Hard Agglomerates Research Articles

Assessing ceramic powder quality by activated Sinterability Test: The case of UO2

Ceramics fail by brittle fracture due to flaws and affect process yield. The starting material is usually in powder form. UO2 pellets are obtained by pressing powder, sintering and finish grinding. Large powder blends are usually accepted for pressing and sintering after evaluating a small representative powder sample by conducting a sinterability test under regular process conditions. On the other hand, this paper recommends activated sintering conditions, such as those achieved with additives or sintering atmosphere control. Many defects in ceramics have origins in the powder. For example, large hard agglomerates in the powder can cause packing difficulties in pressing. Defects that are not detected in normal sintering may be noticed more readily in activated sintering due to defect amplification. In sintering, open porosity ceases after reaching a density of ∼93 % TD. The residual closed porosity tends to shrink on further sintering. The temperature at which open porosity or permeability is lost shifts to a lower temperature in activated sintering. Yet, activated sintering is to be carried out at conventional high sintering temperature, to be able to amplify and expose pellet defects due to powder. Desintering is a result of large sized packing defects in the green body and premature loss of open porosity in the course of sintering. A descriptive model of desintering is suggested that takes into account powder specific surface area, sintering additive and atmosphere. There is no desintering when green microstructure is homogeneous with no density gradients and with uniformly distributed fine voids that shrink and close during sintering. A high-quality powder sample is one that results in high pelleting yield both in conventional and activated sintering. The low temperature sintering process for UO2 manufacture that did not progress due to thermal stability concerns in nuclear reactor, may be revived to lower nuclear fuel costs.

Understanding and mitigating temperature-induced agglomeration in silica-based chemical mechanical planarization (CMP) slurry storage

This study explores the impact of temperature on silica particle agglomeration in Chemical Mechanical Planarization (CMP) slurries during storage. Slurries were stored at 15 °C, room temperature, and 45 °C, and analyzed. ATR-FTIR, RAMAN, SEM, zeta potential, and LPC were employed providing qualitative and quantitative data on slurry stability and agglomeration tendencies. Elevated temperature storage significantly increased agglomeration and large particle counts with particle counts value of ∼1.2×107 Part./ml, likely due to water molecule dehydration leading to destabilization. Low-temperature storage also induced agglomeration but to a lesser extent with particle counts the value of ∼4.0×106 Part./ml compared with the RT (∼2.0×106 Part./ml). Short-term storage yielded soft agglomerates with LPC of ∼(2.0–4.0)×106 Part./ml, while long-term high-temperature storage led to hard agglomerates with LPC of ∼3.0×107 Part./ml. The ATR-FTIR and Raman analysis indicate that the spectroscopic features of the original slurry exhibited changes upon variation of storage temperature from RT to 15 and 45 °C. The study also explored the reversibility of agglomeration post-treatment, indicating a potential mitigation pathway. The results demonstrated an inverse relationship between temperature and dissolved oxygen (DO) in silica slurries. For example. the curves depict a decrease in oxygen content from ∼10 ppm at RT to 7 ppm at 45 °C with increasing aging time. A mechanism outlining the temperature and aging-induced agglomeration was proposed, linking temperature fluctuations and thermodynamic aspects to colloidal stability. These findings offer a robust understanding of temperature-induced agglomeration in silica-based CMP slurry storage, paving the way for developing strategies to alleviate these issues and ensuring consistent CMP performance in semiconductor manufacturing.

Pomegranate plasma heterostructure regulated 1D biomass derived microtube networks for lightweight broadband microwave absorber

The excessive aggregation of magnetic metal particles and the resulting skin effect tend to cause a serious imbalance in impedance matching, which hinders its application in aerospace and military wave absorption fields. Obviously, effective dispersion configuration and network construction are two practical measures to develop broadband lightweight absorbers. Based on the recycling theme, pomegranate plasma heterostructure regulated one-dimensional (1D) biomass derived microtube networks are achieved through the conversion and utilization of waste Platanus ball fibers. The metal–organic framework strategy successfully avoids the hard agglomeration of metal particles. The pomegranate seed-like heterostructure effectively modulated the impedance of carbon microtubes, resulting in coordinated dielectric and magnetic losses. Such composites exhibited an effective absorbing bandwidth of 6.08 GHz and a minimum reflection loss of −29.8 dB. This work provides a new approach for constructing sustainable ultralight electromagnetic wave absorbers using plasmon modification and a 1D built-up network structure.

Microstructure and high-temperature deformation performance of liquid-dispersed evaporated Nano-ZrTiO4 doping molybdenum alloy

To enhance the low-temperature plasticity and high-temperature strength of molybdenum alloys, we introduce a method of uniformly dispersing nano-ZrTiO4 particles within and between molybdenum grains. This approach effectively eliminates the formation of hard agglomerations between particles and leads to a further refinement of molybdenum grains. The research employs molecular level solid-liquid doping and subsequent liquid dispersion evaporation techniques to successfully synthesize Mo-ZrTiO4 nano-composite powder following H2 reduction. Subsequently, a novel fine-grained Mo-ZrTiO4 alloy sintered billet is successfully fabricated through cold isostatic pressing and high-temperature sintering. To assess the efficacy of the process, three sets of comparative experiments are designed, each employing different methods. The comparative studies have revealed compelling advantages of the liquid dispersed evaporated fine-grained samples of Mo-ZrTiO4. The key advantages identified are as follows:the samples demonstrate a refined grain size, ranging from 2 μm to 4 μm. Within the samples, the nano ZrTiO4 particles have an average size of approximately 200 nm. The density and Vickers hardness of the samples is measured at 10.21 g/cm3 and 268.5 ± 17HV0.2, respectively. The samples exhibit impressive toughness even at room temperature, notably, the high-temperature compressive strength of these samples surpasses that of the deformed samples reported in previous literature concerning this system. The mechanism of liquid dispersion evaporation method in grain nucleation, growth, and powder drying, reduction, and sintering processes was systematically elaborated. Simultaneously, a detailed analysis was conducted on two high-temperature strengthening mechanisms that impact the mechanical properties. The results indicate that this excellent performance can be attributed to the synergistic effect of both fine grain strengthening and uniform dispersion strengthening of second-phase nanoparticles.

5Y–ZrO2 NPs with high dispersity and excellent sintering performance prepared by a novel sol-gel-flux method in the NaCl system

Herein, to alleviate the hard agglomeration of ZrO2 nanoparticles (NPs) fabricated by the traditional sol-gel method (SGM), a novel sol-gel-flux method (SGFM) is applied to tailor ZrO2 nanoparticles (NPs) stabilized by 5 mol% Y2O3 (5Y–ZrO2) by in situ introduction of NaCl NPs among xerogel particles. The phase composition, micromorphology, surface area, and sintering performances of 5Y–ZrO2 products fabricated by SGM and SGFM are compared. The effects of calcination temperature on the phase composition, micromorphology, and particle size of 5Y–ZrO2 products prepared by SGFM are systematically investigated. The results show that the 5Y–ZrO2 particles prepared by SGM are severely agglomerated and irregular, while the 5Y–ZrO2 NPs prepared by SGFM are well dispersed, uniformly distributed, and quasispherical. The former can hardly be densified by sintering, while the latter shows excellent sintering performance. By sintering 5Y–ZrO2 NPs prepared by SGFM at 1200 °C for 3 h, 5Y-TZP with a high density and an average grain size of 0.29 μm is fabricated. The in situ generated NaCl particles effectively separate ZrO2 particles during sintering. The calcination temperature plays a crucial role in controlling the phase composition, agglomeration degree, micromorphology, particle size distribution, and particle size of 5Y–ZrO2 products synthesized by SGFM, and the optimal calcination temperature is suggested to be 790 °C.

Study of the interaction between a Mn ore and alkali chlorides in chemical looping combustion

Chemical looping combustion (CLC) is a novel technology for heat and power generation with inherent CO2 capture. Using biomass in CLC (bio-CLC), negative CO2 emissions can be attained. Biomass usually contains high content of alkalis (mainly K and Na) which can be problematic in the process, such as potential alkali-bed interaction, and this is the focus of current work. This work uses charcoal with and without the impregnation with alkali chlorides, KCl and NaCl. The results are compared to previous data from samples impregnated with K2CO3 and Na2CO3. A low-alkali braunite manganese ore is used as bed material to study the oxygen carrier interaction with the alkalis in cyclic experiments at 950 °C in a quartz batch fluidized-bed reactor. As compared to charcoal without alkali impregnation, the impregnation with KCl, NaCl, K2CO3, and Na2CO3 can improve the rate of gasification by a factor of 4, 3, 10, 8, respectively. Partial-defluidization of the braunite particles was found with all the alkali-fuels, although the extent differed, e.g., K2CO3 and KCl resulted in earlier onset of defluidization than Na2CO3 and NaCl. Further, indications of partial defluidization were earlier and more permanent with the carbonates than the chlorides. Partial agglomeration with soft agglomerates of the bed was observed, while hard agglomerations were never seen. Accumulation of K, Na, Si, and Ca was found in the agglomerates after cycles with K2CO3-charcoal and Na2CO3-charcoal, while little K and Na was detected in the bridges between particles after the KCl and NaCl cycles. A significant fraction of the alkali added was found in the oxygen carrier, with 80% or more being retained for the Na salts, and around 40% for the K salts. There was no clear difference between chlorides and carbonates with respect to retention. The fresh and used braunite have very similar reactivity with CH4 and H2, whereas some decrease in reactivity is noticed with CO.

Ta(B, C, N) and (Ta, Mi)(B, C, N) (Mi = Nb, W) ceramics by high‐energy ball milling: processing and solution mechanisms

AbstractIn order to study the solid‐solution process between amorphous BCN and metal Ta, Ta(B, C, N), (Ta, Nb)(B, C, N), and (Ta, W)(B, C, N) ceramics were prepared by high‐energy ball milling, and their phase composition, microstructures, and binding bonds have been analyzed. The results show that all the three ceramics are hard agglomeration state, formed by stacking of nanoparticles. The mechanical alloying process is accompanied by the formation of chemical bonds, such as B–Ta, N–Ta, C–Ta, and O–Ta for Ta(B, C, N) ceramic, and the order of solid solution is C > N > B. When heated at 1500°C, a second diboride phase precipitates from (Ta, Nb)(B, C, N) ceramic, whereas the second phase of WC gradually dissolved from (Ta, W)(B, C, N) ceramic. This work provides theoretical and data supporting to analyze the solid‐solution process of Ta(B, C, N) ceramic.

DEM modelling of breakage behaviour of semi-brittle agglomerates subject to compaction and impaction

Drug powder in API-only dry powder inhalers (DPIs) is prepared in a form of agglomerates for easy handling and transport. Agglomerates tend to recrystallize due to temperature variation or being stored in a high humidity environment, causing the formation of solid bonds between particles which makes the agglomerates more difficult to disperse. This paper conducted a numerical study of breakage of hard, semi-brittle agglomerates using the discrete element method (DEM). A solid bonding model was adopted to mimic the brittle behaviour of the agglomerates and the coarse grain (CG) approach was applied to reduce the number of particles in the simulations. The simulated agglomerates showed the breakage behaviour upon impaction with a wall comparable to the experimental observation. The agglomerates with reasonable CG scaling ratios had similar structural properties and mechanical strengths upon compaction. Upon impaction with a wall at different velocities and angles, the agglomerate breakage was dominated by the normal impact energy with impact angle approaching to 90-degree causing more damage to the agglomerates. Such behaviour was different from that of soft agglomerates held by the van der Waals force in which both normal and shear forces played important roles in agglomerate breakage. • The breakage of semi-brittle agglomerates subject to compaction and impaction was modelled by DEM. • Solid bonding force was adopted to mimic the brittle behaviour of agglomerates. • The simulations were comparable to experimental observation. • The distinctive semi-brittle breakage pattern of the agglomerates was different from that of the soft agglomerates. • The normal impact energy dominated the breakage of hard agglomerates.

Preparation of YAG nanopowders and ceramics via coprecipitation: Effects of treatment modes of precipitates

Effects of treatment modes of precipitates in the coprecipitation method on the resulting YAG nanopowders and ceramics are investigated. Three treatment modes for precipitates, namely, single water washing, water–ethanol washing, and water washing–ethanol immersion, are conducted to prepare the YAG nanopowders. The average particle size (∼62 nm) and distribution (mainly ranging from 30 to 110 nm) of the powders obtained by the three modes are similar. However, the dispersity of the three powders shows large differences. The nanopowder obtained via water washing–ethanol immersion possesses optimal dispersity without any agglomeration, whereas that obtained via single water washing comprises substantially hard agglomerations. The relative density, Vickers hardness, and optical in-line transmittance of the ceramics prepared via water washing–ethanol immersion, respectively, reach 99.85%, 14.1 ± .4 GPa, and 77.8% at 1064-nm wavelengths after spark plasma sintering. These results are markedly superior to those of the ceramics prepared using the two other modes (97.43%, 6.8 ± .7 GPa, and 17.2% at 1064-nm wavelengths and 98.97%, 10.2 ± .5 GPa, and 47.8% at 1064-nm wavelengths, correspondingly). Therefore, water washing–ethanol immersion is a sensible and advisable treatment mode of precipitates for preparing YAG nanopowder and ceramics via coprecipitation.

Low-Temperature Synthesis of Hollow β-Tricalcium Phosphate Particles for Bone Tissue Engineering Applications.

β-Tricalcium phosphate (β-TCP) has been extensively used in bone tissue engineering in the form of scaffolds, granules, or as reinforcing phase in organic matrices. Solid-state reaction route at high temperatures (>1000 °C) is the most widely used method for the preparation of β-TCP. The high-temperature synthesis, however, results in the formation of hard agglomerates and fused particles which necessitates postprocessing steps such as milling and sieving operations. This, inadvertently, could lead to introducing unwanted trace elements, promoting particle shape irregularity as well as compromising the biodegradability and bioactivity of β-TCP because of the solid microstructure of particles. In this study, we introduce a one-pot wet-chemical method at low temperatures (between 160 and 170 °C) to synthesize hollow β-TCP (hβ-TCP) submicron particles of an average size of 300 nm with a uniform rhombohedral shape. We assessed the cytocompatibility of the hβ-TCP using primary human osteoblasts (HOB), adipose-derived stem cells (ADSC), and antigen-presenting cells (APCs). We demonstrate the bioactivity of the hβ-TCP when cultured with HOB, ADSC, and APCs at a range of particle concentrations (up to 1000 μg/mL) for up to 7 days. hβ-TCP significantly enhances osteogenic differentiation of ADSC without the addition of osteogenic supplements. These findings offer a new type of β-TCP particles prepared at low temperatures, which present various opportunities for developing β-TCP based biomaterials.

Investigation of the influence of the mode of heat treatment of the initial powder on the efficiency of sintering zirconium ceramics by dilatometry

Using methods of synchronous thermal and X-ray structural analyzes applied to zirconium dioxide powders partially stabilized with yttrium obtained by chemical coprecipitation the processes of dehydration of these powders during annealing in air have been investigated. Using the dilatometry method, the regularities of compaction of powder compacts have been investigated with thermal sintering. It was found that the resulting powders mainly consist of the tetragonal modification zirconium dioxide and are nano-sized. The average particle size was 25 nm. The resulting powders are characterized by a high degree of agglomeration. It is shown that an increase in the thermal annealing temperature from 500 to 700ºС leads to partial baking of individual particles inside the agglomerate, and causes the formation of hard agglomerates, the presence of which complicates the processes of compaction and subsequent sintering. The presence of such agglomerates prevents the production of ceramics with high mechanical characteristics: density and porosity. Thermal annaling temperature increase leads to a decrease in the density of the sintered ceramic and a decrease in itshardness.

Bioactive Co(II), Ni(II), and Cu(II) Complexes Containing a Tridentate Sulfathiazole-Based (ONN) Schiff Base.

New Co(II), Ni(II), and Cu(II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with salicylaldehyde. Their characterization was performed by elemental analysis, molar conductance, spectroscopic techniques (IR, diffuse reflectance and UV–Vis–NIR), magnetic moments, thermal analysis, and calorimetry (thermogravimetry/derivative thermogravimetry/differential scanning calorimetry), while their morphological and crystal systems were explained on the basis of powder X-ray diffraction results. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from azomethine group and thiazole ring and one O atom from phenolic group. The composition of the complexes was found to be of the [ML2]∙nH2O (M = Co, n = 1.5 (1); M = Ni, n = 1 (2); M = Cu, n = 4.5 (3)) type, having an octahedral geometry for the Co(II) and Ni(II) complexes and a tetragonally distorted octahedral geometry for the Cu(II) complex. The presence of lattice water molecules was confirmed by thermal analysis. XRD analysis evidenced the polycrystalline nature of the powders, with a monoclinic structure. The unit cell volume of the complexes was found to increase in the order of (2) < (1) < (3). SEM evidenced hard agglomerates with micrometric-range sizes for all the investigated samples (ligand and complexes). EDS analysis showed that the N:S and N:M atomic ratios were close to the theoretical ones (1.5 and 6.0, respectively). The geometric and electronic structures of the Schiff base ligand 4-((2-hydroxybenzylidene) amino)-N-(thiazol-2-yl) benzenesulfonamide (HL) was computationally investigated by the density functional theory (DFT) method. The predictive molecular properties of the chemical reactivity of the HL and Cu(II) complex were determined by a DFT calculation. The Schiff base and its metal complexes were tested against some bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The results indicated that the antibacterial activity of all metal complexes is better than that of the Schiff base.

Improved thermal stability and luminescence properties of SrSi2O2N2:Eu2+ green phosphor by a heterogeneous precipitation protocol for solid-state lighting applications

The SrSi2O2N2:Eu2+ green-emitting phosphor, as a member of oxynitride phosphors, could greatly enhance the color quality of the white-light conversed by single yellow-emitting phosphor. However, SrSi2O2N2:Eu2+ phosphors prepared by traditional solid-state ways normally consist hard agglomerates with unevenly dispersed particles and therefore suppress the luminescence properties. This research proposes a heterogeneous precipitation protocol where precipitation process is introduced, in order to produce a precursor in the first phase. And in the second phase, a high-temperature solid-state process is adopted for obtaining the final product. The main results show that, for an optimized SrSi2O2N2:Eu2+ phosphor prepared using our protocol, (1) the SrSi2O2N2:Eu2+ particles are faceted and with smooth faces and (2) the phosphor photoluminescence, external quantum efficiency, stability against thermal exposure, and physical stability consistently outperform the current commercially used product. This research essentially provides an economic way for production of solid-state lighting with enhanced color quality.

Preparation of CaAlSiN3:Eu2+ red-emitting phosphor by a two-step method for solid-state lighting applications

In solid-state lighting applications, the CaAlSiN3:Eu2+ red-emitting phosphor can effectively improve the color quality of traditional white light produced by yellow phosphor conversion of light emitted by a blue chip. However, CaAlSiN3:Eu2+ phosphor synthesized by various methods usually consists of hard agglomerates with poorly dispersed particles, with consequently suboptimal luminescent properties. In this study, a two-step method is proposed in which a precipitation process is used to produce a precursor in the first step, and a high-temperature solid-state method is used to obtain the final product in the second step. NH4Cl flux is added in the second step to further improve the quality of phosphors. The main results show that: (1) CaAlSiN3:Eu2+ phosphor particles are well dispersed without any agglomerates, while the NH4Cl plays a key role in manipulating particle shape; (2) the photoluminescence intensity and external quantum efficiency of optimized CaAlSiN3:Eu2+ phosphor synthesized by the two-step method substantially outperform those of the corresponding commercial product.

Synthesis of SrFe(Al)O[formula omitted]–SrAl2O4 nanocomposites via green route

A ceramic nanocomposite of SrFe(Al)O3−δ and Sr3Al2O6 was obtained using the controlled combustion of a previously synthesized chitosan-Sr-Fe-Al precursor. The complex formed by chitosan and metal ions in the organometallic precursor was confirmed by FTIR, TGA and DSC analysis. The nanocomposite consisted of hard agglomerates containing nanoparticles of Sr-Fe-Al oxides with oval morphology and an average diameter ≤ 9 nm. The DRX analysis indicated a composition of SrFe(Al)O3−δ and Sr3Al2O6 phases. Also, HRTEM and XPS verified the formation of a principal phase of ceramic composite identified as SrFeO3–x(2.5 ≤ x ≤ 3.0) possibly of aluminum-substituted structure, and minority phases of SrAl12O19 and SrAl2O4. Furthermore, a by-product of strontium carbonate was found as traces on the composite oxide surface. It was attributed to solid-gas reactions of strontium oxide with carbon dioxide, the latter produced during the oxidative decomposition of the biotemplate. Also, moderated calcination temperature limits the total decomposition of SrCO3.

Electrical Explosion of Wires for Manufacturing Bimetallic Antibacterial Ti–Ag and Fe–Ag Nanoparticles

Using a simultaneous electrical explosion of two twisted wires, bimetallic Ti–Ag and Fe–Ag nanoparticles are synthesized, where the component ratios are 76–24 and 75–25, respectively. The resulting nanoparticles are characterized by the methods of X-ray diffraction analysis, transmission electron microscopy, thermal desorption of nitrogen, and microelectrophoresis. It is found out that the synthesized nanoparticles are mainly structured as Janus-nanoparticles, and in nanopowders they form weakly-bonded aggregates and hard agglomerates, where the particles are connected by silver ‘necks’. The negative charge of the particles and their ability towards degassing under ultrasonic action make it possible for the Ti–Ag and Fe–Ag to be used as effective antimicrobial modifiers of water-soluble polymers forming stable gel-like compositions. These compositions possess significant antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) bacteria, which exceeds that of similar compositions containing silver nanoparticles only.

Processing and Characterization of Extremely Hard and Strong Cu-(0-15 wt pct)Al Alloys

The present work investigates the microstructure development and mechanical properties of mechanically alloyed and hot-pressed copper (Cu)-X wt pct aluminum (Al) (X = 0, 3, 5, 10, 15) alloys. The morphology of the ball-milled Cu-Al powders changed from coarse flaky structure to small hard agglomerates with the addition of Al. It was observed that the density of Cu-Al samples varied between ~ 95 and 98 pct of theoretical density (ρth) after hot pressing (Temperature: 500 °C, Pressure: 500 MPa, Time: 30 min). The crystallite size of Cu-Al samples decreased for both the milled powders and hot-pressed samples. The XRD and SEM-EDS analyses of the hot-pressed samples confirmed the presence of α-Cu solid solution phases for the Cu alloyed with Al up to 5 wt pct. On the other hand, further addition of Al to Cu leads to the formation of both intermetallic compound (Cu9Al4) and solid solution phase. The nano-indentation tests indicated a significant increase in hardness (2.4 to 7.9 GPa) and elastic modulus (121.1 to 177.4 GPa) of Cu-Al alloys. The Cu-Al alloys were measured with very high compressive strength (813.8 to 1120.2 MPa) and the compressive strain varied in the range of 29.81 to 5.81 pct.

Poly(Lactic Acid)/Zno Bionanocomposite Films with Positively Charged Zno as Potential Antimicrobial Food Packaging Materials.

A series of PLA/ZnO bionanocomposite films were prepared by introducing positively surface charged zinc oxide nanoparticles (ZnO NPs) into biodegradable poly(lactic acid) (PLA) by the solvent casting method, and their physical properties and antibacterial activities were evaluated. The physical properties and antibacterial efficiencies of the bionanocomposite films were strongly dependent on the ZnO NPs content. The bionanocomposite films with over 3% ZnO NPs exhibited a rough surface, poor dispersion, hard agglomerates, and voids, leading to a reduction in the crystallinity and morphological defects. With the increasing ZnO NPs content, the thermal stability and barrier properties of the PLA/ZnO bionanocomposite films were decreased while their hydrophobicity increased. The bionanocomposite films showed appreciable antimicrobial activity against Staphylococcus aureus and Escherichia coli. Especially, the films with over 3% of ZnO NPs exhibited a complete growth inhibition of E. coli. The strong interactions between the positively charged surface ZnO NPs and negatively charged surface of the bacterial membrane led to the production of reactive oxygen species (ROS) and eventually bacterial cell death. Consequently, these PLA/ZnO bionanocomposite films can potentially be used as a food packaging material with excellent UV protective and antibacterial properties.

Synthesis of highly sinterable Yb:Lu2O3 nanopowders via spray co-precipitation for transparent ceramics

Abstract Highly sinterable Yb:Lu2O3 nano-powders without hard agglomeration were synthesized via a highly efficient spray co-precipitation method. The effects of the spray speeds on morphology and composition of the powders were investigated. The results showed that the composition and dispersion of precursor powders changed with the spray speed. When the spray speed reached 40 mL/min, the particles were spherical and showed higher uniformity. The pure phase Yb:Lu2O3 powder was obtained after calcining at 1000 °C for 2 h. The calcined powders were ball milled and dry-formed to prepare green body. Then the Yb:Lu2O3 transparent ceramic was fabricated by vacuum sintering at 1500 °C for 8 h and further hot isostatic pressing in an argon atmosphere.. The in-line optical transmittance of Yb:Lu2O3 transparent ceramic reached 82.05%@1000 nm and 81.08%@400 nm, respectively, and it had submicron level average grain size, which is an effective way to improve the optical properties of the transparent ceramic.

A novel green synthesis of γ-Al2O3nanoparticles using soluble starch

In this research, nanocrystalline [Formula: see text]-[Formula: see text] powders have been synthesized by a novel mechanochemical method, through thermal decomposition of the ammonium aluminum carbonate hydroxide (AACH) precursor. The route involved using low-cost [Formula: see text] and [Formula: see text] as raw materials and environmental-friendly soluble starch as an effective dispersant. The precursor and product were characterized by simultaneous thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show that spherical [Formula: see text]-[Formula: see text] nanoparticles without hard agglomeration and with particle size in the range of 20–30 nm can be obtained. The crystallite size of products measured from XRD, SEM and TEM were in good agreement. This novel mechanochemical method combined with the use of environmentally benign starch has the advantages of simple operation, low calcination temperature and environmental safety, and will have good prospects for commercial production.