Low-temperature Solid-state Reaction Research Articles

Formation of CoAl2O4 nanoparticles via low-temperature solid-state reaction of fine gibbsite and cobalt precursor

Nanocrystalline cobalt aluminate (CoAl2O4) was synthesized by the solid-state reaction method with cobalt chloride hexahydrate (CoCl2 ċ 6H2O) as the source of Co and gibbsite (Al(OH)3) as the sourc...

Synthesis and electrochemical properties of submicron sized sheet-like LiV 3O 8 crystallites for lithium secondary batteries

Submicron sized sheet-like LiV 3O 8 cathode materials for lithium secondary batteries were synthesized via a simple processing, microwave hydrothermal improved low temperature solid-state reaction, with LiOH·H 2O, NH 4VO 3 and PVP as raw materials. The LiV 3O 8 crystallites prepared without PVP consists of smaller particle size than that prepared with PVP, and it exhibits relatively better electrochemical performance. The LiV 3O 8 crystallites prepared without PVP delivers an initial discharge capacity of 282.2 mAh/g at a current density of 100 mA/g. After 20 cycles, the discharge capacity retains 228.4 mAh/g corresponded to 80.9% of the initial value. The small submicron sized sheet-like LiV 3O 8 crystallites are expected to shorten the Li + ions diffusion path for its electrochemical properties. The good electrochemical properties of the as-synthesized LiV 3O 8 make them a promising candidate as a cathode material for lithium secondary batteries.

Facile Synthesis of Ammonium Aluminum Carbonate Hydroxide Multilayered Nanofiber by Using Solid State Reaction

In this paper, we make systematical investigation for the new synthesis pathway of AACH multilayered nanofiber, which has been prepared by a low-temperature solid-state reaction. The phase transformation sequence of AACH on heating is found that the precursor converts into γ-Al2O3at 700-900°C and elevated temperature results in the θ-Al2O3and α- Al2O3crystal phase formation at 1000°C. With a higher calcination temperature at 1100°C, α- Al2O3pattern appears. The specific surface area (SBET) of aluminum oxide specie calcined at 500°C for 4h is still in 420.2m2/g. Meanwhile, it suggests a partial change in particle sizes and morphology of sample calcined at 500°C for 4h.

Fabrication and Luminescent Enhancement of Eu3+-Doped Y2O3@YOF Core–Shell Nanocrystals

In this paper, a two-step synthesis method for preparing Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals is introduced. Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals were prepared by combining an autocombustion process with a low temperature solid state reaction. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and fluorescence decay were employed to characterize the prepared samples. The results of XRD, TEM and EDS indicated that the products prepared by this method were not a mixture of Y2O3:Eu3+ and YOF:Eu3+ nanocrystals, but Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals. Compared with Y2O3:Eu3+ nanocrystals, a 20% increment in luminescence intensity was observed in the Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals, thus suggesting that coating with a YOF:Eu3+-shell can efficiently block the nonradiative relaxation channels that are induced by surface defect states.

Electrochemical investigation of MnO 2 electrode material for supercapacitors

MnO 2 electrode material is synthesized by low temperature solid state reaction between KMnO 4 and MnCl 2. Effects of the KMnO 4:MnCl 2 molar ratio on the structure, morphology and electrochemical properties of the as-prepared sample were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. Results showed that the obtained MnO 2 is α-MnO 2, the average diameter is about 0.5–1.5 μm, which are constituted of nanoparticles of 20 nm. Under 100 mA g −1, the specific capacitances of the prepared sample is 258.7, 219.6, 215.3, 198.5 and 209.5 F g −1 at the KMnO 4/MnCl 2 molar ratio of 3:2, 2:1, 1:1, 1:2 and 2:3, respectively. And the MnO 2 sample with a KMnO 4/MnCl 2 molar ratio of 3:2 exhibits the best discharge capacitance and cycle performance. When the charge/discharge rate increases to 300 mA g −1, the sample still remains initial discharge capacitance of 165.3 F g −1, and the discharge capacitance is 145.9 F g −1 after 200 cycles, the capacitance retention rate is 102.4% during the 20–200th cycles. Therefore, the MnO 2 sample is an excellent material for use in supercapacitors because of its large specific capacitance and good cycle performance.

Structure and Magnetic Properties of MgFe<sub>2</sub>O<sub>4</sub> Nanoparticles Prepared by the Low-Temperature Solid-State Reaction Method

MgFe2O4 nanoparticles with different grain sizes were prepared by the low-temperature solid-state reaction method. The X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), superconducting quantum interference devices (SQUID) and 57Fe Mössbauer spectroscopy (MS) were used to characterize the structure, magnetic properties and surface anisotropy of nanoparticles. Oxygen parameters suggested that lattice distortion was decreased with reducing particle size. In comparison with the bulk material, smaller saturation magnetization (Ms) and larger coercive force (Hc) for nanoparticles were observed. The critical sizes for transition from multidomain to single domain and for superparamagnetic transition were estimated to be 25 nm and 28 nm, respectively. In summary, the fabricating conditions for the low-temperature solid-state reaction method are studied to improve Ms and reduce Hc of the films, making the films suitable to the applications of the magnetic targeted drug.

Synthesis of nanocrystalline yttrium iron garnet by low temperature solid state reaction

Abstract In this work, nanocrystalline yttrium iron garnet powders were produced by low temperature solid state reaction. The phase evolution during the procedure was determined from the thermogravimetric and differential thermal analysis, and the x-ray diffraction patterns. The results of transmission electron microscopy indicated that the prepared powders exhibited grain size at the nano-level of 20 ~ 40 nm. Dense ceramics with a theoretical density of around 98% were obtained from the prepared powders after sintering at 1280 °C, a relative low sintering temperature compared with conventional ceramic processes, and the saturation magnetizations of sintered samples were also determined.

Reaction Kinetics of the Intermediate in Synthesis of LiCoPO<sub>4</sub> by Solid-State Reaction

A precursor NH4CoPO4 containing Li + was synthesized using a low temperature solid-state reaction with ammonium dihydrogen phosphate, cobalt acetate, and lithium hydroxide. LiCoPO4 powder was manufactured by high temperature baking. The products were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetry-differential thermal analysis (TG-DTA). The results showed that the formation of the intermediates was effected by the baking atmosphere. NH4CoPO4 containing Li + was dehydrated and deaminated in air at 210−500 °C and then the (CoHPO4·LiCoPO4·Co2(OH)PO4·Li3PO4) intermediate (acid-base community) was emerged during the reaction process. The intermediate formation reaction mechanism followed the interfacial reaction power-law with an apparent activation energy of 50.0 kJ·mol - 1 . The kinetic function was found to be g(x)= (1−α) - 1 . The intermediate was dehydrated to form LiCoPO4 with an average apparent activation energy of 54.2 kJ·mol −1 . The formation of the intermediate was not affected by the process of crystallization or non- crystallization of the materials. High temperatures accelerated the decomposition reaction of the intermediate and then the formation of LiCoPO4 crystals. A perfect crystal of LiCoPO4 was obtained by the decomposition of the intermediate at temperatures higher than 550 °C.

Magnetic properties and microwave absorption in Ni–Zn and Mn–Zn ferrite nanoparticles synthesized by low-temperature solid-state reaction

In this work, Mn0.7Zn0.3Fe2O4 and Ni0.7Zn0.3Fe2O4 nanoparticles with super-paramagnetic properties and size distribution from 10 to 52nm were investigated. These particles were produced by a low-temperature solid-state reaction method without the ball-milling process. The size and morphology of the nanocrystallites were determined by X-ray diffraction, transmission electron microscopy and scanning tunneling microscopy methods. Magnetic measurements such as alternating gradient field magnetometers were used to justify the super-paramagnetic properties of these nanoparticles. Their microwave absorption in the range of 8–18GHz was studied by a vector network analyzer. Responses of the device under tests were studied. Also, the percentage of the resin, the size and thickness of the mount were determined. The band width of 2.3GHz was obtained with reflection-loss/written-loss of −16dB around 10.4GHz.

A New Red Emitting Phosphor Mg<sub>2</sub>SnO<sub>4</sub>: Eu

Mg2SnO4 was adopted as the host material of a new red emitting phosphor. Lumin-escence properties of the europium-doped magnesium tin oxide prepared by the low temperature solid state reaction were investigated under 395nm excitation. Under 395 nm excitation, the Mg2SnO4: Eu phosphor exhibits novel red emission at about 613 nm which is assigned to the 5D0 → 7F2 electric – dipole transition. Furthermore, the emission transition 5D0 → 7F2 has been found to be more prominent over the normal orange emission transition 5D0 → 7F1.

Low Temperature Synthesis and Luminescent Properties of Ca<sub>2</sub>SnO<sub>4</sub>: Eu<sup>3</sup>

A novel red emitting phosphor, Ca2SnO4: Eu3+, was prepared by the low temperature solid state reaction. X-ray powder diffraction (XRD) analysis confirmed the formation of Ca2SnO4: Eu3+. Scanning electron-microscopy (SEM) observation indicated a narrow size distribution of about 500 nm for the particles with spherical shape. Under 396 nm excitation, the Ca2SnO4: Eu3+ phosphor exhibits novel red emission at about 613 nm which is assigned to the 5D0→7F2 electric-dipole transition. Furthermore, the emission transition 5D0→7F2 has been found to be more prominent over the normal orange emission transition 5D0→7F1.

The Preparation of Ni/ZnO Adsorbent via a Low-Temperature Solid-State Method for Ultra-deep Desulfurization

One novel synthetic approach has been proposed to prepare Ni/ZnO adsorbent via low-temperature solid-state reaction. Thermal analysis (thermogravimetry differential scanning calorimetry [TG-DSC]) revealed that the nickel–zinc oxalate precursor obtained is a single-phase composite oxalate. Transmission electron microscopy analysis (TEM) shows that the NiO/ZnO composite materials are composed of nanoparticles with good dispersivity, whereas the elements of Ni and Zn are well distributed. The activity evaluation indicates that the Ni/ZnO adsorbent has good ultra-deep desulfurization activity of removing organic sulfur compounds. The sulfur concentration in the treated gasoline is less than 1.0 μg/g, which meets the need of ultra-low-sulfur fuels for use in fuel cells.

Synthesis, Structural, and Transport Properties of Novel Bihydrated Fluorosulphates NaMSO4F·2H2O (M = Fe, Co, and Ni)

3d-metal fluorosulphates that have a tavorite-type structure (e.g., LiFeSO4F) were recently reported as attractive positive electrode candidates for future Li-ion batteries aimed at large volume markets. These new fluorosulphates had to be synthesized via ionothermal synthesis owing to both their thermal instability at temperatures greater than 300 °C and their water solubility. In an attempt to depart from ionothermal synthesis, low-temperature solid-state reactions and solvothermal processes were successfully tried. The latter technique, which is reported herein, proceeds with water as the solvent and has led to a new family of fluorosulphates NaMSO4F·2H2O that crystallize in a monoclinic unit cell (SG =P21/m) similar to the uklonskovite-type structure earlier proposed for NaMgSO4F·2H2O. These new phases show no electrochemical activity with either Li or Na metal and have room temperature ionic conductivities on the order of 1 × 10−9 S cm−1. Additionally, we have discovered the feasibility, upon controlled dehydration of the NaMSO4F.2H2O phases, to prepare NaMSO4F phases adopting a derived tavorite-type structure and displaying ionic conductivities around 10−7 S cm−1. Finally, this finding opens the possibility to achieve Li-based fluorosulphates via two-step synthetic pathways.

Reactive adsorption of thiophene on Ni/ZnO adsorbent: Effect of ZnO textural structure on the desulfurization activity

To better understand the nature of reactive adsorption of thiophene on Ni/ZnO adsorbent, the effect of ZnO textural structure on the desulfurization activity was investigated. ZnO materials were synthesized by low-temperature solid-state reaction and the corresponding Ni/ZnO adsorbents were prepared by incipient impregnation method. The analysis results showed that the crystalline sizes of ZnO as-synthesized as well as the BET surface areas varied obviously with the calcination temperature. The activity evaluations indicated that the Ni/ZnO adsorbents prepared with ZnO possessed a favorable textural structure as active component exhibited good activity of removing thiophene. The evolutions of the main crystalline phases of Ni/ZnO adsorbents before and after reaction confirmed that ZnO played a crucial role in taking up S element and converting it into ZnS in the reactive adsorption process. It was concluded that ZnO with larger surface area and smaller crystal particles resulted in better desulfurization activity, which may be the main reason for the different activities of the Ni/ZnO adsorbents prepared with ZnO calcined at different temperatures.

Comparison of Characteristics of Gd2BaCuO5 Powders Prepared by Different Processes

Abstract Ultra-fine Gd 2 BaCuO 5 (Gd211) powders were prepared by three different routes including low temperature combustion synthesis (LCS), coprecipitation and solid state reaction. The powders were characterized in terms of morphology, chemical purity, specific surface area and particle size. The results show that LCS process yields the most weakly agglomerated powder with smallest average particle size. The microstructure and superconductor property of GdBa 2 Cu 3 O 5 (Gd123) bulk material fabricated from the precursor of Gd211 powders were also studied. It is found that the employment of fine Gd211 starting powder is effective for the size reduction of Gd211 particles in the bulk samples. Gd123 bulk produced from LCS powder achieved the largest critical current density ( J c ) value compared with those from other two powders.

An Alkali-Metal Ion Extracted Layered Compound as a Template for a Metastable Phase Synthesis in a Low-Temperature Solid-State Reaction: Preparation of Brookite from K0.8Ti1.73Li0.27O4

We have designed a new approach to synthesize brookite, i.e., to extract alkali-metal ions from K(0.8)Ti(1.73)Li(0.27)O(4) (KTLO) and to apply simultaneous heat treatment to the remaining lepidocrocite-type layers of TiO(6) octahedra. For the alkali-metal ion extraction and the simultaneous heat treatment, KTLO was heated at 400 degrees C with polytetrafluoroethylene (PTFE) in flowing Ar. PTFE has been found to be an effective agent to extract strongly electropositive alkali-metal ions from KTLO because of the strong electronegativity of F as its component. The product of this reaction consists of a mixture of brookite, K(2)CO(3), LiF, and PTFE derivatives, indicating the complete extraction of K(+) and Li(+) from KTLO and formation of brookite from the lepidocrocite-type layer of TiO(6) octahedra as a template. This brookite has a partial replacement of O(2-) with F(-) and/or slight oxygen deficiency; thus, its color is light-bluish gray. Fully oxidized brookite formation and complete decomposition of PTFE derivatives have been achieved by further heating in flowing air, and coproduced alkali-metal salts have been removed by washing in water. Powder X-ray diffraction, Raman spectroscopy, and chemical analysis results have confirmed that the final brookite product treated at 600 degrees C is single phase, and it is white. The method to extract alkali-metal ions from a crystalline material using PTFE is drastically different from the common methods such as soft-chemical and electrochemical reactions. It is likely that this new synthetic approach is applicable to other layered systems to prepare a diverse family of compounds, including novel metastable ones.

Low-temperature solid state reaction synthesis and thermoelectric properties of high-performance and low-cost Sb-doped Mg2Si0.6Sn0.4

Mg2Si1−xSnx compounds are a type of low-price, environment-friendly medium temperature thermoelectric materials with very important prospects for practical application, and the exploration of high performance Mg2Si1−xSnx compounds is currently attracting worldwide interest. In this study, Sb-doped Mg2Si0.6Sn0.4 compounds were prepared through a two-step, low-temperature solid state reaction method combined with the spark plasma sintering technique for rapid densification. The influence of Sb doping amount on the thermoelectric properties of Mg2Si0.6−ySn0.4Sby (0 ⩽ y ⩽ 0.015) compounds was investigated. The solid solubility limit of Sb in Mg2Si0.6Sn0.4 compounds was estimated around y = 0.0125. As y increased, the electrical conductivity of Mg2Si0.6−ySn0.4Sby (0 ⩽ y ⩽ 0.0125) compounds increased considerably, while the absolute value of the Seebeck coefficient and the lattice thermal conductivity decreased. The sample with y = 0.0125 had the highest ZT, reaching 1.11 at 860 K, and the samples with 0.005 ⩽ y ⩽ 0.015 all attained ZTmax > 0.95. The adopted synthesis process also showed very good repeatability and regularity in obtaining thermoelectric properties, together with the capability of precise composition control of Mg2Si0.6−ySn0.4Sby, making it promising for the practical application of Mg2Si based thermoelectric materials.

Synthesis, crystal structure, and third-order nonlinear optical properties of a copper(I) one-dimensional coordination polymer

A copper(I) thiocyanate coordination polymer [Cu(Phen)(μ-NCS)]n (I) (Phen = 1,10-phenan-throline) has been synthesized by the low-temperature solid-state reaction. Single-crystal X-ray analyses reveal that compound I possesses a type of one-dimensional (1D) framework structure. Polymer I was characterized by elemental analyses, IR spectra, and UV-visifele spectra. The third-order nonlinear optical properties were also investigated, and they exhibit good nonlinear absorption and self-defocusing performance with modulus of the hyperpolarizability 4.94 × 10−30 esu for I in a 6.35 × 10−4 mol dm−3 DMF solution.

Enhanced critical current properties of in situ processed MgB2 wires using milled boron powder and low temperature solid-state reaction

Abstract To get the fine grain structure of MgB 2 with high critical current properties, mechanical milling for as-received boron (B) powder and low temperature solid-state reaction of 550 or 600 °C were attempted to in situ powder-in-tube processed MgB 2 /Fe wires. The comparisons for the phase formation, crystallinity, grain size, microstructure and superconducting properties were performed for the wires using un-milled B powder or high temperature heat-treatment of 800 °C. It was found that the MgB 2 phase formation in the wires using the milled B powder was more activated when compared to the wires using the un-milled B powder under the same heat-treatment conditions, because of the improved reactivity of the B powder after milling. The upper critical fields and critical current densities of the MgB 2 wires using the milled B powder were also enhanced due to a smaller grain size and an increased volume of the superconducting phase. In addition, the low temperature heat-treatment of 550 and 600 °C also contributed to the enhanced superconducting properties by minimizing the grain growth for an increased grain boundary pinning when compared to a conventional high temperature heat-treatment of 800 °C. The solid-state reaction of a low temperature process for the samples using the milled B powder resulted in poorer crystallinity with a smaller grain size, which improved the superconducting properties.

Synthesis and performance of carbon-coated Li 3V 2(PO 4) 3 cathode materials by a low temperature solid-state reaction

The carbon-coated monoclinic Li 3V 2(PO 4) 3 (LVP) cathode materials can be synthesized by a low temperature solid-state reaction route. The influences of different heat treatments on the LVP have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. In the range of 3.0–4.3 V, both LVP/C electrodes present good rate capability and excellent cyclic performance. It is found that the sample (LVP1/C) prepared by the two-step heat treatment with pre-sintering at 350 °C delivers the initial discharge capacity of 99.8 mAh g −1 at 10 C charge–discharge rate and still retains 95.8 mAh g −1 after 300 cycles. For the sample (LVP2/C) synthesized by the one-step heat treatment, 95.9 and 90.0 mAh g −1 are obtained in the 1st and 300th cycles at 10 C rate, respectively. Our results based on the XRD patterns and the SEM images suggest that the good rate capability and cyclic performance may be owing to the pure phases, small particles, large specific surface areas and residual carbon. In the range of 3.0–4.8 V, compared with the LVP2/C, the LVP1/C also exhibits better performance.