氟改性UV固化超支化水性聚氨酯的制备与性能研究

采用HDI三聚体(HDT)和二乙醇胺(DEOA)自制六羟基多元醇;采用异佛尔酮二异氰酸酯(IPDI)、全氟己基乙基醇(TEOH-6)和三羟甲基丙烷(TMP)自制含氟二元醇;以IPDI、聚碳酸酯二元醇(PCDL)、含氟二元醇、二羟甲基丁酸(DMBA)、季戊四醇三丙烯酸酯(PETA)为主要原料合成—NCO半封端的聚氨酯,将六羟基多元醇加入到聚氨酯中,制备了氟改性UV固化超支化水性聚氨酯(FWPU)。采用光学接触角、纳米粒度仪、电子拉力机、原子力显微镜等对涂膜的结构与性能进行了测试。研究了含氟二元醇添加量对涂膜疏水性、力学性能、硬度、热稳定性等的影响。结果表明:随着含氟二元醇的加入,乳液粒径逐渐增大、分布变宽,涂膜接触角增加、吸水率大幅降低、热稳定性增强、拉伸强度大幅度增大、硬度达到4H。当含氟二元醇含量为8%时,涂膜的综合性能最佳。     

氟改性水性聚氨酯复合乳液的合成及其性能研究

采用聚四氢呋喃醚二元醇（PTMG-1000）和聚碳酸酯二元醇（PCDL-1000）作为混合软段,以异佛尔酮二异氰酸酯（IPDI）、二羟甲基丙酸（DMPA）及 1,4-丁二醇（BDO）作为硬段,并通过全氟己基乙基甲基丙烯酸酯改性制备了水性含氟聚氨酯乳液（WFPUA）。研究了含氟单体用量对乳液稳定性、胶膜耐水性以及织物防水性能的影响。结果表明：随着含氟单体用量的增加, WFPUA胶膜的水接触角随之增大,当含氟单体质量分数达到 25%时,胶膜水接触角达到 119. 9°,吸水率仅为 10. 05%,处理过的织物沾水等级高达 4~5级。     

氟改性UV固化六臂型阻燃聚氨酯的制备与性能研究

采用十三氟辛醇（ TEOH-6）、异佛尔酮二异氰酸酯（ IPDI）、三乙醇胺（ TEOA）自制含氟二元醇（ DE-TEOH）;并采用六氯环三磷氰、对羟基苯甲醛、硼氢化钠合成六臂型阻燃单体;以异佛尔酮二异氰酸酯（ IPDI）、聚碳酸酯二元醇（ PCDL）、二羟甲基丁酸（ DMBA）、含氟二元醇（ DE-TEOH）、季戊四醇三丙烯酸酯（PETA）为主要原料合成— NCO半封端线型聚氨酯;将六臂型阻燃单体加入聚氨酯体系,采用无皂相反转乳化工艺制成了含氟、氮、磷复合改性水性 UV固化六臂型阻燃聚氨酯（ UV-WFPU）。通过红外光谱、核磁共振氢谱对 UV-WFPU的结构进行表征,并对胶膜的性能进行了研究,考察了含氟二元醇的添加量以及六臂型阻燃单体加入对胶膜结构和性能的影响。结果表明：与传统的聚氨酯相比,六臂型阻燃单体的加入,胶膜的阻燃性能大幅度提高,极限氧指数（ LOI）提高了 45%;随着自制二元醇添加量的增加,胶膜吸水率降低,接触角增加,热稳定性提高。     

UV固化含氟低聚物的制备及性能研究

首先由甲基丙烯酸十二氟庚酯（ DFHMA）与乙醇胺通过 Michael加成反应得到含氟醇;其次以含氟醇、马来酸酐和甲基丙烯酸缩水甘油酯（ GMA）合成活性含氟中间体;最后将之与异佛尔酮二异氰酸酯（ IPDI）、季戊四醇三丙烯酸酯（ PETA）反应得到可紫外光（ UV）固化的含氟低聚物。采用红外光谱、核磁共振对产物结构进行表征。以所得低聚物制备 UV固化涂膜,通过测试涂膜接触角、热稳定性、硬度等研究不同含氟醇添加量对涂膜性能的影响。结果表明：当含氟醇质量分数从 0增加到 10%时,涂膜水接触角从 56. 3°上升到 98. 2°,表面自由能由 52. 62 mN/m降至 22. 96 mN/m,且涂膜热稳定性提高,硬度提高。     

可聚合含氟聚氨酯低聚物的合成及其UV固化性能

由丙烯酸十二氟庚酯和二乙醇胺的Michael加成反应合成了十二氟二元醇,其与异佛尔酮二异氰酸酯和丙烯酸羟乙酯反应得到一种可聚合含氟聚氨酯低聚物,并将该低聚物应用于紫外光固化涂料中。采用红外光谱和核磁共振氢谱表征了十二氟二元醇和含氟聚氨酯低聚物的结构,通过涂层接触角、硬度、耐磨性、吸水率和耐化学品性测定研究了其含氟低聚物用量对光固化涂层性能的影响。结果表明,当含氟低聚物添加质量分数从0增加到20%时,涂层的水接触角从53.5°增加到98.8°,邵氏硬度由43.3提高到90.3,耐磨性由45 r增加至145 r,吸水率由1.32%下降到0.55%,同时涂层耐化学品性明显改善。     

含氟聚合物纳米SiO2复合涂层的制备及性能研究

以1-甲基丙烯酰氧基丙基三甲氧基硅烷(MPTMS)、N-甲基全氟辛基磺酰基胺基丙烯酸乙酯(MPSAEA)、甲基丙烯酸甲酯(MMA)共聚，然后利用原位复合技术引入纳米SiO2微粒，制备了均匀透明的SiO2纳米复合含氟聚合物材料。用红外光谱(FT—IR)、透射电镜(TEM)和电子衍射(ED)等表征了复合材料的形貌和结构。将聚合物用做涂层材料，用扫描电镜(SEM)、X-射线光电子能谱(XPS)、接触角测定仪和显微硬度仪测定了涂层的形貌、涂层表面的化学成分、涂层与水的接触角随时间的变化、涂层的硬度变化，结果表明纳米复合聚合物可在玻片表面形成均匀光滑的涂层，涂层表面纳米SiO2和含氟成分共同存在，纳米SiO2复合涂层在室外放置半年以后仍保持良好的疏水性，并且纳米复合聚合物涂层的硬度随含氟单体含量的增加而增加。     

含氟硅涂料的制备与性质研究

以甲苯为溶剂,以过氧化苯甲酰（BPO）引发由苯乙烯（St）、甲基丙烯酸酯类（包括MMA、BMA、IBMA和IBOMA）、含氟甲基丙烯酸酯类（包括甲基丙烯酸三氟乙酯（3F）、甲基丙烯酸六氟丁酯（6F）和甲基丙烯酸十二氟庚酯（12F））和γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH570）组成的反应体系,在80～85℃下,分别采用一步加料法和分步加料法工艺,合成了含氟涂料清漆.聚合物的IR图表明,在744～748 cm-1间出现了C-F的特征谱带,在1 000～1 100cm-1间出现了Si-O键吸收峰.讨论了合成工艺、不同的共聚单体对漆膜的水接触角、表面性能和吸水性的影响.结果表明：分步加料法为最佳工艺;IBMA和IBOMA为甲基丙烯酸酯类单体中的优选共聚单体;含氟单体中,随着含氟量的增加,水接触角增大;以粘度为3 000 cs的羟基硅油为改性剂,可以提高漆膜的水接触角和硬度,其耐蚀性（包括耐水性、耐盐水性、耐碱性、耐洗刷性和耐污染性等）良好。     

TiO2/含氟树脂复合超疏水涂层的制备

采用自由基溶液聚合法与共混法制备Ti O2/含氟树脂（FA）超疏水涂层。分别以甲基丙烯酸丁酯（BA）和苯乙烯（ST）为软硬单体,甲基丙烯酸十二氟庚酯（DFMA）为低表面能单体,丙烯酸（AA）为功能单体,甲苯（MB）为溶剂,通过自由基溶液聚合法制备含氟树脂（FA）。将无机纳米TiO2粒子均匀分散于含氟树脂中,然后以提拉法涂覆于基质表面即得TiO2/含氟树脂复合涂层。用接触角仪、紫外可见光光度计、红外光谱、扫描电镜、综合热分析对涂层进行了测试表征。实验结果表明：当DFMA含量为15%,含氟树脂涂层与水的接触角为105°,涂层在310℃以下可基本保持稳定结构。当TiO2（60nm）粒子的掺杂质量分数为15%时,所制备复合涂层的疏水角为151°,透过率可达65-75%。     

含氟三羟甲基三聚氰胺树脂的制备与性能

以十三氟辛醇、异佛尔酮二异氰酸酯、六羟甲基三聚氰胺为原料合成了含氟三羟甲基三聚氰胺树脂。通过核磁共振和红外光谱表征了产物结构以及反应程度。将含氟三羟甲基三聚氰胺树脂与三聚氰胺甲醛树脂以不同比例进行固化成膜,测定了不同氟含量的涂膜的接触角、固化交联率、吸水率、硬度、附着力和耐水性。结果表明:氟含量为12%时,反应转化率可达91%;涂层的综合性能较好,水接触角达106°。     

多臂UV固化含氟聚碳酸酯聚氨酯的制备及应用

聚碳酸酯二元醇(PCDL)与异佛尔酮二异氰酸酯(IPDI)反应后,再分别与丙烯酸羟乙酯(HEA)及十三氟辛醇反应,得到双键半封端物及含氟半封端物,随后以二聚甘油为核将两者按物质的量比1∶1反应得到多臂UV固化含氟PCDL基聚氨酯丙烯酸酯(FPUA)。采用傅里叶变换红外光谱(FT-IR)、核磁共振(1H-NMR)表征了FPUA的结构。并以其为添加剂,加入到市售聚氨酯中,制备了低表面能的疏水涂层,通过表面水油接触角、硬度及附着力测试,对疏水涂层的表面性能及物化性能进行了表征。     

Effect of FA chain length on normal- and reversed-phase HPLC of phospholipids

Forty-seven saturated synthetic diacyl PA, PC, PE, PG, and PS and five unsaturated diacyl phospholipids (PL) underwent normal- and reversed-phase (RP) HPLC with isocratic isopropanol/hexane/water (5∶4∶1) and methanol/chloroform/acetonitrile/water (79.5∶9∶8∶3.5) mobile phases, respectively. For normal-phase HPLC, capacity factors (k′ _i ) decrease with chain length (n) of the two identical PL FA residues, whereas the opposite occurs with RP (C₁₈)-HPLC. Plots of In k′ _i vs. n for individual PL classes are in general curved, violating the linear free-energy relationship. For PL of the same n but with different head groups, k′ _i with normal-phase HPLC varies as PE<PG<PA<PS<PC, except when n≥16, when the order is PE<PS≈PA≈PG<PC. For RP-HPLC, the order of k′ _i values is PG<_A≈PS≤PC≈PE until n≥16, when it is PA≈PG<PS≪PC≈PE. With normal-phase HPLC, k′ _i values of PL with unsaturated FA of n=18 are ordered as PE<PA<PC. Increasing degrees of unsaturation lead to increasing k′ _i .     

Gas-liquid chromatography-mass spectrometry of the 4,4-dimethyloxazoline derivatives of Δ5-unsaturated polymethylene-interrupted fatty acids from conifer seed oils

The fatty acids from the seed oils of three Conifer species (one Pinaceae,Pinus pinaster, and two Cupressaceae,Chamaecyparis lawsoniana andBiota orientalis) have been analyzed as their 4,4-dimethyloxazoline (DMOX) derivatives by gas-liquid chromatography coupled with mass spectrometry. The structures of six Δ5-unsaturated polymethylene-interrupted fatty acids (Δ5-UPIFA) were established, confirming previous studies in which they were identified by their equivalent chainlengths (ECL) and by comparison with related authentic standards. These acids were:cis-5,cis-9 18∶2,cis-5,cis-9,cis-12 18∶3 (P. pinaster),cis-5,cis-9,cis-12,cis-15 18∶4 (C.lawsoniana),cis-5,cis-11 20∶2,cis-5,cis-11,cis-14 20∶3 (all species),cis-5,cis-11,cis-14,cis-17 20∶4 (B. orientalis) acids. In addition,cis-9 18∶1,cis-9,cis-12 18∶2 (all species) andcis-9,cis-12,cis-15 18∶3 (Cupressaceae) acids, together with their elongation products [cis-11 20∶1,cis-11,cis-14 20∶2 (all species) andcis-11,cis-14,cis-17 20∶3 (B. orientalis) acids] were also identified. In the mass spectra, DMOX derivatives of all Δ5-UPIFA showed an intense peak atm/z 153, which is a diagnostic ion of fatty acid derivatives with a Δ5-ethylenic bond. Other double bonds were localized by ion pairs that differed by 12 atomic mass units. The present study fully justifies the use of ECL to identify Δ5-UPIFA in Conifer seed oils, in which they are ordinary components.     

Kinetic studies of dyes sorption from aqueous solutions onto the strongly basic anion-exchanger Lewatit MonoPlus M-600

The sorption of Tartrazine, Allura Red, Sunset Yellow and Indigo Carmine from aqueous solutions onto the strongly basic anion-exchanger (Lewatit MonoPlus M-600) of dimethylethanolamine functional groups and styrene–divinylbenzene matrix was investigated. The experimental data obtained at 50, 100, 200, 300 and 500 mg/dm³ initial concentrations at 20 °C were applied to the pseudo-first order, pseudo-second order and Weber–Morris kinetic models. The calculated sorption capacities (q_1,cal) and the rate constant of the first-order adsorption (k₁) were determined. The pseudo-second order kinetic constants (k₂) and capacities (q_2,cal) were calculated from the plots of t/q_t vs. t, 1/q_t vs. 1/t, 1/t vs. 1/q_t, q_t/t vs. q_t and 1/q₂ − q_t vs. t for type 1, type 2, type 3, type 4 and type 5 of the pseudo-second order expression, respectively.     

Compositional design,structure stability,and microwave dielectric properties in Ca3MgBGe3O12 (B = Zr,Sn) garnet ceramics with tetravalent cations on B-site

Two garnet-structured Ca₃MgBGe₃O₁₂ (B = Zr, Sn) ceramics with tetravalent cations at B-site were prepared by conventional solid state reaction. The crystal structure, microstructure evolution, and microwave dielectric performance were investigated using X-ray powder diffraction, Rietveld refinement, scanning electron microscopy, Raman spectroscopy, and infrared spectroscopy techniques. Dense Ca₃MgZrGe₃O₁₂ and Ca₃MgSnGe₃O₁₂ ceramics were obtained at sintering temperatures of 1420 and 1400 °C, respectively. The dielectric constant, unloaded quality factor, and temperature coefficient of resonance frequency of Ca₃MgZrGe₃O₁₂ were 10.80 ± 0.2; 79,600 ± 1000 GHz (f = 12.61 GHz); and ?66.8 ± 1 ppm/°C, respectively, and the corresponding values for Ca₃MgSnGe₃O₁₂ were 9.68 ± 0.2; 83,400 ± 1000 GHz (f = 14.19 GHz); and ?57.9 ± 1 ppm/°C, respectively. The dielectric performances of the two ceramics were compared by analyzing the ionic polarizability, packing fraction, and bond valence. The intrinsic dielectric properties were predicted by fitting the infrared reflectivity spectra.     

Influence of Interesterification of a Stearic Acid-Rich Spreadable Fat on Acute Metabolic Risk Factors

Chemical and enzymatic interesterification are used to create spreadable fats. However, a comparison between the two processes in terms of their acute metabolic effects has not yet been investigated. A randomised crossover study in obese (plasma TAG > 1.69 mmol/L, and BMI > 30 (BMI = kg/m²) or waist circumference > 102 cm, n = 11, age = 59.3 ± 1.8 years) and non-obese (plasma triacylglycerol (TAG) < 1.69 mmol/L, and BMI < 30  or waist circumference < 102 cm, n = 10, age = 55.8 ± 2.2 years) men was undertaken to compare the effects of chemical versus enzymatic interesterification on postprandial risk factors for type 2 diabetes (T2D) and cardiovascular disease (CVD). TAG, cholesterol, glucose, insulin and free fatty acid concentrations were measured for 6 h following consumption of 1 g fat/kg body mass of non-interesterified (NIE), chemically interesterified (CIE), enzymatically interesterified (EIE) stearic acid-rich fat spread or no fat, each with 50 g available carbohydrate from white bread. Interesterification did not affect postprandial glucose, insulin, free fatty acids or cholesterol (P > 0.05). Following ingestion of NIE, increases in serum oleic acid were observed, whereas both oleic and stearic acids were increased with CIE and EIE (P < 0.05). While postprandial TAG concentrations in non-obese subjects were not affected by fat treatment (P > 0.05), obese subjects had an 85% increase in TAGs with CIE versus NIE (P < 0.05). The differences in TAG response between non-obese and obese subjects suggest that interesterification may affect healthy individuals differently compared to those already at risk for T2D and/or CVD.     

Feasibility of Na-based thermochemical cycles for the capture of CO2 from air—Thermodynamic and thermogravimetric analyses

Three Na-based thermochemical cycles for capturing CO₂ from air are considered: (1) a NaOH/NaHCO₃/Na₂CO₃/Na₂O cycle with 4 reaction steps, (2) a NaOH/NaHCO₃/Na₂CO₃ cycle with 3 reactions steps, and (3) a Na₂CO₃/NaHCO₃ cycle with 2 reaction steps. Depending on the choice of CO₂ sorbent – NaOH or Na₂CO₃ – the cycles are closed by either NaHCO₃ or Na₂CO₃ decomposition, followed by hydrolysis of Na₂CO₃ or Na₂O, respectively. The temperature requirements, energy inputs, and expected products of the reaction steps were determined by thermodynamic equilibrium and energy balance computations. The total thermal energy requirement for Cycles 1, 2, and 3 are 481, 213, and 390 kJ/mol of CO₂ captured, respectively, when heat exchangers are employed to recover the sensible heat of hot streams. Isothermal and dynamic thermogravimetric runs were carried out on the pertinent carbonation, decomposition, and hydrolysis reactions. The extent of the NaOH carbonation with 500 ppm CO₂ in air at 25 °C – applied in Cycles 1 and 2 – reached 9% after 4 h, while that for the Na₂CO₃ carbonation with water-saturated air – applied in Cycle 3 – was 3.5% after 2 h. Thermal decomposition of NaHCO₃ – applied in all three cycles – reached completion after 3 min in the 90–200 °C range, while that of Na₂CO₃ – applied in Cycle 1 – reached completion after 15 min in the 1000–1400 °C range. The significantly slow reaction rates for the carbonation steps and, consequently, the relatively large mass flow rates required, introduce process complications in the scale-up of the reactor technology and impede the application of Na-based sorbents for capturing CO₂ from air.     

Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies

Nitrate (NO₃ ^–) leaching from agriculturalproduction systems is blamed for the rising concentrations ofNO₃ ^– in ground- and surface-waters around the world.This paper reviews the evidence of NO₃ ^– leachinglosses from various land use systems, including cut grassland, grazed pastures,arable cropping, mixed cropping with pasture leys, organic farming,horticultural systems, and forest ecosystems. Soil, climatic and managementfactors which affect NO₃ ^– leaching are discussed.Nitrate leaching occurs when there is an accumulation ofNO₃ ^– in the soil profile that coincides with or isfollowed by a period of high drainage. Therefore, excessive nitrogen (N)fertilizer or waste effluent application rates or N applications at the wrongtime (e.g. late autumn) of the year, ploughing pasture leys early in the autumn,or long periods of fallow ground, can all potentially lead to highNO₃ ^– leaching losses. N returns in animal urine havea major impact on NO₃ ^– leaching in grazed pastures.Of the land use systems considered in this paper, the potential for causingNO₃ ^– leaching typically follow the order: forest< cut grassland < grazed pastures, arable cropping < ploughing ofpasture < market gardens. A range ofmanagement options to mitigate NO₃ ^– leaching isdescribed, including reducing N application rates, synchronizing N supply toplant demand, use of cover crops, better timing of ploughing pasture leys,improved stock management, precision farming, and regulatory measures. This isfollowed by a discussion of future research needs to improve our ability topredict and mitigate NO₃ ^– leaching.     

Tough,strong, hard,and chemically durable enstatite-zirconia glass-ceramic

Strong glass-ceramics (GCs) have been envisaged and widely researched for various applications, including large architectural panels, ballistic impact protection, bioactive medical implants, and odontological prostheses. Here, we report on the development and characterization of a novel hard, strong and tough enstatite-zirconia (MgSiO₃-ZrO₂) glass-ceramic derived from a 51SiO₂–35MgO–6Na₂O–4ZrO₂–4TiO₂ (mol%) glass. The best GC was developed by treating glass samples for nucleation at 700°C for 12 hours, followed by crystal growth at 1090°C for 3 minutes. It was characterized by X-ray fluorescence (XRF), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM), and contained plate-like enstatite, zirconia, and Ti-containing crystals. We investigated the nucleating ability of ZrO₂ and TiO₂ in inducing internal nucleation. In the early stage of crystallization, enstatite spherulites were observed, which were precipitated by heterogeneous nucleation on previously nucleated ZrO₂ nano-crystals. At more advanced stages, at high temperatures, they transformed into plate-like crystals. The ball-on-three-balls strength, elastic modulus, and Vickers micro-hardness of the GC are 323 ± 26 MPa, 146 ± 13 GPa, and 6.9 ± 0.1 GPa (load = 5N), respectively. The indentation (K_C), single-edge notched beam bending (K_IC), and crack tip (K_tip) fracture toughness are 2.8 ± 0.6 MP.m^0.5, 2.2 ± 0.3 MP.m^0.5, 1.9 ± 0.3 MP.m^0.5, respectively. The crack propagation profile after a controlled Vickers indentation was quite intricate. The enstatite and zirconia crystals enhanced crack deflection, bridging and branching, hindering crack propagation. According to the ISO 6872 for dental materials, the chemical solubility of our GC is 80 ± 5 μg/cm². Due to this positive combination of high strength, toughness, hardness, and chemical durability, this new glass-ceramic is envisioned as a candidate for several applications and could be further developed for memory disc substrates, architectural cladding and tiles, ceramic glazes, and dental materials.     

Modification of glassy carbon electrode with multi-walled carbon nanotubes and iron(III)-porphyrin film: Application to chlorate, bromate and iodate detection

In this study, multi-wall carbon nanotubes (MWCTs) is evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on iron-porphyrin. 5,10,15,20-Tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)P) adsorbed on MWCNTs immobilized on the surface of glassy carbon electrode. Cyclic voltammograms of the Fe(III)P-incorporated-MWCNTs indicate a pair of well-defined and nearly reversible redox couple with surface confined characteristics at wide pH range (2-12). The surface coverage (Γ) and charge transfer rate constant (k_s) of Fe(III)P immobilized on MWCNTs were 7.68 × 10⁻⁹ mol cm⁻² and 1.8 s⁻¹, respectively, indicating high loading ability of MWCNTs for Fe(III)P and great facilitation of the electron transfer between Fe(III)P and carbon nanotubes immobilized on the electrode surface. Modified electrodes exhibit excellent electrocatalytic activity toward reduction of ClO₃⁻, IO₃⁻ and BrO₃⁻ in acidic solutions. The catalytic rate constants for catalytic reduction of bromate, chlorate and iodate were 6.8 × 10³, 7.4 × 10³ and 4.8 × 10² M⁻¹ s⁻¹, respectively. The hydrodynamic amperometry of rotating-modified electrode at constant potential versus reference electrode was used for detection of bromate, chlorate and iodate. The detection limit, linear calibration range and sensitivity for chlorate, bromate and iodate detections were 0.5 μM, 2 μM to 1 mM, 8.4 nA/μM, 0.6 μM, 2 μM to 0.15 mM, 11 nA/μM, and 2.5 μM, 10 μM to 4 mM and 1.5 nA/μM, respectively. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantages of this sensor. The obtained results show promising practical application of the Fe(III)P-MWCNTs-modified electrode as an amperometric sensor for chlorate, iodate and bromate detections.     

Fabrication and properties of pressure-sintered reaction-bonded Si3N4 ceramics with addition of Eu2O3–MgO–Y2O3

Dense pressure-sintered reaction-bonded Si₃N₄ (PSRBSN) ceramics were obtained by a hot-press sintering method. Precursor Si powders were prepared with Eu₂O₃–MgO–Y₂O₃ sintering additive. The addition of Eu₂O₃–MgO–Y₂O₃ was shown to promote full nitridation of the Si powder. The nitrided Si₃N₄ particles had an equiaxial morphology, without whisker formation, after the Si powders doped with Eu₂O₃–MgO–Y₂O₃ were nitrided at 1400 °C for 2 h. After hot pressing, the relative density, Vickers hardness, flexural strength, and fracture toughness of the PSRBSN ceramics, with 5 wt% Eu₂O₃ doping, were 98.3 ± 0.2%, 17.8 ± 0.8 GPa, 697.0 ± 67.0 MPa, and 7.3 ± 0.3 MPa m^1/2, respectively. The thermal conductivity was 73.6 ± 0.2 W m^?1 K^?1, significantly higher than the counterpart without Eu₂O₃ doping, or with ZrO₂ doping by conventional methods.