Evaporation-condensation Mechanism Research Articles

Influence of rice husk dosage on PM emissions during the co-firing of coal with refuse derived fuel

A self-designed drop tube furnace (DTF) was constructed to investigate the particulate matter (PM) emissions generated from blending 0–30 wt% refuse derived fuel (RDF) and 0–20 wt% rice husks (RH) with bituminous coal during co-firing. The physiochemical characteristics of PM were determined using XRD, XRF, and SEM-EDS, and the creation of the liquid components at varying temperatures was investigated using theoretical thermodynamic calculations based on fuel composition and combustion atmospheres. The results demonstrated that blending 0–30 wt% RDF with coal did not result in significant PM emissions. PM0.5 and PM2.5 yields declined by 31.5% and 39.5%, respectively, with the addition of 20 wt% RH. By solely adding RDF, more Ca-Al-Si and K/Ca-Si formed viscous surfaces or particle bodies that could capture Ca/K vapor released from the volatiles of RDF in the gas bulk. Si-rich and Al-Si species from coal were consumed and transformed into Na/K-Ca-Al-Si to enhance the production of the liquid phase by the abundant Si in the volatiles of RH. Two possible paths of mineral transformations during co-firing were discussed to prove that alkali metals and alkaline earth metals preferentially condensed on Si-rich and Al-Si species to form liquid substances and capture the vapor and grains in the gas bulk, rather than combining with nonmetallic elements to generate precursors for PM generation via the evaporation–condensation mechanism. This study contributes to the search for an efficient pathway to realize simultaneous waste utilization and greenhouse gas reduction.

Flatbread baking process under time-varying input power in a home-scale electric oven: 3D CFD simulation with experimental validation

This study investigates the flatbread baking process in a home-scale electric oven by developing a three-dimensional transient numerical model using the finite volume method along with the discrete ordinates (DO) model, evaporation–condensation mechanism, and realizable k-ε model for the turbulent regime through the oven chamber. The validity of the proposed numerical model has been examined through a comparison with experimental data provided in this study, considering both scenarios with and without bread in the oven, where good agreement is observed between the numerical and experimental findings. Using the validated model, a qualitative and quantitative analysis is performed to study the flatbread baking process, focusing on temperature distribution within the oven and the bread as well as the degree of starch gelatinization during the baking process. The consideration of input power patterns is crucial in terms of both energy consumption and bread quality, making it imperative for electric oven designers. Consequently, under a fixed energy consumption of the oven, various time-varying input powers are employed to assess the bread baking process. For this purpose, six different scenarios are designed including constant elements power, linear/stepwise increase/decrease in elements power, and ON/OFF modes with constant power. The results demonstrate that employing time-varying input power profiles characterized by linear and stepwise decrease yields superior performance to control the baking process and quality of bread. However, preheating the oven prior to dough baking could potentially mitigate the impact of the input power profile type on the resulting final product.

Swift heavy ion irradiation effect on structural, morphological and mechanical properties of Zr70Ni30 metallic glass

Metallic glass films are considered for coating applications in the nuclear field owing to their advantageous performances. However, the response to irradiation remains to be more thoroughly characterized. Zr70Ni30 metallic glass films were irradiated by 0.71MeV/u129Xe23+ ions in the fluence range from 5 × 1012 to 8 × 1013 ions cm−2. The structural, morphological, and mechanical properties were determined using grazing incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM), and nanoindentation for the as-deposited and irradiated samples. The Xe ion induced surface smoothening, thereby increasing the corrosion resistance. One-dimensional power spectral density of the AFM data of irradiated film demonstrated that the irradiation-induced evolution of the surface morphology could be attributed to a transition between viscous flow and the evaporation-condensation mechanism. The amorphous structure was unaffected after irradiation up to a fluence of 8 × 1013 ions cm−2. Nanoindentation revealed first a softening as the fluence increases up to 4 × 1013 ions cm−2, reflecting the creation of free volume defects. Then the hardness and Young’s modulus slightly increase when reaching 8 × 1013 ions cm−2. Moreover, at a critical dose of 0.008 dpa, the hardness is found to increase. Moreover, the calculation of the inelastic thermal spike model reveals the formation of the track with a radius of 7 nm.

Winking filaments due to cyclic evaporation-condensation

Context. Observations have shown that some filaments appear and disappear in the Hα line wing images periodically. There have been no attempts to model these “winking filaments” thus far. Aims. The evaporation-condensation mechanism is widely used to explain the formation of solar filaments. Here, we demonstrate, for the first time, how multi-dimensional evaporation-condensation in an arcade setup invariably causes a stretching of the magnetic topology. We aim to check whether this magnetic stretching during cyclic evaporation-condensation could reproduce a winking filament. Methods. We used our open-source code MPI-AMRVAC to carry out 2D magnetohydrodynamic simulations based on a quadrupolar configuration. A periodic localized heating, which modulates the evaporation-condensation process, was imposed before, during, and after the formation of the filament. Synthetic Hα and 304 Å images were produced to compare the results with observations. Results. For the first time, we noticed the winking filament phenomenon in a simulation of the formation of on-disk solar filaments, which was in good agreement with observations. Typically, the period of the winking is different from the period of the impulsive heating. A forced oscillator model explains this difference and fits the results well. A parameter survey is also done to look into details of the magnetic stretching phenomenon. We found that the stronger the heating or the higher the layer where the heating occurs, the more significant the winking effect appears.

The Transient Performance-Evaluation Model for Desalination of Seawater Based on Matrix Algorithm – a Requirement for a Ported Arabic Smart City

Abstract Based on the transient performance model for desalination of seawater based on the matrix algorithm, the desalination device is designed according to the evaporation condensation mechanism of falling film in horizontal tube, and its structure operation and operation principle are analyzed. Then, the differential equation of the transient heat-conduction problem of the seawater desalination device is constructed. On the basis of experimental data or numerical calculation results, the temperature field of structure at some time is selected to form the snapshots matrix, and a set of optimal eigenorthogonal decomposition bases is obtained by eigenorthogonal decomposition of the snapshots matrix. Finally, the finite-element discrete scheme of the nonlinear transient heat-conduction problem is reduced by using eigenorthogonal decomposition bases of the linear problem, and the lower-order ordinary differential equations of the reduced-order model for the nonlinear transient heat-conduction problem of the seawater desalination device are obtained. The ordinary differential equations of the reduced-order model are solved by solving the ordinary differential equations of the reduced-order model. The distribution of the temperature field at each time of the structure is obtained. The performance of the model is verified by numerical examples under the conditions of two-stage temperature-difference heating and only the top-level heating. The results show that the model has good accuracy and efficiency.

Effect of TiO2 addition on phase stability and sintering behavior of 1 mol%La2O3 -2 mol%Gd2O3-2 mol%Yb2O3-6 mol%Y2O3 co-doped ZrO2

In this study, 1 mol%La2O3-2 mol%Gd2O3-2 mol%Yb2O3-6 mol%Y2O3 co-doped ZrO2 (LGYYSZ) with 0 mol%, 5 mol% and 10 mol% TiO2 additions were synthesised by solid-state reactions. The effect of TiO2 addition on the phase stability of LGYYSZ and its sintering behaviour at 1500 °C were investigated using XRD, SEM and EDS. The results show that the eutectic temperature of LGYYSZ decreases with increasing TiO2 content. SEM, EDS and XRD results show that the TiO2 addition is reacted with the La2O3 in LGYYSZ to form a orthorhombic La2Ti2O7 phase. When held at 1500 °C, La2Ti2O7 is precipitated on the surface of the samples by evaporation-condensation mechanism. This resulted in the anti-sintering properties of LGYYSZ at 1500 °C decreasing with increasing TiO2 content.

Spontaneous inversion of the submicron ceramic layer deposited on steel and the copper droplet positioned on their top (case of ceramic poorly wetted by liquid Cu)

In this paper, 50 … 680 nm thick AlN-Al2O3 coatings are deposited by magnetron sputtering on the surface of a steel substrate and a piece of copper is melted on top of the ceramic. Upon heating the ceramic layer is cracked, and the phase inversion of the two top phases from steel/ceramic/copper configuration to the steel/copper/ceramic configuration takes place within 30 s of liquid time of copper. This phase inversion process is accompanied by a Gibbs energy change of about − 1.78 J/m2, due to good wettability of solid deoxidized steel by liquid copper in contrary to poor wettability of the ceramic by the copper. When copper is melted on AlN-Al2O3 coating with its thicknesses smaller than a critical value of about 170 ± 60 nm, liquid copper droplets hanging down into the cracks within the ceramic reach the solid steel surface at the bottom of the cracks, thus the flow of Cu down along the cracks is enabled. However, when copper is melted on AlN-Al2O3 with its thickness larger than the critical value of 170 ± 60 nm, Cu first forms a non-wetting droplet on top of the ceramics, and only after a certain incubation time it starts flowing down the cracks. This incubation time was found to depend linearly on the thickness of the ceramic, as cracks are filled from the bottom upwards by liquid copper via the evaporation–condensation mechanism. By the end of the process, the steel/copper/ceramic configuration is further stabilized by gravity.Graphical abstract

In-Operando Observations of Ni-YSZ Patterned Fuel Electrodes Under SOFC and SOEC Operations

Solid oxide cells (SOCs), both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC), have being attracting more and more attention due to its high energy conversion efficiency and fuel flexibility. However, degradation of fuel electrodes after long-term operation remains as one of the main challenges for their commercial application. In particular, migration and coarsening of nickel (Ni) in Ni - yttria-stabilized zirconia (Ni-YSZ) fuel electrodes have strong impacts on the decreases in both active three-phase boundary (TPB) and Ni network connectivity, which result in performance deterioration. One of the mechanisms proposed as an explanation of Ni migration is Ni transport via volatile Ni(OH)x species, so-called evaporation-condensation mechanism [1]. On the other hand, Jiao and Shikazono [2] proposed a model to explain Ni spreading on YSZ surface based on the variation of Ni-YSZ wettability which is modified by the oxygen adsorption. Nevertheless, further investigations are required to understand the mechanisms of Ni migration. In the present study, Ni-film patterned electrodes which can provide well defined TPB configurations are used to investigate the Ni-YSZ degradation under SOFC, SOEC and sequential SOFC and SOEC operations, i.e. reversible operation (RSOC). The edge of sputtered Ni-film contacting with open YSZ surface can be treated as active TPB during operation. Confocal laser scanning microscopy (CLSM, Keyence, VK-X 1000) is used, which enabled in-operando observation of the real-time local morphological change at active TPB [3]. The in-operando potentiostatic experiment was carried out inside a high temperature chamber which was kept at 800oC with 4% H2O-4% H2-92% N2 as fuel gas and 30% O2-70% N2 as oxidant as shown in Fig. 1(a). The correlations between the Ni morphological changes and cells’ electrochemical performances were investigated. The Ni phase dynamically spread and de-percolated only under the SOFC operation, while such a phenomenon was not observed during the SOEC operation, as shown in Figs. 1(c), (d) and (e). Ni coarsening occurred regardless of the operation modes. The competition between Ni-film spreading and breaking-up finally determined the complicated local morphological change and corresponding cell performance variation. The time variations of active TPB and current density showed good correlation as shown in Fig. 1(b). Real-time in-operando observations revealed different Ni migration under SOFC, SOEC and RSOC operations, which may provide new insights for the understanding of Ni-YSZ fuel electrode degradation.Fig. 1. (a) Schematic illustration of in-operando setup. (b) Correlation between current density and Ni morphological evolution. (c)-(e) CLSM images and 3D surface height contour maps of the yellow-frame-enclosed areas after SOFC, SOEC and RSOC modes, respectively.

Interfacial-curvature-driven coarsening in mass-conserved reaction-diffusion systems

Mass conservation in chemical species appears in a broad class of reaction-diffusion systems (RDs) and is known to bring about coarsening of the pattern in chemical concentration. Recent theoretical studies on RDs with mass conservation (MCRDs) reported that the interfacial curvature between two states contributes to the coarsening process, reminiscent of phase separation phenomena. However, since MCRDs do not presuppose a variational principle, it is largely unknown whether description of surface tension is operative or not. In this study, we numerically and theoretically explore the coarsening process of patterns in MCRDs in two and three dimensions. We identify the parameter regions where the homogeneous steady state becomes stable, unstable, and metastable. In the unstable region, pattern formation is triggered by usual Turing instability, whereas in the metastable region, nucleation-growth-type pattern formation is observed. In the later stage, spherical droplet patterns are observed in both regions, where they obey a relation similar to the Young-Laplace law and coarsen following the evaporation-condensation mechanism. These results demonstrate that in the presence of a conserved variable, a physical quantity similar to surface tension is relevant to MCRDs, which provides new insight into molecular self-assembly driven by chemical reactions.

The study on the heater usage for better energy efficiency of domestic convection oven

In this study, the heater usage algorithm has been studied for cooking process in a domestic oven. For the analysis, numerical simulation and experimental study have been performed, focusing on heat distribution and heat loss mechanism. Better fidelity of baking process model was achieved by incorporating enthalpy jump at the phase change and evaporation-condensation mechanism into the thermal properties of cupcake. The result of heat flux calculation over enclosed walls shows that the back surface has the highest heat flux due to high temperature of convection heating during preheating process. During baking process, the heat flux on the top surface of cupcake on a upper tray was found to be about 1.8 times as that on the lower tray due to radioactive heat flux from grill heater. For an energy saving purpose, the more balanced use of heating units, for instance, more use of grill heater than convection heater, was recommended. The thermal conductivity of insulation material was a more important factor than specific heat on the power consumption during preheating.

Experimental study of the thermal characteristics of a heat pipe

The performance of a cylindrical heat pipe under various operating conditions was experimentally analyzed. The heat pipe consists of a copper tube with a diameter of 12.7 mm and 4 layers of copper screen mesh act as the wick. The heat pipe was equipped with a vacuum ball valve in order to charge the heat pipe with different amounts of working fluid. The effect of the working fluid fill volume, inclination angle, and heat input on the equivalent thermal resistance of the heat pipe were investigated. The results showed that in gravity-assisted orientations (condenser located above evaporator), the inclination angle has a negligible effect on the performance of the heat pipe. However, for gravity-opposed orientations (evaporator above condenser), as the inclination angle increases, the temperature difference between the evaporator and condensation increases which results in a higher thermal resistance. It was also found that if the working fluid in the heat pipe is under-filled, the capillary limit of the heat pipe decreases dramatically. However, overfilling of the heat pipe degrades the heat pipe performance due to excess liquid interfering with the evaporation-condensation mechanism. The results obtained from this experiment were also used to verify a previously developed numerical model. Very good agreement between the numerically predicted results and those from the experiment were obtained, thus validating the numerical technique developed and reported in authors’ previous papers.

Formation mechanism of large size plate-like Al4SiC4 grains by a carbothermal reduction method

Al4SiC4 was synthesized by a carbothermal reduction method and the formation process of large size grains is illustrated by an evaporation–condensation mechanism.

On the Effect of Re Addition on Microstructural Evolution of a CoNi-Based Superalloy

In this study, the effect of rhenium (Re) addition on microstructural evolution of a new low-density Co-Ni-Al-Mo-Nb based superalloy is presented. Addition of Re significantly influences the γ' precipitate morphology, the γ/γ' lattice misfit and the γ/γ' microstructural stability during long term aging. An addition of 2 at.% Re to a Co-30Ni-10Al-5Mo-2Nb (all in at.%) alloy, aged at 900°C for 50 hours, reduces the γ/γ' lattice misfit by ~ 40% (from 0.32% to 0.19%, measured at room temperature) and hence alters the γ' morphology from cuboidal to round-cornered cuboidal precipitates. The composition profiles across the γ/γ' interface by atom probe tomography (APT) reveals Re partitions to the γ' phase (KRe=0.34) and also results in the partitioning reversal of Mo to the γ' phase (KMo=0.90) from the γ' precipitate. An inhomogeneous distribution of Gibbsian interfacial excess for the solute Re (ΓRe, ranging from 0.8 to 9.6 atom.nm-2) has been observed at the γ/γ' interface. Coarsening study at 900°C (up to 1000 hours) suggests that the coarsening of γ' precipitates occurs solely by an evaporation-condensation (EC) mechanism. This is contrary to that observed in the Co-30Ni-10Al-5Mo-2Nb alloy as well as in some of the Ni-Al based and high mass density Co-Al-W based superalloys, where γ' precipitates coarsens by coagulation/coalescence mechanism with extensive alignment of γ' along directions as a sign of microstructural instability. The γ' coarsening rate exponent (Kr) and γ/γ' interfacial energy are estimated to be 1.41 x 10-27 (m3/s) and 8.4 mJ/m2, that are comparable and lower than Co-Al-W based superalloys respectively.

A thermophysical battery for storage-based climate control

Climate control applications in the form of heating and cooling account for a significant portion of energy consumption in buildings and transportation. Consequently, improved efficiency of climate control systems can significantly reduce the energy consumption and greenhouse gas emissions. In particular, by leveraging intermittent or continuous sources of waste heat and solar energy, thermally-driven energy storage systems for climate control can play a crucial role. We demonstrate the concept of a thermophysical battery, which operates by storing thermal energy and subsequently releasing it to provide heating and cooling on demand. Taking advantage of the adsorption-desorption and evaporation-condensation mechanisms, the thermophysical battery can be a high-power density and rechargeable energy storage system. We investigated the thermophysical battery in detail to identify critical parameters governing its overall performance. A detailed computational analysis was used to predict its cyclic performance when exposed to different operating conditions and thermodynamic cycles. In addition, an experimental test bed was constructed using a contemporary adsorptive material, NaX-zeolite, to demonstrate this concept and deliver average heating and cooling powers of 900W and 650W, respectively. The maximum power densities and specific powers observed were 103W/l and 65W/kg for heating, and 78W/l and 49W/kg for cooling, respectively, making the thermophysical battery competitive with the state-of-the-art climate control systems that provide relatively lower power densities. Additionally, with further opportunities for development and innovation, especially in synthesizing novel adsorptive materials, the thermophysical battery can achieve significantly higher power densities. With its ability to function using thermal energy input while being compact and lightweight, the thermophysical battery offers an option to address the energy challenges associated with the rising demand for climate control.

Thermal Cycling Behavior of Thermal Barrier Coatings with MCrAlY Bond Coat Irradiated by High-Current Pulsed Electron Beam.

Microstructural modifications of a thermally sprayed MCrAlY bond coat subjected to high-current pulsed electron beam (HCPEB) and their relationships with thermal cycling behavior of thermal barrier coatings (TBCs) were investigated. Microstructural observations revealed that the rough surface of air plasma spraying (APS) samples was significantly remelted and replaced by many interconnected bulged nodules after HCPEB irradiation. Meanwhile, the parallel columnar grains with growth direction perpendicular to the coating surface were observed inside these bulged nodules. Substantial Y-rich Al2O3 bubbles and varieties of nanocrystallines were distributed evenly on the top of the modified layer. A physical model was proposed to describe the evaporation-condensation mechanism taking place at the irradiated surface for generating such surface morphologies. The results of thermal cycling test showed that HCPEB-TBCs presented higher thermal cycling resistance, the spalling area of which after 200 cycles accounted for only 1% of its total area, while it was about 34% for APS-TBCs. The resulting failure mode, i.e., in particular, a mixed delamination crack path, was shown and discussed. The irradiated effects including compact remelted surface, abundant nanoparticles, refined columnar grains, Y-rich alumina bubbles, and deformation structures contributed to the formation of a stable, continuous, slow-growing, and uniform thermally grown oxide with strong adherent ability. It appeared to be responsible for releasing stress and changing the cracking paths, and ultimately greatly improving the thermal cycling behavior of HCPEB-TBCs.

Preparation of Sphere-like α-Al2O3 from Commercial Al(OH)3 with a Mechanical Ball Milling Process

In comparison to the typically worm-like α-Al2O3 powders of 20–30 µm size from unmilled Al(OH)3 precursor fired at 1450°C, almost-spherical α-Al2O3 powders of ∼0.5 µm size were synthesized from 9 h-milled Al(OH)3 precursor with the same heat treatment. The effect of the commercial Al(OH)3 precursor milling treatment on phase transformation and morphology of α-Al2O3 was studied by XRD and SEM. It was found that the milling treatment of the commercial Al(OH)3 precursor not only led ho an accleration of α-transformation during calcination, but also changed the morphology and particle size distribution of the α-Al2O3 powders. As the Al(OH)3 precursors were broken into irregularly shaped pieces with a ≤1 µm size range by the milling treatment, the resulting sharp corners with high vapor pressure would alter the evaporation-condensation mechanism into one that is mainly based on diffusion in the α-Al2O3 calcination process and promotes the tendency to form spherical α-Al2O3 powders.

Analysis of Moisture Transfer During the Drying of Clay Tiles with Particular Reference to an Estimation of the Time-Dependent Effective Diffusivity

The description of the drying process was reduced to the establishment of a series of theoretical and empirical drying models. The complex processes of simultaneous moisture and heat transfer, which are often nonstationary, and the distinct nature and properties of the material to be dried further complicate the description of the drying process. Three theories—diffusion theory, capillary flow theory, and evaporation–condensation theory—have won general recognition for the explanation of moisture transfer in porous media. The mechanisms of moisture movement during drying in the constant and especially in the falling drying period are rather complex and, hitherto, there have been no generally accepted explanations that could identify the exact transition between possible drying mechanisms, such as liquid movement due to capillary forces, liquid diffusion due to concentration gradients, liquid and vapor flow due to differences in total pressure, vapor diffusion due to difference in vapor concentration, vapor diffusion due to partial vapor pressure gradients, Knudsen diffusion, thermodiffusion, and the evaporation–condensation mechanism. The goal of this study was to find a way to better understand the different drying mechanisms, to identify the exact transition between them, and to estimate the time-dependent effective diffusivity. The results presented in this article confirmed that the effective diffusivity represents an overall mass transport property of moisture that includes all possible moisture transport mechanisms that are simultaneously controlling the moisture migration process in a material during drying. The experimental investigations were performed on clay tiles in a laboratory recirculation dryer, for which the drying parameters (humidity, temperature, and velocity) could be programmed, controlled, and monitored during drying.

A study of macrophysical and microphysical properties of warm clouds over the Northern Hemisphere using CloudSat/CALIPSO data

This study investigates the general macrophysical and microphysical properties of single-layer warm clouds over the Northern Hemisphere using standard CloudSat products during 2008. The yearly averaged occurrence frequency of single-layer warm clouds is 20.9% over oceans and 9.5% over land, respectively. The cloud top heights over land in different latitude zones exhibit a broader spectral width and more frequent occurrence of strong cloud systems in tropics than that over higher latitudes. The maximum values of liquid water content over land are approximately 10–30% smaller but the occurring altitudes are about 0.5 km higher than those over oceans with the same liquid water path (LWP). The reflectivity profiles clearly demonstrate the growth processes of cloud particles and how these processes vary with increasing LWP. The evolutions of reflectivity over land show a frequency shift toward weaker dBZ values relative to that over oceans with the same LWP, suggesting that high aerosol concentrations may induce suppressed drizzle and delayed precipitation in warm clouds. Additionally, there exists a significant difference between warm clouds formation at the initial stage over ocean and land areas. When LWP is 0.1–0.2 kg m−2 and optical depth exceeds 25, the dBZ values over oceans increase rapidly downward with increasing optical depth (decreasing height). The faster growth may be caused by the evaporation-condensation mechanism. Over land, however, large droplets are unlikely to appear in the early stage possibly because continental aerosols prevent the evaporation-condensation mechanism to occur, resulting in partially delayed drizzle formation.

Effects of domain morphology on kinetics of fluid phase separation

Kinetics of phase separation in a three-dimensional single-component Lennard-Jones fluid, that exhibits vapor-liquid transition, is studied via molecular dynamics simulations after quenching homogeneous systems, of different overall densities, inside the coexistence region. For densities close to the vapor branch of the coexistence curve, phase separation progresses via nucleation of liquid droplets and collisions among them. This is different from the evaporation-condensation mechanism proposed by Lifshitz and Slyozov, even though both lead to power-law growth of average domain size, as a function of time, with an exponent α = 1∕3. Beyond a certain threshold value of the overall density, we observe elongated, percolating domain morphology which suddenly enhances the value of α. These results are consistent with some existing theoretical expectations.

EFFECTS OF SINTERING TEMPERATURE ON THE DENSITY AND POROSITY OF SODIUM CHLORIDE PREFORMS FOR OPEN CELLED ALUMINIUM FOAM MANUFACTURING

Effects of sintering temperature on the density and porosity of sodium chloride preforms for alu- minium foam manufacturing have been investigated. Cold pressed salt preforms were sintered at 30‰, 760‰ and 790‰ and di erent times ranging between 6- 18 hours in a carbolite furnace at a heating rate of 5‰/minute. The Results of density and porosity measurements show that the density and porosity of the preform can be varied by changing the sintering temperatures of the preforms. It was observed that the density of the preforms increases with sintering temperature at constant time and pre-sintering pressure while porosity has an inverse relationship with tem- perature. Results of scanning electron microscopic analyses, show sintering connection (bonding) between the salt beads at all the temperatures in which sintering was performed. Sintering of the sodium chloride perform was attributed to grain boundary di usion and evaporation condensation mechanisms. Keywords : sintering, preform, density, porosity, aluminium foam