Full Sintering Research Articles

Current rate flash sintering of nickel at ambient temperature in <1 min

AbstractWe show that powder pressed specimens of nickel can be sintered to 99.96% density by injecting electrical current, without the use of a furnace. Full sintering could be accomplished in 10 to 52 s by changing the current rate from 5 to 1 A/s. In all instances, the samples sintered abruptly at a current density of ∼20 A mm−2. The grain size of the sintered samples was somewhat larger than the nickel powder particle size (∼60 μm vs. 40 μm). Tensile testing yielded a yield strength of 98 MPa, ultimate tensile stress of 323 MPa, and ductility of ∼17%. Four in‐operando measurements are reported: (i) sintering, (ii) the change in resistance with current density, (iii) the temperature, and (iv) electroluminescence. The change in resistance during flash sintering exhibited a high peak followed by a steep decline in resistance; the transient is attributed to the breakdown of particle–particle interface resistance. The same cycle repeated with the flash‐sintered, dense sample, did not show the spike, and gave reproducible results. The resistance data for these latter cycles, when viewed as a function of temperature exhibited sigmoidal behavior: initially lower, and then higher than the literature values. This unusual behavior reflects the influence of defects generated during flash. We have also measured the endothermic enthalpy, expressed by the difference between the in situ input electrical energy and the radiation, convection, and specific heat losses. Dividing by the formation energy of Frenkel pairs yields the concentration of defects, estimated to be 0.3–0.4 mol %. These concentrations are far above thermal equilibrium; it is concluded that flash of metals is a far from equilibrium phenomenon.

Сферические субмикронные порошки с нано-поликристаллической субструктурой — перспективное сырье для получения мелкозернистой высокоплотной керамики (обзор)

The review reflects the unique properties and possible areas of application of submicron non-agglomerating powders from refractory oxides obtained by aerosol-spray pyrolysis. An analysis of the experimental results obtained by researchers at different times convincingly proves the promise of using aerosol nanostructured submicron spherical powders to obtain ceramic materials with a high-density, uniform fine-grained structure without pores. The uniqueness of aerosol powders is due to the presence in the particles of the nano-polycrystalline substructure of a developed network of inter-grain boundaries, which during sintering has a significant impact on the efficiency of diffusion mass transfer and contributes to an increase in the speed and completeness of pores overgrowth. Aerosol powders acquire these properties through the use of ultrasonic spray pyrolysis, where equilibrium physicochemical processes occur in ultra-small local volumes of aerosol droplets, ensuring a high degree of uniformity of the resulting powder. The formed ultrathin substructure of aerosol powders ensures their full sintering at low temperatures, making it possible to obtain high-density ceramic materials with extreme physical and mechanical characteristics. The practical use of nanostructured aerosol powders does not require the use of preliminary preparation operations (grinding-grinding, classification, purification from impurities, etc.) and, unlike ultrafine powders, they are easily molded using traditional methods of powder technology (uniaxial pressing, hot casting, etc.).

Processing and Properties of Tungsten-Steel Composites and FGMs Prepared by Spark Plasma Sintering

Tungsten is the prime candidate material for the plasma-facing components of fusion reactors. For the joining of tungsten armor to the cooling system or support structure, composites or graded interlayers can be used to reduce the stress concentration at the interface. These interlayers can be produced by several technologies. Among these, spark plasma sintering appears advantageous because of its ability to fabricate fully dense parts at lower temperatures and in a shorter time than traditional powder metallurgy techniques, thanks to the concurrent application of temperature, pressure, and electrical current. In this work, spark plasma sintering of tungsten-steel composites and functionally graded layers (FGMs) was investigated. As a first step, pure tungsten and steel powders of different sizes were sintered at a range of temperatures to find a suitable temperature window for fully dense compacts. Characterization of the sintered compacts included structure (by SEM); porosity (by the Archimedean method and image analysis); thermal diffusivity (by the flash method) and mechanical properties (microhardness and flexural strength). Compacts with practically full density and fine grains were obtained; while the temperature needed to achieve full sintering decreased with decreasing powder size (down to about 1500 °C for the 0.4 μm powder). For fully sintered compacts, the hardness and thermal diffusivity increased with decreasing powder size. Composites with selected tungsten/steel ratios were produced at several conditions and characterized. At temperatures of 1100 °C or above, intermetallic formation was observed in the composites; nevertheless, without a detrimental effect on the mechanical strength. Finally, the formation of graded layers and tungsten-steel joints in various configurations was demonstrated.

A comparative study on mechanical properties of fully dense 420 stainless steel parts produced by modified binder jet printing

The mechanical properties of the parts produced by binder jet printing (BJP) are often considerably inferior to those of the parts produced by traditional manufacturing processes because BJP parts retain at best about 95% of theoretical density after full sintering. To address this deficiency of BJP, a new processing protocol was developed, which enables us to produce fully dense parts under an isothermal sintering condition. This paper compares the mechanical properties of the stainless steel 420 (SS420) parts produced by the several variations of this new protocol against commercially available cold rolled SS420 parts with and without the heat-treatment under the similar sintering condition used in the new protocol. The mechanical properties examined include elastic modulus and both static and fatigue strengths. The only minor drawback of the new protocol is the dimensional shrinkage occurring during sintering. However, this can be easily compensated by printing the part geometry about 15% larger in the linear dimension with the starting powder used in this study. The final results showed the excellent static and fatigue strengths of the SS420 specimens produced with the new BJP protocol, implicating the potential structural applications of the BJP parts.

Interfacial Engineering of Protonic Ceramic Electrochemical Cells By Acid Etch

The ceramic proton conductors (e.g. BaZr0.1Ce0.7Y0.1Yb0.1O3−δ, noted as BZCYYb) in protonic ceramic electrochemical cells (PCEC) exhibit high ionic conductivity at reduced temperature due to lower activation energy. However, high sintering temperature (≥1400 oC for BZCYYb, ≥1500 oC for BaZr0.8Y0.2O3−δ) was required to densify these ceramic electrolytes during fabrication. The formation of well-annealed electrolyte surface because of the high sintering temperature leads to poor bonding between the electrolyte with oxygen electrode. Here, we proposed a novel and simple acid treatment method to rejuvenate protonic ceramic electrolyte surface. The acid etching process was after the full sintering of half-cell at 1400 oC. 0.3 mL concentrated nitric acid was used to etch the surface of dense electrolyte (for 10 mm button cell) before integration with oxygen electrode. We observed the obvious electrochemical performance improvements with different oxygen electrodes including PrNi0.5Co0.5O3−δ, La0.6Sr0.4Co0.2Fe0.8O3−δ, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ and even with Pt or Ag electrode after acid etching. Large cells (5×5 cm2, 10×10 cm2) with electrolyte treated by nitric acid was prepared and showed enhanced electrochemical performance as well.

Evaluation of Surface Roughness of Some Biomedical Titanium Alloys by Pack Cementation Coating

Titanium possesses a unique ability to bind with bone and living tissue, making it an ideal material for orthopedic implants such as knee and hip replacements. Because of the strength to weight ratio, hermeticity, biocompatibility and light weight makes titanium and its alloy the best choice for implant. The main goal focused on studying the influence of surface coating of some titanium base alloys by Nano (ZrO2&Y2O3) to the surface roughness of implant alloys. Preparation of samples was accomplished by using powder technology technique, in which the raw materials was pure titanium, 10%cobalt,50% nickel, and 30% tantalum powders. The samples were cleaned by ultrasonic device the surface pre- treated by chemical etching, then deposition of nano (ZrO2 with Y2O3) accomplished by pack cementation process. After samples characterization by (X-ray diffraction, hardness test, porosity percentage and Surface roughness). The result showed that diffraction patterns gained for the samples were the phases developed as a result of sintering and after deposition, There are likely no presents of pure metals that prove the time and temperature of sintering utilized in this work results in full sintering reactions, the XRD patterns of samples after (ZrO2,Y2O3) deposition by pack cementation process. It is obvious that Amorphous behavior was observed in the XRD after deposition nearly at 2θ (15.799) for all samples. It is evident that the porosity percent of the samples after (ZrO2, Y2O3) deposition was largely decreases due to the pack cementation process. There was considerable increasing in hardness value, finally the roughness values obtained from the AFM it was found that there are large changes in the roughness value of samples after coating due to full the surface by Nano ceramic material deposition.

Development of silicon nitride ceramic for CAD/CAM restoration.

White Silicon nitride (Si3N4) ceramic has unique characteristics. Because of its high fracture toughness, strength, and biocompatibility, it can therefore be used to fabricate dental restorations. The purpose of this study was to produce partially-sintered block of Si3N4 for fabrication of CAD/CAM dental restorations. The related properties of this novel Si3N4 were evaluated including sintered shrinkage, flexural strength and fracture toughness. Partially sintered Si3N4 ceramic blocks were prepared by heating at 1,400°C for 2 h under N2 gas. After full sintering at 1,650oC for 2 h, the linear shrinkage value was recorded at 19.88±0.56%. The flexural strength and fracture toughness were measured, the results were 891.21±37.25 MPa and 6.33±0.30 MPa•m1/2, respectively. These results showed that flexural strength and fracture toughness of Si3N4 were more than 800 MPa and 5 MPa•m1/2, the white Si3N4 developed in this study can be used to fabricate multi-unit dental restorations According to ISO 6872.

Uniform, Scalable, High-Temperature Microwave Shock for Nanoparticle Synthesis through Defect Engineering

Summary Here we demonstrate a thermal shock synthesis method triggered by microwave irradiation for the rapid synthesis of nanoparticles on reduced graphene oxide (RGO) substrate. With properly controlled reduction, RGO has high electrical conductivity while maintaining functional groups, leading to an extremely efficient microwave absorption of ∼70%. The high utilization of microwaves results in the ability to raise the temperature to 1,600 K in just 100 ms, which is followed by rapid quenching to room temperature. The defects on the RGO are crucial for achieving this record-high microwave-induced temperature as these defects play a fundamental role in absorbing the radiation as well as the self-quenching mechanism. By loading precursors onto RGO, we can utilize rapid temperature change to synthesize nanoparticles. The nanoparticles are ∼10 nm with uniform distribution. This facile, rapid, and universal synthesis technique has the potential to be employed in large-scale production of nanomaterials and suggests a new direction for nanosynthesis.

Influence of processing variables on scratch and shrinkage behaviors and translucency of dental zirconia

AbstractScratch tests were performed on porous 3 mol% Y2O3‐stabilized zirconia dental blocks to relate compaction processing and partial sintering temperature to shrinkage and machinability of the blocks and microstructures and transmittance after full sintering. Scratch hardness of the blocks varied with increasing loads, and the variation was related to the sequential events of densification, densification and cleaving, disruption of the densified region, and chipping and longitudinal cracking. The shrinkage during final sintering was inversely proportional to the compact pressure and temperature with compact pressure having a greater impact. In contrast, the transmittance of fully sintered blocks depended largely on the partial sintering temperature because it governed the number and size of pores after completion of the sintering. Based on the influence of the variable on scratch hardness, a scratch response measure that possibly reflects the machinability of porous CAD/CAM blocks was proposed.

MICROSTRUCTURAL, PHYSICAL AND MECHANICAL ANALYSIS OF RHA PORE MODIFIED POROUS ALUMINA WITH ALUMINUM AS REINFORCEMENT

Porous ceramics are being used in many industrial applications and processes that require extreme environment exposure due to its chemical inertness to corrosive medium and its ability to withstand high temperatures. Tailoring the porosity through pore modifier is one of the method available to ensure that the strength of ceramic is homogeneous. In order to improve the strength of the porous ceramic, the addition of aluminium powders was explored in this research. With the addition of agricultural waste source pore modifier and aluminium as reinforcement, the microstructure, linear shrinkage, porosity (open, closed and total), density, hardness and failure strength of this ceramic composite were examined. The ceramic composites were fabricated through powder metallurgy processing routes. Alumina, Al2O3 with the respective amounts of 0 to 10 wt.% (intervals of 10 wt.%) of RHA and 0 to 10 wt.% (intervals of 2 wt.%) of aluminum, Al, were mixed homogeneously with 12 wt.% of sucrose solution. The mixtures were compacted and heat-treated for 1 h at each of the soaking temperatures of 200°C, 600°C and 1000°C followed by full sintering at 1550°C for 2 h in a furnace. The results have shown that open and total porosity increases with increasing amounts of RHA and aluminum. Meanwhile, the linear shrinkage, close porosity, density, hardness and failure strength was reduced. In this research, the strength was expected to increase with the addition of aluminum. However, due to the increasing percentage of the total porosity with the increased addition of aluminum, the samples behave inversely. Phase transformations to mullite (3Al2O3. 2SiO2) were seen in this research with the addition of RHA. This phase formation helps to increase the overall strength of the ceramic composites, showing that 10 wt% addition of RHA have a positive impact, not only as a medium to modify the pore formation, but it also has a positive effect on the strength property of the ceramic composite.

Five-axis laser milling system that realizes more accurate zirconia CAD/CAM crowns by direct milling from fully sintered blocks

Directly milling zirconia computer-aided design (CAD)/computer-aided manufacturing (CAM) crowns from fully sintered zirconia blocks using a five-axis laser milling system, compared with three-axis milling and full sintering by heating milled semi-sintered crowns, was investigated. The mechanical characteristics of zirconia specimens were similar across groups. The order of the marginal gap was three-axis>conventional (lingual thickness of 1.5 mm>0.5 mm)>five-axis group (close to zero). The marginal shape was almost perfectly circular in all groups. The internal corner shape and gap were almost perfect for the five-axis milled crown but not for conventional and three-axis crowns. The roundness of the marginal and internal shapes was almost perfect in the five-axis milling group but not for the three-axis and conventional groups. These small distortions result in large marginal gaps. Results of the present study suggest the superiority of the five-axis milling system in creating a zirconia prosthesis.

Effect of surface finish metallization on mechanical strength of Ag sintered joint

A micro-sized Ag paste was fabricated with the metal content of approximately 85% as a sinter-bonding material in this study. The sintering reactions and joint strengths of Ag sintered joints with three different surface finishes of Cu, Ag, and electroless Ni-immersion Au (ENIG) were evaluated at different sinter bonding times during the sintering process. Stable interfacial microstructures and relatively dense Ag sintered layers were formed in the three Ag sintered joints, and the interdiffusion behaviors between the Ag paste and substrate metals promoted in the formation of good metallurgical bonding during the Ag sintering process, regardless of surface finish. The bonding time of 10 min was sufficient for full sintering reactions between the chip and different substrate finishes. The shear strength did not increase with increased sintering time regardless of surface finish. The substrate metals strongly affected the die shear strengths of the Ag sintered joints, and the Ag-finished joint had a more stable interfacial microstructure and superior shear strength compared to the other metal-finished joints.

Effects of hydrogen content on powder metallurgy characteristic of titanium hydrides

The titanium dihydride (TiH2) powder metallurgy has been attracted a lot of attention, but TiH2 powder is difficult to press moulding. In this paper, the titanium hydride powder metallurgy including TiH2 and unsaturated titanium hydrides (TiH1.5) was investigated simultaneously compared with pure titanium metal powder metallurgy. The results indicates that the titanium hydride powder metallurgy is accompanied by the deoxidation self-purification effect during dehydrogenation process for both of TiH2 and TiH1.5, which have higher sintering density than pure titanium. There are the three stages relative to densification rate, namely the slow, rapid and full densification stages for all of three materials. The compressive yield strengths increase rapidly in the rapid densification stage and are unchangeable almost in the full densification stage after holding 2 h at 1300 °C. The titanium hydride powder metallurgy is helpful to obtain much better mechanical properties than the pure titanium metal powder metallurgy. Here the compressive yield strength of the as-sintered TiH2 compact with the maximum hydrogen content is the best but has very small difference compared with that of the as-sintered TiH1.5 compact after full sintering densification.

Oscillating-plate shaping method for ceramic ball blanks

To improve the shaping efficiency and the accuracy of ceramic ball blanks, an oscillating-plate shaping method was developed. In the new shaping process, the ceramic ball blanks were pre-sintered to obtain enough strength to resist the crushing force, and then processed by the oscillating-plate shaping method. Owing to the improvements of sphericity and the size consistency of blanks, the efficiency of the followed lapping process for the fully sintered ceramic balls will be enhanced significantly. The motion of ball blank in the shaping process was investigated through kinematic simulation based on ADAMS model. Shaping experiments of O13 mm pre-sintered Si3N4 ceramic ball blanks were carried out. The average diameter of ball blank decreased from 13.097 ± 0.092 mm (Avg. ± SD.) to 12.407 ± 0.007 mm, and the sphericity was improved from113.9 ± 42.7 to 4.5 ± 1.6 μm in 45-min shaping. The lapping experiments to reduce the sphericity error of shaped and unshaped ceramic balls after the full sintering to 1 μm were also carried out. It takes 55 h for the shaped blanks and 135 h for the unshaped blanks respectively. The results show that the oscillating-plate shaping is a promising method to improve the processing efficiency of ceramic balls significantly by the improvements of the sphericity and size consistency of the as-received ceramic ball blank.

Fabrication of Metal-Supported Solid Oxide Fuel Cells by Sinter-Joining Method with Silver Bonding Layer

Solid oxide fuel cell (SOFC) is an energy conversion device which generates electricity from hydrogen. SOFC is attracting attentions because of its high energy conversion efficiency and low material cost. For these reasons, SOFC are widely studied to be applied to various power generation systems such as stationary power plant, residential power system, auxiliary power unit (APU), etc. For APU applications, high mechanical strength is required to endure mechanical vibration and external shock during the driving of vehicles, which makes ceramic-based SOFC unsuitable. To overcome this limitation, metal-supported SOFC has been proposed. Metal-supported SOFCs are composed of metal substrate which supports ceramic layers of anode, electrolyte, and cathode. For more than past ten years, various types of metal-supported SOFC have been developed in many organizations. However, conventional metal-supported SOFCs had limitations of high cost thin film coating process such as sputtering, plasma spray, etc, sintering at reducing atmosphere, and unsintered cathode. In our research group, metal-supported SOFCs fabricated by sinter-joining method were developed. To fabricate metal-supported SOFCs by sinter-joining method, metal substrates were bonded to conventional ceramic cells by bonding paste composed of mixture of stainless steel, nickel oxide, yittria-stabilized zirconia (YSZ). Recently, silver has been proposed as bonding materials. By using silver as bonding materials, bonding of ceramic cell can be performed at temperature lower than 950 °C at air atmosphere, which enables full sintering of cathode. This has been rarely reported because conventional metal-supported SOFCs were fabricated by sintering at reducing atmosphere to prevent oxidation of metal substrate during the sintering. Furthermore, it is believed that electrical conductivity, thermal conductivity are improved, leading to lower ohmic resistance and better temperature distribution of metal-supported cells. In this work, 5 x 5 cm2 metal-supported SOFCs with silver bonding layer was successfully fabricated. The microstructure of bonding layer was investigated, which showed good adhesion of silver bonding layer. Electrochemical performance and impedance spectra were studied. Power density of 433 mW/cm2, ohmic resistance of 0.52 Ω cm2, polarization resistance of 0.16 Ω cm2 at 800 °C were obtained, and it is believed that high power density was attributed to low polarization resistance by full sintering of cathode. Metal-supported SOFCs fabricated by sinter-joining method showed 10 times higher mechanical strength than conventional ceramic cells.

Fabrication of Metal-Supported Solid Oxide Fuel Cells by Sinter-Joining Method with Silver Bonding Layer

Solid oxide fuel cell (SOFC) is an energy conversion device which generates electricity from hydrogen. SOFC is attracting attentions because of its high energy conversion efficiency and low material cost. For transportation applications, high mechanical strength is required, which makes ceramic-based SOFC unsuitable. To overcome this limitation, metal-supported SOFC has been proposed. In this work, metal-supported SOFCs are developed by bonding metal substrates to ceramic cells with silver bonding paste. By using silver as bonding materials, bonding was performed at temperature lower than 950 °C at air atmosphere, which enables full sintering of cathode. Furthermore, electrical conductivity, thermal conductivity are improved, leading to lower ohmic resistance and better temperature distribution of metal-supported cells. As a result, 5 x 5 cm2 metal-supported SOFCs with power density of 433 mW cm-2 at 800 °C were fabricated. The metal-supported SOFCs showed 10 times higher mechanical strength than conventional ceramic cells.

Process development toward full-density stainless steel parts with binder jetting printing

Abstract In the Additive Manufacturing (AM) community, the binder jet printing (BJP) process is known to produce parts not suitable for most structural applications due to the insufficient consolidation of the powder in the finished part. A new processing protocol for the BJP is presented to reach near full density and better surface finish for stainless steel (SS) parts. Two main modifications from the standard BJP processing are (1) the use of the mixtures of various powders and (2) the adaptation of a full sintering cycle in a vacuum furnace. Two distinct average particle sizes of SS powder were used to improve the packing density in the printing stage. Improving the packing density of the printed powder helps to consolidate the powder better and to reduce the shape distortion in the final parts. More importantly, an extremely small amount of the sintering additive was added to enhance the densification, which reduces the sintering time and temperature. In particular, up to 0.5 wt% of boron compounds as sintering additives were used to achieve a near full density in the final part. Thus, the starting powder, consisting of two distinct SS powders and sintering additive, is mixed before building a part in a layer-by-layer fashion. After completing the printing process with a binder phase, the printed powders are cured and the binder phase is burned out at 460 °C before sintering at 1250 °C for 6 h in a vacuum furnace to reach near-full densities (up to 99.6%). A subtle difference between SS 420 and SS 316 was evident because the enhanced oxidation during the binder burnout cycle on SS 316 due to a higher surface area of the SS 316 powder used in the experiment. The main contribution of this work is to provide the BJP process an important ability to fully consolidate the powders under an isothermal condition, which enable us to produce the final parts without residual stresses.

Liquid Phase Sintering of (Ti,Zr)C with WC-Co.

(Ti,Zr)C powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,Zr)C, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,Zr)C phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ1) or Zr (γ2). The γ2 phase grains have a core-shell structure with a (Ti,Zr)C core following the full sintering cycle. The major differences observed in (Ti,Zr)C with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ1, and γ2) is about 10% smaller in WC-(Ti,Zr)C-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

Immobilisation process for contaminated zeolitic ion exchangers from Fukushima

AbstractThe clean-up of the Fukushima Daiichi site, after the March 2011 earthquake and tsunami, continues to generate large amounts of spent adsorbents. These adsorbents need to be disposed of permanently in a low temperature immobilisation process to avoid volatilising radioactive Cs and Sr species. To this end an immobilisation process with a maximum temperature of 600 °C was developed by sintering model waste with glass frit to form a dense Glass Composite Material (GCM) wasteform. A zeolitic model wasteform, chabazite, was sintered with a lead borosilicate glass composition at a maximum temperature of 600 °C. The sintering process was optimised with various thermal treatment steps to ensure that volatile species, aqueous or otherwise, were released before full sintering to yield a dense final wasteform. With this process dense wasteforms of up to 40 wt. % chabazite have been achieved.

Fully-Enclosed Ceramic Micro-burners Using Fugitive Phase and Powder-based Processing.

Ceramic-based microchemical systems (μCSs) are more suitable for operation under harsh environments such as high temperature and corrosive reactants compared to the more conventional μCS materials such as silicon and polymers. With the recent renewed interests in chemical manufacturing and process intensification, simple, inexpensive, and reliable ceramic manufacturing technologies are needed. The main objective of this paper is to introduce a new powder-based fabrication framework, which is a one-pot, cost-effective, and versatile process for ceramic μCS components. The proposed approach employs the compaction of metal-oxide sub-micron powders with a graphite fugitive phase that is burned out to create internal cavities and microchannels before full sintering. Pure alumina powder has been used without any binder phase, enabling more precise dimensional control and less structure shrinkage upon sintering. The key process steps such as powder compaction, graphite burnout during partial sintering, machining in a conventional machine tool, and final densification have been studied to characterize the process. This near-full density ceramic structure with the combustion chamber and various internal channels was fabricated to be used as a micro-burner for gas sensing applications.