Nano-scale surface of ZrO2 ceramics achieved efficiently by peanut-shaped and heart-shaped SiO2 abrasives through chemical mechanical polishing

Zirconia ceramics are regarded as the best development target for 5G mobile phone rear covers. However, it is necessary and urgent to improve the surface quality and processing efficiency of zirconia ceramics. Non-spherical silica abrasives were prepared by the KH550 induction method and were used in chemical mechanical polishing (CMP) of zirconia ceramics for the first time. While achieving low surface roughness of 1.9 nm, it has an efficient polishing rate of 0.31 μm/h which is superior to conventional abrasives. Silica particles are peanut-shaped and heart-shaped in the scanning electron microscopy image, and its distinctive morphology provides the possibility of its excellent polishing performance. X-ray photoelectron spectroscopy analysis shows that during the CMP process, silica abrasives and zirconia ceramic undergo a solid phase chemical reaction to form ZrSiO₄. At the same time, the contact wear model established in combination with the coefficient of friction indicates that the two-dimensional surface contact mode of non-spherical silica abrasives on the surface of zirconia ceramics greatly improves its mechanical effect.     

Effects of polishing parameters on surface quality in sapphire double-sided CMP

To reveal the influence of polishing process parameters on the surface quality of sapphire after double-sided chemical mechanical polishing (CMP), the orthogonal test of sapphire wafer double-sided CMP was carried out by YH2M77110 high-precision vertical double-sided grinding/polishing machine. The effects of polishing parameters, such as polishing pressure(p), polishing carrier rotation speed(v_r), and polishing time(t), were investigated regarding their effects on material removal rate (MRR), surface morphology, surface roughness (SR) and subsurface damage (SSD) depth. The experimental results showed that p and v_r have the similar and significant positive correlation effects on the MRR and the SSD depth. However, as the increase of p and v_r, the SR tends to decrease first and then increase. Prolonging t can effectively reduce the SR and the SSD depth but has a minor positive correlation effect on the MRR. The orthogonal experiment result optimization method based on weight matrix is used to obtain the influence degree of each factor on the orthogonal test index value. The set of optimal process parameter combinations are p = 35.37kPa, v_r = 30r/min, t = 50min, which presented a higher MRR, lower SR and SSD depth. The quality and efficiency of sapphire double-sided CMP can be improved through parameter optimization according to this study.     

Surface planarization of zirconia ceramic achieved by polyacrylamide grafted nanodiamond composite abrasives through chemical mechanical polishing

Zirconia ceramics are the promising materials for cell phone backplanes in the 5G era, and smoother surfaces and higher removal efficiency are sought after for their precision machining. Although nanodiamond abrasives have high polishing rates, it is easy to bring mechanical scratches and pits on the ceramic surface because of their high hardness, resulting in degradation of the surface quality of the finished workpiece. Therefore, polyacrylamide grafted nanodiamond particles were prepared by solution polymerization method for polishing ceramic wafers. As confirmed by Fourier transform infrared spectroscopy (FTIR), the polyacrylamide has been grafted on the nanodiamond surface. According to the scanning electron microscopy (SEM) and particle size distribution, the composite abrasives have better dispersion than pure nanodiamond abrasives. The results of chemical mechanical polishing (CMP) experiments showed that the composite abrasives could reduce the average surface roughness (Sa, arithmetic mean height) of zirconia ceramic from 28.31 nm to 2.68 nm (scanning area is 500 μm × 500 μm), and the polishing rate remained high compared to pure nanodiamond abrasives, showing superior CMP performance. X-ray photoelectron spectroscopy (XPS) demonstrated that solid-phase chemical reactions occurred during the polishing process to form ZrSiO₄. Meanwhile, contact-wear model combined with contact angle testing indicates that the introduction of polyacrylamide increases the contact area of the nanodiamond on the zirconia wafer surface, thereby significantly enhanced the mechanical effect.     

Effect of hydroxy carboxylates as complexing agent on improving chemical mechanical polishing performance of M-plane sapphire and action mechanism analysis

As sapphire device performance continues to improve, greater challenges are posed to the chemical mechanical polishing (CMP) of sapphire, with its high degree of hardness and brittleness. M-plane sapphire substrates are not widely used because they are more difficult to process, despite having higher luminous efficiency than C-plane substrates. In this study, the effect of three hydroxyl carboxylates, namely potassium tartrate (PT), potassium citrate (Cit) and sodium gluconate (Gluc), as complexing agents on the CMP of M-plane sapphire was investigated to obtain a high material removal rate (MRR) and low root mean square surface roughness (Sq). First, the chemical reactivities of the three complexing agents were predicted with Material Studio (MS) software. The predicted results showed that the complexing ability of the three complexing agents was greatest for Gluc, followed by Cit, with PT having the least complexing ability. Experimental results confirmed that Gluc was the optimal complexing agent for the M-plane sapphire CMP. The mechanism of action during CMP was revealed by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). The results showed that the Al(OH)₄^? ions produced by the sapphire were complexed by Gluc to form the soluble complex Al(OH)₄^?/Gluc^?. At the same time, a solid phase reaction also occurred between the M-plane sapphire, SiO₂, and water during CMP, and Al₂Si₂O₇?2H₂O was generated. After polishing with the optimized slurry, the M-plane MRR was improved to 5.358 μm/h, a 50% improvement compared with the reference slurry, and the Sq decreased from 0.345 nm to 0.172 nm. These findings provide important guidance for the development of high-performance sapphire devices.     

Development of Zr- and Gd-doped porous ceria (pCeO2) abrasives for achieving high-quality and high-efficiency oxide chemical mechanical polishing

Porous ceria (pCeO₂), Zr-doped pCeO₂ (pCeZrO₂), and Gd-doped pCeO₂ (pCeGdO₂) abrasives for both surface quality and removal rate improvements were developed using a facile one-pot solvothermal approach. The resulting products were characterized via XRD, SEM, TEM, HRTEM, Raman spectroscopy, UV–visible spectroscopy, and N₂ adsorption-desorption measurements. Raman spectra revealed that oxygen vacancies were the dominant defects in pCeO₂ nanospheres. Zr- and Gd-doping treatments contributed to oxygen vacancy enrichment, thus leading to an increased content of trivalent cerium (Ce³⁺) formed on the pCeO₂ surfaces. Oxide-CMP capability of pure pCeO₂, pCeZrO₂, and pCeGdO₂ abrasives were compared in terms of surface morphology/roughness/defect, topographical variation, as well as material removal rate (MRR). Atomic force microscopy and interferometric microscopy investigations showed that both pCeO₂, pCeZrO₂, and pCeGdO₂ abrasives achieved high-quality surfaces with ultra-low roughness (0.11–0.14 nm Ra, 0.13–0.17 nm RMS). As expected, the MRR was accelerated by 78.7% in alkaline slurries containing pCeGdO₂ abrasives compared to the undoped pCeO₂. The improved CMP performance might be attributed to the reduced modulus, the expend pore size, as well as the enriched Ce³⁺ and oxygen vacancy. Furthermore, the interfacial action and removal mechanism of the pCeO₂ abrasives were discussed on the basis of their structure feature and surface chemistry.     

Self-assembly preparation of popcorn-like colloidal silica and its application on chemical mechanical polishing of zirconia ceramic

Traditional mobile phone backplane materials are difficult to meet the requirements of the 5G era, and zirconia ceramic is one of the most promising backplane materials. However, its precision machining is difficult due to the hard and brittle nature. In this work, a novel popcorn-like colloidal silica was prepared by the self-assembly growth of nanoparticles for chemical mechanical polishing of the yttria-stabilized tetragonal zirconia ceramic sheets. The surface of the popcorn-like colloidal silica particles has a noticeably uneven shape, and the particle size distribution is uniform. The chemical mechanical polishing results show that the material removal rate of the prepared popcorn-like colloidal silica is increased by about 50% compared with the spherical colloidal silica, and the surface morphology is also obtained improvement. In the process of chemical mechanical polishing, the particles form multi-point contact with the ceramic sheet, resulting in an increase in the coefficient of friction, which is beneficial to the tribochemical reaction. In addition, multi-point contact can distribute the load, make the indentation shallower, and help reduce mechanical scratches. In general, the expected results are expected to provide experimental basis for the optimization of the structure of chemical mechanical polishing abrasive particles.     

IBLC effect leading to colossal dielectric constant in layered structured Eu2CuO4 ceramic

Dielectric (ε_r′) studies of phase pure T′-type Eu₂CuO₄ ceramics of two markedly different grain sizes (D), prepared by (i) conventional powder mixing and (ii) citrate complexation-Pechini process, have been carried out in the frequency range 0.1 Hz to 1 MHz, and at temperatures −100 °C to 150 °C. ε_r′ is found to be highly grain size dependent. For the sample with coarse bar-like grains (D²~17×6 μm²) ε_r′ is >10³, and for the finer grain size sample with bimodal distribution (D₁~1 μm, D₂~3 μm) ε_r′ is ~10⁵; for both the samples, high ε_r′ value is nearly frequency independent over 500 Hz≤f<100 kHz and T≥30 °C. The impedance spectroscopy (IS) study has clearly shown that both, the coarse- and the fine-grained samples consist of semiconducting grains and insulating grain boundaries that primarily lead to an internal barrier layer capacitance (IBLC) effect. And thus, manifest colossal dielectric constant (ε_r′>10³) in Eu₂CuO₄ ceramics. The smaller grain size (Pechini) sample, with over an order higher number of grains and grain boundary network, showing over an order higher ε_r′ (~10⁵) compared to the coarse grained one, further endorses the IBLC effect.     

The luminescence spectroscopy and thermal stability of red-emitting phosphor Ca9Eu(VO4)7

Eu-based vanadate Ca₉Eu(VO₄)₇ phosphor was synthesized by the solid state reaction method and was characterized by X-ray powder diffraction (XRD). The photoluminescence excitation and emission spectra, fluorescence decay curves and the dependence of luminescence intensity on temperature were investigated. The phosphor can be efficiently excited by near UV light to realize an intense red luminescence (614 nm) corresponding to the electric dipole transition ⁵D₀ → ⁷F₂ of Eu³⁺ ions. The crystallographic site-occupations of the Eu³⁺ ions in Ca₉Eu(VO₄)₇ were investigated by the site-selective excitation and emission spectra, and the fluorescence decay curves in the ⁵D₀ → ⁷F₀ region using a pulsed, tunable, narrowband dye laser. The red luminescence together with the thermal stability was discussed on the base of the Eu³⁺ site-distribution in Ca₉Eu(VO₄)₇ host.     

Effect of storing on the microstructure of Ag/Cu/HA powder

The nanosized Ag/Cu/HA powder is thermodynamically unstable and easily congregates during storing, which may make it lose the nanomaterial's properties. In this work, the performances of Ag/Cu/HA during storing were studied. The Ag/Cu/HA powders were prepared using a one-step co-precipitation method. The effects of storing on powder microstructures were investigated. The microstructures of Ag/Cu/HA powders were characterized by X-ray diffraction and scanning electron microscopy. The results show that the diffraction intensities and the sizes of the calcined Ag/Cu/HA powders are reduced during storing. Storing makes the diffraction angles of 0 0 2 and 3 0 0 peaks decreased and makes that of 2 1 1 peak increased. In addition, storing increases the crystal growth along the c-axis without the effect on the crystal morphology of powders. The stored Ag/Cu/HA powders can induce the formation of new HA crystal the same as the stored Ag/Cu/HA powders with platelet morphology and low intensity and crystallinity similar to nature bone.     

Studies on cermet behavior of Ni doped YSZ

A simple and cost effective combustion process is employed to prepare Ni/YSZ cermet from an aqueous solution containing ZrO(NO₃)₂·6H₂O, Y(NO₃)₃·6H₂O, Ni(NO₃)₂·6H₂O and urea followed by H₂ reduction. As prepared cermet was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy techniques. Processed powder of NiO-YSZ was found to be in crystalline form with homogeneous mixture of YSZ and NiO phases. On reduction, its mixed conductivity is suppressed partially. The impedance and dielectric properties of the cermet were studied over a frequency range 10?Hz to 2?MHz at different temperatures. M ? H behavior at different temperature (down to 5?K) including ZFC and FC at 500?Oe were studied. To understand and corroborate the conductivity behavior and mechanism involved with the magnetic Ni ion mediated YSZ cermet, we have also studied the electric field induced polarization behavior and predict that Ni magnetic ion has specific role towards the contribution of conductivity mechanism generally included in Ni/YSZ cermet used for SOFC applications.     

化学机械抛光中Co/Ti电偶腐蚀与去除速率选择性研究

通过电化学测试研究了pH、配位剂(柠檬酸钾)和缓蚀剂[包括1,2,4-三氮唑(TAZ)和3-氨基-5-巯基-1,2,4-三氮唑(AMTA)]对Co/Ti电偶腐蚀的影响.结果表明,溶液pH升高会增大Co与Ti之间的腐蚀电位差.当pH=8时,加入0.5％(质量分数)柠檬酸钾会加剧Co和Ti之间的电偶腐蚀,而再加入缓蚀剂TA...     

Synthesis of LaAlO3 powder using triethanolamine

LaAlO₃ powders were successfully synthesized by pyrolysis of complex compounds of lanthanum and aluminum with triethanolamine (TEA). The precursors and the derived powders were characterized by simultaneous thermogravimetry analysis (TG) and differential scanning calorimetry analysis (DSC), X-ray diffractometry (XRD), specific surface area measurements, and transmission electron microscopy (TEM). Pure LaAlO₃ phase was obtained at 775 °C for 2 h or 750 °C for 4 h, without formation of any intermediate phase. Pores were found from TEM images of LaAlO₃ powders prepared at 800 °C for 2 h.     

Polishing behaviors of ceria abrasives on silicon dioxide and silicon nitride CMP

The effects of ceria (CeO₂) abrasives in chemical mechanical polishing (CMP) slurries were investigated on silicon dioxide (SiO₂) and silicon nitride (Si₃N₄) polishing process. The ceria abrasives were prepared by the flux method, using potassium hydroxide (KOH) as the grain growth accelerator. The primary particle size of the ceria abrasives was controlled in the range of ~ 84-417 nm by changing the concentration of potassium hydroxide and the calcination temperature without mechanical milling process. The removal rate of silicon dioxide film strongly depended upon abrasive size up to an optimum abrasive size (295 nm) after CMP process. However, the surface uniformity deteriorated as abrasive size increases. The observed polishing results confirmed that there exists an optimum abrasive size (295 nm) for maximum removal selectivity between oxide and nitride films. In this study, polishing behaviors of the ceria abrasives were discussed in terms of morphological characteristics.     

Hydrothermal synthesis of tellurium nanorods by using recovered tellurium from waste electronic devices

Tellurium (Te) nanostructures with controlled morphology have received the considerable attention in various applications owing to tunable optic, thermoelectric, photoelectronic, piezoelectric, and electrochemical properties. Herein, we introduce the cost-effective and eco-friendly synthesis of Te nanorods (Te NRs) from end of life electronic devices via hydrothermal methods. The Te NRs show the average diameter of 44.6?nm and a length of 358?nm in presence of polyvinylpyrrolidone, as a stabilizing agent. Moreover, the bismuth and intact p-type semiconductor (i.e., Bi_0.5Sb_1.5Te₃) are selectively recovered as intermediated products. The Te NRs exhibit the NO₂ gas sensing properties with concentration as low as 1?ppm at room temperature and fast response/recovery times of 1.59 and 2.10?s at 1?ppm, respectively. We believe that this powerful approach can be expanded to not only selective recovery of valuable materials but synthesis of various nanomaterials from waste electronic devices.     

碱性阻挡层抛光液中ULK介质抛光性能的研究

研究了化学机械抛光(CMP)过程中抛光液的Si02磨料质量分数和表面活性剂对多孔SiOCH薄膜(ULK介质)介电常数(k)及抛光速率的影响.所用抛光液(pH = 10)主要由0％-4％(质量分数,下同)SiC2、0.075％H202、1％邻苯二甲酸氢钾和不同质量浓度的表面活性剂组成,其中表面活性剂为非离子表面活性剂脂肪...     

Polyaminocarboxylate promoted synthesis of Hafnium/ Zirconium substituted anion excess In2O3: Structure,optical and electrical conductivity properties

The current study aimed to generate Hf/Zr substituted In₂O₃ with the ultimate aim of realizing a potential transparent conducting oxide. We applied a co-complexation method to bring the reactively dissimilar In and Hf/Zr together in one oxide network. We prepared an EDTA complex containing an equimolar concentration of In and Hf/Zr and examined their characteristics with FTIR and TG-DSC traces. Rietveld refinement results of calcined complexes and their Raman spectra confirmed the formation of anion excess bixbyite structure for (In_1-xM_x)₂O_3+δ (M = Hf, Zr, and x = 0.50). The lattice expanded after substituting with Hf/Zr, and the optical bandgap increased from 2.87 eV (In₂O₃) to 3.20–3.60 eV. The high percentage reflectance in the visible region and absorbance in the UV region fulfilled some of the prerequisites of transparent conducting oxide. Electrical resistivity reduced up to two orders in magnitude with increasing temperature for Hf and Zr incorporated In₂O₃.     

Solution Combustion Synthesis of nanoscale Cu-Cr-O spinels: Mechanism,properties and catalytic activity in CO oxidation

Nano-structured Cu-Cr-O-based catalysts were successfully prepared by Solution Combustion Synthesis (SCS), and it has been found that their physical properties and atomic structure depend (in a complex way) on the initial composition of SCS processing, that the temperature of combustion and composition of initial mixture influences metal concentration in the nanocomposite, and that metal formation is going through metal oxide reduction by NO, H₂, CO. Presence of CO, NH₃ and H₂ in the gas phase, during SCS, was determined chromatographically. Connection between structural changes during reaction and properties of final nanocomposite material was determined. The catalysts were characterized by XRD, SEM/EDX, and their catalytic activity has been determined in CO oxidation. The pore structure of the samples was calculated with the Barrett-Joyner-Halenda (BJH) academic model, and the specific surface area was calculated with the Brunauer-Emmett-Teller (BET) adsorption equation. The specific surface area of the catalysts is varied between 10 m²/g and 37 m²/g. Understanding the interrelationships between activity of catalyst and the ensuing atomic structure has allowed a degree of optimization of the catalytic properties of the new catalysts.     

S-doping effects on optical properties and highly enhanced photocatalytic performance of Cu3Se2 nanoparticles under solar-light irradiation

Undoped and S-doped Cu₃Se₂ nanostructures (NSs) with different sulfur concentrations were synthesized by a green, simple, and cost-effective co-precipitation method in ambient conditions. X-ray diffraction patterns (XRD) of the samples indicated that, all samples had a tetragonal phase of Cu₃Se₂. Fourier transform infrared spectroscopy (FTIR) results revealed that, some vibration modes were appeared by sulfur. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that, sulfur had a significant role to change of morphology of the products. UV–vis and Photoluminescence (PL) results showed that, the band gap value of the pristine sample was 1.72–1.85 eV, while S-doped (4%) sample had a band-gap value between 1.61 eV and 1.67 eV. On the other hand, further increase of sulfur up to 6% caused band gap value increase in compared to the 4% sulfur doped. In addition, the PL results revealed that, the products had surface-trap states (STS) energy as well as different intrinsic defects such as Cu-vacancy. Furthermore, the PL spectrum of the S-doped sample showed that, sulfur ions caused increase natural donor-acceptor (D°→A°) recombination energy intensity. Finally, photocatalytic measurements showed that, the photocatalytic performance of the samples under solar-light irradiation was enhanced by an increase of sulfur concentration up to 4%.     

Effect of the solid precursors on the formation of nanosized TiBx powders in RF thermal plasma

Continuous synthesis of TiB_x (x≈0.5–2) nanoparticles from various low cost solid precursors such as titanium and titanium dioxide admixed with boron and/or carbon in radiofrequency thermal plasma was studied. Feasibility of TiB₂ formation was predicted by thermodynamic equilibrium calculations in the 500–5000 K temperature range. In all the investigated system high temperature reactions resulted in nanometer-sized TiB_x powders with a mean size varying between 13 and 83 nm. The yield of particular runs ranged from 38% to 97%. Among the synthesized products in addition to TiB_x, oxidized precursor residues were also found in smaller quantities. Although addition of carbon to the precursors could not completely prevent surface oxidation of boride particles, it contributed to the reduction of the mean particle size of the formed TiB₂.     

One-pot hydrothermal synthesis of MoS2 nanosheets/C hybrid microspheres

Uniform MoS₂ nanosheets/C hybrid microspheres with mean diameter of 320 nm have been successfully synthesized via a facile one-pot hydrothermal route by sodium molybdate reacting with sulfocarbamide in d-glucose solutions. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). XRD patterns showed that the MoS₂ was kept as a two-dimensional nanosheet crystal and C was retained as amorphous even after their annealing treatment at 800 °C. TEM and SEM images indicated that the MoS₂ nanosheets were uniformly dispersed in the amorphous carbon. The experiment results also revealed that the appropriate amount of d-glucose had an obvious effect on the formation of uniform MoS₂ nanosheets/C hybrid microspheres. A possible formation process of MoS₂ nanosheets/C hybrid microspheres was preliminarily presented.