are normally operated in the temperature range of 700-1000 °C in dual atmospheres, the wiring material must be able to function at this condition. Currently, the material used to make the wires is platinum because of its high electrical conductivity, high melting point and oxidation resistant. However, platinum is expensive, especially for the practical operation of SOFCs. Silver could be an alternative choice due to its very high electrical conductivity. Nevertheless, the melting point of silver is rather low (900-960 °C). In our study, a modified silver current collecting wire has been used in the temperature range of 100-1000 °C. Their conductivity curves have demonstrated higher performances in comparison with the systems employing Pt and gold wires. In addition, the cost is reduced approximately 800-1000 times from that of the traditional material used.

V&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-Doped M&lt;sup&gt;2+&lt;/sup&gt;Cu&lt;sub&gt;2&lt;/sub&gt;Nb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;8&lt;/sub&gt; Compounds (M&lt;sup&gt;2+&lt;/sup&gt;= Zn, Co, Ni, Mg &amp; Ca) for Microwave Dielectric LTCCs

The copper-niobates, M2+Cu¬2Nb2O8 (M2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985 – 1010oC, and 1110oC for CaCu¬2Nb2O8. Therefore they would be potential dielectric Low Temperature Co-fired Ceramic (LTCC) materials if they could be made to sinter below 960oC (melting point of silver). To this end, additions of 3wt% V2O5 were made to ZnCu2Nb2O8, CoCu2Nb2O8, NiCu2Nb2O8, MgCu2Nb2O8 and CaCu2Nb2O8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950oC. Doping lowered sintering temperatures to below the 960oC limit in all cases. Doping had the general effect of reducing r, density, Qf and f, although doped CaCu2Nb2O8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. When doped and undoped samples all fired to 935oC were compared, all doped samples had greater r and density, and all except ZnCu2Nb2O8 had a smaller f.

Novel microwave dielectric LTCCs based uponV 2O 5 doped M 2+Cu 2Nb 2O 8 compounds (M 2+ = Zn, Co, Ni, Mg and Ca)

The copper-niobates, M 2+Cu 2Nb 2O 8 (M 2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985–1010 °C and 1110 °C for CaCu 2Nb 2O 8. Therefore, they would be potential dielectric LTCC materials if they could be made to sinter below 960 °C (melting point of silver). To this end, additions of 3 wt.% V 2O 5 were made to ZnCu 2Nb 2O 8, CoCu 2Nb 2O 8, NiCu 2Nb 2O 8, MgCu 2Nb 2O 8 and CaCu 2Nb 2O 8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950 °C. Doping lowered sintering temperatures to below the 960 °C limit in all cases. Doping had the general effect of reducing ɛ r, density, Qf and τ f, although doped CaCu 2Nb 2O 8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. Doped ZnCu 2Nb 2O 8 fired to 935 °C had Qf = 10,200 GHz, and for doped CoCu 2Nb 2O 8 fired to 885 °C Qf = 7500 GHz. When doped and undoped samples all fired to 935 °C were compared, all doped samples had greater ɛ r and density, and all except ZnCu 2Nb 2O 8 had a smaller τ f. All doped samples had a more linear relationship between frequency and temperature in the range 250–300 K.

Silver Nanoparticles from Ultrasonic Spray Pyrolysis of Aqueous Silver Nitrate

Silver particles less than 20 nm in diameter were synthesized by pyrolysis of an ultrasonically atomized spray of highly dilute aqueous silver nitrate solution at temperatures above 650°C and below the melting point of silver. Feed solution concentration and ultrasound power applied to the atomizer were found to have a significant impact on the particle size of the silver nanoparticles. Average particle size was found to be controllable in the range of 20 nm to 300 nm by varying the solution concentration and the ultrasound power to the atomizer.

Low temperature sintering of iron deficient Z type hexagonal ferrites

Low temperature sintering of iron deficient hexagonal Co 2Z type ferrites is attempted to prepare a chip inductor for ultra high frequency uses. It should be attained below the melting point of silver (960 °C) used as the electrode material of the chip inductor. The best result is obtained for the sample with the composition 2.15Co 0.6Cu 0.4O·3Ba 0.79Sr 0.16Bi 0.05O·9.725Fe 2O 3 sintered at 925 °C containing 0.5 wt.% of lithium bismuth oxide as a sintering additive. Its density and permeability reaches 5.0 g/cm 3 and 7, respectively. As a result, the impedance of the chip inductor also reaches 390 ohm at 2 GHz using this material.

Evaporation of Silver during Cofiring with Barium Titanate

Silver and Ag‐Pd alloy are cofired with BaTiO3‐based dielectrics during the manufacturing of capacitors. The diffusion of silver into BaTiO3 during sintering is very slow. However, the vapor pressure of silver is high at temperatures greater than the melting point of silver (960°C). The effect of the evaporation of silver during the sintering with BaTiO3 at 1200°, 1250°, and 1290°C is investigated in the present study. The silver vapor can transport through the pore channel of the dielectrics to a distance of a few hundred micrometers. The melting point of Ag‐Pd alloy is higher than that of silver; therefore, the transportation of silver vapor from Ag‐Pd alloy is hardly observed at temperatures &gt;1200°C.

Improved compositions for melt processing

Melt texture processing of is limited by the slow cooling rate and the high temperatures required. Changing the rare earth can improve the processing conditions. The melting point of can be reduced below the melting point of silver by adding silver, and/or reducing the oxygen partial pressure. The recrystallization rate of is shown to be extremely rapid. For low values of x, solid solutions of may be able to be melt processed rapidly below the melting point of silver.