Powder Paste Research Articles

반응표면분석법을 이용한 연잎분말과 백앙금 첨가 양갱의 제조조건 최적화

반응표면분석법을 이용한 연잎분말과 백앙금 첨가 양갱의 제조조건 최적화

Development of copper powder paste for direct printing and soft mold casting

Recently, additive manufacturing (AM) of metals has enjoyed significant advancement. While the mainstream AM methods utilize high-energy power beams to melt metal powders, other low-cost alternatives are also being developed (e.g., direct ink printing). In this study, a copper powder-binder paste is developed, which is not only capable to be used for direct printing, but also to be cast using soft molds. Dense three-dimensional parts can be obtained by sintering green bodies. The electrical and mechanical properties of the sintered samples are evaluated by conductivity, hardness measurements and tensile tests, respectively. The results are comparable to other powder processed copper materials.

Cause and mitigation of dilatancy in cement powder paste

Superplasticiser (SP) becomes essential in contemporary concrete manufacturing because it decreases the water demand for a prescribed set of concurrent strength and workability requirement. On the other hand, SP also creates unfavourable dilatancy (i.e. shear thickening) that decreases the uniformity of mixing and pumpable distance of concrete, as well as creates difficulty in in-situ handling. Although it is known that the dilatancy is created by clustering of free and adsorbed polymers of SP, the correlation of them is not fully understood. Herein, the dilatancy of cement powder paste was studied using a co-axial rheometer. It is evident that with the addition of SP, dilatancy of paste increases initially from zero up to certain dosage. Further addition of SP decreases dilatancy as it effectively disperses the cement particles. At a given SP dosage, replacing cement partially with pozzolanic filler such as fly ash or silica fume can effectively decrease dilatancy depending on SP dosage. It is because the fillers can fill up the interstitial void of the cement particles and free up more water for cement hydration to produce Ca2+ via ettringite formation. Hence, it attracts more negatively charged SP to adsorb to the cement surface, and decreases the free SP polymers that cause dilatancy.

Understanding the effect of particle size of waste concrete powder on phosphorus removal efficiency

Reusing of fine particles of waste concrete (FPWC) is a disturbing problem for waste concrete recycling process. In this study, the FPWC developed from waste concrete was used as an innovative absorbent to remove phosphorus (P) from wastewater. The results showed, with the change of particle size of the FPWC, the maximum phosphorus binding capacity of the FPWC varies in the range of 1.07–4.96 mg P/g. The P-removal ability of FPWC increases as its particle size decreases, because of the FPWC with smaller particle size has more Ca-rich and porous hardened cement paste (HCP) powder. A “components separation” mechanism was proposed to explain the change of HCP powder content in FPWC with different particle size distribution. Both the Thomas and Yoon-Nelson model can be used to describe the P-removal behaviors of FPWC. The phosphorus removal mechanism is that the Ca2+ and OH− can release from HCP powder and forms a local alkaline condition with high Ca2+ concentration. The condition was beneficial to the formation of Ca5(PO4)3(OH) which could be attached on the surface of the FPWC. Based on the Fick’s law, the Ca2+ release behavior form FPWC can be separated into two stages, and it could be described by pseudo-second order model. Totally, FPWC developed from waste concrete blocks exhibited sufficient potential in phosphate removal.

Development of lime-pozzolan green binder: The influence of anhydrous gypsum and high ambient temperature curing

This study aims to improve the physico-mechanical properties of slaked lime – fly ash (FA) – ceramic waste powder (CWP) pastes through the incorporation of anhydrous gypsum (G) supported by thermal curing. Initially, the lime- FA paste was prepared with a ratio of (30/70 wt) as a reference binder. The FA was partially replaced with 5–25% of CWP material. The substitution of FA by CWP up to 20% exhibited a slight enhancement in the compressive strength at early and later ages of hydration. Adding 10% G provided additional improvements in the compressive strength, capillary water absorption and microstructure; this is confirmed by the thermogravimetric (TGA) and scanning electron microscopy (SEM) analyses. The high ambient temperature curing at 50 ͦC was found to be remarkably useful for improving the compressive strength of the gypsum containing composites at early age. The developed composites showed high solar reflectivity values which recommend for green building rendering applications. Such a kind of binder material could be helpful in reducing the negative impact of traditional Portland cement (PC), decreasing the ceramic waste disposal and contributing to the energy saving approach in building sectors.

Preparation of Metal Lead from Waste Lead Paste by Direct Electrochemical Reduction in NH3-NH4Cl Solution

Metal lead was first prepared from waste lead paste by direct electrochemical reduction in NH3-NH4Cl solution. Cyclic voltammetry of waste lead paste powders indicated that waste lead paste could be directly electrochemically reduced to metal lead. After constant cell voltage electrolysis for 3 h, waste lead paste pellets were almost completely converted into metal containing 98.3% lead, and the current efficiency and energy consumption were approximately 86.3% and 689.4 kW h/t, respectively. In addition, an empirical model of direct electrochemical reduction of waste lead paste pellets in NH3-NH4Cl solution has been proposed. Metal lead was initially formed at a three-phase interface of the current collector, waste lead paste and electrolyte; then, the newly formed three-phase interface of the metal lead, waste lead paste and electrolyte quickly expanded along the surface of the pellets and eventually extended into the interior of the pellets.

A Microstructure Obtained on AISI 1018 and AISI M2 Steel by Powder Paste Pack Boriding Process

A Microstructure Obtained on AISI 1018 and AISI M2 Steel by Powder Paste Pack Boriding Process

Improved efficiency in front-side illuminated dye sensitized solar cells based on free-standing one-dimensional TiO2 nanotube array electrodes

Although morphological disorder of nanotube structure is further down than the nanoparticular electrode, its density of traps are the hindering effects in the charge transport. In this study, crack-free TiO2 nanotube membranes, which obtained through a re-anodizing process, are fixed on transparent fluorine–tin-oxide glass by applying a few drops of Titanium Isopropoxide without needing the TiO2 powder paste. Front-side illuminated dye sensitized solar cells fabricated by undoped, N-doped and blue TiO2 nanotube membranes are investigated. The electrical characteristics of TiO2 nanotube based dye sensitized solar cells are followed by theoretical analysis using simple one-diode model. Morphology improvement is utilized to remove top irregular layers and the efficiency can be increased up to 56%. Annealing temperature, dopant, and tube orientation effects are examined on the cell efficiencies. The results show that elevating annealing temperature from 480 to 520 °C improve the cell efficiency up to 70%. Also, in the N-doped TiO2 nanotube membranes, improvement in efficiency is observed up to 40% as compared to undoped samples. Finally, different orientations of N-doped TiO2 nanotubes are studied and it is found that the through-hole morphology of N-doped TiO2 nanotube membrane shows noteworthy enhancement and an efficiency of about 8%.

Tailoring a Silver Paste for Additive Manufacturing of Co-Fired Ferrite Magnetic Components.

Additive manufacturing (AM), or 3D-printing, has the potential for rapid prototyping of innovative designs of magnetic components used in power electronics converters. In this study, we tailored a silver paste as the metal feedstock of an extrusion 3D printer so that the metal would be compatible with a ferrite paste feedstock for 3D-printing of ferrite magnetic components. We focused on adjusting the metal formulation to match its shrinkage to that of the ferrite and to improve adhesion during the co-sintering process of the printed part. We found that a 5 wt % addition of ferrite powder in the metal paste can achieve matched shrinkage and strong adhesion. Evaluation of the co-sintered magnetic components showed no significant defects, such as cracks, warpage, or delamination, between the metal and ferrite. The shear strength between the two sintered materials was greater than 50 MPa, and the electrical resistivity of the sintered metal winding was less than twice that of the bulk silver, which is lower than those of most 3D-printed winding metals reported in the literature.

Optimum Volume of Water Needed for the Paste State of Pediatric Powders: Considerations Based on Yield Values and Applications to Generic Medicine

To clarify the volume of water required to paste pediatric powders, we herein established a standard for the powder paste state by measuring yield values when water was added to powders. The powders used in the present study were selected from 8 types including original and generic drugs. Tipepidine hibenzate is prescribed in the pediatric field in combination with ambroxol hydrochloride and l-carbocysteine. The volumes of water needed to achieve the paste state of ambroxol hydrochloride between the original and generic drugs were similar. However, the volumes of water needed for l-carbocysteine markedly differed between the original and generic drugs due to differences in their additives. The spreadability of the mixture when water was added to the powders was evaluated using a spread meter. Among the powders tested in the present study, the yield value to achieve a paste state with the addition of water was approximately 1000 dyne/cm2. The optimum volume of water estimated from this yield value using the linear proportional relationship for the amount of powder may be applied to the mixture of each pediatric power for dosage/body weight.

Effect of Dispersant and Silane on Dispersion of Magnetic Powder Paste

Effect of Dispersant and Silane on Dispersion of Magnetic Powder Paste

Korean Traditional Seasoning Dried Soybean Paste Powder Prepared by Different Air Drying Temperatures

Korean Traditional Seasoning Dried Soybean Paste Powder Prepared by Different Air Drying Temperatures

Carbonation-cementation of recycled hardened cement paste powder

Well-hydrated cement paste powder was prepared to imitate recycled hardened cement paste powder. Compacted blocks were formed with the powder, and subjected to carbonation at different CO2 pressures. The effects of water/powder (w/p) ratio and compacting pressure in block preparation, and the CO2 pressure on the carbonation degree and compressive strength of the carbonated blocks were studied. The mineral compositions, microstructures and pore structures of the carbonated blocks were analyzed by XRD, SEM and MIP. The results show that the hardened cement paste powder in the blocks is able to re-cement and produce high level strength by carbonation. In the CO2 pressure range of 0.05–0.40 MPa, the higher the CO2 pressure was, the higher the carbonation degree and compressive strength of the blocks at all the carbonation times. Carbonated blocks with the compressive strength as high as 62.6 MPa were prepared by carbonation in 0.4 MPa CO2 for 24 h. The calcium hydroxide, calcium silicate hydrates and the un-hydrated β-C2S in the hardened cement paste powder were almost fully carbonated in 24 h. There was no new well-crystallized mineral other than the three polymorphs of calcium carbonate, mainly calcite, formed during the carbonation. The microstructures became more compacted due to the filling of the pores by CaCO3 and the other carbonation products such as low calcium silicate hydrates, companied with the decrease of the porosity and the pore sizes.

Behavior of high performance concrete pastes with different mineral admixtures in simulated seawater environment

With the blooming of ocean construction engineering, the influence of seawater on concrete durability draws increasing attentions. This paper investigates the performances of five high performance concrete (HPC) pastes, including pure cement paste, fly ash (FA) paste, limestone powder (LP) paste, ground granulated blast-furnace slag (GGBS) paste and silica fume (SF) paste, soaked in simulated seawater. The results indicate that the addition of FA would improve the strength of paste soaked in simulated seawater compared to pure cement paste from 90 d to 360 d and the order of strength in 360 d was, FA paste > Pure cement paste > LP paste > GGBS paste > SF paste. All mineral admixtures except LP can inhibit the expansion of paste soaked in simulated seawater at later age and the order of expansion rate in 360 d was, LP paste > Pure cement paste > FA paste > GGBS paste > SF paste. The internal structure of pastes soaked in simulated seawater at 360 d mainly contains Ca(OH)2, AFt, gypsum, Mg(OH)2, C3S and C2S while the external structure of pastes mainly contains Mg(OH)2, CaCO3 and AFt through the XRD spectra. SEM results proved that the addition of mineral admixtures can make the structure of the pastes denser.

3D printed milk protein food simulant: Improving the printing performance of milk protein concentration by incorporating whey protein isolate

Abstract This paper aimed to establish a milk protein based 3D printing food simulant and investigated the effect of whey protein isolate (WPI) concentration on the printing performance of milk protein concentrate (MPC). WPI and MPC powders at different ratios were prepared in paste (35 wt%, total dry matter content). The rheological properties and water distribution of protein matrix prepared with different MPC/WPI ratios were characterized with a rheometer and low field nuclear magnetic resonance (LF-NMR), respectively. Moreover, the variations in the microstructure of printed objects were observed with a scanning electron microscope (SEM). The printed objects showed different appearance and physical properties; the printing fidelity was also evaluated by measuring the geometric accuracy of printed objects. The rheological and texture data showed that the presence of WPI could reduce the apparent viscosity and soften the MPC paste, benefiting the printing process. The results showed that the milk powder paste mixture prepared with MPC/WPI at a ratio of 5/2 was the most desirable material for extrusion-based 3D printing, which could be successfully printed and matched the designed 3D model best. Industrial relevance 3D printing in food sector has been an attractive and emerging technology owing to its potential advantages, such as customized food designs, personalized and digitalized nutrition, simplifying supply chain and so on. This paper established a high protein food simulant for 3D printing, optimized its printing performance with whey protein isolate, and studied the physicochemical property of prepared protein pastes. The overall results indicated that milk protein powders could be the promising materials for the application in food 3D printing. In flowing studies or practical production, the glycerol could be replaced by ingredients such as syrup, honey etc. This study may give more insights into 3D printing applied in food sector and facilitate the further developments of 3D food printing.

Effects of carbonated hardened cement paste powder on hydration and microstructure of Portland cement

Recovering aggregates from recycled concrete produces a large amount of powder, which contains hardened cement paste and is classified as a corrosive hazardous material. This study used CO2 to treat hardened cement paste powder and to investigate how the incorporation of uncarbonated and carbonated hardened cement paste powder into cement affects the hydration and microstructure development of cement. Carbonated hardened cement paste powder consists mainly of calcite and silica gel. Replacement of cement by uncarbonated cement paste powder content from 10 to 30% by the mass of cement decreases, while replacement of cement with 10–20% carbonated hardened cement paste powder increases the strength of cement up to 90 days. The replacement of cement with 30% carbonated waste paste powder slightly decrease the strength of the cement. The silica gel in carbonated hardened cement paste powder quickly reacts with calcium hydroxide and results in the formation of more C-S-H. The presence of calcite in carbonated hardened paste powder leads to the formation of calcium aluminate hemi-carbonate (CAHC) and calcium aluminate mono-carbonate (CAMC) thus to a stabilization of ettringite (AFt) compared with the control cement paste, in which portion of AFt converts to mono-sulphoaluminate. CAHC is less stable than CAMC and transforms to CAMC in about one week after its formation. These chemical actions lead to a lower porosity and a higher compressive strength for cement paste with carbonated hardened paste powder compared with the control cement paste.

Deterioration Characteristics of Cement-Limestone Powder Paste Under Compound Erosion Solution

The deterioration characteristics of cement-limestone powder paste under compound erosion solution were studied in this paper by determining the compressive and flexural strength of pastes, the hydration products and SEM micrographs. The results indicate that H+ and SO42- ions play major roles in compound erosion solution. Besides the neutralization reaction between H+ ions and Ca(OH)2, the reaction between Ca2+ ions and SO42- ions generates CaSO4·2H2O and results in expansion. The crystal hydration products of all pastes before erosion are Ca(OH)2 and some CaCO3 from unhydrated limestone powder. While after erosion, the content of CaCO3 and Ca(OH)2 decreases rapidly and more gypsum forms. Limestone powder may improve the resistance to compound erosion sometimes. The resistance to compound erosion solution of compressive strength becomes weaker with the increase of the dosage of limestone powder (LP), while that of flexural strength becomes stronger. The compound erosion resistance is strong for the pastes with fly ash (FA) and LP, which can accelerate the compressive and flexural strength over curing age. DOI: http://dx.doi.org/10.5755/j01.ms.24.2.17644

Laser Cladding by Printing Si Powder Paste on A1050 Al Alloy Surface

Laser Cladding by Printing Si Powder Paste on A1050 Al Alloy Surface

Study of the Effects of Marble Powder Amount on the Self‐Compacting Concretes Properties by Microstructure Analysis on Cement‐Marble Powder Pastes

The marble powder (MP), obtained from waste sludge marble processing, has a high specific surface area; this could mean that it can be used as filler added to self‐compacting concrete (SCC). The aim of this experimental work is to study the effects of the cement‐MP paste volume on the rheology in the fresh state and the hardened properties (compressive strength) of SCC by a microstructure analysis on paste samples with different amounts of MP. For all pastes, the morphological forms and the chemical composition of the main mineral components were analyzed by the scanning electron microscope (SEM) and X‐ray diffraction (XRD). The hydration, microstructure, and mineralogical changes has been studied. Experimental results show that the cement‐MP paste volume has significant effects on the self‐compacting and the self‐leveling properties in the fresh state of SCC. In addition, the paste volume has a significant contribution on the compressive strength of SCC. Results indicate also that the difference in chemical composition between MP and cement have not any contribution on the paste volume effects.

Raman spectroscopic investigation of Friedel's salt

Friedel's salt (FS) forms upon chloride binding in monosulphoaluminate (AFm) phase. This removes chlorides from the pore solution, hence, delays the initiation of steel-bar corrosion. Apparently, characterising and, in particular, monitoring the formation and the status of FS facilitate the prediction of the service life of reinforced concrete structures. Raman spectroscopy offers a potential for investigating FS. The current work characterised FS, including the synthesised pure FS, and the FS formed in a Portland cement (PC) paste powder, using a bench-mounted Raman spectrometer. The results revealed the full Raman spectra of pure FS between 200 and 4000 cm−1, including the featured Raman bands at 534/568 cm−1 and 783 cm−1 which correspond to the Al-OH stretching and bending vibration of FS respectively. Furthermore, similar Raman bands of FS were identified in PC paste sample subjected to accelerated chloride attack, further confirming the potential of Raman spectroscopy for distinguishing FS in cementitious materials.