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The purpose of this paper is to report on a study of the movement of the powder bed material during selective laser sintering (SLS) of bisphenol‐A polycarbonate (PC) powder and its effect on the morphology of the sintered specimen.

Two sintering experiments, i.e. single‐spot laser sintering and raster‐scan laser sintering, were carried out and the material movement mechanisms were investigated in situ and subsequently by scanning electron microscopy.

During the raster‐scan laser sintering process, the movement of the powder was found to be primarily perpendicular to the scanning direction. When sintering at a high laser power, it significantly affected the surface morphology of the sintered specimens and parallel surface bands occurred along the scanning direction.

Experiments were carried out on a modified laser engraving machine rather than a commercial SLS machine.

A schematic model of the material movement mechanism for each of the sintering strategies is presented.

The results further the understanding of the sintering behaviour of the powder bed.

Selective laser sintering (SLS) is an essential technology in the field of additive manufacturing. However, SLS technology is limited by the traditional point-laser sintering method and has reached the bottleneck of efficiency improvement. This study aims to develop an image-shaped laser sintering (ISLS) system based on a digital micromirror device (DMD) to address this problem. The ISLS system uses an image-shaped laser light source with a size of 16 mm × 25.6 mm instead of the traditional SLS point-laser light source.

The ISLS system achieves large-area image-shaped sintering of polymer powder materials by moving the laser light source continuously in the x-direction and updating the sintering pattern synchronously, as well as by overlapping the splicing of adjacent sintering areas in the y-direction. A low-cost composite powder suitable for the ISLS system was prepared using polyether sulfone (PES), pinewood and carbon black (CB) powders as raw materials. Large-sized samples were fabricated using composite powder, and the microstructure, dimensional accuracy, geometric deviation, density, mechanical properties and feasible feature sizes were evaluated.

The experimental results demonstrate that the ISLS system is feasible and can print large-sized parts with good dimensional accuracy, acceptable geometric deviations, specific small-scale features and certain density and mechanical properties.

This study has achieved the transition from traditional point sintering mode to image-shaped surface sintering mode. It has provided a new approach to enhance the system performance of traditional SLS.

This study aims at compensating for sintering deformation of components manufactured by metal binder jetting (MBJ) technology.

In the present research, numerical simulations are used to predict sintering deformation. Subsequently, an algorithm is developed to counteract the deformations, and the compensated deformations are morphed into a CAD model for printing. Several test cases are designed, compensated and manufactured to evaluate the accuracy of the compensation calculations. A consistent accuracy measurement method is developed for both green and sintered parts. The final sintered parts are compared with the desired final shape, and the accuracy of the model is discussed. Furthermore, the effect of initial assumptions in the calculations, including green part densities, and green part dimensions on the final dimensional accuracy are studied.

The proposed computational framework can compensate for the sintering deformations with acceptable accuracy, especially in the directions, for which the used material model has been calibrated. The precise assumption of green part density values is important for the accuracy of compensation calculations. For achieving tighter dimensional accuracy, green part dimensions should be incorporated into the computational framework.

Several studies have already predicted sintering deformations using numerical methods for MBJ parts. However, very little research has been dedicated to the compensation of sintering deformations with numerical simulations, and to the best of the best of the authors' knowledge, no previous work has studied the effect of green part properties on dimensional accuracy of compensation calculations. This paper introduces a method to omit or minimize the trial-and-error experiments and leads to the manufacturing of dimensionally accurate geometries.

The purpose of this paper on the one hand is to reduce the sintering temperature, shorten the sintering time and improve the electrical properties of the sample through the two-step flash sintering method and on the other hand is to study the effect of electric field on the phase structure, microstructure and electrical properties of the flash sintering sample.

In this paper, (Mg_1/3Ta_2/3)_0.01Ti_0.99O₂ giant dielectric ceramics were prepared by conventional sintering and two-step flash sintering, respectively. Further, the effect of electric field (600–750 V/cm) on the electrical properties of (Mg_1/3Ta_2/3)_0.01Ti_0.99O₂ giant dielectric ceramics was studied.

The results show that compared with the conventional sintering, the sintering temperature of the two-step flash sintering can be reduced by 200°C and the sintering time can be shortened by 12 times. All sintered samples were single rutile TiO₂ structure. Compared with conventional sintering, two-step flash sintering samples have finer grain size. The two-step flash sintered sample has similar dielectric properties to the conventional sintered sample. The dielectric constant of flash sintered samples decreases with the increase of electric field. When the electric field is 700 V/cm, the ceramic sample has the optimal dielectric properties, where the dielectric constant is approximately 5.5 × 10³ and the dielectric loss is about 0.18 at 1 kHz. Impedance spectroscopy analysis shows that the excellent dielectric properties are attributed to the internal barrier layer capacitance model.

This paper not only provides a new method for the preparation of co-doped TiO₂ giant dielectric ceramics but also has great potential in greatly improving efficiency and saving energy.

This study aims to develop a facile ligand-exchange strategy to promote nano-sintering of oleylamine (OAM)-capped silver nanoparticles (AgNPs). By using ligand exchange process with NH₄OH to remove OAM from the surface of AgNP, this study reports effectively reducing the sintering temperature of AgNPs to achieve low-temperature nano-sintering. Compared with untreated AgNPs of OAM-capped, NH₄OH-treated AgNPs possess superior sintering performance that could be applied to a fractional generator device as conductor and in favour of the fabrication of flexible circuit modules.

First, oleylamine is used as reductant to synthesize monodisperse AgNPs by a simple one-step method. Then ligand exchange is used with NH₄OH at different treating times to remove OAM, and micro-Fourier transform infrared spectroscopy and contact angle test are applied to clear the mechanism and structure characteristics of these processes. Finally, NH₄OH-treated AgNPs sediment sintering is used at different temperatures to test electrical resistivity and use ex situ scanning electron microscopy combined with in situ X-ray diffraction to study changes in microstructure in the whole nano-sintering process.

The AgNPs are always capped by organic ligands to prevent nanoparticles agglomeration. And oleylamine used as reductant could synthesize desirable size distributions of 8–32 nm with monodisperse globular shapes, but the low-temperature nano-sintering seemed not to be achieved by the oleylamine-capped AgNPs because OAM is an organic with long C-chain. The ligand exchange approach was enabled to replace the original organic ligands capped on AgNPs with organic ligands of low thermal stability which could promote nano-sintering. After ligand exchange treated AgNPs could be sintered on photo paper, polydimethylsiloxane (PDMS) and polyethylene terephthalate flexible substrates at low temperature.

In this research, the method ligand exchange is used to change the ligand of AgNPs. During ligand exchange, NH₄OH was used to treat AgNPs. Through the treatment of NH₄OH, the change of hydrophilic and hydrophobic properties of AgNPs was successfully realized. The sintering temperature of AgNPs can also be reduced and the properties can be improved. Finally, the applicability of the AgNPs sediment with this nano-sintering process at low temperature for obtaining conductive patterns was evaluated using PDMS as substrates.

This purpose of this study was to develop a 3D printer based on powder particle. The best degreasing and sintering process of a blank body was investigated to obtain a metal product with high precision and high surface finish. This process will greatly reduce the difficulty and cost of forming a complex metal product with high application value.

Stainless steel powder and polymer materials were mixed using a rubber mixing machine. The powders were granulated to prepare a mixed material. A powder feed 3D printer was used at low temperature (about 200°C) to print and degrease the body. A series of sintering experiments were performed to study the different sintering temperatures, and the physical and mechanical properties of the sample sintered under various conditions were compared to determine the best degreasing and sintering process.

The reaction at 1,370°C was the optimal route for the metal billet degreasing. The resulting metal products had fine structure and stable performance compared with the products with traditional powder metallurgy composition.

Most 3D printed metal powder materials rely on imports, which are expensive and increase the manufacturing cost. These drawbacks limit the application and development of metal 3D printing technology to a certain extent. The successful study of this molding method greatly reduces the difficulty and cost of forming complex metal products with high application value. This report will provide valuable guidance for sintering process and forming methods.

Projection sintering, a system for selectively sintering large areas of polymer powder simultaneously with a high-power projector is introduced. This paper aims to evaluate the suitability of laser sintering (LS) process parameters for projection sintering, as it uses substantially lower intensities, longer exposure times and larger areas than conventional LS.

The tradeoffs in sintering outcomes are evaluated by creating single layer components with varied exposure times and optical intensities. Some of these components were cross-sectioned and evaluated for degree of densification, while the single-layer thickness and the maximum tensile force was measured for the rest.

Shorter exposure times and higher intensities can create thicker and therefore stronger parts than when equal energy is applied over longer exposures. This is different from LS in which energy input (Andrew’s Number) is accepted as a reliable process variable. This difference is likely because significant thermal energy is lost from the sintering region during the exposure time – resulting in reduced peak temperatures. These thermal losses can be offset by imparting additional energy through increased exposure time or light intensity.

Most methods for evaluating LS process parameters, such as the energy melt ratio and Andrew’s Number, estimate energy input from basic process parameters. These methods do not account for thermal losses and assume that the powder absorbs all incident light. These methods become increasingly inaccurate for projection sintering with visible light where exposure times are much higher (>1s) and a larger portion of the light is reflected from the power’s surface. Understanding the appropriate sintering criteria is critical for the development of long-exposure sintering.

A new method of selectively sintering large areas is introduced that could sinter a wider variety of materials by enabling longer sintering times and may increase productivity relative to LS. This work shows that new processing parameters are required for projection sintering as traditional LS process parameters are inadequate.

This paper aims to find proper technological parameters of low-temperature joining technique by silver sintering to eventually use this technique for reliable electronic packaging.

Based on the literature and author’s own experience, the factors influencing the nanosized Ag particle sintering results were identified, and their significance was assessed.

It has been shown that some important technological parameters clearly influence the quality of the joints, and their choice is unambiguous, but the meaning of some parameters is dependent on other factors (interactions), and they should be selected experimentally.

The value of this research is that the importance of all technological factors was analyzed, which makes it easy to choose the technological procedures in the electronic packaging.

The purpose of the paper is the elucidation of certain mechanisms of laser material processing in general and laser micro sintering in particular. One major intention is to emphasize the synergism of the various effects of q‐switched laser pulses upon metal and ceramic powder material and to point out the non‐equilibrium character of reaction steps.

Recent results and observations, obtained in development of “laser micro sintering,” are surveyed and analyzed. By breaking down the overall process into relevant steps and considering their possible kinetics, an approach is made towards interpreting specific phenomena of laser micro sintering. Thermodynamics upon heating of the material as well as its photo‐electronic response to the incident radiation are considered.

The findings corroborate a model whereby short pulses of high intensity provide non‐equilibrium pressure conditions at the location of incidence, that allow for the melting of metal powder with an almost immediate expansion of a plasma and/or vapor bulb. Thereby the molten material is condensed and propelled towards the substrate. A final boiling eruption after each pulse is the reason for the morphology of the laser micro‐sintered surfaces and can prevent oxidation when the process is conducted under normal atmosphere. In sintering of ceramics, the short pulsed and intensive radiation increases the chance to excite the material even with photon energies below the bandgap value and it lowers the risk of running into a destructive avalanche.

Owing to the stochastic character of the respective sintering event, that is initiated by each individual pulse, the gathered data are not suitable yet for the formulation of an exact quantitative function between sintering behavior and laser parameters.

The qualitative findings yield a good rule of thumb for the choice of parameters in laser sintering on a micrometer scale and the model is conducive for advanced interpretation of other phenomena in laser material processing besides sintering.

The kinetics and thermodynamics of laser sintering with q‐switched pulses are approached by a qualitative explanation. The heterogeneous and non‐equilibrium character of the processes is taken into account; this character is often neglected by researchers in the area.

The purpose of this paper is to find optimal sintering conditions of silver-based nano-inks for achieving the high electrical conductivity of the deposited layers applied on polyimide foils as well as the influence of ageing on the electrical conductivity. Therefore, the investigation in the field of silver layers deposited by inkjet printing technology is presented in this paper.

The four-point resistance measurements were realized for a detailed and precise analysis of the resistance of two different silver layers under different sintering conditions depending on the type of nano-ink varied about the recommended values. Highly accelerated stress tests (HASTs) were also applied as an ageing method for confirmation of the high electrical stability of the silver layers.

The results prove the strong influence of the temperature and the time of the sintering process on the sheet resistance of the investigated silver-based layers deposited by inkjet printing technology on polyimide foils. The HASTs caused significant changes in the electrical conductivity for both nano-inks presented in this paper. The existence of noticeable dependence among the resistivity, thermal treatment and ageing was proved.

The main benefit lays in the optimization of sintering conditions to improve the electrical conductivity of the silver layers. The paper also presents a new approach for a stability analysis of the silver layers by HASTs.