Preparation and properties of porous ceramics from spodumene flotation tailings by low-temperature sintering

Porous ceramics were prepared with spodumene flotation talings(SFT),kaolin and low-melting point glass(LPG)powder,whose pores were formed by the chemical reaction of hydrogen peroxide(H_(2)O_(2)).LPG was used to reduce the sintering temperature of porous ceramics and kaolin was used to realize the adsorption to methylene blue(MB)of porous ceramics.The average flexural strength,compressive strength,apparent porosity,water absorption and maximum MB adsorption capacity were 5.60 MPa,4.66 MPa,52.27%,44.32%and 0.7 mg/g,respectively.Moreover,the results of orthogonal experiments present that the sintering temperature and the dosage of H_(2)O_(2)had great influence on the mechanical properties and apparent porosity of porous ceramics,respectively.The main reason for the improvement of mechanical properties of porous ceramics was that LPG gradually became soft with increasing the sintering temperature,which made the mineral particles adhere to each other closely.Kaolinite was not completely converted into metakaolin at 550℃,which might be the main reason why porous ceramics had adsorption properties.

Low-Temperature Sintering and Microwave DielectricProperties of Ba_2Ti_3Nb_4O_(18) Ceramics

The effects of CuO and H3BO3 additions on the low-temperature sintering,microstructure,and microwave dielectric properties of Ba2Ti3Nb4O18 ceramics were investigated.The addition of less amount of CuO （ 〈1 wt%） considerably facilitated the densification of Ba2Ti3Nb4O18 ceramics.Appropriate addition of H3BO3 （ 〈3.5 wt%） remarkably improved the microwave dielectric properties of ceramics.The addition of H3BO3 and CuO successfully reduced the sintering temperature of Ba2Ti3Nb4O18 ceramics from 1300 to 1050 ℃.Ba2Ti3Nb4O18 ceramics sintered at 1 050 ℃ for 4 h with the addition of 1.0 wt% CuO and 3.5 wt% H3BO3 exhibited good microwave dielectric properties：er=33.74,Q？f=13 812 GHz,and tf=-5.35 ppm/°C at about 5.0 GHz.

Sintering behavior and mechanical properties of sintered ceramics based on spodumene tailings

In this study,ceramics was prepared by slip casting(no pressure was used during shaping step)and atmospheric pressure sintering with low-melting point glass(LPG)powder as the binding material to facilitate the transformation of spodumene flotation tailings(SFTs)into ceramics at lower temperatures.The influence of sintering temperature and mass ratio of LPG on the mechanical properties(flexural strength and compressive strength)of ceramic materials was studied by orthogonal test.The results showed that when the mass ratio of LPG powder was higher than or equal to 20 wt%and the sintering temperature was higher than or equal to 550℃,mutual adhesion between the sample particles was realised and consequently the ceramic materials could be prepared with good mechanical properties(the maximum flexural strength=19.55 MPa,the maximum compressive strength=42.25 MPa,average porosity=24.52%,average apparent density=1.66 g/cm^(3),and average water absorption=14.79%).The sintered ceramics were characterized by XRF,XRD,optical microscopy analysis,SEM,TGA-DSC and FT-IR.The formation of liquid phase at high temperature may lead to the mutual bonding between particles,which might be the main reason for the improvement of mechanical properties of ceramic materials.Overall,SFTs were successfully sintered at low temperature to prepare ceramic materials with good mechanical properties,which are crucial for energy conservation and environmental preservation.

Sintering of monoclinic SrAl_(2)Si_(2)O_(8) ceramics and their Sr immobilization

Monoclinic SrAl_(2)Si_(2)O_(8) ceramics for Sr immobilization were prepared by a liquid-phase sintering method.The sintering temperature,mineral phase composition,microstructure,flexural strength,bulk density,and Sr ion leaching characteristics of the SrAl_(2)Si_(2)O_(8) ceramics were investigated.A crystalline monoclinic SrAl_(2)Si_(2)O_(8) phase formed through liquid-phase sintering at 1223 K.The introduction of four flux agents(B_(2)O_(3),CaO·2B_(2)O_(3),SrO·2B_(2)O_(3),and BaO·2B_(2)O_(3))to the SrAl_(2)Si_(2)O_(8) ceramics not only reduced the densification temperature and decreased the volatilization of Sr during high-temperature sintering but also impacted the mechanical properties of the ceramics.Product consistency tests showed that the leaching concentration of Sr ions in the sample with flux agent B_(2)O_(3) was the lowest,whereas that of Sr ions in the sample with flux agent BaO·2B_(2)O_(3) was the highest.These results show that the leaching concentration of Sr ions depends largely on the amorphous phase in the ceramics.Meanwhile,the formation of mineral analog ceramics containing Sr is an important factor to improve Sr immobilization.

STUDY ON STRENGTH AND PETROGRAPHIC STRUCTURE OF CLINKER BY LOW-TEMPERATURE BURNING

In this paper,the strength and petrographic structure of clinker by low-temperature burning are studied. The results show that both the calcining temperature of Ca-CO3 and sintering temperature clinker decreases by 150 degrees C compared with those in traditional rotary kiln,the rate of f-CaO in the clinker sintered at 1300 degrees C is 0.29% similar to 2.81%, the strength of the clinker is 62. 5MPa with maximum 69. 4MPa at a specific area of 2900 similar to 3400cm(2)/g. The results also show that the types of petrographic structure of the clinker can be classified as: homogeneous structure, inlaid or edged structure,stain-melting structure and porous structure. The clinker sintered at 1300 +/- 15 degrees C temperature and with enough retention period is mainly in homogeneous structure.

Fast and Balanced Charge Transport Enabled by Solution-Processed Metal Oxide Layers for Efficient and Stable Inverted Perovskite Solar Cells

Metal oxide charge transport materials are preferable for realizing long-term stable and potentially low-cost perovskite solar cells(PSCs).However,due to some technical difficulties(e.g.,intricate fabrication protocols,high-temperature heating process,incompatible solvents,etc.),it is still challenging to achieve efficient and reliable all-metal-oxide-based devices.Here,we developed efficient inverted PSCs(IPSCs)based on solution-processed nickel oxide(NiO_(x))and tin oxide(SnO_(2))nanoparticles,working as hole and electron transport materials respectively,enabling a fast and balanced charge transfer for photogenerated charge carriers.Through further understanding and optimizing the perovskite/metal oxide interfaces,we have realized an outstanding power conversion efficiency(PCE)of 23.5%(the bandgap of the perovskite is 1.62 eV),which is the highest efficiency among IPSCs based on all-metal-oxide charge transport materials.Thanks to these stable metal oxides and improved interface properties,ambient stability(retaining 95%of initial PCE after 1 month),thermal stability(retaining 80%of initial PCE after 2 weeks)and light stability(retaining 90%of initial PCE after 1000 hours aging)of resultant devices are enhanced significantly.In addition,owing to the low-temperature fabrication procedures of the entire device,we have obtained a PCE of over 21%for flexible IPSCs with enhanced operational stability.

烧结温度对Micro-FAST制备TC4钛合金的影响

采用多物理场活化烧结微成形技术(Micro-FAST)快速制备TC4微型圆柱,研究烧结温度对TC4微型圆柱的致密化过程及力学性能的影响。研究发现,Micro-FAST技术可在5 min内实现TC4的快速成形,在900～1200℃的烧结温度区间均可获得相对密度大于97%的微型圆柱件,其显微组织由条状α相和β相组成,组织分布均匀、晶粒细小。当烧结温度为1000℃时,硬度达到最大值380.3HV0.5,较传统方法制备的TC4零件硬度提高10%。随着烧结温度的提高,烧结体中出现魏氏组织,合金的韧性逐渐降低。

Micro-FAST中升温速率和烧结温度对零件致密化的影响

采用Gleeble-1500D热模拟机对316L不锈钢粉末进行烧结,制备出尺寸为Φ1.0 mm×1.0 mm的微型零件,并研究了升温速率和烧结温度对微型零件微观组织及性能的影响。结果表明:随着升温速率和烧结温度的提高,烧结试样体系的孔隙数量减少,试样的相对密度增加;在升温速率为50℃/s、烧结温度为900℃时,得到了近全致密的试样,且烧结温度低于传统烧结方法的烧结温度;试样最大轴向尺寸变化出现在快速升温阶段,说明在多物理场活化烧结微成形中升温速率对致密化的贡献比烧结温度更大。

Low-temperature sintering and microwave dielectric properties of CaMg1−xLi2xSi2O6(x=0−0.3)ceramics

In this study, low-temperature fired CaMg1−xLi2xSi2O6 microwave dielectric ceramics were prepared via the traditional solid-state reaction method. In this process, 0.4 wt% Li2CO3-B2O3-SiO2-CaCO3-Al2O3 (LBSCA) glass was added as a sintering aid. The results showed that ceramics consisted of CaMgSi2O6 as the main phase. The second phases were CaSiO3 always existing and Li2SiO3 occurring at substitution content x > 0.05. Li+ substitution effectively lowered sintering temperature due to 0.4 wt% LBSCA and contributed to grain densification, and the most homogeneous morphology could be observed at x = 0.05. The effects of relative density, the second phase, and ionic polarizability on dielectric constant (εr) were investigated. The quality factor (Q × f) varied with packing fraction that concerned the second phase. Moreover, the temperature coefficient of the resonant frequency (τf) was influenced by MgO6 octahedral distortion and bond valence. Excellent dielectric properties of the CaMg1−xLi2xSi2O6 ceramic was exhibited at x = 0.05 with εr = 7.44, Q × f = 41,017 GHz (f = 15.1638 GHz), and τf = −59.3 ppm/°C when sintered at 900 °C. It had a good application prospect in the field of low-temperature co-fired ceramic (LTCC) substrate and devices.

Tailoring Nitrogen Terminals on MXene Enables Fast Charging and Stable Cycling Na-Ion Batteries at Low Temperature

Sodium-ion batteries stand a chance of enabling fast charging ability and long lifespan while operating at low temperature(low-T).However,sluggish kinetics and aggravated dendrites present two major challenges for anodes to achieve the goal at low-T.Herein,we propose an interlayer confined strategy for tailoring nitrogen terminals on Ti_(3)C_(2) MXene(Ti_(3)C_(2)-N_(funct)) to address these issues.The introduction of nitrogen terminals endows Ti_(3)C_(2)-N_(funct) with large interlayer space and charge redistribution,improved conductivity and sufficient adsorption sites for Na^(+),which improves the possibility of Ti_(3)C_(2) for accommodating more Na atoms,further enhancing the Na^(+) storage capability of Ti_(3)C_(2).As revealed,Ti_(3)C_(2)-N_(funct) not only possesses a lower Na-ion diffusion energy barrier and charge trans-fer activation energy,but also exhibits Na^(+)-solvent co-intercalation behavior to circumvent a high de-solvation energy barrier at low-T.Besides,the solid electrolyte interface dominated by inorganic com-pounds is more beneficial for the Na^(+)transfer at the electrode/electrolyte interface.Compared with of the unmodified sample,Ti_(3)C_(2)-Nfunct exhibits a twofold capacity(201 mAh g^(-1)),fast-charging ability(18 min at 80% capacity retention),and great superiority in cycle life(80.9%@5000 cycles)at -25℃.When coupling with Na_(3)V_(2)(PO_(4))_(2)F_(3) cathode,the Ti_(3)C_(2)-N_(funct)//NVPF exhibits high energy density and cycle stability at -25℃.

Structure,far-infrared spectroscopy,microwave dielectric properties,and improved low-temperature sintering characteristics of tri-rutile Mg_(0.5)Ti_(0.5)TaO_(4) ceramics

In this study,tri-rutile type Mg_(0.5)Ti_(0.5)TaO_(4) ceramics were synthesized,where the structure–property relationship,especially the structural configuration and intrinsic dielectric origin of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,and the low-firing characteristics were studied.It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis,the selected area electron diffraction(SAED),and the high-resolution transmission electron microscopy(HRTEM)along the[110]zone axis.With the increase in sintering temperature,the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics.Intrinsically,theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values,indicating the importance of structural features to dielectric properties.Furthermore,a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,where 2–4 wt%Li_(2)O–MgO–ZnO–B_(2)O_(3)–SiO_(2)(LMZBS)glass frit was adopted to reduce the suitable temperature from 1275 to 1050℃ without significantly deteriorating the microwave dielectric characteristics.Specifically,Mg_(0.5)Ti_(0.5)TaO_(4) ceramics containing 2 wt% glass addition sintered at 1050℃for 4 h possess excellent microwave dielectric properties:dielectric constant(ε_(r))=44.3,quality factor multiplied by resonant frequency(Q×f)=23,820 GHz(f=6.2 GHz),and the temperature coefficient of resonant frequency(τ_(f))=123.2 ppm/℃.

Enhanced piezoelectric properties in low-temperature sintering PZN-PZT ceramics by adjusting Zr/Ti ratio

Pb_(0.96)Sr_(0.04)(Zr,Ti)_(0.7)(Zn_(1/3)Nb_(2/3))_(0.3)O_(3)(PZN-PZT)piezoceramics with various Zr/Ti ratios and Li_(2)CO_(3)sintering aid were sintered at 900°C by the solid-state reaction route.The samples with different Zr/Ti ratios were compared according to microstructure,phase structure,piezoelectricity,ferroelectricity,and dielectric relaxation.The Zr/Ti ratio in the PZN-PZT ceramics greatly affects the electrical properties.The Zr/Ti ratio affects the proportion between the rhombohedral and tetragonal phases and also affects the grain size.The PZN-PZT ceramics with the Zr/Ti ratio of 53:47 have the largest grain size and have optimized piezoelectric prop-erties(k_(p)=0.58,d_(33)=540 pC/N,and T_(C)=250°C).The larger the grain size,the lesser the grain boundary,the easier the domain wall motion,and the better the piezoelectric properties.The PZT ceramic with Zr/Ti ratio of 53:47 locates the morphotropic phase boundary(MPB)region which is one of the key factors for the high piezoelectric properties of the PZT.

Micro-FAST制备氧化铝微型零件

采用多物理场活化烧结微成形技术(简称Micro-FAST)制备了氧化铝微型圆柱,研究了烧结温度对Micro-FAST制备氧化铝微型圆柱致密化过程的影响。结果表明,Micro-FAST的烧结致密化过程可分为4个阶段:预热阶段、升温阶段、保温阶段和冷却阶段,试样的线收缩主要发生在升温阶段;烧结温度是影响原子扩散系数的重要因素,随着烧结温度的升高,试样的线收缩率和相对密度均是增加的;Micro-FAST制备氧化铝陶瓷的平均烧结活化能比传统真空烧结要低得多,说明Micro-FAST是一种活化烧结技术。

Low-temperature oxidation behavior and mechanism of semi-dry desulfurization ash from iron ore sintering flue gas

The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash. The effects of the ammonium citrate concentration, oxidation temperature, solid/liquid ratio, and oxidation time on the wet oxidation behavior of desulfurization ash were studied. Simultaneously, the oxidation mechanism of desulfurization ash was revealed by means of X-ray diffraction, Zeta electric resistance, and X-ray photoelectron spectroscopy (XPS) analysis. Under the optimal conditions with ammonium citrate, the oxidation ratio of CaSO_(3) was up to the maximum value (98.49%), while that of CaSO_(3) was only 8.92% without ammonium citrate. Zeta electric resistance and XPS results indicate that the dissolution process of CaSO_(3) could be significantly promoted by complexation derived from the ammonium citrate hydrolysis. As a result, the oxidation process of CaSO_(3) was transformed from particle oxidation to SO_(3)^(2−) ion oxidation, realizing the rapid transformation of desulfurization ash from CaSO_(3) to CaSO_(4) at low temperature. It provides a reference for the application of semi-dry desulfurization ash and contributes to sustainable management for semi-dry desulfurization ash.

稀土氧化物强化钨铼合金的制备与力学性能研究

采用快速热压烧结技术制备稀土氧化物掺杂钨铼合金,对比研究添加不同种类稀土氧化物对钨铼合金微观组织和力学性能的影响,并分析讨论其强化机理。结果表明:稀土氧化物不仅能提高钨铼合金的相对密度和强度,还能减小钨铼合金的晶粒尺寸。在3种稀土氧化物中,氧化钇的强化效果最明显。W-3%Re-0.8%Y_(2)O_(3)(质量分数,下同)的相对密度为95.5%,硬度为412.5 HV1,变形量到50%时压缩强度为3158 MPa,对比合金基体(W-3%Re),分别提高了3.1%、49.0%和24.0%。另外,W-3%Re-0.8%Y_(2)O_(3)的平均晶粒尺寸仅为5.8μm,比合金基体降低了约63.6%。

Low-temperature sintered(Na_(1/2)Bi_(1/2))TiO_(3)-based incipient piezoceramics for co-fired multilayer actuator application

Low-temperature sintered(Na_(1/2)Bi_(1/2))_(0.935)Ba_(0.065)Ti_(0.975)(Fe_(1/2)Nb_(1/2))_(0.025)O_(3)(NBT-BT-0.025FN)lead-free incipient piezoceramics were investigated using high-purity Li_(2)CO_(3) as sintering aids.With the ≤0.5 wt%Li_(2)CO_(3) addition,the introduced Li^(+) cations precede to enter the A-sites of the perovskite lattice to compensate for the A-site deficiencies.Once the addition exceeds 0.5 wt%,the excess Lit cations will occupy B-sites and give rise to the generation of oxygen vacancies,which accelerate the mass transport and thus lower the sintering temperature effectively from 1100℃ down to 925℃.It was also found that a small amount of Lit addition has little effect on the phase structure and electromechanical properties of the system,but overweight seriously disturbs these characteristics because of the large lattice distortion.The sintered NBT-BT-0.025FN incipient piezoceramics with 1.25 wt%Li_(2)CO_(3) addition at 925℃ provides a large strain of 0.33% and a corresponding large signal piezoelectric coefficient d_(33)^(*) of 550 pm/V at 60 kV/cm,indicating this system is a very promising candidate for lead-free co-fired multilayer actuator application.

纳米复合WC-6Co粉末的快速烧结

以液相复合-连续还原碳化方法制备的纳米复合WC-6Co粉末为原料,采用放电等离子烧结(SPS),制取了超细硬质合金。利用扫描电镜、维氏硬度仪、洛氏硬度仪、密度测试仪、MTS陶瓷测试系统等,观察烧结体显微结构,测试其硬度、密度、断裂强度、矫顽磁力、磁饱和度。结果表明采用放电等离子烧结获得的烧结体的硬度HV1≥19500MPa,断裂强度TRS≥2800MPa,平均晶粒度150nm^300nm。制备了高强度、高硬度的超细WC-6Co硬质合金。

“化学炉”加机械压力法超快速制备超细晶氧化铝陶瓷

报道了一种制备具有微米级以下微观结构的完全致密氧化铝(Al2O3)陶瓷的新方法。用燃烧合成所产生的热量为热源代替传统烧结炉。用燃烧合成原料将Al2O3包裹起来作为“化学炉”,在燃烧反应完成的同时施加机械压力快速烧结制备Al2O3陶瓷。实验中,用平均粒径为600nm的Al2O3为原料,当施加的压力为120MPa时,得到完全致密的烧结体,整个过程为5min。扫描电镜和透射电镜分析结果显示:烧结后晶粒间结合良好,平均尺寸为600nm,与原料粒径相比无明显长大。

纳米-亚微米结构SiC-Al_2O_3复合陶瓷快速制备

采用粒径为600nm和200nm的高纯氧化铝、40nm碳化硅为原料,应用放电等离子(SPS)烧结工艺,在200℃/min的升温速率条件下,研究了原料粒径、温度条件对于纳米SiC-Al2O3复合陶瓷制备过程中晶粒生长以及致密度变化的影响。研究结果表明:在烧结温度1450℃、压力100MPa、保温2min的条件下,2种不同原料的纳米复合陶瓷的晶粒尺寸均在亚微米范围,烧结体致密度达98%。在相同温度压力条件下,小粒径烧结体密度小于大粒径烧结体。

特种陶瓷材料快速烧结新技术研究

特种陶瓷作为工程材料的重要组成部分具有广阔的工业应用前景。传统烧结方法制备的特种陶瓷晶粒粗大且性能较差,高耗能和高耗时的特点也不符合绿色可持续发展的要求。快速烧结新技术的发展为这一难题提供了解决方法,利用快速烧结技术,陶瓷材料的制备时间和能耗大大降低,同时其在烧结过程中的晶粒生长也受到抑制,材料性能得以优化。主要围绕放电等离子体烧结(SPS)、高温自蔓延烧结(SHS)和基于这两种技术发展的烧结新方法(SPS Plus, SHS Plus),从烧结机理和实际应用的角度总结了特种陶瓷材料快速烧结新技术的发展。研究表明快速烧结新方法在快速制备、陶瓷连接、梯度和纳米陶瓷制备方面有独特的技术优势。